U.S. patent application number 14/180057 was filed with the patent office on 2014-06-12 for process to produce biofuels from biomass.
This patent application is currently assigned to SHELL OIL COMPANY. The applicant listed for this patent is SHELL OIL COMPANY. Invention is credited to Juben Nemchand CHHEDA, Joseph Broun POWELL.
Application Number | 20140161689 14/180057 |
Document ID | / |
Family ID | 45496296 |
Filed Date | 2014-06-12 |
United States Patent
Application |
20140161689 |
Kind Code |
A1 |
CHHEDA; Juben Nemchand ; et
al. |
June 12, 2014 |
PROCESS TO PRODUCE BIOFUELS FROM BIOMASS
Abstract
A process for producing biofuels from biomass is provided by
removing sulfur compounds and nitrogen compounds from the biomass
by contacting the biomass with a digestive solvent to form a
pretreated biomass containing soluble carbohydrates and having less
than 35% of the sulfur content and less than 35% of the nitrogen
content, based on untreated biomass on a dry mass basis, prior to
carrying out aqueous phase reforming and further processing to form
a liquid fuel.
Inventors: |
CHHEDA; Juben Nemchand;
(Houston, TX) ; POWELL; Joseph Broun; (Houston,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SHELL OIL COMPANY |
Houston |
TX |
US |
|
|
Assignee: |
SHELL OIL COMPANY
Houston
TX
|
Family ID: |
45496296 |
Appl. No.: |
14/180057 |
Filed: |
February 13, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13332292 |
Dec 20, 2011 |
8692041 |
|
|
14180057 |
|
|
|
|
61424832 |
Dec 20, 2010 |
|
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|
Current U.S.
Class: |
422/630 |
Current CPC
Class: |
C10G 1/002 20130101;
C10G 2300/4081 20130101; Y02E 50/13 20130101; C10G 2300/44
20130101; Y02E 50/10 20130101; C10G 2300/1014 20130101; C07G 1/00
20130101; C10G 1/00 20130101; C10G 2300/202 20130101; Y02P 30/20
20151101; Y02T 50/678 20130101 |
Class at
Publication: |
422/630 |
International
Class: |
C10G 1/00 20060101
C10G001/00 |
Claims
1. A system comprising: a digester that receives a biomass
feedstock and a digestive solvent operating under conditions to
effectively remove nitrogen compounds and sulfur compounds from
said biomass feedstock and discharges a treated stream comprising a
carbohydrate having less than 35% of the sulfur content and less
than 35% of the nitrogen content based on untreated biomass
feedstock on a dry mass basis; an aqueous phase reforming reactor
comprising an aqueous phase reforming catalyst that receives the
treated stream and discharges an oxygenated intermediate stream,
wherein a first portion of the oxygenated intermediate stream is
recycled to the digester as at least a portion of the digestive
solvent; and a fuels processing reactor comprising a condensation
catalyst that receives a second portion of the oxygenated
intermediate stream and discharges a liquid fuel.
2. A system comprising: a digester that receives a biomass
feedstock and a digestive solvent operating under conditions to
effectively remove nitrogen, phosphorus and sulfur compounds from
said biomass feedstock and discharges a treated stream comprising a
carbohydrate having less than 35% of the sulfur content and less
than 35% of the nitrogen content based on untreated biomass
feedstock on a dry mass basis; an aqueous phase reforming reactor
comprising an aqueous phase reforming catalyst that receives the
treated stream and discharges an oxygenated intermediate, wherein a
first portion of the oxygenated intermediate stream is recycled to
the digester as at least a portion of the digestive solvent; a
first fuels processing reactor comprising a dehydrogenation
catalyst that receives a second portion of the oxygenated
intermediate stream and discharges an olefin-containing stream; and
a second fuels processing reactor comprising an alkylation catalyst
that receives the olefin-containing stream and discharges a liquid
fuel.
Description
PRIORITY CLAIM
[0001] This application is a divisional of U.S. Non-Provisional
application Ser. No. 13/332,292 filed Dec. 20, 2011 which claims
the benefit of U.S. Provisional Application Ser. No. 61/424,832
filed Dec. 20, 2010, the entire disclosure of which is hereby
incorporated by reference.
FIELD OF THE INVENTION
[0002] The invention relates to the production of higher
hydrocarbons suitable for use in transportation fuels and
industrial chemicals from biomass.
BACKGROUND OF THE INVENTION
[0003] A significant amount of attention has been placed on
developing new technologies for providing energy from resources
other than fossil fuels. Biomass is a resource that shows promise
as a fossil fuel alternative. As opposed to fossil fuel, biomass is
also renewable.
[0004] Biomass may be useful as a source of renewable fuels. One
type of biomass is plant biomass. Plant biomass is the most
abundant source of carbohydrate in the world due to the
lignocellulosic materials composing the cell walls in higher
plants. Plant cell walls are divided into two sections, primary
cell walls and secondary cell walls. The primary cell wall provides
structure for expanding cells and is composed of three major
polysaccharides (cellulose, pectin, and hemicellulose) and one
group of glycoproteins. The secondary cell wall, which is produced
after the cell has finished growing, also contains polysaccharides
and is strengthened through polymeric lignin covalently
cross-linked to hemicellulose. Hemicellulose and pectin are
typically found in abundance, but cellulose is the predominant
polysaccharide and the most abundant source of carbohydrates.
However, production of fuel from cellulose poses a difficult
technical problem. Some of the factors for this difficulty are the
physical density of lignocelluloses (like wood) that can make
penetration of the biomass structure of lignocelluloses with
chemicals difficult and the chemical complexity of lignocelluloses
that lead to difficulty in breaking down the long chain polymeric
structure of cellulose into carbohydrates that can be used to
produce fuel.
[0005] Most transportation vehicles require high power density
provided by internal combustion and/or propulsion engines. These
engines require clean burning fuels which are generally in liquid
form or, to a lesser extent, compressed gases. Liquid fuels are
more portable due to their high energy density and their ability to
be pumped, which makes handling easier.
[0006] Currently, bio-based feedstocks such as biomass provide the
only renewable alternative for liquid transportation fuel.
Unfortunately, the progress in developing new technologies for
producing liquid biofuels has been slow in developing, especially
for liquid fuel products that fit within the current
infrastructure. Although a variety of fuels can be produced from
biomass resources, such as ethanol, methanol, and vegetable oil,
and gaseous fuels, such as hydrogen and methane, these fuels
require either new distribution technologies and/or combustion
technologies appropriate for their characteristics. The production
of some of these fuels also tends to be expensive and raise
questions with respect to their net carbon savings.
[0007] Carbohydrates are the most abundant, naturally occurring
biomolecules. Plant materials store carbohydrates either as sugars,
starches, celluloses, lignocelluloses, hemicelluloses, and any
combination thereof. In one embodiment, the carbohydrates include
monosaccharides, polysaccharides or mixtures of monosaccharides and
polysaccharides. As used herein, the term "monosaccharides" refers
to hydroxy aldehydes or hydroxy ketones that cannot be hydrolyzed
to smaller units. Examples of monosaccharides include, but are not
limited to, dextrose, glucose, fructose and galactose. As used
herein, the term "polysaccharides" refers to saccharides comprising
two or more monosaccharide units. Examples of polysaccharides
include, but are not limited to, cellulose, sucrose, maltose,
cellobiose, and lactose. Carbohydrates are produced during
photosynthesis, a process in which carbon dioxide is converted into
organic compounds as a way to store energy. The carbohydrates are
highly reactive compounds that can be easily oxidized to generate
energy, carbon dioxide, and water. The presence of oxygen in the
molecular structure of carbohydrates contributes to the reactivity
of the compound. Water soluble carbohydrates react with hydrogen
over catalyst(s) to generate polyols and sugar alcohols, either by
hydrogenation, hydrogenolysis or both.
[0008] U.S. Publication Nos. 20080216391 and 20100076233 to
Cortright et al. describes a process for converting carbohydrates
to higher hydrocarbons by passing carbohydrates through a
hydrogenation reaction followed by an Aqueous Phase Reforming
("APR") process. The hydrogenation reaction produces polyhydric
alcohols that can withstand the conditions present in the APR
reaction. Further processing in an APR reaction and a condensation
reaction can produce a higher hydrocarbon for use as a fuel.
Currently APR is limited to feedstocks including sugars or
starches, which competes with the use of these materials for food
resulting in a limited supply. There is a need to directly process
biomass into liquid fuels.
SUMMARY OF THE INVENTION
[0009] In an embodiment, a method comprises: (i) providing a
biomass containing celluloses, hemicelluloses, lignin, nitrogen
compounds and sulfur compounds; (ii) removing sulfur compounds and
nitrogen compounds from said biomass by contacting the biomass with
a digestive solvent to form a pretreated biomass containing
carbohydrates and having less than 35% of sulfur content and less
than 35% of the nitrogen content untreated biomass on a dry mass
basis; (iii) contacting the pretreated biomass with an aqueous
phase reforming catalyst to form a plurality of oxygenated
intermediates, and (vi) processing at least a portion of the
oxygenated intermediates to form a liquid fuel.
[0010] In yet another embodiment, a first portion of the oxygenated
intermediates are recycled to form in part the solvent in step
(ii); and processing at least a second portion of the oxygenated
intermediates to form a liquid fuel.
[0011] In yet another embodiment, a method comprises: (i) providing
a biomass containing celluloses, hemicelluloses, lignin, nitrogen,
and sulfur compounds; (ii) removing sulfur compounds and nitrogen
compounds from said biomass by contacting the biomass with a
digestive solvent to form a pretreated biomass containing soluble
carbohydrates and having less than 35% of the sulfur content and
less than 35% of the nitrogen content based on untreated biomass on
a dry mass basis; (iii) contacting at least a portion of the
pretreated biomass with a recycle solvent stream to form a digested
portion of the pulp; (iv) contacting at least a portion of the
digested portion of the pulp with an aqueous phase reforming
catalyst to form a plurality of oxygenated intermediates, and (v) a
first portion of the oxygenated intermediates are recycled to form
in part the recycle solvent in step (iii), and (vi) processing at
least a second portion of the oxygenated intermediates to form a
liquid fuel.
[0012] In yet another embodiment, a method comprises: (i) providing
a biomass containing celluloses, hemicelluloses, lignin, nitrogen,
and sulfur compounds; (ii) removing sulfur compounds and nitrogen
compounds from said biomass by contacting the biomass with a
digestive solvent to form a pretreated biomass containing soluble
carbohydrates and having less than 35% of the sulfur content and
less than 35% of the nitrogen content based on untreated biomass on
a dry mass basis; (iii) contacting at least a portion of the
pretreated biomass with a recycle solvent stream to form a digested
stream; (iv) contacting at least a portion of the digested portion
of the digested stream with an aqueous phase reforming catalyst to
form a plurality of oxygenated intermediates, (v) a first portion
of the first intermediate stream is recycled to form in part the
recycle solvent in step (iii), (vi) contacting at least a portion
of the first intermediate stream with an aqueous phase reforming
catalyst to form a plurality of oxygenated intermediates, and (vii)
processing at least a first portion of the oxygenated intermediates
to form a liquid fuel.
[0013] In yet another embodiment, a system comprises: a digester
that receives a biomass feedstock and a digestive solvent operating
under conditions to effectively remove nitrogen compounds and
sulfur compounds from said biomass feedstock and discharges a
treated stream comprising a carbohydrate having less than 35% of
the sulfur content and less than 35% of the nitrogen content based
on untreated biomass feedstock on a dry mass basis; an aqueous
phase reforming reactor comprising an aqueous phase reforming
catalyst that receives the treated stream and discharges an
oxygenated intermediate stream, wherein a first portion of the
oxygenated intermediate stream is recycled to the digester as at
least a portion of the digestive solvent; and a fuels processing
reactor comprising a condensation catalyst that receives a second
portion of the oxygenated intermediate stream and discharges a
liquid fuel.
[0014] In yet another embodiment, a system comprises: a digester
that receives a biomass feedstock and a digestive solvent operating
under conditions to effectively remove nitrogen compounds and
sulfur compounds from said biomass feedstock and discharges a
treated stream comprising a carbohydrate having less than 35% of
the sulfur content and less than 35% of the nitrogen content based
on untreated biomass feedstock on a dry mass basis; an aqueous
phase reforming reactor comprising an aqueous phase reforming
catalyst that receives the treated stream and discharges an
oxygenated intermediate, wherein a first portion of the oxygenated
intermediate stream is recycled to the digester as at least a
portion of the digestive solvent; a first fuels processing reactor
comprising a dehydrogenation catalyst that receives a second
portion of the oxygenated intermediate stream and discharges an
olefin-containing stream; and a second fuels processing reactor
comprising an alkylation or olefin oligomerization catalyst that
receives the olefin-containing stream and discharges a liquid
fuel.
[0015] The features and advantages of the invention will be
apparent to those skilled in the art. While numerous changes may be
made by those skilled in the art, such changes are within the
spirit of the invention.
BRIEF DESCRIPTION OF THE DRAWING
[0016] These drawings illustrate certain aspects of some of the
embodiments of the invention, and should not be used to limit or
define the invention.
[0017] FIG. 1 schematically illustrates a block flow diagram of an
embodiment of a higher hydrocarbon production process 100A of this
invention.
[0018] FIG. 2 schematically illustrates a block flow diagram of an
embodiment of a higher hydrocarbon production process 100B of this
invention.
[0019] FIG. 3 schematically illustrates a block flow diagram of an
embodiment of a higher hydrocarbon production process 100C of this
invention.
[0020] FIG. 4 schematically illustrates a block flow diagram of an
embodiment of a higher hydrocarbon production process 100D of this
invention.
[0021] FIG. 5 schematically illustrates a block flow diagram of an
embodiment of a higher hydrocarbon production process 100E of this
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0022] The invention relates to the production of higher
hydrocarbons suitable for use in transportation fuels and
industrial chemicals from biomass. The higher hydrocarbons produced
are useful in forming transportation fuels, such as synthetic
gasoline, diesel fuel, and jet fuel, as well as industrial
chemicals. As used herein, the term "higher hydrocarbons" refers to
hydrocarbons having an oxygen to carbon ratio less than the oxygen
to carbon ratio of at least one component of the bio-based
feedstock. As used herein the term "hydrocarbon" refers to an
organic compound comprising primarily hydrogen and carbon atoms,
which is also an unsubstituted hydrocarbon. In certain embodiments,
the hydrocarbons of the invention also comprise heteroatoms (i.e.,
oxygen sulfur, phosphorus, or nitrogen) and thus the term
"hydrocarbon" may also include substituted hydrocarbons. The term
"soluble carbohydrates" refers to oligosaccharides and
monosaccharides that are soluble in the digestive solvent and that
can be used as feedstock to the APR reaction (e.g., pentoses and
hexoses).
[0023] The methods and systems of the invention have an advantage
of converting a raw biomass feedstock through digestive solvent to
digest and remove a substantial amount of nitrogen compounds, and
sulfur compounds contained in the biomass. The nitrogen and sulfur
compounds removed can otherwise poison catalysts used in subsequent
processing. The method may also remove phosphorus compounds
contained in the biomass that can potentially poison catalysts used
in subsequent processing. The treated biomass is then converted by
aqueous phase reforming reactions to form an oxygenated
intermediate stream comprising polyols, alcohols, ketones,
aldehydes, and other oxygenated reaction products that can be fed
directly to a processing reaction to form higher hydrocarbons. The
process results in an increased conversion and conversion
efficiency by minimizing catalyst poisoning and extending catalyst
life.
[0024] In some embodiments, at least a portion of oxygenated
intermediates produced in the APR reaction are recycled within the
process and system to at least in part form the in situ generated
solvent, which is used in the biomass digestion process. This
recycle saves costs in provision of a solvent that can be used to
extract nitrogen, sulfur, and optionally phosphorus compounds from
the biomass feedstock. Further, by controlling the degradation of
carbohydrate in the APR process, the hydrogenation reaction can be
conducted along with the APR reaction at temperatures ranging from
175.degree. C. to 275.degree. C. As a result, a separate
hydrogenation reaction section can optionally be avoided, and the
fuel forming potential of the biomass feedstock fed to the process
can be increased. This process and reaction scheme described herein
also results in a capital cost savings and process operational cost
savings. Advantages of specific embodiments will be described in
more detail below.
[0025] In some embodiments, the invention provides methods
comprising: providing a biomass feedstock, optionally contacting
the biomass feedstock with a digestive solvent to extract and
remove a portion of the lignin, and nitrogen, and sulfur compounds,
further contacting the biomass feedstock with a digestive solvent
in a digestion system to form an intermediate stream comprising
soluble carbohydrates, contacting the intermediate stream with an
APR catalyst to form a plurality of oxygenated intermediates,
wherein a first portion of the oxygenated intermediates are
recycled to form the solvent; and contacting at least a second
portion of the oxygenated intermediates with a catalyst to form a
liquid fuel.
[0026] In reference to FIG. 1, in one embodiment of the invention
process 100A, biomass 102 is provided to digestion system 106 that
may have one or more digester(s), whereby the biomass is contacted
with a digestive solvent. The solvent liquor 110, contains
dissolved nitrogen compounds and dissolved sulfur compounds and
optionally dissolve phosphorus compounds, which are removed from
the treated biomass pulp 120, such that the treated biomass pulp
120 contains solid carbohydrates having less than 35% of the sulfur
content, preferably less than 10% of the sulfur content, and most
preferably less than 3% of the sulfur content, and less than 35% of
the nitrogen content, preferably less than 10% of the nitrogen
content, and most preferably less than 3% of the nitrogen content
based on untreated biomass feedstock on a dry mass basis. At least
a portion of the treated biomass pulp 120 is fed to an aqueous
phase reforming system 126 whereby the treated biomass pulp is
contacted with an aqueous reforming catalyst to produce a plurality
of oxygenated intermediates 130, and at least a portion of the
oxygenated intermediates is processed 136 to produce higher
hydrocarbons to form a liquid fuel 150.
[0027] In reference to FIG. 2, in one embodiment of the invention
process 100B, biomass 102 is provided to digestion system 106 that
may have one or more digester(s), whereby the biomass is contacted
with a digestive solvent. The digestive solvent is optionally at
least a portion recycled from the regenerated chemical liquor
stream 168. In such a system at least a portion of the solvent
liquor 110 is processed 160 to regenerate at least a portion of the
digestive solvent that is then recycled to the digestion system.
The regeneration and recycle of the chemical liquor varies
depending on the digestive solvent used as some examples are
discussed below. The solvent liquor 162 containing the dissolved
nitrogen compounds and dissolved sulfur compounds are removed from
the treated biomass pulp 120 that contains carbohydrates and has
less than 35% of the sulfur content, preferably less than 10% of
the sulfur content, and most preferably less than 3% of the sulfur
content, and less than 35% of the nitrogen content, preferably less
than 10% of the nitrogen content, and most preferably less than 3%
of the nitrogen content based on untreated biomass on a dry mass
basis. At least a portion of the treated biomass pulp 120 is fed to
an aqueous phase reforming system 126 whereby the treated biomass
pulp is contacted with an aqueous reforming catalyst to produce a
plurality of oxygenated intermediates 130, and at least a portion
of the oxygenated intermediates is processed 136 to produce higher
hydrocarbons to form a liquid fuel 150. The treated pulp 120 may be
optionally washed prior to feeding to the aqueous phase reforming
system 126. If washed, water is most typically used as wash
solvent.
[0028] Any suitable (e.g., inexpensive and/or readily available)
type of biomass can be used. Suitable lignocellulosic biomass can
be, for example, selected from, but not limited to, forestry
residues, agricultural residues, herbaceous material, municipal
solid wastes, waste and recycled paper, pulp and paper mill
residues, and combinations thereof. Thus, in some embodiments, the
biomass can comprise, for example, corn stover, straw, bagasse,
miscanthus, sorghum residue, switch grass, bamboo, water hyacinth,
hardwood, hardwood chips, hardwood pulp, softwood, softwood chips,
softwood pulp, and/or combination of these feedstocks. The biomass
can be chosen based upon a consideration such as, but not limited
to, cellulose and/or hemicelluloses content, lignin content,
growing time/season, growing location/transportation cost, growing
costs, harvesting costs and the like.
[0029] Prior to treatment with the digestive solvent, the untreated
biomass can be washed and/or reduced in size (e.g., chopping,
crushing or debarking) to a convenient size and certain quality
that aids in moving the biomass or mixing and impregnating the
chemicals from digestive solvent. Thus, in some embodiments,
providing biomass can comprise harvesting a
lignocelluloses-containing plant such as, for example, a hardwood
or softwood tree. The tree can be subjected to debarking, chopping
to wood chips of desirable thickness, and washing to remove any
residual soil, dirt and the like.
[0030] It is recognized that washing with water prior to treatment
with digestive solvent is desired, to rinse and remove simple salts
such as nitrate, sulfate, and phosphate salts which otherwise may
be present, and contribute to measured concentrations of nitrogen,
sulfur, and phosphorus compounds present. This wash is accomplished
at a temperature of less than about 60 degrees Celsius, and where
hydrolysis reactions comprising digestion do not occur to a
significant extent. Other nitrogen, sulfur, and phosphorus
compounds are bound to the biomass and are more difficult to
remove, and requiring digestion and reaction of the biomass, to
effect removal. These compounds may be derived from proteins, amino
acids, phospholipids, and other structures within the biomass, and
may be potent catalyst poisons. The removal process described
herein, allows removal of some of these more difficult to remove
nitrogen and sulfur compounds. In the context of the percentage of
nitrogen and sulfur removed in the invention process, it is
measured as percent reduction after treatment compared to a rinsed
but untreated biomass, whereby the biomass is rinsed with water at
ambient temperature, and referred to as a percent reduction based
on "untreated biomass on a dry mass basis" or "untreated biomass
feedstock on a dry mass basis".
[0031] It is also recognized that while nitrogen and sulfur
compounds are most readily measured in treated and untreated
biomass, phosphorous compounds which may also serve as catalyst
poisons are also likely to be removed during purification to remove
nitrogen and sulfur compounds found in washed biomass.
[0032] In the digestion system, the size-reduced biomass is
contacted with the digestive solvent in at least one digester where
the digestion reaction takes place. The digestive solvent must be
effective to digest lignins and the nitrogen and sulfur compounds,
to effect removal of at least a portion of the nitrogen, and sulfur
compounds from the biomass.
[0033] In one aspect of the embodiment, the digestive solvent maybe
a Kraft-like digestive solvent that contains (a) at least 0.5 wt %,
more preferably at least 4 wt %, to 20 wt %, more preferably to 10
wt %, based on the digestive solvent, of at least one alkali
selected from the group consisting of sodium hydroxide, sodium
carbonate, sodium sulfide, potassium hydroxide, potassium
carbonate, ammonium hydroxide, and mixtures thereof, (b)
optionally, 0 to 3%, based on the digestive solvent, of
anthraquinone, sodium borate and/or polysulfides; and (c) water (as
remainder of the digestive solvent). In some embodiments, the
digestive solvent may have an active alkali of between 5 to 25%,
more preferably between 10 to 20%. The term "active alkali" (AA),
as used herein, is a percentage of alkali compounds combined,
expressed as sodium oxide based on weight of the biomass less water
content (dry solid biomass). If sodium sulfide is present in the
digestive solvent, the sulfidity can range from about 15% to about
40%, preferably from about 20 to about 30%. The term "sulfidity",
as used herein, is a percentage ratio of Na2S, expressed as Na2O,
to active alkali. digestive solvent to biomass ratio can be within
the range of 0.5 to 50, preferably 2 to 10. The digestion is
carried out typically at a cooking liquor to biomass ratio in the
range of 2 to 6, preferably 3 to 5. The digestion reaction is
carried out at a temperature within the range of 60.degree. C. to
230.degree. C., preferably 80 to 180 C, and a residence time within
0.25 h to 24 h. The reaction is carried out under conditions
effective to provide a digested biomass stream containing digested
biomass having a lignin content of 1% to 20% by weight, based on
the digested biomass, and a chemical liquor stream containing
alkali compounds and dissolved lignin and hemicelluloses
material.
[0034] The digester can be, for example, a pressure vessel of
carbon steel or stainless steel or similar alloy. The digestion
system can be carried out in the same vessel or in a separate
vessel. The cooking can be done in continuous or batch mode.
Suitable pressure vessels include, but are not limited to the
"PANDIATM Digester" (Voest-Alpine Industrienlagenbau GmbH, Linz,
Austria), the "DEFIBRATOR Digester" (Sunds Defibrator AB
Corporation, Stockholm, Sweden), M&D (Messing & Durkee)
digester (Bauer Brothers Company, Springfield, Ohio, USA) and the
KAMYR Digester (Andritz Inc., Glens Falls, N.Y., USA). The
digestive solvent has a pH from 10 to 14, preferably around 12 to
13 depending on AA. The contents can be kept at a temperature
within the range of from 100.degree. C. to 230.degree. C. for a
period of time, more preferably within the range from about
130.degree. C. to about 180.degree. C. The period of time can be
from about 0.25 to 24.0 hours, preferably from about 0.5 to about 2
hours, after which the pretreated contents of the digester are
discharged. For adequate penetration, a sufficient volume of liquor
is required to ensure that all the biomass surfaces are wetted.
Sufficient liquor is supplied to provide the specified digestive
solvent to biomass ratio. The effect of greater dilution is to
decrease the concentration of active chemical and thereby reduce
the reaction rate.
[0035] In a system using the digestive solvent such as a Kraft-like
digestive solvent similar to those used in a Kraft pulp and paper
process, the chemical liquor may be regenerated in a similar manner
to a Kraft pulp and paper chemical regeneration process. For
example, in reference to FIG. 2 when used in a Kraft-like digestive
solvent system, the recaustisized chemical recycle stream 168
obtained by regenerating at least a portion of the solvent liquor
stream through a chemical regeneration system 160. In an
embodiment, chemical liquor stream is obtained by concentrating at
least a portion of the solvent liquor stream 110 in a concentration
system thereby producing a concentrated chemical liquor stream then
burning the concentrated chemical liquor stream in a boiler system
thereby producing chemical recycle stream 168 and a flue gas stream
then converting the sodium containing compounds to sodium hydroxide
in the recaustisizing system by contacting with lime (CaO)
producing the recaustisized chemical recycle stream 168 that can be
used as a portion of the digestive solvent containing sodium
hydroxide.
[0036] In another embodiment, an at least partially water miscible
organic solvent that has partial solubility in water, preferably
greater than 2 weight percent in water, may be used as digestive
solvent to aid in digestion of lignin, and the nitrogen, and sulfur
compounds. In one such embodiment, the digestive solvent is a
water-organic solvent mixture with optional inorganic acid
promoters such as HCl or sulfuric acid. Oxygenated solvents
exhibiting full or partial water solubility are preferred digestive
solvents. In such a process, the organic digestive solvent mixture
can be, for example, methanol, ethanol, acetone, ethylene glycol,
triethylene glycol and tetrahydrofufuryl alcohol. Organic acids
such as acetic, oxalic, acetylsalicylic and salicylic acids can
also be used as catalysts (as acid promoter) in the at least
partially miscible organic solvent process. Temperatures for the
digestion may range from about 130 to about 220 degrees Celsius,
preferably from about 140 to 180 degrees Celsius, and contact times
from 0.25 to 24 hours, preferably from about one to 4 hours.
Preferably, a pressure from about 250 kPa to 7000 kPa, and most
typically from 700 kPa to 3500 kPa, maintained on the system to
avoid boiling or flashing away of the solvent.
[0037] Optionally the pretreated biomass stream can be washed prior
to aqueous reforming. In the wash system, the pretreated biomass
stream can be washed to remove one or more of non-cellulosic
material, non-fibrous cellulosic material, and non-degradable
cellulosic material prior to aqueous phase reforming. The
pretreated biomass stream is washed with water stream under
conditions to remove at least a portion of lignin and
hemicellulosic material in the pretreated biomass stream and
producing washed pretreated biomass stream having solids content of
5% to 15% by weight, based on the washed pretreated biomass stream.
For example, the pretreated biomass stream can be washed with water
to remove dissolved substances, including degraded, but
non-processable cellulose compounds, solubilised lignin, and/or any
remaining alkaline chemicals such as sodium compounds that were
used for cooking or produced during the cooking (or pretreatment).
The washed digested biomass stream may contain higher solids
content by further processing such as mechanical dewatering as
described below.
[0038] In a preferred embodiment, the pretreated biomass stream is
washed counter-currently. The wash can be at least partially
carried out within the digester and/or externally with separate
washers. In one embodiment of the invention process, the wash
system contains more than one wash steps, for example, first
washing, second washing, third washing, etc. that produces washed
pretreated biomass stream from first washing, washed digested
biomass stream from second washing, etc. operated in a counter
current flow with the water, that is then sent to subsequent
processes as washed pretreated biomass stream. The water is
recycled through first recycled wash stream and second recycled
wash stream and then to third recycled wash stream. Water recovered
from the chemical liquor stream by the concentration system can be
recycled as wash water to wash system. It can be appreciated that
the washed steps can be conducted with any number of steps to
obtain the desired washed digested biomass stream. Additionally,
the washing may adjust the pH for subsequent steps where the pH is
about 2.0 to 10.0, where optimal pH is determined by the catalyst
employed in the APR step. Bases such as alkali base may be
optionally added, to adjust pH.
[0039] In some embodiments, the reactions described are carried out
in any system of suitable design, including systems comprising
continuous-flow, batch, semi-batch or multi-system vessels and
reactors. One or more reactions or steps may take place in an
individual vessel and the process is not limited to separate
reaction vessels for each reaction or digestion. In some
embodiments the system of the invention utilizes a fluidized
catalytic bed system. Preferably, the invention is practiced using
a continuous-flow system at steady-state equilibrium.
[0040] In reference to FIG. 3, in one embodiment of the invention
process 100C, biomass 102 is provided to digestion system 106 that
may have one or more digester(s), whereby the biomass is contacted
with a digestive solvent. The digestive solvent is optionally at
least a portion recycled from the APR reaction as an recycle stream
128. The APR recycle stream 128 can comprise a number of components
including in situ generated solvents, which may be useful as
digestive solvent at least in part or in entirety. The term "in
situ" as used herein refers to a component that is produced within
the overall process; it is not limited to a particular reactor for
production or use and is therefore synonymous with an in-process
generated component. The in situ generated solvents may comprise
oxygenated intermediates. The digestive process to remove nitrogen,
and sulfur compounds may vary within the reaction media so that a
temperature gradient exists within the reaction media, allowing for
nitrogen, and sulfur compounds to be extracted at a lower
temperature than cellulose. For example, the reaction sequence may
comprise an increasing temperature gradient from the biomass
feedstock 102. The non-extractable solids may be removed from the
reaction as an outlet stream 120. The treated biomass stream 120 is
an intermediate stream that may comprise the treated biomass at
least in part in the form of carbohydrates. The composition of the
intermediate carbohydrate stream 120 may vary and may comprise a
number of different compounds. Preferably, the carbohydrates have 2
to 12 carbon atoms, and even more preferably 2 to 6 carbon atoms.
The carbohydrates may also have an oxygen to carbon ratio from
0.5:1 to 1:1.2. At least a portion of the digested portion of the
pulp 120 is fed to a hydrogenolysis system 126 whereby at least a
portion of the digested pulp is contacted with an aqueous reforming
catalyst to produce a plurality of oxygenated intermediates 130. A
first portion of the oxygenated intermediate stream 128 is recycled
to digester 106. A second portion of the oxygenated intermediates
is processed 136 to produce higher hydrocarbons to form a liquid
fuel 150.
[0041] In reference to FIG. 4, in one embodiment of the invention
process 100D, biomass 102 is provided to digestion system 106 that
may have one or more digester(s), whereby the biomass is contacted
with a digestive solvent. The solvent liquor 110 containing the
dissolved nitrogen compounds and dissolved sulfur compounds and at
least a portion of the lignin are removed from the treated biomass
pulp 120 that contains carbohydrates and having less than 35% of
sulfur content, preferably less than 10% of sulfur content, and
most preferably less than 3% of sulfur content, and less than 35%
nitrogen content, preferably less than 10% of nitrogen content, and
most preferably less than 3% of nitrogen content, based on the
nitrogen content or sulfur content, respectively, of the untreated
biomass 102 on a dry mass basis. At least a portion of the treated
biomass pulp 120 is fed to a first zone of an aqueous phase
reforming system 126A, whereby the treated biomass pulp is
contacted with a recycle solvent stream 124. Undigested portion of
the pulp from 126A is discharged as undigested solids stream 125.
At least a portion of the digested portion of the pulp from 126A,
122, is provided to a second zone of an aqueous phase reforming
system 126B whereby the digested portion of the pulp is contacted
with an aqueous reforming catalyst to produce a plurality of
oxygenated intermediates. A first portion of the oxygenated
intermediate stream 124 is recycled to the first zone of the
aqueous phase reforming system 126A. A second portion of the
oxygenated intermediates 130 is processed 136 to produce higher
hydrocarbons to form a liquid fuel 150. A precipitate solids stream
127, containing some of the lignin, produced upon separation of the
first portion of the oxygenated intermediates stream that is
recycled 124, is discharged. The treated pulp 120 may be optionally
washed prior to feeding to the first zone aqueous phase reforming
system 126A. If washed, water is most typically used as wash
solvent. The aqueous phase reforming system 126A and 126B may be
carried out in the vessel in a separate zone or in a separate
vessel.
[0042] In reference to FIG. 5, in one embodiment of the invention
process 100E, biomass 102 is provided to digestion system 106 that
may have one or more digester(s), whereby the biomass is contacted
with a digestive solvent. The solvent liquor 110 containing the
dissolved nitrogen compounds and dissolved sulfur compounds and at
least a portion of the lignin are removed from the treated biomass
pulp 120 that contains carbohydrates and having less than 35% of
the sulfur content, preferably less than 10% of the sulfur content,
and most preferably less than 3% of the sulfur content, and less
than 35% of the nitrogen content, preferably less than 10% of the
nitrogen content, and most preferably less than 3% of the nitrogen
content, based on the nitrogen content or sulfur content,
respectively, of the untreated biomass 102 on a dry mass basis. At
least a portion of the treated biomass pulp 120 is fed to a first
digestive zone of an aqueous reforming system 126A, whereby the
treated biomass pulp is contacted with a recycle first
intermediates solvent stream 124, and an optional monooxygenates
solvent stream 128 to produce digested stream 122 and a undigested
pulp 125. Undigested portion of the pulp from 126A is discharged as
undigested solids stream 125. At least a portion of the digested
portion of the pulp from 126A comprises stream 122, and is provided
to a second zone of an aqueous reforming system 126B whereby the
digested portion of the pulp is contacted with an aqueous reforming
catalyst or with a hydrogenolysis catalyst optionally in the
presence of external hydrogen source to produce a first
intermediates stream 123, containing diols and polyols and sugar
alcohols, and some monooxygenates. A first portion of the first
oxygenated intermediate stream 124 is recycled to the first zone of
the aqueous reforming system 126A. A second portion of the
oxygenated intermediates is processed via 126C whereby the soluble
intermediates stream is provided to a third zone of an aqueous
reforming system 126C whereby the soluble intermediates stream is
contacted with an aqueous reforming catalyst to produce a plurality
of oxygenated intermediates 130 containing monooxygenates. A first
portion of the oxygenated intermediates is processed 136 to produce
higher hydrocarbons to form a liquid fuel 150. A second portion of
the oxygenated intermediate stream is optionally recycled back 128
to digestive zone 126A, to provide additional solvent for digestion
of the treated pulp 120. Precipitate solids streams 127 and 129
containing some of the lignin, are optionally produced by cooling
of the reactor products or removing a portion of the oxygenated
solvents from 126B and 126C, respectively. The treated pulp 120 may
be optionally washed prior to feeding to the first zone aqueous
phase reforming system 126A. If washed, water is most typically
used as wash solvent. The aqueous reforming system 126A, 126B, and
126C may be carried out in the vessel in a separate zone or in a
separate vessel.
[0043] Use of separate processing zones for steps 126B and 126C
allows conditions to be optimized for digestion and hydrogenation
or aqueous reforming of the digested pulp components in 126B,
independent from optimization of the conversion of oxygenated
intermediates to monooxygenates in 126C, before feeding to step 136
to make higher hydrocarbon fuels. A lower reaction temperature in
126B may be advantageous to minimize heavy ends byproduct
formation, by conducting the hydrogenation and hydrogenolysis steps
initially at a low temperature. This has been observed to result in
an intermediates stream which is rich in diols and polyols, but
essentially free of non-hydrogenated monosaccharides which
otherwise would serve as heavy ends precursors. The subsequent
conversion in 126C of mostly solubilized intermediates can be done
efficiently at a higher temperature, where residence time is
minimized to avoid the undesired continued reaction of
monooxygenates to form alkane or alkene byproducts. In this manner,
overall yields to desired monooxygenates may be improved, via
conducting the conversion in two or more stages.
[0044] Use of separate processing zones for steps 126B and 126C
allows conditions to be optimized for digestion and aqueous phase
reforming of the digested pulp components in 126B, independent from
optimization of the conversion of oxygenated intermediates to
mono-oxygenates in 126C, before feeding to step 136 to make higher
hydrocarbon fuels. A lower reaction temperature in 126B may be
advantageous to minimize heavy ends byproduct formation, by
conducting the aqueous phase reforming reaction step initially at a
low temperature. This has been observed to result in an
intermediates stream which is rich in diols and polyols, but
essentially free of non-hydrogenated monosaccharides which
otherwise would serve as heavy ends precursors. The subsequent
conversion in 126C of mostly solubilized intermediates can be done
efficiently at a higher temperature, where residence time is
minimized to avoid the undesired continued reaction of
monooxygenates to form alkane or alkene byproducts In this manner,
overall yields to desired monooxygenates may be improved, via
conducting the conversion in two or more stages.
[0045] Various factors affect the extraction of sulfur compounds
and nitrogen compounds of the biomass feedstock in the extractive
process. In some embodiments, hemicellulose along with nitrogen,
phosphorus and sulfur compounds may be extracted from the biomass
feedstock with a digestive solvent.
[0046] Nitrogen, phosphorus and sulfur compounds extraction begins
above 100.degree. C., with solubilization and hydrolysis becoming
complete at temperatures around 170.degree. C., aided by organic
acids (e.g., carboxylic acids) formed from partial degradation of
carbohydrate components. Some lignins can be solubilized before
cellulose, while other lignins may persist to higher temperatures.
Organic, in situ generated solvents, which may comprise a portion
of the oxygenated intermediates, including, but not limited to,
light alcohols and polyols, can assist in solubilization and
extraction of lignin and other components.
[0047] At temperatures above about 120.degree. C., carbohydrates
can degrade through a series of complex self-condensation reactions
to form caramelans, which are considered degradation products that
are difficult to convert to fuel products. In general, some
degradation reactions can be expected with aqueous reaction
conditions upon application of temperature, given that water will
not completely suppress oligomerization and polymerization
reactions.
[0048] In some embodiments of the invention, nitrogen and sulfur
compounds are removed from the biomass feedstock in a digestive
solvent medium by at least a partial hydrolysis such as, including,
but not limited to, the Kraft type process and organic-solvent
assisted process described above and acid hydrolysis and other
biomass hydrolysis processes that can partially digest the biomass
and extract nitrogen and sulfur compounds to be separated from the
solid biomass (pulp). In certain embodiments, the hydrolysis
reaction can occur at a temperature between 20.degree. C. and
250.degree. C. and a pressure between 1 bar and 100 bar. An enzyme
may be used for hydrolysis at low temperature and pressure. In
embodiments including strong acid and enzymatic hydrolysis, the
hydrolysis reaction can occur at temperatures as low as ambient
temperature and pressure between 1 bar (100 kPa) and 100 bar
(10,100 kPa). In some embodiments, the hydrolysis reaction may
comprise a hydrolysis catalyst (e.g., a metal or acid catalyst) to
aid in the hydrolysis reaction. The catalyst can be any catalyst
capable of effecting a hydrolysis reaction. For example, suitable
catalysts can include, but are not limited to, acid catalysts, base
catalysts, metal catalysts, and any combination thereof. Acid
catalysts can include organic acids such as acetic, formic,
levulinic acid, and any combination thereof. In an embodiment the
acid catalyst may be generated in the APR reaction and comprise a
component of the oxygenated intermediate stream.
[0049] In some embodiments, the digestive solvent may contain an in
situ generated solvent. The in situ generated solvent generally
comprises at least one alcohol or polyol capable of solvating some
of the sulfur compounds, and nitrogen compounds of the biomass
feedstock. For example, an alcohol may be useful for solvating
nitrogen, sulfur, and optionally phosphorus compounds, and in
solvating lignin from a biomass feedstock for use within the
process. The in situ generated solvent may also include one or more
organic acids. In some embodiments, the organic acid can act as a
catalyst in the removal of nitrogen and sulfur compounds by some
hydrolysis of the biomass feedstock. Each in situ generated solvent
component may be supplied by an external source, generated within
the process, and recycled to the hydrolysis reactor, or any
combination thereof. For example, a portion of the oxygenated
intermediates produced in the APR reaction may be separated in the
separator stage for use as the in situ generated solvent in the
hydrolysis reaction. In an embodiment, the in situ generated
solvent can be separated, stored, and selectively injected into the
recycle stream so as to maintain a desired concentration in the
recycle stream.
[0050] Each reactor vessel of the invention preferably includes an
inlet and an outlet adapted to remove the product stream from the
vessel or reactor. In some embodiments, the vessel in which at
least some digestion occurs may include additional outlets to allow
for the removal of portions of the reactant stream. In some
embodiments, the vessel in which at least some digestion occurs may
include additional inlets to allow for additional solvents or
additives.
[0051] The digestion step may occur in any contactor suitable for
solid-liquid contacting. The digestion may for example be conducted
in a single or multiple vessels, with biomass solids either fully
immersed in liquid digestive solvent, or contacted with solvent in
a trickle bed or pile digestion mode. As a further example, the
digestion step may occur in a continuous multizone contactor as
described in U.S. Pat. No. 7,285,179 (Snekkenes et al., "Continuous
Digester for Cellulose Pulp including Method and Recirculation
System for such Digester"), which is hereby incorporated by
reference. Alternately, the digestion may occur in a fluidized bed
or stirred contactor, with suspended solids. The digestion may be
conducted batchwise, in the same vessel used for pre-wash, post
wash, and/or subsequent reaction steps.
[0052] The relative composition of the various carbohydrate
components in the treated biomass stream affects the formation of
undesirable by-products such as coke in the APR reaction. In
particular, a low concentration of carbohydrates present as
reducing sugars, or containing free aldehyde groups, in the treated
biomass stream can minimize the formation of unwanted by-products.
In preferred embodiments, it is desirable to have a concentration
of no more than 5 wt %, based upon total liquid, of readily
degradable carbohydrates or heavy end precursors in the treated
biomass, while maintaining a total organic intermediates
concentration, which can include the oxygenated intermediates
(e.g., mono-oxygenates, diols, and/or polyols) derived from the
carbohydrates, as high as possible, via use of concerted reaction
or rapid recycle of the liquid between the digestion zone, and a
catalytic reaction zone converting the solubilized carbohydrates to
oxygenated intermediates.
[0053] For any of the configurations 100A through D, a substantial
portion of lignin is removed with solvent 110 from digesting step
106. In configuration, the remaining lignin, if present, can be
removed upon cooling or partial separation of oxygenates from APR
product stream 130, to comprise a precipitated solids stream 131 as
shown for 100D in FIG. 4. Optionally, the precipitated solids
stream containing lignin may be formed by cooling the digested
solids stream 129 prior to APR reaction 126. In yet another
configuration, the lignin which is not removed with digestion
solvent 110 is passed into step 136, where it may be precipitated
upon vaporization or separation of APR product stream 130, during
processing to product higher hydrocarbons stream 150.
[0054] Aqueous phase reforming (APR) converts polyhydric alcohols
to carbonyls and/or aldehydes, which react over a catalyst with
water to form hydrogen, carbon dioxide, and oxygenated
intermediates, which comprise smaller alcohols (e.g., monohydric
and/or polyhydric alcohols) such as, for example, disclosed in U.S.
Publication Nos. 20080216391 which disclosure is herein
incorporated by reference. The alcohols can further react through a
series of deoxygenation reactions to form additional oxygenated
intermediates that can produce higher hydrocarbons through a
processing reaction such as a condensation reaction.
[0055] Referring again to FIG. 1, according to one embodiment, the
treated biomass stream 120 from the removal system 106 can be
passed to an APR reaction to produce oxygenated intermediates. The
treated biomass stream 120 may comprise C5 and C6 carbohydrates
that can be reacted in the APR reaction. For embodiments comprising
thermocatalytic APR, oxygenated intermediates such as sugar
alcohols, sugar polyols, carboxylic acids, ketones, and/or furans
can be converted to fuels in a further processing reaction. The APR
reaction can comprise an APR catalyst to aid in the reactions
taking place. The APR reaction conditions can be such that an APR
reaction can take place along with a hydrogenation reaction, a
hydrogenolysis reaction, or hydrodeoxygenation reaction, or all
together as many of the reaction conditions overlap or are
complimentary. The various reactions can result in the formation of
one or more oxygenated intermediate streams 130. As used herein, an
"oxygenated intermediate" can include one or more polyols,
alcohols, ketones, or any other hydrocarbon having at least one
oxygen atom.
[0056] In some embodiments, the APR catalysts can be a
heterogeneous catalyst capable of catalyzing a reaction between
hydrogen and carbohydrate, oxygenated intermediate, or both to
remove one or more oxygen atoms to produce in-situ hydrogen for APR
and to produce alcohols and polyols to be fed to the condensation
reactor. The APR catalyst can generally include Cu, Re, Ni, Fe, Co,
Ru, Pd, Rh, Pt, Os, Ir, Sn, and alloys or any combination thereof,
either alone or with promoters such as W, Mo, Au, Ag, Cr, Zn, Mn,
B, P, Bi, and alloys or any combination thereof. Other effective
APR catalyst materials include either supported nickel or ruthenium
modified with rhenium. In some embodiments, the APR catalyst also
includes any one of the supports, depending on the desired
functionality of the catalyst. The APR catalysts may be prepared by
methods known to those of ordinary skill in the art. In some
embodiments the APR catalyst includes a supported Group VIII metal
catalyst and a metal sponge material (e.g., a sponge nickel
catalyst). Raney nickel provides an example of an activated sponge
nickel catalyst suitable for use in this invention. In some
embodiments, the APR reaction in the invention is performed using a
catalyst comprising a nickel-rhenium catalyst or a
tungsten-modified nickel catalyst. One example of a suitable
catalyst for the APR reaction of the invention is a
carbon-supported nickel-rhenium catalyst.
[0057] In some embodiments, a suitable Raney nickel catalyst may be
prepared by treating an alloy of approximately equal amounts by
weight of nickel and aluminum with an aqueous alkali solution,
e.g., containing about 25 weight % of sodium hydroxide. The
aluminum is selectively dissolved by the aqueous alkali solution
resulting in a sponge shaped material comprising mostly nickel with
minor amounts of aluminum. The initial alloy includes promoter
metals (e.g., molybdenum or chromium) in the amount such that 1 to
2 weight % remains in the formed sponge nickel catalyst. In another
embodiment, the APR catalyst is prepared using a solution of
ruthenium(III) nitrosylnitrate, ruthenium (III) chloride in water
to impregnate a suitable support material. The solution is then
dried to form a solid having a water content of less than 1% by
weight. The solid is then reduced at atmospheric pressure in a
hydrogen stream at 300.degree. C. (uncalcined) or 400.degree. C.
(calcined) in a rotary ball furnace for 4 hours. After cooling and
rendering the catalyst inert with nitrogen, 5% by volume of oxygen
in nitrogen is passed over the catalyst for 2 hours.
[0058] In certain embodiments, the APR catalyst may include a
catalyst support. The catalyst support stabilizes and supports the
catalyst. The type of catalyst support used depends on the chosen
catalyst and the reaction conditions. Suitable supports for the
invention include, but are not limited to, carbon, silica,
silica-alumina, zirconia, titania, ceria, vanadia, nitride, boron
nitride, heteropolyacids, hydroxyapatite, zinc oxide, chromia,
zeolites, carbon nanotubes, carbon fullerene and any combination
thereof.
[0059] The conditions for which to carry out the APR reaction will
vary based on the type of starting material and the desired
products. In general, the APR reaction is conducted at temperatures
of 80.degree. C. to 300.degree. C., and preferably at 120.degree.
C. to 300.degree. C., and most preferably at 200.degree. C. to
280.degree. C. In some embodiments, the APR reaction is conducted
at pressures from 500 kPa to 14000 kPa.
[0060] The APR reaction can optionally be conducted with
pre-addition of a fraction of the hydrogen required for conversion,
to facilitate hydrogenation reactions which are advantageous in
converting species containing less stable carbonyl groups such as
monosaccharides to more stable alcohols such as sugar alcohols. The
hydrogen may be supplied from an external source, or via recycle of
excess hydrogen formed in the APR reaction section, after
initiation of the reaction sequence.
[0061] The hydrogen used in the hydrogenolysis reaction of the
current invention can include external hydrogen, recycled hydrogen,
in situ generated hydrogen, and any combination thereof.
[0062] In an embodiment, the use of a hydrogenolysis reaction may
produce less carbon dioxide and a greater amount of polyols than a
reaction that results in reforming of the reactants. For example,
reforming can be illustrated by formation of isopropanol (i.e.,
IPA, or 2-propanol) from sorbitol:
C6H14O6+H2O.fwdarw.4H2+3CO2+C3H8O; dHR=-40kJ/g-mol (Eq. 1)
[0063] Alternately, in the presence of hydrogen, polyols and
mono-oxygenates such as IPA can be formed by hydrogenolysis, where
hydrogen is consumed rather than produced:
C6H14O6+3H2.fwdarw.2H2O+2C3H8O2; dHR=+81kJ/gmol (Eq. 2)
C6H14O6+5H2.fwdarw.4H2O+2C3H8O; dHR=-339kJ/gmol (Eq. 3)
[0064] As a result of the differences in the reaction conditions
(e.g., presence of hydrogen), the products of the hydrogenolysis
reaction may comprise greater than 25% by mole, or alternatively,
greater than 30% by mole of polyols, which may result in a greater
conversion in a subsequent processing reaction. In addition, the
use of a hydrolysis reaction rather than a reaction running at
reforming conditions may result in less than 20% by mole, or
alternatively less than 30% by mole carbon dioxide production. As
used herein, "oxygenated intermediates" generically refers to
hydrocarbon compounds having one or more carbon atoms and between
one and three oxygen atoms (referred to herein as C.sub.1+O.sub.1-3
hydrocarbons), such as polyols and smaller molecules (e.g., one or
more polyols, alcohols, ketones, or any other hydrocarbon having at
least one oxygen atom).
[0065] In an embodiment, hydrogenolysis is conducted under neutral
or acidic conditions, as needed to accelerate hydrolysis reactions
in addition to the hydrogenolysis. Hydrolysis of oligomeric
carbohydrates may be combined with hydrogenation to produce sugar
alcohols, which can undergo hydrogenolysis.
[0066] A second aspect of hydrogenolysis entails the breaking of
--OH bonds such as:
RC(H).sub.2--OH+H.sub.2.fwdarw.RCH.sub.3+H.sub.2O
[0067] This reaction is also called "hydrodeoxygenation", and may
occur in parallel with C--C bond breaking hydrogenolysis. Diols may
be converted to mono-oxygenates via this reaction. As reaction
severity is increased by increases in temperature or contact time
with catalyst, the concentration of polyols and diols relative to
mono-oxygenates will diminish, as a result of this reaction.
Selectivity for C--C vs. C--OH bond hydrogenolysis will vary with
catalyst type and formulation. Full de-oxygenation to alkanes can
also occur, but is generally undesirable if the intent is to
produce mono-oxygenates or diols and polyols which can be condensed
or oligomerized to higher molecular weight fuels, in a subsequent
processing step. Typically, it is desirable to send only
mono-oxygenates or diols to subsequent processing steps, as higher
polyols can lead to excessive coke formation on condensation or
oligomerization catalysts, while alkanes are essentially unreactive
and cannot be combined to produce higher molecular weight
fuels.
[0068] The APR product stream 130 may comprise APR products that
include oxygenated intermediates. As used herein, "oxygenated
intermediates" generically refers to hydrocarbon compounds having
one or more carbon atoms and between one and three oxygen atoms
(referred to herein as C.sub.1+O.sub.1-3 hydrocarbons), such as
ketones, aldehydes, furans, hydroxy carboxylic acids, carboxylic
acids, alcohols, diols and triols. Preferably, the oxygenated
intermediates have from one to six carbon atoms, or two to six
carbon atoms, or three to six carbon atoms. The ketones may
include, without limitation, hydroxyketones, cyclic ketones,
diketones, acetone, propanone, 2-oxopropanal, butanone,
butane-2,3-dione, 3-hydroxybutane-2-one, pentanone, cyclopentanone,
pentane-2,3-dione, pentane-2,4-dione, hexanone, cyclohexanone,
2-methyl-cyclopentanone, heptanone, octanone, nonanone, decanone,
undecanone, dodecanone, methylglyoxal, butanedione, pentanedione,
diketohexane, and isomers thereof. The aldehydes may include,
without limitation, hydroxyaldehydes, acetaldehyde,
propionaldehyde, butyraldehyde, pentanal, hexanal, heptanal,
octanal, nonal, decanal, undecanal, dodecanal, and isomers thereof.
The carboxylic acids may include, without limitation, formic acid,
acetic acid, propionic acid, butanoic acid, pentanoic acid,
hexanoic acid, heptanoic acid, isomers and derivatives thereof,
including hydroxylated derivatives, such as 2-hydroxybutanoic acid
and lactic acid. Alcohols may include, without limitation, primary,
secondary, linear, branched or cyclic C1+ alcohols, such as
methanol, ethanol, n-propyl alcohol, isopropyl alcohol, butyl
alcohol, isobutyl alcohol, butanol, pentanol, cyclopentanol,
hexanol, cyclohexanol, 2-methyl-cyclopentanonol, heptanol, octanol,
nonanol, decanol, undecanol, dodecanol, and isomers thereof. The
diols may include, without limitation, ethylene glycol, propylene
glycol, 1,3-propanediol, butanediol, pentanediol, hexanediol,
heptanediol, octanediol, nonanediol, decanediol, undecanediol,
dodecanediol, and isomers thereof. The triols may include, without
limitation, glycerol, 1,1,1 tris(hydroxymethyl)-ethane
(trimethylolethane), trimethylolpropane, hexanetriol, and isomers
thereof. In an embodiment, any alcohols, diols, triols are
dehydrogenated in a dehydrogenation reaction to produce a carbonyl
useful in an aldol condensation reaction. Furans and furfurals
include, without limitation, furan, tetrahydrofuran, dihydrofuran,
2-furan methanol, 2-methyl-tetrahydrofuran,
2,5-dimethyl-tetrahydrofuran, 2-methyl furan,
2-ethyl-tetrahydrofuran, 2-ethyl furan, hydroxylmethylfurfural,
3-hydroxytetrahydrofuran, tetrahydro-3-furanol, 2,5-dimethyl furan,
5-hydroxymethyl-2(5H)-furanone,
dihydro-5-(hydroxymethyl)-2(3H)-furanone, tetrahydro-2-furoic acid,
dihydro-5-(hydroxymethyl)-2(3H)-furanone, tetrahydrofurfuryl
alcohol, 1-(2-furyl)ethanol, hydroxymethyltetrahydrofurfural, and
isomers thereof.
[0069] The oxygenated intermediate stream may generally be
characterized as comprising components corresponding to the
formula: CnOmHx. In an embodiment, n=1-6 and m=1 to 6, m.ltoreq.n,
and x is an integer that completes the molecular structure (e.g.,
between 1 and 2n+2). Other elements such as nitrogen, phosphorus or
sulfur may also be present in these molecules. Additional
components that may be present in the APR products stream can
include hydrogen and other gases such as carbon dioxide. These
components can be separated from the oxygenated intermediates or
they can be fed to the condensation reaction for removal after the
condensation reaction.
[0070] The oxygenated intermediate stream 130 may then pass from
the APR reaction to a further processing stage 136. In some
embodiments, optional separation stage includes elements that allow
for the separation of the oxygenated intermediates into different
components. In some embodiments of the present invention, the
separation stage can receive the oxygenated intermediate stream 130
from the APR reaction and separate the various components into two
or more streams. For example, a suitable separator may include, but
is not limited to, a phase separator, stripping column, extractor,
filter, or distillation column. In some embodiments, a separator is
installed prior to a processing reaction to favor production of
higher hydrocarbons by separating the higher polyols from the
oxygenated intermediates. In such an embodiment, the higher polyols
can be recycled back through to the APR reaction, while the other
oxygenated intermediates are passed to the processing reaction 136.
In addition, an outlet stream from the separation stage containing
a portion of the oxygenated intermediates may act as in situ
generated digestive solvent when recycled to the removal reactor or
digester 106. In one embodiment, the separation stage can also be
used to remove some or all of the lignin from the oxygenated
intermediate stream. The lignin may be passed out of the separation
stage as a separate stream, for example as output stream.
[0071] In some embodiments, the oxygenated intermediates can be
converted into higher hydrocarbons through a processing reaction
shown schematically as processing reaction 136 in FIG. 1. In an
embodiment, the processing reaction may comprise a condensation
reaction to produce a fuel blend. In an embodiment, the higher
hydrocarbons may be part of a fuel blend for use as a
transportation fuel. In such an embodiment, condensation of the
oxygenated intermediates occurs in the presence of a catalyst
capable of forming higher hydrocarbons. While not intending to be
limited by theory, it is believed that the production of higher
hydrocarbons proceeds through a stepwise addition reaction
including the formation of carbon-carbon bond. The resulting
reaction products include any number of compounds, as described in
more detail below.
[0072] Referring to FIG. 1, in some embodiments, an outlet stream
130 containing at least a portion of the oxygenated intermediates
can pass to a processing reaction or processing reactions. Suitable
processing reactions may comprise a variety of catalysts for
condensing one or more oxygenated intermediates to higher
hydrocarbons. The higher hydrocarbons may comprise a fuel product.
The fuel products produced by the processing reactions represent
the product stream from the overall process at higher hydrocarbon
stream 150. In an embodiment, the oxygen to carbon ratio of the
higher hydrocarbons produced through the processing reactions is
less than 0.5, alternatively less than 0.4, or preferably less than
0.3.
[0073] In one embodiment of the process shown in FIG. 1, the
nitrogen and sulfur compounds are removed, and the treated biomass
intermediate stream is passed through an APR reaction to form
suitable oxygenated intermediates for the condensation reaction
136. For yet a second embodiment of the process shown in FIG. 1,
the nitrogen and sulfur compounds are removed, and the treated
biomass stream is passed through an APR reaction to form suitable
oxygenated intermediates for the dehydrogenation reaction and
alkylation reaction (both represented in system 136).
[0074] The oxygenated intermediates can be processed to produce a
fuel blend in one or more processing reactions. In an embodiment, a
condensation reaction can be used along with other reactions to
generate a fuel blend and may be catalyzed by a catalyst comprising
acid or basic functional sites, or both. In general, without being
limited to any particular theory, it is believed that the basic
condensation reactions generally consist of a series of steps
involving: (1) an optional dehydrogenation reaction; (2) an
optional dehydration reaction that may be acid catalyzed; (3) an
aldol condensation reaction; (4) an optional ketonization reaction;
(5) an optional furanic ring opening reaction; (6) hydrogenation of
the resulting condensation products to form a C4+ hydrocarbon; and
(7) any combination thereof. Acid catalyzed condensations may
similarly entail optional hydrogenation or dehydrogenation
reactions, dehydration, and oligomerization reactions. Additional
polishing reactions may also be used to conform the product to a
specific fuel standard, including reactions conducted in the
presence of hydrogen and a hydrogenation catalyst to remove
functional groups from final fuel product. A catalyst comprising a
basic functional site, both an acid and a basic functional site,
and optionally comprising a metal function, may be used to effect
the condensation reaction. In an embodiment, a method of forming a
fuel blend from a biomass feedstock may comprise a digester that
receives a biomass feedstock and a digestive solvent operating
under conditions to effectively remove nitrogen and sulfur
compounds from said biomass feedstock and discharges a treated
stream comprising a carbohydrate having less than 35% of the sulfur
content and less than 35 wt % nitrogen content based on untreated
biomass feedstock on a dry mass basis; an aqueous phase reforming
reactor comprising an aqueous phase reforming catalyst that
receives the treated stream and discharges an oxygenated
intermediate stream, wherein a first portion of the oxygenated
intermediate stream is recycled to the digester as at least a
portion of the digestive solvent; and a fuels processing reactor
comprising a condensation catalyst that receives a second portion
of the oxygenated intermediate stream and discharges a liquid
fuel.
[0075] In an embodiment, the aldol condensation reaction may be
used to produce a fuel blend meeting the requirements for a diesel
fuel or jet fuel. Traditional diesel fuels are petroleum
distillates rich in paraffinic hydrocarbons. They have boiling
ranges as broad as 187.degree. C. to 417.degree. C., which are
suitable for combustion in a compression ignition engine, such as a
diesel engine vehicle. The American Society of Testing and
Materials (ASTM) establishes the grade of diesel according to the
boiling range, along with allowable ranges of other fuel
properties, such as cetane number, cloud point, flash point,
viscosity, aniline point, sulfur content, water content, ash
content, copper strip corrosion, and carbon residue. Thus, any fuel
blend meeting ASTM D975 can be defined as diesel fuel.
[0076] The present invention also provides methods to produce jet
fuel. Jet fuel is clear to straw colored. The most common fuel is
an unleaded/paraffin oil-based fuel classified as Aeroplane A-1,
which is produced to an internationally standardized set of
specifications. Jet fuel is a mixture of a large number of
different hydrocarbons, possibly as many as a thousand or more. The
range of their sizes (molecular weights or carbon numbers) is
restricted by the requirements for the product, for example,
freezing point or smoke point. Kerosene-type Airplane or aviation
fuel (including Jet A and Jet A-1) has a carbon number distribution
between about C8 and C16. Wide-cut or naphtha-type Airplane fuel
(including Jet B) typically has a carbon number distribution
between about C5 and C15. A fuel blend meeting ASTM D1655 can be
defined as jet fuel.
[0077] In certain embodiments, both aviation fuels (Jet A and Jet
B) contain a number of additives. Useful additives include, but are
not limited to, antioxidants, antistatic agents, corrosion
inhibitors, and fuel system icing inhibitor (FSII) agents.
Antioxidants prevent gumming and usually, are based on alkylated
phenols, for example, AO-30, AO-31, or AO-37. Antistatic agents
dissipate static electricity and prevent sparking. Stadis 450 with
dinonylnaphthylsulfonic acid (DINNSA) as the active ingredient, is
an example. Corrosion inhibitors, e.g., DCI-4A are used for
civilian and military fuels and DCI-6A is used for military fuels.
FSII agents, include, e.g., Di-EGME.
[0078] In an embodiment, the oxygenated intermediates may comprise
a carbonyl-containing compound that can take part in a base
catalyzed condensation reaction. In some embodiments, an optional
dehydrogenation reaction may be used to increase the amount of
carbonyl-containing compounds in the oxygenated intermediate stream
to be used as a feed to the condensation reaction. In these
embodiments, the oxygenated intermediates and/or a portion of the
bio-based feedstock stream can be dehydrogenated in the presence of
a catalyst.
[0079] In an embodiment, a dehydrogenation catalyst may be
preferred for an oxygenated intermediate stream comprising
alcohols, diols, and triols. In general, alcohols cannot
participate in aldol condensation directly. The hydroxyl group or
groups present can be converted into carbonyls (e.g., aldehydes,
ketones, etc.) in order to participate in an aldol condensation
reaction. A dehydrogenation catalyst may be included to effect
dehydrogenation of any alcohols, diols, or polyols present to form
ketones and aldehydes. The dehydration catalyst is typically formed
from the same metals as used for hydrogenation or aqueous phase
reforming, which catalysts are described in more detail above.
Dehydrogenation yields are enhanced by the removal or consumption
of hydrogen as it forms during the reaction. The dehydrogenation
step may be carried out as a separate reaction step before an aldol
condensation reaction, or the dehydrogenation reaction may be
carried out in concert with the aldol condensation reaction. For
concerted dehydrogenation and aldol condensation, the
dehydrogenation and aldol condensation functions can be on the same
catalyst. For example, a metal hydrogenation/dehydrogenation
functionality may be present on catalyst comprising a basic
functionality.
[0080] The dehydrogenation reaction may result in the production of
a carbonyl-containing compound. Suitable carbonyl-containing
compounds include, but are not limited to, any compound comprising
a carbonyl functional group that can form carbanion species or can
react in a condensation reaction with a carbanion species, where
"carbonyl" is defined as a carbon atom doubly-bonded to oxygen. In
an embodiment, a carbonyl-containing compound can include, but is
not limited to, ketones, aldehydes, furfurals, hydroxy carboxylic
acids, and, carboxylic acids. The ketones may include, without
limitation, hydroxyketones, cyclic ketones, diketones, acetone,
propanone, 2-oxopropanal, butanone, butane-2,3-dione,
3-hydroxybutane-2-one, pentanone, cyclopentanone,
pentane-2,3-dione, pentane-2,4-dione, hexanone, cyclohexanone,
2-methyl-cyclopentanone, heptanone, octanone, nonanone, decanone,
undecanone, dodecanone, methylglyoxal, butanedione, pentanedione,
diketohexane, dihydroxyacetone, and isomers thereof. The aldehydes
may include, without limitation, hydroxyaldehydes, acetaldehyde,
glyceraldehyde, propionaldehyde, butyraldehyde, pentanal, hexanal,
heptanal, octanal, nonal, decanal, undecanal, dodecanal, and
isomers thereof. The carboxylic acids may include, without
limitation, formic acid, acetic acid, propionic acid, butanoic
acid, pentanoic acid, hexanoic acid, heptanoic acid, isomers and
derivatives thereof, including hydroxylated derivatives, such as
2-hydroxybutanoic acid and lactic acid. Furfurals include, without
limitation, hydroxylmethylfurfural, 5-hydroxymethyl-2(5H)-furanone,
dihydro-5-(hydroxymethyl)-2(3H)-furanone, tetrahydro-2-furoic acid,
dihydro-5-(hydroxymethyl)-2(3H)-furanone, tetrahydrofurfuryl
alcohol, 1-(2-furyl)ethanol, hydroxymethyltetrahydrofurfural, and
isomers thereof. In an embodiment, the dehydrogenation reaction
results in the production of a carbonyl-containing compound that is
combined with the oxygenated intermediates to become a part of the
oxygenated intermediates fed to the condensation reaction.
[0081] In an embodiment, an acid catalyst may be used to optionally
dehydrate at least a portion of the oxygenated intermediate stream.
Suitable acid catalysts for use in the dehydration reaction
include, but are not limited to, mineral acids (e.g., HCl,
H.sub.2SO.sub.4), solid acids (e.g., zeolites, ion-exchange resins)
and acid salts (e.g., LaCl.sub.3). Additional acid catalysts may
include, without limitation, zeolites, carbides, nitrides,
zirconia, alumina, silica, aluminosilicates, phosphates, titanium
oxides, zinc oxides, vanadium oxides, lanthanum oxides, yttrium
oxides, scandium oxides, magnesium oxides, cerium oxides, barium
oxides, calcium oxides, hydroxides, heteropolyacids, inorganic
acids, acid modified resins, base modified resins, and any
combination thereof. In some embodiments, the dehydration catalyst
can also include a modifier. Suitable modifiers include La, Y, Sc,
P, B, Bi, Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, and any combination
thereof. The modifiers may be useful, inter alia, to carry out a
concerted hydrogenation/dehydrogenation reaction with the
dehydration reaction. In some embodiments, the dehydration catalyst
can also include a metal. Suitable metals include Cu, Ag, Au, Pt,
Ni, Fe, Co, Ru, Zn, Cd, Ga, In, Rh, Pd, Ir, Re, Mn, Cr, Mo, W, Sn,
Os, alloys, and any combination thereof. The dehydration catalyst
may be self supporting, supported on an inert support or resin, or
it may be dissolved in solution.
[0082] In some embodiments, the dehydration reaction occurs in the
vapor phase. In other embodiments, the dehydration reaction occurs
in the liquid phase. For liquid phase dehydration reactions, an
aqueous solution may be used to carry out the reaction. In an
embodiment, other solvents in addition to water, are used to form
the aqueous solution. For example, water soluble organic solvents
may be present. Suitable solvents can include, but are not limited
to, hydroxymethylfurfural (HMF), dimethylsulfoxide (DMSO),
1-methyl-n-pyrollidone (NMP), and any combination thereof. Other
suitable aprotic solvents may also be used alone or in combination
with any of these solvents.
[0083] In an embodiment, the processing reactions may comprise an
optional ketonization reaction. A ketonization reaction may
increase the number of ketone functional groups within at least a
portion of the oxygenated intermediate stream. For example, an
alcohol or other hydroxyl functional group can be converted into a
ketone in a ketonization reaction. Ketonization may be carried out
in the presence of a base catalyst. Any of the base catalysts
described above as the basic component of the aldol condensation
reaction can be used to effect a ketonization reaction. Suitable
reaction conditions are known to one of ordinary skill in the art
and generally correspond to the reaction conditions listed above
with respect to the aldol condensation reaction. The ketonization
reaction may be carried out as a separate reaction step, or it may
be carried out in concert with the aldol condensation reaction. The
inclusion of a basic functional site on the aldol condensation
catalyst may result in concerted ketonization and aldol
condensation reactions.
[0084] In an embodiment, the processing reactions may comprise an
optional furanic ring opening reaction. A furanic ring opening
reaction may result in the conversion of at least a portion of any
oxygenated intermediates comprising a furanic ring into compounds
that are more reactive in an aldol condensation reaction. A furanic
ring opening reaction may be carried out in the presence of an
acidic catalyst. Any of the acid catalysts described above as the
acid component of the aldol condensation reaction can be used to
effect a furanic ring opening reaction. Suitable reaction
conditions are known to one of ordinary skill in the art and
generally correspond to the reaction conditions listed above with
respect to the aldol condensation reaction. The furanic ring
opening reaction may be carried out as a separate reaction step, or
it may be carried out in concert with the aldol condensation
reaction. The inclusion of an acid functional site on the aldol
condensation catalyst may result in a concerted furanic ring
opening reaction and aldol condensation reactions. Such an
embodiment may be advantageous as any furanic rings can be opened
in the presence of an acid functionality and reacted in an aldol
condensation reaction using a base functionality. Such a concerted
reaction scheme may allow for the production of a greater amount of
higher hydrocarbons to be formed for a given oxygenated
intermediate feed.
[0085] In an embodiment, production of a C4+ compound occurs by
condensation, which may include aldol-condensation, of the
oxygenated intermediates in the presence of a condensation
catalyst. Aldol-condensation generally involves the carbon-carbon
coupling between two compounds, at least one of which may contain a
carbonyl group, to form a larger organic molecule. For example,
acetone may react with hydroxymethylfurfural to form a C9 species,
which may subsequently react with another hydroxymethylfurfural
molecule to form a C15 species. The reaction is usually carried out
in the presence of a condensation catalyst. The condensation
reaction may be carried out in the vapor or liquid phase. In an
embodiment, the reaction may take place at a temperature in the
range of from about 5.degree. C. to about 375.degree. C., depending
on the reactivity of the carbonyl group.
[0086] The condensation catalyst will generally be a catalyst
capable of forming longer chain compounds by linking two molecules
through a new carbon-carbon bond, such as a basic catalyst, a
multi-functional catalyst having both acid and base functionality,
or either type of catalyst also comprising an optional metal
functionality. In an embodiment, the multi-functional catalyst will
be a catalyst having both a strong acid and a strong base
functionality. In an embodiment, aldol catalysts can comprise Li,
Na, K, Cs, B, Rb, Mg, Ca, Sr, Si, Ba, Al, Zn, Ce, La, Y, Sc, Y, Zr,
Ti, hydrotalcite, zinc-aluminate, phosphate, base-treated
aluminosilicate zeolite, a basic resin, basic nitride, alloys or
any combination thereof. In an embodiment, the base catalyst can
also comprise an oxide of Ti, Zr, V, Nb, Ta, Mo, Cr, W, Mn, Re, Al,
Ga, In, Co, Ni, Si, Cu, Zn, Sn, Cd, Mg, P, Fe, or any combination
thereof. In an embodiment, the condensation catalyst comprises a
mixed-oxide base catalyst. Suitable mixed-oxide base catalysts can
comprise a combination of magnesium, zirconium, and oxygen, which
may comprise, without limitation: Si--Mg--O, Mg--Ti--O, Y--Mg--O,
Y--Zr--O, Ti--Zr--O, Ce--Zr--O, Ce--Mg--O, Ca--Zr--O, La--Zr--O,
B--Zr--O, La--Ti--O, B--Ti--O, and any combinations thereof.
Different atomic ratios of Mg/Zr or the combinations of various
other elements constituting the mixed oxide catalyst may be used
ranging from about 0.01 to about 50. In an embodiment, the
condensation catalyst further includes a metal or alloys comprising
metals, such as Cu, Ag, Au, Pt, Ni, Fe, Co, Ru, Zn, Cd, Ga, In, Rh,
Pd, Ir, Re, Mn, Cr, Mo, W, Sn, Bi, Pb, Os, alloys and combinations
thereof. Such metals may be preferred when a dehydrogenation
reaction is to be carried out in concert with the aldol
condensation reaction. In an embodiment, preferred Group IA
materials include Li, Na, K, Cs and Rb. In an embodiment, preferred
Group IIA materials include Mg, Ca, Sr and Ba. In an embodiment,
Group IIB materials include Zn and Cd. In an embodiment, Group IIIB
materials include Y and La. Basic resins include resins that
exhibit basic functionality. The base catalyst may be
self-supporting or adhered to any one of the supports further
described below, including supports containing carbon, silica,
alumina, zirconia, titania, vanadia, ceria, nitride, boron nitride,
heteropolyacids, alloys and mixtures thereof.
[0087] In one embodiment, the condensation catalyst is derived from
the combination of MgO and Al.sub.2O.sub.3 to form a hydrotalcite
material. Another preferred material contains ZnO and
Al.sub.2O.sub.3 in the form of a zinc aluminate spinel. Yet another
preferred material is a combination of ZnO, Al.sub.2O.sub.3, and
CuO. Each of these materials may also contain an additional metal
function provided by a Group VIIIB metal, such as Pd or Pt. Such
metals may be preferred when a dehydrogenation reaction is to be
carried out in concert with the aldol condensation reaction. In one
embodiment, the base catalyst is a metal oxide containing Cu, Ni,
Zn, V, Zr, or mixtures thereof. In another embodiment, the base
catalyst is a zinc aluminate metal containing Pt, Pd Cu, Ni, or
mixtures thereof.
[0088] Preferred loading of the primary metal in the condensation
catalyst is in the range of 0.10 wt % to 25 wt %, with weight
percentages of 0.10% and 0.05% increments between, such as 1.00%,
1.10%, 1.15%, 2.00%, 2.50%, 5.00%, 10.00%, 12.50%, 15.00% and
20.00%. The preferred atomic ratio of the second metal, if any, is
in the range of 0.25-to-1 to 10-to-1, including ratios there
between, such as 0.50, 1.00, 2.50, 5.00, and 7.50-to-1.
[0089] In some embodiments, the base catalyzed condensation
reaction is performed using a condensation catalyst with both an
acid and base functionality. The acid-aldol condensation catalyst
may comprise hydrotalcite, zinc-aluminate, phosphate, Li, Na, K,
Cs, B, Rb, Mg, Si, Ca, Sr, Ba, Al, Ce, La, Sc, Y, Zr, Ti, Zn, Cr,
or any combination thereof. In further embodiments, the acid-base
catalyst may also include one or more oxides from the group of Ti,
Zr, V, Nb, Ta, Mo, Cr, W, Mn, Re, Al, Ga, In, Fe, Co, Ir, Ni, Si,
Cu, Zn, Sn, Cd, P, and combinations thereof. In an embodiment, the
acid-base catalyst includes a metal functionality provided by Cu,
Ag, Au, Pt, Ni, Fe, Co, Ru, Zn, Cd, Ga, In, Rh, Pd, Ir, Re, Mn, Cr,
Mo, W, Sn, Os, alloys or combinations thereof. In one embodiment,
the catalyst further includes Zn, Cd or phosphate. In one
embodiment, the condensation catalyst is a metal oxide containing
Pd, Pt, Cu or Ni, and even more preferably an aluminate or
zirconium metal oxide containing Mg and Cu, Pt, Pd or Ni. The
acid-base catalyst may also include a hydroxyapatite (HAP) combined
with any one or more of the above metals. The acid-base catalyst
may be self-supporting or adhered to any one of the supports
further described below, including supports containing carbon,
silica, alumina, zirconia, titania, vanadia, ceria, nitride, boron
nitride, heteropolyacids, alloys and mixtures thereof.
[0090] In an embodiment, the condensation catalyst may also include
zeolites and other microporous supports that contain Group IA
compounds, such as Li, NA, K, Cs and Rb. Preferably, the Group IA
material is present in an amount less than that required to
neutralize the acidic nature of the support. A metal function may
also be provided by the addition of group VIIIB metals, or Cu, Ga,
In, Zn or Sn. In one embodiment, the condensation catalyst is
derived from the combination of MgO and Al.sub.2O.sub.3 to form a
hydrotalcite material. Another preferred material contains a
combination of MgO and ZrO.sub.2, or a combination of ZnO and
Al.sub.2O.sub.3. Each of these materials may also contain an
additional metal function provided by copper or a Group VIIIB
metal, such as Ni, Pd, Pt, or combinations of the foregoing.
[0091] If a Group IIB, VIIB, VIIB, VIIIB, IIA or IVA metal is
included in the condensation catalyst, the loading of the metal is
in the range of 0.10 wt % to 10 wt %, with weight percentages of
0.10% and 0.05% increments between, such as 1.00%, 1.10%, 1.15%,
2.00%, 2.50%, 5.00% and 7.50%, etc. If a second metal is included,
the preferred atomic ratio of the second metal is in the range of
0.25-to-1 to 5-to-1, including ratios there between, such as 0.50,
1.00, 2.50 and 5.00-to-1.
[0092] The condensation catalyst may be self-supporting (i.e., the
catalyst does not need another material to serve as a support), or
may require a separate support suitable for suspending the catalyst
in the reactant stream. One exemplary support is silica, especially
silica having a high surface area (greater than 100 square meters
per gram), obtained by sol-gel synthesis, precipitation, or fuming.
In other embodiments, particularly when the condensation catalyst
is a powder, the catalyst system may include a binder to assist in
forming the catalyst into a desirable catalyst shape. Applicable
forming processes include extrusion, pelletization, oil dropping,
or other known processes. Zinc oxide, alumina, and a peptizing
agent may also be mixed together and extruded to produce a formed
material. After drying, this material is calcined at a temperature
appropriate for formation of the catalytically active phase, which
usually requires temperatures in excess of 450.degree. C. Other
catalyst supports as known to those of ordinary skill in the art
may also be used.
[0093] In some embodiments, a dehydration catalyst, a
dehydrogenation catalyst, and the condensation catalyst can be
present in the same reactor as the reaction conditions overlap to
some degree. In these embodiments, a dehydration reaction and/or a
dehydrogenation reaction may occur substantially simultaneously
with the condensation reaction. In some embodiments, a catalyst may
comprise active sites for a dehydration reaction and/or a
dehydrogenation reaction in addition to a condensation reaction.
For example, a catalyst may comprise active metals for a
dehydration reaction and/or a dehydrogenation reaction along with a
condensation reaction at separate sites on the catalyst or as
alloys. Suitable active elements can comprise any of those listed
above with respect to the dehydration catalyst, dehydrogenation
catalyst, and the condensation catalyst. Alternately, a physical
mixture of dehydration, dehydrogenation, and condensation catalysts
could be employed. While not intending to be limited by theory, it
is believed that using a condensation catalyst comprising a metal
and/or an acid functionality may assist in pushing the equilibrium
limited aldol condensation reaction towards completion.
Advantageously, this can be used to effect multiple condensation
reactions with dehydration and/or dehydrogenation of intermediates,
in order to form (via condensation, dehydration, and/or
dehydrogenation) higher molecular weight oligomers as desired to
produce jet or diesel fuel.
[0094] The specific C4+ compounds produced in the condensation
reaction will depend on various factors, including, without
limitation, the type of oxygenated intermediates in the reactant
stream, condensation temperature, condensation pressure, the
reactivity of the catalyst, and the flow rate of the reactant
stream as it affects the space velocity, GHSV and WHSV. Preferably,
the reactant stream is contacted with the condensation catalyst at
a WHSV that is appropriate to produce the desired hydrocarbon
products. The WHSV is preferably at least about 0.1 grams of
oxygenated intermediates in the reactant stream per hour, more
preferably the WHSV is between about 0.1 to 40.0 g/g hr, including
a WHSV of about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
20, 25, 30, 35 g/g hr, and increments between.
[0095] In general, the condensation reaction should be carried out
at a temperature at which the thermodynamics of the proposed
reaction are favorable. For condensed phase liquid reactions, the
pressure within the reactor must be sufficient to maintain at least
a portion of the reactants in the condensed liquid phase at the
reactor inlet. For vapor phase reactions, the reaction should be
carried out at a temperature where the vapor pressure of the
oxygenates is at least about 10 kPa, and the thermodynamics of the
reaction are favorable. The condensation temperature will vary
depending upon the specific oxygenated intermediates used, but is
generally in the range of from about 75.degree. C. to 500.degree.
C. for reactions taking place in the vapor phase, and more
preferably from about 125.degree. C. to 450.degree. C. For liquid
phase reactions, the condensation temperature may be from about
5.degree. C. to 475.degree. C., and the condensation pressure from
about 0.1 kPa to 10,000 kPa. Preferably, the condensation
temperature is between about 15.degree. C. and 300.degree. C., or
between about 15.degree. C. and 250.degree. C. for difficult
substrates.
[0096] Varying the factors above, as well as others, will generally
result in a modification to the specific composition and yields of
the C4+ compounds. For example, varying the temperature and/or
pressure of the reactor system, or the particular catalyst
formulations, may result in the production of C4+ alcohols and/or
ketones instead of C4+ hydrocarbons. The C4+ hydrocarbon product
may also contain a variety of olefins, and alkanes of various sizes
(typically branched alkanes). Depending upon the condensation
catalyst used, the hydrocarbon product may also include aromatic
and cyclic hydrocarbon compounds. The C4+ hydrocarbon product may
also contain undesirably high levels of olefins, which may lead to
coking or deposits in combustion engines, or other undesirable
hydrocarbon products. In such event, the hydrocarbon molecules
produced may be optionally hydrogenated to reduce the ketones to
alcohols and hydrocarbons, while the alcohols and unsaturated
hydrocarbon may be reduced to alkanes, thereby forming a more
desirable hydrocarbon product having low levels of olefins,
aromatics or alcohols.
[0097] The condensation reactions may be carried out in any reactor
of suitable design, including continuous-flow, batch, semi-batch or
multi-system reactors, without limitation as to design, size,
geometry, flow rates, etc. The reactor system may also use a
fluidized catalytic bed system, a swing bed system, fixed bed
system, a moving bed system, or a combination of the above. In some
embodiments, bi-phasic (e.g., liquid-liquid) and tri-phasic (e.g.,
liquid-liquid-solid) reactors may be used to carry out the
condensation reactions.
[0098] In a continuous flow system, the reactor system can include
an optional dehydrogenation bed adapted to produce dehydrogenated
oxygenated intermediates, an optional dehydration bed adapted to
produce dehydrated oxygenated intermediates, and a condensation bed
to produce C4+ compounds from the oxygenated intermediates. The
dehydrogenation bed is configured to receive the reactant stream
and produce the desired oxygenated intermediates, which may have an
increase in the amount of carbonyl-containing compounds. The
de-hydration bed is configured to receive the reactant stream and
produce the desired oxygenated intermediates. The condensation bed
is configured to receive the oxygenated intermediates for contact
with the condensation catalyst and production of the desired C4+
compounds. For systems with one or more finishing steps, an
additional reaction bed for conducting the finishing process or
processes may be included after the condensation bed.
[0099] In an embodiment, the optional dehydration reaction, the
optional dehydrogenation reaction, the optional ketonization
reaction, the optional ring opening reaction, and the condensation
reaction catalyst beds may be positioned within the same reactor
vessel or in separate reactor vessels in fluid communication with
each other. Each reactor vessel preferably includes an outlet
adapted to remove the product stream from the reactor vessel. For
systems with one or more finishing steps, the finishing reaction
bed or beds may be within the same reactor vessel along with the
condensation bed or in a separate reactor vessel in fluid
communication with the reactor vessel having the condensation
bed.
[0100] In an embodiment, the reactor system also includes
additional outlets to allow for the removal of portions of the
reactant stream to further advance or direct the reaction to the
desired reaction products, and to allow for the collection and
recycling of reaction byproducts for use in other portions of the
system. In an embodiment, the reactor system also includes
additional inlets to allow for the introduction of supplemental
materials to further advance or direct the reaction to the desired
reaction products, and to allow for the recycling of reaction
byproducts for use in other reactions.
[0101] In an embodiment, the reactor system also includes elements
which allow for the separation of the reactant stream into
different components which may find use in different reaction
schemes or to simply promote the desired reactions. For instance, a
separator unit, such as a phase separator, extractor, purifier or
distillation column, may be installed prior to the condensation
step to remove water from the reactant stream for purposes of
advancing the condensation reaction to favor the production of
higher hydrocarbons. In an embodiment, a separation unit is
installed to remove specific intermediates to allow for the
production of a desired product stream containing hydrocarbons
within a particular carbon number range, or for use as end products
or in other systems or processes.
[0102] The condensation reaction can produce a broad range of
compounds with carbon numbers ranging from C4 to C30 or greater.
Exemplary compounds include, but are not limited to, C4+ alkanes,
C4+ alkenes, C5+ cycloalkanes, C5+ cycloalkenes, aryls, fused
aryls, C4+ alcohols, C4+ ketones, and mixtures thereof. The C4+
alkanes and C4+ alkenes may range from 4 to 30 carbon atoms (C4-C30
alkanes and C4-C30 alkenes) and may be branched or straight chained
alkanes or alkenes. The C4+ alkanes and C4+ alkenes may also
include fractions of C7-C14, C12-C24 alkanes and alkenes,
respectively, with the C7-C14 fraction directed to jet fuel blend,
and the C12-C24 fraction directed to a diesel fuel blend and other
industrial applications. Examples of various C4+ alkanes and C4+
alkenes include, without limitation, butane, butene, pentane,
pentene, 2-methylbutane, hexane, hexene, 2-methylpentane,
3-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane, heptane,
heptene, octane, octene, 2,2,4,-trimethylpentane, 2,3-dimethyl
hexane, 2,3,4-trimethylpentane, 2,3-dimethylpentane, nonane,
nonene, decane, decene, undecane, undecene, dodecane, dodecene,
tridecane, tridecene, tetradecane, tetradecene, pentadecane,
pentadecene, hexadecane, hexadecene, heptyldecane, heptyldecene,
octyldecane, octyldecene, nonyldecane, nonyldecene, eicosane,
eicosene, uneicosane, uneicosene, doeicosane, doeicosene,
trieicosane, trieicosene, tetraeicosane, tetraeicosene, and isomers
thereof.
[0103] The C5+ cycloalkanes and C5+ cycloalkenes have from 5 to 30
carbon atoms and may be unsubstituted, mono-substituted or
multi-substituted. In the case of mono-substituted and
multi-substituted compounds, the substituted group may include a
branched C3+ alkyl, a straight chain C1+ alkyl, a branched C3+
alkylene, a straight chain C1+ alkylene, a straight chain C2+
alkylene, a phenyl or a combination thereof. In one embodiment, at
least one of the substituted groups include a branched C3-C12
alkyl, a straight chain C1-C12 alkyl, a branched C3-C12 alkylene, a
straight chain C1-C12 alkylene, a straight chain C2-C12 alkylene, a
phenyl or a combination thereof. In yet another embodiment, at
least one of the substituted groups includes a branched C3-C4
alkyl, a straight chain C1-C4 alkyl, a branched C3-C4 alkylene, a
straight chain C1-C4 alkylene, a straight chain C2-C4 alkylene, a
phenyl, or any combination thereof. Examples of desirable C5+
cycloalkanes and C5+ cycloalkenes include, without limitation,
cyclopentane, cyclopentene, cyclohexane, cyclohexene,
methyl-cyclopentane, methyl-cyclopentene, ethyl-cyclopentane,
ethyl-cyclopentene, ethyl-cyclohexane, ethyl-cyclohexene, and
isomers thereof.
[0104] Aryls will generally consist of an aromatic hydrocarbon in
either an unsubstituted (phenyl), mono-substituted or
multi-substituted form. In the case of mono-substituted and
multi-substituted compounds, the substituted group may include a
branched C3+ alkyl, a straight chain C1+ alkyl, a branched C3+
alkylene, a straight chain C2+ alkylene, a phenyl or a combination
thereof. In one embodiment, at least one of the substituted groups
includes a branched C3-C12 alkyl, a straight chain C1-C12 alkyl, a
branched C3-C12 alkylene, a straight chain C2-C12 alkylene, a
phenyl, or any combination thereof. In yet another embodiment, at
least one of the substituted groups includes a branched C3-C4
alkyl, a straight chain C1-C4 alkyl, a branched C3-C4 alkylene,
straight chain C2-C4 alkylene, a phenyl, or any combination
thereof. Examples of various aryls include, without limitation,
benzene, toluene, xylene (dimethylbenzene), ethyl benzene, para
xylene, meta xylene, ortho xylene, C9 aromatics.
[0105] Fused aryls will generally consist of bicyclic and
polycyclic aromatic hydrocarbons, in either an unsubstituted,
mono-substituted or multi-substituted form. In the case of
mono-substituted and multi-substituted compounds, the substituted
group may include a branched C3+ alkyl, a straight chain C1+ alkyl,
a branched C3+ alkylene, a straight chain C2+ alkylene, a phenyl or
a combination thereof. In another embodiment, at least one of the
substituted groups includes a branched C3-C4 alkyl, a straight
chain C1-C4 alkyl, a branched C3-C4 alkylene, a straight chain
C2-C4 alkylene, a phenyl, or any combination thereof. Examples of
various fused aryls include, without limitation, naphthalene,
anthracene, tetrahydronaphthalene, and decahydronaphthalene,
indane, indene, and isomers thereof.
[0106] The moderate fractions, such as C7-C14, may be separated for
jet fuel, while heavier fractions, (e.g., C12-C24), may be
separated for diesel use. The heaviest fractions may be used as
lubricants or cracked to produce additional gasoline and/or diesel
fractions. The C4+ compounds may also find use as industrial
chemicals, whether as an intermediate or an end product. For
example, the aryls toluene, xylene, ethyl benzene, para xylene,
meta xylene, ortho xylene may find use as chemical intermediates
for the production of plastics and other products. Meanwhile, the
C9 aromatics and fused aryls, such as naphthalene, anthracene,
tetrahydronaphthalene, and decahydronaphthalene, may find use as
solvents in industrial processes.
[0107] In an embodiment, additional processes are used to treat the
fuel blend to remove certain components or further conform the fuel
blend to a diesel or jet fuel standard. Suitable techniques include
hydrotreating to reduce the amount of or remove any remaining
oxygen, sulfur, or nitrogen in the fuel blend. The conditions for
hydrotreating a hydrocarbon stream are known to one of ordinary
skill in the art.
[0108] In an embodiment, hydrogenation is carried out in place of
or after the hydrotreating process to saturate at least some
olefinic bonds. In some embodiments, a hydrogenation reaction may
be carried out in concert with the aldol condensation reaction by
including a metal functional group with the aldol condensation
catalyst. Such hydrogenation may be performed to conform the fuel
blend to a specific fuel standard (e.g., a diesel fuel standard or
a jet fuel standard). The hydrogenation of the fuel blend stream
can be carried out according to known procedures, either with the
continuous or batch method. The hydrogenation reaction may be used
to remove a remaining carbonyl group or hydroxyl group. In such
event, any one of the hydrogenation catalysts described above may
be used. Such catalysts may include any one or more of the
following metals, Cu, Ni, Fe, Co, Ru, Pd, Rh, Pt, Ir, Os, alloys or
combinations thereof, alone or with promoters such as Au, Ag, Cr,
Zn, Mn, Sn, Cu, Bi, and alloys thereof, may be used in various
loadings ranging from about 0.01 wt % to about 20 wt % on a support
as described above. In general, the finishing step is carried out
at finishing temperatures of between about 80.degree. C. to
250.degree. C., and finishing pressures in the range of about 700
kPa to 15,000 kPa. In one embodiment, the finishing step is
conducted in the vapor phase or liquid phase, and uses in situ
generated H2 (e.g., generated in the APR reaction step), external
H2, recycled H2, or combinations thereof, as necessary.
[0109] In an embodiment, isomerization is used to treat the fuel
blend to introduce a desired degree of branching or other shape
selectivity to at least some components in the fuel blend. It may
be useful to remove any impurities before the hydrocarbons are
contacted with the isomerization catalyst. The isomerization step
comprises an optional stripping step, wherein the fuel blend from
the oligomerization reaction may be purified by stripping with
water vapor or a suitable gas such as light hydrocarbon, nitrogen
or hydrogen. The optional stripping step is carried out in a
counter-current manner in a unit upstream of the isomerization
catalyst, wherein the gas and liquid are contacted with each other,
or before the actual isomerization reactor in a separate stripping
unit utilizing counter-current principle.
[0110] After the optional stripping step the fuel blend can be
passed to a reactive isomerization unit comprising one or several
catalyst bed(s). The catalyst beds of the isomerization step may
operate either in co-current or counter-current manner. In the
isomerization step, the pressure may vary from 2000 kPa to 15,000
kPa, preferably in the range of 2000 kPa to 10,000 kPa, the
temperature being between 200.degree. C. and 500.degree. C.,
preferably between 300.degree. C. and 400.degree. C. In the
isomerization step, any isomerization catalysts known in the art
may be used. Suitable isomerization catalysts can contain molecular
sieve and/or a metal from Group VII and/or a carrier. In an
embodiment, the isomerization catalyst contains SAPO-11 or SAPO41
or ZSM-22 or ZSM-23 or ferrierite and Pt, Pd or Ni and Al2O3 or
SiO2. Typical isomerization catalysts are, for example,
Pt/SAPO-11/Al2O3, Pt/ZSM-22/Al2O3, Pt/ZSM-23/Al2O3 and
Pt/SAPO-11/SiO2.
[0111] Other factors, such as the concentration of water or
undesired oxygenated intermediates, may also effect the composition
and yields of the C4+ compounds, as well as the activity and
stability of the condensation catalyst. In such event, the process
may include a dewatering step that removes a portion of the water
prior to the condensation reaction and/or the optional dehydration
reaction, or a separation unit for removal of the undesired
oxygenated intermediates. For instance, a separator unit, such as a
phase separator, extractor, purifier or distillation column, may be
installed prior to the condensation step so as to remove a portion
of the water from the reactant stream containing the oxygenated
intermediates. A separation unit may also be installed to remove
specific oxygenated intermediates to allow for the production of a
desired product stream containing hydrocarbons within a particular
carbon range, or for use as end products or in other systems or
processes.
[0112] Thus, in one embodiment, the fuel blend produced by the
processes described herein is a hydrocarbon mixture that meets the
requirements for jet fuel (e.g., conforms with ASTM D1655). In
another embodiment, the product of the processes described herein
is a hydrocarbon mixture that comprises a fuel blend meeting the
requirements for a diesel fuel (e.g., conforms with ASTM D975).
[0113] Yet in another embodiment of the invention, the C2+ olefins
are produced by catalytically reacting the oxygenated intermediates
in the presence of a dehydration catalyst at a dehydration
temperature and dehydration pressure to produce a reaction stream
comprising the C2+ olefins. The C2+ olefins comprise straight or
branched hydrocarbons containing one or more carbon-carbon double
bonds. In general, the C2+ olefins contain from 2 to 8 carbon
atoms, and more preferably from 3 to 5 carbon atoms. In one
embodiment, the olefins comprise propylene, butylene, pentylene,
isomers of the foregoing, and mixtures of any two or more of the
foregoing. In another embodiment, the C2+ olefins include C4+
olefins produced by catalytically reacting a portion of the C2+
olefins over an olefin isomerization catalyst. In an embodiment, a
method of forming a fuel blend from a biomass feedstock may
comprise a digester that receives a biomass feedstock and a
digestive solvent operating under conditions to effectively remove
nitrogen and sulfur compounds from said biomass feedstock and
discharges a treated stream comprising a carbohydrate having less
than 35% of the sulfur content and less than 35% of the nitrogen
content based on the untreated biomass feedstock on a dry mass
basis; an aqueous phase reforming reactor comprising an aqueous
phase reforming catalyst that receives the treated stream and
discharges an oxygenated intermediate, wherein a first portion of
the oxygenated intermediate stream is recycled to the digester as
at least a portion of the digestive solvent; a first fuels
processing reactor comprising a dehydrogenation catalyst that
receives a second portion of the oxygenated intermediate stream and
discharges an olefin-containing stream; and a second fuels
processing reactor comprising an alkylation catalyst that receives
the olefin-containing stream and discharges a liquid fuel.
[0114] The dehydration catalyst comprises a member selected from
the group consisting of an acidic alumina, aluminum phosphate,
silica-alumina phosphate, amorphous silica-alumina,
aluminosilicate, zirconia, sulfated zirconia, tungstated zirconia,
tungsten carbide, molybdenum carbide, titania, sulfated carbon,
phosphated carbon, phosphated silica, phosphated alumina, acidic
resin, heteropolyacid, inorganic acid, and a combination of any two
or more of the foregoing. In one embodiment, the dehydration
catalyst further comprises a modifier selected from the group
consisting of Ce, Y, Sc, La, Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, P,
B, Bi, and a combination of any two or more of the foregoing. In
another embodiment, the dehydration catalyst further comprises an
oxide of an element, the element selected from the group consisting
of Ti, Zr, V, Nb, Ta, Mo, Cr, W, Mn, Re, Al, Ga, In, Fe, Co, Ir,
Ni, Si, Cu, Zn, Sn, Cd, P, and a combination of any two or more of
the foregoing. In yet another embodiment, the dehydration catalyst
further comprises a metal selected from the group consisting of Cu,
Ag, Au, Pt, Ni, Fe, Co, Ru, Zn, Cd, Ga, In, Rh, Pd, Ir, Re, Mn, Cr,
Mo, W, Sn, Os, an alloy of any two or more of the foregoing, and a
combination of any two or more of the foregoing.
[0115] In yet another embodiment, the dehydration catalyst
comprises an aluminosilicate zeolite. In one version, the
dehydration catalyst further comprises a modifier selected from the
group consisting of Ga, In, Zn, Fe, Mo, Ag, Au, Ni, P, Sc, Y, Ta, a
lanthanide, and a combination of any two or more of the foregoing.
In another version, the dehydration catalyst further comprises a
metal selected from the group consisting of Cu, Ag, Au, Pt, Ni, Fe,
Co, Ru, Zn, Cd, Ga, In, Rh, Pd, Ir, Re, Mn, Cr, Mo, W, Sn, Os, an
alloy of any two or more of the foregoing, and a combination of any
two or more of the foregoing.
[0116] In another embodiment, the dehydration catalyst comprises a
bifunctional pentasil ring-containing aluminosilicate zeolite. In
one version, the dehydration catalyst further comprises a modifier
selected from the group consisting of Ga, In, Zn, Fe, Mo, Ag, Au,
Ni, P, Sc, Y, Ta, a lanthanide, and a combination of any two or
more of the foregoing. In another version, the dehydration catalyst
further comprises a metal selected from the group consisting of Cu,
Ag, Au, Pt, Ni, Fe, Co, Ru, Zn, Cd, Ga, In, Rh, Pd, Ir, Re, Mn, Cr,
Mo, W, Sn, Os, an alloy of any two or more of the foregoing, and a
combination of any two or more of the foregoing.
[0117] The dehydration reaction is conducted at a temperature and
pressure where the thermodynamics are favorable. In general, the
reaction may be performed in the vapor phase, liquid phase, or a
combination of both. In one embodiment, the dehydration temperature
is in the range of about 100.degree. C. to 500.degree. C., and the
dehydration pressure is in the range of about 0 kPa to 6500 kPa. In
another embodiment, the dehydration temperature is in the range of
about 125.degree. C. to 450.degree. C., and the dehydration
pressure is at least 15 kPa. In another version, the dehydration
temperature is in the range of about 150.degree. C. to 350.degree.
C., and the dehydration pressure is in the range of about 750 kPa
to 6000 kPa. In yet another version, the dehydration temperature is
in the range of about 175.degree. C. to 325.degree. C.
[0118] The C6+ paraffins are produced by catalytically reacting the
C2+ olefins with a stream of C4+ isoparaffins in the presence of an
alkylation catalyst at an alkylation temperature and alkylation
pressure to produce a product stream comprising C6+ paraffins. The
C4+ isoparaffins include alkanes and cycloalkanes having 4 to 7
carbon atoms, such as isobutane, isopentane, naphthenes, and higher
homologues having a tertiary carbon atom (e.g., 2-methylbutane and
2,4-dimethylpentane), isomers of the foregoing, and mixtures of any
two or more of the foregoing. In one embodiment, the stream of C4+
isoparaffins comprises of internally generated C4+ isoparaffins,
external C4+ isoparaffins, recycled C4+ isoparaffins, or
combinations of any two or more of the foregoing.
[0119] The C6+ paraffins will generally be branched paraffins, but
may also include normal paraffins. In one version, the C6+
paraffins comprises a member selected from the group consisting of
a branched C6-10 alkane, a branched C6 alkane, a branched C7
alkane, a branched C8 alkane, a branched C9 alkane, a branched C10
alkane, or a mixture of any two or more of the foregoing. In one
version, the C.sub.6+ paraffins comprise dimethylbutane,
2,2-dimethylbutane, 2,3-dimethylbutane, methylpentane,
2-methylpentane, 3-methylpentane, dimethylpentane,
2,3-dimethylpentane, 2,4-dimethylpentane, methylhexane,
2,3-dimethylhexane, 2,3,4-trimethylpentane, 2,2,4-trimethylpentane,
2,2,3-trimethylpentane, 2,3,3-trimethylpentane, dimethylhexane, or
mixtures of any two or more of the foregoing.
[0120] The alkylation catalyst comprises a member selected from the
group of sulfuric acid, hydrofluoric acid, aluminum chloride, boron
trifluoride, solid phosphoric acid, chlorided alumina, acidic
alumina, aluminum phosphate, silica-alumina phosphate, amorphous
silica-alumina, aluminosilicate, aluminosilicate zeolite, zirconia,
sulfated zirconia, tungstated zirconia, tungsten carbide,
molybdenum carbide, titania, sulfated carbon, phosphated carbon,
phosphated silica, phosphated alumina, acidic resin,
heteropolyacid, inorganic acid, and a combination of any two or
more of the foregoing. The alkylation catalyst may also include a
mixture of a mineral acid with a Friedel-Crafts metal halide, such
as aluminum bromide, and other proton donors.
[0121] In one embodiment, the alkylation catalyst comprises an
aluminosilicate zeolite. In one version, the alkylation catalyst
further comprises a modifier selected from the group consisting of
Ga, In, Zn, Fe, Mo, Ag, Au, Ni, P, Sc, Y, Ta, a lanthanide, and a
combination of any two or more of the foregoing. In another
version, the alkylation catalyst further comprises a metal selected
from the group consisting of Cu, Ag, Au, Pt, Ni, Fe, Co, Ru, Zn,
Cd, Ga, In, Rh, Pd, Ir, Re, Mn, Cr, Mo, W, Sn, Os, an alloy of any
two or more of the foregoing, and a combination of any two or more
of the foregoing.
[0122] In another embodiment, the alkylation catalyst comprises a
bifunctional pentasil ring-containing aluminosilicate zeolite. In
one version, the alkylation catalyst further comprises a modifier
selected from the group consisting of Ga, In, Zn, Fe, Mo, Ag, Au,
Ni, P, Sc, Y, Ta, a lanthanide, and a combination of any two or
more of the foregoing. In another version, the alkylation catalyst
further comprises a metal selected from the group consisting of Cu,
Ag, Au, Pt, Ni, Fe, Co, Ru, Zn, Cd, Ga, In, Rh, Pd, Ir, Re, Mn, Cr,
Mo, W, Sn, Os, an alloy of any two or more of the foregoing, and a
combination of any two or more of the foregoing. In one version,
the dehydration catalyst and the alkylation catalyst are atomically
identical.
[0123] The alkylation reaction is conducted at a temperature where
the thermodynamics are favorable. In general, the alkylation
temperature is in the range of about -20.degree. C. to 300.degree.
C., and the alkylation pressure is in the range of about 0 kPa to
8000 kPa. In one version, the alkylation temperature is in the
range of about 100.degree. C. to 300.degree. C. In another version,
the alkylation temperature is in the range of about 0.degree. C. to
100.degree. C., and the alkylation pressure is at least 750 kPa. In
yet another version, the alkylation temperature is in the range of
about 0.degree. C. to 50.degree. C. and the alkylation pressure is
less than 2500 kPa. In still yet another version, the alkylation
temperature is in the range of about 70.degree. C. to 250.degree.
C., and the alkylation pressure is in the range of about 750 kPa to
8000 kPa. In one embodiment, the alkylation catalyst comprises a
mineral acid or a strong acid and the alkylation temperature is
less than 100.degree. C. In another embodiment, the alkylation
catalyst comprises a zeolite and the alkylation temperature is
greater than 100.degree. C.
[0124] Another aspect of the present invention is that the C4+
isoparaffins may be generated internally by catalytically reacting
an isoparaffin feedstock stream comprising C4+ normal paraffins,
aromatics and/or naphthenes in the presence of an isomerization
catalyst at an isomerization temperature and isomerization pressure
to produce internally generated C4+ isoparaffins. The C4+ normal
paraffins will generally include alkanes having 4 to 7 carbon
atoms, such as n-butane, n-pentane, n-hexane, n-heptane, and
mixtures of any two or more of the foregoing. In one arrangement,
the isoparaffin feedstock stream is collected upstream of the
alkylation catalyst from the reaction stream having the oxygenated
intermediates or the reaction stream having the C2+ olefins and
processed for the production of the internally generated C4+
isoparaffins. In another arrangement, the C4+ normal paraffins,
aromatics and/or naphthenes are collected downstream of the
alkylation catalyst from the product stream having the C6+
paraffins and then recycled for use in the production of the
internally generated C4+ isoparaffins. The C4+ isoparaffins may
also be provided solely from an external source or used to
supplement the internally generated C4+ isoparaffins. In another
version, the C4+ isoparaffins are recycled C4+ isoparaffins
collected from the product stream having the C6+ paraffins.
[0125] The isomerization catalyst is a catalyst capable of reacting
a C4+ normal paraffin, aromatic or naphthene to produce a C4+
isoparaffin. In one version, the isomerization catalyst includes a
zeolite, zirconia, sulfated zirconia, tungstated zirconia, alumina,
silica-alumina, zinc aluminate, chlorided alumina, phosphoric acid,
or mixtures of any two or more of the foregoing. In another
version, the isomerization catalyst is an acidic beta, mordenite,
or ZSM-5 zeolite. In yet another version, the isomerization
catalyst further comprises a metal selected from the group
consisting of Y, Pt, Ru, Ad, Ni, Rh, Ir, Fe, Co, Os, Zn, a
lanthanide, or an alloy or combination of any two or more of the
foregoing. In still yet another version, the isomerization catalyst
comprises a support, the support comprising alumina, sulfated
oxide, clay, silica gel, aluminum phosphate, bentonite, kaolin,
magnesium silicate, magnesium carbonate, magnesium oxide, aluminum
oxide, activated alumina, bauxite, silica, silica-alumina,
activated carbon, pumice, zirconia, titania, zirconium, titanium,
kieselguhr, or zeolites.
[0126] In an embodiment of the present invention, the fuel yield of
the current process may be greater than other bio-based feedstock
conversion processes. Without wishing to be limited by theory, it
is believed that substantially removing nitrogen compounds and
sulfur compounds from the biomass prior to the direct APR allows
for a greater percentage of the biomass to be converted into higher
hydrocarbons while limiting the formation of degradation
products.
[0127] To facilitate a better understanding of the present
invention, the following examples of certain aspects of some
embodiments are given. In no way should the following examples be
read to limit, or define, the entire scope of the invention.
EXAMPLES
[0128] Catalyst poisoning, biomass extraction, pretreatment,
digestion and reaction studies were conducted in a Parr5000
Hastelloy multireactor comprising 6.times.75-milliliter reactors
operated in parallel at pressures up to 14,000 kPa, and
temperatures up to 275.degree. C., stirred by magnetic stir bar.
Alternate studies were conducted in 100-ml Parr4750 reactors, with
mixing by top-driven stir shaft impeller, also capable of 14,000
kPa and 275.degree. C. Larger scale extraction, pretreatment and
digestion tests were conducted in a 1-Liter Parr reactor with
annular basket housing biomass feed, or with filtered dip tube for
direct contacting of biomass slurries.
[0129] Reaction samples were analyzed for sugar, polyol, and
organic acids using an HPLC method entailing a Bio-Rad Aminex
HPX-87H column (300 mm.times.7.8 mm) operated at 0.6 ml/minute of a
mobile phase of 5 mM sulfuric acid in water, at an oven temperature
of 30.degree. C., a run time of 70 minutes, and both RI and UV (320
nm) detectors.
[0130] Product formation (mono-oxygenates, diols, alkanes, acids)
were monitored via a gas chromatographic (GC) method "DB5-ox",
entailing a 60-m.times.0.32 mm ID DB-5 column of 1 um thickness,
with 50:1 split ratio, 2 ml/min helium flow, and column oven at
40.degree. C. for 8 minutes, followed by ramp to 285.degree. C. at
10.degree. C./min, and a hold time of 53.5 minutes. Injector
temperature was set at 250.degree. C., and detector temperature at
300.degree. C.
[0131] Gasoline production potential by condensation reaction was
assessed via injection of one microliter of liquid intermediate
product into a catalytic pulse microreactor entailing a GC insert
packed with 0.12 grams of ZSM-5 catalyst, held at 375.degree. C.,
followed by Restek Rtx-1701 (60-m) and DB-5 (60-m) capillary GC
columns in series (120-m total length, 0.32 mm ID, 0.25 um film
thickness) for an Agilent/HP 6890 GC equipped with flame ionization
detector. Helium flow was 2.0 ml/min (constant flow mode), with a
10:1 split ratio. Oven temperature was held at 35.degree. C. for 10
minutes, followed by a ramp to 270.degree. C. at 3.degree. C./min,
followed by a 1.67 minute hold time. Detector temperature was
300.degree. C.
Example 1
Catalyst Poisoning by N,S Amino Acid
[0132] Two Parr5000 reactors were charged with 20 grams of a
mixture of 50% glycerol in deionized water, and 0.35 grams of 1.9%
Pt--Re/zirconia catalyst reduced at 400.degree. C. under hydrogen.
Glycerol is one of the intermediates derived from monosaccharides
or sugar alcohols in the aqueous phase reforming reaction sequence,
and can react via APR to form hydrogen and CO2, as well as
monooxygenate intermediates such as acetone and 2-propanol. It
therefore represents a model component for the study of the APR
reaction.
[0133] 0.03 grams of the N,S amino acid cysteine were added to
reactor B, but not to A. Reactors were pressured with 3500 kPa of
H2, and heated to 255.degree. C. for 6.5 hours under conditions
corresponding to aqueous phase reforming reaction (APR) with
pre-addition of a fraction of the hydrogen required for reaction,
before cooling for GC analysis of products. Results indicated 84.7%
conversion of glycerol to mono oxygenate and other expected
products for reactor A, but only 57.6% conversion for reactor B.
Calculated first order rate constants, per weight fraction of
catalyst, were 16.5/h/wt-cat for A, vs. 7.5/h/wt-cat for B. The
addition of 1500 ppm cysteine was observed to decrease the apparent
activity for conversion of glycerol via APR, by a factor of more
then two.
[0134] A third reaction C was conducted under identical conditions,
except with 1500 ppm alanine (N-only amino acid), and exhibited an
apparent rate constant of 14/h/wt-cat, or an approximate 12%
reduction in activity.
[0135] These results indicate substantial poisoning by cysteine
(N,S-amino acid), and moderate poisoning by alanine (N-only amino
acid), for the Re-promoted Pt catalyst which can be employed in
aqueous phase reforming (APR).
Example 2
Poisoning of Pt/Alumina Catalyst by N,S and N-Only Amino Acid
[0136] The experiment of Example 1 was repeated with 5% Pt/alumina
catalyst Escat 2941 (Strem Chemicals). In addition to reactors A
(no amino acid) and B (1500 ppm cysteine), a third reactor C was
charged with 1500 ppm of alanine, a N-only amino acid. Measured
conversions were 56.7%, 42.3%, and 45.4% for reactors A through C,
corresponding to apparent first order rate constants of 10.2, 3.0,
and 3.2/h/wt-cat. Addition of 1500 ppm of either N,S or N-only
amino acid was observed to decrease glycerol APR reaction rates by
more than a factor of 3, for the unpromoted Pt/alumina
catalyst.
Example 3
Poisoning of Ru Catalyst Under APR Conditions
[0137] Examples 1A and B were repeated with 5% Ru/C Escat 4401
catalyst (Strem Chemicals, 50% wet), with an initial charge of 6000
kPa H.sub.2. Conversion for reactor A (no amino acid) was 56.5%,
while conversion for reactor B (1500 ppm cysteine) was only 9%.
Apparent first order rate constant for B (1500 ppm cysteine) was
only 1.7/h/wt-cat, vs. a rate constant of reactor A of
14.7/h/wt-cat. This result indicates poisoning by amino acid of a
Ru-based catalyst, in testing conducted under aqueous phase
reforming (APR) conditions with pre-addition of a fraction of the
required hydrogen needed for reaction.
Example 4
Poisoning of APR Catalyst Under N2 and H2
[0138] For examples 4A and 4B, the experiment of Example 1 was
repeated with 5% Pt/alumina catalyst Escat 2941 (Strem Chemicals),
but with 3000 kPa N2 instead of H2 as the initial gas, such that
all required hydrogen must be generated by the aqueous phase
reforming reaction. Reactor A (no amino acid) exhibited an apparent
first-order rate of 18.6/h/wt-cat, while B (1500 ppm cysteine) was
severely poisoned with a rate of glycerol conversion of only
0.9/h/wt-catalyst. These results indicate substantial poisoning by
cysteine (N,S-amino acid) for the unpromoted Pt catalyst employed
in aqueous phase reforming (APR), conducted under conditions where
all H2 was generated in situ via the aqueous phase reforming
reaction.
[0139] For examples 4C through 4E, the experiment of Example 1 was
repeated with a Re-modified 1.9% Pt/zirconia catalyst calcined at
400.degree. C. after impregnation, and then reduced at 400.degree.
C. under hydrogen. The reaction was conducted with an initial
pressure of 5000 kPa H2. Reactor C (no poison) indicated a
first-order rate constant of 53.9/h/wt-cat, while Reactor D with
1500 ppm cysteine (N,S amino acid) gave lower conversions
corresponding to a rate of only 4.8/h/wt-cat. Reactor E with 1500
ppm alanine (N-only amino acid) showed moderate activity,
corresponding to a rate of 20.2/h/wt-catalyst. This experiment
shows substantial poisoning by N,S amino acid cysteine, and
moderate poisoning by N-only amino acid alanine, for aqueous phase
reforming experiments conducted with glycerol as feed and with
pre-addition of a fraction of the required hydrogen at the start of
reaction.
Example 5
N,S- and N Poisoning of Pt/C Catalyst Used for Sorbitol APR
[0140] An experiment was conducted in the Parr5000 multireactor
using 0.5 grams of 5% Pt/C as catalyst (50% wet), and 40 grams of
50% sorbitol as feed, for 3 hours at 250.degree. C., with an
initial gas feed of 3500 kPa H.sub.2. Final liquids were analyzed
for remaining unconverted sorbitol content by HPLC analysis.
Conversion of reactor A (no amino acid) corresponded to an apparent
first order rate constant of 28.8/h/wt-cat, while reactor B (3000
ppm cysteine) exhibited an apparent rate of only 2.8/h/wt-cat.
Reactor C (2250 ppm alanine) exhibited an apparent first order rate
constant for sorbitol conversion of 6.0/h/wt-cat. These results
indicate poisoning of sorbitol aqueous phase reforming reaction by
cysteine and alanine despite pre-addition of a fraction of the
hydrogen required for reaction.
Example 6
Extraction of Biomass
[0141] For Example 6, Parr5000 reactors A-C were loaded with 2.1
grams of softwood (pine) chips, comprising 2 whole chips of
approximate 1-inch.times.1-inch.times.3 mm size, trimmed to fit the
reactor body, and 20 grams of a solvent mixture of 25% by weight
acetone, 25% isopropanol, and 2% acetic acid in deionized water,
designated as "A"-solvent. Reactors D-F were loaded with the same
amount of pine chips, and deionized water only. The reactors were
heated overnight under nitrogen, at temperatures of 170, 190, and
210.degree. C. for reactors A, B, and C, respectively, and for
reactors D, E. F, respectively (Table 1).
[0142] Partially digested whole chips were carefully removed to
Petri dish for vacuum drying overnight at 90.degree. C. to assess
undigested dry solids. Fine solids were washed into a filter funnel
with Whatman GF/F filter paper, which was also vacuum dried
overnight at 90.degree. C. to assess the residual fines solids
which precipitated after cooling of the reactors to ambient
temperature. Mass loss from the whole chips was recorded as percent
digested at the extraction temperature. This amount was corrected
by the mass of fines redeposited upon cool down to 25.degree. C.,
and recorded as the "% dissolved at 25 C".
[0143] Samples of liquid were analyzed for nitrogen by elemental
X-ray analysis.
TABLE-US-00001 TABLE 1 Extraction and Pre-treatment by solvent
leaching Liquid/ N leached T dry Chips Dissolved % ppm-dry Sx
solvent deg C. wd % digest @25.degree. C. wood A A-solv 170 11.896
38.4% 34.1% 416 B A-solv 190 11.925 52.4% 45.9% 405 C A-solv 210
12.138 100.0% 66.5% 449 D DIWater 170 11.930 29.0% 24.2% 143 E
DIWater 190 12.756 33.7% 27.5% 268 F DIWater 210 11.106 61.6% 45.7%
n.a.
[0144] As shown in Table 1 extraction and dissolution of biomass
was enhanced by the use of water-soluble oxygenated organic solvent
in deionized water over deionized water. The extent of extraction
and digestion was also increased by an increase in temperature,
with complete digestion of wood chips at 210.degree. C. in
A-solvent. Solvent also increased the extraction of nitrogen,
presumed from proteins and amino acids in the wood matrix, where
nitrogen observed in the liquid extract is expressed relative to
the mass of dry wood extracted. Sulfur analyses were low, at
detection limits for these samples.
[0145] This example demonstrates the use of oxygenated solvent,
selected from components produced in situ via APR of bio-based feed
materials in water, to facilitate extraction and pretreatment of a
biomass sample, including N-containing components attributed to the
presence of amino acids and proteins.
Example 7
Biomass Extraction and Reprecipitation in Water and Oxygenated
Solvents
[0146] A series of experiments were conducted in a 100-ml Parr
reactor fitted with 0.5 micron stainless steel filtered dip tube.
Extraction of southern hardwood was examined, with removal of
samples via filtered via dip tube at 210.degree. C. temperature (17
hours), to compare the % precipiated solids in the sample after
cooling to ambient temperature (nominal 25.degree. C.), with the %
solids in the final mixture recovered from the reactor as
determined via cold filtration. The fraction of biomass extracted
and digested was also assessed, by GC analysis of the intermediates
formed. In addition to testing of "A-solvent" and deionized water,
50% ethanol in water, and "B-solvent" entailing 20 wt % ethylene
glycol, 20% wt % 1,2-propylene glycol, and 2% acetic acid in
deionized water, were also examined. "B-solvent" represents diol
intermediates formed in the APR reaction. Assessment of the percent
digestion of initial dry wood was again made by recovering the
undigested solids by filtration on Whatman GF/F filter paper, and
drying overnight in a vacuum oven at 90.degree. C.
[0147] Results (Table 2) show all solvents can digest a portion of
the wood sample at 210.degree. C. A-solvent (25% acetone, 25%
isopropanol, and 2% acetic acid) gave the best digestion, or
dissolution of biomass. Addition of oxygenate solvent including
those components formed in an APR reaction of bio-based feeds, was
observed to improve the retention of dissolved biomass components
in solution upon cooling to ambient temperature. Presence of lignin
in precipitating samples was confirmed by UV-vis analysis in the
region of 190-400 nm. While water-only solvent gave good extraction
results at the 210.degree. C. extraction temperature, a substantial
portion precipitated upon cooling to 25.degree. C.
TABLE-US-00002 TABLE 2 Extraction and re-precipitation of biomass
initial 25.degree. C. 210.degree. C. Solvent wood % digest % digest
A A-Solvent 5.43% 72.19% 73.84% B B-Solvent 5.80% 41.57% 28.92% C
50% EtOH 5.42% 54.24% 42.32% D DI water 5.32% 29.10% 69.33%
Example 8
Short Contact Time Pretreatment and Extraction
[0148] For Example 8A, 42.25-grams of an A-solvent mixture (25%
acetone, 25% isopropanol, 2% acetic acid) were contacted with 4.308
grams of southern hardwood for 5 hours at 170.degree. C., followed
by cooling to room temperature for recovery of undigested solids by
filtration (Whatman GF/F). Separated liquor was black, indicating
removal of color bodies. The recovered solid pulp was water washed
to remove residual solvent. A portion was dried overnight in a
vacuum oven at 90.degree. C., to assess dry solids content of the
recovered pulp. Results indicate extraction of 47.5% of the
original softwood, on a dry mass basis, using a contact time of 5
hours. X-ray analysis indicated removal of 860 ppm nitrogen basis
the mass of dry wood charged, using the extractive solvent
pretreatment. Sulfur was below detection in this sample.
[0149] In example 8B, extraction and pretreatment were examined
with series of consecutive experiments conducted with 22.4 grams of
softwood (pine) and 500-grams deionized water in the 1-Liter
stirred reactor with filtered dip tube, and sampling for total
organic carbon (TOC) analysis versus time. The leaching studies
were conducted overnight at 170, 190, and 210.degree. C. A maximum
in the TOC content was obtained after only 2 hours at 170.degree.
C., where 73% of the final leached carbon was obtained. Further
increase to 210.degree. C. before removal of liquid by hot
filtration, resulted in 65% digestion of the initially charged
biomass, as determined by filtration (Whatman GF/F) of solids
remaining in the reactor after cooling.
[0150] These results indicate an ability to pretreat and extract
biomass samples with water and with oxygenated organic solvents in
water, with a contact time as low as 2-5 hours. Up to 65% of the
nitrogen present in the biomass was also extracted in a single
stage of extraction, providing a pretreated biomass that can be
used in subsequent aqueous phase reforming reactions to form liquid
fuels.
Example 9
APR Reaction with Pretreated Biomass Pulp
[0151] For Example 9, 2.639 grams of wet pulp from Example 8A were
added, along with 20.2 grams of deionized water, 0.45 grams of 5%
Pt/alumina Escat 2941 catalyst (Strem Chemicals), and 6000 kPa N2,
to a Parr5000 reactor. The reactor was heated with a temperature
profile from 170-240.degree. C. over 5 hours, followed by
isothermal reaction at 240.degree. C. to comprise an 18-hour total
reaction cycle.
[0152] Filtration recovery and overnight vacuum dry of residual
solids indicated 39.5% digestion of the treated pulp. Analysis for
product formation by the DB5-ox method indicated 13.4% yield of
products, while injection of final supernatant into the ZSM-5 pulse
microreactor demonstration production of benzene, toluene, xylenes,
methyl benzenes, and naphthalenes at a yield corresponding to 20.4%
of the original mass of dry pulp charged. This result indicates the
feasibility of forming gasoline via APR reactive digestion of a
solvent-treated hardwood pulp.
Example 10
APR of Aqueous Digestive Solvent-Pretreated Biomass Pulp
[0153] A sample of mixed hardwoods pulp was obtained from an
organic solvent (ethanol-water) extract step. An APR reaction was
conducted in a the Parr100 reactor using 5% Pt/alumina Escat 2941
as catalyst in APR mode under 3500 kPa of N2, and a heating
schedule of 2.5 hours at 170.degree. C., followed by 2.5 hours at
210.degree. C., followed by overnight (20.25 hours total) at
250.degree. C.
[0154] Following reaction, solids were recovered by filtration on
Whatman #2 filter paper, and oven dried overnight at 90.degree. C.
to assess recovery. 85% of the pulp was digested. Acetic acid
formation was evident at 0.10 wt % (GC). Final pH of 3.14 was
observed, despite no acid addition to feed. Total estimated GC wt %
via the DB-5ox method matched or exceeded that calculated from the
mass of pulp digested, indicating high selectivity to desired
monooxygenates intermediates. ZSM-5 pulse microreactor indicated
formation of alkanes, benzene, toluene, xylenes, trimethlybenzenes,
and naphthalenes, at yields in excess of 30% of the original pulp
fed.
[0155] This example demonstrates the in situ formation of organic
acids which can aid in the reaction and digestion of biomass
samples to form intermediates which can be further reacted to
liquid fuels.
Example 11
Hydrogenolysis and APR of an Digestive Solvent-Pretreated Biomass
Pulp
[0156] 5.14 grams of southern hardwood were treated with 50.3 grams
of A-solvent in a Parr5000 reactor under 3500 kPa N2 using a
temperature ramp of 150.degree. C.-170.degree. C. over 1 hour,
followed by 4 hours at 170.degree. C. A dark brown liquor was
obtained, indicating extraction of color bodies and other
extractables. pH of the recovered liquid was 2.9. Undigested solids
were recovered by filtration on Whatman GF/F filter paper, and a
solid pulp sample was dried overnight in a vacuum oven at
90.degree. C. to assess recovery. 48.8% of the initially charged
hardwood was extracted, leaving a light brown solid pulp.
[0157] 3.0 grams of the wet pulp were charged to a Parr5000
reactor, with 0.35-grams of a Re-promoted 1.9% Pt/zirconia
catalyst. H2 was added at 5000 kPa, before ramping in temperature
from 170 to 210.degree. C. over 3 hours, followed by 15 hours at
210.degree. C. to complete reaction. GC analysis by the DB5-ox
method indicated 96% yield of polyols and mono-oxygenates with
retention time less than sorbitol. Final reaction product was
cycled to yet another Parr5000 reactor charged with the same
Re--Pt/zirconia catalyst, to effect aqueous phase reforming at
240.degree. C.
[0158] This examples demonstrates that the combination of biomass
pretreatment with an oxygenated organic solvent mixture in water,
followed by reaction of the pretreated biomass pulp with an APR
catalyst in the presence of a portion of the hydrogen required for
reaction at a first reaction temperature of 170-210.degree. C.,
produces a high yield of diols and mono-oxygenates. The diol and
mono-oxygenate intermediate product can be further converted to
mono-oxygenates and additional hydrogen by an additional reaction
at a second, higher temperature (240.degree. C.).
Example 12
APR of Alkali Pretreated Biomass Pulp
[0159] 22.4 grams of softwood (pine) were contacted with 500-grams
of deionized water in a 1-liter stirred reactor, with overnight
heating at 210.degree. C. Filtration and recovery of solids
indicated 65.1% digestion to form a liquid extract at pH 3.7.
[0160] 4.484 grams of the water-extracted solids were contacted
with 25.03 grams of 1N NaOH at 155.degree. C. for 2 hours, to
simulate alkali (Kraft) pulping. A black liquid extract was
obtained. The residual solids were water washed to remove residual
base. 3.51 grams of the washed, treated pulp solids were added with
20.194 grams of an aqueous solvent, along with 0.454 grams of 5%
Pt/alumina Escat 2941 catalyst (Strem Chemicals), and 4800 kPa of
nitrogen. Temperature was ramped from 170-240.degree. C. over 5
hours, followed by isothermal reaction at 240.degree. C. to
complete an 18 hour cycle.
[0161] Final pH of the reaction mixture was 6.73, indicating water
wash was only partially effective in removing alkali base.
Digestion of the pulp was only 11%, and injection of final liquid
into the ZSM-5 pulse microreactor gave an estimated conversion to
alkanes, benzene, toluene, xylenes, trimethlybenzenes, and
naphthalenes of only about 6%, relative to the mass of biomass pulp
charged to the initial reaction step. These results indicate that
failure to remove residual alkali base via effective water washing
following alkaili pulping of softwood, can result in low yields for
a subsequent hydrogenolysis and APR conversion reaction.
* * * * *