U.S. patent application number 13/391766 was filed with the patent office on 2012-12-20 for process for converting cellulose and/or hemicellulose in a liquid fuel comprising dissolution in ionic liquid.
This patent application is currently assigned to KiOR, Inc.. Invention is credited to Jacobus Johannes Heinerman, Jacob Adriaan Moulijn, Paul O'Connor, Jacobus Cornelis Rasser, Armand Eduard Rosheuvel.
Application Number | 20120323057 13/391766 |
Document ID | / |
Family ID | 43038054 |
Filed Date | 2012-12-20 |
United States Patent
Application |
20120323057 |
Kind Code |
A1 |
Heinerman; Jacobus Johannes ;
et al. |
December 20, 2012 |
Process for Converting Cellulose and/or Hemicellulose in a Liquid
Fuel Comprising Dissolution in Ionic Liquid
Abstract
A process is disclosed for converting cellulose to liquid fuels.
In the process the cellulose is dissolved in an ionic Liquid
medium. The conversion process may comprise pyrolysis, thermal
cracking, hydrocracking, catalytic cracking, hydrotreatment, or a
combination thereof. The Ionic Liquid medium preferably is an
inorganic molten salt hydrate.
Inventors: |
Heinerman; Jacobus Johannes;
(Abcoude, NL) ; Moulijn; Jacob Adriaan; (Den Haag,
NL) ; O'Connor; Paul; (Hoevelaken, NL) ;
Rasser; Jacobus Cornelis; (Redondo Beach, CA) ;
Rosheuvel; Armand Eduard; (Kasterlee, BE) |
Assignee: |
KiOR, Inc.
Pasadena
TX
|
Family ID: |
43038054 |
Appl. No.: |
13/391766 |
Filed: |
September 1, 2010 |
PCT Filed: |
September 1, 2010 |
PCT NO: |
PCT/US10/47500 |
371 Date: |
August 31, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61238720 |
Sep 1, 2009 |
|
|
|
Current U.S.
Class: |
585/240 |
Current CPC
Class: |
C10G 1/06 20130101; C10G
2300/44 20130101; Y02P 30/20 20151101; C08B 1/003 20130101; C10G
3/42 20130101; C10G 45/04 20130101; C10G 1/045 20130101; C10G
2300/1014 20130101; C10G 1/04 20130101; C10G 2400/26 20130101; C10G
1/02 20130101; C10G 1/065 20130101; C10G 2400/02 20130101; C10G
3/00 20130101; C08H 8/00 20130101 |
Class at
Publication: |
585/240 |
International
Class: |
C10L 1/04 20060101
C10L001/04 |
Claims
1. A process for converting a cellulosic material to a liquid fuel,
said process comprising the steps of: (i) dissolving at least the
cellulose component of the cellulosic material in an Ionic Liquid;
and (ii) converting the dissolved cellulose component to a liquid
fuel.
2. The process of claim 1 wherein the Ionic Liquid is an inorganic
molten salt hydrate or an organic cation.
3. (canceled)
4. The process of claim 1 wherein the cellulosic material is
substantially fully soluble in the Ionic Liquid.
5. The process of claim 4 wherein the cellulosic material is
selected from aquatic biomass, cotton linters, paper, cardboard and
mixtures thereof.
6. The process of claim 1 wherein the cellulosic material comprises
at least one component that is insoluble in the Ionic Liquid.
7. The process of claim 6 wherein the cellulosic material comprises
lignocellulose.
8. The process of claim 6 comprising the further step of separating
the at least one component that is insoluble in the Ionic Liquid
prior to converting the dissolved cellulose component.
9. The process of claim 6 wherein the at least one component that
is insoluble in the Ionic Liquid comprises lignin.
10. The process of claim 1 wherein step (ii) is carried out in the
absence of a catalyst or in the presence of a catalyst.
11. (canceled)
12. The process of claim 1 wherein step (ii) is selected from
pyrolysis, thermal cracking, hydrocracking, catalytic cracking,
hydrotreatment or a combination thereof.
13. The process of claim 1 wherein step (ii) is carried out at a
temperature in the range of from 200.degree. C. to 600.degree. C.,
or at a temperature in the range of from 200.degree. C. to
450.degree. C.
14. (canceled)
15. The process of claim 1 wherein the Ionic Liquid medium
comprises a molten salt hydrate.
16. The process of claim 15 wherein the molten salt hydrate
comprises a halogen anion.
17. The process of claim 16 wherein the halogen anion is
chloride.
18. The process claim 15 wherein the molten salt hydrate comprises
a cation selected from the group consisting of Zn, Ba, Ca, Li, Al,
Cu, Fe, Cu(NH.sub.3).sub.x and Cr.
19. The process of claim 1 wherein the Ionic Liquid is a molten
salt hydrate comprising ZnCl.sub.2, CaCl.sub.2, LiCl, or a mixture
thereof.
20. The process of claim 1 wherein step (ii) is carried out under
autogenous pressure.
21. The process of claim 1 wherein water is removed from the Ionic
Liquid during step (ii).
22. The process of claim 1 wherein the liquid fuel is insoluble in
the Ionic Liquid.
23. The process of claim 1 comprising the further step (iii) of
removing the fuel from the Ionic Liquid.
Description
RELATED APPLICATIONS
[0001] This application claims benefit under 35 U.S.C. .sctn.119(e)
of the U.S. provisional patent application Ser. No. 61/238,720,
filed Sep. 1, 2009, the content of which is incorporated herein by
reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates generally to the conversion of
cellulose to a liquid fuel, and more particularly to such a
conversion process in an Ionic Liquid medium.
[0004] 2. Description of the Related Art
[0005] Several processes have been proposed for converting
cellulose to hydrocarbons. One such process comprises gasification
of cellulose to synthesis gas ("syngas", a mixture of carbon
monoxide and hydrogen), and conversion of the syngas in a
Fischer-Tropsch reaction to hydrocarbons. This process is
inherently inefficient, because long-chain polymeric materials are
first broken down to small molecules, which are subsequently built
back up to larger molecules. It is inefficient also because the
oxygen content is first increased (syngas has higher oxygen content
than cellulose), and subsequently reduced or eliminated.
[0006] Another process is the pyrolysis, in particular fast or
flash pyrolysis. High liquid yields have been reported, but the
pyrolysis liquids have high oxygen content. The liquids are highly
acidic and corrosive. They are unstable, due to their propensity to
polymerization. Moreover, the liquids contain large amounts of
water, which is difficult to separate from the organic components
due to the hydrophilic nature of the organic compounds. The liquids
need to be subjected to a separate upgrading to provide usable
hydrocarbon products. Upgrading processes reported in the prior art
generally comprise two hydrotreatment steps. In a first step, which
is carried out in the presence of the water component of the
pyrolysis liquid, the organic compounds are deoxygenated to the
point that they become sufficiently hydrophobic to cause phase
separation into an aqueous phase and an oil phase. The oil phase is
further deoxygenated to form hydrocarbons. The three-step process
has a rather poor overall yield.
[0007] It has been known to dissolve cellulose in Ionic Liquids. S.
Fischer et al., "Inorganic molten salts as solvents for cellulose",
Cellulose 10: 227-236, 2003, discloses the use of various molten
salt systems as solvent media for cellulose. Upon dissolution,
cellulose can be derivatized by carboxymethylation or acetylation.
The derivation reactions leave the cellulose polymer backbone in
tact.
[0008] Sheldrake and Schleck, "Dicationic molten salts (ionic
liquids) as re-usable media for the controlled pyrolysis of
cellulose to anhydrosugars", Green Chem 2007, pp 1044-1046, reports
on low temperature pyrolysis of cellulose in ionic liquid media.
The pyrolysis temperature is low enough that the ionic liquid can
be recovered and re-used after the pyrolysis reaction. The
pyrolysis products are anhydrosugars. The reported conversion
yields are 3.5 wt % or less.
[0009] Thus, there is a need for a process in which cellulose is
converted to liquid fuels at a high yield. There is a particular
need for such a process in which the chemical reaction is carried
out in one step. There is a further need for such a process that
can be carried out in continuous mode.
BRIEF SUMMARY OF THE INVENTION
[0010] The present invention addresses these problems by providing
a process for converting a cellulosic material to a liquid fuel,
said process comprising the steps of: [0011] (i) dissolving at
least the cellulose component of the cellulosic material in an
Ionic Liquid; [0012] (ii) converting the dissolved cellulose
component to a liquid fuel.
DETAILED DESCRIPTION OF THE INVENTION
[0013] The present invention relates to a process for converting a
cellulosic material to a liquid fuel, said process comprising the
steps of: [0014] (i) dissolving at least the cellulose component of
the cellulosic material in an Ionic Liquid; [0015] (ii) converting
the dissolved cellulose component to a liquid fuel.
[0016] Preferably the liquid fuel is insoluble in the Ionic
Liquid.
[0017] The process can comprise the additional step (iii) of
removing the liquid fuel from the Ionic Liquid.
[0018] In a preferred embodiment the process comprises the
additional step (iv) of regenerating the Ionic Liquid medium
obtained in step (iii). This additional regeneration step can
comprise removing water from the Ionic Liquid medium. The
regeneration step can comprise removing sludge from the Ionic
Liquid medium. The term "sludge" as used herein refers to solid
reaction products that are insoluble in the Ionic Liquid medium.
The term encompasses such reaction products as coke and certain
types of char. In general the process can be operated such that
little or no coke and char are formed. However, it may be desirable
to produce liquid hydrocarbons under conditions that promote
cracking. Such reaction conditions can promote the formation of
coke and/or char. The operator of the process may well accept a
certain amount of coke yield as a price to pay for a high liquid
yield, as coke is easily removed from the Ionic Liquid medium. In
general, coke removal can be accomplished by passing the Ionic
Liquid through a suitable filter medium, such as a bed of silica or
alumina. The filter medium can be regenerated by burning off the
coke and any other components of the sludge. Heat generated during
this regeneration process can be used in the conversion process, in
particular in step (ii).
[0019] The removal of water can generally be accomplished by
distillation. As will be explained in more detail below, step (ii)
is generally carried out under increased pressure, at temperatures
exceeding 100.degree. C. By releasing the pressure while the
temperature of the Ionic Liquid medium is maintained above
100.degree. C., water is flashed off in a process sometimes
referred to as flash-distillation.
[0020] After regeneration the Ionic Liquid medium may be recycled
to step (i) of the process. This feature is particularly useful if
the process is conducted in continuous mode. It will be understood,
however, that the process can be conducted in batch mode as
well.
[0021] Any cellulosic material can be used in the process of the
invention. It is possible to use pure cellulose as the
cellulose-containing feedstock. Preferably, the cellulosic material
is substantially fully soluble in the Ionic Liquid.
[0022] Importantly, the process is suitable for feedstocks
comprising the cellulosic material and at least one contaminant.
Suitable examples include aquatic biomass, cotton linters, paper,
cardboard, and mixtures thereof.
[0023] For example, the feedstock may be paper or paper board. Low
grade paper contains lignin as a contaminant. Higher grades of
paper can contain fillers and sizing agents, such as clay, titanium
dioxide, and the like. Post-consumer waste paper or paperboard may
further contain inks and pigments. Contaminants such as sizing
agents, fillers, and pigments are insoluble in the Ionic Liquid
medium. Accordingly, these contaminants are preferably removed from
the process prior to step (ii).
[0024] Lignin is insoluble in certain Ionic Liquid media, and
partially soluble in others. Undissolved lignin is removed from the
process prior to step (ii). Dissolved lignin is converted to
hydrocarbon compounds during step (ii). Thus, the process of the
invention offers flexibility to the operator of the process. The
operator may select an Ionic Liquid medium in which lignin is at
least partially soluble. The advantage is that a greater portion of
the feedstock is converted to hydrocarbons. The mixture of
hydrocarbon compounds is more complex if lignin is present in the
Ionic Liquid medium during step (ii). This is not necessarily a
disadvantage. For example, if the hydrocarbon products produced by
the process are to be used as a gasoline mixing stock, the presence
of lignin conversion products tends to increase the octane rating
of the mixture.
[0025] In an alternate embodiment the operator of the process can
select an Ionic Liquid medium in which lignin is substantially
insoluble. As a general rule, lignin is insoluble in inorganic
molten salt hydrates. It has surprisingly been found that
nevertheless these materials are capable of dissolving the
cellulose component of a lignocellulosic composite material. This
makes it possible to isolate the cellulose portion of a
lignocellulosic material, without requiring a separate process,
such as the Kraft process, which involves the use of aggressive and
environmentally undesirable chemicals.
[0026] Undissolved lignin can be removed from the Ionic Liquid
medium prior to step (ii). In this embodiment, if in Ionic Liquid
is used in which lignin is insoluble, essentially no lignin is
present during step (ii). As a result, the hydrocarbon mixture
produced in the reaction is relatively simple.
[0027] Many sources of cellulosic material further contain
inorganic materials. To the extent these materials are insoluble in
the Ionic Liquid medium they are easily removed from the process
prior to step (ii). Inorganic materials that are dissolved in the
Ionic Liquid medium can be removed in a regeneration step, for
example using solvent extraction.
[0028] It is desirable to at least partially hydrolyze dissolved
cellulose and hemicellulose to the corresponding sugars. This can
be accomplished by adding an acid catalyst, for example
hydrochloric acid (HCl); by increasing the temperature of the Ionic
Liquid medium to above about 70.degree. C.; or by a combination of
these two measures.
[0029] Step (ii) can be carried out in the absence or of a
catalyst. Dissolved cellulose, in particular when hydrolyzed to
sugars, is far more reactive than cellulose in solid form so that
suitable conversion yields can be obtained even in the absence of a
catalyst.
[0030] It can be advantageous to carry out step (ii) in the
presence of a catalyst. The presence of a catalyst accelerates the
conversion reaction of dissolved cellulose, which reduces the
reaction time; or permits the reaction to be carried out at a lower
temperature than the uncatalyzed reaction; or a combination of
these two advantages. In addition, use of a catalyst generally
results in a more selective hydrogenation reaction.
[0031] Examples of suitable catalysts include catalysts selected
from the group consisting of hydrotreatment catalysts;
hydrogenation catalysts; hydrocracking catalysts; and combinations
thereof.
[0032] In one embodiment the catalyst comprises a hydrotreatment
catalyst. Suitable examples include catalysts comprising one or
more of the elements from the group consisting of Ni, Co, Mo, and
W. Preferred are catalysts comprising Mo. More preferred are
catalysts comprising Mo and Ni or Co.
[0033] In a specific embodiment the hydrotreatment catalyst is in a
sulfided form. The catalyst may be converted to the sulfided form
by contacting it with a feedstock that has been spiked with a
sulfur-containing compound. The practice of sulfiding
hydrotreatment catalysts is well known in the world of oil
refining, and will not be further disclosed here.
[0034] As a general rule, hydrotreatment catalysts are more active
when in a sulfided form, as compared to an oxide form. However, the
use of sulfur results in consumption of hydrogen for the formation
of H.sub.2S. This is undesirable from a perspective of a loss of
valuable hydrogen, as well as from the resulting need to remove
H.sub.2S from the reaction mixture. Moreover, as lignocellulosic
feedstocks typically contain little or no sulfur, it is necessary
to spike the feedstock with sulfur in order to keep the catalyst in
its sulfided form.
[0035] In many cases it is economically more attractive to forego
sulfidization of the hydrotreatment catalyst, as the lower catalyst
activity is more than outweighed by the advantage of being able to
operate sulfur-free.
[0036] In an alternate embodiment the catalyst comprises a
hydrogenation catalyst. Examples include catalysts containing Ni,
Fe, or a metal from the Pt group in its metallic form. Particularly
preferred are the noble transition metals.
[0037] In yet another embodiment the catalyst comprises a
hydrocracking catalyst. For the purpose of the present invention
the term "hydrocracking catalyst" refers to catalysts containing
both a hydrogenation functionality and a cracking functionality.
The hydrogenation functionality is generally provided by one or
more of the typical hydrogenation metals (Ni, Fe, noble transition
metals). The cracking functionality is generally provided by acidic
sites in the catalyst material. Thus, a hydrogenation metal on a
solid acid support, such as an acidic zeolite, is typically a very
effective hydrocracking catalyst.
[0038] It should be recognized that many Ionic Liquids are strong
Lewis acids, and can act as acidic catalysts. Thus, the combination
of a hydrogenation catalyst in an Ionic Liquid medium that is a
strong Lewis acid can show strong hydrocracking properties.
[0039] The Ionic Liquid medium can comprise an organic anion. In
particular dicationic organic Ionic Liquids are excellent solvents
for cellulose and hemicellulose. Several organic Ionic Liquids have
been reported in the literature as being capable of (partially)
dissolving the lignin component of lignocellulosic materials.
Organic Ionic Liquids also have major disadvantages, the most
important ones being high cost, and limited temperature resistance.
Many have the additional disadvantage that they are poor solvents
for cellulose when contaminated with water.
[0040] Preferred Ionic Liquids are inorganic Ionic Liquids, in
particular inorganic molten salt hydrates. As compared to organic
Ionic Liquids, inorganic Ionic Liquids are more temperature stable,
and have a lower cost. In addition, in particular the inorganic
molten salt hydrates are effective solvents for cellulose even in
the presence of water. In fact, as their name indicates, a certain
amount of water needs to be present for these materials to function
as Ionic Liquid media.
[0041] Inorganic Ionic Liquids have an inorganic anion. The anion
can contain a halogen atom. Examples include halides, oxyhalides
and hydroxyhalides, in particular chloride, oxychlorides, and
hydroxychlorides. The anion can also be hydroxide; for example, the
hydroxide of the Cu/ammonia complex is a suitable Ionic Liquid
medium for use in the process of the present invention.
[0042] The molten salt hydrate further comprises a cation, in
particular Zn, Ba, Ca, Li, Al, Cr, Fe, or Cu.
[0043] Mixtures of inorganic salts can also be used, in particular
eutectic mixtures. In general, any salt or salt hydrate that is
liquid at a temperature of 200.degree. C. or below, and is capable
of dissolving cellulose, is suitable as the Ionic Liquid medium in
the process of the present invention.
[0044] Particularly preferred are the hydrates of ZnCl.sub.2, in
particular ZnCl.sub.2.4H.sub.2O.
[0045] If step (ii) comprises reaction with hydrogen
(hydrogenation, hydrotreatment or hydrocracking, this step is
preferably carried out at a hydrogen partial pressure in the range
of from 1 to 200 bar, more preferably from 5 to 60 bar. The
temperature used in step (iii) to obtain the desired conversion of
cellulose and/or sugars to hydrocarbons will depend on the amount
and type of catalyst used, and on the contact time between the
reactants and the catalyst. In general reaction temperatures in the
range of from 150 to 400.degree. C. are suitable, temperatures in
the range of from 180 to 350.degree. C. being preferred.
[0046] If step (ii) is carried out in the substantial absence of
hydrogen (thermal cracking, catalytic cracking), this step is
generally carried out at a temperature in the range of from
200.degree. C. to 600.degree. C., preferably from 200.degree. C. to
450.degree. C.
[0047] Even when step (ii) is carried out in the presence of
hydrogen, the reaction products obtained in step (ii) can still
contain residual oxygen. The main objective of step (ii) is to
convert cellulose, hemicellulose and their hydrolysis products
(C.sub.6 and C.sub.5 sugars, respectively) to reaction products
that do not dissolve in the Ionic Liquid medium.
[0048] In one embodiment the reaction products are a C.sub.6 and
C.sub.5 hydrocarbon mixture that is oxygen-free, or has an oxygen
content low enough for the mixture to be used as a blending stock
for gasoline.
[0049] In an alternate embodiment step (ii) is operated such that
the reaction products have oxygen content just low enough for them
to be insoluble in the Ionic Liquid medium, and miscible with a
refinery feedstock. The reaction products can be easily recovered
from the Ionic Liquid medium, due to their insolubility therein.
The reaction products can also easily be co-processed with a
refinery stream, due to their miscibility therewith.
[0050] In yet another embodiment step (ii) is operated to produce
primarily dry gas, in particular C.sub.2 and C.sub.3
hydrocarbons.
* * * * *