U.S. patent application number 13/521462 was filed with the patent office on 2013-05-23 for method of producing sugars using a combination of acids to selectively hydrolyze hemicellulosic and cellulosic materials.
This patent application is currently assigned to ARCHER DANIELS MIDLAND COMPANY. The applicant listed for this patent is Thomas P. Binder, Paul D. Bloom, Perry H. Doane, Chi-Cheng Ma. Invention is credited to Thomas P. Binder, Paul D. Bloom, Perry H. Doane, Chi-Cheng Ma.
Application Number | 20130130331 13/521462 |
Document ID | / |
Family ID | 44356034 |
Filed Date | 2013-05-23 |
United States Patent
Application |
20130130331 |
Kind Code |
A1 |
Binder; Thomas P. ; et
al. |
May 23, 2013 |
METHOD OF PRODUCING SUGARS USING A COMBINATION OF ACIDS TO
SELECTIVELY HYDROLYZE HEMICELLULOSIC AND CELLULOSIC MATERIALS
Abstract
A method is provided for producing sugars using a combination of
acids to hydrolyze hemicellulosic and cellulosic materials in
biomass, said combination of acids namely comprising a first, weak
organic acid (such as acetic acid or formic acid) for providing a
pentose product or stream from hydrolyzing hemicellulosic materials
in the biomass on a batchwise, semi-continuous or continuous basis,
and a second, strong mineral acid (such as sulfuric acid) for
providing a hexose product or stream from hydrolyzing cellulosic
materials in the biomass.
Inventors: |
Binder; Thomas P.; (Decatur,
IL) ; Bloom; Paul D.; (Decatur, IL) ; Doane;
Perry H.; (Decatur, IN) ; Ma; Chi-Cheng;
(Forsyth, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Binder; Thomas P.
Bloom; Paul D.
Doane; Perry H.
Ma; Chi-Cheng |
Decatur
Decatur
Decatur
Forsyth |
IL
IL
IN
IL |
US
US
US
US |
|
|
Assignee: |
ARCHER DANIELS MIDLAND
COMPANY
Decatur
IL
|
Family ID: |
44356034 |
Appl. No.: |
13/521462 |
Filed: |
January 18, 2011 |
PCT Filed: |
January 18, 2011 |
PCT NO: |
PCT/US11/21518 |
371 Date: |
July 11, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61300853 |
Feb 3, 2010 |
|
|
|
Current U.S.
Class: |
435/115 ; 127/37;
435/137; 435/139; 435/165 |
Current CPC
Class: |
C08B 30/12 20130101;
C08L 1/02 20130101; C13B 10/003 20130101; C08L 97/00 20130101; Y02E
50/16 20130101; Y02E 50/10 20130101; C12P 2203/00 20130101; C12P
7/10 20130101; A23V 2002/00 20130101; C13K 13/00 20130101; A23V
2002/00 20130101; A23V 2250/02 20130101; C08L 97/00 20130101; C08L
1/02 20130101; C08L 1/02 20130101; C08L 97/00 20130101 |
Class at
Publication: |
435/115 ;
435/165; 435/139; 127/37; 435/137 |
International
Class: |
C13K 13/00 20060101
C13K013/00 |
Claims
1. A method of processing a lignocellulosic biomass including
cellulose, hemicellulose and lignin fractions, comprising the steps
of: applying a weak organic acid to the biomass to at least partly
depolymerize the hemicellulosic and lignin materials in the
biomass; drying the weak-acid treated biomass to provide a
sufficiently high solids content material as to be pelletized;
pelletizing the material from the drying step; and shipping the
pelletized material to a second location; at the second location,
recovering a cellulosic solids product from the pelletized
material; and contacting the cellulosic solids so isolated with a
strong mineral acid to hydrolyze the same and provide a hexose
product or stream.
2. A method according to claim 1, wherein the cellulosic solids
product is recovered from the pelletized material by solvent
washing the pelletized material in one or more iterations with
filtration, whereby the at least partly depolymerized
hemicellulosic and lignin materials from the pelletized material
are separated together from the remaining cellulosic solids.
3. A method according to claim 2, further comprising, in one or
more iterations, washing the at least partly depolymerized
hemicellulosic and lignin materials with filtering to separate
water-insoluble lignin solids from water-soluble hemicellulosic
materials.
4. A method according to claim 1, wherein the at least partly
depolymerized hemicellulosic materials are first separated from the
pelletized material by water washing the pelletized material in one
or more iterations with filtration, and the lignins are
subsequently separated from the cellulosic solids product by a
separate solvent wash with filtration, also in one or more
iterations.
5. A method according to either of claim 3 or 4, comprising a
further acid hydrolysis step conducted on the at least partly
depolymerized hemicellulosic materials after the same have been
separated from the lignins and cellulosic solids product.
6. A method according to claim 5, further comprising fermenting the
product of the further acid hydrolysis of the hemicellulosic
materials to produce ethanol, lysine, threonine, lactic, gluconic
or other organic acids, or hydrogenating and hydrotreating the
product of the further acid hydrolysis step to yield a fuel
additive product for transportation fuels.
7. A method according to either of claim 3 or 4, wherein the
water-insoluble lignins are subjected to ozonolysis or exposure to
one or more other oxidants, or combusted as a fuel, or supplied to
a coking process for making a liquid hydrocarbon product and coke,
or fed to a gasifier for producing a synthesis gas.
8. A method according to claim 1, further comprising fermenting the
hexose product or stream to produce ethanol, lysine, threonine,
lactic, gluconic or other organic acids.
9. A method according to any of claims 1-8, wherein the
lignocellulosic biomass is characterized as having an
acid-detergent insoluble lignin content of 6 percent or greater by
weight, on a dry weight basis.
10. A method according to claim 9, wherein the lignocellulosic
biomass is comprised of one or more of a mature grass, grain crop
residue separately or contained in a grain silage, corn stover,
wheat straw, barley straw, miscanthus specie, switchgrass, bahia
grass, Sorghum specie, sugar cane bagasse, orchardgrass, reed
canarygrass and cotton gin trash.
11. A method according to claim 10, wherein the lignocellulosic
biomass processed comprises corn stover and corn fiber.
12. A method according to claim 11, wherein the lignocellulosic
biomass processed is ensiled whole plant corn, and wherein the
biomass is preprocessed before the weak organic acid is applied to
isolate and remove at least one component of the ensiled whole
plant corn.
13. A method according to claim 12, wherein corn oil is recovered
from the ensiled whole plant corn biomass before the same is
contacted with the weak organic acid.
14. A method according to claim 12, wherein the leaf fraction of
corn stover is isolated and removed mechanically from the ensiled
whole plant corn biomass before the same is contacted with the weak
organic acid.
15. A method according to claim 12, wherein one or more components
which are higher in sulfur, nitrogen or ash content are
mechanically isolated and removed from the ensiled whole plant corn
biomass is contacted with the weak organic acid.
16. A method according to any of claims 1-15, wherein the weak
organic acid is applied in the vapor phase at an elevated
temperature of 50 degrees Celsius or greater.
17. A method according to claim 16, wherein the weak organic acid
is acetic acid or formic acid, and the acid is applied at a
temperature of from 50 degrees Celsius to 160 degrees Celsius, a
pressure of from atmospheric pressure to 3.5 MPa, gauge, and for a
time period of 30 minutes and more.
18. A method according to any of claims 1-17, wherein the weak
organic acid or acids are applied to the lignocellulosic biomass at
a concentration of at least 50 percent of such acid or acids in
water.
19. A method according to claim 18, wherein the weak organic acid
or acids are applied to the biomass at a concentration of 70
percent or more of such acid or acids in water.
20. A method according to any of claims 1-19, wherein the weak
acid-treated biomass is dried to a moisture content of 10 percent
or less by weight.
21. A method according to claim 20, wherein the dried biomass is
pelletized without the addition of a further binder.
22. A method according to any of claims 1-21, wherein the weak acid
treatment, drying and pelletizing steps are applied at a plurality
of locations for shipment of pelletized material to a common second
location.
23. A method according to claim 22, wherein the plurality of sites
are on average a distance of 50 or more kilometers from the common
second location.
24. A method according to claim 23, wherein the plurality of sites
are on average a distance of 80 or more kilometers from the common
second location.
25. A method according to claim 20, wherein the weak acid
hydrolysis, drying and pelletizing steps are applied to produce a
pelletized material at a location that is at least 50 kilometers
from the second location.
26. A method according to claim 1, further comprising preprocessing
the biomass before contact with the weak organic acid to isolate
and remove at least one component of the biomass that is higher in
protein and suitable for use in or for an animal feed, or that has
a higher than desired sulfur, nitrogen or ash content.
27. A method of processing a lignocellulosic biomass including
cellulose, hemicellulose and lignin fractions, comprising the steps
of: applying a weak organic acid to the biomass to hydrolyze
hemicellulosic and lignin materials in the biomass; in one or more
iterations, washing the weak acid-treated material with a solvent
or solvent mixture and filtering to separate hemicellulosic and
lignin materials in the filtrate and cellulosic materials as a
solid residue; drying the solid residue to provide a sufficiently
high solids content material as to be pelletized; pelletizing the
material from the drying step; shipping the pelletized material to
a second location; and at the second location, contacting the
cellulosic materials so isolated with a strong mineral acid to
hydrolyze the same and provide a hexose product or stream.
28. A method of processing a lignocellulosic biomass including
cellulose, hemicellulose and lignin fractions, comprising the steps
of: applying a weak organic acid to the biomass to hydrolyze
hemicellulosic and lignin materials in the biomass; in one or more
iterations, washing the weak organic acid-treated material with a
solvent or solvent mixture and filtering to separate hemicellulosic
and lignin materials in the filtrate and cellulosic materials as a
solid residue; and contacting the cellulosic materials so isolated
with a strong mineral acid to hydrolyze the same and provide a
hexose product or stream.
29. A method according to either of claim 27 or 28, wherein the
weak organic acid is applied in the vapor phase at an elevated
temperature of 50 degrees Celsius and greater.
30. A method according to claim 29, wherein the weak organic acid
is acetic acid or formic acid, and the acid is applied at a
temperature of from 50 degrees Celsius to 160 degrees Celsius, a
pressure of from atmospheric pressure to 3.5 MPa, gauge, and for a
time period of 30 minutes and more.
31. A method according to claim 30, wherein the weak organic acid
or acids are applied to the lignocellulosic biomass at a
concentration of at least 50 percent of such acid or acids in
water.
32. A method according to claim 31, wherein the weak organic acid
or acids are applied to the biomass at a concentration of 70
percent or more of such acid or acids in water.
Description
[0001] This invention concerns an improved process for
accomplishing the hydrolysis of materials containing cellulose and
hemicellulose, and especially of lignocellulosic biomasses for
further use in the synthesis of chemicals or the preparation of
biobased fuels or fuel additives.
[0002] The use of biomass--of materials whose carbon content is of
biological rather than fossil origin--for providing chemicals and
fuel products presently derived from fossil-origin materials such
as petroleum, or for providing acceptable biobased, functional
alternatives to such chemicals and fuel products, has increasingly
become a focus of research and development investment and effort in
recent years as supplies of fossil-origin materials have been
compromised or been more difficult or expensive to acquire and
use.
[0003] Certain chemical and fuel product replacements or
alternatives are already produced on a large, commodity scale from
biomasses. For the liquid fuel products area, for instance, ethanol
and biodiesel (fatty acid alkyl esters) have heretofore been
produced on a commodity scale from corn or other grains and from
sugar cane (for ethanol) and from various vegetable oils and fats
(for biodiesel).
[0004] It has been long recognized, though, that it would be
preferable to be able to make suitable liquid fuels and fuel
additives from lignocellulosic biomasses containing typically 6
percent or more of acid detergent insoluble lignin (on a dry weight
basis) and which are not used as food products, or which can be
harvested or sourced and used without materially adversely
affecting land use patterns and behaviors (for example,
deforestation to produce additional soy, corn or like crops). A
number of non-food, lignocellulosic biomasses might be contemplated
of this character, including, for example, purpose-grown non-food
biomass crops (such as grasses, sweet sorghum, fast growing trees),
or more particularly wood wastes (such as prunings, wood chips,
sawdust) and green wastes (for instance leaves, grass clippings,
vegetable and fruit wastes). It has been estimated in addition as
to lands already under cultivation for food crops or other purposes
that about three quarters of the biomass generated is waste, so
that whether the biomass in question is waste in the production of
a food crop or some other crop to which land has been devoted in
cultivation or arises from sources unconnected to any cultivated
crop, it would seem with the abundance of lignocellulosic feeds
available that the various chemical and fuel products we require
that could be made starting with lignocellulosic biomasses, should
in fact be capable of being made economically.
[0005] Unfortunately, the truth of the matter is that there are a
number of practical, real-world difficulties that must be overcome
in order for this proposition to hold true. A first difficulty
arises from the very different characteristics of the various
components comprising lignocellulosic biomasses.
[0006] In this regard, as is true of fossil-based materials such as
petroleum, the practical, real-world capability of producing the
full range of commodity chemicals and fuel product replacements or
alternatives that are or will be needed, on the scale and with the
qualities, economy and efficiency that are needed, depends to an
extent on how effectively and efficiently the
feedstock--lignocellulosic biomass--can be fractionated into its
component parts and on how effectively and efficiently these
component parts can in turn be further processed to yield the
desired commodity chemicals and fuel product replacements or
alternatives.
[0007] With respect to the present invention, lignocellulosic
biomasses are comprised mainly of cellulose, hemicellulose and
lignin fractions, with cellulose being the largest of these three
components. Cellulose derives from the structural tissue of plants,
and consists of long chains of beta glucosidic residues linked
through the 1,4 positions. These linkages cause the cellulose to
have a high crystallinity and thus a low accessibility to the
enzymes or acid catalysts which have been suggested for hydrolyzing
the cellulose to C6 sugars or hexoses for further processing.
Hemicellulose by contrast is an amorphous heteropolymer which is
easily hydrolyzed, while lignin, an aromatic three-dimensional
polymer, is interspersed among the cellulose and hemicellulose
within a plant fiber cell and lends itself to still other process
options.
[0008] Parenthetically in regards to the lignin fraction, the
materials understood as encompassed within the term "lignin" and
the method by which lignin content has been correspondingly
quantified in a biomass have historically depended on the context
in which the lignin content has been considered, "lignin" lacking a
definite molecular structure and thus being determined empirically
from biomass to biomass. In animal science and agronomy, in
considering the digestible energy content of lignocellulosic
biomasses, for example, the amount of lignin in a given biomass has
more commonly been determined using an acid detergent lignin method
(Goering and Van Soest, Forage Fiber Analyses (Apparatus, Reagents,
Procedures, and Some Applications), Agriculture Handbook No. 379,
Agricultural Research Service, United States Dept of Agriculture
(1970); Van Soest et al., "Methods for Dietary Fiber, Neutral
Detergent Fiber, and Nonstarch Polysaccharides in Relation to
Animal Nutrition", J. Dairy Sci., vol. 74, pp 3583-3597 (1991)). In
the paper and pulp industry, by contrast, the amount of lignin in a
given biomass has been conventionally determined by the Klason
lignin method (Kirk and Obst, "Lignin Determination", Methods in
Enzymology, vol 16, pp.: 89-101 (1988)). For purposes of the
present invention, we are especially concerned with those
lignocellulosic biomasses having at least a lignin content
consistent with mature temperate grasses having relatively low
nutritive value for ruminants and which consequently are diverted
to other uses in the main, such grasses typically being
characterized by 6% or more of acid detergent insoluble materials
(on a dry weight basis).
[0009] Because of the differences in the cellulosic, hemicellulosic
and lignin fractions of biomass, as well as considering other
lesser fractions present in various biomasses to different degrees,
as related in U.S. Pat. No. 5,562,777 to Farone et al., "Method of
Producing Sugars Using Strong Acid Hydrolysis of Cellulosic and
Hemicellulosic Materials", a number of processes have been
developed or proposed over the years to fractionate lignocellulosic
biomasses and hydrolyze the cellulosic and hemicellulosic
fractions.
[0010] Fundamentally both biological and non-biological processes
have been disclosed, with the oldest and best known non-biological
methods of producing sugars from cellulose involving acid
hydrolysis, most commonly sulfuric acid-based hydrolysis using a
dilute acid approach, a concentrated acid approach or a combination
of the two. The '777 patent to Farone et al. describes the
advantages and disadvantages of the various sulfuric acid-based
processes then known to the art, and suggests a further variation
using strong acid/sulfuric acid hydrolysis and employing one or
more iterations of a combination of a decrystallization step
wherein the biomass (and/or including the solids left from the
decrystallization step in a previous iteration) is mixed with a
25-90 percent sulfuric acid solution to solubilize a portion of the
biomass, then the acid is diluted to between 20 and 30 percent and
the mixture heated to preferably between 80 and 100 degrees Celsius
for a time to solubilize the cellulosic fraction and any
hemicellulosic material that had not been hydrolyzed.
[0011] A further difficulty arises from the fact that, as mentioned
previously, it has been estimated that about three quarters of the
biomass generated on cultivated lands and grasslands is waste.
While these waste biomasses represent a vast potential resource for
the production of various biobased chemical and fuel products, the
means for making and distributing such chemical and fuel products
as an alternative to petroleum-based materials--as well as the end
use markets for such chemical and fuel products--are generally not
located where (or near where) the waste biomasses are produced or
generated. The same observation holds true of the purpose-grown,
non-food biomass crops that have been proposed or are being
considered. Consequently, one seeking to make use of the various
lignocellulosic biomasses available for making chemicals, fuels and
fuel alternatives or additives has heretofore been faced either
with constructing a number of smaller capacity, greenfield chemical
plants or refineries near where the biomasses are collected or
generated but remote from distribution channels and customers, with
constructing a number of processing facilities to process the
biomasses to an intermediate product or products (sugar syrup or
sugar alcohols, for example) and then shipping the intermediate
product or products to a further chemicals or fuels manufacturing
and/or refining facility located (in the main) closer to
distribution channels and customers, or with shipping the biomasses
from the places where these have been collected or generated to a
central facility wherein the biomasses will be processed from the
beginning.
[0012] With respect to the processing and associated
transportation/logistical/distribution and sales options just
mentioned, one difficulty inherent to the use of lignocellulosic
biomass feeds but not encountered with petroleum-based feedstocks,
derives from the fact that biomasses arise from living matter. For
example, one of the challenges to using corn stover as a biomass
feed, whether for producing ethanol by fermentation or other
chemicals, biobased fuels or fuel alternatives that can be made
starting from a corn stover feed (e.g., diols and polyols,
acrylates, hydroxymethylfurfural and other furanics, levulinates,
epichlorohydrin), has been determining how much of the stover
should be collected, as well as how it should be chopped, packaged
or bundled, stored and transported to provide a consistent biomass
feed with the right qualities; in this regard, as with any
transformative process, consistency of the feedstock is always a
concern, and as biomass is derived from living organisms the
quality of collected biomass is inherently somewhat changeable so
that proximity to storage, transport and processing facilities has
needed to be factored into biomass selection.
[0013] The present invention provides methods for processing
lignocellulosic biomasses in ways that can address and overcome
some or all of the above-mentioned difficulties. In particular, the
present invention concerns a method for producing sugars using a
combination of acids to hydrolyze hemicellulosic and cellulosic
materials in biomass, said combination of acids namely comprising a
first, weak organic acid (such as acetic acid or formic acid) for
providing a pentose product or stream from hydrolyzing
hemicellulosic materials in the biomass on a batchwise,
semi-continuous or continuous basis, and a second, strong mineral
acid (such as sulfuric acid) for providing a hexose product or
stream from hydrolyzing cellulosic materials in the biomass.
[0014] In a first aspect--after optionally preprocessing the
biomass to isolate a component higher in protein that may be
desirable for animal feed or fertilizer (by mechanically breaking
down the biomass and by air classification, as one example) and/or
to isolate a component or components which have a comparatively
high content of a species or material that will be more difficult
to remove downstream and that may interfere with or make intended
downstream conversions more difficult and/or may adversely affect
the contemplated products from further processing (for example,
nitrogen compounds, sulfur compounds, higher ash components)--the
first, weak organic acid is applied to the biomass, near a
collection point for the biomass, under conditions (for example, in
terms of acid concentrations, temperatures, pressures and residence
times) sufficient to depolymerize hemicellulosic materials and
solubilize lignins in the biomass. The "cooked" acidified biomass
is then dried to remove water therefrom to an extent whereby the
dried solids can be pelletized for shipment to a central facility.
Then, at the central facility, pelletized, weak acid-processed
biomass is washed with a solvent or solvent mixture which is
effective for separating the solubilized and depolymerized
hemicelluloses and lignins from a cellulosic fraction of the
biomass, and then the cellulosic fraction is contacted with the
second, strong mineral acid (or acids) under conditions suited to
providing a hexose product or stream. Preferably, the first, weak
organic acid is applied to the biomass in a vapor form at elevated
temperatures, in part to reduce the drying load prior to the
pelletization step.
[0015] In a related, second aspect, the first, weak organic
acid--which will be understood in common with references to the
second, strong mineral acid to embrace both a single acid so
characterized as well as combinations of acids so characterized--is
applied to the biomass (or that portion of the biomass left after
optionally preprocessing the biomass as a whole, as described
above) under suitable conditions for hydrolyzing hemicellulosic
materials in the biomass, and then the weak acid-processed biomass
is washed with a solvent or solvent mixture to separate the pentose
product or stream (from hydrolyzing the hemicellulosic materials in
the biomass) from a remaining predominantly cellulosic solids
fraction. The cellulosic solids fraction is then dried, pelletized
and shipped to a central location for further processing with the
second, strong mineral acid, while solubilized hemicellulosic
materials and lignins are retained and optionally further processed
at the first site, near a collection point for the biomass.
Generally, this further processing will include at least a water
wash, to effect a separation of water-insoluble lignins as a solids
residue from the pentose product or stream resulting from
hydrolysis of hemicellulosic materials in the biomass. It is also
understood that pending local market conditions the "cooked"
acidified biomass or cellulosic solids could be made available as a
feed ingredient.
[0016] In a related, further aspect, the first, weak organic acid
is applied to the biomass (or to the remainder after optional
preprocessing of the biomass, again), but then the weak
acid-processed biomass is washed with a solvent or solvent mixture
to separate the solubilized hemicellulosic materials and lignins
from a predominantly cellulosic solids fraction, followed by
contacting the cellulosic solids fraction with a strong mineral
acid or acids, with the weak acid and strong acid hydrolyses
occurring at the same location. Preferably, the first, weak organic
acid is again applied to the biomass in a hot vapor form.
[0017] Dependent on conventional siting considerations such as the
logistics involved in moving either collected biomass to a central
processing facility or for getting derivative products to the
markets and customers served by those products, access to
utilities, labor and other process inputs etc., those skilled in
the art will appreciate that in this last general conception of the
inventive process the location in question may ideally be near a
grouping of collection points for the biomass, or may more
preferably be at a central location relative to the biomass sources
to be drawn upon for the facility and convenient to the markets and
customers to be served by the facility.
[0018] FIG. 1 is a schematic drawing illustrating a process
according to the present invention, according to the first
aspect.
[0019] FIG. 2 is a schematic drawing illustrating a process
according to the present invention, according to the second
aspect.
[0020] FIG. 3 is a schematic drawing illustrating a process
according to the present invention, according to the further aspect
described above.
[0021] The present, combined acids process for producing sugars by
hydrolyzing hemicellulosic and cellulosic materials in
lignocellulosic biomass is more readily understood by reference to
the accompanying drawings, by which the present invention is shown
in a first aspect or general embodiment 100 (FIG. 1), in a second
aspect or general embodiment 200 (FIG. 2), and in a still further
aspect or general embodiment 300 (FIG. 3).
[0022] Turning first to FIG. 1, a lignocellulosic biomass, in a
preferred embodiment containing typically 6 percent or more of acid
detergent insoluble lignin and preferably not having any
substantial alternative use in or for making human food products,
is initially collected in step 102 at a convenient location (Site
A) close to where the biomass is grown or produced.
[0023] Mixtures of biomasses from various sources, including
biomasses from the harvesting and processing of food crops, are
obviously contemplated as well and should be considered as
encompassed by the use of the singular "a lignocellulosic biomass".
Where several different biomasses are employed from various
sources, preferably a purpose-grown non-food biomass or an
agricultural waste biomass comprises the largest fraction of those
several biomasses in the mixture. An example of a mixed biomass
feed would be comprised of corn stover and corn fiber, with
preferably corn stover comprising a greater proportion of the feed
than the corn fiber. As well, a mixed biomass feed may simply be
whole plant silage, for example, whole plant corn harvested and
stored largely anaerobically, `ensiled` to form silage, as most
facilities for making renewable source-based chemicals, fuels and
fuel additives will require year-round access to the biomass or
biomass-based feeds to those facilities, in the same manner as
facilities relying on petroleum-dependent feeds, and silage
represents much more of a "known commodity" for the operator of
such facilities than other processed biomasses.
[0024] The present invention in embodiment 100 fundamentally
partially processes (at Site A) the biomass collected in step 102,
in order to place the material in a condition to be more
economically transported from Site A, a convenient location close
to where the biomass is grown or produced, to a central processing
facility ("Central Facility") located typically closer to means for
making and distributing the desired biobased chemical and fuel
products and closer to the customers who would ultimately purchase
these chemical and fuel products. Conventionally it is expected
that a Site A and the Central Facility will be 50 or more
kilometers (30 miles or more) from one another, and for a number of
Sites A to be on average at least the same distance removed from a
Central Facility. Often, the Sites A will be on average 80 km (50
miles) or more removed from a Central Facility.
[0025] Obviously it may also be possible that the Central Facility
and Site A are much closer geographically, for example, where the
means for making a desired biobased chemical or fuel are already in
place near a Site A--or where Site A is near a source of demand so
that the embodiment of FIG. 3 would ordinarily be preferred, but
considerations specific to Site A (for example, zoning and
permitting considerations or space limitations) prevent the
embodiment of FIG. 3 from being implemented.
[0026] Returning now to FIG. 1, as an initial step in the process
100, biomass is collected and washed as necessary to remove dirt
and other contaminants. The materials are then optionally dried,
preferably to a moisture content of 10% or less. The biomass is
then comminuted by any of a number of means, including without
limitation by grinding, chopping and hammermilling. Depending on
the biomass and on the intended downstream processing and slate of
products to be produced from the various cellulosic, hemicellulosic
and lignin fractions of the biomass, included preprocessing of the
biomass may include separating out and recovering (through air
classification or other known separatory methods) a higher protein
portion of the biomass for use in animal feed and fertilizer, for
example, the leaf fraction from corn stover has a greater content
of nitrogen and the approximate nutritional value of hay. For a
mixed biomass such as whole grain corn silage, preprocessing of the
biomass may involve recovery of corn oil from the grain as an
additional valued co-product.
[0027] Alternatively or additionally, and again dependent on the
biomass and on the intended downstream processing and slate of
products to be produced from the various cellulosic, hemicellulosic
and lignin fractions of the biomass, the biomass can be
preprocessed to separate out and remove portions of the whole
biomass which have a comparatively high content of a species or
material that will be more difficult to remove downstream and that
may interfere with or make intended downstream conversions more
difficult and/or may adversely affect the contemplated products
from further processing. For example, a number of useful chemicals
have been suggested as derivable from the pentose and/or hexose
products through various catalytic transformations, and portions of
the biomass may contain materials (or precursors of such materials)
that would tend to deactivate a contemplated catalyst, through
coking, polymerization, blocking active sites on the catalyst or
other mechanisms. As well, as suggested above an intended product
from the processing of the biomass may be an animal feed, and the
nitrates in a lignocellulosic biomass--if more highly concentrated
in a portion of the biomass that can be separated out and removed
prior to further processing--would be desirably removed by
preprocessing the whole biomass.
[0028] The collected or preprocessed biomass is then contacted with
weak, organic acid to at least partly solubilize/depolymerize
hemicellulosic materials and preferably some of the lignins in the
biomass as well in weak acid step 104. Preferred acids include
formic acid, malic acid, acetic acid, succinic acid and propionic
acid, with formic and acetic acids being more preferred. Preferably
the weak acid(s) are applied to the biomass in a hot vapor form to
minimize water removal requirements in the subsequent drying step
106.
[0029] We have found that a weak acid solution of 50 percent or
more in water can, with sufficient heating, be sufficient to
depolymerize the hemicellulosic and lignin materials in the biomass
to an extent whereby the partly depolymerized materials can serve
as a binder, in effect, in the subsequent pelletization or
densification step. Preferably, no additional binders are required
to achieve pellets having the desired durability as further
discussed below.
[0030] The weak acid can thus be applied in a preferred embodiment
in the form of a hot vapor of from 50 percent acid and greater, but
more preferably is applied as a concentrated vapor containing from
70 percent acid up to in excess of 90 percent acid, at a
temperature of from 50 degrees Celsius to 160 degrees Celsius, a
pressure of from atmospheric pressure to 3.5 MPa, gauge (500 psig),
and for a residence time of at least about thirty minutes, to break
down the hemicellulosic fraction and at least some of the lignins
in the biomass as much as possible without compromising the
durability of the subsequently-formed pellets to an undue extent
whereby significant amounts of a binder must be added.
[0031] The weak acid-processed biomass then undergoes a drying or
dewatering step 106 to remove sufficient moisture for allowing the
dried biomass to be pelletized in step 108. The drying/dewatering
step 106 can be accomplished by a number of conventional devices or
combinations of such devices for concentrating an aqueous slurry
and removing water therefrom to a level suited for pelletization of
the remaining solids, for example, centrifuges, hydroclones, belt
filter press driers, fluid bed driers, indirect or direct rotary
drum driers, spin flash driers and the like. Preferably, the
biomass leaving the drying step 106 will have a moisture content of
10 percent by weight or less, more preferably 8 percent or less by
weight and most preferably 6 percent or less by weight to
facilitate its pelletization and reduce transportation costs.
[0032] Pelletization of the solids leaving drying step 106 can be
accomplished in step 108 using methods and equipment conventionally
known to those skilled in the art, as pelletization of animal feeds
and of woody biomass for fuels has become well-established, and
will preferably result in a material with sufficient cohesiveness
and integrity to withstand transport pneumatically or by conveyor
belts/systems, by truck, ship or rail, or by some other means or
combination of means for conveying a material from Site A to the
Central Facility. For convenience, the transport of the pelletized
material from Site A to a second location will be described in the
claims below and elsewhere herein as "shipping" the material from a
local Site A to a second location, and the use of "shipping" is not
intended to be limited to ships, planes, trains or trucks or like
means of vehicular transport but should be understood as inclusive
of any manner in which such pelletized materials may be moved from
a Site A to a second location.
[0033] In this regard, the pelletized material's needed
durability--principally meaning the pellet does not produce an
excessive quantity of fines in handling, transport and
storage--will depend more particularly on how the material is
handled, transported and stored at a given Site A, between Site A
and a given Central Facility, and at the Central Facility. As well,
there are several devices and related methods which have been
developed for assessing pellet durability, so that precise
numerical values for durability may not reasonably be assigned a
priori. Preferably, however, whether by the manner in which the
pelletized material is processed or by virtue of binders added to
the material or both, the pelletized, partially processed biomass
will be sufficiently durable so as not to experience more than five
percent loss of mass by dusting or fines formation from the
completion of the pelletizing step 108 to the start of solvent
washing at the Central Facility, and preferably not more than three
percent of the pelletized, partially processed biomass will be lost
as fines in this transition.
[0034] The pelletized, partially processed biomass is then
conveniently shipped to the central facility for further
processing, which includes at least washing with a solvent or
combination of solvents in step 110, the solvent or solvents being
selected to effectively separate the at least partly depolymerized
hemicellulosic materials in a product or stream 112 containing
pentoses from the hydrolysis of hemicellulosic materials in the
biomass, and a cellulosic solids fraction 114. The solvent wash
step 110 can optionally comprise several iterations of washing and
filtration, as desired.
[0035] Optionally, an additional solvent wash step 116 (in one or
more iterations of washing and filtration) is employed along with
the solvent wash step 110 to separate out the lignins fraction 118
of the biomass. The manner in which steps 110 and 116 are performed
will depend on how the biomass has been processed at Site A, but in
all cases will be conducted so as to provide a clean cellulosic
pulp product or stream 114 which can then by hydrolyzed by exposure
to the strong mineral acid in step 124 to yield a hexose product or
stream 122.
[0036] For example, while application at a Site A of a hot, 50
percent solution of acetic acid in water, for example, is
sufficient as discussed above for at least partly depolymerizing
the hemicelluloses and lignins in the biomass so that the material
can be pelletized and transported efficiently, the lignins in the
biomass will largely not be soluble in a 50 percent solution. For
step 110, a preferred approach would be to use hot water to
separate the at least partly depolymerized hemicelluloses and
soluble salts from the cellulosic solids fraction 114 which would
also contain the water-insoluble lignins. The solvent wash step 116
would then be performed on the fraction 114 to solubilize and
separate out the lignins in stream 118 and yield a material in
product or stream 114 which can be acid hydrolyzed with a strong,
mineral acid, a useful solvent for this purpose being a more
concentrated organic acid solution applied at the requisite
temperature to solubilize the lignins and separate the same from
the remaining cellulosic fraction.
[0037] In an alternative embodiment wherein a more concentrated
(e.g., 70 percent acid and greater versus 50 percent) weak organic
acid is employed at a Site A, however, the clean cellulosic pulp
114 can be recovered in step 110 without the necessity of a further
solvent wash step 116. Ethyl lactate has been found to be an
effective solvent for use in step 110 in this embodiment. Other
effective solvents include tetrahydrofuran, 2-methyl
tetrahydrofuran, ethyl formate and ethyl acetate. The optional
further solvent wash step 116 in this embodiment would be used to
separate the lignins fraction 118, preferably involving washing
simply with hot water to recover the water-insoluble lignins in
stream 118.
[0038] Cellulosic solids fraction 114 recovered or fractionated out
in this manner is then converted to a hexose product or
substantially hexose stream 122 through conventional strong,
mineral acid hydrolysis 124 under conditions suited to carry out
this conversion. The hexose product or stream produced by the
present invention in its several embodiments (as stream 122 in FIG.
1, stream 220 in FIG. 2 and stream 314 in FIG. 3) will preferably
be comprised substantially entirely of C6 monosaccharides, and of a
character suited for upgrading to desired biobased chemical and
fuel products with minimal further preprocessing or cleanup.
Exemplary biobased chemical and fuel products which have been
suggested as derivable from the C6 monosaccharides include fuel
additive products through hydrogenation and hydrotreating, or
ethanol, lysine, threonine, lactic, gluconic or other organic acids
through fermentation.
[0039] Likewise, the pentose product or stream produced by the
present invention in its several embodiments (as stream 112/120 in
FIG. 1, stream 208 in FIG. 2, stream 316 in FIG. 3) will preferably
be comprised substantially entirely of C5 monosaccharides, and of a
character suited for upgrading to those biobased chemical and fuel
products which are derivable from such C5 monosaccharides, for
example, ethanol, threonine, lysine, lactic, gluconic or other
organic acids by fermentation, furfural, furfuryl alcohol, methyl
tetrahydrofurfural, furfurylic acid and fuel additives generally by
hydrogenation and hydrotreating.
[0040] A preferred strong, mineral acid for step 124 is sulfuric
acid, applied as a 1 to 80, and preferably from 40 to 80, percent
concentration aqueous sulfuric acid solution, at a temperature of
from 25 degrees Celsius to 100 degrees Celsius, a pressure of from
atmospheric pressure up to 0.7 MPa, gauge (100 psig), and a
residence time of 15 minutes to 2 hours dependent primarily on the
temperature conditions used.
[0041] The lignins fraction (as stream 118 in FIG. 1, stream 212 in
FIG. 2 and stream 318 in FIG. 3) can in like manner be put to
practical further use, for example, ozonolysis to an aromatic fuel
additive based, for example, on the teachings of United States
Published Patent Application No. 2009/0718498A1, as a gasification
feed for producing synthesis gas, as a combustion fuel, or
ozonolysis to produce an aromatic sulfonation feed for producing
biobased linear alkylbenzene sulfonates.
[0042] Turning now to FIG. 2, an alternate embodiment 200 is shown
schematically. In the embodiment 200, only the cellulosic fraction
from the biomass is collected in solid form and pelletized for
shipment and processing at a central facility to produce a hexose
product or stream, while the hemicellulosic and lignin fractions
are hydrolyzed at a first site, Site A, that is preferably
convenient to where the biomass has been produced or grown. It is
expected that the alternate embodiment 200 would be advantageous
where the biomass has a comparatively high lignin content but no
ready outlet for the products to be made from the cellulosic or
lignin fractions.
[0043] More particularly, in the general embodiment 200
lignocellulosic biomass is collected and prepared for subsequent
weak acid hydrolysis in step 202, in the same manner as described
above for step 102 of embodiment 100. The collected and
preprocessed biomass then undergoes a weak acid hydrolysis step
204, again preferably corresponding to the weak acid hydrolysis
step 104 of embodiment 100. The weak acid hydrolyzed biomass,
comprising at least partly depolymerized lignins and hemicellulosic
materials and a cellulosic solids fraction, is in one or more
iterations solvent washed and filtered in a solvent wash step 206,
just as in the solvent wash step 110 described above for embodiment
100. A pentose product or stream 208 ("product" being understood
herein as contemplative of a batchwise or generally discontinuous
mode of operation, and "stream" being conventionally understood as
referencing a continuous mode of operation) from the weak acid
hydrolysis of hemicelluloses in the biomass is then optionally
washed in step 210 in one or more iterations of washing and
filtering, to produce a solid lignin product or stream 212 and a
liquid pentose product or stream 214.
[0044] Concurrently, the cellulosic solids from the solvent wash
step 206 are dried in a drying step 216, to remove moisture from
the solids prior to their being pelletized in step 218 for shipment
to a second venue--denominated a "Central Facility" in FIG. 2.
Drying step 216 and pelletizing step 218 will for embodiment 200
generally be carried out as described above for drying step 106 and
pelletizing step 108 of FIG. 1.
[0045] At the "Central Facility", preferably being located near a
significant source of demand for a hexose product or stream 220 to
be produced from the pelletized cellulosic solids from step 218,
these same pelletized cellulosic solids from step 218 at a given
Site A will preferably be combined with pelletized cellulosic
solids from steps 218 at other localized Site A's and hydrolyzed in
a strong, mineral acid hydrolysis step 222. Strong, mineral acid
hydrolysis step 222 in embodiment 200 will preferably be as
described above for embodiment 100, for step 124.
[0046] Turning now to FIG. 3, a third general embodiment 300 is
schematically illustrated and may be briefly described as
comprising the same basic biomass collection and preprocessing,
weak acid hydrolysis, solvent washing, optional water washing and
strong acid hydrolysis steps performed in common with embodiments
100 and 200, but, for example, omitting the drying and
pelletization steps from embodiment 200, as the embodiment 300 is
contemplated for practice at a given, localized site, ideally near
where the biomass to be processed is grown or produced. Thus, the
biomass is collected and preprocessed in a collection step 302,
then undergoes a weak acid hydrolysis step 304 followed by a
solvent wash and filtration process 306 for substantially
separating the solid cellulosic fraction 308 from the
solubilized/hydrolyzed hemicellulosic and lignin fractions 310. The
cellulosic solids 308 are in turn hydrolyzed in a strong acid
hydrolysis step 312 to yield a hexose product or stream 314, while
the water-soluble pentoses and water-insoluble lignins are
optionally separated and recovered as products (or streams) 316 and
318 through a wash step 320 performed on the stream 310.
[0047] Embodiment 300 is thus advantageously employed where the
biomass to be processed is grown or produced near a source of
demand for the pentoses and/or hexoses to be produced therefrom,
for example, for making biobased chemicals, fuels and/or fuel
additives. As an example, sugar cane--and the bagasse left in its
processing to make cane sugar and related products--is grown
extensively in the Mississippi River petrochemical processing
corridor between Baton Rouge and New Orleans, La. Those skilled in
the art will appreciate that because of the variety of
lignocellulosic biomasses that can be processed according to the
present invention, numerous other similar examples can be
considered wherein a sufficient supply of a suitable biomass exists
near a source of demand for the pentoses and/or hexoses. In
economies with well-developed chemical and fuel industries located
near large population centers, opportunities for making use of the
embodiment 300 (as opposed to the embodiments 100 and 200) may be
relatively more limited, while for economies with developed or
developing chemical and fuel industries and fewer large population
centers--or wherein the chemical and fuel industries have developed
away from large population centers and nearer agrarian areas--the
embodiment 300 may be preferred. In any event, those skilled in the
art will be well able to determine which of the three embodiments
described herein is to be preferred in a particular set of
circumstances.
[0048] The embodiments 100, 200 and 300 may comprise additional
steps as well, of course. It will typically be desirable, for
instance, to include acid recovery and recycle for recovering and
recycling for reuse either or both of the weak, organic acid(s) and
the strong, mineral acid(s), and those skilled in the art will be
well able to select and employ suitable means for accomplishing the
separation of the acid(s) from the sugar streams in the inventive
process. Acetic acid when used as the weak acid can be recovered by
simple distillation, whereas formic acid forms an azeotrope with
water and so requires azeotropic distillation methods when formic
acid is applied as in the pulping art, as a concentrated aqueous
liquid solution. Where the formic acid, however, is applied as a
very concentrated vapor with small amounts of steam, the formic
acid can be recovered, recycled and reused in concentrated form
without the need of separating out the included water through
simple distillation, preferably employing ethyl formate as an
entrainer. Various methods for recovering and reusing the strong
mineral acid, sulfuric acid, are described in U.S. Pat. No.
5,562,777 to Farone et al. Alternatively, either or both of the
weak, organic acid(s) and strong, mineral acid(s) may be simply
neutralized. In the application of weak, organic acid(s) in a
concentrated vapor phase, in particular, the amount of such acid
employed may be insufficient to justify the expense of recovery and
recycle, so that neutralization may be preferred.
[0049] A further refinement to simplify recovery of the acid used
in the weak acid hydrolysis step in each of the embodiments 100,
200 and 300 would involve preparing the biomass leading into the
weak acid hydrolysis step as an aqueous slurry, and providing the
weak acid in a solid form that can be recovered by filtration. A
zeolite would be exemplary of the types of acidic solids that could
be used.
[0050] Those skilled in the art will appreciate that while
preferred embodiments of the invention have been described herein,
numerous variations and alternatives can in like manner be
conceived. For example, an enzymatic hydrolysis can be employed in
addition to or alongside the referenced acid hydrolyses to improve
the efficiency of the fractionation of certain biomasses. Where
silage is used for the biomass, anaerobic fermentation of the
silage feed itself over a period of time produces lactic acid, and
this lactic acid can be used as a weak organic acid for the initial
hydrolysis either alone or in combination with weak organic acids
from other sources. Still other variations will be evident to those
skilled in the art, which do not depart from the true scope of the
present invention, as expressed in the claims that follow.
* * * * *