U.S. patent application number 13/391720 was filed with the patent office on 2012-12-06 for temperature-optimized conversion of lignocellulosic biomass.
This patent application is currently assigned to KiOR, Inc.. Invention is credited to Paul O'Connor, Jacobus Cornelis Rasser.
Application Number | 20120304529 13/391720 |
Document ID | / |
Family ID | 43466376 |
Filed Date | 2012-12-06 |
United States Patent
Application |
20120304529 |
Kind Code |
A1 |
O'Connor; Paul ; et
al. |
December 6, 2012 |
Temperature-Optimized Conversion of Lignocellulosic Biomass
Abstract
A process is disclosed for converting lignocellulosic material
to liquid fuels. In the process the cellulose is dissolved in an
Ionic Liquid. The conversion process may comprise pyrolysis,
thermal cracking, hydrocracking, catalytic cracking,
hydrotreatment, or a combination thereof. Undissolved lignin is
removed from the Ionic Liquid medium, and is converted in a
separate conversion process. The Ionic Liquid preferably is an
inorganic molten salt hydrate.
Inventors: |
O'Connor; Paul; (Hoevelaken,
NL) ; Rasser; Jacobus Cornelis; (Redondo Beach,
CA) |
Assignee: |
KiOR, Inc.
Pasadena
CA
|
Family ID: |
43466376 |
Appl. No.: |
13/391720 |
Filed: |
September 1, 2010 |
PCT Filed: |
September 1, 2010 |
PCT NO: |
PCT/US2010/047507 |
371 Date: |
August 17, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61238728 |
Sep 1, 2009 |
|
|
|
Current U.S.
Class: |
44/307 |
Current CPC
Class: |
C10G 1/04 20130101; C10G
2300/4006 20130101; B01J 29/084 20130101; C10G 2300/1014 20130101;
C10G 2300/44 20130101; C10G 1/02 20130101; C08H 8/00 20130101; C08B
1/003 20130101; B01J 29/40 20130101; B01J 23/007 20130101; C10G
2400/02 20130101; C10G 3/42 20130101; C10G 1/08 20130101; C10G
45/04 20130101; C10G 1/086 20130101; B01J 21/16 20130101; C10G 3/49
20130101; C10G 45/02 20130101; C10G 2400/26 20130101; Y02P 30/20
20151101; C10G 3/57 20130101 |
Class at
Publication: |
44/307 |
International
Class: |
C10L 1/00 20060101
C10L001/00 |
Claims
1. A process for converting lignocellulosic biomass material to a
liquid fuel, said process comprising the steps of: (i) contacting
the lignocellulosic biomass material with an Ionic Liquid to form a
solution of at least part of the cellulose component of the biomass
material; (ii) separating undissolved lignin from the cellulose
solution; (iii) converting the dissolved cellulose material to a
liquid fuel at a first temperature T.sub.1; and (iv) converting the
undissolved lignin to a liquid fuel at a second temperature
T.sub.2; wherein T.sub.1<T.sub.2.
2. The process of claim 1 wherein T.sub.2-T.sub.1 is at least
50.degree. C., at least 100.degree. C., or at least 200.degree.
C.
3. (canceled)
4. (canceled)
5. The process of claim 1 wherein T.sub.1 is less than 200.degree.
C.
6. The process of claim 1 wherein T.sub.2 is 200.degree. C. or
above.
7. The process of claim 1 wherein step (iii) is carried out in the
presence of a catalyst, or wherein step (iv) is carried out in the
presence of a catalyst or wherein steps (iii) and (iv) are carried
out in the presence of a catalyst.
8. (canceled)
9. The process of claim 7 wherein step (iv) is carried out in a
cyclone reactor, a fixed fluidized bed reactor, or a transported
fluidized bed reactor.
10. The process of claim 7 the catalyst in step (iv) acts as a heat
transfer medium.
11. The process of claim 7 wherein the catalyst in step (iv)
comprises a solid acid.
12. The process of claim 11 wherein the catalyst comprises a
zeolite.
13. The process of claim 12 wherein the zeolite comprises zeolite
Y, ZSM-5, or a combination thereof.
14. The process of claim 7 wherein the catalyst of step (iv)
comprises a solid base, hydrotalcite, a hydrotalcite-like material,
a mixed metal oxide, a layered hydroxy salt, a clay, or a
calcination product thereof.
15. (canceled)
16. The process of claim 7 wherein the catalyst in step (iv)
comprises alumina.
17. The process of claim 7 wherein the catalyst in step (iv) is
mixed with a particulate inert heat transfer medium.
18. The process of claim 7 wherein step (iv) is carried out at a
temperature in the range of from 300.degree. C. to 600.degree.
C.
19. The process of claim 1 wherein the liquid fuel produced in step
(iii) is insoluble in the Ionic Liquid.
20. The process of claim 1 wherein the Ionic Liquid comprises an
organic cation or molten salt hydrate.
21. (canceled)
22. The process of claim 21 wherein the molten sat hydrate
comprises a halogen anion.
23. (canceled)
24. The process of claim 20 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.
25. The process of claim 20 wherein the Ionic Liquid is a molten
salt hydrate comprising ZnCl.sub.2, CaCl.sub.2, LiCl, or a mixture
thereof.
26. The process of claim 1 comprising the further step of upgrading
the liquid fuel obtained in step (iii) and/or (iv).
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. 61/238,728,
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
lignocellulosic biomass, and more particularly to such a conversion
process comprising use of an Ionic Liquid medium.
[0004] 2. Description of the Related Art
[0005] Several processes have been proposed for converting
lignocellulose 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 lignocellulosic
biomass is converted to liquid fuels at a high yield. There is a
particular need for such a process in which cellulose and lignin
are each converted at a feedstock-specific conversion temperature.
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 lignocellulosic biomass material to a
liquid fuel, said process comprising the steps of: [0011] (i)
contacting the lignocellulosic biomass material with an Ionic
Liquid to form a solution of at least part of the cellulose
component of the biomass material; [0012] (ii) separating
undissolved lignin from the cellulose solution; [0013] (iii)
converting the dissolved cellulose material to a liquid fuel at a
first temperature T.sub.1; [0014] (iv) converting the undissolved
lignin to a liquid fuel at a second temperature T.sub.2; [0015]
wherein T.sub.1<T.sub.2.
DETAILED DESCRIPTION OF THE INVENTION
[0016] The present invention relates to a process for converting
lignocellulosic biomass material to a liquid fuel, said process
comprising the steps of: [0017] (i) contacting the lignocellulosic
biomass material with an Ionic Liquid to form a solution of at
least part of the cellulose component of the biomass material;
[0018] (ii) separating undissolved lignin from the cellulose
solution; [0019] (iii) converting the dissolved cellulose material
to a liquid fuel at a first temperature T.sub.1; [0020] (iv)
converting the undissolved lignin to a liquid fuel at a second
temperature T.sub.2; [0021] wherein T.sub.1<T.sub.2.
[0022] Any lignocellulosic material can be used in the process of
the invention. Preferred are lignocellulosic biomass materials, in
particular forestry waste materials (wood chips, saw dust; tree
bark; leaves); agricultural waste materials (straw; bagasse; corn
stover; and the like); and energy crops (switch grass; coppice;
fast-growing trees, such as eucalyptus, willow, poplar).
[0023] Lignin is insoluble in certain Ionic Liquid media, and
partially soluble in others. It is an essential part of the process
that undissolved lignin is removed from the Ionic Liquid in step
(ii). Dissolved lignin is at least partially converted to
hydrocarbon compounds during step (iii). The mixture of hydrocarbon
compounds is more complex as a result when lignin is present in the
Ionic Liquid medium during step (iii). This can provide a distinct
advantage. 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.
[0024] 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 unlock 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. Accordingly, the process of
the present invention permits separate processing of the cellulose
(and hemicellulose) components of a lignocellulosic biomass
material, on the one hand, and the lignin component on the
other.
[0025] Many sources of lignocellulosic 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 (iii). Inorganic materials that are dissolved in the
Ionic Liquid medium can be removed in a regeneration step, for
example using solvent extraction.
[0026] 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.
[0027] An important aspect of the process of the present invention
is that the (hemi-)cellulose and cellulose component of the
lignocellulosic biomass material are converted at one temperature,
T.sub.1, whereas the lignin component is converted at a different
temperature, T.sub.2. Generally, the (hemi-)cellulose conversion is
carried out at a lower temperature than the lignin conversion. In
other words, T.sub.1<T.sub.2.
[0028] Preferably T.sub.2 is at least 50.degree. C. higher than
T.sub.1, more preferably at least 100.degree. C.; most preferably
at least 200.degree. C.
[0029] The conversion of the (hemi-)cellulose component takes place
in solution, which permits the use of low conversion temperatures.
Preferably, T.sub.1 is less than 200.degree. C.
[0030] The conversion of solid lignin generally requires a
temperature greater than 200.degree. C., preferably in the range of
from 300.degree. C. to 600.degree. C.
[0031] Step (iii) 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.
[0032] It can be advantageous to carry out step (iii) 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.
[0033] Examples of suitable catalysts include catalysts selected
from the group consisting of hydrotreatment catalysts;
hydrogenation catalysts; hydrocracking catalysts; and combinations
thereof.
[0034] 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.
[0035] 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.
[0036] 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.
[0037] 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.
[0038] 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.
[0039] 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.
[0040] 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.
[0041] 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.
[0042] Step (iv) can, for example, be carried out in a cyclone
reactor, a fixed fluidized bed reactor, or a transported fluidized
bed reactor.
[0043] The process of step (iv) can be carried out in the absence
of a catalyst, for example a pyrolytic conversion or a thermal
cracking process.
[0044] Preferably step (iv) is carried out in the presence of a
catalyst, for example a hydrocracking, catalyst, a cracking
catalyst, or a hydrotreatment catalyst. The catalyst can be used as
a heat transfer medium to apply heat to the endothermic conversion
reaction.
[0045] In one embodiment the catalyst in step (iv) comprises a
solid acid. Examples of suitable solid acids include acidic
zeolites, such as zeolite-Y, ZSM-5 (in particular HZSM-5), and
combinations thereof.
[0046] In an alternate embodiment the catalyst comprises a solid
base.
[0047] Examples of suitable solid base materials include
hydrotalcite; hydrotalcite-like materials; mixed metal oxides;
layered hydroxy salts; clays; and the calcination products of any
of these materials.
[0048] The catalyst can comprise alumina.
[0049] The catalyst can be mixed with an inert heat transfer
medium, such as silica sand. Mixing the catalyst with an inert heat
transfer medium permits independent adjustment of the
lignin/catalyst ratio and the lignin/heat carrier ratio.
[0050] 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.
[0051] 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.
[0052] The molten salt hydrate further comprises a cation, in
particular Zn, Ba, Ca, Li, Al, Cr, Fe, or Cu.
[0053] 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.
[0054] Particularly preferred are the hydrates of ZnCl.sub.2, in
particular ZnCl.sub.2.4H.sub.2O.
[0055] 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.
[0056] If step (ii) is carried out in the substantial absence of
hydrogen (pyrolysis, 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.
[0057] 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.
[0058] 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.
[0059] 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.
[0060] In yet another embodiment step (ii) is operated to produce
primarily dry gas, in particular C.sub.2 and C.sub.3
hydrocarbons.
[0061] In a preferred embodiment at least part of the lignin
present in the Ionic Liquid is converted to a liquid fuel.
[0062] Preferably the liquid fuel is insoluble in the Ionic
Liquid.
[0063] The process can comprise the additional step (v) of removing
the liquid fuel from the Ionic Liquid.
[0064] The process can comprise the additional step of upgrading
the liquid fuel.
[0065] In a preferred embodiment the process comprises the
additional step (vi) of regenerating the Ionic Liquid medium
obtained in step (v). 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 (iv).
[0066] The removal of water can generally be accomplished by
distillation. Step (iii) 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.
[0067] 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.
[0068] It will be understood that steps (iii) and (iv) can be
conducted independent from each other. For example, lignin
recovered from step (ii) can be transported to a separate location
for conversion in step (iv).
[0069] Even when steps (iii) and (iv) are carried out at the same
location, they can be carried out at different points in time. For
example, step (iii) can be carried out immediately after step (ii),
while lignin from step (ii) can be stockpiled for conversion in
step (iv) at a later time.
[0070] It can be advantageous to carry out steps (iii) and (iv)
simultaneously, as this facilitates integration of the heat
balances of the two process steps. For example, excess heat as may
be generated during a catalyst regeneration step of (iv) can be
used to fuel the reaction of step (iii).
* * * * *