U.S. patent application number 12/862649 was filed with the patent office on 2010-12-16 for methods for conversion of carbohydrates in ionic liquids to value-added chemicals.
This patent application is currently assigned to BATTELLE MEMORIAL INSTITUTE. Invention is credited to Johnathan E. Holladay, Zongchao C. Zhang, Haibo Zhao.
Application Number | 20100317879 12/862649 |
Document ID | / |
Family ID | 38610628 |
Filed Date | 2010-12-16 |
United States Patent
Application |
20100317879 |
Kind Code |
A1 |
Zhao; Haibo ; et
al. |
December 16, 2010 |
METHODS FOR CONVERSION OF CARBOHYDRATES IN IONIC LIQUIDS TO
VALUE-ADDED CHEMICALS
Abstract
Methods are described for converting carbohydrates including,
e.g., monosaccharides, disaccharides, and polysaccharides in ionic
liquids to value-added chemicals including furans, useful as
chemical intermediates and/or feedstocks. Fructose is converted to
5-hydroxylmethylfurfural (HMF) in the presence of metal halide and
acid catalysts. Glucose is effectively converted to HMF in the
presence of chromium chloride catalysts. Yields of up to about 70%
are achieved with low levels of impurities such as levulinic
acid.
Inventors: |
Zhao; Haibo; (The Woodlands,
TX) ; Holladay; Johnathan E.; (Kennewick, WA)
; Zhang; Zongchao C.; (Norwood, NJ) |
Correspondence
Address: |
BATTELLE MEMORIAL INSTITUTE;ATTN: IP SERVICES, K1-53
P. O. BOX 999
RICHLAND
WA
99352
US
|
Assignee: |
BATTELLE MEMORIAL INSTITUTE
Richland
WA
|
Family ID: |
38610628 |
Appl. No.: |
12/862649 |
Filed: |
August 24, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11774036 |
Jul 6, 2007 |
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12862649 |
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60836188 |
Aug 7, 2006 |
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60851545 |
Oct 13, 2006 |
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60938988 |
May 18, 2007 |
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Current U.S.
Class: |
549/489 |
Current CPC
Class: |
C07D 307/46
20130101 |
Class at
Publication: |
549/489 |
International
Class: |
C07D 307/50 20060101
C07D307/50 |
Goverment Interests
[0002] This invention was made with Government support under
Contract DE-AC05-76RLO1830 awarded by the U.S. Department of
Energy. The Government has certain rights in the invention.
Claims
1. A method for selective conversion of a glucose containing
carbohydrate to produce a furan said method comprising the steps
of: mixing said carbohydrate up to a limit of solubility with an
ionic liquid; and heating said carbohydrate in the presence of a
catalyst at a reaction temperature and a reaction time sufficient
for conversion of same.
2. The method of claim 1, wherein said ionic liquid has a chemical
formula 1-R.sub.1-3-R.sub.2-imidazolium chloride, where R.sub.1 and
R.sub.2 are alkyl groups of formula (C.sub.xH.sub.2x+1) where X=1
to 18.
3. The method of claim 1, wherein said ionic liquid includes a
cation of chemical formula 1-R.sub.1-3-R.sub.2-imidazolium where
R.sub.1 and R.sub.2 are alkyl groups of formula (C.sub.xH.sub.2x+1)
where X=1 to 18, and an anion.
4. The method of claim 3, wherein said anion is selected from the
group consisting of halides, sulfates, sulfonates, phosphates,
acetates, phosphates, triflates, hexafluorophosphates,
tetrafluoroborates, hexafluoroborates, and aluminum chloride.
5. The method of claim 3, wherein said anion is selected from the
group consisting of methanesulfonate or
trifluoromethanesulfonate.
6. The method of claim 1, wherein said ionic liquid is selected
from the group consisting of pyridinium salts, phosphonium salts,
tetralkylammonium salts, and combinations thereof.
7. The method of claim 1, wherein said reaction temperature is
about 100.degree. C. and said reaction time is between about 3
hours and about 8 hours.
8. The method of claim 1, wherein said reaction temperature is
about 120.degree. C. and said reaction time is between about 1 hour
and about 3 hours.
9. The method of claim 1, wherein said catalyst is an acid.
10. The method of claim 1, wherein said catalyst is a metal
halide.
11. The method of claim 1, wherein said metal halide is selected
from the group consisting of AlCl.sub.3, CrCl.sub.2, CrCl.sub.3,
FeCl.sub.2, FeCl.sub.3, CuCl, CuBr, CuCl.sub.2, CuBr.sub.2,
VCl.sub.3, MoCl.sub.3, PdCl.sub.2, PtCl.sub.2, PtCl.sub.4,
RuCl.sub.3, RhCl.sub.3, and combinations thereof.
12. The method of claim 1, wherein said reaction temperature is
about 80.degree. C. and said reaction time is between about 1 hour
and about 4 hours.
13. The method of claim 1, wherein said ionic liquid is
1-ethyl-3-methylimidazolium methanesulfonate and said catalyst is
methane sulfonate or its conjugate acid; and wherein said reaction
temperature and said reaction time are between about 80.degree. C.
for 2 hours and about 30.degree. C. for 12 hours.
14. The method of claim 1, wherein yield of levulinic acid and
.alpha.-angelicalactone is below about 0.1 percent by weight.
15. The method of claim 1, wherein said catalyst is a chromium
halide.
16. The method of claim 1, wherein said furan is furfural.
17. The method of claim 1, wherein said carbohydrate is converted
in a batch reactor or a batch reactor system.
18. The method of claim 1, wherein conversion of said carbohydrate
is greater than or equal to about 80 percent and said yield of said
furan is greater than or equal to about 50 percent on a mole
basis.
19. The method of claim 1, wherein said yield of said furan is at
least about 35 percent by weight.
20. A method for selective conversion of fructose to produce a
furan said method comprising the steps of: mixing said carbohydrate
up to a limit of solubility with an ionic liquid; and heating said
carbohydrate at a reaction temperature and a reaction time
sufficient for conversion of same.
21. A method for selective conversion of a carbohydrate to produce
a furan said method comprising the steps of: mixing said
carbohydrate up to a limit of solubility with an ionic liquid; and
heating said carbohydrate in the presence of a catalyst at a
reaction temperature and a reaction time sufficient for conversion
of same.
22. The method of claim 21 wherein said carbohydrate is selected
from the group selected from cellulose, sorbitol, glucose and
fructose.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority from and is a divisional of
U.S. patent application Ser. No. 11/774,036 filed Jul. 6, 2007,
which in turn claims priority from Provisional application
60/836,188 filed Aug. 7, 2006; Provisional application 60/851,545
filed Oct. 13, 2006; and Provisional application 60/938,988 filed
May 18, 2007 incorporated herein their entirety.
FIELD OF THE INVENTION
[0003] The present invention relates to methods for conversion of
carbohydrates in ionic liquids to value-added chemicals at
substantial yields.
BACKGROUND OF THE INVENTION
[0004] Replacing petroleum feedstocks with biomass feedstocks will
require efficient methods for converting carbohydrates to a diverse
number of chemical compounds. A major barrier to achieving this
goal is a current inability to effectively utilize 5-carbon (C5)
and 6-carbon (C6) carbohydrate building blocks derived from nature
as potential feedstocks, including such abundant sugars as, e.g.,
glucose and fructose. 5-Hydroxymethylfurfural (HMF), an important
versatile sugar derivative, is also considered a key intermediate
between petroleum-based industrial organic chemistry and bio-based
carbohydrate chemistry [Werpy et al. in. "Top Value Added Chemicals
from Biomass" United States Department of Energy report number
DOE/GO-102004-1992; and Kamm et al. "Lignocellulose-based Chemical
Products and Product Family Trees" in "Biorefineries-Industrial
Processes and Products", 133 pp, Vol. 2 Edited by Kamm, B., Gruber,
P. R. & Kamm, M, WILEY-VCH Verlag GmbH & Co. KGaA,
Weinheim, 2006]. For example, HMF and its derivatives can
potentially replace petroleum-based building blocks [Bicker et al.
in Green Chem. 5, 280-284 (2003)] used to make plastics and fine
chemicals. However, processes that produce pure HMF from abundant
renewable carbohydrates as a basis for biorefinery platforms based
on utilization of HMF must produce high yields and have low energy
costs. For example, while HMF has been proposed as a key
intermediate to produce liquid alkanes from renewable biomass
resources [Leshkov et al., Science 312, 1933-1937 (2006)], high
production costs currently limit availability and use of HMF
industrially. Further, processes that produce HMF involve use of
acid catalysts and are essentially limited to fructose as a feed
material [Asghari et al., Ind. Eng. Chem. Res. 45, 2163-2173
(2006); Kuster et al, STARCH-STARKE 42, 314-321 (1990); Leshkov et
al., Science 312, 1933-1937 (2006); Tyrlik et al., Carbohydr. Res.
315, 268-272 (1999)]. FIG. 1 illustrates a conventional process for
acid-catalyzed conversion of carbohydrates. In the figure,
conversion of 6-carbon sugars employs concentrated acid (e.g.,
sulfuric acid) as a catalyst. Acids are corrosive, however, and
have drawbacks including product contamination, and difficult
recycling and waste disposal issues. Acids further catalyze side
reactions leading to byproducts that require complicated product
separations for product purification that increase costs. For
example, in water under acidic conditions, HMF decomposes to
levulinic acid and formic acid, making purification of HMF
difficult. Challenges obtaining high yields of dehydration products
from conversion of fructose are described, e.g., by Carlini et al.
[Applied Catalysis A: General 275 (2004) 111-118].
[0005] When glucose is the feed material, HMF yields are usually
low [Tyrlik et al., Carbohydr. Res. 315, 268-272 (1999); Watanabe
et al., Carbohydr. Res. 340, 1925-1930 (2005)]. Under normal
processing conditions, glucose fails to convert to HMF at high
yields. Generally, glucose is poorly converted, presumably a
consequence of competing reaction pathways that lead to formation
of byproducts. With fructose, HMF yield is reported to increase in
systems which partition HMF from H.sub.2O. For example, HMF yields
increase in strong polar organic solvents such as dimethylsulfoxide
(DMSO) as part of an aqueous-organic reaction medium [Leshkov et
al., Science 312, 1933-1937 (2006)]. In another solvent system, HMF
is reported to be formed from fructose in an ionic liquid solvent
consisting of [BMIM]PF.sub.6 or [BMIM]PF.sub.4 with added
co-solvent (e.g., DMSO) further including AMBERLYST-15.RTM., an
acidic polymer, as catalyst [Lansalot-Matras et al., Catal. Commun.
4, 517-520 (2003)]. In the absence of DMSO co-solvent, best yield
of HMF is reported to be 40% to 52%. [Lansalot-Matras et al.,
Catal. Commun. 4, 517-520 (2003); and Moreau et al., J. Mol. Catal.
A: Chem. 253, 165-169 (2006)]. In another system, a specialized
ionic liquid, [HMIM]Cl is reported to act as a proton-transfer
agent, or acid catalyst [Moreau et al., J. Mol. Catal. A: Chem.
253, 165-169 (2006)].
[0006] Polysaccharides (e.g., cellulose) are another class of
carbohydrates that are a rich source of carbohydrate building
blocks with both high conversion and high yield potential. However,
polysaccharides typically require pretreatment to depolymerize the
carbohydrates and provide necessary building blocks for conversion.
Cellulose, for example, is presently pretreated with acid and
subsequently converted to glucose via enzymatic hydrolysis.
However, enzyme costs are high and complexity of processing leads
to high capital costs. Alternatives such as acid hydrolysis produce
by-products which are metabolic poisons to biological fermentation
organisms, eliminating fermentation as a route to product
conversion. Consequently, while carbohydrates can be converted
through various processes including hydrolysis and biological
fermentation, poisoning, slow processing, high production costs,
and difficult separations result in high processing costs.
[0007] Accordingly, there remains a need for new processes that
provide conversion of carbohydrates to value-added chemicals and
chemical feedstock products at high conversion, high selectivity,
and high yields.
SUMMARY OF THE INVENTION
[0008] The invention relates to the use of ionic liquids for
selective conversion of carbohydrates to value-added chemicals. In
one method of the invention, selective conversion of a carbohydrate
to value-added chemical(s) includes the steps of: mixing the
carbohydrate up to a limit of solubility with an ionic liquid;
heating the carbohydrate in the ionic liquid at a reaction
temperature in the absence of added catalyst for a reaction time
sufficient for conversion of the carbohydrate. Conversion of the
carbohydrate produces furans at substantial yield.
[0009] In various embodiments, preferred ionic liquids used as
solvents for conversion of carbohydrates have a chemical formula:
1-R.sub.1-3-R.sub.2-imidazolium chloride ([R.sub.1R.sub.2IM]Cl),
where R.sub.1 and R.sub.2 are alkyl groups of formula
(C.sub.xH.sub.2x+1) where X=1 to 18. In another embodiment, ionic
liquids include a cation of chemical formula
1-R.sub.1-3-R.sub.2-imidazolium, where R.sub.1 and R.sub.2 are
alkyl groups of formula (C.sub.xH.sub.2x+1) where X=1 to 18, and an
anion. Anions include, but are not limited to, e.g., halides,
sulfates, sulfonates, phosphates, acetates, phosphates, triflates,
hexafluorophosphates, tetrafluoroborates, hexafluoroborates, and
aluminum chloride. In another embodiment, the anion is
methanesulfonate or trifluoromethanesulfonate. In other
embodiments, an ionic liquid is 1-ethyl-3-methyl-imidazolium
chloride ([EMIM]Cl) or 1-butyl-3-methyl-imidazolium chloride
([BMIM]Cl).
[0010] In other embodiments, ionic liquids selected for use include
pyridinium salts (e.g., N-alkylpyridinium salts), phosphonium salts
(e.g., P,P,P,P-tetraalkylphosphonium salts), and tetraalkylammonium
salts (e.g., N,N,N,N-tetraalkylammonium salts) that include a
stoichiometric quantity of a suitable anion, described herein.
[0011] In yet other embodiments, carbohydrates including, e.g.,
monosaccharides (e.g., glucose, fructose, mannose, and galactose,
and derivatives thereof, e.g., sorbitol, anhydrosorbitol),
disaccharides (e.g., sucrose, maltose, lactose, cellobiose, and
derivatives thereof), and polysaccharides (e.g., maltodextrins,
starches, cellulose, and derivatives thereof) are converted in the
absence of a co-solvent to value-added chemicals including, e.g.,
furfurals, e.g., 5-hydroxymethylfurfural (HMF).
[0012] In still yet other embodiments, 5-carbon sugars (e.g.,
arabinose, xylose, ribose, and lyxose) are converted to value-added
chemicals including, e.g., furfural.
[0013] In yet other embodiments, 6-carbon sugars (e.g., glucose,
fructose, mannose, and galactose) are converted to value-added
chemicals, including, e.g., 5-hydroxymethylfurfurals.
[0014] In other embodiments, a furan obtained from conversion of
fructose by the process of the invention includes
5-hydroxymethylfurfural (HMF). In another embodiment, a furan is
obtained in the absence of a catalyst.
[0015] In other embodiments, fructose is converted to HMF in
conjunction with a catalyst that is an acid. In other embodiments,
fructose is converted to HMF with a catalyst that is a metal
halide. Metal halides include, but are not limited to, e.g.,
AlCl.sub.3, CrCl.sub.2, CrCl.sub.3, FeCl.sub.2, FeCl.sub.3, CuCl,
CuBr, CuCl.sub.2, CuBr.sub.2, VCl.sub.3, MoCl.sub.3, PdCl.sub.2,
PtCl.sub.2, PtCl.sub.4, RuCl.sub.3, RhCl.sub.3, and combinations
thereof.
[0016] Reaction times for conversion of carbohydrates vary, e.g.,
from about 0.01 minutes to about 300 minutes; or from about 0.01
minutes to about 30 minutes; or from about 0.01 minutes to about 5
minutes. Reaction temperatures for conversion of carbohydrates vary
from about 20.degree. C. to about 400.degree. C.; or from about
80.degree. C. to about 250.degree. C.; or from about 100.degree. C.
to about 200.degree. C.
[0017] In one embodiment, fructose is converted to HMF at a
reaction temperature of about 80.degree. C. and a reaction time of
between about 1 hour and about 4 hours.
[0018] In still yet another embodiment, fructose is converted to
HMF at a reaction temperature of about 120.degree. C. and a
reaction time of about 180 minutes. In another embodiment, reaction
time and reaction temperature is between about 1 hour and about 3
hours at about 120.degree. C.
[0019] In yet another embodiment, fructose is converted to HMF in
1-ethyl-3-methylimidazolium [EMIM]CH.sub.3SO.sub.3 to which methane
sulfonate or its conjugate acid are added as a catalyst. Reaction
temperature and reaction time are between about 80.degree. C. for
about 2 hours and about 30.degree. C. for about 12 hours.
[0020] In another embodiment, conversion of fructose gives a yield
of levulinic acid and .alpha.-angelicalactone below about 1 percent
by weight and more particularly below about 0.1 percent by
weight.
[0021] In one embodiment, conversion of glucose to HMF proceeds at
a reaction temperature of about 100.degree. C. and a reaction time
of about 3 hours.
[0022] In yet another embodiment, conversion of glucose produces a
furan that is furfural.
[0023] In another embodiment, the carbohydrate converted is a sugar
alcohol yielding a furan that is an anhydrosugar alcohol or a
dianhydrosugar alcohol. In another embodiment, the sugar alcohol is
sorbitol.
[0024] In another embodiment, conversion of carbohydrates is
achieved in a batch reactor or a batch reactor system. In other
embodiments, conversion of carbohydrates is achieved in a
continuous flow reactor or a continuous flow reactor system.
[0025] In still yet other embodiments, reaction times and reaction
temperatures for conversion of carbohydrates are from about 0.01
minutes at about 400.degree. C. to about 10 h at about 20.degree.
C. Conversion of carbohydrates can also be achieved at reaction
times of less than or equal to about 0.01 minutes, e.g., in
conjunction with a flash conversion process.
[0026] In yet other embodiments, conversion of carbohydrates
includes a reaction time of from about 0.01 minutes to about 5
hours and a reaction time of from about 400.degree. C. down to
about 20.degree. C.
[0027] In another embodiment, conversion of glucose to HMF includes
a reaction time of from about 0.01 minutes to about 5 hours and a
reaction time of from about 400.degree. C. down to about 20.degree.
C.
[0028] In still yet another embodiment, conversion of carbohydrates
is effected in a reaction time of about 0.01 minutes, e.g., in
conjunction with a flash conversion process.
[0029] In yet another embodiment, carbohydrates are converted in a
reaction time and a reaction temperature of between about 0.01
minutes at about 250.degree. C. and about 12 hours at about
20.degree. C.
[0030] In various embodiments, conversion of carbohydrates is
greater than or equal to about 80 percent and yield of furans is
greater than or equal to about 50 percent on a mole basis; or at
least about 35 percent by weight.
[0031] In another embodiment, conversion of glucose gives yields of
levulinic acid and .alpha.-angelicalactone of less than about 3
percent by weight.
[0032] A more complete appreciation of the invention will be
readily obtained by reference to the following description of the
accompanying drawings in which like numerals in different figures
represent the same structures or elements.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIG. 1 (Prior Art) illustrates a process for conversion of
carbohydrates to HMF by conventional acid catalyzed
dehydration.
[0034] FIG. 2 illustrates a reaction process for conversion of
fructose to HMF in an exemplary ionic liquid, with added metal
halide catalysts to promote desired chemistry, according to
embodiments of the process of the invention.
[0035] FIG. 3 illustrates a reaction process for conversion of
glucose to HMF in an exemplary ionic liquid, with added CrCl.sub.2
metal halide catalyst to promote desired chemistry, according to
another embodiment of the process of the invention.
[0036] FIG. 4 is a plot comparing conversion results for fructose
and glucose to HMF as a function of temperature, according to
different embodiments of the process of the invention.
[0037] FIG. 5 is a plot showing conversion results for fructose in
an exemplary ionic liquid treated with various metal halide
catalysts, according to different embodiments of the process of the
invention.
[0038] FIG. 6 is a plot showing conversion results for glucose in
an exemplary ionic liquid treated with various metal halide
catalysts, according to different embodiments of the process of the
invention.
[0039] FIG. 7 is a plot showing conversion results for glucose as a
function of time in an exemplary ionic liquid treated with
CrCl.sub.2, CuCl.sub.2, and FeCl.sub.2 metal halide catalysts.
[0040] FIG. 8 is a plot presenting conversion results for glucose
in an exemplary ionic liquid treated with CrCl.sub.2 metal halide
catalyst, according to a preferred embodiment of the process of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0041] The term "Imidazoles" as used herein refers to the class of
heterocyclic aromatic compounds of general structural formula
[A]:
##STR00001##
where R represents functional groups as will be understood by those
of skill in the chemical art.
[0042] The term "Imidazole" [CAS No. 288-32-4] [Mol. Wt.: 68.08] as
used herein refers to the chemical compound of chemical formula
(C.sub.3H.sub.4N.sub.2) having general structural formula [B]:
##STR00002##
[0043] The term "Imidazolium" as used herein refers to the cationic
portion of ion-forming salts from the imidazole class of organic
compounds, having general structural formula [C]:
##STR00003##
where R.sub.1 and R.sub.2 are alkyl groups of formula
(C.sub.xH.sub.2x+1) where X=1 to 18.
[0044] The terms "Furans" and "a Furan" as used herein refer to
compounds from the class of heterocyclic organic compounds having
general structural formula [D1] and [D2]:
##STR00004##
where R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are functional groups
including, e.g., H or C; C may further include O and/or H,
defining, e.g., aldehyde or alcohol functional groups. "Furan" [CAS
Number 110-00-9] (C.sub.4H.sub.4O) is included in this class of
compounds having structural formula [01], where R.sub.1 and R.sub.2
are H.
[0045] The term "Sugar Alcohols" as used herein refers to compounds
of chemical formula [C.sub.nH.sub.2n+2O.sub.n] where n=1, 2, 3,
etc. General structural formulas for representative 5-carbon and
6-carbon sugar alcohols are illustrated in [E1] and [E2]:
##STR00005##
[0046] The term "Anhydro sugar alcohols" as used herein refers to
compounds having general structural formula [F1] and [F2]:
##STR00006##
[0047] The term "Dianhydrosugar alcohols" as used herein refers to
compounds having general structural formula [G]:
##STR00007##
[0048] While preceding compounds have been illustrated using
generalized structures, no limitation to specific stereoisomers is
implied.
[0049] Abbreviation nomenclature used herein to denote ionic
liquids identifies the cationic portion of the ionic liquid, e.g.,
1-ethyl-3-methyl-imidazolium, by bracket, e.g., [EMIM] or
[EMIM].sup.+. The anionic portion of the ionic liquid, e.g.,
chloride (Cl or Cl.sup.-) is identified by placement outside the
bracket (e.g., [EMIM]Cl or [EMIM].sup.+Cl.sup.-). Unless otherwise
noted, nomenclature for ionic liquids with or without ionic charges
are used interchangeably, e.g., [EMIM].sup.+Cl.sup.- or
[EMIM]Cl.
[0050] The term "triflates" has reference to chemical compounds
that include a trifluoromethanesulfonate functional group
(CF.sub.3SO.sub.3.sup.-) or a corresponding acid conjugate
(CF.sub.3SO.sub.3H).
[0051] The term "Selectivity" as used herein is defined by equation
[1]:
Selectivity = ( Moles Product Formed Moles Starting Material
Reacted ) [ 1 ] ##EQU00001##
[0052] The term "Conversion" as used herein is defined by equation
[2]:
Conversion = 1 - ( Moles Unreacted Starting Material Moles Starting
Material ) [ 2 ] ##EQU00002##
[0053] The term "Yield" as used herein is defined by equation
[3]:
Yield = ( Moles Product Formed Moles Starting Material ) [ 3 ]
##EQU00003##
Ionic Liquids
[0054] Ionic liquids (IL) suitable for use as solvents in
conjunction with the invention provide solubility to the
carbohydrates selected for conversion therein. Properties of the
ionic liquid solvents vary according to the cationic, alkyl, and
anionic group constituents of the liquids. Preferred ionic liquids
include salts of the 1-R.sub.1-3-R.sub.2-imidazolium class of
compounds, where R.sub.1 and R.sub.2 are alkyl groups of formula
(C.sub.xH.sub.2x+1) where X=1 to 18, further including a
stoichiometric quantity of a selected anion. In these ionic
liquids, the cationic portion (or cation) of the ionic liquid
includes a 5-member imidazolium ring and alkyl groups R.sub.1 and
R.sub.2. The anionic portion (or anion) of the ionic liquid can
vary. Anions include, but are not limited to, e.g., halides
including, e.g., chloride (Cl.sup.-), bromide (Br.sup.-), and
iodide (I.sup.-); halogen-free anions, including, e.g., sulfates,
sulfonates (e.g., alkyl sulfonates), phosphates, acetates, and
triflates (e.g., alkyl triflates); hexafluorophosphates
(PF.sub.6.sup.-); tetrafluoroborates (BF.sub.4.sup.-);
hexafluoroborates (BF.sub.6.sup.-); and aluminum chloride
(AlCl.sub.4.sup.-). Other ionic liquids suitable for use include
pyridinium salts (e.g., N-alkylpyridinium salts), phosphonium salts
(e.g., P,P,P,P-tetraalkylphosphonium salts), and tetralkylammonium
salts (e.g., N,N,N,N-tetraalkylammonium salts) that include a
stoichiometric quantity of a suitable anion, described herein.
[0055] Ionic liquids can contain impurities that are catalytic. In
an illustrative example, reactivity of a carbohydrate in an
"as-received" [EMIM]CH.sub.3SO.sub.3 ionic liquid had high activity
due to presence of contaminants and/or impurities in the ionic
liquid. However, when the "as-received" ionic liquid was purified
to remove contaminants and/or impurities, reactivity of the
carbohydrate was negligible. In general, at low reaction
temperatures, catalysts are required for conversion of
carbohydrates in ionic liquids.
[0056] Conversion of fructose to HMF is demonstrated using three
exemplary [AMIM]Cl ionic liquid solvent systems, where A is an
alkyl group, including, but not limited to, e.g., ethyl, butyl,
octyl, and the like. Corresponding ionic liquids are:
1-ethyl-3-methylimidazolium [EMIM]Cl; 1-butyl-3-methylimidazolium
chloride [BMIM]Cl; and 1-octyl-3-methylimidazolium chloride
[OMIM]Cl, but is not limited thereto. These ionic liquids are
preferred ionic liquid (IL) solvent systems for conversion of
carbohydrates to versatile chemicals at high yields, including,
e.g., 5-hydroxymethylfurfural (HMF).
[0057] In one process, according to an embodiment of the invention,
fructose is converted in the presence of metal halide catalysts to
HMF at high yields. In another process, fructose is converted to
HMF at selected reaction temperatures in the absence of any added
catalyst. In another process, fructose is converted in the presence
of a mineral acid to HMF at high yields.
Conversion of 6-Carbon Sugars
[0058] Conversion of 6-C sugars (e.g., glucose and fructose) to HMF
in ionic liquids has been demonstrated.
[0059] FIG. 2 illustrates a reaction process for conversion of
fructose to HMF in an exemplary ionic liquid, [EMIM]Cl, with metal
halide catalysts or acid catalysts added to promote desired
chemistry. While the furanose form of fructose is illustrated in
the figure, other forms of fructose (e.g., pyranose forms) are
equally converted. Thus, no limitations are intended.
[0060] In a preferred embodiment, in the ionic liquid [EMIM]Cl,
reaction time and reaction temperature is about 1 h to 3 h at about
80.degree. C., but is not limited thereto. For example, reaction
times and reaction temperatures may be selected in the range from
about 0.01 minutes at 400.degree. C. to about 12 h at 80.degree. C.
Alternatively, reaction times and reaction temperatures may be
selected in the range from about 0.01 minutes at 250.degree. C. to
about 8 h at 80.degree. C.
[0061] In other ionic liquids, the melting point is lower, allowing
for a lower reaction temperature. For example,
[EMIM]CH.sub.3SO.sub.3 is a liquid at room temperature. Reaction
times and reaction temperatures may be selected at between about 20
h at 20.degree. C. and from about 0.01 minutes at 250.degree.
C.
[0062] Continued processing of product furans may lead to formation
polymeric products that are easily separated from products of
interest.
[0063] FIG. 3 illustrates a reaction process for conversion of
glucose to HMF in an exemplary ionic liquid, e.g., ([EMIM]Cl), with
CrCl.sub.2 metal halide catalyst added, according to another
embodiment of the process of the invention. As illustrated in the
figure, in the ionic liquid treated with CrCl.sub.2 metal halide
catalyst, conversion of glucose to HMF occurs.
[0064] In a preferred embodiment, a reaction time and a reaction
temperature are 3 h at about 100.degree. C. are used, but is not
limited thereto. For example, reaction temperatures and reaction
times may be selected in the range from 1 minute to about 20
minutes at 150.degree. C. or about 0.01 minutes at 250.degree. C.;
or 0.01 minutes at about 400.degree. C.
[0065] In other embodiments, hydrolysis of cellulose to glucose,
dehydration of glucose to HMF has been demonstrated. In a preferred
embodiment, a reaction time and a reaction temperature of
[0066] In a preferred embodiment, a reaction time and reaction
temperature are 0.5 h at about 140.degree. C. is used, but is not
limited thereto. For example, reaction temperatures and reaction
times may be selected in the range from about 5 minutes and about
200.degree. C.; or about 0.1 minutes at about 250.degree. C.; or
about 0.01 minutes at about 400.degree. C.
[0067] FIG. 4 is a histogram that compares conversion results for
fructose and glucose to HMF as a function of temperature in an
exemplary ionic liquid, [EMIM]Cl, with no added catalyst. As shown
in the figure, at sufficiently high temperatures, fructose is
converted to HMF, with yields that decrease in the temperature
range between about 120.degree. C. and about 80.degree. C. In
contrast, glucose does not produce any significant quantity of HMF,
even at 180.degree. C. When water is added to the solvent
([EMIM]Cl) at a ratio of about 5:1, glucose is effectively
inert.
[0068] A wide range of metal halide catalysts can be added to
increase yields of desired end products. Fructose, for example, is
rapidly converted to HMF in ionic liquids treated with metal halide
catalysts. The catalysts provide efficient conversion. In such
reactions, a very low quantity of levulinic acid impurity is
formed, typically below about 1% and more particularly below about
0.1%.
[0069] In yet other processes, high yields of HMF are obtained from
conversion of glucose in ionic liquids with a metal halide catalyst
added. Chromium chlorides (e.g., CrCl.sub.2 and CrCl.sub.3) are
uniquely effective catalysts for selective conversion of glucose to
HMF, providing yields of greater than or equal to about 70%,
described further herein.
[0070] In still yet other embodiments, HMF is produced from
conversion of complex biomass materials, including e.g., cellulose
in ionic liquid solvents Yields of approximately 50% are
obtained.
[0071] While the exact mechanism for action of metal halide
catalysts is unknown in these processes, at catalytic quantities of
catalyst (e.g., 0.5% by weight), the ionic liquid solvent is
believed to employ an equimolar amount of ionic liquid (e.g.,
[EMIM]Cl) and the associated metal halide. For purposes of
illustration, addition of CrCl.sub.2 in the ionic liquid [EMIM]Cl
proceeds as denoted in equation [4]:
[EMIM].sup.+Cl.sup.-+CrCl.sub.2.fwdarw.[EMIM].sup.+CrCl.sub.3.sup.-
[4]
Experiments Demonstrating Conversion of Fructose to HMF in Ionic
Liquids Treated with Metal Halide Catalysts
[0072] Fructose conversion in ionic liquids treated with and
without addition of a catalyst demonstrates broad applicability and
advantages of the processes of the invention described herein. For
example, fructose can be selectively dehydrated to
5-hydroxymethylfurfural (HMF) with low yields of levulinic acid if
treated with metal halide catalysts, described further
hereafter.
[0073] Catalysts. Metal halide catalysts were tested using a high
pressure reactor (e.g., a Symyx.RTM. high pressure reactor system
equipped with a heated orbital shaker, Symyx Technologies Inc.,
Santa Clara, Calif., USA), but is not limited thereto. Ionic
liquids and selected catalysts and were to reaction vials by mass.
Vials were shaken at 700 rpm and heated at 150.degree. C. between
about 10 min. and 30 min. (0.5 h) to mix ionic liquid and
catalyst.
[0074] Protocol. Fructose was added to reaction vials and
introduced to the reactor. The reactor was purged at room
temperature with N.sub.2 or air, heated to an operating temperature
of 80.degree. C., and shaken at 700 rpm for 3 h, before cooling and
venting.
[0075] Sample Analysis. 500 .mu.L of water was added to each
reaction vial followed by centrifugation at 3000 rpm for 30 min.
Samples were then diluted with water by a factor of two for
analysis by high pressure liquid chromatography (HPLC). For initial
analyses, samples were injected onto an Aminex Fast Acid column and
analyzed by refractive index on an Agilent 1100 series HPLC using a
flow rate of 1 mL/min, column temperature of 60.degree. C., and a
0.005M H.sub.2SO.sub.4 mobile phase. Select samples were chosen
from the primary HPLC screen for a secondary HPLC analysis on a
long column (e.g., an Aminex.RTM. model HPX-87H, 7.8 mm.times.300
mm, 9 .mu.m particle size, column available commercially from
Bio-Rad Laboratories, Richmond, Calif., USA) at a flow rate of 0.55
mL/min, a temperature of 60.degree. C., and a 0.005M
H.sub.2SO.sub.4 mobile phase. HPLC results were recorded and used
to calculate feed conversion percentages, product selectivity, and
molar balances. Catalysts were also ranked for effectiveness.
Preferred catalysts, for example, exhibited high conversion and
good selectivity yields to HMF.
[0076] FIG. 5 is a histogram showing conversion results for
fructose in an exemplary ionic liquid treated with various metal
halide catalysts, according to different embodiments of the process
of the invention. In the figure, metal halide catalysts included:
CrCl.sub.2, CrCl.sub.3, FeCl.sub.2, FeCl.sub.3, CuCl, CuCl.sub.2,
VCl.sub.3, MoCl.sub.3, PdCl.sub.2, PtCl.sub.2, PtCl.sub.4,
RuCl.sub.3, or RhCl.sub.3. As shown, dehydration of fructose to HMF
is catalyzed by many metal halide catalysts and mineral acids,
e.g., sulfuric acid, (H.sub.2SO.sub.4). Two metal halides were
ineffective, i.e., LaCl.sub.3, and MnCl.sub.2. Alkali metal halides
(e.g., NaCl, and LiCl) were also ineffective. HMF yields from
conversion of fructose ranged from about 63% to about 83% at
reaction times of about 3 h at 80.degree. C. Product mixtures were
very clean, as evidenced by NMR analysis. For example, yields of
levulinic acid and .alpha.-angelicalactone were low, typically less
than about 0.1%.
Conversion of Glucose to HMF
[0077] Conversion experiments for fructose were repeated using
glucose as a feed material. Temperature was raised to 100.degree.
C. due to a lower expected reactivity of glucose relative to
fructose.
[0078] FIG. 6 is a histogram showing conversion results for glucose
in an exemplary ionic liquid, [EMIM]Cl, pretreated with various
metal halide catalysts. As shown in the figure, Glucose conversion
was high for many of the metal halide catalysts tested, including
AlCl.sub.3, FeCl.sub.3, CuCl.sub.2, CuCl, VCl.sub.3, MoCl.sub.3,
PtCl.sub.2, PtCl.sub.4, RuCl.sub.3, and RhCl.sub.3. These metal
halides showed a conversion of glucose of 40% or greater. However,
HMF yields were low. HMF yields from conversion of glucose were
also low using acids (e.g., H.sub.2SO.sub.4) as catalysts. One
catalyst, CrCl.sub.2, gave HMF yields of 68-70%, a previously
elusive efficiency for conversion of glucose. HMF yields for ionic
liquid solvent systems not containing CrCl.sub.2 or CrCl.sub.3 were
on the order of 10%. HMF yields could not be accounted for by
product instability under reaction conditions. Results indicate
that high conversion of glucose is achieved with various metal
halide catalysts, in many ionic liquid systems. However, low
product yields suggest these metal halides catalyze undesired
reaction pathways.
Conversion of Glucose in Ionic Liquid Containing Metal Halide
Catalysts CrCl.sub.2, CuCl.sub.2, and FeCl.sub.2
[0079] In additional experiments, conversion of glucose was tested
for three specific catalysts, CrCl.sub.2, CuCl.sub.2, and
FeCl.sub.2, at 100.degree. C. To ensure uniform catalyst loading,
each catalyst-ionic liquid mixture was prepared in a single batch
and then added to the reaction vial (500 mg aliquots) containing
glucose (50 mg). Following reaction times at selected reaction
temperatures, samples were analyzed by HPLC.
[0080] FIG. 7 plots glucose conversion (mol %) in [EMIM]Cl ionic
liquid treated with each of three metal halide catalysts, i.e.,
CrCl.sub.2, CuCl.sub.2, and FeCl.sub.2, respectively, as a function
of time. Glucose conversion is highest in ionic liquid containing
CrCl.sub.2. Glucose is reactive in ionic liquid containing
CuCl.sub.2, but does not provide a high yield of HMF. In ionic
liquid containing FeCl.sub.2, glucose shows essentially no
reactivity. Results suggest chemistry for conversion of the
carbohydrate differs for each of the metal halide catalysts tested.
Effectiveness of CrCl.sub.2 catalyst for conversion of glucose to
HMF was unexpected.
[0081] FIG. 8 is a histogram showing results for conversion of
glucose in two exemplary ionic liquids, [EMIM]Cl and [BMIM]Cl,
treated with a preferred metal halide catalyst, CrCl.sub.2. As
shown in the figure, conversion of glucose is greater than 90%
(mole basis), with yields of HMF of about 68% (in [EMIM]Cl) and 60%
(in [BMIM]Cl), respectively.
Conversion of Cellulose
[0082] Conversion of cellulose in an ionic liquid is described
hereafter optionally in conjunction with a catalyst. Ionic liquids
catalyze all, or a majority, of the chain of necessary reactions,
including, e.g., decrystallization, hydrolysis, and/or dehydration,
yielding the desired conversion products. For example, hydrolysis
of cellulose in ionic liquids that yields simple sugars including
HMF with low yields of levulinic acid was an unexpected result.
And, use of additional acids is not required for dehydration to
occur. Further, conversion of cellulose and other complex
carbohydrates in ionic liquids exhibits high selectivity to desired
value-added products. Cellulose can also be converted selectively
to other products in different ionic liquids systems. Thus, by
appropriate selection of ionic liquid, product can be selectively
tuned. Conversion in ionic liquids is applicable to conversion of
other carbohydrates and polysaccharides including starch. Thus, the
disclosure is not intended to be limited to exemplary embodiments
and exemplary carbohydrates described herein.
[0083] Following examples provide a further understanding of the
invention
Example 1
Conversion of Fructose to HMF in [EMIM]Cl
Metal Halide or Acid Catalyst
[0084] Fructose (99.9%) was supplied by Mallinckrodt. [EMIM]Cl
(99%) was supplied by Solvent-Innovation (GmbH, Cologne, GE). Metal
halide catalysts were CuCl, CuCl.sub.2, CuBr.sub.2, MoCl.sub.3,
FeCl.sub.2, FeCl.sub.3, CrCl.sub.2, CrCl.sub.3, VCl.sub.3,
AlCl.sub.3, MnCl.sub.3, PdCl.sub.2, PtCl.sub.2, PtCl.sub.4,
RuCl.sub.3, RhCl.sub.3 were supplied by Sigma-Aldrich (St. Louis,
Mo., USA) Acid catalyst was H.sub.2SO.sub.4, supplied by
Sigma-Aldrich (St. Louis, Mo., USA). 500 mg [EMIM]Cl was loaded
into reaction vials. Metal halide catalysts were added to
respective vials at a concentration of .about.6 mol % with respect
to fructose. 2 mg CrCl.sub.2 was added to its reaction vial. Vials
were installed into the high pressure reactor, heated at
150.degree. C. and shaken at 700 rpm to mix contents. After
cooling, 50 mg fructose was added to each vial and heated at
80.degree. C. for 3 h. After cooling, 2.0 mL of water was added for
analysis by HPLC. Results are presented in TABLE 1 (see FIG.
5).
TABLE-US-00001 TABLE 1 Conversion of Fructose to HMF, and product
yields. Feedstock Product Example Feedstock Catalyst conversion (%)
yields (%)* 1.1 Fructose None 10.92 HMF: 1.36 1.2 Fructose CuCl
91.25 HMF: 78.81 1.3 Fructose CuCl.sub.2 99.54 HMF: 76.02 1.4
Fructose CuBr.sub.2 99.59 HMF: 77.48 1.5 Fructose MoCl.sub.3 98.67
HMF: 70.88 1.6 Fructose FeCl.sub.2 76.40 HMF: 63.15 1.7 Fructose
FeCl.sub.3 99.80 HMF: 77.08 1.8 Fructose CrCl.sub.2 95.32 HMF:
65.26 1.9 Fructose CrCl.sub.3 95.41 HMF: 69.28 1.10 Fructose
VCl.sub.3 100.00 HMF: 77.03 1.11 Fructose AlCl.sub.3 99.00 HMF:
76.00 1.12 Fructose MnCl.sub.3 10.22 HMF: 5.02 1.13 Fructose
PdCl.sub.2 92.00 HMF: 77.00 1.14 Fructose PtCl.sub.2 99.00 HMF:
83.00 1.15 Fructose PtCl.sub.4 99.00 HMF: 80.00 1.16 Fructose
RuCl.sub.3 98.00 HMF: 79.00 1.17 Fructose RhCl.sub.3 99.00 HMF:
83.00 1.18 Fructose H.sub.2SO.sub.4 99.00 HMF: 80.00 *Yields of
levulinic acid and .alpha.-angelicalactone were less than 0.1% for
all experiments.
Example 2
Conversion of Fructose to HMF in Alternate Ionic Liquids
Metal Halide or Acid Catalyst
[0085] Fructose was processed as in Example 1 in various ionic
liquids containing a metal halide or acid catalyst. Ionic liquids
were [EMIM]CH.sub.3SO.sub.3 (Solvent-Innovations, GmbH, Cologne,
GE); tetrabutylammonium chloride (Fluka-Sigma-Aldrich, Steinheim,
GE); tetrabutylphosphonium chloride (Ionic Liquid Technologies,
GmbH, Denzlingen, GE); 1,2,4-trimethylpyrazolium methyl sulfate
(Fluka-Sigma-Aldrich, Steinheim, GE). [EMIM]CH.sub.3SO.sub.3,
tetrabutylphosphonium chloride, and 1,2,4-trimethylpyrazolium
methyl sulfate each contained a catalytic quantity of acid. Results
are presented in TABLE 2.
TABLE-US-00002 TABLE 2 Conversion of Fructose to HMF, and product
yields. Feedstock conversion Product Example Feedstock Ionic Liquid
(IL) and Catalyst (%) Yields (%) 2.1 Fructose IL:
[EMIM]CH.sub.3SO.sub.3; 99.6 HMF: 86.5 Catalyst: acid 2.2 Fructose
IL: tetrabutylammonium chloride; -- HMF: 59.1 Catalyst: VCl.sub.3
2.3 Fructose IL: tetrabutylphosphonium chloride; -- HMF: 65.2
Catalyst: acid 2.4 Fructose IL: 1,2,4-trimethylpyrazolium methyl --
HMF: 52.1 sulfate; Catalyst: acid
Example 3
Carbohydrate Reactivity in "as-Received" and Purified Ionic
Liquid
[0086] Carbohydrate reactivity was compared in both "as-received"
(as purchased) and purified ionic liquid. Fructose was processed as
in Example 1 in 99% [EMIM]CH.sub.3SO.sub.3 (Solvent-Innovation,
GmbH, Cologne, GE) in both the "as-received" ionic liquid and the
ionic liquid purified with basic alumina to remove any contaminants
(e.g., methane sulfonic acid). Reaction time and temperature was 3
h at 80.degree. C. Conversion of fructose in the "as-received"
ionic liquid was 99.9%; yield of HMF was 83.9%. Conversion of
fructose in purified ionic liquid was 0%; yield of HMF was 0%.
Results demonstrate that some impurities present in ionic liquids
(e.g., as purchased) are sufficient to catalyze reaction of
carbohydrates. When purified, the ionic liquid does not exhibit
reactivity at the same temperature.
Example 4
Conversion of Fructose to HMF in [EMIM]CH.sub.3SO.sub.3
Acid Catalyst
[0087] Fructose was processed as in Example 1 in (99%)
[EMIM]CH.sub.3SO.sub.3 (Solvent-Innovation, GmbH, Cologne, GE)
ionic liquid, containing a catalytic quantity of CH.sub.3SO.sub.3.
Liquid products were analyzed by HPLC. Conversion of fructose was
99.6%; yield of HMF was 86.5%; yield of levulinic acid yield was
0.5%. Yields of HMF in repeat experiments ranged from 86% to
90%.
Example 5
Conversion of Fructose to HMF in [EMIM]Cl
No Metal Halide or Acid Catalyst
[0088] Fructose was processed as in Example 1 in [EMIM]Cl at a
reaction temperature of 120.degree. C. for 3 h. Conversion of
fructose was 98%; yield of HMF was 73% (see FIG. 4).
Example 6
Conversion of Glucose to HMF in [EMIM]Cl;
CrCl.sub.2 Metal Halide Catalyst
[0089] Glucose was processed as in Example 1 at a reaction
temperature of 100.degree. C. for 3 h in [EMIM]Cl. Metal halide
catalyst was CrCl.sub.2. Results are listed in FIG. 6 and TABLE
3.
Example 7
Conversion of Glucose to HMF in [EMIM]Cl
CrCl.sub.3 Metal Halide Catalyst
[0090] Glucose was processed as in Example 1 at a reaction
temperature of 100.degree. C. for 3 h in [EMIM]Cl. Metal halide
catalyst was CrCl.sub.3. Results are listed in FIG. 6 and TABLE
3.
Example 8
Conversion of Glucose to HMF in [EMIM]Cl Various Metal Halide and
Acid Catalysts
[0091] Glucose was processed as in Example 1 in [EMIM]Cl at a
reaction temperature of 100.degree. C. for 3 h. Metal halide
catalysts were CuCl, CuCl.sub.2, CuBr.sub.2, MoCl.sub.3,
FeCl.sub.2, FeCl.sub.3, CrCl.sub.2, CrCl.sub.3, VCl.sub.3,
AlCl.sub.3, MnCl.sub.3, PdCl.sub.2, PtCl.sub.2, PtCl.sub.4,
RuCl.sub.3, RhCl.sub.3. Acid catalyst was H.sub.2SO.sub.4. Results
are presented in FIG. 6 and TABLE 3.
TABLE-US-00003 TABLE 3 Conversion of Glucose to HMF, and product
yields. Feedstock Product Example Feedstock Catalyst conversion (%)
yields (%)* 6 Glucose CrCl.sub.2 94.4 HMF: 68.0 7 Glucose
CrCl.sub.3 71.5 HMF: 44.3 8.1 Glucose None 0 HMF: 0 8.2 Glucose
CuCl 0 HMF: 0 8.3 Glucose CuCl.sub.2 85.0 HMF: 6.4 8.4 Glucose
CuBr.sub.2 40.4 HMF: 4.7 8.5 Glucose MoCl.sub.3 46.8 HMF: 7.2 8.6
Glucose FeCl.sub.2 0 HMF: 0 8.7 Glucose FeCl.sub.3 47.8 HMF: 6.4
8.8 Glucose VCl.sub.3 61.2 HMF: 8.1 8.9 Glucose AlCl.sub.3 97.3
HMF: 10.8 8.10 Glucose MnCl.sub.3 0 HMF: 0 8.11 Glucose PdCl.sub.2
20.0 HMF: 0.7 8.12 Glucose PtCl.sub.2 65.0 HMF: 7.6 8.13 Glucose
PtCl.sub.4 88.0 HMF: 13.0 8.14 Glucose RuCl.sub.3 65.0 HMF: 7.1
8.15 Glucose RhCl.sub.3 55.0 HMF: 3.9 8.16 Glucose H.sub.2SO.sub.4
94.4 HMF: 11.0 *Yields of levulinic acid and
.alpha.-angelicalactone were less than 0.1% for all
experiments.
Example 9
Conversion of Cellulose to HMF in [EMIM]Cl
CrCl.sub.2 Metal Halide Catalyst
[0092] 500 mg [EMIM]Cl, (99.5%) (Solvent-Innovation GmbH, Cologne,
Germany) and 0.037 mmol/mL of CrCl.sub.2 metal halide catalyst were
added to a reaction vial. The vial was heated to 180.degree. C. to
create a homogenous catalyst system. 50 mg of cellulose
(Sigma-Aldrich, St. Louis, Mo., USA) was added and mixed at 700 rpm
to swell the cellulose. Vial was heated at 180.degree. C. for 1 h.
50 .mu.L of water was added for analysis by HPLC. Yield of HMF was
49.8%.
Example 10
Conversion of Cellulose in [EMIM]Cl
CrCl.sub.3 Metal Halide Catalyst
[0093] Cellulose was processed as in Example 9 in [EMIM]Cl at
140.degree. C. for 0.5 h. Metal halide catalyst was CrCl.sub.3.
Products were analyzed by HPLC. Yield of HMF was 50.7%; yield of
levulinic acid was 1.4%; yield of formic acid was 2.5%. Results for
Examples 9-10 are listed in TABLE 4.
TABLE-US-00004 TABLE 4 Conversion of Cellulose to HMF, and product
yields. Process conditions for Feedstock hydrolysis and conversion
Product Example Feedstock dehydration (%) yields (%) 9 Cellulose
Temp: 180.degree. C., -- HMF: 49.8 Time: 3 h Catalyst: CrCl.sub.2
10 Cellulose Temp: 140.degree. C., -- HMF: 50.7 Time: 0.5 h,
Levulinic acid: 1.4 Catalyst: CrCl.sub.3 Formic acid: 2.3
Example 11
Conversion of Sorbitol in [OMIM]Cl
No Metal Halide Catalyst
[0094] 50 mg sorbitol and 500 mg [OMIM]Cl were introduced to a
vial. The vial was installed into a high pressure reactor,
evacuated, purged with N.sub.2. The vial was shaken at 700 rpm and
heated at 150.degree. C. under 25-torr vacuum for 1 h. The vial was
cooled and 2.0 mL water was added for analysis by HPLC. Conversion
of sorbitol was 97.2%, yield of 1,4-sorbitan was 51.6%; yield of
isosorbide was 20.0%.
Example 12
Conversion of Sorbitol in [OMIM]Cl
CuCl.sub.2 Metal Halide Catalyst
[0095] Sorbitol was processed as in Example 9 in [OMIM]Cl with 50
mg CuCl.sub.2 added as catalyst. Conversion of sorbitol was 95.8%;
yield of 1,4-sorbitan was 36.3%; and yield of isosorbide was
37.3%.
Example 13
Conversion of Sorbitol in [EMIM]CH.sub.3SO.sub.3
No Metal Halide Catalyst
[0096] Sorbitol was processed as in Example 9 in
[EMIM]CH.sub.3SO.sub.3. Liquid products were analyzed by HPLC.
Conversion of sorbitol was 82.4%; yield of 1,4-sorbitan was 63.8%;
yield of isosorbide was 1.6%.
Example 14
Conversion of Sorbitol in [EMIM]Cl;
ZnCl.sub.2 Metal Halide Catalyst
[0097] Sorbitol was processed as in Example 9 in [EMIM]Cl with 50
mg ZnCl.sub.2 added as catalyst. Products were analyzed by HPLC.
Conversion of sorbitol was 92.1%; yield of 1,4-sorbitan was 76.0%;
yield of isosorbide was 3.8%.
[0098] Results of Examples 11-14 are summarized in TABLE 5.
TABLE-US-00005 TABLE 4 Conversion of Sorbitol, and product yields.
Feedstock Product yields Example Feedstock Ionic Liquid and
Catalyst conversion (%) (%) 11 Sorbitol IL: [OMIM]Cl, 97.2
1,4-sorbitan: 51.6 Catalyst: None Isosorbide: 20.0 12 Sorbitol IL:
[OMIM]Cl, 95.8 1,4-sorbitan: 36.3 Catalyst: CuCl.sub.2 Isosorbide:
37.3 13 Sorbitol IL: [EMIM]CH.sub.3SO.sub.3, 82.4 1,4-sorbitan:
63.8 Catalyst: None Isosorbide: 1.6 14 Sorbitol IL: [EMINA]Cl, 92.1
1,4-sorbitan: 76.0 Catalyst: ZnCl.sub.2 Isosorbide: 3.8
[0099] As demonstrated in Examples 11-14, sorbitol is dehydrated to
products including, e.g., isosorbide and 1,4-sorbitan. Yields are
selectively tunable by choices of ionic liquid and catalyst.
[0100] While Examples presented herein demonstrate conversion of
carbohydrates using a single batch process and reactor, the
invention is not limited thereto. Those of skill in the art will
appreciate that many reactors and reactor configurations are
suitable for use in conjunction with the invention, including,
e.g., step-wise and/or serial processing, multistage processing and
reactors, continuous flow processing and reactors, and/or tandem
stage processing and reactors. All reactor configurations and
processes as will be contemplated and implemented by those of skill
in the art in view of the present disclosure are within the scope
of the invention.
[0101] While preferred embodiments of the invention have been shown
and described herein, many changes and modifications may be made
without departing from the invention in its broader aspects. The
appended claims are therefore intended to cover all such changes
and modifications as fall within the scope of the invention.
* * * * *