Process for preparing 2,5-diformylfuran from carbohydrates

Details Process for preparing 2,5-diformylfuran from carbohydrates Process for preparing 2,5-diformylfuran from carbohydrates

2002-09-13

2004-03-16

Solola, Taofiq A. (Department: 1626)

Organic compounds -- part of the class 532-570 series

Organic compounds

Heterocyclic carbon compounds containing a hetero ring...

Reexamination Certificate

active

06706900

ABSTRACT:

FIELD OF INVENTION
The present invention relates to a one-pot, two-step, catalytic process to prepare 2,5-diformylfuran from a source of fructose or other carbohydrates.
BACKGROUND
2,5-(Hydroxymethyl)furfural (HMF) is a versatile intermediate that can be obtained in high yield from biomass sources such as naturally occurring carbohydrates, including fructose, glucose, sucrose, and starch. Specifically, HMF is a conversion product of hexoses with 6 carbon atoms.
2,5-Diformylfuran (DFF) has been prepared from HMF using CrO
3
and K
2
Cr
2
O
7
(L. Cottier et al.,
Org. Prep. Proced. Int.
(1995), 27(5), 564; JP 54009260) but these methods are expensive and result in large amounts of inorganic salts as waste. Heterogeneous catalysis using vanadium compounds has also been used, but the catalysts have shown low turnover numbers (DE 19615878, Moreau, C. et al.,
Stud. Surf. Sci. Catal.
(1997), 108, 399-406). Catalytic oxidation has been demonstrated using hydrogen peroxide (M. P. J. Van Deurzen,
Carbohydrate Chem.
(1997), 16(3), 299) and dinitrogen tetraoxide (JP 55049368) which are expensive. The relatively inexpensive molecular oxygen (O
2
) has been used with a Pt/C catalyst (U.S. Pat. No. 4,977,283) to form both DFF and furan-2,5-dicarboxylic acid (FDA), but yielded low amounts of DFF.
DFF is itself a useful intermediate for many compounds. DFF has been polymerized to form polypinacols and polyvinyls, and used as a starting material for the synthesis of antifungal agents, drugs, and ligands. DFF can also be used to produce unsubstituted furan. In spite of its proven usefulness, DFF is not readily available commercially.
Selective oxidation of HMF is the only industrially feasible route to DFF. A process that converts a carbohydrate to DFF that avoids the costly HMF isolation step would have an economic advantage. French patent application 2,669,636 describes a one-pot reaction using acetic anhydride in dimethyl sulfoxide for the desired process, but includes additional process steps and is sensitive to water content. After formation of HMF, water is partially removed and an additional solvent is added.
It is therefore the object of the present invention to provide a single solvent, simple, catalytic process that can be run in the presence of water to convert a carbohydrate to DFF without the isolation of HMF.
SUMMARY OF THE INVENTION
The invention is directed to a process for the preparation of 2,5-diformylfuran comprising the steps of: a) combining a source of carbohydrate with a first solvent; b) heating the reaction mixture of step (a) at a temperature sufficient to form 2,5-hydroxymethylfurfural; c) adding an oxidant and a catalytic amount of a vanadium compound to the reaction mixture of step (b); and d) heating the reaction mixture of step (c) at a temperature sufficient to form 2,5-diformylfuran; without adding an additional solvent after steps (b), (c) or (d). Preferably the source of carbohydrate is a source of fructose. More preferably the source of fructose is selected from the group consisting of crude fructose, purified fructose, a fructose-containing biomass, corn syrup, sucrose, and polyfructanes.
Also preferred is a method wherein the solvent in step (a) is dimethylsulfoxide, and in step (b), a catalyst or promoter, preferably a cation exchange resin, is added to the first reaction mixture before heating said first reaction mixture to form the second reaction mixture. The process can also further comprise the step of removing said catalyst or promoter from the second reaction mixture before step (c).
The preferred process comprises cooling the second reaction mixture to 15° C.-100° C. before step (c). Preferably the temperature of step (b) is 50° C. to 150° C. and temperature of step (d) is 120° C. to 180° C. More preferably the temperature of step (d) is 140° C. to 160° C.
A preferred vanadium compound is selected from the group consisting of vanadium oxide or vanadium phosphorus oxide; more preferred is a vanadium compound selected from the group consisting of VO(PO
3
)
2
, (VO)
2
P
2
O
7
, VOPO
4
, VOHPO
4
.0.5H
2
O, [(VO)
4
(P
2
O
7
)
2
(OCH
3
)
4
]
−4
[(C
8
H
12
N)
4
]
+4
,[(VO)
12
(C
6
H
5
PO
3
)
8
(OH)
12
]
−4
[(C
8
H
12
N)
4
]
+4
, (VO)
4
(C
12
H
10
PO
2
)
2
(OCH
3
)
6
(CH
3
OH)
2
, and V
2
O
5
.
The process can further comprise the step of isolating and/or purifying the 2,5-diformylfuran formed in step (d).
DETAILED DESCRIPTION OF THE INVENTION
The present invention is a process to prepare diformylfuran (DFF), also known as furan 2,5-dicarboxaldehyde, in a single pot, two step process from a source of carbohydrate. As used herein, a “source of carbohydrate” is meant fructose, other hexoses, or any biomass that contains carbohydrates that will produce HMF upon dehydration. As used herein, by a “source of fructose” is meant fructose itself, purified or crude, or any biomass that contains fructose or precursors to fructose, such as corn syrup, sucrose, and polyfructanes. Preferred is high fructose corn syrup. As used herein, “biomass” is meant any microbial, animal or plant-based material of carbohydrate composition including herbaceous and woody energy crops, agricultural food and feed crops, agricultural crop wastes and residues, wood wastes and residues, aquatic plants, and other waste materials including some municipal wastes.
The source of carbohydrate, preferably fructose, is mixed with a suitable solvent. The fructose itself or its precursors should be at least partially soluble in the solvent used, and preferably completely dissolved. Preferred is a single solvent, but combinations of solvents may be used. By “solvent” is meant a single solvent or a combination of suitable solvents. Water may be present up to a concentration of about 5%. A suitable solvent is one in which the resulting HMF is fairly soluble, does not interfere with the dehydration reaction, and is stable at reaction conditions. Preferred solvents are dimethyl sulfoxide (DMSO), dimethylacetamide (DMA), sulfolane, N-methylpyrrolidinone (NMP), tetramethylurea (TMU), tributyl phosphate and dimethylformamide (DMF), and combinations thereof. Most preferred are dimethyl sulfoxide, tetramethylurea, or a combination thereof. The reaction mixture formed above is then heated to promote a dehydration reaction to produce HMF from fructose without adding any additional solvent. The water formed from the dehydration reaction is not considered an additional solvent.
A catalyst or promoter can optionally be added to the reaction mixture for the fructose to HMF reaction step. Catalysts include Bronsted and Lewis acids, transition metal salts and complexes, and ion exchange resins. These include, but are not limited to, oxalic acid, H
2
SO
4
, H
3
PO
4
, HCl, levulinic acid, p-toluene sulfonic acid, I
2
, ammonium sulfate, ammonium sulfite, pyridinium phosphate, pyridinium HCl, BF
3
and complexes, ion-exchange resins, zeolites, and Zn, Al, Cr, Ti, Th, Zr and V salts and complexes. For other examples of catalysts and promoters, see Kuster et al.,
Starch
42 (1990), No. 8, pg. 314, which is hereby incorporated by reference. A preferred catalyst is a cation ion exchange resin, such as acid forms of Dowex® type ion-exchange resins (Dow Chemicals Co., Midlands, Mich.). More preferred are Bio-Rad AG-50W resins (Bio-Rad Laboratories, Hercules, Calif.).
The preferred temperature range will vary with solvent and catalyst or promoter used but is generally about 50° C. to about 150° C. when a catalyst or promoter is used, and is generally about 140-165° C. when a catalyst or promoter is not used. If the reaction mixture is not already at the preferred temperature it may be heated until the desired temperature is attained. The time of reaction will vary with reaction conditions and desired yield, but is generally about 1 to about 48 hours. Agitation may also be used.
In most instances, the reaction will occur faster at higher temperatures, but higher selectivities are observed at lower temperatures. At lower temperature the reaction gives better

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