# Patent

## Title
Method of carbon chain extension using novel aldol reaction

## Abstract

Method of producing C8-C15 hydrocarbons comprising providing a ketone starting material; providing an aldol starting material comprising hydroxymethylfurfural; mixing the ketone starting material and the aldol starting material in a reaction in the presence of a proline-containing catalyst selected from the group consisting of Zn(Pro)2, Yb(Pro)2, and combinations thereof, or a catalyst having one of the structures (I), (II) or (III), and in the presence of a solvent, wherein the solvent comprises water and is substantially free of organic solvents, where (I), (II) and (III) respectively are:




    
    
        where R1 is a C1-C6 alkyl moiety, X=(OH) and n=2.
    
    






In (III), X may be CH2, sulfur or selenium, M may be Zn, Mg, or a lanthanide, and R1 and R2 each independently may be a methyl, ethyl, phenyl moiety.

## Background
RELATED APPLICATIONS
This application is a continuation of U.S. application Ser. No. 12/542,475, filed Aug. 17, 2009, the entirety of which is incorporated by reference herein.


STATEMENT OF FEDERAL RIGHTS
The United States government has rights in this invention pursuant to Contract No. DE-AC52-06NA25396 between the United States Department of Energy and Los Alamos National Security, LLC for the operation of Los Alamos National Laboratory.


FIELD OF THE INVENTION
The present invention relates to methods of producing C8-C15 hydrocarbons from renewable feedstocks such as cellulosics, sugars and glycerin, by means of an organo-catalyzed aldol reaction.
BACKGROUND OF THE INVENTION
Development of sustainable methods of making transportation fuels and surfactants from renewable resources is becoming increasingly important, due to the desirability of decreasing dependence on petroleum resources. Carbohydrates obtained from biomass are renewable and readily available, and there has been much focus on producing fuel and other useful materials from biomass-derived starting materials. Other readily available starting materials include simple sugars, glycerol and the oxidation product of glycerol, dihydroxyacetone (DHA). Compounds suitable for use as transportation fuels generally include C8-C15 hydrocarbons. Commercially useful surfactants may comprise from about 10 to about 22 carbon atoms. Therefore, in order to produce transportation fuels and surfactants from biomass-derived starting materials, the carbon chain length of the starting material must be increased. One common method of achieving this is through the aldol reaction, which forms a carbon-carbon bond between an aldehyde and a ketone. Cellulosics, sugars and glycerin can readily be converted to suitable reagents for the aldol reaction. For example, cellulose and glucose can be converted to hydroxymethylfurfural (HMF). Dihydroxyacetone can be formed from glycerol.
Use of the aldol reaction with reagents derivable from cellulosics and sugars has been described previously (see, e.g., Huber et al., Science, vol. 208, Jun. 3, 2005, pp. 1446-1450). However, the reactions resulted in a range of carbon chain lengths, and thus exhibited poor selectivity. In addition, the reactions required high temperatures (approximately 100° C.), and the use of an organic solvent in addition to water. Most important, the reaction was shown to be unsuccessful with ketone reagents other than acetone. All of these factors contribute to making the process less suitable for large-scale industrial use.
The use of a zinc-proline (Zn(Pro)2) catalyst has been shown to be successful in certain types of aldol reactions, and addresses some of the above drawbacks. Zinc-proline catalysts result in higher selectivity, and have been shown to work with DHA as a ketone reagent. To date, however, zinc-proline catalysts have shown only to successfully catalyze reactions between ketones and aromatic aldehydes (for example, benzaldehydes) and not between ketones and reagents derived from biomass sources, such as HMF. Although able to catalyze reactions in aqueous solvents and at lower temperatures, the reactions described to date using zinc-proline catalysts have required the addition of an organic co-solvent, such as tetrahydrofuran (THF).
There exists a need, therefore, for a method of increasing carbon chain length via the aldol reaction that utilizes reagents derived from biomass sources, is highly selective, can be performed at room temperature and does not require the use of an organic co-solvent, thus making the process more suitable for large-scale production with specificity. There exists a further need for additional catalysts that allow the aldol reaction to proceed under conditions suitable for large-scale use.
SUMMARY OF THE INVENTION
The present invention meets the aforementioned needs by providing a method of increasing carbon chain length by utilizing the aldol reaction that can be performed with either zinc-proline, ytterbium-proline, or metal chelated N-(2-hydroxy-2-methylpropyl)pyrrolidine-2-carboxamide based catalysts, and which can be performed at room temperature using only water as the solvent. The reaction utilizes DHA (and other ketones or aldehydes) as the ketone reagent and HMF as the aldehyde reagent, which can be obtained from biomass cellulosics. The reaction has high specificity, and results in formation of (E)-4-(5-(hydroxymethyl)furan-2-yl)but-3-en-2-one, (1E,4E)-1,5-bis(5-(hydroxymethyl)furan-2-yl)penta-1,4-dien-3-one, 3,4-dihydroxy-4-(5-(hydroxy-methyl)furan-2-yl)butan-2-one, and/or 1,3,4-trihydroxy-4-(5-(hydroxymethyl)furan-2-yl)butan-2-one, with a yield of about 60%.
The following describe some non-limiting embodiments of the present invention.
According to one embodiment of the present invention, a method of producing C8-C15 hydrocarbons is provided, comprising providing a ketone starting material; providing an aldol starting material comprising hydroxymethylfurfural; and mixing the ketone starting material and the aldol starting material in a reaction in the presence of a proline-containing catalyst selected from the group consisting of Zn(Pro)2, Yb(Pro)3, and combinations thereof, and a solvent, wherein the solvent comprises water and is substantially free of organic solvents, to produce the C8-C15 hydrocarbons.
According to another embodiment of the present invention, method of producing C8-C15 hydrocarbons is provided, comprising providing a ketone starting material; providing an aldol starting material; and mixing the ketone starting material and the aldol starting material in a reaction in the presence of a catalyst having the structure:




and a solvent, wherein the solvent comprises water and is substantially free of organic solvents, to produce the C8-C15 hydrocarbons.

According to yet another embodiment of the present invention, a method of producing C8-C15 hydrocarbons is provided, comprising providing a ketone starting material; providing an aldol starting material; and mixing the ketone starting material and the aldol starting material in a reaction in the presence of a catalyst having the structure:




wherein R1 is a C1-C6 alkyl moiety, X=(OH) and n=2, and in the presence of a solvent, wherein the solvent comprises water and is substantially free of organic solvents, to produce the C8-C15 hydrocarbons.

According to yet another embodiment of the present invention, a method of producing C8-C15 hydrocarbons is provided, comprising providing a ketone starting material; providing an aldol starting material; and mixing the ketone starting material and the aldol starting material in a reaction in the presence of a catalyst having the structure:




where X is CH2, sulfur or selenium, M is Zn, Mg, or a lanthanide, and R1 and R2 each independently are a methyl, ethyl, or phenyl moiety; and in the presence of a solvent, wherein the solvent comprises water and is substantially free of organic solvents, to produce the C8-C15 hydrocarbons.




BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 depicts one exemplary reaction scheme of the present invention, wherein acetone and HMF are the initial aldehyde and ketone reagents.
FIG. 2 depicts reactions of 5-(hydroxymethyl)furan-2-carbaldehyde (HMF) with 1 and 0.5 equivalents of acetone to produce (E)-4-(5-(hydroxymethyl)furan-2-yl)but-3-en-2-one and (1E,4E)-1,5-bis(5-(hydroxmethyl)furan-2-yl)penta-1,4-dien-3-one, respectively.
FIG. 3 depicts the reaction of HMF with hydroxyacetone to produce 3,4-dihydroxy-4-(5-(hydroxyl-methyl)furan-2-yl)butan-2-one.
FIG. 4 depicts the reaction of HMF with dihydroxyacetone to produce 1,3,4-trihydroxy-4-(5-(hydroxymethyl)furan-2-yl)butan-2-one.



DETAILED DESCRIPTION OF THE INVENTION
All documents cited in the Detailed Description of the Invention are, in relevant part, incorporated herein by reference; the citation of any document is not to be construed as an admission that it is prior art with respect to the present invention. To the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.
The present invention relates to a method of producing hydrocarbons by increasing the carbon chain length of carbohydrates, which may be derived from herbaceous and woody biomass. As used herein, “hydrocarbons” is understood to include alcohols, olefins, ketones and other compounds comprising carbon, hydrogen and oxygen (as depicted in FIG. 1), and is not intended to mean only compounds consisting of carbon and hydrogen atoms. Suitable reagents may be obtained from abundant chemical feedstocks such as glycerin. The method results in production of C8-C15 alcohols or olefins, which may be subsequently hydrogenated and dehydrated to produce, among other compounds, transportation fuels and surfactants. The method utilizes the aldol reaction, also known as the aldol condensation reaction, which forms a carbon-carbon bond between an aldehyde and a ketone (herein referred to as an “aldehyde reagent” and a “ketone reagent,” respectively).
Aldehyde reagents suitable for use in the present invention include, but are not limited to, hydroxymethylfurfural (HMF) and furan-2-carbaldehyde. Suitable ketone reagents in the present invention include acetone, dihydroxyacetone (DHA), methylacetoacetate, ethylacetoacetate, and combinations thereof.
The reaction of the aldehyde and ketone reagents proceeds in the presence of a suitable catalyst. A suitable catalyst must allow the reaction to proceed at room temperature, with water as a solvent, and result in a selectively high yield of the desired product. One suitable catalyst of the present invention is Zn(Proline)2, which may have the following structure:




Another suitable catalyst is Yb(Proline)3, or Yb(Pro)3, which has a structure similar to Zn(Proline)2, wherein the Zn is replaced by Yb.
Other suitable catalysts include the following structures (I), (II) and (III):




where R1 is a C1-C6 alkyl moiety, where “alkyl” is understood to mean a substituted or unsubstituted alkane, alkene or alkyne, X=(OH) and n=2.




In (III), X may be CH2, sulfur or selenium, M may be Zn, Mg, or a lanthanide, and R1 and R2 each independently may be a methyl, ethyl, phenyl moiety. It is to be understood that the phenyl group may comprise heteroatoms such as nitrogen or oxygen, provided that the atoms in R1 or R2 which are closest to the N-(2-hydroxy-2-methylpropyl)pyrrolidine-2-carboxamide core structure are a CH2 group. In one embodiment, the reaction is performed in a solvent which comprises water and is substantially free of organic solvents. By “substantially free of organic solvents” is meant that the amount of organic solvent is about 1% or less. By “organic solvent” organic solvents other than water or salts that would be understood by one of skill in the art to be used in synthesis reactions, including but not limited to dimethylformamide (DMF), tetrahydrofuran (THF), alcohols, etc. The solvent further may comprise a salt, brine, saturated sodium chloride, or natural waters comprising salts. The reaction may be performed at room temperature (25° C.), and alternatively at a temperature of from about 0° C. to about 100° C. The reaction may have a yield of at least 60%, alternatively of at least 75%, alternatively of at least 90%, and alternatively of at least 99%. The reaction sequence can be tuned to give desired fuel properties by reaction with, for example, the DHA-furan complex, by employing selective regiochemistry.
EXAMPLES
Example 1
The reactions were performed in water without adjustment of pH. Piperidine was used in 5 mol %. HMF (0.631 g, 5.00 mmol) was charged in a small round bottom flask with a stirring bar, water (4.0 mL) was added. Acetone (0.290 g, 5.00 mmol (1 equivalent) or 0.25 mmol (0.5 equivalent) was then added. The mixture was then stirred while piperidine was added at room temperature. The reaction mixture was kept closed with a plastic cap and stirred for 20 hrs. The stirring bar was removed and silica gel was added. The mixture was dried with rotary evaporation. The residue was loaded on silica gel and eluted with 50% ethyl acetate in hexanes to provide mono-HMF adduct (0.191 g, 23%) as a light yellow solid. 1H NMR (CDCl3) δ 7.16 (d, J=16.0 Hz), 6.55 (d, J=3.45 Hz), 6.51 (d, J=16.0 Hz), 6.32 (d, J=3.40 Hz), 4.57 (s), 2.23 (s). 13C NMR (CDCl3) δ 198.6, 157.5, 150.6, 129.8, 123.9, 117.1, 110.5, 57.4, 27.9. And di-HMF adduct (0.469 g, 68%) as a dark reddish solid. 1H NMR (CDCl3) δ 7.43 (d, J=15.5 Hz), 6.90 (d, J=15.6 Hz), 6.60 (d, J=3.29 Hz), 6.39 (d, J=3.29 Hz), 4.65 (s). 13C NMR (CDCl3) δ 188.4, 157.0, 151.6, 129.4, 123.3, 117.2, 110.8, 57.8. The yield of the di-HMF adduct was about 68% when 1 equivalent of acetone was used, and about 73% when 0.5 equivalents of acetone were used.
Example 2
In a 100 mL single-necked round bottom flask was placed HOBT (hydroxybenzotriazole) (1.95 g), L-Boc-proline (3.00 g), and 2-hydroxy-2-methyl-propyl-1-amine To this was added 70 mL of anhydrous acetonitrile. This was stirred until homogenous and then chilled to 0° C. The EDC (1-ethyl-3-(3-dimethylaminopropyl) carbodiimide), (3.20 g) was added in one portion to this mixture. The mixture was allowed to warm to room temperature and stirred overnight. The solvent was removed in vacuo. The remaining material was then taken up in 60 mL of methylene chloride and subsequently washed 4x with 10 mL of 5% citric acid. The suspension was filtered and dried over sodium sulfate. Filtration and removal of the solvent gave rise to the crude material. Purification by silica gel chromatography using 10% methanol/methylene chloride as eluent afforded 3.0336 g of an amide having the structure (IV), tert-butyl 2-(2-hydroxy-2-methylpropylcarbamoyl)pyrrolidine-1-carboxylate. 1H NMR (CDCl3) d 4.29 (J=4.2 Hz, 1H), 3.45 (m, 2H), 3.26 (m 2H), 1.92 (m, 2H), 1.62 (m, 2H), 1.47 (s, 9H), 1.22 (s, 6H).




Whereas particular embodiments of the present invention have been illustrated and described, it would be clear to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.

## Claims

1. A method of producing a C8-C15 hydrocarbon comprising:
a) providing a ketone starting material;
b) providing an aldol starting material comprising hydroxymethylfurfural; and
c) mixing the ketone starting material and the aldol starting material in a reaction in the presence of a piperidine-containing catalyst and a solvent, wherein the solvent comprises water that is substantially free of organic solvents, to produce the C8-C15 hydrocarbon.

2. The method of claim 1, wherein the ketone starting material comprises acetone, dihydroxyacetone, or combinations thereof.

3. The method of claim 1, wherein the reaction occurs at about 25° C.

4. The method of claim 1, wherein the solvent further comprises a salt.

5. The method of claim 1, further comprising hydrogenating and dehydrating the C8-C15 hydrocarbon.