Method of converting levulinic acid or a derivative thereof to hydrocarbons and hydrogen, and methods of the production of hydrocarbons and hydrogen

Abstract

The present invention relates to a method of converting levulinic acid or a derivative thereof to hydrocarbons and hydrogen by providing a source of levulinic acid or a derivative thereof and converting the levulinic acid or a derivative thereof in the source to hydrocarbons and hydrogen, where converting is carried out in a single reactor. The present invention also relates to methods for producing hydrocarbons and hydrogen.

Claims

1. A method of converting levulinic acid or a derivative thereof to hydrocarbons and hydrogen, said method comprising: providing a source of levulinic acid or a derivative thereof and converting levulinic acid or a derivative thereof in the source to hydrocarbons and hydrogen, wherein said converting is carried out in a single reactor.

2. The method according to claim 1, wherein said converting is carried out in the presence of a catalyst.

3. The method according to claim 2, wherein the catalyst is selected from a metal, metal oxide, zeolite, or mixture thereof.

4. The method according to claim 3, wherein the catalyst is selected from Fe, Co, Ni, Ru, Sn, Mo, Pt, or a mixture thereof.

5. The method according to claim 2, wherein said catalyst is present on a support material.

6. The method according to claim 5, wherein the support material is selected from carbon, graphene, silicon dioxide, titanium oxide, zirconium oxide, cerium oxide, zeolite, or a mixture thereof.

7. The method according to claim 1, wherein said converting is carried out in the presence of water.

8. The method according to claim 1, wherein said converting is carried out in the presence of formic acid.

9. The method according to claim 1, wherein carbon dioxide is produced as a product.

10. The method according to claim 1, wherein said converting is carried out at temperature of about 200-400 C.

11. The method according to claim 1, wherein said reactor is a high pressure vessel.

12. The method according to claim 1, wherein said reactor is a flow reactor.

13. The method according to claim 1, wherein said converting is carried out at a pressure of about 500-5000 psi.

14. The method according to claim 1, wherein said converting is carried out under an inert atmosphere.

15. The method according to claim 14, wherein said converting is carried out in the presence of nitrogen gas, helium, argon, or carbon dioxide.

16. The method according to claim 1, wherein said converting is carried out in the presence of a reducing agent selected from hydrogen, carbon monoxide, or a mixture thereof.

17. The method according to claim 1, wherein said converting is carried out in the presence of hydrocarbons.

18. The method according to claim 1, wherein said converting is carried out for a period of about 1 to about 24 hours.

19. The method according to claim 1, wherein said converting yields less than about 10% oxygenates.

20. The method according to claim 1, wherein said converting results in an overall yield of 60-99% hydrocarbons.

21. The method according to claim 1, wherein said hydrocarbons comprise olefins, aromatics, and alkanes.

22. The method according to claim 21, wherein said olefins, aromatics, and alkanes comprise one or more of the following: ##STR00004##

23. The method according to claim 1, wherein levulinic acid is converted to hydrocarbons.

24. The method according to claim 1, wherein levulinate ester is converted to hydrocarbons.

25. A method of producing hydrocarbons and hydrogen, said method comprising: providing a reactor comprising: levulinic acid or a derivative thereof; water; and formic acid and heating the reactor or contents therein under conditions effective to convert the levulinic acid or derivative thereof to hydrocarbons and hydrogen.

26. The method according to claim 25, wherein the reactor further comprises a metal or metal oxide catalyst.

27. The method according to claim 25, wherein said heating is carried out to a temperature of about 200-400 C.

28. The method according to claim 25, wherein said heating is carried out for about 1 to about 24 hours.

29. A method for producing hydrocarbons and hydrogen from biomass, said method comprising: providing lignocellulosic biomass; reacting the biomass with reagents under conditions effective to produce levulinic acid or a derivative thereof; and converting the levulinic acid or derivative thereof to hydrocarbons and hydrogen, wherein said converting is carried out in a single reactor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows GC spectrum of oil layer products. The samples were diluted with acetone. 100 L of 3-methyl-2-butanone and 100 L of 1,4-dioxane were used as internal standards. The typical components were identified by GC-MS, such as 2-butanone, 3,5-dimethylcyclopentene, 1,3-dimethylcyclohexene, 3,5-dimethylcyclohexene, 1,4-dimethylcyclohexene, 3-methylcyclopentanone, xylenes, GVL, 2,3-dimethylcyclopentanone, tetrahydrodimethylnaphthalene, etc. (listed by retention time).

(2) FIG. 2 shows the chemical structures of representative C4+ products obtained from the conversion of levulinic acid in the presence of NiSn/SiO.sub.2 catalyst. The structures were determined by gas chromatography mass spectrography (GC-MS) analysis.

(3) FIG. 3 shows images of products obtained after reaction. Reaction conditions: 1 g catalyst, 15 g levulinic acid, 15 g water, 5.9 g formic acid, 300 C., 12 hours. The left image shows the products after centrifugation. 4.84 g of oil products was obtained from the top layer. 73 wt % liquid was recovered from the oil products with distillation under reduced pressure (the remaining was wax residue).

(4) FIG. 4 shows .sup.13C NMR of oily product. CDCl.sub.3 was used as the solvent. The major component (>97%) of carbon is olefinic, aromatic, and alkyl carbon. The amount of ketonic and carboxylic carbon is less than 3%.

(5) FIG. 5 shows .sup.1H NMR of oily products. CDCl.sub.3 was used as the solvent. The major component of hydrogen is also olefinic, aromatic, and alkyl hydrogen, which agrees with the .sup.13C NMR of the oily product.

(6) FIG. 6 shows gas chromatography (GC) spectra of the oil sample (solid line) and acetone (blank sample; dashed line) obtained on nonpolar HP-5 capillary column. The oil sample was diluted with acetone before GC analysis. N-hexadecane was added before the reaction as the solvent. 1: acetone; 2: 3-methyl-2-butanone (internal standard); 3: 1,4-dioxane (internal standard); 4: n-hexadecane. Inset picture: Oil layer sample obtained after reaction (14.7 g in total; containing approximately 4.7 g oil products and 10 g n-hexadecane). The picture was not subjected to any artificial adjustment to retain its natural appearance.

DETAILED DESCRIPTION OF THE INVENTION

(7) Disclosed herein is a method of converting levulinic acid or a derivative thereof to hydrocarbons and hydrogen, and methods of the production of hydrocarbons and hydrogen in the same process.

(8) One aspect of the present invention relates to a method of converting levulinic acid or a derivative thereof to hydrocarbons and hydrogen. This method involves providing a source of levulinic acid or a derivative thereof and converting levulinic acid or a derivative thereof in the source to hydrocarbons and hydrogen, where said converting is carried out in a single reactor.

(9) Levulinic acid is a well-known compound having the following chemical structure:

(10) ##STR00001##

(11) Levulinic acid derivatives are also well-known and include, without limitation, esters of levulinic acid (e.g., levulinate ester), salts of levulinic acid (e.g., ammonium levulinate), amides of levulinic acid, acid halides of levulinic acid, nitriles of levulinic acid, and anhydrides of levulinic acid.

(12) In one embodiment, this and other aspects of the present invention are carried out to convert levulinic acid to hydrocarbons and hydrogen. In another embodiment, this and other aspects of the present invention are carried out to convert levulinate ester (or another levulinic acid derivative, or a mixture of levulinic acid derivatives) to hydrocarbons and hydrogen. In a further embodiment, this and other aspects of the present invention are carried out to convert a mixture of levulinic acid and one or more levulinic acid derivatives to hydrocarbons and hydrogen.

(13) As used herein the term source of levulinic acid or a derivative thereof or source refers to a starting material for carrying out this and other methods of the present invention. Suitable sources of levulinic acid or a derivative thereof include any material that contains levulinic acid or a levulinic acid derivative and can be used as a starting material in carrying out this and other methods of the present invention. According to one embodiment, the source of levulinic acid or a derivative thereof is pure or substantially pure levulinic acid, pure or substantially pure derivative of levulinic acid, pure or substantially pure mixture of derivatives of levulinic acid, or pure or substantially pure mixture of levulinic acid and one or more derivatives of levulinic acid. In one embodiment, filtration, liquid-liquid extraction, or distillation is used to generate a source of levulinic acid or a derivative thereof to separate levulinic acid or a derivative thereof from carbon precipitates, water, mineral acid catalyst, and/or furfural. According to another embodiment, the source of levulinic acid or a derivative thereof is not pure or substantially pure, but contains an amount of levulinic acid or a derivative thereof sufficient as a starting material in carrying out this and other methods of the present invention.

(14) According to one embodiment, a suitable but non-limiting source of levulinic acid or a derivative thereof is biomass material, such as cellulosic biomass or lignocellulosic biomass. As used herein, the terms biomass, cellulosic biomass, or lignocellulosic biomass refer to any plant material, vegetation, or vegetative agricultural waste from any source that can be used to supply carbohydrates to be used as reactants in any of the methods of the present invention where a source of levulinic acid or a derivative thereof is used. Exemplary cellulosic biomass includes, without limitation, corn stover, sugarcane bagasse, wheat straw, saw mill and paper mill discards (e.g., pine saw dust), and energy crops (e.g., switch grass) which are known to give high yield of levulinic acid. Energy crops are crops with high yield of lignocellulosic biomass produced to serve as a raw material for production of second generation biofuel. Suitable non-limiting examples include switch grass (Panicum virgatum), sorghum, and Elephant grass.

(15) In one embodiment, it may be desirable to purify or partly purify the biomass to a higher concentration of levulinic acid or a derivative thereof than what naturally exists in the biomass. For example, methods of obtaining levulinic acid from cellulosic biomass are well known and include, without limitation, the methods described in U.S. Pat. No. 6,054,611 to Farone and Cuzens, which is hereby incorporated by reference in its entirety.

(16) Accordingly, in carrying out this and other methods of the present invention, providing a source of levulinic acid or a derivative thereof, is meant that the source of levulinic acid or a derivative thereof is used as a starting material for carrying out a reaction that converts levulinic acid or a derivative thereof to hydrocarbons and hydrogen. The source of levulinic acid or a derivative thereof may be provided as a pure or substantially pure source, as discussed supra, or a solution or mixture containing levulinic acid or a derivative thereof in something other than a pure or substantially pure form. By providing it is also meant that the source of levulinic acid or a derivative thereof is in a reactor, placed in a reactor, or capable of being introduced into a reactor to carry out this and other methods of the present invention.

(17) As used herein, converting levulinic acid or a derivative thereof means using the source of levulinic acid or a derivative thereof as the starting material in a chemical reaction that chemically converts the levulinic acid or derivative thereof to hydrocarbons and hydrogen.

(18) According to this and other aspects of the present invention, converting levulinic acid or a derivative thereof is carried out in a single reactor. A significant achievement of the present invention is in converting levulinic acid or a derivative thereof to hydrocarbons and hydrogen together in a single reactor, without having to separate reactants, carry out multiple processing steps, or use multiple reactors to achieve the desired product (i.e., hydrocarbons and hydrogen). In other words, the source of levulinic acid or a derivative thereof is directly converted to hydrocarbons and hydrogen without having to carry out multiple reaction steps in multiple reactors or reactor chambers, as has historically been the case. Instead, converting levulinic acid or a derivative thereof to hydrocarbons and hydrogen, according to this and other aspects of the present invention, occurs in a single reactor, pot, or reaction chamber, without it being necessary to transfer reactants or products from one reactor or reaction chamber to another to carry out multiple reaction or processing steps.

(19) In carrying out this and other methods of the present invention, the reactor can include a high pressure vessel (e.g., a sealed reactor), a batch reactor, or a continuous flow reactor. In one embodiment, the reactor used in carrying out this and other methods of the present invention is a high pressure vessel. In another embodiment, the reactor used in carrying out this and other methods of the present invention is a continuous flow reactor. In a continuous flow reactor, material (e.g., a source of levulinic acid or a derivative thereof) flows as a stream through the reactor, and reactants are continuously fed into the reactor and emerge as a stream of product. The continuous flow reactor is operated at elevated pressures. Alternatively, the reactor is not a continuous flow reactor, and the method is carried out by converting levulinic acid or a derivative thereof according to batch production.

(20) In one embodiment of this and other methods of the present invention, converting levulinic acid or a derivative thereof in the source to hydrocarbons and hydrogen is carried out in the presence of a catalyst, although a catalyst is not required to carry out the method of this and other aspects of the present invention. When used, a suitable catalyst may include, without limitation, a metal, metal oxide, zeolite, or a mixture thereof. For example, the catalyst may be selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Ru, Ag, W, Pt, and Sn. In one particular embodiment, the catalyst is selected from Fe, Co, Ni, Ru, Sn, Mo, Pt, or mixture thereof.

(21) In one embodiment, converting levulinic acid or a derivative thereof is carried out using a catalyst. According to one embodiment, the catalyst is present on or with a support material. Suitable support materials include, without limitation, carbon (e.g., graphite, activate carbon, carbon black, carbon nanotube, graphene, and any of their functionalized derivatives), silicon dioxide, titanium oxide, zirconium oxide, cerium oxide, zinc oxide, zeolite, or mixtures thereof. By being present on or with a support material the catalyst may be contained in a reaction solution on the support material, attached or in contact with a surface of the support material, or part of the surface chemistry of the support material. Alternatively, converting levulinic acid or a derivative thereof is carried out using a catalyst that is added to a reactor containing the source of levulinic acid or a derivative thereof. For example, catalyst may be added drop-wise into the reactor, or may be mixed with the starting material before or during the conversion reaction in the reactor.

(22) Converting levulinic acid or a derivative thereof according to this and other aspects of the present invention may be carried out in the presence of water. A suitable amount of water includes, without limitation, an equal amount of water to the amount of levulinic acid. Other amounts of water may be used, including water in a ratio of water to levulinic acid or a derivative thereof of about 1:1, 0.9:1, 0.8:1, 0.7:1, 0.6:1, 0.5:1, 0.4:1, 0.3:1, 0.2:1, 0.1:1, 0:1, 1:0.9, 1:0.8, 1:0.7, 1:0.6, 1:0.5, 1:0.4, 1:0.3, 1:0.2, or 1:0.1.

(23) In another embodiment of this and other methods of the present invention, converting is carried out in the presence of formic acid. When carried out in the presence of formic acid, the formic acid may be present in the reactor in an amount of formic acid to levulinic acid or derivative thereof of about 0:1 (i.e., no formic acid), 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, or 2.0:1.

(24) In carrying out this and other methods of the present invention, in addition to hydrocarbons, hydrogen is produced as a product. In yet another embodiment, carbon dioxide is also produced as a product.

(25) Converting levulinic acid or a derivative thereof to hydrocarbons and hydrogen according to this and other methods of the present invention is carried out at temperature of about 200 C.-400 C., about 250 C.-350 C., or about 280 C.-320 C. While reaction temperatures may vary, as described herein, so too may the reaction times. For example, in carrying out this and other methods of the present invention, converting is carried out for a period of about 1 to about 24 hours, about 2 to about 23 hours, about 3 to about 22 hours, about 4 to about 21 hours, about 5 to about 20 hours, about 6 to about 19 hours, about 6 to about 12 hours, about 7 to about 11 hours, about 8 to about 10 hours, or about 9 hours.

(26) In carrying out this and other methods of the present invention, converting is carried out in the reactor at a pressure of about 500 to about 5,000 psi, about 750 to about 4,500 psi, about 1,000 to about 4,000 psi, about 1,500 to about 3,500 psi, or about 2,000 to about 3,000 psi.

(27) In the method of this and other aspects of the present invention, converting is carried out under an inert atmosphere. Alternatively, converting may be carried out in the presence of nitrogen gas, helium, argon, or carbon dioxide. In another embodiment, converting is carried out in the presence of a reducing agent selected from hydrogen, carbon monoxide, or a mixture thereof. In yet another embodiment, converting is carried out in the presence of hydrocarbons (e.g., n-hexadecane).

(28) In carrying out this and other methods of the present invention, converting levulinic acid or a derivative thereof to hydrocarbons and hydrogen yields less than about 10% oxygenates, less than about 9% oxygenates, less than about 8% oxygenates, less than about 7% oxygenates, less than about 6% oxygenates, less than about 5% oxygenates, less than about 4% oxygenates, less than about 3% oxygenates, less than about 2% oxygenates, or less than about 1% oxygenates. The term oxygenates refers to chemical compounds that contain oxygen as a part of their chemical structure, except for carbon monoxide, carbon dioxide, and water.

(29) In carrying out the method of this and other aspects of the present invention, converting levulinic acid or a derivative thereof to hydrocarbons and hydrogen results in an overall yield of at least about 60%, 65%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% hydrocarbons. Alternatively, converting levulinic acid or a derivative thereof to hydrocarbons results in an overall yield of about 60%-99% hydrocarbons or 70%-90% hydrocarbons.

(30) In carrying out the method of this and other aspects of the present invention, when hydrogen is produced as a product, converting levulinic acid or a derivative thereof to hydrocarbons and hydrogen results in a hydrogen to hydrocarbon ratio of at least about 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, or 0.5:1. The hydrogen to hydrocarbon ratio refers to the molar ratio of dihydrogen gas to carbon atoms of hydrocarbons.

(31) As used herein, hydrocarbons includes aromatics, olefins (e.g., linear chain olefins), cycloalkenes, and saturated hydrocarbons (e.g., alkanes). For example, and without limitation, hydrocarbons produced according to this and the other methods of the present invention include olefins, aromatics, and alkanes comprising one or more of the following:

(32) ##STR00002##

(33) Another aspect of the present invention relates to a method of producing hydrocarbons and hydrogen. This method involves providing a reactor that includes levulinic acid or a derivative thereof, water, and formic acid. The reactor or contents therein are heated under conditions effective to convert the levulinic acid or derivative thereof to hydrocarbons and hydrogen.

(34) In carrying out this aspect of the present invention, in one embodiment, the reactor further comprises a metal or metal oxide catalyst as described supra.

(35) Moreover, any and all descriptions related to the aspect of the invention described supra, are also applicable to the method of this aspect of the present invention.

(36) Another aspect of the present invention relates to a method of producing hydrogen. This method involves providing a reactor that includes levulinic acid or a derivative thereof, water, and formic acid. The reactor or contents therein are heated under conditions effective to convert the levulinic acid or a derivative thereof, water, and formic acid to hydrogen.

(37) Yet another aspect of the present invention relates to a method for producing hydrocarbons and hydrogen from biomass. This method involves providing lignocellulosic biomass; reacting the biomass with reagents under conditions effective to produce levulinic acid or a derivative thereof and converting the levulinic acid or derivative thereof to hydrocarbons and hydrogen, where the converting is carried out in a single reactor.

(38) In carrying out this aspect of the present invention, reacting biomass with reagents under conditions effective to produce levulinic acid or a derivative thereof are well known in the art. See, e.g., Rackemann & Doherty, The Conversion of Lignocellulosics to Levulinic Acid, Biofuels, Bioproducts, and Biorefining 5(2):198-214 (2011), which is hereby incorporated by reference in its entirety.

(39) Further, any and all descriptions related to the aspects of the invention described supra, e.g., with respect to converting levulinic acid or a derivative thereof to hydrocarbons and hydrogen, are also applicable to the method of this aspect of the present invention.

(40) A further aspect of the present invention relates to a method for producing hydrocarbons and hydrogen from biomass. This method involves providing lignocellulosic biomass and reacting the biomass with reagents under conditions effective to produce levulinic acid or a derivative thereof. A reactor is provided that includes the levulinic acid or a derivative thereof, water, and formic acid. The reactor or contents therein is heated under conditions effective to convert the levulinic acid or derivative thereof to hydrocarbons and hydrogen.

(41) Any and all descriptions related to the aspects of the invention described supra, are also applicable to the method of this aspect of the present invention.

EXAMPLES

Example 1The Conversion of Levulinic Acid to Hydrocarbons and Hydrogen I

(42) Experimental Conditions

(43) The conversion of levulinic acid to hydrocarbons and hydrogen was carried out in a 100 mL Parr 4590 high-pressure/high-temperature micro stirred reactor equipped with mechanical stirring. In a typical experiment, 0.5-2 g of catalyst, 15.0 g of levulinic acid (>97%, Sigma Aldrich), and 15.0 g deionized water were added into a glass liner, which was placed in the vessel. Formic acid (5.9 g; formic acid/levulinic acid=1 molar ratio) was added. The reactor was purged with N.sub.2 (99.997%) three times, and finally sealed at a N.sub.2 pressure of 10 bar. After maintaining the reaction at the target temperature for a certain amount of time, the reaction was terminated by ceasing mechanical stirring and removing the furnace.

(44) After cooling down to room temperature, the gaseous product was collected in a gas sample bag, and analyzed using gas chromatography (GC) and gas chromatography mass spectrography (GC-MS). The amounts of carbon dioxide and other hydrocarbons in the gaseous sample were determined using nitrogen as the internal standard on the same GC system equipped with a packed column (HAYESEP D, 15 FT, 100/120 mesh), a 10-way sampling valve, and a thermal conductivity detector. The amount of hydrogen was determined using an external standard on the same GC system. The amounts of hydrocarbons in the gaseous sample were also analyzed on a HP 5890 GC system equipped with a capillary column (HP-PLOT Q, 30 m0.32 mm20.0 m), a 10-way sampling valve and a flame ionization detector. 1-Butene, trans-2-butene, and cis-2-butene were identified using an on-line mass spectrometer (Agilent 5973N) connected to the outlet of the thermal conductivity detector of a GC system.

(45) The liquid phase, also containing solids, was collected in centrifuge tubes. After centrifugation at 8,000 rpm for 10 minutes, the oily layer, the aqueous layer, and solid precipitate were separated. The solid precipitate was extracted with 10 mL acetone 3 times. The extracted solution was combined and then analyzed using GC and GC-MS. The solid precipitate was dried in an oven at 110 C. overnight and then weighed. The yield of humin was calculated using the change in the mass of solids before and after reaction.

(46) Liquid phase products, including oily layer, aqueous layer, and extracted acetone solution, were analyzed using GC and GC-MS. Around 100 L of 3-methyl-2-butanone (Aldrich, 99%) and 100 L of 1,4-dioxane (Fisher Scientific) were added into the oily layer, aqueous layer, or extracted acetone solution as internal standards.

(47) The components in liquid phase were identified on a GC-MS system (Agilent 6890N GC/5975N MSD) equipped with a capillary column (HP-5 ms, 30 m0.32 mm0.25 m). For quantitative analysis, a calibration standard solution containing 2-butanone, gamma-valerolactone (GVL), levulinic acid, 3-methyl-2-butanone, 1,4-dioxane, cyclohexene (Alfa Aesar), m-xylene (99+%, Acros Organics), and hexadecane (Sigma-Aldrich) was prepared to determine the response factor of the products.

(48) The amounts of levulinic acid and GVL were measured on a HP 5890 GC system equipped with a capillary column (DB-WAXetr, 30 m0.25 mm0.25 m), which can provide better resolution for levulinic acid detection.

(49) The yield of humin was calculated using the change in the mass of solids before and after reaction.

(50) The aqueous phase products were separated and subjected to vacuum distillation to remove water. The remaining residue was dark brown liquid or tar. These byproducts could come from side reactions of levulinic acid conversion and was therefore considered in a carbon balance calculation (assume it has the same elemental composition as levulinic acid). Carbon balance was calculated using the total amount of carbon detected from GC analysis of the products after reaction, including CO.sub.2, C1-C4 gaseous products, C4+ hydrocarbons in liquid phase, divided by the total amount of carbon from levulinic acid and formic acid. The CHN elemental analysis was carried out on a Perkin Elmer 2100 Series II CHN/S Analyzer. .sup.1H and .sup.13C NMR analysis of oily products was carried out using a Varian MR-400 NMR instrument.

(51) Results

(52) The results indicated that in all cases levulinic acid could be converted to olefins, aromatics (shown in FIGS. 1 and 2), hydrogen, and carbon dioxide in one pot (Scheme 1), on the basis of GC and GC-MS analysis.

(53) ##STR00003##

Example 2The Conversion of Levulinic Acid to Hydrocarbons and Hydrogen II

(54) In another experiment, levulinic acid (15 g; 0.13 mol), formic acid (6.9 g; 0.13 mole), water (15 g), and 10 wt % NiSn/SiO.sub.2 catalyst (1.0 g) were mixed and heated to 300 C. in a high pressure vessel. The reactants were kept at this temperature for 12 hours. After reaction, a phase separation in the product solution which included a hydrocarbon phase at the upper layer (5 g) and an aqueous phase at the bottom layer (18 g) (FIG. 3) was observed. The products from oily phase, aqueous phase, and gas phase were analyzed with GC and GC-MS. The yield of C4+ hydrocarbons was calculated. It was found that the overall yield of C4+ hydrocarbon products can reach 60-90% of the theoretical value during several parallel runs. Based on GC-MS analysis, it was found that the oily products mainly included olefins and monocyclic aromatics (97 wt %), such as 3,5-dimethylcyclopentene, 1,3-dimethylcyclohexene, 3,5-dimethylcyclohexene, 1,4-dimethylcyclohexene, xylene, and tetrahydrodimethylnaphthalene (FIG. 2). Only small amounts of oxygenates (3 wt %), such as butanone, gamma-valerolactone, and 2,3-dimethylcyclopentanone, were detected. .sup.13C and .sup.1H NMR spectroscopy (FIGS. 4 and 5) revealed that major component of carbon (>97%) is olefinic, aromatic, and alkyl carbon. The amount of ketonic and carboxylic carbon is less than 3%.

(55) Higher heating value of crude hydrocarbon products was measured to be 39.7 MJ/kg, which is close to those of benzene (41.9 MJ/kg) and biodiesel (40.2 MJ/kg), suggesting that the products are suited for use as transportation fuels.

(56) Olefins and monocyclic aromatics are common components in conventional petroleum based gasoline, diesel, and jet fuels. Hence, in principle, the products obtained from the proposed process could be used as drop in gasoline, diesel, and jet fuels after distillation (Scheme 1). Vacuum distillation for the products was performed, and it was found that at least 73 wt % of the products can be separated with distillation (FIG. 3). These lower boiling point products can be directly used as drop in gasoline, diesel, and jet fuels when separated with appropriate boiling point range. The remaining residue (27 wt %) is mainly wax product, which could be used as lubricants, coatings, etc.

(57) Furthermore, it was found that butenes, hydrogen, and carbon dioxide are the major products in gas phase, based on GC analysis. It was determined that the amount of hydrogen is 0.11 mole, which is very close to the amount of levulinic acid reactant (0.13 mole). Hydrogen produced from this process is significant because hydrogen is required in many biomass conversion processes in order to remove excessive oxygen from cellulosic biomass. In the process described here, the production of hydrogen is mainly due to the formation of cycloalkenes and aromatics. The H/C ratio of oily products is 1.55, which was determined by CHNS elemental analysis.

Example 3Influence of Water in the Conversion of Levulinic Acid to Hydrocarbons and Hydrogen

(58) It was found that water is necessary for the reaction set forth in Examples 1 and 2 above in order to obtain high yields, lighter color, and less viscosity for liquid products. When ethanol was used instead of water as the solvent and other reaction parameters are the same as those in Example 2, the product distribution was changed, where gamma-valerolactone and ethyl levulinate became the major products.

Example 4Influence of Catalysts in the Conversion of Levulinic Acid to Hydrocarbons and Hydrogen

(59) A variety of catalysts, including 10% Mo/graphene, 10% Fe/graphene, 10% Co/graphene, 10% Ni/graphene, 10% NiSn/SiO.sub.2, 1% Ru-10% Ni/SiO.sub.2, 1% Ru-10% NiSn/SiO.sub.2, 10% NiSn/carbon black (Vulcan XC72), 10% NiSn/TiO.sub.2, 5% Pt/CeO.sub.2, 5% Pt/Ce.sub.0.27Zr.sub.0.73O.sub.2 were tested using the same reaction condition as Example 2 (catalyst amount may vary). Those catalysts were prepared with wetness impregnating the corresponding metal salt precursors with appropriate support materials, followed by reduction at elevated temperatures (400-900 C.) under 10% hydrogen/helium flow. The results of levulinic acid conversion were shown in Table 1.

(60) It was found that hydrocarbons and hydrogen could be obtained in all cases. In the absence of any catalysts though, the yield of C4+ hydrocarbon products is relatively low (56.2%) and the liquid products are more viscous (estimated with eye).

(61) When suitable catalysts such as 10% NiSn/SiO.sub.2, 1% Ru-10% Ni/SiO.sub.2, 1% Ru-10% NiSn/SiO.sub.2, 10% NiSn/TiO.sub.2, 5% Pt/CeO.sub.2, 5% Pt/Ce.sub.0.27Zr.sub.0.73O.sub.2, 10% Ni/graphene, 10% Mo/graphene, MgOSiO.sub.2 (2:1 in molar ratio) and HZSM-5 zeolite were used, higher yields of hydrocarbon products could be obtained (>60%). The yield of hydrogen is typically in the range of 0.075-0.18 mole under current reaction conditions.

(62) When 10% NiSn/carbon black (Vulcan XC72), 10% Fe/graphene, 10% Co/graphene was used as the catalyst, lower hydrocarbons yields were obtained. Moreover, high humin yields were found when 10% NiSn/carbon black (Vulcan XC72), 10% Mo/graphene, and MgOSiO.sub.2 (2:1 in molar ratio) were used as the catalyst. Therefore, selected catalysts may be better suited for use in this reaction.

(63) TABLE-US-00001 TABLE 1 Summary of the Conversion of LA to Hydrocarbons and Hydrogen Over Various Catalysts Mass of Yield of C4+ Yield of catalyst Conversion hydrocarbons Humin Entry Catalyst (g) (%) H.sub.2 (mol) (%) (%) 1 Blank 0 96.8 0.17 56.2 0.9 2 10% NiSn/SiO.sub.2 0.05 97.4 0.11 75.3 2.2 3 1% Ru10% NiSn/SiO.sub.2 1.0 97.3 0.078 85.6 ND 4 1% Ru10% Ni/SiO.sub.2 1.0 98.9 0.091 92.8 1.1 5 10% NiSn/carbon black 0.2 97.7 0.10 15.7 13.1 (Vulcan XC72) 6 10% NiSn/TiO.sub.2 0.2 97.4 0.14 67.6 0.2 7 5% Pt/Ce.sub.0.27Zr.sub.0.73O.sub.2 0.2 96.2 0.18 76.7 0.7302 8 5% Pt/CeO.sub.2 0. 2 97.2 0.16 73.6 0 9 10% Fe/graphene 0.05 98.3 0.17 43.9 1.9 10 10% Co/graphene 0.05 99.2 ND 38.7 1.5 11 10% Ni/graphene 0.05 96.9 ND 61.4 1.0 12 10% Mo/graphene 0.2 98.4 0.075 70.3 11.1 13 MgOSiO.sub.2 0.2 99.9 0.12 74.3 28.7 14 HZSM-5 0. 2 96.7 0.057 98.0 0.5 ND: not determined.

Example 5Influence of Formic Acid in the Conversion of Levulinic Acid to Hydrocarbons and Hydrogen

(64) The influence of formic acid was studied in the absence of catalyst. In the experiment, 15 g of levulinic acid, 0 g or 5.9 g of formic acid, and 15.0 g water were added together. The mixture was heated to 300 C. under 10 bar N.sub.2, and kept at this temperature for 24 hours. After reaction, the similar yields of C4+ hydrocarbons (54.5 and 61.7%) and humin (4.1 and 5.2%) were obtained. The major difference is the amount of generated hydrogen. Significantly more hydrogen (0.096 mole vs 0.024 mole) could be obtained after adding formic acid.

(65) TABLE-US-00002 TABLE 2 Influence of Formic Acid Formic Con- Yield of C4+ Yield of acid version H.sub.2 hydrocarbons Humin Entry Catalyst (g) (%) (mol) (%) (%) 1 No catalyst 0 97.1 0.024 54.5 4.1 2 No catalyst 5.9 99.6 0.096 61.7 5.2

Example 6Influence of Reaction Temperature in the Conversion of Levulinic Acid to Hydrocarbons and Hydrogen

(66) The influence of reaction temperature was studied in the absence of catalyst. In the experiment, 15 g of levulinic acid, 5.9 g of formic acid, and 15.0 g water were added together. The mixture was heated to target temperature (240, 270, or 300 C.) under 10 bar N.sub.2, and kept at this temperature for 12 hours. It was found that the conversion of levulinic acid, the amount of generated hydrogen, the yield of C4+ hydrocarbons, and the yield of humin increased with rising reaction temperatures. The conversion of levulinic acid is almost complete at 300 C. even in the absence of catalyst.

(67) TABLE-US-00003 TABLE 3 Influence of Reaction Temperature Tem- Con- Yield of C4+ Yield of perature version H.sub.2 hydrocarbons Humin Entry Catalyst ( C.) (%) (mol) (%) (%) 1 No catalyst 240 92.1 0.033 27.8 0 2 No catalyst 270 93.6 0.10 48.0 0.5 3 No catalyst 300 96.8 0.17 56.2 0.9

Example 7Influence of Hydrophobic Solvent in the Conversion of Levulinic Acid to Hydrocarbons and Hydrogen

(68) The influence of hydrophobic solvent was studied by adding 10 g n-hexadecane to the mixture containing 15 g of levulinic acid, 5.9 g of formic acid, 15.0 g water, and 1.0 g 10% NiSn/SiO.sub.2 catalyst. A bi-phase system was formed which contains n-hexadecane as the top layer and aqueous solution as the bottom layer (Table 4, entries 6-9). It was found that the top layer gained weight (15 g) after the reaction at 320 C. for 12 hours, indicating that oily products formed. The top layer products showed light brownish color, suggesting that less heavy products formed (inset picture in FIG. 6). GC and GC-MS analysis showed that the similar products were obtained after the addition of n-hexadecane (FIG. 6). 68.3% of theoretical yield for C4+ products was obtained at the first run. This 10% NiSn/SiO.sub.2 catalyst was reused for at least 4 runs, without any loss in conversion or oil yield. Moreover, produced hydrogen was in the range of 0.084-0.14 mole.

(69) TABLE-US-00004 TABLE 4 Influence of Hydrophobic Solvent Yield of Mass of Con- C4+ hydro- Yield of catalyst version H.sub.2 carbons Humin.sup.a Entry Catalyst (g) (%) (mol) (%) (%) 1 10%NiSn/SiO.sub.2, 1.0 100.0 0.084 68.3 ND 1.sup.st run 2 10%NiSn/SiO.sub.2, 1.0 95.3 0.14 69.9 ND 2.sup.nd run 3 10%NiSn/SiO.sub.2, 1.0 100.0 0.12 66.0 ND 3.sup.rd run 4 10%NiSn/SiO.sub.2, 1.0 94.9 0.14 77.5 7.6 4.sup.th run ND: not determined. .sup.aThe 7.6% of humin is the total amount generated during 4 recycle runs. The catalysts after the 1.sup.st, 2.sup.nd, and 3.sup.rd recycle runs were not dried. Therefore the yields of humin in the 1.sup.st, 2.sup.nd, and 3.sup.rd recycle runs were not calculated.