A method for preparing gamma-valerolactone using photocatalysis

Abstract

The invention provides a method for preparing gamma-valerolactone by utilizing photocatalysis. Metal-loaded TiO2 is used as a photocatalyst and air is used as an oxidant in a normal temperature and normal pressure environment. The reaction process comprises the following steps: tetrahydro-5-methyl-2-furanmethanol, a solvent, and a catalyst are mixed and placed in a photocatalytic reactor, and irradiated at room temperature for 10 minutes to 10 hours in air under a 365nm LED lamp to generate an oxidation product, gamma-valerolactone. The method provided by the invention can achieve efficient conversion of tetrahydro-5-methyl-2-furanmethanol under mild conditions, with a yield of gamma-valerolactone reaching up to 90%. The catalyst provided by the invention is easy to separate and can be recycled repeatedly. Air is used as an oxidant, and the reaction operation is simple and the cost is low. The raw material, tetrahydro-5-methyl-2-furanmethanol used in the invention can be obtained by hydrogenating 5-methylfurfural using biomass as a raw material, and is independent of fossil resources.

Description

Technical Field

[0001] The invention relates to the technical field of gamma-valerolactone synthesis, and in particular to a method for preparing gamma-valerolactone by utilizing photocatalysis. Background Art

[0002] Since the Industrial Revolution, fossil fuels have served as the primary source of energy and organic carbon, but they have also caused serious environmental pollution. Therefore, there is an urgent need for renewable energy sources with a low carbon footprint to replace fossil fuels. In recent years, lignocellulose, including cellulose, hemicellulose, and lignin, has rapidly developed as a major biomass resource and an ideal carbon-neutral energy source. Catalytic conversion of lignocellulose can produce a variety of platform compounds, such as 5-methylfurfural, 5-hydroxymethylfurfural, and levulinic acid. Industrially, tetrahydro-5-methyl-2-furanmethanol is primarily produced by hydrogenation of 5-methylfurfural (5-MF). Catalytic conversion of these biomass platform molecules to produce high-value-added chemicals is a current research hotspot. With the advancement of science and technology, there is a need to develop more environmentally friendly and economical technologies, which remains of great significance to the fields of energy, environment, and chemical industry.

[0003] γ-Valerolactone is a five-membered ring lactone widely used in materials synthesis, pharmaceutical intermediates, perfumes, and chemical synthesis. It is commonly used in the synthesis of herbicides and rubber additives, and is also used as an industrial solvent, diluent, paint stripper, and curing agent. γ-Valerolactone is one of the most valuable alternatives to environmentally harmful chlorinated solvents and is considered an ideal bio-derived monomer for the polyester industry.

[0004] Current methods for preparing γ-valerolactone include succinic anhydride hydrogenation (Appl. Catal. B Environ. 2013; 43: 131-138), 1,4-butanediol dehydrogenation cyclization (Catal. Commun. 2020; 143: 106049), succinic acid reductive esterification (Chin. J. Catal. 2018; 39: 250-257), cyclobutanone Bayer-Villiger oxidation (J. Org. Chem. 2005; 70: 10879-10882), and catalytic oxidative C-C bond cleavage of cyclohexanol (Chem Cat Chem. 2020; 12: 1-7). However, existing catalytic systems are limited by high temperature and high pressure environments, stoichiometric oxidants, and poor selectivity. Although many methods are currently available for preparing γ-valerolactone, the development of efficient and green methods remains necessary. Summary of the Invention

[0005] The present invention aims to provide a method for preparing γ-valerolactone by utilizing photocatalysis, and at the same time provides a simple and easy-to-synthesize metal-loaded semiconductor photocatalyst, and utilizes the catalyst to realize the photocatalytic oxidation of tetrahydro-5-methyl-2-furanmethanol to prepare γ-valerolactone at room temperature and pressure; at the same time, the effects of different TiO2-based catalysts, different light intensities and reaction times on the photocatalytic oxidation of tetrahydro-5-methyl-2-furanmethanol to prepare γ-valerolactone are studied; the photocatalytic conversion pathway of biomass resources is expanded, and the photocatalytic synthesis of γ-valerolactone from biomass resources is realized under mild conditions.

[0006] In one aspect, the present invention provides a method for preparing γ-valerolactone using photocatalysis, the reaction path of which is as follows:

[0007]

[0008] The path includes the following steps:

[0009] Under the action of a photocatalyst, after air is introduced, tetrahydro-5-methyl-2-furanmethanol in the solvent is oxidized under light source to generate gamma-valerolactone; the photocatalyst is metal-loaded titanium dioxide.

[0010] Optionally, the method for preparing the photocatalyst comprises the following steps:

[0011] Calcine solution A and solution B at 200-500°C for 1-12 hours to obtain titanium dioxide;

[0012] The solution A is a mixed solution of polyoxypropylene polyoxyethylene copolymer and anhydrous ethanol; the volume ratio of the copolymer to anhydrous ethanol in the solution A is (1-2): (1-5);

[0013] The solution B is a mixed solution of titanium isopropoxide and hydrochloric acid; the volume ratio of titanium isopropoxide to hydrochloric acid in the solution B is (1-2): (1-5);

[0014] The titanium dioxide and the metal salt aqueous solution are mixed and stirred for 6-12 hours and then dried; and reduced and calcined at 300-600° C. by hydrogen for 4-6 hours to prepare a photocatalyst.

[0015] Optionally, the metal supporting titanium dioxide in the photocatalyst includes at least one of Ag, Au, Ni, Co, Pd, Ru, and Pt.

[0016] Optionally, the mass ratio of titanium dioxide to metal in the photocatalyst is 0.1-10.0 wt%.

[0017] Optionally, the solvent includes at least one of acetonitrile, water, tetrahydrofuran, and 1,4-dioxane.

[0018] Optionally, the light source includes at least one of an LED and a xenon lamp.

[0019] Optionally, the concentration of tetrahydro-5-methyl-2-furanmethanol in the solvent is 15-25 g / L.

[0020] Optionally, the temperature of the photocatalytic reaction is 10-40° C., and the reaction time is 10 min-10 h.

[0021] The beneficial effects of the present invention include:

[0022] (1) The photocatalytic preparation method of γ-valerolactone provided by the present invention has a high yield of γ-valerolactone, which can reach up to 90%;

[0023] (2) The photocatalytic preparation method of γ-valerolactone provided by the present invention expands the photocatalytic conversion pathway of biomass resources and realizes the photocatalytic synthesis of γ-valerolactone using biomass resources under mild conditions, i.e., at room temperature and pressure;

[0024] (3) The present invention also provides a photocatalyst that is simple to synthesize, easy to separate, has good stability, and can be recycled for secondary catalysis;

[0025] (4) In the preparation method provided by the present invention, the oxidant is air, and no by-products are generated during the reaction, which meets the requirements of green chemistry. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the synthesis of γ-valerolactone using biomass as raw material. DETAILED DESCRIPTION

[0027] The present invention will be further described through the following examples with reference to the accompanying drawings.

[0028] The present invention provides a method for preparing γ-valerolactone using biomass resources, such as Figure 1 As shown, biomass resources are hydrogenolyzed to obtain 5-methylfurfural, and 5-methylfurfural is hydrogenated to obtain tetrahydro-5-methyl-2-furanmethanol. Tetrahydro-5-methyl-2-furanmethanol is used as the substrate of the present invention. Figure 1 In the reaction, M is loaded on TiO2, where M is a metal, and γ-valerolactone is obtained at room temperature and pressure.

[0029] The present invention provides a method for preparing a metal-supported titanium dioxide photocatalyst, which comprises the following steps:

[0030] The polyoxypropylene polyoxyethylene copolymer solution (P123) was stirred and mixed with anhydrous ethanol to prepare solution A;

[0031] Under vigorous stirring, titanium isopropoxide was added dropwise to the HCl solution to prepare solution B;

[0032] Solution B was added dropwise to solution A, and ethylene glycol was added after stirring to prepare a mixed solution;

[0033] The mixed solution was reacted in an autoclave; after the reaction was completed, it was cooled to room temperature and washed with anhydrous ethanol;

[0034] After washing, the product is dried and calcined to produce titanium dioxide (TiO2);

[0035] The obtained TiO2 is mixed with a metal salt aqueous solution for 6-12 hours and then dried; the mixture is calcined in hydrogen at 300-600°C. After the metal ions are reduced, the metal element is loaded on the TiO2 to prepare a photocatalyst.

[0036] Specifically, the metal supporting titanium dioxide in the photocatalyst includes at least one of Ag, Au, Ni, Co, Pd, Ru, and Pt.

[0037] Specifically, the mass ratio of titanium dioxide to metal in the photocatalyst is 0.1-10.0 wt%.

[0038] In a second aspect, an embodiment of the present invention provides a method for preparing γ-valerolactone using photocatalysis, and the reaction path is as follows:

[0039]

[0040] The path includes the following steps:

[0041] Under the action of a photocatalyst, after air is introduced, tetrahydro-5-methyl-2-furanmethanol in the solvent is oxidized under light source to generate gamma-valerolactone; the photocatalyst is metal-loaded titanium dioxide.

[0042] In some embodiments, the solvent includes at least one of acetonitrile, water, tetrahydrofuran, and 1,4-dioxane.

[0043] In some embodiments, the light source includes at least one of an LED and a xenon lamp.

[0044] In some embodiments, the concentration of tetrahydro-5-methyl-2-furanmethanol in the solvent is 15-25 g / L.

[0045] In some embodiments, the temperature of the photocatalytic reaction is 10-40° C., and the reaction time is 10 min-10 h.

[0046] Example 1

[0047] Example 1 of the present invention provides a method for preparing an Ag / TiO2 catalyst, comprising the following steps:

[0048] The polyoxypropylene polyoxyethylene copolymer solution (P123) and anhydrous ethanol were stirred and mixed in a volume ratio of 2:1 to prepare solution A;

[0049] Under vigorous stirring, titanium isopropoxide was added dropwise to a 5 mol / L HCl solution at a volume ratio of titanium isopropoxide to HCl of 2:1 to prepare solution B.

[0050] Solution B was added dropwise to solution A at a volume ratio of 1:1, stirred for 0.5 h to prepare a mixed solution, and ethylene glycol was added at a volume ratio of ethylene glycol to the mixed solution of 0.2:1;

[0051] The mixed solution was placed in a 50 mL polytetrafluoroethylene-lined autoclave at 100 °C for 5 h;

[0052] After the reaction was completed, the mixture was cooled to room temperature and the product was washed with anhydrous ethanol 4 times;

[0053] After washing, the product was dried in a vacuum oven for 12 h. After drying, it was calcined in a muffle furnace at 200 °C for 1 h to obtain titanium dioxide (TiO2).

[0054] Silver nitrate is used as a precursor and mixed with titanium dioxide aqueous solution for 6 hours, then dried and calcined in hydrogen at 600°C for 4 hours. After the silver ions are reduced, the silver element is loaded on TiO2 to prepare an Ag / TiO2 catalyst.

[0055] Example 2

[0056] Example 2 of the present invention provides a method for preparing a Ru / TiO2 catalyst, comprising the following steps:

[0057] The polyoxypropylene polyoxyethylene copolymer solution (P123) and anhydrous ethanol were stirred and mixed at a volume ratio of 5:1 to prepare solution A;

[0058] Under vigorous stirring, titanium isopropoxide was added dropwise to a 5 mol / L HCl solution with a volume ratio of titanium isopropoxide to HCl of 5:1 to prepare solution B.

[0059] Solution B was added dropwise to solution A at a volume ratio of 1:1 and stirred for 4 hours to prepare a mixed solution. The volume ratio of ethylene glycol to the mixed solution was 2:1.

[0060] The mixed solution was placed in a 50 mL polytetrafluoroethylene-lined autoclave at 200 °C for 30 h;

[0061] After the reaction was completed, the mixture was cooled to room temperature and the product was washed with anhydrous ethanol 4 times;

[0062] After washing, the product was dried in a vacuum oven for 12 h. After drying, it was calcined in a muffle furnace at 500 °C for 12 h to obtain TiO2.

[0063] Ruthenium nitrate is used as a precursor and mixed with titanium dioxide aqueous solution for 12 hours, then dried and calcined in hydrogen at 600°C for 6 hours. After the ruthenium ions are reduced, the ruthenium element is loaded on TiO2 to prepare a Ru / TiO2 catalyst.

[0064] Example 3

[0065] Example 3 of the present invention provides a method for preparing γ-valerolactone by photocatalysis, comprising the following steps:

[0066] 116.2 mg of tetrahydro-5-methyl-2-furanmethanol (1 mmol), 1.0 mg of Pt / TiO2 (1 wt%) photocatalyst, and 1 mL of acetonitrile were added to a photocatalytic reactor and air was introduced;

[0067] After sealing, the mixture was irradiated with a 365 nm LED for 10 h. The obtained product was analyzed by GC, and 0.9 mmol of γ-valerolactone was generated in the reaction, with a calculated molar yield of 90%.

[0068] Example 4

[0069] Example 4 of the present invention provides a method for preparing γ-valerolactone by photocatalysis, comprising the following steps:

[0070] 58.1 mg of tetrahydro-5-methyl-2-furanmethanol (0.5 mmol), 5.0 mg of Au / TiO2 (1 wt%) photocatalyst, and 1 mL of tetrahydrofuran were added into a photocatalytic reactor and air was introduced;

[0071] After sealing, the container was irradiated with a 365 nm LED for 10 min. The obtained product was analyzed by GC, and 0.35 mmol of γ-valerolactone was generated. The calculated molar yield was 70%.

[0072] Example 5

[0073] Example 5 of the present invention provides a method for preparing γ-valerolactone by photocatalysis, comprising the following steps:

[0074] 1162 mg of tetrahydro-5-methyl-2-furanmethanol (10 mmol), 10.0 mg of Cu / TiO2 (3 wt%) photocatalyst, and 1 mL of water were added to a photocatalytic reactor and air was introduced;

[0075] After sealing, the mixture was irradiated with a 150W xenon lamp for 5 hours. The obtained product was analyzed by GC. 8 mmol of γ-valerolactone was generated, and the calculated molar yield was 80%.

[0076] Example 6

[0077] Example 6 of the present invention provides a method for preparing γ-valerolactone by photocatalysis, comprising the following steps:

[0078] 11.62 mg of tetrahydro-5-methyl-2-furanmethanol (0.1 mmol), 5.0 mg of Ru / TiO2 (7 wt%) photocatalyst, and 1 mL of water were added to a photocatalytic reactor and air was introduced;

[0079] After sealing, the mixture was irradiated with a 150W xenon lamp for 30 minutes. The obtained product was analyzed by GC. The reaction produced 0.085 mmol of γ-valerolactone, and the calculated molar yield was 85%.

[0080] Example 7

[0081] Example 7 of the present invention provides a method for preparing γ-valerolactone by photocatalysis, comprising the following steps:

[0082] 116.2 mg of tetrahydro-5-methyl-2-furanmethanol (1 mmol), 5.0 mg of Ni / TiO2 (0.1 wt%) photocatalyst, and 5 mL of 1,4-dioxane were added to a photocatalytic reactor and air was introduced;

[0083] After sealing, the mixture was irradiated with a 150W xenon lamp for 10 h. The obtained product was analyzed by GC, and 0.88 mmol of γ-valerolactone was generated. The calculated molar yield was 88%.

[0084] Example 8

[0085] Example 8 of the present invention provides a method for preparing γ-valerolactone by photocatalysis, comprising the following steps:

[0086] 116.2 mg of tetrahydro-5-methyl-2-furanmethanol (10 mmol), 100.0 mg of Co / Tio2 (0.1 wt%) photocatalyst, and 20 mL of acetonitrile were added to a photocatalytic reactor and air was introduced;

[0087] After sealing, the mixture was irradiated with a 365 nm LED for 1 h. The obtained product was analyzed by GC, and 7.7 mmol of γ-valerolactone was produced. The calculated molar yield was 77%.

[0088] Example 9

[0089] Example 9 of the present invention provides a method for preparing γ-valerolactone by photocatalysis, comprising the following steps:

[0090] 11.62 mg of tetrahydro-5-methyl-2-furanmethanol (0.1 mmol), 1.0 mg of Pd / TiO2 (2 wt%) photocatalyst, and 1 mL of acetonitrile were added to a photocatalytic reactor and air was introduced;

[0091] After sealing, the container was irradiated with a 365 nm LED for 2 h. The obtained product was analyzed by GC, and 0.081 mmol of γ-valerolactone was produced. The calculated molar yield was 81%.

[0092] Example 10

[0093] Example 10 of the present invention provides a method for preparing γ-valerolactone by photocatalysis, comprising the following steps:

[0094] 1.16 mg of tetrahydro-5-methyl-2-furanmethanol (0.01 mmol), 1.0 mg of Au / TiO2 (10 wt%) photocatalyst, and 5 mL of acetonitrile were added to a photocatalytic reactor and air was introduced;

[0095] After sealing, the container was irradiated with a 365 nm LED for 1 h. The obtained product was analyzed by GC, and 0.0088 mmol of γ-valerolactone was produced. The calculated molar yield was 88%.

[0096] Example 11

[0097] Example 11 of the present invention provides a method for preparing γ-valerolactone by photocatalysis, comprising the following steps:

[0098] 116.2 mg of tetrahydro-5-methyl-2-furanmethanol (1 mmol), 5.0 mg of Ru / TiO2 (10 wt%) photocatalyst, and 10 mL of water were added to a photocatalytic reactor and air was introduced;

[0099] After sealing, the container was irradiated with a 365 nm LED for 10 h. The obtained product was analyzed by GC, and 0.75 mmol of γ-valerolactone was generated. The calculated molar yield was 75%.

[0100] Example 12

[0101] Example 12 of the present invention provides a method for preparing γ-valerolactone by photocatalysis, comprising the following steps:

[0102] 2324 mg of tetrahydro-5-methyl-2-furanmethanol (20 mmol), 100.0 mg of Ru / TiO2 (10 wt%) photocatalyst, and 10 mL of water were added to a photocatalytic reactor and air was introduced;

[0103] After sealing, the container was irradiated with a 365 nm LED for 10 h. The obtained product was analyzed by GC, and 16.8 mmol of γ-valerolactone was generated. The calculated molar yield was 84%.

[0104] Example 13

[0105] Example 13 of the present invention provides a method for preparing γ-valerolactone by photocatalysis, comprising the following steps:

[0106] 1162 mg of tetrahydro-5-methyl-2-furanmethanol (10 mmol), 100.0 mg of Ag / TiO2 (0.1 wt%) photocatalyst, and 20 mL of water were added to a photocatalytic reactor and air was introduced;

[0107] After sealing, the mixture was irradiated with a 365 nm LED for 5 h. The obtained product was analyzed by GC, and 98 mmol of γ-valerolactone was generated in the reaction, with a calculated molar yield of 90%.

[0108] Example 14

[0109] Example 14 of the present invention provides a method for preparing γ-valerolactone by photocatalysis, comprising the following steps:

[0110] 581 mg of tetrahydro-5-methyl-2-furanmethanol (5 mmol), 200.0 mg of Ru / TiO2 (1 wt%) photocatalyst, and 10 mL of acetonitrile were added to a photocatalytic reactor and air was introduced;

[0111] After sealing, the container was irradiated with a 365 nm LED for 7 h. The obtained product was analyzed by GC, and 4.25 mmol of γ-valerolactone was generated. The calculated molar yield was 85%.

[0112] Example 15

[0113] Example 15 of the present invention provides a method for preparing γ-valerolactone by photocatalysis, comprising the following steps:

[0114] 464.8 mg of tetrahydro-5-methyl-2-furanmethanol (4 mmol), 150.0 mg of Cu / TiO2 (5 wt%) photocatalyst, and 10 mL of 1,4-dioxane were added to a photocatalytic reactor and air was introduced;

[0115] After sealing, the container was irradiated with a 365 nm LED for 7 h. The obtained product was analyzed by GC, and 3.16 mmol of γ-valerolactone was produced. The calculated molar yield was 79%.

[0116] Example 16

[0117] Example 16 of the present invention provides a method for preparing γ-valerolactone by photocatalysis, comprising the following steps:

[0118] 1394.4 mg of tetrahydro-5-methyl-2-furanmethanol (12 mmol), 110.0 mg of Pt / TiO2 (4 wt%) photocatalyst, and 5 mL of tetrahydrofuran were added to a photocatalytic reactor and air was introduced;

[0119] After sealing, the container was irradiated with a 365 nm LED for 6 h. The obtained product was analyzed by GC, and 8.64 mmol of γ-valerolactone was generated. The calculated molar yield was 72%.

[0120] Example 17

[0121] Example 17 of the present invention provides a method for preparing γ-valerolactone by photocatalysis, comprising the following steps:

[0122] The catalyst after the reaction in Example 16 was filtered, separated, and dried to obtain a recycled Co / TiO2 catalyst;

[0123] 1740 mg of tetrahydro-5-methyl-2-furanmethanol (15 mmol), 200.0 mg of recycled Co / TiO2 (10 wt%) photocatalyst, and 10 mL of acetonitrile were added to a photocatalytic reactor and air was introduced;

[0124] After sealing, the container was irradiated with a 365 nm LED for 10 min. The obtained product was analyzed by GC. The reaction produced 10.5 mmol of γ-valerolactone, and the calculated molar yield was 80%.

[0125] While the embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations of these embodiments are possible. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as set forth in the claims. Furthermore, the invention described herein is susceptible to other embodiments and may be practiced or implemented in a variety of ways.

Claims

1. A method for preparing γ-valerolactone by photocatalysis, characterized in that: The reaction path is as follows: ； The path includes the following steps: Under the action of a photocatalyst, after air is introduced, tetrahydro-5-methyl-2-furanmethanol in the solvent is oxidized to generate γ-valerolactone under light; the photocatalyst is metal-loaded titanium dioxide, and the loaded metal is at least one of Ag, Au, Ni, Co, Pd, Ru, and Pt.

2. The method according to claim 1, characterized in that The preparation method of the photocatalyst comprises the following steps: Calcine solution A and solution B at 200-500 °C for 1-12 h to obtain titanium dioxide; The solution A is a mixed solution of polyoxypropylene polyoxyethylene copolymer and anhydrous ethanol; the volume ratio of the copolymer to anhydrous ethanol in the solution A is (1-2): (1-5); The solution B is a mixed solution of titanium isopropoxide and hydrochloric acid; the volume ratio of titanium isopropoxide to hydrochloric acid in the solution B is (1-2): (1-5); The titanium dioxide and the metal solution are calcined together to prepare a photocatalyst.

3. The method according to claim 2, characterized in that The mass ratio of titanium dioxide to metal in the photocatalyst is 0.1-10.0 wt%.

4. The method according to claim 1, wherein The solvent is at least one of acetonitrile, water, tetrahydrofuran, and 1,4-dioxane.

5. The method according to claim 1, wherein The light is at least one of an LED and a xenon lamp.

6. The method according to claim 1, characterized in that The concentration of tetrahydro-5-methyl-2-furanmethanol in the solvent is 15-25 g / L.

7. The method according to claim 1, characterized in that The temperature of the photocatalytic reaction is 10-40°C, and the reaction time is 10 min-10 h.

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