阅读说明：本技术 一种乙酰丙酸制备γ-戊内酯的方法 (Method for preparing gamma-valerolactone from levulinic acid ) 是由 王峰 刘美江 刘慧芳 李宏基 于 2019-11-20 设计创作，主要内容包括：本发明涉及一种乙酰丙酸加氢制备γ-戊内酯的方法。该方法采用氢气为氢源,在磷化镍催化剂的作用下将乙酰丙酸加氢制备γ-戊内酯。其反应过程如下：将乙酰丙酸、溶剂与催化剂混合后,放入压力容器中,充入氢气,压力不小于0.5MPa,密闭搅拌,反应温度在80-250℃,γ-戊内酯的收率可达到96％。同时反应后催化剂与反应体系通过离心分离后可以多次循环使用,γ-戊内酯的收率仍可达到90％。(The invention relates to a method for preparing gamma-valerolactone by hydrogenation of levulinic acid. The method adopts hydrogen as a hydrogen source, and prepares the gamma-valerolactone by hydrogenating levulinic acid under the action of a nickel phosphide catalyst. The reaction process is as follows: mixing levulinic acid, a solvent and a catalyst, putting the mixture into a pressure container, filling hydrogen under the pressure of not less than 0.5MPa, stirring the mixture in a closed manner, wherein the reaction temperature is between 80 and 250 ℃, and the yield of gamma-valerolactone can reach 96 percent. Meanwhile, after the reaction, the catalyst and the reaction system can be recycled for many times after centrifugal separation, and the yield of the gamma-valerolactone can still reach 90%.)

1. A method for preparing gamma-valerolactone by hydrogenation of levulinic acid is characterized in that:

hydrogen is used as a hydrogen source, the reaction temperature is 80-250 ℃, the pressure of hydrogen filled into a reaction system is not less than 0.5MPa, the reaction time is 1-20h, and levulinic acid is hydrogenated under the action of a solid hydrogenation catalyst which takes nickel phosphide as an active ingredient or contains the nickel phosphide active ingredient, so that gamma-valerolactone serving as a reaction product is obtained.

2. The method of claim 1, wherein:

the solid hydrogenation catalyst taking nickel phosphide as an active ingredient or containing the nickel phosphide active ingredient comprises one or more than two of a supported nickel phosphide material and nickel phosphide;

the supported nickel phosphide material carrier is one or more than two of activated carbon, hydroxyapatite, titanium dioxide, alumina and an acidic molecular sieve, wherein the mass loading of nickel phosphide of the nickel phosphide supported catalyst is 5-20%.

3. The method according to claim 1 or 2, characterized in that:

the reaction is carried out in a solvent, and the reaction solvent is one or more of methanol, ethanol, n-propanol, n-butanol, 1, 4-dioxane and water;

the concentration of the levulinic acid in an initial reaction system is 5-30 wt%;

the reaction temperature is 160-200 ℃, and the reaction time is 3-24 hours;

the pressure of the reaction hydrogen is 0.5MPa-5 MPa.

4. The method according to claim 1 or 2, characterized in that:

the optimal hydrogenation solid catalyst is a nickel phosphide supported catalyst;

the preferable carrier of the catalyst is activated carbon;

the reaction solvent is preferably water;

the pressure of the reaction hydrogen is 0.5MPa-2 MPa.

5. The method according to claim 1 or 2, characterized in that:

the preparation method of the supported nickel phosphide material comprises the following steps:

(1) loading nickel on different carriers by using a deposition method, roasting to form a nickel oxide supported catalyst, and reducing the nickel oxide by using generated phosphine gas to form the nickel phosphide supported catalyst;

(2) in-situ reduction: mixing the precursor nickel nitrate, diammonium hydrogen phosphate and citric acid, stirring, aging, evaporating to dryness, roasting and reducing by hydrogen to prepare the nickel phosphide supported carbon catalyst;

(3) mixing nickel nitrate, diammonium hydrogen phosphate and a carrier, stirring and aging, evaporating to dryness, roasting and reducing by hydrogen to prepare the nickel phosphide supported carbon catalyst.

The nickel phosphide material is prepared by any one of the following steps:

(1) reducing metallic nickel by using phosphine generated in situ to obtain an unsupported nickel phosphide catalyst;

(2) in-situ reduction: and stirring and aging precursor nickel nitrate and diammonium hydrogen phosphate, evaporating to dryness, roasting and reducing by hydrogen to prepare the nickel phosphide supported carbon catalyst.

Technical Field

The invention relates to a preparation method of gamma-valerolactone, in particular to a method for preparing gamma-valerolactone by hydrogenation of levulinic acid.

Background

Biomass is used as a rich renewable energy source, and can provide green raw materials to produce carbon-based chemicals. The method for catalyzing biomass to be converted into the biofuel and the high-value-added chemicals is a means for solving the problem that fossil resources are increasingly exhausted and energy is needed. Gamma-valerolactone is a biomass-based platform compound with very useful development prospect and has very wide application. Gamma-valerolactone (GVL) is non-toxic, biodegradable, stable in properties, and has a high boiling point and a high calorific value, and thus can be used as a green solvent, a fuel additive and a food additive. In addition, the gamma-valerolactone is used as a raw material, and chemicals with high added values, such as 1, 4-pentanediol, 2-methylfuran, nylon intermediates and long-chain alkane liquid fuels, can be prepared through a series of reactions.

The homogeneous catalyst and the heterogeneous catalyst can realize selective hydrogenation of levulinic acid to prepare gamma-valerolactone, and the homogeneous catalyst has high activity and selectivity, but is difficult to recover, has high cost and the like and still has the problem of limiting the large-scale use of the homogeneous catalyst. In heterogeneous catalysts, noble metal (Ru/C, Pt/C, Pd/C) supported catalysts, transition metal nickel-based catalysts, copper-based catalysts, and the like are often used. Chinese patent CN105289592A discloses a supported catalyst with ruthenium loading of 0.05-5%, the reaction temperature is 30-150 ℃, the reaction pressure is 1MPa-6MPa, the conversion rate of levulinic acid is 100%, and the selectivity of gamma-valerolactone can reach 99.9%. CN105566258A adopts a catalyst prepared by matching Pt and a molecular sieve carrier, and the gamma-valerolactone is prepared by efficiently catalyzing and converting biomass-based ethyl levulinate and hydrogenating. In patent CN102617519A, framework copper is used as a catalyst, sodium hydroxide is used as an auxiliary agent, and the yield of gamma-valerolactone prepared by catalytically converting levulinic acid can reach 99%.

As described above, although noble metals exhibit excellent activity for hydrogenation of levulinic acid, there are still problems of high cost and catalyst deactivation. Non-noble metal catalysts (copper, nickel and the like) are easy to dissolve and separate out copper due to the acidity of levulinic acid, so that the activity of the catalyst is reduced quickly. Meanwhile, the levulinic acid is generated by the reaction of cellulose, 5-hydroxymethyl furfural and furfural under an acidic condition. It is therefore difficult to avoid the presence of H in the levulinic acid solution obtained in this way⁺While levulinic acid can dissociate to H in water⁺Therefore, the crude levulinic acid aqueous solution is used as a raw material for preparing the gamma-valerolactone through hydrogenation catalysis, and the catalyst needs to keep certain activity under an acidic condition. The use of alcohol as a solvent not only increases the cost, but also reacts with levulinic acid to produce levulinic acid esters, resulting in a decrease in selectivity. Meanwhile, water is a preferred reaction system from the viewpoint of environmental protection and cost. Thus, the development of a catalyst capable of high-efficiency catalytic conversion in an aqueous solutionThe catalyst for preparing valerolactone by hydrogenating levulinic acid has important significance.

Disclosure of Invention

The invention provides a method for preparing gamma-valerolactone by efficiently hydrogenating levulinic acid in an acidic aqueous solution, wherein a citric acid modified nickel phosphide catalyst is adopted, the catalyst has efficient hydrogenation activity, the conversion rate of the levulinic acid and the selectivity of the gamma-valerolactone can reach more than 90 percent, the activity of the catalyst is not obviously reduced after multiple cycles, the catalyst has good stability and good application prospect.

The gamma valerolactone of the invention is prepared by the following scheme. Hydrogen is taken as a hydrogen source, the reaction temperature is 80-250 ℃, the pressure of hydrogen filled into a reaction system is not less than 0.5MPa, the reaction time is 1-20h, and levulinic acid is hydrogenated under the action of a solid hydrogenation catalyst which takes nickel phosphide as an active ingredient or contains the nickel phosphide active ingredient, so that the reaction product gamma-valerolactone is obtained. The solid hydrogenation catalyst taking nickel phosphide as an active ingredient or containing the nickel phosphide active ingredient comprises one or more than two of a supported nickel phosphide material and nickel phosphide; the supported nickel phosphide material carrier is one or more than two of activated carbon, hydroxyapatite, titanium dioxide, alumina and acidic molecular sieve, wherein the nickel phosphide loading capacity of the nickel phosphide supported catalyst is 5-20%. The reaction is carried out in a solvent, and the reaction solvent is one or more of methanol, ethanol, n-propanol, n-butanol, 1, 4-dioxane and water; the concentration of the levulinic acid in an initial reaction system is 1-30 wt%; the reaction temperature is 160-200 ℃, and the reaction time is 3-24 hours; the pressure of the reaction hydrogen is 0.5MPa-5 MPa.

The preferable reaction conditions are as follows: the concentration of the levulinic acid in the initial reaction system is 10-20 wt%; the solid hydrogenation catalyst is a nickel phosphide supported catalyst; the reaction solvent is water; the reaction temperature is 150-200 ℃, and the reaction time is 3-12 hours; the pressure of the reaction hydrogen is 0.5MPa-2 MPa.

Compared with the prior art, the invention has the following characteristics:

1. the system can realize that the selectivity of the levulinic acid is higher than 90% and the yield of the gamma-valerolactone can reach 90% without using noble metals;

2. the catalyst is simple to prepare, and compared with a copper-based catalyst, the catalyst can keep activity under an acidic water phase and can be recycled for multiple times;

3. the product is gamma-valerolactone aqueous solution, pure gamma-valerolactone can be obtained by simple separation, and meanwhile, the whole process does not need to use organic solvent, and the system is favorable for reducing the production cost.

Detailed Description

The present invention will be described in further detail with reference to examples, which mainly exemplify nickel phosphide catalysts having a preferable activity, but the embodiments of the present invention are not limited thereto.

Example 1

The preparation process of the in-situ carbonized supported nickel phosphide catalyst comprises the following steps: adding diammonium hydrogen phosphate, nickel nitrate, citric acid and 150mL of ultrapure water according to a certain proportion, and mixing to form a dark green solution, so that the loading capacity of nickel phosphide is 5%; putting the solution into an oil bath at 90 ℃, heating and stirring for 12 hours, and then placing the solution in an oven at 124 ℃ for drying for 24 hours; grinding the dried solid into powder by using an agate mortar, putting the powder into a crucible, putting the crucible into a muffle furnace, heating the powder to 500 ℃ at a heating rate of 5 ℃ per minute, roasting the powder for 3 hours at 500 ℃, cooling the roasted powder to room temperature, taking out the roasted sample, putting the sample into a tubular roasting furnace, heating the sample to 350 ℃ at a heating rate of 5 ℃ per minute, heating the sample to 700 ℃ at a heating rate of 1 ℃ per minute, roasting the sample at the constant temperature for 2.5 hours, carrying out the whole process under a hydrogen atmosphere, blowing the roasted sample for 3 hours by using nitrogen after roasting, and taking the sample out without further protection treatment to obtain the in-situ nickel carbide catalyst.

Example 2

According to the preparation scheme of example 1, the in-situ nickel phosphide carbide catalyst with 15% nickel phosphide loading can be obtained by adjusting the addition amount of citric acid.

Example 3

The preparation process of the nickel phosphide supported activated carbon catalyst is as follows: and uniformly mixing the activated carbon, the nickel nitrate and 150mL of deionized water according to a ratio to ensure that the loading capacity of the nickel is 15%, stirring the mixture at room temperature for 12 hours, and then stirring and evaporating at 120 ℃. Grinding the evaporated catalyst into powder, putting the powder into a crucible, putting the powder into a muffle furnace, heating the powder to 500 ℃ at a heating rate of 5 ℃ per minute, roasting the powder for 3 hours at 500 ℃, cooling the roasted sample to room temperature, taking the roasted sample out of the furnace, heating the sample to 350 ℃ at a heating rate of 5 ℃ per minute, roasting the sample at the constant temperature for 2.5 hours, reducing the sample by using phosphine gas generated by decomposing sodium hypophosphite in the reduction process, blowing the sample for 3 hours by using nitrogen after roasting is finished, and taking the sample out without further protection treatment to obtain the nickel phosphide-loaded active carbon catalyst.

Example 4

According to the preparation scheme of example 3, titanium dioxide is added as a carrier, and a nickel phosphide-supported titanium dioxide catalyst with 15% of nickel phosphide loading can be obtained.

Example 5

According to the preparation scheme of the embodiment 3, the added carrier is hydroxyapatite, and the nickel phosphide-loaded hydroxyapatite catalyst with 15% of nickel phosphide loading can be obtained.

Example 6

The preparation process of the supported nickel phosphide catalyst comprises the following steps: adding diammonium hydrogen phosphate, nickel nitrate, activated carbon and 150mL of ultrapure water according to a certain proportion, and mixing to ensure that the loading capacity of nickel phosphide is 15%; putting the solution into an oil bath at 90 ℃, heating and stirring for 12 hours, and then stirring and evaporating at 124 ℃ to dryness; grinding the dried solid into powder by using an agate mortar, putting the powder into a crucible, putting the crucible into a muffle furnace, heating the powder to 500 ℃ at a heating rate of 5 ℃ per minute, roasting the powder for 3 hours at 500 ℃, cooling the roasted powder to room temperature, taking out the roasted sample, putting the sample into a tubular roasting furnace, heating the sample to 350 ℃ at a heating rate of 5 ℃ per minute, heating the sample to 700 ℃ at a heating rate of 1 ℃ per minute, roasting the sample at the constant temperature for 2.5 hours, carrying out the whole process under a hydrogen atmosphere, blowing the roasted sample for 3 hours by using nitrogen after roasting is finished, and taking the sample out without further protection treatment to obtain the nickel phosphide loaded carbon catalyst.

Example 7

The preparation process of the nickel phosphide catalyst comprises the following steps: adding diammonium hydrogen phosphate, nickel nitrate and 150mL of ultrapure water according to a certain proportion, and mixing; putting the solution into an oil bath at 90 ℃, heating and stirring for 12 hours, and then placing the solution in an oven at 124 ℃ for drying for 24 hours; grinding the dried solid into powder by using an agate mortar, putting the powder into a crucible, putting the crucible into a muffle furnace, heating the powder to 500 ℃ at a heating rate of 5 ℃ per minute, roasting the powder for 3 hours at 500 ℃, cooling the roasted powder to room temperature, taking out the roasted sample, putting the sample into a tubular roasting furnace, heating the sample to 350 ℃ at a heating rate of 5 ℃ per minute, heating the sample to 700 ℃ at a heating rate of 1 ℃ per minute, roasting the sample at the constant temperature for 2.5 hours, carrying out the whole process under a hydrogen atmosphere, blowing the roasted sample by using nitrogen for 3 hours, taking the sample out, and obtaining the nickel phosphide catalyst without further protection treatment.

Example 8

1g of the catalyst prepared in example 1, 40mmol of levulinic acid and 80mL of water were charged into a 150mL autoclave, the autoclave was sealed, charged with hydrogen gas to 1MPa, and heated and stirred at 160 ℃ for reaction for 3 hours. After the reaction is finished, the products and reactants in the water phase are extracted by ethyl acetate, and the raw materials and the products are quantitatively analyzed by chromatography, the conversion rate of the levulinic acid is 80 percent, and the yield of the gamma-valerolactone is 78 percent.

Example 9

1g of the catalyst prepared in example 2, 60mmol of levulinic acid and 80mL of water were charged into a 150mL autoclave, the autoclave was sealed, charged with hydrogen gas to 2MPa, and heated and stirred at 160 ℃ for reaction for 3 hours. After the reaction is finished, the products and reactants in the water phase are extracted by ethyl acetate, and the raw materials and the products are quantitatively analyzed by chromatography, the conversion rate of the levulinic acid is 96 percent, and the yield of the gamma-valerolactone is 92 percent.

Example 10

1g of the catalyst prepared in example 3, 40mmol of levulinic acid and 80mL of water were charged into a 150mL autoclave, the autoclave was sealed, charged with hydrogen to 2MPa, and heated and stirred at 180 ℃ for 4 hours. After the reaction is finished, the products and reactants in the water phase are extracted by ethyl acetate, and the raw materials and the products are quantitatively analyzed by chromatography, the conversion rate of the levulinic acid is 75 percent, and the yield of the gamma-valerolactone is 70 percent.

Example 11

1g of the catalyst prepared in example 4, 40mmol of levulinic acid and 80mL of water were charged into a 150mL autoclave, the autoclave was sealed, charged with hydrogen to 2MPa, and heated and stirred at 190 ℃ for reaction for 5 hours. After the reaction is finished, the products and reactants in the water phase are extracted by ethyl acetate, and the raw materials and the products are quantitatively analyzed by chromatography, the conversion rate of the levulinic acid is 79 percent, and the yield of the gamma-valerolactone is 76 percent.

Example 12

1g of the catalyst prepared in example 5, 40mmol of levulinic acid and 80mL of water were charged into a 150mL autoclave, the autoclave was sealed, charged with hydrogen to 2MPa, and heated and stirred at 170 ℃ for reaction for 6 hours. After the reaction is finished, the products and reactants in the water phase are extracted by ethyl acetate, and the raw materials and the products are quantitatively analyzed by chromatography, the conversion rate of the levulinic acid is 82 percent, and the yield of the gamma-valerolactone is 80 percent.

Example 13

1g of the catalyst prepared in example 6, 50mmol of levulinic acid and 80mL of water were charged into a 150mL autoclave, the autoclave was sealed, charged with hydrogen gas to 1MPa, and heated and stirred at 200 ℃ for reaction for 8 hours. After the reaction is finished, the products and reactants in the water phase are extracted by ethyl acetate, and the raw materials and the products are quantitatively analyzed by chromatography, the conversion rate of the levulinic acid is 82 percent, and the yield of the gamma-valerolactone is 78 percent.

Example 14

1g of the catalyst prepared in example 7, 40mmol of levulinic acid and 80MlmL of water were charged into a 150mL autoclave, the autoclave was sealed, charged with hydrogen gas to 2MPa, and heated and stirred at 200 ℃ for reaction for 6 hours. After the reaction is finished, the products and reactants in the water phase are extracted by ethyl acetate, and the raw materials and the products are quantitatively analyzed by chromatography, the conversion rate of the levulinic acid is 67 percent, and the yield of the gamma-valerolactone is 60 percent.

Example 15

1g of the catalyst prepared in example 2, 50mmol of levulinic acid and 80mL of ethanol were added to a 150mL autoclave, the autoclave was sealed, then charged with hydrogen to 1MPa, and heated and stirred at 180 ℃ for reaction for 6 hours. After the reaction is finished, the raw materials and the products are quantitatively analyzed by chromatography, the conversion rate of the levulinic acid is 100 percent, and the yield of the gamma valerolactone is 70 percent.

Example 16

1g of the catalyst prepared in example 2, 80mmol of levulinic acid and 80mL of water were charged into a 150mL autoclave, the autoclave was sealed, charged with hydrogen gas to 2MPa, and heated and stirred at 180 ℃ for reaction for 7 hours. After the reaction is finished, the products and reactants in the water phase are extracted by ethyl acetate, and the raw materials and the products are quantitatively analyzed by chromatography, the conversion rate of the levulinic acid is 95 percent, and the yield of the gamma-valerolactone is 92 percent.

Example 17

1g of the catalyst prepared in example 2, 80mmol of levulinic acid and 80mL of water were charged into a 150mL autoclave, the autoclave was sealed, charged with hydrogen gas to 1MPa, and heated and stirred at 180 ℃ for reaction for 10 hours. After the reaction is finished, the products and reactants in the water phase are extracted by ethyl acetate, and the raw materials and the products are quantitatively analyzed by chromatography, the conversion rate of the levulinic acid is 97 percent, and the yield of the gamma-valerolactone is 92 percent.

Example 18

1g of the catalyst prepared in example 1, 60mmol of levulinic acid and 80mL of water were charged into a 150mL autoclave, the autoclave was sealed, charged with hydrogen gas to 1MPa, and heated and stirred at 150 ℃ for reaction for 2 hours. After the reaction is finished, the products and reactants in the water phase are extracted by ethyl acetate, and the raw materials and the products are quantitatively analyzed by chromatography, the conversion rate of the levulinic acid is 57 percent, and the yield of the gamma-valerolactone is 55 percent.

Comparative example 1

1g of nickel sulfide, 40mmol of levulinic acid and 80mL of water are added into a 150mL high-pressure reaction kettle, the reaction kettle is sealed and then filled with hydrogen to 2MPa, and the reaction kettle is heated and stirred at 150 ℃ for 5 hours. After the reaction is finished, the products and reactants in the water phase are extracted by ethyl acetate, and the raw materials and the products are quantitatively analyzed by chromatography, the conversion rate of the levulinic acid is 13 percent, and the yield of the gamma-valerolactone is 10 percent.

Comparative example 2

Preparation of nickel-loaded activated carbon catalyst: mixing nickel nitrate and activated carbon according to a proportion, wherein the loading capacity of nickel is 15%, stirring, evaporating to dryness, roasting, and reducing at 350 ℃ under hydrogen to obtain the nickel-loaded activated carbon catalyst.

Adding 1g of nickel-supported activated carbon catalyst, 40mmol of levulinic acid and 80mL of water into a 150mL high-pressure reaction kettle, sealing the reaction kettle, filling hydrogen to 2MPa, heating and stirring at 150 ℃, and reacting for 5 hours. After the reaction is finished, the products and reactants in the water phase are extracted by ethyl acetate, and the raw materials and the products are quantitatively analyzed by chromatography, the conversion rate of the levulinic acid is 30 percent, and the yield of the gamma-valerolactone is 28 percent.

Comparative example 3:

preparation of a nickel-loaded titanium dioxide catalyst: mixing nickel nitrate and titanium dioxide according to a proportion, wherein the loading capacity of nickel is 15%, stirring, evaporating to dryness, roasting, and reducing at 350 ℃ in hydrogen to obtain the nickel-loaded activated carbon catalyst.

1g of nickel-supported titanium dioxide catalyst, 40mmol of levulinic acid and 80mL of water are added into a 150mL high-pressure reaction kettle, the reaction kettle is sealed and then filled with hydrogen to 2MPa, and the reaction kettle is heated and stirred at 160 ℃ for 5 hours. After the reaction is finished, the products and reactants in the water phase are extracted by ethyl acetate, and the raw materials and the products are quantitatively analyzed by chromatography, the conversion rate of the levulinic acid is 35 percent, and the yield of the gamma-valerolactone is 30 percent.

Comparative example 4:

1g of the nickel-supported titanium dioxide catalyst of comparative example 3, 40mmol of levulinic acid and 80mL of ethanol were added to a 150mL autoclave, the autoclave was sealed, charged with hydrogen to 2MPa, and heated and stirred at 160 ℃ for reaction for 5 hours. After the reaction is finished, the raw materials and the products are quantitatively analyzed by chromatography, the conversion rate of the levulinic acid is 100 percent, and the yield of the gamma valerolactone is 40 percent.

Comparative example 5

The preparation process of the in-situ carbonized supported cobalt phosphide catalyst comprises the following steps: adding diammonium hydrogen phosphate, cobalt nitrate, citric acid and 150mL of ultrapure water according to a certain proportion, and mixing to ensure that the loading capacity of cobalt phosphide is 15%; putting the solution into an oil bath at 90 ℃, heating and stirring for 12 hours, and then placing the solution in an oven at 124 ℃ for drying for 24 hours; grinding the dried solid into powder by using an agate mortar, putting the powder into a crucible, putting the crucible into a muffle furnace, heating the powder to 500 ℃ at a heating rate of 5 ℃ per minute, roasting the powder for 3 hours at 500 ℃, cooling the roasted powder to room temperature, taking out the roasted sample, putting the sample into a tubular roasting furnace, heating the sample to 350 ℃ at a heating rate of 5 ℃ per minute, heating the sample to 700 ℃ at a heating rate of 1 ℃ per minute, roasting the sample at the constant temperature for 2.5 hours, carrying out the whole process under a hydrogen atmosphere, blowing the roasted sample for 3 hours by using nitrogen after roasting, and taking the sample out without further protection treatment to obtain the in-situ nickel carbide catalyst.

1g of in-situ cobalt carbide phosphide catalyst, 40mmol of levulinic acid and 80mL of water are added into a 150mL high-pressure reaction kettle, the reaction kettle is sealed and then filled with hydrogen to 2MPa, and the reaction kettle is heated and stirred at 160 ℃ for 5 hours. After the reaction is finished, the products and reactants in the water phase are extracted by ethyl acetate, and the raw materials and the products are quantitatively analyzed by chromatography, the conversion rate of the levulinic acid is 52 percent, and the yield of the gamma-valerolactone is 47 percent.

Comparative example 6

Catalyst recycling

Reaction test: a150 mL autoclave was charged with 1.0g of the catalyst prepared in example 2, 40mmol of levulinic acid and 80mL of water, the autoclave was sealed and charged with hydrogen to 2MPa, and the reaction was stirred at 160 ℃ for 3 hours. After the reaction is finished, the products and reactants in the water phase are extracted by ethyl acetate, and the raw materials and the products are quantitatively analyzed by chromatography, the conversion rate of the levulinic acid is 96 percent, and the yield of the gamma-valerolactone is 92 percent. Recovering the catalyst after the reaction, washing the catalyst with water and ethanol, drying the catalyst in an oven at 80 ℃, performing a circulation experiment, performing extraction analysis on the product after the circulation experiment is finished each time, performing 4 circulation experiments in total, wherein the circulation results are shown in Table 1

TABLE 1 hydrogenation of levulinic acid to gamma valerolactone cycle test results

Number of cycles	Time/h	Temperature/. degree.C	pressure/MPa	LA conversion/%	GVL yield/%)
						Initial	3	160	2	96	92
For the first time	3	160	2	95	90
						For the second time	3	160	2	95	90
The third time	3	160	2	90	85
						Fourth time	3	160	2	90	90

It can be seen from the above examples and comparative examples that the nickel phosphide catalyst has better catalytic activity for aqueous levulinic acid, wherein the nickel phosphide catalyst has the best activity by in-situ carbonization, and after many cycles, the catalyst still has high stability, but has poor activity for metallic nickel supported catalyst and nickel sulfide catalyst in aqueous phase. And the activity of the dried catalyst is poor, so that the nickel phosphide has great application potential to the hydrogenation of aqueous phase levulinic acid.