Method for mildly and efficiently catalyzing levulinic acid and levulinic acid ester hydrogenation to prepare gamma-valerolactone

Abstract

The invention discloses a method for preparing gamma-valerolactone by efficiently catalyzing levulinic acid and ester hydrogenation thereof under mild conditions, which comprises the following steps: by taking water as a reaction solvent, catalyzing levulinic acid and ester thereof by using a Ni3P / SBA-15 catalyst, and preparing gamma-valerolactone at high selectivity in a high-pressure reaction kettle or a fixed bed reactor under low-temperature conditions. Wherein the Ni3P / SBA-15 catalyst is obtained by loading a Ni3P precursor on SBA-15 through an impregnation method and then reducing in a hydrogen atmosphere. The preparation method is simple, raw materials are easy to obtain, the cost is low, the reaction process is environmentally friendly and free of pollution, a catalytic system is relatively simple, the conversion rate of the reaction raw materials is high, and the yield of gamma-valerolactone can reach 100%; after the reaction is carried out for 50 hours in a fixed bed reactor, the yield of the gamma-valerolactone is kept stable, the stability of the catalyst is relatively good, resources can be saved, the cost is reduced, and the method has a good industrial application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of clean and green catalytic synthesis of high-value-added chemicals using biomass resources, and specifically relates to a method for preparing gamma-valerolactone by catalytic hydrogenation of levulinic acid and its esters. Background Art

[0002] The reduction of crude oil reserves and the increase of environmental problems caused by the excessive consumption of fossil raw materials have made scientists urgently look for new renewable alternatives. More and more studies have shown that converting renewable biomass and biomass platform molecules into value-added chemicals is a very promising way to alleviate the current energy crisis and environmental problems. In recent years, with the increasing attention paid to biomass energy, the conversion of biomass into bio-based chemicals and biofuels has been a research hotspot and has made great progress.

[0003] γ-Valerolactone is a very promising biomass platform molecule. γ-Valerolactone can not only be used as a green solvent, fuel additive, and liquid fuel, but also as an intermediate for the production of various other value-added chemicals. Further hydrogenation can produce other important chemicals such as 1,4-pentanediol and 2-methyltetrahydrofuran.

[0004] Over the years, researchers have developed a variety of catalysts for the hydrogenation of levulinic acid and its esters to prepare γ-valerolactone. Among them, some progress has been made in the related research using precious metals as active centers. Yang et al. (Journal of Colloid and Interface Science, 2021, 581: 167-176) developed a core-shell structured N-Ru1 / Fe 3 O 4 @void@PMO catalyst, in the presence of appropriate amine promoters and the action of core-shell dual stabilization strategy, the Ru single atom catalyst can be used at 150℃ and 4.5MPa H 2 Under the reaction conditions, a 99.0% conversion rate of levulinic acid and a 98.9% yield of γ-valerolactone were obtained. Hsiao et al. (Chemical Engineering Communications, 2021, 208: 1511-1522) used a microwave heating-assisted process to convert levulinic acid and compared the catalytic activity of three typical carbon-supported catalysts Ru / C, Pt / C and Pd / C. Among these catalysts, Ru / C has the highest catalytic activity. At 160°C, the conversion rate of levulinic acid is 100%, and the selectivity of γ-valerolactone can reach 99%. Although precious metals have shown significant advantages in the hydrogenation of levulinic acid to γ-valerolactone, their application in industrial production faces great challenges due to their limited reserves, high prices, and harsh conditions in preparation and reaction.

[0005] To increase the possibility of industrialization, more and more people have begun to devote themselves to the research of non-noble metal catalysts. Among them, transition metals have attracted much attention due to their rich reserves and moderate prices. At present, research on the hydrogenation of levulinic acid and its esters to prepare γ-valerolactone using transition metals such as Cu, Ni, Fe, Co, etc. as catalysts has made some progress. Obregón et al. (Chinese Journal of Catalysis, 2014, 35: 656-662) used a Cu / Al 2 O 3 catalyst, with water as the solvent, and obtained a levulinic acid conversion rate of 75% and a γ-valerolactone selectivity of 66% under the conditions of 250 °C and 6.5 MPa H 2 . When tetrahydrofuran was used as the solvent instead, the reaction was carried out at 180 °C and 1.4 MPa H 2 for 4 hours, and 100% conversion of levulinic acid could be achieved, with a γ-valerolactone selectivity of 99%. Zhou et al. (Green Chemistry, 2014, 16: 3870-3875) first proposed a Co catalyst for the hydrogenation reaction of ethyl levulinate. The reaction was carried out at 130 °C and 3.3 MPaH 2 for 3 hours, and an ethyl levulinate conversion rate of 99% and a γ-valerolactone selectivity of 95% were obtained. Later, Li et al. (Sustainable Energy & Fuels, 2020, 4: 2043-2054) also developed a core-shell structured magnetic recyclable Co-based catalyst Co / Al 2 O 3 for the reaction of hydrogenating levulinic acid to prepare γ-valerolactone. Using 1,4-dioxane as the solvent, the reaction was carried out at the optimal reaction conditions of 180 °C and 5.0 MPaH 2 for 3 hours, and the yield of γ-valerolactone could reach 99%. Sosa et al. (Catalysis Today, 2021, 381: 86-95.) prepared a series of nickel catalysts Ni / CNT supported on carbon nanotubes (CNT). In a trickle-bed reactor, under the optimal reaction conditions of 180 °C and 3.0 MPaH 2 , the levulinic acid conversion rate was 24% and the γ-valerolactone selectivity was 98%. Although high yields of γ-valerolactone can also be obtained through the selective hydrogenation of levulinic acid and its esters using these non-noble metal catalysts, the high yields of γ-valerolactone rely on harsh reaction conditions (high temperature, high H 2 pressure). Therefore, it is very attractive to develop a catalytic method that still has high activity under low temperature and low H 2 pressure conditions. Summary of the Invention

[0006] The object of the present invention is to solve the problems of harsh reaction conditions and low yield of non-noble metal catalysts in the prior art, and to provide a method for preparing γ-valerolactone by hydrogenation of levulinic acid and its esters, which has high catalytic activity, low cost, environmental friendliness and high yield.

[0007] For the above object, the method for preparing γ-valerolactone by hydrogenation of levulinic acid and its esters provided by the present invention is as follows: Ni 3 P / SBA-15 catalyst, reaction substrate and water are added into a high-pressure reaction kettle, and the reaction is carried out under stirring at a constant temperature of 30-90 °C for 2-16 hours in a hydrogen atmosphere of 1.0-3.0 MPa to obtain γ-valerolactone; or Ni 3 P / SBA-15 catalyst is loaded into a fixed-bed reactor, hydrogen is introduced, the reactor is heated to 50-90 °C under a hydrogen flow, and then an aqueous solution of the reaction substrate is pumped in for catalytic hydrogenation to prepare γ-valerolactone.

[0008] The above reaction substrate is any one or more of levulinic acid, methyl levulinate and ethyl levulinate;

[0009] The above Ni 3 P / SBA-15 catalyst is SBA-15 loaded with Ni 3 P, and the mass ratio of element Ni to SBA-15 in the catalyst is 0.05-0.4; the preparation method of the catalyst is as follows: Ni(NO 3 ) 2 and phytic acid are dissolved in deionized water, mesoporous molecular sieve SBA-15 is added, and the mixture is dispersed evenly under ultrasonic waves. After magnetic stirring at room temperature for 20-24 hours, it is dried at 50-80 °C for 10-12 hours to obtain a catalyst precursor; then the catalyst precursor is reduced in a hydrogen atmosphere at 500-600 °C for 3-5 hours, and after natural cooling, Ni 3 P / SBA-15 catalyst is obtained; the molar ratio of Ni element in Ni(NO 3 ) 2 to P element in phytic acid is 2-4.

[0010] Further, in the above Ni 3 P / SBA-15 catalyst, the mass ratio of element Ni to SBA-15 is preferably 0.1-0.3.

[0011] Further, in the above preparation method of the catalyst, it is preferred to reduce the catalyst precursor in a hydrogen atmosphere at 550 °C for 4 hours.

[0012] Further, in the above preparation method of the catalyst, the heating rate of reducing the catalyst precursor in a hydrogen atmosphere is preferably 3-8 °C / minute.

[0013] Furthermore, in the above method for preparing γ-valerolactone by hydrogenating levulinic acid and its esters, Ni is preferably used. 3 The addition amount of the Ni 3 P / SBA-15 catalyst is 2% - 20% of the mass of the reaction substrate, and more preferably, the addition amount of the Ni 3 P / SBA-15 catalyst is 5% - 10% of the mass of the reaction substrate. 3

[0014] Furthermore, in the above method for preparing γ-valerolactone by hydrogenating levulinic acid and its esters, it is preferably carried out in a high-pressure reaction kettle under a hydrogen atmosphere of 2.0 MPa at a constant temperature of 80 - 90 °C with sealed stirring for 6 - 8 hours.

[0015] Furthermore, in the above method for preparing γ-valerolactone by hydrogenating levulinic acid and its esters, the mass space velocity of the catalyst in the fixed-bed reactor is preferably 0.5 - 2 h -1 . -1

[0016] Furthermore, in the above method for preparing γ-valerolactone by hydrogenating levulinic acid and its esters, the mass concentration of the aqueous solution of the reaction substrate in the fixed-bed reactor is preferably 1% - 25%.

[0017] Furthermore, in the above method for preparing γ-valerolactone by hydrogenating levulinic acid and its esters, the pressure of the fixed-bed reactor is preferably 1 - 3 MPa, and the hydrogen flow rate is preferably 15 - 25 mL / min.

[0018] The beneficial effects of the present invention are as follows:

[0019] Using water as the reaction solvent and the supported catalyst Ni 3 P / SBA-15 to catalyze levulinic acid (methyl levulinate, ethyl levulinate), γ-valerolactone can be prepared with high activity and high selectivity under low-temperature conditions whether in a high-pressure reaction kettle or a fixed-bed reactor. The preparation process of the present invention is simple, the raw materials are easy to obtain, the cost is low, the reaction process is environmentally friendly and pollution-free, and the catalytic system is relatively simple, the raw material conversion rate is high, the yield of γ-valerolactone can reach up to 100% at most, and after the reaction in the fixed-bed reactor for 50 hours, the yield of γ-valerolactone still remains stable, the catalyst has good stability, can save resources, reduce costs, and has good industrial application prospects. 3 BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is the TEM image of the Ni 3 P / SBA-15 catalyst prepared in Example 1. 3

[0021] Figure 2 It is the stability test diagram of the Ni 3 P / SBA-15 catalyst prepared in Example 1 (taking the methyl levulinate system as an example). 3 DETAILED DESCRIPTION OF THE INVENTION​​​​​

[0022] The technical solution of the present invention will be described in detail below in conjunction with the accompanying drawings and embodiments, but the protection scope of the present invention is not limited to these embodiments only.

[0023] Example 1

[0024] 1. Preparation of Ni 3 P / SBA-15 catalyst

[0025] 0.2477 g of Ni(NO 3 ) 2 ·6H 2 O and 0.0535 g of an aqueous solution of phytic acid with a mass concentration of 50% are added to 5 mL of water. The molar ratio of Ni element in Ni(NO 3 ) 2 ·6H 2 O to P element in phytic acid is 3.5. Ultrasonic for 1 hour to fully mix the two, and then add 0.5 g of mesoporous molecular sieve SBA-15 (purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., BET specific surface area 700 - 800 m 2 / g, pore diameter 6 - 13 nm), and ultrasonic disperse for another 1 hour. Then stir magnetically at room temperature for 24 hours. After the stirring is completed, stir and dry in a constant temperature oil bath at 60 °C for 12 hours to obtain a light green catalyst precursor. After fully grinding, heat it to 550 °C at a heating rate of 5 °C / minute in a hydrogen atmosphere, keep the temperature constant and reduce for 4 hours, and then naturally cool to obtain Ni 3 P / SBA-15 catalyst. The mass ratio of element Ni to SBA-15 in the catalyst is 0.1. As Figure 1 can be seen, the TEM diffraction fringes present a typical Ni 3 P(141) crystal plane, from which it can be confirmed that Ni 3 P / SBA-15 is synthesized.

[0026] 2. Preparation of γ-valerolactone by catalytic hydrogenation

[0027] 1 g of levulinic acid (methyl levulinate, ethyl levulinate) and 50 mL of water are placed in a 100 mL high-pressure reaction kettle, and then 50 mg of Ni 3 P / SBA-15 catalyst is added. Evacuate with N 2 at room temperature, and then introduce hydrogen into the high-pressure reaction kettle. Stir and react at a constant temperature of 90 °C under a hydrogen atmosphere of 2 MPa for 6 hours, and cool to room temperature in an ice bath. Analyze the product by liquid chromatography (mobile phase: 0.005 mol / L H 2 SO 4 aqueous solution, flow rate: 0.05 mL / minute, column temperature: 50 °C). The reaction results are shown in Table 1.

[0028] Example 2

[0029] Place 1 g of levulinic acid (methyl levulinate, ethyl levulinate) and 50 mL of water in a 100 mL high-pressure reactor, and then add 50 mg of Ni 3 P / SBA-15 catalyst (prepared in the same way as in Example 1), evacuate with N 2 at room temperature, then introduce hydrogen into the high-pressure reactor, and carry out a constant-temperature closed stirring reaction at 80 °C for 8 hours under a hydrogen atmosphere of 2 MPa. Cool to room temperature in an ice bath, and analyze the product by liquid chromatography (mobile phase: 0.005 mol / L H 2 SO 4 aqueous solution, flow rate: 0.05 mL / min, column temperature: 50 °C). The reaction results are shown in Table 1.

[0030] Example 3

[0031] Place 1 g of levulinic acid (methyl levulinate, ethyl levulinate) and 50 mL of water in a 100 mL high-pressure reactor, and then add 50 mg of Ni 3 P / SBA-15 catalyst (prepared in the same way as in Example 1), evacuate with N 2 at room temperature, then introduce hydrogen into the high-pressure reactor, and carry out a constant-temperature closed stirring reaction at 70 °C for 10.5 hours under a hydrogen atmosphere of 2 MPa. Cool to room temperature in an ice bath, and analyze the product by liquid chromatography (mobile phase: 0.005 mol / L H 2 SO 4 aqueous solution, flow rate: 0.05 mL / min, column temperature: 50 °C). The reaction results are shown in Table 1.

[0032] Example 4

[0033] Place 1 g of levulinic acid (methyl levulinate, ethyl levulinate) and 50 mL of water in a 100 mL high-pressure reactor, and then add 50 mg of Ni 3 P / SBA-15 catalyst (prepared in the same way as in Example 1), evacuate with N 2 at room temperature, then introduce hydrogen into the high-pressure reactor, and carry out a constant-temperature closed stirring reaction at 50 °C for 13.5 hours under a hydrogen atmosphere of 2 MPa. Cool to room temperature in an ice bath, and analyze the product by liquid chromatography (mobile phase: 0.005 mol / L H 2 SO 4 aqueous solution, flow rate: 0.05 mL / min, column temperature: 50 °C). The reaction results are shown in Table 1.

[0034] Example 5

[0035] Place 1 g of levulinic acid (methyl levulinate, ethyl levulinate) and 50 mL of water in a 100 mL high-pressure reactor, and then add 50 mg of Ni 3P / SBA-15 catalyst (prepared as in Example 1) was heated to room temperature with N 2 The autoclave was emptied and then hydrogen was introduced into the autoclave. The reaction was carried out under a 2MPa hydrogen atmosphere at 30°C with constant temperature and stirring for 16 hours. The autoclave was cooled to room temperature in an ice bath and the product was analyzed by liquid chromatography (mobile phase: 0.005 mol / L H 2 SO 4 Aqueous solution, flow rate: 0.05 mL / min, column temperature: 50°C), the reaction results are summarized in Table 1.

[0036] Example 6

[0037] 1. Ni 3 Preparation of P / SBA-15 catalyst

[0038] 0.1239 g Ni(NO 3 ) 2 6H 2 O and 0.0268 g of 50% phytic acid aqueous solution were added to 5 mL of water. The Ni(NO 3 ) 2 6H 2 The molar ratio of Ni in O and P in phytic acid was 3.5. Ultrasonication was performed for 1 hour to fully mix the two elements. Then, 0.5 g of mesoporous molecular sieve SBA-15 (purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd., with a BET specific surface area of ​​700-800 m 2 / g, pore size 6-13nm), and then ultrasonically dispersed for 1 hour, and then magnetically stirred at room temperature for 24 hours. After the stirring was completed, it was stirred and dried in a 60°C constant temperature oil bath for 12 hours to obtain a light green catalyst precursor. After sufficient grinding, it was heated to 550°C at a heating rate of 5°C / min in a hydrogen atmosphere, and reduced at a constant temperature for 4 hours. After natural cooling, Ni 3 P / SBA-15 catalyst: The mass ratio of element Ni to SBA-15 in the catalyst is 0.05.

[0039] 2. Preparation of γ-valerolactone by catalytic hydrogenation

[0040] 1 g of levulinic acid (methyl levulinate, ethyl levulinate) and 50 mL of water were placed in a 100 mL autoclave, and 50 mg of Ni 3 P / SBA-15 catalyst was used at room temperature with N 2 The autoclave was emptied and then hydrogen was introduced into the autoclave. The reaction was carried out at 90°C in a sealed state with constant temperature and stirring for 10 hours under a 2MPa hydrogen atmosphere. The reaction was cooled to room temperature in an ice bath and the product was analyzed by liquid chromatography (mobile phase: 0.005 mol / L H 2 SO 4Aqueous solution, flow rate: 0.05 mL / min, column temperature: 50 °C), the summary of the reaction results is shown in Table 1.

[0041] Example 7

[0042] 1. Ni 3 Preparation of NiP / SBA-15 catalyst

[0043] 0.7431 g of Ni(NO 3 ) 2 ·6H 2 O and 0.2811 g of an aqueous solution of phytic acid with a mass concentration of 50% were added to 5 mL of water. The molar ratio of Ni element in Ni(NO 3 ) 2 ·6H 2 O to P element in phytic acid was 2. They were ultrasonically mixed for 1 hour, and then 0.5 g of mesoporous molecular sieve SBA-15 (purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., BET specific surface area 700 - 800 m 2 / g, pore diameter 6 - 13 nm) was added. Then it was ultrasonically dispersed for 1 hour, and then magnetically stirred at room temperature for 24 hours. After the stirring was completed, it was stirred and dried in a constant temperature oil bath at 60 °C for 12 hours to obtain a light green catalyst precursor. After thorough grinding, it was heated to 550 °C at a heating rate of 5 °C / min in a hydrogen atmosphere and kept at a constant temperature for reduction for 4 hours. After natural cooling, Ni 3 P / SBA-15 catalyst was obtained. The mass ratio of element Ni to SBA-15 in the catalyst was 0.3.

[0044] 2. Preparation of γ-valerolactone by catalytic hydrogenation

[0045] 1 g of levulinic acid (methyl levulinate, ethyl levulinate) and 50 mL of water were placed in a 100 mL high-pressure reaction kettle, and then 50 mg of Ni 3 P / SBA-15 catalyst was added. It was evacuated with N 2 at room temperature, and then hydrogen was introduced into the high-pressure reaction kettle. It was stirred and reacted at a constant temperature of 90 °C in a hydrogen atmosphere of 2 MPa for 4 hours, and then cooled to room temperature in an ice bath. The products were analyzed by liquid chromatography (mobile phase: 0.005 mol / L H 2 SO 4 aqueous solution, flow rate: 0.05 mL / min, column temperature: 50 °C), the summary of the reaction results is shown in Table 1.

[0046] Example 8

[0047] 1. Ni 3 Preparation of NiP / SBA-15 catalyst

[0048] 0.9908 g of Ni(NO 3 )2 ·6H 2 O and 0.214 g of an aqueous solution of phytic acid with a mass concentration of 50% are added to 5 mL of water. The molar ratio of Ni element in Ni(NO 3 ) 2 ·6H 2 O to P element in phytic acid is 3.5. Ultrasonic treatment is carried out for 1 hour to fully mix the two. Subsequently, 0.5 g of mesoporous molecular sieve SBA-15 (purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., BET specific surface area 700 - 800 m 2 / g, pore diameter 6 - 13 nm) is added, and ultrasonic dispersion is carried out for another 1 hour. Then, magnetic stirring is carried out at room temperature for 24 hours. After the stirring is completed, it is stirred and dried in a constant temperature oil bath at 60 °C for 12 hours to obtain a light green catalyst precursor. After sufficient grinding, it is heated to 550 °C at a heating rate of 5 °C / minute in a hydrogen atmosphere and kept at a constant temperature for reduction for 4 hours. After natural cooling, the Ni 3 P / SBA-15 catalyst is obtained. The mass ratio of element Ni to SBA-15 in the catalyst is 0.4.

[0049] 2. Preparation of γ-valerolactone by catalytic hydrogenation

[0050] 1 g of levulinic acid (methyl levulinate, ethyl levulinate) and 50 mL of water are placed in a 100 mL high-pressure reactor, and then 50 mg of Ni 3 P / SBA-15 catalyst is added. It is evacuated with N 2 at room temperature, and then hydrogen is introduced into the high-pressure reactor. Under a hydrogen atmosphere of 2 MPa, it is stirred and reacted at a constant temperature of 90 °C for 2.5 hours, and then cooled to room temperature in an ice bath. The product is analyzed by liquid chromatography (mobile phase: 0.005 mol / L H 2 SO 4 aqueous solution, flow rate: 0.05 mL / minute, column temperature: 50 °C). The reaction results are summarized in Table 1.

[0051] Table 1 Conversion rate of methyl levulinate and selectivity of γ-valerolactone at different temperatures

[0052]

[0053]

[0054] As can be seen from Table 1, the method of the present invention can achieve efficient catalytic hydrogenation of methyl levulinate to γ-valerolactone under mild conditions. The yield of γ-valerolactone reaches 100% at a low temperature of 90 °C, and as the temperature decreases, methyl levulinate can still be highly selectively converted to γ-valerolactone. Especially at 30 °C, the selectivity of γ-valerolactone still remains at 100%.

[0055] Example 9

[0056] Load 0.2 g of Ni 3 The P / SBA-15 catalyst was loaded into a fixed-bed reactor, hydrogen was introduced at a flow rate of 20 mL / min, the reactor pressure was raised to 2 MPa, and the reactor was heated to 90 °C under H 2 flow; then an aqueous solution of methyl levulinate with a mass concentration of 2% was introduced into the reactor through a high-pressure liquid metering pump, and the mass space velocity of the catalyst was 0.54 h -1 . Samples were taken every 3 hours and detected using a high-performance liquid chromatograph. The reaction was carried out for a total of 50 hours, and the reaction results are shown in Figure 2 .

[0057] It can be seen from Figure 2 that after 50 hours of reaction, the yield of γ-valerolactone remained basically unchanged, indicating that the catalyst has good stability.

Claims

1. A method for preparing γ-valerolactone by mild and efficient catalytic hydrogenation of levulinic acid and its esters, characterized in that: Add Ni3P / SBA-15 catalyst, reaction substrate and water into a high pressure reactor, and react at 30-90°C in a sealed state with constant temperature and stirring for 2-16 hours under a 1.0-3.0 MPa hydrogen atmosphere to obtain γ-valerolactone; Alternatively, the Ni3P / SBA-15 catalyst is loaded into a fixed bed reactor, hydrogen is introduced, the reactor is heated to 50-90° C. under the hydrogen flow, and then an aqueous solution of the reaction substrate is pumped into the reactor to perform catalytic hydrogenation to prepare γ-valerolactone; The reaction substrate is any one or more of levulinic acid, methyl levulinate, and ethyl levulinate; The Ni3P / SBA-15 catalyst is SBA-15 loaded with Ni3P, and the mass ratio of element Ni to SBA-15 in the catalyst is 0.05-0.4; the preparation method of the catalyst is: dissolve Ni(NO3)2 and phytic acid in deionized water, add mesoporous molecular sieve SBA-15, and disperse them evenly under ultrasound, stir magnetically at room temperature for 20-24 hours, and dry at 50-80°C for 10-12 hours to obtain a catalyst precursor; then reduce the catalyst precursor in a hydrogen atmosphere at 500-600°C for 3-5 hours, and obtain the Ni3P / SBA-15 catalyst after natural cooling; the molar ratio of the Ni element in the Ni(NO3)2 and the P element in the phytic acid is 2-4.

2. The method for preparing γ-valerolactone by mild and efficient catalytic hydrogenation of levulinic acid and its esters according to claim 1, characterized in that: In the Ni3P / SBA-15 catalyst, the mass ratio of element Ni to SBA-15 is 0.1 to 0.

3.

3. The method for preparing γ-valerolactone by mild and efficient catalytic hydrogenation of levulinic acid and its esters according to claim 1, characterized in that: The catalyst precursor was reduced at 550°C in a hydrogen atmosphere for 4 hours.

4. The method for preparing γ-valerolactone by mild and efficient catalytic hydrogenation of levulinic acid and its esters according to claim 1 or 3, characterized in that: The heating rate for reducing the catalyst precursor in a hydrogen atmosphere is 3-8°C / min.

5. The method for preparing γ-valerolactone by mild and efficient catalytic hydrogenation of levulinic acid and its esters according to claim 1, characterized in that: The added amount of the Ni3P / SBA-15 catalyst is 2% to 20% of the reaction substrate mass.

6. The method for preparing γ-valerolactone by mild and efficient catalytic hydrogenation of levulinic acid and its esters according to claim 1, characterized in that: The added amount of the Ni3P / SBA-15 catalyst is 5% to 10% of the reaction substrate mass.

7. The method for preparing γ-valerolactone by mild and efficient catalytic hydrogenation of levulinic acid and its esters according to claim 1, characterized in that: The reaction was carried out under a 2.0 MPa hydrogen atmosphere at a constant temperature of 80 to 90°C with stirring in a closed manner for 6 to 8 hours.

8. The method for preparing γ-valerolactone by mild and efficient catalytic hydrogenation of levulinic acid and its esters according to claim 1, characterized in that: The mass space velocity of the catalyst in the fixed bed reactor is 0.5 to 2 h -1 .

9. The method for preparing γ-valerolactone by mild and efficient catalytic hydrogenation of levulinic acid and its esters according to claim 1, characterized in that: In the aqueous solution of the reaction substrate, the mass concentration of the reaction substrate is 1% to 25%.

10. The method for preparing γ-valerolactone by mild and efficient catalytic hydrogenation of levulinic acid and its esters according to claim 1, characterized in that: The pressure of the fixed bed reactor is 1-3 MPa, and the hydrogen flow rate is 15-25 mL / min.

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