A mild and efficient catalytic method for the hydrogenation of levulinic acid and its esters to prepare γ-valerol.

Abstract

This invention discloses a method for the efficient catalytic hydrogenation of levulinic acid and its esters to prepare γ-valerol under mild conditions. The method uses water as the reaction solvent and a Ni3P / SBA-15 catalyst to catalyze the hydrogenation of levulinic acid and its esters in a high-pressure reactor or fixed-bed reactor under low-temperature conditions to selectively prepare γ-valerol. The Ni3P / SBA-15 catalyst is obtained by impregnating a Ni3P precursor onto SBA-15 and then reducing it in a hydrogen atmosphere. This invention offers a simple preparation method, readily available raw materials, low cost, and an environmentally friendly, pollution-free reaction process. Furthermore, the catalytic system is relatively simple, with high conversion rates of the reactants, and the γ-valerol yield can reach 100%. After 50 hours of reaction in a fixed-bed reactor, the yield of γ-valerol remains stable, indicating good catalyst stability. This method saves resources, reduces costs, and has promising prospects for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of clean and green catalytic synthesis of high-value-added chemicals using biomass resources, specifically relating to a method for the catalytic hydrogenation of levulinic acid and its esters to prepare γ-valerolactone. Background Technology

[0002] The excessive consumption of fossil fuels, leading to reduced crude oil reserves and increased environmental problems, has prompted scientists to urgently seek new renewable alternatives. A growing body of research indicates that converting renewable biomass and biomass platform molecules into value-added chemicals is a very promising method for alleviating the current energy crisis and environmental issues. In recent years, with increasing attention to biomass energy, the conversion of biomass into bio-based chemicals and biofuels has been a research hotspot and has achieved significant progress.

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

[0004] Over the years, researchers have developed various catalysts for the hydrogenation of levulinic acid and its esters to prepare γ-valerol. Among these, research using noble metals as active centers has made some progress. Yang et al. (Journal of Colloid and Interface Science, 2021, 581: 167-176) developed a core-shell structured N-Ru1 / Fe3O4@void@PMO catalyst. With the presence of appropriate amine promoters and a core-shell bistable strategy, this Ru single-atom catalyst achieved a 99.0% conversion of levulinic acid and a 98.9% yield of γ-valerol under reaction conditions of 150 °C and 4.5 MPa H2. Hsiao et al. (Chemical Engineering Communications, 2021, 208: 1511-1522) used a microwave-assisted heating process to convert levulinic acid and compared the catalytic activities of three typical carbon-supported catalysts: Ru / C, Pt / C, and Pd / C. Among these catalysts, Ru / C exhibits the highest catalytic activity, achieving 100% conversion of levulinic acid and a selectivity of 99% for γ-valerolactone at 160°C. Although noble metals have shown significant advantages in the hydrogenation of levulinic acid to γ-valerolactone, their limited reserves, high prices, and stringent requirements in preparation and reaction conditions pose significant challenges to their industrial application.

[0005] To increase the possibility of industrialization, more and more people are focusing on the research of non-precious metal catalysts. Among them, transition metals have attracted much attention due to their abundant reserves and moderate prices. Currently, some progress has been made in the research of using transition metals such as Cu, Ni, Fe, and Co as catalysts to catalyze the hydrogenation of levulinic acid and its esters to prepare γ-valerolactone. Obregón et al. (Chinese Journal of Catalysis, 2014, 35: 656-662) used a Cu / Al2O3 catalyst with water as solvent and obtained a 75% conversion of levulinic acid and a 66% selectivity of γ-valerolactone under conditions of 250℃ and 6.5MPa H2. When tetrahydrofuran was used as the solvent, 100% conversion of levulinic acid and a γ-valerolactone selectivity of 99% could be achieved by reacting at 180℃ and 1.4MPa H2 for 4 hours. Zhou et al. (Green Chemistry, 2014, 16:3870-3875) first proposed a Co catalyst for the hydrogenation of ethyl levulinate, achieving a 99% conversion of ethyl levulinate and a 95% selectivity for γ-valerolactone at 130 °C and 3.3 MPa H₂ for 3 hours. Later, Li et al. (Sustainable Energy & Fuels, 2020, 4:2043-2054) developed a core-shell structured, magnetically recyclable Co-based catalyst, Co / Al₂O₃, for the hydrogenation of levulinate to γ-valerolactone. Using 1,4-dioxane as a solvent, and under optimal reaction conditions of 180 °C and 5.0 MPa H₂ for 3 hours, the yield of γ-valerolactone reached 99%. Sosa et al. (Catalysis Today, 2021, 381:86-95.) prepared a series of carbon nanotube (CNT) supported nickel catalysts (Ni / CNT). In a trickle-bed reactor, under optimal reaction conditions of 180 °C and 3.0 MPa H₂, the conversion of levulinic acid was 24%, and the selectivity for γ-valerolactone was 98%. Although these non-noble metal catalysts can also be used to selectively hydrogenate levulinic acid and its esters to obtain high yields of γ-valerolactone, the high yield of γ-valerolactone depends on harsh reaction conditions (high temperature, high H₂ pressure). Therefore, developing a catalytic method that still maintains high activity under low temperature and low H₂ pressure conditions is very attractive. Summary of the Invention

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

[0007] To achieve the above objectives, the present invention provides a method for the hydrogenation of levulinic acid and its esters to prepare γ-valerol: Ni3P / SBA-15 catalyst, reaction substrate, and water are added to a high-pressure reactor and reacted under a constant temperature and sealed environment at 30-90°C for 2-16 hours in a hydrogen atmosphere of 1.0-3.0 MPa to obtain γ-valerol; or Ni3P / SBA-15 catalyst is loaded into a fixed-bed reactor, hydrogen is introduced, and the reactor is heated to 50-90°C under the hydrogen flow, then an aqueous solution of the reaction substrate is pumped in to perform catalytic hydrogenation to prepare γ-valerol.

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

[0009] The aforementioned Ni3P / SBA-15 catalyst is SBA-15 supported on Ni3P, with a mass ratio of Ni to SBA-15 of 0.05–0.4. The catalyst is prepared as follows: Ni(NO3)2 and phytic acid are dissolved in deionized water, mesoporous molecular sieve SBA-15 is added, and the mixture is dispersed uniformly under ultrasonication. After magnetic stirring at room temperature for 20–24 hours, the mixture is dried at 50–80°C for 10–12 hours to obtain a catalyst precursor. The catalyst precursor is then reduced in a hydrogen atmosphere at 500–600°C for 3–5 hours, and after natural cooling, the Ni3P / SBA-15 catalyst is obtained. The molar ratio of Ni in Ni(NO3)2 to P in phytic acid is 2–4.

[0010] Furthermore, in the above-mentioned Ni3P / SBA-15 catalyst, the preferred mass ratio of Ni to SBA-15 is 0.1 to 0.3.

[0011] Furthermore, in the above-mentioned method for preparing the catalyst, it is preferable to reduce the catalyst precursor at 550°C in a hydrogen atmosphere for 4 hours.

[0012] Furthermore, in the above-mentioned method for preparing the catalyst, it is preferable that the heating rate for reducing the catalyst precursor in a hydrogen atmosphere is 3 to 8 °C / min.

[0013] Furthermore, in the above method for preparing γ-valerol by hydrogenation of levulinic acid and its esters, the amount of Ni3P / SBA-15 catalyst added is preferably 2% to 20% of the mass of the reaction substrate, and more preferably 5% to 10% of the mass of the reaction substrate.

[0014] Furthermore, in the above method for preparing γ-valerol by hydrogenation of levulinic acid and its esters, it is preferable to conduct a constant temperature and closed stirring reaction in a high-pressure reactor at 80-90°C for 6-8 hours under a hydrogen atmosphere of 2.0 MPa.

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

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

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

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

[0019] This invention uses water as the reaction solvent and a supported catalyst, Ni3P / SBA-15, to catalyze the reaction of levulinic acid (methyl levulinate and ethyl levulinate) to produce γ-valerolactone with high activity and selectivity under low-temperature conditions, whether in a high-pressure reactor or a fixed-bed reactor. The preparation process of this invention is simple, uses readily available raw materials, and is low-cost. The reaction process is environmentally friendly and pollution-free. Furthermore, the catalytic system is relatively simple, with high raw material conversion rates. The yield of γ-valerolactone can reach up to 100%, and the yield remains stable even after 50 hours of reaction in a fixed-bed reactor, indicating good catalyst stability. This method saves resources, reduces costs, and has promising prospects for industrial application. Attached Figure Description

[0020] Figure 1 This is a TEM image of the Ni3P / SBA-15 catalyst prepared in Example 1.

[0021] Figure 2 This is a stability test diagram of the Ni3P / SBA-15 catalyst prepared in Example 1 (using methyl levulinate system as an example). Detailed Implementation

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

[0023] Example 1

[0024] 1. Preparation of Ni3P / SBA-15 catalyst

[0025] 0.2477 g of Ni(NO3)2·6H2O and 0.0535 g of a 50% phytic acid aqueous solution were added to 5 mL of water. The molar ratio of Ni in Ni(NO3)2·6H2O to P in phytic acid was 3.5. The mixture was sonicated for 1 hour to ensure thorough mixing. Subsequently, 0.5 g of mesoporous molecular sieve SBA-15 (purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., with a BET specific surface area of ​​700-800 m²) was added. 2 / g (pore size 6-13nm), then ultrasonically dispersed for 1 hour, followed by magnetic stirring at room temperature for 24 hours. After stirring, it was dried in a 60℃ constant-temperature oil bath for 12 hours to obtain a light green catalyst precursor. After thorough grinding, it was heated to 550℃ at a heating rate of 5℃ / min under a hydrogen atmosphere, and reduced at that temperature for 4 hours. After natural cooling, the Ni3P / SBA-15 catalyst was obtained. The mass ratio of Ni to SBA-15 in the catalyst was 0.1. Figure 1 As can be seen, the TEM diffraction fringes exhibit a typical Ni3P(141) crystal plane, which confirms the synthesis of Ni3P / SBA-15.

[0026] 2. Catalytic hydrogenation to prepare γ-valerol

[0027] 1g of levulinic acid (methyl levulinate, ethyl levulinate) and 50mL of water were placed in a 100mL high-pressure reactor, and then 50mg of Ni3P / SBA-15 catalyst was added. The reactor was purged with N2 at room temperature, and then hydrogen gas was introduced into the high-pressure reactor. The reactor was stirred at 90℃ under a hydrogen atmosphere of 2MPa for 6 hours. The reactor was then cooled to room temperature in an ice bath. The product was analyzed by liquid chromatography (mobile phase: 0.005mol / L H2SO4 aqueous solution, flow rate: 0.05mL / min, column temperature: 50℃). The reaction results are shown in Table 1.

[0028] Example 2

[0029] 1g of levulinic acid (methyl levulinate, ethyl levulinate) and 50mL of water were placed in a 100mL high-pressure reactor, and then 50mg of Ni3P / SBA-15 catalyst (prepared in the same way as in Example 1) was added. The reactor was purged with N2 at room temperature, and then hydrogen gas was introduced into the high-pressure reactor. The reactor was stirred at 80℃ under a 2MPa hydrogen atmosphere for 8 hours. The reactor was then cooled to room temperature in an ice bath. The product was analyzed by liquid chromatography (mobile phase: 0.005mol / L H2SO4 aqueous solution, flow rate: 0.05mL / min, column temperature: 50℃). The reaction results are shown in Table 1.

[0030] Example 3

[0031] 1g of levulinic acid (methyl levulinate, ethyl levulinate) and 50mL of water were placed in a 100mL high-pressure reactor, and then 50mg of Ni3P / SBA-15 catalyst (prepared in the same way as in Example 1) was added. The reactor was purged with N2 at room temperature, and then hydrogen gas was introduced into the high-pressure reactor. The reactor was stirred at 70℃ under a hydrogen atmosphere of 2MPa for 10.5 hours. The reactor was then cooled to room temperature in an ice bath. The product was analyzed by liquid chromatography (mobile phase: 0.005mol / L H2SO4 aqueous solution, flow rate: 0.05mL / min, column temperature: 50℃). The reaction results are shown in Table 1.

[0032] Example 4

[0033] 1g of levulinic acid (methyl levulinate, ethyl levulinate) and 50mL of water were placed in a 100mL high-pressure reactor, and then 50mg of Ni3P / SBA-15 catalyst (prepared in the same way as in Example 1) was added. The reactor was purged with N2 at room temperature, and then hydrogen gas was introduced into the high-pressure reactor. The reactor was stirred at 50℃ under a 2MPa hydrogen atmosphere for 13.5 hours. The reactor was then cooled to room temperature in an ice bath. The product was analyzed by liquid chromatography (mobile phase: 0.005mol / L H2SO4 aqueous solution, flow rate: 0.05mL / min, column temperature: 50℃). The reaction results are shown in Table 1.

[0034] Example 5

[0035] 1g of levulinic acid (methyl levulinate, ethyl levulinate) and 50mL of water were placed in a 100mL high-pressure reactor, and then 50mg of Ni3P / SBA-15 catalyst (prepared in the same way as in Example 1) was added. The reactor was purged with N2 at room temperature, and then hydrogen gas was introduced into the high-pressure reactor. The reactor was stirred at 30℃ under a 2MPa hydrogen atmosphere for 16 hours. The reactor was then cooled to room temperature in an ice bath. The products were analyzed by liquid chromatography (mobile phase: 0.005mol / L H2SO4 aqueous solution, flow rate: 0.05mL / min, column temperature: 50℃). The reaction results are summarized in Table 1.

[0036] Example 6

[0037] 1. Preparation of Ni3P / SBA-15 catalyst

[0038] 0.1239 g of Ni(NO3)2·6H2O and 0.0268 g of a 50% phytic acid aqueous solution were added to 5 mL of water. The molar ratio of Ni in Ni(NO3)2·6H2O to P in phytic acid was 3.5. The mixture was sonicated for 1 hour to ensure thorough mixing. Subsequently, 0.5 g of mesoporous molecular sieve SBA-15 (purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., with a BET specific surface area of ​​700-800 m²) was added. 2 / g (pore size 6-13nm), then ultrasonically dispersed for 1 hour, followed by magnetic stirring at room temperature for 24 hours. After stirring, it was dried in a 60℃ constant temperature oil bath for 12 hours to obtain a light green catalyst precursor. After thorough grinding, it was heated to 550℃ at a heating rate of 5℃ / min under a hydrogen atmosphere and reduced at that temperature for 4 hours. After natural cooling, the Ni3P / SBA-15 catalyst was obtained. The mass ratio of Ni to SBA-15 in the catalyst was 0.05.

[0039] 2. Catalytic hydrogenation to prepare γ-valerol

[0040] 1g of levulinic acid (methyl levulinate, ethyl levulinate) and 50mL of water were placed in a 100mL high-pressure reactor, and then 50mg of Ni3P / SBA-15 catalyst was added. The reactor was purged with N2 at room temperature, and then hydrogen gas was introduced into the high-pressure reactor. The reactor was stirred at 90℃ under a hydrogen atmosphere of 2MPa for 10 hours. The reactor was then cooled to room temperature in an ice bath. The products were analyzed by liquid chromatography (mobile phase: 0.005mol / L H2SO4 aqueous solution, flow rate: 0.05mL / min, column temperature: 50℃). The reaction results are summarized in Table 1.

[0041] Example 7

[0042] 1. Preparation of Ni3P / SBA-15 catalyst

[0043] 0.7431 g of Ni(NO3)2·6H2O and 0.2811 g of a 50% phytic acid aqueous solution were added to 5 mL of water. The molar ratio of Ni in Ni(NO3)2·6H2O to P in phytic acid was 2. The mixture was sonicated for 1 hour to ensure thorough mixing. Subsequently, 0.5 g of mesoporous molecular sieve SBA-15 (purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., with a BET specific surface area of ​​700-800 m²) was added. 2 / g (pore size 6-13nm), then ultrasonically dispersed for 1 hour, followed by magnetic stirring at room temperature for 24 hours. After stirring, it was dried in a 60℃ constant temperature oil bath for 12 hours to obtain a light green catalyst precursor. After thorough grinding, it was heated to 550℃ at a heating rate of 5℃ / min under a hydrogen atmosphere and reduced at that temperature for 4 hours. After natural cooling, the Ni3P / SBA-15 catalyst was obtained. The mass ratio of Ni to SBA-15 in the catalyst was 0.3.

[0044] 2. Catalytic hydrogenation to prepare γ-valerol

[0045] 1g of levulinic acid (methyl levulinate, ethyl levulinate) and 50mL of water were placed in a 100mL high-pressure reactor, and then 50mg of Ni3P / SBA-15 catalyst was added. The reactor was purged with N2 at room temperature, and then hydrogen gas was introduced into the high-pressure reactor. The reactor was stirred at 90℃ under a hydrogen atmosphere of 2MPa for 4 hours. The reactor was then cooled to room temperature in an ice bath. The products were analyzed by liquid chromatography (mobile phase: 0.005mol / L H2SO4 aqueous solution, flow rate: 0.05mL / min, column temperature: 50℃). The reaction results are summarized in Table 1.

[0046] Example 8

[0047] 1. Preparation of Ni3P / SBA-15 catalyst

[0048] 0.9908 g of Ni(NO3)2·6H2O and 0.214 g of a 50% phytic acid aqueous solution were added to 5 mL of water. The molar ratio of Ni in Ni(NO3)2·6H2O to P in phytic acid was 3.5. The mixture was sonicated for 1 hour to ensure thorough mixing. Subsequently, 0.5 g of mesoporous molecular sieve SBA-15 (purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., with a BET specific surface area of ​​700-800 m²) was added. 2 / g (pore size 6-13nm), then ultrasonically dispersed for 1 hour, followed by magnetic stirring at room temperature for 24 hours. After stirring, it was dried in a 60℃ constant temperature oil bath for 12 hours to obtain a light green catalyst precursor. After thorough grinding, it was heated to 550℃ at a heating rate of 5℃ / min under a hydrogen atmosphere and reduced at that temperature for 4 hours. After natural cooling, the Ni3P / SBA-15 catalyst was obtained. The mass ratio of Ni to SBA-15 in the catalyst was 0.4.

[0049] 2. Catalytic hydrogenation to prepare γ-valerol

[0050] 1g of levulinic acid (methyl levulinate, ethyl levulinate) and 50mL of water were placed in a 100mL high-pressure reactor, and then 50mg of Ni3P / SBA-15 catalyst was added. The reactor was purged with N2 at room temperature, and then hydrogen gas was introduced into the high-pressure reactor. The reactor was stirred at 90℃ under a hydrogen atmosphere of 2MPa for 2.5 hours. The reactor was then cooled to room temperature in an ice bath. The products were analyzed by liquid chromatography (mobile phase: 0.005mol / L H2SO4 aqueous solution, flow rate: 0.05mL / min, column temperature: 50℃). The reaction results are summarized in Table 1.

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

[0052]

[0053]

[0054] As shown in 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℃. Moreover, as the temperature decreases, methyl levulinate can still be converted to γ-valerolactone with high selectivity. Especially at 30℃, the selectivity of γ-valerolactone is still maintained at 100%.

[0055] Example 9

[0056] 0.2 g of Ni3P / SBA-15 catalyst was loaded into a fixed-bed reactor, and hydrogen gas was introduced at a flow rate of 20 mL / min to raise the reactor pressure to 2 MPa. The reactor was then heated to 90 °C under H2 flow. A 2% (w / w) aqueous solution of methyl levulinate was then introduced into the reactor via a high-pressure liquid metering pump, with a catalyst mass hourly space velocity (HHSV) of 0.54 h⁻¹. -1 Samples were taken every 3 hours and analyzed using high-performance liquid chromatography (HPLC). The reaction lasted for a total of 50 hours. The results are shown in the figure. Figure 2 .

[0057] Depend on Figure 2 As can be seen, the yield of γ-valerol remained essentially unchanged after 50 hours of reaction, indicating that the catalyst has good stability.

Claims

1. A process for the mild and efficient catalytic hydrogenation of levulinic acid and its esters to γ-valerolactone, characterized in that: The Ni3P / SBA-15 catalyst, the reaction substrate and water are added into a high-pressure reaction kettle, and the reaction is carried out at 1.0-3.0 MPa hydrogen atmosphere and 30-90 ℃ constant temperature for 2-16 hours to obtain gamma-valerolactone. Or the Ni3P / SBA-15 catalyst is loaded into a fixed bed reactor, hydrogen is introduced, the reactor is heated to 50-90 ℃ under hydrogen flow, and then the aqueous solution of the reaction substrate is pumped to prepare gamma-valerolactone by catalytic hydrogenation. 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 as follows: Ni(NO3)2 and phytic acid are dissolved in deionized water, mesoporous molecular sieve SBA-15 is added and uniformly dispersed under ultrasonic, and then the mixture is stirred at room temperature for 20-24 hours, and dried at 50-80 ℃ for 10-12 hours to obtain a catalyst precursor; then the catalyst precursor is reduced at 500-600 ℃ under hydrogen atmosphere for 3-5 hours, and the Ni3P / SBA-15 catalyst is obtained after natural cooling; the molar ratio of Ni element in the Ni(NO3)2 to P element in the phytic acid is 2-4.

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

3.

3. The process for the mild and efficient catalytic hydrogenation of levulinic acid and its esters to γ-valerolactone according to claim 1, characterized in that: The catalyst precursor is reduced at 550 ℃ under hydrogen atmosphere for 4 hours.

4. The process for the mild and efficient catalytic hydrogenation of levulinic acid and its esters to γ-valerolactone according to claim 1 or 3, characterized in that: The heating rate of the catalyst precursor during reduction under hydrogen atmosphere is 3-8 ℃ / min.

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

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

7. The process for the mild and efficient catalytic hydrogenation of levulinic acid and its esters to γ-valerolactone according to claim 1, characterized in that: The reaction is carried out at 2.0 MPa hydrogen atmosphere and 80-90 ℃ constant temperature for 6-8 hours.

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

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

10. The process for the mild and efficient catalytic hydrogenation of levulinic acid and its esters to γ-valerolactone 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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