A ternary metal oxide catalyst and its application in the catalytic synthesis of γ-valerolactone

Abstract

The present invention discloses a ternary metal oxide catalyst and its application in the catalytic synthesis of γ-valerolactone, including: adding ethyl levulinate, the catalyst and an alcohol solvent into a reaction kettle, then sealing the reaction kettle, without adding external hydrogen, carrying out a closed reaction at a stirring speed of 500 rpm at 200-270 °C for 1-5 h, and then cooling to room temperature to obtain the γ-valerolactone; the above catalyst is dried after centrifugal separation and directly used for the next reaction. The catalyst of the present invention prepares γ-valerolactone in the form of in-situ hydrogen production, with high selectivity and yield. Hydrogen does not need to be added during the whole process, reducing the cost of hydrogen transportation equipment. At the same time, the catalyst has excellent stability and can overcome the problem of deactivation during the recycling of the catalyst.

Description

Technical Field

[0001] The present invention belongs to the field of fine chemicals, and particularly relates to the preparation of a ternary metal oxide catalyst and its application in the catalytic synthesis of γ-valerolactone. Background Art

[0002] γ-valerolactone is a bio-based platform compound with broad application prospects. It has a relatively high boiling point and flash point and a low melting point, so it can be stored in large quantities. γ-valerolactone has a wide range of applications. It can be used as an excellent green solvent. Under specific conditions, an aqueous solution of γ-valerolactone can completely dissolve cellulose and can also dissolve lignin well for lignin extraction. γ-valerolactone has a unique fragrance and taste and is often used in the fields of food, cosmetics, fuel additives, synthesis of various chemical intermediates, etc., and can also be used directly as a fuel. It is considered to be one of the most promising raw materials for the production of renewable fuels and chemical products.

[0003] γ-valerolactone can be synthesized by the selective hydrogenation of biomass levulinic acid (ester). Levulinic acid (ester) is considered to be an ideal raw material for the production of γ-valerolactone. According to the difference in the hydrogen source, the reaction system for catalyzing the preparation of γ-valerolactone from levulinic acid (ester) can be divided into three categories: the system with H2 as an external hydrogen source, the system with formic acid as an in-situ hydrogen source, and the system with alcohols as an in-situ hydrogen source. At present, the hydrogenation of levulinic acid (ester) with H2 as an external hydrogen source to prepare γ-valerolactone has been widely studied. Catalysts prepared from noble metals such as Ru, Pt, and Ir can catalyze levulinic acid (ester) to obtain a high yield of γ-valerolactone under mild conditions. However, these noble metal catalysts have disadvantages such as high price and easy loss during the recovery process. Non-noble metal catalysts such as Cu, Mo2C, Ni, and Co can also be used for the hydrogenation of levulinic acid (ester), but the preparation process often requires the use of hydrogen for reduction. In summary, the traditional hydrogenation system with H2 as an external hydrogen source for the preparation of γ-valerolactone has many disadvantages such as easy loss during recovery and low economy. In the catalytic system with formic acid as an in-situ hydrogen source, the catalyst is a bifunctional catalyst that can simultaneously catalyze the decomposition of formic acid to produce hydrogen and the hydrogenation reduction of levulinic acid (ester). Supported bifunctional catalysts such as Ru / C, Ru-P / SiO2, Ni / Cu-SiO2, and Ag-Ni-ZrO2 can effectively catalyze the decomposition of formic acid to produce hydrogen and simultaneously reduce levulinic acid (ester) to synthesize γ-valerolactone. However, these catalysts generally require the presence of excess formic acid to obtain a high yield of γ-valerolactone. In this catalytic system, the acid resistance requirement for the catalyst is very high, and only a few noble metal or non-noble metal-based heterogeneous or homogeneous catalysts can meet these conditions.

[0004] To overcome the deficiencies of the above two catalytic systems, using alcohols as an in-situ hydrogen source and solvent, the preparation of γ-valerolactone by transfer hydrogenation is very promising. It is reported that catalysts such as Zr-Beta, Ru(OH)x / TiO2, and Zr-HBA can catalyze the synthesis of γ-valerolactone from levulinic acid (ester) in a system with alcohols as hydrogen donors, but the stability and activity of the catalysts still need to be further improved. Therefore, there is an urgent need to find non-noble metal catalysts that can overcome the above disadvantages for the selective hydrogenation of levulinic acid (ester) to prepare γ-valerolactone. Summary of the Invention

[0005] The object of the present invention is to overcome the defects of the prior art, and to provide a preparation method of a ternary metal oxide catalyst and its application in the catalytic synthesis of γ-valerolactone.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A method for synthesizing γ-valerolactone, comprising: after mixing ethyl levulinate, a catalyst, and an alcohol solvent, adding ethyl levulinate, the catalyst, and the alcohol solvent into a reaction kettle, then sealing the reaction kettle, without adding external hydrogen, carrying out a closed reaction at 200 - 270 °C for 1 - 5 h at a stirring speed of 500 rpm, and then cooling to room temperature to obtain the γ-valerolactone; after the above catalyst is centrifuged and separated, it is washed with ethanol and dried in a vacuum drying oven at 80 °C for 1 h for the next reaction.

[0008] The preparation method of the catalyst includes: dissolving a cationic active metal precursor in 150 mL of deionized water according to a certain molar ratio, then adding an excessive amount of urea to the mixed solution and hydrolyzing it at 90 °C for 4 h. During the hydrolysis process, the mixed solution is continuously stirred at a stirring rate of 300 - 400 rpm. After the hydrolysis is completed, the obtained slurry is aged at 90 °C for 2 h, cooled to room temperature, and then the slurry is filtered. The obtained filter residue is dried overnight at 110 °C, and then the dried product is ground in a mortar, passed through a 100-mesh sieve, and calcined in a muffle furnace at 300 - 400 °C for 4 h to obtain the catalyst. The cationic active metal precursor is composed of soluble salts containing Zr, Mg, and Cu.

[0009] In a preferred embodiment of the present invention, the mass ratio of the raw material ethyl levulinate to the alcohol solvent is 1:19.

[0010] In a preferred embodiment of the present invention, the mass ratio of the catalyst to the raw material ethyl levulinate is 0.2 - 0.6:1.

[0011] In a preferred embodiment of the present invention, the molar ratio of Mg to Zr in the active metal precursor is 1.15:1 - 2, and the calcination temperature is 300 °C.

[0012] In a preferred embodiment of the present invention, the molar ratio of Cu, Mg, and Zr in the active metal precursor is 1:1.15:1 - 3, and the calcination temperature is 400 °C.

[0013] In a preferred embodiment of the present invention, the precursors of Zr, Mg, and Cu are Cu(NO3)2·3H2O, Mg(NO3)2·6H2O, and Zr(NO3)4·5H2O, respectively.

[0014] In a preferred embodiment of the present invention, the alcohol solvent is isopropanol.

[0015] The beneficial effects of the present invention are as follows:

[0016] 1. The yield of γ-valerolactone of the present invention is relatively high. Under the reaction conditions of 240 °C, 3 h, and 500 rpm, the yield of γ-valerolactone reaches 88%.

[0017] 2. The metal precursor used in the catalyst prepared by the present invention is a non-noble metal, with low preparation cost and convenient recovery.

[0018] 3. The non-noble metal catalyst prepared by the present invention has a simple preparation method. During the preparation process, hydrogen reduction is not required, the preparation cost is relatively low, and excellent activity can be maintained during the recycling process. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 For the XRD pattern of the catalyst Cu1Mg 1.15 Zr2O x ; In the XRD pattern, for the Cu1Mg 1.15 Zr2O x catalyst sample prepared in this experiment, there are characteristic diffraction peaks similar to those of ZrO2 at 2θ = 30.5°, 35.5°, 51.2°, and 60.7° respectively. In the XRD pattern of the Cu1Mg 1.15 Zr2O x catalyst, strong diffraction peaks of CuO and MgO are not observed, which may be due to reasons such as the low loading amount, high dispersion of CuO and MgO, or the amorphous phase caused by the relatively low calcination temperature (400 °C).

[0020] Figures 2(a), 2(b), 2(c), 2(d), and 2(e) are the XPS patterns of the Cu1Mg 1.15 Zr2O x catalyst; X-ray photoelectron spectroscopy analysis is performed on the Cu1Mg 1.15 Zr2O x catalyst, including Cu 2p, Mg 1s, Zr 3d, O 1s, and C1s (Figure 2). It can be seen that for Cu1Mg1.15 Zr2O x The catalyst contains elements Cu, Mg, Zr, and O. Figure 2(b) shows Cu1Mg 1.15 Zr2O x The high-resolution spectrum of Cu 2p of the catalyst, as shown in Figure 2(b), and the BE values of 934.1 eV and 953.7 eV belong to Cu1Mg 1.15 Zr2O x Cu 2p in the catalyst 3 / 2 and Cu 2p 1 / 2 Each Cu 2p emission line can be fitted with one Gaussian line, indicating the possible existence of Cu 2+ As can be seen from Figure 2(c) and Figure 2(d), Cu1Mg 1.15 Zr2O x The possible existence of Mg and Zr in the Cu1Mg 2+ Zr 4+ .

[0021] Figure 3 is the H2-TPR spectrum of the catalyst; from Figure 3 the H2-TPR spectrum, it can be seen that there is an H2 adsorption peak in the Cu1Mg 1.15 Zr2O x catalyst, which may be attributed to the reduction of Cu 2+ , and it also shows that the Cu in the Cu1Mg 1.15 Zr2O x catalyst 2+ is the existing form of Cu element, which is consistent with the XPS results. The highest H2 adsorption peak (226.5 °C) of the Cu1Mg 1.15 Zr2O x catalyst is higher than the highest H2 adsorption peak (149.2 °C) of the Cu1Zr3O x catalyst and the highest H2 adsorption peak (158.9 °C) of the Cu1Mg 1.15 catalyst, indicating that the interaction force between the three metals in the Cu1Mg 1.15 Zr2O x catalyst is stronger, and Cu 2+ is not easily reduced. This may be the possible reason why the Cu1Mg 1.15 Zr2O x catalyst has higher activity than the bimetallic catalyst. Specific implementation manners

[0022] The technical solutions of the present invention are further described and illustrated below through specific implementation manners.

[0023] The preparation method of the catalyst in the following examples includes:

[0024] Dissolve Cu(NO3)2·3H2O, Mg(NO3)2·6H2O, and Zr(NO3)4·5H2O in 150 mL of deionized water according to a certain molar ratio. Then, add an excessive amount of urea to the mixed solution and hydrolyze it at 90 °C for 4 h. During the hydrolysis process, continuously stir the mixed solution at a stirring rate of 300 - 400 rpm. After the hydrolysis is completed, age the obtained slurry at 90 °C for 2 h. Cool it to room temperature and then filter the slurry. Dry the obtained filter residue overnight at 110 °C. Then, grind the dried product in a mortar, pass it through a 100-mesh sieve, and calcine it in a muffle furnace at 300 - 400 °C for 4 h to obtain the catalyst.

[0025] The catalyst is prepared by the urea hydrolysis homogeneous precipitation method. Utilizing the characteristic of urea hydrolysis by heating, urea undergoes hydrolysis at 90 °C, and the hydrolysis reaction is: CO(NH2)2 + 3H2O → 2NH4 + + 2OH - + CO2. Through chemical reactions, the precipitate is slowly formed in the solution. Coupled with slow stirring, the formed catalyst particles are uniform and have good dispersibility. Using ZrO2 as the carrier has good thermal stability, and Zr can inhibit the crystal growth of CuO x so that the catalyst is not easily deactivated. And appropriate MgO can significantly improve the dispersion of Cu. In the present invention, by adjusting the molar ratio of each metal component and optimizing the optimal metal molar ratio, the prepared catalyst has high activity and high stability at the same time. The gas generated during the reaction is detected by GC-TCD, and an obvious H2 peak is detected, indicating that isopropanol dehydrogenates to produce H2 on the highly dispersed metal Cu component. The in-situ generated H2 enables ethyl levulinate to undergo hydrogenation and dehydration to γ-valerolactone.

[0026] Examples 1 - 5

[0027] Catalyst preparation: Dissolve 1 mol of Cu(NO3)2·3H2O, 1.15 mol of Mg(NO3)2·6H2O, and 2 mol of Zr(NO3)4·5H2O in 150 mL of deionized water. Then, add an excessive amount (42.5 g) of urea to the mixed solution and hydrolyze it at 90 °C for 4 h. During the hydrolysis process, continuously stir the mixed solution at a stirring rate of 300 rpm. After the hydrolysis is completed, age the obtained slurry at 90 °C for 2 h. Cool it to room temperature and then filter the slurry. Dry the obtained filter residue overnight at 110 °C. Then, grind the dried product in a mortar, pass it through a 100-mesh sieve, and calcine it in a muffle furnace at 400 °C for 4 h to obtain the catalyst, denoted as Cu1Mg 1.15 Zr2O x .

[0028] Add 1 g of ethyl levulinate and 19 g of isopropanol to a 100 mL high-pressure reactor, and add 0.5 g of catalyst. The molar ratio of Cu, Mg, and Zr in the active metal precursor is 1:1.15:2. After the catalyst precursor is calcined in air at 400 °C, record Cu1Mg 1.15 Zr2O x , displace the air in the reactor with nitrogen and then discharge the nitrogen. Seal the reactor, stir at a speed of 500 rpm, heat to 240 °C and maintain for 1, 2, 3, 4, and 5 h respectively. After the reaction is completed, naturally cool to room temperature. Centrifuge the reaction solution, take the supernatant, and use GC-MS and GC to perform qualitative and quantitative analyses on the supernatant respectively. The test results are listed in Examples 1-5 of Table 1.

[0029] From the reactions of Examples 1-5, it can be seen that at 3 h, the yield of γ-valerolactone reaches 88%, and the yield of γ-valerolactone is relatively high. After that, when the reaction time is continued to be extended, the yield of γ-valerolactone decreases.

[0030] Examples 6-9

[0031] Add 1 g of ethyl levulinate and 19 g of isopropanol to a 100 mL high-pressure reactor, add 0.5 g of the catalyst prepared in Examples 1-5. Displace the air in the reactor with nitrogen and then discharge the nitrogen. Seal the reactor, stir at a speed of 500 rpm, heat to 200, 220, 260, and 270 °C respectively and maintain for 1 h. After the reaction is completed, naturally cool to room temperature. Centrifuge the reaction solution, take the supernatant, use GC-MS to perform qualitative analysis on the supernatant, prepare standard solutions such as ethyl levulinate, isopropanol, and γ-valerolactone, and use GC for quantitative detection. The test results are listed in Examples 6-9 of Table 1.

[0032] From the reactions of Examples 6-9, it can be seen that when the reaction temperature rises from 200 °C to 220 °C, the yield of γ-valerolactone increases; at high reaction temperatures (above 260 °C), the yield of γ-valerolactone decreases.

[0033] Example 10

[0034] Catalyst preparation: Adjust the molar ratio of Cu, Mg, and Zr in the active metal precursor to 1:1.15:1, and the rest of the operations are the same as in Examples 1-5 to prepare the catalyst Cu1Mg 1.15 Zr1O x .

[0035] Add 1 g of ethyl levulinate and 19 g of isopropanol to a 100 mL high-pressure reactor, and add 0.5 g of the catalyst Cu1Mg 1.15 Zr1O x, after replacing the air in the autoclave with nitrogen, the nitrogen was discharged, the reaction autoclave was sealed, stirred at a speed of 500 rpm, heated to 240 °C and maintained for 3 h. After the reaction was completed, it was naturally cooled to room temperature. The reaction solution was centrifuged using a centrifuge, the supernatant was taken, and the supernatant was qualitatively and quantitatively analyzed using GC-MS and GC respectively. The test results are listed in Example 10 of Table 1.

[0036] Example 11

[0037] Catalyst preparation: Adjust the molar ratio of Cu, Mg, and Zr in the active metal precursor to 1:1.15:1.15, and the remaining operations are the same as in Examples 1-5 to prepare the catalyst Cu1Mg 1.15 Zr 1.15 O x .

[0038] Add 1 g of ethyl levulinate and 19 g of isopropanol to a 100 mL high-pressure autoclave, and add 0.5 g of the catalyst Cu1Mg 1.15 Zr 1.15 O x , after replacing the air in the autoclave with nitrogen, the nitrogen was discharged, the reaction autoclave was sealed, stirred at a speed of 500 rpm, heated to 240 °C and maintained for 3 h. After the reaction was completed, it was naturally cooled to room temperature. The reaction solution was centrifuged using a centrifuge, the supernatant was taken, and the supernatant was qualitatively and quantitatively analyzed using GC-MS and GC respectively. The test results are listed in Example 11 of Table 1.

[0039] Example 12

[0040] Catalyst preparation: Adjust the molar ratio of Cu, Mg, and Zr in the active metal precursor to 1:1.15:1.5, and the remaining operations are the same as in Examples 1-5 to prepare the catalyst Cu1Mg 1.15 Zr 1.5 O x .

[0041] Add 1 g of ethyl levulinate and 19 g of isopropanol to a 100 mL high-pressure autoclave, and add 0.5 g of the catalyst Cu1Mg 1.15 Zr 1.5 O x , after replacing the air in the autoclave with nitrogen, the nitrogen was discharged, the reaction autoclave was sealed, stirred at a speed of 500 rpm, heated to 240 °C and maintained for 3 h. After the reaction was completed, it was naturally cooled to room temperature. The reaction solution was centrifuged using a centrifuge, the supernatant was taken, and the supernatant was qualitatively and quantitatively analyzed using GC-MS and GC respectively. The test results are listed in Example 12 of Table 1.

[0042] Example 13

[0043] Catalyst preparation: Adjust the molar ratio of Cu, Mg, and Zr in the active metal precursor to 1:1.15:3, and the remaining operations are the same as in Examples 1-5 to prepare the catalyst Cu1Mg 1.15 Zr3O x 。

[0044] Add 1 g of ethyl levulinate and 19 g of isopropanol to a 100 mL high-pressure reactor, and add 0.5 g of the catalyst Cu1Mg 1.15 Zr3O x , displace the air in the reactor with nitrogen and then discharge the nitrogen, seal the reactor, stir at a speed of 500 rpm, heat to 240 °C and maintain for 3 h. After the reaction is completed, cool naturally to room temperature, centrifuge the reaction solution, take the supernatant, and use GC-MS and GC to perform qualitative and quantitative analyses on the supernatant respectively. The test results are listed in Example 13 of Table 1.

[0045] Example 14

[0046] Add 1 g of ethyl levulinate and 19 g of isopropanol to a 100 mL high-pressure reactor, add 0.5 g of CuO catalyst, displace the air in the reactor with nitrogen and then discharge the nitrogen, seal the reactor, stir at a speed of 500 rpm, heat to 240 °C and maintain for 3 h. After the reaction is completed, cool naturally to room temperature, centrifuge the reaction solution, take the supernatant, and use GC-MS and GC to perform qualitative and quantitative analyses on the supernatant respectively. The test results are listed in Example 14 of Table 1.

[0047] Example 15

[0048] Add 1 g of ethyl levulinate and 19 g of isopropanol to a 100 mL high-pressure reactor, add 0.5 g of MgO catalyst, displace the air in the reactor with nitrogen and then discharge the nitrogen, seal the reactor, stir at a speed of 500 rpm, heat to 240 °C and maintain for 3 h. After the reaction is completed, cool naturally to room temperature, centrifuge the reaction solution, take the supernatant, and use GC-MS and GC to perform qualitative and quantitative analyses on the supernatant respectively. The test results are listed in Example 15 of Table 1.

[0049] Example 16

[0050] Add 1 g of ethyl levulinate and 19 g of isopropanol to a 100 mL high-pressure reactor, add 0.5 g of ZrO2 catalyst, displace the air in the reactor with nitrogen and then discharge the nitrogen, seal the reactor, stir at a speed of 500 rpm, heat to 240 °C and maintain for 3 h. After the reaction is completed, cool naturally to room temperature, centrifuge the reaction solution, take the supernatant, and use GC-MS and GC to perform qualitative and quantitative analyses on the supernatant respectively. The test results are listed in Example 16 of Table 1.

[0051] Example 17

[0052] Catalyst preparation: Adjust the active metal precursors to Mg(NO3)2·6H2O and Zr(NO3)4·5H2O, and the molar ratio of Mg to Zr is 1.15:1. The remaining operations are the same as in Examples 1-5 to prepare the catalyst Mg 1.15 Zr1O x 。

[0053] Add 1 g of ethyl levulinate and 19 g of isopropanol to a 100 mL high-pressure reactor, and add 0.5 g of the catalyst Mg 1.15 Zr1O x , displace the air in the reactor with nitrogen and then discharge the nitrogen. Seal the reactor, stir at a speed of 500 rpm, heat to 240 °C and maintain for 3 h. After the reaction is completed, cool it naturally to room temperature. Centrifuge the reaction solution, take the supernatant, and use GC-MS and GC to perform qualitative and quantitative analyses on the supernatant respectively. The test results are listed in Example 17 of Table 1.

[0054] Example 18

[0055] Catalyst preparation: Adjust the active metal precursors to Mg(NO3)2·6H2O and Zr(NO3)4·5H2O, and the molar ratio of Mg to Zr is 1:1.15. The remaining operations are the same as in Examples 1-5 to prepare the catalyst Mg1Zr 1.15 O x 。

[0056] Add 1 g of ethyl levulinate and 19 g of isopropanol to a 100 mL high-pressure reactor, and add 0.5 g of the catalyst Mg1Zr 1.15 O x , displace the air in the reactor with nitrogen and then discharge the nitrogen. Seal the reactor, stir at a speed of 500 rpm, heat to 240 °C and maintain for 3 h. After the reaction is completed, cool it naturally to room temperature. Centrifuge the reaction solution, take the supernatant, and use GC-MS and GC to perform qualitative and quantitative analyses on the supernatant respectively. The test results are listed in Example 18 of Table 1.

[0057] Example 19

[0058] Catalyst preparation: Adjust the active metal precursors to Mg(NO3)2·6H2O and Zr(NO3)4·5H2O, and the molar ratio of Mg to Zr is 1:2. The remaining operations are the same as in Examples 1-5 to prepare the catalyst Mg1Zr2O x 。

[0059] Add 1 g of ethyl levulinate and 19 g of isopropanol to a 100 mL high-pressure reactor, and add 0.5 g of the catalyst Mg1Zr2Ox , after replacing the air in the autoclave with nitrogen, the nitrogen was discharged, the reaction autoclave was sealed, stirred at a speed of 500 rpm, heated to 240 °C and maintained for 3 h. After the reaction was completed, it was naturally cooled to room temperature. The reaction solution was centrifuged using a centrifuge, the supernatant was taken, and the supernatant was qualitatively and quantitatively analyzed using GC-MS and GC respectively. The test results are listed in Example 19 of Table 1.

[0060] Example 20

[0061] Catalyst preparation: Adjust the active metal precursors to Cu(NO3)2·3H2O and Zr(NO3)4·5H2O, and the molar ratio of Cu to Zr is 1:1. The remaining operations are the same as in Examples 1-5 to prepare the catalyst Cu1Zr1O x .

[0062] Add 1 g of ethyl levulinate and 19 g of isopropanol to a 100 mL high-pressure reaction autoclave, and add 0.5 g of the catalyst Cu1Zr1O x , after replacing the air in the autoclave with nitrogen, the nitrogen was discharged, the reaction autoclave was sealed, stirred at a speed of 500 rpm, heated to 240 °C and maintained for 3 h. After the reaction was completed, it was naturally cooled to room temperature. The reaction solution was centrifuged using a centrifuge, the supernatant was taken, and the supernatant was qualitatively and quantitatively analyzed using GC-MS and GC respectively. The test results are listed in Example 20 of Table 1.

[0063] Example 21

[0064] Catalyst preparation: Adjust the active metal precursors to Cu(NO3)2·3H2O and Zr(NO3)4·5H2O, and the molar ratio of Cu to Zr is 1:2. The remaining operations are the same as in Examples 1-5 to prepare the catalyst Cu1Zr2O x .

[0065] Add 1 g of ethyl levulinate and 19 g of isopropanol to a 100 mL high-pressure reaction autoclave, and add 0.5 g of the catalyst Cu1Zr2O x , after replacing the air in the autoclave with nitrogen, the nitrogen was discharged, the reaction autoclave was sealed, stirred at a speed of 500 rpm, heated to 240 °C and maintained for 3 h. After the reaction was completed, it was naturally cooled to room temperature. The reaction solution was centrifuged using a centrifuge, the supernatant was taken, and the supernatant was qualitatively and quantitatively analyzed using GC-MS and GC respectively. The test results are listed in Example 21 of Table 1.

[0066] Example 22

[0067] Catalyst preparation: Adjust the active metal precursors to Cu(NO3)2·3H2O and Zr(NO3)4·5H2O, with the molar ratio of Cu to Zr being 1:3. The remaining operations are the same as in Examples 1-5, and the catalyst Cu1Zr3O is prepared. x .

[0068] Add 1 g of ethyl levulinate and 19 g of isopropanol to a 100 mL high-pressure reactor, and add 0.5 g of the catalyst Cu1Zr3O. x , displace the air in the reactor with nitrogen and then discharge the nitrogen. Seal the reactor, stir at a speed of 500 rpm, heat to 240 °C and maintain for 3 h. After the reaction is completed, cool naturally to room temperature. Centrifuge the reaction solution, take the supernatant, and perform qualitative and quantitative analyses on the supernatant using GC-MS and GC respectively. The test results are listed in Example 22 of Table 1.

[0069] Example 23

[0070] Catalyst preparation: Adjust the active metal precursors to Cu(NO3)2·3H2O and Mg(NO3)2·6H2O, with the molar ratio of Cu to Mg being 1:2. The remaining operations are the same as in Examples 1-5, and the catalyst Cu1Mg2O is prepared. x .

[0071] Add 1 g of ethyl levulinate and 19 g of isopropanol to a 100 mL high-pressure reactor, and add 0.5 g of the catalyst Cu1Mg2O. x , displace the air in the reactor with nitrogen and then discharge the nitrogen. Seal the reactor, stir at a speed of 500 rpm, heat to 240 °C and maintain for 3 h. After the reaction is completed, cool naturally to room temperature. Centrifuge the reaction solution, take the supernatant, and perform qualitative and quantitative analyses on the supernatant using GC-MS and GC respectively. The test results are listed in Example 23 of Table 1.

[0072] Example 24

[0073] Catalyst preparation: Adjust the active metal precursors to Cu(NO3)2·3H2O and Mg(NO3)2·6H2O, with the molar ratio of Cu to Mg being 1:3. The remaining operations are the same as in Examples 1-5, and the catalyst Cu1Mg3O is prepared. x .

[0074] Add 1 g of ethyl levulinate and 19 g of isopropanol to a 100 mL high-pressure reactor, and add 0.5 g of the catalyst Cu1Mg3O. x, after replacing the air in the autoclave with nitrogen, the nitrogen is discharged, the reaction autoclave is sealed, stirred at a speed of 500 rpm, heated to 240 °C and maintained for 3 h. After the reaction is completed, it is naturally cooled to room temperature. The reaction solution is centrifuged by a centrifuge, the supernatant is taken, and the supernatant is qualitatively and quantitatively analyzed by GC-MS and GC respectively. The test results are listed in Example 24 of Table 1.

[0075] Example 25

[0076] Catalyst preparation: Adjust the active metal precursors to Cu(NO3)2·3H2O and Mg(NO3)2·6H2O, and the molar ratio of Cu to Mg is 1:1.15. The remaining operations are the same as in Examples 1-5 to prepare the catalyst Cu1Mg. 1.15 O x .

[0077] Add 1 g of ethyl levulinate and 19 g of isopropanol to a 100 mL high-pressure autoclave, and add 0.5 g of the catalyst Cu1Mg. 1.15 O x , after replacing the air in the autoclave with nitrogen, the nitrogen is discharged, the reaction autoclave is sealed, stirred at a speed of 500 rpm, heated to 240 °C and maintained for 3 h. After the reaction is completed, it is naturally cooled to room temperature. The reaction solution is centrifuged by a centrifuge, the supernatant is taken, and the supernatant is qualitatively and quantitatively analyzed by GC-MS and GC respectively. The test results are listed in Example 25 of Table 1.

[0078] Example 26

[0079] Add 1 g of ethyl levulinate and 19 g of methanol to a 100 mL high-pressure autoclave, and add 0.4 g of the catalyst Cu1Mg prepared in Examples 1-5. 1.15 Zr2O x , after replacing the air in the autoclave with nitrogen, the nitrogen is discharged, the reaction autoclave is sealed, stirred at a speed of 500 rpm, heated to 240 °C and maintained for 3 h. After the reaction is completed, it is naturally cooled to room temperature. The reaction solution is centrifuged by a centrifuge, the supernatant is taken, and the supernatant is qualitatively and quantitatively analyzed by GC-MS and GC respectively. The test results are listed in Example 26 of Table 1.

[0080] Example 27

[0081] Add 1 g of ethyl levulinate and 19 g of ethanol to a 100 mL high-pressure autoclave, and add 0.4 g of the catalyst Cu1Mg prepared in Examples 1-5. 1.15 Zr2O x, after replacing the air in the autoclave with nitrogen, the nitrogen was discharged, the reaction autoclave was sealed, stirred at a speed of 500 rpm, heated to 240 °C and maintained for 3 h. After the reaction was completed, it was naturally cooled to room temperature. The reaction solution was centrifuged using a centrifuge, the supernatant was taken, and the supernatant was qualitatively and quantitatively analyzed using GC-MS and GC respectively. The test results are listed in Example 27 in Table 1.

[0082] Example 28

[0083] 1 g of ethyl levulinate and 19 g of isobutanol were added to a 100 mL high-pressure autoclave, and 0.4 g of the catalyst Cu1Mg prepared in Examples 1-5 was added 1.15 Zr2O x , after replacing the air in the autoclave with nitrogen, the nitrogen was discharged, the reaction autoclave was sealed, stirred at a speed of 500 rpm, heated to 240 °C and maintained for 3 h. After the reaction was completed, it was naturally cooled to room temperature. The reaction solution was centrifuged using a centrifuge, the supernatant was taken, and the supernatant was qualitatively and quantitatively analyzed using GC-MS and GC respectively. The test results are listed in Example 28 in Table 1.

[0084] Example 29

[0085] 1 g of ethyl levulinate and 19 g of sec-butanol were added to a 100 mL high-pressure autoclave, and 0.4 g of the catalyst Cu1Mg prepared in Examples 1-5 was added 1.15 Zr2O x , after replacing the air in the autoclave with nitrogen, the nitrogen was discharged, the reaction autoclave was sealed, stirred at a speed of 500 rpm, heated to 240 °C and maintained for 3 h. After the reaction was completed, it was naturally cooled to room temperature. The reaction solution was centrifuged using a centrifuge, the supernatant was taken, and the supernatant was qualitatively and quantitatively analyzed using GC-MS and GC respectively. The test results are listed in Examples 1-29 in Table 1.

[0086] Table 1 Test Results of Examples 1-29

[0087]

[0088]

[0089] It can be seen from Examples 1-29 that the optimized metal molar ratio of the ternary metal oxide catalyst composed of Cu, Mg, and Zr is 1:1.15:2, and when the alcohol solvent is isopropanol, the catalytic activity of the ternary metal oxide is the highest, and a γ-valerolactone yield of 88% can be obtained.

[0090] Examples 30-33

[0091] 1 g of ethyl levulinate and 19 g of isopropanol were added to a 100 mL high-pressure autoclave, and different amounts of the catalyst Cu1Mg prepared in Examples 1-51.15 Zr2O x , after replacing the air in the autoclave with nitrogen, the nitrogen was discharged, the reaction autoclave was sealed, stirred at a speed of 500 rpm, heated to 240 °C and maintained for 3 h. After the reaction was completed, it was naturally cooled to room temperature. The reaction solution was centrifuged by a centrifuge, and the supernatant was taken. The supernatant was qualitatively and quantitatively analyzed by GC-MS and GC respectively. The test results are listed in Examples 30 - 33 in Table 2.

[0092] Table 2 Test Results of Examples 30 - 33

[0093]

[0094] It can be seen from Examples 30 - 33 the changes in the conversion rate of the reaction substrate EL and the yield of the target product GVL with the increase of the catalyst dosage from 0.2 g to 0.6 g. Under the same reaction conditions (240 °C, 3 h, 500 rpm), it can be obtained that when the catalyst dosage increases from 0.1 g to 0.5 g, the conversion rate of EL and the yield of GVL also increase. However, in the whole increasing trend, the increasing degree of the conversion rate of EL and the yield of GVL is different for every 0.1 g increase. When Cu1Mg 1.15 Zr2O x When the catalyst dosage increases from 0.3 g to 0.4 g, the conversion rate of EL increases from 88.3% to 99.7%, an increase of 11.4%, while the yield of GVL increases from 70.5% to 87.0%, with an increase amplitude of 16.5%. When the catalyst is continuously increased to 0.5 g, the conversion rate of EL continues to increase to 99.8%, only increasing by 0.1%. At the same time, the yield of GVL continues to increase by 1% to reach 88.0%. When the catalyst dosage increases to 0.6 g, the yields of EL and GVL decrease instead, being 92.1% and 76.7% respectively, indicating that the catalyst dosage is not the more the better. The catalyst dosage is 0.5 g when the GVL yield is the highest.

[0095] Examples 34 - 40

[0096] Add 1 g of ethyl levulinate and 19 g of isopropanol to a 100 mL high-pressure autoclave, and use 0.4 g of the catalyst Cu1Mg prepared in Examples 1 - 5 1.15 Zr2O x, according to the reaction conditions in Table 2, 7 cyclic stability experiments of the catalyst were carried out. After the reaction, it was naturally cooled to room temperature, and the reaction solution was centrifuged. The solid catalyst recovered by centrifugation was dried in a vacuum drying oven at 80 °C for 1 h for the next experiment. The supernatant was taken, and GC-MS was used for qualitative analysis of the supernatant. Standard solutions such as ethyl levulinate, isopropanol, and γ-valerolactone were prepared, and GC was used for quantitative detection. The detection results are listed in Examples 34-40 in Table 3. Among them, the first cycle means repeating the first experiment based on Example 32, and so on for the rest.

[0097] Table 3 Detection Results of Examples 34 - 40

[0098]

[0099] Examples 41 - 42

[0100] The Cu1Mg 1.15 Zr2O x catalyst used once and the Cu1Mg 1.15 Zr2O x catalyst used 8 times were respectively detected for carbon deposition content by an elemental analyzer. The detection results are listed in Examples 41 - 42 in Table 4.

[0101] Table 4 Content of Element C in the Used Cu1Mg 1.15 Zr2O x Catalyst

[0102]

[0103] From Examples 34 - 40, it can be seen that for the representative catalyst Cu1Mg 1.15 Zr2O x , after 7 cycles of use in the experiment, the yield of γ-valerolactone and the conversion rate of ethyl levulinate have excellent stability. It shows that the representative catalyst Cu1Mg 1.15 Zr2O x maintains excellent activity during the cyclic use process. Carbon deposition generated during the use of the catalyst in organic solvents is an important factor leading to the reduction of the catalytic activity of the catalyst. There are two forms in which carbon deposition causes the inactivation of the catalyst: carbon deposition covers the active sites of the catalyst or blocks the pores of the catalyst, resulting in the reactants being unable to enter and contact the active sites on the catalyst. From Examples 41 - 42, it can be seen that when comparing the content of Element C in the recovered catalyst after 8 uses with that in the recovered catalyst after 1 use, it shows that the content of Element C in the Cu1Mg 1.15 Zr2O x catalyst only slightly increases by 0.32% after 7 cycles of use. The analysis results show that Cu1Mg 1.15 Zr2Ox During the recycling process of the catalyst, only a small amount of carbon deposition is generated, which does not significantly affect the catalytic activity of the catalyst, indicating that Cu1Mg 1.15 Zr2O x The catalyst has excellent stability.

[0104] As described above, it is only a preferred embodiment of the present invention, so the scope of implementation of the present invention cannot be limited thereby. That is, equivalent changes and modifications made according to the scope of the present invention patent and the content of the specification should still fall within the scope covered by the present invention.

Claims

1. A method for catalytic synthesis of γ-valerolactone using a ternary metal oxide catalyst, characterized in that: Ethyl levulinate, a ternary metal oxide catalyst, and an alcohol solvent are added to a reaction kettle, and then the reaction kettle is sealed. Without adding external hydrogen, under a stirring speed of 500 rpm, a closed reaction is carried out at 220 - 270 °C for 1 - 5 h, and then it is cooled to room temperature to obtain the γ-valerolactone; The preparation method of the catalyst includes: dissolving an active metal precursor in deionized water according to a certain molar ratio, then adding excessive urea to the mixed solution and hydrolyzing it at 90 °C for 4 h. During the hydrolysis process, the mixed solution is continuously stirred, and the stirring rate is 300 - 400 rpm. After the hydrolysis is completed, the obtained slurry is aged at 90 °C for 2 h. After cooling to room temperature, the slurry is filtered. The obtained filter residue is dried overnight at 110 °C, and then the dried product is ground in a mortar. After passing through a 100-mesh sieve, it is calcined in a muffle furnace at 300 - 400 °C for 4 h to obtain the catalyst; the active metal precursor is composed of soluble salts containing Zr, Mg, and Cu; The mass ratio of the catalyst to ethyl levulinate is 0.2 - 0.6:1; The molar ratio of Cu, Mg, and Zr in the active metal precursor is 1:1.15:1 - 3; The active metal precursors of Zr, Mg, and Cu are Cu(NO3)2·3H2O, Mg(NO3)2·6H2O, and Zr(NO3)4·5H2O respectively; The alcohol solvent is isopropanol.

2. The method according to claim 1, characterized in that: The mass ratio of ethyl levulinate to the alcohol solvent is 1:19.

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