Supported metal oxide catalysts with adjustable acidity and their application in the synthesis of γ-valerolactone

Abstract

The present invention discloses a supported metal oxide catalyst with adjustable acidity and its application in catalytic synthesis of γ-valerolactone. The present invention uses TiO2 as a carrier and 10 )4·xH2O is present to load a metal oxide to prepare the supported metal oxide catalyst. The obtained catalyst can prepare γ-valerolactone by catalytic transfer hydrogenation using an organic alcohol as both a hydrogen donor and a reaction solvent, thereby having a high degree of specificity for the ketone group and not producing excessive hydrogenation products. The present invention uses a cheap and readily available supported metal oxide as a catalyst, has a simple reaction system, does not require an external hydrogen source or other solvents, and is conducive to the separation of the target product. At the same time, the reacted catalyst can be directly used in the next reaction after centrifugation and drying.

Description

Technical Field

[0001] The invention belongs to the field of fine chemicals, and particularly relates to a supported metal oxide catalyst with adjustable acidity and application thereof in catalytic synthesis of gamma-valerolactone. Background Art

[0002] Converting biomass into biofuels and high-value-added chemicals is a means of addressing the current depletion of fossil resources and the demand for energy, and it holds enormous potential. Numerous biomass-based compounds can be readily obtained from biomass, serving as platform compounds for the production of fuels and high-value-added chemicals. Among these platform compounds, levulinic acid is readily produced from cellulose and can be further converted into a number of downstream chemicals, such as γ-valerolactone, valeric acid, 1,4-pentanediol, and 2-methyltetrahydrofuran. γ-valerolactone has attracted extensive research due to its versatility as a green solvent and as a food and fuel additive. It is considered a promising biofuel, exhibiting combustion properties similar to ethanol when mixed with gasoline.

[0003] The production of γ-valerolactone from levulinic acid was first reported in 1930, and since then, numerous catalysts have been investigated for this reaction. Both homogeneous and heterogeneous catalysts can selectively hydrogenate levulinic acid to γ-valerolactone. Although homogeneous catalysts are highly active, difficulties in recovery and high costs limit their large-scale use. Heterogeneous catalysts commonly used include noble metal-supported catalysts (Ru / C, Pt / C, Pd / C), as well as transition metal nickel- and copper-based catalysts. These catalysts include Cu / Al2O3, CuO / Cr2O3, Pt / C, Ru / C, Ru / SiO2, Ru / TiO2, Ru-Sn / C, and Mo2C / CNT. Among the catalysts investigated, Ru-based catalysts are considered the most promising for converting levulinic acid to γ-valerolactone. Ru / TiO2 catalysts achieved excellent γ-valerolactone conversion under high-pressure conditions (5 MPa H2 pressure) at 70°C. Several other studies have used metal oxide scaffolds to support Ru, achieving very high valerolactone conversions. A graphene-supported ruthenium catalyst exhibits high selectivity (100%) for valerolactone, achieving a levulinic acid conversion of 99.7% after 12 h in a 4.0 MPa H₂ aqueous solution.

[0004] In summary, although noble metals show excellent activity for the hydrogenation of levulinic acid, it is generally necessary to achieve a relatively ideal γ-valerolactone yield under relatively harsh high temperature and high pressure reaction conditions. In addition, direct hydrogenation reduction of levulinic acid is often prone to produce an over-reduction product, 2-methyltetrahydrofuran. The present invention uses a cheap and readily available supported metal oxide as a catalyst, uses an organic alcohol as both a hydrogen donor and a reaction solvent, has a simple reaction system, does not require an external hydrogen source and other solvents, and is also safer and more convenient in transportation, management, and use. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and prepare a supported metal oxide catalyst for catalyzing the transfer hydrogenation of levulinic acid to synthesize γ-valerolactone.

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

[0007] A supported metal oxide catalyst with adjustable acidity is prepared by adding a carrier to H3P(Mo3O 10 )4·xH2O aqueous solution, after ultrasonication for 30 min, slowly add the metal oxide precursor aqueous solution dropwise, magnetically stir for 3 h, and then rotary evaporate to remove excess water, and the obtained solid is dried, ground, and calcined to prepare the supported metal oxide catalyst.

[0008] Furthermore, the carrier is TiO2.

[0009] Furthermore, the H3P(Mo3O 10 )The concentration of 4·xH2O aqueous solution is 6 g / L-12 g / L.

[0010] Furthermore, the amount of the metal oxide precursor used is 10%-50% of the mass of the support. The metal oxide precursor is any one of Zr(NO3)4·5H2O, LaCl3·7H2O, SnCl4, and Al(NO3)3·9H2O.

[0011] Furthermore, the drying temperature is 110° C. and the drying time is 12 h.

[0012] Furthermore, the calcination temperature is 300° C. and the calcination time is 2 h.

[0013] The above-mentioned supported metal oxide catalyst can be used to catalyze the synthesis of γ-valerolactone through transfer hydrogenation. Its specific application method is to add levulinic acid, a supported metal oxide catalyst and an organic alcohol into a high-temperature and high-pressure reactor, seal the reactor, and heat the reaction at a stirring speed of 600 rpm. After the reaction time is reached, the reaction is terminated and then cooled to room temperature to obtain γ-valerolactone; after the catalyst is centrifuged, it is dried in a vacuum drying oven at 100°C for 2 hours and used for the next reaction.

[0014] Furthermore, 0.3-0.7 g of supported metal oxide catalyst and 20 mL of organic alcohol were used per 4 mmol of levulinic acid.

[0015] Furthermore, the organic alcohol is selected from any one of methanol, ethanol, n-butanol, sec-butanol, n-propanol, and isopropanol.

[0016] Furthermore, the heating reaction temperature is 160-200° C. and the time is 1-5 h.

[0017] The hydrogenation of levulinic acid to 4-hydroxyvalerate requires a Lewis acid or acid-base catalyst, while the conversion of 4-hydroxyvalerate to valerolactone via lactone transesterification requires a Brönsted acid or base site. Therefore, the present invention designs and prepares a supported metal oxide catalyst with adjustable acidity, which uses nano-TiO2 with good thermal stability and certain acid sites as a support, and is catalyzed by H3P(Mo3O) with Brönsted acid. 10 )4·xH2O was modified and loaded with metal oxides to provide Lewis acid sites. By adjusting H3P(Mo3O 10 The acidity of the supported metal oxide catalyst can be adjusted by the concentration of the 4·xH2O aqueous solution and the loading amount of the metal oxide.

[0018] The advantages of the present invention are:

[0019] 1. The catalyst prepared by the present invention is a non-precious metal catalyst, which is cheap and easily available, which is beneficial to reducing production costs, and the preparation method is simple.

[0020] 2. The present invention uses organic alcohol as both a hydrogen donor and a reaction solvent, does not require an external hydrogen source and other solvents, and the reaction system is simple, which is conducive to the separation of the target product.

[0021] 3. The present invention selectively reduces levulinic acid to synthesize γ-valerolactone by catalytic transfer hydrogenation. The transfer hydrogenation is highly specific for the ketone group and can achieve a high conversion of levulinic acid with a conversion rate of 99.2%, and the yield of γ-valerolactone can reach 90.8%. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1These are SEM images of the 30 wt% ZrO2 / TiO2-PMo catalyst prepared in Example 1 at different magnifications.

[0023] Figure 2 This is the XRD pattern of the 30 wt% ZrO2 / TiO2-PMo catalyst prepared in Example 1. As shown, the catalyst exhibits the same diffraction peaks as the TiO2 support, indicating that the structure of the TiO2 support remains unchanged after modification with the heteropoly acid phosphomolybdic acid. Furthermore, there are no diffraction peaks associated with the metal oxide ZrO2 and the heteropoly acid phosphomolybdic acid, indicating their high dispersion on the TiO2 support.

[0024] Figure 3 NH3-TPD diagrams of 30 wt% ZrO2 / TiO2-PMo, 30 wt% ZrO2 / TiO2 and TiO2-PMo catalysts prepared in examples. DETAILED DESCRIPTION

[0025] In order to make the contents of the present invention easier to understand, the technical solutions of the present invention are further described below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0026] Examples 1-3

[0027] The specific preparation method of 30 wt% ZrO2 / TiO2-PMo catalyst is as follows: 1.35 g of nano-TiO2 is added to 50 mL of 6 g / L H3P(Mo3O 10 )4·xH2O aqueous solution, after ultrasonication for 30 minutes, 1.42 g of Zr(NO3)4·5H2O was dissolved in pure water and slowly added dropwise to the TiO2-PMo mixed aqueous solution. After magnetic stirring for 3 hours, excess water was removed by a rotary evaporator, and the resulting product was dried in a vacuum drying oven at 110°C for about 12 hours. The dried product was ground in a mortar, sieved, and then calcined at 300°C for 2 hours to obtain the catalyst, wherein the mass of the metal oxide ZrO2 was 30% of the carrier TiO2.

[0028] A 100 mL high-temperature, high-pressure reactor was charged with 4 mmol of levulinic acid, 0.5 g of the above catalyst, and 20 mL of isopropanol. The reactor was sealed, and the air in the reactor was replaced with nitrogen and then vented. The reaction was then heated to 160°C, 180°C, and 200°C, stirring at 600 rpm, for 3 h each. After the reaction, the mixture was cooled to room temperature and centrifuged. The supernatant was collected and quantitatively analyzed by gas chromatography. The results are listed in Table 1.

[0029] Examples 4-7

[0030] In a 100 mL high-temperature and high-pressure reactor, 4 mmol of levulinic acid, 0.5 g of a 30 wt% ZrO2 / TiO2-PMo catalyst, and 20 mL of isopropanol were added. The reactor was sealed, and the air in the reactor was replaced with nitrogen and then exhausted. The reactor was heated to 180°C with a stirring speed of 600 rpm and maintained for 1, 2, 4, and 5 h, respectively. After the reaction was completed, the reactor was cooled to room temperature and the reaction solution was centrifuged. The supernatant was collected and quantitatively analyzed by gas chromatography. The test results are listed in Table 1.

[0031] Examples 8-11

[0032] In a 100 mL high-temperature and high-pressure reactor, 4 mmol of levulinic acid was added, followed by 0.3 g, 0.4 g, 0.6 g, and 0.7 g of 30 wt% ZrO2 / TiO2-PMo catalyst and 20 mL of isopropanol. The reactor was sealed, and the air in the reactor was replaced with nitrogen and then discharged. The reactor was heated to 180°C at a stirring speed of 600 rpm and maintained for 3 h. After the reaction was completed, the reactor was cooled to room temperature and the reaction solution was centrifuged. The supernatant was collected and quantitatively analyzed by gas chromatography. The test results are listed in Table 1.

[0033] Examples 12-16

[0034] In a 100 mL high-temperature and high-pressure reactor, 4 mmol of levulinic acid and 0.5 g of a 30 wt% ZrO2 / TiO2-PMo catalyst were added, followed by 20 mL of methanol, ethanol, n-butanol, sec-butanol, and n-propanol, respectively. The reactor was sealed, and the air in the reactor was replaced with nitrogen and then exhausted. The reactor was heated to 180°C at a stirring speed of 600 rpm and maintained for 3 h. After the reaction was completed, the reactor was cooled to room temperature and the reaction solution was centrifuged. The supernatant was collected and quantitatively analyzed by gas chromatography. The test results are listed in Table 1.

[0035] Table 1 Test results of Examples 1-16

[0036]

[0037] From the reactions of Examples 1-3 in Table 1, it can be seen that the yield of γ-valerolactone increases as the reaction temperature rises from 160°C to 180°C; however, as the reaction temperature continues to rise, the yield of γ-valerolactone decreases. At 180°C, the yield of γ-valerolactone reaches its maximum, reaching 90.8%.

[0038] From the reactions of Examples 2 and 4-7, it can be seen that the yield of γ-valerolactone increases when the reaction time is from 1 to 2 h, and 3 h is the optimal reaction time. Thereafter, the yield of γ-valerolactone decreases as the reaction time is further extended.

[0039] From the reactions of Examples 2 and 8-11, it can be seen that the optimal addition amount of the catalyst is 0.5 g.

[0040] From the reactions of Example 2 and Examples 12-16, it can be seen that isopropyl alcohol is the best hydrogen donor among several organic alcohols.

[0041] Example 17

[0042] The specific preparation method of the 10 wt% ZrO2 / TiO2-PMo catalyst is as follows: the addition amount of the metal oxide precursor Zr(NO3)4·5H2O is adjusted to 0.48 g, and the remaining operations are the same as those in Example 1-3 to prepare a catalyst 10 wt% ZrO2 / TiO2-PMo in which the mass of the metal oxide ZrO2 is 10% of that of the carrier TiO2.

[0043] In a 100 mL high-temperature and high-pressure reactor, 4 mmol of levulinic acid, 0.5 g of 10 wt% ZrO2 / TiO2-PMo catalyst, and 20 mL of isopropanol were added. The reactor was sealed, and the air in the reactor was replaced with nitrogen and then discharged. The reactor was heated to 180°C and maintained at a stirring speed of 600 rpm for 3 h. After the reaction was completed, it was cooled to room temperature and the reaction solution was centrifuged. The supernatant was collected and quantitatively analyzed by gas chromatography. The test results are listed in Table 2.

[0044] Example 18

[0045] The specific preparation method of the 20 wt% ZrO2 / TiO2-PMo catalyst is as follows: the addition amount of the metal oxide precursor Zr(NO3)4·5H2O is adjusted to 0.95 g, and the remaining operations are the same as those in Example 1-3 to prepare a catalyst 20 wt% ZrO2 / TiO2-PMo in which the mass of the metal oxide ZrO2 is 20% of that of the carrier TiO2.

[0046] In a 100 mL high-temperature and high-pressure reactor, 4 mmol of levulinic acid, 0.5 g of 20 wt% ZrO2 / TiO2-PMo catalyst, and 20 mL of isopropanol were added. The reactor was sealed, and the air in the reactor was replaced with nitrogen and then discharged. The reactor was heated to 180°C and maintained at a stirring speed of 600 rpm for 3 h. After the reaction was completed, it was cooled to room temperature and the reaction solution was centrifuged. The supernatant was collected and quantitatively analyzed by gas chromatography. The test results are listed in Table 2.

[0047] Example 19

[0048] The specific preparation method of the 40 wt% ZrO2 / TiO2-PMo catalyst is as follows: the addition amount of the metal oxide precursor Zr(NO3)4·5H2O is adjusted to 1.89 g, and the remaining operations are the same as those in Example 1-3 to prepare a catalyst 40 wt% ZrO2 / TiO2-PMo in which the mass of the metal oxide ZrO2 is 40% of that of the carrier TiO2.

[0049] In a 100 mL high-temperature and high-pressure reactor, 4 mmol of levulinic acid, 0.5 g of 40 wt% ZrO2 / TiO2-PMo catalyst, and 20 mL of isopropanol were added. The reactor was sealed, and the air in the reactor was replaced with nitrogen and then discharged. The reactor was heated to 180°C and maintained at a stirring speed of 600 rpm for 3 h. After the reaction was completed, the reactor was cooled to room temperature and the reaction solution was centrifuged. The supernatant was collected and quantitatively analyzed by gas chromatography. The test results are listed in Table 2.

[0050] Example 20

[0051] The specific preparation method of the 50 wt% ZrO2 / TiO2-PMo catalyst is as follows: the addition amount of the metal oxide precursor Zr(NO3)4·5H2O is adjusted to 2.36 g, and the remaining operations are the same as those in Example 1-3 to prepare a catalyst 50 wt% ZrO2 / TiO2-PMo in which the mass of the metal oxide ZrO2 is 50% of that of the carrier TiO2.

[0052] In a 100 mL high-temperature and high-pressure reactor, 4 mmol of levulinic acid, 0.5 g of 50 wt% ZrO2 / TiO2-PMo catalyst, and 20 mL of isopropanol were added. The reactor was sealed, and the air in the reactor was replaced with nitrogen and then discharged. The reactor was heated to 180°C and maintained at a stirring speed of 600 rpm for 3 h. After the reaction was completed, the reactor was cooled to room temperature and the reaction solution was centrifuged. The supernatant was collected and quantitatively analyzed by gas chromatography. The test results are listed in Table 2.

[0053] Example 21

[0054] The specific preparation method of 30 wt% ZrO2 / TiO2 catalyst is as follows: H3P(Mo3O 10 The concentration of the 4·xH2O aqueous solution was adjusted to 0 g / L, and the remaining operations were the same as in Example 1-3 to prepare a 30 wt% ZrO2 / TiO2 catalyst.

[0055] In a 100 mL high-temperature and high-pressure reactor, 4 mmol of levulinic acid, 0.5 g of a 30 wt% ZrO2 / TiO2 catalyst, and 20 mL of isopropanol were added. The reactor was sealed, and the air in the reactor was replaced with nitrogen and then exhausted. The reaction was heated to 180°C and maintained at this temperature for 3 h at a stirring speed of 600 rpm. After the reaction was completed, the reactor was cooled to room temperature and the reaction solution was centrifuged. The supernatant was collected and quantitatively analyzed by gas chromatography. The test results are listed in Table 2.

[0056] Example 22

[0057] The specific preparation method of 30 wt% ZrO2 / TiO2-PMo (12 g / L) catalyst is as follows: H3P(Mo3O 10 )4·xH2O aqueous solution was adjusted to 12 g / L, and the remaining operations were the same as in Example 1-3 to prepare a catalyst 30 wt% ZrO2 / TiO2-PMo (12 g / L).

[0058] In a 100 mL high-temperature and high-pressure reactor, 4 mmol of levulinic acid, 0.5 g of 30 wt% ZrO2 / TiO2-PMo (12 g / L) catalyst, and 20 mL of isopropanol were added. The reactor was sealed, and the air in the reactor was replaced with nitrogen and then discharged. The reaction was heated to 180°C and maintained for 3 h at a stirring speed of 600 rpm. After the reaction was completed, the reactor was cooled to room temperature and the reaction solution was centrifuged. The supernatant was collected and quantitatively analyzed by gas chromatography. The test results are listed in Table 2.

[0059] Example 23

[0060] The specific preparation method of TiO2-PMo catalyst is as follows: 1.35 g of nano-TiO2 is added to 50 mL of 6 g / L H3P(Mo3O 10 )4·xH2O aqueous solution, ultrasonicated for 30 min, then magnetically stirred for 3 h, and then excess water was removed by rotary evaporation. The resulting product was dried in a vacuum drying oven at 110°C for about 12 h. The dried product was ground in a mortar, sieved, and then calcined at 300°C for 2 h to prepare the catalyst TiO2-PMo.

[0061] 4 mmol of levulinic acid, 0.5 g of TiO2-PMo catalyst, and 20 mL of isopropanol were added to a 100 mL high-temperature and high-pressure reactor. The reactor was sealed, and the air in the reactor was replaced with nitrogen and then discharged. The reactor was heated to 180°C and maintained at a stirring speed of 600 rpm for 3 h. After the reaction was completed, it was cooled to room temperature and the reaction solution was centrifuged. The supernatant was collected and quantitatively analyzed by gas chromatography. The test results are listed in Table 2.

[0062] Table 2 Test results of Examples 17-23

[0063]

[0064] It can be seen from Table 2 that the 30 wt% ZrO2 / TiO2 catalyst loaded with ZrO2 alone and the catalyst loaded with H3P(Mo3O 10 The yield of γ-valerolactone catalyzed by the TiO2-PMo catalyst containing 4·xH2O was relatively low, indicating that both Lewis and Brönsted acid sites play an important role in the transfer hydrogenation of levulinic acid to γ-valerolactone. Furthermore, the 30 wt% ZrO2 / TiO2-PMo catalyst possesses both Lewis and Brönsted acid sites, resulting in the best catalytic performance for the transfer hydrogenation of levulinic acid to γ-valerolactone.

[0065] Table 3 lists the total acidity of 30 wt% ZrO2 / TiO2-PMo, 30 wt% ZrO2 / TiO2 and TiO2-PMo catalysts.

[0066] Table 3 Catalyst acid content

[0067]

[0068] It can be concluded from Table 3 that the acidity value mainly depends on the properties of the metal oxide in the catalyst, and the high catalytic activity of 30 wt% ZrO2 / TiO2-PMo is related to its appropriate acid content.

[0069] TPD analysis was further performed using NH3 as the investigation molecule to determine the acidity intensity distribution and total acidity of 30 wt% ZrO2 / TiO2-PMo, 30 wt% ZrO2 / TiO2 and TiO2-PMo catalysts. The results are shown in Figure 3 .like Figure 3TPD analysis reveals three types of NH3 desorption peaks for the three catalysts: weakly acidic, moderately acidic, and strongly acidic sites, appearing in the 100-250°C, 250-450°C, and 450-600°C temperature ranges, respectively. Specifically, all three catalysts exhibit broad, low-intensity peaks in the low-temperature region. ZrO2 loading results in strong desorption peaks at moderately acidic sites for the 30 wt% ZrO2 / TiO2-PMo and 30 wt% ZrO2 / TiO2 catalysts, likely due to the presence of Lewis acidic sites. Meanwhile, the TiO2-PMo and 30 wt% ZrO2 / TiO2-PMo catalysts exhibit correlated desorption peaks in the strongly acidic region, likely due to the presence of Brönsted acidic sites. It can be seen from Example 21 that the 30 wt% ZrO2 / TiO2 catalyst loaded only with ZrO2 only obtained a γ-valerolactone yield of 28.2%. It can be inferred that the Bronsted acid site provided by phosphomolybdic acid in the catalyst plays an important role in the key step of converting the intermediate 4-hydroxyvalerate lactone to valerolactone.

[0070] Examples 24-29

[0071] Catalyst cycle experiment:

[0072] A 100 mL high-temperature, high-pressure reactor was charged with 4 mmol of levulinic acid, 0.5 g of the 30 wt% ZrO2 / TiO2-PMo catalyst used in Example 1, and 20 mL of isopropanol. The reactor was sealed, the air in the reactor was replaced with nitrogen, and then the nitrogen was exhausted. The reactor was heated to 180°C and maintained for 3 hours at a stirring speed of 600 rpm. After the reaction was completed, it was cooled to room temperature and the reaction solution was centrifuged. The solid catalyst was recovered and dried in a vacuum drying oven at 100°C for 2 hours for use in cyclic experiments. The reaction solution after each cyclic experiment was quantitatively analyzed by gas chromatography. The results are listed in Table 4.

[0073] Table 4 Test results of Examples 24-29

[0074]

[0075] As shown in Table 4, compared with Example 2, the yield of γ-valerolactone obtained by the 30 wt% ZrO2 / TiO2-PMo catalyst after 6 cycle experiments was only slightly reduced.

[0076] Examples 30-32

[0077] An elemental analyzer was used to measure the carbon deposit content of a fresh 30 wt% ZrO2 / TiO2-PMo catalyst, a 30 wt% ZrO2 / TiO2-PMo catalyst that had been used once, and a 30 wt% ZrO2 / TiO2-PMo catalyst that had been used seven times. The results are listed in Table 5.

[0078] Table 5 Test results of Examples 30-32

[0079]

[0080] Table 5 shows that compared to the fresh catalyst, the C content of the catalyst increased by 0.94% after one use, and by 0.43% after seven uses. Carbon deposits formed during catalyst use are one of the factors that reduce catalytic activity. However, the catalyst of the present invention exhibits minimal carbon deposits, resulting in a smaller decrease in γ-valerolactone yield upon repeated use.

[0081] Example 33

[0082] The specific preparation method of the 30 wt% La2O3 / TiO2-PMo catalyst is as follows: the Zr(NO3)4·5H2O used in Example 1 is replaced with 0.93 g LaCl3·7H2O, and the remaining operations are the same as those in Examples 1-3 to prepare a catalyst 30 wt% La2O3 / TiO2-PMo in which the mass of the metal oxide La2O3 is 30% of that of the carrier TiO2.

[0083] In a 100 mL high-temperature and high-pressure reactor, 4 mmol of levulinic acid, 0.5 g of a 30 wt% La2O3 / TiO2-PMo catalyst, and 20 mL of isopropanol were added. The reactor was sealed, and the air in the reactor was replaced with nitrogen and then exhausted. The reactor was heated to 180°C at a stirring speed of 600 rpm and maintained for 3 h. After the reaction was completed, the reactor was cooled to room temperature and the reaction solution was centrifuged. The supernatant was collected and quantitatively analyzed by gas chromatography. The test results are listed in Table 6.

[0084] Example 34

[0085] The specific preparation method of the 30 wt% SnO2 / TiO2-PMo catalyst is as follows: the Zr(NO3)4·5H2O used in Example 1 is replaced with 0.71 g SnCl4, and the remaining operations are the same as those in Examples 1-3 to prepare a catalyst 30 wt% SnO2 / TiO2-PMo in which the mass of the metal oxide SnO2 is 30% of that of the carrier TiO2.

[0086] In a 100 mL high-temperature and high-pressure reactor, 4 mmol of levulinic acid, 0.5 g of 30 wt% SnO2 / TiO2-PMo catalyst, and 20 mL of isopropanol were added. The reactor was sealed, and the air in the reactor was replaced with nitrogen and then discharged. The reactor was heated to 180°C at a stirring speed of 600 rpm and maintained for 3 h. After the reaction was completed, the reactor was cooled to room temperature and the reaction solution was centrifuged. The supernatant was collected and quantitatively analyzed by gas chromatography. The test results are listed in Table 6.

[0087] Example 35

[0088] The specific preparation method of the 30 wt% Al2O3 / TiO2-PMo catalyst is as follows: the Zr(NO3)4·5H2O used in Example 1 is replaced with 2.99 g Al(NO3)3·9H2O, and the remaining operations are the same as those in Examples 1-3 to prepare a catalyst 30 wt% Al2O3 / TiO2-PMo in which the mass of the metal oxide Al2O3 is 30% of that of the carrier TiO2.

[0089] In a 100 mL high-temperature and high-pressure reactor, 4 mmol of levulinic acid, 0.5 g of a 30 wt% Al2O3 / TiO2-PMo catalyst, and 20 mL of isopropanol were added. The reactor was sealed, and the air in the reactor was replaced with nitrogen and then exhausted. The reactor was heated to 180°C at a stirring speed of 600 rpm and maintained for 3 h. After the reaction was completed, the reactor was cooled to room temperature and the reaction solution was centrifuged. The supernatant was collected and quantitatively analyzed by gas chromatography. The test results are listed in Table 6.

[0090] Table 6 Test results of Examples 33-35

[0091]

[0092] Comparative Example 1

[0093] 4 mmol of levulinic acid, 0.5 g of carrier nano-TiO2 and 20 mL of isopropanol were added to a 100 mL high-temperature and high-pressure reactor. The reactor was sealed, and the air in the reactor was replaced with nitrogen and then the nitrogen was discharged. The reactor was heated to 180°C at a stirring speed of 600 rpm and maintained for 3 h. After the reaction was completed, it was cooled to room temperature and the reaction liquid was centrifuged. The supernatant was taken and quantitatively analyzed by gas chromatography. The test results are listed in Table 7.

[0094] Comparative Example 2

[0095] The specific preparation method of the 30 wt% ZrO2 / ZSM-5-PMo catalyst is as follows: replace nano-TiO2 with an equal mass of ZSM-5, and perform the remaining operations as in Example 1-3 to prepare the catalyst 30 wt% ZrO2 / ZSM-5-PMo.

[0096] In a 100 mL high-temperature and high-pressure reactor, 4 mmol of levulinic acid, 0.5 g of 30 wt% ZrO2 / ZSM-5-PMo catalyst, and 20 mL of isopropanol were added. The reactor was sealed, and the air in the reactor was replaced with nitrogen and then discharged. The reactor was heated to 180°C at a stirring speed of 600 rpm and maintained for 3 h. After the reaction was completed, the reactor was cooled to room temperature and the reaction solution was centrifuged. The supernatant was collected and quantitatively analyzed by gas chromatography. The test results are listed in Table 7.

[0097] Comparative Example 3

[0098] The specific preparation method of the 30 wt% ZrO2 / SiO2-PMo catalyst is as follows: replace nano-TiO2 with an equal mass of SiO2, and perform the remaining operations as in Example 1-3 to prepare the catalyst 30 wt% ZrO2 / SiO2-PMo.

[0099] In a 100 mL high-temperature and high-pressure reactor, 4 mmol of levulinic acid, 0.5 g of a 30 wt% ZrO2 / SiO2-PMo catalyst, and 20 mL of isopropanol were added. The reactor was sealed, and the air in the reactor was replaced with nitrogen and then exhausted. The reactor was heated to 180°C at a stirring speed of 600 rpm and maintained for 3 h. After the reaction was completed, the reactor was cooled to room temperature and the reaction solution was centrifuged. The supernatant was collected and quantitatively analyzed by gas chromatography. The test results are listed in Table 7.

[0100] Table 7 Test results of comparative examples 1-3

[0101]

[0102] The above description is merely a preferred embodiment of the present invention and therefore cannot be used to limit the scope of the present invention. In other words, equivalent changes and modifications made within the scope of the present invention and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A supported metal oxide catalyst for preparing γ-valerolactone by transfer hydrogenation of levulinic acid, characterized in that: 1.35 g of nano-TiO2 was added to 50 mL of 6 g / L H3P(Mo3O 10 )4·xH2O aqueous solution, and ultrasonicated for 30 minutes to obtain a TiO2-PMo mixed aqueous solution; 1.42 g of Zr(NO3)4·5H2O was dissolved in pure water and slowly added dropwise to the TiO2-PMo mixed aqueous solution. After magnetic stirring for 3 hours, excess water was removed by a rotary evaporator, and the resulting product was dried in a vacuum drying oven at 110°C for 12 hours. The dried product was ground in a mortar, sieved, and then calcined at 300°C for 2 hours to obtain a ZrO2 / TiO2-PMo catalyst, wherein the mass of the metal oxide ZrO2 was 30% of the mass of the carrier TiO2; The obtained catalyst was applied by adding 4 mmol of levulinic acid and 0.5 g of ZrO2 / TiO2-PMo catalyst into a 100 mL high-temperature and high-pressure reactor, then adding 20 mL of isopropanol, sealing the reactor, replacing the air in the reactor with nitrogen and then exhausting the nitrogen, heating to 180°C at a stirring speed of 600 rpm and maintaining for 3 hours, and cooling to room temperature after the reaction was completed to obtain γ-valerolactone.

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