Preparation method for metal oxide / ruthenium-tungsten composite catalyst and use of metal oxide / ruthenium-tungsten composite catalyst in catalysis of cleavage of c-o bond in lignin

Abstract

Provided in the present invention is a preparation method for a metal oxide / ruthenium-tungsten composite catalyst and the use of the metal oxide / ruthenium-tungsten composite catalyst in the catalysis of the cleavage of a C-O bond in lignin. The preparation method comprises: weighing a tungstate, dissolving same in deionized water, and stirring the resulting solution until uniform, so as to obtain a solution a; weighing ruthenium chloride, dissolving same in deionized water, and stirring the resulting solution until uniform, so as to obtain a solution b; mixing the solution a with the solution b, so as to obtain a solution c; dissolving a nanometer metal oxide in deionized water, and stirring same, so as to obtain a solution d; S4, adding, in a dropwise manner, the solution c to the solution d, so as to obtain a solution e, and subjecting the solution e to rotary evaporation and a vacuum drying treatment, so as to obtain a catalyst precursor; and S5, placing the catalyst precursor into a tubular furnace, and reducing same in a H2 / Ar atmosphere, so as to obtain a metal oxide / ruthenium-tungsten composite catalyst. In the present invention, a metal oxide carrier is loaded with ruthenium and tungsten by means of an impregnation method, the preparation process is simple, and environmental pollution and energy consumption are low; and a lignin model compound is efficiently catalytically cracked into an aromatic compound under mild conditions, and few by-products are produced.

Description

A method for preparing a metal oxide / ruthenium-tungsten composite catalyst and its application in catalyzing CO bond cleavage in lignin. Technical Field

[0001] This invention relates to the field of composite catalyst preparation technology, specifically to a method for preparing a metal oxide / ruthenium-tungsten composite catalyst and its application in catalyzing the cleavage of CO bonds in lignin. Background Technology

[0002] The gradual depletion of petroleum-based fuels has led to a global energy crisis. Biomass, as one of the most important renewable resources on Earth and the only renewable resource that can be converted into liquid fuels, has received considerable attention in recent years as an alternative to fossil fuels is sought. The main components of biomass are cellulose, hemicellulose, and lignin. Cellulose and hemicellulose are composed of complex polysaccharides. Cellulose and hemicellulose can be efficiently converted into value-added chemicals and biofuels through various technologies, while lignin is relatively more challenging. Although lignin accounts for only 15–30 wt% of lignocellulosic biomass, it accounts for 40% of its energy. Furthermore, lignin is the only component of the aromatic skeleton, providing possibilities for obtaining value-added chemicals.

[0003] Lignin is primarily composed of three phenolic monomers: p-coumarol, sine, and sinapyl. These monomers polymerize to form different types of phenylpropane units, including phenylalanine units, hydroxyphenyl units, guaiacol, and eugenyl units. Phenylaceane units can link together to form Cβ-O bonds (also known as β-O-4 aromatic ether bonds) and CCC bonds (such as β-5 and β-β bonds). In the structure of lignin, approximately 50-65% of the bonds are β-O-4 aromatic ether bonds and abundant aliphatic and aromatic hydroxyl groups. Due to the large number of CO and CCC bonds in lignin, it is difficult to break it down into single aromatic compounds using conventional chemical or biological methods.

[0004] To successfully depolymerize lignin into aromatic polymers, existing literature reports the use of catalysts such as Co, Ni / C, Pd / C, and NiRu to catalyze the depolymerization of lignin Cβ-O (β-O-4 aromatic ether) bonds. However, hydrogenolysis requires high H2 pressure, which can lead to excessive hydrogenation, cracking, and coke formation as side reactions of aromatic ring monomers. Furthermore, hydrogen is a non-renewable resource, making large-scale industrial utilization difficult. To minimize the impact of side reactions, the industry requires efficient lignin depolymerization under hydrogen-free or low-hydrogen conditions.

[0005] The preparation of ruthenium catalysts for catalyzing the cleavage of lignin ether bonds has attracted widespread attention. Ruthenium-based catalysts not only exhibit strong interactions with oxygen atoms in the adsorbate, leading to direct cleavage of CO bonds, but also possess Lewis acid sites in reducible ruthenium oxide catalysts, facilitating the hydrogenation and deoxygenation of oxygen-containing compounds in the liquid phase. Therefore, ruthenium-based catalysts possess broader substrate versatility. Currently reported ruthenium-based catalysts often require more stringent reaction conditions; therefore, constructing ruthenium-based catalysts to catalytically depolymerize lignin model compounds into aromatic monomers under mild conditions is of great significance for organic chemistry research and practical industrial applications.

[0006] Although ruthenium-tungsten composite catalysts have been used to catalyze the conversion of lignin, while highly efficient, they suffer from drawbacks such as reduced ruthenium hydrogenolysis in solvents under low hydrogen pressure. Furthermore, ruthenium-tungsten composite catalysts typically exhibit low activity during benzene ring hydrogenolysis, leading to additional hydrogen consumption and low yields of the target product. Therefore, improvements to ruthenium-tungsten composite catalysts are needed to enhance their ability to catalyze the cleavage of CO bonds in lignin. Currently, there are no reports on the preparation of ruthenium-tungsten composite catalysts using metal oxides as supports for catalyzing the cleavage of CO bonds in lignin.

[0007] Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a method for preparing a metal oxide / ruthenium-tungsten composite catalyst and its application in catalyzing the cleavage of CO bonds in lignin. This invention uses a metal oxide as a support to construct a ruthenium-tungsten composite catalyst, which efficiently catalyzes the conversion of lignin model compounds to aromatic compounds under mild conditions, with mild reaction conditions and few byproducts.

[0009] The first objective of this invention is to provide a method for preparing a metal oxide / ruthenium-tungsten composite catalyst, the method comprising:

[0010] S1 Weigh a certain amount of nano-metal oxide and place it in a muffle furnace. Then, perform high-temperature calcination in air atmosphere to obtain pretreated nano-metal oxide.

[0011] S2 weighs a certain amount of tungstate and dissolves it in deionized water, stirring until homogeneous at room temperature and pressure to obtain solution a; weighs a certain amount of ruthenium chloride and dissolves it in deionized water, stirring until homogeneous at room temperature and pressure to obtain solution b; then mixes solution a and solution b and stirs until homogeneous to obtain solution c;

[0012] S3 dissolves the pretreated nano-metal oxides in deionized water and stirs them at room temperature and pressure to obtain solution d;

[0013] S4. Solution c is added dropwise to solution d and stirred evenly at room temperature and pressure to obtain solution e. Solution e is subjected to rotary evaporation and vacuum drying to obtain the metal oxide / ruthenium tungsten composite catalyst precursor.

[0014] S5 involves adding a reducing agent to the metal oxide / ruthenium-tungsten composite catalyst precursor for reduction treatment to obtain the metal oxide / ruthenium-tungsten composite catalyst.

[0015] Preferably, the high-temperature calcination treatment in step S1 is carried out at a temperature of 500–700°C for 4–6 hours.

[0016] Preferably, the metal oxide in step S1 is any one of titanium dioxide, zinc oxide, zirconium oxide, niobium pentoxide, magnesium oxide, and cerium oxide.

[0017] Preferably, the tungstate in step S2 is any one of ammonium metatungstate, tungsten chloride, and tungsten nitrate.

[0018] Preferably, in step S2, the concentration of solution a is 0.15–0.3 g / ml; the concentration of solution b is 0.04–0.06 g / ml; and the volume ratio of solution a to solution b in solution c is 1:1.

[0019] Preferably, the concentration of solution d in step S3 is 0.06 to 0.08 g / ml.

[0020] Preferably, in step S4, the volume ratio of solution c to solution d in solution e is 1:5; the vacuum drying process uses a vacuum drying oven with a drying temperature of 80–200°C and a drying time of 12–36 hours.

[0021] Preferably, the reducing agent in step S5 is either H2 / Ar gas containing 10% or hydrazine hydrate; the reduction treatment time is 1 to 3 hours.

[0022] Preferably, the molar doping ratio of ruthenium in the metal oxide / ruthenium-tungsten composite catalyst is 0.01–9%; and the molar doping ratio of tungsten in the metal oxide / ruthenium-tungsten composite catalyst is 1–30%.

[0023] The second objective of this invention is to provide an application of the above-mentioned metal oxide / ruthenium tungsten composite catalyst in catalyzing the CO bond cleavage in lignin. The method is characterized by using a lignin model compound as a substrate, a small molecule alcohol as a solvent, adding a certain amount of the metal oxide / ruthenium tungsten composite catalyst, stirring evenly in a closed high-pressure reactor, then purging with H2 or N2 to maintain the pressure inside the reactor at 0.1–2.0 MPa, adjusting the temperature inside the reactor to 165–380°C, and carrying out the catalytic cleavage reaction of the substrate for 8–32 hours to prepare an aromatic monomer compound.

[0024] Preferably, the amount of catalyst used is 0.05-0.2g, the volume of small molecule alcohol is 5-10ml, and the concentration of lignin model compound is 0.2-0.1mol / L.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] (1) This invention proposes a novel bifunctional composite catalyst, using ruthenium-tungsten as the active component and metal oxide as the support, to prepare a novel titanium dioxide-ruthenium-tungsten composite catalyst, which provides more active sites in the catalytic cracking of lignin model compounds, with mild catalytic cracking reaction conditions, high yield of aromatic monomers, and reduced by-product generation.

[0027] (2) The composite catalyst preparation method provided by the present invention is simple, the raw materials are readily available, the reaction conditions are mild, and the pollution and energy consumption to the environment are small. At the same time, by controlling the content ratio of ruthenium and tungsten, the effective synergistic effect between ruthenium and tungsten can be brought into play, the active sites of the catalyst can be better controlled, and the stability of the catalyst can be improved by using metal oxide as a support. Thus, the composite catalyst with both high activity and stability is conducive to the large-scale industrial production of the catalyst and promotes its widespread application in the field of lignin depolymerization.

[0028] (3) In this invention, a titanium dioxide-ruthenium tungsten composite catalyst is used to catalyze the cracking of CO bonds in lignin. The catalyst can still exhibit excellent catalytic performance in hydrogen-free and low-hydrogen atmospheres, achieving efficient CO bond breaking, while reducing costs and energy consumption, and also improving the yield of aromatic compounds. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1(a) is a transmission electron microscope (TEM) image of the 1-TiO2 / RuW composite catalyst prepared in Example 1 of the present invention;

[0031] Figure 1(b) is a scanning electron microscope (SEM) image of the 1-TiO2 / RuW composite catalyst prepared in Example 1 of the present invention;

[0032] Figure 2 is a schematic diagram of the preparation of TiO2 / RuW composite catalysts in Examples 1 and 2 and their application in catalyzing CO bond cleavage in lignin and lignin model compounds.

[0033] Figure 3(a) shows the effect of catalyst dosage on catalytic efficiency of the 1-TiO2 / RuW composite catalyst prepared in Example 1 of the present invention in catalyzing the CO bond cleavage of 2-phenoxy-1-acetophenone.

[0034] Figure 3(b) shows the effect of reaction temperature on catalytic efficiency of the 1-TiO2 / RuW composite catalyst prepared in Example 1 of the present invention in the catalytic CO bond cleavage of 2-phenoxy-1-acetophenone.

[0035] Figure 3(c) shows the effect of reaction time on catalytic efficiency of the 1-TiO2 / RuW composite catalyst prepared in Example 1 of the present invention in the catalytic CO bond cleavage of 2-phenoxy-1-acetophenone.

[0036] Figure 3(d) shows the effect of the number of cycles on the catalytic efficiency of the 1-TiO2 / RuW composite catalyst prepared in Example 1 of this invention in catalyzing the cleavage of the CO bond in 2-phenoxy-1-acetophenone.

[0037] Figure 4(a) shows the conversion rate of 2-phenoxy-1-acetophenone in the CO bond of 2-phenoxy-1-acetophenone as a function of reaction time for different types of catalysts prepared in Example 1 and Comparative Examples 1-3 of the present invention.

[0038] Figure 4(b) shows the yield of phenol as a function of reaction time for different types of catalysts prepared in Example 1 and Comparative Examples 1-3, and Comparative Example 4 without catalyst, in the cleavage of the CO bond of 2-phenoxy-1-acetophenone.

[0039] Figure 4(c) shows the yield of methyl benzoate, a product of cleavage of the CO bond of 2-phenoxy-1-acetophenone, as a function of reaction time for different types of catalysts prepared in Example 1 and Comparative Examples 1-3, and for Comparative Example 4 without catalyst.

[0040] Figure 4(d) shows the yield of acetophenone, a product of different types of catalysts prepared in Example 1 and Comparative Examples 1-3, and Comparative Example 4 without catalyst, as a function of reaction time in the cleavage of the CO bond of 2-phenoxy-1-acetophenone.

[0041] Figure 5 shows the X-ray diffraction (XRD) patterns of different types of catalysts prepared in Example 1 and Comparative Examples 1-3 of this invention.

[0042] Figure 6 shows the adsorption / desorption isotherms of different types of catalysts prepared in Example 1 and Comparative Examples 1-3 of this invention. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] The instruments or testing methods used for performance testing in this invention are as follows:

[0045] Transmission electron microscopy (TEM) was performed using a Tecnai F20G2S-TWIN TEM from FEI, operating at 200 kV. Scanning electron microscopy (SEM) was performed using a Hitachi S4800 field emission scanning electron microscope from Japan, accelerating at 5 kV. Energy dispersive spectroscopy (EDS) data were collected and processed using Horiba 350 software. Physicochemical data, including the BET specific surface area and pore structure of the composite catalyst, were determined using a low-temperature nitrogen adsorption-desorption method. X-ray diffraction (XRD) was performed using a Bruker AXS D8 Advance X-ray diffractometer from Germany to analyze the crystal structure of the catalyst material. A Cu target, Ni filter, and Si-Li detector were used. The test voltage was 40 kV × 40 mA, the scan range was 3–90°, the scan speed was 5° / min, and a Ni filter was used for scanning.

[0046] Example 1

[0047] (1) Preparation of titanium dioxide / ruthenium tungsten composite catalyst (TiO2 / RuW)

[0048] S1 pretreatment was performed by placing nano-TiO2 in a muffle furnace and calcining it at 550°C for 4 hours in an air atmosphere;

[0049] S2 Weigh 1.5g of ammonium metatungstate and dissolve it in 10ml of deionized water. Stir for 30min at room temperature and pressure to completely dissolve it to obtain solution a1. Then weigh 0.474g of ruthenium chloride and dissolve it in 10ml of deionized water. Stir for 30min at room temperature and pressure to completely dissolve it to obtain solution b1. Mix the two solutions and stir evenly to obtain solution c1.

[0050] S3 weighed 3.18g of nano TiO2 and dissolved it in 50ml of deionized water. After stirring for 30min, solution d1 was obtained.

[0051] S4 added solution c1 dropwise to solution d1 and stirred the mixture for 24 hours at room temperature and pressure until homogeneous to obtain solution e1. Solution e1 was then placed in a rotary evaporator for rotary evaporation to obtain a 1-solid mixture. The 1-solid mixture was then transferred to a vacuum drying oven and dried at 100°C under vacuum for 12 hours to obtain the 1-TiO2 / RuW precursor.

[0052] S5 The 1-TiO2 / RuW precursor was placed in a tube furnace and reduced for 1 hour in an atmosphere containing 10% H2 / Ar to obtain the 1-TiO2 / RuW composite catalyst prepared in Example 1.

[0053] Structural characterization:

[0054] Please refer to Figures 1(a) to 1(d). Figure 1(a) is a transmission electron microscope (TEM) image of the 1-TiO2 / RuW composite catalyst prepared in Example 1 of the present invention; Figure 1(b) is a scanning electron microscope (SEM) image of the 1-TiO2 / RuW composite catalyst prepared in Example 1 of the present invention. As can be seen from Figures 1(a) and 1(b), the morphology of the 1-TiO2 / RuW composite catalyst is mainly irregular particles, and the irregular particles are stacked together.

[0055] Inductively coupled plasma atomic emission spectrometry (ICP) analysis of the 1-TiO2 / RuW composite catalyst revealed that the catalyst contained 1.25% ruthenium and 15.66% tungsten.

[0056] (2) The 1-TiO2 / RuW composite catalyst prepared in Example 1 was used to catalytically crack the CO bond in 2-phenoxy-1-acetophenone to obtain aromatic compounds (phenol, acetophenone and methyl benzoate).

[0057] Using 1 mmol of 0.2 mol / L 2-phenoxy-1-acetophenone as the substrate, 10 mL of methanol as the reaction solvent, and 0.1 g of 1-TiO2 / RuW composite catalyst, the mixture was thoroughly mixed in a sealed high-pressure reactor. N2 was then introduced to bring the pressure inside the reactor to 0.3 MPa, and the temperature was raised to 185 °C. The reaction was allowed to proceed for 24 h. The reaction process is as follows:

[0058] After the reaction was completed, the mixture was cooled to room temperature, and the supernatant after centrifugation was subjected to chromatographic analysis. The conversion rate of 2-phenoxy-1-acetophenone was 90.1%, the yield of the target product phenol was 88.8%, the yield of acetophenone was 74.7%, and the yield of methyl benzoate was 11.5%.

[0059] (3) Parameter optimization and selection experiment in catalyst application

[0060] The 1-TiO2 / RuW composite catalyst prepared above was used to catalyze the cleavage of CO bonds in a lignin model compound (2-phenoxy-1-acetophenone) to yield aromatic compounds (phenol, acetophenone, and methyl benzoate). Optimization experiments were conducted by setting gradient variations in reaction time, reaction temperature, and catalyst dosage. In each experiment, only a single parameter was varied, while other parameters remained constant.

[0061] ① Optimization of catalyst dosage

[0062] 1 mmol of 0.2 mol / L 2-phenoxy-1-acetophenone was used as the substrate, and 10 ml of methanol was used as the reaction solvent. 0.05 g, 0.1 g, 0.15 g, 0.2 g, and 0.25 g of 1-TiO2 / RuW composite catalyst were added sequentially. After being mixed evenly in a closed high-pressure reactor, N2 was introduced to bring the pressure inside the reactor to 0.3 MPa. The reaction was carried out at 185 °C for 24 h. Experiments were conducted separately.

[0063] ② Optimization of reaction temperature parameters

[0064] 1 mmol of 0.2 mol / L 2-phenoxy-1-acetophenone was used as the substrate, and 10 ml of methanol was used as the reaction solvent. 0.1 g of 1-TiO2 / RuW composite catalyst was added and mixed evenly in a closed high-pressure reactor. N2 was then introduced to bring the pressure inside the high-pressure reactor to 0.3 MPa. The reaction temperatures were set sequentially to 165℃, 185℃, 205℃, and 225℃, and the reaction time was 24 h for each reaction. Reaction experiments were conducted accordingly.

[0065] ③ Optimization of reaction time parameters

[0066] 1 mmol of 0.2 mol / L 2-phenoxy-1-acetophenone was used as the substrate, and 10 ml of methanol was used as the reaction solvent. 0.1 g of 1-TiO2 / RuW composite catalyst was added and mixed evenly in a closed high-pressure reactor. N2 was then introduced to make the pressure in the high-pressure reactor reach 0.3 MPa, and the temperature was raised to 185 °C. The reaction time was set to 8, 16, 24 h and 32 h, and the reaction experiments were carried out respectively.

[0067] ④ Performance test of 1-TiO2 / RuW composite catalyst recycling

[0068] Using 1 mmol of 0.2 mol / L 2-phenoxy-1-acetophenone as the substrate and 10 mL of methanol as the reaction solvent, 0.15 g of 1-TiO2 / RuW composite catalyst was added sequentially. After thorough mixing in a sealed high-pressure reactor, N2 was introduced to bring the reactor pressure to 0.3 MPa. The reaction was carried out at 185 °C for 8 h. The 1-TiO2 / RuW composite catalyst was recycled 10 times, and the conversion rate and product yield were tested for each reaction.

[0069] Please refer to Figures 3(a)-(d). Figure 3(a) shows the effect of catalyst dosage on catalytic efficiency of the 1-TiO2 / RuW composite catalyst prepared in Example 1 of this invention in catalyzing the CO bond cleavage of 2-phenoxy-1-acetophenone; Figure 3(b) shows the effect of reaction temperature on catalytic efficiency of the 1-TiO2 / RuW composite catalyst prepared in Example 1 of this invention in catalyzing the CO bond cleavage of 2-phenoxy-1-acetophenone; Figure 3(c) shows the effect of reaction time on catalytic efficiency of the 1-TiO2 / RuW composite catalyst prepared in Example 1 of this invention in catalyzing the CO bond cleavage of 2-phenoxy-1-acetophenone; Figure 3(d) shows the effect of the number of cycles on catalytic efficiency of the 1-TiO2 / RuW composite catalyst prepared in Example 1 of this invention in catalyzing the CO bond cleavage of 2-phenoxy-1-acetophenone.

[0070] As shown in Figure 3(a), the effect of catalyst dosage on catalytic conversion efficiency was investigated when using a 1-TiO2 / RuW composite catalyst to catalyze the cleavage of the CO bond in 2-phenoxy-1-acetophenone. With increasing catalyst dosage, the conversion and yield of 2-phenoxy-1-acetophenone reached their optimal values ​​at 0.2 g, indicating that increasing the catalyst dosage promotes the reaction. However, excessive catalyst can hinder the forward reaction. Therefore, the optimal catalyst dosage should be controlled between 0.05 g and 0.2 g, with 0.2 g of composite catalyst being preferred for catalyzing the CO bond cleavage reaction of 2-phenoxy-acetophenone. As shown in Figure 3(b), the effect of reaction temperature on catalytic conversion efficiency was investigated. With increasing reaction temperature, both conversion and yield increased. At a reaction temperature of 225℃, the conversion reached 99.9%, the phenol yield reached 92.3%, the acetophenone yield reached 86.7%, and the methyl benzoate yield reached 9.8%, representing the optimal reaction temperature. As shown in Figure 3(c), the effect of reaction time on catalytic conversion efficiency was investigated. With increasing reaction time, the conversion rate of 2-phenoxy-1-acetophenone increased significantly, reaching 97.8% at a reaction time of 32 h. After the reaction was completed, the catalyst was recovered for recycling. As shown in Figure 3(d), the recycling performance of the composite catalyst prepared in Example 1 (1-TiO2 / RuW) during the catalytic breaking of the CO bond in 2-phenoxy-1-acetophenone was analyzed. The figure shows that after 10 cycles of catalyst recycling, the conversion rate and yield did not decrease significantly, indicating good catalyst stability.

[0071] The application of the 1-TiO2 / RuW composite catalyst prepared in Example 1 demonstrates that this catalyst can efficiently catalyze the breaking of β-O-4 bonds in aromatic compounds and efficiently convert them into aromatic monomers. It achieves high conversion rates while maintaining high yields during the catalytic process. It successfully breaks the CO bonds without excessive hydrogenation that generates numerous byproducts.

[0072] Example 2

[0073] Please refer to Figure 2, which is a schematic diagram of the preparation of TiO2 / RuW composite catalysts in Examples 1 and 2 and their application in catalyzing the cleavage of CO bonds in lignin and lignin model compounds.

[0074] (1) Preparation of titanium dioxide / ruthenium tungsten composite catalyst (TiO2 / RuW)

[0075] S1 pretreatment was performed by placing nano-TiO2 in a muffle furnace and calcining it at 700°C for 6 hours in air atmosphere;

[0076] S2 Weigh 3g of ammonium metatungstate and dissolve it in 10ml of deionized water. Stir at room temperature and pressure for 30min until it is completely dissolved to obtain solution a2. Then weigh 0.54g of ruthenium chloride and dissolve it in 10ml of deionized water. Stir at room temperature and pressure for 30min until it is completely dissolved to obtain solution b2. Mix the two solutions and stir evenly to obtain solution c2.

[0077] S3 weighed 3.7g of nano TiO2 and dissolved it in 50ml of deionized water. After stirring for 30min, solution d2 was obtained.

[0078] S4 added solution c2 dropwise to solution d2 and stirred the mixture for 24 hours at room temperature and pressure until homogeneous to obtain solution e2. Solution e2 was then placed in a rotary evaporator for rotary evaporation to obtain a 2-solid mixture. The 2-solid mixture was then transferred to a vacuum drying oven and dried at 200°C under vacuum for 36 hours to obtain the 2-TiO2 / RuW precursor.

[0079] S5. 40 ml of 80% hydrazine hydrate was added to the 2-TiO2 / RuW precursor and the mixture was reduced for 3 h to obtain the 2-TiO2 / RuW composite catalyst prepared in Example 2.

[0080] Inductively coupled plasma atomic emission spectrometry (ICP) analysis of the 2-TiO2 / RuW composite catalyst revealed that the catalyst contained 4.67% ruthenium and 21.54% tungsten.

[0081] (2) The 2-TiO2 / RuW composite catalyst prepared in Example 2 was used to catalytically cleave CO bonds in lignin to obtain aromatic monomer compounds (4-(3-hydroxypropyl)-2,6-dimethoxyphenol and 1,2,3-methoxybenzene).

[0082] Using 1 mmol of 0.2 mol / L lignin as the substrate and 5 ml of methanol as the reaction solvent, 0.2 g of 2-TiO2 / RuW composite catalyst was added. After thorough mixing in a sealed high-pressure reactor, H2 was introduced to bring the pressure inside the reactor to 2 MPa, and the temperature was raised to 380 °C. The reaction was carried out for 24 h. The reaction process is as follows:

[0083] After the reaction was completed, the mixture was cooled to room temperature, and the supernatant after centrifugation was analyzed by chromatography. The conversion rate of lignin was 90.1%, the yield of the target product 4-(3-hydroxypropyl)-2,6-dimethoxyphenol was 85.3%, and the yield of 1,2,3-methoxybenzene was 76.8%.

[0084] Example 3

[0085] (1) Preparation of zinc oxide / ruthenium tungsten composite catalyst (ZnO / RuW)

[0086] S1 pretreatment involves placing nano-ZnO in a muffle furnace and calcining it at 600°C for 5 hours in air atmosphere.

[0087] S2 Weigh 2.5g of tungsten chloride and dissolve it in 10ml of deionized water. Stir at room temperature and pressure for 30min to completely dissolve it to obtain solution a3. Then weigh 0.5g of ruthenium chloride and dissolve it in 10ml of deionized water. Stir at room temperature and pressure for 30min to completely dissolve it to obtain solution b3. Mix the two solutions and stir evenly to obtain solution c3.

[0088] S3: Weigh 3.5g of nano ZnO and dissolve it in 50ml of deionized water. After stirring for 30min, solution d3 is obtained.

[0089] S4. Solution c3 was added dropwise to solution d3. The mixture was stirred for 24 hours at room temperature and pressure until homogeneous to obtain solution e3. Solution e3 was placed in a rotary evaporator for rotary evaporation to obtain a 3-solid mixture. The 3-solid mixture was then transferred to a vacuum drying oven and dried at 150°C under vacuum for 24 hours to obtain the 3-ZnO / RuW precursor.

[0090] S5 reduced the 3-ZnO / RuW precursor in an atmosphere containing 10% H2 / Ar for 2 hours to obtain the 3-ZnO / RuW composite catalyst prepared in Example 3.

[0091] Inductively coupled plasma atomic emission spectrometry (ICP) analysis of the 3-ZnO / RuW composite catalyst revealed that the catalyst contained 0.78% ruthenium and 2.33% tungsten.

[0092] (2) The 3-ZnO / RuW composite catalyst prepared in Example 3 was used to catalyze the cleavage of CO bonds in the lignin model compound (phenylacetic acid) to obtain aromatic compounds (phenol and methyl benzoate).

[0093] Using 1 mmol of 0.15 mol / L phenylacetic acid ester as the substrate, and 8 mL of methanol as the reaction solvent, 0.2 g of 3-ZnO / RuW composite catalyst was added. After thorough mixing in a sealed high-pressure reactor, N2 was introduced to bring the pressure inside the reactor to 0.3 MPa, and the temperature was raised to 205 °C. The reaction was allowed to proceed for 24 h. The reaction process is as follows:

[0094] After the reaction was completed, the mixture was cooled to room temperature, and the supernatant after centrifugation was analyzed by chromatography. The conversion rate of phenylacetic acid phenyl ester was 99.9%, the yield of the target product phenol was 91.9%, and the yield of methyl benzoate was 90.3%.

[0095] Example 4

[0096] (1) Preparation of zirconium oxide / ruthenium tungsten composite catalyst (ZrO2 / RuW)

[0097] S1 pretreatment involves placing nano-ZrO2 in a muffle furnace and calcining it at 650°C for 4 hours in an air atmosphere.

[0098] S2 Weigh 2.5g of tungsten nitrate and dissolve it in 10ml of deionized water. Stir at room temperature and pressure for 30min until it is completely dissolved to obtain solution a4. Then weigh 0.5g of ruthenium chloride and dissolve it in 10ml of deionized water. Stir at room temperature and pressure for 30min until it is completely dissolved to obtain solution b4. Mix the two solutions and stir evenly to obtain solution c4.

[0099] S3 weighed 3.5g of nano ZrO2 and dissolved it in 50ml of deionized water. After stirring for 30min, solution d4 was obtained.

[0100] S4. Solution c4 was added dropwise to solution d4. The mixture was stirred for 24 hours at room temperature and pressure until homogeneous to obtain solution e4. Solution e4 was placed in a rotary evaporator for rotary evaporation to obtain a 4-solid mixture. The 4-solid mixture was then transferred to a vacuum drying oven and dried at 150°C under vacuum for 24 hours to obtain the 4-ZrO2 / RuW precursor prepared in Example 4.

[0101] S5 reduced the 4-ZrO2 / RuW precursor in an atmosphere containing 10% H2 / Ar for 1 hour to obtain the 4-ZrO2 / RuW composite catalyst prepared in Example 4.

[0102] Inductively coupled plasma atomic emission spectrometry (ICP) analysis of the 4-ZrO2 / RuW composite catalyst revealed that the catalyst contained 0.024% ruthenium and 28.93% tungsten.

[0103] (2) The 4-ZrO2 / RuW composite catalyst prepared in Example 4 was used to catalytically cleave the CO bond in the lignin model compound (phenoxyphenylethanol) to obtain aromatic compounds (phenol, ethylbenzene, and phenoxyethylbenzene).

[0104] Using 1 mmol of 0.15 mol / L 2-phenoxy-1-phenylethanol as the substrate and 5 ml of methanol as the reaction solvent, 0.2 g of 4-ZrO2 / RuW composite catalyst was added. After thorough mixing in a sealed high-pressure reactor, N2 was introduced to bring the pressure inside the reactor to 0.8 MPa, and the temperature was raised to 225 °C. The reaction was allowed to proceed for 18 h. The reaction process is as follows:

[0105] After the reaction was completed, the mixture was cooled to room temperature, and the supernatant after centrifugation was analyzed by chromatography. The conversion rate of 2-phenoxy-1-phenylethanol was 99.9%, the yield of the target product phenol was 90.9%, the yield of ethylbenzene was 80.3%, and the yield of phenoxyethylbenzene was 8.1%.

[0106] Example 5

[0107] (1) Preparation of niobium pentoxide / ruthenium tungsten composite catalyst (Nb2O5 / RuW)

[0108] S1 pretreatment was performed by placing nano-Nb2O5 in a muffle furnace and calcining it at 550°C for 4 hours in air atmosphere;

[0109] S2 Weigh 1.5g of ammonium metatungstate and dissolve it in 10ml of deionized water. Stir at room temperature and pressure for 30min to completely dissolve it to obtain solution a5. Then weigh 0.474g of ruthenium chloride and dissolve it in 10ml of deionized water. Stir at room temperature and pressure for 30min to completely dissolve it to obtain solution b5. Mix the two solutions and stir evenly to obtain solution c5.

[0110] S3 weighed 3.18g of nano Nb2O5 and dissolved it in 50ml of deionized water. After stirring for 30min, solution d5 was obtained.

[0111] S4 added solution c5 dropwise to solution d5 and stirred the mixture for 24 hours at room temperature and pressure until homogeneous to obtain solution e5. Solution e5 was then placed in a rotary evaporator for rotary evaporation to obtain a 5-solid mixture. The 5-solid mixture was then transferred to a vacuum drying oven and dried at 100°C under vacuum for 12 hours to obtain the 5-Nb2O5 / RuW precursor.

[0112] S5 The 5-Nb2O5 / RuW precursor was placed in a tube furnace and reduced for 1 hour in an atmosphere containing 10% H2 / Ar to obtain the 5-Nb2O5 / RuW composite catalyst prepared in Example 5.

[0113] Inductively coupled plasma atomic emission spectrometry (ICP) analysis of the 5-Nb2O5 / RuW composite catalyst revealed that the catalyst contained 4.65% ruthenium and 15.62% tungsten.

[0114] (2) The 5-Nb2O5 / RuW composite catalyst prepared in Example 5 was used to catalytically cleave the CO bond in 2-phenoxy-1-acetophenone to obtain aromatic compounds (phenol, acetophenone and methyl benzoate).

[0115] Using 1 mmol of 0.2 mol / L 2-phenoxy-1-acetophenone as the substrate, and 5 ml of methanol as the reaction solvent, 0.05 g of 5-Nb₂O₅ / RuW composite catalyst was added. After thorough mixing in a sealed high-pressure reactor, N₂ was introduced to bring the pressure inside the reactor to 0.3 MPa, and the temperature was raised to 185 °C. The reaction was allowed to proceed for 24 h. The reaction process is as follows:

[0116] After the reaction was completed, the mixture was cooled to room temperature, and the supernatant after centrifugation was subjected to chromatographic analysis. The conversion rate of 2-phenoxy-1-acetophenone was 90.1%, the yield of the target product phenol was 85.0%, the yield of acetophenone was 67.3%, and the yield of methyl benzoate was 45.3%.

[0117] Example 6

[0118] (1) Preparation of magnesium oxide / ruthenium tungsten composite catalyst (MgO / RuW)

[0119] S1 pretreatment involves placing nano-MgO in a muffle furnace and calcining it at 550°C for 4 hours in an air atmosphere.

[0120] S2 Weigh 1.5g of ammonium metatungstate and dissolve it in 10ml of deionized water. Stir for 30min at room temperature and pressure to completely dissolve it to obtain solution a6. Then weigh 0.474g of ruthenium chloride and dissolve it in 10ml of deionized water. Stir for 30min at room temperature and pressure to completely dissolve it to obtain solution b6. Mix the two solutions and stir evenly to obtain solution c6.

[0121] S3 weighed 3.18g of nano MgO and dissolved it in 50ml of deionized water. After stirring for 30min, solution d6 was obtained.

[0122] S4 added solution c6 dropwise to solution d5 and stirred the mixture for 24 hours at room temperature and pressure until homogeneous to obtain solution e6. Solution e6 was then placed in a rotary evaporator for rotary evaporation to obtain a 6-solid mixture. The 6-solid mixture was then transferred to a vacuum drying oven and dried at 100°C under vacuum for 12 hours to obtain the 6-MgO / RuW precursor.

[0123] S5 The 6-MgO / RuW precursor was placed in a tube furnace and reduced for 1 hour in an atmosphere containing 10% H2 / Ar to obtain the 6-MgO / RuW composite catalyst prepared in Example 6.

[0124] Inductively coupled plasma atomic emission spectrometry (ICP) analysis of the 6-MgO / RuW composite catalyst revealed that the catalyst contained 5.74% ruthenium and 1.59% tungsten.

[0125] (2) The 6-MgO / RuW composite catalyst prepared in Example 6 was used to catalytically cleave the CO bond in 2-phenoxy-1-acetophenone to obtain aromatic compounds (phenol, acetophenone and methyl benzoate).

[0126] Using 1 mmol of 0.2 mol / L 2-phenoxy-1-acetophenone as the substrate, and 5 ml of methanol as the reaction solvent, 0.1 g of 6-MgO / RuW composite catalyst was added. After thorough mixing in a sealed high-pressure reactor, N2 was introduced to bring the pressure inside the reactor to 0.3 MPa, and the temperature was raised to 225 °C. The reaction was allowed to proceed for 24 h. The reaction process is as follows:

[0127] After the reaction was completed, the mixture was cooled to room temperature, and the supernatant after centrifugation was subjected to chromatographic analysis. The conversion rate of 2-phenoxy-1-acetophenone was 93.8%, the yield of the target product phenol was 92.8%, the yield of acetophenone was 75.3%, and the yield of methyl benzoate was 18.7%.

[0128] Example 7

[0129] (1) Preparation of cerium oxide / ruthenium tungsten composite catalyst (CeO2 / RuW)

[0130] S1 pretreatment involves placing nano-CeO2 in a muffle furnace and calcining it at 550°C for 4 hours in an air atmosphere.

[0131] S2 Weigh 1.5g of ammonium metatungstate and dissolve it in 10ml of deionized water. Stir for 30min at room temperature and pressure to completely dissolve it to obtain solution a7. Then weigh 0.474g of ruthenium chloride and dissolve it in 10ml of deionized water. Stir for 30min at room temperature and pressure to completely dissolve it to obtain solution b7. Mix the two solutions and stir evenly to obtain solution c7.

[0132] S3 weighed 3.18g of nano CeO2 and dissolved it in 50ml of deionized water. After stirring for 30min, solution d7 was obtained.

[0133] S4 added solution c7 dropwise to solution d7 and stirred the mixture for 24 hours at room temperature and pressure until homogeneous to obtain solution e7. Solution e7 was then placed in a rotary evaporator for rotary evaporation to obtain a 7-solid mixture. The 7-solid mixture was then transferred to a vacuum drying oven and dried at 100°C under vacuum for 12 hours to obtain the 7-CeO2 / RuW precursor.

[0134] S5 The 7-CeO2 / RuW precursor was placed in a tube furnace and reduced for 1 hour in an atmosphere containing 10% H2 / Ar to obtain the 7-CeO2 / RuW composite catalyst prepared in Example 7.

[0135] Inductively coupled plasma atomic emission spectrometry (ICP) analysis of the 7-CeO2 / RuW composite catalyst revealed that the catalyst contained 5.79% ruthenium and 9.48% tungsten.

[0136] (2) The 7-CeO2 / RuW composite catalyst prepared in Example 7 was used to catalytically cleave the CO bond in 2-phenoxy-1-acetophenone to obtain aromatic compounds (phenol, acetophenone and methyl benzoate).

[0137] Using 1 mmol of 0.2 mol / L 2-phenoxy-1-acetophenone as the substrate, and 5 ml of methanol as the reaction solvent, 0.1 g of 7-CeO2 / RuW composite catalyst was added. After thorough mixing in a sealed high-pressure reactor, N2 was introduced to bring the pressure inside the reactor to 0.3 MPa, and the temperature was raised to 185 °C. The reaction was allowed to proceed for 24 h. The reaction process is as follows:

[0138] After the reaction was completed, the mixture was cooled to room temperature, and the supernatant after centrifugation was subjected to chromatographic analysis. The conversion rate of 2-phenoxy-1-acetophenone was 92.78%, the yield of the target product phenol was 85.41%, the yield of acetophenone was 75.34%, and the yield of methyl benzoate was 25.89%.

[0139] Comparative Example 1

[0140] (1) Preparation of pure titanium dioxide catalyst (TiO2)

[0141] S1 pretreatment was performed by placing nano-TiO2 in a muffle furnace and calcining it at 550°C for 4 hours in an air atmosphere;

[0142] S2 weighed 3.18g of nano TiO2 and dissolved it in 50ml of deionized water. After stirring for 30min, solution d1' was obtained.

[0143] S3 put solution d1' into a rotary evaporator for rotary evaporation to obtain a solid mixture, and then transferred the solid mixture to a vacuum drying oven and dried at 100°C under vacuum for 12 hours to obtain TiO2 precursor;

[0144] S4 The TiO2 precursor was placed in a tube furnace and reduced for 1 hour in an atmosphere containing 10% H2 / Ar to obtain the TiO2 catalyst prepared in Comparative Example 1.

[0145] ① Changes in reaction time parameters

[0146] 1 mmol of 0.2 mol / L 2-phenoxy-1-acetophenone was used as the substrate, 10 ml of methanol was used as the reaction solvent, and 0.15 g of TiO2 was added as the catalyst. After mixing evenly in a closed high-pressure reactor, N2 was introduced to make the pressure in the high-pressure reactor reach 0.3 MPa, and the temperature was raised to 185 °C. The reaction time was set to 8, 16, 24 h and 32 h respectively, and the reaction experiments were carried out.

[0147] Comparative Example 2

[0148] (1) Preparation of pure titanium dioxide catalyst (TiO2 / W)

[0149] S1 pretreatment was performed by placing nano-TiO2 in a muffle furnace and calcining it at 550°C for 4 hours in an air atmosphere;

[0150] S2 Weigh 1.5g of ammonium metatungstate and dissolve it in 10ml of deionized water. Stir for 30min at room temperature and pressure until it is completely dissolved to obtain solution a2'.

[0151] S2 weighed 3.18g of nano TiO2 and dissolved it in 50ml of deionized water. After stirring for 30min, solution d2' was obtained.

[0152] S4. Solution a2' was added dropwise to solution d2'. The mixture was stirred for 24 hours at room temperature and pressure until homogeneous to obtain solution e2'. Solution e2' was placed in a rotary evaporator for rotary evaporation to obtain a solid mixture. The solid mixture was then transferred to a vacuum drying oven and dried at 100°C under vacuum for 12 hours to obtain the TiO2 / W precursor.

[0153] S5 The TiO2 / W precursor was placed in a tube furnace and reduced for 1 hour in an atmosphere containing 10% H2 / Ar to obtain the TiO2 / W composite catalyst prepared in Comparative Example 2.

[0154] (2) The TiO2 / W composite catalyst prepared above was used to catalytically crack the CO bond in 2-phenoxy-1-acetophenone to obtain aromatic compounds (phenol, acetophenone and methyl benzoate), and the reaction time parameters were set to change in a gradient for the experiment.

[0155] ① Changes in reaction time parameters

[0156] 1 mmol of 0.2 mol / L 2-phenoxy-1-acetophenone was used as the substrate, 10 ml of methanol was used as the reaction solvent, and 0.15 g of TiO2 / W composite catalyst was added. After mixing evenly in a closed high-pressure reactor, N2 was introduced to make the pressure in the high-pressure reactor reach 0.3 MPa, and the temperature was raised to 185 °C. The reaction time was set to 8, 16, 24 h and 32 h respectively, and the reaction experiments were carried out.

[0157] Comparative Example 3

[0158] (1) Preparation of pure titanium dioxide catalyst (TiO2 / Ru)

[0159] S1 pretreatment was performed by placing nano-TiO2 in a muffle furnace and calcining it at 550°C for 4 hours in an air atmosphere;

[0160] S2 Weigh 0.474g of ruthenium chloride and dissolve it in 10ml of deionized water. Stir for 30min at room temperature and pressure until it is completely dissolved to obtain solution b3'.

[0161] S2 weighed 3.18g of nano TiO2 and dissolved it in 50ml of deionized water. After stirring for 30min, solution d3' was obtained.

[0162] S4. Solution b3' was added dropwise to solution d3'. The mixture was stirred for 24 hours at room temperature and pressure until homogeneous to obtain solution e3'. Solution e3' was placed in a rotary evaporator for rotary evaporation to obtain a solid mixture. The solid mixture was then transferred to a vacuum drying oven and dried at 100°C under vacuum for 12 hours to obtain the TiO2 / Ru precursor.

[0163] S5 The TiO2 / Ru precursor was placed in a tube furnace and reduced for 1 hour in an atmosphere containing 10% H2 / Ar to obtain the TiO2 / Ru composite catalyst prepared in Comparative Example 3.

[0164] (2) The TiO2 / W composite catalyst prepared above was used to catalyze the cleavage of the CO bond in 2-phenoxy-1-acetophenone to obtain aromatic compounds (phenol, acetophenone, and methyl benzoate). The reaction time parameters were set with gradient changes for the experiment. After the reaction was completed, the mixture was cooled to room temperature, and the supernatant after centrifugation was used for chromatographic analysis.

[0165] ① Changes in reaction time parameters

[0166] 1 mmol of 0.2 mol / L 2-phenoxy-1-acetophenone was used as the substrate, 10 ml of methanol was used as the reaction solvent, and 0.15 g of TiO2 / Ru composite catalyst was added. After mixing evenly in a closed high-pressure reactor, N2 was introduced to make the pressure in the high-pressure reactor reach 0.3 MPa, and the temperature was raised to 185 °C. The reaction time was set to 8, 16, 24 h and 32 h respectively, and the reaction experiments were carried out.

[0167] Comparative Example 4

[0168] The difference between Comparative Example 4 and the other comparative examples is that the catalyst prepared in this invention was not added, and 2-phenoxy-1-acetophenone was directly converted using the same method as described above.

[0169] ① Changes in reaction time parameters

[0170] 1 mmol of 0.2 mol / L 2-phenoxy-1-acetophenone was used as the substrate, and 10 ml of methanol was used as the reaction solvent. After being mixed evenly in a closed high-pressure reactor, N2 was introduced to make the pressure in the high-pressure reactor reach 0.3 MPa, and the temperature was raised to 185 °C. The reaction time was set to 8, 16, 24 h and 32 h respectively, and the reaction experiments were carried out.

[0171] Comparative performance test

[0172] In this embodiment of the invention, the effects of reaction time and different types of catalysts on the conversion of 2-phenoxy-1-acetophenone and the yields of the target products phenol, acetophenone, and methyl benzoate were investigated when different types of catalysts prepared in Example 1 and Comparative Examples 1-3 were used to catalyze the CO bond cleavage in 2-phenoxy-1-acetophenone and when the CO bond cleavage in 2-phenoxy-1-acetophenone was performed without a catalyst in Comparative Example 4. Gas chromatography was used for qualitative and quantitative analysis of the products.

[0173] Please refer to Figures 4(a)-4(d). Figure 4(a) shows the conversion rate of 2-phenoxy-1-acetophenone in the CO bond cleavage of 2-phenoxy-1-acetophenone by different types of catalysts prepared in Example 1 and Comparative Examples 1-3 of the present invention as a function of reaction time. Figure 4(b) shows the yield of phenol in the CO bond cleavage of 2-phenoxy-1-acetophenone by different types of catalysts prepared in Example 1 and Comparative Examples 1-3 of the present invention and Comparative Example 4 without catalyst as a function of reaction time. Figure 4(c) shows the yield of methyl benzoate in the CO bond cleavage of 2-phenoxy-1-acetophenone by different types of catalysts prepared in Example 1 and Comparative Examples 1-3 of the present invention and Comparative Example 4 without catalyst as a function of reaction time. Figure 4(d) shows the yield of acetophenone in the CO bond cleavage of 2-phenoxy-1-acetophenone by different types of catalysts prepared in Example 1 and Comparative Examples 1-3 of the present invention and Comparative Example 4 without catalyst as a function of reaction time. As can be seen from Figure 4(a), the 1-TiO2 / RuW composite catalyst prepared in Example 1 showed the highest conversion rate of 2-phenoxy-1-acetophenone substrate, significantly higher than other types of catalysts, exhibiting better activity and yield. By setting different reaction times, it can be observed that when the reaction temperature is 185℃ and the reaction time is 32h, the conversion rate can reach 62%, and the yields of phenol, methyl benzoate, and acetophenone can reach 56%, 16%, and 43%, respectively. Under mild conditions, 1-TiO2 / RuW exhibits higher catalytic activity for 2-phenoxy-1-acetophenone compared to other catalysts.

[0174] Please refer to Figures 5 and 6. Figure 5 shows the X-ray diffraction (XRD) patterns of different types of catalysts prepared in Example 1 and Comparative Examples 1-3 of the present invention. Figure 6 shows the adsorption / desorption isotherms of different types of catalysts prepared in Example 1 and Comparative Examples 1-3 of the present invention.

[0175] As shown in Figure 5, the 1-TiO2 / RuW composite catalyst prepared in Example 1 contains both the TiO2 crystal structure and the RuW alloy crystal structure. The BET characterization in Figure 6 shows that, compared to other catalysts, 1-TiO2 / RuW has a larger specific surface area, reaching 78.25 m² / g, indicating that the RuW bimetallic catalyst was successfully impregnated onto the TiO2 support. This novel composite catalyst exhibits higher activity and stability.

[0176] This invention employs an impregnation method to load RuW alloys onto a metal oxide support. The key advantage lies in the absence of organic solvents during preparation, along with mild reaction conditions that allow for mixing and stirring at room temperature and pressure. This catalyst is used to catalyze the cleavage of CO bonds in lignin model compounds to prepare aromatic compounds, exhibiting high catalytic efficiency, strong stability, high lignin conversion rate, and improved yield of the target product.

[0177] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments. It should be noted that many modifications and improvements can be made by those skilled in the art, and all modifications or improvements not exceeding the scope of the claims should be considered within the protection scope of the present invention.

Claims

1. A method for preparing a metal oxide / ruthenium-tungsten composite catalyst, the method comprising: S1 Weigh a certain amount of nano-metal oxide and place it in a muffle furnace. Then, perform high-temperature calcination in air atmosphere to obtain pretreated nano-metal oxide. S2 weighs a certain amount of tungstate and dissolves it in deionized water, stirring until homogeneous at room temperature and pressure to obtain solution a; weighs a certain amount of ruthenium chloride and dissolves it in deionized water, stirring until homogeneous at room temperature and pressure to obtain solution b; then mixes solution a and solution b and stirs until homogeneous to obtain solution c; S3 dissolves the pretreated nano-metal oxides in deionized water and stirs them at room temperature and pressure to obtain solution d; S4. Solution c is added dropwise to solution d and stirred evenly at room temperature and pressure to obtain solution e. Solution e is subjected to rotary evaporation and vacuum drying to obtain the metal oxide / ruthenium tungsten composite catalyst precursor. S5 involves adding a reducing agent to the metal oxide / ruthenium-tungsten composite catalyst precursor for reduction treatment to obtain the metal oxide / ruthenium-tungsten composite catalyst.

2. The preparation method according to claim 1, characterized in that, The metal oxide mentioned in step S1 is any one of titanium dioxide, zinc oxide, zirconium oxide, niobium pentoxide, magnesium oxide, and cerium oxide; the high-temperature calcination treatment temperature in step S1 is 500-700℃, and the treatment time is 4-6h.

3. The preparation method according to claim 1, characterized in that, The tungstate in step S2 is any one of ammonium metatungstate, tungsten chloride, and tungsten nitrate; the concentration of solution a in step S2 is 0.15–0.3 g / ml; the concentration of solution b is 0.04–0.06 g / ml; and the volume ratio of solution a to solution b in solution c is 1:

1.

4. The preparation method according to claim 1, characterized in that, The concentration of solution d in step S3 is 0.06–0.08 g / ml.

5. The preparation method according to claim 1, characterized in that, In step S4, the volume ratio of solution c to solution d in solution e is 1:5; the vacuum drying process uses a vacuum drying oven with a drying temperature of 80–200°C and a drying time of 12–36 hours.

6. The preparation method according to claim 1, characterized in that, The reducing agent in step S5 is either H2 / Ar gas containing 10% or hydrazine hydrate; the reduction treatment time is 1 to 3 hours.

7. The preparation method according to claim 1, characterized in that, The molar doping ratio of ruthenium in the metal oxide / ruthenium-tungsten composite catalyst is 0.01–9%; the molar doping ratio of tungsten in the metal oxide / ruthenium-tungsten composite catalyst is 1–30%.

8. A metal oxide / ruthenium-tungsten composite catalyst obtained by the preparation method as described in claims 1 to 7.

9. The application of the metal oxide / ruthenium-tungsten composite catalyst as described in claim 8 in catalyzing the cleavage of CO bonds in lignin, characterized in that, Using lignin model compounds as substrates and small molecule alcohols as solvents, a certain amount of metal oxide / ruthenium-tungsten composite catalyst was added. After being stirred evenly in a closed high-pressure reactor, H2 or N2 was introduced to make the pressure inside the reactor 0.1–2.0 MPa, and the temperature inside the reactor was adjusted to 165–380 °C to carry out the catalytic cracking reaction of the substrate. The reaction time was 8–32 h to prepare aromatic monomer compounds.

10. The application according to claim 9, characterized in that, The catalyst is used in an amount of 0.05–0.2 g, the volume of the small molecule alcohol is 5–10 ml, and the concentration of the lignin model compound is 0.1–0.2 mol / L.

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