Vanadium-based catalyst for the catalytic oxidation of 4-methylphenol to synthesize vanillin and preparation and method for manufacturing vanillin

Abstract

The present application provides a kind of for catalytic oxidation 4-methyl phenol synthesis vanadium-based catalyst and preparation and vanillin class of manufacturing method, vanadium-based support, the support contains the composite particles of vanadium and X (X indicates at least one element selected from the group consisting of cobalt, iron, nickel, cerium) constitute oxidation state and load the carrier of the above composite nanoparticles, wherein shell surface does not contain composite particles, and composite particles are distributed in the local area below the outer surface of composite nanoparticle support.The catalyst is used for catalytic oxidation 4-methyl phenol synthesis vanillin class of reaction.The catalyst of the present application is good in water resistance, acid and alkali resistance compared with existing catalyst, can still maintain high mechanical strength and chemical stability during long time reaction process, and has the advantages such as simple preparation method, relatively low cost.

Description

Technical Field

[0001] This invention relates to a composite particle supported on a support, comprising vanadium in an oxidized state and X (X representing at least one element selected from the group consisting of cobalt, iron, nickel, and cerium), and a method for manufacturing the composite particle supported on a support as a catalyst for the catalytic oxidation of 4-methylphenols to vanillin. Background Technology

[0002] Vanillin, also known as vanillin, with the chemical name 3-methoxy-4-hydroxybenzaldehyde, is an organic compound extracted from vanilla beans, a plant in the Rutaceae family. Vanillin has a rich milky and vanilla bean aroma, and acts as a fixative and flavor enhancer. It is widely used in cosmetics, tobacco, pastries, confectionery, and baked goods industries, and is one of the world's largest-produced synthetic flavorings. Industrial production of vanillin has a history of over 100 years.

[0003] Currently, the main industrial processes for producing vanillin include the lignin process, the guaiacol process, the safrole process, and the eugenol process. These traditional synthesis processes suffer from varying degrees of problems, such as long reaction routes, low yields, numerous side reactions, and high levels of waste. Since 2005, some domestic companies have adopted the glyoxylic acid process to produce vanillin. However, the price of domestically produced glyoxylic acid is relatively high, and some key technical issues, such as oxidation stability, wastewater reuse (approximately 20 tons of wastewater are generated for every ton of vanillin produced), and low product yields, have not yet been well resolved.

[0004] Patent reports have described the direct oxidation of vanillin to vanillin using heterogeneous catalysts. For example, patent CN102527389A describes a heterogeneous catalyst using cobalt-iron as the active component; patent CN101234351A discloses a supported solid metal oxide catalyst using transition metal oxides as the active component, at least one of alumina, silica, titanium dioxide, and activated carbon as the support, and rare earth elements as co-catalysts; and patent CN104607182A discloses a supported catalyst with nano-palladium as the active component for the direct oxidation of vanillin. However, due to the relatively high price of vanillin and the immature synthesis process, widespread application is currently not possible.

[0005] The p-cresol process, which uses p-cresol as a raw material and involves the one-step oxidation of 4-methylguaiacol to prepare vanillin, has attracted considerable attention. This method utilizes widely available raw materials, has a simple process route, is inexpensive, and is characterized by its simplicity, safety, and convenient post-processing. Furthermore, it generates minimal waste and produces a high-quality product, equivalent to its natural counterpart. Therefore, the p-cresol oxidation process holds significant development potential and technological advantages. However, the one-step oxidation of 4-methylguaiacol to vanillin is a challenging aspect of this process, resulting in a relatively low yield. Therefore, the preparation of a suitable catalyst is crucial for this process route.

[0006] In recent years, many patents have reported the homogeneous synthesis of vanillin in strong alkali and alcohol solutions using transition metal salts (such as Co, Cr, Mn, Cu, Ni, Zn, etc.) as catalysts, achieving a conversion rate of up to 90% (among which cobalt salt catalysts are common and widely used, vanillin yields can reach over 70%). However, using homogeneous catalysts in homogeneous reactions results in low vanillin yields, difficulty in separation, and secondary environmental pollution. Therefore, preparing an excellent heterogeneous catalyst and implementing a heterogeneous process is a way to solve this technical problem. Patent CN106986756 A introduces a heterogeneous reaction system to prepare a heterogeneous supported catalyst with nano-cobalt as the active component and porous nitrogen-doped carbon material as the support. This layered catalyst heterogeneously catalyzes the oxidation of 4-methylguaiacol, achieving a 100% conversion rate and a maximum selectivity of 90%. Patent CN104162444 A discloses a layered catalyst with cobalt as the active component. This layered catalyst achieves 100% conversion and a selectivity of up to 66% in the heterogeneous oxidation of 4-methylguaiacol. However, due to market monopolies, these technologies cannot meet the demands of my country's market, making the development of more superior novel heterogeneous catalysts essential. Summary of the Invention

[0007] To fill a technological gap in my country, our research group has developed a vanadium-based composite particle catalyst for the catalytic oxidation of 2-methoxy-4-methylphenol to vanillin. Compared to existing catalysts, this catalyst is free of precious metals, exhibits excellent water and acid / alkali resistance, maintains high mechanical strength and chemical stability during prolonged reactions, and boasts advantages such as simple preparation method and low cost. When used for the catalytic synthesis of vanillin, it achieves a maximum 4-methylphenol conversion of 98% and a maximum selectivity of 93%, while reducing other byproducts and post-processing costs.

[0008] This patent provides a multi-component water-resistant catalyst with a "core-shell" structure. The shell surface does not contain VmXn composite particles; instead, these composite particles are distributed locally below the outer surface of the supported material. This design offers advantages such as simple preparation, low cost, and good long-term reaction stability. The VmXn composite particles are not uniformly loaded into the support, reducing the diffusion barrier between the support and reactants / products. The absence of composite particles in the "shell" reduces the problem of active sites being covered and deactivated due to byproduct adsorption. Furthermore, the catalyst shell minimizes the loss of active components caused by mechanical wear.

[0009] When this composite particle-supported material is used in the preparation reaction of vanillin, the conversion rate of 2-methoxy-4-methylphenol is as high as 98% and that of 2-methoxy-4-methylphenol is as high as 93%. After 9 reactions, the activity of the catalyst remains basically unchanged. ICP detection before and after the reaction shows only trace amounts of vanadium stripping and dissolution, which effectively solves the above-mentioned problems.

[0010] The implementation method of the present invention is as follows:

[0011] 1. A vanadium-based catalyst for the catalytic oxidation of 4-methylphenol to vanillin, characterized in that the catalyst contains vanadium in an oxidized state and X supported on a support in an atomic ratio of V / X ranging from 0.01 to 6 (preferably 0.3 to 0.8, more preferably 0.5 to 0.8).

[0012] Vanadium is in the pentavalent state, and X represents at least one element selected from the group consisting of cobalt, iron, nickel, and cerium.

[0013] 2. The vanadium-based catalyst for the catalytic synthesis of vanillin according to claim 1, characterized in that the catalyst is composed of composite nanoparticles of oxidized vanadium and oxides of X, with a particle size of... Here, X represents iron. Transmission electron microscopy (TEM) observations show that nearly spherical nanoparticles of 2-5 nm in size are uniformly dispersed and loaded onto a support. Elemental analysis of the nanoparticles using energy-dispersive X-ray spectroscopy (EDS) revealed that each particle contains both vanadium and iron, with the iron forming a coating on the surface of the vanadium nanoparticles.

[0014] 3. The vanadium-based catalyst for the catalytic synthesis of vanillin according to claim 2, characterized in that the aforementioned composite nanoparticles are formed by first preparing a support, and then loading oxidized vanadium and oxidized X onto the support. A comparison of Examples 5 and 6, 7, 8, and 9 suggests that vanadium and X are loaded onto the support in a composite manner, and that vanadium and X may form an alloy-like structure, altering their electron cloud state. The oxidized vanadium and oxidized X are the active components, and the support surface contains very few active components, which are mainly distributed in a localized area below the outer surface of the composite particle support. Example 7, through EDX electron imaging, shows that the vanadium content on the support surface is extremely low, thus suggesting that the active component composite particles should be mainly distributed below the surface of the support.

[0015] 4. The vanadium-based catalyst for the catalytic synthesis of vanillin according to claim 1, wherein the support is a composite oxide containing silica, alumina, and oxides of other metal elements, wherein the molar proportions of the elements other than oxygen are as follows: Silicon in the molar range The proportions of aluminum, silicon, and other elements in the range of molar percentage are as follows: mole %;

[0016] Other elements are selected from one or more of the five elements: magnesium, iron, erbium, lanthanum, and cerium (e.g., silicon dioxide-aluminum oxide-magnesium oxide, silicon dioxide-aluminum oxide-magnesium oxide-titanium oxide, silicon dioxide-aluminum oxide-lanthanum oxide, silicon dioxide-aluminum oxide-magnesium oxide-cerium dioxide, etc.).

[0017] 5. The vanadium-based catalyst for the catalytic synthesis of vanillin according to claim 4, characterized in that the specific surface area of ​​the support is [missing information]. The diameter of the fine hole is The pore capacity is Particle size

[0018] 6. Based on the above The vanadium-based catalyst for the catalytic synthesis of vanillin has a manganese to silicon oxide composition ratio based on the Mn / Si atomic ratio of [missing information]. (Preferred 0.01-0.2, more preferably 0.01-0.1).

[0019] 7. Based on the above The vanadium-based catalyst for the catalytic synthesis of vanillin according to any one of the claims is characterized in that the catalyst is prepared by first preparing a support, and then loading oxidized vanadium and oxidized X onto the support;

[0020] Preparation of composite oxide supports:

[0021] An aqueous solution of two or three oxides selected from Al2O3, MgO, Ti2O3, La2O3, and CeO2, and an aqueous solution of SiO2 precursor, is prepared at 0-100°C (preferably 30-50°C) and concentrated nitric acid (concentration range 60%-85%, weight equal to 30% of the silica sol weight). Mix thoroughly (times by weight), stir and mature at 50-80℃ for 10-48 hours, and then use spray drying molding technology to obtain composite oxide carriers (particle size 20-450μm, specific surface area of...). Hole diameter is The orifice capacity is ).

[0022] The precursor of SiO2 is selected from […]. Silica sol;

[0023] The precursor of MgO is selected from one or more magnesium salts such as magnesium oxalate, magnesium acetate, magnesium nitrate, magnesium chloride, magnesium hydroxide, magnesium carbonate, or magnesium oxide.

[0024] The precursor of Al2O3 is selected from one or more aluminum salts such as aluminum hydroxide, ammonium aluminum carbonate, ammonium aluminum sulfate, aluminum bicarbonate, aluminum nitrate, or aluminum trichloride.

[0025] The precursor of La2O3 is selected from one or more lanthanum salts such as lanthanum nitrate and lanthanum acetate;

[0026] The precursor of TiO2 is selected from one or more titanium salts such as titanium nitrate and titanium acetate;

[0027] The precursor of CeO2 is selected from one or both of cerium nitrate and cerium ammonium nitrate.

[0028] 8. The method for preparing the catalyst according to claim 7, wherein loading oxidized vanadium and oxidized X onto a support comprises the following steps:

[0029] In the first step, prepare an aqueous solution containing soluble metal salts of vanadium and X, add a precipitant and a composite oxide support, and react at 50-100°C. After cooling the mixture to room temperature, filter it to obtain the solid.

[0030] The concentration of vanadium in aqueous solution is (Preferably 0.01-0.05, more preferably 0.01-0.04);

[0031] The precipitant is selected from one or both of urea and hexamethyltetramine, and its concentration in aqueous solution is [missing information]. (Preferably 0.1-0.6, more preferably 0.2-0.5);

[0032] The soluble metal salts of vanadium are one or two of sodium metavanadate and potassium metavanadate.

[0033] The soluble metal salt of X is one or more of the following: cobalt nitrate, cobalt acetate, cerium nitrate hexahydrate, cerium ammonium nitrate, ferric nitrate nonahydrate, ferric acetate, nickel acetate, and nickel nitrate.

[0034] The second step involves drying the obtained catalyst precursor by heat treatment at 30-100℃, followed by high-temperature calcination to bring vanadium to an oxide state.

[0035] The calcination is carried out in a muffle furnace; the calcination temperature is 300–900℃, preferably 400–600℃, and the calcination time is 2–20h, preferably 2–8h.

[0036] A method for producing vanillin, characterized in that: 4-methylphenol is oxidized in one step to produce vanillin in the presence of the vanadium-based catalyst and oxygen and / or air;

[0037] The reaction conditions are as follows: 4-methylphenol, a protic solvent, an inorganic base, and the catalyst prepared in steps 1-11 above are placed in a reaction vessel. An oxygen source, such as oxygen, air, or a mixture containing oxygen, is added. The reaction is carried out at 70-100°C for 8-15 hours, and the gas phase reaction is completed under control. The reaction solution is treated as follows: the reaction solution is filtered, and the filtrate is neutralized with concentrated hydrochloric acid to a pH of 3-6. A certain amount of the treated liquid is measured and subjected to qualitative and quantitative analysis using high-performance gas chromatography. Based on the established standard curve, the yield of the product vanillin is determined using the internal standard method.

[0038] The reactor has a capacity of 250 ml and is matched to the oxygen source gas flow rate.

[0039] The aforementioned 4-methylphenol refers to 4-methylphenol and 2-methoxy-4-methylphenol.

[0040] The aforementioned proton solvents are ethylene glycol, ethylene glycol monomethyl ether, isopropanol, ethylene glycol dimethyl ether, and water, and the mass ratio of 4-methylphenol to the proton solvent is [missing information].

[0041] The aforementioned inorganic base is sodium hydroxide, lithium hydroxide, or potassium hydroxide, and the molar ratio of 4-methylphenol to the inorganic base is [missing information]. Detailed implementation method:

[0042] The present invention is not limited to the following embodiments, and can be implemented in various ways within the scope of its spirit.

[0043] Carrier preparation examples

[0044] Example 1

[0045] 30% silica sol (pH=4.5) (20g, 10mmol), aluminum nitrate nonahydrate (3g, 8mmol), magnesium hydroxide (0.116g, 2mmol), 6g of 65% concentrated nitric acid, and 120mL of deionized water were mixed thoroughly at 25℃. The mixture was then stirred and matured at 50℃ for 24h to obtain a homogeneous solid solution suspension. A spray-drying process was used to obtain a composite oxide-supported SiO2-Al2O3-MgO (the molar ratio of silicon, aluminum, and magnesium in this support is 50:40:10; particle size is 50-100μm; specific surface area is 280m²). 2 / g, pore diameter is The pore capacity is 0.7 mL / g.

[0046] Example 2

[0047] 30% silica sol (pH=4.5) (20g, 10mmol), aluminum nitrate nonahydrate (2.25g, 6mmol), magnesium hydroxide (0.058g, 1mmol), titanium nitrate (0.3g, 1mmol), 4g of 80% concentrated nitric acid, and 120mL of deionized water were mixed uniformly at 25℃. The mixture was then stirred and matured at 50℃ for 24h to obtain a homogeneous solid solution suspension. A spray-drying process was used to obtain a composite oxide carrier SiO2-Al2O3-MgO-TiO2 (the molar ratio of silicon, aluminum, magnesium, and titanium in this carrier is 55.6:33.3:5.6:5.5; particle size is 63-105μm; specific surface area is 302m² / g; pore diameter is...). The pore capacity is 0.7 mL / g.

[0048] Example 3

[0049] A mixture of 30% silica sol (pH=4.5) (20 g, 10 mmol), aluminum nitrate nonahydrate (2.25 g, 6 mmol), lanthanum nitrate hexahydrate (0.433 g, 1 mmol), 6 g of 60% concentrated nitric acid, and 120 mL of deionized water was stirred and matured at 50 °C for 24 h to obtain a homogeneous solid solution suspension. A spray-drying process was then used to obtain a composite oxide support SiO2-Al2O3-La2O3 (the molar ratio of silicon, aluminum, and lanthanum in this support was 58.8:35.3:5.9; the particle size was 55-105 μm; and the specific surface area was 310 m²). 2 / g, pore diameter is The pore capacity is 0.8 mL / g.

[0050] Example 4

[0051] 30% silica sol (pH=4.5) (20g, 10mmol), aluminum nitrate nonahydrate (1.13g, 3mmol), magnesium hydroxide (0.058g, 1mmol), and cerium nitrate hexahydrate (0.434g, 1mmol) were mixed with 6g of 75% concentrated nitric acid and 120mL of deionized water at 25℃ until homogeneous. The mixture was then stirred and matured at 50℃ for 24h to obtain a homogeneous solid solution suspension. A spray-drying process was used to obtain a composite oxide carrier SiO2-Al2O3-MgO-CeO2 (the molar ratio of silicon, aluminum, magnesium, and cerium in this carrier is 66.7:20:6.7:6.6, the particle size is 58-100μm, and the specific surface area is 320m²). 2 / g, pore diameter is The pore capacity is 0.9 mL / g.

[0052]

[0053] Catalyst Preparation Examples

[0054] Example 5

[0055] In a reactor, 6 g of SiO2-Al2O3-MgO support A, 1.5 g of urea, 0.244 g of sodium metavanadate (2 mmol), and 60 mL of deionized water were added sequentially and mixed thoroughly. The mixture was reacted at 80 °C for 0.5 h. After cooling to room temperature, the mixture was filtered. The resulting solid was vacuum dried at 80 °C for 1 h and then calcined in a muffle furnace at 600 °C for 3 h. After cooling, catalyst A1 was obtained, with a vanadium content of 1.32% and a V / Si atomic ratio of 0.0290. Electron microscopy (EM) images showed that the vanadium content on the support surface was 0. The particle size of the active vanadium particles was determined to be 2-3 nm.

[0056] Example 6

[0057] In a reactor, 6 g of SiO2-Al2O3-MgO support A, 1.5 g of urea, 0.244 g (2 mmol) of sodium metavanadate, 1.74 g (4 mmol) of cerium nitrate hexahydrate, and 60 mL of deionized water were added sequentially and mixed thoroughly. The mixture was reacted at 80 °C for 0.5 h. After cooling to room temperature, the mixture was filtered. The resulting solid was vacuum dried at 80 °C for 1 h and then calcined at 600 °C for 3 h in a muffle furnace. After cooling, catalyst A2 was obtained, with a vanadium content of 1.23%, a cerium content of 5.91%, a V / Ce atomic ratio of 0.571, and a V / Si atomic ratio of 0.0286. Electron microscopy (EM) images showed that the vanadium content on the support surface was 0.001 of all elements (i.e., the support surface contained very few active components, which were mainly distributed in a localized area below the outer surface of the composite particle support). SEM measurements showed that the particle size of the active vanadium-cerium composite particles was 2-3 nm.

[0058] Example 7

[0059] In a reactor, 6 g of SiO2-Al2O3-MgO support A, 1.5 g of urea, 0.244 g (2 mmol) of sodium metavanadate, 1.21 g (3 mmol) of ferric nitrate nonahydrate, and 60 mL of deionized water were added sequentially and mixed thoroughly. The mixture was reacted at 80 °C for 0.5 h. After cooling to room temperature, the mixture was filtered. The resulting solid was vacuum dried at 80 °C for 1 h and then calcined at 600 °C for 3 h in a muffle furnace. After cooling, catalyst A3 was obtained, with a vanadium content of 1.29%, an iron content of 1.86%, and a V / Fe atomic ratio of 0.762. The particle size of the active manganese-cerium composite particles was determined to be 2-5 nm by electron microscopy (SEM). The V / Si atomic ratio was 0.0285. EDX electron images showed that the vanadium content on the support surface was 0 (i.e., the support surface contained very little active component, and the active component was mainly distributed in a local area below the outer surface of the composite particle support). The particle size of the active vanadium-iron composite particles was determined to be 2-3 nm by electron microscopy (SEM).

[0060] Example 8

[0061] In a reactor, 6 g of SiO2-Al2O3-MgO support A, 1.5 g of urea, 0.244 g (2 mmol) of sodium metavanadate, 0.873 g (3 mmol) of cobalt nitrate hexahydrate, and 60 mL of deionized water were added sequentially and mixed thoroughly. The mixture was reacted at 80 °C for 0.5 h. After cooling to room temperature, the mixture was filtered. The resulting solid was vacuum dried at 80 °C for 1 h and then calcined in a muffle furnace at 600 °C for 3 h. After cooling, catalyst A4 was obtained, with a vanadium content of 1.29%, a cobalt content of 1.96%, a V / Co atomic ratio of 0.761, and a V / Si atomic ratio of 0.0288. Electron microscopy (EM) images showed that the vanadium content on the support surface was 0 (i.e., the support surface contained very little active component, and the active component was mainly distributed in a local area below the outer surface of the composite particle support). SEM measurements showed that the particle size of the active vanadium-cobalt composite particles was 2-3 nm.

[0062] Example 9

[0063] In a reactor, 6 g of SiO2-Al2O3-MgO support A, 1.5 g of urea, sodium metavanadate (0.244 g, 2 mmol), nickel hexahydrate, nickel nitrate (0.872 g, 3 mmol), and 60 mL of deionized water were added sequentially and mixed thoroughly. The mixture was reacted at 80 °C for 0.5 h. After cooling to room temperature, the mixture was filtered. The resulting solid was vacuum dried at 80 °C for 1 h and then calcined in a muffle furnace at 600 °C for 3 h. After cooling, catalyst A5 was obtained, with a vanadium content of 1.29%, a nickel content of 1.95%, a V / Ni atomic ratio of 0.760, and a V / Si atomic ratio of 0.0286. EDX electron imaging showed that the vanadium content on the support surface was 0.001 of all elements (i.e., the support surface contained very few active components, which were mainly distributed in a local area below the outer surface of the composite particle support). SEM analysis showed that the particle size of the active vanadium-nickel composite particles was 2-3 nm.

[0064] Example 10

[0065] In a reactor, 6 g of SiO2-Al2O3-MgO-TiO2 support B, 0.8 g of hexamethyltetramine, sodium metavanadate (0.244 g, 2 mmol), ferric nitrate nonahydrate (1.21 g, 3 mmol), and 60 mL of deionized water were added sequentially and mixed thoroughly. The mixture was reacted at 80 °C for 0.5 h. After cooling to room temperature, the mixture was filtered. The resulting solid was vacuum dried at 80 °C for 1 h and then calcined in a muffle furnace at 600 °C for 3 h. After natural cooling, catalyst B was obtained, with a vanadium content of 1.29%, an iron content of 2.74%, a V / Fe atomic ratio of 0.761, and a V / Si atomic ratio of 0.0286. Electron microscopy (EM) images showed that the vanadium content on the support surface was 0.001 of all elements (i.e., the support surface contained very few active components, which were mainly distributed in a localized area below the outer surface of the composite particle support). SEM measurements showed that the particle size of the active vanadium-iron composite particles was 2-3 nm.

[0066] Example 11

[0067] In a reactor, 6 g of SiO2-Al2O3-La2O3 support C, 0.8 g of hexamethyltetramine, 0.244 g (2 mmol) of sodium metavanadate, and 60 mL of deionized water were added sequentially and mixed thoroughly. The mixture was reacted at 80 °C for 0.5 h. After cooling to room temperature, the mixture was filtered, and the resulting solid was vacuum dried at 80 °C for 1 h and then calcined at 600 °C for 3 h in a muffle furnace. After natural cooling, catalyst C1 was obtained, with a vanadium content of 1.32% and a V / Si atomic ratio of 0.0285. EDX electron imaging showed that the vanadium content on the support surface was 0 (i.e., the support surface contained very little active component, and the active component was mainly distributed in a local area below the outer surface of the composite particle support). SEM analysis showed that the particle size of the active vanadium particles was 2-3 nm.

[0068] Example 12

[0069] In a reactor, 6 g of SiO2-Al2O3-La2O3 support C, 0.8 g of hexamethyltetramine, sodium metavanadate (0.244 g, 2 mmol), ferric nitrate nonahydrate (1.21 g, 3 mmol), and 60 mL of deionized water were added sequentially and mixed thoroughly. The mixture was reacted at 80 °C for 0.5 h. After cooling to room temperature, the mixture was filtered. The resulting solid was vacuum dried at 80 °C for 1 h and then calcined in a muffle furnace at 600 °C for 3 h. After natural cooling, catalyst C2 was obtained, with a vanadium content of 1.29%, an iron content of 1.85%, a V / Fe atomic ratio of 0.763, and a V / Si atomic ratio of 0.0284. Electron microscopy (EM) images showed that the vanadium content on the support surface was 0.001 of all elements (i.e., the support surface contained very few active components, which were mainly distributed in a localized area below the outer surface of the composite particle support). SEM measurements of the active vanadium-iron composite particles showed a particle size of 2-3 nm.

[0070] Example 13

[0071] In a reactor, 6 g of SiO2-Al2O3-La2O3 support C, 0.8 g of hexamethyltetramine, sodium metavanadate (0.244 g, 2 mmol), nickel hexahydrate, nickel nitrate (0.872 g, 3 mmol), and 60 mL of deionized water were added sequentially and mixed thoroughly. The mixture was reacted at 80 °C for 0.5 h. After cooling to room temperature, the mixture was filtered. The resulting solid was vacuum dried at 80 °C for 1 h and then calcined in a muffle furnace at 600 °C for 3 h. After natural cooling, catalyst C3 was obtained, with a vanadium content of 1.293%, a nickel content of 1.96%, a V / Ni atomic ratio of 0.760, and a V / Si atomic ratio of 0.0285. EDX electron imaging showed that the vanadium content on the support surface was 0.001 of all elements (i.e., the support surface contained very few active components, which were mainly distributed in a local area below the outer surface of the composite particle support). SEM analysis showed that the particle size of the active vanadium-nickel composite particles was 2-3 nm.

[0072] Example 14

[0073] In a reactor, 6 g of SiO2-MgO-Al2O3-CeO2 support D, 0.8 g of hexamethyltetramine, 0.244 g (2 mmol) of sodium metavanadate, and 60 mL of deionized water were added sequentially and mixed thoroughly. The mixture was reacted at 80 °C for 0.5 h. After cooling to room temperature, the mixture was filtered, and the resulting solid was vacuum dried at 80 °C for 1 h and then calcined in a muffle furnace at 500 °C for 3 h. After cooling, catalyst D1 was obtained, with a vanadium content of 1.325% and a V / Si atomic ratio of 0.0257. Electron microscopy (EM) images showed that the vanadium content on the support surface was 0 (i.e., the support surface contained very little active component, and the active component was mainly distributed in a local area below the outer surface of the composite particle support). SEM measurements showed that the particle size of the active vanadium particles was 2-3 nm.

[0074] Example 15

[0075] In a reactor, 6 g of SiO2-MgO-Al2O3-CeO2 support D, 0.8 g of hexamethyltetramine, sodium metavanadate (0.244 g, 2 mmol), cerium nitrate hexahydrate (1.31 g, 3 mmol), and 60 mL of deionized water were added sequentially and mixed thoroughly. The mixture was reacted at 80 °C for 0.5 h. After cooling to room temperature, the mixture was filtered. The resulting solid was vacuum dried at 80 °C for 1 h and then calcined in a muffle furnace at 500 °C for 3 h. After cooling, catalyst D2 was obtained, with a vanadium content of 1.252%, a cerium content of 6.67%, a V / Ce atomic ratio of 0.516, and a V / Si atomic ratio of 0.0256. Electron microscopy (EM) images showed that the vanadium content on the support surface was 0.001. SEM analysis of the active vanadium-cerium EDX images showed that the vanadium content on the support surface was 0.001 of all elements (i.e., the support surface contained very few active components, which were mainly distributed in a localized area below the outer surface of the composite particle support). Electron microscopy (SEM) determined the particle size of the active vanadium-nickel composite particles to be 2-3 nm.

[0076] Experimental results of catalysts for the preparation of vanillin (1):

[0077] 13.8 g of 2-methoxy-4-methylphenol, 82.8 g of ethylene glycol monomethyl ether, 8 g of sodium hydroxide, and 1.38 g of the catalysts prepared in Examples 5-15 above were placed in a 250 ml reactor. Oxygen was introduced at a rate of 10 ml / min, and the reaction was carried out at 80 °C for 12 hours until the reaction was completed.

[0078] The reaction solution was treated as follows: the reaction solution was filtered, and the filtrate was neutralized with concentrated hydrochloric acid to a pH of 3–6 (5 in this case). 5g of the treated solution was measured. Qualitative and quantitative analysis was performed using high-performance gas chromatography. Based on the established standard curve, 150mg of internal standard was added, and the yield of vanillin, the product of the reaction, was determined using the internal standard method.

[0079] Using biphenyl as an internal standard, a gas chromatography standard curve was prepared. 150 mg of internal standard was used to prepare standard solutions of 2-methoxy-4-methylphenol and 2-methoxy-4-aldehyde phenol with mass contents of 7%, 18%, 29%, 40%, 51%, 62%, 73%, 84%, and 95%, respectively, and then the standard curve was prepared.

[0080] The results of one and nine reactions (the catalyst was filtered out after the reaction and the above reaction process was repeated) are shown in Table 1.

[0081] Table 1

[0082]

[0083]

[0084] The results showed that when the composite particle-supported material was used for the preparation of vanillin, the conversion rate of 2-methoxy-4-methylphenol was the highest at 98%, and the selectivity of 2-methoxy-4-aldehyde phenol was the highest at 93%. After nine reactions, the activity of the catalyst remained basically unchanged.

Claims

1. A vanadium-based catalyst for the catalytic oxidation of 4-methylphenol and its derivatives to synthesize vanillin, characterized in that, The catalyst contains vanadium in its oxidized state and X, supported on a support in a V / X atomic ratio ranging from 0.01 to 6. Vanadium is in the pentavalent state, and X represents at least one or more elements selected from the group consisting of cobalt, iron, nickel, and cerium. The support is a composite oxide containing silicon dioxide, aluminum oxide, and oxides of other metal elements. The molar proportion of the metal elements other than oxygen is as follows: it contains 40-90 mol% silicon, 5.5-38 mol% aluminum, and 2-40 mol% other metal elements, selected from one or more of magnesium, lanthanum, cerium, and titanium. The support surface contains very few active components, which are mainly distributed in a local area below the outer surface of the composite particle load. The specific surface area of ​​the support is 20-360 m². 2 / g, with a pore diameter of 3-80nm, a pore capacity of 0.1-1.0mL / g, and a particle size of 20-450um, 4-methylphenol and its derivatives are 4-methylphenol and / or 2-methoxy-4-methylphenol.

2. The vanadium-based catalyst for the catalytic synthesis of vanillin-like compounds according to claim 1, characterized in that, The catalyst contains composite nanoparticles composed of vanadium in its oxidized state and X, with a particle size of 2-100 nm. X represents at least one or more elements selected from the group consisting of cobalt, iron, nickel, and cerium.

3. The vanadium-based catalyst according to claim 2, characterized in that, The catalyst contains composite nanoparticles composed of oxidized vanadium and X, with a particle size of 2-10 nm.

4. The vanadium-based catalyst for the catalytic synthesis of vanillin according to claim 1, The carrier is silicon dioxide-alumina-magnesium oxide, silicon dioxide-alumina-magnesium oxide-titanium oxide, silicon dioxide-alumina-lanthanum oxide, or silicon dioxide-alumina-magnesium oxide-cerium dioxide.

5. A method for preparing a vanadium-based catalyst for the catalytic synthesis of vanillin as described in any one of claims 1 to 3, characterized in that, The catalyst is prepared by first preparing a support, and then loading oxidized vanadium and oxidized X onto the support; Preparation of composite oxide supports: An aqueous solution of Al2O3 precursor, precursors of two or three oxides selected from MgO, TiO2, La2O3, and CeO2, and SiO2 precursor were mixed uniformly at 0-100℃ with concentrated nitric acid at a concentration of 60%-85%, where the weight of the concentrated nitric acid was 0.1-1.5 times the weight of the silica sol. The mixture was stirred and matured at 50-80℃ for 10-48 hours. A composite oxide carrier with a particle size of 20-450µm and a specific surface area of ​​20-360m² was obtained using spray drying molding technology. 2 / g, pore diameter of 3-80nm, pore capacity of 0.1-1.0mL / g; The precursor of SiO2 is selected from 20-60 wt% silica sol; The precursor of MgO is selected from one or more of magnesium oxalate, magnesium acetate, magnesium nitrate, magnesium chloride, magnesium hydroxide, magnesium carbonate, or magnesium oxide. The precursor of Al2O3 is selected from one or more of aluminum hydroxide, ammonium aluminum carbonate, ammonium aluminum sulfate, aluminum bicarbonate, aluminum nitrate or aluminum trichloride; The precursor of La2O3 is selected from one or both of lanthanum nitrate and lanthanum acetate. The precursor of TiO2 is selected from one or both of titanium nitrate and titanium acetate. The precursor of CeO2 is selected from one or both of cerium nitrate and cerium ammonium nitrate.

6. The method for preparing the catalyst according to claim 5, wherein loading oxidized vanadium and oxidized X onto a support comprises the following steps: In the first step, an aqueous solution containing soluble metal salts of vanadium and X is prepared, a precipitant and a composite oxide support are added, and the mixture is reacted at 50-100 °C for 0.5-3 h. After the mixture is cooled to room temperature, it is filtered to obtain a solid. The concentration of vanadium in aqueous solution is 0.01–0.1 mol / L; The precipitant is selected from one or two of urea and hexamethyltetramine, and its concentration in aqueous solution is 0.05-1 mol / L; The soluble metal salts of vanadium are one or two of sodium metavanadate and potassium metavanadate. The soluble metal salt of X is one or more of the following: cobalt nitrate, cobalt acetate, cerium nitrate hexahydrate, cerium ammonium nitrate, ferric nitrate nonahydrate, ferric acetate, nickel acetate, and nickel nitrate. The second step involves drying the obtained catalyst precursor by heat treatment at 30-100℃, followed by high-temperature calcination to bring vanadium to an oxide state. The roasting is carried out in a muffle furnace; the roasting temperature is 300–900℃, and the roasting time is 2–20 h.

7. In the method for preparing the catalyst according to claim 6, the concentration of vanadium in the aqueous solution is 0.01-0.05 mol / L; The precipitant is selected from one or two of urea and hexamethyltetramine, and its concentration in aqueous solution is 0.1-0.6 mol / L; The roasting is carried out in a muffle furnace; the roasting temperature is 400-600℃ and the roasting time is 2-8 h.

8. A method for producing vanillin, characterized in that: 4-methylphenol and its derivatives are oxidized in one step to generate vanillin in the presence of a vanadium-based catalyst as described in any one of claims 1 to 3, and oxygen and / or air; The reaction conditions are as follows: 4-methylphenol and its derivatives are placed in a reaction vessel with a protic solvent, an inorganic base and the catalyst described in any one of claims 1-3 above; one or more oxygen sources, such as oxygen or a mixture containing oxygen, are introduced; and the reaction is carried out at 70-100°C for 8-15 hours until the reaction is complete.

9. The manufacturing method according to claim 8, characterized in that: The reactor has a capacity of 250 ml and is matched with an oxygen source gas flow rate of 10-30 ml / min. The aforementioned proton solvent is one or more of ethylene glycol, ethylene glycol monomethyl ether, isopropanol, ethylene glycol dimethyl ether, and water, and the mass ratio of 4-methylphenol and its derivatives to the proton solvent is 1:2 to 10. The aforementioned inorganic base is one or more of sodium hydroxide, lithium hydroxide, and potassium hydroxide, and the molar ratio of 4-methylphenol and its derivatives to the inorganic base is 1:1 to 5.

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