A method for preparing vanillin from eugenol

Abstract

The application provides a method for preparing vanillin by using eugenol, and belongs to the technical field of organic synthesis, and comprises the following steps: S1, preparing Ni-Mo / aluminosilicate / carbon-based material; S2, preparing isoeugenol; S3, mixing isoeugenol, the Ni-Mo / aluminosilicate / carbon-based material, anhydrous ethanol and deionized water in a closed pressure-resistant reaction kettle, adding sodium hydroxide solution dropwise, stirring, heating, passing in oxygen, stirring and reacting, cooling, separating, adjusting pH to acidity, aging, suction filtering, washing, adding into an ethanol aqueous solution, heating and stirring, decoloring, filtering, recrystallizing, washing, and vacuum drying to obtain vanillin. The application can effectively inhibit the occurrence of side reactions, and improve the yield and purity of the target product.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of organic synthesis, and particularly relates to a method for preparing vanillin from eugenol. BACKGROUND

[0002] Vanillin is one of the largest monomer fragrances in the world, and has a sweet and sweet bean fragrance and a powdery fragrance. It can be used as a fixative, a coordinator and a flavoring agent, and is applied to the cosmetics, daily chemicals, food, beverage and other industries. Vanillin naturally exists in vanilla beans and other plants, has been successfully applied in many fields, and the demand is increasing year by year. The natural source of vanillin is very limited and the price is very high because the vanilla flower pod plant has very high requirements for soil and climate factors, and the fermentation treatment process of natural processing is complex. At present, the vanillin products on the market are mainly derived from chemical synthesis.

[0003] Vanillin can be obtained by chemical synthesis, and the main synthesis methods include safrole synthesis route, guaiacol synthesis route, lignin synthesis route and eugenol synthesis route. The safrole synthesis route has the problems of difficult raw material source, high cost and long synthesis process route, so the safrole synthesis route is rarely used for synthesizing vanillin at present; the guaiacol synthesis route also has the problems of high production cost, complex process route and low yield, which do not meet the green production requirements; the lignin synthesis route has the problems of wide raw material source and convenient operation, but the aroma is not superior; the vanillin produced by the eugenol synthesis route has attractive aroma, is most similar to natural vanillin, is safe for eating, and has high economic value.

[0004] Most of the traditional eugenol synthesis processes use inorganic bases as catalysts. For example, the patent application file with the publication number CN103626643B discloses a preparation method for synthesizing vanillin from natural eugenol. Although the method can efficiently synthesize vanillin from natural eugenol and has high yield, the isomerization reaction in the method uses potassium hydroxide as a catalyst. The catalyst produces by-products during the reaction process, generates a large amount of hazardous waste, has low selectivity of the reaction, and needs to go through a complex post-treatment step. In addition, nitrobenzene is used for oxidation in the process of oxidizing isoeugenol. The process involves a strong oxidation reaction, which may cause peroxidation and the generation of by-products, and further increases the difficulty of product purification.

[0005] Therefore, it is necessary to provide a method for preparing vanillin from eugenol to solve the problems existing in the prior art. SUMMARY

[0006] Therefore, the present application provides a method for preparing vanillin from eugenol, which can effectively inhibit the occurrence of side reactions and improve the yield and purity of the target product.

[0007] To achieve the above objectives, the present invention provides a method for preparing vanillin using eugenol, comprising the following steps:

[0008] S1. Mix and stir the Ni-Mo mixed impregnation solution and the aluminosilicate / carbon-based support, let it stand for aging, heat and evaporate, dry and calcine under inert gas protection to obtain Ni-Mo / aluminosilicate / carbon-based material;

[0009] S2. Potassium carbonate was dissolved in water and added dropwise to a g-C3N4 suspension. After stirring and aging by standing, the mixture was filtered, washed, dried, and calcined under inert gas protection to obtain a K2CO3 / g-C3N4 solid base catalyst. Subsequently, eugenol, anhydrous isopropanol, and the K2CO3 / g-C3N4 solid base catalyst were added to a closed high-pressure reactor and heated under nitrogen protection. The mixture was then separated and distilled under reduced pressure to obtain isoeugenol.

[0010] S3. Add isoeugenol, Ni-Mo / aluminosilicate / carbon-based material, anhydrous ethanol and deionized water to a sealed pressure-resistant reactor and mix. Add sodium hydroxide solution dropwise and stir. Heat, introduce oxygen, stir and react, cool, separate, adjust pH to acidic, age, filter, wash, add to ethanol aqueous solution, heat and stir, decolorize, filter, recrystallize, wash, and vacuum dry to obtain vanillin.

[0011] This invention employs a K2CO3 / g-C3N4 solid base catalyst for the isomerization reaction of eugenol. K2CO3 supported on the surface and interlayer of g-C3N4 can coordinate / electrostatically interact with the nitrogen-containing sites of the support, forming surface bonds / interactions such as KO-(C / N), thereby constructing a catalyst based on carbonate-related components (CO3). 2- The catalyst contains basic sites, primarily composed of hydroxyl groups (–OH), which enhance the adsorption and activation of eugenol molecules. These basic sites facilitate the deprotonation of eugenol hydroxyl groups and promote allylic rearrangement, thereby increasing the conversion rate of eugenol. Simultaneously, the high specific surface area and porous structure of the g-C3N4 sheets promote the uniform dispersion of K2CO3, resulting in uniform adsorption and orderly contact of eugenol on the surface of the solid base catalyst. This also improves the effective accessibility of the basic sites on the solid base catalyst surface and makes the base strength more suitable, avoiding the coverage or passivation of basic sites by side reactions such as condensation and polymerization caused by excessively strong local bases. This allows eugenol to be converted more along the isomerization pathway while maintaining the catalytic activity of the solid base catalyst, further improving the conversion rate of eugenol.

[0012] The application adopts the impregnation method to prepare the Ni-Mo / aluminosilicate / carbon-based material for preparing vanillin by selective oxidation of isoeugenol, thereby improving the yield and purity of the final vanillin. Ni and Mo are mainly dispersed in the aluminosilicate / carbon-based carrier in the oxidation state, and there is a synergistic electronic effect between Ni and Mo, which is conducive to building a stable redox cycle system. Among them, Ni can promote the adsorption and dehydrogenation of isoeugenol molecules, and preferentially activates the side chain allyl position / unsaturated bond related reaction sites; Mo is prone to reversible conversion between Mo 6+ / Mo 5+ / Mo 4+ valence states, which is conducive to activating molecular oxygen to form surface activated adsorbed oxygen (such as O - , O2 - ), thereby participating in the selective oxidation reaction; the electronic interaction between Ni and Mo can adjust the electronic structure of the metal center, so that it can efficiently activate O2 while avoiding excessive oxidation tendency, thereby realizing the directional oxidation of the side chain of isoeugenol, preferentially generating vanillin, and inhibiting further deep oxidation to generate carboxylic acids or CO2 and other deep oxidation products, thereby improving the yield and purity of the final vanillin.

[0013] In addition, the inorganic framework of the aluminosilicate / carbon-based carrier can provide certain Lewis acid sites (Al 3+ ), which is conducive to promoting the directional adsorption and activation of isoeugenol near the metal center. At the same time, the carbon-based carrier contains a porous structure and a π conjugated system, which can enhance the π-π interaction with aromatic substrates, realize the enrichment and directional adsorption of isoeugenol, improve the effective utilization rate of the metal active site, and thereby improve the selectivity and yield of vanillin.

[0014] Optionally, the Ni-Mo mixed impregnation solution is obtained by sequentially adding 0.4-1 mass parts of nickel nitrate hexahydrate and 0.3-0.8 mass parts of ammonium heptamolybdate tetrahydrate to 40-60 volume parts of deionized water and magnetically stirring for 20-40 min.

[0015] Optionally, the aluminosilicate / carbon-based carrier is prepared by mixing 1-1.5 parts by mass of APTES-activated carbon and 150-200 parts by volume of anhydrous ethanol, ultrasonic dispersion for 10-15 min, adding 4.2-6 parts by mass of cetyltrimethylammonium bromide and stirring for 10-15 min, adding 2.8-4 parts by volume of di-sec-butoxyaluminoxysilane and continuing to stir for 1-2 h, slowly adding 100-150 parts by volume of deionized water and 20-50 parts by volume of a 0.2 wt%-0.8 wt% sodium hydroxide solution and continuously stirring for 2-4 h, continuing to stir for 3-5 h after the addition is completed, hydrothermal treatment at 90-110°C for 36-48 h in a sealed container, cooling to room temperature, filtering to separate the solid, adding 300-400 parts by volume of anhydrous ethanol and stirring for 2-3 h at 60-80°C to extract, filtering, washing with anhydrous ethanol, and drying at 80-100°C for 8-12 h to obtain.

[0016] The present application uses APTES-activated carbon as a carbon-based carrier, and under the conditions of cetyltrimethylammonium bromide (CTAB) as a template and alkali catalysis (provided by a NaOH solution), di-sec-butoxyaluminoxysilane is hydrolyzed and polycondensed, and an aluminosilicate porous framework is formed in situ on the carbon-based surface; this inorganic framework not only improves the structural stability of the carrier under solvent immersion conditions, but also introduces Al-related Lewis acid sites and Si-OH and other surface functional groups, thereby constructing an interface environment that is synergistic with acidic sites, metal anchoring sites, and carbon-based π conjugated adsorption sites, which is more conducive to the uniform infiltration, anchoring, and dispersion of subsequent Ni and Mo precursors, thereby improving the effective utilization rate and cyclic stability of metal active centers. Further, after removing the CTAB template by ethanol extraction, an aluminosilicate / carbon-based carrier with a mesoporous aluminosilicate framework is obtained, and the mesoporous channels formed provide a smooth path for the entry and diffusion of substrates and oxygen inside the carrier, thereby facilitating the adsorption and effective contact of substrates in the pores of the carrier, improving the transfer and diffusion conditions of reactants in the pores, and helping to improve the effective specific surface area and pore accessibility of the carrier and improve the accessibility and uniformity of active sites.

[0017] Optionally, the APTES-activated carbon is prepared by mixing 2-3 parts by mass of chlorinated activated carbon and 150-200 parts by volume of dichloromethane and stirring for 10-15 min, adding 1.2-2.5 parts by volume of 3-aminopropyltrimethoxysilane and magnetically stirring for 20-24 h, filtering, washing with dichloromethane and methanol in sequence, and drying at 60-80°C for 8-12 h; the chlorinated activated carbon is prepared by mixing 3-5 parts by mass of activated carbon and 120-160 parts by volume of toluene and ultrasonic dispersion for 10-15 min, adding 4-10 parts by volume of thionyl chloride, refluxing at 115-125°C for 4-6 h, filtering, washing the filter cake with toluene 2-3 times, and drying at 80-100°C for 10-12 h.

[0018] The present application adopts thionyl chloride to acyl chloride treatment on the surface of activated carbon carboxyl and other oxygen-containing functional groups, introduces the acyl chloride site (such as -COCl) with higher reactivity on the surface of activated carbon, thereby improving the density of the reactive site on the surface of carbon-based carrier, providing active center for the subsequent covalent grafting of 3-aminopropyltrimethoxysilane (APTES), thereby improving the surface functionalization degree of carbon-based carrier, providing more firm interface combination for the in-situ growth of aluminosilicate porous framework and the stable loading of Ni and Mo active components.

[0019] Optionally, in the step S1, the Ni-Mo mixed impregnation solution is mixed with 1-1.5 parts by mass of aluminosilicate / carbon-based carrier and stirred for 1-3 h, and then is left to stand for aging for 8-16 h, and then is slowly evaporated to remove water under the condition of water bath at 60-80℃, and then is dried at 100-120℃ for 8-12 h, and then is placed in a tube furnace, and then is heated to 350-450℃ under nitrogen protection, and then is kept for 2-4 h, and then is cooled to room temperature to obtain the Ni-Mo / aluminosilicate / carbon-based material.

[0020] Optionally, the K2CO3 / g-C3N4 solid base catalyst is obtained by mixing 1-3 parts by mass of potassium carbonate and 30-40 parts by volume of deionized water, and then is slowly added dropwise to the g-C3N4 suspension after magnetic stirring for 10-15 min, and then the dropwise adding time is controlled to be 20-30 min, and then the magnetic stirring is continued for 4-6 h after the dropwise adding is completed, and then is left to stand for aging for 8-12 h, and then is suction filtered, and then the solid is collected, and then is washed with deionized water and anhydrous ethanol for 2-4 times in sequence, and then is dried at 75-80℃ for 10-12 h, and then is placed in a tube furnace, and then is heated to 300-350℃ under nitrogen protection, and then is kept for 2-3 h, and then is cooled to room temperature; the g-C3N4 suspension is obtained by mixing 2-5 parts by mass of g-C3N4 and 450-600 parts by volume of isopropanol solution, and then is ultrasonically treated for 3-5 h under ice water bath condition, and then is centrifuged at 3000 rpm for 10-15 min to take the supernatant, and then is centrifuged at 8000 rpm for 15-20 min to collect the precipitate, and then is dried at 60-70℃ for 10-12 h, and then is added into 100 mL of 50v / v% ethanol aqueous solution for ultrasonic dispersion for 20-30 min.

[0021] The present application makes K2CO3 uniformly dispersed and firmly loaded on the surface and interlayer of g-C3N4 by impregnation, aging and calcination at 300-350℃ under inert atmosphere; the calcination process can promote K + Electrostatic adsorption / weak coordination occurs with the nitrogen-containing sites of the carrier, and interface interaction such as K-O-(C / N) is formed, thereby constructing CO3 2- The related components are mainly solid basic sites, accompanied by a small amount of surface hydroxyl (-OH), thereby improving the number and accessibility of the basic sites of the solid base catalyst.

[0022] In addition, the g-C3N4 is effectively peeled into a sheet layer by the isopropanol ultrasonic peeling and centrifugal classification process, so that the g-C3N4 has a higher specific surface area and exposes more surface nitrogen-containing basic sites, and then the g-C3N4 is dispersed in an ethanol aqueous solution again, so that a uniform contact interface is provided for subsequent potassium carbonate impregnation, and K2CO3 is uniformly loaded and anchored on the surface and between the layers of the sheet layer.

[0023] Optionally, in the step S2, 45-60 parts by mass of eugenol, 80-120 parts by volume of anhydrous isopropanol, and 2-4 parts by mass of K2CO3 / g-C3N4 solid base catalyst are added into a sealed high-pressure reaction kettle, and then the temperature is increased to 100-120 DEG C under nitrogen protection, and after stirring for 4-6 h, the K2CO3 / g-C3N4 solid base catalyst is separated by filtration and washed with isopropanol for 2-3 times, the filtrates are combined, and isoeugenol is obtained by distillation under reduced pressure.

[0024] Optionally, in the step S3, the isoeugenol, the Ni-Mo / aluminosilicate / carbon-based material, anhydrous ethanol, and deionized water are added into a sealed pressure-resistant reaction kettle and mixed and stirred for 10-20 min, a sodium hydroxide solution is slowly added dropwise and stirred for 10-20 min, the temperature is increased to 90-100 DEG C, oxygen is introduced and the oxygen pressure is maintained at 0.3-0.5 MPa, and the stirring reaction is carried out for 4-6 h, the oxygen supply is stopped, the temperature is cooled to room temperature, the Ni-Mo / aluminosilicate / carbon-based material is separated and recovered and washed with ethanol and deionized water, the filtrates are combined, the pH is adjusted to 2-3 by using a hydrochloric acid solution, and the aging is continued for 30-60 min, the solid is collected by filtration and washed with deionized water for 3-5 times, and then the solid is added into an ethanol aqueous solution, heated and stirred at 60-80 DEG C for 10-15 min, activated carbon is added, and the solution is stirred and decolorized at 50-60 DEG C for 10-20 min, and then the solution is filtered while hot, the filtrate is cooled to room temperature, and then the solution is continuously cooled to 0-5 DEG C to crystallize, the crystals are collected by filtration, washed with an ethanol aqueous solution at 0-5 DEG C for 2-3 times, and then the crystals are dried under vacuum at 60-80 DEG C for 4-6 h to obtain vanillin.

[0025] In the application, the sodium hydroxide is added to make the isoeugenol exist in the form of sodium salt, so that the solubility of the isoeugenol in the ethanol / water phase is improved, the deprotonation degree of the phenolic hydroxyl group is enhanced, the substrate is adsorbed and activated by the metal active sites and the aluminosilicate Lewis acid sites on the surface of the catalyst in the form of anion, and the alkaline environment can further inhibit the side reactions such as self-condensation and polymerization.

[0026] Optionally, the concentration of the sodium hydroxide solution is 20 wt%, the concentration of the hydrochloric acid solution is 10 wt%, and the concentration of the ethanol aqueous solution is 50v / v%-70v / v%.

[0027] Optionally, the vanillin comprises the following raw materials: 20-30 parts by weight of isoeugenol, 1-2 parts by weight of Ni-Mo / aluminosilicate / carbon-based material, 50-80 parts by volume of anhydrous ethanol, 40-60 parts by volume of deionized water, and 30-50 parts by volume of sodium hydroxide solution.

[0028] The above-described technical solution of the present invention has at least the following beneficial effects:

[0029] 1. This invention utilizes a K2CO3 / g-C3N4 solid base catalyst, where K2CO3 is uniformly supported on the surface and interlayer of g-C3N4 to construct carbonate-related components (CO3). 2- The basic sites, mainly composed of hydroxyl groups (–OH), combined with the high specific surface area and porous structure of g-C3N4, improve the accessibility of basic sites and make the base strength more suitable. This reduces the coverage or passivation of basic sites by side reactions such as condensation and polymerization and their byproducts, allowing eugenol to be converted more along the isomerization pathway while maintaining the catalytic activity of the solid base catalyst, further improving the conversion rate of eugenol.

[0030] 2. This invention employs an impregnation method to prepare Ni-Mo / aluminosilicate / carbon-based materials for the selective oxidation of isoeugenol to vanillin. Ni and Mo are mainly dispersed in the oxidized state on the aluminosilicate / carbon-based support, forming synergistic electronic interactions and a stable redox cycle. Ni is beneficial for substrate adsorption / dehydrogenation, while Mo is beneficial for O2 activation and oxygen supply. The two work together to achieve directional oxidation of the isoeugenol side chain, preferentially generating vanillin and inhibiting further deep oxidation to generate carboxylic acids or CO2 and other deep oxidation products, thereby improving the yield and purity of the final vanillin.

[0031] 3. Aluminosilicate / carbon-based supports can provide metal anchoring and interfacial adsorption sites. The carbon-based porous structure and π-π interaction have an enrichment effect on aromatic substrates, which is beneficial to improve the utilization rate of metal active sites and reduce the selectivity loss caused by diffusion limitation, thereby further improving the selectivity and yield of vanillin and the stability of the catalyst. Attached Figure Description

[0032] Figure 1 The structural formulas of the intermediate and vanillin of this invention are as follows;

[0033] Figure 2 This is a liquid chromatogram of the intermediate obtained in Example 3 of the present invention;

[0034] Figure 3 This is a liquid chromatogram of vanillin obtained in Example 3 of the present invention. Detailed Implementation

[0035] In order to make the purposes, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions of the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. The described embodiments are part of the embodiments of the present application, and all other embodiments obtained by those skilled in the art based on the described embodiments of the present application belong to the scope of protection of the present application.

[0036] Embodiment 1

[0037] 4g of g-C3N4 and 500mL of isopropanol solution were mixed, ultrasonic treatment was carried out under the condition of ice water bath for 4h, the supernatant was obtained by centrifugation at 3000rpm for 13min, and the precipitate was collected by centrifugation at 8000rpm for 18min, then g-C3N4 suspension was obtained by adding the precipitate into 100mL of 50v / v% ethanol aqueous solution and ultrasonic dispersion for 27min; 2g of potassium carbonate and 38mL of deionized water were mixed, magnetic stirring was carried out for 14min, then the mixture was slowly added into the g-C3N4 suspension, the dropping time was controlled for 25min, after the dropping was completed, magnetic stirring was continued for 5.5h, and aging was carried out for 11h, then the solid was collected by suction filtration, washed with deionized water and anhydrous ethanol for 3 times respectively, dried at 78℃ for 11h, then the solid was put into a tube furnace, heated to 330℃ under the protection of nitrogen, kept for 2.5h, cooled to room temperature, and then K2CO3 / g-C3N4 solid base catalyst was obtained.

[0038] Mix 4.5 g activated carbon, 150 mL toluene, and ultrasonically disperse for 14 min, add 8 mL thionyl chloride, reflux at 120 °C for 5.5 h, filter, wash the filter cake with toluene 3 times, and dry at 90 °C for 11 h to obtain chlorinated activated carbon; mix 2.8 g chlorinated activated carbon, 160 mL dichloromethane, and stir for 14 min, add 2 mL 3-aminopropyltrimethoxysilane (APTES), and magnetically stir for 22 h, filter, wash with dichloromethane and methanol in sequence, and dry at 70 °C for 10 h to obtain APTES-activated carbon; mix 1.4 g APTES-activated carbon, 180 mL anhydrous ethanol, and ultrasonically disperse for 14 min, add 5.5 g cetyltrimethylammonium bromide (CTAB) and stir for 14 min, add 3.5 mL di-sec-butoxyaluminoxysilane (CAS: 68959-06-8) and continue to stir for 1.5 h, slowly drop 130 mL deionized water and 40 mL 0.7 wt% sodium hydroxide solution, and continue to stir for 3.5 h, after the drop is completed, continue to stir for 4 h, hydrothermal treatment at 100 °C in a sealed container for 42 h, cool to room temperature, filter and separate the solid, add 360 mL anhydrous ethanol, stir and extract at 70 °C for 2.5 h, filter, wash with anhydrous ethanol, and dry at 90 °C for 10 h to obtain an aluminosilicate / carbon-based carrier; mix 0.8 g nickel nitrate hexahydrate and 0.7 g ammonium heptamolybdate tetrahydrate in 50 mL deionized water, magnetically stir for 30 min to obtain a Ni-Mo mixed impregnation solution, add 1.3 g aluminosilicate / carbon-based carrier, mix and stir for 2.5 h, stand for 15 h, slowly evaporate water at 70 °C in a water bath, dry at 110 °C for 10 h, place in a tube furnace, heat to 400 °C under nitrogen protection, keep for 3.5 h, cool to room temperature, and obtain a Ni-Mo / aluminosilicate / carbon-based material.

[0039] A mixture of 56 g of eugenol, 110 mL of anhydrous isopropyl alcohol, 3.5 g of K2CO3 / g-C3N4 solid base catalyst was added to a sealed high-pressure reaction kettle, and heated to 110°C under nitrogen protection. After stirring for 5 h, the K2CO3 / g-C3N4 solid base catalyst was separated by suction filtration and washed with isopropyl alcohol for 3 times. The filtrates were combined and distilled under reduced pressure to obtain isoeugenol. A mixture of 28 g of isoeugenol, 1.8 g of Ni-Mo / aluminosilicate / carbon-based material, 70 mL of anhydrous ethanol and 50 mL of deionized water was added to a sealed pressure-resistant reaction kettle and stirred for 18 min. Then, 40 mL of 20 wt% sodium hydroxide solution was slowly added dropwise and stirred for 18 min. The temperature was raised to 95°C, oxygen was introduced, and the stirring was continued for 5 h under the condition of maintaining the oxygen pressure at 0.4 MPa. The oxygen supply was stopped, and the temperature was cooled to room temperature. The Ni-Mo / aluminosilicate / carbon-based material was separated and washed with ethanol and deionized water. The filtrates were combined, and the pH was adjusted to 2.6 with 10 wt% hydrochloric acid solution. The stirring was continued for 50 min, and the solid was collected by suction filtration and washed with deionized water for 4 times. The solid was added to 60 v / v% aqueous ethanol solution, heated and stirred at 70°C for 13 min. Then, 0.7 g of activated carbon was added, and the solution was stirred at 55°C for 16 min for decolorization. The solution was filtered while hot. The filtrate was cooled to room temperature and then to 2°C for crystallization. The crystals were collected by suction filtration, washed with 2°C 60 v / v% aqueous ethanol solution for 3 times, and dried at 70°C under vacuum for 5 h to obtain vanillin.

[0040] Example 2

[0041] A mixture of 2 g of g-C3N4 and 450 mL of isopropyl alcohol was ultrasonically treated for 3 h in an ice water bath. The supernatant was obtained by centrifugation at 3000 rpm for 10 min, and the precipitate was collected by centrifugation at 8000 rpm for 15 min. After drying at 60°C for 10 h, the g-C3N4 suspension was obtained by ultrasonic dispersion of the precipitate in 100 mL of 50 v / v% aqueous ethanol solution for 20 min. A mixture of 1 g of potassium carbonate and 30 mL of deionized water was prepared and magnetically stirred for 10 min. Then, the mixture was slowly added dropwise to the g-C3N4 suspension, and the dropwise addition was controlled for 20 min. After the dropwise addition was completed, the mixture was magnetically stirred for 4 h and aged for 8 h. The solid was collected by suction filtration and washed with deionized water and anhydrous ethanol for 2 times. The solid was dried at 75°C for 10 h, and then placed in a tube furnace. The temperature was raised to 300°C under nitrogen protection, and the temperature was maintained for 2 h. After cooling to room temperature, K2CO3 / g-C3N4 solid base catalyst was obtained.

[0042] Mix 3 g activated carbon, 120 mL toluene and ultrasonically disperse for 10 min, add 4 mL thionyl chloride, reflux at 115 °C for 4 h, filter, wash the filter cake with toluene twice, and dry at 80 °C for 10 h to obtain chlorinated activated carbon; mix 2 g chlorinated activated carbon, 150 mL dichloromethane and stir for 10 min, add 1.2 mL 3-aminopropyltrimethoxysilane (APTES), and magnetically stir for 20 h, filter, wash with dichloromethane and methanol in sequence, and dry at 60 °C for 8 h to obtain APTES-activated carbon; mix 1 g APTES-activated carbon, 150 mL anhydrous ethanol, ultrasonically disperse for 10 min, add 4.2 g cetyltrimethylammonium bromide (CTAB) and stir for 10 min, add 2.8 mL di-sec-butoxyaluminumoxysilane (CAS: 68959-06-8) and continue to stir for 1 h, slowly drop 100 mL deionized water and 20 mL 0.2 wt% sodium hydroxide solution and continue to stir for 2 h, after the drop is completed, continue to stir for 3 h, then hydrothermal treatment at 90 °C for 36 h in a sealed container, cool to room temperature, filter and separate the solid, add 300 mL anhydrous ethanol and stir at 80 °C for 3 h, filter, wash with anhydrous ethanol, and dry at 80 °C for 8 h to obtain aluminosilicate / carbon-based carrier; mix 0.4 g nickel nitrate hexahydrate and 0.3 g ammonium heptamolybdate tetrahydrate in 40 mL deionized water and magnetically stir for 20 min to obtain a Ni-Mo mixed impregnation solution, add 1 g aluminosilicate / carbon-based carrier and mix and stir for 1 h, stand for aging for 8 h, remove water by slow evaporation under the condition of 60 °C water bath, dry at 100 °C for 8 h, place in a tube furnace, heat to 350 °C under the protection of nitrogen, keep for 2 h, cool to room temperature, and obtain Ni-Mo / aluminosilicate / carbon-based material.

[0043] Into a sealed autoclave, 45 g of eugenol, 80 mL of anhydrous isopropanol, 2 g of K2CO3 / g-C3N4 solid base catalyst were added, and the temperature was raised to 100 °C under nitrogen protection. After stirring for 4 h, the K2CO3 / g-C3N4 solid base catalyst was separated and washed with isopropanol twice. The combined filtrate was distilled under reduced pressure to obtain isoeugenol. Into a sealed pressure-resistant autoclave, 20 g of isoeugenol, 1 g of Ni-Mo / aluminosilicate / carbon-based material, 50 mL of anhydrous ethanol, and 40 mL of deionized water were added and stirred for 10 min. Then, 30 mL of 20 wt% sodium hydroxide solution was slowly added dropwise and stirred for 10 min. The temperature was raised to 90 °C, oxygen was introduced, and the reaction was stirred for 4 h under the condition of maintaining the oxygen pressure at 0.3 MPa. The oxygen supply was stopped, and the temperature was cooled to room temperature. The Ni-Mo / aluminosilicate / carbon-based material was separated and washed with ethanol and deionized water. The combined filtrate was adjusted to pH 2 with 10 wt% hydrochloric acid solution, and stirring was continued for 30 min. The solid was collected by suction filtration, washed with deionized water three times, added to 50 v / v% aqueous ethanol solution, heated and stirred at 60 °C for 10 min, added with 0.5 g of activated carbon, decolorized by stirring at 50 °C for 10 min, filtered while hot, and the filtrate was cooled to room temperature and then to 0 °C for crystallization. The crystals were collected by suction filtration, washed with 0 °C 50 v / v% aqueous ethanol solution twice, and dried at 60 °C under vacuum for 4 h to obtain vanillin.

[0044] Example 3

[0045] Into a sealed autoclave, 45 g of eugenol, 80 mL of anhydrous isopropanol, 2 g of K2CO3 / g-C3N4 solid base catalyst were added, and the temperature was raised to 100 °C under nitrogen protection. After stirring for 4 h, the K2CO3 / g-C3N4 solid base catalyst was separated and washed with isopropanol twice. The combined filtrate was distilled under reduced pressure to obtain isoeugenol. Into a sealed pressure-resistant autoclave, 20 g of isoeugenol, 1 g of Ni-Mo / aluminosilicate / carbon-based material, 50 mL of anhydrous ethanol, and 40 mL of deionized water were added and stirred for 10 min. Then, 30 mL of 20 wt% sodium hydroxide solution was slowly added dropwise and stirred for 10 min. The temperature was raised to 90 °C, oxygen was introduced, and the reaction was stirred for 4 h under the condition of maintaining the oxygen pressure at 0.3 MPa. The oxygen supply was stopped, and the temperature was cooled to room temperature. The Ni-Mo / aluminosilicate / carbon-based material was separated and washed with ethanol and deionized water. The combined filtrate was adjusted to pH 2 with 10 wt% hydrochloric acid solution, and stirring was continued for 30 min. The solid was collected by suction filtration, washed with deionized water three times, added to 50 v / v% aqueous ethanol solution, heated and stirred at 60 °C for 10 min, added with 0.5 g of activated carbon, decolorized by stirring at 50 °C for 10 min, filtered while hot, and the filtrate was cooled to room temperature and then to 0 °C for crystallization. The crystals were collected by suction filtration, washed with 0 °C 50 v / v% aqueous ethanol solution twice, and dried at 60 °C under vacuum for 4 h to obtain vanillin.

[0046] Mixing 5 g activated carbon, 160 mL toluene, ultrasonic dispersion for 15 min, add 10 mL thionyl chloride, reflux reaction at 125 ℃ for 6 h, filter, filter cake is washed with toluene 3 times, dry at 100 ℃ for 12 h, to get chlorinated activated carbon; 3 g chlorinated activated carbon, 200 mL dichloromethane mixed stirring for 15 min, add 2.5 mL 3-aminopropyl trimethoxysilane (APTES) magnetic stirring for 24 h, filter, washed with dichloromethane and methanol in turn, and dry at 80 ℃ for 12 h, to get APTES-activated carbon; 1.5 g APTES-activated carbon, 200 mL anhydrous ethanol mixed, ultrasonic dispersion for 15 min, add 6 g cetyltrimethylammonium bromide (CTAB) stirring for 15 min, add 4 mL di-sec-butoxyaluminumoxysilane (CAS: 68959-06-8) continue stirring for 2 h, slowly drop 150 mL deionized water and 50 mL 0.8wt% sodium hydroxide solution and continue stirring for 4 h, after the end of drop, continue stirring for 5 h, then hydrothermal treatment at 110 ℃ for 48 h in a sealed container, cool to room temperature, filter separation of solids, add 400 mL anhydrous ethanol in 60 ℃ stirring extraction for 2 h, filter, washed with anhydrous ethanol, and dry at 100 ℃ for 12 h, to get aluminosilicate / carbon-based carrier; 1 g nickel nitrate hexahydrate and 0.8 g ammonium heptamolybdate tetrahydrate are added to 60 mL deionized water in turn, magnetic stirring for 40 min to get Ni-Mo mixed impregnation solution, add 1.5 g aluminosilicate / carbon-based carrier mixed stirring for 3 h, stand aging for 16 h, slowly evaporate water at 80 ℃ water bath, dry at 120 ℃ for 12 h, placed in a tube furnace, heated to 450 ℃ under nitrogen protection, keep for 4 h, cool to room temperature, to get Ni-Mo / aluminosilicate / carbon-based material.

[0047] A mixture of 60 g of eugenol, 120 mL of anhydrous isopropyl alcohol, 4 g of K2CO3 / g-C3N4 solid base catalyst was added to a sealed high-pressure reaction kettle, and heated to 120°C under nitrogen protection. After stirring for 6 h, the K2CO3 / g-C3N4 solid base catalyst was separated by suction filtration and washed with isopropyl alcohol for 3 times. The filtrate was combined and distilled under reduced pressure to obtain isoeugenol. A mixture of 30 g of isoeugenol, 2 g of Ni-Mo / aluminosilicate / carbon-based material, 80 mL of anhydrous ethanol and 60 mL of deionized water was added to a sealed pressure-resistant reaction kettle and stirred for 20 min. Then, 50 mL of 20 wt% sodium hydroxide solution was slowly added dropwise and stirred for 20 min. The temperature was increased to 100°C, and oxygen was introduced while maintaining the oxygen pressure at 0.5 MPa. The reaction was stirred for 6 h, and then the oxygen supply was stopped. The temperature was cooled to room temperature, and the Ni-Mo / aluminosilicate / carbon-based material was separated and washed with ethanol and deionized water. The filtrate was combined, and the pH was adjusted to 3 with 10 wt% hydrochloric acid solution. The stirring was continued for 60 min, and then the solid was collected by suction filtration and washed with deionized water for 5 times. The solid was added to 70 v / v% aqueous ethanol solution and heated and stirred at 80°C for 15 min. Then, 0.8 g of activated carbon was added and stirred at 60°C for 20 min to decolorize. The mixture was filtered while hot, and the filtrate was cooled to room temperature and then to 5°C for crystallization. The crystals were collected by suction filtration, washed with 5°C 70 v / v% aqueous ethanol solution for 3 times, and dried at 80°C under vacuum for 6 h to obtain vanillin.

[0048] Example 4

[0049] A mixture of 3 g of g-C3N4 and 550 mL of isopropyl alcohol solution was ultrasonically treated for 4 h under ice water bath condition. The supernatant was obtained by centrifugation at 3000 rpm for 12 min, and the precipitate was collected by centrifugation at 8000 rpm for 16 min. After drying at 62°C for 10.5 h, the g-C3N4 suspension was obtained by ultrasonic dispersion of the precipitate in 100 mL of 50 v / v% aqueous ethanol solution for 25 min. A mixture of 2 g of potassium carbonate and 35 mL of deionized water was prepared and magnetically stirred for 12 min. Then, the mixture was slowly added dropwise to the g-C3N4 suspension, and the dropwise time was controlled for 25 min. After the dropwise addition was completed, the mixture was magnetically stirred for 5 h, and then aged for 10 h. The solid was collected by suction filtration and washed with deionized water and anhydrous ethanol for 3 times, respectively. The K2CO3 / g-C3N4 solid base catalyst was obtained by drying the solid at 76°C for 11 h, placing it in a tube furnace, and heating to 320°C under nitrogen protection for 2.5 h, and then cooling to room temperature.

[0050] Mix 3.5 g activated carbon, 140 mL toluene, and ultrasonically disperse for 12 min, add 5 mL thionyl chloride, and reflux at 120°C for 5 h. Filter, wash the filter cake with toluene twice, and dry at 90°C for 10.5 h to obtain chlorinated activated carbon; mix 2.2 g chlorinated activated carbon, 160 mL dichloromethane, and stir for 12 min. Add 1.8 mL 3-aminopropyltrimethoxysilane (APTES), and magnetically stir for 22 h. Filter, wash with dichloromethane and methanol in sequence, and dry at 65°C for 10 h to obtain APTES-activated carbon; mix 1.2 g APTES-activated carbon, 170 mL anhydrous ethanol, and ultrasonically disperse for 12 min. Add 5 g cetyltrimethylammonium bromide (CTAB) and stir for 12 min. Add 3 mL di-sec-butoxyaluminoxysilane (CAS: 68959-06-8) and continue to stir for 1.5 h. Slowly add 120 mL deionized water and 30 mL 0.3 wt% sodium hydroxide solution and continue to stir for 2.5 h. After the addition is completed, continue to stir for 3.5 h. After hydrothermal treatment at 95°C for 40 h in a sealed container, cool to room temperature, filter to separate the solid, stir and extract at 75°C for 2.2 h, filter, wash with anhydrous ethanol, and dry at 95°C for 10 h to obtain an aluminosilicate / carbon-based carrier; mix 0.5 g nickel nitrate hexahydrate and 0.5 g ammonium heptamolybdate tetrahydrate in 50 mL deionized water, and magnetically stir for 30 min to obtain a Ni-Mo mixed impregnation solution. Add 1.2 g aluminosilicate / carbon-based carrier, mix and stir for 2 h, stand for aging for 10 h, slowly evaporate the water under the condition of a 75°C water bath, and dry at 112°C for 9 h. Place in a tube furnace, heat to 380°C under the protection of nitrogen, and keep the temperature for 3 h. Cool to room temperature to obtain a Ni-Mo / aluminosilicate / carbon-based material.

[0051] A 50 g eugenol, 90 mL anhydrous isopropyl alcohol, 2.5 g K2CO3 / g-C3N4 solid base catalyst were added to a sealed high-pressure reaction kettle, heated to 105°C under nitrogen protection, stirred for 4.5 h, then K2CO3 / g-C3N4 solid base catalyst was separated by suction filtration and washed with isopropyl alcohol for 3 times, the filtrate was combined, and distilled under reduced pressure to obtain isoeugenol; 26 g isoeugenol, 1.1 g Ni-Mo / aluminosilicate / carbon-based material, 60 mL anhydrous ethanol and 50 mL deionized water were added to a sealed pressure-resistant reaction kettle and mixed and stirred for 18 min, then 40 mL of 20 wt% sodium hydroxide solution was slowly added dropwise and stirred for 12 min, heated to 95°C, oxygen was introduced, and the reaction was stirred for 4.5 h under the condition of maintaining the oxygen pressure at 0.35 MPa, the oxygen supply was stopped, and the temperature was cooled to room temperature, the Ni-Mo / aluminosilicate / carbon-based material was separated and recovered and washed with ethanol and deionized water, the filtrate was combined, the pH was adjusted to 2.2 with 10 wt% hydrochloric acid solution, and the stirring was continued for 40 min, the solid was collected by suction filtration and washed with deionized water for 4 times, added to 65 v / v% ethanol aqueous solution, heated and stirred at 75°C for 15 min, added 0.6 g activated carbon, decolorized at 60°C for 20 min, filtered while hot, the filtrate was cooled to room temperature and then cooled to 3°C for crystallization, the crystals were collected by suction filtration, washed with 5°C 65 v / v% ethanol aqueous solution for 3 times, and dried at 75°C under vacuum for 5.5 h to obtain vanillin.

[0052] Example 5

[0053] A 4 g g-C3N4 and 480 mL isopropyl alcohol solution were mixed, ultrasonic treated for 4 h under ice water bath condition, centrifuged at 3000 rpm for 12 min to take the supernatant, and then centrifuged at 8000 rpm for 16 min to collect the precipitate, which was dried at 62°C for 10.5 h, added to 100 mL 50 v / v% ethanol aqueous solution, and ultrasonic dispersed for 26 min to obtain g-C3N4 suspension; 2 g potassium carbonate and 32 mL deionized water were mixed, magnetically stirred for 14 min, then slowly added dropwise to the g-C3N4 suspension, the dropwise time was controlled for 24 min, after the dropwise addition was completed, the magnetic stirring was continued for 4 h, and the aging was performed for 12 h, then the solid was collected by suction filtration, washed with deionized water and anhydrous ethanol for 2 times, and dried at 76°C for 12 h, then placed in a tube furnace, heated to 350°C under nitrogen protection, kept for 2 h, and cooled to room temperature to obtain K2CO3 / g-C3N4 solid base catalyst.

[0054] Mixing 5 g activated carbon, 120 mL toluene, ultrasonic dispersion for 15 min, add 5 mL thionyl chloride, reflux reaction at 125℃ for 4h, filter, filter cake is washed with toluene 2 times, dry at 80℃ for 12h, get chlorinated activated carbon; 3 g chlorinated activated carbon, 190 mL dichloromethane mixing stirring 15 min, add 2.5 mL 3-aminopropyl trimethoxysilane (APTES) magnetic stirring 24h, filter, washed with dichloromethane and methanol in turn, dry at 60℃ for 12h, get APTES-activated carbon; 1.5 g APTES-activated carbon, 200 mL anhydrous ethanol mixing, ultrasonic dispersion for 10 min, add 6 g cetyl trimethyl ammonium bromide (CTAB) stirring 10 min, add 2.8 mL di-sec-butoxy aluminum oxy triethoxysilane (CAS: 68959-06-8) continue stirring 1h, slowly drop 150 mL deionized water and 40 mL 0.6wt% sodium hydroxide solution and continue stirring 3h, after the end of drop continue stirring 3h, in a sealed container, hydrothermal treatment at 110℃ for 36h, cool to room temperature, filter separation of solids, stirring extraction at 65℃ for 3h, filter, washed with anhydrous ethanol again, dry at 80℃ for 12h, get aluminosilicate / carbon based carrier; 0.4 g nickel nitrate hexahydrate and 0.8 g ammonium heptamolybdate tetrahydrate are added to 40 mL deionized water in turn, magnetic stirring 40 min to get Ni-Mo mixed impregnation solution, add 1.5 g aluminosilicate / carbon based carrier mixing stirring 3h, stand aging 8h, remove water slowly at 80℃ water bath condition, dry at 100℃ for 12h, placed in a tube furnace, under the protection of nitrogen, heating to 450℃, keep 2h, cool to room temperature, get Ni-Mo / aluminosilicate / carbon based material.

[0055] Into a sealed high-pressure reaction kettle, 60 g of eugenol, 100 mL of anhydrous isopropanol, and 4 g of K2CO3 / g-C3N4 solid base catalyst were added, and the temperature was raised to 120°C under nitrogen protection. After stirring for 4 h, the K2CO3 / g-C3N4 solid base catalyst was separated by suction filtration and washed twice with isopropanol. The filtrates were combined and distilled under reduced pressure to obtain isoeugenol. Into a sealed pressure-resistant reaction kettle, 30 g of isoeugenol, 1.7 g of Ni-Mo / aluminosilicate / carbon-based material, 80 mL of anhydrous ethanol, and 40 mL of deionized water were added and stirred for 20 min. Then, 30 mL of 20 wt% sodium hydroxide solution was slowly added and stirred for 20 min. The temperature was raised to 90°C, oxygen was introduced, and the stirring was continued for 4 h under the condition of maintaining the oxygen pressure at 0.5 MPa. The oxygen supply was stopped, and the temperature was cooled to room temperature. The Ni-Mo / aluminosilicate / carbon-based material was separated and washed with ethanol and deionized water. The filtrates were combined, and the pH was adjusted to 3 with 10 wt% hydrochloric acid solution. The stirring was continued for 30 min, and the solid was collected by suction filtration and washed 5 times with deionized water. The solid was added to 62 v / v% aqueous ethanol solution, heated and stirred at 65°C for 14 min. Then, 0.7 g of activated carbon was added, and the solution was stirred at 55°C for 15 min to decolorize. The solution was filtered while hot. The filtrate was cooled to room temperature and then to 1°C to crystallize. The crystals were collected by suction filtration, washed twice with 1°C 62 v / v% aqueous ethanol solution, and dried under vacuum at 65°C for 5.5 h to obtain vanillin.

[0056] The present application also conducts comparative examples and related tests.

[0057] Comparative Example 1

[0058] Comparative Example 1

[0059] Comparative Example 2

[0060] Comparative Example 2

[0061] Comparative Example 3

[0062] Comparative Example 3

[0063] Performance test

[0064] The Ni-Mo / aluminosilicate / carbon-based material prepared in Examples 1-5 was tested according to GB / T 19587-2017 Gas Adsorption BET Method for Determining Specific Surface Area of Solid Substances, GB / T 21650.2-2008 Mercury Intrusion Method and Gas Adsorption Method for Determining Pore Size Distribution and Porosity of Solid Materials to obtain the specific surface area, average pore size and total pore volume; the specific test results are shown in Table 1.

[0065] Table 1

[0066]

[0067] It can be seen from the data in Table 1 that the Ni-Mo / aluminosilicate / carbon-based material prepared in Examples 1-5 has a high specific surface area and total pore volume, which provides a basis for achieving a high vanillin yield in the subsequent oxidation step.

[0068] During the test of the above Examples 1-5 and Comparative Examples 1-3, the obtained isoeugenol was recorded as an intermediate, and the structural diagram is shown in FIG. 1. Figure 1 The structural diagram of the finally prepared vanillin is shown in FIG. 2. Figure 1 The content of the intermediate and the purity of the final vanillin sample were detected, and the detection method and related results are as follows:

[0069] I. Purity detection method:

[0070] Instrument: Agilent 1260 high performance liquid chromatograph;

[0071] Mobile phase: 0.1% acetic acid in water: methanol = 45:55;

[0072] Flow rate: 0.8 mL / min;

[0073] Chromatographic column: Capcell PAK C18;

[0074] Column temperature: 40℃;

[0075] Wavelength: 280nm

[0076] Injection volume: 10 μL.

[0077] Solution preparation:

[0078] 1) Accurately weigh 5.00 mg of the intermediate sample into a 10 mL volumetric flask, dissolve with acetonitrile, and then dilute to the mark, shake well to obtain the intermediate sample solution.

[0079] 2) Accurately weigh 5.00 mg of the vanillin sample into a 10 mL volumetric flask, dissolve with acetonitrile, and then dilute to the mark, shake well to obtain the vanillin sample solution.

[0080] II. Yield calculation method:

[0081] Yield = m ;

[0082] Wherein, M R : relative molecular mass of raw material, m R : raw material input mass; m P : actual product output mass, M p : relative molecular mass of product.

[0083] III. Purity calculation method: HPLC area normalization method, the specific calculation formula is as follows:

[0084] Purity of sample = ;

[0085] Wherein, C: target peak area, C0: sum of total area of all chromatographic peaks.

[0086] After detecting the intermediates in examples 1-5 and comparative examples 1-3 and vanillin by high performance liquid chromatography, the data was sorted, and the yield of the intermediates and vanillin samples and the purity of the final vanillin sample were recorded in table 2.

[0087] Table 2

[0088]

[0089] As can be seen from table 2, the yield of the intermediates and vanillin prepared in examples 1-5 is greater than 88%, and the purity of vanillin is more than 99%, which is obviously better than that of comparative examples 1-3; the yield of vanillin in example 3 is the highest, the yield of vanillin can reach 93.8%, and the purity reaches 99.7%, which corresponds to the largest specific surface area and pore volume in table 1, and the liquid chromatogram of the vanillin prepared finally is shown in the attached figure 2. Figure 3 It can be seen that the vanillin prepared in example 3 has no impurity peak and high purity; comparative example 1 uses K2CO3 / isopropanol mixed system instead of K2CO3 / g-C3N4 solid base catalyst, and the yield of isoeugenol and vanillin decreases obviously, and in addition, from the attached figure 3, it can be seen that the vanillin prepared in comparative example 1 has impurity peaks, and the purity is not high. Figure 2The liquid chromatogram of the intermediate (isoeugenol) prepared in Example 3 can also show that in the preparation method of Example 3, eugenol shows a high conversion rate, thereby making the intermediate yield high and having no obvious impurity peaks; in Comparative Example 2, without the Ni-Mo / aluminosilicate / carbon-based material, only under the alkaline condition and oxygen, the autoxidation reaction is difficult to proceed, the yield of vanillin is only 18.5%, and the purity is obviously decreased; in Comparative Example 3, when the aluminosilicate / carbon-based carrier is used without loading Ni-Mo, the yield and purity of vanillin are obviously lower than those in Example 3, which shows that the simple carrier only plays a limited adsorption and mass transfer role and cannot replace the Ni-Mo / aluminosilicate / carbon-based catalytic material. In summary, the final product obtained by using the preparation method of the present application has a high purity and reaches an excellent yield.

[0090] The above is the preferred embodiment of the present application, and those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for preparing vanillin using eugenol, characterized in that, Includes the following steps: S1. Mix and stir the Ni-Mo mixed impregnation solution and the aluminosilicate / carbon-based support, let it stand for aging, heat and evaporate, dry and calcine under inert gas protection to obtain Ni-Mo / aluminosilicate / carbon-based material; S2. Potassium carbonate was dissolved in water and added dropwise to a g-C3N4 suspension. After stirring and aging by standing, the mixture was filtered, washed, dried, and calcined under inert gas protection to obtain a K2CO3 / g-C3N4 solid base catalyst. Subsequently, eugenol, anhydrous isopropanol, and the K2CO3 / g-C3N4 solid base catalyst were added to a closed high-pressure reactor and heated under nitrogen protection. The mixture was then separated and distilled under reduced pressure to obtain isoeugenol. S3. Add isoeugenol, Ni-Mo / aluminosilicate / carbon-based material, anhydrous ethanol and deionized water to a sealed pressure-resistant reactor and mix. Add sodium hydroxide solution dropwise and stir. Heat, introduce oxygen, stir and react, cool, separate, adjust pH to acidic, age, filter, wash, add to ethanol aqueous solution, heat and stir, decolorize, filter, recrystallize, wash, and vacuum dry to obtain vanillin.

2. The method for preparing vanillin using eugenol according to claim 1, characterized in that, The Ni-Mo mixed impregnation solution is obtained by sequentially adding 0.4-1 parts by mass of nickel nitrate hexahydrate and 0.3-0.8 parts by mass of ammonium heptamolybdate tetrahydrate to 40-60 parts by volume of deionized water and stirring magnetically for 20-40 minutes.

3. The method for preparing vanillin using eugenol according to claim 1, characterized in that, The aluminosilicate / carbon-based support is prepared by mixing 1-1.5 parts by weight of APTES-activated carbon and 150-200 parts by volume of anhydrous ethanol, ultrasonically dispersing for 10-15 min, adding 4.2-6 parts by weight of hexadecyltrimethylammonium bromide and stirring for 10-15 min, adding 2.8-4 parts by volume of disec-butoxyaluminoxytriethoxysilane and stirring for 1-2 h, then slowly adding 100-150 parts by volume of deionized water and 20-50 parts by volume of 0.2wt%-0.8wt% sodium hydroxide solution and stirring for 2-4 h, continuing stirring for 3-5 h after the addition is completed, hydrothermally treating in a sealed container at 90-110℃ for 36-48 h, cooling to room temperature, filtering to separate the solid, adding 300-400 parts by volume of anhydrous ethanol and stirring and extracting at 60-80℃ for 2-3 h, filtering, washing with anhydrous ethanol, and drying at 80-100℃ for 8-12 h.

4. The method for preparing vanillin using eugenol according to claim 3, characterized in that, The APTES-activated carbon is obtained by mixing and stirring 2-3 parts by mass of chlorinated activated carbon and 150-200 parts by volume of dichloromethane for 10-15 min, adding 1.2-2.5 parts by volume of 3-aminopropyltrimethoxysilane and magnetically stirring for 20-24 h, filtering, washing successively with dichloromethane and methanol, and drying at 60-80℃ for 8-12 h; the chlorinated activated carbon is obtained by mixing and ultrasonically dispersing 3-5 parts by mass of activated carbon and 120-160 parts by volume of toluene for 10-15 min, adding 4-10 parts by volume of thionyl chloride, refluxing at 115-125℃ for 4-6 h, filtering, washing the filter cake with toluene 2-3 times, and drying at 80-100℃ for 10-12 h.

5. The method for preparing vanillin using eugenol according to claim 1, characterized in that, In step S1, the Ni-Mo mixed impregnation solution and 1-1.5 parts by mass of aluminosilicate / carbon-based carrier are mixed and stirred for 1-3 hours, allowed to stand for aging for 8-16 hours, and then the moisture is slowly evaporated under a water bath at 60-80°C. After drying at 100-120°C for 8-12 hours, the material is placed in a tube furnace and heated to 350-450°C under nitrogen protection, held for 2-4 hours, and then cooled to room temperature to obtain the Ni-Mo / aluminosilicate / carbon-based material.

6. The method for preparing vanillin using eugenol according to claim 1, characterized in that, The K2CO3 / g-C3N4 solid base catalyst is prepared by mixing 1-3 parts by mass of potassium carbonate and 30-40 parts by volume of deionized water, stirring magnetically for 10-15 min, and then slowly adding it dropwise to a g-C3N4 suspension, controlling the dropwise addition time to 20-30 min. After the dropwise addition is complete, continue magnetic stirring for 4-6 h, allow to stand for aging for 8-12 h, filter, collect the solid, wash with deionized water and anhydrous ethanol 2-4 times sequentially, dry at 75-80℃ for 10-12 h, and place in a tube furnace. The process involves heating the mixture to 300-350℃ under nitrogen protection, holding it at that temperature for 2-3 hours, and then cooling it to room temperature. The g-C3N4 suspension is obtained by mixing 2-5 parts by mass of g-C3N4 and 450-600 parts by volume of isopropanol solution, ultrasonically treating it under ice-water bath conditions for 3-5 hours, centrifuging at 3000 rpm for 10-15 minutes to collect the supernatant, centrifuging at 8000 rpm for 15-20 minutes to collect the precipitate, drying it at 60-70℃ for 10-12 hours, and then adding it to 100 mL of 50 v / v% ethanol aqueous solution and ultrasonically dispersing it for 20-30 minutes.

7. The method for preparing vanillin using eugenol according to claim 1, characterized in that, In step S2, 45-60 parts by mass of eugenol, 80-120 parts by volume of anhydrous isopropanol, and 2-4 parts by mass of K2CO3 / g-C3N4 solid base catalyst are added to a sealed high-pressure reactor. Under nitrogen protection, the temperature is raised to 100-120°C, and the reaction is stirred for 4-6 hours. The K2CO3 / g-C3N4 solid base catalyst is separated by filtration and washed 2-3 times with isopropanol. The filtrates are combined and distilled under reduced pressure to obtain isoeugenol.

8. The method for preparing vanillin using eugenol according to claim 1, characterized in that, In step S3, isoeugenol, Ni-Mo / aluminosilicate / carbon-based material, anhydrous ethanol, and deionized water are added to a sealed, pressure-resistant reactor and mixed and stirred for 10-20 minutes. Sodium hydroxide solution is slowly added dropwise and stirred for 10-20 minutes. The temperature is raised to 90-100°C, oxygen is introduced and maintained at an oxygen pressure of 0.3-0.5 MPa, and the reaction is stirred for 4-6 hours. Oxygen supply is stopped, and the mixture is cooled to room temperature. The Ni-Mo / aluminosilicate / carbon-based material is separated and recovered, and washed with ethanol and deionized water. The filtrates are combined and then... Adjust the pH to 2-3 with hydrochloric acid solution, continue aging for 30-60 min, collect the solid by vacuum filtration, wash with deionized water 3-5 times, add to ethanol aqueous solution, heat and stir at 60-80℃ for 10-15 min, add activated carbon and stir at 50-60℃ for decolorization for 10-20 min, filter while hot, cool the filtrate to room temperature and continue cooling to 0-5℃ for crystallization, collect the crystals by vacuum filtration, wash with ethanol aqueous solution at 0-5℃ 2-3 times, and vacuum dry at 60-80℃ for 4-6 h to obtain vanillin.

9. A method for preparing vanillin using eugenol according to claim 8, characterized in that, The concentration of the sodium hydroxide solution is 20 wt%, the concentration of the hydrochloric acid solution is 10 wt%, and the concentration of the ethanol aqueous solution is 50 v / v%~70 v / v.

10. A method for preparing vanillin using eugenol according to claim 1, characterized in that, The vanillin comprises the following raw materials: 20-30 parts by weight of isoeugenol, 1-2 parts by weight of Ni-Mo / aluminosilicate / carbon-based material, 50-80 parts by volume of anhydrous ethanol, 40-60 parts by volume of deionized water, and 30-50 parts by volume of sodium hydroxide solution.

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