Method for preparing vanillin from eugenol

Abstract

The invention provides a method for preparing vanillin from eugenol, and belongs to the technical field of organic synthesis, and the method comprises the following steps: S1, preparing a Ni-Mo / aluminosilicate / carbon-based material; s2, preparing isoeugenol; s3, isoeugenol, the Ni-Mo / aluminosilicate / carbon-based material, absolute ethyl alcohol and deionized water are added into a closed pressure-resistant reaction kettle to be mixed, a sodium hydroxide solution is dropwise added to be stirred, the temperature is increased, oxygen is introduced, stirring reaction, cooling, separation, pH adjustment to be acidic, aging, suction filtration and washing are conducted, the mixture is added into an ethanol water solution to be heated and stirred, decoloration, filtration, recrystallization and washing are conducted, and the Ni-Mo / aluminosilicate / carbon-based material is obtained. And drying in vacuum to obtain vanillin. According to the invention, side reactions can be effectively inhibited, and the yield and purity of the target product are improved.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and specifically to a method for preparing vanillin using eugenol. Background Technology

[0002] Vanillin is one of the world's most widely used single flavoring agents, possessing a sweet, bean-like, and powdery aroma. It can be used as a fixative, harmonizer, and flavoring agent in the cosmetics, daily chemical, food, and beverage industries. Vanillin is naturally found in plants such as vanilla beans and has been successfully applied in many fields, with demand increasing year by year. Due to the extremely high requirements of vanilla beans for soil and climate, and the complex fermentation process involved in natural processing, the natural source of vanillin is very limited, making it very expensive. Currently, most vanillin products on the market are chemically synthesized.

[0003] Vanillin can be synthesized chemically, primarily through the safrole, guaiacol, lignin, and eugenol routes. The safrole route suffers from difficult-to-find raw materials, high costs, and a lengthy synthesis process, thus it is rarely used for vanillin synthesis. Similarly, the guaiacol route is costly, complex, and has low yields, failing to meet green production requirements. The lignin route offers a wider range of raw material sources and is convenient, but its aroma is not as superior. The eugenol route produces vanillin with an appealing aroma, most closely resembling natural vanillin, and is safe for consumption, making it economically valuable.

[0004] Traditional eugenol synthesis processes mostly employ inorganic bases as catalysts. For example, patent application CN103626643B discloses a method for synthesizing vanillin from natural eugenol. While this method can efficiently synthesize vanillin from natural eugenol with a high yield, the isomerization reaction uses potassium hydroxide as a catalyst. This catalyst generates byproducts and a large amount of hazardous waste during the reaction. Furthermore, the reaction has low selectivity and requires complex post-treatment steps. Secondly, the oxidation of isoeugenol requires nitrobenzene, a process involving strong oxidation that may lead to peroxidation and the formation of byproducts, further increasing the difficulty of product purification.

[0005] Therefore, there is a need to provide a method for preparing vanillin using eugenol to solve the problems existing in the prior art. Summary of the Invention

[0006] In view of this, the present invention provides a method for preparing vanillin using eugenol, which can effectively suppress 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: 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.

[0008] 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.

[0009] This invention employs an impregnation method to prepare Ni-Mo / aluminosilicate / carbon-based materials for the selective oxidation of isoeugenol to vanillin, thereby improving the yield and purity of the final vanillin. Ni and Mo are predominantly dispersed in their oxidized states on the aluminosilicate / carbon-based support. A synergistic electronic interaction exists between Ni and Mo, which is beneficial for constructing a stable redox cycle system. Specifically, Ni promotes the adsorption and dehydrogenation of isoeugenol molecules, preferentially activating allylic / unsaturated bond-related reaction sites in the side chains; while Mo readily... 6+ / Mo 5+ / Mo 4+ Reversible transitions between valence states facilitate the activation of molecular oxygen, leading to the formation of surface-activated adsorbed oxygen (such as O). - O2 - Ni and Mo can participate in selective oxidation reactions; the electronic interaction between Ni and Mo can regulate the electronic structure of the metal center, so that it can efficiently activate O2 while avoiding excessive oxidation tendency, thereby achieving 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.

[0010] In addition, the inorganic framework of aluminosilicate / carbon-based supports can provide certain Lewis acid sites (Al 3+ This facilitates the directional adsorption and activation of isoeugenol near the metal center. Simultaneously, the porous structure and π-conjugated system of the carbon-based support enhance the π-π interaction with aromatic substrates, enabling the enrichment and directional adsorption of isoeugenol, improving the effective utilization of the metal active sites, and thus increasing the selectivity and yield of vanillin.

[0011] Optionally, 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.

[0012] Optionally, 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 to stir 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.

[0013] This invention utilizes APTES-activated carbon as a carbon-based support, and under alkaline catalysis (provided by NaOH solution) with cetyltrimethylammonium bromide (CTAB) as a template agent, to hydrolyze and condense disec-butoxyaluminoxytriethoxysilane, forming an in-situ porous aluminosilicate framework on the carbon-based surface. This inorganic framework not only enhances the structural stability of the support under solvent immersion conditions but also introduces Al-related Lewis acidic sites and surface functional groups such as Si-OH, thereby constructing a synergistic interfacial environment of acidic sites, metal anchoring sites, and carbon-based π-conjugated adsorption sites. This is more conducive to the uniform wetting, anchoring, and dispersion of subsequent Ni and Mo precursors, thus improving the effective utilization rate and cycle stability of the metal active centers. After further ethanol extraction to remove the CTAB template, an aluminosilicate / carbon-based support with a mesoporous aluminosilicate framework was obtained. The resulting mesoporous channels provide unobstructed pathways for the entry and diffusion of substrates and oxygen within the support, thereby facilitating the adsorption and effective contact of substrates within the support channels, improving the transport and diffusion conditions of reactants within the channels, and helping to increase the effective specific surface area and pore accessibility of the support, as well as enhancing the accessibility and uniformity of active sites.

[0014] Optionally, 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.

[0015] This invention employs thionyl chloride to acyl chloride-containing oxygen-containing functional groups such as carboxyl groups on the surface of activated carbon, introducing more reactive acyl chloride sites (such as –COCl) onto the activated carbon surface. This increases the density of reactive sites on the carbon-based support surface, providing active centers for the subsequent covalent grafting of branched 3-aminopropyltrimethoxysilane (APTES). This enhances the surface functionalization of the carbon-based support and provides a stronger interfacial bond for the subsequent in-situ growth of the aluminosilicate porous framework and the stable loading of Ni and Mo active components.

[0016] Optionally, in step S1, the Ni-Mo mixed impregnation solution and 1-1.5 parts by weight 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.

[0017] Optionally, 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 minutes, and then slowly adding it dropwise to a g-C3N4 suspension, controlling the dropwise addition time to 20-30 minutes. After the addition is complete, continue magnetic stirring for 4-6 hours, allow to stand for aging for 8-12 hours, filter, collect the solid, wash it 2-4 times with deionized water and anhydrous ethanol, dry it at 75-80℃ for 10-12 hours, and place it in a tube. In a furnace, under nitrogen protection, the temperature is raised to 300-350℃, held for 2-3 hours, and then cooled to room temperature to obtain the g-C3N4 suspension. 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 for 3-5 hours under ice-water bath conditions, 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.

[0018] This invention achieves uniform dispersion and firm loading of K2CO3 on the surface and between layers of g-C3N4 through impregnation, aging, and calcination at 300-350°C under an inert atmosphere; the calcination process promotes the growth of K2CO3. + It undergoes electrostatic adsorption / weak coordination with nitrogen-containing sites on the support, forming interfacial interactions such as KO-(C / N), thereby constructing CO3-based structures on the support surface. 2- The solid basic sites, which are mainly composed of relevant components and accompanied by a small number of surface hydroxyl groups (–OH), thereby increasing the number and accessibility of basic sites in solid basic catalysts.

[0019] In addition, the present invention processes g-C3N4 through isopropanol ultrasonic peeling and centrifugal grading, which can effectively peel the block g-C3N4 into sheets, giving it a higher specific surface area and exposing more nitrogen-containing basic sites on the surface. Subsequently, it is redispersed in an ethanol aqueous solution to provide a uniform contact interface for subsequent potassium carbonate impregnation, which is beneficial to the uniform loading and anchoring of K2CO3 on the surface and between the sheets.

[0020] Optionally, 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.

[0021] Optionally, 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. 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.

[0022] The present invention adds sodium hydroxide to make isoeugenol exist in its sodium salt form, which improves its solubility in ethanol / water phase and enhances the degree of deprotonation of phenolic hydroxyl groups. This is beneficial for the substrate to be adsorbed and activated in anionic form by the metal active sites and aluminosilicate Lewis acid sites on the catalyst surface. At the same time, the alkaline environment can further inhibit side reactions such as self-condensation and polymerization.

[0023] 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 50 v / v% to 70 v / v.

[0024] 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.

[0025] The above-described technical solution of the present invention has at least the following beneficial effects: 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.

[0026] 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.

[0027] 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

[0028] Figure 1 The structural formulas of the intermediate and vanillin of this invention are as follows; Figure 2 This is a liquid chromatogram of the intermediate obtained in Example 3 of the present invention; Figure 3 This is a liquid chromatogram of vanillin obtained in Example 3 of the present invention. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. The described embodiments are some embodiments of the present invention, and all other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0030] Example 1 4 g g-C3N4 was mixed with 500 mL isopropanol solution and sonicated in an ice-water bath for 4 h. The supernatant was collected by centrifugation at 3000 rpm for 13 min, and the precipitate was collected by centrifugation at 8000 rpm for 18 min. After drying at 65 °C for 11.5 h, the precipitate was added to 100 mL of 50 v / v% ethanol aqueous solution and sonicated for 27 min to obtain a g-C3N4 suspension. 2 g potassium carbonate and 38 mL deionized water were mixed and magnetically stirred for 14 min. The mixture was then slowly added dropwise to the g-C3N4 suspension, with the addition time controlled at 25 min. After the addition was complete, magnetic stirring was continued for 5.5 h. The mixture was allowed to stand for 11 h, filtered, and the solid was collected. The solid was washed three times with deionized water and anhydrous ethanol, respectively, and dried at 78 °C for 11 h. The solid was then placed in a tube furnace, heated to 330 °C under nitrogen protection, held at that temperature for 2.5 h, and cooled to room temperature to obtain a K2CO3 / g-C3N4 solid base catalyst.

[0031] 4.5 g of activated carbon and 150 mL of toluene were mixed and ultrasonically dispersed for 14 min. 8 mL of thionyl chloride was added, and the mixture was refluxed at 120 °C for 5.5 h. After filtration, the filter cake was washed three times with toluene and dried at 90 °C for 11 h to obtain chlorinated activated carbon. 2.8 g of chlorinated activated carbon and 160 mL of dichloromethane were mixed and stirred for 14 min. 2 mL of 3-aminopropyltrimethoxysilane (APTES) was added, and the mixture was magnetically stirred for 22 h. After filtration, the mixture was washed successively with dichloromethane and methanol and dried at 70 °C for 10 h to obtain APTES-activated carbon. 1.4 g of APTES-activated carbon and 180 mL of anhydrous ethanol were mixed and ultrasonically dispersed for 14 min. 5.5 g of hexadecyltrimethylammonium bromide (CTAB) was added, and the mixture was stirred for 14 min. 3.5 mL of disec-butoxyaluminoxytriethoxysilane (CAS: 68959-06-8) was added, and the mixture was stirred for 1.5 h. 130 mL of deionized water and 40 mL of [unspecified ethanol] were slowly added dropwise. A 0.7 wt% sodium hydroxide solution was added and stirred continuously for 3.5 h. After the addition was completed, stirring continued for 4 h. The solution was then hydrothermally treated at 100 °C for 42 h in a sealed container. After cooling to room temperature, the solid was separated by filtration. The solid was then added to 360 mL of anhydrous ethanol and extracted by stirring at 70 °C for 2.5 h. After filtration, the solid was washed with anhydrous ethanol and dried at 90 °C for 10 h to obtain an aluminosilicate / carbon-based support. 0.8 g of nickel nitrate hexahydrate and 0.7 g of ammonium heptamolybdate tetrahydrate were added sequentially to 50 mL of deionized water and magnetically stirred for 30 min to obtain a Ni-Mo mixed impregnation solution. 1.3 g of aluminosilicate / carbon-based support was added and stirred for 2.5 h. The solution was allowed to stand for aging for 15 h. After slowly evaporating the water under a 70 °C water bath, the solution was dried at 110 °C for 10 h. The solution was then placed in a tube furnace and heated to 400 °C under nitrogen protection, held at that temperature for 3.5 h, and cooled to room temperature to obtain the Ni-Mo / aluminosilicate / carbon-based material.

[0032] 56g of eugenol, 110mL of anhydrous isopropanol, and 3.5g of K2CO3 / g-C3N4 solid base catalyst were added to a sealed high-pressure reactor. The mixture was heated to 110℃ under nitrogen protection and stirred for 5 hours. The K2CO3 / g-C3N4 solid base catalyst was then separated by filtration and washed three times with isopropanol. The filtrates were combined and distilled under reduced pressure to obtain isoeugenol. 28g of isoeugenol, 1.8g of Ni-Mo / aluminosilicate / carbon-based material, 70mL of anhydrous ethanol, and 50mL of deionized water were added to a sealed pressure-resistant reactor and stirred for 18 minutes. Then, 40mL of [unspecified liquid] was slowly added dropwise. Stirring a 20wt% sodium hydroxide solution for 18 min, heating to 95℃, introducing oxygen, and stirring for 5 h while maintaining an oxygen pressure of 0.4 MPa, then stopping the oxygen supply and cooling to room temperature, separating and recovering the Ni-Mo / aluminosilicate / carbon-based material, and washing with ethanol and deionized water, combining the filtrates, adjusting the pH to 2.6 with a 10wt% hydrochloric acid solution, continuing stirring and aging for 50 min, collecting the solid by vacuum filtration, washing four times with deionized water, adding it to a 60v / v% ethanol aqueous solution, heating and stirring at 70℃ for 13 min, adding 0.7 g of activated carbon, stirring and decolorizing at 55℃ for 16 min, filtering while hot, cooling the filtrate to room temperature, and then further cooling to 2℃ for crystallization, collecting the crystals by vacuum filtration, washing three times with a 2℃ 60v / v% ethanol aqueous solution, and drying under vacuum at 70℃ for 5 h to obtain vanillin.

[0033] Example 2 2 g g-C3N4 was mixed with 450 mL isopropanol solution and sonicated for 3 h in an ice-water bath. The supernatant was collected 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 precipitate was added to 100 mL of 50 v / v% ethanol aqueous solution and sonicated for 20 min to obtain g-C3N4 suspension. 1 g potassium carbonate and 30 mL deionized water were mixed and magnetically stirred for 10 min. The mixture was then slowly added dropwise to the g-C3N4 suspension, with the addition time controlled at 20 min. After the addition was complete, magnetic stirring was continued for 4 h. The mixture was allowed to stand for 8 h, filtered, and the solid was collected. The solid was washed twice with deionized water and anhydrous ethanol, respectively, and dried at 75 °C for 10 h. The solid was placed in a tube furnace, heated to 300 °C under nitrogen protection, held at that temperature for 2 h, and then cooled to room temperature to obtain K2CO3 / g-C3N4 solid base catalyst.

[0034] 3g of activated carbon was ultrasonically dispersed in 120mL of toluene for 10min. 4mL of thionyl chloride was added, and the mixture was refluxed at 115℃ for 4h. After filtration, the filter cake was washed twice with toluene and dried at 80℃ for 10h to obtain chlorinated activated carbon. 2g of chlorinated activated carbon was mixed with 150mL of dichloromethane and stirred for 10min. 1.2mL of 3-aminopropyltrimethoxysilane (APTES) was added, and the mixture was magnetically stirred for 20h. After filtration, the mixture was washed successively with dichloromethane and methanol, and dried at 60℃ for 8h to obtain APTES-activated carbon. 1g of APTES-activated carbon was mixed with 150mL of anhydrous ethanol and ultrasonically dispersed for 10min. 4.2g of hexadecyltrimethylammonium bromide (CTAB) was added, and the mixture was stirred for 10min. 2.8mL of disec-butoxyaluminoxytriethoxysilane (CAS: 68959-06-8) was added, and the mixture was stirred for 1h. 100mL of deionized water and 20mL of [unspecified ethanol] were slowly added dropwise. A 0.2 wt% sodium hydroxide solution was added and stirred continuously for 2 hours. After the addition was completed, stirring was continued for 3 hours. The solution was then hydrothermally treated at 90°C for 36 hours in a sealed container. After cooling to room temperature, the solid was separated by filtration. The solid was then added to 300 mL of anhydrous ethanol and extracted by stirring at 80°C for 3 hours. After filtration, the solid was washed with anhydrous ethanol and dried at 80°C for 8 hours to obtain an aluminosilicate / carbon-based support. 0.4 g of nickel nitrate hexahydrate and 0.3 g of ammonium heptamolybdate tetrahydrate were added sequentially to 40 mL of deionized water and magnetically stirred for 20 minutes to obtain a Ni-Mo mixed impregnation solution. 1 g of aluminosilicate / carbon-based support was added and stirred for 1 hour. The solution was allowed to stand for aging for 8 hours. After slowly evaporating the water in a 60°C water bath, the solution was dried at 100°C for 8 hours. The solution was then placed in a tube furnace and heated to 350°C under nitrogen protection. The temperature was maintained for 2 hours and then cooled to room temperature to obtain the Ni-Mo / aluminosilicate / carbon-based material.

[0035] 45g of eugenol, 80mL of anhydrous isopropanol, and 2g of K2CO3 / g-C3N4 solid base catalyst were added to a sealed high-pressure reactor. The mixture was heated to 100℃ under nitrogen protection and stirred for 4 hours. The K2CO3 / g-C3N4 solid base catalyst was then separated and washed twice with isopropanol. The filtrates were combined and distilled under reduced pressure to obtain isoeugenol. 20g of isoeugenol, 1g of Ni-Mo / aluminosilicate / carbon-based material, 50mL of anhydrous ethanol, and 40mL of deionized water were added to a sealed pressure-resistant reactor and stirred for 10 minutes. Then, 30mL of [unspecified material] was slowly added dropwise. Stirring a 20wt% sodium hydroxide solution for 10 min, heating to 90℃, introducing oxygen, and stirring for 4 h while maintaining an oxygen pressure of 0.3 MPa, then stopping the oxygen supply and cooling to room temperature, separating and recovering the Ni-Mo / aluminosilicate / carbon-based material and washing with ethanol and deionized water, combining the filtrates, adjusting the pH to 2 with a 10wt% hydrochloric acid solution, continuing stirring and aging for 30 min, collecting the solid by vacuum filtration, washing three times with deionized water, adding it to a 50v / v% ethanol aqueous solution, heating and stirring at 60℃ for 10 min, adding 0.5 g of activated carbon, stirring and decolorizing at 50℃ for 10 min, filtering while hot, cooling the filtrate to room temperature, and then further cooling to 0℃ for crystallization, collecting the crystals by vacuum filtration, washing twice with a 0℃ 50v / v% ethanol aqueous solution, and drying under vacuum at 60℃ for 4 h to obtain vanillin.

[0036] Example 3 5g of g-C3N4 was mixed with 600mL of isopropanol solution and sonicated for 5h under ice-water bath conditions. The supernatant was collected by centrifugation at 3000rpm for 15min, and the precipitate was collected by centrifugation at 8000rpm for 20min. After drying at 70℃ for 12h, the precipitate was added to 100mL of 50v / v% ethanol aqueous solution and sonicated for 30min to obtain g-C3N4 suspension. 3g of potassium carbonate and 40mL of deionized water were mixed and magnetically stirred for 15min. The mixture was then slowly added dropwise to the g-C3N4 suspension, with the addition time controlled at 30min. After the addition was completed, magnetic stirring was continued for 6h. The mixture was allowed to stand for 12h for aging, filtered, and the solid was collected. The solid was washed 4 times with deionized water and anhydrous ethanol, respectively, and dried at 80℃ for 12h. The solid was placed in a tube furnace, heated to 350℃ under nitrogen protection, held for 3h, and cooled to room temperature to obtain K2CO3 / g-C3N4 solid base catalyst.

[0037] 5g of activated carbon and 160mL of toluene were mixed and ultrasonically dispersed for 15min. 10mL of thionyl chloride was added, and the mixture was refluxed at 125℃ for 6h. After filtration, the filter cake was washed three times with toluene and dried at 100℃ for 12h to obtain chlorinated activated carbon. 3g of chlorinated activated carbon and 200mL of dichloromethane were mixed and stirred for 15min. 2.5mL of 3-aminopropyltrimethoxysilane (APTES) was added, and the mixture was magnetically stirred for 24h. After filtration, the mixture was washed successively with dichloromethane and methanol and dried at 80℃ for 12h to obtain APTES-activated carbon. 1.5g of APTES-activated carbon and 200mL of anhydrous ethanol were mixed and ultrasonically dispersed for 15min. 6g of hexadecyltrimethylammonium bromide (CTAB) was added, and the mixture was stirred for 15min. 4mL of di-sec-butoxyaluminoxytriethoxysilane (CAS: 68959-06-8) was added, and the mixture was stirred for 2h. 150mL of deionized water and 50mL of [unclear text] were slowly added dropwise. A 0.8 wt% sodium hydroxide solution was added and stirred continuously for 4 hours. After the addition was completed, stirring was continued for 5 hours. The solution was then hydrothermally treated at 110℃ for 48 hours in a sealed container. After cooling to room temperature, the solid was separated by filtration. The solid was then added to 400 mL of anhydrous ethanol and extracted by stirring at 60℃ for 2 hours. After filtration, the solid was washed with anhydrous ethanol and dried at 100℃ for 12 hours to obtain an aluminosilicate / carbon-based support. 1 g of nickel nitrate hexahydrate and 0.8 g of ammonium heptamolybdate tetrahydrate were added sequentially to 60 mL of deionized water and magnetically stirred for 40 minutes to obtain a Ni-Mo mixed impregnation solution. 1.5 g of aluminosilicate / carbon-based support was added and stirred for 3 hours. The solution was allowed to stand for aging for 16 hours. After slowly evaporating the water in an 80℃ water bath, the solution was dried at 120℃ for 12 hours. The solution was then placed in a tube furnace and heated to 450℃ under nitrogen protection, held for 4 hours, and cooled to room temperature to obtain Ni-Mo / aluminosilicate / carbon-based material.

[0038] 60g of eugenol, 120mL of anhydrous isopropanol, and 4g of K2CO3 / g-C3N4 solid base catalyst were added to a sealed high-pressure reactor. The mixture was heated to 120℃ under nitrogen protection and stirred for 6 hours. The K2CO3 / g-C3N4 solid base catalyst was then separated by filtration and washed three times with isopropanol. The filtrates were combined and distilled under reduced pressure to obtain isoeugenol. 30g of isoeugenol, 2g of Ni-Mo / aluminosilicate / carbon-based material, 80mL of anhydrous ethanol, and 60mL of deionized water were added to a sealed pressure-resistant reactor and stirred for 20 minutes. Then, 50mL of [unspecified material] was slowly added dropwise. Stirring a 20wt% sodium hydroxide solution for 20 min, heating to 100℃, introducing oxygen, and stirring for 6 h while maintaining an oxygen pressure of 0.5 MPa, then stopping the oxygen supply and cooling to room temperature, separating and recovering the Ni-Mo / aluminosilicate / carbon-based material, and washing with ethanol and deionized water, combining the filtrates, adjusting the pH to 3 with a 10wt% hydrochloric acid solution, continuing stirring and aging for 60 min, collecting the solid by vacuum filtration, washing 5 times with deionized water, adding it to a 70v / v% ethanol aqueous solution, heating and stirring at 80℃ for 15 min, adding 0.8 g of activated carbon, stirring and decolorizing at 60℃ for 20 min, filtering while hot, cooling the filtrate to room temperature, and then further cooling to 5℃ for crystallization, collecting the crystals by vacuum filtration, washing 3 times with a 5℃ 70v / v% ethanol aqueous solution, and vacuum drying at 80℃ for 6 h to obtain vanillin.

[0039] Example 4 3g of g-C3N4 was mixed with 550mL of isopropanol solution and sonicated in an ice-water bath for 4h. The supernatant was collected by centrifugation at 3000rpm for 12min, and the precipitate was collected by centrifugation at 8000rpm for 16min. After drying at 62℃ for 10.5h, the precipitate was added to 100mL of 50v / v% ethanol aqueous solution and sonicated for 25min to obtain a g-C3N4 suspension. 2g of potassium carbonate and 35mL of deionized water were mixed and magnetically stirred for 12min. The mixture was then slowly added dropwise to the g-C3N4 suspension, with the addition time controlled at 25min. After the addition was complete, magnetic stirring was continued for 5h. The mixture was allowed to stand for aging for 10h, filtered, and the solid was collected. The solid was washed three times with deionized water and anhydrous ethanol, respectively, and dried at 76℃ for 11h. The solid was then placed in a tube furnace, heated to 320℃ under nitrogen protection, held at that temperature for 2.5h, and cooled to room temperature to obtain a K2CO3 / g-C3N4 solid base catalyst.

[0040] 3.5 g of activated carbon and 140 mL of toluene were mixed and ultrasonically dispersed for 12 min. 5 mL of thionyl chloride was added, and the mixture was refluxed at 120 °C for 5 h. After filtration, the filter cake was washed twice with toluene and dried at 90 °C for 10.5 h to obtain chlorinated activated carbon. 2.2 g of chlorinated activated carbon and 160 mL of dichloromethane were mixed and stirred for 12 min. 1.8 mL of 3-aminopropyltrimethoxysilane (APTES) was added, and the mixture was magnetically stirred for 22 h. After filtration, the mixture was washed successively with dichloromethane and methanol and dried at 65 °C for 10 h to obtain APTES-activated carbon. 1.2 g of APTES-activated carbon and 170 mL of anhydrous ethanol were mixed and ultrasonically dispersed for 12 min. 5 g of hexadecyltrimethylammonium bromide (CTAB) was added, and the mixture was stirred for 12 min. 3 mL of disec-butoxyaluminoxytriethoxysilane (CAS: 68959-06-8) was added, and the mixture was stirred for 1.5 h. 120 mL of deionized water and 30 mL of [unspecified ethanol] were slowly added dropwise. A 0.3 wt% sodium hydroxide solution was added and stirred continuously for 2.5 h. After the addition was completed, stirring was continued for 3.5 h. The solution was then hydrothermally treated at 95 °C for 40 h in a sealed container. After cooling to room temperature, the solid was separated by filtration. The solid was extracted by stirring at 75 °C for 2.2 h, filtered, washed with anhydrous ethanol, and dried at 95 °C for 10 h to obtain an aluminosilicate / carbon-based support. 0.5 g of nickel nitrate hexahydrate and 0.5 g of ammonium heptamolybdate tetrahydrate were added sequentially to 50 mL of deionized water and magnetically stirred for 30 min to obtain a Ni-Mo mixed impregnation solution. 1.2 g of aluminosilicate / carbon-based support was added and stirred for 2 h. The solution was allowed to stand for aging for 10 h. After slowly evaporating the water under a 75 °C water bath, the solution was dried at 112 °C for 9 h. The solution was then placed in a tube furnace, heated to 380 °C under nitrogen protection, held for 3 h, and cooled to room temperature to obtain the Ni-Mo / aluminosilicate / carbon-based material.

[0041] 50g of eugenol, 90mL of anhydrous isopropanol, and 2.5g of K2CO3 / g-C3N4 solid base catalyst were added to a sealed high-pressure reactor. The mixture was heated to 105℃ under nitrogen protection and stirred for 4.5h. The K2CO3 / g-C3N4 solid base catalyst was then separated by filtration and washed three times with isopropanol. The filtrates were combined and distilled under reduced pressure to obtain isoeugenol. 26g of isoeugenol, 1.1g of Ni-Mo / aluminosilicate / carbon-based material, 60mL of anhydrous ethanol, and 50mL of deionized water were added to a sealed pressure-resistant reactor and stirred for 18min. Then, 40mL of [unspecified liquid] was slowly added dropwise. Stirring a 20wt% sodium hydroxide solution for 12 min, heating to 95℃, introducing oxygen, and stirring for 4.5 h while maintaining an oxygen pressure of 0.35 MPa, then stopping the oxygen supply and cooling to room temperature, separating and recovering the Ni-Mo / aluminosilicate / carbon-based material, and washing with ethanol and deionized water, combining the filtrates, adjusting the pH to 2.2 with a 10wt% hydrochloric acid solution, continuing stirring and aging for 40 min, collecting the solid by vacuum filtration, washing it four times with deionized water, adding it to a 65v / v% ethanol aqueous solution, heating and stirring at 75℃ for 15 min, adding 0.6 g of activated carbon, stirring and decolorizing at 60℃ for 20 min, filtering while hot, cooling the filtrate to room temperature, and then further cooling to 3℃ for crystallization, collecting the crystals by vacuum filtration, washing it three times with a 5℃ 65v / v% ethanol aqueous solution, and drying it under vacuum at 75℃ for 5.5 h to obtain vanillin.

[0042] Example 5 4 g g-C3N4 was mixed with 480 mL isopropanol solution and sonicated in an ice-water bath for 4 h. The supernatant was collected 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 precipitate was added to 100 mL of 50 v / v% ethanol aqueous solution and sonicated for 26 min to obtain g-C3N4 suspension. 2 g potassium carbonate and 32 mL deionized water were mixed and magnetically stirred for 14 min. The mixture was then slowly added dropwise to the g-C3N4 suspension, with the addition time controlled at 24 min. After the addition was complete, magnetic stirring was continued for 4 h. The mixture was allowed to stand for 12 h, filtered, and the solid was collected. The solid was washed twice with deionized water and anhydrous ethanol, respectively, and dried at 76 °C for 12 h. The solid was then placed in a tube furnace, heated to 350 °C under nitrogen protection, held at that temperature for 2 h, and cooled to room temperature to obtain K2CO3 / g-C3N4 solid base catalyst.

[0043] 5g of activated carbon and 120mL of toluene were mixed and ultrasonically dispersed for 15min. 5mL of thionyl chloride was added, and the mixture was refluxed at 125℃ for 4h. After filtration, the filter cake was washed twice with toluene and dried at 80℃ for 12h to obtain chlorinated activated carbon. 3g of chlorinated activated carbon and 190mL of dichloromethane were mixed and stirred for 15min. 2.5mL of 3-aminopropyltrimethoxysilane (APTES) was added, and the mixture was magnetically stirred for 24h. After filtration, the mixture was washed successively with dichloromethane and methanol, and dried at 60℃ for 12h to obtain APTES-activated carbon. 1.5g of APTES-activated carbon and 200mL of anhydrous ethanol were mixed and ultrasonically dispersed for 10min. 6g of hexadecyltrimethylammonium bromide (CTAB) was added, and the mixture was stirred for 10min. 2.8mL of disec-butoxyaluminoxytriethoxysilane (CAS: 68959-06-8) was added, and the mixture was stirred for 1h. 150mL of deionized water and 40mL of [unspecified ethanol] were slowly added dropwise. A 0.6 wt% sodium hydroxide solution was added and stirred continuously for 3 hours. After the addition was completed, stirring was continued for another 3 hours. The solution was then hydrothermally treated at 110°C for 36 hours in a sealed container. After cooling to room temperature, the solid was separated by filtration. The solid was extracted by stirring at 65°C for 3 hours, filtered, washed with anhydrous ethanol, and dried at 80°C for 12 hours to obtain an aluminosilicate / carbon-based support. 0.4 g of nickel nitrate hexahydrate and 0.8 g of ammonium heptamolybdate tetrahydrate were added sequentially to 40 mL of deionized water and magnetically stirred for 40 minutes to obtain a Ni-Mo mixed impregnation solution. 1.5 g of aluminosilicate / carbon-based support was added and stirred for 3 hours. The solution was allowed to stand for aging for 8 hours. After slowly evaporating the water in an 80°C water bath, the solution was dried at 100°C for 12 hours. The solution was then placed in a tube furnace and heated to 450°C under nitrogen protection, held for 2 hours, and cooled to room temperature to obtain the Ni-Mo / aluminosilicate / carbon-based material.

[0044] 60g of eugenol, 100mL of anhydrous isopropanol, and 4g of K2CO3 / g-C3N4 solid base catalyst were added to a sealed high-pressure reactor. The mixture was heated to 120℃ under nitrogen protection and stirred for 4 hours. The K2CO3 / g-C3N4 solid base catalyst was then separated by filtration and washed twice with isopropanol. The filtrates were combined and distilled under reduced pressure to obtain isoeugenol. 30g of isoeugenol, 1.7g of Ni-Mo / aluminosilicate / carbon-based material, 80mL of anhydrous ethanol, and 40mL of deionized water were added to a sealed pressure-resistant reactor and stirred for 20 minutes. Then, 30mL of [unspecified liquid] was slowly added dropwise. Stirring a 20wt% sodium hydroxide solution for 20 min, heating to 90℃, introducing oxygen, and stirring for 4 h while maintaining an oxygen pressure of 0.5 MPa, then stopping the oxygen supply and cooling to room temperature, separating and recovering the Ni-Mo / aluminosilicate / carbon-based material, and washing with ethanol and deionized water, combining the filtrates, adjusting the pH to 3 with a 10wt% hydrochloric acid solution, continuing stirring and aging for 30 min, collecting the solid by vacuum filtration, washing 5 times with deionized water, adding it to a 62v / v% ethanol aqueous solution, heating and stirring at 65℃ for 14 min, adding 0.7 g of activated carbon, stirring and decolorizing at 55℃ for 15 min, filtering while hot, cooling the filtrate to room temperature, and then further cooling to 1℃ for crystallization, collecting the crystals by vacuum filtration, washing twice with a 1℃ 62v / v% ethanol aqueous solution, and drying under vacuum at 65℃ for 5.5 h to obtain vanillin.

[0045] The present invention also includes comparative examples and related experiments.

[0046] Comparative Example 1 Compared with Example 3, the only difference is that a K2CO3 and isopropanol mixed system is used instead of the K2CO3 / g-C3N4 solid base catalyst. The other preparation steps and components are completely consistent, and vanillin is finally obtained.

[0047] Comparative Example 2 Compared with Example 3, the only difference is that Ni-Mo / aluminosilicate / carbon-based materials were not used. The other preparation steps and components were completely consistent, and vanillin was finally obtained.

[0048] Comparative Example 3 Compared with Example 3, the only difference is that an aluminosilicate / carbon-based support is used instead of the Ni-Mo / aluminosilicate / carbon-based material. The other preparation steps and components are completely consistent, and vanillin is finally obtained.

[0049] Performance testing The Ni-Mo / aluminosilicate / carbon-based materials prepared in Examples 1-5 were tested according to "GB / T19587-2017 Determination of Specific Surface Area of ​​Solid Materials by Gas Adsorption BET Method" and "GB / T21650.2-2008 Determination of Pore Size Distribution and Porosity of Solid Materials by Mercury Intrusion Porosimetry and Gas Adsorption Method" to obtain the specific surface area, average pore size and total pore volume; the specific test results are shown in Table 1.

[0050] Table 1

[0051] As can be seen from the data in Table 1, the Ni-Mo / aluminosilicate / carbon-based materials prepared in Examples 1-5 of this invention have high specific surface area and total pore volume, which provides a basis for achieving a high vanillin yield in the subsequent oxidation step.

[0052] In the experiments of Examples 1-5 and Comparative Examples 1-3 above, the obtained isoeugenol was referred to as an intermediate, and its structural diagram is shown in the appendix. Figure 1 The structural diagram of vanillin obtained by Chinese formula (Ⅰ) is attached. Figure 1 The Chinese formula (II) was used to detect the content of intermediates and vanillin samples, as well as the purity of the final vanillin. The detection methods and related results are as follows: I. Purity Testing Methods: Instrument: Agilent 1260 high performance liquid chromatograph; Mobile phase: Water containing 0.1% acetic acid: Methanol = 45:55; Flow rate: 0.8 mL / min; Column: Capcell PAK C18; Column temperature: 40℃; Wavelength: 280nm Injection volume: 10 μL.

[0053] Solution preparation: 1) Accurately weigh 5.00 mg of the intermediate sample, place it in a 10 mL volumetric flask, dissolve it in acetonitrile, and dilute to the mark. Shake well to obtain the intermediate sample solution.

[0054] 2) Accurately weigh 5.00 mg of vanillin sample, place it in a 10 mL volumetric flask, dissolve it in acetonitrile, dilute to the mark, and shake well to obtain vanillin sample solution.

[0055] II. Yield Calculation Method: Yield = ; Among them, M R : Relative molecular mass of raw materials, m R : Raw material input quality; m PActual output quality of the product, M p : Relative molecular mass of the product.

[0056] III. Purity Calculation Method: HPLC area normalization method, the specific calculation formula is as follows: Sample purity = ; Where C: target peak area, C0: sum of the total areas of all chromatographic peaks.

[0057] After high-performance liquid chromatography (HPLC) analysis of the intermediates and vanillin in Examples 1-5 and Comparative Examples 1-3, the data were compiled, and the yields of the intermediates and vanillin samples and the purity of the final vanillin sample were recorded in Table 2.

[0058] Table 2

[0059] As shown in Table 2, the yields of the intermediates and vanillin obtained in Examples 1-5 were all greater than 88%, and the purity of vanillin was all above 99%, which were significantly better than those of Comparative Examples 1-3. Example 3 showed the highest vanillin yield, reaching 93.8% with a purity of 99.7%, which corresponds to its highest specific surface area and pore volume as indicated in Table 1. The final liquid chromatogram of the vanillin obtained is shown in the appendix. Figure 3 It can be clearly seen that the vanillin prepared in Example 3 has no impurity peaks and has high purity; in Comparative Example 1, the yields of isoeugenol and vanillin were significantly reduced by using a K2CO3 and isopropanol mixed system instead of the K2CO3 / g-C3N4 solid base catalyst. Furthermore, from the attached... Figure 2 The liquid chromatogram of the intermediate (isoeugenol) obtained in Example 3 also shows that eugenol exhibits a high conversion rate in the preparation method of Example 3 of this invention, resulting in a high yield of the intermediate and no obvious impurity peaks. In Comparative Example 2, without the addition of Ni-Mo / aluminosilicate / carbon-based material, the auto-oxidation reaction is difficult to proceed under alkaline conditions and oxygen alone, resulting in a vanillin yield of only 18.5% and a significant decrease in purity. In Comparative Example 3, using only an aluminosilicate / carbon-based support without loading Ni-Mo, the vanillin yield and purity are significantly lower than in Example 3, indicating that the simple support only plays a limited role in adsorption and mass transfer and cannot replace the Ni-Mo / aluminosilicate / carbon-based catalytic material. In summary, the final product obtained using the preparation method of this invention has high purity and achieves excellent yield.

[0060] The above are preferred embodiments of the present invention. Those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

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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