Vanadium-based catalyst and use thereof

Abstract

This application provides a vanadium-based catalyst and its application. The catalyst includes a main catalyst, a co-catalyst, and a porous support. The main catalyst and the co-catalyst are dispersed on the porous support. The main catalyst includes vanadium and optionally molybdenum, and the co-catalyst includes fullerene. Using this vanadium-based catalyst to catalyze the methylation reaction of mixed tocopherols to produce D-α-tocopherol can effectively improve the yield and content of D-α-tocopherol.

Description

Technical Field

[0001] This application relates to the field of chemical materials, specifically to a vanadium-based catalyst and its applications. Background Technology

[0002] Tocopherols are widely used in pharmaceuticals, food, cosmetics, animal feed, and plastic products, and can be divided into two main categories: natural and synthetic. Naturally occurring tocopherols are primarily derived from the deodorized distillate of vegetable oils. Through a series of physical or chemical methods, a mixed tocopherol composition consisting of α, β, γ, and δ-tocopherols can be obtained. The three chiral carbon atoms of naturally occurring α, β, γ, and δ-tocopherols are all dextrorotatory, hence they are named D-α-tocopherol, D-β-tocopherol, D-γ-tocopherol, and D-δ-tocopherol, respectively. Synthetic α-tocopherol consists of eight equal amounts of optical isomers and is racemic; it is named DL-α-tocopherol, where D represents dextrorotatory and L represents levorotatory.

[0003] The chemical structures of tocopherols are shown in Formula 1. For α-tocopherol, R1 = CH3, R2 = CH3; for β-tocopherol, R1 = CH3, R2 = H; for γ-tocopherol, R1 = H, R2 = CH3; and for δ-tocopherol, R1 = H, R2 = H. Among these, D-α-tocopherol exhibits the highest biological activity, while other tocopherols possess only 1%–50% of its biological activity.

[0004]

[0005] However, the content of D-α-tocopherol in natural mixed tocopherols is relatively low, about 10% to 15%, with the remainder being non-α-tocopherols with low biological activity. Separating and purifying to obtain high-purity D-α-tocopherol not only incurs high raw material costs but also easily leads to resource waste. Structurally, D-α-tocopherol has 1-2 more methyl groups on the 6-hydroxyoxanaphthalene ring than non-α-tocopherols. If a certain method is adopted to add methyl groups to non-α-tocopherols, it is hoped that the conversion of non-α-tocopherols to α-tocopherols can be achieved, thereby obtaining high-purity D-α-tocopherols with high added value. Currently, the main conversion methods include chloromethylation-reduction, aminomethylation-reduction, hydroxymethylation-reduction, formylation-reduction, and direct methylation. Compared with other methods, direct methylation can achieve one-step conversion, has a simple process, and does not suffer from problems such as product instability, harsh reaction conditions, and long reaction times, making it a promising method for industrial applications. However, the conversion rate of D-α-tocopherol using this method still needs to be improved, and the challenge lies in preparing an efficient methylation catalyst.

[0006] In the prior art, catalysts for the direct methylation of mixed tocopherols generally employ one or more metal oxides. European patent application EP 0176690A1 discloses a method for the direct methylation conversion of non-α-tocopherols to α-tocopherols in a gas / liquid phase. This method uses methanol as the methylating agent and a metal oxide as the catalyst, preferably oxides of Be, Mg, Ca, Ti, Zr, V, Mo, Cr, Mn, Tc, Fe, Co, Ni, Zn, Cd, In, Sn, Si, Al, La, Ce, Pr, or Nd. This method has a relatively low conversion rate of non-α-tocopherols, but increases the D-α-tocopherol content from 5.2 wt% to 15.0 wt%. Chinese patent application CN 1201792A discloses a method for the direct methylation synthesis of D-α-tocopherol using mixed tocopherols. This method uses a mixed oxide obtained from hydrotalcite as a catalyst, which contains CuO, MgO and at least one trivalent metal oxide. Gas chromatography analysis shows that the content of D-α-tocopherol in the product can be increased to 91.2% GC area.

[0007] Chinese patent application CN 1428341A discloses a method for preparing high-content natural D-α-tocopherol using a chemical semi-synthetic approach. In this method, the catalyst is a vanadium-based catalyst or a mixture of vanadium and chromium catalysts, with a vanadium to chromium elemental weight ratio of 19:1 to 21:1. The vanadium catalyst is mainly V₂O₅, and the chromium catalyst is mainly Cr₂O₃. The catalyst amount is 5-7% (w / w) of the tocopherol concentrate. After the reaction, the purity of the product D-α-tocopherol is above 90%, but the total tocopherol recovery rate is low.

[0008] In summary, due to limitations in the performance of methylation catalysts, there is still room for further improvement in the yield and content of D-α-tocopherol in the above-mentioned direct methylation reactions. Summary of the Invention

[0009] This application provides a vanadium-based catalyst and its application to improve the yield and content of D-α-tocopherol.

[0010] The first aspect of this application provides a vanadium-based catalyst comprising a main catalyst, a co-catalyst, and a porous support, wherein the main catalyst and the co-catalyst are dispersed on the porous support, the main catalyst comprising vanadium and optionally molybdenum, and the co-catalyst comprising a fullerene.

[0011] In any embodiment of the first aspect, the main catalyst of the vanadium-based catalyst includes V2O5 and optionally MoO3; preferably, the vanadium-based catalyst includes 10-60% V2O5 and 0-40% MoO3 by mass percentage.

[0012] In any embodiment of the first aspect, the vanadium-based catalyst contains 0.5% to 10% by mass of fullerene; preferably, the fullerene comprises C1. 50 Fullerene, C 60 Fullerene, C 70 Any one or more of fullerenes and fullerene derivatives.

[0013] In any embodiment of the first aspect, the porous support for the vanadium-based catalyst is selected from titanium dioxide, cerium dioxide, silicon dioxide, alumina, porous silicon carbide, zeolite molecular sieve, kaolin, diatomaceous earth, and activated carbon.

[0014] In any embodiment of the first aspect, the main catalyst in the vanadium-based catalyst is in contact with a fullerene.

[0015] The second aspect of this application provides the application of the vanadium-based catalyst of the first aspect, including but not limited to using the vanadium-based catalyst of the first aspect as a catalyst for selective catalytic reduction denitration reaction, a catalyst for alkylation reaction of phenolic substances, or a catalyst for catalytic synthesis of pyruvate from lactic acid esters.

[0016] The third aspect of this application provides a method for preparing D-α-tocopherol, which includes catalytically methylating a tocopherol feedstock to obtain D-α-tocopherol. The tocopherol feedstock includes one or more of β-tocopherol, γ-tocopherol, and δ-tocopherol. The D-α-tocopherol is obtained by catalyzing the methylation of tocopherol using the vanadium-based catalyst provided in the first aspect.

[0017] In any embodiment of the third aspect, the preparation method includes: mixing the raw material tocopherol with a methylating agent and an optional co-solvent, wherein the methylating agent includes methanol or a mixture of hydrogen and carbon monoxide, or a mixture of hydrogen and carbon dioxide, preferably methanol, and the co-solvent includes n-hexane, cyclohexane, or ethanol; and in a methylating atmosphere, the vanadium-based catalyst provided in the first aspect catalyzes the methylation reaction of the raw material tocopherol and the methylating agent to obtain D-α-tocopherol, wherein the methylating atmosphere includes a hydrogen atmosphere, a nitrogen atmosphere, or an inert gas atmosphere.

[0018] In any embodiment of the third aspect, the mass-to-volume ratio (w / v) of the raw material tocopherol to the methylating agent is (0.05 g to 0.8 g): 1 mL, preferably (0.1 g to 0.3 g): 1 mL, wherein the volume of the methylating agent is calculated as an equal amount of methanol.

[0019] In any embodiment of the third aspect, the mass ratio of vanadium-based catalyst to tocopherol is 0.05 to 0.5:1, preferably 0.08 to 0.2:1.

[0020] In any embodiment of the third aspect, the temperature of the methylation reaction is 200–300°C, preferably 220–260°C, and more preferably 250–255°C.

[0021] In any embodiment of the third aspect, the initial pressure is 0.1 to 1 MPa, preferably 0.3 to 0.5 MPa.

[0022] In the vanadium-based catalyst of this application, the fullerene-modified main catalyst, due to its unique electronic structure and more suitable HOMO-LUMO, can interact with the active components of the main catalyst, thereby improving catalytic activity. For example, during the reaction, the presence of fullerene can capture electrons from low-valence vanadium in the catalyst, causing low-valence vanadium to transform into high-valence vanadium and restoring some catalytic activity. When this catalyst is applied to reactions such as the methylation of tocopherol, the content and yield of the target product are increased. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0024] Figure 1 The impregnation ball milling of Example 13 of this application with 1.5% C is shown. 60 Thermogravimetric curves were obtained from dynamic thermogravimetric analysis of a 30% V2O5 / TiO2 catalyst sample.

[0025] Figure 2 The analysis of the impregnated ball-milled 1.5% C sample in Example 13 of this application using MALDI-TOF mass spectrometry is shown. 60 The mass spectrum of the -30% V2O5 / TiO2 catalyst sample is shown in the inset, which is a local magnification of the peak between 720 and 724.

[0026] Figure 3 The impregnation ball milling of 1.5% C in Example 13 of this application is shown. 60 Microscopic morphology of a 30% V2O5 / TiO2 catalyst sample under a high-resolution transmission electron microscope (HRTEM). The white box in the image shows a lattice spacing of 0.276 nm and a crystal plane of V2O5(011). Detailed Implementation

[0027] The embodiments of this application will be described in further detail below with reference to the examples. The detailed description of the following embodiments is used to illustrate the principles of this application, but should not be used to limit the scope of this application, that is, this application is not limited to the described embodiments.

[0028] As described in the background section, current reactions involving the methylation of non-D-α-tocopherol to generate highly active D-α-tocopherol are limited by the performance of the methylation catalyst, resulting in significant room for improvement in both the yield and content of D-α-tocopherol. To address these shortcomings, this application provides a vanadium-based catalyst and its application.

[0029] In a first embodiment of this application, a vanadium-based catalyst is provided, comprising a main catalyst, a co-catalyst, and a porous support, wherein the main catalyst and the co-catalyst are dispersed on the porous support, the main catalyst comprising vanadium and optionally molybdenum, and the co-catalyst comprising fullerene.

[0030] The vanadium-based catalyst of this application features a fullerene-modified main catalyst. Due to the unique electronic structure and more suitable HOMO-LUMO properties of fullerenes, they can interact with the active components of the main catalyst, thereby enhancing catalytic activity. For example, during the reaction, the presence of fullerenes can capture electrons from low-valence vanadium in the catalyst, causing low-valence vanadium to transform into high-valence vanadium and restoring some catalytic activity. When this catalyst is applied to reactions such as the methylation of tocopherol, it increases the content and yield of the target product.

[0031] In this application, the vanadium and optional molybdenum in the main catalyst can be in the commonly used form of main catalyst. In some embodiments of this application, the main catalyst of the above-mentioned vanadium-based catalyst includes V2O5 and optional MoO3; preferably, by mass percentage, the vanadium-based catalyst includes 10-60% V2O5 and 0-40% MoO3. When the main catalyst includes MoO3, MoO3, as another active component for tocopherol methylation, combines with V2O5 to play a co-catalytic role, which can further improve the yield of D-α-tocopherol. In some embodiments, the vanadium-based catalyst includes 10% V2O5, 15% V2O5, 20% V2O5, 25% V2O5, 30% V2O5, 35% V2O5, 40% V2O5, 45% V2O5, 50% V2O5, 55% V2O5, or 60% V2O5. In some embodiments, the vanadium-based catalyst comprises 1% MoO3, 3% MoO3, 5% MoO3, 7% MoO3, 10% MoO3, 15% MoO3, 20% MoO3, 25% MoO3, 30% MoO3, 35% MoO3, or 40% MoO3. In some embodiments, the vanadium-based catalyst comprises, by mass percentage, 10–30% V2O5 and 0–10% MoO3.

[0032] Geometrically, fullerenes are convex polyhedra composed of pentagonal and hexagonal faces, possessing unique electronic structures and suitable HOMO-LUMO properties, enabling them to interact with active components and thus enhance catalytic activity. Therefore, fullerenes with typical fullerene geometries can be used in this application. In some embodiments of this application, the fullerene includes C... 50 C 60 C 70 Any one or more of a series of fullerenes and fullerene derivatives. The term "fullerene derivative" as used herein includes exosubstituted fullerenes and fullerene inclusion compounds, wherein an exosubstituted fullerene is a fullerene derivative having substituent groups outside a carbon cage, and a fullerene inclusion compound is characterized by molecules or atoms bound within a carbon cage. In some embodiments, fullerene derivatives include, but are not limited to, polymeric fullerenes, fullerols, and nitrofullerene derivatives.

[0033] Fullerenes, as co-catalysts, can improve the catalytic effect of the main catalyst. However, when used alone, they do not catalyze the methylation of mixed tocopherols. In some embodiments of this application, the fullerene content in the vanadium-based catalyst is in the range of 0.5% to 10% by mass, for example, the mass percentage of fullerene in the vanadium-based catalyst is 0.5%, 1%, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%, and more preferably in the range of 1% to 10% or 1% to 5%, to further improve the selectivity of D-α-tocopherol and the recovery rate of total tocopherols. Controlling the fullerene content within the above range avoids increased costs and dilution of the effective content of the main catalyst due to excessive use of fullerenes, and significantly improves the catalytic effect of the main catalyst.

[0034] In some embodiments of this application, the vanadium-based catalyst has a large BET specific surface area, around 100 m². 2 / g or more. Vanadium-based catalysts with the above-mentioned BET specific surface area can provide more active contact sites, thus allowing the active components of the catalyst to exert their effects better.

[0035] The term "specific surface area" as used in this application refers to the total surface area possessed by a unit mass of catalyst particles. The test method for the BET specific surface area of ​​the above-mentioned vanadium-based catalyst can be found in standard GB / T19587-2004 "Determination of Specific Surface Area of ​​Solid Substances by Gas Adsorption BET Method".

[0036] The porous support used in this application can be selected from commonly used catalyst supports, such as materials with excellent chemical stability, high specific surface area, abundant pore structure, and excellent mechanical strength. In some embodiments of this application, the porous support for the vanadium-based catalyst is selected from titanium dioxide, cerium dioxide, silicon dioxide, alumina, porous silicon carbide, zeolite molecular sieves, kaolin, diatomaceous earth, and activated carbon. This porous support serves to disperse and support the main catalyst and the co-catalyst, preventing the agglomeration of the main catalyst and the co-catalyst, increasing the effective surface area of ​​the catalyst, thereby improving the catalyst's activity, mechanical strength, and thermal stability, extending the catalyst's lifespan, and saving costs.

[0037] In some embodiments of this application, the main catalyst is in contact with a fullerene. Compared to undoped fullerene-based vanadium catalysts, fullerene-doped vanadium catalysts exhibit better methylation catalysis under the same catalyst dosage conditions.

[0038] The vanadium-based catalyst of this application can be prepared by referring to the conventional methods for preparing supported catalysts, such as impregnation, sol-gel, mechanical ball milling, and impregnation-ball milling. The following is a brief description of each of these methods.

[0039] In some embodiments, the vanadium-based catalyst is prepared by impregnation, including the following steps:

[0040] The co-catalyst and the main catalyst raw material are mixed with water to obtain a slurry;

[0041] The carrier powder is mixed with the slurry obtained in the previous step, and then dried after heat treatment for a predetermined time to obtain a mixed dry material. The heat treatment temperature is 30-100℃ and the predetermined time is 10-72h. Preferably, the heat treatment temperature is 50-70℃ and the predetermined time is 10-24h.

[0042] The mixed dry matter obtained in the previous step is calcined in an oxidizing atmosphere to obtain a catalyst. The calcination temperature is 200-600℃ and the calcination time is 2-12h. Preferably, the calcination temperature is 300-600℃ and the calcination time is 6-10h.

[0043] The main catalyst raw materials mentioned above can be conventional metal salts, such as ammonium metavanadate and oxalic acid dihydrate as main catalyst raw materials.

[0044] In some embodiments, the vanadium-based catalyst is prepared using the sol-gel method, including the following steps:

[0045] A first sol containing a co-catalyst and a support material and a second sol containing a main catalyst material are prepared, and the first sol and the second sol are mixed to form a mixed sol.

[0046] The mixed sol is heat-treated for a predetermined time and then dried to obtain a mixed dry material. The preferred heat treatment temperature is 30–70°C, and the preferred predetermined time is 24–72 hours.

[0047] The mixed dry matter obtained in the previous step is calcined in an oxidizing atmosphere to obtain a catalyst; preferably, the calcination temperature is 300-600℃ and the calcination time is 6-10h.

[0048] Taking titanium dioxide as a carrier as an example, the carrier raw materials mentioned above can be a commonly used mixture of tetrabutyl titanate and hydrogen peroxide. The second sol can be formed by a mixture of metal oxide and hydrogen peroxide.

[0049] In some embodiments, vanadium-based catalysts are prepared using a mechanical ball milling method, including the following steps:

[0050] The main catalyst, co-catalyst and support raw materials are mixed and then mechanically ball-milled to obtain the catalyst. Preferably, the grinding balls used in the ball mill are stainless steel balls, the preferred ball milling frequency is 25-50Hz, the preferred ball-to-material ratio during ball milling is 10-100:1, and the preferred ball milling time is 1-8h.

[0051] In some embodiments, vanadium-based catalysts are prepared using an impregnation-ball milling method, comprising the following steps:

[0052] The main catalyst raw material is mixed with water to obtain a slurry;

[0053] The carrier raw material is mixed with the slurry and heat-treated for a predetermined time, then dried to obtain a mixed dry material. The heat treatment temperature is 30-100℃ and the predetermined time is 10-72h, preferably 50-70℃ and preferably 10-24h.

[0054] The mixed dry matter is calcined in an oxidizing atmosphere to obtain a catalyst precursor. The preferred calcination temperature is 300–600°C and the calcination time is 6–10 h.

[0055] The catalyst precursor and the co-catalyst are mechanically ball-milled together to obtain the catalyst. Preferably, the grinding balls used for ball milling are stainless steel balls, the preferred ball-to-material ratio during ball milling is 10 to 100:1, and the ball milling time is 1 to 8 hours.

[0056] Among the above preparation methods, the vanadium-based catalyst prepared by the sol-gel method has better catalytic methylation effect. From the perspective of catalyst preparation process, the ball milling method is the simplest and suitable for large-scale synthesis.

[0057] In a second embodiment of this application, an application of the vanadium-based catalyst in the first embodiment is provided, specifically including using the vanadium-based catalyst as a catalyst for selective catalytic reduction (SCR) denitration reactions, alkylation reactions of phenolic substances, or catalytic synthesis of pyruvate from lactic esters. The vanadium-based catalyst provided in this application has a wide range of applications and high application value, and based on the fullerene effect in the vanadium-based catalyst, the target product has a higher yield and content. Furthermore, this vanadium-based catalyst exhibits cycle stability during use, can be reused multiple times, and saves costs.

[0058] In a third embodiment of this application, a method for preparing D-α-tocopherol is provided. The method includes catalyzing a methylation reaction of tocopherol to obtain D-α-tocopherol, wherein the tocopherol includes one or more of β-tocopherol, γ-tocopherol, and δ-tocopherol, and the vanadium-based catalyst of the first embodiment is used to catalyze the methylation reaction of tocopherol to obtain D-α-tocopherol.

[0059] Because this application introduces fullerenes with unique electronic structures and suitable HOMO-LUMO into vanadium-based catalysts, it effectively improves the activity of vanadium-based catalysts and increases the content and yield of the reaction of direct methylation synthesis of α-tocopherol from non-α-tocopherol.

[0060] The raw material tocopherol used in the above preparation method can be pure tocopherol or a mixture containing tocopherol, such as a mixture in which the mass content of tocopherol in the raw material tocopherol is between 25% and 90%.

[0061] Since tocopherols are difficult to separate in nature, the tocopherols used in the above reaction can be mixed tocopherols, such as a mixture of multiple tocopherols including β-tocopherol, γ-tocopherol, and δ-tocopherol, or even mixed tocopherols containing α-tocopherol, which can also be used as the raw material tocopherols in this application. In some embodiments, the raw material tocopherols include D-α-tocopherol, D-β-tocopherol, D-γ-tocopherol, and D-δ-tocopherol.

[0062] The above-described method for preparing D-α-tocopherol can be implemented with reference to the conventional method for preparing D-α-tocopherol using a methylation reaction. In some embodiments, the above-described method for preparing D-α-tocopherol includes: mixing raw material tocopherol with a methylating agent and optionally a co-solvent, wherein the methylating agent includes methanol or a mixture of hydrogen and carbon monoxide, or a mixture of hydrogen and carbon dioxide, preferably methanol, and the co-solvent includes n-hexane, cyclohexane, or ethanol; and in a methylation atmosphere, a vanadium-based catalyst catalyzes the methylation reaction of the raw material tocopherol and the methylating agent to obtain D-α-tocopherol, wherein the methylation atmosphere includes a hydrogen atmosphere, a nitrogen atmosphere, or an inert gas atmosphere.

[0063] When methanol is chosen as the methylating agent, no co-solvent needs to be added; when a mixture of hydrogen and carbon monoxide or a mixture of hydrogen and carbon dioxide is chosen as the methylating agent, the raw material tocopherol is dispersed in the co-solvent.

[0064] In some embodiments, the mass-to-volume ratio (w / v) of the raw material tocopherol and the methylating agent used in the above-described method for preparing D-α-tocopherol is (0.05 g to 0.8 g): 1 mL, preferably (0.1 g to 0.3 g): 1 mL, wherein the methylating agent is calculated as an equal volume of methanol (calculated as an equal volume of methanol, meaning that if a mixture of hydrogen and carbon monoxide or a mixture of hydrogen and carbon dioxide is used as the methylating agent, the ratio of C, H, and O is used for measurement). By controlling the ratio of the raw material tocopherol and the methylating agent, production efficiency can be improved, and excessive reactants can be avoided, which would lead to incomplete reaction and affect the conversion rate and yield.

[0065] In some embodiments, the mass ratio of vanadium-based catalyst to tocopherol used in the above-described method for preparing D-α-tocopherol is 0.05–0.5:1, preferably 0.08–0.2:1. This improves both catalyst utilization and the conversion rate of tocopherol.

[0066] In some embodiments, in the above-mentioned method for preparing D-α-tocopherol, the temperature of the methylation reaction is 200-300°C, preferably 220-260°C, and more preferably 250-255°C, so as to fully utilize the catalytic activity and selectivity of the catalyst.

[0067] In some embodiments, the initial pressure in the above-described method for preparing D-α-tocopherol is 0.1–1 MPa, preferably 0.3–0.5 MPa. Adjusting the initial pressure using a methylation atmosphere reduces the oxygen partial pressure in the system, preventing oxidation of tocopherol and thus improving its stability at high temperatures. Furthermore, this controlled initial pressure allows the methylation reaction to proceed at a more suitable pressure, ensuring sufficient contact between the reactants, which is beneficial for increasing the content and yield of D-α-tocopherol.

[0068] In some embodiments, the raw material tocopherol is mixed with a methylating agent and an optional cosolvent by stirring, preferably at a stirring speed of 400-800 r / min.

[0069] The above preparation method can be carried out in a high-pressure reactor, or other reactors, such as a fixed-bed reactor, can be selected. Those skilled in the art can choose according to the existing experimental conditions, and will not be elaborated here.

[0070] The beneficial effects of this application will be further illustrated below with reference to embodiments and comparative examples, but the scope of the present invention is not limited to these embodiments.

[0071] In the following examples and comparative examples, the definitions of selectivity, conversion rate, yield, purity, and recovery rate are as follows:

[0072] The amounts of D-α-tocopherol and non-D-α-tocopherol in the mixed tocopherol reactants are denoted as A and B, respectively. The amounts of D-α-tocopherol and non-D-α-tocopherol after the reaction are denoted as A' and B', respectively.

[0073] The conversion rate of the reaction raw materials, X, is calculated as (B - B') / B × 100%.

[0074] The yield of D-α-tocopherol, Y = (A'-A) / B × 100%;

[0075] The selectivity of D-α-tocopherol is S = Y / X = (A'-A) / (B-B') × 100%;

[0076] The content of D-α-tocopherol is the percentage of the mass of D-α-tocopherol in the reaction product to the total mass of the reaction product;

[0077] The purity of D-α-tocopherol is the percentage of the mass of D-α-tocopherol in the reaction product to the mass of the total tocopherol in the reaction product.

[0078] The total tocopherol content is the percentage of the total tocopherol mass in the reaction product to the total mass of the reaction product;

[0079] The recovery rate of total tocopherols is the percentage of the total tocopherols in the reaction product relative to the total tocopherols in the feedstock.

[0080] Example 1

[0081] This embodiment uses the sol-gel method to prepare vanadium-based catalysts.

[0082] Step 1: Weigh 0.048g of co-catalyst C 60 Fullerene was ultrasonically treated for 30 minutes to uniformly disperse it in 100 mL of deionized water. Stirring was carried out during ultrasonic treatment. Then, 16.12 g of tetrabutyl titanate was slowly added dropwise for hydrolysis. After hydrolysis, 20 mL of 30% hydrogen peroxide was added dropwise. After stirring for 1 hour, titanium peroxide sol was formed.

[0083] Step 2: Weigh 0.96g of the main catalyst V2O5, disperse it in 25mL of deionized water, add 5mL of 30% hydrogen peroxide, and stir for 0.5 hours to form vanadium peroxide sol.

[0084] Step 3: Add the above vanadium peroxide sol to the above titanium peroxide sol, heat at 40°C and stir for 36 hours to evaporate the solvent, place in an oven at 120°C for 12 hours, grind and then pass through a 100-mesh sieve.

[0085] Step 4: Place the sieved powder into a muffle furnace and calcine it in air at 300℃, increasing the temperature at a rate of 2℃ / min. After calcine for 10 hours, the catalyst is obtained. The resulting vanadium-based catalyst is designated as "sol-gel 1% C". 60 -20% V2O5 / TiO2 (1% C 60 This indicates that the vanadium-based catalyst C 60 The mass percentage content is 1%, and 20% V2O5 indicates that the mass percentage content of V2O5 in the vanadium-based catalyst is 20%. The percentages in the catalyst composition of subsequent examples are the mass percentage content of the corresponding substances in the catalyst.

[0086] Subsequently, the vanadium-based catalyst obtained in step four was used for the direct methylation synthesis of D-α-tocopherol from tocopherol:

[0087] Step 5: Weigh 4g of the mixed tocopherols used in the reaction and analyze them by high performance liquid chromatography (HPLC). The contents of D-α-tocopherol in the mixed tocopherols are 9.2%, D-β-tocopherol and D-γ-tocopherol are 61.1%, D-δ-tocopherol is 21.7%, and the remainder are tocotrienols, sterols, etc. Methanol is used as the methylation reagent to prepare a tocopherol methanol solution with a mass concentration of 0.11g / mL (i.e., the mass-volume ratio of mixed tocopherols to methanol is 0.11g:1mL).

[0088] Step 6: The reaction was carried out in a 100mL high-pressure reactor with a catalyst dosage of 0.7g, a hydrogen atmosphere, an initial pressure of 0.3MPa, a temperature of 255℃, a stirring rate of 600r / min, and a reaction time of 2 hours.

[0089] Step 7: After the reaction is complete, reduce the pressure to atmospheric pressure and the temperature to room temperature. Filter, dry and dilute the product to a fixed volume, and then perform quantitative analysis by liquid chromatography.

[0090] Example 2

[0091] This embodiment uses the sol-gel method to prepare vanadium-based catalysts, following the method in Example 1, with the only difference being step one:

[0092] Weigh out 0.024g of co-catalyst C. 60Fullerene was ultrasonically treated for 30 minutes to uniformly disperse it in 100 mL of deionized water. Stirring was carried out during ultrasonic treatment. Then, 16.12 g of tetrabutyl titanate was slowly added dropwise for hydrolysis. After hydrolysis, 20 mL of 30% hydrogen peroxide was added dropwise. After stirring for 1 hour, titanium peroxide sol was formed.

[0093] The remaining preparation and reaction steps are the same as in Example 1. The catalyst obtained in this example is referred to as "sol-gel 0.5% C". 60 -20% V2O5 / TiO2.

[0094] Example 3

[0095] This embodiment uses the sol-gel method to prepare vanadium-based catalysts, following the method in Example 1, with the only difference being step one:

[0096] Weigh 0.53g of co-catalyst C 60 Fullerene was ultrasonically treated for 30 minutes to uniformly disperse it in 100 mL of deionized water. Stirring was carried out during ultrasonic treatment. Then, 16.12 g of tetrabutyl titanate was slowly added dropwise for hydrolysis. After hydrolysis, 20 mL of 30% hydrogen peroxide was added dropwise. After stirring for 1 hour, titanium peroxide sol was formed.

[0097] The remaining preparation and reaction steps are the same as in Example 1. The catalyst obtained in this example is referred to as "sol-gel 10% C". 60 -20% V2O5 / TiO2.

[0098] Example 4

[0099] This embodiment uses the sol-gel method to prepare vanadium-based catalysts, following the method in Example 1, with the only differences being steps one and two:

[0100] Step 1: Weigh 0.044g of co-catalyst C 60 Fullerene was ultrasonically treated for 30 minutes to uniformly disperse it in 100 mL of deionized water. Stirring was carried out during ultrasonic treatment. Then, 16.12 g of tetrabutyl titanate was slowly added dropwise for hydrolysis. After hydrolysis, 20 mL of 30% hydrogen peroxide was added dropwise. After stirring for 1 hour, titanium peroxide sol was formed.

[0101] Step 2: Weigh 0.44g of the main catalyst V2O5, stir and disperse it in 25mL of deionized water, add 5mL of 30% hydrogen peroxide, stir for 0.5 hours to form vanadium peroxide sol;

[0102] The remaining preparation and reaction steps are the same as in Example 1. The catalyst obtained in this example is referred to as "sol-gel 1% C". 60 -10% V2O5 / TiO2.

[0103] Example 5

[0104] This embodiment uses the sol-gel method to prepare vanadium-based catalysts, following the method in Example 1, with the only difference being step two:

[0105] Step 2: Weigh 1.63g of the main catalyst V2O5, stir and disperse it in 25mL of deionized water, add 5mL of 30% hydrogen peroxide, stir for 0.5 hours to form vanadium peroxide sol;

[0106] The remaining preparation and reaction steps are the same as in Example 1. The catalyst obtained in this example is referred to as "sol-gel 1% C". 60 -30% V2O5 / TiO2.

[0107] Comparative Example 1

[0108] This comparative example uses the sol-gel method to prepare vanadium-based catalysts. The difference between the preparation steps and steps one to four in Example 1 is that fullerene C was not added in step one. 60 The resulting catalyst was labeled as “sol-gel 20% V2O5 / TiO2”.

[0109] The catalyst “sol-gel 20% V2O5 / TiO2” was used for the direct methylation of tocopherol to synthesize D-α-tocopherol, and the reaction steps were the same as in Example 1.

[0110] The results are recorded in Table 1.

[0111] Table 1

[0112]

[0113]

[0114] According to the data in Table 1, compared to Comparative Example 1, the addition of 1% C 60 Example 1 of fullerenes showed significant improvements in the conversion rate, selectivity, content, and purity of D-α-tocopherol via catalytic methylation, while the increase in total tocopherol content and recovery rate was relatively small. (C) 60 Fullerenes played a supporting role in enhancing the activity of V₂O₅. Example 2 contained 0.5% C. 60 Fullerenes with a conversion rate and D-α-tocopherol purity exceeding 99%. In Example 1, C... 60 The fullerene content was further increased to 1%, which significantly improved the content and yield while maintaining high levels of conversion and D-α-tocopherol purity, thereby improving selectivity. The total tocopherol content and recovery also increased slightly.

[0115] Furthermore, comparing the data from Examples 1 to 3, it can be seen that when preparing vanadium-based catalysts using the sol-gel method, maintaining the consistency of the type and content of the main catalyst and support, and changing the co-catalyst C... 60 The effect of fullerene content on catalytic effect. C 60 The catalyst with a fullerene content of 1% showed better selectivity, yield, D-α-tocopherol content, and total tocopherol recovery than C. 60 A catalyst with a fullerene content of 0.5%, and 0.5% C 60 The conversion rate and D-α-tocopherol purity of the -20% V2O5 / TiO2 catalyst both reached 99%, significantly better than the results of other examples. (The last sentence appears to be incomplete and possibly refers to a different example.) 60 When the fullerene content increases to 10%, the catalytic effect is comparable to that of 1% C, as shown in the table of catalytic indicators. 60 The performance of the -20% V2O5 / TiO2 catalyst remained essentially unchanged.

[0116] According to the data from Examples 1, 4, and 5 in Table 1, when using the sol-gel method to prepare vanadium-based catalysts, maintaining the same type and content of co-catalyst and support, and changing the content of the active catalyst component V₂O₅, affects the catalytic effect. Reducing the V₂O₅ content from 20% to 10% only kept the total tocopherol content and recovery rate at the same level; however, catalytic indicators related to D-α-tocopherol, such as selectivity, yield, content, and purity, all showed a significant decrease. This indicates that the V₂O₅ content has a major impact on the catalytic methylation effect of mixed tocopherols. However, as the V₂O₅ content increased from 20% to 30%, the degree of polymerization of vanadium oxide species increased. , The overall catalytic performance of the catalyst deteriorated.

[0117] Example 6

[0118] This embodiment describes the use of vanadium-based catalysts in a sol-gel process with 1% C content. 60 Cyclic experiments were conducted using "-20% V2O5 / TiO2":

[0119] Recovery of catalyst "sol-gel 1% C" after reaction in Example 1 60 -20% V2O5 / TiO2”, calcined in air for 6 hours at a calcination temperature of 300℃;

[0120] If the catalyst after calcination is less than 0.7g, the fresh catalyst prepared in Example 1 is used to supplement the amount to 0.7g, and the direct methylation reaction of tocopherol is carried out. The specific reaction conditions are the same as in Example 1, and the catalyst "sol-gel 1% C" is recycled. 60The reaction was carried out four times with 20% V2O5 / TiO2. After each reaction, the pressure was reduced to atmospheric pressure and the temperature was reduced to room temperature. The product was then filtered, dried, and diluted to a fixed volume, followed by quantitative analysis using liquid chromatography.

[0121] The catalytic effect of the cycle life experiment is shown in Table 2.

[0122] Table 2

[0123]

[0124] Table 2 shows the "sol-gel 1% C" 60 The catalytic performance of the -20% V₂O₅ / TiO₂ catalyst changed with increasing cycle number during five cycles. During the first cycle, the catalytic conversion, yield, and D-α-tocopherol content and purity all decreased by 4%–5%, but remained within the optimal range. Selectivity, total tocopherol content, and recovery remained essentially unchanged. The catalytic performance during the second to fourth cycles was essentially the same as during the second cycle, reflecting the catalyst's excellent cycle life and catalytic stability.

[0125] Example 7

[0126] In this embodiment, the vanadium-based catalyst "sol-gel 1% C" prepared by the sol-gel method in Example 1 is used. 60 -20% V2O5 / TiO2.

[0127] In the reaction process of direct methylation of tocopherol to synthesize D-α-tocopherol, the only difference between this example and Example 1 is the operation of step six:

[0128] The reaction was carried out in a 100 mL high-pressure reactor with a catalyst dosage of 0.5 g, a hydrogen atmosphere, an initial pressure of 0.3 MPa, a temperature of 255 °C, a stirring rate of 600 r / min, and a reaction duration of 5 hours.

[0129] The remaining steps are the same as in Example 1.

[0130] Example 8

[0131] In this embodiment, the vanadium-based catalyst "sol-gel 1% C" prepared by the sol-gel method in Example 1 is used. 60 -20% V2O5 / TiO2.

[0132] In the reaction process of direct methylation of tocopherol to synthesize D-α-tocopherol, the only difference between this example and Example 1 is the operation of step six:

[0133] The reaction was carried out in a 100 mL high-pressure reactor with a catalyst dosage of 0.7 g, under a nitrogen atmosphere, an initial pressure of 0.1 MPa, a temperature of 255 °C, a stirring rate of 600 r / min, and a reaction duration of 2 hours.

[0134] The remaining steps are the same as in Example 1.

[0135] Example 9

[0136] In this embodiment, the vanadium-based catalyst "sol-gel 1% C" prepared by the sol-gel method in Example 1 is used. 60 -20% V2O5 / TiO2.

[0137] In the reaction process of direct methylation of tocopherol to synthesize D-α-tocopherol, the difference between this example and Example 1 lies in the operation of steps five and six:

[0138] 4g of the mixed tocopherols used in the reaction were weighed and analyzed by high performance liquid chromatography (HPLC). The contents of D-α-tocopherol were 6.2%, D-β and D-γ-tocopherol were 32.6%, D-δ-tocopherol was 15.0%, and the remainder were tocotrienols, sterols, etc. Methanol was used as the methylation reagent to prepare a tocopherol methanol solution with a mass concentration of 0.14g / mL (i.e., the mass-volume ratio of mixed tocopherols to methanol was 0.14g:1mL).

[0139] The reaction was carried out in a 100 mL high-pressure reactor with a catalyst dosage of 0.5 g, under a nitrogen atmosphere, at an initial pressure of 0.1 MPa, using a segmented heating method. The temperature was first increased to 245 °C at a heating rate of 5 °C / min, held for 3 min, and then increased to 250 °C at a heating rate of 3 °C / min. The stirring rate was 600 r / min, and the reaction time was 2 hours.

[0140] The remaining steps are the same as in Example 1.

[0141] The catalytic effects of Examples 7 to 9 are listed in Table 3.

[0142] Table 3

[0143]

[0144] Table 3 can be used to compare the effects of different methylation reaction conditions on the catalytic effect. The catalyst used should be consistent, all being "sol-gel 1% C". 60-20% V2O5 / TiO2 catalyst. Using Example 1 as a reference system, Example 7, with a catalyst dosage of 0.5g and a reaction time of 5 hours, and with other reaction conditions unchanged, showed an improvement in catalytic conversion, yield, D-α-tocopherol content, and purity compared to Example 1, with an improvement of approximately 3%. Selectivity, total tocopherol content, and recovery were essentially the same as in Example 1. Example 9 employed a segmented heating method, which improved the catalytic conversion and D-α-tocopherol purity.

[0145] Example 10

[0146] This embodiment uses the impregnation method to prepare vanadium-based catalysts.

[0147] Step 1: Weigh 1.0g of ammonium metavanadate and 1.75g ​​of oxalic acid dihydrate, the main catalyst raw materials, and weigh the co-catalyst C. 60 0.0253 g of fullerene was ultrasonically treated for 30 min to uniformly disperse the above raw materials in 100 mL of deionized water. During ultrasonic treatment, stirring was carried out to completely dissolve ammonium metavanadate and oxalic acid dihydrate to obtain a slurry.

[0148] Step 2: Weigh out a sample with a specific surface area of ​​243.3 m². 2 1.75 g of TiO2 powder with an average particle size of 5 nm was used as a carrier and added to the slurry prepared in step one above while stirring. The mixture was heated at 60°C and stirred for 15 hours. Then it was placed in an oven at 120°C for 8 hours, ground, and then passed through a 100-mesh sieve.

[0149] Step 3: Place the sieved powder into a muffle furnace and calcine it in air at 300℃, increasing the temperature at a rate of 2℃ / min. After calcination for 10 hours, the catalyst is obtained. The resulting vanadium-based catalyst is designated as "1% C impregnation". 60 -30% V2O5 / TiO2.

[0150] Subsequently, the vanadium-based catalyst obtained in step three was used for the direct methylation synthesis of D-α-tocopherol from tocopherol:

[0151] Step 4: Weigh 4g of the mixed tocopherols used in the reaction. The mixed tocopherols contain 9.2% D-α-tocopherol, 61.1% D-β-tocopherol and D-γ-tocopherol, and 21.7% D-δ-tocopherol. Methanol is used as the methylation reagent to prepare a tocopherol methanol solution with a mass concentration of 0.11g / mL (i.e., the mass-to-volume ratio of the mixed tocopherols to methanol is 0.11g:1mL).

[0152] Step 5: The reaction was carried out in a 100mL high-pressure reactor with a catalyst dosage of 0.5g, a hydrogen atmosphere, an initial pressure of 0.3MPa, a temperature of 255℃, a stirring rate of 600r / min, and a reaction time of 2 hours.

[0153] Step 6: After the reaction is complete, reduce the pressure to atmospheric pressure and the temperature to room temperature. Filter, dry and dilute the product to a fixed volume, and then perform quantitative analysis on liquid chromatography.

[0154] Example 11

[0155] In this embodiment, a vanadium-based catalyst was prepared using a mechanical ball milling method.

[0156] Step 1: Weigh out 0.3g of the main catalyst raw material V2O5, 0.69g of the support raw material TiO2, and 0.01g of the co-catalyst C. 60 Fullerene was placed in a 0.15L ball mill jar, along with 50g of stainless steel grinding balls with a diameter of 5mm.

[0157] Step 2: Using a planetary ball mill at 30 Hz and unidirectional rotation, the catalyst was obtained after 2 hours of ball milling. The resulting vanadium-based catalyst was designated as "mechanically ball-milled 1% C". 60 -30% V2O5 / TiO2.

[0158] Subsequently, the vanadium-based catalyst obtained in step two was used for the direct methylation of tocopherol to synthesize D-α-tocopherol, and the reaction process and conditions were the same as in Example 1.

[0159] Example 12

[0160] This embodiment also uses mechanical ball milling to prepare vanadium-based catalysts, the only difference from the preparation method in Example 11 is step one:

[0161] Weigh out 0.2g of V₂O₅ and 0.1g of MoO₃ as the main catalyst raw materials, 0.69g of TiO₂ as the support raw material, and 0.01g of C as the co-catalyst. 60 Fullerene was placed in a 0.15L ball mill jar, along with 50g of stainless steel grinding balls with a diameter of 5mm.

[0162] The remaining preparation and reaction steps are the same as in Example 11. The catalyst obtained in this example is denoted as "mechanically ball-milled 1% C". 60 -20%V2O5-10% MoO3 / TiO2”.

[0163] Example 13

[0164] In this embodiment, vanadium-based catalysts are prepared using an impregnation-ball milling method.

[0165] Step 1: Weigh 1.0g ammonium metavanadate and 1.75g ​​oxalic acid dihydrate, add them to 5mL of deionized water, and sonicate for 30min to dissolve them completely. As the sonication time increases, the solution changes from bright yellow to orange-red, then to dark green, and finally to dark blue.

[0166] Step 2: Weigh out a sample with a specific surface area of ​​243.3 m². 2 1.75g ​​of TiO2 powder with a particle size of 5nm was used as a carrier and added to the dark blue solution described in step one while stirring. The solution was heated at 60°C and stirred for 15 hours. After being placed in an oven at 110°C for 8 hours, it was ground and then passed through a 100-mesh sieve.

[0167] Step 3: Place the sieved powder into a muffle furnace and calcine it in air at a temperature of 550°C, with the temperature increasing at a rate of 5°C / min. After calcine for 6 hours, the catalyst precursor is obtained.

[0168] Step 4: The catalyst precursor is prepared at a mass ratio of C... 60 Fullerene:milling ball = 1:0.015:50 catalyst precursor, C 60 Fullerenes, along with grinding balls, were added to a 0.15L stainless steel ball mill jar and milled for 2 hours using a planetary ball mill at 30Hz and unidirectional rotation to obtain the catalyst. The resulting vanadium-based catalyst was designated as "impregnated ball-milled 1.5% C". 60 -30% V2O5 / TiO2.

[0169] Subsequently, the vanadium-based catalyst obtained in step five was used for the direct methylation of tocopherol to synthesize D-α-tocopherol, with the reaction process and conditions being the same as in Example 10.

[0170] The impregnated ball milled 1.5% C 60 Thermal stability analysis, mass spectrometry analysis, and transmission electron microscopy analysis of -30% V₂O₅ / TiO₂ were performed, and the results are recorded in […]. Figures 1 to 3 middle.

[0171] Figure 1 The impregnation ball milling of Example 13 with 1.5% C was shown. 60 The thermogravimetric curves obtained from dynamic thermogravimetric analysis of a -30% V₂O₅ / TiO₂ catalyst sample are shown in the figure. The horizontal axis represents temperature (°C), and the vertical axis represents the mass percentage of the sample. The curves illustrate the decrease in the mass percentage of the sample with increasing temperature. As shown in the figure, the mass loss of the sample between 300°C and 400°C is due to C 60 It is produced by thermal decomposition.

[0172] Depend on Figure 2 A mass spectrum peak of MS (MALDI-TOF) m / z = 720 can be clearly observed, proving that C60 It is indeed present in the catalyst.

[0173] Figure 3 The catalyst contains spherical structures without a distinct lattice (within the white elliptical frame), which are C atoms uniformly coated around the V₂O₅. 60 .

[0174] Comparative Example 2

[0175] This comparative example uses an impregnation method to prepare a vanadium-based catalyst. It is prepared according to the method of Example 10 without adding fullerene or TiO2 support powder during the preparation process. The resulting catalyst is referred to as "impregnated V2O5".

[0176] The only difference from the preparation method in Example 10 is step three: the sieved powder is placed in a muffle furnace and calcined in air at a temperature of 550°C, with the temperature increasing at a rate of 5°C / min, for 6 hours.

[0177] Subsequently, the vanadium-based catalyst obtained in step three was used for the direct methylation of tocopherol to synthesize D-α-tocopherol, with the reaction process and conditions being the same as in Example 10.

[0178] Comparative Example 3

[0179] This comparative example uses an impregnation method to prepare a vanadium-based catalyst, prepared according to the method of Example 10 without the addition of fullerenes. The resulting catalyst is denoted as "impregnated with 30% V₂O₅ / TiO₂". Subsequently, the vanadium-based catalyst obtained in step three is used for the direct methylation of tocopherol to synthesize D-α-tocopherol, and the reaction process and conditions are the same as in Example 10.

[0180] The catalytic effects of Examples 10-13 and Comparative Examples 2 and 3 are listed in Table 4.

[0181] Table 4

[0182]

[0183] As shown in Table 4, the catalytic effect of the catalysts in each embodiment was significantly improved compared with Comparative Examples 2 and 3. For catalysts with the same composition, the catalytic effect prepared by the impregnation method was slightly better than that prepared by the mechanical ball milling method. The catalytic effects of the impregnation-ball milling method and the mechanical ball milling method were similar, which may be related to the degree of contact between the co-catalyst and the active ingredient. Comparing Examples 11 and 12, when MoO3 was included, the selectivity and yield of methylation catalyzed by mixed tocopherols were effectively improved under the action of co-catalysis, thereby increasing the content of D-α-tocopherol in the reaction product, and the total tocopherol content and recovery rate were also relatively high.

[0184] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. The application of a vanadium-based catalyst in the methylation reaction of tocopherol to obtain D-α-tocopherol, wherein the tocopherol comprises one or more of β-tocopherol, γ-tocopherol, and δ-tocopherol, characterized in that, The catalyst comprises a main catalyst, a co-catalyst, and a porous support. The main catalyst and the co-catalyst are dispersed on the porous support. The main catalyst comprises V2O5 and optionally MoO3. The co-catalyst comprises fullerene. The vanadium-based catalyst contains 0.5 to 10% fullerene by mass.

2. The application according to claim 1, characterized in that, The vanadium-based catalyst comprises 10-60% V2O5 and 0-40% MoO3 by mass percentage.

3. The application according to claim 1 or 2, characterized in that, The fullerene includes C 50 Fullerene, C 60 Fullerene, C 70 Any one or more of fullerenes and fullerene derivatives.

4. The application according to claim 1 or 2, characterized in that, The porous carrier is selected from one of titanium dioxide, cerium dioxide, silicon dioxide, alumina, porous silicon carbide, zeolite molecular sieve, kaolin, diatomaceous earth, and activated carbon.

5. The application according to claim 1 or 2, characterized in that, The main catalyst is in contact with the fullerene.

6. A method for preparing D-α-tocopherol, the method comprising catalytically methylating a tocopherol feedstock to obtain D-α-tocopherol, wherein the tocopherol feedstock comprises one or more of β-tocopherol, γ-tocopherol, and δ-tocopherol, characterized in that, D-α-tocopherol is obtained by methylating the raw material tocopherol using the vanadium-based catalyst in any one of claims 1 to 5.

7. The preparation method according to claim 6, characterized in that, The preparation method includes: The raw material tocopherol is mixed with a methylating agent and an optional cosolvent, wherein the methylating agent includes methanol or a mixture of hydrogen and carbon monoxide, or a mixture of hydrogen and carbon dioxide, and the cosolvent includes n-hexane, cyclohexane or ethanol. In a methylation atmosphere, the vanadium-based catalyst catalyzes the methylation reaction of the raw material tocopherol and the methylation reagent to obtain D-α-tocopherol, wherein the methylation atmosphere includes a hydrogen atmosphere or an inert gas atmosphere.

8. The preparation method according to claim 7, characterized in that, The methylating agent is methanol.

9. The preparation method according to claim 7, characterized in that, The inert gas atmosphere includes a nitrogen atmosphere.

10. The preparation method according to claim 7, characterized in that, The mass-to-volume ratio (w / v) of the raw material tocopherol to the methylating agent is (0.05g~0.8g):1mL, wherein the volume of the methylating agent is calculated as an equal volume of methanol.

11. The preparation method according to claim 10, characterized in that, The mass-to-volume ratio (w / v) of the raw material tocopherol to the methylation reagent is (0.1g~0.3g):1mL.

12. The preparation method according to any one of claims 6 to 11, characterized in that, The mass ratio of the vanadium-based catalyst to the tocopherol is 0.05~0.5:

1.

13. The preparation method according to claim 12, characterized in that, The mass ratio of the vanadium-based catalyst to the tocopherol is 0.08~0.2:

1.

14. The preparation method according to any one of claims 6 to 11, characterized in that, The methylation reaction is carried out at a temperature of 200-300 °C.

15. The preparation method according to claim 14, characterized in that, The methylation reaction is carried out at a temperature of 220-260 °C.

16. The preparation method according to claim 14, characterized in that, The methylation reaction is performed at a temperature of 250-255 °C.

17. The preparation method according to any one of claims 7 to 11, characterized in that, The initial pressure of the methylation atmosphere is 0.1~1 MPa.

18. The preparation method according to claim 17, characterized in that, The initial pressure of the methylation atmosphere is 0.3~0.5 MPa.

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