Preparation method of catalyst for preparing p-cresol from toluene and preparation method of p-cresol

Abstract

The present invention provides a method for preparing a catalyst for preparing p-cresol from toluene and a method for preparing p-cresol, comprising the following steps: S1: preparing a TS-1 titanium silicalite; S2: placing the TS-1 titanium silicalite in step S1 in a treatment liquid A, separating and cleaning the TS-1 titanium silicalite; S3: placing the TS-1 titanium silicalite obtained in step S2 in a treatment liquid B, separating and cleaning the TS-1 titanium silicalite, drying and calcining to obtain a catalyst; treatment liquid A is an organic acid solution, and treatment liquid B is a solution containing fluoride ions. The modified titanium silicalite catalyst provided by the present invention has the advantage of high selectivity for p-cresol.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical synthesis, and in particular relates to a method for preparing a catalyst for preparing p-cresol from toluene and a method for preparing p-cresol. Background Art

[0002] Cresol has three isomers, namely o-cresol, m-cresol and p-cresol. Cresol is widely used in the synthesis of flavors and fragrances. It is also an important fine chemical intermediate and plays an important role in organic synthesis.

[0003] p-Cresol is widely used in the synthesis of phenolic resins, plasticizers, antioxidants, pharmaceuticals, herbicides, pesticides, fragrances and dyes.

[0004] 60% of global p-cresol production capacity is used to produce 2,6-di-tert-butyl-p-cresol, commercially known as butylated hydroxytoluene (BHT). It is widely used in the manufacture of phenolic resins, antioxidants, and polymerization inhibitors. The price of 2,6-di-tert-butyl-p-cresol is relatively stable, consistently above 20,000 yuan per ton. p-cresol is also used to produce p-hydroxybenzonitrile (p-HBN), an important pesticide, and p-anisaldehyde, a key intermediate in the synthesis of pharmaceuticals such as the coronary artery treatment drug diltiazem and the chemotherapy drug trimethoprim. p-Toluene methyl ether and p-toluene propyl ether, prepared from p-cresol, can be used as organic synthesis intermediates in the production of pesticides, pharmaceuticals, and fragrances. Nitration of p-cresol with dilute nitric acid produces o-nitro-p-cresol, which is used to synthesize the herbicide methylphosphonium, the dye intermediate 2-amino-4-methylanisole, and the fluorescent brightener DT.

[0005] The three isomers of cresol are usually produced together in the same process. Early cresols were mostly obtained by fractionation from coal tar and waste liquid from washing petroleum fractions in refineries. Now the production methods of cresol include sulfonation alkali fusion method, chlorination hydrolysis method, phenol alkylation method, isopropyl toluene oxidation method and other methods.

[0006] Among them, the phenol alkylation method is a method for preparing cresol using metal oxides as catalysts and phenol and methanol as raw materials, including gas phase method and liquid phase method.

[0007] In the liquid-phase process, the reaction is carried out at a temperature of 300-400°C and a pressure of 1-3 MPa, using aluminum oxide as a catalyst. The resulting product has a selectivity of approximately 43%-51% for o-cresol, 17%-36% for m-cresol, and 17%-36% for p-cresol. Disadvantages of this method include the catalyst's tendency to deactivate due to carbonization, the need for high temperature and pressure, and the production of certain byproducts that affect product quality, such as anisole, which reacts at the hydroxyl group rather than the phenyl ring, where the methyl group reacts.

[0008] The vapor-phase method offers numerous improvements over the liquid-phase method and has become a key method for producing o-cresol worldwide. This method involves vaporizing phenol and methanol and then passing them at a constant flow rate through a fixed-bed reactor containing a catalyst. Common catalysts include Al₂O₃, Fe₂O₃, and MgO. The final product is primarily o-cresol and the byproduct 2,6-dimethylphenol. This method offers a relatively simple process with few reaction steps and high selectivity, making it suitable for large-scale production. The byproduct, 2,6-dimethylphenol, also has numerous industrial applications.

[0009] This method has cost and environmental advantages and is widely used in the production of o-cresol and p-cresol. However, this process is not widely used in major domestic p-cresol production enterprises, but is more widely used in m-cresol production enterprises.

[0010] The sulfonation alkaline fusion method is an early industrial method for preparing cresols, primarily used to produce p-methylphenol. It uses abundant toluene as a raw material, which reacts with concentrated sulfuric acid to produce toluene sulfonate. This is then alkali-fused to produce sodium phenolate, which is then acidified to produce methylphenol.

[0011] In addition to concentrated H2SO4, chlorosulfonic acid and SO3 can also be used as sulfonating agents. Concentrated sulfuric acid is widely used in China due to its low price. However, since concentrated H2SO4 generates water in addition to toluenesulfonic acid when used as a sulfonating agent, the resulting toluenesulfonic acid tends to contain water of crystallization and has a high melting point (104°C). Therefore, alkali fusion requires the use of a 40% sodium hydroxide solution for dissolution. This additional step increases reaction energy consumption and is now being phased out.

[0012] As an early chemical synthesis method for producing cresol, the sulfonation alkaline fusion method played a significant role in meeting market demand for p-cresol due to its readily available raw materials, simple reaction equipment, mature technology, high yield, and scalable production. However, this process, which uses large amounts of strong acids and bases, poses significant equipment corrosion risks and is environmentally unfriendly, and is now being phased out.

[0013] The toluene chlorination hydrolysis method refers to a method in which toluene is used as a raw material, first reacted with chlorine gas to allow chlorine to replace hydrogen on the benzene ring to generate chlorotoluene, and then the chlorotoluene is reacted with sodium hydroxide solution in the presence of a catalyst under high temperature and high pressure environment to generate sodium methylphenolate, which is then acidified to generate methylphenol.

[0014] The chlorination reaction involves passing Cl2 through a reactor containing toluene in the presence of a Cu-Fe catalyst at 230°C. This reaction produces a mixture of o-, m-, and p-chlorotoluene. Hydrolysis is then carried out at 425°C using silica as a catalyst to produce a mixture of sodium methylphenolates. This mixture is then neutralized with an acid to produce a cresol mixture. The acid required for neutralization can be hydrogen chloride, a byproduct of the chlorination process. The resulting cresol mixture exhibits a selectivity ratio of approximately 1:2:1 for o-, m-, and p-cresol.

[0015] This method has relatively low requirements for equipment, but it has many reaction steps and produces many by-products, especially dimethylhydroxybiphenyl and dimethyl diether, which are easily hydrolyzed, making it difficult for the product quality to meet the standards. Therefore, this method still needs further improvement.

[0016] The cymene oxidation process produces meta-cresol and p-cresol as its main products, along with acetone as a byproduct. The selectivity ratio of meta-cresol to p-cresol is approximately 7:3, making it the predominant method for industrially producing meta-cresol. This process involves an alkylation reaction of toluene with propylene over the catalyst AlCl3 to produce cymene. The cymene is then oxidized to produce a peroxide of cymene, which is then reacted with dilute sulfuric acid for acidolysis to produce the corresponding cresols and acetone as a byproduct. While this process yields relatively high product purity, it is technically challenging, requires a long process route, and requires significant product separation effort. Furthermore, for every molecule of cresol produced, one molecule of acetone is also produced, resulting in poor atom economy.

[0017] Researchers have been diligently pursuing the direct oxidation of toluene to produce cresols. Due to the readily available and inexpensive raw material, toluene holds great industrial value. Using hydrogen peroxide as an oxidant for the hydroxylation of toluene is a preferred method. Compared to these traditional processes, the one-step direct hydroxylation of toluene and hydrogen peroxide to produce cresols offers significant advantages, including lower cost, simpler production, higher molecular weight, and reduced waste generation and emissions.

[0018] Generally, the preparation of cresol produces three isomers: o-cresol, m-cresol and p-cresol. Among them, the boiling point difference between m-cresol and p-cresol is very small, only 0.8°C, which makes separation and purification difficult, greatly increasing the production cost of m-cresol and p-cresol. Therefore, the problem of separation and purification of p-cresol needs to be solved urgently. Summary of the Invention

[0019] In view of this, the present invention aims to provide a method for preparing a catalyst for preparing p-cresol from toluene and a method for preparing p-cresol, so as to solve the problems of difficulty in separating and purifying p-cresol and high production cost.

[0020] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0021] A method for preparing a catalyst for preparing p-cresol from toluene comprises the following steps:

[0022] S1: Preparation of TS-1 titanium silicate molecular sieve;

[0023] S2: placing the TS-1 titanium silicate molecular sieve in step S1 into treatment solution A, separating and cleaning the TS-1 titanium silicate molecular sieve;

[0024] S3: placing the TS-1 titanium silicate molecular sieve obtained in step S2 into treatment solution B, separating and washing the TS-1 titanium silicate molecular sieve, drying and calcining the TS-1 titanium silicate molecular sieve to obtain a catalyst;

[0025] Treatment liquid A is an organic acid solution, and treatment liquid B is a solution containing fluoride ions.

[0026] Preferably, the method for separating the TS-1 titanium silicate molecular sieve in steps S2 and S3 comprises filtration.

[0027] Preferably, the end point of the cleaning in steps S2 and S3 is neutral.

[0028] Furthermore, the organic acid solution of the treatment liquid A includes one or more of acetic acid, propionic acid, acrylic acid, citric acid, oxalic acid, and benzoic acid, and the mass concentration of the organic acid solution is 1 to 5%;

[0029] Preferably, the TS-1 titanium silicate molecular sieve obtained in step S1 is immersed in the treatment solution A at a temperature of 20 to 80° C. and for a time of 10 to 200 minutes.

[0030] Furthermore, the solution containing fluoride ions includes one or both of ammonium fluoride and hydrogen fluoride;

[0031] Preferably, the fluoride ion solution is ammonium fluoride, and the mass concentration of ammonium fluoride is 0.5-10%;

[0032] Preferably, the TS-1 titanium silicate molecular sieve obtained in step S2 is immersed in the treatment solution B at a temperature of 20 to 80° C. and for a time of 10 to 200 minutes.

[0033] Furthermore, the preparation method of TS-1 titanium silicate molecular sieve in step S1 comprises the following steps:

[0034] T1: Dissolve tetrapropylammonium hydroxide and organic amine in water and stir until dissolved to obtain mixed solution A;

[0035] T2: Add the silicon source, titanium source, and metal salt to the mixed solution A in step T1, respectively, and stir until a uniform gel is formed;

[0036] T3: Stir the glue obtained in step T2, transfer the glue to a hydrothermal kettle, crystallize, wash to neutrality, dry and calcine.

[0037] Furthermore, in step T1, the organic amine includes one or more of n-butylamine, triethylamine, tri-n-propylamine, n-propylamine, diethylamine, and ethylenediamine, and the molar ratio of tetrapropylammonium hydroxide to the organic amine is 1:(0.02-0.8);

[0038] Preferably, the silicon source in step T2 includes one or more of fumed silicon oxide, tetraethyl orthosilicate, and silica sol;

[0039] Preferably, the titanium source in step T2 includes one or more of isobutyl titanate, titanium oxide powder, and titanium tetrachloride;

[0040] Preferably, the cation of the metal salt includes one or more of iron ion, cobalt ion, nickel ion, copper ion, molybdenum ion, manganese ion, calcium ion, magnesium ion, ruthenium ion, palladium ion, and platinum ion; and the anion of the metal salt is one of acetate, oxalate, citrate, sulfate, nitrate, and benzoate;

[0041] Preferably, the molar ratio of the silicon source, the titanium source and the metal salt is 1:(0.01-0.1):(0.01-0.05).

[0042] Furthermore, in step T3, the stirring time of the glue solution is 2 to 12 hours; the crystallization temperature in the hydrothermal reactor is 80 to 200° C., and the crystallization reaction time is 10 to 120 hours;

[0043] The drying temperature is 100-140°C, the drying time is 11-13 hours, the calcination temperature is 500-600°C, and the calcination time is 3-5 hours.

[0044] Furthermore, in step S3, the drying temperature is 120° C., the drying time is 12 h, the calcination temperature is 550° C., and the calcination time is 4 h.

[0045] A method for preparing p-cresol comprises the following steps:

[0046] C1: Add the catalyst, toluene and solvent into the reactor and start stirring until a uniform slurry is formed;

[0047] C2: heating the slurry obtained in step C1, adding hydrogen peroxide to the slurry for reaction, and keeping the temperature to obtain a p-cresol product;

[0048] The catalyst is prepared by the above-mentioned method for preparing a catalyst for preparing p-cresol from toluene.

[0049] Furthermore, the solvent in step C1 includes one or more of methanol, ethanol, isopropanol, tert-butanol, formic acid, acetic acid, acetonitrile, and 1,2-dichloroethane;

[0050] The mass ratio of toluene, catalyst and solvent is 1:(0.5-2):(0.2-4).

[0051] Furthermore, the mass concentration of the hydrogen peroxide in step C2 is 20-50%;

[0052] The molar ratio of toluene to hydrogen peroxide in hydrogen peroxide is 1:(0.15-1.1); preferably 1:(0.15-1.0).

[0053] In step C2, the slurry heating temperature is 50-90° C., and the reaction time is 5-60 min.

[0054] This method uses silicon and titanium sources as raw materials and, through modification, prepares a TS-1 catalyst. This catalyst is then used with toluene and hydrogen peroxide to produce p-cresol. This method exhibits extremely high selectivity for p-cresol, eliminating the need for separation of m-cresol and p-cresol to produce a high-purity p-cresol product.

[0055] This method uses hydrogen peroxide as an oxidant. Compared with existing processes, this process has the advantages of mild reaction conditions, high product yield, low pollution, low production cost, and no need to separate m-cresol and p-cresol, and is suitable for industrial production.

[0056] Compared with the prior art, the method for preparing the catalyst for preparing p-cresol from toluene and the method for preparing p-cresol of the present invention have the following advantages:

[0057] 1. The modified titanium silicate molecular sieve catalyst provided by the present invention has the advantage of high selectivity for p-cresol.

[0058] 2. The p-cresol production method provided by the present invention has a relatively low content of the difficult-to-separate meta-cresol component, thereby saving costs.

[0059] 3. The present invention uses toluene as a raw material and hydrogen peroxide as an oxidant, with mild reaction conditions, low by-products, little pollution and low production cost. DETAILED DESCRIPTION

[0060] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features therein may be combined with each other.

[0061] The present invention will be described in detail below with reference to examples.

[0062] Example 1

[0063] 200g of tetrapropylammonium hydroxide and 10g of triethylamine were added to water and stirred until dissolved. 400g of ethyl orthosilicate, 17g of isobutyl titanate, and 10g of nickel citrate were then added to the solution and stirred until a uniform gel was formed. Stirring was continued for 6 hours. The gel was then added to a hydrothermal reactor and crystallized at 180°C for 96 hours to obtain TS-1 molecular sieve. The obtained molecular sieve was washed until neutral, dried at 120°C for 12 hours, and then calcined in a muffle furnace at 550°C for 4 hours.

[0064] Prepare 5% acetic acid solution as treatment solution A, heat treatment solution A to 60°C, and place TS-1 catalyst in treatment solution A for 30 minutes. Wash the treated molecular sieve until it is neutral, and then dry it at 120°C for 12 hours.

[0065] Prepare a 1% ammonium fluoride solution as treatment solution B, heat it to 60°C, and treat the TS-1 catalyst in this solution for 30 minutes. Wash the treated molecular sieve until neutral, then dry it at 120°C for 12 hours, and calcine it in a muffle furnace at 550°C for 4 hours. This yields the modified TS-1 molecular sieve catalyst.

[0066] Dissolve 100g of toluene in 200g of methanol, then add 100g of modified TS-1 molecular sieve catalyst to the solution and stir until a uniform slurry forms. Heat the slurry to 60°C, then gradually add 125g of 30% hydrogen peroxide solution and continue the reaction for 30 minutes.

[0067] The product solution was analyzed and the toluene conversion rate was 47.12%, the selectivity of p-cresol was 96.76%, and the m 对甲酚 / (m 对甲酚 +m 间甲酚 ) is 99.23%.

[0068] Example 2

[0069] 200g of tetrapropylammonium hydroxide and 2g of n-butylamine were added to water and stirred until dissolved. 400g of ethyl orthosilicate, 8g of titanium chloride, and 10g of manganese nitrate were then added to the solution and stirred until a uniform gel was formed. Stirring was continued for 6 hours. The gel was then added to a hydrothermal reactor and crystallized at 190°C for 72 hours to obtain TS-1 molecular sieve. The obtained molecular sieve was washed until neutral, dried at 120°C for 12 hours, and then calcined in a muffle furnace at 550°C for 4 hours.

[0070] Prepare a 2% acrylic acid solution as treatment solution A, heat treatment solution A to 60°C, and place the TS-1 catalyst in treatment solution A for 30 minutes. Wash the treated molecular sieve until it is neutral, and then dry it at 120°C for 12 hours.

[0071] Prepare a 1% ammonium fluoride solution as treatment solution B, heat it to 60°C, and treat the TS-1 catalyst in this solution for 30 minutes. Wash the treated molecular sieve until neutral, then dry it at 120°C for 12 hours, and calcine it in a muffle furnace at 550°C for 4 hours. This yields the modified TS-1 molecular sieve catalyst.

[0072] Dissolve 100g of toluene in 200g of methanol, then add 150g of modified TS-1 molecular sieve catalyst to the solution and stir until a uniform slurry forms. Heat the slurry to 70°C, then gradually add 125g of 30% hydrogen peroxide solution and continue the reaction for 30 minutes.

[0073] The product solution was analyzed and the toluene conversion rate was 35.35%, the selectivity of p-cresol was 93.10%, and m 对甲酚 / (m 对甲酚 +m 间甲酚 ) is 99.08%.

[0074] Example 3

[0075] 200g of tetrapropylammonium hydroxide and 12g of n-propylamine were added to water and stirred until dissolved. 300g of fumed silica, 40g of titanium oxide powder, and 20g of calcium benzoate were then added to the solution and stirred until a uniform gel was formed. Stirring was continued for 12 hours. The gel was then added to a hydrothermal reactor and crystallized at 200°C for 120 hours to obtain TS-1 molecular sieve. The obtained molecular sieve was washed until neutral, dried at 120°C for 12 hours, and then calcined in a muffle furnace at 550°C for 4 hours.

[0076] Prepare 5% citric acid solution as treatment solution A, heat treatment solution A to 60°C, and place TS-1 catalyst in treatment solution A for 30 minutes. Wash the treated molecular sieve until it is neutral, and then dry it at 120°C for 12 hours.

[0077] Prepare a 5% ammonium fluoride solution as treatment solution B, heat it to 60°C, and treat the TS-1 catalyst in this solution for 30 minutes. Wash the treated molecular sieve until neutral, dry it at 120°C for 12 hours, and calcine it in a muffle furnace at 550°C for 4 hours. This yields the modified TS-1 molecular sieve catalyst.

[0078] Dissolve 100g of toluene in 100g of acetonitrile, then add 400g of modified TS-1 molecular sieve catalyst to the solution and stir until a uniform slurry forms. Heat the slurry to 70°C, then gradually add 74g of 50% hydrogen peroxide to the slurry and continue the reaction for 60 minutes.

[0079] The product solution was analyzed and found to have a toluene conversion rate of 73.83%, a p-cresol selectivity of 95.50%, and m 对甲酚 / (m 对甲酚 +m 间甲酚 ) is 97.89%.

[0080] Example 4

[0081] 200g of tetrapropylammonium hydroxide and 13g of ethylenediamine were added to water and stirred until dissolved. 400g of ethyl orthosilicate, 8g of isobutyl titanate, and 5g of magnesium acetate were added to the solution and stirred until a uniform gel was formed. Stirring was continued for 2 hours. The gel was then added to a hydrothermal reactor and crystallized at 185°C for 72 hours to obtain TS-1 molecular sieve. The obtained molecular sieve was washed until neutral, dried at 120°C for 12 hours, and then calcined in a muffle furnace at 550°C for 4 hours.

[0082] Prepare 3% citric acid solution as treatment solution A, heat treatment solution A to 30°C, and place TS-1 catalyst in treatment solution A for 60 minutes. Wash the treated molecular sieve until it is neutral, and then dry it at 120°C for 12 hours.

[0083] Prepare a 1% ammonium fluoride solution as treatment solution B, heat it to 30°C, and treat the TS-1 catalyst in this solution for 10 minutes. Wash the treated molecular sieve until neutral, dry it at 120°C for 12 hours, and calcine it in a muffle furnace at 550°C for 4 hours. This yields the modified TS-1 molecular sieve catalyst.

[0084] Dissolve 100g of toluene in 200g of tert-butyl alcohol, then add 100g of modified TS-1 molecular sieve catalyst to the solution and stir until a uniform slurry forms. Heat the slurry to 80°C, then gradually add 15g of 50% hydrogen peroxide solution and continue the reaction for 30 minutes.

[0085] The product solution was analyzed and the toluene conversion rate was 19.65%, the selectivity of p-cresol was 96.63%, and the m 对甲酚 / (m 对甲酚 +m 间甲酚 ) is 99.67%.

[0086] Example 5

[0087] 200g of tetrapropylammonium hydroxide and 10g of tri-n-propylamine were added to water and stirred until dissolved. 800g of 30% silica sol, 10g of titanium tetrachloride, and 1g of palladium acetate were then added to the solution and stirred until a uniform colloid was formed. Stirring was continued for 2 hours. The colloid was then added to a hydrothermal reactor and crystallized at 160°C for 24 hours to obtain TS-1 molecular sieve. The obtained molecular sieve was washed until neutral, dried at 120°C for 12 hours, and then calcined in a muffle furnace at 550°C for 4 hours.

[0088] Prepare 1% acetic acid solution as treatment solution A, heat treatment solution A to 80°C, and place TS-1 catalyst in treatment solution A for 10 minutes. Wash the treated molecular sieve until it is neutral, and then dry it at 120°C for 12 hours.

[0089] Prepare a 2% ammonium fluoride solution as treatment solution B, heat it to 50°C, and treat the TS-1 catalyst in this solution for 20 minutes. Wash the treated molecular sieve until neutral, dry it at 120°C for 12 hours, and calcine it in a muffle furnace at 550°C for 4 hours. This yields the modified TS-1 molecular sieve catalyst.

[0090] Dissolve 100g of toluene in 200g of acetic acid, then add 125g of modified TS-1 molecular sieve catalyst to the solution and stir until a uniform slurry forms. Heat the slurry to 60°C, then gradually add 61g of 30% hydrogen peroxide solution and continue the reaction for 30 minutes.

[0091] The product solution was analyzed and the toluene conversion rate was 38.62%, the selectivity of p-cresol was 97.62%, and m 对甲酚 / (m 对甲酚 +m 间甲酚 ) is 98.25%.

[0092] Example 6

[0093] 200g of tetrapropylammonium hydroxide and 3g of diethylamine were added to water and stirred until dissolved. 800g of 30% silica sol, 25g of isobutyl titanate, and 5g of ferric sulfate were added to the solution and stirred until a uniform colloid was formed. Stirring was continued for 4 hours. The colloid was then added to a hydrothermal reactor and crystallized at 180°C for 72 hours to obtain TS-1 molecular sieve. The obtained molecular sieve was washed until neutral, dried at 120°C for 12 hours, and then calcined in a muffle furnace at 550°C for 4 hours.

[0094] Prepare 2% citric acid solution as treatment solution A, heat treatment solution A to 60°C, and place TS-1 catalyst in treatment solution A for 60 minutes. Wash the treated molecular sieve until it is neutral, and then dry it at 120°C for 12 hours.

[0095] Prepare a 1% ammonium fluoride solution as treatment solution B, heat it to 60°C, and treat the TS-1 catalyst in this solution for 10 minutes. Wash the treated molecular sieve until neutral, then dry it at 120°C for 12 hours and calcine it in a muffle furnace at 550°C for 4 hours. This yields the modified TS-1 molecular sieve catalyst.

[0096] Dissolve 100g of toluene in 200g of 1,2-dichloroethane, then add 100g of modified TS-1 molecular sieve catalyst to the solution and stir until a uniform slurry forms. Heat the slurry to 80°C, then gradually add 61g of 30% hydrogen peroxide solution and continue the reaction for 30 minutes.

[0097] The product solution was analyzed and the toluene conversion rate was 38.62%, the selectivity of p-cresol was 97.62%, and m 对甲酚 / (m 对甲酚 +m 间甲酚 ) is 98.25%.

[0098] It can be seen from Examples 1 to 6 that the selectivity of p-cresol can reach at least 93% and above. 对甲酚 / (m 对甲酚 +m 间甲酚 ) can reach 97% and above, and even can reach above 99%. The content of the difficult-to-separate meta-cresol is relatively low, which saves costs.

[0099] Comparative Example 1

[0100] 200g of tetrapropylammonium hydroxide and 10g of triethylamine were added to water and stirred until dissolved. 400g of ethyl orthosilicate, 17g of isobutyl titanate, and 10g of nickel citrate were then added to the solution and stirred until a uniform gel was formed. Stirring was continued for 6 hours. The gel was then added to a hydrothermal reactor and crystallized at 180°C for 96 hours to obtain TS-1 molecular sieve. The obtained molecular sieve was washed until neutral, dried at 120°C for 12 hours, and then calcined in a muffle furnace at 550°C for 4 hours.

[0101] Dissolve 100g of toluene in 200g of methanol, then add 100g of TS-1 molecular sieve catalyst to the solution and stir until a uniform slurry forms. Heat the slurry to 60°C, then gradually add 125g of 30% hydrogen peroxide solution to the slurry and continue the reaction for 30 minutes.

[0102] The product solution was analyzed and the toluene conversion rate was 26.73%, the selectivity of p-cresol was 92.82%, and m 对甲酚 / (m 对甲酚 +m 间甲酚 ) is 94.62%.

[0103] Comparative Example 2

[0104] 200g of tetrapropylammonium hydroxide and 2g of n-butylamine were added to water and stirred until dissolved. 400g of ethyl orthosilicate and 8g of titanium chloride were then added to the solution and stirred until a uniform gel was formed. Stirring was continued for 6 hours. The gel was then added to a hydrothermal reactor and crystallized at 190°C for 72 hours to obtain TS-1 molecular sieve. The obtained molecular sieve was washed until neutral, dried at 120°C for 12 hours, and then calcined in a muffle furnace at 550°C for 4 hours.

[0105] Prepare a 2% acrylic acid solution as treatment solution A, heat treatment solution A to 60°C, and place the TS-1 catalyst in treatment solution A for 30 minutes. Wash the treated molecular sieve until it is neutral, and then dry it at 120°C for 12 hours.

[0106] Prepare a 1% ammonium fluoride solution as treatment solution B, heat it to 60°C, and treat the TS-1 catalyst in this solution for 30 minutes. Wash the treated molecular sieve until neutral, then dry it at 120°C for 12 hours, and calcine it in a muffle furnace at 550°C for 4 hours. This yields the modified TS-1 molecular sieve catalyst.

[0107] Dissolve 100g of toluene in 200g of methanol, then add 150g of modified TS-1 molecular sieve catalyst to the solution and stir until a uniform slurry forms. Heat the slurry to 70°C, then gradually add 125g of 30% hydrogen peroxide solution and continue the reaction for 30 minutes.

[0108] The product solution was analyzed and the toluene conversion rate was 37.97%, the selectivity of p-cresol was 54.64%, and m 对甲酚 / (m 对甲酚 +m 间甲酚 ) is 64.73%.

[0109] Comparative Example 3

[0110] 200g of tetrapropylammonium hydroxide and 10g of triethylamine were added to water and stirred until dissolved. 400g of ethyl orthosilicate, 17g of isobutyl titanate, and 10g of nickel citrate were then added to the solution and stirred until a uniform gel was formed. Stirring was continued for 6 hours. The gel was then added to a hydrothermal reactor and crystallized at 180°C for 96 hours to obtain TS-1 molecular sieve. The obtained molecular sieve was washed until neutral, dried at 120°C for 12 hours, and then calcined in a muffle furnace at 550°C for 4 hours.

[0111] Prepare a 1% ammonium fluoride solution as treatment solution B, heat it to 60°C, and treat the TS-1 catalyst in this solution for 30 minutes. Wash the treated molecular sieve until neutral, then dry it at 120°C for 12 hours, and calcine it in a muffle furnace at 550°C for 4 hours. This yields the modified TS-1 molecular sieve catalyst.

[0112] Dissolve 100g of toluene in 200g of methanol, then add 100g of modified TS-1 molecular sieve catalyst to the solution and stir until a uniform slurry forms. Heat the slurry to 60°C, then gradually add 125g of 30% hydrogen peroxide solution and continue the reaction for 30 minutes.

[0113] Analysis of the product solution showed that the toluene conversion was 27.73%, the selectivity for p-cresol was 92.61%, and the m-p-cresol / (m-p-cresol+m-m-cresol) ratio was 93.69%.

[0114] Comparative Example 4

[0115] 200g of tetrapropylammonium hydroxide and 10g of triethylamine were added to water and stirred until dissolved. 400g of ethyl orthosilicate, 17g of isobutyl titanate, and 10g of nickel citrate were then added to the solution and stirred until a uniform gel was formed. Stirring was continued for 6 hours. The gel was then added to a hydrothermal reactor and crystallized at 180°C for 96 hours to obtain TS-1 molecular sieve. The obtained molecular sieve was washed until neutral, dried at 120°C for 12 hours, and then calcined in a muffle furnace at 550°C for 4 hours.

[0116] Prepare a 2% acrylic acid solution as treatment solution A, heat treatment solution A to 60°C, and place the TS-1 catalyst in treatment solution A for 30 minutes. Wash the treated molecular sieve until it is neutral, and then dry it at 120°C for 12 hours.

[0117] Dissolve 100g of toluene in 200g of methanol, then add 100g of modified TS-1 molecular sieve catalyst to the solution and stir until a uniform slurry forms. Heat the slurry to 60°C, then gradually add 125g of 30% hydrogen peroxide solution and continue the reaction for 30 minutes.

[0118] Analysis of the product solution showed that the toluene conversion rate was 42.01%, the selectivity for p-cresol was 92.61%, and the m-p-cresol / (m-p-cresol+m-m-cresol) ratio was 93.91%.

[0119] Comparative Example 5

[0120] 200g of tetrapropylammonium hydroxide and 10g of triethylamine were added to water and stirred until dissolved. 400g of ethyl orthosilicate, 17g of isobutyl titanate, and 10g of nickel citrate were then added to the solution and stirred until a uniform gel was formed. Stirring was continued for 6 hours. The gel was then added to a hydrothermal reactor and crystallized at 180°C for 96 hours to obtain TS-1 molecular sieve. The obtained molecular sieve was washed until neutral, dried at 120°C for 12 hours, and then calcined in a muffle furnace at 550°C for 4 hours.

[0121] Prepare a 2% nitric acid solution as the treatment solution, heat the treatment solution A to 60°C, and place the TS-1 catalyst in the treatment solution A for 30 minutes. Wash the treated molecular sieve until it is neutral, and then dry it at 120°C for 12 hours.

[0122] Dissolve 100g of toluene in 200g of methanol, then add 100g of modified TS-1 molecular sieve catalyst to the solution and stir until a uniform slurry forms. Heat the slurry to 60°C, then gradually add 125g of 30% hydrogen peroxide solution and continue the reaction for 30 minutes.

[0123] Analysis of the product solution showed that the toluene conversion was 29.12%, the selectivity for p-cresol was 47.73%, and the m-p-cresol / (m-p-cresol+m-m-cresol) ratio was 48.47%.

[0124] By comparing Comparative Example 1 with Example 1, it can be seen that when the treatment liquid A and the treatment liquid B are not used, the conversion rate of toluene decreases, and the selectivity of p-cresol decreases. 对甲酚 / (m 对甲酚 +m 间甲酚 ) decreased;

[0125] By comparing Comparative Example 2 with Example 2, it can be seen that when no metal salt is added, the selectivity of p-cresol decreases, m 对甲酚 / (m 对甲酚 +m 间甲酚 ) decreased;

[0126] By comparing Comparative Example 3 with Example 1, it can be seen that when only treatment liquid B is used without using treatment liquid A and treatment liquid C, the conversion rate of toluene decreases, and the selectivity of p-cresol decreases. 对甲酚 / (m 对甲酚 +m 间甲酚 ) value decreased.

[0127] By comparing Comparative Examples 4 and 5 with Example 1, it can be seen that when the treatment liquid B is not used after the treatment liquid A, the conversion rate of toluene decreases, and the selectivity of p-cresol decreases. 对甲酚 / (m 对甲酚 +m间甲酚 ) value decreased.

[0128] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a catalyst for preparing p-cresol from toluene, characterized in that: The steps include: S1: Preparation of TS-1 titanium silicate molecular sieve; S2: placing the TS-1 titanium silicate molecular sieve in step S1 into treatment solution A, separating and cleaning the TS-1 titanium silicate molecular sieve; S3: placing the TS-1 titanium silicate molecular sieve obtained in step S2 into treatment solution B, separating and washing the TS-1 titanium silicate molecular sieve, drying and calcining the TS-1 titanium silicate molecular sieve to obtain a catalyst; Treatment liquid A is an organic acid solution, and treatment liquid B is a solution containing fluoride ions; The organic acid solution of the treatment liquid A includes one or more of acetic acid, propionic acid, acrylic acid, citric acid, oxalic acid, and benzoic acid, and the mass concentration of the organic acid solution is 1-5%; The TS-1 titanium silicate molecular sieve obtained in step S1 is immersed in the treatment solution A at a temperature of 20 to 80° C. for a time of 10 to 200 min; The treatment solution B contains fluoride ions and includes one or both of ammonium fluoride and hydrogen fluoride; The fluoride ion solution is ammonium fluoride, and the mass concentration of ammonium fluoride is 0.5~10%; The TS-1 titanium silicate molecular sieve obtained in step S2 is immersed in the treatment solution B at a temperature of 20-80° C. and a time of 10-200 min.

2. The method for preparing a catalyst for preparing p-cresol from toluene according to claim 1, wherein: The preparation method of TS-1 titanium silicate molecular sieve in step S1 comprises the following steps: T1: Dissolve tetrapropylammonium hydroxide and organic amine in water and stir until dissolved to obtain mixed solution A; T2: Add the silicon source, titanium source, and metal salt to the mixed solution A in step T1 and stir until a uniform gel is formed; T3: Stir the glue obtained in step T2, transfer the glue to a hydrothermal kettle, crystallize, wash to neutrality, dry and calcine.

3. The method for preparing a catalyst for preparing p-cresol from toluene according to claim 2, wherein: In step T1, the organic amine includes one or more of n-butylamine, triethylamine, tri-n-propylamine, n-propylamine, diethylamine, and ethylenediamine, and the molar ratio of tetrapropylammonium hydroxide to the organic amine is 1:(0.02-0.8).

4. The method for preparing a catalyst for preparing p-cresol from toluene according to claim 3, wherein: The silicon source in step T2 includes one or more of fumed silicon oxide, ethyl orthosilicate, and silica sol.

5. The method for preparing a catalyst for preparing p-cresol from toluene according to claim 3, wherein: The titanium source in step T2 includes one or more of isobutyl titanate, titanium oxide powder, and titanium tetrachloride.

6. The method for preparing a catalyst for preparing p-cresol from toluene according to claim 3, wherein: The cations of the metal salt include one or more of iron ions, cobalt ions, nickel ions, copper ions, molybdenum ions, manganese ions, calcium ions, magnesium ions, ruthenium ions, palladium ions, and platinum ions; and the anions of the metal salt are one of acetate, oxalate, citrate, sulfate, nitrate, and benzoate.

7. The method for preparing a catalyst for preparing p-cresol from toluene according to claim 3, wherein: The molar ratio of the silicon source, the titanium source and the metal salt is 1:(0.01-0.1):(0.01-0.05).

8. The method for preparing a catalyst for preparing p-cresol from toluene according to claim 2, wherein: In step T3, the stirring time of the glue solution is 2 to 12 hours; the crystallization temperature in the hydrothermal reactor is 80 to 200° C., and the crystallization reaction time is 10 to 120 hours.

9. The method for preparing a catalyst for preparing p-cresol from toluene according to claim 2, wherein: The drying temperature is 100-140°C, the drying time is 11-13 h, the calcination temperature is 500-600°C, and the calcination time is 3-5 h.

10. A method for preparing p-cresol, characterized in that: The steps include: C1: Add the catalyst, toluene and solvent into the reactor and start stirring until a uniform slurry is formed; C2: heating the slurry obtained in step C1, adding hydrogen peroxide to the slurry for reaction, and keeping the temperature to obtain a p-cresol product; Wherein, the catalyst is prepared by the preparation method of the catalyst for preparing p-cresol from toluene according to any one of claims 2 to 9.

11. The method for preparing p-cresol according to claim 10, wherein: The solvent in step C1 includes one or more of methanol, ethanol, isopropanol, tert-butanol, formic acid, acetic acid, acetonitrile, and 1,2-dichloroethane; The mass ratio of toluene, catalyst and solvent is 1:(0.5~2):(0.2~4).

12. The method for preparing p-cresol according to claim 10, wherein: The mass concentration of hydrogen peroxide in step C2 is 20-50%; The molar ratio of toluene to hydrogen peroxide in hydrogen peroxide is 1:(0.15~1.1); In step C2, the slurry heating temperature is 50-90° C., and the reaction time is 5-60 min.