A catalyst for direct hydroxylation of toluene to produce cresol and a preparation method thereof

Abstract

The present application relates to a kind of catalyst for toluene direct hydroxylation preparation carbinol and its preparation method, it is characterized in that the structural formula of catalyst is: A m B n SiO x Wherein: A is any one of Cu, Fe, Ni, Mn or Al;B is any one of Co, Cr, Ce, Zn or V.Surfactant is added to the solution of water and ethanol, after stirring evenly, then add metal A salt and metal B salt, finally add silicon source, the product of aging is washed, calcined to obtain the catalyst.The above-mentioned catalyst is used for toluene and hydrogen peroxide reaction direct synthesis carbinol, solve the defects such as low conversion rate, long reaction time in the reaction of toluene hydroxylation preparation carbinol in the past.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of catalytic oxidation of toluene, and particularly relates to a catalyst for directly hydroxylating toluene to prepare methyl phenol and a preparation method thereof; the present application also relates to application of the catalyst in direct hydroxylation of toluene to prepare methyl phenol. BACKGROUND

[0002] Methyl phenol is an important fine chemical intermediate, and there are three isomers, namely o-methyl phenol, m-methyl phenol and p-methyl phenol, all of which are important chemical raw materials and have wide industrial applications. The o-methyl phenol can be used for synthesizing resins, and also can be used for pesticides, herbicides, spices, polymerization inhibitors and chemical reagents. The m-methyl phenol is an intermediate for synthesizing rubber, color film, plasticizer and spice, and also can be used for manufacturing vitamin E, dyes, pesticides and cosmetics. The p-methyl phenol can be used for producing phenolic resin in the plastic industry, and also can be used as an intestinal anthelmintic and disinfectant in the pharmaceutical industry, and can be used as a raw material to manufacture antioxidants and rubber anti-aging agents.

[0003] Traditional methyl phenol production processes mainly include chemical synthesis methods such as sulfonation alkali fusion method, chlorination hydrolysis method, cumene oxidation method, phenol alkylation method, diazotization hydrolysis method and direct oxidation method. These methods often require high temperature and high pressure in the reaction process, and the process is complex and seriously pollutes the environment. Hydrogen peroxide has been widely concerned due to its simple process, green and only water as by-product.

[0004] Direct one-step hydroxylation of toluene to prepare methyl phenol with hydrogen peroxide is an ideal method with less steps and low cost, and therefore, if an efficient process for producing methyl phenol can be obtained, it will have high application value.

[0005] The patent (catalyst for preparing methyl phenol by oxidizing toluene with hydrogen peroxide and preparation method thereof CN105289612B) adopts a titanium-silicon molecular sieve catalyst, the methyl phenol product has high selectivity, the toluene conversion rate is low, the toluene conversion rate is 12%, the methyl phenol selectivity is 79%, and the reaction time is 1-7h.

[0006] The patent (a method for preparing methyl phenol by one-step hydroxylation of toluene CN105566071A) uses a titanium-silicon molecular sieve loaded with iron salt as a catalyst. The method has high selectivity of methyl phenol product. The toluene conversion rate is 30%, the methyl phenol selectivity is 90%, and the reaction time is 4-12h.

[0007] The patent (catalytic synthesis method for preparing methyl phenol by one-step hydroxylation of toluene CN101786943A) selects a composite catalyst composed of titanium-silicon molecular sieve and diatomite. The toluene conversion rate is low, the methyl phenol product has high selectivity, the toluene conversion rate is 15.9%, the methyl phenol selectivity is 90%, and the reaction time is 1h.

[0008] The catalyst for directly hydroxylating toluene to prepare cresol is basically titanium-silicon molecular sieve, which has certain advantages in the process of catalytic oxidation synthesis of cresol, but the synthesis cost of titanium-silicon molecular sieve is high, and the long reaction time limits the industrial development. SUMMARY

[0009] The present application aims to improve the problems of complex process and long reaction time in the current cresol production, and provides a catalyst for directly hydroxylating toluene to prepare cresol, and also aims to provide a preparation method of the catalyst, and also aims to provide a method for directly hydroxylating toluene to prepare cresol by using the catalyst.

[0010] The technical scheme of the present application is: a catalyst for directly hydroxylating toluene to prepare cresol, characterized in that the structural formula of the catalyst is

[0011] A m B n SiO x ;

[0012] Wherein: A is any one of Cu, Fe, Ni, Mn or Al;

[0013] B is any one of Co, Cr, Ce, Zn or V;

[0014] The value range of m is 0.04-0.06;

[0015] The value range of n is 0.01-0.04;

[0016] x is the number of oxygen atoms coordinated with other elements, and the value range is 2.05-2.16.

[0017] The present application also provides a method for preparing the above-mentioned catalyst, and the specific steps are as follows: a surfactant is added to a solution of ethanol and water and stirred uniformly; then metal A salt and metal B salt are added to the solution according to the stoichiometric ratio, and a silicon source is added under water bath condition, and after stirring and dispersing uniformly, the precipitate is aged; after centrifugation, washing, drying and calcination, the catalyst for directly hydroxylating toluene to prepare cresol is obtained; the molar ratio of the silicon source to the surfactant is 3-4.5. m B n SiO x

[0018] Preferably, the volume ratio of the above-mentioned water and ethanol is 1.8-3.5; preferably, the surfactant is one of tetrapropylammonium hydroxide, dodecylamine or cetyl ammonium bromide; and the silicon source is tetraethyl orthosilicate.

[0019] ​Preferably, the metal A salt is a nitrate, chloride or sulfate of metal A; and the metal B salt is a nitrate, chloride or sulfate of metal B.

[0020] Preferably, the temperature of the water bath is 30-70℃; the stirring and dispersing time is 2-6 hours; the aging time is 8-24 hours; the calcination temperature is 450-550℃; and the calcination time is 4-6 hours.

[0021] The application also provides a method for preparing methyl phenol by direct hydroxylation of toluene using the catalyst described above, which comprises the following steps: adding the catalyst, solvent, toluene and hydrogen peroxide solution into a reactor equipped with an electric stirring device and a constant temperature reflux device after the reactor is heated to the reaction temperature, and preparing methyl phenol after constant temperature reaction.

[0022] Preferably, the reaction temperature is 55-100℃, and the reaction time is 15-45 min.

[0023] Preferably, the mass ratio of toluene to catalyst is 80-130:1; the molar ratio of hydrogen peroxide to toluene is 3-7:1; and the mass ratio of solvent to toluene is 2.5-5.5:1.

[0024] Beneficial effects: The main feature of the catalyst of the application is that the two metal elements of the active center A and B of the oxidation reaction are introduced into the pore of the catalyst, which shortens the reaction time in the process of preparing methyl phenol by direct hydroxylation of toluene, and improves the toluene conversion rate and catalytic activity.

[0025] Compared with the prior art, the application has the following outstanding advantages and effects:

[0026] (1) Compared with titanium-silicon molecular sieve, the application has a lower price. The introduction of metal into the pore effectively inhibits the aggregation and loss of metal oxide and active center particles.

[0027] (2) Compared with the common methyl phenol synthesis process, the application has a simple process and shortens the reaction time to 15-45 min. DETAILED DESCRIPTION

[0028] The application is described in detail below through examples.

[0029]

Example 1

[0030] A solution of 0.015 mol of tetrapropylammonium hydroxide was added to a mixture of 60 ml of ionized water and 30 ml of ethanol and stirred for 45 min in a water bath at 55°C. 6 mmol of Fe(NO3)3-9H2O and 1.5 mmol of Co(NO3)2-6H2O were added to the above mixture and stirred for 30 min. While stirring, 0.054 mol of tetraethyl orthosilicate was added dropwise and stirred for 6 hours in a water bath at 45°C and aged for 24 hours. After centrifugation, washing and drying, the catalyst was calcined at 550°C for 4 hours to obtain the catalyst, which was designated as Fe 0.06 Co 0.015 SiO 2.105 .

[0031] Example 2: Synthesis of catalyst

[0032] A solution of 0.01 mol of dodecylamine was added to a mixture of 70 ml of ionized water and 25 ml of ethanol and stirred for 30 min in a water bath at 45°C. 4 mmol of Cu(NO3)2-3H2O and 2 mmol of VOSO4-4H2O were added to the above mixture and stirred for 25 min. While stirring, 0.044 mol of tetraethyl orthosilicate was added dropwise and stirred for 5 hours in a water bath at 55°C and aged for 20 hours. After centrifugation, washing and drying, the catalyst was calcined at 500°C for 4 hours to obtain the catalyst, which was designated as Cu 0.04 V 0.02 SiO 2.13 .

[0033] Example 3: Synthesis of catalyst

[0034] A solution of 0.011 mol of cetyl ammonium bromide was added to a mixture of 60 ml of ionized water and 20 ml of ethanol and stirred for 25 min in a water bath at 60°C. 5

[0035] mmol of MnSO4-5H2O and 3 mmol of Cr(NO3)3-9H2O were added to the above mixture and stirred for 35 min. While stirring, 0.034 mol of tetraethyl orthosilicate was added dropwise and stirred for 4 hours in a water bath at 40°C and aged for 18 hours. After centrifugation, washing and drying, the catalyst was calcined at 525°C for 6 hours to obtain the catalyst, which was designated as Mn 0.05 Cr 0.03 SiO 2.14 .

[0036] Example 4: Synthesis of catalyst

[0037] A solution of 0.012 mol of dodecylamine was added to a mixed solution of 55 ml of ionized water and 25 ml of ethanol, and stirred for 40 min in a water bath at 45°C. 5 mmol of Ni(NO3)2-6H2O and 1 mmol of CeCl3-7H2O were added to the mixed solution, and stirred for 15 min. While stirring, 0.041 mol of tetraethyl orthosilicate was added dropwise, and stirred for 2 hours in a water bath at 35°C, and aged for 12 hours. After centrifugation, washing, and drying, the catalyst was calcined at 450°C for 6 hours to obtain the catalyst, which was designated as Ni 0.05 Ce 0.01 SiO 2.12 .

[0038] Example 5. Synthesis of catalyst

[0039] A solution of 0.009 mol of dodecylamine was added to a mixed solution of 65 ml of ionized water and 20 ml of ethanol, and stirred for 20 min in a water bath at 45°C. 4 mmol of Al(NO3)3-6H2O and 2.5 mmol of ZnSO4-7H2O were added to the mixed solution, and stirred for 45 min. While stirring, 0.038 mol of tetraethyl orthosilicate was added dropwise, and stirred for 2 hours in a water bath at 65°C, and aged for 18 hours. After centrifugation, washing, and drying, the catalyst was calcined at 550°C for 4 hours to obtain the catalyst, which was designated as Al 0.04 Zn 0.025 SiO 2.085 .

[0040] Example 6. Oxidation of toluene with hydrogen peroxide to produce cresol

[0041] The catalyst Fe 0.06 Co 0.015 SiO 2.105 was used for the hydroxylation of toluene, and the reaction was carried out in a reactor equipped with an electric stirring device and a constant temperature reflux device, under the following conditions: 80°C, molar ratio of hydrogen peroxide / toluene 5, toluene 0.95 g, solvent methanol 4.22 g, mass ratio of toluene / catalyst 120, and reaction time 40 min. The results of the reaction are shown in Table 1.

[0042] Example 7. Oxidation of toluene with hydrogen peroxide to produce cresol

[0043] The catalyst Cu 0.04 V 0.02 SiO 2.13 was used for the hydroxylation of toluene, and the reaction was carried out in a reactor equipped with an electric stirring device and a constant temperature reflux device, under the following conditions: 90°C, molar ratio of hydrogen peroxide / toluene 6, toluene 1.12 g, solvent acetonitrile 3.96 g, mass ratio of toluene / catalyst 100, and reaction time 25 min. The results of the reaction are shown in Table 1.

[0044] Example 8 Toluene hydroperoxide oxidation to cresols

[0045] Catalyst Mn 0.05 Cr 0.03 SiO 2.14 The toluene hydroxylation reaction was carried out in a reactor equipped with an electric stirring device and a constant temperature reflux device, with the reaction conditions being 75°C, a hydrogen peroxide / toluene molar ratio of 4, toluene 1.42 g, solvent acetone 4.21 g, toluene / catalyst mass ratio 90, and a reaction time of 30 min. The reaction results are shown in Table 1.

[0046] Example 9 Toluene hydroperoxide oxidation to cresols

[0047] Catalyst Ni 0.05 Ce 0.01 SiO 2.12 The toluene hydroxylation reaction was carried out in a reactor equipped with an electric stirring device and a constant temperature reflux device, with the reaction conditions being 85°C, a hydrogen peroxide / toluene molar ratio of 5, toluene 0.95 g, solvent butanol 5.03 g, toluene / catalyst mass ratio 100, and a reaction time of 20 min. The reaction results are shown in Table 1.

[0048] Example 10 Toluene hydroperoxide oxidation to cresols

[0049] Catalyst Al 0.04 Zn 0.025 SiO 2.085 The toluene hydroxylation reaction was carried out in a reactor equipped with an electric stirring device and a constant temperature reflux device, with the reaction conditions being 60°C, a hydrogen peroxide / toluene molar ratio of 3.5, toluene 0.89 g, solvent methanol 4.89 g, toluene / catalyst mass ratio 85, and a reaction time of 35 min. The reaction results are shown in Table 1.

[0050] Table 1. Evaluation table of toluene catalytic effect in different examples

[0051]

Claims

1. A method for the direct hydroxylation of toluene to produce cresol, comprising the following steps: in a reactor equipped with an electric stirrer and a constant temperature reflux device, after the reaction temperature is reached, a catalyst, a solvent, toluene, and a hydrogen peroxide solution are added, and the reaction is carried out at a constant temperature to prepare cresol; wherein the catalyst has the structural formula A. m B n SiO x ; in: A is any one of Cu, Fe, Ni, Mn or Al; B is any one of Co, Cr, Ce, Zn or V; The value of m ranges from 0.04 to 0.06; The value of n ranges from 0.01 to 0.04; The value of x ranges from 2.05 to 2.16; The catalyst was prepared by the following method, the specific steps of which are as follows: The surfactant was added to a solution of ethanol and water and stirred until homogeneous; then, according to step A... m B n SiO x According to the stoichiometric ratio, metal A salt and metal B salt are added to the solution, and silicon source is added under water bath conditions. After stirring and dispersing evenly, the solution is aged and precipitated. After centrifugation, washing, drying, and calcination, a catalyst for the direct hydroxylation of toluene to produce cresol is obtained; the molar ratio of silicon source to surfactant is 3 to 4.

5.

2. The method according to claim 1, characterized in that... The volume ratio of water to ethanol is 1.8 to 3.5; the surfactant is one of tetrapropylammonium hydroxide, dodecylamine, or hexadecylammonium bromide; and the silicon source is tetraethyl orthosilicate.

3. The method according to claim 1, characterized in that... The metal A salt is a nitrate, chloride, or sulfate of metal A; the metal B salt is a nitrate, chloride, or sulfate of metal B.

4. The method according to claim 1, characterized in that... The water bath temperature is 30–70℃; the stirring and dispersion time is 2–6 hours; the aging time is 8–24 hours; the calcination temperature is 450–550℃, and the calcination time is 4–6 hours.

5. The method according to claim 1, characterized in that... The reaction temperature is 55–100℃, and the reaction time is 15–45 min.

6. The method according to claim 1, characterized in that... The solvent is one of acetonitrile, methanol, butanol or acetone.

7. The method according to claim 1, characterized in that... The mass ratio of toluene to catalyst is 80–130:1; the molar ratio of hydrogen peroxide to toluene is 3–7:1; and the mass ratio of solvent to toluene is 2.5–5.5:1.

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