Methyl phenol compound alkylation method

Abstract

The invention belongs to the technical field of synthesis of chemical products, and discloses a methyl phenol compound alkylation method. The method comprises the following steps: adding a catalyst cresol sulfonic acid and an auxiliary agent ferrous salt into a methylphenol compound under a normal pressure condition, introducing isobutene into a reaction solution at a certain gas speed under a stirring condition, and reacting to obtain an alkylated compound; phenol in the methyl phenol compound is raw material phenol, and the amount of isobutene introduced in the reaction is 0.5-1.1 times of the amount of the raw material phenol; the catalyst cresol sulfonic acid accounts for 0.1-1% of the amount of the phenol substance of the raw material; and the use amount of the auxiliary agent ferrous salt is 0.5-5% of the amount of cresol sulfonic acid substance. And the method has the advantages of low catalyst consumption, short reaction time and mildness. The conversion rate is high.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical product synthesis, and relates to a method for alkylating methylphenol compounds. Background Art

[0002] Tert-butylmethylphenol compounds are an important type of sterically hindered phenol antioxidants, which are widely used in petroleum products, polymer materials, rubber anti-aging and food industries. Among them, important antioxidants include 2,6-di-tert-butyl-p-cresol (abbreviated as BHT or antioxidant 264), 4,4'-thiobis(6-tert-butyl-m-cresol) (abbreviated as antioxidant 300) and antioxidant 2246, etc. Cresol is one of the important raw materials for the production of antioxidants, and these common antioxidants can be prepared by the alkylation method of cresol.

[0003] At present, there are many methods for the tert-butylation of phenols. According to different alkylating reagents, they can be divided into isobutene method, tert-butanol method and methyl tert-butyl ether method. When alkylation is carried out by the tert-butanol method and methyl tert-butyl ether method, products such as water and methanol will be generated, which brings trouble to the subsequent separation. The isobutene method is the most atom-economic method and is also the mainstream process in the current production of phenol tert-butylation. When alkylating cresol and isobutene, an acid is generally required as a catalyst. Usually, the optional catalysts include solid acids and liquid acids. Among them, solid acids include strongly acidic cation exchange resins, acidic molecular sieves and solid superacids, etc., and liquid acids include sulfuric acid, phosphoric acid, p-toluenesulfonic acid, heteropolyacids and acidic ionic liquids, etc. When using a solid acid as a catalyst, a higher reaction temperature is required, which is likely to cause the polymerization of isobutene. Moreover, the deeper the degree of alkylation, the more serious the polymerization of isobutene and the shorter the catalyst life. Therefore, it is only suitable for the production of mono-tert-butylphenol products. When using a liquid acid as a catalyst, the catalytic efficiency is relatively high and it is suitable for the production of deep alkylation products. Therefore, it is also the main catalyst selected in the current synthesis of antioxidants such as BHT.

[0004] Although the catalytic efficiency of liquid acids is relatively high, the amount of catalyst used in current production is relatively large. Usually, 3%-10% of the mass of raw material phenol is required (CN201310157977, Dhaka Univ Stud Part B, 1990, 38(2): 197-198.). The reaction temperature is usually 60-70°C, and the time required to complete the reaction is usually more than 5 hours. Not only are more equipment required and the equipment is more easily corroded, but it also brings certain difficulties to the post-treatment. Therefore, it is necessary to find a more efficient and mild catalyst and a simpler preparation method to solve the problems in current production. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, the present invention provides a method for alkylating methylphenol compounds, which shortens the reaction time, and provides a highly efficient catalyst. When the catalyst is applied to the method for alkylating methylphenol compounds, the amount of catalyst used is small, the reaction time is short, the reaction conditions are mild, and the conversion rate is high.

[0006] The above object of the present invention is achieved by the following technical solutions:

[0007] A method for alkylating methylphenol compounds. Under atmospheric pressure conditions, methylphenol compounds are added with cresol sulfonic acid as a catalyst and ferrous salt as an auxiliary agent. Isobutene is introduced into the reaction solution at a certain gas velocity under stirring conditions. After the reaction is completed, an alkylated compound is obtained; the phenol in the methylphenol compounds is the raw material phenol, and the amount of isobutene introduced into the reaction is 0.5 - 1.1 times the amount of the raw material phenol used; the cresol sulfonic acid as the catalyst is 0.1% - 1% of the amount of the raw material phenol in terms of the amount of substance; the amount of the ferrous salt as the auxiliary agent is 0.5% - 5% of the amount of substance of the cresol sulfonic acid.

[0008] Furthermore, the methylphenol compounds are any one or two or more of o - cresol, p - cresol, m - cresol, 2,4 - xylenol, and 2,6 - xylenol.

[0009] Furthermore, the cresol sulfonic acid is any one or two or more of o - cresol sulfonic acid, p - cresol sulfonic acid, and m - cresol sulfonic acid.

[0010] Furthermore, the ferrous salt is any one of ferrous chloride, ferrous sulfate, ferrous hydroxide, ferrous cresol sulfonate, and ferrous acetate.

[0011] Furthermore, the reaction temperature is 50°C to 60°C, and the reaction time is 1 - 2 hours.

[0012] Furthermore, the gas velocity of introducing isobutene is the calculated amount for completing the reaction within 1 - 2 hours.

[0013] The beneficial effects of the present invention compared with the prior art are as follows:

[0014] The method for alkylating methylphenol compounds provided by the present invention requires a small amount of catalyst, has mild reaction conditions, less isobutene polymerization, high reaction efficiency, and can obtain higher output with less equipment investment. Specific Embodiments

[0015] The present invention will be described in detail below through specific embodiments, but the protection scope of the present invention is not limited. Unless otherwise specified, the experimental methods adopted in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can all be obtained from commercial channels.

[0016] Example 1

[0017] A specified amount of p-cresol, a catalyst, and an auxiliary agent are mixed in a molar ratio of p-cresol:p-cresol sulfonic acid:ferrous chloride = 100:0.5:0.01 and placed in a reaction kettle. Stirring is started, and the temperature is raised to 50 °C. Isobutene is introduced under normal pressure, and the reaction temperature is controlled at 50 - 55 °C. The total amount of isobutene introduced is 1.1 times the mass of p-cresol and is controlled to be introduced within 2 hours. After the reaction is completed, sampling and analysis are carried out. The content of p-cresol in the reaction solution is 0.03% (conversion rate is 99.9%), the content of 2,6-di-tert-butyl-p-cresol is 91.32%, the content of 2-tert-butyl-p-cresol is 6.58%, the content of isobutene polymer is 1.46%, and the content of other impurities is 0.61%.

[0018] Example 2

[0019] A specified amount of m-cresol, a catalyst, and an auxiliary agent are mixed in a molar ratio of m-cresol:m-cresol sulfonic acid:ferrous acetate = 100:1:0.04 and placed in a reaction kettle. Stirring is started, and the temperature is raised to 50 °C. Isobutene is introduced under normal pressure, and the reaction temperature is controlled at 50 - 55 °C. The total amount of isobutene introduced is 1.1 times the mass of m-cresol and is controlled to be introduced within 2 hours. After the reaction is completed, sampling and analysis are carried out. The content of m-cresol in the reaction solution is 1.2% (conversion rate is 97.7%), the content of 4,6-di-tert-butyl-m-cresol is 87.50%, the content of 6-tert-butyl-m-cresol is 8.61%, the content of 4-tert-butyl-m-cresol is 0.26%, the content of isobutene polymer is 1.73%, and the content of other impurities is 0.70%.

[0020] Example 3

[0021] A specified amount of 2,4-xylenol, a catalyst, and an auxiliary agent are mixed in a molar ratio of 2,4-xylenol:p-cresol sulfonic acid:ferrous p-cresol sulfonate = 100:0.2:0.008 and placed in a reaction kettle. Stirring is started, and the temperature is raised to 50 °C. Isobutene is introduced under normal pressure, and the reaction temperature is controlled at 50 - 55 °C. The total amount of isobutene introduced is 0.55 times the mass of p-cresol and is controlled to be introduced within 1.5 hours. After the reaction is completed, sampling and analysis are carried out. The content of 2,4-xylenol in the reaction solution is 0.59% (conversion rate is 99.4%), the content of 6-tert-butyl-2,4-xylenol is 97.13%, the content of isobutene polymer is 1.76%, and the content of other impurities is 0.52%.

[0022] Example 4

[0023] A specified amount of o-cresol, a catalyst, and an auxiliary agent are mixed in a molar ratio of o-cresol: o-cresol sulfonic acid: ferrous sulfate = 100: 0.8: 0.02 and placed in a reaction kettle. Stirring is started, and the temperature is raised to 50 °C. Isobutene is introduced under normal pressure, and the reaction temperature is controlled at 50 - 55 °C. The total amount of isobutene introduced is 1.1 times the mass of o-cresol, and it is controlled to be introduced within 2 hours. After the reaction is completed, sampling and analysis are carried out. The content of o-cresol in the reaction solution is 0.04% (conversion rate is 99.9%), the content of 4,6-di-tert-butyl o-cresol is 92.33%, the content of 6-tert-butyl o-cresol is 2.31%, the content of 4-tert-butyl o-cresol is 3.05%, the content of isobutene polymer is 1.67%, and the content of other impurities is 0.63%.

[0024] Example 5

[0025] A specified amount of m,p-cresol (m:p = 75:25), a catalyst, and an auxiliary agent are mixed in a molar ratio of m,p-cresol: m-cresol sulfonic acid: ferrous sulfate = 100: 0.7: 0.03 and placed in a reaction kettle. Stirring is started, and the temperature is raised to 50 °C. Isobutene is introduced under normal pressure, and the reaction temperature is controlled at 50 - 55 °C. The total amount of isobutene introduced is 1.1 times the mass of m-cresol, and it is controlled to be introduced within 2 hours. After the reaction is completed, sampling and analysis are carried out. The content of m,p-cresol in the reaction solution is 0.81% (conversion rate is 99.1%), the content of 4,6-di-tert-butyl m-cresol is 66.82%, the content of 2,6-di-tert-butyl p-cresol is 23.09%, the content of 2-tert-butyl p-cresol is 0.52%, the content of 6-tert-butyl m-cresol is 6.14%, the content of 4-tert-butyl m-cresol is 0.19%, the content of isobutene polymer is 1.77%, and the content of other impurities is 0.66%.

[0026] Comparative Example 1

[0027] The implementation conditions are the same as those in Example 1, except that 98% concentrated sulfuric acid is used as the catalyst, and the molar ratio of p-cresol to concentrated sulfuric acid is p-cresol: sulfuric acid = 100: 1. After the reaction is completed, sampling and analysis are carried out. The content of p-cresol in the reaction solution is 5.20% (conversion rate is 90.1%), the content of 2,6-di-tert-butyl p-cresol is 67.41%, the content of 2-tert-butyl p-cresol is 28.27%, the content of isobutene polymer is 3.23%, and the content of other impurities is 1.09%.

[0028] Comparative Example 2

[0029] The implementation conditions are the same as those in Example 1, except that no auxiliary agent is added during the reaction. After the reaction is completed, sampling and analysis are carried out. The content of p-cresol in the reaction solution is 2.18% (conversion rate is 95.7%), the content of 2,6-di-tert-butyl p-cresol is 82.10%, the content of 2-tert-butyl p-cresol is 13.67%, the content of isobutene polymer is 1.41%, and the content of other impurities is 0.64%.

[0030] The above-described embodiments are only the preferred embodiments of the present invention, and not all the feasible embodiments of the present invention. For those of ordinary skill in the art, any obvious changes made without departing from the principles and spirit of the present invention should be considered to be included within the scope of the claims of the present invention.

Claims

1. A method for alkylating methylphenol compounds, characterized in that: Under normal pressure, a methylphenol compound is added with a catalyst cresol sulfonic acid and an auxiliary divalent iron salt, and isobutylene is introduced into the reaction liquid at a certain gas speed under stirring conditions, and an alkylated compound is obtained after the reaction is completed; the phenol in the methylphenol compound is the raw material phenol, the catalyst cresol sulfonic acid is 0.1%-1% of the amount of the raw material phenol substance; the amount of the auxiliary divalent iron salt is 0.5%-5% of the amount of the cresol sulfonic acid substance.

2. A method for alkylating methylphenolic compounds as claimed in claim 1, characterized in that: The amount of isobutylene introduced into the reaction is 0.5-1.1 times the amount of raw material phenol.

3. A method for alkylating methylphenol compounds as claimed in claim 1, characterized in that: The methylphenol compound is any one or two or more of o-cresol, p-cresol, m-cresol, 2,4-xylenol and 2,6-xylenol.

4. A method for alkylating methylphenolic compounds as claimed in claim 1, characterized in that: The divalent iron salt is any one of ferrous chloride, ferrous sulfate, ferrous hydroxide, ferrous cresol sulfonate, and ferrous acetate.

5. A method for alkylating methylphenol compounds as claimed in claim 1, characterized in that: The reaction temperature is 50°C to 60°C.

6. A method for alkylating methylphenol compounds as claimed in claim 1, characterized in that: The reaction time is 1-2 hours.