An alkylation method for methylphenol compounds

Abstract

This invention belongs to the field of chemical product synthesis technology and discloses a method for alkylating methylphenolic compounds. Under normal pressure, methylphenolic compounds are added to a catalyst, cresolsulfonic acid, and an auxiliary agent, a ferrous salt. Isobutylene is then introduced into the reaction solution at a certain gas rate under stirring. After the reaction is complete, an alkylated compound is obtained. The phenol in the methylphenolic compound is the raw phenol, and the amount of isobutylene introduced into the reaction is 0.5-1.1 times the amount of the raw phenol. The catalyst, cresolsulfonic acid, accounts for 0.1%-1% of the amount of the raw phenol. The auxiliary agent, the ferrous salt, accounts for 0.5%-5% of the amount of the cresolsulfonic acid. This method uses a small amount of catalyst, has a short and mild reaction time, and achieves a high conversion rate.

Description

Technical Field

[0001] This invention belongs to the field of chemical product synthesis technology, and relates to a method for alkylation of methylphenol compounds. Background Technology

[0002] tert-butylcresols are an important class of hindered phenolic antioxidants, widely used in petroleum products, polymer materials, rubber anti-aging, and the food industry. Important antioxidants include 2,6-di-tert-butyl-p-cresol (BHT or Antioxidant 264), 4,4'-thiobis(6-tert-butyl-m-cresol) (Antioxidant 300), and Antioxidant 2246. Cresol is a crucial raw material for antioxidant production; these commonly used antioxidants can be prepared through cresol alkylation.

[0003] Currently, there are many methods for the tert-butylation of phenols. Depending on the alkylating reagent, they can be divided into the isobutylene method, the tert-butanol method, and the methyl tert-butyl ether method. The tert-butanol and methyl tert-butyl ether methods produce products such as water and methanol, which complicates subsequent separation. The isobutylene method, however, is the most atom-economical and is currently the mainstream process in the tert-butylation of phenols. The alkylation of cresol and isobutylene generally requires an acid catalyst. Commonly used catalysts include solid acids and liquid acids. Solid acids include strongly acidic cation exchange resins, acidic molecular sieves, and solid superacids, while liquid acids include sulfuric acid, phosphoric acid, p-toluenesulfonic acid, heteropoly acids, and acidic ionic liquids. When using solid acids as catalysts, the reaction temperature is relatively high, which can easily cause isobutylene polymerization. Moreover, the deeper the degree of alkylation, the more intense the isobutylene polymerization and the shorter the catalyst life. Therefore, it is only suitable for the production of monotert-butylphenol products. When using liquid acids as catalysts, the catalytic efficiency is relatively high, which is suitable for the production of deeply alkylated products. Therefore, it is also the main catalyst chosen for the synthesis of antioxidants such as BHT.

[0004] Although the catalysts for liquid acids are generally highly efficient, the amount of catalyst used in current production is relatively large, usually requiring 3%-10% of the mass of the raw material phenol (CN201310157977, Dhaka Univ Stud Part B, 1990, 38(2): 197-198.). The reaction temperature is usually 60-70℃, and the reaction time usually takes more than 5 hours. This not only requires a large number of equipment, which is more prone to corrosion, but also brings certain difficulties to the post-processing. Therefore, it is necessary to find a more efficient and milder catalyst and a simpler preparation method to solve the current production problems. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a method for the alkylation of methylphenolic compounds, which shortens the reaction time and provides a highly efficient catalyst. When applied to the alkylation method of methylphenolic compounds, the catalyst dosage is low, and the reaction time is short and mild, resulting in high conversion rates.

[0006] The above-mentioned objective of this invention is achieved through the following technical solution:

[0007] A method for alkylating methylphenolic compounds involves adding cresolsulfonic acid as a catalyst and a ferrous salt as an auxiliary agent to the methylphenolic compound under normal pressure. Isobutylene is then introduced into the reaction solution at a certain gas rate under stirring. After the reaction is complete, an alkylated compound is obtained. The phenol in the methylphenolic compound is the raw phenol, and the amount of isobutylene introduced into the reaction is 0.5-1.1 times the amount of the raw phenol. The cresolsulfonic acid catalyst accounts for 0.1%-1% of the amount of the raw phenol, and the ferrous salt auxiliary agent accounts for 0.5%-5% of the amount of the cresolsulfonic acid.

[0008] Furthermore, the methylphenolic compound is any one or more of o-cresol, p-cresol, m-cresol, 2,4-xylenol, and 2,6-xylenol.

[0009] Furthermore, cresol sulfonic acid is any one 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 cresolsulfonate, and ferrous acetate.

[0011] Furthermore, the reaction temperature is 50℃~60℃. The reaction time is 1-2 hours.

[0012] Furthermore, the gas flow rate of isobutylene is the calculated amount required to complete the reaction within 1-2 hours.

[0013] The advantages of this invention compared to the prior art are:

[0014] The present invention provides a method for alkylating methylphenolic compounds that requires less catalyst, has mild reaction conditions, produces less isobutylene polymerization, has high reaction efficiency, and achieves higher output with less equipment investment. Detailed Implementation

[0015] The present invention is described in detail below through specific embodiments, but this does not limit the scope of protection of the present invention. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can all be obtained commercially.

[0016] Example 1

[0017] A specified amount of p-cresol, catalyst, and auxiliaries were mixed in a molar ratio of p-cresol:p-cresolsulfonic acid:ferrous chloride = 100:0.5:0.01 and placed in a reaction vessel. Stirring was started, and the temperature was raised to 50°C. Isobutylene was introduced under normal pressure, and the reaction temperature was controlled at 50-55°C. The total amount of isobutylene introduced was 1.1 times the mass of p-cresol, and the introduction was completed within 2 hours. After the reaction was completed, samples were taken for analysis. The p-cresol content in the reaction solution was 0.03% (conversion rate of 99.9%), the 2,6-di-tert-butyl-p-cresol content was 91.32%, the 2-tert-butyl-p-cresol content was 6.58%, the isobutylene polymer content was 1.46%, and the content of other impurities was 0.61%.

[0018] Example 2

[0019] A specified amount of m-cresol, catalyst, and auxiliaries were mixed in a molar ratio of m-cresol:m-cresolsulfonic acid:ferrous acetate = 100:1:0.04 and placed in a reaction vessel. Stirring was started, and the temperature was raised to 50°C. Isobutylene was introduced under normal pressure, and the reaction temperature was controlled at 50-55°C. The total amount of isobutylene introduced was 1.1 times the mass of m-cresol, and the introduction was completed within 2 hours. After the reaction was completed, samples were taken for analysis. The content of m-cresol in the reaction solution was 1.2% (conversion rate of 97.7%), the content of 4,6-di-tert-butyl-m-cresol was 87.50%, the content of 6-tert-butyl-m-cresol was 8.61%, the content of 4-tert-butyl-m-cresol was 0.26%, the content of isobutylene polymer was 1.73%, and the content of other impurities was 0.70%.

[0020] Example 3

[0021] A specified amount of 2,4-xylenol was mixed with catalyst and auxiliaries in a molar ratio of 2,4-xylenol: p-cresolsulfonic acid: ferrous p-cresolsulfonate = 100:0.2:0.008 and placed in a reaction vessel. Stirring was started, and the temperature was raised to 50°C. Isobutylene was introduced under normal pressure, and the reaction temperature was controlled at 50-55°C. The total amount of isobutylene introduced was 0.55 times the mass of p-cresol, and the introduction was completed within 1.5 hours. After the reaction was completed, samples were taken for analysis. The content of 2,4-xylenol in the reaction solution was 0.59% (conversion rate of 99.4%), the content of 6-tert-butyl-2,4-xylenol was 97.13%, the content of isobutylene polymer was 1.76%, and the content of other impurities was 0.52%.

[0022] Example 4

[0023] A specified amount of o-cresol, catalyst, and auxiliaries were mixed in a molar ratio of o-cresol: o-cresol sulfonic acid: ferrous sulfate = 100:0.8:0.02 and placed in a reaction vessel. Stirring was started, and the temperature was raised to 50°C. Isobutylene was introduced under normal pressure, and the reaction temperature was controlled at 50-55°C. The total amount of isobutylene introduced was 1.1 times the mass of o-cresol, and the introduction was completed within 2 hours. After the reaction was completed, samples were taken for analysis. The o-cresol content in the reaction solution was 0.04% (conversion rate of 99.9%), the 4,6-di-tert-butyl-o-cresol content was 92.33%, the 6-tert-butyl-o-cresol content was 2.31%, the 4-tert-butyl-o-cresol content was 3.05%, the isobutylene polymer content was 1.67%, and the content of other impurities was 0.63%.

[0024] Example 5

[0025] A specified amount of m-p-cresol (m:p = 75:25) was mixed with catalyst and auxiliaries in a molar ratio of m-p-cresol:m-cresolsulfonic acid:ferrous sulfate = 100:0.7:0.03 and placed in a reaction vessel. Stirring was started, and the temperature was raised to 50°C. Isobutylene was introduced under normal pressure, and the reaction temperature was controlled at 50-55°C. The total amount of isobutylene introduced was 1.1 times the mass of m-cresol, and the process was completed within 2 hours. After the reaction was completed, samples were taken for analysis. The reaction solution contained 0.81% m-cresol (conversion rate 99.1%), 66.82% 4,6-di-tert-butyl-m-cresol, 23.09% 2,6-di-tert-butyl-p-cresol, 0.52% 2-tert-butyl-p-cresol, 6.14% 6-tert-butyl-m-cresol, 0.19% 4-tert-butyl-m-cresol, 1.77% isobutylene polymer, and 0.66% other impurities.

[0026] Comparative Example 1

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

[0028] Comparative Example 2

[0029] The implementation conditions were the same as in Example 1, except that no additives were added during the reaction. After the reaction was completed, samples were taken for analysis. The content of p-cresol in the reaction solution was 2.18% (conversion rate of 95.7%), the content of 2,6-di-tert-butyl-p-cresol was 82.10%, the content of 2-tert-butyl-p-cresol was 13.67%, the content of isobutylene polymer was 1.41%, and the content of other impurities was 0.64%.

[0030] The embodiments described above are merely preferred embodiments of the present invention, and not all feasible embodiments of the present invention. Any obvious modifications made by those skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. A method for alkylating methylphenolic compounds, characterized in that, Under normal pressure, methylphenol compounds are added to the catalyst cresolsulfonic acid and the auxiliary agent ferrous salt. Isobutylene is introduced into the reaction solution at a certain gas rate under stirring. After the reaction is completed, alkylated compounds are obtained. The phenol in the methylphenol compound is the raw phenol, and the catalyst cresolsulfonic acid is 0.1%-1% of the molar amount of the raw phenol. The amount of auxiliary agent ferrous salt is 0.5%-5% of the molar amount of cresolsulfonic acid. The methylphenol compound is any one or more of o-cresol, p-cresol, m-cresol, 2,4-xylenol, and 2,6-xylenol. The ferrous salt is any one of ferrous chloride, ferrous sulfate, ferrous hydroxide, ferrous cresolsulfonate, and ferrous acetate. The reaction temperature is 50℃~60℃.

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

3. The alkylation method for methylphenolic compounds as described in claim 1, characterized in that, The reaction time is 1-2 hours.