The production method of 3,5-di-tert-butyl-4-hydroxybenzoic acid

Abstract

The invention discloses a production method of 3,5-di-tert-butyl-4-hydroxybenzoic acid. The production method sequentially comprises the steps as follows: 2,6-di-tert-butylphenol, a potassium hydroxide aqueous solution and toluene are added to a reactor under protection of nitrogen to be subjected to a reflux reaction under a water distribution condition; CO2 is introduced into the reactor until the pressure is 0.1-3.0 MPa, a Kolbe-Schmitt reaction is conducted under a pressure holding condition, after the reaction, corresponding aftertreatment is carried out, and a crude product of 3,5-di-tert-butyl-4-hydroxybenzoic acid is obtained. The method has short reaction time and high conversion rate, has obvious advantages as compared with traditional gas-solid processes and existing solvent-process synthesis processes and is suitable for further industrialization.

Description

technical field [0001] The invention relates to a novel process for producing 3,5-di-tert-butyl-4-hydroxybenzoic acid. Background technique [0002] 3,5-di-tert-butyl-4-hydroxyphenyl compound has anti-inflammatory, anti-virus and anti-tumor effects, and is an important pharmaceutical and chemical intermediate. 3,5-di-tert-butyl-4-hydroxybenzoic acid and its derivatives are also widely used antioxidants and ultraviolet absorbers, as well as intermediates for the synthesis of mosquito killers, and can also be used for the synthesis of 3 ,5-di-tert-butyl-4-hydroxybenzoic acid-2',4'-di-tert-butylphenyl ester and 3,5-di-tert-butyl-4-hydroxybenzoic acid n-hexadecyl, 3,5 -Di-tert-butyl-4-hydroxybenzoic acid n-octadecyl ester and other widely used antioxidants, light stabilizers and UV absorbers in the fields of plastics, rubber and photocurable coatings. [0003] The known production method of 3,5-di-tert-butyl-4-hydroxybenzoic acid is to react 2,6-di-tert-butylphenol with alkali...

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Problems solved by technology

[0006] In the traditional process, the dry 2,6-di-tert-butylphenol alkali metal salt powder is reacted with carbon dioxide to prepare 3,5-di-tert-butyl-4-hydroxybenzoic acid. This process has many disadvantages: 2, The powder of 6-di-tert-butylphenol alkali metal salt is prone to spontaneous combustion and has a high risk; the gas-solid reaction requires special transmission equipment and a special gas-solid stirring paddle, and the equipment cost is high; the gas-solid reaction has poor heat transfer and the product The problem of easy coking, the product yield is low

However, phenolic compounds do not azeotrope with water, and an additional azeotropic dehydrating agent needs to be added when removing water, which increases the cost; phenolic compounds generally have higher viscosity, and the power cost is higher when the phenolic compound is used as a solvent for the reaction ; Excessive phenolic compounds are easily oxidized during recycling, resulting in a decline in the quality of phenolic compounds and an increase in cost

[0008] Patent CN1289760A once mentioned a process for synthesizing salicylic acid with octanol as a solvent. However, octanol has a high boiling point and needs to be carried out in a vacuum environment when preparing sodium phenate, which increases the cost of the process. At the same time, under vacuum environment The loss rate of octanol is also high; at the same time, Stanescu and Achenie mentioned in the article "An in-silico study of solvent effects on the Kolbe–Schmitt reaction using a DFT method", that the solvent in the Kolbe-Schmitt reaction The greater the polarity, the lower the conversion rate of the reaction, and the larger polarity of octanol makes the yield of salicylic acid prepared by this method not high

[0009] Wei Wanmao mentioned in the article "Research on the production process of 3,5-di-tert-butyl-4-hydroxybenzoic acid" that DMF was used as a solvent to carry out the Kolber-Schmidt reaction. However, DMF is miscible with water, making the follow-up treatment very difficult. Trouble; DMF is a nitrogen-containing solvent, which pollutes a lot and is not conducive to environmental protection

[0010] Patent EP0834494A reports a catalyst that can promote the reaction of NaOH and 2,6-di-tert-butylphenol: 1,3-dimethyl-2-imidazolinone, but 1,3-dimethyl-2-imidazole Phenones are expensive and difficult to recycle

[0011] Another part of the literature has reported that alkali metal salts of alcohols are used as reactants to synthesize alkali metal salts of phenolic substances, but the cost of alkali metal salts of alcohols is high, difficult to preserve, and the process is difficult to industrialize

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