Development Of Clean Production Process For Tert-butyl Hydroquinone

Tert-butyl-substituted phenolic antioxidants are very important fine chemical products,including tert-butyl hydroquinone(TBHQ),butyl-hydroxyanisole(BHA),2,6-di-tert-butyl-4-methylphenol(BHT)and other derivatives.Among them,TBHQ has the strongest antioxidant capacity and the highest safety,and can effectively inhibit the growth of bacteria and molds,so it is the key oil antioxidant developed and utilized in China at present.At present,the production process of tert-butyl hydroquinone is mainly catalyzed by liquid acid catalysts.This old process has disadvantages such as serious corrosion of equipment,waste emissions and difficulty in catalyst separation,etc.,so it is difficult to meet the needs of industrial production in the future.In this paper,in order to develop an efficient,green and cheap industrial production process of TBHQ,the synthesis process of TBHQ was optimized at different levels with hydroquinone and tert-butanol over modified active clay catalysts.The specific research contents and results are as follows:(1)Eastablishing the qualitative and quantitative analysis and detection method of the products and by-products to provide guidance for the optimization of the synthesis process.(2)The catalysts were screened and characterized to determine the best synthesis process of the catalysts.The experimental results showed that the active clay catalyst modified by hydrochloric acid had a better effect.The best preparation conditions of catalysts were as follows:the active clay was treated with 10 wt%hydrochloric acid at room temperature,and the activation temperature of the catalyst was 110℃.(3)The synthetic process of TBHQ was optimized systematically and the optimum synthesis conditions were determined.The optimum conditions for the synthesis of TBHQ were as follows:the molar ratio of tert-butanol to hydroquinone was 3:1,the catalyst dosage was 3.0 wt%,the reaction temperature was 150℃.Under these conditions,the yield of the target product TBHQ reached 54.6%,and the selectivity reached 90.0%.The results showed that the molar ratio of alcohol to hydroquinone had the greatest influence on the yield and selectivity of target product TBHQ.High molar ratio of alcohol to hydroquinone would inhibit the reaction,which was not conducive to the improvement of hydroquinone conversion,but could improve the selectivity of TBHQ.The catalysts can be quickly regenerated by washing with ethanol,and the good selectivity and yield of target product TBHQ could still be retained after repeated applications(more than 5 times).(4)Based on the synthesis process of TBHQ designed in this paper,the separation and purification process of TBHQ was optimized to obtain a better purification process of TBHQ,which could purify the crude TBHQ to 99.0%with a recovery of 74.7%.(5)The production process of TBHQ over active clay catalysts was designed to provide a basis for the industrial production process of TBHQ.