Research For The Preparation And Industrialization Of P-Methyl Thiophenol

Alkyl substituted thiophenols are important building blocks for the preparation of medicinal,pesticides compounds,as well as chemical additives.The synthetic methods of these compounds have become research focus.However,the thiophenols' process reported are reductive cleavage of disulfides,conversion of halogenated benzenes and reductive of alkylbenzene sulfonic acid?sulfonyl chloride?,which has been proven complex,hard to control,long period and serious pollution.Recently,reduction of alkyl substituted sulfonic acid to corresponding thiophenols has been industrialized,such as ethyl thiophenol,isopropyl thiophenol and tertbutyl thiophenol.But p-methyl thiophenol is not success for high by-product ratio,difficult in separation and low yield because of small steric hindrance.The paper therefor would disclose the problems above and investigate its industrial matters.This paper firstly discussed sulfonating mechanism and reaction kinetics.The activation energys of o-,m-,p-methylbenzene sulfonic acid have calculated to be 23.54 kJ·mol^-1,48.18 kJ·mol^-1 and 24.4 kJ·mol^-1.The activation energys of o-,m-,p-methylbenzene sulfone have calculated to be 59.03 kJ·mol^-1,79.20 kJ·mol^-1 and 38.03 kJ·mol^-1.Under this guidance,anhydrous sodium sulfate which is cheap and easily got was chosen as catalyst to inhibit the generation of sulfone.The preparation technology of p-methyl thiophenol used methylbenzene as material and then down to sulfonation,sulfonylation with chlorosulfonic acid,reduction with iron powder.The crude product was obtained by water stream distillation and pure product by reduced pressure rectify,yield 74%,purity?96%.This paper optimized the process,confirmed the best reaction conditions in sulfonylation: the feed ratio 2.1:1,temperature 25?,time 3h and iron powder in reduction: the feed ratio 4.1:1,temperature 85?,time 3h,and other reaction conditions.In order to avoid pollution,a two-stage absorption equipment for HCl,a waste gas treatment equipment and treatment process of waste water have been designed.Ferrous sulfate and Polymeric ferric sulfate used as flocculant have been prepared to extend the product chains based on the idea of recycling economy.