Continuous process for preparation of dian

Abstract

The dian is prepared by the condensation of phenol with acetone in the presence of acid ion-exchange catalyst of the type of sulfonated co-polymer of styrene and divinylbenzene. The three-stage process is conducted in two reactors packed with a stationary catalyst bed. In each of the reactors the bed height is 5-20 m and in addition, in both reactors the beds are divided into bottom and upper zones. At various stages of the process, a reaction mixture is circulated with a different linear velocity, the first step of the process being conducted at a temperature of 60.degree.-85.degree. C. in the bed of the first reactor, in succession in the bottom and then upper zone of the catalytic bed; the second stage of the process is accomplished in the bottom zone of the second reactor at a temperature of 70.degree.-90.degree. C.; and the third step is carried out in the upper zone of the second reactor at a temperature of 75.degree.-95.degree. C. The linear velocity of the reaction mixture flow through the bottom zones of the bed is not greater than 10 m/h, and the linear velocity of flow through the upper zones of the reactor bed is not higher than 4 m/h. The sequence of the reaction mixture flow through the reactors is being changed in cycles, and at interstage intervals the reaction mixture is filtered to separate minus mesh and comminuted particles of the catalyst.