Effect of si to tiratio and pretreatment condition of titanium silicalites-1 catalyst on hydroxylation of benzene by hydrogen peroxide in a periodically operated three phase, co-current downflow packed bed reactor

Abstract

The titanium silicalite-1 (TS-1) catalysts were prepared for the hydroxylation of benzene by hydrogen peroxide in a periodic operation mode in a co-current down flow pack bed reactor. The research studied the effects of different Si/Ti ratio and the effects of pretreatment on the catalytic activity of TS-1. The results of the reaction show that initially when the amount of titanium is increased, the activity of the catalysts increase. Too much the amount of titanium, however, cause the formation of some extra-framework titanium, inactive titanium species. After the catalysts were pretreated by nitric acid aqueous solution, the framework structure of TS-1 is not destroyed and titanium in the framework is not removed. But, the extra-framework can be removed partly, which leads to the decrease of acid concentration of the TS-1 catalysts. As a result, the activity of the pretreated catalysts is improved