Zeolite-catalyzed chlorination of toluene by sulfuryl chloride: Activity, selectivity, and deactivation of ZSM-5

The chlorination of toluene by sulfuryl chloride was studied using ZSM-5 as the catalyst. A simple rate expression was developed that provides a reasonable quantitative description of the dependence of the initial rate of reaction upon temperature and reactant ratio. The selectivity did not vary significantly as temperature and reactant ratio changed. The effects of framework silica-alumina ratio and exchange cation were also examined. Changing the exchange cation had essentially no effect upon selectivity, but the catalytic activity was higher when K⁺ was used as the exchange cation compared to Na⁺ or H⁺. Varying the silica-alumina ratio of the zeolite had a very minor effect upon the activity, but the para-chlorotoluene/ortho-chlorotoluene product ratio increased from 1-1.5 to greater than 2.5 at the highest silica-alumina ratio. In all cases, the catalyst deactivated rapidly, but an oxidative treatment at elevated temperature fully restored the catalytic activity.