Dual-bed catalyst system for improving product purity and catalytic stability in alkylbenzene transalkylation Original Research Article

A versatile catalyst system for the transalkylation of alkylbenzenes was developed, comprising Pt/ZSM-12 as the top bed catalyst and H-Beta as the bottom bed catalyst. The dual-bed catalyst system could improve the purity of the benzene product as well as the catalyst stability. The minimum ratio of H-Beta/ZSM-12 can achieve the industrial specification by interplaying the reaction temperatures, feed compositions, and the relative activities for the hydrogenation over Pt/ZSM-12 and the selective naphthene-cracking reaction rate over H-Beta. With increasing the trimethylbenzene (TMB) content of the feed mixture, the product yields of the dual-bed catalyst systems approached thermodynamic compositions due to the enhancement of the TMB reactivity; and the required amount of H-Beta and the minimum reaction temperature to meet benzene product specification became lower. Performance curves in terms of feed compositions, catalyst bed ratios, and reaction temperatures were constructed to aid the design of optimum dual-bed catalyst systems.