Abstract：The dual-bed catalyst system, comprised of Pt/MOR as top bed catalyst and ZSM-5 acidic zeolite as bottom bed catalyst, was applied in transalkylation of toluene with heavy aromatics to improve the product purity and xylene yield. The effects of zeolite acidity, the ratio of catalyst in the dual bed and reaction temperature on the composition distribution and benzene purity in product were investigated. The results showed that high purity of benzene as well as high yield of xylene in product could be achieved through the optimization of ratio of two catalyst beds in the dual-bed system. Strong acid site of zeolite in the bottom bed was benefit to benzene purity. Heavy aromatic conversion as well as xylene yield decreased with the rise of bottom bed catalyst ratio, but the benzene yield and purity increased with that. Reaction temperature has a significant effect for all bed ratio system on the product distribution as well as benzene purity. A reaction model was also proposed for the dual-bed system, and this dual-bed system is an effective way to improve reaction performance of the transalkylation of toluene with heavy aromatics.
