Catalytic para-xylene maximization. V. Toluene methylation with methanol and disproportionation of toluene using Pt/ZSM-5 and Pt/mordenite catalysts

摘要

Toluene was methylated with methanol and disproportionated using catalysts containing different Pt contents (0.2, 0.4 and 0.6%) supported on H-ZSM-5 or H-mordenite (H-M) zeolites in a fixed-bed flow-reactor operated atmospherically at temperatures of 300-500degreesC in a flow of hydrogen. Platinum dispersion in the zeolite supports and acid sites Strength distribution were. evaluated using hydrogen chemisorption (1: 1 stoichiometry) and ammonia temperature programmed desorption (TPD) in a differential scanning calorimeter (DSC). Toluene methylation was much faster on all catalysts than toluene disproportionation (DISP). Both reactions were more accelerated using H-ZSM-5 containing catalysts than H-M containing catalysts. The yield of xylenes, and in particular para-xylene, was significantly influenced by the yield of trimethylbenzenes (TMBs) in product. The selectivities for para-, ortho- and meta-xylenes production were found largely dependent on the Pt content in the catalysts, particularly when supported on H-ZSM5-zeolite. However, using Pt/H-M catalysts, these selectivities were not strictly controlled by Pt content in the catalysts.