Catalytic conversion of dimethyl ether to toluene over the molecular sieves modified with tungsten oxide

The catalytic performance of various zeolites modified with tungsten oxide in the conversion of dimethyl ether (DME) to toluene in the presence of oxygen was investigated in a continuous flow fixed-bed reactor. The results indicated that WO₃/HZSM-5 as a catalyst is highly selective in the conversion of DME to toluene; under the optimized conditions, i.e. atmospheric pressure, 290 ℃, and with a DME/O₂ mol ratio of 2:1, the conversion of DME is 98.97%, with the selectivity of 39.71% to toluene. The characterization results about the catalyst structure and acidity illustrate that the porous structure of ZSM-5 is suitable for the formation of toluene from DME. The doping of WO₃ adjusts the distribution of the surface acid sites and then inhibits the formation of side-products in the presence of oxygen, which is able to enhance the selectivity to toluene.