Comparison of HZSM-5 Zeolite and SAPO (-18 and -34) Based Catalysts for the Production of Light Olefins from DME

Abstract

The catalytic transformation of dimethyl ether (DME) for the selective production of light olefins has been studied over HZSM-5 zeolite (with SiO2/Al2O3 = 280) and silicoaluminophosphate (SAPO-18 and -34) based catalysts in order to asses the effect of shape selectivity on the catalytic performance. The catalysts have been synthesized by agglomerating the active materials with bentonite (as a binder) and alpha-alumina (as inert filler). The runs have been carried out at a pressure of 1.5 bar in a fixed bed reactor, under the following reaction conditions: temperature, 350 and 400 °C; space time, 1.6 and 0.064 gcatalyst h molC −1; time on stream, 60 min. The results reveal the importance of the severity of the shape selectivity of the catalysts on the reaction indices (conversion, yield and selectivity of olefins, and catalyst stability). The HZSM-5 zeolite based catalyst has the best kinetic behavior, being stable at 350 °C, with a DME conversion of 4.5 % and selectivity to ethylene, propylene and butenes of 27, 50 and 16 %, respectively.