IR Operando study of ethanol dehydration over MFI zeolite.

Zeolite-catalyzed dehydration of ethanol is an attractive economically feasible route for production of ethylene and butenes. The goal of this contribution is to monitor the intermediate species on the surface of “working” catalyst to rationalize the influence of the reaction conditions and zeolite characteristics on the dehydration pathways. With this respect the rates of diethyl ether (DEE) and ethylene formation in ethanol dehydration along with the quantification of the surface-intermediates (ethanol monomer and dimer) were simultaneously assessed under different reaction conditions in H- MFI zeolite. The reaction conditions (pressure, temperature, and ethanol conversion) control the population of surface intermediates and hence determine the dominant reaction mechanism. The results support the prevalence of dimer-assisted etherification at high ethanol pressures and enhanced contribution of ethoxide-mediated route with increasing the temperature. At high conversion, the DEE decomposition route producing ethylene was confirmed for H- MFI at 488 K along with ethoxide-mediated pathway. [ABSTRACT FROM AUTHOR]