Influence of Catalytic Functionalities of Zeolites on Product Selectivities in Methanol Conversion

In an attempt to understand the textural and acidic properties of zeolites on the methanol conversion and product selectivities, three zeolites, ferrierite, clinoptilolite, and SAPO-34, are studied, Temperature-programmed desorption of ammonia (NH3-TPD) indicated the presence of more weak acidity on ferrierite and clinoptilolite compared to the considerable strong acidity on SAPO-34. At 250 degrees C, all three samples exhibited comparable methanol conversions, but relatively lower dimethyl ether (DME) and higher light olefins are observed on SAPO-34. Ferrierite and clinoptilolite samples exhibited high selectivity for the formation of DME even at higher reaction temperatures (400 degrees C), while the product shifted from DME to light olefins with an increasing reaction temperature on SAPO-34. Especially, ferrierite, owing to its mild acidity and small pore size, is found to be a good catalyst for the methanol conversion to DME at 250 degrees C without significant deactivation for 100 h time on stream.