Development of desilicated EU-1 zeolite and its application in conversion of dimethyl ether to olefins

Abstract

Creating mesoporosity in one-dimensional pore zeolites is still a challenging task in zeolite scientific community. Desilicated EU-1 (EUO), an one-dimensional pore zeolite, with Si/Al of 25 was developed using with different NaOH concentrations for different times to extract Si atoms from the framework and to form mesoporosity at fixed treatment temperature. Simple hexamethonium bromide was used as a template for EU-1 synthesis. The effects of concentration of NaOH and time of desilication on Si/Al, crystallinity, acidity and surface area have been investigated. A series of treated EU-1 samples was then applied for conversion of dimethyl ether to olefins (DTO). The sample treated with lower NaOH concentration (0.25 M) had the highest increase in mesopore volume with no significant change in acidity. An increase in mesopore volume contributed to higher selectivity toward propylene. The lower catalytic activity was observed over desilicated EU-1 as compared with the parent sample. The physicochemical properties of desilicated zeolites were analyzed using many characterization techniques. X-ray diffraction (XRD) was used to evaluate the effect of desilication on the crystallinity. Nitrogen adsorption–desorption isotherms and temperature-programmed desorption were used to evaluate the porosity and acidity, respectively. Morphology was analyzed using scanning electron microscope (SEM) and Transmission electron microscope (TEM).