Dimethyl ether-to-olefins over aluminum rich ZSM-5: The role of Ca and La as modifiers

Dimethyl ether (DME) has a strategic role both as an alternative fuel and a feedstock for petrochemicals. Aluminum rich H-ZSM-5 modified with Ca and La species were investigated in the conversion of Dimethyl ether (DME) to olefins. The crystallinity and morphology of Ca-ZSM-5, La-ZSM-5 and Ca-La-ZSM-5 were similar to the parent H-ZSM-5 as observed in XRD and FE-SEM analysis. The addition of both Ca and La ions, and their co-impregnation affects the acidity of parent H-ZSM-5 zeolite. In addition, Ca and La ions also induced the formation of basic sites in the zeolite framework. DME conversion of over 97% was observed over all catalyst systems during the 2 h time on stream. Ca-ZSM-5 showed the highest selectivity to light olefins especially propylene due to the presence of weak and medium acid sites.