Conversion of methanol to olefins over Al-rich ZSM-5 modified with alkaline earth metal oxides

Aluminum-rich H-ZSM-5 zeolites modified with alkaline earth metal oxides of Mg, Ca and Ba were applied in the conversion of methanol to olefins (MTO). The pores of the parent H-ZSM-5 zeolite were blocked with a surfactant prior to metal oxide modification. The resulting Mg-ZSM-5, Ca-ZSM-5 and Ba-ZSM-5 exhibited similar structural and morphological patterns to the parent H-ZSM-5. The addition of these alkaline metal oxides affected the acidity of the ZSM-5-based catalysts. Mg-ZSM-5 was found to be the most stable in the MTO reaction, maintaining a conversion of 100% for over 8 h and having the highest selectivity of ca. 46% to propylene due to the presence of weak Brønsted acidity.