Preparation of composite zeolites in polymer hydrogels and their catalytic performances in the methanol-to-olefin reaction

ZSM-5/AlPO4-5 composite zeolites were prepared in polyacrylamide (PAM) hydrogels and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), N2 isothermal adsorption-desorption, nuclear magnetic resonance (NMR) and temperature-programmed desorption of ammonia (NH3-TPD). In addition, the catalytic performances of the composite zeolites in the methanol-to-olefin (MTO) reaction were examined. The results indicate that introducing PAM into the synthesis gel of ZSM-5/AlPO4-5 facilitates both the formation of the ZSM-5/AlPO4-5 composite zeolite and the improvement of the catalyst performance. Moreover, the catalyst acidities are closely related to their selectivities for the MTO reaction. The composite zeolite obtained in the PAM hydrogel has a lower density of total acid sites and a higher selectivity for light olefins compared with the composite zeolite prepared without the PAM.