Catalytic performance of cerium modified Silicalite-1 molecular sieves in the conversion of methanol to propene

Abstract

A series of cerium modified Silicalite-1 molecular sieves were prepared by incipient wetness impregnation and used as the catalysts in the conversion of methanol to propene (MTP). The cerium modified Silicalite-1 catalysts were characterized by X-ray diffraction (XRD), N2 sorption, pyridine adsorption Fourier transform infrared spectroscopy (Py-FTIR) and temperature-programmed desorption of NH3 (NH3-TPD); their catalytic performance in MTP was evaluated in a continuous flow fixed-bed micro-reactor at atmospheric pressure and 450°C, with a methanol weight hourly space velocity (WHSV) of 9.6 h−1. The results showed that Silicalite-1 exhibits superior catalytic performance in MTP in terms of catalytic stability and selectivity to propene, in comparison with the HZSM-5 zeolite with a SiO2/Al2O3 molar ratio of 200. The introduction of Ce can effectively adjust the acid properties and pore structure of Silicalite-1; modification with an appropriate concentration of Ce can reduce the amount of strong acid sites and then enhance the catalytic performance of Silicalite-1 in MTP. Over the cerium modified Silicalite-1 with a CeO2 content of 5.0%, the selectivity to propene is increased from 31.9% to 38.2% and the catalytic lifetime is extended from 51 to 72 h, in comparison with those over the parent Silicalite-1.