Synthesis of highly selective and stable mesoporous Ni–Ce/SAPO-34 nanocatalyst for methanol-to-olefin reaction: Role of polar aprotic N,N-dimethylformamide solvent

Abstract

A series of mesoporous nanocrystalline silicoaluminophosphate (SAPO) zeolites (SAPO-34) were synthesized via an ultrasonic and microwave-assisted hydrothermal method in the presence of [3-(trimethoxysilyl)propyl]octadecyldimethylammonium chloride and cetyltrimethylammonium bromide surfactants as soft templates. Nickel and cerium were then doped on SAPO-34 using incorporation and impregnation methods, and all the catalysts were applied to the methanol-to-olefin (MTO) reaction. The catalysts were characterized using X-ray diffraction, field-emission scanning electron microcopy, inductively coupled plasma–atomic emission spectroscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, Brunauer–Emmett–Teller analysis, NH3 temperature-programmed desorption analysis, and thermogravimetric analysis. For the impregnation method, the effect of using protic or aprotic solvents as impregnation media on the physico-chemical properties of the metal-based SAPO-34 was investigated. Water and N,N-dimethylformamide (DMF) were employed as the protic and aprotic solvents, respectively. The catalyst prepared using the aprotic DMF solvent exhibited higher dispersion and lower aggregation of metal species compared with that prepared using the protic water solvent. Furthermore, the sample synthesized using the incorporation method exhibited good catalytic performance; however, the Ni–Ce/SAPO-34 sample prepared using the impregnation method and aprotic DMF solvent exhibited superior catalytic performance in the MTO reaction.