Study On Zinc-based Oxide And SAPO-34 Bifunctional Catalysts For Syngas-to-olefins

Syngas-to-olefins(STO)over bifunctional catalysts has attracted great attention because of simple process route and high selectivity of light olefins.Recently,the main challenge of this technology is to develop high-efficient oxides to improve CO conversion.In this paper,the Zn-based catalysts were synthesized by impregnation and MOF calcination method and the SAPO-34 was synthesized by hydrothermal method.Characteristic technologies,like Ar adsorption/desorption、XRD、ICP-OES、FESEM、HRTEM、H2-TPR、CO-TPD、XPS、In-situ DRIFTS,were used to study the effects of catalyst structure on STO catalytic performance.The Zn-based catalysts were prepared by impregnation method using Al2O3、CeO2 and SiO2 supports.The metal-support interaction obviously influenced the Zn dispersion and oxygen vacancy contents,which gave rise to the difference of CO adsorption ability of catalysts,among these catalysts,Zn/Al2O3 exhibited strongest CO adsorption ability.Under 400℃、2 MPa and 3600 ml/(gcat·h),Zn/Al2O3+SAPO-34 achieved 11.7%of CO conversion and 74.1%of light olefins selectivity among hydrocarbons.The AlCeOx supports with different Ce contents were prepared by sol-gel method,and the catalysts were prepared by impregnation method.The addition of moderate Ce can increase the oxygen vacancy contents,which enhanced the CO adsorption ability and further improved the STO catalytic performance.But,the superfluous Ce deteriorated the ZnAl2O4,contributing to the decline of oxygen vacancy,which gave rise to the decrease of CO conversion.The ZnZrOx-400 and ZnZrOx-P catalysts were prepared by MOF calcination method and co-precipitation method,respectively.MOF-derived catalysts exhibited high contents of Zn-O-Zr and oxygen vacancy,and strongest CO adsorption ability,which were beneficial to CO conversion and the formation of reaction intermediate.The catalytic performance of bifunctional catalysts containing ZnZrOxand SAPO-34 was evaluated under 400℃、3MPa and 3600 ml/(gcat·h).ZnZrOx-400+SAPO-34 achieved 22.5%CO conversion and 79.7 light olefins selectivity among hydrocarbons,which were higher than those of ZnZrOx-P+SAPO-34.