Facile synthesis of hierarchical SAPO-56 zeolite as a highly efficient catalyst for CO2 hydrogenation to methanol

Abstract

Catalytic conversion of CO2 over zeolite-based catalysts has been deemed as a promising route and extensively investigated, while many issues remain intractable. Herein, for the first time, the novel AFX-type zeolite SAPO-56 was developed and impregnated with Cu nanoparticles to construct the bifunctional catalyst for further promoting CO2 transformation. By a systematically comparative analysis on the physicochemical properties and catalytic performance of different catalysts, the corresponding catalytic mechanism for a highly efficient methanol synthesis process from CO2 was comprehensively understood. The results showed that up to 16.4 % of CO2 can be converted into methanol with a relatively high selectivity of 80.9 % via 5% Cu/SAPO-56 catalysts at 280 °C though the formate activation pathway. This may be directly related to the specific Lewis acid sites (LAS) derived from the EFAl (extra framework aluminum) species located in the six-membered rings of SAPO-56 that endows it with distinguished adsorption capability of CO2. Furthermore, the copper nanoparticles that are highly dispersed on the surface or in the porous channel of SAPO-56 zeolite facilitate the ease of CO2 activation. Besides, the introduced hierarchical structure was considered to have played an indispensable role in improving methanol productivity. Meanwhile, all its own multiple superiorities also ensure Cu/SAPO-56 a remarkable stability, indicating the great potential for practical and industrial application.