Preparation, Structure and Performance of [CuO-ZnO-Al 2 O 3 ]/ [HZSM-5] Core-Shell Bifunctional Catalysts for One-Step Synthesis of Dimethyl Ether from CO 2 +H 2

A series of core-shell bifunctional catalysts [CuO-ZnO-Al2O3]/[HZSM-5] for one-step synthesis of dimethyl ether from CO2 hydrogenation were prepared by a hydrothermal synthesis method, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The catalyst has a core-shell structure with an integral and compact shell of HZSM-5 coated on the surface of a pre-shaped CuO-ZnO-Al2O3 pellet. The crystallite size and thickness of the zeolite shell can be controlled by the crystallization time. Compared with the mechanically mixed catalyst, the core-shell catalyst shows much higher selectivity for dimethyl ether synthesis from CO2 + H2. The core-shell catalyst with a crystallization time of 3 d shows the best catalytic performance, with a CO2 conversion of 38.9% and a dimethyl ether selectivity of 77.0%.