One-step synthesis of dimethyl ether from biomass-derived syngas on CuO-ZnO-Al2O3/HZSM-5 hybrid catalyst: Combination method, synergistic effect, water-gas shift reaction and catalytic performance.

The hybrid systems of CuO-ZnO-Al 2 O 3 /HZSM-5 for the one-step synthesis of DME from biomass-derived syngas were prepared by four different combination methods (granule-mixing, powder-mixing, physical coating and dual-bed fixing) and characterized by N 2 adsorption, XRD, N 2 O titration, H 2 -TPR, NH 3 -TPD and TG techniques. The influences of combination method on the physicochemical properties and catalytic performances of hybrid catalyst were investigated, and the relationship among the combination method, the synergistic effect and the WGS reaction was discussed based on the composition features of the biomass-derived syngas (CO 2 -rich and H 2 -deficient). A maximum of CO conversion and DME yield was obtained over the hybrid catalyst prepared by granule-mixing method. There is a synergistic effect, which remarkably promotes the formation of DME, between the methanol synthesis and the methanol dehydration over the hybrid catalysts except for the hybrid system configured using the dual-bed fixing method. The WGS reaction, playing a pivotal role in the direct DME synthesis because of the in-situ produced hydrogen, relates to the combination method closely. An interaction between the two catalyst components arising in the combination process affects the properties of active sites and further the catalytic performances. The deactivation of the hybrid catalyst is ascribed mainly to the increase in the particle size of Cu in CuO-ZnO-Al 2 O 3. [Display omitted] • Combination method affects synergistic effect, WGS reaction and catalytic property. • Synergistic effect was observed in direct DME synthesis from biomass-derived syngas. • Hydrogen produced via WGS reaction plays an important role for direct DME synthesis. • Interaction between CZA and HZSM-5 changes the amount and property of active site. • Deactivation of hybrid catalyst is ascribed to the increase in d Cu in CZA component. [ABSTRACT FROM AUTHOR]