The influence of composition on the functionality of hybrid CuO-ZnO-Al2O3/HZSM-5 for the synthesis of DME from CO2 hydrogenation

A series of CuO-ZnO-Al2O3/HZSM-5 hybrid catalysts with different Cu/Zn ratios and disparate Al2O3 doping were prepared and characterized by XRD, BET, H-2-TPR, NH3-TPD and XPS techniques. The optimal Cu/Zn ratio is 7:3, and the introduction of a suitable amount of Al2O3 to form hybrid catalysts increased the BET specific area and micropore volume, facilitated the CuO dispersion, decreased the CuO crystallite size, increased the interaction between CuO and ZnO, enhanced the number of weak acid sites, altered the copper chemical state and improved the catalytic performance consequently. The highest CO2 conversion, DME selectivity and DME yield of 27.3%, 67.1% and 18.3%, respectively, were observed over the CZA(7)H catalyst. The suitable temperature of 260 degrees C and the appropriate space velocity of 1500 h(-1) for one-step synthesis of dimethyl ether (DME) from carbon dioxide (CO2) hydrogenation were also investigated. The 50 h stability of the CZA(7)H catalyst was also tested.