Hydrogen production by steam reforming of dimethyl ether over ZnO–Al2O3 bi-functional catalyst

A series of ZnO–Al2O3 catalysts with various ZnO/(ZnO + Al2O3) molar ratios have been developed for hydrogen production by dimethyl ether (DME) steam reforming within microchannel reactor. The catalysts were characterized by N2 adsorption-desorption, X-ray diffraction and temperature programmed desorption of NH3. It was found that the catalytic activity was strongly dependent on the catalyst composition. The overall DME reforming rate was maximized over the catalyst with ZnO/(ZnO + Al2O3) molar ratio of 0.4, and the highest H2 space time yield was 315 mol h−1·kgcat−1 at 460 °C. A bi-functional mechanism involving catalytic active site coupling has been proposed to account for the phenomena observed. An optimized bi-functional DME reforming catalyst should accommodate the acid sites and methanol steam reforming sites with a proper balance to promote DME steam reforming, whereas all undesired reactions should be impeded without sacrificing activity. This work suggests that an appropriate catalyst composition is mandatory for preparing good-performance and inexpensive ZnO–Al2O3 catalysts for the sustainable conversion of DME into H2-rich reformate.

► ZnO-Al2O3 is an efficient bi-functional catalyst for DME steam reforming.
► ZnO–Al2O3 provides dual active sites in mutual interaction with atomic scale.
► The catalyst is inexpensive, easily prepared and environmental benign.
► The catalytic activity is strongly dependent on the catalyst composition.