Catalytic properties of Pd supported on ZnO/ZnAl2O4/Al2O3 mixtures in dimethyl ether autothermal reforming

The catalytic properties of Pd supported on mixtures of zinc oxide, zinc aluminate, and alumina, prepared from γ-alumina and zinc nitrate, were studied for autothermal reforming (ATR) of dimethyl ether (DME). The performance of the catalysts was tested in a small-scale reactor, using cordierite monoliths as substrate. The catalysts exhibited high activity and generated hydrogen-rich product gases with CO concentrations below 5 vol.% in the temperature range between 350 and 450 °C (at O2:DME = 0.7, H2O:DME = 2.5, and GHSV = 15000 h−1). The highest DME conversion was obtained for a catalyst in which the support comprised mainly ZnAl2O4. Physical mixing of the catalysts with γ-Al2O3 resulted in increased DME conversion but a lowering of the CO2 selectivity.The catalysts were characterized by CO chemisorption, liquid nitrogen adsorption, temperature-programmed desorption of ammonia, temperature-programmed reduction, transmission electron microscopy, and X-ray diffraction. It was found that decreasing surface area and decreasing number of acid sites, caused by thermal treatment during generation of the supports, did not affect the activity negatively. The high CO2 selectivity of the catalysts was correlated with PdZn alloy formation.