Study of Pd/ZnO catalyst for hydrogen production from steam reforming of methanol

Pd/ZnO catalysts with Pd loadings between 5.2 and 21.9% for steam reforming of methanol to hydrogen were prepared by co-precipitation. The effects of Pd loadings and the reduction temperatures on the catalytic performance was studied in a stainless steel reactor. The 15.9% Pd/ZnO catalyst at a reduction temperature of 523-573 K had the best methanol conversion. PdO can be reduced to Pd at room temperature, and some of ZnO can be initially reduced at about 440 K. Introduction of Pd facilitates the reduction of ZnO. A marked PdZn alloy occurs when the reduction temperature rises up to 573 K, suggesting that PdZn alloy forms easily over Pd/ZnO catalysts prepared by co-precipitation. Though the hydrogen product can reduce the catalyst, the best reduction atmosphere is under pure hydrogen conditions. Methanol conversion over 15.9% Pd/ZnO remains a constant value for 8 hr without deactivation. In contrast, the methanol conversion over CuO/ZnO/Al₂O₃ catalyst gradually decreases with time on stream.