SELECTIVE PDZN ALLOY FORMATION IN THE REDUCTION OF PD ZNO CATALYSTS/

Temperature programmed reduction (TPR) experiments were carried out ov er Pd/ZnO with different Pd loadings. Combined results with an X-ray d iffraction method and X-ray photoelectron spectroscopy showed that a P d-Zn alloy with a structure of PdZn was selectively produced in the co urse of TPR of Pd/ZnO. It was suggested that hydrogen retained in Pd s pilled over to ZnO. The ZnO was reduced to metallic Zn, being converte d to PdZn. The molar amounts of the ZnO reduced were practically the s ame as the those of Pd loaded. Hence, all the Pd loaded was completely transformed to the PdZn alloys upon reduction.