Soot-combustion Catalyst of Pd/ZrO2 Composites Prepared from Zr65Pd35 Amorphous Alloy by Oxidation Treatment

Metal-dispersed Pd/ZrO2 composites were derived from amorphous Zr65Pd35 alloy and their catalytic behavior for diesel soot combustion was studied. X-ray diffractograms and scanning electron micrographs indicated that mixtures of ZrO2 phase and the dispersed metallic phase were formed in the resulting material after heat treatment at 800 degrees C in air. The oxidized alloy resulted in the enhanced soot combustion activity. The removal property of catalyst, evaluated as temperature, is almost 100 degrees C better than that in the non-catalyzed reaction. The combustion processes were observed by in situ high temperature optical microscopy (HTOM) and ex situ electron microscopy with different scales. The secondary soot particle started the combustion at the primary soot near catalyst. Upon heating to higher temperature between 570 degrees C and 590 degrees C the soot layer rapidly disappeared in in situ HTOM, while both the black band and dispersed part of soot on a alumina substrate remained without combustion even kept at 650 degrees C. Therefore, soot did not move with micron-order distance and its combustion process should depend on their contact points of catalyst surfaces and soot aggregate. This work provided a new type of catalytic material prepared from amorphous alloys which was effective soot combustion catalysis. (c) 2019 The Japan Society of Applied Physics