Property of Pd-supported catalysts for catalytic combustion

Abstract

The catalytic properties of Pd/Sr 0.8La 0.2XAl 11O 19 (X = Al and Mn) and Pd/Al 2O 3MO χ (M = Co, Cr, Cu, Fe, Mn and Ni) catalysts were investigated for use in catalytic combustion. The activity of Pd/Sr 0.8La 0.2 Al 12O 19 initially increased with rise in temperature, but decreased at high temperatures (ca. 700°C). The drop in catalytic activity was steep when the supported Pd particles were sintered after calcination above 1000°C. The activity drop accompanied dissociation of PdO into metallic Pd. Such significant drop in catalytic activity can be avoided by the use of Mn-substituted hexaaluminate (X = Mn) as a catalyst support, due to its activity for combustion. The drop could be also avoided by use of Pd/A1 2O 3-NiO catalysts calcined at low temperatures. Although the surface area decreased with increasing NiO content, the catalytic activity increased. Pd particle size is an important factor in determining catalytic activity.