Carbon Monoxide Oxidation on Pt-Pd Catalysts Supported on Calcium Aluminate-Silicon Dioxide-Titanium Dioxide Molds

Abstract

We have studied and developed the molded catalyst bound by calcium aluminate which is composed of AC (stands for alumina cement), fused silicon dioxide, titanium dioxide as the carrier and a small amount of Pt and Pd. This catalyst has good performance because it has no washcoat layer and also it has a high specific surface area. It has been commercially available as a home-use catalyst. The production method of the cataly st is as follows. carrier components in powder form are well mixed and then adequate water is added to the mixed powder to make the mixture paste for molding honeycomb. The curing of the molding carrier is done in hot water and then Pt and Pd are supported on the carrier and the catalyst is calcined at low temperature. The purpose of the paper is to study the molded catalyst bound by AC. The relationships among CO conversion efficiency, several kinds of AC, effect of TiO₂ contents in the carrier, effect of catalyst combination (Pt/Pd), effect of thermal decomposition of noble metals salts, optimum amounts of noble metals, catalyst performance in kerosine space heater have been investigated. The main results obtained were as follows. 1) This molded catalyst using AC of 1st grade shows the best CO conversion and deflection strength than other AC's. 2) Optimum Ti0₂ contents in this carrier are 20 to 50 wt% of carrier components (Al₂0₃.CaO, Ti0₂, Si0₂), and TiO₂ improves CO conversion at 150 to 700°C, but does not improve conversion above the temperature of 800°C.3) Pt/Pd: 2/1 catalyst combination is effective a nd shows better CO conversion and longer life than Pt only catalyst.4) Optimum th ermal decomposition temperature of noble metal salts is 500 to 600°C for this catalyst.5) This catalyst shows good performance in kerosine heaters.