Hideo Sobukawa

Effect of Alkaline Addition on Hydrocarbon Oxidation Activities of Palladium Three-way Catalyst

The effect of alkaline addition on hydrocarbon oxidation activities of Pd catalyst supported on γ-alumina was investigated using simulated automotive exhaust gases. The hydrocarbon oxidation activity of the Pd catalyst with alkaline earth metal such as Mg, Ca, Sr, and Ba is higher than that with nothing added. On the other hand, the activity of the Pd catalyst with alkali metal such as K and Cs is lower than that with nothing added. From the results of the partial reaction orders in C3H6 oxidation, TPR, and XPS, it was concluded that the alkaline addition to the Pd catalyst increased electron density of Pd on the catalyst and weakened the adsorption strength of Pd with hydrocarbons. The addition of alkaline earth metal suppressed the hydrocarbon chemisorption on the Pd catalyst and therefore allowed the catalytic reaction to proceed smoothly. On the other hand, the addition of alkali metal caused such a strong oxygen adsorption on Pd that rejected the hydrocarbon adsorption and suppressed the reaction.

Development of Three-way Catalyst Using Composite Alumina-Ceria-Zirconia

Abstract To realize the high performance of the three-way catalyst, a new catalytic promoter. “ACZ” was proposed. ACZ consists of nanometer-size CeO2-ZrO2 solid solution (CZ) particles and diffusion barrier layers made of alumina (A) among the CZ particles. The specific surface area of ACZ was larger than that of the conventional CZ after durability test. The sintering of Pt on the ACZ-added catalyst is inhibited and the crystal size of CZ in the ACZ-added catalyst is smaller than that in the CZ-added catalyst. The dynamic OSC and the light off temperature of the ACZ-added catalyst are improved.

91 Development of three-way catalyst using composite alumina-ceria-zirconia

To realize the high performance of the three-way catalyst, a new catalytic promoter. “ACZ” was proposed. ACZ consists of nanometer-size CeO2-ZrO2 solid solution (CZ) particles and diffusion barrier layers made of alumina (A) among the CZ particles. The specific surface area of ACZ was larger than that of the conventional CZ after durability test. The sintering of Pt on the ACZ-added catalyst is inhibited and the crystal size of CZ in the ACZ-added catalyst is smaller than that in the CZ-added catalyst. The dynamic OSC and the light off temperature of the ACZ-added catalyst are improved.

Effect of Ba Addition on Catalytic Activity of Pt and Rh Catalysts Loaded on γ-Alumina

The catalytic activity of Pt catalyst loaded on γ-alumina was improved by Ba addition in simulated automotive exhaust gases. On the other hand, the result of Rh catalyst was the opposite. From the results of the partial reaction orders in C3H6–O2 reaction and TPR, it was concluded that the Ba addition to Pt catalyst suppressed the hydrocarbon chemisorption on the Pt catalyst and therefore allowed the catalytic reaction to proceed smoothly. On the other hand, Ba addition to Rh catalyst caused such a strong oxygen adsorption on Rh that rejected the hydrocarbon adsorption and suppressed the reaction.

High Oxygen Storage Ceria-Zirconia Solid Solutions Synthesized by Atmospheric Pressure Solvothermal Process

Ceria-zirconia solid solution is one of the most important components of three way catalyst (TWC) for cleaning automotive exhaust. Ceria-zirconia solid solution has a function as an oxygen storage material, which keeps air to fuel ratio (A/F) at the surface of TWC on a stoichiometric composition. The dissolved zirconia into ceria lattice makes cerium ions to be reduced easier and enhances especially bulk oxygen to release. However, there is a large difference of oxygen storage capacity (OSC) between a theoretical value and that of the prior ceria zirconia solid solutions. The cause of the large difference of OSC might be come from the inhomogeneous dispersion of Zr ions in ceria lattice. Atmospheric pressure solvothermal (APS) process was applied to ceria-zirconia solid solutions in this study. The APS ceria-zirconia showed excellent OSC. The excellent OSC performance was presumed to come from further uniformity of zirconium ions in the ceria lattice.