Catalytic reduction of nitric oxide with carbon monoxide by rare earth oxides

Abstract

An experimental study of the relative catalytic activities of rare earth oxides for reducing nitric oxide in the presence of carbon monoxide is reported. The tests were conducted at atmospheric pressure with nitric oxide and carbon monoxide concentrations in the range of about 0.002–0.04 atm at temperatures from 200 to 475°C to permit comparisons to automobile exhaust conditions. Cerium dioxide was found to be the most active catalyst among the rare earth oxides examined with activity being similar to that of platinum and palladium catalysts tested under similar conditions. The second most active of the rare earth oxides was praseodymium oxide, while the most active of the noble metal catalysts tested was ruthenium. A dual-site-model empirical equation is presented for correlation of the experimental data for the cerium oxide catalyst.