Optimization of ruthenium-containing, stabilized, nitric oxide reduction catalysts

Abstract

To optimize the stabilized ruthenate catalysts for NOx reduction in automotive exhaust treatment with respect to selectivity and stability, we studied dilution of ruthenium in the ruthenates by Ni3+ and Mn4+ ions in presynthesized specimens and the effect of stabilizer content in sequentially impregnated specimens. The replacement of Ru in BaRuO3 by Mn4+ and in LaRuO3 by Ni3+ increases the stability of the ruthenates with respect to volatilization in oxidizing environments. An increase in the resistance to volatilization is also observed in impregnated samples with the increase in the content of stabilizing component. These effects are substantial in shifting the onset of volatilization by several hundred degrees centigrade upwards on the temperature scale. However, all of these stabilization improvements result in decrease in the desired selectivity. © 1975.