RUTHENIUM PEROVSKITE CATALYSTS FOR LEAN NOX AUTOMOTIVE EMISSION CONTROL

Perovskite-type catalyst samples LaySr1-yRuxCr1-xO3 (y = 0.7; 0.025 le ss than or equal to x less than or equal to 0.100), synthesized by the ceramic method, were used in activity measurements in the simultaneou s conversion of CO, hydrocarbons (HC), and NOx in the pulse-flame cata lyst testing (PFCT) system and synthetic dry gas mixtures. In the pres ence of water vapor, in the reaction mixture (PFCT system), an unusual ly high level of CO oxidation and a higher concentration of H-2 detect ed in the outlet reactor gases, compared to the inlet reactor gases, c an be ascribed to a water gas shift reaction. The generated hydrogen, present on the catalyst surface in its dissociated form, could be resp onsible for the higher NOx conversion under net oxidizing (lean) condi tions, which favors ruthenium synthesized catalysts as three-way auto exhaust catalysts.