KINETICS OF REACTION BETWEEN NITROGEN MONO-OXIDE AND CARBON MONO-OXIDE OVER PALLADIUM-ALUMINA AND RUTHENIUM-ALUMINA CATALYSTS

The kinetics of reaction between CO and NO overalumina-supported palladium and ruthenium catalysts have been studied in a closed system by monitoring gas composition mass spectrometrically. Over the palladium catalyst the reaction may be represented by (i) in the range 300–450 °C (at total pressures up to ca. 10 kN m–2 and dpCO2/dt= 2.0 × 106 exp (–91.2 ± 19 kJ mol–1/RT)pNO2/PCO molecules cm–2 s–1(1), forpCO/pNO between 1 and 1.6. Over the ruthenium catalyst the rate is given by (ii) in the range 250–350 °C and dpCO2/dt= 6.6 × 108 exp (–82.4 ± 15 kJ mo–1/RT) PNO0 PCO0(ii) for PCO/PNO between 1 and 5. When PCO/PNO is greater than 5 for the ruthenium-catalyzed reaction the rate changes to dPCO2=kpNOPCO0. The kinetic behaviour agrees with the concept that, in the presence of CO–NO mixtures, palladium catalysts tend to favour adsorption of CO, whereas ruthenium catalysts favour adsorption of NO.