Kinetics of reaction between nitrogen mono-oxide and carbon mono-oxide over palladium–alumina and ruthenium–alumina catalysts

Abstract

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 dp_CO2/dt= 2.0 × 10⁶ exp (–91.2 ± 19 kJ mol^–1/RT)p_NO²/P_CO molecules cm^–2 s^–1(1), forp_CO/p_NO between 1 and 1.6. Over the ruthenium catalyst the rate is given by (ii) in the range 250–350 °C and dp_CO2/dt= 6.6 × 10⁸ exp (–82.4 ± 15 kJ mo^–1/RT) P_NO⁰ P_CO⁰(ii) for P_CO/P_NO between 1 and 5. When PCO/PNO is greater than 5 for the ruthenium-catalyzed reaction the rate changes to dP_CO2=kp_NOP_CO⁰. 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.