The CO H2 reaction on Rh Al2O3. II. Kinetic study by transient isotopic methods

Abstract

Transient isotopic methods have been used to study the CO H2 reaction over 5% Rh Al2O3 in the temperature range 180-260 °C. The steady-state tracing method permits the determination of the surface coverage of CO and active carbon Cα during reaction, without the need for quenching in helium and subsequent titration by hydrogen. The results confirm that the sequence of steps for methane formation passes through a small reservoir of active carbon (θcα < 0.05), although there is also a large reservoir of surface CO. Rate control is largely determined by the rate of CO dissociation on the surface. The simultaneous presence of a formate species, located on the alumina and which does not participate in the reaction, has been supported by the results of isotopic experiments. © 1989.