Catalytic Oxidation of Carbon Monoxide over Ru/SiO2. An in Situ Infrared and Kinetic Study

Article abstract of DOI:10.1021/j150649a014

The partial deactivation of a series of Ru/SiO2 catalysts during the CO oxydation reaction has been studied by using "in situ" infrared spectroscopy.The decrease in catalytic activity was fast in an oxygen-rich reactant gas mixture.At a CO/O2 ratio greater than that required for stoichiometry, partial deactivation was slow, continuing for several hours.When the rate of the oxidation reaction was decreased following 100percent conversion in the diffusion-controlled kinetic regime, a significant decrease in the reaction rate was observed.This reaction rate hysteresis was considerably larger when the catalyst was exposed to an oxygen-rich reactant gas misture.During catalyst deactivation, the absorbance of the IR doublet centered at 2130 and 2060 cm^-1 was observed to icrease.This IR doublet, assigned to CO adsorbed on an oxidized Ru surface species, increased very rapidly when the reactant gas mixture was either net oxidizing or close to stoichiometry.The results of a temperature-programmed desorption (TPD) and a temperature-programmed oxidation study suggest that partial deactivation occurs as the result of the formation of a more tightly bound oxygen species, perhaps lattice oxygen which reacts more slowly with adsorbed CO than oxygen in the reactant gas mixture.Multiple steady-state oscillations were observed following the attainment of steady-state reaction rates.The results of a temperature-programmed reduction study show that the CO species responsible for the CO adsorption band at 2010 cm^-1 reacts preferentially with H2 to form CH4.