INFLUENCE OF ADSORBED CH3O ON CO DESORPTION FROM NI/AL2O3

The desorption rate of CO from the Ni surface of a 5.1% Ni/Al2O3 catalyst was significantly increased by the presence of CH3O on the support. The CH3O was formed by CO and H2 coadsorption at 385 K. Reverse spillover of CH3O, as CO desorbed, maintained the Ni surface at a high coverage of CO and H2. This increased the rate of CO desorption because of the repulsive interactions present between CO molecules on Ni at high coverages and because readsorption on Ni was decreased. These studies show that CH3O must undergo reverse spillover onto the Ni surface in order to decompose. Decomposition directly on the A12O3 surface does not occur at these temperatures. Carbon isotope labeling and temperature-programmed desorption were used to study this process. For hydrogen isotope labeling, a kinetic isotope effect for CH3O decomposition indicated that C-H bond breaking or surface diffusion limited CH3O decomposition. Oxygen isotope labeling showed that the carbon-oxygen bond did not break upon the formation or decomposition of CH3O. © 1992.