THEORETICAL-STUDIES OF CO ADSORPTION AND DISSOCIATION ON RU IN PRESENCE OF CL OR MOOX

Using the extended Huckel molecular orbital method we studied the adsorption and dissociation of CO over a Ru cluster with Cl or MoO preadsorbed onto it. Previous experimental information oriented us to think that the remaining Cl present in Ru/SiO2 and RuMo/SiO2 catalysts could influence their chemisorptive and catalytic properties. On this basis our theoretical model explains the observed activity and selectivity during the CO + H-2 reaction, that is, Cl decreases the adsorption of CO and hinders its dissociation. This could lead to the appearance of methanol as a synthesis product. On the other hand, our theoretical calculations indicate that the presence of MoO on top of the Ru cluster favors the adsorption of CO parallel to the cluster surface. They also predict an energy barrier for its dissociation which is interpreted in terms of the possible insertion of this CO molecule into a metal-methyl bond thereby forming the ethanol precursor.