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 adso rption and dissociation of CO over a Ru cluster with Cl or MoO preadso rbed onto it. Previous experimental information oriented us to think t hat 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 d uring the CO + H-2 reaction, that is, Cl decreases the adsorption of C O and hinders its dissociation. This could lead to the appearance of m ethanol as a synthesis product. On the other hand, our theoretical cal culations indicate that the presence of MoO on top of the Ru cluster f avors 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-meth yl bond thereby forming the ethanol precursor.