THE EFFECT OF CHLORINE MODIFICATION OF SILICA-SUPPORTED RU ON ITS CO HYDROGENATION PROPERTIES

An investigation of CO hydrogenation on Cl-modified supported Ru catalysts has been carried out using both steady-state Fischer-Tropsch synthesis and steady-state isotopic transient kinetic analysis of methanation. The steady-state reaction results illustrate how the presence of chlorine acts to decrease catalytic activity and to enhance the selectivity of methane formation even though it is present on the catalyst only during the initial stages of the reaction. The deactivation results for F-T as well as the isotopic transient results suggest that structural rearrangements induced by the presence of chlorine, rather than selective site blocking or electronic interactions, may be the primary mechanism of chlorine modification of the catalytic properties of supported ruthenium for CO hydrogenation. Isotopic transients indicated that the decrease in methanation activity with increasing initial Cl concentration was a function of a decrease in the number of reactive surface intermediates (or sites) and not of a change in site activity. © 1990.