GRAVIMETRIC ADSORPTION STUDY OF HYDROGEN AND CARBON MONOXIDE ON A SUPPORTED RUTHENIUM CATALYST

The adsorption kinetics and equilibrium uptake of hydrogen and carbon monoxide have been measured gravimetrically for a 4 wt percent ruthenium/silica catalyst. These measurements were performed over a temperature range of 20 to 250/sup 0/C. The results were used to evaluate the catalyst-adsorbate interactions. Hydrogen adsorption was also used to determine the metal surface area and crystallite size. The adsorption isotherms of hydrogen were used to determine the heat of adsorption for hydrogen on ruthenium. A low heat of adsorption indicating a weak interaction of hydrogen with the metal surface was found for surface coverages greater than half a monolayer. The adsorption isotherms were found to be composed of two portions, reversible and irreversible hydrogen. Reversible hydrogen could be desorbed by evacuation of the catalyst at the adsorption temperature, while irreversible hydrogen could not be desorbed under these same conditions. The rate of hydrogen adsorption was found to follow the Elovich equation. Thermal desorption spectra revealed that at least two forms of hydrogen exist on the ruthenium surface. The carbon monoxide adsorption isotherm could also be divided into reversibly and irreversibly adsorbed components. The heats of adsorption for carbon monoxide obtained indicate a strong binding of the adsorbate to themore » ruthenium surface. Comparison of carbon monoxide and hydrogen isotherms indicates that the catalyst surface is permanently altered by carbon monoxide adsorption.« less