Heterogeneity of adsorption and reaction sites on the surface of (10%Co + 0.5%Pd)/TiO₂ catalysts during CO hydrogenation

Adsorption and reaction site heterogeneity of titania-supported (10%Co + 0.5%Pd) catalysts in CO hydrogenation was studied by chemisorption, temperature-programmed desorption, and diffuse reflectance infrared Fourier transform spectroscopy techniques. Precursor material was treated in various media as reductive, inert, or oxidative. Cobalt metal sites and TiO₂ support heterogeneity were proved. Upon H₂ chemisorption, a pre-reduced sample exposed mostly homogeneous metal surface. Surface heterogeneity toward CO chemisorption depended on preliminary treatment. A catalyst prepared in inert medium revealed moderate activity dynamics of adsorption and reaction sites. Weak to medium strength sites toward hydrogen adsorption were relatively strong in terms of CO adsorption. Carbonate-(like) species occupied medium and strong sites on the support. Sites of weak strength for CO adsorption were active in hydrogenation but very strong in terms of CH_x intermediates adsorption.