Effect of Pd/TiO2-Al2O3 catalyst support on naphthalene hydrogenation in the presence of CO

Abstract

Hydrogenation of naphthalene in the presence of CO was examined as a step in the organic hydride method for utilizing low grade hydrogen. Development of CO-tolerant hydrogenation catalysts will allow this process to achieve purification and storage of hydrogen simultaneously, and hydrogen with high purity can be obtained by the dehydrogenation step. Pd catalysts supported on TiO2, Al2O3 and TiO2-Al 2O3 mixed oxides prepared by the sol-gel method were evaluated. Using pure hydrogen as the reactant, Pd/TiO2-Al 2O3 catalysts containing 50-80 wt% of TiO2 had high activity. Using hydrogen containing 2% CO, Pd/TiO2-Al 2O3 catalyst containing 80 wt% of TiO2 had the highest activity. The synergetic effect of the mixed oxide support was more clearly observed in the presence of CO impurity than with pure hydrogen. CO probe FT-IR spectra contained 5 peaks, corresponding to the surface geometry. Adsorbed CO on coordinatively unsaturated sites, such as corner and edge sites, increased with higher TiO2 content. These sites released adsorbed CO at lower temperatures, indicating weaker adsorption. These coordinatively unsaturated sites are active for hydrogenation in the presence of CO.