Ru/TiO2 catalyst for selective hydrogenation of benzene: Effect of surface hydroxyl groups and spillover hydrogen

Three Ru/TiO2 catalysts were prepared via an impregnation-chemical reduction method by supporting Ru on three different TiO2 supports, namely TiO2-A (anatase), TiO2-R (rutile) and TiO2-A-750 (annealing TiO2-A at 750 degrees C). The amount of surface hydroxyl groups in the TiO2 supports and Ru/TiO2 catalysts is evaluated by the FTIR technique, which is found to be affected by crystal and textural property of TiO2. It is found that, for the Ru/TiO2 catalyst, the presence of more spillover hydrogen, and more hydroxyl groups that lead to stronger surface hydrophilicity and lower benzene diffusion rate, thereby improve its catalytic activity and selectivity towards selective hydrogenation of benzene. For the Ru/TiO2-A catalyst, it has much more spillover hydrogen and hydroxyl groups than the other two, hence showing the best catalytic activity (TOF of 0.8s(-1)) and cyclohexene selectivity (66%) at a benzene conversion of 50%.