Mechanism of hydrogen spillover over carbon supported metal catalysts

Two series of metallic catalysts (Ru and Pt) have been prepared using high surface area graphites as supports. A careful control of the amount and nature of the oxygen surface groups exhibited on the surface of these carbons have been carried out. Synthetized catalysts have been characterized by temperature programmed reduction and by selective chemisorption measurements. From temperature programmed desorption of deuterium it is concluded that the oxygen surface groups participate in the phenomenon of hydrogen spillover. It is shown that carboxylic and lactonic groups are implicated in the spillover of hydrogen. However, these spiltover hydrogens seem to be unable to hydrogenate an aromatic molecule as benzene. It is suggested that carbonaceous species or intermediates produced in the porous structure of activated carbons could be the vehicle to transfer hydrogen atoms and hydrogenate substrates using spiltover hydrogen.