Gas phase hydrogenation of crotonaldehyde over Pt/activated carbon catalysts. Influence of the oxygen surface groups on the support

Three activated carbons were prepared with different content of oxygen surface complexes and impregnated with aqueous solutions of [Pt(NH3)(4)]Cl-2. The catalysts were characterized by H-2 and CO chemisorption at room temperature, temperature-programmed decomposition (TPD) and X-ray photoelectron spectroscopy, and their catalytic behavior in the vapor phase hydrogenations of benzene and crotonaldehyde (trans-2-butenal) was determined. Metal dispersion is highly dependent on the degree of support oxidation, being lower for the catalyst support containing the highest amount of surface acidic complexes. This is attributed to the decomposition of the surface complexes, which act as anchoring centers for the platinum precursor, upon the reduction treatments at which the catalysts are subjected. The specific catalytic activity in the gas phase hydrogenation of crotonaldehyde is higher as the starting support is more oxidized, and the activity per gram of platinum increases with reduction temperature. The selectivity for the hydrogenation of the carbonilic C=O bond instead of the olefinic C=C bond is also improved when an oxidized support is used, and the production of the unsaturated alcohol, crotyl alcohol, is enhanced when catalysts are reduced at higher temperature, especially those prepared with oxidized supports.