Propene hydeogenation over truncated octahedral Pt nanoparticles supported on alumina

摘要

Colloidal Pt nanoparticles synthesized by a 1:5 concetration ratio of K_2PtCL_4 to polyacrylate were loaden on nanoporous alumina using the impregnation method at room temperature.The depostited Pt particles,Present on the external surfces of the support,were characterized by transmission electron microscopy,which indiated predominantly truncated octahedral(TO) shapes with a mean diameter of 10 nm.Their catalytic performance in the hydrogenation of propene at 30-80 deg C was studied as a test reaction.The initial rate,reaction order ,rate constant,activation energy,and turnover frequency were detdermined.The activation energy was found to be 8.4+-0.2 kcal/mol,which is slightly lower than results reported for other platium systems(10-14 kcal/mol).The TO platinum nanoparticles have atom-hith surface steps,ledges,and kinks,and these atomic-scale fine structures are expected to decrease the activation energy.The reactivity of the surface atoms in this nanoparticle is so high that above 50 deg C side reactions leading to complete durface poisoning take place within a few mintues.The effect of the polymer concentration of the polycrylate-capped To Pt/Al_2o_3 on the hydrogenation catalytic activity was also investigated.