Preparation of monodispersed Pt nanoparticles in MCM-41, catalytic applications

Pt nanoparticles were synthesized in MCM-41 by applying a cationic surfactant, which acts as both a structure directing agent and a stabilizer. The structural characterization of Pt-MCM-41 was performed by ICP-AES, N-2 sorption, X-ray diffraction and transmission electron microscopy. It was established that a significant proportion of the monodispersed Pt particles formed upon reduction was incorporated into the pore channels of a regular MCM-41 framework. The Pt-MCM-41 sample was tested as a catalyst in the liquid-phase hydrogenations of 1-hexene, cyclohexene, styrene, 1-pentyne and 1-hexyne under mild conditions. The hydrogenation rates were affected by diffusion limitations, which was attributed to the predominance of Pt particles encapsulated inside the mesopores. The highest catalytic activity was observed for the reactant of the smallest size, I-pentyne. The catalytic activity was found to diminish as the molecular dimensions of the reactants increased, which indicated that Pt-MCM-41 was a shape selective catalyst. (c) 2007 Elsevier B.V. All rights reserved.