Chemically modified cyclodextrins as supramolecular tools to generate carbon-supported ruthenium nanoparticles: An application towards gas phase hydrogenation

A series of carbon-supported ruthenium catalysts was synthesized from zerovalent ruthenium nanoparticles stabilized by randomly methylated cyclodextrins (alpha-, beta- and gamma-CD) followed by their adsorption onto the carbon support. The catalysts were characterized by N-2 physisorption and thermal analyses. The deposited ruthenium nanoparticles were characterized by transmission electron microscopy, which has highlighted predominantly spherical shapes with a mean diameter of 2.4 nm. Catalytic activity was investigated in the gas phase hydrogenation of o-, m- and p-xylene at 85 degrees C, both separately and in a two-component mixture (o- and p-xylene). The catalyst prepared by a 1:3 concentration ratio of RuCl3 to randomly methylated beta-cyclodextrin exhibited the highest hydrogenation activity and stereoselectivity toward the formation of trans-dimethylcyclohexane. The beta-cyclodextrin appeared as multifunctional molecular receptors enabling the stabilization and dispersion of the metallic nanoparticles onto the support and the promotion of the catalytic reaction through host-guest interactions. (C) 2010 Elsevier B.V. All rights reserved.