Dendrimer-Stabilized Ru Nanoparticles Immobilized in Organo-Silica Materials for Hydrogenation of Phenols

New hybrid catalysts based on Ru nanoparticles, encapsulated into poly(propylene imine dendrimers), immobilized into silica pores, were synthesized and examined for the hydrogenation of alkyl-substituted phenols. The corresponding alkyl-substituted cyclohexanols were presented as the major reaction products, while incomplete hydrogenation products appeared to be minor. A competition between the sterical factors of dendrimer-containing carriers and the electronic factors of substrate substituents influenced the hydrogenation rate of the alkyl-substituted phenols. The carrier structure was found to have a significant influence on both the physical and chemical properties of the catalysts and their hydrogenation activity. The synthesized hybrid catalysts appeared to be stable after recycling and could be re-used several times without significant loss of activity.