A comparison between silica-immobilized ruthenium(II) single sites and silica-supported ruthenium nanoparticles in the catalytic hydrogenation of model hetero- and polyaromatics contained in raw oil materials

A comparative study of the hydrogenation of various heterocycles, model compounds in raw oil materials, by either a Ru(II) complex immobilized on mesoporous silica or Ru(0) nanoparticles deposited on the same support has been performed. The single-site catalyst contains the molecular precursor [Ru(NCMe)3(sulphos)](OSO2CF3) tethered to partially dehydroxylated high-surface area silica through hydrogen-bonds between silanol groups of the support and SO3- groups from both the sulphos ligand [-O3S(C4H4)CH2C(CH2PPh2)3] and the triflate counter-anion. Highly dispersed ruthenium nanoparticles were prepared by calcination/reduction of silica-supported Ru3(CO)12. A complete characterization of both heterogeneous catalysts has been achieved by a variety of solid-state techniques (EXAFS, IR/DRIFT, HRTEM, BET surface-area measurements, CP MAS 31P NMR). Under the experimental conditions employed in this work, the heterocycles (benzo[b]thiophene, quinoline, indole, acridine) have been hydrogenated to cyclic thioethers or amines. The support surface may have a relevant role in the adsorption as well as reactivity of the various heterocycles.