HOMOGENEOUS RH-SN ALKOXIDE COATINGS ON SILICA SURFACES - A NOVEL ROUTE FOR PREPARATION OF BIMETALLIC RH-SN CATALYSTS

The reaction of [{(COD)Rh}2Sn(OEt)6], where COD = 1,5-cyclooctadiene and Et = ethyl, with silanol groups on silica surfaces is shown to lead to near-monolayer coverage of the silica by the Rh-Sn organometallic compound. Heating the supported compound at 498 K yields a catalyst that is active for benzene hydrogenation at room temperature. When the catalyst is reduced in H-2 at 823 K, the benzene hydrogenation activity increases with a simultaneous drop in the activity for n-butane hydrogenolysis. High temperature reduction leads to formation of Rh-Sn alloy particles with an average particle diameter of 2.5 nm. These particles are stable towards oxidation-reduction cycles involving oxidation at 773 K in 15% O2. When normalized to the benzene hydrogenation activity, the n-butane hydrogenolysis activity of the bimetallic catalyst is suppressed by over 3 orders of magnitude when compared to a monometallic Rh catalyst.