PREPARATION, CHARACTERIZATION AND PERFORMANCE OF ENCAPSULATED COPPER-RUTHENIUM BIMETALLIC CATALYSTS DERIVED FROM MOLECULAR CLUSTER CARBONYLPRECURSORS

The advantages of producing high-performance, bimetallic nanoparticle catalysts from their precursor metal-cluster carbonylates anchored ins ide the mesoporous channels of silica (MCM41) are described. In situ X -ray absorption and FT-TR spectroscopies as well as ex situ high-resol ution scanning transmission electron microscopy were used to charr the progressive conversion, by gentle thermolysis, of the parent carbonyl ates to the denuded, bimetallic nanoparticle catalysts. Separate toppe r and ruthenium K-edge X-ray absorption spectra yield a detailed struc tural picture of the active, approximately 15 Angstrom diameter cataly st: it is a rosette-shaped entity in which twelve exposed Ru atoms are connected to a square base composed of relatively concealed Cu atoms, These in turn are anchored by four oxygen bridges to four Si atoms of the mesopore lining. The bimetallic catalysts exhibit no tendency to sinter, aggregate or fragment into their component metals during use. The nanoparticles perform well in the catalytic hydrogenation of hex-1 -ene-a detailed kinetic study at 373 K and 20 bar H-2 is presented her e (maximum TOF in [(mol(substr)) (mol(cluster))(-1) h(-1)] 51 200; ave rage TOF 22 400)-and also in the hydrogenations at 65 bar H-2 and 373 K of diphenylacetylene, phenylacetylene, stilbene, cis-cyclooctene and D-limonene, the average TOFs being 17, 610, 70, 150 and 360, respecti vely.