Preparation, characterisation and performance of encapsulated copper-ruthenium bimetallic catalysts derived from molecular cluster carbonyl precursors

Abstract

The advantages of producing high-performance, bimetallic nanoparticle catalysts from their precursor metalcluster carbonylates anchored inside the mesoporous channels of silica (MCM41) are described. In situ X-ray absorption and FT-IR spectroscopies as well as ex situ high-resolution scanning transmission electron microscopy were used to chart the progressive conversion, by gentle thermolysis, of the parent carbonylates to the denuded, bimetallic nanoparticle catalysts. Separate copper and ruthenium K-edge X-ray absorption spectra yield a detailed structural picture of the active, approximately 15 Å diameter catalyst: 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 H2 is presented here (maximum TOF in [(mol(substr)) (mol(cluster))-1 h-1] 51200, average TOF 22 400)-and also in the hydrogenations at 65 bar H2 and 373 K of diphenylacetylene, phenylacetylene, stilbene, cis-cyclooctene and D-limonene, the average TOFs being 17, 610, 70, 150 and 360, respectively.