Heterogeneous Copper Catalysts in the Aqueous Phase Hydrogenation of Maltose to Sorbitol

A one-pot hydrogenolysis/hydrogenation reaction of maltose to two moles of sorbitol has been carried out over different supported Cu catalysts in water at 180 °C and 40 bar of H2. Only the catalysts supported on silicas were found to be effective in this reaction, giving up to 86% yield in the desired product while the bare supports and the catalysts supported on alumina or silica alumina gave messy reactions. The peculiar activity of the two Cu/Silica systems tested was ascribed to high metal dispersion and suitable polarity of the catalyst surface. In exposing metallic Cu particles on the surface, the reduced catalyst showed unusual stability in the presence of water as a solvent and could be reused several times without any treatment.