The peculiar role of copper in the saccharides hydrogenation in aqueous phase

The paper reports on the use of heterogeneous supported Cu catalysts in the aqueous phase reduction of mono and disaccharides to reduced sugars. The huge availability of the starting materials present also in many side streams of the agri-food industry and the growing interest in polyols not only in the food and pharma sectors but also in the polymer one make this reaction a relevant one in the current scenario. Although less active than Ru and Ni based ones, low loaded Cu catalysts show very interesting performance. Conversions up to 100 % can be reached in the hydrogenation of galactose at 160°C and 40 bar of H₂. Moreover, they allow to directly obtain reduced sugars in the hydrogenation of disaccharides through a one pot bifunctional hydrolysis-hydrogenation process. The high dispersion of the Cu metallic phase and the presence of weak acidic sites on the catalyst surface can give account of the observed activity and selectivity.