Cooperation between the surface hydroxyl groups of the support and organic additives in the highly selective hydrogenation of citral

A Ru/AlO(OH) catalyst was prepared by co-precipitation and characterised by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), thermo-gravimetry (TG), and Fourier transform infrared spectroscopy (FT-IR). Its catalytic performance was tested in the selective hydrogenation of citral. The results showed that the combination of Ru/AlO(OH) and water obviously improved the catalyst activity and its selectivity to geraniol and nerol. Introducing organic additives increased the hydrophilicity of metal particles, which favoured the adsorption of the citral C=O bond over the adsorption of the conjugated C=C bond, improving the selectivity to and inhibiting the further hydrogenation of geraniol and nerol. The maximum yield of geraniol and nerol (81%) was achieved in water with ethylenediamine as an additive. (C) 2012 Elsevier B.V. All rights reserved.