Selective Hydrogenation of Cinnamaldehyde over Cobalt Supported on Alumina, Silica and Titania

The liquid phase selective hydrogenation of cinnamaldehyde has been investigated on cobalt (15 wt%) impregnated on alumina, silica and various phases of titania supports. The multiple reduction stages observed in the TPR studies suggest the presence of cobalt aluminate/silicate/titanate species, and DRIFT spectra results seem to corroborate this observation. An optimum level of conversion and selectivity to cinnamyl alcohol was observed at 120 degrees C and 10 kg/cm(2) hydrogen pressure. Co/TiO2 exhibited a greater conversion (47.4%) and selectivity to cinnamyl alcohol (58%) than Co/Al2O3 and Co/SiO2, which may be attributed to the presence of TiOx (x < 2) species on the catalyst surface and to the preferential adsorption of C=O on the catalyst surface. The stability of Co/TiO2 was found to be better than Co/Al2O3 and Co/SiO2. Between the various phases of titania (high surface area, anatase and rutile), the crystalline phases exhibited a better conversion and selectivity to cinnamyl alcohol, while the stability was found to be better for high surface area titania.