Catalytic hydrogenation of xylose to xylitol using ruthenium catalyst on NiO modified TiO2 support

The activity of Ru catalyst on a new class of NiO modified TiO2 support, Ru/(NiO-TiO2), was studied in the liquid phase catalytic hydrogenation of xylose to xylitol. The TiO2 support was modified by simple impregnation method using nickel chloride precursor and subsequent oxidation. Various catalysts with different targeted compositions of Ru (1.0 and 5.0 wt%) and NiO (1.0, 5.0 and 10 wt%) in NiO-TiO2 were prepared. These catalysts were characterized by using energy dispersive X-ray analysis (EDX/EDS), temperature-programmed reduction (TPR), inductively coupled plasma (ICP) mass spectrometry, transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and CO chemisorption. The novel catalysts are evaluated for selective hydrogenation of xylose and the results compared with those obtained from conventional Raney Ni, Ru/C and Ru/TiO2 catalysts carried out under identical reaction conditions. The effect of NiO additive in the catalyst Ru/(NiO-TiO2), clearly found to enhance the conversion, yield and selectivity to xylitol. Furthermore, the order of catalytic activity may be given as Ru (1.0%)/NiO (5.0%)-TiO2 > Ru (1.0%)/TiO2 > Ru (1.0%)/C> Raney Ni. The effects of Ru and NiO loading, xylose concentration (2.5, 15 and 30 wt%) and temperature (100, 120 and 140 degrees C) were studied. Although at higher temp 140 degrees C, the conversion of xylose was increased to optimum level, xylose to xylitol selectivity decreased due to formation of by-products. (C) 2012 Elsevier B.V. All rights reserved.