Preparation of hydrotreating catalysts via an oxalic acid-assisted hydrothermal deposition method

An oxalic acid-assisted hydrothermal deposition method to prepare highly dispersed W/gamma-Al2O3 and NiW/gamma-Al2O3 hydrodesulfurization catalysts without strengthening the metal-support interaction was developed and compared with the conventional impregnation method. The resulting oxidic and sulfided catalysts were characterized, and their catalytic performance was assessed. The results showed that the oxalic acid-assisted hydrothermal deposition method can better disperse tungsten oxide on gamma-Al2O3 while decreasing the metal-support interaction, resulting in more efficient sulfidation of tungsten oxide and formation of highly stacked WS2 slabs with short length, and thereby the significantly enhanced hydrodesulfurization activity of the resulting catalysts. The improved dispersion of W species is attributed to the anti-aggregation effect of the oxalic acid adsorbed on active metal particles formed during the hydrothermal deposition process, whereas the strong interaction between carboxyl groups of oxalic acid and hydroxyl groups or unsaturated Al3+ on alumina surface accounts for the weakened metal-support interaction. (C) 2008 Elsevier Inc. All rights reserved.