Preparation of composite titanium-zirconium oxides and their application in hydrodesulfurization catalyst

TiO₂, ZrO₂ and composite titanium-zirconium oxides with various Ti to Zr molar ratios (4:1, 3: 2, 1: 1, 2: 3 and 1: 4) were prepared by coprecipitation method, and active components (10% MoO₃) were impregnated on these supports to form relative catalysts. These catalysts were characterized by X-ray diffraction, nitrogen adsorption and their hydrodesulfurization activities were evaluated using a high-pressure reactor. Results showed that after calcination at 550 °C for 2 h, TiO₂-ZrO₂( 1: 1), TiO₂-ZiO₂(2: 3) and TiO₂-ZrO₂(3: 2) supports were all amorphous, the other two supports exhibited certain crystallization. In comparison with the single metal oxide, mixed oxides had larger surface areas, among them the surface area of TiO₂-ZrO₂( 1: 1) was the largest (191.2 m²/g). Thiophene hydrodesulfurization was taken as the model reaction for evaluating the HDS activities of these catalysts. It was found that HDS activities increased with the increase of zirconia content in mixed oxides and a maximum activity was observed for the 10% MoO₃/ TiO₂-ZrO₂(1: 1) catalyst. With further increase of zirconia content, the catalytic activities decreased and the minimum activity belonged to the catalyst using ZrO₂ support.