Effect of solvo-thermal treatment temperature on the properties of sol-gel ZrO2-TiO2 mixed oxides as HDS catalyst supports

ZrO2-TiO2 mixed oxide (30-70 mol/mol) was prepared by low-temperature sol-gel followed by solvo-thermal treatment (1 day) at various temperatures (40, 80, 120, 160 and 200 degrees C). Selected samples of the corresponding single oxides were also prepared. Materials characterization was carried out by N-2 physisorption, XRD, thermal analysis (TG-DTA) and UV-vis DRS, infra-red and Laser-Raman spectroscopies. Binary solids of enhanced pore volume and pore size diameter were obtained by increasing the post-treatment severity. Anatase TiO2 micro-segregation was evidenced by Raman spectroscopy for the mixed oxide solvo-treated at the highest temperature. This solid also showed the highest crystallization temperature to ZrTiO4 (similar to 702 degrees C). Mo impregnated (2.8 atom nm(-2)) on various mixed oxides was sulfided under H2S/H-2 (400 degrees C, 1 h), the catalysts being tested in the dibenzothiophene hydrodesulfurization (HDS, T= 320 degrees C, P = 5.59 MPa). By increasing the severity of the solvo-treatment improved supports for MoS2 phase were obtained. The HDS activity of the catalyst with carrier post-treated at 200 degrees C was similar to 40% higher (in per total mass basis) than that of sulfided Mo supported on the binary oxide solvo-treated at 80 degrees C. The ZrO2-TiO2-supported catalysts showed higher selectivity to products from the hydrogenation route than their counterparts supported on either single oxide. (C) 2006 Elsevier B.V. All rights reserved.