Characterization of molybdenum hydrodesulfurization catalysts supported on ZrO2-Al2O3 and ZrO2-SiO2 carriers

Two series of Mo-containing catalysts supported on alumina and silica, respectively, modified with different amounts of zirconium, were prepared by wet impregnation method. X-ray diffraction, temperature-programmed reduction (TPR), X-ray photoelectron and Fourier transform infrared spectroscopic techniques were used for physicochemical characterization of the samples in oxidic, reduced and sulfided state. The effect of zirconium content on the state and dispersion of molybdenum is reported: introduction of a small amount of zirconium into the support leads to a significant increase of the dispersion of supported molybdenum oxide species, especially, on silica. ZrO2-Al2O3 supported Mo catalysts show higher Lewis acidity compared to those supported on ZrO2-SiO2, Zirconium influences the reducibility of molybdenum. The reduction of molybdenum oxide species on ZrO2-Al2O3 supports proceeds easily compared to that supported on ZrO2-SiO2, however increasing the Zr02 content leads to a decreasing of the hydrogen consumption during the reduction for both series catalysts due to a strong interaction between molybdenum species and modified supports. The maximum in HDS activity is observed for Mo/ZrO2-SiO2 catalysts with the lowest Zr content (6.6 wt.%) related to a higher dispersion of molybdenum sulfide species. (C) 2002 Elsevier Science B.V. All rights reserved.