Preparation and properties of chromium-containing hydrotreating catalysts (Ni-Mo)/ZrO2-Cr2O3

The properties of hydrotreating catalysts (Ni-Mo)/ZrO2-Cr2O3 containing either 10 or 90 mol% of Cr2O3 have been studied in the model reactions of thiophene hydrodesulfurisation (HDS) and tetralin hydrogenation (HYD). Catalysts were characterized by X-ray diffraction, UV-visible spectroscopy and measurements of textural properties. It has been shown that the presence of chromium in the NiMo/ZrO2 systems makes them more hydrogenating, because of the formation of chromium sulphide Cr2S3. Mixed hydrous or crystalline oxide Cr-Zr can be sulfided under mild conditions (400 degrees C, H2S/H-2) leading to highly dispersed Cr2S3 which is impossible for individual Cr2O3. Such systems are several times more active in HYD of tetralin than industrial NiMo/Al2O3 reference catalyst. At the same time in the presence of chromium, the synergy of catalytic activity between Ni and Mo in the reaction of HDS of thiophene was lowered, apparently because of hindering of formation of mixed sulfide Ni-Mo-S active sites due to the stronger interaction between Ni and Cr species than that of Ni and Mo.