Alumina–titania binary mixed oxide used as support of catalysts for hydrotreating of Maya heavy crude

Abstract

Three different methods are applied to prepare alumina–titania binary mixed oxide supports. These supports are used to prepare catalysts for hydrotreating of Maya heavy crude. Sequential incipient wetness and co-impregnation techniques were employed for preparation of catalysts. Ammonium heptamolybdenum was used as precursor for MoO 3. Catalysts are characterized by XRD, TPR and pore size distribution. Hydrodemetallation (HDM), hydrodesulfurization (HDS), hydrodenitrogenation (HDN), and asphaltene conversion (HDAsp) reactions are studied on these catalysts. One reference catalyst is also taken for comparison. Coke and metals depositions on spent catalysts are measured. Catalyst deactivation rate is also studied. A combined method of urea hydrolysis and pH variation is suitable to prepare bigger size of pore diameter and more pore volume support. XRD results indicate that prepared alumina–titania oxides are amorphous or very poor crystalline in nature. Very complex nature of TPR profiles is observed. Two catalysts (C and D) show very high activities and also give very good stability compared to reference catalyst. We observe an average correlation between pore diameter of catalyst with HDM and HDAsp conversions. It indicates that bigger pore diameter catalyst is suitable for removal of metals and asphaltenes, but bigger pore size is not only criterion to show good HDM activity. Total pore volume is also an important parameter in this regard. Enhancement of activities is observed on P containing catalyst. Coke is deposited on the catalyst pore mouth and it caused a drastic reduction of specific surface area of spent catalyst. Coke deposition is more on the catalyst having bigger pore diameter. We also observe that rate of V removal is higher than rate of Ni removal.