Deactivation of a hydrotreating catalyst during hydroprocessing of synthetic crude by metal bearing compounds

Abstract The objective of this study is to investigate the deactivation of CoMo/γ-Al 2 O 3 catalyst by the metals present in the heavy oils. For this, a synthetic feed is prepared in which coke precursors are minimized. Therefore, dewaxing of a heavy crude is performed which contains very less amount of microcarbon residue (MCR) and asphaltene. A spent catalyst was generated from the hydrotreating of dewaxed oil in a microflow continuous reactor (MFU). The activities of spent (from MFU unit) and regenerated catalysts were compared with the fresh catalyst using the same dewaxed oil in a batch reactor. Detailed characterisations of fresh, spent, and regenerated catalysts were performed using thermogravimetric analysis (TGA), N 2 -sorption isotherms, Raman spectroscopy, scanning electron microscopy (SEM), and high resolution-transmission electron microscopy (HR-TEM). Hydrocracking and hydrotreating activities of the catalysts were evaluated with contact time. It has been found that the hydrodesulfurization (HDS) activity of the regenerated catalyst was even lower than that of spent catalyst. This confirmed that the deactivation occurs by metals from the feed. HR-TEM results indicates that low HDS activity of the regenerated catalyst was observed may be due to the phase change from type II to type I Co-Mo-S during the high-temperature regeneration process. Also, the HDS activity of the spent catalysts showed that Ni deposited from the feed perform the autocatalysis function. The higher hydrocracking activity of the regenerated catalyst suggests that bare alumina-support takes part in the cracking activity, particularly at a higher reaction temperature. The amount of MCR and n-heptane analyzed during the reaction at different contact times concluded that sediments are formed during the early stage of the reaction. As the reaction precedes these sediments agglomerated and separated out from the liquid hydrocarbons.