Accelerated pre-coking of NiMo/Γ-Al₂O₃ catalyst: Effect on the hydroprocessing activity of vacuum residue

A pre-coking process for acceleration of hydrotreating catalyst deactivation is proposed in this work. An artificial pre-coked catalyst is synthesized by using methylnaphthalene as a coke precursor. During the pre-coking process, coke precursor got cracked into smaller aromatic hydrocarbons which penetrates into the pore cavity and covers the active sites. The carbon-coated catalyst has been characterized using N₂-sorption isotherms, thermogravimetric analyser (TGA), X-ray electron microscopy (XPS), scanning electron microscopy (SEM), and high resolution-transmission electron microscopy (HR-TEM). The activity of the carbon-coated catalyst has been evaluated using vacuum residue as feed and results were compared with fresh catalyst. The findings indicate that proposed methodology is able to deactivate the catalyst effectively. It also indicates that proposed pre-coking process can predict the causes of catalyst deactivation in advance. Kinetic parameters of hydrodesulfurization (HDS) reactions are also estimated. The quality of the hydrotreated products at different reaction temperature is also studied. The amount of aromatic and resin are higher in the products obtained with carbon coated catalyst.