Effect of coke and metal deposition on catalyst deactivation during middle stage of resid hydrodesulfurization operation

Measurements of remaining hydrodesulfurization activity and physical properties of 5 catalysts with different coke and metal contents after using them year operation in commercial hydrodesulfurization operation were carried out to elucidate the interactive effect of coke and metal depositions on catalyst deactivation. The properties of the deposited coke on the used catalysts were also examined. Hydrodesulfurization of an atmospheric residue was performed over a new catalyst in the same manner as used one for of the coke properties. The physical properties, such as surface area, pore volume and mean pore diameter, and the remaining activity were correlated with the volume of deposits (coke and metal) calculated from the specific volume of coke and metal. Since the C/H ratio of deposited coke was directly proportional to the coke content, it was considered that the coke was formed from the same coke precursor that had gradually condensed and/or dehydrogenated. The coke content on the catalyst decreased with the content of the metal. At the same time, the decreasing in the aliphatic hydrocarbons in the coke was faster than that in the aromatic hydrocarbons. The remained catalytic activity of the commercially used catalysts decreased linearly with the content of the deposits. From these results, it was considered that the removal of coke with the deposition of metal had partly contributed the decreased catalyst deactivation by coke deposition during the MOR after fast deactivation during the SOR. The depositions of coke and metal on the hydrodesulfurization catalyst were mutually interacted to affect the catalyst deactivation.