Characterization of Initial Coke Deposits on MoO_3/Al_2O_3 Catalyst By Temperature Programmed Oxidation

摘要

Coke is one of the most significant factors of the catalyst deactivation in hydroprocessing (1). In particular, the coke deposition is believed to be rapid at the initial period. Most of the earlier works on the subject are promarily concerned with the nature of the long term aged catalysts. Studies on the nature of the initial coke formed during the early hours of process are scarece in residue hydrotreating process (2,3). Especially, the factor influencing the initial coking and its role on catalyst functionality and property have not received much attention. In a previous study, we investigated the nature of the coke deposited on a Ni-Mo/Al_2O_3 hydortreating catalyst during the early period of the operation and its role in catalyst deactivation (1). In the present work, coke deposition on an industrial MoO_3/Al_2O_3 hydordemetallization catalyst was studied as a function of operating time during hydrotreating of Kuwait atmospheric residue. The coked catalysts were characterized by temperature programmed oxidation (TPO) analysis to gain a clear under-standing of the nature of the initial coke, its location on the catalyst surface and the nature of the heteroatoms such as nitrogen and sulfur in the coke.