TABLE OF CONTENTS The studies on the simultaneous deactivation by coke and N-bases have focused on the VGO and HGO feeds as well as on the asphaltenes and metals containing feeds. However, in the number of latter studies, little attention was paid to the contribution of metals to the overall deactivation. Therefore, they are included in this part of the book separately from those works in which attempts were made to decouple the deactivation by coke from that by metals.
To various extent, the deactivation by coke and N-compounds occurs in parallel. For N-compounds, deactivation results from their strong adsorption on the catalytic sites. This slows down the activation of hydrogen, the availability of which is crucial for hydroprocessing reactions to occur as well as for slowing down coke formation (63). Moreover, the prolonged adsorption of N-compounds diminishes the access of other reactant molecules to catalytic sites. Therefore, at least part of the coke is formed as a consequence of the catalyst poisoning by N-compounds. The extensive information on catalyst deactivation by the N-compounds has been recently reviewed in detail (76). This included both the model compound feeds and the real feeds.
Among the heavy feeds of interest, the formation of coke and poisoning by N-compounds are the primary reasons for catalyst deactivation only during the hydroprocessing of Heavy feeds such as VGO and HGO. Thus, because of only trace amount present, the contribution of metals and asphaltenes to deactivation is rather...
