TABLE OF CONTENTS The frequent reference to catalyst deactivation is being made in all preceding chapters. This is rather obvious when the type of the feeds evaluated in this book is taken into consideration. In this case, deactivation was evidenced by decline in the rate of hydroprocessing reactions with time on stream (TOS). The primary objective of the development and testing of catalysts was to minimize this activity decline, which could be quantified by kinetic measurements. The phenomena occurring on catalyst surface, which were related to deactivation, were receiving less attention. The aim of this chapter is to describe catalyst deactivation in terms of the modifying effect of components of heavy feeds as well as that of operating parameters on catalyst surface leading to the loss of activity. Among the latter, temperature, H 2 pressure and H 2S/H 2 ratio are the parameters which have pronounced effects on the structure of catalyst surface in relation to deactivation. The properties of catalysts influence deactivation patterns as well.
The preceding chapters clearly indicated a significant difference between the catalyst deactivation during hydroprocessing of heavy feeds and that of light feeds. For the former, continuous attempts have been made to extend the catalyst life by improving properties of the conventional catalysts and/or by developing new catalyst formulations. This requires understanding of the catalyst deactivation phenomena. Part of the activity may be lost because of the change in catalyst structure due to the prolonged exposure to hydroprocessing temperatures. The adverse effect may be...
