Chapter 4 - Catalyst Deactivation

Abstract

Deactivation is evidenced by decline in the rate of hydroprocessing (HPR) reactions with time on stream. An optimal selection of catalyst and reactor can minimize the loss of activity as well as catalyst consumption and generation of spent catalysts associated with it. Catalyst deactivation during the HPR of heavy feeds differs markedly from that of light feeds. The presence of resins, asphaltenes, and metals in heavy feeds are the main reason for more extensive catalyst deactivation compared with distillate feeds. Chemical composition and textural properties of catalyst are chosen to match particular feed, while the size and shape of catalyst particles are chosen to match the features of catalytic reactor. For distillate feeds, the loss of catalyst activity is caused by coke deposition, sintering of active phase, poisoning by N-compounds, inhibition by S-, O-compounds and aromatics, and contaminants in feeds. Principal causes of the loss of catalyst activity during the HPR operations using distillate feeds of petroleum origin may differ from those for residual feeds and attrition. In addition to these causes, fouling catalyst surface by resins and asphaltenes, deposition of metals present in the feed, and sediment formation are always present during HPR of heavy feeds.