Mechanistic Insights into Catalyst Deactivation from Fines Deposition during Hydrotreating of Bitumen-Derived Gas Oil

Abstract

Hydrotreating of bitumen-derived oils is hindered by fines deposition, which causes pressure drop buildup and premature reactor shutdown. While the hydrodynamic effects of fines deposition are well established, its role in catalyst deactivation remains poorly understood. In this study, a three-zone reactor was used to investigate the mechanisms of catalyst deactivation under industrially relevant temperature gradients. Pressure drop monitoring, catalytic activity evaluation, and postreaction characterization showed that fines deposition occurred sequentially, beginning in the hottest bottom zone (390 °C) before progressing upward to the middle (370 °C) and top (350 °C) zones. At 390 °C, fines chemically interacted with the catalyst support to form linkages that caused catalyst activity loss. In contrast, deposition at 350–370 °C was primarily physical, with catalyst deactivation occurring only after prolonged accumulation produced dense deposits and external mass transfer limitations. These findings provide guidance for improving reactor operability and catalyst lifespan.