Impact of Fine Solids on Hydrotreating of Bitumen-Derived Gas Oil

Abstract

Bitumen-derived gas oils that enter hydrotreaters contain fine solids such as minerals, heavy metals, and coke. The deposition of these fines will eventually restrict the flow and result in pressure buildup across the hydrotreater, which eventually necessitate the premature shutting down of the reactor system. To determine if certain types of fine particles had a greater detriment to the hydrotreating process, a series of experiments were performed by accelerated fine deposition in a trickle bed catalytic reactor under industrial conditions using bitumen-derived light gas oil. Kaolinite, montmorillonite, pyrite, and petroleum coke fines had no significant impact on the catalyst activity and catalyst deactivation toward hydrodenitrogenation (HDN), hydrodesulfurization (HDS), and hydrodearomatization. Unlike the above fines, iron(III)oxide was found to convert into FeS under hydrotreating conditions, which provided a promoting effect for HDN and HDS reactions. When comparing the trends in pressure drop across the catalyst bed, there was a delayed period during the initial fine deposition where no change in pressure drop was observed, followed by an exponential increase in pressure due to the decrease in bed porosity. The difference found between these fines was the length of this delayed period, with iron(III)oxide and petroleum coke having the longest periods of no pressure growth. From inductively coupled plasma, scanning electron microscopy with energy-dispersive spectroscopy, X-ray diffraction, and Brunauer–Emmett–Teller analysis of the fresh and spent catalysts, it was determined that the deposition of all fines occurred within the packing material in the preheating zone, with only petroleum coke and iron(III)oxide fines being found on the surface of the catalysts.