posted on 2023-01-06, 20:33authored byCarson Polischuk, Sundaramurthy Vedachalam, John Eleeza, Anakaren Botana de la Cruz, Ajay Dalai, John Adjaye
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.