Coke and minerals removal from bitumen hydroconversion catalysts

Hydroconversion of bitumen is an important technology for cracking the residue fraction, but the use of catalysts in ebullated beds suffers from high catalyst consumption. The catalyst pellets accumulate coke, vanadium and nickel sulfides and an external skin of calcium and iron minerals. Spent hydroprocessing catalysts from conversion of Athabasca bitumen were extracted with a hydrotreated gas oil and heteroatomic solvents in order to remove coke and rejuvenate catalyst activity. The extraction conditions ranged from 25 to 430°C and times from 1 to 24 h. The gas oil was a good solvent for removing coke that had been deposited on fresh catalyst for only a few hours, but it was not effective for the removal of aged coke from catalyst from an industrial reactor. Heteroatomic solvents such as quinoline tended to deposit or adsorb on the catalyst, rather than extract the coke material. The optimal conditions for coke removal were at temperatures below 400°C and under a hydrogen atmosphere. thods were used to remove the skin of mineral deposits from the commercial spent catalyst: abrading the surface with aluminum oxide and washing with dilute acid. Grinding off the mineral skin had little effect on the hydrodesulfurization activity of catalysts, while acid washing was able to recover part of activity of the spent catalysts.