Coke and minerals removal from bitumen hydroconversion catalysts

Hydroconversion of bitumen is an important technology for cracking the resi due fraction, but the use of catalysts in ebullated beds suffers from high catalyst consumption. The catalyst pellets accumulate coke, vanadium and ni ckel sulfides and an external skin of calcium and iron minerals. Spent hydr oprocessing catalysts from conversion of Athabasca bitumen were extracted w ith a hydrotreated gas oil and heteroatomic solvents in order to remove cok e and rejuvenate catalyst activity. The extraction conditions ranged from 2 5 to 430 degrees C and times from 1 to 24 h. The gas oil was a good solvent for removing coke that had been deposited on flesh 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 materia l. The optimal conditions for coke removal were at temperatures below 400 d egrees C and under a hydrogen atmosphere. Two methods were used to remove the skin of mineral deposits from the comme rcial spent catalyst: abrading the surface with aluminum oxide and washing with dilute acid. Grinding off the mineral skin had little effect on the hy drodesulfurization activity of catalysts, while acid washing was able to re cover part of activity of the spent catalysts. (C) 2000 Elsevier Science Lt d. All rights reserved.