Catalysts for upgrading coal-dervied liquids. Final report, June 9, 1975--March 8, 1978

Abstract

Trickle-bed reactors were used to assess the nitrogen and sulfur removal of eight catalysts, mostly Co--Mo--alumina types. A total of seven different liquids were studied, but not all liquids with all catalysts. Under typical hydrotreating conditions all of the liquids could be desulfurized to about 80 to 100% sulfur removal, with much of this achieved during the first 0.5 to 1.0 hour space time. There is little to be gained by increasing space times much beyond this. No liquid on any catalyst exhibited ease of nitrogen removal. Conditions approaching 427C (800F) and pressures over 2000 psig are necessary to achieve nitrogen removal; unfortunately, conditions leading to rapid coking of catalysts and deactivation. The lighter raw anthracene oil was much easier to process than were the heavier liquids such as the Synthoil fluids, as would be expected. The ease of sulfur removal from a coal liquid is also related to its level of nitrogen. Increased nitrogen levels resulted in increased difficulty in sulfur removal. The catalyst deactivation studies revealed that coking with deposition of carbonaceous material is the primary mode of desulfurization and denitrogenation activity loss. Inorganics from the ash are also accumulated on the catalysts outer suface (coke is deposited throughout) and lead to some deactivation. This coking and ash pickup cause significant surface area loss, typically from 250 to 50 M/sup 2//g. Most of this surface area is recovered following catalyst burn-off, but the ash deposition results in permanent decay. The raw anthracene oil exhibited no catalyst activity decay for tests lasting up to 200 hous of catalyst-oil contact. All other liquids exhibited rather significant decay over intervals up to 700 total contact hours. Much of this deactivation occurs within the first 40-60 reactor turnovers, usually 100 hours of contact.