Effect of water and hydrogen partial pressures during direct liquefaction in catalyzed systems with a low solvent-to-coal ratio

Abstract

Illinois No. 6 bituminous coal with small concentrations of coal-derived solvent was subjected to hydroliquefaction in batch reactors to which substantial amounts of water were sometimes added. The reactions were catalyzed by 0.1% molybdenum on mf coal, added as a water-soluble salt. It was shown previously that a substantial water partial pressure, at fixed hydrogen partial pressure, increases coal conversion in uncatalyzed systems. The present work investigated the effect of added water in catalyzed systems. Considerations of process economics led to the performance of series of reactions at constant total pressure while the partial pressures of water and hydrogen were varied. For catalyzed systems containing solvent, at fixed total pressure, highest conversions are obtained without added water. Conversion to THF solubles is independent of the solvent-to-coal (S/C) ratio to very low values, S/C ^0.25, due to the catalyst. At 427 °C and 1500 psig hydrogen partial pressure, THF and benzene conversions exceeding 90% and 85%, respectively, were achieved. It is concluded that reaction systems with catalyst deposited from solution on the coal particles are highly reactive. Added water is preferentially excluded from the reactor, but water retains a role as a solvent for the catalyst and potentially as a transport medium for coal feed in continuous processing.

Subtask 3.3 - Feasibility of Direct Coal Liquefaction in the Modern Economic Climate

“…One option for increasing catalyst activity and reducing costs would be to use catalysts in which metals are dispersed as either water-or oil-soluble liquids (Derbyshire and Hager, 1994;Ruether et al, 1987;Zhan and Givens, 1999;Demirel and Givens, 2000a), allowing the metals to deposit and interact directly on coal surfaces. Dispersed catalysts are reported to give higher liquid yields and require lower catalyst loadings than do supported catalysts Givens, 1998, 2000a, b;Ni et al, 1994).…”

Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Technical progress report, July--September 1996

“…Because aryl ethers cleave in H20 at high temperature above 315 "C through ionic mechanism [5], this ionic effect of H 2 0 on the cleavage of C-0 bond in DNE is investigated. Even though water alone has inhibition effect on conversion of DNE as described above.…”

The use of NMR techniques for the analysis of water in coal and the effect of different coal drying techniques on the structure and reactivity of coal. Final report

“…Mikita and Fish (1986) suggested that water acts to open new ionic reaction pathways through its solvation effect. In a later study, Ruether et al (1987) investigated hydroliquefaction coal conversion in the presence of catalysts and found that highest conversions are obtained without added water. They concluded that for reaction systems with the catalyst deposited from solution onto the coal particles, the resultant particles are highly reactive and that water retains a role as a solvent for the catalyst.…”