Measurement of solvent quality by electron spin resonance. [10. 4 MPa; ambient to 473/sup 0/C]

Solvents from three coal liquefaction processes, Lummus Integrated Two-Stage Liquefaction (ITSL), H-Coal, and Wilsonville SRC-I, were analyzed by high-temperature, high-pressure, flow-through electron spin resonance (ESR) spectroscopy. Relative radical concentrations (product of the double integral of the derivative spectrum and the absolute temperature) were measured over a temperature range of ambient to 473/sup 0/C. System pressure was maintained at 10.4 MPa for all except ambient-temperature runs, which were performed at atmospheric pressure. A comparison of solvents from the same process derived from the same coal indicated that those designated, by means of kinetic microautoclave analysis, as having higher quality generally had the lowest relative radical concentrations. Operating data compiled by International Coal Refining Company personnel for the Wilsonville Pilot Plant raised questions concerning the advisability of comparing ESR or any other potential measurement of solvent quality (SQ) with SQ values determined by microautoclave analysis utilizing a standard coal different from that from which the solvent was derived.