Kinetics of vapor-phase secondary reactions of prompt coal pyrolysis tars

The kinetics of vapor-phase secondary reactions of newly formed coal pyrolysis tars were studied at temperatures and residence times of 500-900/sup 0/C and 0.6-3.9 s, respectively. Tar vapors, generated by heating a helium-swept, shallow packed bed of Pittsburgh No. 8 bituminous coal from room temperature to 550/sup 0/C, at 3/sup 0/C/min, were either rapidly conveyed to collection traps for subsequent characterization or else passed through an adjacent reactor for controlled thermal treatment prior to trapping. Results are described. A multiple, independent, parallel, first-order reaction model also performed well but could not predict step-like behavior in conversion at 0.6-s residence time. A single-reaction first-order decomposition model correlated the conversion data poorly at 0.6- and 1.1-s residence times, and use of the resulting best fit parameters gave totally inadequate predictions of conversions measured at 2.5 and 3.9 s.