The conversion of moisture and ash free (maf) coal to pyridine solubles and gas was investigated in a microautoclave batch reactor. Two washed Kentucky coal samples (KY #9 and KY #11) were studied in liquefaction solvents of various donor strength. The liquefaction solvent hydrogen donor strength was varied by changing the tetralin content of a mixed 1-methylnaphthalene-tetralin mixture. Primary liquefaction conversions in excess of 90 wt% in 10 minutes of reaction time @ 700° K (427° C or 800° F) were achieved with liquefaction solvents of moderate donor strength, i. e. 40% tetralin. A modified irreversible first order rate expression (eq. 1) described the experimental data: (1) $$x\, = \,\alpha - (\alpha - \beta )\,e{\,^{ - {x_1}\,\theta }}$$ where: α is the intrinsic reactive fraction of the maf coal, β is the pyridine solubles of the starting maf coal, κ is a specific reaction velocity constant, Θ is reaction time, and x is the primary liquefaction fractional coal conversion. Primary liquefaction rates as measured by κ1 were found to be quite temperature sensitive and independant of coal when liquefaction solvents containing ≥ 40 wt% tetralin were used. Both α and κ1 appear to depend on solvent donor strength when the liquefaction solvent contained less than 40 wt% tetralin. The intrinsic reactives fraction a appears to be about equal to the reactive macerals content for the two coals studied in liquefaction solvents with a tetralin content ≥ 40 wt%.