Methyl, ethyl, octyl, naphthylmethyl, or tetralylmethyl groups were introduced to acid-washed Morwell brown coal by O-alkylation (Liotta method). Then the alkylated coals as well as acid-washed raw coal were pyrolyzed at a heating rate of 10 °C/s. The role of alkyl groups as inhibitor of cross-linking reactions and stabilizer of fragment radicals during the pyrolysis was affected by their chain length. The increase in tar yield on the basis of alkyl-free coal mass was most significant with octylated coal. Further, Morwell and Wandoan coals were impregnated with higher paraffinic alcohols, 1-octanol and 1-octadecanol, by a thermally induced solvent swelling method and were pyrolyzed in a free-fall reactor at 700–900 °C. Both alcohols effectively increased the yield of volatile matters by 3–9 wt % on the daf coal mass basis, indicating that long alkyl chains promoted the production of liquid compounds in flash pyrolysis even if they were not chemically bound to coal molecules.
All Science Journal Classification (ASJC) codes