PHYSICAL AND CHEMICAL MODIFICATION OF LOW-RANK COALS WITH ALKYL CHAINS AND THE ROLES OF INCORPORATED GROUPS IN PYROLYSIS

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-degrees-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-degrees-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.