Nakayama lignite that contained much humus easily reacted with chromic anhydride (CrO3) in aqueous solution. CrO3 was reduced to Cr2O3 at the temperature coal pyrolysis oc-curred (<500°C). Therefore, the hydrogenation of Nakayama lignite pre-treated with CrO3 was car-ried out at 500°C. As a result, the yields of liquefied oil and low boiling components gradually increas-ed with increasing the amount of CrO3. 1HNMR spectroscopy and ultimate analysis showed that the values of Hα, Hβ, Hγ and σ were larger and those of Ha, fa and Ra were smaller with increasing the amount of CrO3. This means that the average structure of liquefied oil was continuously converted in-to naphtene rings and alkyl side chains with increasing the amount of CrO3. The above facts could sup-port the following mechanism: Cr03 causes oxidative decomposition of coal structure under reducing (CrO3/Cr2O3) temperature. Furthermore, oxidative chromium formed by the reduction of CrO3 pro-motes the hydrogenation of produced oil.
