Nakayama lignite that contained much humus easily reacted with chromic anhydride (CrO
3) in aqueous solution. CrO
3 was reduced to Cr
2O
3 at the temperature coal pyrolysis oc-curred (<500°C). Therefore, the hydrogenation of Nakayama lignite pre-treated with CrO
3 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 CrO
3.
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 CrO
3. 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 CrO
3. The above facts could sup-port the following mechanism: Cr0
3 causes oxidative decomposition of coal structure under reducing (CrO
3/Cr
2O
3) temperature. Furthermore, oxidative chromium formed by the reduction of CrO
3 pro-motes the hydrogenation of produced oil.
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