On the co-liquefaction of high rank coal (Huaipei coal) and Co exchanged low rank coal (Adaro coal), the yield of residue was higher than the yield calculated from those individual liquefactions. On the other hand, the yield of residue was lower than the calculated yield on the co-liquefaction of Yilan coal and Co exchanged Morwell coal. It was considered that the catalytic effect of Co for the liquefaction of coal appeared due to the fine dispersion of Co on the coal surface.
