Humic acid derived from Loy Yang coal and the product of mild O-methylation of this humic acid have been reacted with CO/H2O/sodium aluminate (NaAlO2) and H-2/Ni/Mo in 35 mi autoclaves at 365 degrees C and 400 degrees C. The O-methylated humic acid gave lower conversions for CO/H2O/NaAlO2 reactions than the original humic acid but similar conversions for H-2/Ni/Mo reactions. These results provide strong evidence in support of the mechanistic proposals of Ross for the involvement of phenols in the initial stages of low rank coal liquefaction with CO/H2O/NaAlO2 but much less evidence for their involvement in H-2/Ni/Mo reactions. The humic acid and methylated humic acid have also been reacted with H-2/MeOH both with and without added ZnCl2 catalyst. The results are compared with previous work of Kuznetsov et al. and confirm that the autoclave constitutes a well-mixed system and that the H-2/MeOH/ ZnCl2 system more closely resembles the H2/Ni/Mo rather than the CO/H2O/NaAlO2 system.