Well-characterized coals of different H/C atomic ratio and rank were reacted at 365°C with CO, H2 and COH2 mixtures in water in the presence and absence of sodium aluminate. The optimum H2/CO ratio for conversion was found to vary with the type of coal. It was <1 : 1 for low-rank and subbituminous coals, whereas the conversion of bituminous coals either did not vary with H2/CO ratio or reached a maximum at a higher H2/CO ratio (2 : 1). Even for a bituminous coal there was no advantage in reducing the water/coal ratio below 2 : 1 in NaAlO2-catalysed reactions. The conversions increased with increasing H/C atomic ratio of the coal and decreasing rank, with or without NaAlO2. Asphaltene yields increased with increasing coal rank and increasing proportion of CO in the H2CO reacting gases. The mechanistic implications of these results are briefly discussed.
- coal liquefaction
- COH mixtures