Chemical alteration of coals and their reactivity with tetralin and methanol under liquefaction conditions

The effect was studied of pretreatment techniques, including O-methylation with (CH3)2SO4, reduction with both K-isopropanol in THF and LiAlH4, reductive methylation with KCH3I in THF and combination thereof, on the extractability in THF of coals of different rank and on their reactivity in non-catalytic hydroliquefaction in methanol and tetralin at 380 °C. Dramatic changes in composition of the treated coals and products were found. Chemical pretreatment had a beneficial effect on coal solubility in THF and on hydroliquefaction in tetralin. O-methylation was the most effective for lignite, but reductive methylation had the most beneficial effect for high-rank coal. With methanol as solvent, reduction and O-methylation had a small effect on coal reactivity for liquefaction. The role of cross-links is discussed in order to explain the liquefaction behaviour of coals in solvents.