Lignin depolymerization in hydrogen-donor solvents

The conversion of different types of lignin to monophenolic compounds has been studied between 500 and 650 K, under typical coal liquefaction conditions using 9,10-dihydroanthracene (AnH(2)) and 7H-benz[de]anthracene (BzH) as the hydrogen-donor solvents. The yield of phenolic compounds was found to increase with the capacity of the hydrogen donor. The application of a polar cosolvent appeared to be beneficial as well. The differences in product distribution could be related to the origin of lignin. The maximum yield amounted to 11 % after 4 h at 625 K using milled wood lignin in AnH(2). It has been found that lignin itself is a hydrogen-donating substance and capable of cleaving aromatic ketones such as alpha-phenoxyacetophenone.