Demethylation of Lignin in Inorganic Ionic Liquid

This work describes the demethylation of lignin and model compounds in an inorganic ionic liquid (acidic lithium bromide trihydrate – ALBTH), which was previously proved to be effective for the saccharification of cellulose and hemicellulose, the simultaneous isolation of lignin from lignocellulose biomass, and the selective cleavage of aryl ether bonds in lignin. In this study, creosol, syringol and 1,2,3-trimethoxybenzene, as lignin model compounds, were successfully converted to corresponding phenols in this system via demethylation. Organosolv ethanol poplar lignin was demethylated under the optimized conditions, and 72% of methoxyl groups were converted to aromatic hydroxyl groups with an 81% selectivity.