Bond cleavage of lignin model compounds into aromatic monomers using supported metal catalysts in supercritical water.

More efficient use of lignin carbon is necessary for carbon-efficient utilization of lignocellulosic biomass. Conversion of lignin into valuable aromatic compounds requires the cleavage of C-O ether bonds and C-C bonds between lignin monomer units. The catalytic cleavage of C-O bonds is still challenging, and cleavage of C-C bonds is even more difficult. Here, we report cleavage of the aromatic C-O bonds in lignin model compounds using supported metal catalysts in supercritical water without adding hydrogen gas and without causing hydrogenation of the aromatic rings. The cleavage of the C-C bond in bibenzyl was also achieved with Rh/C as a catalyst. Use of this technique may greatly facilitate the conversion of lignin into valuable aromatic compounds.