Hydrothermal Liquefaction of Lignin

Abstract

The majority of platform chemicals are currently provided through crude oil processes. Nevertheless, the substitution of the crude oil with biomass should be the ecological aim. Lignin, an aromatic macromolecule, may play an important role in that exchange, as it is the only bio based source of aromatic compounds. For instance, it could be a source of bifunctional aromatic molecules, like the monocyclic compounds catechol or guaiacol, or bifunctional oligomers. However, no process for the production of aromatics from lignin in technical scale has been established until now. Hence, the focus of this work is to clarify the chemical degradation mechanism under hydrothermal conditions, to liquefy lignin delivering high functional molecules and to increase the yield and selectivity of the cleavage towards bifunctional molecules like catechol. The combination of fast hydrolysis, thermal degradation reactions and hydrogenation drives the hydrothermal liquefaction; this gives the possibility to narrow down the product spectrum in comparison to other “dry” cleavage methods, towards a higher yield of e.g. catechols.