Exploiting the photocatalytic activity of TiO2 towards the depolymerization of Kraft lignin

Lignin is a promising renewable source of aromatic chemicals. Described herein is a new photocatalytic methodology for depolymerization of oxidized Kraft lignin to industrially relevant aromatic platform chemicals. The photooxidation route begins with oxidation of alcohol moieties using a gold nanoparticle/hydrotalcite composite. Next, the oxidized lignin is subjected to UVA irradiation in the presence of TiO2, leading to a 3-fold decrease of its molecular weight and to the formation of various monolignols. The products obtained in both steps were characterized using FTIR, SEC, GC-MS, and 2D NMR spectroscopy, which confirm the depolymerization of lignin to smaller molecular weight products. This method offers both energetic and chemical advantages over thermochemical processing for lignin valorisation.

Automated summary

A new photocatalytic methodology was developed for the depolymerization of oxidized Kraft lignin to industrially relevant aromatic platform chemicals. The process involves oxidation of alcohol moieties using a gold nanoparticle/hydrotalcite composite, followed by UVA irradiation with TiO2 to decrease the molecular weight of lignin. Characterization of the products confirmed the depolymerization of lignin to smaller molecular weight products. This method offers both energetic and chemical advantages over thermochemical processing for lignin valorisation.