Degradation of solvolysis lignin using Lewis acid catalysts

Alcell‐derived lignin was depolymerized in a batch reactor using the Lewis acid catalysts NiCl₂ and FeCl₃. The objective was to investigate the use of Lewis acids in the production of useful liquid products directly from solvolysis lignin. The effects of reaction temperature, time and catalyst were studied on the conversion of this lignin to gas, solid and liquid products. Also, selected monomeric compounds in the ether solubles were monitored in terms of the variation in their yields with different reaction conditions. The highest conversions, 30% and 26% from Ni and Fe, respectively, were both attained at the reaction conditions of 305°C and 1 h reaction time. The Ni produced a somewhat higher yield of ether solubles, reflecting its slightly higher performance. Under the reaction conditions studied, both catalysts apparently favour condensation reactions leading to the formation of insoluble reactor residue from solvolysis lignin. Low quantities of monomeric compounds were produced, with phenols dominating over ketones and aldehydes for both catalysts.