Catalytic functionalization of lignin oils derived from reductive catalytic fractionation of lignocellulosic biomass

Abstract

This project aims to functionalize the oligomer fractions of lignin oils (LO) obtained through reductive catalytic fractionation (RCF) into antioxidants for biolubricants. Two routes were explored: an indirect ester synthesis via alkoxycarbonylation with methanol (MeOH AKC) followed by transesterification and a direct route using heptanol for the AKC reaction (HeptOH AKC). The products were quantified using 2D HSQC NMR. In the indirect route, MeOH AKC converted 100% of the double bonds into carboxymethyl esters (ME), which were then transesterified with heptanol using various catalysts. The best results were obtained with 10% KOH, providing a more specific reaction with 55.9% heptyl ester yield relative to ME compared to H2SO4, which produced a yield of 230% (Heptyl ester related to ME), thus less specific. The direct route examined four conditions, varying additives and reaction times. The highest yield (68.2%) was achieved with RCFLO, HeptOH, and BmimCl for 36 hours, while a 20-hour reaction was more specific but had a lower yield of heptyl esters (45%). The economic analysis indicated that the direct ester synthesis reduced costs by 24% due to fewer washing steps and overall process simplification, highlighting its potential for efficient production in the future.