Single-step conversion of wood lignin into phenolic amines

Abstract

•Woody lignin is directly converted into aromatic amines •Lignin is selectively removed while (hemi)cellulose is kept intact •The process does not compromise the further processing property of (hemi)cellulose •The aromatic amines have the potential to be upgraded into useful fine chemicals Although the transformation of lignin monomers and model compounds into nitrogenated chemicals has been actively investigated, the production of organonitrogen chemicals directly from lignin has been scarcely reported. Here, we communicate a single-step catalytic strategy for producing phenolic amines directly from wood lignin via reductive fractionation in an aqueous ammonia-alcohol mixture over Ru catalyst. Depending on the type of alcohol used, primary, secondary, and ternary phenolic amines can all be synthesized and reach a maximum yield of 26.6%. During the process, native lignin was selectively removed from woody biomass, leaving other constituents, especially (hemi)cellulose, largely unaffected. The obtained phenolic amines were further upgraded into products with enhanced functions. This work exemplifies the possibility for the production of N-functional compounds from lignin, expanding the options for the lignin-first strategy in biomass refinery. Although the transformation of lignin monomers and model compounds into nitrogenated chemicals has been actively investigated, the production of organonitrogen chemicals directly from lignin has been scarcely reported. Here, we communicate a single-step catalytic strategy for producing phenolic amines directly from wood lignin via reductive fractionation in an aqueous ammonia-alcohol mixture over Ru catalyst. Depending on the type of alcohol used, primary, secondary, and ternary phenolic amines can all be synthesized and reach a maximum yield of 26.6%. During the process, native lignin was selectively removed from woody biomass, leaving other constituents, especially (hemi)cellulose, largely unaffected. The obtained phenolic amines were further upgraded into products with enhanced functions. This work exemplifies the possibility for the production of N-functional compounds from lignin, expanding the options for the lignin-first strategy in biomass refinery.