Synthesis of renewable nylon monomers with poplar wood

Abstract

The substitution of fossil energy with biomass as the feedstock for polymer production has drawn tremendous attention. Here, we describe a process for the synthesis of nylon monomers (3-methylglutaric acid [MGA], glutaric acid [GA], dimethyl adipate [DMAP], and dimethyl methyladipate [DMMAP]) with poplar wood. This process involves the selective hydrogenolysis of cellulose and hemicellulose into 2,5-hexanedione (HD) and cyclopentanone (CPO) in an acid-free system, the cascade intramolecular aldol condensation/hydrogenation of HD to 3-methylcyclopentanone (MCPO), and the catalytic oxidation of MCPO and CPO to GA and MGA (or a condensation/ring-opening reaction of MCPO and CPO to DMAP and DMMAP). Experiments reveal that the presence of Cl− ions restrains the decarbonylation and the furan-ring hydrogenation over the Pd/C catalyst, which leads to high selectivity of HD and CPO in the hydrogenolysis process. This work offers a new method for the direct conversion of raw biomass without the separation of cellulose, hemicellulose, and lignin.