Bagasse lignin depolymerization into p-hydroxycinnamate esters in a novel microemulsion reactor

The new technology for lignin to value-added aromatic chemicals is of great significance in the fields of spices, cosmetics and pharmaceutical industry. Herein, a novel surfactant-free microemulsion reactor composed of methanol, n -butanol and n -hexane was designed for bagasse lignin depolymerization and in-situ esterification to p -hydroxycinnamate esters (PCE) using dicationic ionic liquid as the catalyst. Due to amphipathy of the ionic liquid and lignin, both of them can be enriched on the surface of so constructed microemulsion, resulting to an efficient process intensification for lignin conversion. Therefore, 13.8 % yield of PCE are obtained with a selectivity of 81.2 % after 4 h at 453 K. Experimental results about lignin model compound conversion reveal that the dicationic ionic liquid can efficiently activate the C-O and ester bonds in lignin and enhance the in-situ esterification process to generate PCE selectively. Therefore, this work provides a novel strategy for producing PCE from agricultural residues under mild conditions.