Co(salen) catalysed oxidation of synthetic lignin-like polymer: Pyridine effects

Abstract

Co(salen) [salen = N, N'-bis(salicylidene)ethylenediamine] complexes can perform catalytic oxidations, but their corresponding reaction pathways are still not fully understood. In this study, the Co(salen)catalyzed oxidization of synthetic lignin-like polymer (S- and G-type lignin model polymer) by H2O2 in alkaline aqueous solution in the presence of pyridine was elucidated with FTIR, 13C NMR and gas chromatography–mass spectrometry. Co(salen) was active catalyst, increasing the oxidation rate of the S- and G-type lignin model polymer. The oxidation of lignin model polymer, irrespective of the S- and G-type, occurs selectively at benzylic position as in all experiments as benzaldehyde was the main observed product. The effect of pyridine was noted to be critical and the reactivity of the catalyst increased with addition of pyridine.