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

Xue-Fei Zhou,Jing Liu

doi:10.2298/hemind120124031z

Abstract

In this paper, Co(salen) [salen = N, N?-bis(salicylidene)ethylenediamine] complex was studied as oxygen activators for the catalytic oxidation of a lignin model polymer using water as the solvent, with molecular oxygen and hydrogen peroxide as the oxidants. The effect of Co(salen) on oxidation was tested by spectroscopic methods (FTIR, 13C-NMR and GC-MS). The reactions catalysed by Co(salen) included C?-alcohol oxidation, C?-C? side chain cleavage, demethoxylation, aromatic ring cleavage, and ?-O-4 cleavage. In addition to the mechanistic information obtained, the effect of Co(salen) suggests that Co(salen) can be important for the catalytic oxidation, as they affect the oxidation of lignin model polymer. The reaction performed in the presence of Co(salen) was more efficient than without it. The formation of aldehyde in the catalytic oxidation, as shown by GC-MS, could be identified as the mechanism of oxidative cleavage of the ?-O-4 bonds.

Highlights

Salen-type transition metal complexes are an important class of organometallic compounds, which have been used since 1933 as catalysts for a wide variety of reactions
In this paper, Co(salen) complex, salen = N,N’-bis(salicylidene)ethylenediamine, was studied as oxygen activator for the catalytic oxidation of a lignin model polymer using water as the solvent, with molecular oxygen and hydrogen peroxide as the oxidants
The Fourier transform infrared spectroscopy (FTIR) and 13C-NMR of lignin model polymer are presented in Figures 4 and 5

Summary

Introduction

Salen-type transition metal complexes are an important class of organometallic compounds, which have been used since 1933 as catalysts for a wide variety of reactions. We have used guaiacyl-type (G-type) lignin model polymer that include native β-O-4 linkage to investigate the relationship between lignin structure and Co(salen) catalytic process. Referring to the methods of Kishimoto et al [10], the lignin model polymer composed of only the β-O-4 structure were prepared using simple aromatic compounds as starting materials.

Results

Conclusion