Oxidative cleavage of lignin model substrates with Co(salen) catalyst: an experimental study on the effect of different reaction parameters in batch and continuous flow

Abstract

This study investigates the Co(salen)-catalyzed oxidative cleavage of monomeric lignin model substrates to benzoquinones in a continuous flow system and maps the impact of various reaction parameters on the selectivity and yield of the cleavage. Our findings highlight the crucial role of precise oxygen dosing and its interplay with product solubility to achieve a successful reaction. Exposing the substrates to excess oxygen in a continuous flow system resulted in lower yields, while product precipitation was shown to be crucial in batch systems. Additionally, we explored the effects of added bases, oxygen pressure, solvents, and reaction time in a batch set-up. Overall, this work presents a valuable overview of what conditions are favourable when conversion towards benzoquinones is desired and what conditions should be avoided.