Process of lignin oxidation in an ionic liquid coupled with separation

A novel approach has been developed in order to use lignin as a renewable resource for the production of a high added-value aromatic aldehyde. The concept is based on the use of an ionic liquid as a reversible medium coupled with the separation process, which prevents the aromatic aldehyde products from oxidizing and increases their yields. The conversion of lignin reached 100%, and the total yield of the aromatic aldehydes (vanillin, syringaldehyde and p-hydroxybenzaldehyde) was 29.7% in the coupled process. In addition, the mixture of product and IL phase was easily separated, and the IL phase demonstrated good reusability. Hence, a clean and environmentally friendly strategy for overall utilization of lignin and preparation of an aromatic aldehyde is developed.