Aromatic acids have wide applications in pharmaceutical industry, antioxidant in the food industry, and monomeric precursor for high performance plastics. Therefore, the conversion of lignin, the most abundant aromatic polymers in nature, to value-added aromatic acids, serves as a critical sustainable approach. However, instead of aromatic acids, current research shows aromatic aldehydes represent a significant portion of the lignin depolymerized products. Lignin derived aromatic aldehydes usually have hydroxyl group at para position and methoxy groups at para position. These substitute groups introduce possibilities of generating unwanted byproducts during an oxidation reaction, resulting in low yield of aromatic acid products. Previous research also show that expensive and complicated catalysts or harsh reacting conditions are required to oxidize phenomonomeric aldehydes to corresponding aromatic acids. The conversion from lignin is even more challenge due to the complicated and heterogeneous structure of lignin polymer. In this study, we investigated that the introduction of acetyl group in vanillin or lignin derived aromatic aldehydes prevents unwanted side reactions. The yield of aromatic acids could be significantly increased up to 90% conversion yield using eco-friendly and economical catalyst system from the lignin model compound study. After that, the method was tested for three pristine lignins under the optimized reaction condition. The total yield of aromatic acids could be up to 17.9% (based on lignin) via a two-step oxidative process from the pristine lignin.

Selective conversion of lignin to aromatic acids in high yield via two-step oxidation method

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.