Tandem conversion of lignin to catechols via demethylation and catalytic hydrogenolysis

Abstract

Lignin is regarded as a potential source of various aromatic compounds and chemicals, replacing petrochemicals. Catechol and its derivatives are important platform chemicals in many industrial sectors, including agrochemicals and pharmaceuticals. The global market of catechols is expected to increase with emerging demand in end-use industries. Considering that the current production of catechols relies on fossil fuels, it is critical to seek alternative renewable sources to respond to sustainability challenges. In this respect, lignin is viewed as a promising material due to its abundance and renewable character. Also, the structural similarity to catechols has made lignin a potential feedstock for the production of bio-catechols. However, the lignin-to-catechols conversion approach is still in an early stage because the intractable nature of lignin and the complex mixture of the depolymerized products make its valorization less feasible. Herein, we report a selective production of catechols via tandem conversion of lignin, namely, demethylation followed by catalytic hydrogenolysis (DFCH). The DFCH of lignin resulted in catechol- and catechol derivatives-rich liquid, accounting for 80 % in the identified products. The reaction mechanisms were also studied by quantum calculations to provide a fundamental understanding of the conversion. The result proves that selective modification of lignin structure is a promising approach to produce specific platform chemicals, providing insights toward an efficient strategy for lignin valorization.