Recent advances in the acid-catalyzed conversion of lignin

Abstract

As the only natural aromatic high molecular compound that was obtained from a renewable resource, lignin is resistant to conversion due to its complex structure and stable linkages. The catalytic conversion of lignin via acid catalysts leading to a high yield of phenolic monomers has gained great interest due to its potential for producing biofuels and chemicals. However, up to now, the acid-catalyzed conversion of lignin has not yet been comprehensively summarized. In order to fill this gap, mechanism analysis and influential factors of the acid catalysis process and the latest studies and advancements on the catalytic conversion of lignin via various types of acid catalysts, such as mineral acids, organic acids, acidic ionic liquids, immobilized liquid acids, metal salts, metal oxides, heteropoly acids, and zeolites, are systematically outlined and discussed. Although many exciting results have been achieved, the sufficient utilization of lignin by this technology still faces enormous challenges. To improve the technical feasibility, intensive investigations on improving the solubility, catalytic activity, stability, reusability, and designability of the acid catalysts are crucially important and imperative.