Synchronous catalytic depolymerization of alkaline lignin to monophenols with in situ-converted hierarchical zeolite for bio-polyurethane production

Catalytic depolymerization of lignin to high-value chemicals is crucial to the comprehensive achievement of sustainable and economic concerns. Herein, we propose a green, practical, and economic strategy for the synchronous catalytic depolymerization of lignin based on in situ conversion of geopolymer precursor to hierarchical zeolite, using water as a mild solvent and without external H-2, additives, co-catalysts or co-solvents. The in situ-converted hierarchical analcime (ANA) zeolite outperformed previously reported representative catalysts, such as PTA/MCM-41 and CuAlMgOx in lignin depolymerization with a high monophenol yield (95.61 +/- 7.89 mg/g). The synergetic effect of the micro-mesoporous structure and enhanced acidic sites of the ANA played a vital role in regulating the monomer composition and the yield of monophenols. The obtained monophenols are rich in -OH groups and can be utilized as a substitute for petroleum resources, such as ethylene glycol or glycerin for the synthesis of bio-polyurethane foams (bio-PUFs). This work expands the scope of using biomass in a sustainable manner to make high-value chemicals and biomaterials.

Automated summary

This work proposes a green, practical, and economic strategy for the catalytic depolymerization of lignin using water as a solvent and in situ conversion of geopolymer precursor to hierarchical zeolite. The in situ-converted hierarchical analcime zeolite showed excellent catalytic performance in lignin depolymerization, producing high yields of monophenols. These monophenols, which are rich in -OH groups, can be used as substitutes for petroleum resources in the synthesis of bio-polyurethane foams and other high-value chemicals.