Catalytic lignin valorization over HSZ-supported CuNiAl-based catalysts with microwave heating

Abstract

Microwave assisted lignin depolymerization was investigated over HSZ-supported CuNiAl-based catalysts. The synergistic effect between the acidic HSZ support and mixed metal oxides was studied in detail to explore the difference in catalytic activity during the lignin depolymerization process. Improvements in bio-oil properties, such as the H/C ratio and HHV value, were observed in comparison with raw lignin under rather mild conditions (140 °C, 80 min) in the absence of external hydrogen. The molecular weight of bio-oil obtained over HSZ-supported catalysts decreased, indicating that the increased acidity in the catalyst could facilitate microwave assisted lignin depolymerization. The product distributions in bio-oil were also analyzed and plausible depolymerization mechanisms were proposed considering the distributions of lignin-derived dimers/trimers and monomers.