One-step depolymerization of calcium lignosulfonate to produce phenolics with the action of solid base oxides

Abstract

Lignin, as the world’s second-largest biomass resource, has a low utilization rate. Converting lignin into high-value chemicals can not only alleviate the shortage of fossil fuels but also reduce environmental pollution caused by indiscriminate accumulation and combustion. In this study, a method for preparing phenolic compounds by depolymerization of calcium lignosulfonate (CLS) catalyzed by solid base oxides was proposed. MgO, NiO, Fe _2 O _3 , binary metal oxides (MgFeO _x and NiFeO _x ), and ternary metal oxide (NiMgFeO _x ) were synthesized. MgO, NiO, and Fe _2 O _3 exhibit pure and regular structures. The binary and ternary metal oxides synthesized using hydrotalcites as precursors exhibit layered morphologies and process distinct primary and secondary phases. The alkalinity of oxides can be adjusted through the synergistic effect of Ni, Mg, and Fe. Under the catalytic action of metal oxides, the selectivity of hydrocarbons in gaseous products increases, along with the yield of liquid products. The presence of multiple metal elements enhances catalytic performance, indicating the synergistic effects among metal elements. NiMgFeO _x demonstrates the highest catalytic efficiency, achieving a liquid product yield of 75.8 wt% and a total phenolic compound selectivity of 78.6%. After five cycles of catalytic regeneration, NiMgFeO _x maintains its satisfactory structure and catalytic stability. This study provides both theoretical and experimental insights into CLS depolymerization catalyzed by solid base oxides.

Keywords

• solid base oxides
• calcium lignosulfonate (CLS)
• phenolic compounds
• hydrolysis