Microwave-assisted lignin processing to produce synthesis gas and aromatic compounds

Abstract

Lignin is an abundant raw material, but its utilization in the synthesis of high-added-value products is a great challenge. Microwave activation provides benefits compared to conventional thermal heating in a variety of processes, including catalytic reactions of oxidation and hydrogenation/hydrocracking. Herein, we utilize low-power resonant microwave radiation (5.7 GHz, ≤10 W) to activate and transform lignin, resulting in a significant decrease in the reaction temperature for the onset of catalytic processes compared to conventional thermal activation. The reaction of microwave-assisted partial oxidation of lignin on an Mo_1.0V_0.37Te_0.17Nb_0.12O₃ catalyst yields a synthesis gas product with 57.6% CO selectivity and near-complete lignin conversion at 310–340 °C. The MW-activated hydrocracking of lignin on Pt/C catalysts yields methoxyphenols, alkylated derivatives, as well as light aromatic and aliphatic C₆–C₁₀ hydrocarbon products with a high yield at 260–290 °C. The energy-efficient microwave-assisted approach significantly lowered reaction temperatures compared to conventional heating, highlighting its potential for sustainable lignin valorization.