Effect of Cu-modified HZSM-5 zeolites on catalytic pyrolysis of lignin to producing aromatic hydrocarbons

Lignin catalytic pyrolysis presents a promising and sustainable approach to producing aromatic molecules. Herein, we investigated the effect of modified zeolite with copper (Cu/HZSM-5) catalyst on efficiently pyrolyzed kraft lignin into aromatic hydrocarbons (AHs) production, especially mononuclear aromatic hydrocarbons (MAHs). Time-of-flight mass spectrometry (TOF-MS) was employed to compare the volatile product profiles of lignin during catalytic pyrolysis. The highest yield of MAHs reached 70.59 mg/g based on dry lignin at 550 °C, accounting for 70.23% among lignin pyrolysis products, compared to the pristine HZSM-5 zeolite catalytic system with MAHs yield of only 54.31 mg/g and of 40.34% in products. At 550 °C and 60 s residence time, the 5% Cu/HZSM-5 catalyst demonstrated the best performance compared to all other catalysts in terms of selectively producing MAHs. The results are ascribed to the enhancement of decarboxylation and aromatization processes by the doping of copper. This work demonstrates a cost-effective pathway that potentially converts kraft lignin into aromatic hydrocarbon production at a phenomenally high selectivity, providing a concept for industrial application toward biomass utilization and high value-added production.