Synergistic effect in the co-pyrolysis of lignin and petrochemical heavy oil: Kinetic characteristics and product composition

Lignin and heavy oil (HO) possess complementary properties, thus rendering their synergistic co-pyrolysis a promising strategy to overcome the limitations of their individual pyrolysis processes. This study is designed to advance biomass valorization, facilitate the clean utilization of heavy oil, and enable the production of high-quality fuels. In this study, the co-pyrolysis behavior of lignin and HO was investigated using an integrated TG-FTIR-MS system combined with fixed-bed pyrolysis experiments, with a focus on the kinetic characteristics and synergistic effects at different HO blending ratios (10 %, 30 %, and 50 %). The results revealed a significant overlap in the primary pyrolysis temperature ranges of lignin (152.43°C-598.77 °C) and HO (68.68°C-402.34 °C). Kinetic analysis based on the FWO and DAEM methods demonstrated that the average activation energy during co-pyrolysis decreased progressively below the theoretically calculated values with increasing HO content. Fourier transform infrared analysis indicated enhanced C–H absorption peak intensities and reduced C–O peaks. A notable synergistic effect was observed at the C–H absorption peak when the HO blending ratio reached 50 %, which confirmed the feasibility of co-pyrolysis. Fixed-bed pyrolysis experiments further confirmed that co-pyrolysis increased the yields of phenolic and aromatic compounds, thereby improving the overall quality of the pyrolysis oil. This study provides fundamental data to support the development of innovative co-conversion pathways for lignin and petroleum-based HO.