Tar classification and analysis for the co-pyrolysis of oil-rich coal and lignocellulosic biomass

Pyrolysis is a key thermochemical pathway for converting carbonaceous resources into valuable fuels and chemicals. Tar, the primary liquid product of pyrolysis, exhibits complex and varied composition, which poses significant challenges to its characterization and utilization. To improve the utilization efficiency of tar, this study proposes a comprehensive classification framework for tars derived from the co-pyrolysis of lignocellulosic biomass and Xinjiang oil-rich coal. This framework integrates temperature-dependent evolution behavior with molecular structural features, offering new insight into tar component analysis. It is found that biomass addition significantly enhances the formation of primary oxygen-containing compounds (by up to 21.6%) and alkanes (up to 35.0%), while markedly suppressing phenolics and heavy PAHs. Moreover, co-pyrolysis improved tar yield by 2.0–7.0% compared to individual coal pyrolysis, demonstrating clear synergistic effects through the proposed classification system. These enhancements are attributed to biomass-derived hydrogen radicals that stabilize coal pyrolysis intermediates and inhibit aromatization, coupled with early release of oxygenated volatiles from biomass at lower temperatures. The aromaticity of the coal significantly influences the extent and nature of these synergistic interactions. This work provides a classification model and a mechanistic explanation of the synergistic production of upgraded liquid fuels through the co-pyrolysis of biomass and coal. © 2026 Elsevier Ltd.