Fast pyrolysis of biomass: recent advances in molecular-level reaction mechanisms and detailed kinetic modeling

Fast pyrolysis offers a promising pathway for converting biomass into liquid bio-oil, yet its high oxygen content, chemical instability, and complex composition hinder direct application as fuels or chemicals. Recent advances in experimental platforms and computational methods have reshaped research in this field. Multidimensional chromatography, high-resolution spectroscopies, synchrotron-based diagnostics, and quantum chemical modeling now enable accurate quantification of products, detection of reactive intermediates, and the development of predictive kinetic frameworks for individual yields. These innovations provide the scientific context for more systematic evaluations of biomass pyrolysis chemistry and facilitate the establishment of mechanistic links between molecular-level reactions and process performance. To ensure comprehensive coverage and transparency, this review applies the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines for literature selection and analysis. Through this systematic approach, key studies on model compounds—including cellulose, hemicellulose, and especially lignin derivatives—are critically assessed, highlighting bond scission routes, reaction intermediates, cross-component coupling, and the origins of major pyrolysis vapors. The resulting insights have informed the construction of detailed kinetic models, though challenges remain in addressing multiphase effects, expanding reaction families, and reducing uncertainties in large-scale simulations. By integrating state-of-the-art methodologies with systematic literature synthesis, this review identifies both progress and persisting gaps in molecular-level understanding of fast pyrolysis, providing guidance for advancing detailed kinetic modeling and accelerating the development of efficient, mechanism-based pyrolysis technologies.