Distillation as a cornerstone for upgrading pyrolysis oils to drop-in fuels: A systematic review and prospects

Converting biomass, plastic, and waste tire feedstocks into drop-in fuels is constrained by the poor quality and instability of raw pyrolysis oils. This systematic review synthesises 51 experimental studies published between 2007 and 2025 and evaluates eight distillation-based method categories: simple/atmospheric, fractional, vacuum, molecular, steam, reactive, azeotropic, and catalytic distillation. Distillation improved the biomass oil properties, with mean increases in the higher heating value of 58% and mean water reductions of 76%. Plastic- and tire-derived distillates achieved mean higher heating values of 43.5 and 42.1 MJ/kg, respectively, which approached the conventional fuel-property ranges. Method selection is feedstock-dependent: atmospheric and fractional distillation suit hydrocarbon-rich plastic and tire oils, whereas vacuum, molecular, reactive, and azeotropic approaches better limit thermal degradation and improve the dewatering or deacidification of biomass oils. Distillation rarely produces fully specification-compliant fuels alone; its principal role is to stabilise, fractionate, and manage contaminants before downstream catalytic upgrading. Commercialisation requires continuous pilot-scale validation, heat integration, techno-economic assessment, and a fouling-resistant integrated process design.