Investigating Oxidation Characteristics and Pollutant Formation of the Light Distillate Fraction of Tire Pyrolysis Oil

This work explores the oxidation and pollutant formation characteristics of the light-distillate fraction of tire pyrolysis oil (TPOLight), whose physicochemical properties are comparable to those of commercial gasoline, indicating its potential as an alternative waste-derived fuel. Due to the compositional complexity of TPOLight, a surrogate fuel was formulated for fundamental combustion studies using a palette of pure compounds representing paraffins, aromatics, olefins, and naphthenes. The surrogate components were selected based on detailed hydrocarbon and functional group analyses. An optimization workflow identified the surrogate mixture that reproduces the key physicochemical (i.e., heating value, H/C ratio, density, etc.) and reactivity metrics of TPOLight. Oxidation experiments were conducted in a jet-stirred reactor (JSR) to compare the intermediate and final species from TPOLight and the surrogate across matched equivalence ratios (ϕ) and temperature ranges. Thereafter, pyrolysis tests were performed using the validated surrogate to assess the propensity for polycyclic aromatic hydrocarbons (PAH) and soot formation under fuel-rich conditions. Numerical simulations using an established kinetic model for the surrogate species were also carried out to identify operating windows for TPOLight that favor reduced pollutant formation. Operational maps indicate that fuel-lean operation at moderate-to-high temperatures (>800 °C) could suppress the formation of PAHs during TPOLight oxidation, as its aromatic and cyclic constituents may otherwise favor their production under fuel-rich conditions. The presence of a trace tar-like residue in the exhaust lines at ϕ > 1 during experiments with the real fuel further supports the idea of operating under lean conditions. This study provides foundational combustion and pyrolysis experimental data for TPOLight and defines a framework for subsequent investigations of its combustion and pollutant formation behavior using conventional experimental and modeling platforms.