Advancing the generalized kinetic model for wet oxidation and its application to hydrothermal liquefaction aqueous phases

Hydrothermal liquefaction (HTL) of organic feedstocks generates aqueous phases (APs) rich in organics and nitrogenous compounds, creating both treatment challenges and opportunities for resource recovery. This study presents a structurally lean kinetic model, adapted from a Generalized Kinetic Model (GKM), to describe HTL-AP behavior under continuous wet oxidation (WO) conditions. Kinetic parameters for three reaction pathways were derived by fitting experimental data, and the model was implemented in Aspen Plus® for process simulation. The model was tested with two compositionally distinct HTL-APs by predicting total organic carbon (TOC), chemical oxygen demand (COD), acetic acid (AA), ammonium (NH₄ + ), and heat release. For one sample, good agreement was achieved across all indicators, with an average normalized root mean square error (NRMSE) of 15% and a mean R 2 of 0.78. For the second sample, TOC and COD were well predicted, while larger deviations for AA and NH₄ + indicated the need for improved representation of intermediate formation and oxidation dynamics. Overall, the model captures the key transformation pathways of HTL-AP during WO and is designed for system-level scenario analysis of integrated HTL–WO refinery concepts. It is therefore intended to support future techno-economic and life-cycle assessments.