Oxidation kinetics of ammonia methanol blends: An experimental and kinetic modeling study

Ammonia is emerging as a key hydrogen energy carrier for decarbonization. However, its low reactivity necessitates blending with hydrocarbons and/or oxygenates, such as alcohols, to improve combustion properties. Understanding the oxidation kinetics of such blends is essential for evaluating ammonia’s potential as a sustainable fuel. The experimental data on ammonia blended with simple alcohols like methanol remains scarce. This study investigates the oxidation kinetics of ammonia/methanol blends for the first time using a plug-flow reactor coupled with a time-of-flight mass spectrometer setup. This advanced setup enabled simultaneous quantification of temperature-dependent reactant conversion and product distribution over a temperature range of 373–973 K, a pressure of 3 bar, and equivalence ratios of 1 and 2. Adding 10 % methanol significantly enhances radical formation, reducing oxidation onset temperature compared to neat ammonia. Interestingly, the conversion onset temperature was only slightly influenced by the mixture composition or the equivalence ratio. The temperature dependence of the product distribution as a function of the equivalence ratio was further analyzed. Experimental results were compared to simulation using selected kinetic models from the literature, revealing significant disparities in predicting capabilities. Among the kinetic models, Shrestha 2025, He 2023 and Wang 2024 performed well, capturing our experimental data for NH₃/CH₃OH blends. Reaction flux and sensitivity analyses highlighted some key reactions involving the reactive combustion species (OH, HO₂ and NH₂), such as CH₃OH+HO₂ ⇌ CH₂OH+H₂O₂ and CH₃OH+NH₂, governing the oxidation kinetics of NH₃/CH₃OH blends. This combined experimental and kinetic modeling approach provides valuable insights into fundamental reaction mechanisms of NH₃/CH₃OH blends, aiding the development of cleaner and more efficient combustion systems.