Reaction Kinetics of NH2 With H2CO and CH3CHO: Modeling Implications for NH3-Dual Fuel Blends

Carbon-free fuels like ammonia (NH₃) and hydrogen (H₂) offer significant potential in combating global warming by reducing greenhouse gas emissions and moving toward zero carbon emissions. Over the past few years, our research has focused on understanding the combustion behavior of carbon-neutral and carbon-free fuels. In particular, we have explored the combustion characteristics of NH₃ when blended with various hydrocarbons and oxygenates. Our investigation revealed that carbon-nitrogen cross-chemistry plays a crucial role in shaping the combustion properties of NH₃-hydrocarbon/oxygenate blends. Specifically, the chemistry of amino (NH₂) radicals is vital in influencing the low-temperature reactivity of these blends. Understanding the interactions between carbon and nitrogen is essential for optimizing combustion processes and improving the emissions profile of NH₃-based fuels. Recognizing the significance of this cross-chemistry, we investigated the reaction kinetics of NH₂ radicals with formaldehyde (H₂CO) and acetaldehyde (CH₃CHO) using high-level ab initio and transition state theory calculations. We computed the potential energy profiles of these reactions at the CCSD(T)/CBS//M06-2X/aug-cc-pVTZ level of theory to analyze the reactivity of NH₂ radicals at various C─H bond sites. The newly derived rate constants have proven to be highly sensitive for modeling the low-temperature oxidation of NH₃-dual fuel blends, significantly enhancing the predictive accuracy of our previously published kinetic models. This work offers valuable insights into the role of NH₂ radicals, thereby advancing the development of NH₃-dual fuel systems.