Mutual inhibition effect of hydrogen and ammonia in oxidation processes and the role of ammonia as “strong” collider in third-molecular reactions

Abstract

Ammonia/hydrogen interaction in oxidation chemistry has been extensively valued for traditional flames, while no-experimental evidences have been provided at lower temperatures, relevant for MILD combustion. Herein, ter-molecular reactions play a fundamental role, boosted by “strong” colliders (CO2, H2O). H2O “strong” collider nature derives from its polar nature. Ammonia exhibits a polar behavior similar to water. Given this background, the aim of this work is to value the “strong” collisional nature of ammonia through experimental tests in a Jet Stirred Flow Reactor for H2–O2/Ar or N2 mixtures in presence of H2O or NH3. Results show NH3 inhibits H2 reactivity more than H2O. Numerical analyses suggest a hydrogen/ammonia mutual inhibiting effect under MILD conditions. Simulations are very sensitive to the declaration of NH3 third-body collisional efficiencies in third-molecular reactions in detailed kinetic mechanisms. These effects may infer the possibility to develop economic hydrogen transport/store systems while minimizing ammonia production costs.