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Updated: Apr 24, 2026
Ammonia Synthesis at Low Pressure
Published on: August 23, 2017
Kinetics of the NH3 and CO2 solid-state reaction at low temperature
J A Noble1, P Theule, F Duvernay
1Aix-Marseille Univ., CNRS, PIIM UMR 7345, Marseille, 13397, France. patrice.theule@univ-amu.fr.
Abstract:
Ammonia and carbon dioxide play an important role in both atmospheric and interstellar ice chemistries. This work presents a theoretical and experimental study of the kinetics of the low-temperature NH3 and CO2 solid-state reaction in ice films, the product of which is ammonium carbamate (NH4(+)NH2COO(-)). It is a first-order reaction with respect to CO2, with a temperature-dependent rate constant fitted to the Arrhenius law in the temperature range 70 K to 90 K, with an activation energy of 5.1 ± 1.6 kJ mol(-1) and a pre-exponential factor of 0.09-0.08(+1.1) s(-1). This work helps to determine the rate of removal of CO2 and NH3, via their conversion into ammonium carbamate, from atmospheric and interstellar ices. We also measure first-order desorption energies of 69.0 ± 0.2 kJ mol(-1) and 76.1 ± 0.1 kJ mol(-1), assuming a pre-exponential factor of 10(13) s(-1), for ammonium carbamate and carbamic acid, respectively.
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