Ammonia decomposition using 15N labelled ammonia was performed over a lithium imide (Li2NH) catalyst with mass spectrometry (see Figure 1). The results show that all the nitrogen is released from the bulk of the lithium imide catalyst during the ammonia decomposition reaction as determined by the 14N-containing species observed in the mass spectrometer. Comparison of the 14N15N signal with that expected for an ideally scrambled system shows, however, that the decomposition itself occurs at the catalyst surface. A reaction mechanism is proposed which entails the action of a lithium-rich intermediate (proposed to be lithium nitride hydride, Li4NH), which reacts with ammonia to produce lithium imide and hydrogen. Mixtures of lithium imide with transition metals also indicate that lithium imide decomposes ammonia and does not merely act as a promoter to transition metal catalysts.

Isotopic studies of the ammonia decomposition reaction using lithium imide catalyst

254th National Meeting (2017)

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