This thesis describes the preparation and reactivity of lithium molybdenum nitride samples and the preparation and characterisation of the nitride precursors. It has been shown that samples containing lithium molybdenum nitride (LiMoN2) can be formed from the direct ammonolysis of lithium molybdate (Li2MoO4), although it has proved challenging to produce the nitride as a single phase material.
The “LiMoN2” samples were observed to be catalytically active for ammonia synthesis in reaction with nitrogen containing feed gas (25% N2/H2). An impurity, which cannot be indentified through powder X-ray diffraction, was demonstrated to be the likely active phase in the sample.
The role of ‘lattice’ nitrogen in the ammonia synthesis reaction was investigated through reactions with a feed gas with no source of nitrogen present (25% Ar/H2). It was shown that this proposed active phase will produce ammonia, in the absence of nitrogen in the feed gas.
One candidate impurity that could be responsible for this anomalous activity was lithium nitride. Reactions were conducted and it was seen that lithium nitride was very active in the production of ammonia. Subsequent investigations showed that the generation of ammonia probably originates from the direct decomposition of lithium amide.
Gregory, Prof Duncan H. and Hargreaves, Dr Justin S. J.