Wood Thomas J, Makepeace Joshua W, David William I F
ISIS Facility, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, OX11 0QX, UK.
Phys Chem Chem Phys. 2017 Oct 18;19(40):27859-27865. doi: 10.1039/c7cp04494a.
Ammonia decomposition over iron catalysts is known to be affected by whether the iron exists in elemental form or as a nitride. In situ neutron diffraction studies with simultaneous gravimetric analysis were performed on the nitriding and denitriding reactions of iron under ammonia decomposition conditions. The gravimetric analysis agrees well with the Rietveld analysis of the neutron diffraction data, both of which confirm that the form of the iron catalyst is strongly dependent on ammonia decomposition conditions. Use of ammonia with natural isotopic abundance as the nitriding agent means that the incoherent neutron scattering of any hydrogen within the gases present is able to be correlated to how much ammonia had decomposed. This novel analysis reveals that the nitriding of the iron occurred at exactly the same temperature as ammonia decomposition started. The iron nitriding and denitriding reactions are shown to be related to steps that take place during ammonia decomposition and the optimum conditions for ammonia decomposition over iron catalysts are discussed.
已知铁催化剂上的氨分解会受到铁是以单质形式存在还是以氮化物形式存在的影响。在氨分解条件下，对铁的氮化和脱氮反应进行了原位中子衍射研究，并同时进行了重量分析。重量分析与中子衍射数据的Rietveld分析结果吻合良好，二者均证实铁催化剂的形态强烈依赖于氨分解条件。使用具有天然同位素丰度的氨作为氮化剂意味着，所存在气体中任何氢的非相干中子散射都能够与分解的氨量相关联。这种新颖的分析表明，铁的氮化恰好发生在氨分解开始的温度。铁的氮化和脱氮反应与氨分解过程中发生的步骤相关，并讨论了铁催化剂上氨分解的最佳条件。
