First principles design of novel ammonia synthesis catalysts

用于工业规模合成氨的哈伯-博施工艺的开发是世纪的主要成就之一。通过提供一条获取合成肥料的途径，它可以直接归功于维持全球人口。该方法基于纯N2和H2进料流在促进的铁基催化剂上的反应。它在高压（>100个大气压）和中等温度下运行，整个过程目前占全球能源需求的很大比例（>1%）。在这项研究中，我们试图开发替代催化剂，通过在较低的反应温度下促进反应（在那里有热力学优势）来节省能源。所采取的方法将涉及计算设计和实验测试的混合物，并且基于先前对金属氮化物催化剂的研究，所述金属氮化物催化剂表现出令人感兴趣的氨合成活性。金属氮化物在其结构内潜在地含有“活化”氮，并且这种晶格氮的反应性可能是其高活性的关键。使用计算建模，理解实验结果将获得，并将扩展到潜在的高催化活性的氮化物材料的识别。在平行的实验室实验中，将合成和测试所确定的材料，并将结果反馈到计算模型中，以提供更好的理解。以这种方式，将确定最佳的催化剂配方，并且将在工业相关的氨合成条件下制备和测试这些配方，并且将结果与来自常规工业应用的铁基催化剂的那些进行比较。

The development of the Haber Bosch Process for the synthesis of ammonia on an industrial scale was one of the major achievements of the 20th Century. It can be directly credited with sustaining the global population through the provision of an accessible route to synthetic fertilizers. The process is based upon the reaction of pure N2 and H2 feedstreams over a promoted iron based catalyst. It is operated at high pressure (>100 atmospheres) and moderate temperature and the process as a whole currently accounts for a significant proportion of global energy demand (>1%). In this research, we are attempting to develop alternative catalysts which will contribute to energy savings by facilitating the reaction at lower reaction temperatures (where there is a thermodynamic advantage.) The approach to be taken will involve a mixture of computational design and experimental testing and is based upon previous studies of metal nitride catalysts which exhibit interesting activity for ammonia synthesis. Metal nitrides potentially contain "activated" nitrogen within their structure and it is the reactivity of this lattice nitrogen which which could be the key to their high activity. Using computational modelling, understanding of experimental results will be obtained and will be extended to the identification of nitride materials of potential high catalytic activity. In parallel laboratory experiments, the identified materials will be synthesised and tested and the results fed back into the computational modelling to provide improved understanding. In this way, optimal catalyst formulations will be identified and these will be prepared and tested under industrially relevant ammonia synthesis conditions and the results will be compared to those from conventional industrially applied iron based catalysts.