First principles design of novel ammonia synthesis catalysts

哈伯博世合成氨工业规模的发展是20世纪的主要成就之一。可以直接归功于它通过提供一条获取合成化肥的通道来维持全球人口。该工艺是基于纯氮气和氢气进料在促进的铁基催化剂上的反应。它是在高压(&gt；100大气压)和中等温度下运行的，整个过程目前占全球能源需求的很大比例(&gt；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(在热力学上有优势)来帮助节省能源。将采取的方法将包括计算设计和实验测试的混合，并基于以前对金属氮化物催化剂的研究，这些催化剂对氨合成表现出有趣的活性。金属氮化物的结构中可能含有“活性”氮，而正是这种晶格氮的反应性可能是它们高活性的关键。利用计算模型，将获得对实验结果的理解，并将扩展到识别潜在的高催化活性的氮化物材料。在平行的实验室实验中，将对识别出的材料进行合成和测试，并将结果反馈到计算模型中，以提供更好的理解。通过这种方式，将确定最佳催化剂配方，这些配方将在工业相关的氨合成条件下进行制备和测试，并将结果与传统工业应用的铁基催化剂进行比较。

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.