DFT-based Design and Experimental Testing of Catalytic Metallic Membranes for Selective N2-

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Technical ImpactsThe current world population is just above 7 billion, of which 3-3.5 billion would not exist without the ammonia synthesis process. However, this process constitutes approximately 2.5% of the world's energy consumption. The United Nations estimate that world population is forecasted to reach 10 billion by the end of the century, which will inevitably lead to further reliance on the world's limited energy resources to produce ammonia fertilizer. There will be a corresponding increase in CO2 emissions, since the energy will likely be sourced from hydrocarbon oxidation. Replacement of this process technology with an improved process has been identified as one of the highest priorities in the recently published Technology Roadmap for Energy and GHG Reductions in the Chemical Industry (IEA, ICCA and Dechema, 2013). This award made jointly from the National Science Foundation Catalysis & Biocatalysis Program and the Chemical & Biological Separations Program is made to Professor Jennifer Wilcox of Stanford University to investigate an alternative strategy for ammonia synthesis with significantly reduced energy requirements. The technology involves the design and testing of a catalytic membrane reactor that will be used to dissociate N2 from the feed stream (front side of the membrane), leading to atomic N transport through the bulk crystal structure of the metallic membrane. In the permeate stream (backside of the membrane), H2 will be used as a sweep gas, ideally resulting in N-H coupling reactions and subsequent ammonia synthesis. This technology allows for the Earth-abundant elements such as vanadium and niobium (and not precious metals) to be used as the primary metals for nitrogen dissociation and transport. Wilcox has demonstrated preliminary data for some of the separations and reactions through an earlier NSF EAGER project. The remaining large technical risk is in devising the membrane and reactor system which performs the separations and catalyzes all the reactions together at a useful rate. Broader Impacts Broader impacts of the results of the proposed work are many. This technology offers a route to carry out the ammonia synthesis process at atmospheric pressures, adding huge savings to the agricultural chemical industry. Fertilizers are one of the most important factors in securing sufficient global food production. Demand is guaranteed to increase, as it is directly proportional to world population increase. Through the application of selective-N2 membrane technology, ammonia could be produced at a lower energy cost than the traditional high-pressure Haber-Bosch process. In addition to the science- and technology-based broader impacts, the PI plans to incorporate results from this research into a Carbon Capture course she developed in the Energy Resources Engineering department at Stanford University. Wilcox serves as a female role model for women in science, exhibited by the high number of female undergraduate and graduate students she has mentored. The exciting potential in this project should serve as a further attraction to increase females in engineering disciplines. Further dissemination of the results of the work will take place through the PI?s participation in the summer school program, Research Experience for Carbon Sequestration, which is supported by the Office of Fossil Energy of DOE and hosted annually by Southern Company. The summer school provides students with hands-on experience regarding CO2 capture and storage, with additional hosts including Alabama Power and the National Carbon Capture Center, which supports the testing of early capture technologies at the pilot scale. The PI will present findings through a course offered in the summer school program each year throughout the duration of the award.