Novel SiC Nanoporous Materials for Separation Applications

摘要：纳米多孔碳分子筛膜（CMSM）一直是混合物分离的研究热点。虽然CMSM在聚合物膜上表现出更好的性能，但在高于300℃的温度下，它们本身在O2和蒸汽存在下不稳定；这些都是氢气生产的反应分离和燃料电池应用中通常遇到的条件。其他无机膜，如陶瓷（如氧化铝、二氧化硅和沸石）和金属（钯、银及其合金），到目前为止，在这些高温应用中，特别是在蒸汽和CO存在的情况下，也被证明是不稳定的。在这个项目中，我们提出对SiC膜的研究，显示出克服这些困难的潜力。SiC具有断裂韧性高、抗热震性能好、耐高温、耐腐蚀等特点，是一种很有发展前景的材料。SiC纳米孔膜的制备包括两个关键步骤。首先，制备合适的SiC支架，然后在这些支架上沉积无裂纹和无针孔的纳米多孔SiC薄膜。以往的研究主要集中在制备合适的宏孔和介孔SiC膜载体上。在这个项目中，南加州大学将通过热解预陶瓷聚合物前体在这些基底上沉积纳米多孔薄膜。与CMSM一样，研究人员将基于分子迁移率和分子-孔表面相互作用的差异，重点了解决定这些SiC材料分离气体混合物能力的因素。研究将沿着两个方向进行：(1)SiC膜的制备和表征，以及其分子结构的计算建模；(2)测量和同时计算机模拟混合物通过这些膜的吸附和传输。耦合实验和模拟将有助于将膜的分子结构与其运输性质和分离效果联系起来。反过来，这将使第一性原理分子工程和设计用于吸附和分离的改进材料的长期目标取得进展。这个研究项目将为研究生和本科生提供宝贵的教育经验和训练，通过训练他们准备和表征一类新的新材料，并学习许多最先进的计算和实验技术。南加州大学的城市环境提供了与该地区各种2-4年制大学合作的机会。研究人员将招募合格的本科生作为暑期实习生，并有可能作为即将入学的研究生。实验结果将通过同行评议的出版物、技术会议上的报告以及在网络上提供所有报告来传播。pi设想将研究成果和他们的工作方面整合为反应堆分析，传输现象和分离课程的学位项目。所提出的新型碳化硅膜在氢气生产和燃料电池应用方面具有良好的应用潜力。除了将注意力集中在一类重要的材料上，该项目还将产生根本性的见解，这将影响纳米多孔介质中传输和反应的更广泛领域的知识库，并可能催化该领域的新思维和快速的新进展。

Abstract: Nanoporous carbon molecular sieve membranes (CMSM) have been the focus of much previous research for separation of mixtures. Though CMSM exhibit improved properties over polymeric membranes, they are themselves unstable in the presence of O2 and steam at temperatures higher than 300 oC; these are the conditions typically encountered in reactive separations for H2 production, and in fuel-cell applications. Other inorganic membranes, like ceramic (e.g., alumina, silica, and zeolite) and metal (Pd, Ag, and their alloys) have, so far, also proven unstable, in these high-temperature applications, particularly in the presence of steam and CO. In this project we propose the study of SiC membranes that show the potential to overcome some of these difficulties. SiC is a promising material that has high fracture toughness, good thermal shock resistance, and is capable of withstanding high temperatures and corrosive environments. The preparation of SiC nanoporous membranes involves two key steps. First, the preparation of appropriate SiC supports, and second the deposition on these supports of crack- and pinhole-free, thin nanoporous SiC films. Previous research focused on the preparation of appropriate macro and mesoporous SiC membrane supports. In this project, the University of Southern California will deposit thin nanoporous films on these substrates by the pyrolysis of pre-ceramic polymeric precursors. As with the CMSM, the researchers emphasis will be on understanding the factors determining the ability of these SiC materials to separate gas mixtures, based on differences in molecular mobility and molecule-pore surface interactions. Research will proceed along two paths: (1) the preparation and characterization of SiC membranes, and the computational modeling of their molecular structure; and (2) the measurement and simultaneous computer simulation of sorption and transport of mixtures through these membranes. Coupling experiments and simulations will facilitate efforts to relate the membrane's molecular structure with its transport properties, and separation efficacy. This, in turn, will enable progress toward the long-term goal of first-principle molecular engineering and design of improved materials for adsorption and separation. This research project will provide a valuable educational experience and training for the graduate and undergraduate students involved, by training them to prepare and characterize a novel class of new materials, and to learn a host of state-of-the-art computational and experimental techniques. The urban setting of USC affords the opportunity to work with a variety of 2-4 year colleges in the area. The researchers will recruit qualified undergraduates as summer interns, and potentially as incoming graduate students. The experimental results will be disseminated through peer-reviewed publications, presentations at technical meetings, and by makings all reports available on the Web. The PIs envision integrating research findings and aspects of their work as the degree projects in the Reactor Analysis, Transport Phenomena, and Separation courses. The proposed novel SiC membranes show good potential for reactive applications for the production of hydrogen and for fuel-cell applications. In addition to focusing attention on an important class of materials, this project will also generate fundamental insight, which will impact the knowledge-base of the broader field of transport and reaction in nanoporous media, and is likely to catalyze new thinking and rapid new advances in the area.