NIRT: Precise Building Blocks for Hierarchical Nanomanufacturing of Membranes with Molecular Resolution

这项研究是响应活性纳米结构和纳米系统计划，NSF 06-595，类别NIRT。它的重点是在分离领域最有前途的发展之一：分子筛或沸石膜技术。很明显，用于大规模工艺的沸石膜技术依赖于可靠的制造，能够产生大的膜面积，同时实现基本的膜特性：低缺陷密度的膜连续性，适当的孔取向，以及微米范围内的小膜厚度。这个NIRT团队承担了向开发这样一个过程飞跃的挑战。在过去的十年中，已经确定了一套分子筛材料成核和生长的机理原理。这些原理激发了研究实验的努力，试图将沸石纳米颗粒的大小和形状控制到前所未有的水平，并将这些纳米颗粒作为通过分层纳米制造制造的分子筛薄膜的精确工程构建块。据推测，在密闭环境中合成将能够操纵和控制不希望的聚集步骤，并最终产生理想的完美的沸石颗粒形状和所需的尺寸单分散性。精确成形的纳米颗粒随后将被用作构建块，通过反应性附着形成封闭的、晶体排列的单层。在二次生长之后，将测试所开发的连续膜的渗透性能，并将其微观结构和性能与目前最先进的膜进行比较。显著的分子筛膜资本和运营成本效益是所提出的工作的预期结果。这些改进为更广泛地应用节能分子筛膜分离技术迈出了重要的一步。除了制造出有史以来最薄、生产率最高的沸石膜外，分层膜处理技术的研究还可能影响其他技术，如微电子和传感器。这些潜在用途之一，即微处理器的低k电介质，也将进行评估。分离目前占全球能源消耗的15%。到2040年，全球大宗商品产量预计将增长6倍，一切照旧是不可持续的。将分离和净化过程的效率提高一个数量级是实现可持续全球繁荣的必要步骤。分子筛或沸石膜技术是膜分离领域中最有前途的发展之一。通过使分子分辨率分离取代热驱动过程，它可以实现这一效率目标，并且正在成为纳米技术和能源研究的一个领域。沸石和其他分子筛是晶体无机框架，具有能够通过形状和大小识别分子的孔。这种能力，以及它们的热化学稳定性和催化活性，使它们在催化剂、吸附剂和离子交换剂等方面得到了广泛的应用。将这些材料结合到具有分子分辨率的薄膜器件中的愿望可以追溯到20世纪40年代。然而，自第一个针对小规模分布式应用（即约10平方米的膜模块）的商业沸石膜出现以来，只有大约十年的时间。从那时起，商业化进程一直停滞不前，受到从实验室规模到商业规模的扩大问题的阻碍。提出的全面和系统的研究将导致可扩展和经济的制造技术的发展，从而使最薄的沸石膜成为有史以来最薄的分子筛膜，将节能分子筛膜的愿景转变为商业现实。

This research was received in response to the Active Nanostructures and Nanosystems initiative, NSF 06-595, category NIRT. Its focus is on one of the most promising developments in the field of separations: molecular sieve or zeolite membrane technology. It has become evident that zeolite membrane technology for large scale processes depends on reliable manufacturing that can generate large membrane areas while achieving essential film characteristics: film continuity with low defect density, appropriate pore orientation, and small membrane thickness well under the micrometer range. This NIRT team undertakes the challenge to make the leap forward towards developing such a process.In the last decade, a set of mechanistic principles for the nucleation and growth of certain molecular sieve materials has been identified. These principles motivated the research experimental efforts, which attempt to control size and shape of zeolite nanoparticles to an unprecedented level and use these nanoparticles as precisely engineered building blocks for molecular sieve thin films made by hierarchical nanomanufacturing. It was hypothesized that synthesis in a confined environment will enable manipulation and control of undesirable aggregation steps and will ultimately yield the desirable perfection in zeolite particle shape and the needed monodispersity in size. The precisely shaped nanoparticles will be used subsequently as building blocks to form closed packed, crystallographically aligned, monolayers using reactive attachment. Following secondary growth, the developed continuous films will be tested for permeation properties, and their microstructure and performance will be compared with the current state-of-the-art. Significant molecular sieve membrane capital and operating cost benefits are the expected outcome of the proposed work. These improvements represent a major leap forward for wider use of energy efficient molecular sieve membrane separation technology. In addition to enabling the thinnest, and consequently most productive, zeolite membranes ever made, the research hierarchical film processing technology may impact other technologies, like microelectronics and sensors. One of these potential uses, i.e., low-k dielectrics for microprocessors, will also be evaluated. Separations currently represent 15% of global energy consumption. With the global commodity production expected to increase six-fold by 2040, a business as usual scenario is not sustainable. An order of magnitude increase in efficiency of separation and purification processes is a necessary step towards sustainable global prosperity. One of the most promising developments in the field of separations using membranes is that of molecular sieve or zeolite membrane technology. By enabling separations with molecular resolution to replace thermally driven processes, it can meet this efficiency goal and is emerging as an area of nanotechnology and energy research. Zeolites and other molecular sieves are crystalline inorganic frameworks with pores capable of recognizing molecules by shape and size. This ability, along with their thermochemical stability and catalytic activity, has led to their use in a broad variety of applications as catalysts, adsorbents, and ion exchangers. The desire of incorporating these materials in thin film devices with molecular resolution can be traced back in the 1940's. However, it has been only about a decade since the first commercial zeolite membranes targeting small scale distributed applications (i.e., membrane modules of about ten square meters) became available. Since then, commercialization progress has been stagnant, hampered by problems in scale-up from laboratory to commercial scale. The proposed comprehensive and systematic investigations will lead to the development of a scalable and economic fabrication technique resulting in the thinnest zeolite membranes ever made transforming the vision of energy efficient molecular sieve membranes to a commercial reality.