CAREER: Molecular Transport Theory for Nanoporous Solids

CTS-9734153奥尔巴赫 大多数环境友好技术依赖于从良性材料中去除污染物的分离。沸石分子筛由如下所示的规则间隔的分子大小的笼组成，非常适合这些分离。虽然我们对沸石有很多了解，但还没有简单的理论来准确预测分子如何通过沸石扩散。这是因为在模拟罕见的事件动力学耦合强吸附物-吸附物相互作用的困难。此外，沸石被物理科学中最重要的一门课--大一化学所忽视。 为了解决这些问题，首席研究员将开发新的教育技术和分子传输理论，旨在加速新兴化学技术的材料和工艺筛选。 工业上重要的沸石中的许多烃的流动性是非常缓慢的，排除了使用简单的分子动力学模拟，因此需要专门用于罕见事件的建模技术。以前的过渡态模拟在沸石分子筛中的扩散是在低负载下进行的，因此吸附质-吸附质相互作用可以忽略不计。这些条件与工业过程无关，工业过程在基本上完全的烃负载下进行。为了模拟工业条件下沸石的运输，首席研究员将开发三种具有不同精度和速度的新技术。一个加速的分子动力学算法，增加了一个新的提高潜在的减少网站到网站的活化能将预测基本上准确的扩散率提供的提高避免过渡状态。将开发一种晶格蒙特卡罗模拟，其中包括一种新的处理活化能修改吸附质-吸附质相互作用。最后，一个完整的分析理论将得出，第一次合成波动的激活能与流体的平均场理论。这种新的层次结构提供了根据过程优化中的速度或准确性需求选择模型的机会。这些模型将被纳入一个新生的化学模块，题为：“工业中的ZEERGY”，涉及新的基于网络的，互动的软件，模仿这些系统的物理和化学特性。 这项研究将在许多层面上影响科学和社会。 首先，将沸石科学和技术纳入大一化学将激发和告知成千上万的学生关于工业化学和工程的现实世界的好处。第二，这种化学反应动力学和平均场理论的新组合将产生第一个真正的分子理论在沸石中的运输，阐明如何主客体之间的竞争和主客体之间的相互作用控制这些运输过程。这将指导和补充新的扩散测量，并将加速筛选新的化学过程。第三，当应用于大孔沸石中的芳烃分离和氢氟碳化合物分离时，这些计算将有助于指导科学家和工程师选择最佳的沸石Si：Al比、沸石通道结构、温度和压力，以进行有效和具有成本效益的分离。

CTS-9734153 Auerbach Most environmentally friendly technologies rely on separations that remove pollutants from benign materials. Zeolite molecular sieves, consisting of regularly spaced, molecular-sized cages shown below, are ideally suited for these separations. Although much is known about zeolites, no simple theory exists for accurately predicting how molecules diffuse through them. This is because of the difficulty in modeling infrequent event dynamics coupled with strong adsorbate-adsorbate interactions. Furthermore, zeolites are ignored by the single most important class in physical science: freshman chemistry. To address these issues, the Principal Investigator will develop novel educational techniques and molecular transport theories aimed at accelerating material and process screening of emerging chemical technologies. The mobility of many hydrocarbons in industrially important zeolites is exceedingly sluggish, precluding the use of straightforward molecular dynamics simulations, and hence requiring modeling techniques specialized for infrequent events. Previous transition state simulations of diffusion in zeolites were performed at low loadings, so that adsorbate-adsorbate interactions could be neglected. These conditions are irrelevant to industrial processes, which are carried out at essentially full hydrocarbon loading. To model transport in zeolites under industrial conditions, the Principal Investigator will develop a hierarchy of three new techniques with varying accuracy and speed. An accelerated molecular dynamics algorithm that adds a novel boost potential for reducing site-to-site activation energies will predict essentially exact diffusivities provided that the boost avoids transition states. A lattice Monte Carlo simulation will be developed that includes a new treatment of activation energies modified by adsorbate-adsorbate interactions. Finally, a completely analytical theory will be derived that synthesizes for the first time fluctua ting activation energies with the mean field theory of fluids. This new hierarchy provides the opportunity of choosing a model based on the need for speed or accuracy in process optimization. These models will be incorporated into a freshman chemistry module entitled: "Zeolites in Industry," involving new Web-based, interactive software that mimics the physical and chemical properties of these systems. This research will impact science and society on many levels. First, incorporating zeolite science and technology into freshman chemistry will excite and inform thousands of students about real-world benefits of industrial chemistry and engineering. Second, this novel combination of chemical reaction dynamics and mean field theory will yield the first truly molecular theory for transport in zeolites, elucidating how the competition between host-guest and guest-guest interactions controls these transport processes. This will guide and complement new diffusion measurements, and will accelerate screening of new chemical processes. Third, when applied to aromatic separations and hydrofluorocarbon separations in large-pore zeolites, these calculations will help guide scientists and engineers in choosing optimal zeolite Si:Al ratios, zeolite channel structures, temperatures and pressures for carrying out efficient and cost-effective separations.