Developing New Theoretical Tools and Materials to Improve the Separation Performance of Inorganic Mesoporous Membranes

介孔无机膜由二氧化硅和氧化铝等材料组成，孔径在2到50纳米之间，具有分离小分子混合物的巨大潜力。重要的例子包括从烟道气中去除二氧化碳和从发酵液中回收乙醇。化学家和材料科学家现在在合成介孔无机膜时，对孔的几何形状和表面化学性质有了惊人的控制。然而，对于给定的分离，究竟应该选择什么样的孔几何结构和化学性质仍然是一个突出的问题，部分原因是缺乏将详细的材料结构与膜流速联系起来的适当模型。在这个项目中，提出了一种新的建模方法来捕捉分离过程中膜孔内发生的复杂吸附和流动机制。该模型基于动态平均场理论（DMFT），在预测实验室或工业规模的膜性能时保留了分子水平的细节。理论发展、计算机模拟、材料合成和渗透测量相结合的项目将使DMFT成为化学家和材料科学家可以用来指导新膜制造的工具，工程师可以用来模拟工业膜单元的性能。一种新型的介孔膜材料也将作为该项目的关键部分进行开发。PIs提出了一个合作的理论/实验研究计划，将通过进一步的发展和DMFT来改变介孔无机膜分离的建模。DMFT对与其密切相关的吸附在介孔材料中的应用产生了巨大的影响。随着该理论在动力学方面的进一步发展，DMFT也可以满足预测通过介孔膜的渗透的挑战。该项目的研究团队横跨分子理论与建模（Ford, Monson）、膜科学与技术（Ford）以及介孔材料的材料科学与工程（Fan, Monson）。这一建议的智力价值在于两个主要目标。首先是扩展和发展动态平均场理论（DMFT），以定量准确地预测小分子在介孔膜中的渗透。这可以通过以下方法来实现：(i)在低维、几何简单的孔隙模型上建立方法；（ii）修改动力学以定量捕捉相关的运输机制。第二个主要目标是应用DMFT来模拟特定的介孔膜渗透实验。这将通过(i)合成一组孔径和几何形状可控的膜来实现；（ii）将DMFT预测与这些膜上的分离实验进行比较；（iii）使用DMFT来提高通过过渗法获得的孔径的准确性，过渗法使用轻气体和可冷凝蒸汽的共渗透来获得有关孔径的信息。如果成功，这项研究的产品有可能推动美国膜工业的发展，特别是当它应用于传统和新兴的能源生产领域时。提出的工作可能是统计热力学、吸附和膜群落之间的桥梁，同时为膜群落提供了一种新的计算工具，用于预测和解释介孔膜的渗透。这些pi提议将这项研究整合到马萨诸塞大学阿默斯特分校的本科和研究生课程中，通过其中一名pi （Fan）教授的一门受欢迎的本科纳米材料选修课和另一名pi （Ford或Monson）教授的统计热力学核心研究生课程。马萨诸塞大学现有的外展和招聘项目也将得到利用。

1403542FordUMass AmherstMesoporous inorganic membranes, composed of materials such as silica and alumina and having pore sizes on the order of 2 to 50 nanometers, have significant potential for performing separations of mixtures of small molecules. Important examples include the removal of carbon dioxide from flue gases and the recovery of ethanol from fermentation broths. Chemists and materials scientists now have an amazing amount of control over the geometry and surface chemistry of the pores when synthesizing mesoporous inorganic membranes. However, actually knowing what pore geometry and chemistry to choose for a given separation remains an outstanding problem, partially due to the lack of appropriate models that connect detailed material structure to membrane flow rates. In this project, a new modeling approach is proposed to capture the complex adsorption and flow mechanisms that take place inside the membrane pores during separation operations. The modeling, based dynamic mean field theory (DMFT), retains molecular-level detail while predicting membrane performance at the laboratory or industrial scale. A combined program of theoretical development, computer simulation, materials synthesis, and permeation measurement will develop DMFT into a tool that chemists and materials scientists can use to guide the manufacture of new membranes, and engineers can use to model the performance of industrial membrane units. A novel class of mesoporous membrane materials will also be developed as a key part of the project. The PIs propose a collaborative theoretical/experimental research program that will transform the modeling of separations with mesoporous inorganic membranes through the further development and DMFT. DMFT has had an enormous impact on the closely related application of adsorption in mesoporous materials. With some further development to the dynamic aspects of the theory, DMFT msy also meet the challenge of predicting permeation through mesoporous membranes. The research team for this project spans molecular theory and modeling (Ford, Monson), membrane science and technology (Ford) and the materials science and engineering of mesoporous materials (Fan, Monson). The intellectual merit of this proposal lies in two main objectives. The first is to extend and develop dynamic mean field theory (DMFT) for quantitatively accurate prediction of permeation of small molecules in mesoporous membranes. This is proposed to be accomplished by (i) establishing the method on lower-dimensional, geometrically simple pore models; and (ii) modifying the dynamics to quantitatively capture relevant transport mechanisms. The second major objective is to apply DMFT to model specific mesoporous membrane permeation experiments. This will be accomplished by (i) synthesizing a set of membranes with controlled pore size and geometry; (ii) comparing DMFT predictions to separation experiments on these membranes; and (iii) using DMFT to improve the accuracy of pore sizes obtained by permporometry, which uses co-permeation of a light gas and a condensable vapor to gain information about pore size. If successful, the products of this research have the potential to advance the membrane industry in the U.S., especially as it is applied to the traditional and emerging fields of energy production. The proposed work may bridge the statistical thermodynamics, adsorption, and membrane communities while providing the membrane community with a new computational tool for predicting and interpreting permeation through mesoporous membranes. The PIs propose to integrate the research into the undergraduate and graduate curricula at UMass Amherst, through a popular undergraduate nanomaterials elective taught by one of the PIs (Fan) and a core graduate course in statistical thermodynamics taught by one of the other PIs (Ford or Monson). Existing outreach and recruitment programs at UMASS will also be leveraged.