CAREER: Fundamentals of the Relationship between Pore Structure and Transport of Light Gases in Materials with a Hierarchy of Pore Sizes

职业：具有孔径等级的材料中孔结构与轻气体传输之间关系的基础

• 批准号: 0951812
• 负责人: Sergey Vasenkov
• 金额: $ 40万
• 依托单位: University of Florida
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-04-15 至 2016-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0951812&HistoricalAwards=false
• 关键词: CAREER; Fundamentals; Relationship; between; Pore

This NSF award by the Chemical and Biological Separations program supports work by Professor Sergey Vasenkov at University of Florida to obtain fundamental knowledge of the relationship between structural properties of materials with a hierarchy of pore sizes and transport properties of gases in these materials on different length scales of molecular displacements. Porous membranes fabricated for separations of gas mixtures are usually structurally heterogeneous. In particular, mixed matrix membranes contain interconnected networks of pores of different sizes, i.e. networks of micropores with pore sizes approaching the sizes of gas molecules and networks of much larger mesopores. Such membranes have great potential for effective separations of small gas molecules such as CO2, CH4, and N2. Over the last decade significant progress has been made in understanding gas transport in pore networks with uniform or similar pore sizes. At the same time, diffusion in materials containing a hierarchy of pore networks with very different pore sizes is still poorly understood. The research goal of the project is to quantify different types of gas transport on small (i.e. micrometer and submicrometer) length scales in materials with a hierarchy of pore networks and to find a relationship between such transport and macroscopic long range diffusion. The proposed studies focus on measurements of sorbate diffusion along and through the interfaces between microporous particles and their surroundings. In addition, the effect of correlated motions of sorbate molecules on small length scales on the long range diffusion will be investigated. The hypothesis is that these types of transport can make a significant and quantifiable contribution to long range diffusion of gases in hierarchical porous materials. Measurements of gas transport will be carried out using a unique experimental approach: pulsed field gradient (PFG) NMR at high field (17.6 T) and high gradients (up to 36 T/m). Experimental studies will be complemented by dynamic Monte Carlo simulations.In the framework of the education plan of the project a new departmental program for minority undergraduate students will be introduced. The program includes organizing mentoring seminars, providing research experiences, and pairing freshmen minority students with the students who obtained research experience in the groups of the PI and other faculty members of the department. High field and high gradient PFG NMR hardware and measurement methodology will be developed as a new multi-user resource at the National Magnet Lab. The PI's plans to reach this goal include: (i) training his students to advise other users on the procedures of PFG NMR measurements, and (ii) development of a manual for such measurements. The outreach activities include expansion of the local symposium (JSEHS) for high school teachers and students and hosting 10th and 11th grade students at the PI?s group during summer months.The proposed research will quantify different types of gas transport on small length scales and establish a quantitative relationship between these types of transport and macroscopic long range diffusion in porous membranes and related materials. Molecular fluxes through macroscopic porous systems are determined by long-range diffusivities. Hence, new knowledge generated in the proposed research will enable designing concrete strategies for optimizing gas fluxes in porous membranes while preserving separation selectivities.

这项由化学和生物分离项目颁发的 NSF 奖项支持佛罗里达大学 Sergey Vasenkov 教授的工作，以获取具有孔径层次结构的材料的结构特性与这些材料中气体在不同长度尺度上的传输特性之间关系的基础知识分子位移。用于分离气体混合物而制造的多孔膜通常在结构上是异质的。特别地，混合基质膜包含相互连接的不同尺寸的孔网络，即孔径接近气体分子尺寸的微孔网络和更大的中孔网络。此类膜在有效分离 CO2、CH4 和 N2 等小气体分子方面具有巨大潜力。在过去的十年中，在理解具有均匀或相似孔径的孔隙网络中的气体传输方面取得了重大进展。与此同时，对于含有孔径差异很大的孔隙网络层次结构的材料中的扩散仍然知之甚少。该项目的研究目标是量化具有孔隙网络层次结构的材料中小（即微米和亚微米）长度尺度上不同类型的气体传输，并找到这种传输与宏观长程扩散之间的关系。拟议的研究重点是测量山梨酸盐沿着微孔颗粒与其周围环境之间的界面以及通过该界面的扩散。此外，还将研究山梨酸盐分子在小长度尺度上的相关运动对长程扩散的影响。假设这些类型的传输可以对分层多孔材料中气体的长距离扩散做出重大且可量化的贡献。气体传输的测量将使用独特的实验方法进行：高场（17.6 T）和高梯度（高达 36 T/m）的脉冲场梯度（PFG）NMR。实验研究将得到动态蒙特卡罗模拟的补充。在该项目的教育计划框架内，将为少数民族本科生引入一个新的院系课程。该计划包括组织指导研讨会、提供研究经验以及将新生少数民族学生与在 PI 和系内其他教职人员小组中获得研究经验的学生配对。高场和高梯度 PFG NMR 硬件和测量方法将在国家磁力实验室开发为新的多用户资源。 PI 实现这一目标的计划包括：(i) 培训学生向其他用户提供有关 PFG NMR 测量程序的建议，以及 (ii) 编写此类测量手册。外展活动包括扩大针对高中教师和学生的当地研讨会 (JSEHS)，以及在夏季期间在 PI 小组中接待 10 年级和 11 年级的学生。拟议的研究将量化小长度范围内不同类型的气体传输和建立多孔膜和相关材料中这些类型的传输与宏观长程扩散之间的定量关系。通过宏观多孔系统的分子通量由长程扩散率决定。因此，拟议研究中产生的新知识将有助于设计具体策略，以优化多孔膜中的气体通量，同时保持分离选择性。