Adsorbed-Induced Changes in Zeolite Membrane Structures

建议编号：0730047 PRINCIPAL研究员：John Falconer研究：美国科罗拉多大学研究标题：吸附诱导的沸石膜结构变化本项目的主要目标是：(1)更好地了解沸石膜如何工作以及非沸石孔如何影响分离，(2)了解吸附诱导的晶体膨胀和非沸石孔的收缩如何改变分离选择性，(3)通过向二元(或多组分)混合物中添加第三组分来提高分离选择性，以利用这些吸附诱导的变化，以及(4)开发更好的沸石膜表征方法。该项目将基于最近的一项发现，即某些分子(如正己烷、正辛烷)在MFI分子筛膜中的吸附使MFI晶体略有膨胀(~1%的线性膨胀)，这种膨胀足以缩小非沸石孔(缺陷)的大小，从而显著减少通过非沸石孔的渗透。这项研究的成功完成将对沸石膜的微观结构有新的认识，将为改进沸石膜的制备指明方向，并可能产生通过向混合物中添加某些分子来分离沸石膜的新方法。它将识别可以通过缩小非沸石孔的大小来提高选择性的分子。比较不同实验室制备的膜是困难的，将开发测量通过非沸石孔的通量和测量其孔大小的表征方法。将使用流经非沸石孔的不同比例的MFI膜。测量晶体或膜的吸附变化的方法包括X射线衍射法、热释光分析法和共聚焦显微镜。渗透方法包括渗透汽化以获得更具工业应用代表性的高吸附负载量、作为压力函数的蒸汽渗透(以及非沸石孔中的毛细管冷凝)、渗透法以及利用质谱仪检测混合物的瞬时渗透。对于二元和三元混合物，将通过渗透汽化进行分离。在美国，膜分离使用的能源占能源的很大一部分，而膜分离有可能显著减少这一使用量。了解吸附引起的沸石膜微结构变化将影响沸石膜的制备和利用。分子筛膜具有分离有机异构体(结构和立体异构体)和共沸物的潜力，这些能力与其高温稳定性相结合，使其相对于聚合物膜具有显著的优势。沸石层在储氢和微器件方面具有潜在的应用前景。预计膜技术专利将有可能通过商业化迅速和直接造福社会。预计至少有一名学生将得到GAANN奖学金的支持，该奖学金将K-12和社区外联作为必要方面之一。本科生将得到资助，每年夏天将有一名高中生参与这项研究。

PROPOSAL NUMBER: 0730047PRINCIPAL INVESTIGATOR: John FalconerINSTITUTION: University of ColoradoPROPOSAL TITLE: Adsorbed-Induced Changes in Zeolite Membrane Structures The main goals of this project are: (1) to better understand how zeolite membranes work and how non-zeolitic pores affect separations, (2) to understand how adsorbed-induced crystal expansion and shrinkage of non-zeolitic pores change separation selectivities, (3) improve separation selectivities by adding a third component to a binary (or multi-component) mixture to take advantage of these adsorbed-induced changes, and (4) to develop better characterization methods for zeolite membranes. The project will build on the recent discovery that adsorption of certain molecules (e.g., n-hexane, n-octane) in MFI zeolite membranes swells the MFI crystals slightly (~1% linear expansion), and this expansion shrinks the size of the non-zeolitic pores (defects) sufficiently to dramatically decrease permeation through non-zeolitic pores. The successful completion of this research will result in new understanding of the micro-structure of zeolite membranes, will indicate directions for improved zeolite membrane preparation, and will potentially result in new methods of zeolite membrane separations by addition of certain molecules to mixtures. It will identify molecules that can cause improved selectivity by shrinking the size of non-zeolitic pores. Comparing membranes prepared in different laboratories is difficult, and characterization methods that measure flux through non-zeolitic pores and measure their pore sizes will be developed. MFI membranes with different fractions of their flow through non-zeolitic pores will be used. Methods to measure changes due to adsorption, for crystals or membranes, include XRD, TPD, and confocal microscopy. Permeation methods include pervaporation to obtain high adsorbed loadings, which are more representative of industrial applications, vapor permeation as a function of pressure (and capillary condensation in non-zeolitic pores), permporosimetry, and transient permeation of mixtures with mass spectrometer detection. Separations will be carried out by pervaporation for binary and ternary mixtures. Separations use a significant fraction of the energy in the US, and membrane separations have the potential to significantly reduce that usage. Understanding adsorbed-induced microstructural changes in zeolite membranes will impact how zeolite membranes are prepared and utilized. Zeolite membranes have the potential to separate organic isomers (structural and stereo isomers), and azeotropes, and these abilities combined with their high temperature stability give them significant advantages over polymer membranes. Zeolite layers have potential applications for hydrogen storage and in micro devices. Continuation of membrane technology patents having the potential to rapidly and directly benefiting society through commercialization is anticipated. It is anticipated that at least one student will be supported by a GAANN fellowship, which has K-12 and community outreach as one of the required aspects. Undergraduate students will be supported, and one high school student will be involved in this research each summer.