Adsorbed-Induced Changes in Zeolite Membrane Structures

提案号：0730047首席研究员：John FalconerINSTITUTION: University of colorado提案题目：沸石膜结构的吸附诱导变化(1)更好地了解沸石膜的工作原理以及非沸石孔对分离的影响；(2)了解吸附诱导的非沸石孔的晶体膨胀和收缩如何改变分离选择性；(3)通过在二元（或多组分）混合物中添加第三组分来利用这些吸附诱导的变化来提高分离选择性；(4)开发更好的沸石膜表征方法。该项目将建立在最近的发现，某些分子（例如，正己烷，正辛烷）在MFI沸石膜上的吸附会使MFI晶体轻微膨胀（~1%的线性膨胀），这种膨胀会缩小非沸石孔（缺陷）的大小，足以显著减少通过非沸石孔的渗透。本研究的成功完成将使人们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，并有可能产生通过在混合物中加入某些分子分离沸石膜的新方法。它将通过缩小非沸石孔隙的大小来确定可以提高选择性的分子。比较不同实验室制备的膜是困难的，测量非沸石孔隙通量和测量其孔径的表征方法将被开发出来。将使用具有不同分数的MFI膜通过非沸石孔流动。测量晶体或膜吸附变化的方法包括XRD， TPD和共聚焦显微镜。渗透方法包括渗透汽化，以获得高吸附负荷，这更具有工业应用的代表性，蒸汽渗透作为压力的函数（和非沸石孔隙中的毛细管冷凝），渗透法，以及用质谱仪检测混合物的瞬态渗透。二元和三元混合物的分离将通过渗透蒸发进行。在美国，分离使用了很大一部分能源，而膜分离有可能显著减少这种使用。了解沸石膜吸附引起的微观结构变化将影响沸石膜的制备和利用。沸石膜具有分离有机异构体（结构异构体和立体异构体）和共沸体的潜力，这些能力加上它们的高温稳定性使它们比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。膜技术专利有望通过商业化迅速、直接地造福社会。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和社区外展作为必需的方面之一。本科生将得到支持，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.