Zeolite Membranes

无机膜具有高选择性的潜力 以及在高温下操作的能力， 反应性气氛。 这使得这些膜适用于 应用范围以外的完善的有机 聚合物膜 例如，一个应用程序是在 膜反应器，其中平衡限制反应， 当烃脱氢用 同时进行氢气分离，以增加 产率 沸石膜具有高度的 选择性分离各种气体混合物。 他们可以 在环境温度下操作，在稳定状态下， 目前通过非稳态压力进行的分离 或变温吸附。 或者它们可以用于 在催化膜反应器中升高温度， 提高反应产率或选择性。 实现这一 潜在的，沸石膜必须制备为薄的，但 支撑在多孔管或其他材料上的机械稳定层 支持元素。 本项目研究合成薄型沸石的技术 将研究多孔管壁内的层。 一般的方法是这样配置反应物 有利于沸石结晶的条件占优势 仅在多孔载体内部的薄区域上。 三 将研究具体的技术， 结晶区 第一个将基于 反应物在两种水溶液之间的反向扩散， 第二种是将反应前沿固定在界面上 在水相和有机相之间，以及第三， 前体凝胶的局部沉淀。 的形成 沸石将通过X射线衍射（XRD）确定， 固态核磁共振（NMR）、红外和 物理吸附，而扫描电子显微镜（SEM- EDX）将用于定义的位置和厚度的 层. 渗透速率系数和分离因子 将在环境温度和升高温度下测量几种气体的 温度。 最后，使用沸石膜作为 膜反应器将在一些催化剂中进行探索 反应如异丁烷的脱氢和 异丙苯的烷基化。

Inorganic membranes have the potential for high selectivity and the ability to operate at elevated temperatures and reactive atmospheres. This makes these membranes suitable for applications outside the range of the well-established organic polymer membranes. One application, for example, is in membrane reactors where an equilibrium-limited reaction such as hydrocarbon dehydrogenation is carried out with simultaneous hydrogen separation in order to increase the yield. Zeolite membranes have the potential of highly selective separations for a variety of gas mixtures. They can operate at ambient temperatures to carry out, at steady state, separations which are currently performed by unsteady pressure or temperature swing adsorption. Or they can be used at elevated temperatures in catalytic membrane reactors to increase the reaction yield or selectivity. To realize this potential, the zeolite membranes must be prepared as thin but mechanically stable layers supported on porous tubes or other support elements. In this project, techniques for synthesizing thin zeolite layers within the walls of porous tubes will be investigated. The general approach is to deploy the reactants in such a way that conditions favorable to zeolite crystallization prevail only over a thin region inside the porous support. Three specific techniques will be investigated for delimiting the crystallization region. The first will be based on counterdiffusion of reactants between two aqueous solutions, the second on fixing the reaction front at the interface between an aqueous and an organic phase, and third on the localized precipitation of a precursor gel. The formation of the zeolite will be ascertained by X-ray diffraction (XRD), solid state nuclear magnetic resonance (NMR), infrared and physical adsorption, while scanning electron microscopy (SEM- EDX) will be used to define the location and thickness of the layer. Permeation rate coefficients and separation factors will be measured for several gases at ambient and elevated temperatures. Finally, the use of zeolite membranes as membrane reactors will be explored in a few catalytic reactions such as the dehydrogenation of isobutane and the alkylation of cumene.