Preparation and Testing of Microporous Glass Membranes for Gas Separations

CTS-0085480气体分离用微孔玻璃膜的制备与测试乔治·R·加瓦拉斯加利福尼亚理工学院采用分相玻璃浇注技术研制了适用于气体分离的支撑玻璃膜。膜是通过首先在玻璃组分(Na2O-B2O-SiO_2-Al_2O_3)悬浮液中浸涂平板或管状多孔氧化铝支撑物制成的。然后将颗粒涂层加热，使各组分反应生成5-10毫米厚的连续玻璃膜。冷却后，玻璃分成两个相互缠绕的相，一个溶于酸，另一个不溶。在酸中浸出去除了固相，留下了不溶于水的多孔膜，根据初始成分和工艺条件的不同，其孔径从小于1 nm到10 nm不等。为了实现高的膜选择性，必须确定孔径小于1 nm的组合物。为此目的，在广泛的玻璃成分上制备膜样品。使用传统的膜制备技术，这样的努力是令人望而却步的。在这个项目中，并行处理被用来快速而彻底地探索大的多组分组合空间。具体地说，几个小圆形膜的阵列，每个不同的成分，同时沉积在单个氧化铝盘上。经过热处理和淋洗后，用扫描电子显微镜对膜进行了表征，并测试了膜对各种气体混合物的渗透性和选择性，包括CO2-CH4和C1-C4烃的组合。渗透测试是使用质谱仪探头连续进行的。在这个项目的过程中，大约有50个圆盘，每个圆盘包含30多个膜。无机膜为天然气和石化等材料的工业加工以及燃料电池中所需的气体分离提供了一种实用且节能的技术。一种这样的耐用膜由支撑在多孔陶瓷板或管上的薄微孔玻璃膜组成。为了获得良好的膜性能，有必要将孔径降低到分子尺寸，为此，有必要测试各种制备条件。按照传统技术，这种必要的大规模实验工作将非常耗时。在该项目中，正在开发在单个支撑盘上同时沉积和测试多个膜制剂的技术。这种并行或组合工艺所带来的生产率的提高允许对1000多种膜组合物进行评估，以优化其分离性能。这种优化的膜将有助于提高天然气和石油行业的分离效率和经济性。

CTS-0085480Preparation and Testing of Microporous Glass Membranes for Gas Separations George R. GavalasCalifornia Institute of TechnologyAbstract Supported glass membranes suitable for gas separations are developed using phase-separated-glass casting techniques. Membranes are made by first dip-coating flat or tubular porous alumina supports in a suspension of the glass components (Na2O-B2O3-SiO2-Al2O3). The particle coating is then heated to react the components into a continuous glass film 5-10 mm thick. Upon cooling, the glass separates into two intertwined phases, one soluble in acid and the other insoluble. Leaching in acid removes the solid phase, leaving behind the insoluble phase as a porous film with pore sizes varying from below 1 nm to 10 nm depending on the initial composition as well as on the processing conditions. To achieve high membrane selectivity it is essential to identify compositions that give pore size below 1 nm. For this purpose membrane specimens are being prepared over a broad range of glass compositions. Such an effort is prohibitive using conventional membrane-preparation techniques. In this project parallel processing is used to explore quickly and thoroughly a large multicomponent composition space. Specifically, arrays of several small circular membranes, each of different composition, are deposited simultaneously on a single alumina disk. After thermal treatment and leaching the membranes are characterized by scanning electron microscopy and tested for permeance and selectivity with various gas mixtures, including CO2-CH4 and combinations of C1-C4 hydrocarbons. The permeation testing is carried out serially using a mass spectrometer probe. Approximately fifty disks, each containing upwards of thirty membranes, are being processed in the course of this project. Inorganic membranes offer a practical and energy-efficient technology for gas separations needed in industrial processing of materials such as natural gas and petrochemicals and in fuel cells. One type of such durable membranes consists of thin microporous glass films supported on porous ceramic plates or tubes. To achieve good membrane properties it is necessary to bring the pore sizes down to molecular dimensions, and for this purpose it is necessary to test a wide range of preparation conditions. This necessarily extensive experimental effort would be extremely time consuming by conventional techniques. In this project techniques for simultaneously depositing and testing a number of membrane formulations on a single support disk is being developed. The increased productivity afforded by this parallel, or combinatorial, processing permits evaluation of over one thousand membrane compositions in order to optimize their separation properties. Such optimized membranes will contribute to improved efficiency and economy in separations pertaining to the natural-gas and petroleum industries.