New Coating Techniques for Composite Membranes

膜扩散本质上是一个缓慢的过程。因此，只有使用极薄、无缺陷的膜，基于膜的分离工艺才能在经济上可行。利用现有的技术，可以制备具有低至约0.5 um的超选择层厚度的薄膜复合膜。具有比这更薄的超选择层的膜将大大提高膜分离的经济性。该项目的目标是开发工业规模复合膜的技术，使其超选择层厚度降至0.1微米或以下。该膜将通过修改用于施加薄透选择层的溶液涂层工艺制成。所使用的涂层溶液的特点是在低聚合物浓度下具有高粘度。先前的实验数据表明，与传统技术相比，使用这种溶液可以获得更薄的无缺陷涂层。如果该技术可以应用于许多不同的聚合物，它将使经济上可行的膜分离系统被制造出来，并应用于广泛的气体分离问题。由提议的工艺制成的膜可能对许多工业气体分离产生重大影响，例如，氧/氮分离，从流出流中去除酸性气体，或从许多来源回收氢气。在这些和其他应用中，膜系统具有足够的吸引力，可以与传统的分离方法竞争。

Membrane diffusion is an inherently slow process. Consequently, membrane-based separation processes can only be economically viable if extremely thin, defect-free membranes are used. Thin-film composite membranes with a permselective layer thickness down to about 0.5 um can be made by presently available techniques. Membranes with permselective layers thinner than this would dramatically improve the economics of membrane separation. The goal of this program is to develop the technology for making industrial-scale composite membranes with permselective layer thicknesses down to 0.1 um or below. The membranes will be made by modifying the solution coating process used to apply the thin permselective layer. The coating solutions to be used will be characterized in having high viscosity at low polymer concentration. Previous experimental data indicate that the use of such solutions enables a much thinner defect-free coating to be applied than is possible with conventional techniques. If the technique can be applied to many different polymers, it will enable economically viable membrane-based separation systems to be made and applied to a broad range of gas separation problems. Membranes made by the proposed process could have a significant impact on many industrial gas separations, for example, oxygen/nitrogen separation, removal of acid gases from effluent streams, or hydrogen recovery from many sources. The process economics could be sufficiently attractive to make membrane systems competitive with conventional separation methods in these and other applications.