Fabrication of Molecular Sieving Silica Membrane Using Atomic Layer Controlled Chemical Vapor Deposition

在膜气体分离小分子（如N2， H2, O2， CH4和CO）中实现特殊选择性的一种技术是调整膜的孔径，以便只有所需的分子才能通过孔。由于N2、H2、CO等分子的直径范围在3- 6 A之间，因此有必要制作孔径大小的膜，孔径大小可以在此范围内调节到所需的值。为了实现这一目标，本研究提出了一种独特的方法来制造和定制微孔无机膜的孔径。膜的起始材料是廉价的Vycor玻璃，其孔直径约为40 A或更大。这种玻璃的孔表面含有硅烷醇基团（Si-OH）。PI建议将这些基团（通过CVD工艺）与SiCl4反应形成-Si-O-SiCl3。这种反应在表面覆盖了一层原子层，从而减小了孔径。氯化后的表面可与水发生羟基化反应生成Si-O-SiCl2-OH，从而进一步减小了孔径。通过连续反应，可以实现孔径的原子层控制。将制作具有特定孔径的微孔膜，并测试其在各种二元分离中的选择性。

One technique for achieving exceptional selectivity in the membrane gas separation of small molecules such as N2, H2, O2, CH4, and CO is to tailor the pore size of the membrane so that only the desired molecules can fit through the pores. Since molecules such as N2, H2, and CO have diameters in the range of from 3-to-6 A, it is necessary to make membranes with pore sizes, which can be adjusted to a desired value within this range. To achieve this goal, this research suggests a unique approach to making and tailoring the pore size of microporous inorganic membranes. The starting material for the membrane is inexpensive Vycor glass, whose pores are approximately 40 A or larger in diameter. The pore surfaces of this glass contain silanol groups (Si-OH). The PI Proposes reacting these groups (via a CVD process) with SiCl4 to form -Si-O-SiCl3. This reaction coats the surface with an atomic layer, which reduces the pore diameter. The chlorinated surface can then be hydroxylated by the reaction with H2O to form Si-O-SiCl2-OH, which further reduces the pore diameter. By successive reactions one can achieve atomic layer control of the pore size. Microporous membranes with particular pore sizes will be made, and will be tested for their selectivity in various binary separations.