(47d) Synthesis of Highly C-Oriented AlPO4-5 Membranes

AlPO4-5 is one of the most important molecular sieves. In powder form it has been used as shape-selective catalysts for alkylation of many important hydrocarbons. Its unique large unidimensional and straight channels have been used as hosts for supramolecular organization. The ability of controlling molecules in the molecular level has leaded to novel applications such as microlaser, which is achieved by alighing dye molecules within the straight channels. However, the small crystal size has limited their practical use. The length scale of alignment can be greatly extended if a compact thin film consisting of well oriented AlPO4-5 single crystals or grains can be formed. Such a thin film will also greatly extend the application of AlPO4-5 into many novel applications such as separations, membrane reactors and chemical sensors, etc.

In this presentation we will demonstrate a modified seeded growth technique to make highly c-oriented AlPO4-5 film. This modified seeded growth technique has been used to prepare the first functional b-oriented MFI membrane. The basic idea of this technique is to convert an oriented seed layer into an oriented continuous thin film by secondary growth. Similarly in this work the synthesis starts from a c-oriented AlPO4-5 seed layer followed by secondary growth to convert this seed layer into a continuous AlPO4-5 film. The condition of the seondary growth was controlled so that the orientation of seed layer was maintained untill a continuous and highly c-oriented AlPO4-5 film was formed.