LTA Zeolite Membranes

LTA zeolite membrane is one of the most well-studied zeolite membranes for the separation of light gases and dewatering of organics. LTA (Linde type A) zeolite has a three-dimensional pore structure, consisting of secondary building units (SBUs) 4, 6, 8, and 4-4 (Meier et al.). An example material is NaA zeolite (Linde type A sodium form) with chemical formula of Na₁₂Al₁₂Si₁₂O₄₈ · 27H₂O. The unit cell of NaA zeolite is cubic (a = 24.61 Å) with Fm-3c symmetry. The pore diameter of NaA zeolite is defined by an eight-member oxygen ring with size around 4.3 Å. Generally, LTA zeolite membranes exist in the form of composite membranes, for which porous ceramic supports, typically alumina tubes, are usually used as substrates. The effective LTA zeolite separating layer is usually in the thickness of several microns (Fig. 1).

LTA Zeolite Membranes, Fig. 1

(a) Framework structure of LTA zeolite, (b) typical SEM image of a NaA zeolite single crystal, (c, d) typical SEM image of a LTA zeolite...