(396b) Small Pore Zeolite Membranes for CO2 Capture

From the environmental and energy perspective, purification and recovery of carbon dioxide from flue gas and natural gas are of great interest. CO₂ must be separated from CH₄ because it reduces the energy content of the natural gas, and it is acidic and corrosive in the presence of water. Although polymeric membranes such as cellulose acetate, polyimide and polyaramide can separate CO₂ from CH₄ and H₂ mixtures, the high CO₂ pressures plasticize them and decrease their separation ability considerably. Zeolite membranes have significant advantages over polymeric membranes. They do not deform under high CO₂ pressures, have high thermal, mechanical, and chemical stability, and good erosion resistance. Of particular interest are small pore zeolites having three dimensional structures with pore sizes in the 3.5-3.6 Å range  which represents an ideal pore window to molecular sieve CO₂ (3.3 Å)  from CH₄ (3.8 Å) and N₂ (3.6 Å). Herein, we present our initial efforts to develop small pore zeolite membranes (including SAPO-56, DNL-6 and zeolite Rho) and evaluate its separation performance for CO₂/CH₄ gas mixtures. The membranes were supported on porous alumina tubes, and were grown via secondary seeded method. In particular, SAPO-56 displayed moderate CO₂ permeances and selectivities for equimolar CO₂/CH₄ mixtures.