Preparation of CHA zeolite (chabazite) crystals and membranes without organic structural directing agents for CO2 separation

CHA zeolite (chabazite) crystals and membranes were prepared from organic structural directing agents-free (OSDA-free) gels. Chabazite membranes were grown on the tubular alumina supports. The effect of cesium and fluoride salts on the crystallization of chabazite crystals and membranes were investigated. Highly crystalline chabazite and uniform chabazite membranes were only obtained from the gel containing the cesium and fluoride salts. Single CO2, N-2 and CH4 permeances and mixed gas separations in CO2/N-2 and CO2/CH4 binary mixtures through chabazite membranes were measured. Temperature and pressure affected the permeances and separation selectivities in two mixtures. The best membrane showed CO2/N-2 and CO2/CH4 separation selectivities as high as 16 and 46 together with CO2 permeances of similar to 1.0 x 10(-7) mol/(m(2) s Pa) at a high temperature of 473 K in equimolar dry CO2/N-2 and CO2/CH4 binary mixtures, respectively. The CO2/N-2 and CO2/CH4 selectivities lost only 11% and 15%, and CO2 permeances lost only 18% and 20% in equimolar wet CO2/N-2 and CO2/CH4 mixtures (8% in mole of water vapor) at 473 K compared to these values in dry mixtures, respectively. The OSDA-free chabazite membranes were hydrothermally stable in the presence of vapor water for 4 d at 378 K.