Preparation of steam-stable high-silica CHA (SSZ-13) membranes for CO2/CH4 and C2H4/C2H6 separation

High-quality SSZ-13 membranes were synthesized using the combinative structure-directing agents of N,N,N, trimethtyl-1-adamantammonium hydroxide and tetraethylammonium hydroxide by one hydrothermal treatment step. The two organics took a “cooperative structural-directing” role on SSZ-13 crystallization. The best membrane had a CO2 permeance of 2.0×10−7 mol/(m2 s Pa) with a CO2/CH4 selectivity of 300 and a C2H4 permeance of 2.9×10−9 mol/(m2 s Pa) with a C2H4/C2H6 selectivity of 11, at 303 K and 0.2 MPa feed pressure for these equimolar binary mixtures, respectively. SSZ-13 membranes also displayed high performances for CO2/CH4 and C2H4/C2H6 separations at higher feed pressures of 0.8–1 MPa. These SSZ-13 membranes were hydrothermally stable at steam for at least 4 days at 378 K and acid-resistance at pH=1.