Fluoride-free synthesis of SSZ-13 zeolite membranes from clear-solution with reduced time

High-silica CHA (SSZ-13) zeolite membranes, with the high gas permeance, excellent separation performance and remarkable stability, are exceptional materials for natural gas purification. Herein, by simply raising the synthesis temperature up to 453 K, with the aid of sodium hydroxide as the mineralizer and a fluoride-free and clear solution, we successfully obtained the pure-phase SSZ-13 membrane in a short 12 h synthesis time, and the Si/Al ratio in membrane is approximately 11.7. The influences of synthesis temperature, synthesis time and H₂O/SiO₂ ratio on membrane separation performance were investigated. The optimal synthesis temperature, synthesis time and H₂O/SiO₂ ratio for the SSZ-13 membranes were 453 K, 12 h and 120, respectively. Pressure drops and temperatures dependence on membrane separation performance were also explored. The optimal SSZ-13 membrane presented N₂ and CO₂ permeances of 3.8 × 10⁻⁸ mol·m⁻²·s⁻¹·Pa⁻¹, 5.7 × 10⁻⁷ mol·m⁻²·s⁻¹·Pa⁻¹, and the corresponding selectivities for N₂-CH₄ and CO₂-CH₄ mixtures were 11.8, 246 at 298 K, 0.2 MPa, respectively. Besides, the prepared SSZ-13 membrane was hydrothermal stable and showed good N₂-CH₄ separation performance when exposed to water within a water vapor pressure of 4.2 kPa. The SSZ-13 membranes obtained within 12 h through the traditional secondary growth method demonstrated a promising industrial application in natural gas separation.