Static state synthesis of STT zeolite membranes for high-pressure H₂/CH₄ separation

STT zeolite membrane with seven-membered rings (7 MR) and nine-membered rings (9 MR) is an ideal alternative for the separation of hydrogen (H₂) and methane (CH₄). However, the successful synthesis is only possible in rotation conditions, which is difficult to achieve at an industrial scale. Herein we developed a static synthesis approach to prepare high-quality STT zeolite membranes. The precursor transformed in-situ from a liquid state to a semi-solid state to efficiently suppress the nucleation in the bulk gel. This did not affect the growth of the seed layer to form a continuous membrane. The water content was modulated between y = 44 and y = 124 in the molar composition of 1 SiO₂: 0.2 TMAdaOH: y H₂O. The precursor could be re-used one more time to reduce the total amount of chemical waste. The optimal H₂ permeance and H₂/CH₄ mixture selectivity was up to 6.1 × 10⁻⁸ mol m⁻² s⁻¹ Pa⁻¹ and 115 at atm pressure. The H₂ permeation flux monotonically increased to 2.0 Nm³ m⁻² h⁻¹ under feed pressure up to 2.1 MPa. This paves the way for zeolite membranes to high-pressure H₂ separation in practical applications.