Fluorine-free synthesis of all-silica STT zeolite membranes for H₂/CH₄ separation

Hydrogen (H₂) is the most promising alternative to fossil energy for zero-emission of CO₂. However, the by-produced H₂ from coking process was generally burned as fuel. It is highly desired to recycle the H₂ from coke oven gas as the clean energy resource. Herein all-silica STT zeolite membranes were prepared from the fluorine-free precursor for H₂/CH₄ separation. The crystallization period was shortened by 75% at the elevated temperature. After hydrothermal synthesis of 2 days, the membrane showed H₂ permeance up to 2.8 × 10⁻⁸ mol·m⁻²·s⁻¹·Pa⁻¹ and H₂/CH₄ selectivity up to 49.6 at 0.2 MPa and 298 K. More importantly, STT zeolite membrane was resistant to CO and H₂S, which should be prevented from feeding to the commercial polymeric and Pd membranes. The membrane was stable up to 336 h in the simulated coke oven gas of 63 H₂: 28 CH₄: 7 CO: 2 C₂H₆ containing 100 ppm H₂S. This would pave the way of zeolite membranes to H₂ separation in practical applications.