Synthesis of all-silica ZSM-58 zeolite membranes on hollow fibers for CO2/H2 separation

Hydrogen separation is a significant process in hydrogen production from syngas. Membrane separation is well-known as an energy-saving and environmental-friendly technique to remove CO₂ from syngas. ZSM-58 zeolite membrane, owning good affinity to CO₂ molecules and narrowed aperture size (0.36 nm × 0.44 nm), has been attractive in CO₂ gas separations. In this work, all-silica ZSM-58 zeolite membranes were synthesized on ceramic hollow fibers to lower the membrane cost and firstly employed in CO₂/H₂ gas separation. A high-quality ZSM-58 zeolite membrane was hydrothermally synthesized for 48 h by using ball-milled zeolite seeds. The membrane exhibited a high CO₂/H₂ separation selectivity of 81.6 as well as a CO₂ gas permeance of 1.08 × 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ at 233 K. Effects of temperature, feed pressure and feed CO₂ concentration on separation performance of the membrane were investigated extensively. High separation selectivity was favored at low temperature, low feed pressure and high feed CO₂ concentration. The maximum CO₂ permeance was obtained at 253 K. The membrane also maintained very good stability in the separation at low temperature, indicating the availability of ZSM-58 zeolite membrane in CO₂ removal from syngas.