Fabrication of high-selective hollow fiber DD3R zeolite membrane modules for high-pressure CO₂/CH₄ separation

All-silica Decadodecasil 3 R (DD3R) zeolite membranes, possessing small pore size of 0.36 nm × 0.44 nm, have been attractive in CO₂ removal from natural gas. In this work, hollow fiber DD3R zeolite membrane modules with membrane length of 40 cm and effective membrane area of 811 cm² for each were successfully fabricated by ensemble synthesis strategy. Different membrane segments including that was grown on sealing glaze have similar thickness in the range of 4–6 μm. The ozone detemplation time of membrane unit was reduced by a half with the assistance of Teflon spiral column. The resulting membrane module exhibited a good CO₂/CH₄ separation selectivity (105) as well as a stage-cut of 25.7% at high feed pressure of 3.1 MPa. Effects of feed pressure, feed gas flow rate and permeate pressure on separation performance of the membrane module and concentration polarization were investigated extensively. When the feed gas flow rate was 2 L min⁻¹, the retentate CO₂ concentration was lowered to 9.45% and the CH₄ loss was limited to 4.87% at the feed and permeate pressures of 3.1 MPa and 2 kPa. The concentration polarization effect became more serious at higher feed pressure or lower feed gas flow rate.