Simultaneous separation of H2S and CO2 from CH4 by a high silica CHA-type zeolite membrane

A high silica CHA-type membrane was synthesized by the in-situ crystallization method on a disk like α-alumina porous support to separate both acid (H2S, CO2) gases from methane. The membrane showed a permeance of 3.39×10−8 mol/m2 s Pa for pure CO2with CO2/CH4 ideal selectivity of 21.6 at 303 K and 100 kPa pressure difference across the membrane. The membrane was also tested with N2 and O2 pure gases indicating a small O2/N2 selectivity of 1.2-1.4, which shows that this type of membrane is not suitable for O2/N2 separation. The membrane performance was also analyzed by binary (CO2-CH4) and ternary (H2S-CO2-CH4) gas mixtures, with compositions near the real sour natural gas (CO2: 2.13 mol%, H2S: 0.3 mol% and CH4:97.57 mol %), at 298 K and 400 kPa pressure difference. The results revealed that the synthesized membrane is able to separate H2S from CH4 so that both acid gases (CO2, H2S) can be removed from CH4 simultaneously. H2S permeance was 1.70×10−8 mol/m2 s Pa with H2S/CH4 selectivity of 3.24.