Preparation of supported carbon membranes from furfuryl alcohol by vapor deposition polymerization

Supported carbon membranes were prepared from furfuryl alcohol (FA) precursor by vapor deposition polymerization (VDP). For this purpose γ-Al2O3/α-Al2O3 or glass/α-Al2O3 support tubes were pretreated with an acid catalyst and exposed to FA vapors at 90°C. The tubes were then heated at 200°C to crosslink the poly(furfuryl alcohol) (PFFA) polymer and carbonized slowly to 600°C. The polymerization and carbonization cycle was repeated once to improve the permeation properties. The membranes were examined by scanning electron microscopy (SEM) and tested in a permeation cell with single gases (H2, N2, O2, CO2, CH4) and with the mixture CO2–CH4. After the first polymerization/carbonization cycle the membranes had little selectivity for gas separations. After the second polymerization/carbonization cycle the membranes had ideal selectivities 10–13 for O2:N2, 80–90 for CO2:CH4, and 90–350 for H2:N2 at room temperature. The permeance was 0.6–2.5 for H2, 0.27–0.58 for CO2 and 0.08 for O2, all in MPU (1 MPU=10−8 mol/m2 Pa s). The permeances were sharply higher at 150°C but the selectivities were lower, e.g. one of the membranes had H2 permeance 10.6 MPU and H2:N2 ideal selectivity 30.