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 (1MPU=10^-8mol/m²Pas). The permeances were sharply higher at 150°C but the selectivities were lower, e.g. one of the membranes had H₂ permeance 10.6MPU and H₂:N₂ ideal selectivity 30. Copyright (C) 2000 Elsevier Science B.V.