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

Abstract

Supported carbon membranes were prepared from furfuryl alcohol (FA) precursor by vapor deposition polymerization (VDP). For this purpose γ-Al_2O_3/α-Al_2O_3 or glass/α-Al_2O_3 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 (H_2, N_2, O_2, CO_2, CH_4) and with the mixture CO_2–CH_4. 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 O_2:N_2, 80–90 for CO_2:CH_4, and 90–350 for H_2:N_2 at room temperature. The permeance was 0.6–2.5 for H_2, 0.27–0.58 for CO_2 and 0.08 for O_2, all in MPU (1 MPU=10^(−8) mol/m^2 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 H_2:N_2 ideal selectivity 30.