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

Supported carbon membranes were prepared from furfuryl alcohol (FA) precurs or by vapor deposition polymerization (VDP). For this purpose gamma-Al2O3/a lpha-Al2O3 or glass/alpha-Al2O3 support tubes were pretreated with an acid catalyst and exposed to FA vapors at 90 degrees C. The tubes were then heat ed at 200 degrees C to crosslink the poly(furfuryl alcohol) (PFFA) polymer and carbonized slowly to 600 degrees C. The polymerization and carbonizatio n cycle was repeated once to improve the permeation properties. The membran es were examined by scanning electron microscopy (SEM) and tested in a perm eation cell with single gases (H-2, N-2, O-2, CO2, CH4) and with the mixtur e CO2-CH4. After the first polymerization/carbonization cycle the membranes had little selectivity for gas separations. After the second polymerizatio n/carbonization cycle the membranes had ideal selectivities 10-13 for O-2:N -2, 80-90 for CO2:CH4, and 90-350 for H-2:N-2 at room temperature. The perm eance was 0.6-2.5 for H-2, 0.27-0.58 for CO2 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 degr ees C but the selectivities were lower, e.g. one of the membranes had H-2 p ermeance 10.6 MPU and H-2:N-2 ideal selectivity 30. (C) 2000 Elsevier Scien ce B.V. All rights reserved.