Fabrication and CO₂ separation performance of carbon membranes doped with TiO₂ nanoparticles

A TiO₂ sol was prepared from tetrabutyltitanate using polyethylene glycol as a stabilizer, and this was homogeneously mixed with polyfurfuryl alcohol, dip-coated on a porous Al ₂O₃ substrate and carbonized at 700°C for 4h to produce TiO₂-doped carbon membranes. SEM, TEM, XRD and granulometry were used to characterize the membranes, and their permeation performance for CO₂ , N₂ and CH₄ were tested. It was found that polyethylene glycol is effective in controlling the hydroxylation of the tetrabu-tyltitanate. This not only favored the formation of spherical TiO₂ nanoparticles with a small size and narrow size distribution but also improved the homogeneity of the dispersion of the TiO₂ nanoparticles in polyfurfuryl alcohol. The doping of the membranes with TiO₂ nanoparticles greatly improved the CO₂ permeance and permselectivity. The TiO₂ doping helps to create diffusion paths, but it may also block the pores in the carbon matrix. Therefore, the CO₂ permeance reached a maximum of 7. 0×10 ^-8 mol·m ^-2·s ^-1·Pa ^-1 with a mass ratio of TiO₂ sol to polyfurfuryl alcohol of 2, where the CO₂ / N₂ and the CO₂ / CH4 selectivities were 34 and 64, respectively.