Zeolite L/carbon nanocomposite membranes on the porous alumina tubes and their gas separation properties

With one step of vacuum coating and pyrolysis, the thin zeolite L/carbon nanocomposite membranes (about 3–4 μm) were obtained on the porous alumina tubes by incorporating nano-sized zeolite L (about 100 nm) into polymeric precursor (polyfurfuryl alcohol (PFA)). The permeation properties of pure H2, CO2, N2 and CH4, together with CO2/CH4 and CO2/N2 mixtures through the composite membrane were measured and analyzed. A notable increase was observed in the permeances of gas species in comparison with the pure carbon membrane owing to the enhancement of the pore structure properties, including pore volume, surface area, pore size and its distribution. Due to the restricted diffusion of non-adsorbable gas by adsorbable component in the micropores, the CO2/CH4 and CO2/N2 permselectivities in the mixed gas system were higher than the results from pure gas permeation. The effects of permeation temperature, pressure difference and CO2 content in feed gases on separation performances of the composite membranes were also investigated. It was found that the CO2/CH4 and CO2/N2 separation factors decreased with increasing the permeation temperature and pressure difference, and increased with increasing CO2 content in the mixtures.