Authors: J.C. Diniz da Costa; G.Q. Lu; V. Rudolph

Source: Journal of Nanoscience and Nanotechnology, Volume 4, Number 3, March 2004 , pp. 265-269(5)

Publisher: American Scientific Publishers

Abstract:

High-quality nanometer thick ultramicroporous membranes were prepared from silica sol-gel processes and tested for the permeation of binary gas mixtures of He, H₂, CO₂, and CH₄ across different temperature and partial pressure regimens. Pore size distribution by molecular probing showed that the majority of pore sizes had dimensions below 2.9 Å. In 50:50 binary mixtures, the fluxes of gases increased as a function of temperature, indicating an activated transport mechanism. The ultramicroporous membranes showed high selectivities at 150 °C for He/CO₂ (30), He/CH₄ (93), H₂/CO₂ (10), and H₂/CH₄ (9) with lower selectivities for CO₂/CH₄ (5). High activation energies (E_a) were observed for the permeance of 50:50 binary mixtures containing He and H₂ of 22.1-27.5 and 17.6-23.1 kJ·mol^-1, respectively. The E_a for the permeance of the total mixture approached the E_a for the permeance of the molecule with the smaller kinetic diameter (He or H₂).

Keywords: ULTRAMICROPOROUS MEMBRANES; PERMEATION; SELECTIVITY; ACTIVATION ENERGY

Document Type: Research article

DOI: http://dx.doi.org/10.1166/jnn.2004.036

Publication date: 2004-03-01

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