Hydrogen separation from reforming gas using organic templating silica/alumina composite membrane

The separation characteristics and dynamics of hydrogen mixture produced from natural gas reformer were studied on methyltriethoxysilane (MTES) templating silica membrane. The permeation and separation of CO pure gas, H₂/CO (50/50, vol.%) binary mixture and H₂/CH₄/CO/CO₂ (69/3/2/26, vol.%) quaternary mixture were investigated both experimentally and theoretically. Since the permeance of pure CO on the MTES membrane was very low (CO ≈ 4.79-6.46 × 10^-11 mol m^-2 s^-1 Pa^-1), comparatively high hydrogen selectivity could be obtained from the H₂/CO mixture (separation factor = 93-110). This implies that CO, which should be eliminated prior to use in fuel cells, can be separated from hydrogen mixtures using MTES membranes. The permeance of the H₂ quaternary mixture on the MTES membrane was 2.07-3.37 × 10^-9 mol m^-2 s^-1 Pa^-1 and the separation factor of H₂/(CO + CH₄ + CO₂) was 6-24 at 323-473 K. Since the permeation flux in the MTES membrane was affected by both molecular sieving and surface diffusion, high H₂ selectivity could be obtained at elevated temperatures. The transient permeation/separation behaviours of hydrogen multi-component systems on the MTES membrane were predicted by the Generalized Maxwell-Stefan model incorporating the dusty gas model and Langmuir isotherm model.