Permeation and separation of a carbon dioxide/nitrogen mixture in a methyltriethoxysilane templating silica/α-alumina composite membrane

The experimental and theoretical study of gas permeation and separation characteristics of an MTES (methyltriethoxysilane) templating nano-porous silica/α-alumina composite membrane was conducted using a carbon dioxide/nitrogen binary system. The adsorption equilibriums of carbon dioxide and nitrogen on the MTES templating silica layer were measured using a gravimetric method. The surface diffusion was a dominant transport mechanism on the MTES templating silica layer rather than micro-pore diffusion. On the other hand, the surface diffusion effect of nitrogen was much smaller than that of carbon dioxide. In the separation of the carbon dioxide/nitrogen mixture on the composite membrane, the strong adsorbate on the MTES templating silica layer permeated through the membrane more rapidly than the weak adsorbate due to the surface diffusion and/or the pore-blocking phenomenon. The permeation and separation of multi-component permeation were well predicted by the combined GMS (generalized Maxwell–Stefan) and DGM (dusty gas model) model. The separation characteristics of the composite membrane were tested under various experiment conditions such as feed pressure, temperature, stage cut and sweeping gas flow rate.