Inorganic membranes for carbon dioxide and nitrogen separation

Inorganic membranes capable of separating carbon dioxide and nitrogen mixture offer potential applications in membrane process for postcombustion carbon dioxide capture. This article provides a concise review of carbon dioxide permeation and separation characteristics and the chemical and thermal stability of microporous carbon, silica, and zeolite membranes. Gas permeation and separation through these microporous membranes generally occur by the solution (adsorption) and diffusion mechanism. All of these membranes are permselective for carbon dioxide over nitrogen because carbon dioxide has a large solubility and mobility in membrane micropores in comparison to nitrogen. These microporous membranes exhibit good carbon dioxide permeance (up to 10 ^-6 mol m ^-2 s ^-1 Pa ^-1) and extremely high carbon dioxide to nitrogen selectivity (up to 500) at around room temperature. The selectivity diminishes above 200°C because the membrane selectivity is controlled by diffusion, and the diffusivity ratio for carbon dioxide to nitrogen is < 2. At around room temperature, zeolite (especially Y type) membranes offer attractive properties for use in postcombustion carbon dioxide capture. New membranes such as dense mixed-conducting ceramic-carbonate dual-phase membranes show high carbon dioxide separation performance at high temperatures and may be used in precombustion processes for carbon dioxide capture.