Adsorption BT - Carbon Capture

Abstract

In an adsorption process a gas mixture contacts small porous particles, which can selectively adsorb or complex with CO2 for its effective removal from the gas mixture. Sorbent technologies may also be developed to capture CO2 indirectly by focusing on the selective adsorption of other gases in a given gas mixture, e.g., N2, O2, CH4, H2, etc. Adsorption is particularly known for its effectiveness in the separation of dilute mixtures. Molecules of CO2 may be held loosely by weak intermolecular forces, termed physisorption or strongly via covalent bonding, termed chemisorption. Generally, physisorption occurs when the heat of adsorption is less than approximately 10–15 kcal/mol, while chemisorption occurs with heats of adsorption greater than 15 kcal/mol. These are rules of thumb, however, and exceptions do exist. For instance, the heat of physisorption of CO2 in some zeolites has been reported to be as high as 50 kcal/mol, with heats of chemisorption known to extend from as low as 15 kcal/mol to over 100 kcal/mol. The heat of adsorption is a direct measure of the binding strength between a fluid molecule and the surface.