In industry there are many examples of absorption of a gas with or without chemical reaction in the liquid phase. In physical absorption, a particular gaseous component is removed from a gas mixture due to its larger solubility in the liquid phase solvent. The removal of butane and pentane from a refinery gas mixture by a heavy oil in the liquid phase is an example of physical absorption. In absorption with chemical reaction, the gaseous component to be removed transfers across the gas-liquid interface due to a difference in the bulk chemical potentials or concentrations in the two phases. The transferred gas then reacts with a liquid-phase component while simultaneously diffusing in the liquid phase mixture. The gas purification processes, such as removal of chlorine from nitrogen or air by means of water, removal of carbon dioxide from synthesis gas by means of aqueous solutions of hot potassium carbonate or monoethanolamine, and removal of H2S and CO2 from hydrocarbon cracking gas by means of ethanolamine or sodium hydroxide, are some examples of absorption with chemical reaction.
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