Sterically-Hindered Amines for Acid-Gas Absorption

This paper reviews sterlcally-hindered amines for removal of add gases such as CO2 and H2S from gaseous streams. Steric hindrance of amines reduces carbamate stability. Moderately hindered amines are characterized by high rates of CO2 absorption and high capacities for CO2. The moderately hindered amine in use with organic solvent has considerably higher capacity than the conventional amine-solvent system for simultaneous removal of CO2and H2S from synthesis gas and natural gas. A severely-hindered-amine absorbent, characterized by a very low rate of CO2absorption, has much higher capacity and selectivity than the current industry standard, methyldiethanolamine, for selective removal of H2S from CO2-containing streams. Use of hindered amines represents new advances in gas treating. Hindered amines save energy and capital in gas treating significantly. In addition, hindered amines used commercially have much better stability than conventional amines. As of today, fourteen commercial plants use hindered amines.