Sterically-Hindered Amines for Acid-Gas Absorption

Abstract

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.