Diisopropanolamine (DIPA) is a secondary amine used in the Shell ADIP process to sweeten natural gas. DIPA systems are similar to MEA systems but offer the following advantages: carbonyl sulfide (COS) can be removed and regenerated easily and the system is generally noncorrosive and requires less heat input.
One feature of this process is that at low pressures DIPA will preferentially remove H2S. As pressure increases the selectivity of the process decreases. The DIPA removes increasing amounts of CO2 as well as the H2S. Therefore, this system can be used either selectively to remove H2S or to remove both CO2 and H2S.