Corrosivity Difference among Alkanolamine Solutions Saturated with CO₂

Abstract

In the CO₂ separation and recovery process of CCS, high concentration alkanolamine (amine) solutions are widely used. However there exists a basic chemical structure difference between primary and tertiary amines. Therefore, corrosion tests were carried out on CO₂-saturated DGA (primary amine) and CO₂-saturated MDEA (tertiary amine). There was no distinct difference in corrosivity between DGA and MDEA at their low concentrations. However, remarkable difference was confirmed at their high concentrations. MDEA absorbs CO₂ as bicarbonate, whereas DGA absorbs CO₂ mainly as carbamate at high concentrations. It was concluded that DGA carbamate produces a stable water-soluble five-membered chelate ring with Fe²⁺, resulting in the high corrosivity. Carbamates, which do not produce a five-membered chelate ring with Fe²⁺ do not show very high corrosivity as DGA carbamate.