SELECTIVE REMOVAL OF HYDROGEN SULPHIDE BY MDEA SOLUTIONS.

When compared with primary or secondary amines, tertiary amines possess both 'thermodynamic' and 'kinetic' selectivity for removal of H//2S from mixtures of hydrogen sulphide and carbon dioxide. One of these amines, methyl diethanolamine, is used industrially as an aqueous solution, but the selectivity achieved may be less than that calculated by taking into account the alkalinity of the solution. Gas absorption experiments in the stirred cell confirmed that CO//2 reacts in aqueous MDEA solutions where the rate is proportional to the amine concentration. On the other hand, no reaction took place when a nonaqueous solution of MDEA in n-propanol was used. These results confirmed that MDEA acts as a homogeneous catalyst for CO//2 hydrolysis.