Abstract: The invention relates to an alkanolamine composition for the removal of acid gas impurities comprising CO2, H2S, COS, or mixtures thereof, from a gaseous or liquefied gas stream containing said acid gases, and to a process of using the alkanolamine composition. The process involves contacting the gas stream with the alkanolamine composition, or an aqueous solution thereof, comprising a mixture of methyldiethanolamine (MDEA) and methylmonoethanolamine (MMEA) in an amount sufficient to generate in situ at least 5% by weight of N,N'-bis(dimethyl)-N-hydroxyethyl-ethylenediamine (DMHEED), in a contact zone, regenerating said amine composition in a regeneration zone, and recycling said regenerated amine composition to said contact zone. The invention also resides in an aqueous solution comprising from about 20% to about 70% by weight of DMHEED. The invention further resides in the addition of DMHEED in an amount of from about 5% to about 30% by weight to compositions or solutions containing other alkanolamines.