Separation of CO2 and/or H2S from gases is effected by washing the gases with aq. solns. contg. -dimethyl aminobutyric acid dimethylamide, having formua Me2N-(CH2)3-CONMe2, (I), as absorbent. Absorption takes place under press. Solvent is regenerated after releasing press. Process can be used for purifying natural gas, coke oven gas, coal gasification gas and synthesis gas. (I) is low-foaming and causes less corrosion than standard tert. N-contg. alkanolamines. E.g. foaming with (I) was 0.2 mm compared to 2 mm with methyl diethanolamine. Yearly linear corrosion wt. loss of appts. was reduced from 1 to 0.6. In an example, CO2-content of synthesis gas, was reduced from 29.4- to 0.1 vol. % by counter-current contact of 270 m3/hr synthesis gas at 17 bar, 75 degrees C, with 3.1 m3/hr 2.5 molar soln. of (I) at 75 degrees C.
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