TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Activator: The activator is of formula (Ia).p = 2-4.(The disclosure indicates that this compound is of formula H2N-(CH2)p-NH-CH2-CH2OH).Preferred Absorbent: The absorbent liquid is in the form of an aqueous solution of MDEA and the activator. The solution further contains a minor amount of organic solvent(s) of CO2 which are soluble in water, particularly sulfolane, methanol or N-methylpyrrolidone. The concentration of MDEA in the absorbent liquid is 1-6N (preferably 2.5-5N). The ratio of the number of moles of activator to the total number of moles of activator and MDEA is between 0.01 and 0.5 (preferably 0.05-0.25).Preferred Process: The gas to be treated may contain additional acid gases e.g. hydrogen sulfide. The liquid hydrocarbon content is up to 10 cubic meters per million standard cubic meters of gas. The gas is contacted with the absorbent at 10-100 degreesC (preferably 30-60 degreesC) under an absolute pressure of 1.5-120 bar. The partial pressure of CO2 is preferably at least 3 bar. The absorption zone is provided with structured or unstructured packing. At least part of the absorbent liquid loaded with CO2 (and other acid gases) is regenerated by pressure reduction in one or more steps. The reduced-pressure liquid is then subjected to complementary regeneration by steam stripping or (in)direct heating and recycled to the absorption zone. When only part of the reduced pressure liquid is subjected to complementary regeneration, the liquid resulting from this is recycled into the upper part of the absorption zone, while the portion not subjected to complementary regeneration is recycled into the absorption zone below the absorbent liquid regenerated by stripping. SPECIFIC COMPOUNDS - The activator is aminoethylethanolamine.    EXAMPLE - A mixture of CO2 (20 volume%) and methane (80 volume%) was fed at 330 m3 (STP)/hour to the bottom of an absorption column (0.2 meters diameter, 3.5 meters high) packed with Mellapak (RTM) structured packing. An injection of 0.33 l/hour of a 9-13C liquid hydrocarbon cut (density 0.8) was added at the gas inlet. An aqueous solution of methyldiethanolamine (3.4 mol/l), aminoethylethanolamine (0.6 mol/l) and CO2 (60 g/l) was introduced to the top of the column at a flow rate of 2.3 m3/hour. Gas depleted in CO2 was removed from the top of the column and CO2-loaded absorbent liquid was withdrawn from the bottom. The absolute pressure and temperature at the head of the column were 40 bar and 50 degreesC respectively. The purified gas contained only 3.3 volume% CO2. In contrast, when using diethylenetriamine as activator the purified gas contained 6.5 volume% CO2.