Experiments were performed in a customized double stirred tank reactor to study the kinetics of CO2 absorption into NH3 solutions at concentrations ranging from 0.42 to 7.67 kmol.m(-3) and temperatures between 273.15 and 293.15 K. The results show that the reactive absorption was first order with respect to CO2 but fractional order (1.6-1.8) with respect to ammonia. Experimental data can be satisfactorily interpreted by a termolecular mechanism using k(NH3)(T) = 7.6089x10(8) exp (-4018.4/T) and k(H2O)(T) = 7.9161x10(7) exp (-4356.4/T). (C) 2016 American Institute of Chemical Engineers AIChE J, 62: 3673-3684, 2016