The neutralization of NaOH with CO2 in a continuously operated airlift reactor with gas flow rates up to 10 NL min(-1) and gas phase recycle was investigated. Neutralization experiments were performed at 25 degrees C and the amount of absorbed CO2, as well as the NaOH feed rate, were recorded. The reaction rate was calculated based on the two-film theory and empirical equations for several parameters. The calculations of the volumetric mass transfer coefficient, the liquid phase circulation velocity, and the gas holdup were experimentally validated. The reaction rate and the process efficiency were modeled with a deviation of 5 %.