CO2 hydrate formation experiments are performed in a 20L semi-batch stirred tank reactor using three different impellers (a down-pumping pitched blade turbine, a Maxblend, and a Dispersimax) at various rotational speeds to examine the impact of the flow conditions on the CO2 hydrate formation rate. An original mathematical model of the CO2 hydrate formation process that assigns a resistance to each of its constitutive steps is established. For each experimental condition, the formation rate is measured and the rate-limiting step is determined on the basis of the respective values of the resistances. The efficiencies of the three considered impellers are compared and, for each impeller, the influence of the rotational speed on the rate-limiting step is discussed. For instance, it is shown that a formation rate limitation due to heat transfer can occur at the relatively small scale used to perform our experiments. (c) 2015 American Institute of Chemical Engineers