Rapid measurement of gas diffusivity in liquids using a tube-in-tube reactor with an unsteady-state strategy

In this work, an unsteady-state strategy for rapid measurement of gas diffusivity in liquid is proposed, which has a quick perturbation of the liquid flow rate in inner tube for obtaining the change of gas flow rate across the membrane with time. The strategy has taken full advantages of the tube-in-tube reactor that possesses a high permeability Teflon AF-2400 membrane to accelerate the diffusion rate of gas to liquid without direct contact between the two phases. With a developed mathematical model fitting the recorded variation of gas flow rate with time, the gas diffusivity in liquid can be determined within 0.5–3 min compared with the conventional methods of 4–14 hr. In addition, the strategy is demonstrated with several gas–liquid systems (O 2 -DMSO, CO 2 -[Emim] [NTf 2 ] and CO 2 -[Bmim] [BF 4 ]) with varied viscosities and temperatures, showing a good agreement with literature values with less than 10% deviation.