On the Determination of the Diffusivity of CO 2 in Aqueous and NonAqueous Solvents: Investigations with Laminar Jets and Wetted Wall Columns

Abstract

The diffusivity of CO 2 in ethanol, n-heptane and methyl tertiary butyl ether (MTBE) has been determined using a laminar jet reactor and a wetted wall column at two temperatures (293 K and 298 K). The reactors have been operated in the laminar and transition regime. In the transition regime, the effective diffusivity of CO 2 was found to increase with Reynolds number, which could be explained by the increasing contribution of eddy diffusivity to the overall mass transfer. However, even in the laminar regime, the molecular diffusivity of CO 2 was found to vary with experimental conditions, i.e., the Reynolds number. It has been observed that the value of D CO 2 reduces with increasing Re in the case of ethanol, while the opposite trend is observed for n-heptane. These effects can be (partially) explained by accounting for combined molecular and eddy diffusivity within the laminar regime as proposed by the mass transfer model of King (1966). To the knowledge of the authors, these effects of gas absorption in nonaqueous/organic solvents have not been reported earlier. The present findings indicate that data on gas absorption in these types of systems should be used with caution.