11. Interfacial Mechanism and Kinetics of Phase-Transfer Catalysis

The mass transfer resistances strongly depend on the nature of the hydrodynamics inthe contacting device and the mode of operation. Many devices have been used to studytwo-phase mass transfer at or near the liquid–liquid interface. Hence, the hydrodynamiccharacteristics of ion transport through a membrane were presented to evaluate the feasibilitythat this permeation system can be calibrated as a standardized liquid–liquidsystem for studying the membrane-moderated PT-catalyzed reaction. The individualmass transfer coefficients and diffusivities for the aqueous phase, organic phase, andmembrane phase were determined and then correlated in terms of the conventional Sh–Re–Sc relationship. The transfer time of quaternary salt across the membrane and thethickness of the hydrodynamic diffusion boundary layer are calculated and then the effectof environmental flow conditions on the rate of membrane permeation can be accuratelyinterpreted [127].The mass transfer of quaternary salt from the organic phase into the aqueous phasethrough a lipophilic membrane is indicated in Fig. 3. Assume that the solute activity in thislipophilic membrane is identical to that in the bulk organic solution, then the mass fluxvalues for the individual species are described byN ¼ k o ½QXŠ ½QXŠ i ð57ÞN ¼ k a ½QXŠ i ½QXŠ ð58ÞN ¼ k m ½QXŠ i ½QXŠ ið59ÞThe asterisk denotes the species in the organic phase and the membrane phase, respectively.The distribution coefficients of quaternary salts between membrane and aqueousphase or organic phase are defined asm ¼ ½QXŠ i½QXŠ ið60Þandm ¼ ½QXŠ i½QXŠ ið61ÞFIG. 3Mass transfer of the catalyst between two phases and membrane.Copyright © 2003 by Taylor & Francis Group, LLC