Triphase catalysis: a correlation for Sherwood number using the rotating disk contactor (RDC) developed earlier

Abstract

Triphase catalysis (TPC) has the potential for conducting phase-transfer catalyzed reactions in the continuous mode. However, there is so far no industrial acceptance of this possibility since the reaction rates achieved are usually low due to diffusional limitations. Triphase catalytic systems are strongly influenced by mass transfer, and thus an experimental technique using a rotating disk contactor was specifically designed by the authors to estimate individual mass transfer coefficients for the liquid phases [Glatzer, Desikan, & Doraiswamy, Chem. Eng. Sci. 53 (13) (1998) 2431]. The key to precise measurements is the choice of the model system which should have an almost negligible noncatalytic reaction but yet a high enough catalytic rate to be mass transfer controlled at low agitation speeds. The synthesis of octyl acetate from octyl bromide and potassium acetate has these attributes and was chosen as the test system. The reaction was mediated by polymer-supported tributylmethylammonium chloride or the corresponding phosphonium chloride. Mass transfer coefficients could be determined as a function of the agitation speed. Despite limited available data, an equation that correlates the Sherwood number to the Reynolds and Schmidt numbers has been proposed.