11. Interfacial Mechanism and Kinetics of Phase-Transfer Catalysis

@CQXS ¼ D e@t@C s QY@th i@ r 2 @CQXS =@r r 2 k@rs¼ D e @ r 2 @C s QY =@rr 2 þ k@rsIn the organic bulk solution:dC orgQX¼ kdt 2 C orgRX Corg QYdC orgRX¼dtC orgQY ¼ q 0k 2 C orgRX Corg QYhk q aC oegQXC s QXC s QXC s QXiC s QYKCQYs Kð155Þð156Þð157Þð158ÞC orgQXC s QX;a C s QY;a ð159ÞC s QX;a ¼ 3ð 10 2 C s QXdThe initial and boundary conditions are:IC: t ¼ 0; C orgRX ¼ C0 RX; C s QX ¼ 0; C s QY ¼ 0; C orgQX ¼ q 0; C orgQY ¼ 0ð160Þð161ÞBC: r ¼ 0; dCs QXdrr ¼ R; D qdC s QXdrr ¼ R; D qdC s QYdr¼ dCs QYdr¼ 0h¼ k q C orgQXh¼ k q C orgQYC s QX;RC s QY;Riið162Þð163Þð164ÞThe above equations can be rendered dimensionless in terms of Thiele’s modulus, Biotnumber for mass transfer, and nondimensional time and distance, which are defined as 2 ¼ k sR 2; BiD m ¼ k qR; ¼ D ete D q R 2 ; ¼ r Rð165ÞIn the analysis of heterogeneous solubilization, the role of the solid-phase reaction ininfluencing the overall reaction is different from that for the usual gas–solid catalyticreaction. The most important situation is that the film and internal diffusion effects withinthe solid and at the solid–liquid interface are significant.V. TRI-LIQUID PHASE TRANSFER CATALYSISNeumann and Sasson [221] investigated the isomerization of allylanisole using PEG as thecatalyst in a toluene and aqueous KOH solution. They observed that a third-liquid phasewas formed between the aqueous and the organic phases. This was the first report regardingtri-liquid PTC. In 1987, Wang and Weng [222] performed the reaction of benzylchloride and sodium bromide using tetra-n-butylammonium bromide as the PT catalystin liquid–liquid phases. They found that the overall reaction rate rapidly increased whenthe amount of catalyst used exceeded some critical value. In such reaction conditions, thePT catalyst was found to be concentrated within a viscous liquid phase that was insolubleCopyright © 2003 by Taylor & Francis Group, LLC