11. Interfacial Mechanism and Kinetics of Phase-Transfer Catalysis

Taking the mass balance for the cation Q of the PT catalyst in the system givesC orgQX;0 ¼ Corg QX þ Corg QI þ Corg QrOQThe expression for the active intermediate isC orgArOQ ¼1 þ 1C org ArOKC orgQX;0C orgKXþ Corg KIK 3 K 4ð135Þ ð136ÞThe concentration of ArOQ depends on the amounts of ArOK, KX, and KI, and theinitial usage of the catalyst QX. Combining the mass balance equation for initial RX in theorganic phase with Eq. (134), a deactivation function can be introduced in the situationunder decline of catalytic efficiency, leading to the following equations:withdC orgArORdt¼ k app;0C orgRX;0C orgArORk app;0 ¼ðk a þ k b K 2 C orgKI =Corg KX ÞCorg QX;0ð137Þand1 ¼ 1 þ K 2C org ð138ÞKIC org 1 þ 1 C orgKXC org KXþ Corg KIArOK K 3 K 4In Eq. (137), k app;0 is the initial apparent reaction rate constant and is dependent on theamounts of KI, KX, and QX in the organic phase. If the rate of change of ArOR follows apseudo-first-order reaction, then would be approximately a constant. In such cases, nodeactivation effect appears. If the reaction rate behaves as a diminished first order, then decreases with the progress of the overall reaction.To evaluate the exact variation of with time is to measure the rate of deposition ofKX and the other parameters directly or to apply an empirical correlation relating to theeffect of the decrease in C orgArOKon the overall reaction. The expression of the deactivationfunction and the kinetic data would determine the form of , such as1 ¼ð1 þ k d tÞ 2 or ¼ 1ð139Þ1 þ k d tLepertit and Che [220] discussed the definitions of interfacial co-ordination chemistry(ICC) and surface organometallic chemistry (SOMC) and compared their maincharacteristics and applications. The concepts of ICC applied to catalyst preparation,adsorption, and relations with catalysis are also useful in the development of interfacialmechanisms.C. Mass Transfer EffectsSufficient kinetic information should be collected to proceed the process design for aspecific reaction system. The factors affecting the performance of SLPTC includes agitationrate, particle size of solid salt, reaction temperature, the amount of solid reactant, thekinds and amount of PT catalyst, the solubility and the dissolution rate of solid reactant inthe organic solvent, extra addition of other metal salts, the polarity, surface tension, andCopyright © 2003 by Taylor & Francis Group, LLC