11. Interfacial Mechanism and Kinetics of Phase-Transfer Catalysis

26 > Dowex 1 2 > A-27 IRA-410 > IRA-904 > mi4-20 (4%). Most commercial ionexchangeresins are of the hydrophilic functional group type.In addition, the immobilized amount of the functional group of -NðC 4 H 9 Þ 3 in theresin was determined from the mass fraction of nitrogen by EA for C, H, and N, and fromthe chloride ion density titrated by the Volhard method. The sequence of determiningmethod for the immobilized content of tri-n-butylamine in the resin wasTGA > EA > Volhard. The analyzed result of the TGA (or EA) method was based onthe elemental weight, and it revealed the real immobilized content. However, the analyzedresult of the Volhard method determined the free chloride ion in the solution by theAgNO 3 titration method. The immobilized content of tri-n-butylamine in the resin bythe TGA (or EA) method was > 20% larger than that determined by the Volhard method.The immobilized content of tri-n-butylamine in the resin by the TGA (or EA) method wasindependent of the number of cross-linkages, and only dependent of the number of thering substitution.These experimental results demonstrate that tri-n-butylamine could be immobilizedcompletely with the active site on the resin for an immobilizion duration of 6 days.However, the immobilized content of tri-n-butylamine by the Volhard method was dependenton both the number of cross-linkages and the number of ring substitutions. Theimmobilized contents for the Volhard method are about 50–70% that for TGA (orEA). Since the analyzed results of the Volhard method determined the free chlorideions in the solution by the AgNO 3 titration method, the free chloride ion of the activesite were only measured at 50–70% of the amount of immobilized content. The trend ofthe varied content for microresin is larger than that for macroresin. This result indicatesthat the analysis by the Volhard method may be influenced by the diffusion problem, andmay be because the resin did not swell completely in the aqueous solution. On the otherhand, if the resin is used as a TC to react in an actual reaction system, and the resin couldnot swell completely to release all free chloride ions, then the reaction environment wouldbe influenced by the mass transfer of the reactant.As indicated by Ohtani et al. [32] both organic reactant and aqueous reactant existwithin the pores of the polymer pellet. The HLB of the support structure determines thedistribution of the two phases within the catalyst support [167,168]. Therefore, the distributionof the organic reactant and aqueous reactant within the pores of the polymerpellet will directly influence the reaction. The swollen capability of the resin is used toestimate the validity of the resin. The effect factor of the swollen capability of the resinincludes the cross-linkage, the number of ring substitutions (total exchange capability), theelectronic charge and diameter of the counterion, the polarity of the organic solvent, thecomposition of the functional group, the chemical bonding type between both exchangeions, and the electrolyte concentration in the aqueous solution.Wu and Lee [166] and Tang [169] reported the amount of imbibed solvent, volumeratio, and porosity of 12 kinds of ion-exchange resin for seven kinds of solvents (dichloromethane,chloroform, 1,2-dichloroethane, benzene, toluene, chlorobenzene, and water)when 1 g of the resin was placed in 25 mL of the pure solvent. The experimental results forthe commercial ion-exchange resin were as follows:1. The amounts of the imbibed solvent for the aromatic solvents (benzene,toluene, and chlorobenzene) were larger than those for halide aliphatic solvents(dichloromethane, chloroform, and 1,2-dichloroethane) since the resin was ofthe styrene type; the sequence of the imbibed amount for the aromatic solventswas benzene > toluene > chlorobenzene.Copyright © 2003 by Taylor & Francis Group, LLC