11. Interfacial Mechanism and Kinetics of Phase-Transfer Catalysis

FIG. 4 Yields of products and conversion of reactant as a function of reactant C 6 H 5 OH=ðNPCl 2 Þ 3consumption ratio at different NaOH concentrations: (abcd) 0.5 kmol=m 3 , (efgh) 0.9 kmol=m 3 , (ijkl)1.8 kmol=m 3 ;(*) (NPCl 2 Þ 3 ,(*)N 3 P 3 Cl 5 ðOC 6 H 5 Þ 1 ,(!)N 3 P 3 Cl 4 ðOC 6 H 5 Þ 2 ,(&)N 3 P 3 Cl 3 ðOC 6 H 5 Þ 3 ,(^) N 3 P 3 Cl 2 ðOC 6 H 5 Þ 4 ; ðÞ N 3 P 3 CLðOC 6 H 5 Þ 5 .reactant in the particle. In Fig. 4, the maximum yield of monophenolated product shifts tothe right by more than 0.2 unit, and the maximum yield of diphenolated product shifts tothe right by more than 0.1 unit. This reveals that the effect of intraparticle diffusion on theorganic reaction influences the reaction rate. This trend of shifting to the right of themaximum yield was increased with increasing concentration of NaOH.The reactivity of a triphase reaction is influenced by the structure of the active sites,particle size, degree of cross-linkage, degree of ring substitution, swollen volume, andspacer chain of a catalyst pellet. All these make the triphase reaction a complicatedone. Past efforts have carried out this investigation macroscopically. However, themechanism and effects of the internal molecular structure of the polymer support haveseldom been discussed.According to the steric effect of phenolate ion reacting with hexachlorocyclotriphosphazeneand the reports of Wu and Meng two-phase catalysis [69]; triphase catalysis[165]), the maximum yield of partially substituted phenolated product was increasedwith increasing degree of substitution reaction. Figure 4 shows that the maximum yieldof monophenolated product was larger than that of the diphenolated product, and themaximum yield of partially phenolated product decreased when the NaOH concentrationincreased (i.e., reactivity of the active site increased). This result reveals that the reactionrate of phenolate reacting with monophenolated (or diphenolated) product was greaterthan the diffusion rate of monophenolated (or diphenolated) product from active site tobulk solution and hexachlorocyclotriphosphazene from bulk solution to active site. Mostmonophenolated (or diphenolated) product reacted in situ with Resin þ OC 6 H 5 in theCopyright © 2003 by Taylor & Francis Group, LLC