The reactor design and kinetics of the substitution reaction of hexachlorocyclotriphosphazene, (NPCl2)(3), with phenol to synthesize the partially substituted (phenoxy)chlorocyclotriphosphazene was investigated by using triphase catalysis in an organic phase/alkaline solution. Two reactors, the slurry reactor and the fixed-bed reactor were proposed to evaluate a liquid-solid-liquid triphase reaction. The design problems of these reactors were evaluated to obtain the best performance. A cross type "+" Teflon magnetic stirrer was put in the bottom of the slurry reactor that can reduce the liquid flow rate to prevent solid catalyst to flow out of the reactor. Because the mass-transfer rate for the first and second degree of the substitution of the series phosphazene reaction were slow, they reacted in situ with sodium phenolate in the interior of the resin to form the two to five degrees of the substituted products. The kinetic parameter of the phosphazene reaction was influenced by the particle diffusion of the reactant. The effectiveness factor and Thiele modulus of the system and the diffusivity of the reactants were also obtained. The relationship of the coverage of catalyst onto the interfacial area between the two phases with the reaction-rate constant was studied. (C) 2003 Elsevier Ltd. All rights reserved.