Fluorination of 2,4-dinitrochlorobenzene (DNCB) with solid KF was conducted in the presence of polymer-supported tetraphenylphosphonium chloride catalyst under solid-solid-liquid (S-S-L) phase transfer conditions. The triphase fluorination obeyed zero-order kinetics with respect to DNCB concentration and first-order kinetics with respect to the catalyst concentration. The apparent activation energy for the fluorination was estimated as about 40 kJ/mol. On the basis of these results, the ion exchange reaction between the Cl- ion of the supported catalyst and the F- ion of KF was concluded to be rate-determining in this S-S-L triphase fluorination. The addition effect of water on the triphase fluorination was discussed by means of both the prompted dissolution of solid KF and the decreased reactivity of the F- ion, induced by increased hydration. (C) 2000 Elsevier Science B.V. All rights reserved.