A homogeneous kinetic model for preparation of peracetic acid (PAA) from acetic acid (AA) and hydrogen peroxide (HP) under the catalysis of sulfuric acid (SA) in the liquid phase was investigated. The kinetic equations of PAA synthesis and hydrolysis were given and the kinetic constants were estimated according to the experimental data by a simplex optimization method. It was found that the synthesis and hydrolysis of PAA were both first-order reactions with respect to reactant concentrations and H+ concentration. Linear relationships were discovered between the observed rate constants and H+ concentrations at a certain temperature, with the slopes being corresponding intrinsic rate constants. The intrinsic activation energies of PAA synthesis and hydrolysis were 57.8 and 60.4kJ mol(-1), respectively. The mechanisms of PAA synthesis and hydrolysis were discussed. It has been proved that the rate-determining step in the synthesis of PAA is the reaction between H2O2 with active carbonyl intermediary, and in the hydrolysis of PAA the reaction between water and corresponding active carbonyl intermediary. (C) 2007 Elsevier B.V. All rights reserved.