Esterification-the reaction of acetic acid and butanol in a trickle bed reactor, packed with a strong acid ion-exchange resin, operating with partial evaporation of reaction mixture into inert gas (nitrogen) stream-was investigated in this study. The experiments were carried out under atmospheric pressure. Reaction temperature was maintained in the interval from 70 to 120 degreesC. i.e. above the boiling point of the azeotropic mixture containing part of unreacted alcohol and both reaction products, i.e. ester and water. Partial evaporation of the reaction mixture into the inert gas (nitrogen) stream passing through the catalyst bed and consequent separation of reaction products into vapour and liquid phases shifted the chemical equilibrium of the reaction. The paper propose two different techniques for increasing the performance of trickle bed reactor for mentioned esterification: simultaneous reaction and evaporation and periodic modulation of the feed rate. (C) 2003 Elsevier Science B.V. All rights reserved.