The behaviour of a low-productive V2O5-TiO2 (anatase) supported catalyst for oxidation of o-xylene to phthalic anhydride is investigated. The catalyst operates by inlet reagent concentration 40 g m(-3) (STP) (usual concentration in the industry) and is calcined under conditions, which differ in comparison with those applied in the industry. It is experimentally specified that the amount of the vanadium chemically bonded with the TiO2 support depends considerably on the conditions of calcination. Experiments are carried out in a pilot installation with a fixed catalyst bed composed by a catalyst, which is calcined, but has not undergone other preliminary operations. The dependence of the hot spot temperature on the variation of the process parameters is studied. By means of a heterogeneous two-dimensional model an identification problem is solved. As a result the energies of activation valid for the calcined catalyst are determined. It is found that a calcined but not pretreated sample is considerably more active than the pretreated form. A brief statistic analysis of the experimental and predicted results is performed. (c) 2005 Elsevier B.V. All rights reserved.