A study of the ethylbenzene disproportionation at a wide range of reaction pressures, from gas to supercritical conditions, was carried out in order to determine the influence of the reaction media properties, such as density, on the reaction parameters and especially on the deactivation by coke deposition. Pressure does not only favour the ethylbenzene disproportionation but also the formation of ethylene, a well-known coke precursor, by dealkylation reactions. However, coke extraction is also favoured by pressure. leading to an equilibrium between coke formation and extraction at high pressures, which is called in situ regeneration. So that, under certain supercritical conditions such as 400 degrees C and 91 bar, the reaction media properties make possible to obtain high ethylbenzene conversion and reduced deactivation by coking. (C) 2011 Elsevier B.V. All rights reserved.