This article presents new results concerning a bistability phenomenon observed recently in the oxidative dehydrogenation of 2- propanol over copper catalysts. In this system, an activity hysteresis loop is observed when the partial oxygen pressure is varied. This bistability has been explained by the oxidation of metallic copper when the partial oxygen pres sure increases and copper oxide reduction when the partial oxygen pressure decreases. In the experiments reported here, an external second phase (alpha-Sb2O4, SnO2, Cr2O3, CeO2, Co3O4, MoO3, PbO2, NiO, Bi2O3 and MnO2) has been mixed with the copper catalysts. This modifies the hysteresis loop. The possible role played by the oxygen spillover at low temperature (150 degrees C) on this modification is discussed.