The effect of potassium loading on the structural and catalytic properties of MoOx/ZrO2 catalysts for oxidative dehydrogenation of propane was investigated. Catalysts have been prepared by modified sol-gel method, and they were characterized by nitrogen physisorption, XRD, FT-Raman spectroscopy, XPS and temperature-programmed reduction (TPR). Catalytic activity measurements have been carried out between 400 and 530degreesC under atmospheric pressure. It was observed that potassium addition prevented crystalline Zr(MoO4)(2) formation, suppressing the interaction of molybdenum oxide and zirconia phases, and it also favored the formation of three-dimensional molybdenum oxide and two-dimensional polymolybdates. Both propylene selectivity and yield were enhanced with a certain amount of potassium addition. (C) 2004 Elsevier B.V. All rights reserved.