Mixed oxide catalysts on the basis of molybdenum and vanadium are industrially important catalysts for the partial oxidation of acrotein to acrylic acid. For a better understanding of the oxygen pathways for an optimised model catalyst with the stoichiometric composition Mo7.5V2.5W0.5Ox, the so-called Steady State Isotopic Transient Kinetic Analysis (SSITKA) method was employed. After switching from O-16(2) to O-18(2) the formation of O-18-labelled acrolein was observed. Acrolein exchanges its carbonyl oxygen with oxygen from the solid catalyst. This exchange is also reflected in the isotopic distribution of the oxidation products (acrylic acid and combustion products). Subsequent desorption of acrolem, as well as further reaction to the oxidation products, can take place. Compared to the partial oxidation the incorporation of the isotopic tracer oxygen into the combustion by-products is much slower. This might be an indicator of an intermediate layer in the combustion pathway. To obtain activation parameters SSITKA experiments were per-formed over a temperature range between 322 and 391 degrees C. Based on the observations, a macro kinetic model was adapted upon. The activation energy for the exchange of the carbonyl oxygen of acrolein was found to be approximately 30 kJ mol(-1). (c) 2005 Elsevier B.V. All rights reserved.