Activation procedures of Mo-based catalysts were investigated in terms of their activity in reaction of n-hexane isomerization. Temperature programmed activation and oxidation (TPA/TPO) in different gaseous environments were used to correlate catalyst activity/selectivity properties with the nature of active phases and with activation procedures required for their formation. A beneficial activation procedure giving Mo-oxycarbide comprises very low ramping temperature of 1 degrees C/min, 550 degrees C as the final temperature and a flow of methane and hydrogen with a preferable ratio 1:4. In addition, some minimal time for keeping both initial and final temperature constant is required, indicating benefit of both periods of initialization and active phase slow aging. Neither different diluent (He) nor other gas as a C-source (CO, n-hexane) gives an active catalyst. The catalyst activity can be enhanced by exposing it to air at room temperature, and decayed in the same environment at 300 degrees C. (c) 2006 Elsevier B.V. All rights reserved.