The effect of the P/V ratio on the structure, properties, and reactivity of titania-supported vanadia is evaluated. The Raman spectra and temperature-programmed reduction studies reveal a progressive P-V interaction with increasing P/V ratio until nanoscaled alpha(I)-VOPO4 forms above a monolayer. Propane oxidative dehydrogenation (ODH) studies reveal that the conversion and selectivities of the catalysts strongly depend on the P-V interaction. For a Mars-van Krevelen model, kinetic parameters are successfully estimated by minimization of an objective function with the use of a genetic algorithm. With an increase in the P/V ratio the kinetic parameters reveal a progressive decrease in the primary ODH reaction rate constant and in the rate constant ratio for propene degradation to propene formation. The decrease in the rate constant ratio for propene degradation and propene formation with increasing P/V ratio leads to a more efficient catalyst. Thus, with the proper design of the catalyst the propene yield can be increased. (c) 2005 Elsevier Inc. All rights reserved.