In-situ-Charakterisierung von (Vanadium-oxid/Titan-oxid)-Katalysatoren bei der partiellen Oxidation von o-Xylol

Abstract

Dedicated to Professor Andre M. Braun on the occasion of his 60th birthdayIn situ Characterization of Vanadia ± Titania Catalysts in the Partial Oxidation of o-Xylene Different doped vanadia ± titania catalysts have been studied by combined kinetic and electrochemical measurements. Solid electrolyte potentiometry (SEP) allowed the determination of the oxidation state of the oxides under working conditions. The results show that there is no chemisorption equilibrium between the oxide and the oxygen in the gas phase. Further, the results allow to differentiate between the influence of dopants on the rate of oxygen uptake by and the rate of oxygen release from the oxidic catalyst. Doping with Li or Cs leads to a diminuition of the catalytic activity due to the decrease of the rate of oxygen transfer from the catalyst to the gaseous oxygen acceptor. Neither alcali doping nor the addition of Pd, Sn, or Bi improves the selectivity of the formation of phthalic anhydride.