In situ characterization of vanadia-titania catalysts in the partial oxidation of o-Xylene

Different doped vanadia-titania catalysts have been studied by combined kin etic and electrochemical measurements. Solid electrolyte potentiometry (SEP ) allowed the determination of the oxidation state of the oxides under work ing conditions, The results show that there is no chemisorption equilibrium between the oxide and the oxygen in the gas phase. Further, the results al low 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 d ecrease of the rate of oxygen transfer from the catalyst to the gaseous oxy gen acceptor. Neither alcali doping nor the addition of Pd. Sn, or Bi impro ves the selectivity of the formation of phthalic anhydride.