CATALYTIC PROPERTIES OF LA1-XSRXBO3 (B = MN, FE, CO, NI) FOR TOLUENE OXIDATION

The alkaline coprecipitation method was employed to prepare La1-xSrxBO3 (x = 0-1 and B = Mn, Fe, Co, Ni). The activities of the resulting catalysts for oxidizing toluene were measured by a differential flow reactor, and their physical properties were characterized by BET, XRD, AES, SIMS, XPS, SEM, TGA/DTGA, and stepwise oxygen desorption. The results indicate that substitution of La by Sr affects activity due to the oxygen vacancy. Among the Co and Fe series catalysts, those for which x = 0.3 demonstrate the highest activity. The catalytic activity of the Mn series catalysts was found to increase not only with the quantity of Mn atoms but also with the sum of Mn and O atoms. In this series, the amount of chemically adsorbed oxygen, instead of the lattice oxygen, plays an important role in the catalytic activity, especially in the temperature range of toluene oxidation, with the catalytic activity for toluene oxidation increasing with the amount of oxygen chemically adsorbed. The activity of the Ni series catalysts does not increase with increasing amounts of NiO and La2NiO4; the highest activity occurs at x = 0.5. The experimental results are discussed in terms of the role played by various B-site cations, the influence of catalytic surface composition on catalytic activity, and the effect of lattice and chemically adsorbed oxygen. Four influencing factors on the catalytic activity of these four series catalysts were discriminated by analysis of the results of kinetic measurements and by surface characterization.