Influence of the Thermal Processing and Doping on LaMnO3 and La0.8A0.2MnO3 (A = Ca, Sr, Ba) Perovskites Prepared by Auto-Combustion for Removal of VOCs

Single-phase oxygen stoichiometric LaMnO3 and doped La0.8A0.2MnO3 (A = Ca, Sr, Ba) perovskites have been prepared by a simple one-step auto-combustion method. Cation-deficient LaMnO3+δ La0.8A0.2MnO3+δ were obtained calcination of the former samples in air at 750 °C. The characterized X-ray powder diffraction, photoelectron spectroscopy, temperature-programmed reduction, desorption, N2 physisorption order to apply them as catalysts complete catalytic oxidation acetone model volatile organic compound. studied phases show expected orthorhombic rhombohedral perovskite crystal structures. Catalytic experiments performed with all measurable activity already 100 At 200 °C, higher than undoped LaMnO3, increasing conversion larger A-cation size. Calcined also as-prepared ones making La0.8Ba0.2MnO3+δ best catalyst this temperature. All >95% T ≥ 250 °C weak dependence on sample processing or A cation doping. collected evidence confirms that most important factors for these oxides are Mn4+/Mn3+ molar ratio surface cation-deficiency bulk structure. In addition, symmetry structure appears an additional favourable effect. Despite observation presence carbonates, we it is possible use without further thermal treatment good results acetone.