Nanostructured GdAlO₃ perovskite, a new possible catalyst for combustion of volatile organic compounds

The purpose of this paper was to obtain nanosize GdAlO₃ perovskite powders for catalyst applications. Two different thermal treatments (900 °C for 1 h and 1000 °C for 7 h) were applied to amorphous powder obtained by combined sol–gel and self-combustion method to promote crystallization of GdAlO₃ perovskite. The structural and phase transformations after each thermal treatment have been studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), and N₂ adsorption. After treatment at 900 °C the formation of perovskite phase, GdAlO₃ (with orthorhombic structure) in mixture with other phases (Gd₂O₃, Al₂O₃, Gd₄Al₂O₉, and Gd₃Al₅O₁₂) was detected. A monophase crystalline material, GdAlO₃ pure perovskite, with crystallite size of 40 nm and S_BET of 10 m²/g was obtained after a longer treatment, 7 h at 1000 °C. The catalytic activity of the two nanocrystalline samples in the combustion reaction of acetone, propane, benzene, and Pb free gasoline was studied. Both samples exhibit the best catalytic activity for acetone combustion (80 % acetone conversion at 500 °C) and proved poor catalytic performance in catalytic combustion of Pb free gasoline (24 % conversion at 500 °C). Although S_BET value for sample treated at 900 °C is higher (22 m²/g) than that of the sample treated at 1000 °C (10 m²/g), the treatment at 1000 °C for 7 h assures a good thermo-chemical stability of GdAlO₃ perovskite required by low temperature catalyst applications. GdAlO₃ perovskite seems to be a promising catalyst for low temperature acetone combustion (T < 500 °C).