Synthesis of the high-surface-area CexBa1−xMnAl11Oycatalyst in reverse microemulsions using inexpensive inorganic salts as precursors

Abstract

The high-surface-area Ce_xBa_1−xMnAl₁₁O_y (x = 0, 0.1, 0.2, 0.3) catalysts were synthesized in the nonionic reverse microemulsion (ME), using the inorganic salts as the reactants. The supercritical drying (SCD) and conventional oven drying (CD) methods were used to remove the water in hydrogels, respectively. The Ce_xBa_1−xMnAl₁₁O_y samples were characterized by N₂-adsorption, transmission electron microscopy (TEM), TGA-DTA, and X-ray powder diffraction (XRD). The effects of the microemulsion composition, the drying method, the calcination temperature and the introduction of Ce on the catalysts were investigated. The results showed that the morphology of the catalyst was controlled by the microemulsion microstructure; and the homogeneity of the precursor was improved effectively by the reverse microemulsion method and the supercritical drying method. Due to the high homogeneity of the precursors, the initial formation temperature of the hexaaluminate phase decreased to lower than 1100 °C. The BaMnAl₁₁O₁₉ catalyst had high surface area (72.4 m² g⁻¹) and high catalytic activity (T₁₀ = 445 °C) for methane combustion. When Ce was introduced, the Ce_xBa_1−xMnAl₁₁O_y catalyst (x = 1) had the higher activity (T₁₀ = 430 °C) than that of the BaMnAl₁₁O₁₉ one due to a synergetic effect between Ce and Mn.