Preparation, characterization, and methane total oxidation of AAl12O19 and AMAl11O19 hexaaluminate catalysts prepared with urea combustion method

A series of AAl12O19 (A = La, Sr, Ba, Ca, Ce), AMAl11O19 (A = La, Sr; M = Cu, Mn, Fe, Ni, Mg) and Sr1−xLaxMnAl11O19 (x = 0.2–0.8) hexaaluminates were prepared successfully using urea combustion method. The influences of the molar ratio (R) of urea to the total metal ions in hexaaluminates and the urea combustion temperature on the formation of the hexaaluminates were investigated. The structure of the hexaaluminates was characterized using X-ray powder diffraction (XRD) and temperature-programmed reduction (TPR). The catalytic activity for methane combustion was evaluated. The results indicated that the preparation conditions were: for LaAl12O19, the value of R was 3, the combustion time was in the range from 40 to 60 min, and the combustion temperature was not less than 500 °C; For LaFeAl11O19 and LaMnAl11O19, the value of R was 3–7, the combustion time was 40 min, and the combustion temperature was less than 500 and 400 °C, respectively; for AAl12O19 (A = Sr, Ba, Ca, Ce), LaMAl11O19 (M = Cu, Ni, Mg), SrMAl11O19 (M = Cu, Mn, Fe, Ni, Mg) and Sr1−xLaxMnAl11O19 (x = 0.2–0.8), the value of R was 3, the combustion time was 40 min, and the combustion temperature was 500 °C. The prepared hexaaluminates had pure hexaaluminate phase structure and excellent catalytic activity in the methane combustion.

Graphical abstractA series of AAl12O19 (A = La, Sr, Ba, Ca, Ce), AMAl11O19 (A = La, Sr; M = Cu, Mn, Fe, Ni, Mg) and Sr1−xLaxMnAl11O19 hexaaluminates were prepared successfully by the urea combustion method. The prepared hexaaluminates had a pure and complete phase structure and an excellent catalytic activity for methane combustion. The method is a new, simple and environment friendly preparation method of hexaaluminates.Figure optionsDownload full-size imageDownload as PowerPoint slide