La-Al-O, La-Mg-Al-O, La-Mn-Al-O and La-Mg-Mn-Al-O hexaaluminates have been prepared using the carbonates route previously developed for M-substituted and unsubstituted Ba--Al2O3. Starting from amorphous precursors, the formation of a final magnetoplumbite (MP) phase is observed upon calcination at T ≥ 1100◦C. In the case of LaMn1Al11O19, the MP phase already forms at 900◦C evidencing a promotion effect of Mn ions. Upon calcination at 1300◦C, monophasic samples can be obtained only for Mg-substituted samples (LaMg1Al11O19 and LaMg0.5Mn0.5Al11O19), whereas in the other samples the presence of LaAlO3 is always detected. This behaviour is associated with the stabilisation, via a charge compensation mechanism, of the MP phase due to the introduction of Mg2+ ions in the structure. The co-presence of Mg and Mn in the final catalyst has resulted in a higher specific catalytic activity perMnmol. Such a behaviour is likely associated with the stabilisation of Mn ions at high oxidation state due to the co-presence of Mg2+.
Preparation, characterization and catalytic activity of pure and substituted La-hexaaluminate systems for high temperature catalytic combustion
GROPPI, GIANPIERO;CRISTIANI, CINZIA;FORZATTI, PIO
2001-01-01
Abstract
La-Al-O, La-Mg-Al-O, La-Mn-Al-O and La-Mg-Mn-Al-O hexaaluminates have been prepared using the carbonates route previously developed for M-substituted and unsubstituted Ba--Al2O3. Starting from amorphous precursors, the formation of a final magnetoplumbite (MP) phase is observed upon calcination at T ≥ 1100◦C. In the case of LaMn1Al11O19, the MP phase already forms at 900◦C evidencing a promotion effect of Mn ions. Upon calcination at 1300◦C, monophasic samples can be obtained only for Mg-substituted samples (LaMg1Al11O19 and LaMg0.5Mn0.5Al11O19), whereas in the other samples the presence of LaAlO3 is always detected. This behaviour is associated with the stabilisation, via a charge compensation mechanism, of the MP phase due to the introduction of Mg2+ ions in the structure. The co-presence of Mg and Mn in the final catalyst has resulted in a higher specific catalytic activity perMnmol. Such a behaviour is likely associated with the stabilisation of Mn ions at high oxidation state due to the co-presence of Mg2+.File | Dimensione | Formato | |
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Preparation,-characterisation-and-catalytic-activity-of-pure-and-substituted-La-hexaaluminate-systems-for-high-temperature-catalytic-combustion_2001_Applied-Catalysis-B-Environmental.pdf
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