CATALYTIC COMBUSTION OF METHANE ON COPPER-SUBSTITUTED BARIUM HEXAALUMINATES

Barium hexaaluminates partially substituted by copper have been synthe sized by a sol-gel method. Formation of the parent BaAl12O19 and the m ixed BaCuAl11O18.5 catalysts occurred during calcination at 1200 degre es C. XRD showed a good crystallinity of the structure and expansion o f the unit cell parameter due to the presence of larger Cu2+ ions in p lace of Al3+ in tetrahedral sites. The presence of copper strongly enh ances the catalytic activity in methane combustion, which should be du e to the Cu2+ species evidenced by FTIR of adsorbed CO and by TPR. The introduction of a second copper ion in the structure was not possible , however, as revealed by the formation of copper (II) aluminate in ad dition to the Cu-substituted hexaaluminate phase.