Structural Analysis of some Alkaline-earth-metal-Copper Oxide Catalysts for Hydrocarbon Oxidation or NO Decomposition

Some Ca-Cu-O, Sr-Cu-O and Ca-Sr-Cu-O defective perovskite-like mixtures have been prepared by the sol-gel technique and tested by means of a pulse reactor as possible catalysts for the title reactions. The characterisation of these preparations by several techniques, such as X-ray diffraction (XRD), scanning electron microscopy-electron probe microanalysis (SEM-EPMA), temperature-programmed desorption-temperature-programmed reaction-mass spectrometry (TPD-TPR-MS), electron paramagnetic resonance spectroscopy (EPR) and sorption-desorption of nitrogen, showed that the catalytic activity for both the reactions appears to be connected with the presence of a layer-like crystal structure approximating a two-dimensional antiferromagnet, stable within a sufficiently wide range of temperature. When oxygen, either added during the oxidation reaction or forming after the decomposition of NO, bridges together neighbouring Cu2+ ions not previously linked to oxygen, strongly interacting dipole systems form.