CoAPO molecular sieves of the structure types 5, 11, 16 and 34 have been investigated by means of electron absorption spectroscopy, temperature-programmed reduction and infrared spectroscopy in combination with pyridine adsorption, the purpose being to determine the amounts of framework and non-framework cobalt and to study the properties of incorporated cobalt with respect to stability, redox behaviour and associated acidic properties. It has been shown that framework and non-framework cobalt species exhibit different spectroscopic properties and can be distinguished from each other. The framework cobalt acceptance and the stability of the different structures decrease in the order CoAP0,-5 > CoAP0,-11 > CoAP0,-16 > CoAP0,-34. In stable structures such as 5 and 11, framework cobalt can perform reversible redox reactions Co" = C o ' ' ' , which are accompanied by changes in the concentration of Brsnsted and Lewis acid sites.
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