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 CoAPO4-5 > CoAPO4-11 > CoAPO4-16 > CoAPO4-34. In stable structures such as 5 and 11, framework cobalt can perform reversible redox reactions Co(II) reversible Co(III), which are accompanied by changes in the concentration of Bronsted and Lewis acid sites.
