EXAFS investigation of divalent metal ion substituted AlPOs

Divalent metal ions, cobalt and zinc, substituted in three aluminophosphates structures (MeAPO-5, -18 and -36) have been characterised by EXAFS. The local structure of the three as-prepared materials were closely similar irrespective of the framework structure for the same concentration of Me²⁺ ion. The CoO bond distances are sensitive to the degree of oxidation of the heteroatom in the cobalt-substituted materials, increasing in the order: CoAPO-18 < CoAPO-36 < CoAPO-5 EXAFS analysis suggests that, in the reduced catalysts (CoAPO-18 and calcined ZnAPO-18), there are three short and one long bond associated with Me²⁺O of the Brønsted acid centre.