Synthesis and characterization of CoAlPO₄-5 and CoAlPO₄-31 molecular sieves

Abstract

Cobalt substituted AlPO₄-5 and AlPO₄-31 molecular sieves have been synthesized hydro thermally in the presence of Co(II) species and triethyl amine and di-<i style="">n</i>-propylamine as templating molecule. Various techniques of characterization show that Co²⁺ cations substitute Al³⁺ ions in the framework. Crystals of CoAlPO₄-5 and CoAlPO₄-31 are relatively large, and their morphology changes with the cobalt content. Samples are thermally stable and can be calcined in air without significant loss of the crystallinity. Upon calcination, part of the Co(II) species present in as-synthesized samples are converted into Co(III) species. These Co(III) species can be readily reduced in H₂ at 400^oC. CoAlPO₄-31 has been found to be an active catalyst compared to CoAlPO₄-5 in the ethyl benzene oxidation using tertiary butyl hydro peroxide.