Study of the structure and properties of TAPO-5 molecular sieve

Abstract

The conditions under which some of the Ti4+ ions in TAPO-5 (a titanium containing aluminophosphate) can be reduced to Ti3+ whilst leaving the crystal and pore structure of the molecular sieve intact, have been studied. ESR spectroscopy was used to probe the local geometry round the Ti3+, and was found that this was in a distorted octahedral coordination. The heteroatom was therefore present in a separate microphase locate inside the micropores, in particles too small to be detectable by X-ray diffraction. Two titanium sites were identified. It was found that reduction of Ti4+ involved the lattice oxygens, whilst on exposure to air Ti3+ was oxidised via an electron-transfer mechanism which resulted in the formation of a Superoxide. © 1989 J.C. Baltzer A.G. Scientific Publishing Company.