Original scientific paper

Isomorphous Substitution of Framework Atoms by Titanium in VPI-5 Aluminophosphate Molecular Sieve

Nataša Novak Tušar ; National Institute of Chemistry, Ljubljana, Slovenia
Nataša Zabukovec Logar ; National Institute of Chemistry, Ljubljana, Slovenia
Iztok Arčon ; School of Environmental Sciences, Nova Gorica, Slovenia
Frederic Thibault-Starzyk ; Laboratoire Catalyse & Spectrochimie, ISMRA-CNRS, Caen, France
Venčeslav Kaučič ; National Institute of Chemistry, Ljubljana, Slovenia

Abstract

Extra-large pore aluminophosphate molecular sieve TiVPI-5 was synthesised hydrothermally in the presence of di-n-butylamine and transformed by the calcination process at 500 °C to a large pore TAPO-8. Incorporation of titanium(IV) into VPI-5 framework was studied by elemental and thermogravimetric analyses, combined with X-ray Absorption Near Edge Structure (XANES) spectroscopy and UV-VIS absorption spectroscopy. We found that titanium(IV) incorporated in TiVPI-5 isomorphously substitutes framework aluminium on octahedral sites and that it is not present in the structure in the form of TiO₂ anatase. In situ IR measurements of pyridine adsorption/desorption were used to check the presence of catalytically active centres in the product resulting from titanium incorporation into the VPI-5 framework. Weak Lewis and Brønsted acid sites were found in small amounts in the calcined product TAPO-8.

Keywords

aluminophosphate; molecular sieve; TiVPI-5; titanium; isomorphous substitution; acid sites

Hrčak ID:

131959

URI

https://hrcak.srce.hr/131959

Publication date:

1.11.2001.

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