What Do Tantalum Framework Sites Look Like in Zeolites? A Combined Theoretical and Experimental Investigation

Frederik Tielens (1) , Tetsuya Shishido (2) , Stanislaw Dzwigaj (1)

1 LRS - Laboratoire de Réactivité de Surface
2 Department of Molecular Engineering

Ab initio periodic DFT calculations on the structural and energy properties of different model tantalum framework sites in tantalum-substituted socialite cavities are presented and related to experimental FTIR measurements on Ta-containing SiBEA zeolites. The tantalum framework sites are characterized by their calculated geometrical parameters, vibrational frequencies, and (de)protonation energies. Ta(V) is stabilized in the zeolite framework as a pentacoordinated site possessing one hydroxyl group. The Ta(V)-OH group is not acidic. It is found that hydration of this site is easier than dehydration. This site is found to be only slightly hydrophilic. Dehydration of the site leads to the formation of Lewis acidic and Lewis basic sites. These results are in agreement with experimental data and allow determining the molecular structure of tantalum sites in the zeolite framework.

Mots clés: generalized gradient approximation; density-functional theory; augmented-wave method; vsi-beta zeolite; ab-initio; molecular-sieves; photoluminescence spectroscopies; vanadyl pyrophosphate; diatomic-molecules; mfi structure

Domaines: Catalyse

Frederik Tielens, Tetsuya Shishido, Stanislaw Dzwigaj. What Do Tantalum Framework Sites Look Like in Zeolites? A Combined Theoretical and Experimental Investigation. Journal of Physical Chemistry C, 2010, 114 (21), pp.9923-9930. ⟨10.1021/jp102181m⟩. ⟨hal-00604808⟩