Geometries and Interaction Energies of Toluene on Cs x Na 1– x Mordenite

CABANA, NANCY C.; SERRA, RAMIRO R.; BOIX, ALICIA V.; BOLCATTO, PABLO G.

PHYSICA STATUS SOLIDI B-BASIC RESEARCH

WILEY-V C H VERLAG GMBH

Año: 2020

0370-1972

Calculations for the geometries and energies of alkaline mordenites of the family CsxNa1􀀀xMOR (x = 0; 0:25; 0:5; 0:75; 1) with and without toluene adsorbed and experiments of Differential Scanning Calorimetry (DSC) are reported. Firstly a structural stabilization of a pure silica zeolite was performed and then, fourdifferent structures for sodium substitutions were evaluated on a mordenite with a molar ratio Si/Al=5. From the more stable matrix, a sequential incorporation of counterions from pure Na up to pure Cs was done. In each case the atoms were free to move inside the structure up to reach a local minimum of the total energy.Toluene was initially located in three different geometries and the energy optimization calculation relocate it properly. Mostly of the adsorption situations occurs when the electrons of the aromatic ring can interact withthe counterions inside the main channel. The consideration of dispersive energy correction does not modify the basic physics of the adsorption process although it change the absolute values of the interaction energies. The DSC measurements were done for different amounts of toluene incorporated on two mordenites, one of them with only Na counterions and the other with a 7% of substitution by Cs. The technique gives the desorption energy and the results indicate that the incorporation of Cs enhances the adsorption ability of the zeolite. Theoverall theoretical results are in good agreement with experimental evidence and constitute a reliable basis to advance in the study of new functionalized materials.