The key role of adsorbate-catalyst interactions into catalytic activity of [CTA+]-Si-MCM-41 from electron density analysis

ALEGRE, CLARA IRIS AYMARÁ; CAZULA, BÁRBARA BULHÕES; ALVES, HELTON JOSÉ; ZALAZAR, MARÍA FERNANDA; PERUCHENA, NÉLIDA M.

Molecular Catalysis

Elsevier BV

Lugar: Netherlands; Año: 2021 vol. 504

2468-8231

In this work, we analyzed the role of the interactions involved in the reaction mechanism for the transesterification of ethyl acetate and methanol on the pore mouth of [CTA+]-Si-MCM-41 catalyst. The Quantum Theory of Atoms in Molecules (QTAIM) was applied for the analysis of adsorbate-catalyst interactions in order to gain a deeper understanding about the relationship between bonding and catalytic properties along the reaction coordinate and the role of weak interactions in the catalytic activity. Experimental FT-IR spectrum was supported by the theoretical model for the coadsorption of both reagents following a dual-site mechanism. Our results reveal that the key role of the (CTA+)(SiO- ) ion pair is to stabilize the reactant species. During the reaction coordinate, the silica and the head of the surfactant are bonded through several O⋅⋅⋅H(CH3) interactions forming the bifunctional active site on the surface of the solid catalyst. Four interactions are associated with the reaction mechanism. The rest of weak adsorbate-catalysts interactions along the reaction coordinate are related to the additional stabilization of the reactants on the pore mouth of the catalyst.