Abstract
In this work we studied the host–guest interactions between confined molecules and zeolites and their relationship with the energies involved in the reaction of methylation of benzene by methanol in H-ZSM-5 and H-Beta zeolites employing density functional theory (DFT) methods and the quantum theory of atoms in molecules. Results show that the strength of the interactions related to adsorption and coadsorption processes is higher in the catalyst with the larger cavity; however, the confinement effects are higher in the smaller zeolite, explaining, from an electronic viewpoint, the reason why the stabilization energy is higher in H-ZSM-5 than in H-Beta. The confinement effects of the catalyst on the confined species for methanol adsorption, benzene coadsorption, and the formed intermediates dominate this stabilization. For the transition state (TS), the stability of the TS is achieved due to the stabilizing effect of the surrounding zeolite framework on the formed carbocationic species (CH3+) which is highe...
Highlights
Zeolites are microporous/nanoporous solids widely used in fine chemicals and petrochemicals as heterogeneous catalysts
Results show that the strength of the interactions related to adsorption and co-adsorption processes are higher in the catalyst with larger cavity; the confinement effects are higher in the smaller zeolite, explaining from an electronic viewpoint the reason why the stabilization energy is higher in H-ZSM-5 than in H-Beta
In the present work we study the adsorbate-catalyst interactions between confined molecules and zeolites, and their relationship with energies involved in the reaction
Summary
Zeolites are microporous/nanoporous solids widely used in fine chemicals and petrochemicals as heterogeneous catalysts. They possess pores, cavities and channels with well-defined molecular dimensions.[1] These three-dimensional cavities provide a selective environment, in which a chemical reaction occurs. The confinement effect was proposed to explain the interactions between the zeolite framework and the adsorbed molecules. It plays an important role on adsorption and catalytic properties of zeolites by stabilizing adsorbed molecules, intermediates, and transition states. Due to the confinement effects, zeolites can be described as solid solvents.[2]
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