New approach to determine the surface and interface thermodynamic properties of H-β-zeolite/rhodium catalysts by inverse gas chromatography at infinite dilution

Tayssir Hamieh; Ali Ali Ahmad; Thibault Roques-Carmes; Joumana Toufaily

doi:10.1038/s41598-020-78071-1

New approach to determine the surface and interface thermodynamic properties of H-β-zeolite/rhodium catalysts by inverse gas chromatography at infinite dilution

Sci Rep. 2020 Dec 1;10(1):20894. doi: 10.1038/s41598-020-78071-1.

Authors

Tayssir Hamieh^{1

2}, Ali Ali Ahmad^{3

4}, Thibault Roques-Carmes⁵, Joumana Toufaily⁴

Affiliations

¹ SATIE-IFSTTAR, University Gustave Eiffel, Campus de Marne-La-Vallée, 25, allée des Marronniers, 78000, Versailles, France. tayssir.hamieh@ul.edu.lb.
² Laboratory of Materials, Catalysis, Environment and Analytical Methods (MCEMA), Faculty of Sciences and EDST, Lebanese University, Hariri Campus, Hadath, Beirut, Lebanon. tayssir.hamieh@ul.edu.lb.
³ Laboratory of Materials, Catalysis, Environment and Analytical Methods (MCEMA), Faculty of Sciences and EDST, Lebanese University, Hariri Campus, Hadath, Beirut, Lebanon.
⁴ LEADDER Laboratory, Faculty of Sciences and EDST, Lebanese University, Hariri Campus, Hadath, Beirut, Lebanon.
⁵ Laboratoire Réactions Et Génie Des Procédés (LRGP), UMR CNRS, 7274, Université de Lorraine, 1 Rue Grandville, 54001, Nancy, France.

Abstract

The thermodynamic surface properties and Lewis acid-base constants of H-β-zeolite supported rhodium catalysts were determined by using the inverse gas chromatography technique at infinite dilution. The effect of the temperature and the rhodium percentage supported by zeolite on the acid base properties in Lewis terms of the various catalysts were studied. The dispersive component of the surface energy of Rh/H-β-zeolite was calculated by using both the Dorris and Gray method and the straight-line method. We highlighted the role of the surface areas of n-alkanes on the determination of the surface energy of catalysts. To this aim various molecular models of n-alkanes were tested, namely Kiselev, cylindrical, Van der Waals, Redlich-Kwong, geometric and spherical models. An important deviation in the values of the dispersive component of the surface energy [Formula: see text] determined by the classical and new methods was emphasized. A non-linear dependency of [Formula: see text] with the specific surface area of catalysts was highlighted showing a local maximum at 1%Rh. The study of RTlnVn and the specific free energy ∆G^sp(T) of n-alkanes and polar solvents adsorbed on the various catalysts revealed the important change in the acid properties of catalysts with both the temperature and the rhodium percentage. The results proved strong amphoteric behavior of all catalysts of the rhodium supported by H-β-zeolite that actively react with the amphoteric solvents (methanol, acetone, tri-CE and tetra-CE), acid (chloroform) and base (ether) molecules. It was shown that the Guttmann method generally used to determine the acid base constants K_A and K_D revealed some irregularities with a linear regression coefficient not very satisfactory. The accurate determination of the acid-base constants K_A, K_D and K of the various catalysts was obtained by applying Hamieh's model (linear regression coefficients approaching r² ≈ 1.000). It was proved that all acid base constants determined by this model strongly depends on the rhodium percentage and the specific surface area of the catalysts.