Basic energy characteristics and isotherm of methanol adsorption on Cu²⁺ZSM-5 zeolite

¹ Namangan Institute of Engineering and Technology, 7 Kasansay Street, Namangan, Uzbekistan
² Tashkent University of Information Technologies named after Muhammad al-Khwarizmi, 108 Amir Temur Avenue, Tashkent, Uzbekistan

^* Corresponding author: okergashev711@gmail.com

Abstract

This paper presents isotherm results and basic (ΔH, ΔF and ΔS) thermodynamic characteristics of methanol adsorption in Cu²⁺ZSM-5 zeolite. The trinomial equation of adsorption isotherm by the bulk micropore filling theory (VMOT) is also described. A correlation between adsorption-energy characteristics was found and molecular mechanisms of methanol adsorption in Cu²⁺ZSM-5 zeolite were revealed in the whole filling region. It was determined that Cu²⁺ cations are located in shielded positions of the crystal lattice of zeolite ZSM-5. Adsorption of methanol molecule leads to the migration of Cu²⁺ cations from the zeolite lattice to the crossings formed by the intersection of straight and zigzag channels and to the formation of ion/molecular complexes of different multiplicity in them. It was found that small polar methanol molecules form high-energy hepta complexes with Cu²⁺ cation and are located in the first coordination sphere in Cu²⁺ZSM-5 zeolite. It was determined that the average molar entropy (-65 kJ/mol) of methanol adsorption indicates that in the zeolite the mobility of methanol molecules is lower than the liquid phase and close to the mobility of the solid phase.