Experimental and density functional theory study of the adsorption of N_2O on ion-exchanged ZSM-5: Part II. The adsorption of N_2O on main-group ion-exchanged ZSM-5

摘要

The adsorption and desorption of N_2O on main-group ion-exchanged ZSM-5 was studied using temperature-programmed desorption (TPD) and density functional theory (DFT) calculations. TPD experiments were carried out to determine the desorbed temperature T_(max) corresponding to the maximum mass intensity of N_2O desorption peak and adsorption capacity of N_2O on metal-ion-exchanged ZSM-5s. The results indicated that T_(max) followed a sequence of Ba~(2+) > Ca~(2+) > Cs~+ > K~+ > Na~+ > Mg~(2+) and the amount of adsorbed N_2O on main-group metal cation followed a sequence of Ba~(2+) > Mg~(2+) > Ca~(2+) > Na~+ > K~+ > Cs~+. The DFT calculations were performed to obtain the adsorption energy (E_(ads)), which represents the strength of the interaction between metal cations and the N-end or O-end of N_2O. The calculation results showed that the N-end of the N_2O molecule was favorably adsorbed on ion-exchanged ZSM-5, except for Cs-ZSM-5. For alkali metal cations, the E_(ads) of N_2O on cations followed the order which was the same to that of T_(max): Cs~+ > K~+ > Na~+. The calculated and experimental results consistently showed that the adsorption performances of alkaline-earth metal cations were better than those of alkali metal cations.