DRIFT spectroscopy study of nitrogen sorption and nitrogen–oxygen transport co-diffusion and counter-diffusion in NaLSX and NaZSM-5 zeolites

Abstract

A novel DRIFT Spectroscopy approach to sorption kinetics of nitrogen, N 2, and other simple gases by microporous materials, in particular zeolites, is suggested. It utilizes time evolution of IR-stretching bands of symmetrical molecules such as N 2 due to perturbation that results from their interaction with sorption sites. The method is applied to a study of diffusion-limited sorption of N 2, both pure and in mixtures with oxygen, O 2, by zeolites NaLSX and NaZSM-5. Lower limits to transport-diffusion coefficients of N 2 in these materials were assessed at ambient temperature. Mixture experiments allowed to conclude that the rate of N 2 sorption in O 2-rich mixtures is controlled by co-diffusion of O 2 and N 2 in the secondary pore system between zeolite crystallites. They also demonstrate a weak influence of O 2 on sorption equilibrium of N 2 in NaLSX zeolite from N 2–O 2 mixtures.