Competitive Adsorptive Mechanism of H/N in LTA/FAU Zeolites by Molecular Simulations and Experiments.

For industrial tail gas to be converted into high-purity hydrogen, the H-N mixture needs to be separated efficiently. This work examined the adsorption characteristics and competitive mechanisms of H and N on LTA- and FAU-type zeolites, at 77 K, 298 K, and 0.1-10 bar by thoroughly analyzing results of adsorption capacity experiments and molecular simulations. In the Grand Canonical Monte Carlo (GCMC) simulations, the force field causing a molecular dipole of H and the polarization force field of N are first applied. The accuracy of the force field was experimentally verified. The findings indicate that N and H loading on Ca-FAU (Ca-LTA) are higher than Na-FAU (Na-LTA). On NaX at 77 K, the highest adsorption selectivity (N/H) is observed; on NaA at 298 K, it is the opposite. The GCMC data findings demonstrate that H and N have remarkably similar adsorption sites, with framework oxygen atoms and non-framework cations serving as the main adsorption sites for adsorbate molecules. Furthermore, the rate at which H diffuses is higher than that of N. The study of redistribution charge before and after adsorption demonstrated that N has a greater affinity for the framework oxygen atoms than H. This study provides a molecular theoretical foundation for the adsorption behavior of H-N mixture in zeolites.