Oxidative adsorption mechanism-based screening of zeolites for deep purification and recycling of NOx from humid gases.

[Display omitted] • Comparisons of NO x adsorption and desorption among series of zeolites are conducted. • Effects of zeolite structures, cations, SiO 2 /Al 2 O 3 ratios on NO x sorption are shown. • H-typed 10-membered-ring straight-channel zeolite is selected as preferred sorbent. • Importance of kinetics of NO oxidation-NO 2 physisorption process is revealed. • Accessibility of Brønsted acid sites that drives NO-NO 2 catalytic cycle is discussed. Adsorption is a promising technology for deep purification of nitrogen oxides (NO x) from flue gases and simultaneously recycling NO 2 as an economically valuable chemical. Zeolite as a robust NO x adsorbent provides the key step for success in practical applications, of which the screening remains challenging regarding the NO-NO 2 oxidation and adsorption combined process. In this work, experimental evaluations on practical NO x sorption performances on series of zeolites were conducted. Effects of the zeolite typological structure, compensating cation, and SiO 2 /Al 2 O 3 ratio on deep purification efficacy, water resistance, and regenerability at varying humidity were obtained, revealing the importance of kinetics of the NO oxidation and NO 2 physisorption consecutive process. The H-typed 10-membered-ring straight-channel zeolites (MFI and FER) were demonstrated to be the preferred NO x adsorbents qualified for industrial needs, as compared to other caged-channel, hybrid-channel, larger-sized straight-channel, or Na-typed counterparts. Deeper insights into the key role of Brønsted acid sites (BAS) in driving the NO-NO 2 catalytic cycle and promoting the adsorption competitiveness of NO x over water vapor were revealed based on in-situ diffuse reflectance Fourier transform infrared spectroscopy characterizations. The MFI zeolite with improved performance at the low-silica version could benefit from the efficient utilization of BAS within the highly accessible medium-sized straight channel, while the FAU zeolite (representative caged-channel zeolite) requiring appropriate SiO 2 /Al 2 O 3 ratio for optimal BAS utilization may suffer from the limited site accessibility. The findings clarify the relationships between NO x oxidative adsorption performances and zeolite properties, which provides a fundamental perspective and scientific screening strategy for NO x adsorbents. [ABSTRACT FROM AUTHOR]