Experimental study of NO and NO2 adsorption on a fresh or dried NaY zeolite: influence of the gas composition by breakthrough curves measurements

Adsorption of NO, NO2 and H2O in divalent cation faujasite type zeolites: a density functional theory screening approach

Emissions of diesel exhaust gas in confined work environments are a major health and safety concern, because of exposition to nitrogen oxides (NO_x). Removal of these pollutants from exhaust gas calls for engineering of an optimum sorbent for the selective trapping of NO and NO₂ in the presence of water. To this end, periodic density functional theory calculations along with a recent dispersion correction scheme, namely the Tkatchenko-Scheffler scheme coupled with iterative Hirshfeld partitioning TS/HI, were performed to investigate the interactions between NO, NO₂, H₂O and a series of divalent cation (Be²⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Fe²⁺, Cu²⁺, Zn²⁺, Pd²⁺, and Pt²⁺) faujasites. This enabled the identification of the optimum zeolites to selectively capture NO_x in the presence of H₂O, with respect to two important criteria, such as thermodynamic affinity and regeneration. Our results revealed that Pt²⁺ and Pd²⁺ containing faujasites are the best candidates for effective capture of both NO and NO₂ molecules, which paves the way towards the use of these sorbents to address this challenging application.

A review of Mn-based catalysts for low-temperature NH3-SCR: NOx removal and H2O/SO2 resistance

The development of high-efficiency catalysts is the key to the low-temperature NH₃-SCR technology. The introduction of SO₂ and H₂O will lead to poisoning and deactivation of the catalysts, which severely limits the development and application of NH₃-SCR technology. This review introduces the necessity of NO_x removal, explains the mechanisms of H₂O and SO₂ poisoning on NH₃-SCR catalysts, highlights the Mn-based catalysts of different active metals and supports and their resistance to H₂O and SO₂, and analyses the relationship between metal modification, selection of support and preparation method, morphology and structure design and SO₂/H₂O resistance. Given the current problems, this review points out the future research focus of Mn-based catalysts and also puts forward corresponding countermeasures to solve the existing problems.

NOx removal with efficient recycling of NO2 from iron-ore sintering flue gas: A novel cyclic adsorption process

Conventional flue gas nitrogen oxides (NO_x) abatement technologies commonly convert NO_x into harmless compounds, while less effort has been made to recycle NO₂ as a profitable chemical in many industries. Towards this end, adsorption is a promising technology for which an advanced technique for NO₂ desorption and efficient sorbent regeneration provides the key step for success in practical applications. This work reports a novel cyclic adsorption process for NO_x removal with recycling of NO₂ from iron-ore sintering flue gas of a steel plant. This process using self-prepared and validated pelletized Na-ZSM-5 zeolites as low-cost sorbents involves NO_x catalytic adsorption and reversible desorption using multiple hot gas circulations (GC) within the enclosed fixed bed followed by scavenging and purge at mild conditions. In comparison to conventional cyclic processes, greater amount of recyclable NO₂ was obtained, rendering the NO_x recovery of >92% and the mean NO₂ concentration of >2% significantly enriched from original 20 ppm in feed gas. A robust adsorption-desorption performance with appreciable NO_x working capacity was achieved for up to 16 cycles. The key role of the segmentation of GC in boosting NO_x regenerability was addressed, providing an economical three-tower strategy for continuous NO₂ production for practical use.