Improvement of Alkali Metal Resistance for NH3-SCR Catalyst Cu/SSZ-13: Tune the Crystal Size

Abstract

To improve the alkali metal resistance of commercial catalyst Cu/SSZ-13 for ammonia selective catalytic reduction (NH3-SCR) reaction, a simple method to synthesize Cu/SSZ-13 with a core–shell like structure was developed. Compared with smaller-sized counterparts, Cu/SSZ-13 with a crystal size of 2.3 μm exhibited excellent resistance to Na poisoning. To reveal the influence of the crystal size on Cu/SSZ-13, physical structure characterization (XRD, BET, SEM, NMR) and chemical acidic distribution (H2-TPR, UV-Vis, Diethylamine-TPD, pyridine-DRIFTs, EDS) were investigated. It was found that the larger the crystal size of the molecular sieve, the more Cu is distributed in the crystal core, and the less likely it was to be replaced by Na to generate CuO. Therefore, a 2.3 μm sized Cu/SSZ-13 well-controlled the reactivity of the side reaction NH3 oxidation and the generation of N2O. The result was helpful to guide the extension of the service life of Cu/SSZ-13.

Selective catalytic reduction of NOx with NH3 over copper-based catalysts: recent advances and future prospects

“…149 Besides, the construction of the core-shell structure was confirmed to have practical value. 150 By increasing the crystalline sizes of SSZ-13, the active Cu species were regulated to be located in the subsurface or inner core, thereby buffering alkali metal poisoning on the outer layer of zeolites. The dispersion of acid centers could be adjusted through changing the crystalline sizes, which provided a simple and easy approach to enhance performance against alkali metals.…”

Recent progress in performance optimization of Cu-SSZ-13 catalyst for selective catalytic reduction of NOx

“…There were still some debates about the nano-size effect on the poisoning resistance of Cu-SSZ-13. Compared with nanosized counterparts, Cu/SSZ-13 with a crystal size of 2.3 µm exhibited excellent resistance to Na poisoning ( Chen Z. X. et al, 2021 ). The large crystal size facilitated the distribution of acidic sites and the Cu ions distributed in the deep layer have strong redox stability and are not easily solvated by NH 3 or H 2 O, and are less likely to be replaced by Na to generate CuO.…”

Effect of the Modification of Catalysts on the Catalytic Performance

“…The possible reaction pathway over the ACF catalysts promoted by N5 was also shown. In order to improve the alkali metal resistance of commercial catalyst Cu/SSZ-13 for ammonia-selective catalytic reduction (NH 3 -SCR) reaction, Chen et al [12] developed a simple method to synthesize Cu/SSZ-13 with a core-shell-like structure. Cu/SSZ-13, with a crystal size of 2.3 µm, exhibited excellent resistance to Na poisoning.…”