Promotional effect of ion-exchanged K on the low-temperature hydrothermal stability of Cu/SAPO-34 and its synergic application with Fe/Beta catalysts

Highlights

• K⁺ hinder the structural degradation of Cu/SAPO-34 under humid condition<100°C.

• K⁺ on Cu/SAPO-34 brings lower acidity and inferior SCR activity at high temperature.

• Fe/Beta was used to compensate the low activity of Cu/SAPO-34 at high temperature.

• The hybrid catalysts with KCu/SAPO-34 and Fe/Beta show a great potential for using.

Abstract

K ions were introduced onto Cu/SAPO-34 catalysts via the ion-exchange process in order to improve their stability under low-temperature hydrothermal aging. The changes in structure and copper-species contents of these catalysts upon hydrothermal aging were probed in order to investigate their effects on selective catalytic reduction (SCR) activity. For the fresh Cu/SAPO-34 catalysts, K ions had little influence on the chabazite framework but effected their acidities by exchanging with acid sites. After hydrothermal aging, the structural integrity and amount of active sites decreased on pure Cu/SAPO-34. While the K-loaded catalysts showed improved chabazite structure, acidity, and active site conservation with increasing K loading. However, although the 0.7 wt% K catalyst maintained the same crystallinity, active site abundance, and low-temperature SCR activity as the fresh catalyst upon aging, an apparent decrease in SCR activity at high temperature was observed because of the inevitable decrease in the number of Brönsted acid sites. To compensate for the activity disadvantage of K-loaded Cu/SAPO-34 at high temperature, Fe/Beta catalysts were co-employed with K-loaded Cu/SAPO-34, and a wide active temperature window of SCR activity was obtained. Thus, our study reveals that a combined system comprising Fe/Beta and K-loaded Cu/SAPO-34 catalysts shows promise for the elimination of NO_x in real-world applications.

Graphical abstract

Keywords

Selective catalytic reduction / Cu/SAPO-34 catalyst / Ion-exchanged K / Low-temperature hydrothermal stability / Fe/Beta catalyst

References

[1] Cao Y, Fan D, Sun L, Yang M, Cao L, Sun T, Xu S, Tian P, Liu Z (2019). The self-protection effect of reactant gas on the moisture stability of CuSAPO-34 catalyst for NH₃-SCR. Chemical Engineering Journal, 374: 832–839

[2] Colombo M, Nova I, Tronconi E (2010). A comparative study of the NH₃-SCR reactions over a Cu-zeolite and a Fe-zeolite catalyst. Catalysis Today, 151(3–4): 223–230

[3] Ding D, Xing J, Wang S, Chang X, Hao J (2019). Impacts of emissions and meteorological changes on China’s ozone pollution in the warm seasons of 2013 and 2017. Frontiers of Environmental Science & Engineering, 13(5): 76–84

[4] Duan Y, Wang J, Yu T, Shen M, Wang J (2015). The role and activity of various adsorbed ammonia species on Cu/SAPO-34 catalyst during passive-SCR process. RSC Advances, 5(19): 14103–14113

[5] Fan J, Ning P, Wang Y, Song Z, Liu X, Wang H, Wang J, Wang L, Zhang Q (2019). Significant promoting effect of Ce or La on the hydrothermal stability of Cu-SAPO-34 catalyst for NH₃-SCR reaction. Chemical Engineering Journal, 369: 908–919

[6] Feng X, Lin Q, Cao Y, Zhang H, Li Y, Xu H, Lin C, Chen Y (2017). Neodymium promotion on the low-temperature hydrothermal stability of a Cu/SAPO-34 NH₃-SCR monolith catalyst. Journal of the Taiwan Institute of Chemical Engineers, 80: 805–812

[7] Gao F, Mei D, Wang Y, Szanyi J, Peden C H (2017). Selective catalytic reduction over Cu/SSZ-13: Linking homo- and heterogeneous catalysis. Journal of the American Chemical Society, 139(13): 4935–4942

[8] Gao F, Walter E D, Karp E M, Luo J, Tonkyn R G, Kwak J H, Szanyi J, Peden C H F (2013). Structure–activity relationships in NH₃-SCR over Cu-SSZ-13 as probed by reaction kinetics and EPR studies. Journal of Catalysis, 300: 20–29

[9] Gao F, Wang Y, Washton N M, Kollár M, Szanyi J, Peden C H F (2015). Effects of alkali and alkaline earth cocations on the activity and hydrothermal stability of Cu/SSZ-13 NH₃-SCR catalysts. ACS Catalysis, 5(11): 6780–6791

[10] Hu X, Yang M, Fan D, Qi G, Wang J, Wang J, Yu T, Li W, Shen M (2016). The role of pore diffusion in determining NH₃-SCR active sites over Cu/SAPO-34 catalysts. Journal of Catalysis, 341: 55–61

[11] Huang S, Wang J, Wang J, Wang C, Shen M, Li W (2019). The influence of crystallite size on the structural stability of Cu/SAPO-34 catalysts. Applied Catalysis B: Environmental, 248: 430–440

[12] Tan J, Liu Z, Bao X, Liu X, Han X, He C, Zhai R (2002). Crystallization and Si incorporation mechanisms of SAPO-34. Microporous and Mesoporous Materials, 53(1–3): 97–108

[13] Li Z, Geng Y, Ma L, Chen X, Li J, Chang H, Schwank J W (2020). Catalytic oxidation of CO over Pt/Fe₃O₄ catalysts: Tuning O₂ activation and CO adsorption. Frontiers of Environmental Science & Engineering, 14(4): 65–73

[14] Liu C, Zhang Y (2018). Relations between indoor and outdoor PM_2.5 and constituent concentrations. Frontiers of Environmental Science & Engineering, 13(1): 5–24

[15] Liu X, Wu X, Weng D, Si Z, Ran R (2017). Evolution of copper species on Cu/SAPO-34 SCR catalysts upon hydrothermal aging. Catalysis Today, 281(Part 3): 596–604

[16] Mees F D, Martens L R, Janssen M J, Verberckmoes A A, Vansant E F (2003). Improvement of the hydrothermal stability of SAPO-34. Chemical Communications (Cambridge), (1): 44–45

[17] Metkar P S, Harold M P, Balakotaiah V (2012). Selective catalytic reduction of NO_x on combined Fe- and Cu-zeolite monolithic catalysts: Sequential and dual layer configurations. Applied Catalysis B: Environmental, 111–112: 67–80

[18] Niu C, Shi X, Liu K, You Y, Wang S, He H (2016). A novel one-pot synthesized CuCe-SAPO-34 catalyst with high NH₃-SCR activity and H₂O resistance. Catalysis Communications, 81: 20–23

[19] Shen M, Li X, Wang J, Wang C, Wang J (2018a). Nature identification of Cu active sites in sulfur-fouled Cu/SAPO-34 regeneration. Industrial & Engineering Chemistry Research, 57(10): 3501–3509

[20] Shen M, Zhang Y, Wang J, Wang C, Wang J (2018b). Nature of SO₃ poisoning on Cu/SAPO-34 SCR catalysts. Journal of Catalysis, 358: 277–286

[21] Song J, Wang Y, Walter E D, Washton N M, Mei D, Kovarik L, Engelhard M H, Prodinger S, Wang Y, Peden C H F, Gao F (2017). Toward rational design of Cu/SSZ-13 selective catalytic reduction catalysts: Implications from atomic-level understanding of hydrothermal stability. ACS Catalysis, 7(12): 8214–8227

[22] Tang J, Xu M, Yu T, Ma H, Shen M, Wang J (2017). Catalytic deactivation mechanism research over Cu/SAPO-34 catalysts for NH₃-SCR (II): The impact of copper loading. Chemical Engineering Science, 168: 414–422

[23] Tsukamoto Y, Fukuma T, Kusaka J (2019). Analysis and modeling of NO_x reduction based on the reactivity of Cu active sites and Brønsted acid sites in a Cu-Chabazite SCR catalyst. SAE Technical Paper 2019–24–0150

[24] Wang A, Chen Y, Walter E D, Washton N M, Mei D, Varga T, Wang Y, Szanyi J, Wang Y, Peden C H F, Gao F (2019). Unraveling the mysterious failure of Cu/SAPO-34 selective catalytic reduction catalysts. Nature Communications, 10(1): 1137–1146

[25] Wang A, Chen Y, Walter E D, Washton N M, Varga T, Wang Y, Szanyi J, Wang Y, Peden C H F, Gao F (2020). Remarkable self-degradation of Cu/SAPO-34 selective catalytic reduction catalysts during storage at ambient conditions. Catalysis Today,

[26] Wang C, Wang C, Wang J, Wang J, Shen M, Li W (2018). Effects of Na⁺ on Cu/SAPO-34 for ammonia selective catalytic reduction. Journal of Environmental Sciences (China), 70: 20–28

[27] Wang C, Wang J, Wang J, Yu T, Shen M, Wang W, Li W (2017). The effect of sulfate species on the activity of NH₃-SCR over Cu/SAPO-34. Applied Catalysis B: Environmental, 204: 239–249

[28] Wang D, Zhang L, Kamasamudram K, Epling W S (2013). In situ-drifts study of selective catalytic reduction of NO_x by NH₃ over Cu-Exchanged SAPO-34. ACS Catalysis, 3(5): 871–881

[29] Wang J, Fan D, Yu T, Wang J, Hao T, Hu X, Shen M, Li W (2015a). Improvement of low-temperature hydrothermal stability of Cu/SAPO-34 catalysts by Cu²⁺ species. Journal of Catalysis, 322: 84–90

[30] Wang L, Li W, Schmieg S J, Weng D (2015b). Role of Brønsted acidity in NH₃ selective catalytic reduction reaction on Cu/SAPO-34 catalysts. Journal of Catalysis, 324: 98–106

[31] Woo J, Leistner K, Bernin D, Ahari H, Shost M, Zammit M, Olsson L (2018). Effect of various structure directing agents (SDAs) on low-temperature deactivation of Cu/SAPO-34 during NH₃-SCR reaction. Catalysis Science & Technology, 8(12): 3090–3106

[32] Xue J, Wang X, Qi G, Wang J, Shen M, Li W (2013). Characterization of copper species over Cu/SAPO-34 in selective catalytic reduction of NO_x with ammonia: Relationships between active Cu sites and de-NO_x performance at low temperature. Journal of Catalysis, 297: 56–64

Acknowledgements

This work thanks to the funding from National Key Research and Development Program of China (No. 2017YFC0211302), National Natural Science Foundation for Youth of China (Grant No. 21908207), China Postdoctoral Science Foundation (No. 2020M670659) and Shanxi Province Science Foundation for Youths (Nos. 201901D211224 and 201801D221351).

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