Insight into the Alkali Resistance Mechanism of CoMnHPMo Catalyst for NH₃ Selective Catalytic Reduction of NO

Abstract

The existence of alkali metals in flue gases originating from stationary sources can result in catalyst deactivation in the low-temperature selective catalytic reduction (SCR) of nitrogen oxides (NO _x). It is widely accepted that alkali metal poisoning causes damage to the acidic sites of catalysts. Therefore, in this study, a series of CoMn catalysts doped with heteropolyacids (HPAs) were prepared using the coprecipitation method. Among these, CoMnHPMo exhibited superior catalytic performance for SCR and over 95% NO _x conversion at 150–300 ℃. Moreover, it exhibited excellent catalytic activity and stability after alkali poisoning, demonstrating outstanding alkali metal resistance. The characterization indicated that HPMo increased the specific surface area of the catalyst, which provided abundant adsorption sites for NO _x and NH₃. Comparing catalysts before and after poisoning, CoMnHPMo enhanced its alkali metal resistance by sacrificing Brønsted acid sites to protect its Lewis acid sites. In situ DRIFTS was used to study the reaction pathways of the catalysts. The results showed that CoMnHPMo maintained high NH₃ adsorption capacity after K poisoning and then reacted rapidly with NO intermediates to ensure that the active sites were not covered. Consequently, SCR performance was ensured even after alkali metal poisoning. In summary, this research proposed a simple method for the design of an alkali-resistant NH₃-SCR catalyst with high activity at low temperatures.

Keywords

NH₃-SCR; Alkali resistance; Phosphomolybdic acid; CoMn

References

[1.] Guo Y, Luo L, Mu B, et al.. Ash- and alkali-poisoning mechanisms for commercial vanadium–titanic-based catalysts. Ind Eng Chem Res, 2019, 58(49): 22418-22426,

[2.] Kamata H. The role of K₂O in the selective reduction of NO with NH₃ over a V₂O₅(WO₃)/TiO₂ commercial selective catalytic reduction catalyst. J Mol Catal A Chem, 1999, 139(2–3): 189-198,

[3.] Li X, Li X, Yang RT, et al.. The poisoning effects of calcium on V₂O₅–WO₃/TiO₂ catalyst for the SCR reaction: comparison of different forms of calcium. Mol Catal, 2017, 434: 16-24,

[4.] Zheng Y, Jensen AD, Johnsson JE. Laboratory investigation of selective catalytic reduction catalysts: deactivation by potassium compounds and catalyst regeneration. Ind Eng Chem Res, 2004, 43(4): 941-947,

[5.] Kong M, Liu Q, Zhou J, et al.. Effect of different potassium species on the deactivation of V₂O₅–WO₃/TiO₂ SCR catalyst: comparison of K₂SO₄, KCl and K₂O. Chem Eng J, 2018, 348: 637-643,

[6.] Tian Y, Yang J, Yang C, et al.. Comparative study of the poisoning effect of NaCl and Na₂O on selective catalytic reduction of NO with NH3 over V₂O₅–WO₃/TiO₂ catalyst. J Energy Inst, 2019, 92(4): 1045-1052,

[7.] Su Z, Ren S, Chen Z, et al.. Deactivation effect of CaO on Mn-Ce/AC catalyst for SCR of NO with NH₃ at low temperature. Catalysts, 2020, 10(8): 873,

[8.] Jiang Y, Lai C, Li Q, et al.. The poisoning effect of KCl and K₂O on CeO₂-TiO₂ catalyst for selective catalytic reduction of NO with NH₃. Fuel, 2020, 280,

[9.] Jiang Y, Liu T, Lai C, et al.. Deactivation of CeO₂–TiO₂ catalyst by K₂SO₄ for NH₃-SCR: an experimental and DFT study. Appl Surf Sci, 2021, 547,

[10.] Gao F, Chu C, Zhu W, et al.. High-efficiency catalytic oxidation of nitric oxide over spherical Mn Co spinel catalyst at low temperature. Appl Surf Sci, 2019, 479: 548-556,

[11.] Zhao Q, Chen B, Li J, et al.. Insights into the structure-activity relationships of highly efficient CoMn oxides for the low temperature NH₃-SCR of NOx. Appl Catal B Environ, 2020, 277,

[12.] Wei L, Cui S, Guo H, et al.. The effect of alkali metal over Mn/TiO₂ for low-temperature SCR of NO with NH3 through DRIFT and DFT. Comput Mater Sci, 2018, 144: 216-222,

[13.] Zhou Z, Lan J, Liu L, et al.. Enhanced alkali resistance of sulfated CeO₂ catalyst for the reduction of NO _x from biomass fired flue gas. Catal Commun, 2021, 149,

[14.] Cai S, Xu T, Wang P, et al.. Self-protected CeO₂–SnO₂@SO₄ ^2–/TiO₂ catalysts with extraordinary resistance to alkali and heavy metals for NO _x reduction. Environ Sci Technol, 2020, 54(19): 12752-12760,

[15.] Li Y, Cai S, Wang P, et al.. Improved NO _x reduction over phosphate-modified Fe₂O₃/TiO₂ catalysts via tailoring reaction paths by in situ creating alkali-poisoning sites. Environ Sci Technol, 2021, 55(13): 9276-9284,

[16.] Ghubayra R, Nuttall C, Hodgkiss S, et al.. Oxidative desulfurization of model diesel fuel catalyzed by carbon-supported heteropoly acids. Appl Catal B Environ, 2019, 253: 309-316,

[17.] Geng Y, Jin K, Mei J, et al.. CeO₂ grafted with different heteropoly acids for selective catalytic reduction of NO _x with NH₃. J Hazard Mater, 2020, 382,

[18.] Zhang B, Zhang S, Liu B, et al.. High N₂ selectivity in selective catalytic reduction of NO with NH₃ over Mn/Ti–Zr catalysts. RSC Adv, 2018, 8(23): 12733-12741,

[19.] Ke Y, Huang W, Li S, et al.. Surface acidity enhancement of CeO₂ catalysts via modification with a heteropoly acid for the selective catalytic reduction of NO with ammonia. Catal Sci Technol, 2019, 9(20): 5774-5785,

[20.] Lisi L, Cimino S. Poisoning of SCR catalysts by alkali and alkaline earth metals. Catalysts, 2020, 10(12): 1475,

[21.] Tang X, Wang C, Gao F, et al.. Acid modification enhances selective catalytic reduction activity and sulfur dioxide resistance of manganese–cerium–cobalt catalysts: insight into the role of phosphotungstic acid. J Colloid Interface Sci, 2021, 603: 291-306,

[22.] Inomata Y, Kubota H, Hata S, et al.. Bulk tungsten-substituted vanadium oxide for low-temperature NO _x removal in the presence of water. Nat Commun, 2021, 12(1): 557,

[23.] Jin Q, Xu M, Lu Y, et al.. Simultaneous catalytic removal of NO, mercury and chlorobenzene over WCeMnO _x/TiO₂–ZrO₂: performance study of microscopic morphology and phase composition. Chemosphere, 2022, 295,

[24.] Deng J, Cai S, Gao M, et al.. Crystal-in-amorphous vanadate catalysts for universal poison-resistant elimination of nitric oxide. ACS Catal, 2023, 13(18): 12363-12373,

[25.] Zhang Z, Li Y, Yang P, et al.. Improved NH3-SCR deNOx activity and tolerance to H₂O & SO₂ at low temperature over the Nb _mCu_{0.1– m}Ce_0.9O _x catalysts role of acidity by niobium doping. Fuel, 2021, 303,

[26.] Zhang Y, Li H, Li Z, et al.. Optimization of catalytic activity of MnCoO _x catalyst for NH₃-SCR at low temperature by response surface method. Fuel, 2024, 357,

[27.] Li S, Li C, Liu C, et al.. Mn MOF-derivatives synthesized based upon a mechanochemistry method for low-temperature NH3- SCR: from amorphous precursor to amorphous catalyst. Mol Catal, 2024, 554,

[28.] Zhang Z, Li R, Wang M, et al.. Two steps synthesis of CeTiO _x oxides nanotube catalyst: enhanced activity, resistance of SO₂ and H₂O for low temperature NH₃-SCR of NO _x. Appl Catal B Environ, 2021, 282,

[29.] Yang NZ, Guo RT, Pan WG, et al.. The deactivation mechanism of Cl on Ce/TiO₂ catalyst for selective catalytic reduction of NO with NH3. Appl Surf Sci, 2016, 378: 513-518,

[30.] Wang Q, Wang Y, Wei L, et al.. Promotional mechanism of activity of CeEuMnO ternary oxide for low temperature SCR of NO. J Rare Earths, 2023, 41(6): 965-974,

[31.] Jiang L, Xu Y, Jiang W, et al.. The promotion of NH₃-SCR performance by AC addition on Mn-Fe/Z catalyst. Sep Purif Technol, 2023, 322,

[32.] Geng Y, Lian Z, Zhang Y, et al.. Heteropoly acid-grafted iron oxide catalysts for efficient selective catalytic reduction of NO _x with NH₃. Catal Sci Technol, 2024, 14(11): 3064-3075,

[33.] Shi Y, Yi H, Gao F, et al.. Facile synthesis of hollow nanotube MnCoO _x catalyst with superior resistance to SO₂ and alkali metal poisons for NH₃-SCR removal of NO _x. Sep Purif Technol, 2021, 265,

[34.] Shi Y, Yi H, Gao F, et al.. Evolution mechanism of transition metal in NH₃-SCR reaction over Mn-based bimetallic oxide catalysts: structure-activity relationships. J Hazard Mater, 2021, 413,

[35.] Zhang L, Shi L, Huang L, et al.. Rational design of high-performance DeNO _x catalysts based on Mn _xCo_{3– x}O₄ nanocages derived from metal–organic frameworks. ACS Catal, 2014, 4(6): 1753-1763,

[36.] Kang K, Yao X, Cao J, et al.. Enhancing the K resistance of CeTiO _x catalyst in NH₃-SCR reaction by CuO modification. J Hazard Mater, 2021, 402,

[37.] Ren S, Li S, Su Z, et al.. Poisoning effects of KCl and As₂O₃ on selective catalytic reduction of NO with NH3 over Mn–Ce/AC catalysts at low temperature. Chem Eng J, 2018, 351: 540-547,

[38.] Zhang J, Huang Z, Du Y, et al.. Alkali-poisoning-resistant Fe₂O₃/MoO₃/TiO₂ catalyst for the selective reduction of NO by NH₃: the role of the MoO₃ safety buffer in protecting surface active sites. Environ Sci Technol, 2020, 54(1): 595-603,

[39.] Wang C, Tang X, Yi H, et al.. MnCo nanoarray in situ grown on 3D flexible nitrogen-doped carbon foams as catalyst for high-performance denitration. Colloids Surf A Physicochem Eng Aspects, 2021, 612,

[40.] Zhang X, Cui Y, Li Z, et al.. Cobalt modification for improving potassium resistance of Mn/Ce–ZrO₂ in selective catalytic reduction. Chem Eng Technol, 2016, 39(5): 874-882,

[41.] Meng B, Zhao Z, Wang X, et al.. Selective catalytic reduction of nitrogen oxides by ammonia over Co₃O₄ nanocrystals with different shapes. Appl Catal B Environ, 2013, 129: 491-500,

[42.] Fang N, Guo J, Shu S, et al.. Enhancement of low-temperature activity and sulfur resistance of Fe_0.3Mn_0.5Zr_0.2 catalyst for NO removal by NH₃-SCR. Chem Eng J, 2017, 325: 114-123,

[43.] Zhou X, Wang P, Shen Z, et al.. Low-temperature NO _x reduction over hydrothermally stable SCR catalysts by engineering low-coordinated Mn active sites. Chem Eng J, 2022, 442,

[44.] Qiu L, Meng J, Pang D, et al.. Reaction and characterization of Co and Ce doped Mn/TiO₂ catalysts for low-temperature SCR of NO with NH₃. Catal Lett, 2015, 145(7): 1500-1509,

[45.] Wu X, Feng Y, Liu X, et al.. Redox & acidity optimizing of LDHs-based CoMnAl mixed oxides for enhancing NH₃-SCR performance. Appl Surf Sci, 2019, 495,

[46.] Guo RT, Wang QS, Pan WG, et al.. The poisoning effect of Na and K on Mn/TiO₂ catalyst for selective catalytic reduction of NO with NH₃: a comparative study. Appl Surf Sci, 2014, 317: 111-116,

[47.] Mo D, Qin Q, Huang C, et al.. Regulating the distribution of iron active sites on γ-Fe₂O₃ via Mn-modified α-Fe₂O₃ for NH3-SCR. Appl Catal B Environ Energy, 2024, 349,

[48.] Gao Y, Luan T, Zhang S, et al.. Comprehensive comparison between nanocatalysts of Mn–co/TiO₂ and Mn–Fe/TiO₂ for NO catalytic conversion: an insight from nanostructure, performance, kinetics, and thermodynamics. Catalysts, 2019, 9(2): 175,

[49.] Wu Z, Jin R, Liu Y, et al.. Ceria modified MnO _x/TiO₂ as a superior catalyst for NO reduction with NH₃ at low-temperature. Catal Commun, 2008, 9(13): 2217-2220,

[50.] Huang L, Zha K, Namuangruk S, et al.. Promotional effect of the TiO₂ (001) facet in the selective catalytic reduction of NO with NH₃: in situ DRIFTS and DFT studies. Catal Sci Technol, 2016, 6(24): 8516-8524,

[51.] Liu Z, Zhang S, Li J, et al.. Promoting effect of MoO₃ on the NO _x reduction by NH₃ over CeO₂/TiO₂ catalyst studied with in situ DRIFTS. Appl Catal B Environ, 2014, 144: 90-95,

[52.] Liu Y, Gu T, Weng X, et al.. DRIFT studies on the selectivity promotion mechanism of Ca-modified Ce–Mn/TiO₂ catalysts for low-temperature NO reduction with NH₃. J Phys Chem C, 2012, 116(31): 16582-16592,

[53.] Ma L, Cheng Y, Cavataio G, et al.. In situ DRIFTS and temperature-programmed technology study on NH₃-SCR of NO over Cu-SSZ-13 and Cu-SAPO-34 catalysts. Appl Catal B Environ, 2014, 156–157: 428-437,

[54.] Liu Z, Zhu J, Li J, et al.. Novel Mn–Ce–Ti mixed-oxide catalyst for the selective catalytic reduction of NO _x with NH₃. ACS Appl Mater Interfaces, 2014, 6(16): 14500-14508,

[55.] Sun W, Li X, Zhao Q, et al.. Fe–Mn mixed oxide catalysts synthesized by one-step urea-precipitation method for the selective catalytic reduction of NO _x with NH₃ at low temperatures. Catal Lett, 2018, 148(1): 227-234,

[56.] Liu Z, Liu H, Feng X, et al.. Ni–Ce–Ti as a superior catalyst for the selective catalytic reduction of NO _x with NH₃. Mol Catal, 2018, 445: 179-186,

[57.] Putluru SSR, Mossin S, Riisager A, et al.. Heteropoly acid promoted Cu and Fe catalysts for the selective catalytic reduction of NO with ammonia. Catal Today, 2011, 176(1): 292-297,

[58.] Putluru SSR, Jensen AD, Riisager A, et al.. Heteropoly acid promoted V₂O₅/TiO₂ catalysts for NO abatement with ammonia in alkali containing flue gases. Catal Sci Technol, 2011, 1(4): 631-637,

[59.] Xiong S, Chen J, Liu H, et al.. Like cures like: detoxification effect between alkali metals and sulfur over the V₂O₅/TiO₂ deNO _x catalyst. Environ Sci Technol, 2022, 56(6): 3739-3747,

[60.] Chen R, Fang X, Li J, et al.. Mechanistic investigation of the enhanced SO₂ resistance of Co-modified MnO _x catalyst for the selective catalytic reduction of NO _x by NH₃. Chem Eng J, 2023, 452,

[61.] Wang Y, Xie H, Liu H, et al.. La and Co addition to Mn/TiO₂ catalysts for enhancing low-temperature denitrification activity and H₂O/SO₂ tolerance. Ind Eng Chem Res, 2023, 62(44): 18303-18311,

[62.] Liu Z, Feng X, Zhou Z, et al.. Ce–Sn binary oxide catalyst for the selective catalytic reduction of NO _x by NH₃. Appl Surf Sci, 2018, 428: 526-533,

[63.] Kang K, Yao X, Huang Y, et al.. Insights into the co-doping effect of Fe³⁺ and Zr⁴⁺ on the anti-K performance of CeTiO _x catalyst for NH₃-SCR reaction. J Hazard Mater, 2021, 416,

[64.] Zhu L, Zhong Z, Yang H, et al.. Comparison study of Cu–Fe–Ti and Co–e–Ti oxide catalysts for selective catalytic reduction of NO with NH₃ at low temperature. J Colloid Interface Sci, 2016, 478: 11-21,

[65.] Huang X, Dong F, Zhang G, et al.. A strategy for constructing highly efficient yolk–shell Ce@Mn@TiO _x catalyst with dual active sites for low-temperature selective catalytic reduction of NO with NH₃. Chem Eng J, 2021, 419,

[66.] Hadjiivanov KI. Identification of neutral and charged N _xO _y surface species by IR spectroscopy. Catal Rev, 2000, 42(1–2): 71-144,

[67.] Tang X, Shi Y, Gao F, et al.. Promotional role of Mo on Ce_0.3FeO _xcatalyst towards enhanced NH3-SCR catalytic performance and SO₂ resistance. Chem Eng J, 2020, 398: 125619,

[68.] Wang P, Yan L, Gu Y, et al.. Poisoning-resistant NO _x reduction in the presence of alkaline and heavy metals over H-SAPO-34-supported Ce-promoted Cu-based catalysts. Environ Sci Technol, 2020, 54: 6396-6405,

[69.] Zhang Y, Peng Y, Wang C, et al.. Selective Catalytic Reduction of NO _x with ammonia over copper ion exchanged SAPO-47 zeolites in a wide temperature range. ChemCatChem, 2018, 10: 2481-2487,