采用离子交换法制备了Pd负载量为1.64wt.%的Pd–SSZ–13被动式NOx吸附剂,并在温度为700℃,气氛为10%O2、2%H2O(水热处理时)、N2平衡的温和条件下对Pd–SSZ–13分别进行了10h的热和水热老化处理,考察了热和水热老化处理对Pd–SSZ–13吸脱附NOx性能的影响.采用N2吸脱附、XRF、ICP–OES、XRD、SSNMR、XPS、TEM、NH3–TPD和in situ Drifts等手段对吸附剂理化特性和NO吸附过程进行了表征.结果表明,进气中含2%H2O时SSZ–13载体不具备吸附储存NOx的能力,而Pd–SSZ–13能够在吸附阶段以及程序升温至100~230℃时吸附储存NOx,NOx吸附容量为81.3μmol/g;NOx脱附温度(230~493℃)处于SCR催化剂高效工作的温度区间内,脱附较为完全.热和水热老化处理Pd–SSZ–13后,其含水条件下的NOx吸附容量进一步提高至113.4和126.2μmol/g,热老化处理后的样品具有更好的循环使用稳定性.热和水热老化处理虽然造成了一定程度的分子筛骨架脱Al,但没有改变SSZ–13的微孔特性,也未造成分子筛骨架结构坍塌或破坏,且促使分子筛表面Pd物种向孔道内部迁移,提高了Pd的分散度,增加了Pd2+离子(Z-[Pd2+(OH)]+和Z2-Pd2+)位点的数量,进而提高了Pd–SSZ–13吸附储存NOx的能力.与水热老化处理的样品相比,热老化处理的样品分子筛骨架脱Al较轻微,比表面积和微孔孔容更高,Pd分散更好,可能是其具有更好的循环使用稳定性的原因.含水条件下NO主要吸附储存在Pd2+离子位点上,形成Pd+–NO、Pd2+–NO和水合Pd2+–NO物种,温度升高后H2O对Pd2+离子位点的竞争吸附减弱.Pd–SSZ–13含有的大量Brønsted酸位点可能在热和水热老化处理促使Pd迁移和Pd2+离子的形成中发挥了重要作用.
Abstract
The passive NOx adsorbent, Pd-SSZ-13 with a Pd loading of 1.64wt.%, was prepared by the ion-exchange method. Then, the Pd-SSZ-13 was subjected to thermal and hydrothermal aging treatments separately for 10h under mild conditions: at a temperature of 700℃ and in an atmosphere consisting of 10%O2, 2%H2O (for hydrothermal treatment only), and N2 as the balance. The effects of these treatments on the NOx adsorption/desorption performance of Pd-SSZ-13 were investigated. The physicochemical properties of adsorbents and the NO adsorption process were characterized using N2 adsorption-desorption, XRF, ICP-OES, XRD, SSNMR, XPS, TEM, NH3-TPD and in situ Drifts techniques. The results showed that when the feed gas contained 2%H2O, the SSZ-13 support was unable to adsorb NOx, whereas Pd-SSZ-13 exhibited NOx adsorption during both the adsorption stage and the temperature-programmed stage (100~230℃), demonstrating an adsorption capacity of 81.3μmol/g. The NOx desorption temperature range (230~493℃) fell within the active temperature window of SCR catalysts, and complete NOx desorption was achieved. After undergoing thermal and hydrothermal aging treatments, the NOx adsorption capacity of Pd-SSZ-13 in the presence of H2O further increased to 113.4 and 126.2μmol/g, respectively, and the thermally aged sample showed better cyclic stability. Although thermal and hydrothermal aging treatments induced partial dealumination of the SSZ-13 framework, they neither altered the micropore characteristics of SSZ-13 nor caused structural collapse or framework destruction. Instead, the aging processes promoted the migration of Pd species from external surfaces to interior pores, enhanced the dispersion of Pd, and increased the amount of Pd2+ (Z-[Pd2+(OH)]+ and Z2-Pd2+) sites, thereby improving the NOx adsorption-storage capability of Pd-SSZ-13. Compared with the hydrothermally-aged Pd-SSZ-13, the thermally-aged sample showed less framework dealumination, a higher specific surface area and a larger micropore volume, and better dispersion of Pd species, all of which likely contributed to its superior cyclic stability. With H2O in the feed gas, NO was mainly adsorbed and stored at the Pd2+ sites in the forms of Pd+-NO, Pd2+-NO and hydrated Pd2+-NO species, with the competitive adsorption of H2O attenuated at elevated temperatures. During the thermal and hydrothermal aging of Pd-SSZ-13, the abundant Brønsted acid sites likely played an important role in facilitating the migration of Pd species and the formation of Pd2+ sites.
关键词
NOx /
PNA /
Pd–SSZ–13 /
热老化 /
水热老化
Key words
NOx /
PNA /
Pd-SSZ-13 /
thermal aging /
hydrothermal aging
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参考文献
[1] Chu B W, Ma Q X, Liu J, et al. Air pollutant correlations in China: Secondary air pollutant responses to NOx and SO2 control [J]. Environmental Science & Technology Letters, 2020,7(10):695-700.
[2]蒋凯,侯晓松,程水源.典型工业城市O3污染成因及控制策略研究[J].中国环境科学, DOI:10.19674/j.cnki.issn1000-6923. 20250107.012. Jiang K, Hou X S, Cheng S Y. Research on causes and control strategies of O3 pollution in a typical industrial city [J]. China Environmental Science, DOI: 10.19674/j.cnki.issn1000-6923. 20250107.012.
[3] Yang L H, Franco V, Mock P, et al. Experimental assessment of NOx emissions from 73Euro 6diesel passenger cars [J]. Environmental Science & Technology, 2015,49(24):14409-14415.
[4]潘柔杏,于庆君,唐晓龙,等.被动NOx吸附剂在柴油车冷启动排放控制中的研究进展[J].化工进展, 2022,41(1):400-417. Pan R X, Yu Q J, Tang X L, et al. Research progress of passive NOx adsorbent in diesel vehicle for cold start emission control [J]. Chemical Industry and Engineering Progress, 2022,41(1):400-417.
[5] Rao S, Sarlashkar J, Rengarajan S, et al. A controls overview on achieving ultra-low NOx [A]. SAE Technical Paper, 2020, DOI: 10.4271/2020-01-1404.
[6] Li Y, Chen D D, Xu X, et al. Cold-start NOx mitigation by passive adsorption using Pd-exchanged zeolites: From material design to mechanism understanding and system integration [J]. Environmental Science & Technology, 2023,57(9):3467-3485.
[7] Gu Y T, Epling W S. Passive NOx adsorber: An overview of catalyst performance and reaction chemistry [J]. Applied Catalysis A: General, 2019,570:1-14.
[8] Lee J, Theis J R, Kyriakidou E A. Vehicle emissions trapping materials: Successes, challenges, and the path forward [J]. Applied Catalysis B: Environmental, 2019,243:397-414.
[9] Khivantsev K, Jaegers N R, Kovarik L, et al. Achieving atomic dispersion of highly loaded transition metals in small-pore zeolite SSZ-13: High-capacity and high-efficiency low-temperature CO and passive NOx adsorbers [J]. Angewandte Chemie: International Edition, 2018,57(51):16672-16677.
[10] Theis J R, Ura J, Getsoian A B, et al. Effect of framework Al pairing on NO storage properties of Pd-CHA passive NOx adsorbers [J]. Applied Catalysis B: Environmental, 2023,322:122074.
[11] Gu Y T, Zelinsky P R, Chen Y R, et al. Investigation of an irreversible NOx storage degradation mode on a Pd/BEA passive NOx adsorber [J]. Applied Catalysis B: Environmental, 2019,258:118032.
[12] Gu Y T, Majumdar S S, Pihl J A, et al. Investigation of NO adsorption and desorption phenomena on a Pd/ZSM-5passive NOx adsorber [J]. Applied Catalysis B: Environmental, 2021,298:120561.
[13] Zheng Y, Kovarik L, Engelhard M H, et al. Low-temperature Pd/zeolite passive NOx adsorbers: Structure, performance, and adsorption chemistry [J]. The Journal of Physical Chemistry C, 2017,121(29):15793-15803.
[14] Song I, Khivantsev K, Wu Y Q, et al. Unusual water-assisted NO adsorption over Pd/FER calcined at high temperatures: The effect of cation migration [J]. Applied Catalysis B: Environmental, 2022,318: 121810.
[15] Mandal K, Gu Y T, Westendorff K S, et al. Condition-dependent Pd speciation and NO adsorption in Pd/zeolites [J]. ACS Catalysis, 2020,10(21):12801-12818.
[16] Gupta A, Kang S B, Harold M P. NOx uptake and release on Pd/SSZ-13: Impact of feed composition and temperature [J]. Catalysis Today, 2021,360:411-425.
[17] Khivantsev K, Jaegers N R, Kovarik L, et al. Palladium/zeolite low temperature passive NOx adsorbers (PNA): Structure-adsorption property relationships for hydrothermally aged PNA materials [J]. Emission Control Science and Technology, 2020,6:126-138.
[18] Gao F, Wang Y L, Washton N M, et al. Effects of alkali and alkaline earth cocations on the activity and hydrothermal stability of Cu/SSZ- 13NH3-SCR catalysts [J]. ACS Catalysis, 2015,5(11):6780-6791.
[19] Wang A Y, Lindgren K, Di M Q, et al. Insight into hydrothermal aging effect on Pd sites over Pd/LTA and Pd/SSZ-13 as PNA and CO oxidation monolith catalysts [J]. Applied Catalysis B: Environmental, 2020,278:119315.
[20] Li D, Yang G J, Chen M Y, et al. Na co-cations promoted stability and activity of Pd/SSZ-13 for low-temperature NO adsorption [J]. Applied Catalysis B: Environmental, 2022,309:121266.
[21] Zhao H W, Chen X Y, Bhat A, et al. Insight into hydrothermal aging effect on deactivation of Pd/SSZ-13 as low-temperature NO adsorption catalyst: Effect of dealumination and Pd mobility [J]. Applied Catalysis B: Environmental, 2021,286:119874.
[22] Ryou Y, Lee J, Cho J S, et al. Activation of Pd/SSZ-13 catalyst by hydrothermal aging treatment in passive NO adsorption performance at low temperature for cold start application [J]. Applied Catalysis B: Environmental, 2017,212:140-149.
[23] Lee J, Ryou Y, Hwang S, et al. Comparative study of the mobility of Pd species in SSZ-13and ZSM-5, and its implication for their activity as passive NOx adsorbers (PNAs) after hydro-thermal aging [J]. Catalysis Science & Technology, 2019,9(1):163-173.
[24] Lee J, Kim J, Kim Y, et al. Improving NOx storage and CO oxidation abilities of Pd/SSZ-13 by increasing its hydrophobicity [J]. Applied Catalysis B: Environmental, 2020,277:119190.
[25] Wang Y J, Shi X Y, Liu Z Q, et al. The study of Pd-SSZ-13 as low-temperature passive NOx adsorber materials: High dispersal of Pd in small-pore CHA zeolites by thermal treatment [J]. Applied Catalysis B: Environmental, 2023,324:122254.
[26] Chen H Y, Collier J E, Liu D X, et al. Low temperature NO storage of zeolite supported Pd for low temperature diesel engine emission control [J]. Catalysis Letters, 2016,146(9):1706-1711.
[27] Yasumura S, Ueda T, Ide H, et al. Local structure and NO adsorption/desorption property of Pd2+ cations at different paired Al sites in CHA zeolite [J]. Physical Chemistry Chemical Physics, 2021,23(39):22273-22282.
[28] Villamaina R, Iacobone U, Nova I, et al. Mechanistic insight in NO trapping on Pd/Chabazite systems for the low-temperature NOx removal from diesel exhausts [J]. Applied Catalysis B: Environmental, 2021,284:119724.
[29] Cui Y R, Chen J Z, Peng B, et al. Onset of high methane combustion rates over supported palladium catalysts: From isolated Pd cations to PdO nanoparticles [J]. JACS Au, 2021,1(4):396-408.
[30]司庆宇,樊星,张玮航,等.Fe和Cu分子筛催化剂同时催化NOx还原和N2O分解[J].中国环境科学, 2024,44(9):4826-4834. Si Q Y, Fan X, Zhang W H, et al. Simultaneous reduction of NOx and decomposition of N2O over Fe and Cu zeolite catalysts [J]. China Environmental Science, 2024,44(9):4826-4834.
[31] Wang Y X, Wang Y J, Shi X Y, et al. Unveiling the roles of distinct active sites over Pd/SSZ-13 for low-temperature NOx adsorption [J]. Applied Surface Science, 2024,659:159938.
[32] Li S H, Zheng A M, Su Y C, et al. Brønsted/Lewis acid synergy in dealuminated HY zeolite: A combined solid-state NMR and theoretical calculation study [J]. Journal of the American Chemical Society, 2007,129(36):11161-11171.
[33] Lardinois T M, Bates J S, Lippie H H, et al. Structural interconversion between agglomerated palladium domains and mononuclear Pd(II) cations in Chabazite zeolites [J]. Chemistry of Materials, 2021,33(5): 1698-1713.
[34]杜延年,周祥,周涵,等. FAU分子筛骨架中Al原子的分布规律及对Brønsted酸强度的影响[J].石油学报(石油加工), 2019,35(1): 11-19. Du Y N, Zhou X, Zhou H, et al. Distribution of aluminum atoms in FAU structured framework and their influence on Brønsted acid strength [J]. Acta Petrolei Sinica (Petroleum Processing Section), 2019,35(1):11-19.
[35]马倩,王赫,屈嘉鑫,等.Ni-Ce复合协同促进CO同步催化去除NO的性能和机理[J].中国环境科学, 2025,45(2):671-681. Ma Q, Wang H, Qu J X, et al. Performance and mechanism of Ni-Ce composite synergistically promoting CO-selective catalytic reduction of NO [J]. China Environmental Science, 2025,45(2):671-681.
[36] Van der Mynsbrugge J, Head-Gordon M, Bell A T. Computational modeling predicts the stability of both Pd+ and Pd2+ion-exchanged into H-CHA [J]. Journal of Materials Chemistry A, 2021,9(4):2161- 2174.
[37] Mei D H, Gao F, Szanyi J, et al. Mechanistic insight into the passive NOx adsorption in the highly dispersed Pd/HBEA zeolite [J]. Applied Catalysis A: General, 2019,569:181-189.
[38] Hosseiniamoli H, Bryant G, Kennedy E M, et al. Understanding structure-function relationships in zeolite-supported Pd catalysts for oxidation of ventilation air methane [J]. ACS Catalysis, 2018,8(7): 5852-5863.
基金
国家自然科学基金资助项目(21707004);北京市自然科学基金资助项目(8152011)
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