Effect of the hydrothermal aging temperature and Cu/Al ratio on the hydrothermal stability of CuSSZ-13 catalysts for NH<sub>3</sub>-SCR

Han, Shuai; Ye, Qing; Cheng, Shuiyuan; Kang, Tianfang; Dai, Hongxing

doi:10.1039/c6cy02555b

Cited by 104 publications

(55 citation statements)

References 56 publications

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“…Each XPS spectrum shows two asymmetric signals that could be divided into three components at binding energies (BEs) of 932.6-933, 934.6-936.5, and 945.67-947.7 eV. According to the literature [20], the component at BE = 932.6-933 eV was assigned to the surface CuO species [21], while the one at BE = 934.6-936.5 eV corresponded to the surface isolated Cu 2+ ions, and the peak at BE = 945.67-947.7 eV was due to the shake-up satellite of the surface Cu 2+ species on the fresh catalyst [22]. The Cu + species were not detected by the XPS technique, which might be owing to the lower Cu + content in the catalyst or the lower detection sensitivity of the XPS technique.…”

Section: Xps Resultsmentioning

confidence: 91%

Effects of Lanthanide Doping on the Catalytic Activity and Hydrothermal Stability of Cu-SAPO-18 for the Catalytic Removal of NOx (NH3-SCR) from Diesel Engines

Gao

Han

et al. 2020

Catalysts

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Lanthanide (La, Ce, Nd, Gd, Tb, Ho or Lu)-doped Cu-SAPO-18 samples were prepared using the ion-exchange method. Physicochemical properties of the samples were systematically characterized by a number of analytical techniques, and the effects of lanthanide doping on catalytic activity and hydrothermal stability of the Cu-SAPO-18 catalysts for the NH3-SCR reaction were examined. It is shown that the doping of lanthanide elements could affect the interaction between the active components (copper ions) and the AEI-structured SAPO-18 support. The inclusion of some lanthanides significantly slowed down hydrolysis of the catalyst during hydrothermal aging treatment process, leading to an enhanced catalytic activity at both low and high temperatures and hydrothermal stability. In particular, Ce doping promoted the Cu2+ ions to migrate to the energetically favorable sites for enhancement in catalytic activity, whereas the other lanthanide ions exerted little or an opposite effect on the migration of Cu2+ ions. Additionally, Ce doping could improve hydrothermal stability of the Cu-SAPO-18 catalyst by weakening hydrolysis of the catalyst during the hydrothermal aging treatment process. Ce doping increased the catalytic activity of Cu-SAPO-18 at low and high temperatures, which was attributed to modifications of the redox and/or isolated Cu2+ active centers.

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Section: Xps Resultsmentioning

confidence: 91%

Effects of Lanthanide Doping on the Catalytic Activity and Hydrothermal Stability of Cu-SAPO-18 for the Catalytic Removal of NOx (NH3-SCR) from Diesel Engines

Gao

Han

et al. 2020

Catalysts

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“…The X−ray diffraction (XRD) results of all Cu Ⅱ −SSZ−13 catalysts are shown in Figure S1. The fresh and aged samples exhibit characteristic diffraction peaks of SSZ-13 at 2θ = 9.5°, 14.0°, 16.1°, 17.8°, 20.7°, 25.0°, 30.7° [2,29,30]. The fresh samples show perfect crystal structure and high crystallinity, among which the peaks of the F−Cl sample is stronger than that of F−NO3 and F−SO4 samples ( Figure S1a).…”

Section: Catalytic Activitymentioning

confidence: 98%

“…The emission of nitrogen oxides is a major cause of unhealthy air quality and is strictly regulated in many places. To meet regulations, controlling the emission of nitrogen oxides from diesel exhaust is one important topic in catalysis [1,2]. The selective catalytic reduction of NO x by ammonia (NH 3 -SCR) is one of the most effective approaches to convert NO x due to its high fuel economy, and high denitrification efficiency [3,4].…”

Section: Introductionmentioning

confidence: 99%

“…However, the copper ions from the precursors with small anions ions like NO3 − are more accessible to enter the pore, which generates more isolated Cu Ⅱ , and exhibits excellent NH3−SCR activity. The acid sites of the molecular sieve catalyst are beneficial to adsorption and activation of NH3, which is one of the key steps for the reduction of NO by NH3 molecules [2,37]. The ammonia temperature-programmed desorption (NH3−TPD) spectra of the Cu Ⅱ −SSZ−13 catalysts are shown in Figure 4.…”

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confidence: 99%

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Effect of Copper Precursors on the Activity and Hydrothermal Stability of CuII−SSZ−13 NH3−SCR Catalysts

et al. 2019

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A series of CuII−SSZ−13 catalysts are prepared by in-situ hydrothermal method using different copper precursors (CuII(NO3)2, CuIISO4, CuIICl2) for selective catalytic reduction of NO by NH3 in a simulated diesel vehicle exhaust. The catalysts were characterized by X−ray diffraction (XRD), scanning electron microscope (SEM), X−ray photoelectron spectroscopy (XPS), N2 adsorption-desorption, hydrogen-temperature-programmed reduction (H2−TPR), ammonia temperature-programmed desorption (NH3−TPD), and 27Al and 29Si solid state Nuclear Magnetic Resonance (NMR). The CuII−SSZ−13 catalyst prepared by CuII(NO3)2 shows excellent catalytic activity and hydrothermal stability. The NO conversion of CuII−SSZ−13 catalyst prepared by CuII(NO3)2 reaches 90% at 180 °C and can remain above 90% at a wide temperature range of 180–700 °C. After aging treatment at 800 °C for 20 h, the CuII−SSZ−13 catalyst prepared by CuII(NO3)2 still exhibits above 90% NO conversion under a temperature range of 240–600 °C. The distribution of Cu species and the Si/Al ratios in the framework of the synthesized CuII−SSZ−13 catalysts, which determine the catalytic activity and the hydrothermal stability of the catalysts, are dependent on the adsorption capacity of anions to the cation during the crystallization process due to the so called Hofmeister anion effects, the NO3− ion has the strongest adsorption capacity among the three kinds of anions (NO3−, Cl−, and SO42−), followed by Cl– and SO42– ions. Therefore, the CuII−SSZ−13 catalyst prepared by CuII(NO3)2 possess the best catalytic ability and hydrothermal stability.

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“…It has been found that the resistance of Cu-CHA to HA is due to the exceptional hydrothermal stability of the Z 2 Cu II sites located on 6MR, which also act as structure stabilizers during HA [50][51][52] and prevent dealumination. HA mostly affects the ZCu II OH sites which in turn convert to CuO x clusters [9,50,53] and cause some dealumination [28,54], and clusters in turn grow and destroy the zeolite cage [55] resulting in activity loss with hard HA. For mild aging, these changes in catalyst performance were attributed to the changes in the concentration of the individual active Cu sites.…”

Section: Introductionmentioning

confidence: 99%

An Aging Model of NH3 Storage Sites for Predicting Kinetics of NH3 Adsorption, Desorption and Oxidation over Hydrothermally Aged Cu-Chabazite

et al. 2020

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A unified transient kinetic model which can predict the adsorption, desorption and oxidation kinetics of NH3 over hydrothermally aged Cu-chabazite was developed. The model takes into account the variation of fractional coverages of NH3 storage sites due to hydrothermal aging. In order to determine the fractional coverage of these sites, the catalyst was aged for various times at a certain temperature followed by NH3 adsorption, desorption and temperature-programmed desorption (TPD) experiments. TPD profiles were deconvoluted mainly into three peaks with centres at 317, 456 and 526 °C, respectively. Hydrothermal aging resulted in the progressive increase in the intensity of the peak at 317 °C and decrease in the intensity of the peaks at 456 and 526 °C, along with decreased NH3 oxidation at high temperatures. A model for hydrothermal aging kinetics of the fractional coverage of storage sites was developed using three reactions with appropriate rate expressions with parameters regressed from experimental data. The model was then incorporated into a multi-site kinetic model for the degreened Cu-Chabazite by the addition of aging reactions on each storage site. The effects of both aging time and temperature on the kinetics NH3 adsorption, desorption and oxidation were successfully predicted in the 155-540 °C range. This study is the first step towards the development of a hydrothermal aging-unified kinetic model of NH3-Selective Catalytic Reduction over Cu-chabazite.

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Effect of the hydrothermal aging temperature and Cu/Al ratio on the hydrothermal stability of CuSSZ-13 catalysts for NH₃-SCR

Abstract: The effects of the hydrothermal aging temperature on the catalytic performance and stability of CuSSZ-13 catalysts with various Cu/Al ratios were studied.

Cited by 104 publications

References 56 publications

Effects of Lanthanide Doping on the Catalytic Activity and Hydrothermal Stability of Cu-SAPO-18 for the Catalytic Removal of NOx (NH3-SCR) from Diesel Engines

Effects of Lanthanide Doping on the Catalytic Activity and Hydrothermal Stability of Cu-SAPO-18 for the Catalytic Removal of NOx (NH3-SCR) from Diesel Engines

Effect of Copper Precursors on the Activity and Hydrothermal Stability of CuII−SSZ−13 NH3−SCR Catalysts

An Aging Model of NH3 Storage Sites for Predicting Kinetics of NH3 Adsorption, Desorption and Oxidation over Hydrothermally Aged Cu-Chabazite

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Effect of the hydrothermal aging temperature and Cu/Al ratio on the hydrothermal stability of CuSSZ-13 catalysts for NH3-SCR

Abstract: The effects of the hydrothermal aging temperature on the catalytic performance and stability of CuSSZ-13 catalysts with various Cu/Al ratios were studied.

Cited by 104 publications

References 56 publications

Effects of Lanthanide Doping on the Catalytic Activity and Hydrothermal Stability of Cu-SAPO-18 for the Catalytic Removal of NOx (NH3-SCR) from Diesel Engines

Effects of Lanthanide Doping on the Catalytic Activity and Hydrothermal Stability of Cu-SAPO-18 for the Catalytic Removal of NOx (NH3-SCR) from Diesel Engines

Effect of Copper Precursors on the Activity and Hydrothermal Stability of CuII−SSZ−13 NH3−SCR Catalysts

An Aging Model of NH3 Storage Sites for Predicting Kinetics of NH3 Adsorption, Desorption and Oxidation over Hydrothermally Aged Cu-Chabazite

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Effect of the hydrothermal aging temperature and Cu/Al ratio on the hydrothermal stability of CuSSZ-13 catalysts for NH₃-SCR