Deactivation of Cu/ZSM-5 Catalysts for Lean NOxReduction: Characterization of Changes of Cu State and Zeolite Support

Yan, Ji Yang; Lei, G.D.; Sachtler, Wolfgang M.H.; Kung, Harold H.

doi:10.1006/jcat.1996.0160

Cited by 211 publications

(84 citation statements)

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“…The EPR spectra of |Cu x |[Si 12 Al]-MFI and |Cu 0.38 Ca 0.086 |[Si 12 Al]-MFI catalysts, shown in Figure 6 (curves a, b and c), are similar to those reported by Yan et al 18 and can be attributed to the presence of hydrated Cu 2+ cations in octahedral symmetry. This confirms the conclusions drawn from the H 2 -TPR and DRS-UV-Vis measurements.…”

Section: +supporting

confidence: 82%

Selective catalytic reduction of NO to N2 with copper and cobalt exchanged ZSM-5 zeolites: the effect of calcium addition

Martins¹,

Peguin²,

Wallau³

et al. 2005

J. Braz. Chem. Soc.

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Zeólitas ZSM-5 contendo cobre ou cobalto, ou simultaneamente cobre e cálcio, ou cobalto e cálcio foram preparadas por troca-iônica e testadas como catalisadores na redução de NO a N 2 na presença de metano ou propano. . Nestes catalisadores a presença de cálcio não provocou diferenças significativas na atividade específica para a redução de NO ou para a oxidação do metano.ZSM-5 catalysts containing either Cu or Co cations individually or Cu/Ca or Co/Ca cation combinations were prepared by ion exchange. These materials were tested as catalysts for the reduction of NO to N 2 in the presence of propane or methane. Cu 2+ and [Cu-O-Cu] 2+ species were identified in ion exchangeable sites in the copper-containing catalysts. The amount of the latter cation increased with increasing copper content and in the presence of Ca 2+ and was the most active in the reduction of NO. However, at temperatures higher than 400 ºC its activity decreased markedly. For cobalt-exchanged zeolites, Co 2+ in charge-compensation sites or Co 3+ in extra-framework precipitates were present in the catalysts. It was verified that the amount of Co 3+ diminished with the presence of Ca 2+. For the catalysts prepared in this study no significant differences in specific activity for the reduction of NO or for methane oxidation were observed in the presence of calcium.

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Section: +supporting

confidence: 82%

Selective catalytic reduction of NO to N2 with copper and cobalt exchanged ZSM-5 zeolites: the effect of calcium addition

Martins¹,

Peguin²,

Wallau³

et al. 2005

J. Braz. Chem. Soc.

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“…The same authors [26], for 1 wt% Cu on alumina observed reduction of small CuO clusters at 1308C, accompanied by a broad reduction peak in the range 100±5008C, attributed to copper aluminate. The Cu-exchanged ZSM-5 reduction pro®le had three reduction peaks located at 158C, 1658C and 2758C [26]. The low-temperature peak (158C) was assigned to the reduction of bridged oxocations to Cu 1 , the 1658C reduction peak was assigned to the reduction of isolated Cu 2 ions to Cu 1 , and reduction of CuO clusters, while the high temperature peak (2758C) was assigned to the reduction of Cu 1 to metallic copper [26,31,32].…”

Section: Introductionmentioning

confidence: 71%

“…Yan et al [26] observed a H 2 consumption peak at 2008C for 2 wt% Cu on silica. The same authors [26], for 1 wt% Cu on alumina observed reduction of small CuO clusters at 1308C, accompanied by a broad reduction peak in the range 100±5008C, attributed to copper aluminate. The Cu-exchanged ZSM-5 reduction pro®le had three reduction peaks located at 158C, 1658C and 2758C [26].…”

Section: Introductionmentioning

confidence: 99%

“…Typically hydrogen was used as the reductant (H 2 -TPR). In their study of deactivation of Cu±ZSM-5 zeolite catalysts for the selective catalytic reduction of NO, Yan et al [26] used H 2 -TPR to compare the reduction of copper on various supports. Bulk CuO has been reported to reduce at 200± 3008C [27].…”

Section: Introductionmentioning

confidence: 99%

“…The Cu-exchanged ZSM-5 reduction pro®le had three reduction peaks located at 158C, 1658C and 2758C [26]. The low-temperature peak (158C) was assigned to the reduction of bridged oxocations to Cu 1 , the 1658C reduction peak was assigned to the reduction of isolated Cu 2 ions to Cu 1 , and reduction of CuO clusters, while the high temperature peak (2758C) was assigned to the reduction of Cu 1 to metallic copper [26,31,32]. Amenomiya et al [33] observed two reduction peaks in H 2 -TPR of CuO/ZrO 2 : at low CuO loading (10 wt% CuO) reduction was observed at about 2008C, while at higher CuO loading (40 wt%) a second reduction peak was observed at around 3008C.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Reduction characteristics of copper oxide in cerium and zirconium oxide systems

Kundakovic

Flytzani‐Stephanopoulos

1998

Applied Catalysis A: General

386

173

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The reduction of CuO dispersed on¯uorite-type oxide catalysts, namely La-doped CeO 2 and Y-doped ZrO 2 was studied in this work. On both supports distinct copper species were identi®ed as a function of copper content by temperatureprogrammed reduction (TPR) by H 2 and CH 4 , X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and scanning transmission electron microscopy/energy dispersive X-ray (STEM/EDX) analyses. At low copper loading (<15 at%), the copper phase is present as small clusters, which are reduced at lower temperature than bulk CuO. At higher Cu loading (>15 at%), in addition to clusters, larger CuO particles are present which are reduced at higher temperature close to the reduction temperature of bulk CuO. At copper loading lower than ca. 5 at%, copper is present as highly dispersed clusters or isolated Cu ions, which interact strongly with the¯uorite-type oxide, thus requiring higher reduction temperature. However, the latter is still below the bulk CuO reduction temperature. Copper is more stabilized when dispersed in Ce(La)O 2 than in Zr(Y)O 2 matrix, so that reduction of copper oxide species requires lower temperatures on the Zr(Y)O 2 -based catalysts. The reducibility of the doped ceria is enhanced by the presence of copper in both H 2 -and CH 4 -TPR. On the other hand no such interaction is present in CuZr(Y)O 2 system. The activity of various copper species for methane oxidation is discussed. # 1998 Elsevier Science B.V. All rights reserved.

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Effect of copper on textural and acidic properties of hierarchical nanocrystalline ZSM‐5

P¹,

Kumari²,

Aneesh³

2020

Asia-Pacific J Chem Eng

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In this work, hierarchically porous nanocrystalline ZSM-5 was synthesized hydrothermally. Different concentrations of copper were incorporated into the matrix by ion exchange method. The synthesized samples were characterized by means of X-ray diffraction (XRD), Fourier-transform infrared (FTIR), energydispersive X-ray spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet (UV), 27 Al magic angle spinning nuclear magnetic resonance spectroscopy, and nitrogen sorption analysis. The acid sites on the surface of Cu-ZSM-5 have been systematically investigated using temperature-programmed desorption of ammonia (NH 3-TPD) and pyridine sorption followed by FTIR. The diffraction pattern obtained from XRD studies confirmed the typical Mobil Five. NH 3-TPD reveals the enhancement of acidity achieved by copper. The FTIR spectra of pyridine desorbed samples show that the intensity of bands corresponding to Lewis acidity increases by modification. The ZSM-5 zeolite samples exhibit spherical-shaped MFI crystal structure. The UV spectrum indicates that copper has been doped in the form of cations or in the form of oxides. XPS analysis confirms that the copper exists as Cu(I) and Cu(II). The nitrogen sorption isotherms reveal that the modified samples are mesoporous in nature. The pore volume and diameter were found to be enhanced by the modification. The better textural properties and acidic properties of the Cu-ZSM-5 can make it suitable for catalyzing organic reactions. K E Y W O R D S acidic and textural properties, copper, hierarchical nanocrystalline ZSM-5, ion exchange

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Deactivation of Cu/ZSM-5 Catalysts for Lean NOxReduction: Characterization of Changes of Cu State and Zeolite Support

Cited by 211 publications

References 0 publications

Selective catalytic reduction of NO to N2 with copper and cobalt exchanged ZSM-5 zeolites: the effect of calcium addition

Selective catalytic reduction of NO to N2 with copper and cobalt exchanged ZSM-5 zeolites: the effect of calcium addition

Reduction characteristics of copper oxide in cerium and zirconium oxide systems

Effect of copper on textural and acidic properties of hierarchical nanocrystalline ZSM‐5

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