Structural Characterization of the Redox Behavior in Copper-Exchanged Sodium Zeolite Y by High-Resolution Powder Neutron Diffraction

Fowkes, A. J.; Ibberson, R. M.; Rosseinsky, M. J.

doi:10.1021/cm010504b

Cited by 77 publications

(50 citation statements)

References 41 publications

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“…10,11 XRD studies have shown that site III can be occupied by as many as four Cu/u.c. 10 There are no known H 2 -TPR studies of Cu-Y prepared by vapor-phase exchange with CuCl. While H 2 -TPR spectra of Cu 2+ -exchanged Y have been reported, the assignments of the reduction peaks have been attributed only to general locations described as sodalite, supercage and hexagonal positions.…”

Section: Preparation and Site Occupancy Of Cu-ymentioning

confidence: 99%

“…8 While site III′(III) was not found to be occupied in this study, investigations of Cu-Y prepared by aqueous exchange with either CuCl 2 or Cu(NO 3 ) 2 and subsequent reduction of Cu 2+ to Cu + in H 2 did result in the occupation of this site by Cu + . [10][11][12] Cations in site III are the most accessible to reactants and have been suggested as the active site for NO x reduction by NH 3 . 13,14 The objectives of this work were to determine the site distribution and local structure of Cu + cations in Y zeolite and to assess which types of Cu sites are active for DMC synthesis.…”

Section: Introductionmentioning

confidence: 99%

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The Local Environment of Cu⁺in Cu−Y Zeolite and Its Relationship to the Synthesis of Dimethyl Carbonate

et al. 2006

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Cu-exchanged Y zeolite was investigated in order to determine the location of the copper cations relative to the zeolite framework and to determine which Cu cations are active for the oxidative carbonylation of methanol to dimethyl carbonate (DMC). Cu-Y zeolite was prepared by vapor-phase exchange of H-Y with CuCl. The oxidation state, local coordination, and bond distances of Al and Cu were determined using Al K-edge and Cu K-edge X-ray absorption spectroscopy (XAS). Complimentary information was obtained by H 2 temperature-programmed reduction and by in-situ infrared spectroscopy. Cu-Y has a Cu/Al ratio of unity and very little occluded CuCl. The average Al-O and Al-Cu bond distances are 1.67 Å and 2.79 Å, respectively, and the average Cu-O and Cu-Si(Al) bond distances are 1.99 Å and 3.13 Å, respectively. All of the Cu exchanged is present as Cu + in sites I′, II, and III′. Cu-Y is active for the oxidative carbonylation of methanol, and at low reactant contact time produces DMC as the primary product. With increasing reactant contact time, DMC formation decreases in preference to the formation of dimethoxy methane (DMM) and methylformate (MF). The formation of DMM and MF is attributed to the hydrogenation of DMC and the hydrogenolysis of DMM, respectively. Observation of the catalyst under reaction conditions reveals that most of the copper cations remain as Cu + , but some oxidation of Cu + to Cu 2+ does occur. It is also concluded that only those copper cations present in site II and III′ positions are accessible to the reactants, and hence are catalytically active. The dominant adsorbed species on the surface are methoxy groups, and adsorbed CO is present as a minority species. The relationship of these observations to the kinetics of DMC synthesis is discussed.

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Section: Preparation and Site Occupancy Of Cu-ymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Local Environment of Cu⁺in Cu−Y Zeolite and Its Relationship to the Synthesis of Dimethyl Carbonate

et al. 2006

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“…Cu ϩ cations must be occupying exposed sites in the Y zeolite framework, such as sites II and III according to the nomenclature of Smith (1971), in order to interact with the sulfur-containing molecules. Recent studies by Fowkes et al (2002) have shown that, upon reduction of Cu(II)-Y, there was a redistribution of cation positions and most of the reduced species (Cu ϩ ) occupied sites I* and II. Lamberti et al (1997) showed similar results for both reduced Cu(II)-Y and Cu(I)-Y prepared, respectively, by ion exchange and gas-phase reaction with CuCl vapor.…”

Section: Adsorbent Activation Copper Autoreduction and Migrationmentioning

confidence: 99%

New sorbents for desulfurization of diesel fuels via π‐complexation

2004

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Desulfurization of a commercial diesel fuel by different adsorbents was studied in a fixed-bed adsorber operated at ambient temperature and pressure. In general, the adsorbents tested for total sulfur adsorption capacity at breakthrough followed the order: AC/Cu(I)-Y Ͼ Cu(I)-Y Ͼ Selexsorb CDX (alumina) Ͼ CuCl/␥-Al 2 O 3 Ͼ activated carbon Ͼ Cu(I)-ZSM-5. The best adsorbent, AC/Cu(I)-Y (layered bed of 15 wt % activated carbon followed by Cu(I)Y), is capable of producing 30 cm 3 of diesel fuel per gram of adsorbent with a weighted average content of 0.15 ppmw-S, and about 20 cm 3 of diesel fuel per gram of adsorbent with a weighted average content of 0.06 ppmw-S. These low-sulfur fuels are suitable for fuel cell applications. The added layer of carbon not only delayed the sulfur breakthrough significantly but also sharpened the sulfur wavefronts. GC-FPD results showed that the -complexation sorbents selectively adsorbed highly substituted thiophenes, benzothiophenes, and dibenzothiophenes from diesel, which is not possible with conventional hydrodesulfurization (HDS) reactors. The high sulfur selectivity and high sulfur capacity of Cu(I)Y were because of -complexation. © 2004 AmericanInstitute of Chemical Engineers AIChE J, 50: [791][792][793][794][795][796][797][798][799][800][801] 2004 Keywords: desulfurization of liquid fuels, -complexation sorbent, desulfurization by adsorption, desulfurization of diesel, 4-methyl-dibenzothiophene adsorption, 4, 6-dimethyl- dibenzothiophene adsorption IntroductionThe federal government mandates a reduction in gasoline and diesel sulfur levels to 30 and 15 ppm, respectively, from the current levels of 300 -500 ppmw, to be implemented by 2006(Krause, 2000. This makes refiners consider eliminating production of onboard transportation fuels because of the high costs that will arise from compliance with such regulations (Parkinson, 2001). For fuel cell applications with gasoline as the feed, the sulfur content should be below 1 ppmw. For automotive fuel cells, liquid hydrocarbons are ideal fuels because of their higher energy density, availability, and safety for transportation and storage. However, the water-gas shift catalysts as well as fuel-cell electrode catalysts are poisoned by sulfur, and the sulfur content in the liquid fuel needs to be preferably less than 0.1 ppmw.Hydrodesulfurization (HDS) is very effective in removing thiols and sulfides, but it is not effective for the removal of thiophenic compounds. For example, the H 2 S produced during reaction of some thiophene derivatives is one of the main inhibitors for deep HDS of unreactive species (Ma et al., 1994;Knudsen et al., 1999). Among the unreacted refractory species are 4-methyl-dibenzothiophene (4-MDBT) and 4,6-dimethyldibenzothiophene (4, 6-DMDBT). These molecules are common in diesel fuels. The methyl groups in these species create a steric effect that hinders the capacity of HDS catalysts to chemisorb the sulfur atoms as depicted in Figure 1a. Such steric hindrance is not present for adsorption by -complexatio...

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“…The migration of Cu + cations in zeolites Y induced by the presence of organic molecules (e.g., pyridine, naphthalene, fluorohydrocarbons, butadiene) have been widely discussed [43][44][45][46][47]. It has been demonstrated that the cations placed in S I 0 inside cubooctahedra were more mobile than those in S I sites, which were stabilized by six oxygen atoms.…”

Section: Ethene and Ethyne Adsorptionmentioning

confidence: 99%

Ethene and ethyne molecules interacting with Cu+ sites in zeolites—Quantitative infrared spectroscopic studies

Tarach

Walas

Dátka

et al. 2015

Vibrational Spectroscopy

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Structural Characterization of the Redox Behavior in Copper-Exchanged Sodium Zeolite Y by High-Resolution Powder Neutron Diffraction

Cited by 77 publications

References 41 publications

The Local Environment of Cu⁺in Cu−Y Zeolite and Its Relationship to the Synthesis of Dimethyl Carbonate

The Local Environment of Cu⁺in Cu−Y Zeolite and Its Relationship to the Synthesis of Dimethyl Carbonate

New sorbents for desulfurization of diesel fuels via π‐complexation

Ethene and ethyne molecules interacting with Cu+ sites in zeolites—Quantitative infrared spectroscopic studies

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Structural Characterization of the Redox Behavior in Copper-Exchanged Sodium Zeolite Y by High-Resolution Powder Neutron Diffraction

Cited by 77 publications

References 41 publications

The Local Environment of Cu+in Cu−Y Zeolite and Its Relationship to the Synthesis of Dimethyl Carbonate

The Local Environment of Cu+in Cu−Y Zeolite and Its Relationship to the Synthesis of Dimethyl Carbonate

New sorbents for desulfurization of diesel fuels via π‐complexation

Ethene and ethyne molecules interacting with Cu+ sites in zeolites—Quantitative infrared spectroscopic studies

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Product

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The Local Environment of Cu⁺in Cu−Y Zeolite and Its Relationship to the Synthesis of Dimethyl Carbonate

The Local Environment of Cu⁺in Cu−Y Zeolite and Its Relationship to the Synthesis of Dimethyl Carbonate