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Dynamic CuII/CuI speciation in Cu-CHA catalysts by in situ Diffuse Reflectance UV–vis-NIR spectroscopy.

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Title: Dynamic CuII/CuI speciation in Cu-CHA catalysts by in situ Diffuse Reflectance UV–vis-NIR spectroscopy.
Authors: Negri, Chiara1 (AUTHOR), Signorile, Matteo1 (AUTHOR), Porcaro, Natale G.1 (AUTHOR), Borfecchia, Elisa1 (AUTHOR), Berlier, Gloria1 (AUTHOR) gloria.berlier@unito.it, Janssens, Ton V.W.2 (AUTHOR), Bordiga, Silvia1 (AUTHOR) silvia.bordiga@unito.it
Source: Applied Catalysis A: General. May2019, Vol. 578, p1-9. 9p.
Subjects: Reflectance spectroscopy, Chemical speciation, Charge transfer, Oxidation states, High temperatures, Silicon isotopes
Abstract: Evolution of copper environment in Cu-CHA (Si/Al = 15 and Cu/Al = 0.5) followed by in situ DRS-UV–vis-NIR spectroscopy. • LMCT transitions of hydrated CuII ions in Cu-CHA are strongly affected by Al distribution. • Z[CuII(OH)] and Z 2 CuII sites are characterized by different d-d transitions. • DRS-UV-Vis alone is not able to discern among different Cu-oxo cores formed in O 2 at high temperature. • Resonant Raman shows that [CuII-(μ-O)-CuII]2+ cores are formed irrespective of the starting Cu oxidation state. • [CuII- trans -(μ-1,2-O-O)-CuII]2+ peroxo are favored during the O 2 -dehydration process. Copper exchanged CHA zeolites were investigated by in situ Diffuse Reflectance UV–vis-NIR spectroscopy in order to study the evolution of the copper environment in respect to the sample composition (2 samples differing in Si/Al and Cu content) and the activation procedure (in O 2 or N 2 from room temperature to 400 °C). In situ measurements allowed showing the different behavior of the two samples, both in the d-d and Ligand to Metal Charge Transfer regions, confirming a strong effect of the lattice composition to determine the copper environment and its reactivity. One of the two sample (Si/Al = 15 and Cu/Al = 0.5) was further investigated, in order to clarify the nature of the Cu-oxo species, formed along activation in oxygen. To shed light on this point, in situ measurements starting from a reduced form of the sample, obtained by activation in inert atmosphere at high temperature, were also considered. Additional suggestions on the nature of these species were obtained by resonant Raman measurements conducted in controlled atmosphere. [ABSTRACT FROM AUTHOR]
Copyright of Applied Catalysis A: General is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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  Data: Dynamic CuII/CuI speciation in Cu-CHA catalysts by in situ Diffuse Reflectance UV–vis-NIR spectroscopy.
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  Data: <searchLink fieldCode="AR" term="%22Negri%2C+Chiara%22">Negri, Chiara</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Signorile%2C+Matteo%22">Signorile, Matteo</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Porcaro%2C+Natale+G%2E%22">Porcaro, Natale G.</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Borfecchia%2C+Elisa%22">Borfecchia, Elisa</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Berlier%2C+Gloria%22">Berlier, Gloria</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> gloria.berlier@unito.it</i><br /><searchLink fieldCode="AR" term="%22Janssens%2C+Ton+V%2EW%2E%22">Janssens, Ton V.W.</searchLink><relatesTo>2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Bordiga%2C+Silvia%22">Bordiga, Silvia</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> silvia.bordiga@unito.it</i>
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  Data: <searchLink fieldCode="JN" term="%22Applied+Catalysis+A%3A+General%22">Applied Catalysis A: General</searchLink>. May2019, Vol. 578, p1-9. 9p.
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  Data: <searchLink fieldCode="DE" term="%22Reflectance+spectroscopy%22">Reflectance spectroscopy</searchLink><br /><searchLink fieldCode="DE" term="%22Chemical+speciation%22">Chemical speciation</searchLink><br /><searchLink fieldCode="DE" term="%22Charge+transfer%22">Charge transfer</searchLink><br /><searchLink fieldCode="DE" term="%22Oxidation+states%22">Oxidation states</searchLink><br /><searchLink fieldCode="DE" term="%22High+temperatures%22">High temperatures</searchLink><br /><searchLink fieldCode="DE" term="%22Silicon+isotopes%22">Silicon isotopes</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Evolution of copper environment in Cu-CHA (Si/Al = 15 and Cu/Al = 0.5) followed by in situ DRS-UV–vis-NIR spectroscopy. • LMCT transitions of hydrated CuII ions in Cu-CHA are strongly affected by Al distribution. • Z[CuII(OH)] and Z 2 CuII sites are characterized by different d-d transitions. • DRS-UV-Vis alone is not able to discern among different Cu-oxo cores formed in O 2 at high temperature. • Resonant Raman shows that [CuII-(μ-O)-CuII]2+ cores are formed irrespective of the starting Cu oxidation state. • [CuII- trans -(μ-1,2-O-O)-CuII]2+ peroxo are favored during the O 2 -dehydration process. Copper exchanged CHA zeolites were investigated by in situ Diffuse Reflectance UV–vis-NIR spectroscopy in order to study the evolution of the copper environment in respect to the sample composition (2 samples differing in Si/Al and Cu content) and the activation procedure (in O 2 or N 2 from room temperature to 400 °C). In situ measurements allowed showing the different behavior of the two samples, both in the d-d and Ligand to Metal Charge Transfer regions, confirming a strong effect of the lattice composition to determine the copper environment and its reactivity. One of the two sample (Si/Al = 15 and Cu/Al = 0.5) was further investigated, in order to clarify the nature of the Cu-oxo species, formed along activation in oxygen. To shed light on this point, in situ measurements starting from a reduced form of the sample, obtained by activation in inert atmosphere at high temperature, were also considered. Additional suggestions on the nature of these species were obtained by resonant Raman measurements conducted in controlled atmosphere. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Applied Catalysis A: General is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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        Value: 10.1016/j.apcata.2019.03.018
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      – Code: eng
        Text: English
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      – SubjectFull: Reflectance spectroscopy
        Type: general
      – SubjectFull: Chemical speciation
        Type: general
      – SubjectFull: Charge transfer
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      – SubjectFull: Oxidation states
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      – SubjectFull: High temperatures
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      – SubjectFull: Silicon isotopes
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      – TitleFull: Dynamic CuII/CuI speciation in Cu-CHA catalysts by in situ Diffuse Reflectance UV–vis-NIR spectroscopy.
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              Text: May2019
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