Elucidating the structure of the W and Mn sites on the Mn-Na2WO4/SiO2 catalyst for the oxidative coupling of methane (OCM) at real reaction temperatures

[EN] The performance of the Mn-NaWO/SiO catalyst for oxidative coupling of methane (OCM) has been ascribed to crystalline phases that are not present at reaction temperatures (>700 °C). The evolution of W and Mn sites structure was monitored via in situ TPO-XRD, -Raman, and -XANES spectroscopies....

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Detalhes bibliográficos
Autores: Ortiz-Bravo, Carlos A., Figueroa, Santiago J.A., Portela, Raquel, Chagas, Carlos A., Bañares, Miguel A., Souza Toniolo, Fabio
Formato: artículo
Estado:Versión publicada
Fecha de publicación:2021
País:España
Recursos:Consejo Superior de Investigaciones Científicas (CSIC)
Repositorio:DIGITAL.CSIC. Repositorio Institucional del CSIC
OAI Identifier:oai:digital.csic.es:10261/303082
Acesso em linha:http://hdl.handle.net/10261/303082
Access Level:acceso abierto
Palavra-chave:Methane
OCM
Active sites
XANES
XAS
Raman
In situ
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spelling Elucidating the structure of the W and Mn sites on the Mn-Na2WO4/SiO2 catalyst for the oxidative coupling of methane (OCM) at real reaction temperaturesOrtiz-Bravo, Carlos A.Figueroa, Santiago J.A.Portela, RaquelChagas, Carlos A.Bañares, Miguel A.Souza Toniolo, FabioMethaneOCMActive sitesXANESXASRamanIn situ[EN] The performance of the Mn-NaWO/SiO catalyst for oxidative coupling of methane (OCM) has been ascribed to crystalline phases that are not present at reaction temperatures (>700 °C). The evolution of W and Mn sites structure was monitored via in situ TPO-XRD, -Raman, and -XANES spectroscopies. TPO-XRD shows that the crystalline phases identified on the Mn-NaWO/SiO, NaWO/SiO, and WO/SiO catalysts at room temperature do not exist at relevant OCM temperatures. The γ → β → α-WO, α → β-cristobalite, and cubic → orthorhombic → molten-NaWO phase transitions occur upon heating. TPO-Raman spectra show that the bond order of W sites with octahedral (O) and tetrahedral (T) symmetry changes during the δ → γ → β → α-WO and cubic → orthorhombic → molten-NaWO transitions, respectively. TPO-XANES spectra show that bond order changes are due to distortion degree variations because all samples preserve essentially W valence and O-Mn sites are always present on Mn-NaWO/SiO catalyst. Steady-state OCM tests show that O-W sites are inactive and T-W sites are less distorted and more active towards methane activation in the presence of O-Mn sites.This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES)- Finance Code 001. We acknowledge the Brazilian Synchrotron Light Laboratory (LNLS) at the National Center for Research in Energy and Materials (CNPEM) for making available beam-time under proposal XAFS2-20190152. C.A.O-B gratefully acknowledge the financial support of the CAPES (process No. 88887.368574/2019-00) and Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) (process No. E-26/200.785/2019) for scholarship grant. The Raman system was acquired with Spanish Ministry grant EQC2018-004839-P and co-funded by CSIC.Academic PressFundaçao Capes (Brasil)Centro Nacional de Pesquisa em Energia e Materiais (Brasil)Consejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72]2023202320212023info:eu-repo/semantics/articlehttp://purl.org/coar/resource_type/c_6501Publisher's versioninfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/10261/303082reponame:DIGITAL.CSIC. Repositorio Institucional del CSICinstname:Consejo Superior de Investigaciones Científicas (CSIC)Inglés#PLACEHOLDER_PARENT_METADATA_VALUE#info:eu-repo/grantAgreement///EQC2018-004839-Phttps://doi.org/10.1016/j.jcat.2021.06.021Síinfo:eu-repo/semantics/openAccessoai:digital.csic.es:10261/3030822026-05-22T06:33:51Z
dc.title.none.fl_str_mv Elucidating the structure of the W and Mn sites on the Mn-Na2WO4/SiO2 catalyst for the oxidative coupling of methane (OCM) at real reaction temperatures
title Elucidating the structure of the W and Mn sites on the Mn-Na2WO4/SiO2 catalyst for the oxidative coupling of methane (OCM) at real reaction temperatures
spellingShingle Elucidating the structure of the W and Mn sites on the Mn-Na2WO4/SiO2 catalyst for the oxidative coupling of methane (OCM) at real reaction temperatures
Ortiz-Bravo, Carlos A.
Methane
OCM
Active sites
XANES
XAS
Raman
In situ
title_short Elucidating the structure of the W and Mn sites on the Mn-Na2WO4/SiO2 catalyst for the oxidative coupling of methane (OCM) at real reaction temperatures
title_full Elucidating the structure of the W and Mn sites on the Mn-Na2WO4/SiO2 catalyst for the oxidative coupling of methane (OCM) at real reaction temperatures
title_fullStr Elucidating the structure of the W and Mn sites on the Mn-Na2WO4/SiO2 catalyst for the oxidative coupling of methane (OCM) at real reaction temperatures
title_full_unstemmed Elucidating the structure of the W and Mn sites on the Mn-Na2WO4/SiO2 catalyst for the oxidative coupling of methane (OCM) at real reaction temperatures
title_sort Elucidating the structure of the W and Mn sites on the Mn-Na2WO4/SiO2 catalyst for the oxidative coupling of methane (OCM) at real reaction temperatures
dc.creator.none.fl_str_mv Ortiz-Bravo, Carlos A.
Figueroa, Santiago J.A.
Portela, Raquel
Chagas, Carlos A.
Bañares, Miguel A.
Souza Toniolo, Fabio
author Ortiz-Bravo, Carlos A.
author_facet Ortiz-Bravo, Carlos A.
Figueroa, Santiago J.A.
Portela, Raquel
Chagas, Carlos A.
Bañares, Miguel A.
Souza Toniolo, Fabio
author_role author
author2 Figueroa, Santiago J.A.
Portela, Raquel
Chagas, Carlos A.
Bañares, Miguel A.
Souza Toniolo, Fabio
author2_role author
author
author
author
author
dc.contributor.none.fl_str_mv Fundaçao Capes (Brasil)
Centro Nacional de Pesquisa em Energia e Materiais (Brasil)
Consejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72]
dc.subject.none.fl_str_mv Methane
OCM
Active sites
XANES
XAS
Raman
In situ
topic Methane
OCM
Active sites
XANES
XAS
Raman
In situ
description [EN] The performance of the Mn-NaWO/SiO catalyst for oxidative coupling of methane (OCM) has been ascribed to crystalline phases that are not present at reaction temperatures (>700 °C). The evolution of W and Mn sites structure was monitored via in situ TPO-XRD, -Raman, and -XANES spectroscopies. TPO-XRD shows that the crystalline phases identified on the Mn-NaWO/SiO, NaWO/SiO, and WO/SiO catalysts at room temperature do not exist at relevant OCM temperatures. The γ → β → α-WO, α → β-cristobalite, and cubic → orthorhombic → molten-NaWO phase transitions occur upon heating. TPO-Raman spectra show that the bond order of W sites with octahedral (O) and tetrahedral (T) symmetry changes during the δ → γ → β → α-WO and cubic → orthorhombic → molten-NaWO transitions, respectively. TPO-XANES spectra show that bond order changes are due to distortion degree variations because all samples preserve essentially W valence and O-Mn sites are always present on Mn-NaWO/SiO catalyst. Steady-state OCM tests show that O-W sites are inactive and T-W sites are less distorted and more active towards methane activation in the presence of O-Mn sites.
publishDate 2021
dc.date.none.fl_str_mv 2021
2023
2023
2023
dc.type.none.fl_str_mv info:eu-repo/semantics/article
http://purl.org/coar/resource_type/c_6501
Publisher's version
info:eu-repo/semantics/publishedVersion
format article
status_str publishedVersion
dc.identifier.none.fl_str_mv http://hdl.handle.net/10261/303082
url http://hdl.handle.net/10261/303082
dc.language.none.fl_str_mv Inglés
language_invalid_str_mv Inglés
dc.relation.none.fl_str_mv #PLACEHOLDER_PARENT_METADATA_VALUE#
info:eu-repo/grantAgreement///EQC2018-004839-P
https://doi.org/10.1016/j.jcat.2021.06.021
Sí
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
eu_rights_str_mv openAccess
dc.publisher.none.fl_str_mv Academic Press
publisher.none.fl_str_mv Academic Press
dc.source.none.fl_str_mv reponame:DIGITAL.CSIC. Repositorio Institucional del CSIC
instname:Consejo Superior de Investigaciones Científicas (CSIC)
instname_str Consejo Superior de Investigaciones Científicas (CSIC)
reponame_str DIGITAL.CSIC. Repositorio Institucional del CSIC
collection DIGITAL.CSIC. Repositorio Institucional del CSIC
repository.name.fl_str_mv
repository.mail.fl_str_mv
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score 15,811543

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