Rate and Selectivity Control in Thioether and Alkene Oxidation with H2O2 over Phosphonate-Modified Niobium(V)–Silica Catalysts

Nicholas E. Thornburg; Justin M. Notestein

doi:10.1002/cctc.201700526

Rate and Selectivity Control in Thioether and Alkene Oxidation with H₂O₂ over Phosphonate-Modified Niobium(V)–Silica Catalysts

Nicholas E. Thornburg, Justin M. Notestein

Northwestern University

Research output: Contribution to journal › Article › peer-review

17 Citations (Scopus)

Abstract

Supported metal oxide catalysts are versatile materials for liquid-phase oxidations, including alkene epoxidation and thioether sulfoxidation with H₂O₂. Periodic trends in H₂O₂ activation was recently demonstrated for alkene epoxidation, highlighting Nb-SiO₂ as a more active and selective catalyst than Ti-SiO₂. Three representative catalysts are studied consisting of Nb^V, Ti^IV, and Zr^IV on silica, each made through a molecular precursor approach that yields highly dispersed oxide sites, for thioanisole oxidation by H₂O₂. Initial rates trend Nb>Ti≫Zr, as for epoxidation, and Nb outperforms Ti for a number of other thioethers. In contrast, selectivity to sulfoxide vs. sulfone trends Ti>Nb≫Zr at all conversions. Modifying the Nb-SiO₂ catalyst with phenylphosphonic acid does not completely remove sulfoxidation reactivity, as it did for photooxidation and epoxidation, and results in an unusual material active for sulfoxidation but neither epoxidation nor overoxidation to the sulfone.

Original language	English
Pages (from-to)	3714-3724
Number of pages	11
Journal	ChemCatChem
Volume	9
Issue number	19
DOIs	https://doi.org/10.1002/cctc.201700526
Publication status	Published - Oct 10 2017

Keywords

heterogeneous catalysis
hydrogen peroxide
niobium
oxidative desulfurization
supported catalysts

ASJC Scopus subject areas

Catalysis
Physical and Theoretical Chemistry
Organic Chemistry
Inorganic Chemistry

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@article{a00c65a6a4ac4286bca63006d98509a2,

title = "Rate and Selectivity Control in Thioether and Alkene Oxidation with H2O2 over Phosphonate-Modified Niobium(V)–Silica Catalysts",

abstract = "Supported metal oxide catalysts are versatile materials for liquid-phase oxidations, including alkene epoxidation and thioether sulfoxidation with H2O2. Periodic trends in H2O2 activation was recently demonstrated for alkene epoxidation, highlighting Nb-SiO2 as a more active and selective catalyst than Ti-SiO2. Three representative catalysts are studied consisting of NbV, TiIV, and ZrIV on silica, each made through a molecular precursor approach that yields highly dispersed oxide sites, for thioanisole oxidation by H2O2. Initial rates trend Nb>Ti≫Zr, as for epoxidation, and Nb outperforms Ti for a number of other thioethers. In contrast, selectivity to sulfoxide vs. sulfone trends Ti>Nb≫Zr at all conversions. Modifying the Nb-SiO2 catalyst with phenylphosphonic acid does not completely remove sulfoxidation reactivity, as it did for photooxidation and epoxidation, and results in an unusual material active for sulfoxidation but neither epoxidation nor overoxidation to the sulfone.",

keywords = "heterogeneous catalysis, hydrogen peroxide, niobium, oxidative desulfurization, supported catalysts",

author = "Thornburg, {Nicholas E.} and Notestein, {Justin M.}",

note = "Funding Information: The authors acknowledge financial support from the Dow Chemical Company. Materials characterization was performed at the Northwestern University IMSERC facility with financial support from NSF Grant DMR-0521267. Trace metals analysis was performed at the Quantitative Bio-element Imaging Center. X-ray absorption spectroscopy was performed at the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) experimental station at the Advanced Photon Source at Argonne National Laboratory under DOE Contract No. DE-AC02-06CH11357. N.E.T. thanks Dr. Todd Eaton, Scott Nauert, Prof. Linda Broadbelt, and Prof. Neil Schweitzer for their useful conversations, and Dr. Qing Ma for his assistance with X-ray absorption spectroscopy experiments.",

year = "2017",

month = oct,

day = "10",

doi = "10.1002/cctc.201700526",

language = "English",

volume = "9",

pages = "3714--3724",

journal = "ChemCatChem",

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T1 - Rate and Selectivity Control in Thioether and Alkene Oxidation with H2O2 over Phosphonate-Modified Niobium(V)–Silica Catalysts

AU - Thornburg, Nicholas E.

AU - Notestein, Justin M.

N1 - Funding Information: The authors acknowledge financial support from the Dow Chemical Company. Materials characterization was performed at the Northwestern University IMSERC facility with financial support from NSF Grant DMR-0521267. Trace metals analysis was performed at the Quantitative Bio-element Imaging Center. X-ray absorption spectroscopy was performed at the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) experimental station at the Advanced Photon Source at Argonne National Laboratory under DOE Contract No. DE-AC02-06CH11357. N.E.T. thanks Dr. Todd Eaton, Scott Nauert, Prof. Linda Broadbelt, and Prof. Neil Schweitzer for their useful conversations, and Dr. Qing Ma for his assistance with X-ray absorption spectroscopy experiments.

PY - 2017/10/10

Y1 - 2017/10/10

N2 - Supported metal oxide catalysts are versatile materials for liquid-phase oxidations, including alkene epoxidation and thioether sulfoxidation with H2O2. Periodic trends in H2O2 activation was recently demonstrated for alkene epoxidation, highlighting Nb-SiO2 as a more active and selective catalyst than Ti-SiO2. Three representative catalysts are studied consisting of NbV, TiIV, and ZrIV on silica, each made through a molecular precursor approach that yields highly dispersed oxide sites, for thioanisole oxidation by H2O2. Initial rates trend Nb>Ti≫Zr, as for epoxidation, and Nb outperforms Ti for a number of other thioethers. In contrast, selectivity to sulfoxide vs. sulfone trends Ti>Nb≫Zr at all conversions. Modifying the Nb-SiO2 catalyst with phenylphosphonic acid does not completely remove sulfoxidation reactivity, as it did for photooxidation and epoxidation, and results in an unusual material active for sulfoxidation but neither epoxidation nor overoxidation to the sulfone.

AB - Supported metal oxide catalysts are versatile materials for liquid-phase oxidations, including alkene epoxidation and thioether sulfoxidation with H2O2. Periodic trends in H2O2 activation was recently demonstrated for alkene epoxidation, highlighting Nb-SiO2 as a more active and selective catalyst than Ti-SiO2. Three representative catalysts are studied consisting of NbV, TiIV, and ZrIV on silica, each made through a molecular precursor approach that yields highly dispersed oxide sites, for thioanisole oxidation by H2O2. Initial rates trend Nb>Ti≫Zr, as for epoxidation, and Nb outperforms Ti for a number of other thioethers. In contrast, selectivity to sulfoxide vs. sulfone trends Ti>Nb≫Zr at all conversions. Modifying the Nb-SiO2 catalyst with phenylphosphonic acid does not completely remove sulfoxidation reactivity, as it did for photooxidation and epoxidation, and results in an unusual material active for sulfoxidation but neither epoxidation nor overoxidation to the sulfone.

KW - heterogeneous catalysis

KW - hydrogen peroxide

KW - niobium

KW - oxidative desulfurization

KW - supported catalysts

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