TY - JOUR
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.
Publisher Copyright:
© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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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U2 - 10.1002/cctc.201700526
DO - 10.1002/cctc.201700526
M3 - Article
AN - SCOPUS:85028852528
VL - 9
SP - 3714
EP - 3724
JO - ChemCatChem
JF - ChemCatChem
SN - 1867-3880
IS - 19
ER -