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Rate and Selectivity Control in Thioether and Alkene Oxidation with H 2 O 2 over Phosphonate‐Modified Niobium(V)–Silica Catalysts
Author(s) -
Thornburg Nicholas E.,
Notestein Justin M.
Publication year - 2017
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201700526
Subject(s) - alkene , thioether , thioanisole , catalysis , selectivity , sulfone , sulfoxide , chemistry , niobium oxide , oxide , reactivity (psychology) , sulfide , heterogeneous catalysis , inorganic chemistry , organic chemistry , alternative medicine , medicine , pathology
Supported metal oxide catalysts are versatile materials for liquid‐phase oxidations, including alkene epoxidation and thioether sulfoxidation with H 2 O 2 . Periodic trends in H 2 O 2 activation was recently demonstrated for alkene epoxidation, highlighting Nb‐SiO 2 as a more active and selective catalyst than Ti‐SiO 2 . 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 H 2 O 2 . 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‐SiO 2 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.