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

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Rate and Selectivity Control in Thioether and Alkene Oxidation with H2O2 over Phosphonate‐Modified Niobium(V)–Silica Catalysts
ChemCatChem ( IF 3.8 ) Pub Date : 2017-09-05 , DOI: 10.1002/cctc.201700526
Nicholas E. Thornburg ₁ , Justin M. Notestein ₁

Affiliation

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.

中文翻译：

膦酸酯改性的铌（V）-二氧化硅催化剂用于硫醚和烯烃与H2O2氧化的速率和选择性控制

负载型金属氧化物催化剂是用于液相氧化的多功能材料，包括烯烃环氧化和H ₂ O ₂硫醚硫氧化。最近，烯烃环氧化显示出H ₂ O ₂活化的周期性趋势，突显了Nb-SiO ₂比Ti-SiO ₂具有更高的活性和选择性。研究了三种代表性的催化剂，它们由二氧化硅上的Nb ^V，Ti ^IV和Zr ^IV组成，每种催化剂都是通过分子前体方法制备的，该方法可产生高度分散的氧化物位点，用于H ₂ O ₂氧化硫代苯甲醚。。对于环氧化，初始速率趋于Nb> Ti≫Zr，在许多其他硫醚中，Nb的性能优于Ti。相反，在所有转化率下，对亚砜对砜的选择性都会使Ti> Nb≫Zr趋向于增长。用苯膦酸改性Nb-SiO ₂催化剂并不能完全消除磺氧化反应性，就像它对光氧化和环氧化一样，并导致不寻常的材料对磺化氧化具有活性，但既不环氧化也不对砜过度氧化。

更新日期：2017-09-05

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