Greening Oxidation Catalysis: Water as a Solvent for Efficient Alkene Epoxidation over a Titanosilicate/H₂O₂ System

Abstract

Herein, we disclose the application of water (H2O) solvent in titanosilicate-catalyzed epoxidation of alkenes. A highly efficient H2O-solvent propylene epoxidation system (Ti-MWW/H2O/H2O2/propylene/K+) was achieved, possessing high activity, selectivity, and stability. Our investigation shows that this excellent catalytic performance is ascribed to the structure variation of H2O induced by K+. The superior H2O structure is the one that donates two and accepts one hydrogen bond (HB), which is known as the “DDA” H2O structure. The current report benefits sustainable applications in titanosilicate-catalyzed alkene epoxidation and conforms to the principles of green chemistry.

Evidence of solvent-mediated proton transfer during H2O2activation in titanosilicate-catalyzed oxidation systems

“…6C). In our recent work, 101 in the presence of the pure H 2 O solvent, the introduction of alkali metal ions ( e.g. , K + ) weakens the hydrogen bonding between H 2 O molecules due to their strong polarization effect, and this greatly improves the catalytic activity for the epoxidation of alkenes in the H 2 O solvent, even exceeding that in the ‘so-called’ best solvent MeCN.…”

“…6C). In our recent work, 101 in the presence of the pure H 2 O solvent, the introduction of alkali metal ions (e.g., K + ) weakens the hydrogen bonding between H 2 O molecules due to their strong polarization effect, and this greatly improves the catalytic activity for the epoxidation of alkenes in the H 2 O solvent, even exceeding that in the 'so-called' best solvent MeCN. Therefore, for the H 2 O solvent, we propose a highly efficient alkene epoxidation catalysis system (e.g., Ti-MWW/H 2 O/H 2 O 2 /propylene/K + ), which possesses high activity, selectivity, and performance stability.…”

Oxidation Catalysis of Au Nano-Particles Immobilized on Titanium(IV)- and Alkylthiol-Functionalized SBA-15 Type Mesoporous Silicate Supports

“…Sev-To improve the activity toward hydrocarbon oxidation, Au nano-particle catalysts are combined with other active species, such as titanium(IV) sites of titanosilicates [17,18]. Several titanium(IV) compounds are known to catalyze the alkene epoxidation with hydrogen peroxide in homogeneous and heterogeneous system [19][20][21][22][23][24][25]. The heterogeneous titanosilicate compounds have been reported to catalyze not only the epoxidation of alkenes, but also the oxygenation of alkanes and aromatic rings using hydrogen peroxide as an oxidant [24][25][26][27][28].…”

“…Several titanium(IV) compounds are known to catalyze the alkene epoxidation with hydrogen peroxide in homogeneous and heterogeneous system [19][20][21][22][23][24][25]. The heterogeneous titanosilicate compounds have been reported to catalyze not only the epoxidation of alkenes, but also the oxygenation of alkanes and aromatic rings using hydrogen peroxide as an oxidant [24][25][26][27][28]. During these catalytic reactions based on titanium(IV), peroxido complexes of titanium(IV) might form as the reaction intermediate.…”

Editorial: Preparation of functional materials and utilization of renewable resources in green solvents

“…The as-prepared catalysts were synthesized using a hydrothermal method and showed high reaction selectivities due to high Cu dispersions, small particle sizes, and high proportions of metallic Cu 0 . Water, the most abundant and important solvent on earth, is cheap, green, readily available, and can be used to produce hydrogen or oxygen through electrolysis ( Yu et al, 2022 ). Hui et al reviewed the synthesis of ammonia by nitrogen photo-reduction over tungsten and the related metal semiconductors.…”