Equilibria between Peroxo and Hydroperoxo Species in the Titanosilicates: An In Situ High‐Resolution XANES Investigation

Abstract

The selective catalytic oxidation of organic compounds with an environmental attractive oxidant, aqueous H 2 O 2 , is a challenging goal in fine chemistry. Over the past two decades, hetero-[a] Dr.

Titanium-monosubstituted polyoxometalates: relation between homogeneous and heterogeneous Ti-single-site-based catalysis

“…For successful designing new catalysts and processes, we needed a basic knowledge about the mechanism of the formation of active titanium species and the mechanisms of their interaction with organic substrates. Although considerable efforts, both theoretical and experimental, have been directed to understanding activity observed in TS-1 and related materials [9,[66][67][68][80][81][82][83][84][85][86][87][88][89][90][91][92][93][94], much remained to be realised regarding the nature of the active oxidising species and chemical interactions at the molecular level. This stimulated our interest to model mechanistic studies on the titanium-single-site-catalysed oxidations.…”

Towards selective catalytic oxidations using in situ generated H2O2

“…We conclude that this is related to the initial formation of a titanium hydroperoxo/superoxo species following addition of H 2 O 2 (noted by a change in catalyst colour from white to yellow upon contact with H 2 O 2 ) and that this species endures long after "free" H 2 O 2 in solution has decomposed. These titanium hydroperoxo species have previously been widely reported using EPR and UV-Vis analysis [67][68][69] and we assume they can act as stoichiometric oxidising agents following their formation.…”

Selective Catalysis and Nanoscience: An Inseparable Pair

“…[27] The combination of these two factors results in an ensemble of nanometric dimensions, where the Ti centers can be reached only by reagents of the right size and appropriate hydrophilic/hydrophobic character. [28,29] For this reason TS-1 is an election catalyst for the selective oxidation of organic substrate using hydrogen peroxide as the oxidizing agent. [30][31][32] In particular we can cite phenol hydroxylation, olefin epoxidation, alkane oxidation, oxidation of ammonia to hydroxylamine, conversion of secondary amines to dialkylhydroxylamines, conversion of secondary alcohols to ketones and cyclohexanone ammoximation.…”