The activity of titanium silicalite-1 (TS-1): Some considerations on its origin

Clerici, Mario G.

doi:10.1134/s0023158415040059

Cited by 57 publications

(62 citation statements)

References 19 publications

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“…This reactivity is of particular interest as hydrogen peroxide is used with many titanium silicate systems in catalytic oxidation reactions of organic substrates. 6,[41][42][43] This transformation is not only relevant to oxidation processes, but because these reactions are typically accompanied by the appearence of an intense orange color, titanyl reactivity with hydrogen peroxide has been the basis for a colorimetric H 2 O 2 sensing technology. respectively.…”

Section: ∎ Introductionmentioning

confidence: 99%

“…Examples of molecular peroxotitanium(IV) complexes that serve as oxidants towards organic substrates 46 are rare due to the well documented stability of the titanium-peroxo structural unit, and therefore its corresponding lack of oxidizing capacity. 6,48 It is instead believed that titanium(IV) hydroperoxo species play the active role in substrate oxidation within heterogeneous systems, 10,43,49 and therefore the preparation of well-defined titanium hydroperoxo complexes has been targeted by synthetic chemists. 50 We were unable to observe a stable titanium(IV) hydroperoxo complex, and 1 and 2 did not show any signs of catalytic activity toward organic substrates in the presence of We did, however, test the ability of 3 and 4 to behave as stoichiometric oxidants towards phosphorus(III) compounds and sulfides.…”

Section: ∎ Introductionmentioning

confidence: 99%

“…[PPN] 2 [4] crystallized in the monoclinic space group P2 1 , and Figure 5 shows a thermal ellipsoid plot of the anion that displays the peroxo ligand oriented in an η 2 binding mode in which the O-O moiety is coincident with the O2-Ti1-O3 plane of the [P 3 O 9 ] 3− and acac − ligands. The structure determination revealed unremarkable Ti-Operoxo and O-O Solid-state structure of [O 2 TiP 3 O 9 (acac)] 2− (4) rendered with PLATON 25 with thermal ellipsoids at the 50% probability level, and with [PPN] + cations and solvent molecules of crystallization omitted for clarity.Selected interatomic distances (Å) and angles ( ○ ): Ti1-O20 1.850(4), Ti1-O10 1.823(5), Ti1-O1 2.063(3), Ti1-O2 2.048(2), Ti1-O3 2.040(2), Ti1-O4 1.997(2), Ti1-O5 2.166(2), O10-O20 1.443(6), Σ(Oeq-Ti-Oeq) 353.9(8).…”

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confidence: 99%

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Terminal Titanyl Complexes of Tri- and Tetrametaphosphate: Synthesis, Structures, and Reactivity with Hydrogen Peroxide

Stauber

Cummins

2017

Inorg. Chem.

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The synthesis and characterization of tri- and tetrametaphosphate titanium(IV) oxo and peroxo complexes is described. Addition of 0.5 equiv of [OTi(acac)] to dihydrogen tetrametaphosphate ([POH]) and monohydrogen trimetaphosphate ([POH]) provided a bis(μ,κ,κ) tetrametaphosphate titanyl dimer, [OTiPO] (1; 70% yield), and a trimetaphosphate titanyl acetylacetonate complex, [OTiPO(acac)] (2; 59% yield). Both 1 and 2 have been structurally characterized, crystallizing in the triclinic P1̅ and monoclinic P2 space groups, respectively. These complexes contain Ti≡O units with distances of 1.624(7) and 1.644(2) Å, respectively, and represent rare examples of structurally characterized terminal titanyls within an all-oxygen coordination environment. Complexes 1 and 2 react with hydrogen peroxide to produce the corresponding peroxotitanium(IV) metaphosphate complexes [OTiPO](3; 61% yield) and [OTiPO(acac)] (4; 65% yield), respectively. Both 3 and 4 have been characterized by single-crystal X-ray diffraction studies, and their solid-state structures are presented. Complex 3 functions as an oxygen atom transfer (OAT) reagent capable of oxidizing phosphorus(III) compounds (P(OMe), PPh) and SMe at ambient temperature to result in the corresponding organic oxide with regeneration of dimer 1.

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Section: ∎ Introductionmentioning

confidence: 99%

Section: ∎ Introductionmentioning

confidence: 99%

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confidence: 99%

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Terminal Titanyl Complexes of Tri- and Tetrametaphosphate: Synthesis, Structures, and Reactivity with Hydrogen Peroxide

Stauber

Cummins

2017

Inorg. Chem.

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“…On these grounds, a general oxidation mechanism was proposed for TS-1 and other Ti-zeolites. 41,42 The metal hydroperoxide was also postulated as an active intermediate formed during the epoxidation, catalyzed by layered hydrotalcite in the presence of isobutyramide (Scheme 8). Hydrogen peroxide attack a basis hydroxyl function of the aluminium atoms on the surface of hydrotalcite to form hydroperoxy species, which react with an amide, to generate a peracid together with NH 2 in the aqueous phase.…”

Section: Solid Supported Catalystsmentioning

confidence: 99%

Synthetic utility of metal catalyzed hydrogen peroxide oxidation of C-H, C-C and C=C bonds in alkanes, arenes and alkenes: Recent advances

Wójtowicz‐Młochowska¹

2016

Arkivoc

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This review presents the current state of the art of homogenic and heterogenic oxygen transfer processes using hydrogen peroxide as oxygen source and compounds and complexes of tranisition metals, Fe, V, Cu, Mn, Rh, Mo, Ti, W, Pd, Os, Zr, Cr, Nb, Co, as the catalysts. Based on the reactions of C-H, C-C and C=C bonds in alkanes, arenes and alkenes various mechanisms of the oxygen-transfer processes are discussed and new methodologies for synthesis of alcohols, phenols, aldehydes, ketones, epoxides and carboxylic acids are indicated.

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“…Despite the promising improvement brought by the fine control over the catalyst textural properties, amorphous SiO2-TiO2 mixed oxides are easily deactivated in water [22]. This issue has to be addressed when running epoxidation reactions with aqueous solutions of H2O2 (with final production of H2O) and/or in the presence of large amounts of water in the solvent.…”

Section: Introductionmentioning

confidence: 99%

Mesoporous SiO2–TiO2 Epoxidation Catalysts: Tuning Surface Polarity to Improve Performance in the Presence of Water

Smeets¹,

Mustapha²,

Schnee³

et al. 2018

Preprint

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Herein, we present the preparation by the non-hydrolytic sol-gel route of a mesoporous SiO2-TiO2 epoxidation catalyst with high specific surface area and large pores. This catalyst is active in the catalytic epoxidation of cyclohexene with H2O2 in acetonitrile, showing performances comparable to a TS-1 catalyst. Yet, it is dramatically deactivated when water is used as a cosolvent, which represents an important limitation for the applicability of this catalyst. In order to circumvent the deactivation of the catalyst in the presence of water, we investigate the effect of surface hydrophobization with methyl groups on the catalytic activity and selectivity. Two functionalization methods are investigated: one-pot synthesis with methyltrichlorosilane and post-synthesis silanization with methyltrimethoxysilane. The catalytic performance of the materials are compared to the pristine catalyst and to TS-1 in the presence of an excess of water in the medium. On the one hand, we show that the one-pot methylation does not increase water resistance, in spite of an increased surface hydrophobicity. We interpret this result in the light of a poorer Ti dispersion and lower Ti 4+ surface content in these catalysts. On the other hand, post-synthesis grafting significantly improves the catalytic performances because it combines a hydrophobic surface with a high active site content. At the molecular level, we show that the direct epoxidation pathway is restored thanks to the surface functionalization.

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The activity of titanium silicalite-1 (TS-1): Some considerations on its origin

Cited by 57 publications

References 19 publications

Terminal Titanyl Complexes of Tri- and Tetrametaphosphate: Synthesis, Structures, and Reactivity with Hydrogen Peroxide

Terminal Titanyl Complexes of Tri- and Tetrametaphosphate: Synthesis, Structures, and Reactivity with Hydrogen Peroxide

Synthetic utility of metal catalyzed hydrogen peroxide oxidation of C-H, C-C and C=C bonds in alkanes, arenes and alkenes: Recent advances

Mesoporous SiO2–TiO2 Epoxidation Catalysts: Tuning Surface Polarity to Improve Performance in the Presence of Water

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