Effect of Thermal Treatment of MCM-41 on the Nature and Catalytic Properties of MCM41-supported Alkoxo-Titanium Species in Oxidation of Sulfides to Sulfoxides

Khedher, Ilyes; Ghorbel, Abdelhamid

doi:10.3184/030823410x12867300849443

Cited by 2 publications

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“…In principle this situation should be less problematic than in the case of Ti [36], as in all the surface species exist the possibility of chelation with at least one molecule of tartrate [28] (Scheme 2). Table 1), indicating that the grafting of the precursor is complete.…”

Section: Preparation and Characterization Of The Catalystsmentioning

confidence: 97%

Modified Ta/MCM-41 catalysts for enantioselective oxidation of thioanisole

Fadhli

Khedher

Fraile

2015

Journal of Molecular Catalysis A: Chemical

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Please cite this article as: Marwa Fadhli, Ilyes Khedher, José M.Fraile, Modified Ta/MCM-41 catalysts for enantioselective oxidation of thioanisole, Journal of Molecular Catalysis A: Chemical http://dx.Abstract 3 Highlights-Ta has been grafted on MCM41 and modified with chiral tartrates.-Ta catalyst are active in the oxidation of thioanisole.-They are more efficient with H 2 O 2 than with alkyl hydroperoxides.-Best results are obtained with diisopropyl tartrate (up to 25% ee).-Catalysts are recyclable with respect to activity but without enantioselectivity. 4 Abstract Ta-MCM41 catalysts have been prepared by grafting of Ta(OEt) 5 on MCM41, pre-calcined at three different temperatures (550, 650 and 750°C). These solids have been modified with two chiral ligands: R-(+)-diethyl L-tartrate (DET) and R-(+)-diisopropyl L-tartrate (DIPT). The formation of the chiral tantalum species and their influence on the structure of MCM41 have been studied by several characterization techniques, such as XRD, FTIR, N 2 adsorption isotherms and MAS-NMR. The grafted tantalum species are always much less active than the homogeneous analogues in the oxidation of thioanisole (methyl phenyl sulfide) with either aqueous H 2 O 2 or alkyl (tert-butyl, TBHP, or cumyl, CHP) hydroperoxides. The enantioselectivities obtained with the heterogeneous catalysts are also always lower than those obtained with the homogeneous ones under the same conditions, and the best results are obtained with the DIPT-modified solids, up to 25% ee. The calcination temperature of the support and the nature of the oxidant are also parameters that significantly affect the enantioselectivity. The recovered catalysts show an increase in the catalytic activity and a decrease in the enantioselectivity, in agreement with a loss of chiral tartrate, whereas the Si-O-Ta bond remains stable and recoverable.

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Section: Preparation and Characterization Of The Catalystsmentioning

confidence: 97%