Ti-POSS covalently immobilized onto mesoporous silica: A model for active sites in heterogeneous catalytic epoxidation

Fabio Carniato; Chiara Bisio; Laura Sordelli; Elena Gavrilova; Matteo Guidotti

doi:10.1016/j.ica.2011.11.051

Ti-POSS covalently immobilized onto mesoporous silica: A model for active sites in heterogeneous catalytic epoxidation

Fabio Carniato, Chiara Bisio, Laura Sordelli, Elena Gavrilova, Matteo Guidotti

Dipartimento di Scienze e Innovazione Tecnologica

Risultato della ricerca: Contributo su rivista › Articolo in rivista › peer review

Abstract

A functionalized Ti-containing polyhedral oligomeric silsesquioxane was anchored on the surface of an ordered SBA-15 and a non-ordered amorphous mesoporous silica. The physico-chemical characterization of the textural, thermal and electronic properties of the final anchored materials led to the evaluation of the distribution of Ti-POSS moieties on the silica surface, of the oxidation state and of the coordination geometry of the titanium centres. It was discovered that Ti-POSS are accommodated mainly as dinuclear dimeric species on the external surface of ordered mesoporous silica or in the large mesopores of non-ordered silica supports. Epoxidation tests on unsaturated terpenes (limonene, carveol and α-pinene) with TBHP as oxidant were performed to monitor the activity and accessibility of Ti(IV) sites in the anchored samples and compared with conventional titanocene-grafted Ti/SBA-15 and Ti/SiO ₂ systems. The different chemoselectivity recorded over anchored catalysts, with respect to the grafted ones, can be a potential diagnostic tool to shed light on the mechanism or the molecular intermediates occurring at the surface during the oxidation reaction.

Lingua originale	Inglese
pagine (da-a)	244-251
Numero di pagine	8
Rivista	Inorganica Chimica Acta
Volume	380
Numero di pubblicazione	1
DOI	https://doi.org/10.1016/j.ica.2011.11.051
Stato di pubblicazione	Pubblicato - 15 gen 2012

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10.1016/j.ica.2011.11.051

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title = "Ti-POSS covalently immobilized onto mesoporous silica: A model for active sites in heterogeneous catalytic epoxidation",

abstract = "A functionalized Ti-containing polyhedral oligomeric silsesquioxane was anchored on the surface of an ordered SBA-15 and a non-ordered amorphous mesoporous silica. The physico-chemical characterization of the textural, thermal and electronic properties of the final anchored materials led to the evaluation of the distribution of Ti-POSS moieties on the silica surface, of the oxidation state and of the coordination geometry of the titanium centres. It was discovered that Ti-POSS are accommodated mainly as dinuclear dimeric species on the external surface of ordered mesoporous silica or in the large mesopores of non-ordered silica supports. Epoxidation tests on unsaturated terpenes (limonene, carveol and α-pinene) with TBHP as oxidant were performed to monitor the activity and accessibility of Ti(IV) sites in the anchored samples and compared with conventional titanocene-grafted Ti/SBA-15 and Ti/SiO 2 systems. The different chemoselectivity recorded over anchored catalysts, with respect to the grafted ones, can be a potential diagnostic tool to shed light on the mechanism or the molecular intermediates occurring at the surface during the oxidation reaction.",

keywords = "Epoxidation site, Heterogeneous catalysis, Mesoporous silica, Silsesquioxane, Ti-POSS, Titanium",

author = "Fabio Carniato and Chiara Bisio and Laura Sordelli and Elena Gavrilova and Matteo Guidotti",

note = "Funding Information: This work was supported by the Italian Ministry of Education and Scientific Research through the network “ItalNanoNet” (Protocol No. RBPR05JH2P). The ELETTRA synchrotron light laboratory in Basovizza (Trieste, Italy) is gratefully acknowledged for providing the beamtime (EU supported Project No. 20085187), and the staff of the XAFS beamline for their technical assistance. E.G. thanks the EC 7th Framework Programme, Marie Curie Initial Training Network NANO-HOST (Grant Agreement No. 215193) for a Ph.D. studentship grant.",

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doi = "10.1016/j.ica.2011.11.051",

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AU - Carniato, Fabio

AU - Bisio, Chiara

AU - Sordelli, Laura

AU - Gavrilova, Elena

AU - Guidotti, Matteo

N1 - Funding Information: This work was supported by the Italian Ministry of Education and Scientific Research through the network “ItalNanoNet” (Protocol No. RBPR05JH2P). The ELETTRA synchrotron light laboratory in Basovizza (Trieste, Italy) is gratefully acknowledged for providing the beamtime (EU supported Project No. 20085187), and the staff of the XAFS beamline for their technical assistance. E.G. thanks the EC 7th Framework Programme, Marie Curie Initial Training Network NANO-HOST (Grant Agreement No. 215193) for a Ph.D. studentship grant.

PY - 2012/1/15

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N2 - A functionalized Ti-containing polyhedral oligomeric silsesquioxane was anchored on the surface of an ordered SBA-15 and a non-ordered amorphous mesoporous silica. The physico-chemical characterization of the textural, thermal and electronic properties of the final anchored materials led to the evaluation of the distribution of Ti-POSS moieties on the silica surface, of the oxidation state and of the coordination geometry of the titanium centres. It was discovered that Ti-POSS are accommodated mainly as dinuclear dimeric species on the external surface of ordered mesoporous silica or in the large mesopores of non-ordered silica supports. Epoxidation tests on unsaturated terpenes (limonene, carveol and α-pinene) with TBHP as oxidant were performed to monitor the activity and accessibility of Ti(IV) sites in the anchored samples and compared with conventional titanocene-grafted Ti/SBA-15 and Ti/SiO 2 systems. The different chemoselectivity recorded over anchored catalysts, with respect to the grafted ones, can be a potential diagnostic tool to shed light on the mechanism or the molecular intermediates occurring at the surface during the oxidation reaction.

AB - A functionalized Ti-containing polyhedral oligomeric silsesquioxane was anchored on the surface of an ordered SBA-15 and a non-ordered amorphous mesoporous silica. The physico-chemical characterization of the textural, thermal and electronic properties of the final anchored materials led to the evaluation of the distribution of Ti-POSS moieties on the silica surface, of the oxidation state and of the coordination geometry of the titanium centres. It was discovered that Ti-POSS are accommodated mainly as dinuclear dimeric species on the external surface of ordered mesoporous silica or in the large mesopores of non-ordered silica supports. Epoxidation tests on unsaturated terpenes (limonene, carveol and α-pinene) with TBHP as oxidant were performed to monitor the activity and accessibility of Ti(IV) sites in the anchored samples and compared with conventional titanocene-grafted Ti/SBA-15 and Ti/SiO 2 systems. The different chemoselectivity recorded over anchored catalysts, with respect to the grafted ones, can be a potential diagnostic tool to shed light on the mechanism or the molecular intermediates occurring at the surface during the oxidation reaction.

KW - Epoxidation site

KW - Heterogeneous catalysis

KW - Mesoporous silica

KW - Silsesquioxane

KW - Ti-POSS

KW - Titanium

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VL - 380

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JO - Inorganica Chimica Acta

JF - Inorganica Chimica Acta

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Ti-POSS covalently immobilized onto mesoporous silica: A model for active sites in heterogeneous catalytic epoxidation

Abstract

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