Tripodal titanium silsesquioxane complexes immobilized in polydimethylsiloxane (PDMS) membrane: Selective catalysts for epoxidation of cyclohexene and 1-octene with aqueous hydrogen peroxide

Emad H. Aish; Mark Crocker; Folami T. Ladipo

doi:10.1016/j.jcat.2010.05.003

Tripodal titanium silsesquioxane complexes immobilized in polydimethylsiloxane (PDMS) membrane: Selective catalysts for epoxidation of cyclohexene and 1-octene with aqueous hydrogen peroxide

Emad H. Aish, Mark Crocker, Folami T. Ladipo

Chemistry

Research output: Contribution to journal › Article › peer-review

26 Scopus citations

Abstract

We investigated the activity, epoxide selectivity, H₂O ₂ efficiency, and recyclability of heterogeneous alkene epoxidation catalysts prepared by encapsulation of tripodal Ti silsesquioxane complexes in polydimethylsiloxane (PDMS) membrane. We found that [Ti(NMe₂){(c- C₆H₁₁)₇Si₇O₁₂}]/PDMS (3) and [Ti(NMe₂){(i-C₄H₉)₇Si ₇O₁₂}]/PDMS (4) displayed high activity, epoxide selectivity (≥97%), and H₂O₂ efficiency (≥97%) in cyclohexene-and 1-octene epoxidation with aqueous H₂O₂. Moreover, these catalysts were highly recyclable. The high H₂O ₂ efficiency can be attributed to the uniformly non-polar environment provided about the Ti silsesquioxane complex in 3 and 4 by the PDMS membrane, which presumably results in low local water concentrations and higher [alkene]:[H₂O₂] ratios at the Ti center than in the bulk reaction medium; both of these effects favor the epoxide selectivity and minimal leaching of titanium. Our study of the effect of solvent on catalyst activity revealed that acetonitrile is to be preferred as solvent, since methanol inhibits the epoxidation at long reaction times.

Original language	English
Pages (from-to)	66-72
Number of pages	7
Journal	Journal of Catalysis
Volume	273
Issue number	1
DOIs	https://doi.org/10.1016/j.jcat.2010.05.003
State	Published - Jul 7 2010

Bibliographical note

Funding Information:
Thanks are expressed to the Chemistry Department and the University of Kentucky (Office of the Vice President for Research) for support of this work. Thanks are also expressed to the Egyptian Government (Ministry of Education) for the award of a fellowship to E.A. NMR instruments utilized in this research were funded in part by the CRIF program of the US National Science Foundation (Grant No. CHE-9974810 ). Finally, we thank Mr. John Layton for his assistance with NMR spectroscopy experiments.

Keywords

1-Octene
Cyclohexene
Encapsulated catalyst
Epoxidation
Ti-silsesquioxane

ASJC Scopus subject areas

Catalysis
Physical and Theoretical Chemistry

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10.1016/j.jcat.2010.05.003

Cite this

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title = "Tripodal titanium silsesquioxane complexes immobilized in polydimethylsiloxane (PDMS) membrane: Selective catalysts for epoxidation of cyclohexene and 1-octene with aqueous hydrogen peroxide",

abstract = "We investigated the activity, epoxide selectivity, H2O 2 efficiency, and recyclability of heterogeneous alkene epoxidation catalysts prepared by encapsulation of tripodal Ti silsesquioxane complexes in polydimethylsiloxane (PDMS) membrane. We found that [Ti(NMe2){(c- C6H11)7Si7O12}]/PDMS (3) and [Ti(NMe2){(i-C4H9)7Si 7O12}]/PDMS (4) displayed high activity, epoxide selectivity (≥97%), and H2O2 efficiency (≥97%) in cyclohexene-and 1-octene epoxidation with aqueous H2O2. Moreover, these catalysts were highly recyclable. The high H2O 2 efficiency can be attributed to the uniformly non-polar environment provided about the Ti silsesquioxane complex in 3 and 4 by the PDMS membrane, which presumably results in low local water concentrations and higher [alkene]:[H2O2] ratios at the Ti center than in the bulk reaction medium; both of these effects favor the epoxide selectivity and minimal leaching of titanium. Our study of the effect of solvent on catalyst activity revealed that acetonitrile is to be preferred as solvent, since methanol inhibits the epoxidation at long reaction times.",

keywords = "1-Octene, Cyclohexene, Encapsulated catalyst, Epoxidation, Ti-silsesquioxane",

author = "Aish, {Emad H.} and Mark Crocker and Ladipo, {Folami T.}",

note = "Funding Information: Thanks are expressed to the Chemistry Department and the University of Kentucky (Office of the Vice President for Research) for support of this work. Thanks are also expressed to the Egyptian Government (Ministry of Education) for the award of a fellowship to E.A. NMR instruments utilized in this research were funded in part by the CRIF program of the US National Science Foundation (Grant No. CHE-9974810 ). Finally, we thank Mr. John Layton for his assistance with NMR spectroscopy experiments. ",

year = "2010",

month = jul,

day = "7",

doi = "10.1016/j.jcat.2010.05.003",

language = "English",

volume = "273",

pages = "66--72",

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Tripodal titanium silsesquioxane complexes immobilized in polydimethylsiloxane (PDMS) membrane: Selective catalysts for epoxidation of cyclohexene and 1-octene with aqueous hydrogen peroxide. / Aish, Emad H.; Crocker, Mark; Ladipo, Folami T.
In: Journal of Catalysis, Vol. 273, No. 1, 07.07.2010, p. 66-72.

Research output: Contribution to journal › Article › peer-review

TY - JOUR

T1 - Tripodal titanium silsesquioxane complexes immobilized in polydimethylsiloxane (PDMS) membrane

T2 - Selective catalysts for epoxidation of cyclohexene and 1-octene with aqueous hydrogen peroxide

AU - Aish, Emad H.

AU - Crocker, Mark

AU - Ladipo, Folami T.

N1 - Funding Information: Thanks are expressed to the Chemistry Department and the University of Kentucky (Office of the Vice President for Research) for support of this work. Thanks are also expressed to the Egyptian Government (Ministry of Education) for the award of a fellowship to E.A. NMR instruments utilized in this research were funded in part by the CRIF program of the US National Science Foundation (Grant No. CHE-9974810 ). Finally, we thank Mr. John Layton for his assistance with NMR spectroscopy experiments.

PY - 2010/7/7

Y1 - 2010/7/7

N2 - We investigated the activity, epoxide selectivity, H2O 2 efficiency, and recyclability of heterogeneous alkene epoxidation catalysts prepared by encapsulation of tripodal Ti silsesquioxane complexes in polydimethylsiloxane (PDMS) membrane. We found that [Ti(NMe2){(c- C6H11)7Si7O12}]/PDMS (3) and [Ti(NMe2){(i-C4H9)7Si 7O12}]/PDMS (4) displayed high activity, epoxide selectivity (≥97%), and H2O2 efficiency (≥97%) in cyclohexene-and 1-octene epoxidation with aqueous H2O2. Moreover, these catalysts were highly recyclable. The high H2O 2 efficiency can be attributed to the uniformly non-polar environment provided about the Ti silsesquioxane complex in 3 and 4 by the PDMS membrane, which presumably results in low local water concentrations and higher [alkene]:[H2O2] ratios at the Ti center than in the bulk reaction medium; both of these effects favor the epoxide selectivity and minimal leaching of titanium. Our study of the effect of solvent on catalyst activity revealed that acetonitrile is to be preferred as solvent, since methanol inhibits the epoxidation at long reaction times.

AB - We investigated the activity, epoxide selectivity, H2O 2 efficiency, and recyclability of heterogeneous alkene epoxidation catalysts prepared by encapsulation of tripodal Ti silsesquioxane complexes in polydimethylsiloxane (PDMS) membrane. We found that [Ti(NMe2){(c- C6H11)7Si7O12}]/PDMS (3) and [Ti(NMe2){(i-C4H9)7Si 7O12}]/PDMS (4) displayed high activity, epoxide selectivity (≥97%), and H2O2 efficiency (≥97%) in cyclohexene-and 1-octene epoxidation with aqueous H2O2. Moreover, these catalysts were highly recyclable. The high H2O 2 efficiency can be attributed to the uniformly non-polar environment provided about the Ti silsesquioxane complex in 3 and 4 by the PDMS membrane, which presumably results in low local water concentrations and higher [alkene]:[H2O2] ratios at the Ti center than in the bulk reaction medium; both of these effects favor the epoxide selectivity and minimal leaching of titanium. Our study of the effect of solvent on catalyst activity revealed that acetonitrile is to be preferred as solvent, since methanol inhibits the epoxidation at long reaction times.

KW - 1-Octene

KW - Cyclohexene

KW - Encapsulated catalyst

KW - Epoxidation

KW - Ti-silsesquioxane

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DO - 10.1016/j.jcat.2010.05.003

M3 - Article

AN - SCOPUS:77954216938

SN - 0021-9517

VL - 273

SP - 66

EP - 72

JO - Journal of Catalysis

JF - Journal of Catalysis

IS - 1

ER -

Tripodal titanium silsesquioxane complexes immobilized in polydimethylsiloxane (PDMS) membrane: Selective catalysts for epoxidation of cyclohexene and 1-octene with aqueous hydrogen peroxide

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

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