Abstract
Monomeric and dimeric complexes of Mn 1,4,7-trimethyl-1,4,7-triazacyclononane (tmtacn) were immobilized under reaction conditions onto solid supports to create heterogeneous catalysts for epoxidation with H2O2. These solid supports consist of activated carbon or silica grafted or co-condensed with benzoic or C3/C4 acids that function both as tethering points and as required co-catalysts. Immobilized catalysts were as much as 50-fold faster than the analogous soluble system, and an immobilized, dimeric Mn(tmtacn) complex with a solid benzoic acid co-catalyst gave the highest yields to epoxide. A Hammett study on the catalytic epoxidation of a series of styrenes showed weak increases in yield for more electron-withdrawing p-substituents reactants for both immobilized complexes, which runs counter to previous observations with analogous homogeneous catalysts, and which appears to reflect a previously unappreciated tradeoff between the intrinsic epoxidation reactivity and strong catalyst inhibition by styrene oxides and glycols. Finally, these catalysts were tested with a variety of solid-co-catalysts, and were successfully utilized in the challenging epoxidation of divinylbenzene to industrially-useful divinylbenzene dioxide using a cascade of two catalyst charges.
| Original language | English |
|---|---|
| Pages (from-to) | 78-86 |
| Number of pages | 9 |
| Journal | Applied Catalysis A: General |
| Volume | 511 |
| DOIs | |
| Publication status | Published - Feb 5 2016 |
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Keywords
- Epoxidation
- Hammett relationships
- Hydrogen peroxide
- Manganese
- Supported catalyst
ASJC Scopus subject areas
- Catalysis
- Process Chemistry and Technology
Cite this
Catalyst structure and substituent effects on epoxidation of styrenics with immobilized Mn(tmtacn) complexes. / Ignacio-De Leon, Patricia Anne A; Contreras, Christian A.; Thornburg, Nicholas E.; Thompson, Anthony B.; Notestein, Justin M.
In: Applied Catalysis A: General, Vol. 511, 05.02.2016, p. 78-86.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Catalyst structure and substituent effects on epoxidation of styrenics with immobilized Mn(tmtacn) complexes
AU - Ignacio-De Leon, Patricia Anne A
AU - Contreras, Christian A.
AU - Thornburg, Nicholas E.
AU - Thompson, Anthony B.
AU - Notestein, Justin M
PY - 2016/2/5
Y1 - 2016/2/5
N2 - Monomeric and dimeric complexes of Mn 1,4,7-trimethyl-1,4,7-triazacyclononane (tmtacn) were immobilized under reaction conditions onto solid supports to create heterogeneous catalysts for epoxidation with H2O2. These solid supports consist of activated carbon or silica grafted or co-condensed with benzoic or C3/C4 acids that function both as tethering points and as required co-catalysts. Immobilized catalysts were as much as 50-fold faster than the analogous soluble system, and an immobilized, dimeric Mn(tmtacn) complex with a solid benzoic acid co-catalyst gave the highest yields to epoxide. A Hammett study on the catalytic epoxidation of a series of styrenes showed weak increases in yield for more electron-withdrawing p-substituents reactants for both immobilized complexes, which runs counter to previous observations with analogous homogeneous catalysts, and which appears to reflect a previously unappreciated tradeoff between the intrinsic epoxidation reactivity and strong catalyst inhibition by styrene oxides and glycols. Finally, these catalysts were tested with a variety of solid-co-catalysts, and were successfully utilized in the challenging epoxidation of divinylbenzene to industrially-useful divinylbenzene dioxide using a cascade of two catalyst charges.
AB - Monomeric and dimeric complexes of Mn 1,4,7-trimethyl-1,4,7-triazacyclononane (tmtacn) were immobilized under reaction conditions onto solid supports to create heterogeneous catalysts for epoxidation with H2O2. These solid supports consist of activated carbon or silica grafted or co-condensed with benzoic or C3/C4 acids that function both as tethering points and as required co-catalysts. Immobilized catalysts were as much as 50-fold faster than the analogous soluble system, and an immobilized, dimeric Mn(tmtacn) complex with a solid benzoic acid co-catalyst gave the highest yields to epoxide. A Hammett study on the catalytic epoxidation of a series of styrenes showed weak increases in yield for more electron-withdrawing p-substituents reactants for both immobilized complexes, which runs counter to previous observations with analogous homogeneous catalysts, and which appears to reflect a previously unappreciated tradeoff between the intrinsic epoxidation reactivity and strong catalyst inhibition by styrene oxides and glycols. Finally, these catalysts were tested with a variety of solid-co-catalysts, and were successfully utilized in the challenging epoxidation of divinylbenzene to industrially-useful divinylbenzene dioxide using a cascade of two catalyst charges.
KW - Epoxidation
KW - Hammett relationships
KW - Hydrogen peroxide
KW - Manganese
KW - Supported catalyst
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UR - http://www.scopus.com/inward/citedby.url?scp=84949032943&partnerID=8YFLogxK
U2 - 10.1016/j.apcata.2015.12.002
DO - 10.1016/j.apcata.2015.12.002
M3 - Article
VL - 511
SP - 78
EP - 86
JO - Applied Catalysis A: General
JF - Applied Catalysis A: General
SN - 0926-860X
ER -