Catalyst structure and substituent effects on epoxidation of styrenics with immobilized Mn(tmtacn) complexes

Patricia Anne A. Ignacio-De Leon, Christian A. Contreras, Nicholas E. Thornburg, Anthony B. Thompson, Justin M. Notestein

Research output: Contribution to journalArticle

13 Citations (Scopus)

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 languageEnglish
Pages (from-to)78-86
Number of pages9
JournalApplied Catalysis A: General
Volume511
DOIs
Publication statusPublished - Feb 5 2016

Keywords

  • Epoxidation
  • Hammett relationships
  • Hydrogen peroxide
  • Manganese
  • Supported catalyst

ASJC Scopus subject areas

  • Catalysis
  • Process Chemistry and Technology

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