Bifunctional Silica-based Catalysts for the Conversion of Carbon Dioxide into Cyclic carbonates

  • Jennifer THEISSEN

Student thesis: Master typesMaster in Chemistry Professional focus

Abstract

The use of renewable resources is an important principle of Green Chemistry. Therefore, the CO2 conversion into valuable products such as cyclic carbonates is of growing interest. To achieve this transformation, a suitable catalyst is needed. Among others, organic salts, such as imidazolium halides used in homogeneous conditions, are particularly efficient. However, in the context of Green Chemistry, heterogeneous catalysts are often preferred. Through a heterogenization process, the catalytic active species (e.g. imidazolium halides) can be covalently grafted on a solid support to improve their applicability and reusability in the conversion of CO2 into cyclic carbonates. Among all the possible supports, mesoporous silica-based materials display appealing properties, such as chemical and thermal stabilities, tunable porosity and high surface area. While the exclusive use of an imidazolium-based catalyst allows the production of cyclic carbonates at high temperature, the use of a co-catalyst with Lewis acid properties can considerably improve the overall catalyst efficiency, even under soft conditions. In this context, trivalent organoboron compounds are considered as interesting candidates to act as co-catalyst. Hereby, bifunctional catalysts were synthesized by grafting both imidazolium halides (as a nucleophilic catalyst), and pinacolborane (as Lewis acid co-catalyst), on mesoporous silica. Three imidazolium halides (chloride, bromide and iodide) were employed to study the activity strength. Both, imidazolium and boron-based moieties, were grafted via previously described procedure. Two boron derivatives were selected in order to study the influence of different linkers (i.e. aromatic ring and aliphatic chain) spacing the boron from the silanol surface. The different synthesized materials were fully characterized and tested for the valorization process of carbon dioxide selecting epichlorohydrin as target epoxide.
Date of Award21 Jan 2022
Original languageEnglish
Awarding Institution
  • University of Namur
SupervisorCarmela Aprile (Supervisor) & Guillaume Berionni (Co-Supervisor)

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