Esterification of glycerol and solketal by oxidative NHC- catalysis under heterogeneous batch and flow conditions
| Autor: | Daniele Urbani, Carmela De Risi, Daniele Ragno, Pier Paolo Giovannini, Olga Bortolini, Graziano Di Carmine, Arianna Brandolese, Alessandro Massi |
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| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
mechanism
chemicals 010402 general chemistry Furfural 01 natural sciences Catalysis chemistry.chemical_compound Solketal Glycerol Chemical Engineering (miscellaneous) Organic chemistry N-heterocyclic carbenes liquid conversion Fluid Flow and Transfer Processes 010405 organic chemistry Chemistry Process Chemistry and Technology Vanillin Ambientale electron-transfer 0104 chemical sciences Solvent azide-alkyne cycloaddition immobilization oxygen Chemistry (miscellaneous) Citronellal Selectivity |
| Popis: | The design and synthesis of a set of supported azolium salt pre-catalysts is presented along with their utilization in the production of monoesters of glycerol and solketal by oxidative N-heterocyclic carbene (NHC)-catalysis through batch and continuous-flow approaches. After a propaedeutic study with soluble NHCs, the heterogeneous analogues (silica and polystyrene supports) were tested in a model monoesterification of glycerol using either the Kharasch oxidant or air (in the presence of electron transfer mediators) as the terminal oxidants. The best performing polystyrene-supported triazolium salt pre-catalyst afforded monoacylglycerols (MAGs) in high yields (up to 95%) and almost complete selectivity (monoester/diester >95 : 5) using air and the green solvent Me-THF. The synthesis of fully bio-based MAGs from furfural, 5-hydroxymethylfurfural (HMF), citronellal, and vanillin is also reported. Continuous-flow experiments have been finally performed by fabricating the corresponding packed-bed microreactor, which could be operated for ca. 120 hours with maintenance of conversion efficiency and selectivity. |
| Databáze: | OpenAIRE |
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