Continuous Formation of Limonene Carbonates in Supercritical Carbon Dioxide

We present a continuous flow method for the conversion of bioderived limonene oxide and limonene dioxide to limonene carbonates using carbon dioxide in its supercritical state as a reagent and sole solvent. Various ammonium- and imidazolium-based ionic liquids were initially investigated in batch mo...

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Bibliographic Details
Published in:	Organic process research & development Vol. 26; no. 10; pp. 2799 - 2810
Main Authors:	Mikšovsky, Philipp, Horn, Elias N., Naghdi, Shaghayegh, Eder, Dominik, Schnürch, Michael, Bica-Schröder, Katharina
Format:	Journal Article
Language:	English
Published:	American Chemical Society 21-10-2022
Subjects:	supercritical carbon dioxide bioderived cyclic carbonates ethyl methyl imidazolium halide supported ionic liquid phase continuous flow chemistry tetrabutylammonium halide
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Summary:	We present a continuous flow method for the conversion of bioderived limonene oxide and limonene dioxide to limonene carbonates using carbon dioxide in its supercritical state as a reagent and sole solvent. Various ammonium- and imidazolium-based ionic liquids were initially investigated in batch mode. For applying the best-performing and selective catalyst tetrabutylammonium chloride in continuous flow, the ionic liquid was physisorbed on mesoporous silica. In addition to the analysis of surface area and pore size distribution of the best-performing supported ionic liquid phase (SILP) catalysts via nitrogen physisorption, SILPs were characterized by diffuse reflectance infrared Fourier transform spectroscopy and thermogravimetric analysis and served as heterogeneous catalysts in continuous flow. Initially, the continuous flow conversion was optimized in short-term experiments resulting in the desired constant product outputs. Under these conditions, the long-term behavior of the SILP system was studied for a period of 48 h; no leaching of catalyst from the supporting material was observed in the case of limonene oxide and resulted in a yield of 16%. For limonene dioxide, just traces of leached catalysts were detected after reducing the catalyst loading from 30 to 15 wt %, thus enabling a constant product output in 17% yield over time.
Bibliography:	ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-3 content type line 23 ObjectType-Review-1
ISSN:	1083-6160 1520-586X
DOI:	10.1021/acs.oprd.2c00143