Sustainable Catalytic Processes for the Synthesis and Use of Organic Carbonates

The present study is focused on the development and improvement of sustainable catalytic processes for the synthesis of organic carbonates. In particular, the condensation reaction between carbon dioxide and several alcohols and diols has been investigated using a new generation of mesoporous nanosilicas functionalized by the insertion of amino groups on the catalyst surface. This reaction were performed in a high-pressure batch vessel (autoclave). Moreover, the carbonate interchange reaction (CIR) of the simplest linear organic carbonate, dimethyl carbonate (DMC) with several alcohols has been implemented by means of a new lab-scale reactive distillation system. In this new system, the distilled mixture is continuously passed over molecular sieves able to promote a selective adsorption of methanol (co-product of the reactions) while DMC is continuously refluxed back into the reaction batch. In this way, we were able to promote an efficient shift of the reaction equilibria toward the formation of the desired products. This system allowed us to achieve up to 90% isolated yield of pyrocatechol carbonate (PCC), a new and previously scarcely investigated carbonate. The PCC has been used as a new and more efficient carbonate source for the selective synthesis of symmetric carbonates and for the synthesis of glycerol carbonate (GlyC). GlyC has been also used as glycidol intermediate, for the condensation reaction with catechol in order to obtain the efficient synthesis of 2-hydroxymethy-1,4-benzodioxane (HMB) an important intermediate for the pharma industry. Finally, some of the synthesized carbonates were tested for the gas-phase phenol alkylation showing an interesting reactivity that could be properly modulated by changing the reaction conditions and the catalyst acid-base properties.