Efficiency in Carbon Dioxide Fixation into Cyclic Carbonates: Operating Bifunctional Polyhydroxylated Pyridinium Organocatalysts in Segmented Flow Conditions

Abstract

Novel polyhydroxylated ammonium, imidazolium, and pyridinium salt organocatalysts were prepared through N-alkylation sequences using glycidol as the key precursor. The most active pyridinium iodide catalyst effectively promoted the carbonation of a set of terminal epoxides (80 to >95% yields) at a low catalyst loading (5 mol%), ambient pressure of CO2, and moderate temperature (75 °C) in batch operations, also demonstrating high recyclability and simple downstream separation from the reaction mixture. Moving from batch to segmented flow conditions with the operation of thermostated (75 °C) and pressurized (8.5 atm) home-made reactors significantly reduced the process time (from hours to seconds), increasing the process productivity up to 20.1 mmol(product) h−1 mmol(cat)−1, a value ~17 times higher than that in batch mode.

Keywords

• flow chemistry
• organocatalysis
• carbon dioxide
• cyclic carbonates
• mass transfer