engleski

A comparative study of ultrasound, microwave and microreactor-assisted imidazolium-based ionic liquid synthesis

Synthesis of ionic liquid 1-heptyl-2, 3-dimethylimidazolium bromide was accomplished by the assistance of ultrasound, microwave irradiation and a continuously operated microreactor and compared to a conventional lab scale process applying magnetic stirring and water bath heating. Results were compared with respect to process productivity, energy consumption and product colourization as indicator of its purity. By using non-conventional technologies, volumetric productivity was 10-30 fold superior, while energy consumption was reduced by 45-65%. Among alternatives tested, ultrasound-assisted synthesis was shown as the most efficient one in terms of volumetric productivity (4.40 mol L-1 h-1) and specific power consumption (909.1 W h mol-1), while microwave-assisted process was the least favourable. However, only a microreactor system enabled synthesis of a non-coloured product resulting form very efficient mixing and temperature control. Due to significant process intensification along with high product quality and superior industrial perspectives, a continuous quaternization within microchannels could be selected as the most promising green approach among the alternatives tested in this study. Integration of ultrasound and microreactor technology including miniaturized heat exchanger is foreseen for process intensification.

ionic liquids; solvent-free synthesis; microwave irradiation; ultrasound; microreactor

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