Ultrasound-Assisted Synthesis of Glycerol Carbonate Using Potassium-Modified Silicalite-1 as a Catalyst.

This study investigates the use of potassium-modified silicalite-1 as a catalyst for the transesterification of glycerol to glycerol carbonate (Glyc. Carbonate) with dimethyl carbonate (DMC). Silicalite-1, typically inactive due to the absence of extra-framework cations, was modified with potassium compounds (fluoride, chloride, and hydroxide), which create basic sites by interacting with structural defects formed through silicon removal. This modification significantly enhances the catalyst's performance in glycerol transesterification. The reaction was conducted in both conventional batch reactor and ultrasound-assisted systems, including an ultrasonic bath and an ultrasonic probe, either within the bath or directly in the reactor. The direct ultrasound probe application yielded the most remarkable results, achieving a 96% Glyc. Carbonate yield at 70 °C in just 15 min-dramatically surpassing the batch reactor, which reached approximately 5%. These findings highlight the synergistic effect of potassium modification and ultrasound-assisted transesterification, offering a highly efficient and sustainable approach for glycerol valorization.