Scalable and sustainable synthesis of functionalized terpene acrylates in continuous flow: application of a multiphase, ultrasound-assisted mini-flow reactor

This study presents a sustainable method for producing bio-based acrylic monomers from limonene, a renewable terpene sourced from citrus peel waste. Limonene was prefunctionalized with epoxy groups first, using ultrasound-assisted epoxidation with Oxone®, an eco-friendly oxidant. A continuous mini-flow reactor was employed to epoxidize limonene to limonene oxide (LO) and limonene dioxide (LDO) with high efficiency and selectivity under mild conditions. Ultrasonic treatment improved reaction speed and reduced waste compared to traditional m-CPBA-based epoxidation methods. Full epoxidation was achieved within 20 min with 98% conversion, compared to 110 min in a batch setup. Subsequent esterification with acrylic acid produced acrylate-functionalized monomers, with 97% conversion of limonene acrylate (LA) and diacrylate (LDA) in just 2 h, significantly faster than the 20-h batch process. Finally, the exocyclic double bond of limonene acrylate was successfully epoxidized using Oxone, to yield bifunctional monomers, with quantitative conversion achieved in 11 min. This cost-effective, fast process is an important step in scaling limonene-based acrylates to employ them as sustainable alternatives to petroleum-based monomers in industrial environments.

Graphical abstract