Microdroplet chemical reactor prototype based on multiplexed electrospray†

Abstract

The advent of ambient mass spectrometry has yielded novel approaches to chemical transformations for analytical and preparative applications. These methods utilize the microdroplets generated via spray ionization techniques. Numerous studies have demonstrated the superior efficiency of microdroplet-based chemical reactions. This efficiency is manifested in a substantial acceleration of reactions (up to a million-fold compared to bulk reactions) and a shift in reaction pathways, enabling the synthesis of compounds that are challenging to obtain using conventional methods. However, the widespread implementation of this approach has been hindered by its limited productivity. To address this challenge, this paper introduces a microdroplet chemical reactor prototype (MCR prototype) that employs multiplexed pneumatic/electrospray to enhance productivity. The performance of the MCR prototype was evaluated using the cyclohexanone phenylhydrazone synthesis reaction from phenylhydrazine and cyclohexanone in methanol as a model system. The prototype demonstrated a significant acceleration of the reaction relative to its occurrence in bulk, with the apparent acceleration factor (AAF) exceeding a value of 83 × 10⁶. The MCR prototype can spray the reaction mixture at a rate of up to 17 mL min⁻¹ while maintaining the acceleration effect, achieving a productivity of grams per hour. This prototype offers a promising solution for addressing practical and research challenges in microdroplet chemical synthesis.