Translating High-Temperature Microwave Chemistry to Scalable Continuous Flow Processes

A comparison between batch microwave and convention ally heated continuous flow scale-up protocols for three selected model reactions is presented. Using high-temperature/-pressure conditions as process intensification principles, reaction times for all three transformations were reduced to a few seconds or minutes at temperatures ranging from 180-270 degrees C utilizing sealed vessel microwave conditions on small scale (2 mL). Successful scale-up of two out of three reactions in a multimode batch microwave reactor on a similar to 1 L, scale produced product quantities of similar to 0.5 kg within less than one hour of overall processing time. Moving to a continuous flow format in a high-temperature/high-pressure stainless steel microcapillary microreactor (4-16 mL reactor volume) all three transformations were scalable with significantly increased space-time yields compared to the microwave batch protocols. A critical evaluation of both scale-up principles is made.