Increasing Productivity of Microreactors for Fast Gas-Liquid Reactions: The Case of Direct Fluorination of Toluene

The throughput of a single-channel microreactor used for a fast gas-liquid reaction was increased by up to one order of magnitude relative to previously published results by simultaneously increasing the superficial gas and liquid velocities. Superficial gas and liquid velocities varied between 2.9-14.6 m/s and 0.012-0.061 m/s, respectively. The direct fluorination of toluene in acetonitrile, selected as a model reaction, was performed at room temperature in rnicrochannels formed in a silicon substrate, coated with thermally grown silicon oxide and evaporated nickel, and capped by Pyrex. With faster velocities the toluene conversion increased from 63% to 76%, while the combined selectivity of ortho-, meta-, and para-fluorotoluene isomers remained constant at 26%. Operating at faster gas and liquid velocities appeared to enhance the contacting between the two phases, thus outweighing the reduced liquid residence time.