Photochlorination of toluene – the thin line between intensification and selectivity. Part 1: intensification and effect of operation conditions†
This work reports on the potentials of intensifying the industrially applied side-chain photochlorinations of toluene. The application of microstructured reactors enabled an acceleration of the overall reaction up to 10 times compared to batch reactors and up to 100 times compared to the literature. Unexpectedly, this acceleration is accompanied by a decreased selectivity with respect to the desired side-chain chlorinated products. In contradiction to the in general well established theory of photochlorinations, significant amounts of ring chlorinated species were detected. By applying dynamic irradiation conditions, not only the formation of ring-chlorinated products was suppressed but also the energy consumption could be reduced significantly.