Kolbe‐Schmitt Flow Synthesis in Aqueous Solution – From Lab Capillary Reactor to Pilot Plant

Significant process intensification was achieved for the continuously operated Kolbe-Schmitt synthesis of 2,4-dihydroxybenzoic acid (-resorcylic acid) on laboratory scale by using different approaches opening novel process windows. The results of the optimal process variant, both from the economic and ecological view, were scaled up to the pilot scale. In a first step, the synthesis from resorcinol in aqueous potassium hydrogen carbonate solution was transferred from the capillary reactor to a tailor-made electrically heated microstructured reactor comprising 40 microchannels and enabling a 25-fold increase of the capacity. In a second step, a pilot plant comprising three of such reactors operated in parallel was built and successfully tested with the same reaction.