Integrated electrochemical porous solid electrolyte reactor and packed bed reactor for efficient synthesis of nylon-6 precursor.

The current production of cyclohexanone oxime (CyO), an essential precursor in the global nylon-6 industry, relies on processes that utilize toxic substrates and hazardous oxidizing agents. Here we present a continuous process and reactor design, with integrated electrochemical porous solid electrolyte reactor (PSER) and packed bed reactor (PBR), for an electrolyte-free, scalable, and efficient generation of high-purity CyO product from cyclohexanone (CyH), oxygen and ammonia. By electrochemically converting oxygen into high-purity hydrogen peroxide in a PSER, followed by a direct feeding into a downstream PBR for CyH ammoximation without any intermediate purification steps, we are able to obtain electrolyte-free CyO products. In an integrated 25-cm² PSER (six times larger than our previous design) and a titanium silicate-1 filled PBR system, we successfully demonstrate high CyO product selectivity of 97.2%, high yield of 93.6%, as well as high peroxide utilization efficiency of 96.3%. By operating the PSER under 125 mA/cm2, up to 28.3 mmol/h of CyO production rate can be achieved. Efficient conversions of a broad range of other aliphatic and aromatic ketone substrates are also demonstrated in this integrated PSER-PBR reactor system.