Scaled Oxidative Flow Electrosynthesis of 3-Alkyladipic Acids from 4-Alkylcyclohexanols
Roland J.‐R. Bednarz, Annika S. Gold, Jasmin Hammes, D. Rohrmann, Silvio Natalello, M. E. Mann, Frank Weinelt, Christopher Brauer, Siegfried R. Waldvogel
Abstract
The rapidly advancing climate change necessitates the development of more sustainable synthetic pathways for critical chemicals, such as adipic acid or its derivatives. Here we present an environmentally benign electrochemical formation of 3-ethyladipic acid using 4-ethylcyclohexanol as the precursor, which can be derived from lignin. The preparation was performed in a scaled and commercially available flow electrolyzer with a geometrical anodic surface area of 108 cm 2, allowing for a production rate of 264 mg h –1 for the target compound in a semiflow process. This was an increase in the surface area by a factor of 9 compared to a previously reported electrochemical approach. In this way, 3-ethyladipic acid was obtained in isolated yields of up to 38%, which corresponds to an increase of 15%. The established activation protocol for nickel foams allowed the operation of the foam for more than 1000 h. By monitoring of the reaction progress, substrate feeding was determined to be one crucial parameter to enhance the production rate significantly.