Electrooxidation of cyclohexanol to cyclohexanone using nickel electrodes in an undivided batch cell

Cyclohexanone is an essential intermediate for nylon-6 and nylon-6,6 production, with global demand exceeding five million metric tons annually. Conventional industrial routes (primarily air oxidation of cyclohexane or cyclohexanol) suffer from multiple limitations: low single-pass conversions (3–5%), modest selectivity (70–85%), high operating temperatures (140–180°C), and dependence on stoichiometric chemical oxidants. Electrochemical oxidation represents a promising sustainable alternative, employing electrons as traceless redox reagents under mild conditions without chemical oxidants. This thesis investigates the electrochemical oxidation of cyclohexanol to cyclohexanone using parallel nickel mesh electrodes in an undivided two-electrode batch cell with aqueous alkaline electrolyte. A systematic parametric study examined five key operational variables: the applied current for electrode activation, potassium hydroxide concentration, applied current for electrooxidation of cyclohexanol, substrate concentration, and reaction time. Performance was evaluated using cyclic voltammetry and chronopotentiometry for electrochemical characterization, coupled with gas chromatography for quantitative product analysis. Results demonstrate that electrochemical activation of nickel electrodes is essential for generating catalytically active nickel oxyhydroxide (NiOOH) surface layers, with activated electrodes exhibiting approximately five-fold higher anodic peak currents compared to unactivated surfaces. Among activation currents investigated (18, 27, 36 mA), the intermediate value of 27 mA (12 mA/cm²) applied for 3 minutes yielded optimal performance. Product selectivity depended critically on electrolyte alkalinity and applied current density. Optimal conditions (1 M KOH electrolyte, 22 mM cyclohexanol, 6 mA applied current (2.7 mA/cm²), and 1 hour reaction time following 27 mA activation) achieved 100% selectivity toward cyclohexanone with 25.6% conversion. Within a similar reaction‑time window, this electrochemical system achieves both higher conversion and higher selectivity than conventional KA‑oil oxidation, under much milder operating conditions. Temporal profiling revealed an inherent trade-off: extended electrolysis increased conversion to 90% at 4 hours but reduced selectivity to 62%, confirming consecutive overoxidation of the cyclohexanone product. The systematic parametric framework establishes quantitative relationships between operating conditions and electrochemical performance, providing a foundation for future mechanistic investigations and reactor engineering efforts. The demonstration of complete selectivity under ambient aqueous conditions represents a meaningful advance toward sustainable electrochemical synthesis of commodity chemicals.