Effect of Solvent on Conversion and Selectivity during the Selective Oxidation of Cyclohexane by Nano-V2O5/Ti Membrane Electrode

Abstract

An electrocatalytic membrane reactor (ECMR) with nano-V2O5 loading porous Ti electrode (V2O5/Ti) as an anode was conducted to the selective partial oxidation of cyclohexane (CHA). The ternary phase diagram of CHA, H2O and solvents was determined. The effect of the solvent system on the conversion rate of CHA and selectivity toward cyclohexanone (K) and cyclohexanol (A) during the selective oxidation of CHA was explored. Cyclic voltammetry (CV) and electron spin resonance (ESR) were employed to monitor the electrochemical behavior of CHA-H2O-solvent (acetone and acetic acid) system. Response surface methodology (RSM) was used to optimize the operating parameters of ECMR. Results showed that the conversion of CHA improved with an increasing solvent polarity. The selectivity to K was related to solvent solubility parameter. 16.8% conversion of CHA, 90.2% selectivity to K and 99.9% selectivity to KA oil were obtained from the reaction system with acetone as solvent and acetic acid as co-solvent (CHA concentration 20 mmol L−1). In particular, acetic acid promoted the production of hydroxyl radicals which played a critical role in the selective oxidation of CHA by ECMR.