Analysis and minimization of cell voltage in electro-organic syntheses using the solid polymer electrolyte technology

Using an ion exchange membrane as a solid polymer electrolyte (SPE technology) electro-organic syntheses are possible in non-conductive fluids. In order to expand the application limits in non-aqueous media the methoxylation of p-methoxytoluene was investigated as an example of commercial interest. By means of specially adapted equipment, the electrode potentials and the membrane voltage drop have been determined. Via analysis of current interruption measurements, additional information about the electrode behaviour was available. On this basis, a combination of methods has been developed which enables a stationary operation with a minimized cell voltage. The remarkable result of the experiments is that the membrane achieves sufficient conductivity and that too high cell voltages, observed at the beginning of the investigations, are caused mainly by polymer layers on the anode. Ways to lessen their influence have been realized. The results demonstrate that the SPE technology could be extended to new applications in non-aqueous media. (C) 2001 Elsevier Science B.V. All rights reserved.