Equivalent resistances for current pathways in a bipolar packed-bed electrode cell.

Abstract

The electric currents flowing through the pathways existing in a bipolar packed-bed cell (BPBE cell) were calculated by use of an equivalent resistance model which was a modification of the King-Wright model for the bipolar rod cell. The bypass, Faradaic, and total currents were shown as functions of the resistance coefficient, the specific conductivity of electrolytic solution, the number of bipolar layers, and the decomposition voltage. In the BPBE cell, graphite pellets of 4.74mm diameter and 5mm length were packed in layers which were separated by plastic nets. Methoxylation of furan was studied, where bromine was used as mediator. The resistance coefficient for the bypass current was evaluated from experimental results and the Bruggeman equation. The resistance of the total current flowing in the open space of the insulation net was affected by the cell configuration, such as the arrangement of the insulation nets. In the reactor under discussion, the reaction resistance was negligible, and the respective currents through the pathways could be represented by the model proposed. The overall current efficiency based on the total current and the energy consumption were also evaluated. The intrinsic current efficiency based on the Faradaic current of the reaction was more than 0.9.