The increasing penetration of renewable energy in the energy grid causes intermittency, resulting in fluctuating prices. This in turn forges windows of opportunity for the electrochemical production of chemicals that would otherwise be too expensive. This research aims to optimize a continuous-flow-through reactor hosting the production of chemicals by mediated electrochemical oxidation, using organic aminoxyls (i.e., electrocatalysts), specifically 2,2,6,6-tetramethylpiperidinyloxyl (TEMPO) and 4-acetamido-TEMPO (ACT).
The first chapter addresses the main motivation behind- and the aims of this research. In the second chapter, an extensive literature review is provided on the physico-chemical and electro-catalytic properties of the TEMPO mediators, that are important for the modelling of the electrochemical reactor. The third chapter describes the analytical- and computational models that were created to investigate the influence of mediator properties, current density, specific surface area, velocity, and electrode thickness on the energy efficiency of the reactor. More specifically, a flow-through electrochemical reactor with metal foam electrodes and divided anolyte and catholyte compartments.
The solutions obtained from the analytical model are in good agreement with the solutions of the computational model. The analytical model was extended with the Hatta analysis to include mass transfer in the porous electrode. It was found that ohmic losses, due to an expanding reaction zone from the membrane inward in the anode, caused by mass-transfer and/or kinetic limitations of the mediator, pose the biggest obstacle in reaching high conversion with reasonable efficiency.
The main result of this study is a mathematical formula, that allows for quick prediction of the performance of mediated electrochemical oxidation in a flow-through reactor with a porous foam electrode.