Rational reactor design for the in-situ electrosynthesis of salt-free hydrogen peroxide.

Poster and abstract:Electrochemical production of the strong oxidant hydrogen peroxide (H₂O₂) combines the use of abundant reactants with low emissions and safe working conditions. On-site H₂O₂ production systems can be applied in water treatment and other environmental applications, if the H₂O₂ comes in a salt-free solution. However, for electrosynthesis in two-compartment cells this is impossible. To obtain a salt-free solution, a three-compartment cell is used. The third compartment is sandwiched between anolyte and catholyte, shielded by membranes, and it is filled with a solid electrolyte to provide conductivity. Membranes prevent H₂O₂ from reaching the anode, where it can be consumed, and they shield the salt-free H₂O₂ solutions from most ions.
Energy use in such a system is governed by the characteristics of the resin and membranes, and by flow velocity, H₂O₂ efficiency, electrolyte concentration. These parameters are all integrated in a mathematical model of a lab-scale system. The outcomes of this model are analyzed through a lens of experimental results derived from a corresponding lab-scale reactor. Herewith we establish a theory of mass transport, new to H₂O₂ synthesis, as a function of resin bed geometry and properties. This model is useful for rational design of and choice of material for the H₂O₂ synthesis cell.
We will present results concerning mass transport in spherical resin particles. Since spherical particles present a complex matrix, we have narrowed down the plethora of possible transport pathways to just three types; transport solely through liquid, solely through resin, and a pathway that combines the two. In this model we describe the potential, and the species concentration as functions of position, electrolyte concentration, and current density. We also describe the resin bed properties with dimensionless numbers, which is necessary to describe transport properties of reactors at larger scale.