Microstructured Reactors for Electrochemical Synthesis

Abstract

Electrochemistry is an extremely diversified field describing any kind of system where a chemical reaction takes place at an electrified interface and is coupled with an electron transfer between an electronic and an ionic conductor. Well-known application fields are electroanalytical devices, electrowinning of metals, electroplating, energy storage in batteries, energy conversion in fuel cells and the synthesis of a great variety of inorganic and organic compounds. The electrochemical reactors used in these different application fields are various and it is outwith the scope of this chapter to discuss the impact of microstructuring on all of them. Instead, this chapter focuses on a particular application field: electrochemical synthesis. Moreover, the reactor layout is analyzed from the point of view of process engineering whereas electrocatalytic aspects, even though extremely important in electrochemical engineering, are not treated.In the first section, some fundamentals of electrochemical processes are defined. Common industrially relevant process flow schemes and equipment are described in the second section. The third section discusses the interest of microstructured reactors in electrochemical synthesis and gives an overview of the recent literature in this area. Fundamentals of Electrochemical ProcessesFundamentals of electrochemical processes can be found in several textbooks [1][2][3][4][5]. The electrochemical reactor is an electrolytic cell, shown schematically in Figure 17.1, powered by a current source. The cell contains positively charged anodes and negatively charged cathodes in addition to an electrolyte solution containing ions which permit to carry the electric current through the solution. The reactant and the products are usually at least partially dissolved in the electrolyte.Ã A List of Symbols can be found at the end of this chapter.

Organic Electrosynthesis: From Laboratorial Practice to Industrial Applications

“…Currently, various industrial synthesis processes using macrobatch reactors are facing barriers that affect the global process owing to the interelectrode ohmic drop, mass transfer phenomena, selectivity, or even environmental factors. ,, Electrochemical microreactors (ECMRs) are suitable equipment for solving these limitations mainly in electroorganic systems where the electric conductivity is reduced. This ECMR concept is being used for the development of multiple organic synthetic routes with benefits including energy, time, and space savings; increased current efficiencies; resource preservation; waste/emissions minimization; and fewer required separation and synthetic steps .…”

Microreactors with Electrical Fields

“…The reasons to perform electrochemistry, in particular, electrosynthesis, in a microfluidic system are the following (Rode et al, 2009): (1) reduction of ohmic resistance in the electrochemical cell, by decreasing the distance between anode and cathode, (2) enhancement of mass transport by increase of electrode surface to cell volume ratio, also realized by small interelectrode gaps, (3) performing flow chemistry to establish single-pass conversion, and (4) coupling of cathode and anode processes, permitting simultaneous formation of products at both electrodes. The latter possibility is very interesting from a sustainability point of view (less waste) and examples have started to appear in recent literature, like the epoxidation of propylene (Belmont and Girault, 1995).…”

“…The research on electrochemistry in microreactors has been reviewed in a number of recent publications (Hessel et al, 2004;Rode et al, 2009;Yoshida, 2008;Yoshida et al, 2008); therefore, we do not want to go into too much detail here. But since these reviews almost exclusively concern electroorganic synthesis, a number of other applications will be highlighted here.…”