Electrochemical Reactors Quak Foo Lee Department of Chemical and Biological Engineering The University of British Columbia

Introduction In electrochemical reactions, electrons are supplied to a reactant in the electrolyte or removed from it with the aid of an electric current. A minimum voltage called the decomposition voltage must be applied to the electrodes for this purpose. In addition to the electrochemical reactions occurring on the electrode surface, transport processes and chemical reactions in the electrolyte both are important.

Reactors for Electrochemical Processes A) Metal winning by fused-salt electrolysis; B) Electrolytic metal refining; C) Electrolysis of inorganic material; D) Electrolysis of organic material; E) Mercury amalgam process; F) Diaphragm-cell process; G) Membrane process a) Water; b) Chlorine; c) Sodium chloride; d) Hydrogen; e) Sodium; f) Sodium hydroxide; g) Anode; h) Cathode; i) Membrane; j) Product; k) Amalgam; l) Recycle brine +  chlorine; m) Mercury; n) Graphite; o) Diaphragm; p) Electrolytic salt solution of metal to be refined; q) Anode slime; r) Electrolyte removal; s) Organic feed solution; t) Oxygen

Advantages High product purity (no secondary reactions) Low reaction temperature (except for fused-salt electrolysis) Easy control of reaction rate through variation of electrode voltage

Disadvantages High energy losses in the system Large space requirement High investment costs

When to Use Electrochemical Reactor? Electrochemical processes are used only when no available thermal or catalytic process can accomplish the same purpose, which is especially true in the production of chlorine, aluminum, and copper.

Applications Chlorine production by chlor – alkali electrolysis Mercury amalgam process Diaphragm-cell process Membrane process Metal winning by fused-salt electrolysis Aluminum Magnesium Sodium Metal refining Copper Nickel

Applications Electrolysis of inorganic materials Electrolysis of water Fluorine production by electrolysis of hydrogen fluoride Production of sodium chlorate by electrolysis of sodium chloride Electrochemical oxidation of sodium chlorate to perchlorate Recovery of persulfuric acid Production of ozone Electrolysis of organic materials Production of adiponitrile from acrylonitride Production of dimenthyl sebacate Reduction of nitrobenzene to aniline