Two-phase electrolysis

Since electrochemistry is generally more suited to aqueous media, while organic chemistry is usually favored by the use of an organic solvent, the concept of two-phase electrolysis can be attractive. The best-known example is the second version of the Monsanto process for adiponitrile [8,9], in which an emulsion of aqueous electrolyte and acrylonitrile was employed. The roles of the acrylonitrile phase are to maintain the aqueous electrolyte saturated with acrylonitrile, and to extract the adiponitrile back out of the aqueous electrolyte, thereby simplifying product isolation. The organic medium is separated from the aqueous electrolyte, while the reactant and product are separated by distillation. The combination 

The Fuchigami group have recently proposed a different type of two-phase system with the objective of making electrolysis more convenient and green . For this, they employed solid silica gel-supported piperidine in a methanol medium for the Kolbe reaction [48]. In the solvent, the piperidine protonates to give the medium some conductivity the medium then produces almost quantitative yields for the Kolbe dimer, for example  

After electrolysis, the solid conducting electrolyte is simply removed by filtration, greatly assisting product isolation. The silica gel-supported piperidine can also be reused for many electrolyses. 

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Their synthesis can also be carried out as a two-phase electrolysis, using ammonium salts 326). Sulfenamides can be produced by oxidizing tetraalkylthiuram disulfides in the presence of amines 321 ... 

The effect of sulfuric acid is remarkable, since the absence of sulfuric acid results in a mixture of benzylic chlorides Ig (25%), Ih (20%), and the starting material la (34%) together with complex compounds (20%). Notably, the two-phase electrolysis procedure brings about no hydrolysis products on either the thiazoline or the beta-... 

Bubble electrodes — Figure 2. Bubble electrode for electrosynthesis 1 - bubble electrode, 2 - ion exchange membrane, 3 - Pb02 anode. Arrangement A is for single-phase operation, and arrangement B and C are for two-phase electrolysis (electrolysis of emulsion) (reproduced from [v])... 

See also -> aluminum production, -> Baizer-Mon-santo process, -> chlor-alkali production, -> electrochemical cell, fluidized bed electrodes, -> H-cell, -> Swiss-role cell, -> three-dimensional electrodes, -> two-phase electrolysis. 

Two-phase electrolysis — Electrolysis of two-phase systems, esp. of two liquid phases. The usual case is that an organic compound is dissolved in a nonaqueous solvent and that solution, together with an aqueous electrolyte solution is forced to impinge on an electrode. The electrolysis reaction of the dissolved organic compound can proceed via a small equilibrium concentration in the aqueous phase, or it can proceed as a reaction at the three-phase boundary formed by the aqueous, the nonaqueous phase, and the electrode metal. A very effective way of delivering a two-phase mixture to an electrode is the use of a - bubble electrode. 

Primary to ternary current distribution at a vertical electrode during two-phase electrolysis... 

During two-phase electrolysis for hydrogen or fluorine industrial production, there are bubbles that are created at vertical electrodes, which imply quite important electrical properties and electrochemical processes disturbance. Bubbles are motion sources for the electrolysis cell flow, and then hydrodynamic properties are strongly coupled with species transport and electrical performances. The presence of the bubbles modifies these global and local properties the electrolysis cell and the primary to ternary current density distribution are modified. This disturbance leads to the modification of the local current density. 

The goal of this proposition is to present the electrochemical engineering study and modelling of two-phase electrolysis properties at electrode vicinity. This work is due to the necessity for a better knowledge of the actual interface condition during electrolysis, for example to have a better process optimisation or electrode consumption prevention. 

Keywords two-phase electrolysis, modelling, electrochemical engineering. 

Because of gas evolving in the gravity field, the industrial two-phase electrolysis processes generally use vertical electrodes to promote bubble detachment and avoid gas accumulation. This is the reason why the present work focuses upon vertical electrodes. 

The classical alkaline water electrolysis has been chosen as a representative two-phase electrolysis process ... 

Ph. Mandin, H. Roustan, R. Wiithrich, J. Hamburger G. Picard, Two-phase electrolysis process modelling from the bubble to the electrochemical cell scale Transactions on Engineering Sciences, 2007 WIT Press, Simulation of Electrochemical Processes II, p73... 

Hydrogen production by the Westinghouse cycle modelling and optimization of the two-phase electrolysis cell... 

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