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SPE Electrolysis

 

SPE Electrolysis processes use a membrane as Solid Polymer Electrolyte between electrodes. Typically both electrodes are pressed on the membranes to get a optimum contact.

An example is modern brine electrolysis. But the application is not limited on this process. An other process is the Kolbe Synthesis.

 

 

Kolbe Electrolysis

 

The Kolbe Synthesis is an anodic oxidation process of a carboxylate anion. A radical is formed which decarboxylates. The resulting radical combinates with another to form a dimer.
For example, acetate will react to ethane and propionate will react to butane.
However, in practise, this reaction work in the first case but does not take place in the second case because there are many side processes: the ethyl radical may not only dimerize, it also may eliminate a hydrogen radical to form ethylene. The hydrogen radical may react with a second ethyl radical to form ethane. In the case of propionate, kolbe electrolysis efficiency is sensitive to water. It is essential therefore, to run the reaction in (almost) water free conditions. The process is descibed below:

 

Advantages

 

Running a Kolbe Synthesis as a SPE reaction with anion exchangers has the advantage of solvent and product cotransport into the reaction zone (see picture above). PCA developed an optimized SPE matrix with low resistance in nonaqueous media. Results for propionate are given below:

 

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