Electrochemical Epoxidation of Olefins

The electrosynthesis of propylene oxide (PO) has already been studied intensively by Bayer 49) in the sixties, and has been scaled up to the pilot scale. The synthesis was carried out in a divided cell at Ti/RuOz anodes and steel cathodes. 

A more obvious method of avoiding the inevitable production of CaCl2 is the combination of the chloralkali electrolysis with the chlorohydrin process. This is also being pursued intensively 54-55 . A modification proposal by Lummus is shown in the block diagram below 56)  

The electrosynthesis of hypochlorites has been studied in detail by Olin 37 58). 

Whereas the electrochemical process of the production of propylene oxide has not advanced beyond the stage of experimental production, the electrosynthesis of hexa-fluoropropylene oxide 59 62) has been implemented industrially by Hoechst  

For the continuous process, a special divided cell (Pb02/steel anode, steel cathode, Nafion as cation exchange membrane) based on the principle of a tubular reactor was developed. The final product can be removed in gaseous form, so that the electrolyte can be recycled in a simple manner. The membrane and electrodes are supposed to have lifetimes of at least one year 63). Hexafluoropropylene is a useful monomer for fluorine-containing polymers, e.g., fluorinated polyethers. 

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Electrochemical epoxidation of olefins has been developed for the production of ethylene and propylene oxides in aqueous sodium chloride or bromide solution. However, associated with these electrolyses are difficulties in achieving product selectivity as well as in obtaining high yields of the epoxides. Recently, a regiose-lective )-epoxidation of polyisoprenoids (23) to (24), promoted by electrooxidation in an MeCN/THF/H20-NaBr-(Pt) system, has been achieved (Scheme 10) [52]. 

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