Adiponitrile, electroreduction

A.sahi Chemical EHD Processes. In the late 1960s, Asahi Chemical Industries in Japan developed an alternative electrolyte system for the electroreductive coupling of acrylonitrile. The catholyte in the Asahi divided cell process consisted of an emulsion of acrylonitrile and electrolysis products in a 10% aqueous solution of tetraethyl ammonium sulfate. The concentration of acrylonitrile in the aqueous phase for the original Monsanto process was 15—20 wt %, but the Asahi process uses only about 2 wt %. Asahi claims simpler separation and purification of the adiponitrile from the catholyte. A cation-exchange membrane is employed with dilute sulfuric acid in the anode compartment. The cathode is lead containing 6% antimony, and the anode is the same alloy but also contains 0.7% silver (45). The current efficiency is of 88—89%, with an adiponitrile selectivity of 91%. This process, started by Asahi in 1971, at Nobeoka City, Japan, is also operated by the RhcJ)ne Poulenc subsidiary, Rhodia, in Bra2il under Hcense from Asahi. 

To illustrate this technique, consider the dimerization of the acrylonitrile anion radical (AN") in DMF (26). The electroreductive hydrodimerization of AN is used commercially to produce adiponitrile [(ANH)2], a precursor in Nylon production. The proposed reaction mechanism, an E1.C2 reaction [Section 12.1.1(b)], is... 

It has been shown by studies of the electroreduction of acrylonitrile at Pb, Ni, and Pt cathodes in the presence of quaternary ammonium salts that the yield of adiponitrile depends on the electrode material, with little dependence on cathode potential. On a Pb cathode the yield of adiponitrile was found to be almost independent of quaternary ammonium salt concentration, whilst on a Ni cathode the yield increased with increasing concentration of quaternary salt. The yield of adiponitrile, when a Pt cathode was used, was low and this led to the conclusion that atomic H2 plays a part in the mechanism. The ratio V2/v (dimerization/propionitrile rates) from their common... 

However, the most significant changes in nylon-6, 6 production lie in the newer routes to adiponitrile introduced by Monsanto and Du Pont into both the U.S.A. and Western Europe. The former entails the electroreductive dimerization of acrylonitrile, while Du Pont use the addition of HCN to 1,3-butadiene catalysed by Ni(0) complexes ... 

It might appear likely that electroreduction processes take place directly by electronst on metals which have high hydrogen overpotential and by H(a) on low overpotential metals. Indeed, e.g., electroreduction of acrylonitrile to adiponitrile on Pb or Hg takes place by electronation, followed by proton addition and dimerization, while electrolytic olefin hydrogenation on Pt takes place by transfer of H(a) to the organics. Nevertheless, such... 

It is obtained commercially by the electroreductive coupling of acrylonitrile. By this process about 90% of adiponitrile is obtained. In this process a concentrated solution of certain quaternary ammonium salts (QASs), such as... 

Electrosynthesis is a quite unique tool for synthesis of fine chemicals, wherein highly selective, efficient, and/or environmental benign reactions are performed without use of any oxidizing and reducing reagents under atmospheric conditions. Many successful applications have been accumulated so far [1—3], and some electrosyntheses of useful chemicals in an industrial scale, such as electroreductive coupling acrylonitrile leading to adiponitrile, have been realized [4]. 

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