An Experimental Study of the Competing Cathodic Reactions in Electrohydrodimerization of Acrylonitrile

The production of adiponitrile (ADN) uses an electrochemical reactor in which organic reactant, acrylonitrile (AN), which is very slightly soluble in water and forms an emulsion in the aqueous electrolyte, undergoes an electrohydrodimerization reaction at a solid lead cathode. In addition to ADN, some byproducts including propionitrile (PN) and 1,3,5-tricyanohexane (trimer) are also formed at the surface of the cathode. Since the open literature on the study of the parameters influencing the course of this reaction is scarce, the current study was launched to identify the effects of various process parameters on the selectivity of adiponitrile and its by-products. The electrosynthesis was conducted in an electromembrane reactor employing an oxygen-evolution dimensionally stable anode (DSA-O(2)(R)), a lead cathode, and a Nafion (R) 115 membrane. The concentration of all products was determined through NMR analysis. Process parameters under investigation were: temperature (25-55 degrees C), acrylonitrile concentration (15-30 wt%), current density (1-4 kA/m(2)), catholyte flow rate (100-400 mL/min) and catholyte pH (3-9). The results demonstrate that the selectivity of ADN is enhanced by increasing all studied process parameters, except the current density. In the case of by-products, the selectivity of PN decreases by raising AN concentration, flow rate, and pH. On the other hand, the selectivity of trimer was reduced by temperature, current density, and flow rate. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.016112jes] All rights reserved.