INFLUENCE OF THE EXPERIMENTAL SYSTEM AND OPTIMIZATION OF THE SELECTIVITY FOR THE ELECTROCARBOXYLATION OF CHLOROACETONITRILE TO CYANOACETIC ACID

Abstract

The electrocarboxylation of chloroacetonitrile (ClACN) to cyanoacetic acid in undivided cells equipped with sacrificial anodes was investigated both in a bench-scale electrochemical batch reactor and in a continuous batch recirculation reaction system equipped with a parallel-plate electrochemical cell. Selectivity and faradaic yields higher than 90% were obtained by working under anhydrous conditions with low halide concentrations and at more negative potentials. It was found that the instantaneous selectivity in the carboxylate compound depends mainly on the [CO2]/[ClACN] ratio at high substrate concentration and is close to 100% for low ClACN concentration. These results were consistent with the previsions of a semiempirical model based on the assumption that under adopted experimental conditions the selectivity of the process is mainly determined by the competition between two very fast reactions: the carboxylation and a father-son reaction between the electrogenerated anion and the substrate. The effect of the nature of the solvent and of the concentration of proton donor species was further investigated.