Electrodimerization of acrylonitrile with a rotating rod electrode

Abstract

Adiponitrile (ADN) is an important raw material to produce nylon 66, and can be produced by electrodimerization of acrylonitrile (AN). The commercial processes are operated in flow systems. It is the first time that a rotating rod electrode (RRE), a relatively simple tool, was applied in the electrosynthesis of ADN. The electrode rotation rate was used to simulate high electrolyte velocity in the flow cell systems used in the industry. In addition to AN and ADN, the concentrations of two major by-products, propionitrile (PN) and trimer, were measured to determine the selectivity and current efficiency. Among five investigated quaternary ammonium salts in the electrolyte, tetrabutylammonium hydroxide (TBAP) possessing the smallest hydrophilic ability and hydrophilic-lipophilic balance (HLB) showed the best performance in the selectivity and current efficiency of ADN. A higher electrode rotation rate provided faster mass transport of AN and promoted the production of oligomers, particularly ADN. Higher current density favored the production of PN. The highest selectivity (85%), current efficiency (82%) and highest yield (0.331 g/cm2·hr) of adiponitrile were accomplished at 3000 rpm, corresponding to a velocity of 1.25 m/s in the range of the electrolyte flow velocity in commercial processes that other researches cannot easily reach it.