ES341745A1 - Adiponitrile production by the electrolytic hydrodimerization of acrylonitrile - Google Patents

Abstract

Adiponitrile is produced by the electrolytic hydrodimerization of acrylonitrile by employing as catholyte an aqueous emulsion of acrylo. nitrile containing an electrolyte salt, both the aqueous and oil phases of the emulsion contacting the cathode and the aqueous phase containing at least 5% dissolved acrylonitrile while the oil phase contains sufficient acrylonitrile to replace in the aqueous phase the acrylonitrile consumed. Preferably the catholyte also includes an anion polymerization inhibitor, which is defined as a proton donor, a compound which stabilizes the oil phase so as to prevent the cathode being covered solely by the oil phase of the emulsion, or a substance which reduces the negativity of the activated double bond of acrylonitrile and is intended to exclude "free-radical polymerization" inhibitors. Examples of suitable supporting electrolyte salts are alkali and alkaline earth metal, beryllium, magnesium, ammonium and quaternary ammonium salts of inorganic and organic acids including sulphonic and alkylsulphuric acids. Suitable anion polymerization inhibitors are inorganic acids, ammonia, amines, ammonium and amine salts (but not quaternized amine salts), carboxylic or sulphonic acid compounds, alcohols, acetylenic compounds, oxygen, carbon monoxide or dioxide, carbon oxysulphide or disulphide, mercaptans, alkyl disulphides, or protective colloids such as alkyl- or carboxy celluloses, gum tragacanth or proteins. The emulsion may contain diluents such as adiponitrile or propionitrile and may contain organic solvents such as acetonitrile, dioxane, ethanol, ethylene glycol, dimethyl formamide or dimethyl acetamide. Emulsifying agents such as the above-mentioned protective colloids or surfactants such as soaps or synthetic detergents e.g. alkylbenzene sulphonates may be included in a concentration of 10 p.p.m., to 10% by weight. Preferably the weight ratio of the oil phase to the aqueous phase is from 5:1 to 1: 100, the supporting electrolyte is present in the aqueous phase in an amount of 1 to 60% by weight and the anion polymerization inhibitor is present in an amount by weight of 10 p.p.m. to 10% in the aqueous phase and of 0.01 to 10% in the oil phase. Suitably cathode materials are copper, cadmium, tin, lead, mercury or their alloys, the temperature used is in the range 0 to 80 C., the pH is from 1 to 10, and the cathode current density is from 3 to 30 amps./sq. dm. Preferably electrolysis is carried out in a cell divided by a diaphragm of sintered glass, porous sheet material or parchment paper but preferably by a cation exchange resin diaphragm which may be of either the homogeneous or the heterogeneous type and formed from sulphonated divinyl benzene-styrene-butadiene copolymer, the catholyte being circulated through the cathode compartment while a mineral acid, or less desirably an alkyl sulphuric or a sulphonic acid, is circulated through the anode compartment which contains as anode a non-oxidizing material such as platinum, nickel, nickel silicide, Duriron, lead or lead alloy. The diaphragm thickness may be 1 mm. and the diaphragm-electrode spacings may be maintained also at 1 mm. by spacers.