GB1113497A - Process for electrolytic oxidation of anions - Google Patents

Abstract

Anions contained in an alkaline electrolyte are electrolytically oxidized by the passage of D.C. through the electrolyte in the presence of a phthalocyanine compound. The phthalocyanine compound may be dissolved in the electrolyte, e.g. if a sulphonic acid derivative is used; admixed with a solid particulate carrier, e.g. of carbon, silica, magnesia, alumina or mixtures of these; coated on or impregnated into the anode used, e.g. carbon or platinum. Typically the electrolyte is aqueous NaOH containing dissolved mercaptides derived from treating hydrocarbon distillates to regenerate the hydroxide solution, the mercaptides being converted to disulphides, and the electrolysis may be effected while the electrolyte is still in contact with the hydrocarbon. Water containing ammonium sulphide subjected to electrolysis under alkaline conditions is free of the sulphide with the formation of free sulphur. Phenols, cresols and xylenols may also be anodically oxidized. Specified phthalocyanine compounds are cobalt and vanadium phthalocyanines, phthalocyanine sulphonates and phthalocyanine carboxylates. The oxidation may be effected at 0 to 100 DEG C. e.g. using an electrolyzer comprising 60 cells in series each with separate electrodes, e.g. of nickel-plated cast iron, separated by rubber-gasketed vulcanized asbestos diaphragms and having a port in each corner, the stack of electrodes and diaphragms forming four channels throughout the length of the electrolyzer. Spent caustic enters through the lower port of each anode plate and flows upward to the top port before it enters the anode outlet header. A similar set of ports is provided for the cathode plates for circulation of caustic solution and release of hydrogen.