Obtaining of Trialkylphosphates in Anodic Dissolution of Copper Phosphide

Due to obtain trialkylphosphate is suggested to use anodic solution of copper phosphide in alcohol solutions. At this, it can use copper phosphide, obtained at the processing of wastes of phosphorus production. Moreover, it is presented ways of obtaining of tri-n-butylphosphate and tri-izo-butylphosphate.


INTRODUCTION
In the research 1,2 are shown the possibilities of obtaining of trialkylphosphate by the electrolysis of suspensions of red phosphorus.The authors of work 3 used dialkylphosphoric acid as the initial phosphorus containing compounds for synthesis of trialkylphosphate.Next authors 4 studied the process of synthesis of tryalkyl phosphates, i.e., derivatives of methanol, butanol, and diethylene glycol, by anodic oxidation of dimethyl phosphite in the corresponding alcohol.It was found that three alkyl phosphates corresponding to the three possible combinations of substituents bound to phosphorus in phosphate are formed.
In this regard, it was interesting to investigate the possibilities of obtaining of trialkylphosphates by the using of sacrificial copperphosphorus anode as a donor of phosphorus.The copper-phosphorus alloys are produced by industries, in addition, these alloys are formed at the processing of phosphorus sludge 5 .
Mechanism of anodic dissolution of copper-phosphorus alloys in the alcohol solutions of hydrogen chloride can be represented by the following equations: Cu3P + Cl - 3CuCl+ P + 3e ...( 2) The formed phosphides are subjected to further oxidation.This process may proceed on the anode or in solution with the participation of oxygen or copper compounds.In the latter case, the reaction may be in the form Trialkylphosphates are the efficient complex forming reagents.Particularly, in this regard the valuable substances are tri-n-butylphosphate and tri-izo-butylphosphate, which are used for selective extractions of uranium, thorium 6 .Currently, these reagents are used in nuclear fuel engineering, therefore the development of new methods of the obtaining of trialkylphosphate presents practical interest.

Electrosynthesis of tri-n-butylphosphate
In glass electrolyzer, equipped by water jacket and return refrigerator 200 cm 3 of n-butane alcohol was loaded.Previous of electrolyzing the alcohol was saturated by dry gaseous hydrogen chloride.In this purpose it is very convenient to obtain the dry hydrogen chloride by the action of concentrated sulfuric acids on concentrated hydrochloric acid with the followed passing of hydrogen chloride through a flask with concentrated H 2 SO 4 .
A plate of copper -phosphorus alloys (phosphorus content is 10 mass %) weighing 112 g with the total area 3.5'"10 -3 m 2 , and working surface 2.5'"10 -3 m 2 , the copper plates cathodes with analogous size were used in electrolysis.
Electrolysis was performed at current density of 0.25-0.30A/m 2 '"10 -4 during 5 hours.Temperature of an electrolyte was 65-70 o C. The voltage on the bath was not exceeding 20-22 W. The passed current, which was measured by copper coulometer, was 35 ampere hour (A•h).At this, in the results the electrolysis was dissolved 29.6 g of copper phosphide anode.25.2 g of copper powder was isolated on the cathode, the part of which fell to the bottom of the electrolysis.
After filtration, the solution was subjected to vacuum distillation.The unreacted butyl alcohol was distilled off at the temperature 32-35 o C and the pressure 2.66'"10 3 Pa.The white deposit of copper monochlorides was precipitated in the remains, which it was filtered off.Weight of precipitate after drying was 3.1 g.The volume of filtrate was 30 cm 3 .Moreover, to this filtrate 60 cm 3 of benzene were added and were mixed for 5-6 minutes, after that the solution was poured into the separating funnel and washed out with 40 cm 3 of distilled water until the disappearances of blue color of copper ions in the aqueous layer.The benzene layer was filtered through anhydrous sodium sulfate.After distillation of benzene from liquid leavings by the vacuum distillation at a temperature of 159-165°C (1.60'"103 Pa) 20 cm 3 of liquid containing phosphorus was obtained.

Electrosyntheses of tri-izo-butylphosphate.
Electrolysis with 300 cm 3 of isobutyl alcohol (2-methyl-3-propanol), also previously saturated by hydrogen chloride was performed on the above presented procedure, the electrolysis performed at the current density of i a = (0.2-0.25) '"10 -4 A/m 2 and U = 20 -24 W. At these conditions 60 A/hours of electricity was passed through the electrolyte.The loss of anode mass was 46.1 g.Further processing of electrolyte was conducted same ways, as tri-n-butylphosphate.After distillation of benzene, 35 cm 3 of tri-izobutylphosphate was remained, which has been subjected to vacuum distillation5

Electrosyntheses of tri-n-butylphosphate
The density of tri-n-butylphosphate was