Pyridinium hexafluorophosphate preparation method

FIELD: organic synthesis.

SUBSTANCE: invention relates to technology of preparing pyridinium hexafluorophosphate, which is convenient intermediate for synthesis of lithium hexafluorophosphate used as ionic electrolyte component for lithium chemical power sources. Pyridinium hexafluorophosphate is prepared via reaction phosphorus pentachloride with fluorination agent such as ammonium hydrodifluoride followed by treatment of resulting intermediate with pyridinium salt solution.

EFFECT: avoided use of dangerous and inconvenient liquid anhydrous hydrogen fluoride and use of extreme temperature parameters.

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The invention relates to a technology for obtaining salts hexaphosphoric acid, in particular hexaphosphate pyridinium, which is a convenient connection for the synthesis of other salts of this acid - hexaphosphate, including hexaphosphate lithium. The most important practical application of hexaflurophosphate lithium is used as a component of non-aqueous electrolytes for lithium chemical power sources.

Salt hexaphosphoric acid HPF₆used as polymerization catalysts, refining and processing of metals, in laboratory practice.

There are several well-studied ways to get hexaphosphate lithium, for example the interaction of PENTAFLUORIDE phosphorus from fluoride lithium in liquid hydrogen fluoride [1, 2]. Such processes are complicated and expensive for practical use. Published options exchange ways to get hexaphosphate lithium from the corresponding pyridinium salts [3, 4]. Hexaphosphate pyridinium - thermally stable, kalogeromitros connection, which can be easily purified to a high degree the content of the basic substance (more of 99.5 wt.%) conventional recrystallization from water and lower alcohols [3]. This makes the specified salt comfortable precursor hexaphosphate lithium subject to its availability. Also what about the, from hexaphosphate pyridinium can be obtained, if necessary, any other hexaphosphate salt [5].

There are several ways to obtain hexaphosphate pyridinium.

Thus, in the patent [3] proposed a method of obtaining hexaphosphate pyridinium by neutralizing technical hexaphosphoric acid (65%aqueous solution) stoichiometric amount of pyridine under the control of the conductivity of the reaction mass. The method is simple in implementation, but this requires production of the original hexaphosphoric acid obtained by a fairly sophisticated technology (interaction of phosphorus pentoxide with liquid bezvadnym hydrogen fluoride).

Another published method for the synthesis of this pyridinium salts [5] the acid halides of phosphorus (PCl₅, PBr₅, POCl₃, POBr₃, PSCl₃) foryouth liquid complex of pyridine with hydrogen fluoride - polyhydrated pyridinium composition C₅H₅NH⁺F^-·1,7HF. The original polyhydrated obtained by reaction of pyridine with liquid anhydrous hydrogen fluoride at a temperature of minus 80°that is known technological difficulties and expensive process. This method of obtaining hexaphosphate pyridinium part of the raw materials used and the achieved result is accepted by us for FR is the type.

The aim of the present invention to provide a salt With₅H₅NH⁺PF₆ ^-manner, precluding the use of liquid anhydrous hydrogen fluoride, dangerous to use and creates great technological difficulties when work with him, and excluding the extreme process parameters.

The objective is achieved as follows. The first stage is the interaction of the solution petaluridae phosphorus in 1,1,2,2-tetrachlorethane with added portions of solid powdered hydrovhloride ammonium. The reaction is carried out at a stoichiometric ratio of components in accordance with the equation:

The reaction is carried out at a temperature of 60÷100°C for about 30 minutes while stirring the reaction mass. Use solvent and a gradual dosage hydrovhloride ammonium makes it easy to maintain isothermal mode of conducting the process. Lowering the reaction temperature in comparison with the optimum leads to an increase in interaction time, and increase to an undesirable increase in the share of side processes, reducing output hexaphosphate.

The use of non-stoichiometric (3:1) ratio of reagents is undesirable, as it leads to reduction of yield and productive the tee and heavy pollution resulting mixture of salts of the starting compounds.

The resulting reaction (1) a mixture of salts of approximate composition (NH₄PF₆+2NH₄Cl) insoluble in the reaction medium, is almost completely precipitated and separated by filtration (the solvent is returned for reuse). The output of hexaflurophosphate ammonia according to reaction (1) under the conditions of its carrying out is 75% of theoretical in the calculation of the original Piatigorsky phosphorus.

Next, the mixture of salts (NH₄PF₆+2NH₄Cl) is dried, dissolved in minimum amount of water and treated with stirring, a concentrated aqueous solution of pyridinium chloride at room or low temperature. Instantly, the formation and precipitation of poorly soluble in water hexaphosphate pyridinium in accordance with the equation:

In reaction (2) is used, the stoichiometric ratio of the reactants; the amount of solvent (water) should be minimized to reduce losses hexaphosphate pyridinium from the mother liquor. In the absence of ready pyridinium chloride it is obtained by mixing (when cooled) pyridine with concentrated hydrochloric acid, taken in equimolar ratio. Chloride salt of pyridine is chosen because of the cheapness of hydrochloric acid and to simplify the composition of generated waste, which is ri used is an aqueous solution of ammonium chloride and may be disposed of.

The precipitate of hexaflurophosphate pyridinium then filtered off, carefully pressing the liquid phase, and dried in air at a temperature of 110÷115°C to constant weight. Get the product with the content of the basic substance 91-92 wt.%; then the salt is recrystallized in the usual way from distilled water (1 g salt 2.5 ml of water) and get the product with the content of the basic substance 96-97 wt.% and total yield (per PCl₅) approximately 65% of theoretical.

If necessary to improve the quality of its salt is recrystallized once from water, methanol, or ethanol, getting after drying hexaphosphate pyridinium content of the basic substance more of 99.5 wt.% (determined gravimetrically by precipitation anion PF₆ ^-with Nitron).

The proposed method of obtaining hexaphosphate pyridinium easy to implement, does not require the use of liquid hydrogen fluoride and extreme temperature process parameters.

The subject invention is illustrated by the following examples of its execution.

Example 1.

In a Teflon reactor with a volume of 200 ml equipped with a Teflon stirrer, a thermometer in a plastic casing and glass reflux with potassium chloride tube, load of 20.8 g (0.1 mol) petaluridae phosphorus and poured 100-120 massengo simple distillation 1,1,2,2-tetrachlorethane. There is a complete dissolution petaluridae phosphorus. Then, under stirring at a temperature of 60÷100°to the solution in small portions prisypaetsja powder hydrovhloride ammonium (17.1 g; 0.3 mol) of the receiver attached to the free throat of the reactor through a wide rubber tube. Marked the evolution of gas (HCl) and the temperature rise in the reactor; reaction heat was assigned using a water bath.

After the addition of all hydrovhloride ammonium reaction mass was maintained for another 0.5 hour with stirring and the above-mentioned temperature, then cooled to room temperature. The solid phase was separated from the liquid on the filter and dried in a vacuum at a temperature of about 50°C.

Received of 20.9 g of a mixture of salts containing data analysis 56.3% of NH₄PF₆, 42,0% NH₄Cl, 1.7% of NH₄F and the residual amount of solvent. The output of NH₄PF₆72% of theoretical in the calculation of the original Piatigorsky phosphorus.

Example 2.

In glass chemical glass pour 100 ml of concentrated hydrochloric acid (density 1.18 to; the content of HCl and 36.2 wt.%), place it in a cold bath and under stirring with a glass rod slowly poured 95 ml (92,8 g) of pyridine, preventing temperature rise in the glass over 35÷40°C. the reagent Ratio is stoichiometric. After priba the population of pyridine, the solution is cooled to room temperature; get 210,8 g of the solution of pyridinium chloride concentration and 64.3 wt.% (1,17 mole of salt).

Weighed in a separate beaker 338,7 g of a mixture of salts obtained as described in example 1, and with stirring, dissolve it in a minimum quantity of distilled water (about 500 ml). As a rule, obtained colorless transparent solution; if you have a small, not dissolving when the correlation of phases of sediment or turbidity, the solution is filtered.

Quickly mix both solution under vigorous stirring. Instantly precipitation of hexaflurophosphate pyridinium. The mixture was incubated for 5-10 minutes under stirring to complete the process. The precipitate is filtered off and press it on the filter under vacuum for complete removal of the mother liquor. The precipitate is dried in a porcelain Cup on a hotplate at a temperature of 110÷115°C to constant weight. Obtain 240 g of hexaflurophosphate pyridinium content of the basic substance 91-92% (nitronovoe method). The main impurities in the thus obtained salt is C₅H₅NH⁺Cl^-approximately 6÷8 wt.%; NH₄Cl about 0.3 wt.% and NH₄F approximately 0.15 wt.%.

The salt is recrystallized then the usual way of distilled water (1 g salt 2.5 ml water), dried and obtain 196 g of product with a basic substance content of 97 wt.%.

LITERATURE

1. Vuchkov CENTURIES, Grachev S.E., korobtsev VP, matyukha SV, Smagin A.A. // Patent of Russia №2075435, 1997; CL 6 01 25/455.

2. Vuchkov CENTURIES, V.A. Golubev, Grachev S.E., Small E.N., Mochalov US, Istomin VA, Smagin A.A. // Patent of Russia №2184079, 2002; CL 01 In 25/455.

3. Willman, P., Naejus R., R. Coudert, D. Lemordant // U.S. Patent No. 5993767, 1999

4. Bowden W.L. // U.S. Patent No. 4880714, 1989

5. Syed Mahamed K., Padma D.K., Kalbandkeri R.G., Vasudeva Murthy A.R. // J. Fluorine Chem., 1983, V.23 supported, p.509.

1. The method of producing hexaphosphate pyridinium through interaction petaluridae phosphorus with a fluorinating agent, wherein as the fluorinating agent used hydrolittoral ammonium with the subsequent processing of the obtained intermediate product with a solution of salt of pyridine.

2. The method according to claim 1, characterized in that the reaction petaluridae phosphorus with hydrovhloride ammonium is carried out by gradual batch feed solid hydrovhloride of ammonia in the mixed solution petaluridae phosphorus in 1,1,2,2-tetrachlorethane with subsequent isolation of the intermediate product (a mixture of salts NH₄PF₆and NH₄Cl) filtering and drying.

3. The method according to claim is .1 and 2, characterized in that the reaction petaluridae phosphorus with hydrovhloride ammonium in 1,1,2,2-tetrachlorethane is carried out at a temperature of 60÷100°C.

4. The method according to claims 1, 2, 3, characterized in that as the salt of pyridine hydrochloride use it, and the deposition of hexaflurophosphate from a mixture of pyridinium salts with pyridine hydrochloride is carried out in the aquatic environment.