RU2288214C1 - Method for preparing palladium acetate - Google Patents

Abstract

FIELD: chemical technology.

SUBSTANCE: invention relates to a method for synthesis of platinum metal salts, in particular, palladium salts, namely, palladium (II) acetate. Method for synthesis of palladium (II) acetate involves dissolving metallic palladium in concentrated nitric acid, filtering and evaporation of palladium nitrate solution, its treatment with glacial acetic acid, filtration of formed sediment and its treatment with acetic acid ethyl ester and glacial acetic acid for its conversion to palladium (II) acetate followed by heating the prepared suspension for 6 h. Method provides preparing palladium (II) acetate with high yield in monophase state and without impurities of insoluble polymeric palladium (II) acetate.

EFFECT: improved method of synthesis.

3 cl, 2 tbl, 21 ex

Description

The invention relates to the field of chemistry of platinum metals, in particular the synthesis of palladium compounds, namely the synthesis of palladium (II) acetate, used as a catalyst, for example, to obtain vinyl acetate or a starting salt to obtain other salts of palladium, for example to obtain palladium acetylacetonate.

A known method of producing palladium (II) acetate by dissolving palladium oxide in acetic acid. Palladium oxide is prepared from palladium hydroxide precipitated from sodium palladium chloride solution. (Korean Patent No. 8904783, 1989). The disadvantage of this method is the incomplete dissolution of palladium oxide in acetic acid, which requires an additional filtering operation. In this case, palladium hydroxide obtained by precipitation with alkali requires a special filtering method.

A known method of producing palladium acetate by dissolving palladium black in a mixture of glacial acetic acid and concentrated nitric acid in an inert atmosphere (Japanese Patent No. 61047440, 1986). The disadvantage of this method is the need for the presence of excess palladium black throughout the process, which requires crystallization of the solution from black before crystallizing the product. The absence of black leads to the formation of an oxidizing medium in the solution (due to the presence of nitric acid or nitrogen oxygen compounds), which contributes to the formation of polymeric palladium (II) polymer insoluble in acetic acid and organic solvents [Pd ₃ (СН ₃ СОО) ₂ ] _n .

A known method of producing palladium (II) acetate by reacting palladium nitrate with acetic acid. Palladium nitrate is obtained by evaporation of a dilute nitric acid solution of palladium to wet salts (Guide for Inorganic Synthesis / Edited by G. Brauer. M: Mir, 1985. v.5, p.1832). This method is adopted as a prototype.

The disadvantage of this method is to obtain a product not in a monophasic state and its low yield. Upon receipt of palladium (II) acetate from nitrate solutions of palladium, the presence of nitric acid and its decomposition products is inevitable, which helps to dissolve palladium (II) acetate and reduce product yield, as well as the formation of palladium (II) nitritoacetate [Pd ₃ (СН ₃ СОО) ₅ NO ₂ ], which transforms into a polymeric form.

The technical result to which the invention is directed is to increase the yield of palladium (II) acetate and to obtain it in a monophasic state [Pd ₃ (CH ₃ COO) ₆ ].

The desired technical result is achieved in that the palladium nitrate solution after evaporation, before crystallization of the palladium (II) nitrate salt begins, is treated with glacial acetic acid at a temperature of (20-30) ° C with a flow rate of (10-11) l per 1 kg of palladium in solution for (1-2) hours, filter the precipitate formed, treat it with a mixture of glacial acetic acid and ethyl acetate at a temperature of (60-90) ° С for (2-5) hours with a flow rate of (2-4) l of ice acetic acid and (0.05-0.2) l of ethyl acetate per 1 kg of precipitate and the resulting suspension is heated uw at a temperature (120-140) ° C for at least 6 hours.

The essence of the method is that the synthesis of palladium (II) acetate is carried out through the stage of formation of an intermediate compound - palladium (II) nitritoacetate, which is then converted to palladium (II) acetate at an elevated temperature in acetic acid using ethyl acetate (ethyl acetate) ) Ethyl acetate allows you to restore nitric acid, which is present as an impurity in palladium (II) nitritoacetate, to nitrogen oxides, which are removed from the reaction zone, while ethyl acetate is oxidized to acetic acid, which does not adversely affect the process, because Itself is a reagent. The absence of nitric acid further excludes the formation of polymeric palladium (II) acetate.

In the course of the studies, it was found that for the first stage of the process — the preparation of an intermediate compound of palladium (II) nitritoacetate by precipitation with acetic acid from a palladium nitrate solution, the optimal conditions are:

- consumption of glacial acetic acid (10-11) l per 1 kg of palladium in its nitric acid solution;

- temperature of the deposition process (20-30) ° C;

- the palladium content in the nitric acid solution is at least 500 g / l;

- the content of free nitric acid is not more than 200 g / l;

- the duration of deposition (1-2) hours.

An increase in the consumption of glacial acetic acid during the deposition of palladium (II) nitritoacetate from a palladium nitrate solution of more than 11 L per 1 kg of palladium is inefficient, since it leads to the dissolution of the resulting palladium (II) nitritoacetate and a decrease in yield. Acetic acid consumption of less than 10 l per 1 kg of palladium leads to a decrease in the yield of palladium (II) nitritoacetate.

The temperature of precipitation of palladium (II) nitritoacetate from a palladium nitrate solution above 30 ° C leads to the formation of polymeric palladium (II) acetate; a decrease in the temperature of deposition of palladium (II) nitritoacetate below 20 ° C leads to a decrease in yield.

The content of palladium in a nitric acid solution of less than 500 g / l and nitric acid more than 200 g / l leads to a reduction in the yield of the product.

The duration of the deposition of palladium (II) nitritoacetate from a palladium nitrate solution of less than 1 h leads to a decrease in yield. An increase in the duration of deposition of more than 2 hours is impractical, since it does not increase the yield of the product, but increases the overall duration of the process.

It was found that for the second stage of the process, the removal of impurity nitric acid from palladium (II) nitritoacetate and its conversion to palladium (II) acetate are the optimal conditions:

- the consumption of ethyl acetate and glacial acetic acid (0.05-0.2) L and (2-4) L, respectively, per 1 kg of the original palladium (II) nitritoacetate;

- temperature treatment with a mixture of ethyl acetate and glacial acetic acid (60-90) ° C;

- the duration of treatment at a temperature of (60-90) ° C - (2-5) h;

- temperature of the process of converting palladium (II) nitritoacetate to palladium (II) acetate (120-140) ° С;

- processing time at a temperature of (120-140) ° C for at least 6 hours

The consumption of added ethyl acetate of less than 0.05 L per 1 kg of palladium (II) nitritoacetate leads to incomplete removal of impurity nitric acid, which, subsequently, with increasing temperature leads to the formation of insoluble polymer palladium (II) acetate. An increase in the consumption of added ethyl acetate of more than 0.2 l per 1 kg of palladium (II) nitritoacetate leads to a decrease in the yield of the product. The consumption of glacial acetic acid (less than 2 L per 1 kg of initial salt) leads to incomplete conversion of palladium (II) nitritoacetate to palladium (II) acetate and the formation of polymer palladium (II) acetate upon further heating. An increase in the consumption of glacial acetic acid (more than 4 L per 1 kg of the initial salt) is impractical, since it leads to an increase in the volume of the solution and greater solubility of the product, i.e. reduce output.

The processing temperature of palladium (II) nitritoacetate with a mixture of glacial acetic acid and ethyl acetate is less than 60 ° С, which leads to a decrease in the reactivity of ethyl acetate and nitric acid, which leads to incomplete removal of nitric acid and the formation of palladium (II) polymer acetate upon further heating. A temperature above 90 ° C leads to a strong evaporation of ethyl acetate and to obtain a product with an admixture of the palladium (II) nitritoacetate phase.

The duration of treatment of palladium (II) nitritoacetate in a mixture of ethyl acetate and glacial acetic acid for less than 2 hours leads to incomplete removal of impurity nitric acid, which, subsequently, with increasing temperature leads to the formation of polymeric palladium (II) acetate. An increase in processing time of more than 5 hours is impractical because increases the overall duration of the process.

The temperature of the secondary processing of the reaction mixture below 120 ° C leads to the production of a product with an admixture of palladium (II) nitritoacetate. An increase in temperature above 140 ° C leads to boiling of the reaction mixture.

The duration of the secondary temperature treatment of the reaction mixture for less than 6 hours leads to an incomplete transition of palladium (II) nitritoacetate to palladium (II) acetate. Increasing the warm-up time increases the duration of the process.

Examples of the method:

As a starting product for experiments No. 1-10 (table 1) for the production of palladium (II) acetate, a solution of palladium nitrate was prepared by dissolving palladium metal in nitric acid and evaporating it. The palladium content in the solution is 605 g / l, free nitric acid - 189 g / l. For experiments No. 11-16 (table 1), a solution was prepared with various concentrations of palladium and free nitric acid.

Example 1

The calculated volume of glacial acetic acid was added to a certain volume of the prepared palladium nitrate solution and mixed. The resulting precipitate of palladium (II) nitritoacetate was separated by filtration, unloaded on a baking sheet and dried in an oven at 40 ° C for 24 hours. The precipitate was weighed, analyzed for palladium content and the phase composition was determined. The mother liquor was sent for regeneration. The experimental data are shown in table 1.

The precipitate of palladium (II) nitritoacetate for the second stage of the process (conversion to palladium (II) acetate) was obtained according to the experimental conditions No. 2 (table 1), as the best option for the first stage of the process. The treatment of the precipitate of palladium (II) nitritoacetate in a mixture of acetic acid and ethyl acetate was carried out in a rotary evaporator with heating and a system for trapping and cooling the exhaust vapor. The calculated volume of glacial acetic acid and ethyl acetate were added to a specific sample of the precipitate of palladium (II) nitritoacetate. The reaction mixture was warmed, ethyl acetate was distilled off (condensed ethyl acetate can be reused), then the temperature was raised and warmed still. The pulp was cooled to room temperature, the precipitate was filtered off and dried at 120 ° C for 3 hours. The resulting precipitate of palladium (II) acetate was weighed, analyzed for palladium content and the phase composition was determined. The experimental data are shown in table 2 (experiments No. 1-20).

After separation of the precipitate, the mother liquor can be reused for the conversion of palladium (II) nitritoacetate to palladium (II) acetate.

Example 2

The precipitate of palladium (II) nitritoacetate, obtained from experiment No. 2 (table 1), was processed according to the experimental regimes No. 8 (table 2), as the optimal variant of the second stage of the process, but the temperature treatment at (120-140) ° С was carried out without separation of the precipitate from the mother liquor. After raising the temperature to 120 ° C, the reaction suspension was kept until complete evaporation of acetic acid and obtaining a dry salt. At the same time, the yield of the product increased, but the duration of the process increased (table 2, experiment No. 21).

As can be seen from the above examples, the use of the proposed method allows to obtain palladium (II) acetate in high yield in a monophase state and to eliminate the appearance of impurities of insoluble polymer palladium (II) acetate.

Claims (3)

1. A method of producing palladium acetate, including dissolving palladium metal in concentrated nitric acid, evaporating the resulting solution and treating it with acetic acid, characterized in that the palladium nitrate solution after evaporation before crystallization of the palladium (II) nitrate salt is treated with glacial acetic acid at a temperature of 20 -30 ° C with a flow rate of 10-11 l per 1 kg of palladium in solution for 1 to 2 hours, the precipitate formed is filtered off, treated with a mixture of glacial acetic acid and ethyl ether acetic acid at a temperature of 60-90 ° C with a flow rate of 2-4 l of glacial acetic acid and 0.05-0.2 l of ethyl ester of acetic acid per 1 kg of precipitate for 2 to 5 hours and the resulting suspension is heated at a temperature of 120- 140 ° C for at least 6 hours 2. The method according to claim 1, characterized in that the evaporation of the nitric acid solution of palladium is carried out to a palladium content of at least 500 g / l and free nitric acid of not more than 200 g / l. 3. The method according to claim 1, characterized in that the suspension is heated at 120-140 ° C until dry salts are obtained.