DD288291A7 - METHOD FOR PRODUCING PALLADIUM TETRAMMINDIHYDROGEN CARBONATE - Google Patents

Abstract

The process involves the preparation of palladium tetrammine dihydrogencarbonate * from arbitrary soluble Pd compounds, which are first converted with NH3 into a & Pd (NH3) 4! Xn complex. From this solution is precipitated with the addition of carbonate or bicarbonate ions at p H * *. The process has a high refining effect on Pd and leads to a pure salt, which is advantageously used in many ways in electroplating, for the production of Pd powder and other pure Pd compounds. {Production process; Palladiumtetrammindihydrogencarbonat; Faellungstechnologie}

Description

Field of application of the invention

The invention relates to a process for the preparation of palladium tetrammine dihydrogencarbonate [Pd (NHO ₄ ] (HCO ₃ I ₂ .

Characteristic of the known state of the art

In the literature (Gmelin, Handbuch der Anorg. Chemie, System No.65, Pd, 8th ed., Verlag Chemie 1942; 1.1 ternjaev: synthesis of complex compounds of platinum metals, Nauka Verlag, Moscow 1964 FR Hartley: The chemistry of platinum and palladium, Appl., Sei., Publ., London, 1973), neither the existence of [Pd (NH ₃ I ₄ ] (HCO ₃ I ₂ nor its preparation is described.

Object of the invention

The object of the invention is to provide a process for the preparation of palladium tetrammine dihydrogencarbonate.

Explanation of the essence of the invention

The invention has for its object to develop a method that ensures the production of pure palladium tetramminedihydrogencarbonate by precipitation technology.

According to the invention, this object is achieved in that known palladium compounds in aqueous solution are first converted by means of ammonia, which is added in gaseous form or in the form of an aqueous solution in a palladium-amine complex of the type (Pd (NH ₃ I ₄ ) X _n , where X In this case, the reaction conditions should be selected so that the Pd content is converted as completely as possible into the above tetrammine complex.

This can be best ensured by a turnover at temperatures above 5O ⁰ C and with a stoichiometric excess of ammonia. It is also known palladium-tetrammine complex compounds, such as IPd (NH ₃ I ₄ ] (NO ₃ I ₂ , serve directly in aqueous solution as a precursor material.

Subsequently, carbonate or bicarbonate anions are added to the solution, preferably in the form of ammonium salts, and the pH of the solution is lowered to pH 6.5 to 9.0. This is preferably done by introducing carbon dioxide into the solution.

It is striking [Pd (NH ₃ I _4] (HCO ₃ I ₂ of a crystalline precipitate of pale yellowish color. The precipitate is separated by filtration from the liquid phase and by washing, conveniently with an aqueous solution of ammonium carbonate or hydrogen carbonate, by Residues of the mother liquor freed.

In general, a pure palladium tetrammine dihydrogencarbonate is already hereby obtained. To further increase the purity, the compound can be reprecipitated. For this purpose, an aqueous slurry of this palladium salt is brought into solution, for. B. by heating the solution, or by introducing ammonia or by adding an aqueous ammonia solution. Subsequently, the precipitation of palladium tetrammine dihydrogencarbonate is carried out again by lowering the pH of the solution. It is expedient to add in excess carbonate or bicarbonate, whereby a high yield is achieved. Advantageously, (NH ₄ I ₂ COj or NH ₄ HCO ₃ is added.

embodiments

The invention will be explained with reference to exemplary embodiments.

example 1

By dissolving 100 g of metallic palladium in aqua regia and subsequently evaporating the nitric acid, about 10% palladium chloride solution was prepared. This was mixed with half-concentrated, aqueous ammonia-containing solution in excess and brought to a boil. After a short time, the initially precipitated flesh-colored precipitate of [Pd (NH ₃ I ₄ ) .sub.1 (PdCl ₄ ] dissolved and a clear solution was obtained, which was almost completely free.If necessary, further ammonia-containing solution had to be added. The solution was allowed to cool and treated with about 290 g of solid ammonium carbonate, the mixture was stirred for about 10 minutes until the ammonium carbonate was completely dissolved, and CO _{2 was} introduced after a short time The precipitation of palladium tetrammine dihydrogen carbonate began, and the introduction of CO _{2 was} continued until a pH of 8.0 was reached, and salt precipitation was no longer recognizable, and the precipitate was filtered off and filtered about 5 times with a small, preferably cold 10% After drying, 263 g of salt were applied with a Pd content of 35.0% (theoretical 35.8%) Yield of 92% Pd. The Cr content in the salt was <0.25%.

Example 2

220 g of moist (Pd (NH ₃ I ₂ ) Cl ₂ , as obtained in the course of conventional palladium refining and containing about 100 g of Pd was dissolved as in Example 1 with the addition of NH _3. After evaporation to about 11 solution and After cooling, 220 g of solid NH ₄ HCO _{3 were} added and the (Pd (NH ₃ I ₄ ) (HCO ₃ ) J was precipitated by passing in CO _2. ) After filtration, washing and drying, 260 g of salt with a Pd content of 35 were obtained 91% Pd The Cl ~ content was about 0.38% In order to obtain an even purer product, the salt was dissolved in 0.91 hot semi-concentrated NH ₃ solution After cooling, about 70 g of solid NH ₄ HCO _{3 were added} to the solution, and by passing in CO ₂ , [Pd (NH ₃ ) ₄ ] (HCO ₃ ) _{2 was again} precipitated to give 239 g Salt with a Pd content of 35.3%, which corresponds to a yield of about 93% and the Cl 'content was less than 0.01%.

Example 3 '

750 ml of water were added to 440 g of NH ₄ HCO ₃ , and then 350 g of solid (Pd (NH ₃ M (NO ₃ I _{2 were} introduced

Stir mixture for approx. 5 hours. Thereafter, the precipitate of (Pd (NH ₃ I ₄ ) (HCO ₃ I _{2 was} filtered off with suction and with 2115% NH ₄ HCO ₃ solution

washed. After drying, 297 g of salt were obtained with a Pd content of 36.0%. This corresponds to a yield of 89%

Pd. The NO ₃ "content in the salt was 0.72%. The process according to the invention ensures the preparation of pure palladium tetrammine dihydrogencarbonate

known palladium compounds. The process is equally capable of refining palladium by interfering with it

Contents of other metals and non-metals according to the method are easily separable. The resulting palladium salt is diverse

can be used for the production of galvanic baths or for the production of other technically important palladium compounds.

In addition, from the palladium salt while avoiding harmful Aprodukte by simple thermal decomposition pure Palladium powder produced.

Claims (4)

1. A process for the preparation of palladium tetramminedihydrogencarbonate, characterized in that a palladium-amine complex of the type [Pd (NH ₃ ) ^ X _n in the aqueous phase carbonate or bicarbonate ions are added and the pH of the solution to pH 6.5 to 9 , 0 is set and that the precipitate is optionally aftertreated by redissolving and precipitation. 2. The method according to claim 1, characterized in that the carbonate or bicarbonate ions are added in the form of ammonium salts. 3. The method according to claim 1, characterized in that the pH is adjusted by introducing carbon dioxide to the range pH 6.5 to 8.5. 4. The method according to claim 1, characterized in that the precipitate is transferred for the purpose of reprecipitation with heating in an aqueous solution, is precipitated from the by introducing carbon dioxide palladium tetrammine dihydrogen carbonate.