RU2485053C1 - Method of producing ammonium perrhenate - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to the metallurgy of rare and noble metals, particularly to processing spent platinum-rhenium catalysts and can be used in producing rhenium compounds when extracting rhenium from catalysts on aluminium oxide supports. The method involves desorption of rhenium from a saturated weakly basic anionite with ammonia solution, evaporating the ammonia solution while adding sodium sulphite, adding calcium chloride to the evaporated solution, cooling the pulp and filtering the crude ammonium perrhenate precipitate, which is recrystallised from distilled water.

EFFECT: high quality of ammonium perrhenate due to low content of impurities of platinum, sodium, sulphur and other base elements.

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Description

The invention relates to the field of metallurgy of rare and noble metals, in particular to the processing of spent platinum-rhenium catalysts, and can be used in the technology for producing rhenium compounds in the extraction of rhenium from catalysts on alumina supports.

During operation in the oil refining industry, catalysts on alumina supports containing platinum and rhenium gradually lose their catalytic activity and are recycled to recover valuable components that can be reused. The platinum and rhenium content in various grades of catalysts is from 0.1 to 0.45%. In particular, rhenium in the form of ammonium perrenate or rhenic acid is used in the manufacture of new catalysts and for the production of metallic rhenium, which is widely used in the electronic industry and in the manufacture of heat-resistant alloys.

Spent catalysts contain, along with aluminum oxide and noble metals, a large number of impurity chemical elements and their compounds, mainly Si, Mg, Ca, Fe, Mn, Ni, Mo, Cu, carbon. The extraction of rhenium from this material and its purification from the listed impurities presents significant difficulties and is associated with large material and labor costs.

It is known from public literature that a promising method for the extraction of precious metals from catalysts is their selective leaching with acid solutions in the presence of oxidizing agents, followed by the extraction of metals from the solution. For catalysts containing platinum and rhenium, a method based on the sequential leaching of rhenium first with a dilute solution of sulfuric or hydrochloric acid and then platinum with a more concentrated hydrochloric acid solution in the presence of an oxidizing agent is more effective. [Blokhin A.A., Kleandrov V.T., Gelman G.E., Murashkin Yu.V., Chumakova G.V., Abovsky N.D. Ion-exchange processes for the extraction of platinum and palladium from spent catalysts // Precious metals. Gems. - 2005. - No. 10, S.164-168].

In the analogue method, it was shown that when processing platinum-rhenium catalysts with dilute acid solutions, 5-7% of the platinum contained in the catalysts is leached together with rhenium. When processing the resulting solutions containing platinum and rhenium, platinum follows rhenium and is concentrated in ammonium perrenate, a finished product of the rhenium branch of the process. This fact leads to an increase in the irretrievable loss of platinum, as well as to a decrease in the content of the basic substance in ammonium perrenate. To eliminate the loss of platinum, it is proposed to extract it from solutions containing rhenium on selective Purolite S920 ion exchanger.

The disadvantage of this method of purification of rhenium from impurities of platinum is the introduction of an additional stage of sorption purification into the technological scheme of rhenium production and the associated increase in the number of different types of solutions requiring processing. The number of capacitive equipment is increasing. The number of solutions analyzes for the content of platinum and rhenium is increasing to ensure their high-quality separation, which leads to an increase in material and labor costs for obtaining finished products.

A known method of producing ammonium perrenate, in which on a weakly basic anion exchange resin is carried out sorption of rhenium from sulfuric acid solutions. After that, rhenium is stripped with an ammonia solution, the ammonia solution is evaporated and the rough ammonium perrenate is crystallized. Ammonium rough perrhenate is purified by recrystallization from a saturated aqueous solution, to which sodium sulfite is added at a temperature of 90-95 ° C. The solution is separated from the precipitate of impurities by filtration and cooled to crystallize ammonium perrenate. [RF patent No. 2355640. A method of producing ammonium perrenate, S. Temerov. Novozhilova V.I., publ. May 20, 2009, BI No. 14].

This method is the closest in technical essence to the claimed method and adopted as a prototype.

The disadvantage of the prototype method is that sodium sulfite is added to the solution at the final stage of purification of rough ammonium perrenate by recrystallization. The components contained in it - sodium and sulfur can contaminate the final product (ammonium perrenate) in the form of impurities. The content of sodium and sulfur in the finished product is regulated by TU 48-7-1-90. In addition, its soluble complex compounds formed upon purification from platinum are also found in the mother liquor. To remove these impurities from crystalline ammonium perrenate, it is necessary to thoroughly rinse it with water, which leads to return losses of ammonium perrenate with washing solutions, as well as an increase in the fraction of poorly soluble impurities, primarily potassium perrenate, in the finished product. To the greatest extent, this drawback is manifested in the industrial implementation of the method, where a large amount of crystalline precipitate is formed, heterogeneous in its particle size distribution, the washing of which with water on the filter does not provide the proper quality of the finished product. Washing the product with repulpation in water leads to an increase in the loss of rhenium and the cost of its production.

The proposed method is aimed at obtaining a technical result, which consists in improving the quality of ammonium perrenate by reducing the content of impurities of platinum, sodium, sulfur and other base elements in it.

The achievement of the technical result is ensured by the fact that sodium sulfite is added during evaporation of the ammonia solution, then a solution of calcium chloride is added, then the pulp is cooled and the precipitate of rough ammonium perrenate is filtered off, which is recrystallized from distilled water.

The essence of the proposed method lies in the fact that in an ammonia solution, sodium sulfite interacts with platinum for a long time with the formation of water-soluble aminosulfite complexes, which, together with an excess of other soluble salts, remain in the mother liquor when it is cooled and crystallization of rough ammonium perrenate. After filtering, the mother liquor is transferred to the stage of sorption concentration of rhenium, where rhenium is separated from impurities dissolved in water. The addition of calcium chloride to the solution leads to the precipitation together with ammonium perrenate of poorly soluble calcium sulfite (CaSO ₃ × 2H ₂ O), which, upon subsequent recrystallization of rough ammonium perrenate from distilled water, provides the pH of the solution necessary for the precipitation of base metals by hydrolysis and improves it filtration. Calcium sulfite also contributes to the additional purification of finished products from traces of platinum during recrystallization of ammonium perrenate, without contaminating the finished product with calcium and sulfur impurities due to the very low solubility (0.003 g / l) in aqueous solutions. Thus, a decrease in the content of platinum, sodium, sulfur and other impurities in the finished product is achieved, which leads to an increase in the quality of crystalline ammonium perrenate.

A solution of calcium chloride is added based on the binding of part of the sulfite ions to the precipitate of calcium sulfite, the amount of which is about 1% by weight of the emitted crude ammonium perrenate. This amount of calcium sulfite is sufficient to provide a solution pH of 6.8 ± 0.2 units during recrystallization, to improve the filtering of the precipitate of impurities during recrystallization of rough ammonium perrenate, and also to conduct additional purification of the finished product from platinum.

Usage example.

In a 200-liter column filled with weakly basic Purolite A-170 anion exchange resin, rhenium was sorbed from a sulfuric acid solution, and the column was washed with water to displace the mother liquor. Rhenium was desorbed with 1 m ^{3 of} 5% ammonia solution. 1 kg of anhydrous sodium sulfite was added to the obtained ammonia solution, after which the solution was evaporated to reduce the volume by 10 times. A solution of 100 g of calcium chloride in 1 l of water was added to the hot stripped solution, after which the pulp was cooled with stirring to a temperature of 25 ° C and the precipitate of rough ammonium perrenate was filtered. Received 110 l of a mother liquor containing 19.35 g / l of rhenium and 4.62 g / l of platinum, which was directed to the extraction of platinum and rhenium, and 25.1 kg of rough ammonium perrhenate with a moisture content of 8.5%. Ammonium rough perrhenate was sent for purification by recrystallization.

12.0 kg of ammonium rough perrenate were dissolved in 45 L of distilled water at a temperature of 95 ° C with stirring; the resulting solution was filtered from suspension into a crystallizer, where it was cooled to a temperature of 23 ° C. The precipitated ammonium perrenate crystals were filtered on a suction filter, washed with 5 L of distilled water, and dried in an oven at 105 ° C. Received 8.82 kg of ammonium perrenate, the composition of which is shown in the table, and 50 l of the mother liquor containing 26.89 g / l of rhenium and 88 mg / l of platinum. The solution was used as a reverse solution for recrystallization of three portions of rough ammonium perrenate, after which it was directed to the stage of evaporation and crystallization of ammonium perrenate.

The use of the present invention in the production of ammonium perrenate from catalysts containing platinum and rhenium allows to reduce the cost of purification of rough ammonium perrenate, to ensure the production of ammonium perrenate corresponding to the grade AR-0 according to TU 48-7-1-90, and also to reduce the platinum content in finished products.

Table Ammonium perrenate quality indicators Name The content of impurities, ppm (10 ^-4 %) TU 48-7-1-90, AR-0 Prototype The inventive method K 50,0 7-9 37.0 Na 10.0 5-6 <5.0 Ca 10.0 0.8-1.0 <1.0 Mg 2.0 1,0 <1.0 Al 5,0 2.0 <1.0 Fe 5,0 2.0 <1.0 Mn 2.0 0.1 <0.5 Cu 0.5 0.1 <0.5 Mo 5,0 0.4-1.0 <5.0 Ni 2.0 0.2-0.5 <2.0 S 20,0 17-20 <10.0 P 10.0 1,0 <10.0 Si 10.0 2.0 <2.0 Ft - 6-76 <2.0 Re (%) > 69.0 69.41 69.41

Claims (1)

A method of producing ammonium perrenate, including desorption of rhenium from a saturated weakly basic anion exchange resin with an ammonia solution, evaporation of an ammonia solution, crystallization of a rough ammonium perrenate and its purification by recrystallization, characterized in that sodium sulfite is added to the evaporation of the ammonia solution, calcium chloride is added to the evaporated solution, the pulp is cooled and the precipitate of crude ammonium perrenate is filtered off, which is recrystallized from distilled water.