RU2140999C1 - Method of processing of spent catalytic agents containing metals of platinum group - Google Patents

Abstract

FIELD: metallurgy of noble metals, extraction of metals of platinum group from spent catalytic agents based on aluminum oxide and carrying platinum or palladium. SUBSTANCE: method of processing of spent catalytic agents containing platinum metals based on aluminum oxide consists in milling, in blending with hydroxide of alkaline metal, in caking, in water leaching of cake with transfer of sodium aluminate to solution, in filtration and acidic treatment of solid cake with winning of concentrate of platinum metals. In correspondence with invention milling is conducted to reduce mixture to size of - 3.0 mm, blending is performed with ratio of hydroxide of alkaline metal-catalytic agent (0.8-1.2): 1.0, caking is carried out at temperature of 400-700 C in the course of 1.0-2.0 h, water leaching is conducted in presence of alkaline reagent, acidic treatment at pH=1.5-2.0 is carried out with injection of inorganic reductant. Sodium or potassium hydroxide is used as hydroxide of alkaline metal. Sodium or potassium hydroxide with concentration 10.0-20.0 g/l is used as hydroxide of alkaline reagent. Compounds of copper (I), for example, copper oxide (I) with grain size -0.05 mm with proportion of metals of platinum group 0.2-0.5 from stoichiometry of reducing reaction is used as inorganic reductant. Solution after water leaching is directed for neutralization with winning of commodity compounds of aluminum. Water leaching is conducted with S:L=1:(3-5) in the course of 1.0-2.0 h, acidic treatment is carried out with S:L=1:(3-5) at temperature of 50-90 C and mixing. EFFECT: reduced losses of platinum metals, increased quality of end product-concentrate of platinum metals. 7 cl, 3 tbl

Description

 The invention relates to the metallurgy of noble metals and can be used in the extraction of platinum group metals from spent catalysts, including automotive, based on aluminum, silicon and magnesium oxides containing platinum or palladium.

A known method of processing spent catalysts based on aluminum, silicon and magnesium oxides containing platinum metals, including opening the base by treatment with an alkaline solution in an autoclave. The autopsy is carried out at a temperature of 150 ^o C, a pressure of 10 ATM for 4 hours. Extraction of platinum metals to a solid residue of 99%. About 1% of platinum goes into solution.

 The disadvantages of the method are the need for fine grinding of the starting material (-200 mesh), the complexity of the hardware design (autoclaves) and limitations on the modification of aluminum oxide. Alumina of the α-modification does not open under these conditions (see Precious Metals'89. Ed. By M.C. Jha and S. D. Hill The Minerals, Metals and Materials Soc., 1988, C.512).

A known method of processing spent platinum-containing catalysts, including opening the base by sintering with sodium hydroxide in a reducing medium. Sintering is carried out at a temperature of 900-950 ^o C with the introduction of carbon. Speck is leached with a solution of sulfuric acid in the presence of aluminum to cement platinum that has passed into solution. Platinum remains in an insoluble residue.

 The disadvantages of the method are its high energy intensity and high consumption of reagents at the stage of leaching cake (see US Pat. RU 2100072 C1 (Omsk State University) 12/27/97).

 A known method of processing spent catalysts based on alumina containing platinum group metals, including sintering with caustic soda to convert alumina to sodium aluminate. The cake is leached with water, while sodium aluminate passes into solution, and the platinum group metals remain in the solid residue. The residue is separated by filtration, treated with hydrochloric acid to remove the remaining impurities, filtered off, washed and dried (see I.N. Maslenitsky, L.V. Chugaev. Metallurgy of noble metals. M: Metallurgy, 1972, p. 356-357). The resulting platinum metal concentrate is sent for refining.

 The disadvantages of the method are the inevitability of losses of platinum metals at the stage of acid treatment and a low degree of concentration of the concentrate, because hydrolysis of sodium aluminate is possible at the stage of water leaching of cake.

 The technical result of the claimed invention is to reduce the loss of platinum metals and improving the quality of the final product is a concentrate of platinum metals.

This is achieved by the fact that in the method of processing spent catalysts containing platinum group metals on the basis of aluminum oxide, including grinding, batching with alkali metal hydroxide, sintering, aqueous leaching of cake with the conversion of sodium aluminate into solution, filtration and acid treatment of the solid residue to obtain platinum metal concentrate, according to the invention, grinding is carried out to -3 mm, charge at a ratio of alkali metal hydroxide: catalyst (0.8-1.2): 1, sintering at a temperature of 400-700 ^o C within 1-2 hours, aqueous leaching in the presence of an alkaline reagent, and acid treatment in the presence of an inorganic reducing agent. In this case, sodium or potassium hydroxide is used as an alkali metal hydroxide during sintering, a solution of sodium or potassium hydroxide with a concentration of 10-20 g / l is used as an alkaline reagent for water leaching, and copper (I) compounds are used as a reducing agent in the treatment of the residue with acid fineness of -0.05 mm with a ratio of platinum group metals 0.2-0.5 from the stoichiometry of the reduction reaction of platinum metals; water leaching is carried out at T: W = 1: (3-5) for 1-2 hours, and the acid treatment is carried out with a solution of hydrochloric or sulfuric acid at T: W = 1: (3-5), a temperature of 50-90 ^o C and stirring.

 The invention consists in the following.

During sintering of the catalyst with alkali, aluminum oxide is converted to sodium aluminate. The claimed parameters - temperature 400-700 ^o With, the ratio of alkaline reagent and catalyst (0.8-1.2): 1 and the process time of 1-2 hours - ensure the completeness of the opening of the base. Water leaching in the presence of an alkaline reagent prevents the hydrolysis of sodium aluminate and thereby ensures the most complete transition of aluminum into solution.

 The introduction of a reducing agent at the stage of acid treatment of the residue creates a redox potential in the system that prevents the oxidation and transition of platinum metals into solution. Maintaining a pH of 1.5-2.0 at the stage of acid treatment provides high levels of purification from impurities and enrichment of the concentrate. Modes of acid treatment can intensify the process of concentrate enrichment. The sodium aluminate solution can be neutralized and sent to obtain various commodity aluminum compounds.

 The combination of the claimed techniques and modes allows you to get suitable for refining concentrate with a platinum content of at least 40%, while the extraction of platinum metals 99.1-99.9%.

Justification of the parameters
The grinding of the catalyst to -3 mm is necessary for its complete opening during sintering. A decrease in the ratio of alkaline reagent to catalyst in the charge of less than 0.8: 1 does not provide a complete transition of alumina to sodium aluminate, and an increase of more than 1.2: 1 leads to irrational consumption of the reagent.

At temperatures below 400 ^o C and a sintering time of less than 1 hour, the base is not completely opened, and an increase in temperature of more than 700 ^o C and a time of more than 2 hours does not improve the performance of the opening process, but leads to an excessive consumption of electricity.

 When the concentration of alkaline reagent is less than 10 g / l at the stage of water leaching, hydrolysis of sodium aluminate and the incomplete transition to an aluminum solution are possible, and a concentration above 20 g / l does not intensify its dissolution, and the reagent consumption is irrational.

 Acid treatment of the residue at a pH of more than 2.0 worsens the conditions for the passage of impurity components into the solution and reduces the concentration of the concentrate, and lowering the pH below 1.5 does not increase the cleaning efficiency.

 The use of copper (I) oxide as a reducing agent for a given size and consumption creates a redox potential that prevents the transfer of platinum metals in highly active and finely dispersed form into solution.

 The ratio of T: W = 1: (3: 5) during aqueous and acid leaching is the most technologically advanced, because creates the conditions for the most complete leaching of soluble components without irrational increase in material flows.

 The specified temperature regime of acid treatment intensifies the dissolution process.

Example
Spent alumina-based palladium catalyst containing (wt.%): Pd 1.4; Σ Fe, Ni, Cu, Si 1, Al ₂ O _{3 the} rest, the size of -3 mm is mixed with sodium hydroxide in a ratio of 1: 1 and sintered at a temperature of 550 ^o C for 1.5 hours. The cake was leached with water with the introduction of 15 g / l sodium hydroxide at T: W = 1: 4 for 1.5 hours and then filtered. The solid residue is treated with stirring with a solution of hydrochloric acid at a pH of 1.8 and a temperature of 70 ^o C, T: W = 1: 4 in the presence of copper oxide (I). Copper oxide (I) with a particle size of 0.05 mm is introduced at the rate of 0.3 of the stoichiometry of the palladium reduction reaction. After processing, the pulp is filtered, and the residue is dried.

 The recovery of palladium in concentrate is 99.8%, and the palladium content in the concentrate is 53%.

 The results of the method for other values of the declared parameters are presented in tables 1-3.

 In the table. 1 shows the results of the extraction of platinum group metals upon opening the catalysts with a particle size of -3 mm by sintering with sodium hydroxide in the declared parameter values.

Water leaching of cake is carried out in the presence of alkali in an amount of 15 g / l at T: W = 1: 4, time 1.5 hours; the acid treatment of the cake is carried out with a solution of hydrochloric acid in the presence of copper oxide (I) with a ratio of 0.3% from the platinum group metals from the stoichiometry of the reduction reaction, at a temperature of 70 ^° C., T: W = 1: 4 with stirring.

In the table. 2 shows the results of the extraction of platinum group metals in the processing of spent catalysts with a grain size of -3 mm with aqueous leaching of cake in the presence of sodium hydroxide in the declared values of the parameters. The initial catalyst was blended with sodium hydroxide in a ratio of 1: 1 and sintered at a temperature of 600 ^o C.

The residue after water leaching was subjected to acid treatment with a solution of hydrochloric acid at pH 1.5 with stirring, T: W = 1: 4, a temperature of 70 ^o C and the introduction of copper oxide (I) at a ratio of platinum group metals 0.3 from the stoichiometry of the reduction reaction .

In the table. Figure 3 shows the results of the extraction of platinum group metals upon opening the catalysts with a particle size of -3 mm. Sintering was carried out at a ratio of sodium hydroxide with a catalyst of 1: 1, a temperature of 500 ^o C, a time of 1.5 hours.

 Water leaching of cake was carried out with the introduction of a solution of sodium hydroxide with a concentration of 15 g / l, T: W = 1: 4, time 1 hour. The acid treatment of the solid residue was carried out with a solution of sulfuric acid at the declared values of the parameters in the presence of copper oxide (I).

Claims (8)

1. A method of processing spent catalysts containing platinum metals based on alumina, including grinding, blending with alkali metal hydroxide, sintering, aqueous leaching of cake with the conversion of sodium aluminate into solution, filtration and acid treatment of the solid residue to obtain a platinum metal concentrate, characterized the fact that grinding is carried out to -3 mm, blending at a ratio of alkali metal hydroxide: catalyst (0.8 - 1.2): 1, sintering at a temperature of 400 - 700 ^o C for 1 - 2 hours, aqueous leaching in the presence of an alkaline reagent, and acid treatment at pH 1.5 - 2.0 with the introduction of an inorganic reducing agent.  2. The method according to claim 1, characterized in that as the alkali metal hydroxide during sintering, sodium or potassium hydroxide is used.  3. The method according to claim 1 or 2, characterized in that sodium hydroxide or potassium hydroxide with a concentration of 10 to 20 g / l is used as an alkaline reagent for aqueous leaching.  4. The method according to any one of claims 1 to 3, characterized in that copper (I) compounds are used as an inorganic reducing agent.  5. The method according to any one of claims 1 to 4, characterized in that as the copper (I) compound, copper (I) oxide with a grain size of -0.05 mm is used, with a ratio of platinum group metals 0.2-0.5 from stoichiometry recovery reactions.  6. The method according to any one of claims 1 to 5, characterized in that the solution after water leaching is sent to neutralization, followed by obtaining marketable aluminum compounds.  7. The method according to any one of claims 1 to 6, characterized in that the water leaching is carried out at T: W = 1: (3-5) for 1 to 2 hours. 8. The method according to any one of claims 1 to 7, characterized in that the acid treatment is carried out with a solution of hydrochloric or sulfuric acid at T: W = 1: (3 - 5), a temperature of 50 - 90 ^o C and stirring.

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