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INVENTION
Patent of the Russian Federation RU2083705
METHOD OF REMOVING NOBLE METALS
FROM ALUMINUM MATERIALS AND WASTE PRODUCTION
The name of the inventor: Baum Ya.M .; Yurov SS; Borisov Yu.V.
The name of the patent holder: Closed Joint-Stock Company "Leprekon-666"
Address for correspondence:
The effective date of the patent: 1995.12.13
Use: refers to the recovery of precious metals from alumina materials and production waste, mainly from spent alumina based catalysts containing platinum. Essence: the starting material is mixed with alkali, the mixture is sintered at 500-850 ° C, and then the resulting speck is treated with water. As a result of the interaction between the sinter and water, a precipitate containing a noble metal precipitates. The precipitate is separated from the aluminate solution and treated with an acid to obtain an insoluble composition containing a noble metal at a concentration of up to 30%. Further processing of the said composition, the concentration of the noble metal is adjusted to more than 80%.
DESCRIPTION OF THE INVENTION
The invention relates to the regeneration of platinum group metals from alumina materials and alumina-based waste products, for example from spent alumina based catalysts containing platinum and used in the petrochemical industry for the production of gasoline.
A method for extracting platinum and palladium from spent catalysts based on aluminum oxide is known in which platinum group metals are converted to water-soluble chlorides by chlorinating the catalyst with gaseous chlorine, with the clay being resistant to chlorine remaining in an insoluble form. Chlorination is carried out in a tube furnace at a temperature of 300-500 ° C. After chlorination, the solution is separated from the residue, the residue is thoroughly washed with hot water and a solution of acids. From the solution, the metals of the platinum group are separated by carburizing with aluminum, magnesium or other base metals [1]
The disadvantage of this method is its great environmental hazard to the environment and an immediate danger to humans due to the high toxic properties of chlorine (a danger to human life).
A method is known for the recovery of noble metals, for example, platinum from an alumina based catalyst in which cryolite is injected into the molten aluminum bath and the spent catalyst is melted therein at 970-980 ° C. In this case, platinum is extracted, and cryolite is saturated with alumina. The mixture of aluminum and platinum is poured into water and granules are obtained, from which aluminum is leached with a 10-15% solution of sulfuric acid at a temperature of 100-105 ° C for 4-5 hours [2]
The disadvantage of this method is the high energy costs associated with the need to melt aluminum and then dissolve cryolite in it at 970-980 ° C.
A method for recovering platinum group metals from spent catalysts is known in which a catalyst, copper and / or copper oxide, a flux and a reducing component are mixed. The mixture is then heated and melted to form a copper layer in which platinum is absorbed and a layer of (other) oxide. A layer of metallic copper is separated and oxygen or air is introduced into this layer to form two layers of a layer of partially oxidized copper and a layer of metallic copper with a high content of platinum, the latter layer being separated.
A disadvantage of this method is the need to use expensive equipment in it to ensure the melting of the components of the initial mixture and high energy costs. In addition, this method poses a threat to the environment and human [3]
The proposed method, in contrast to the prototype, provides for a comprehensive processing of alumina materials and wastes containing noble metals, for example platinum, to obtain a granular powder with a noble metal content of up to 80% and an aluminate solution that is taken for further processing. The method makes it possible to significantly reduce energy costs for obtaining precious metal, simplify and reduce the cost of technological equipment, and reduce environmental pollution by the release of harmful gases during the process.
This technical result is achieved by using alkali as a flux in the method for extracting noble metals from alumina materials and production waste containing the process of mixing an alumina material containing a noble metal with a flux. And the resulting mixture is sintered at a temperature of 500-850 ° C and kept until the cake hardens. The cake is then treated with water and the resulting mass is left to settle before it is separated into a precipitate containing a noble metal and an aluminate solution. The precipitate is removed and treated with an acid to obtain a composition with a high content of noble metal. The aluminate solution is fed for further processing.
The figure shows a scheme for implementing the proposed method.
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The starting materials are alumina material, for example, spent catalyst based on alumina material with platinum, and flux, which is used as an alkali. Before mixing, the material and alkali are weighed to obtain the desired mixing ratio. The resulting mixture is introduced into the furnace and heated to 500-850 ° C. The mixture is sintered and the reaction takes place Example 1 . The starting materials are a spent catalyst based on alumina (used in the reforming of oil) with a platinum content of 0.5% and alkali NaOH. The influence of the ratio between the weight of the catalyst and the alkali mass on the efficiency of the process was determined. The following ratios were used between the masses of these components: 1: 1; 1: 2; 1: 3. It was found that the ratio of 1: 2 between Al 2 O 3 and NaOH is optimal. For example, 0.5 kg of catalyst and 0.75 kg of alkali were taken during the experiments. The mixture was placed in a thermal (electric) furnace and heated for about 2 hours to a temperature of about 800 ° C. As a result of heating, the mixture was converted into a cake, removing the residues of water vapor, |
After settling, the yellow aluminate solution was drained. And the precipitate was dried and weighed. Its mass is 85 g (0.085 kg), which is 17% of the initial mass of the catalyst.
After acid treatment, the mass of the finished product was 45 g, whereas at a ratio of 1: 2 the weight of the finished product was less than 10 g.
Thus, a decrease in the amount of alkali below the 1: 2 ratio (alumina-alumina) resulted in an increase in the mass of the insoluble precipitate, and an increase in alkali, above the named ratio, did not improve the solubility of alumina and led to an irrational increase in its consumption.
Example 2 . The dependence of the time and completeness of the process on temperature was established experimentally. For each temperature, the minimum residence time of the cake in the furnace was established.
For example, 30 kg of catalyst, 60 kg of alkali were taken. The mixture was placed in a thermal oven and heated for about 2 hours to 800 ° C. After unloading, the spec was treated with water. The mass was left to stand for 1.5 hours until a cream-colored precipitate containing platinum and a solution containing aluminates were obtained. The solution was drained and the precipitate was washed with water to remove residual alkali in order to reduce the acid consumption in the next step. We took 4-5 kg of oxalic acid. In a container with a precipitate with a platinum content of 8-10%, up to 30 liters of water was added and heated to boiling, then oxalic acid was added in portions to the vessel. As a result of the reaction, a black precipitate formed, which takes about half an hour to settle. The resulting precipitate was washed again with water and dried to a powder of 200 g. The powder was then calcined. The content of platinum in the resulting mass was 80%
Reducing the temperature to 500 o C leads to an increase in the holding time to 3 hours, and its increase in excess of 800 o C entails an increase in energy costs. Not leading to an increase in the efficiency of the process.
Thus, based on the foregoing, it follows that the proposed method compared with the prototype is more economical, since it is not required to melt the catalyst, a simpler and therefore cheaper equipment is used to implement the method, there is no need for copper. The proposed method is much safer for the environment, since the melting process, accompanied by the emission of harmful gases, is excluded.
The use of simple equipment and inexpensive components - alkali and acid in the process makes it highly technological and provides successful application in the industry.
CLAIM
1. A process for recovering precious metals from alumina materials and production wastes, preferably from spent catalysts, comprising mixing the particulate material with a flux, characterized in that an alkali is used as the flux, and the resulting mixture is sintered at 500 ° -850 ° C. and maintained until the cake solidifies , The cake is treated with water and the resulting mass is separated into a noble metal containing residue and a solution of aluminates, the precipitate is treated with an acid to obtain an insoluble composition containing a noble metal, followed by washing with water, drying and calcination, and the aluminate solution is removed.
2. A process according to claim 1, characterized in that oxalic acid is used as the acid.
3. A process according to claim 1 or 2, characterized in that the cake is treated with water at 70.degree.-100.degree . C. and is allowed to settle until the resulting mass is separated into a precipitate containing a noble metal and a solution of aluminates.
4. A process according to claim 1, characterized in that the weight ratio of alkali to catalyst is 1 1 3.
print version
Date of publication 14.03.2007gg
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