RU2564187C2 - Method of platinum-group metals extraction from spent catalysts on carriers out of aluminium oxide - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: spent catalysts on the carriers out of aluminium oxide are mixed with fluxes, the obtained charge is melted on metal accelerator at temperature 1500÷1800°C during several stages with drainage after each stage of the produced slag, and with melting of successive charge portion on accelerator of the previous melting with separation of the alloy of platinum-group metals and accelerator. As flux the wastes and industrial products of refining are used, they include slags, ventilation system dusts, and salts after master solution evaporation at ratio by weight: spent catalysts:slags:ventilation system dusts:salts after master solutions evaporation = 1:0.5÷1.5: max. 0.3:max. 0.3.

EFFECT: increased degree of extraction of platinum-group metals, including from wastes with low content of precious metals.

2 cl, 2 tbl, 2 ex

Description

The invention relates to metallurgy of precious and rare metals and can be used in the processing of deactivated alumina-based catalysts containing platinum group metals (hereinafter referred to as catalysts).

There are a large number of methods for processing catalysts containing platinum metals [M.A. Meretukov, A.M. Orlov. Metallurgy of precious metals (foreign experience). - M.: Metallurgy, 1990, p. 341-343].

A review of the processing methods of alumina-based catalysts shows that these methods can be divided into three main groups:

- dissolution of the catalyst base with obtaining and further processing of the concentrate of recoverable components;

- dissolution of recoverable components with acid solutions with oxidizing agents, followed by processing solutions, as a rule, by sorption methods;

- smelting catalysts on a metal collector.

The first two groups of methods are not universal, because the basis of the catalyst - alumina - is most common in two versions - alpha form and gamma form. Typically, these two forms are mixed. Alumina in alpha form is poorly soluble in both acids and alkalis, which in some cases does not allow to obtain rich concentrates according to the first group of methods. Alumina in gamma form dissolves in acids, which leads to increased consumption of reagents and difficulties in filtering the pulps, if methods from the 2nd group are used. In the third group of methods, the base of the catalyst, alumina, is melted onto the collector, the melting temperature of which is about 1800 ° C, and to obtain slags with a sufficiently low viscosity, they must be heated to 1950 ÷ 2000 ° C. Melting at these temperatures leads to increased energy consumption and accelerated wear of the lining of furnaces. To lower the melting temperature, fluxes are used - borax, soda, fluorspar and others, which, firstly, increases the cost of processing, and secondly, increases the amount of production waste (slag) that must be disposed of.

In the patent RU 2306347 C1 (published on September 20, 2007) a method for processing catalysts containing platinum metals and rhenium on alumina supports is described. The method includes burning catalysts, leaching it in sulfuric acid, adding electrostatic precipitators to the dust concentrate, precipitating platinum metals from the solution by cementation, separating the sulfuric acid solution from the insoluble residue by filtration, sorbing rhenium from the solution, smelting the insoluble residue with the addition of fluxes.

The disadvantages of the above method are:

- high consumption of sulfuric acid to dissolve the catalyst base;

- incomplete dissolution of the catalyst base, if the latter partially or completely consists of aluminum oxide in alpha form, which reduces or practically reduces to zero the degree of concentration of platinoids in the insoluble residue and complicates its further processing;

- the need to wash cake from sulfate leaching of the catalyst;

- the need for disposal of a large number of acidic (in this case, sulfate) solutions.

A known method of extracting precious metals from alumina materials and waste, such as alumina-platinum catalyst (SU 171116 A1, publ. 01.01.1965). Platinum is recovered from alumina-platinum catalysts with cryolite as solvent by liquid aluminum extraction. Isolation of platinum from an aluminoplatinum alloy is carried out using sulfuric acid. The platinum recovery rate is 90%.

The disadvantage of this method is the formation of a large amount of waste in the form of a solid solution of aluminum oxide in cryolite.

In the patent RU 2023036 C2 (publ. 15.11.1994) a method for extracting platinum from recycled materials is disclosed. Secondary raw materials are glass and glass wastes. Secondary raw materials are smelted at a temperature not lower than 1700 ° C in the presence of a metal collector with metal separation. The mass ratio of the starting material and the collector is maintained equal to 1.5-2.5: 1, melting is carried out with a slag viscosity of not more than 10 Pa · s, and platinum is isolated from the material containing it by electrolysis.

In the journal "Non-ferrous metals", 1989, No. 2, p. 57-59 describes a method for the extraction of precious metals from secondary raw materials by melting to a metal collector. When this raw material is pre-mixed with slag-forming oxides and litharge.

The disadvantage of the last two methods is the use of slag-forming fluxes during smelting, which increases the cost and amount of production waste.

A known method of extracting a metal component (platinum) from spent catalysts based on aluminum oxide (Metallurgy of noble metals, under the editorship of L.V. Chugaev, M .: Metallurgy, 1987, S. 426). The catalyst (multicomponent material) is melted with the addition of calcium compounds, for example, calcium fluoride. Copper is added to form the alloy. Melting is carried out at a temperature in the range of 1500-1550 ° C. The disadvantage is the use of fluorine-containing fluxes, which are highly aggressive in relation to the lining of furnaces or crucibles, which leads to increased wear.

In the patent RU 2248406 C1 (publ. 20.03.2005) a method for separating a multicomponent material containing metal components is described. Such materials include, for example, spent catalysts based on platinum supported on alumina, which are used in hydrogenation, dehydrogenation, and cracking processes. The method consists in the fact that the multicomponent material is pre-impregnated with a salt solution of the metal of the collector in an amount providing a mass content in the melt of the metal of the collector (metal-solvent) in excess of the content of metal components. Then it is calcined and melted in a reducing atmosphere with the addition of slag-forming flux based on metal fluorides, possibly with calcium oxide at a temperature of 1000-1800 ° C. After melting, the melt is mixed and kept in a liquid state for a time sufficient to separate the slag and metal phases. Then produce the resulting slag and metal, and their separation is carried out mechanically after they harden. Analysis of the obtained metal showed that 95% of platinum goes into a copper-based ingot, and the rest of the metal is lost in slag. When used under similar conditions with the addition of the same amount of collector metal in the form of a copper powder with a grain size of 20 μm, only 78% of platinum passes into the copper based ingot, the rest - 22% - remains in the slag.

The disadvantages of this method:

- the use of fluorine-containing slag-forming fluxes (CaF ₂ ) during smelting leads to increased wear of the furnace lining or crucibles, increases the amount of production waste and the cost of reagents;

- when the salt of the metal of the collector is decomposed, with the solution of which a multicomponent material (catalyst) is impregnated, environmentally harmful gases, for example NO _x , are emitted if copper nitrate is used, which necessitates the creation of an expensive gas purification system;

- according to the description of the method involves a single use of the collector for the extraction of metals from the base of a multicomponent material, this eliminates the concentration of the extracted components in the collector, which leads to a large consumption of resources during the processing of the collector.

The specified method is the closest to the claimed method and is its prototype.

The objective of the present invention is to simplify the processing scheme of the above catalysts and reduce the consumption of material resources for their processing.

The problem is solved as follows. First, a certain amount of slag is formed, which is formed during the melting of raw materials and intermediate products of refining production (hereinafter referred to as intermediate products) containing noble metals at concentrations higher than dump metals, and also base metals, for example, iron, and the concentration of the latter should be many times higher than the concentration of precious metals. Slag is melted in a reducing medium and heated to a temperature above the melting point of iron (1550 ÷ 1650 ° C). At the same time, an alloy is formed at the bottom of the bath, consisting mainly of base metals, which is subsequently a collector of precious metals. Slag is drained, leaving a boundary layer of slag and a collector in the furnace. The following portion of slag is loaded onto the molten material remaining in the furnace, melted, heated, and drained in the manner described above. The operation is repeated until a sufficient amount of collector is recovered.

The mixture obtained by mixing the catalysts with waste from refining production (hereinafter referred to as waste) and by-products selected from slags from the smelting of raw materials and rich by-products, dusts generated by the smelting of industrial products and captured by ventilation systems (hereinafter dust), salts from evaporation of mother liquors (hereinafter referred to as salts) , usually in the form of a mixture thereof, is melted onto a metal collector formed by the above method. These wastes and industrial products play the role of fluxes that reduce the melting point of the catalyst base and slag viscosity. Melting is carried out at a temperature of 1500-1800 ° C, usually in several stages. After each stage, the resulting slag is poured, and a new portion of the charge is loaded and melted onto the collector from the previous melting, with the result that an alloy of precious metals with a collector is released. The implementation of these methods allows to bring the concentration of precious metals in the reservoir to optimal values. If necessary, lime, glass, sand are added to further reduce the viscosity of the resulting slag. After melting the charge, the metals present in the intermediate products, waste, and catalyst coalesce, forming larger drops of the alloy than when melting the catalyst separately, thereby creating conditions for more complete absorption of metals by the collector and, ultimately, increasing the recovery of platinum metals from the catalyst . Along the way, noble metals are additionally extracted into the collector from industrial products and wastes used as fluxes.

As a result, the method according to the invention, due to the use of intermediate products of refining production, eliminates the introduction of metal into the technological process for the formation of a collector and subsequently the separation of this metal and precious metals, which simplifies the technological scheme and reduces production costs. Thus, the task is completed.

In more detail, the method is as follows.

For the formation of a collector, industrial products are selected with a total noble metal content of not more than 0.005% and a base metal amount (iron, cobalt, nickel, copper, etc.) of at least 0.3%. Selected industrial products are melted according to the method described above to set the required amount of collector, consisting mainly of an alloy of base metals. The required amount of collector depends on the volume of the furnace. The collector is heated until completely melted and a mixture of catalyst and intermediate products is loaded onto it. The composition of the mixture, mass. parts: catalyst: slags: dust: salts = 1: 0.5 ÷ 1.5: not more than 0.3: not more than 0.3. The mixture in the melting furnace is loaded portionwise onto the molten collector, the contents of the furnace are heated to a temperature of 1500 ÷ 1800 ° C to obtain slags of the required viscosity. The viscosity of the slag is determined visually. If necessary, lime, glass, sand are added to further reduce the viscosity of the resulting slag. Next, the furnace is turned off and put on sludge for 5 ÷ 10 minutes, after which the slag is drained, leaving the collector and the boundary layer of slag in the furnace, the next portion of the charge is loaded onto the collector and the boundary layer of slag, and so on. The total amount of catalyst and industrial products charged for smelting is calculated on the basis that the concentration of each of the noble metals in the collector does not exceed 15%. The products of the last heat are poured into the mold and, after cooling, the slags are separated from the collector alloy. Slag will be tested and sold as production waste. An alloy containing mainly metals recovered from industrial products, as well as noble metals extracted from catalysts and industrial products, is processed by known methods, for example, according to the scheme: granulation of the alloy, hydrochlorination or dissolution of granules in "royal vodka", filtration, deposition and refining of silver , selective precipitation from a solution of gold and platinum metals and their further refining.

Example 1

For the experiments, they took the catalyst PR-20 TU 2177-008-03533913-99 with a concentration of platinum of 0.37%. For the smelting of the collector, an intermediate product of 3 kg mass with an iron concentration of 1.5% (45 g) was used, and the amount of noble metals was 0.004% (0.12 g).

Prepared a mixture of catalyst with intermediate products, the composition of which is presented in table 1, and was divided into 10 parts of 482 g.

Melting was carried out in an induction furnace IST-0.06 in a graphite crucible. First, the industrial product was smelted for smelting the collector, and 30 g of an alloy based on iron was obtained - the collector. The collector was melted, a portion of the charge was loaded onto it and the contents of the furnace were heated until melted. To reduce the viscosity of the slag was added 20 g of lime and 15 g of glass break.

Table 1. The composition of the charge 1.

Sufficient viscosity slags acquired at a temperature of 1710 ° C. At this temperature, and with the furnace turned on, they held it for 10 minutes, after which they covered the crucible with a graphite chamotte lid, turned off the furnace and stood for 5 minutes. Then the slag was drained, leaving the collector and the boundary layer of slag in the crucible, loaded a new portion of the charge, repeated melting, and so on. After melting the last portion of the charge, the boundary layer of slag together with the metal was poured into a cast iron mold and, after cooling, the slag was separated from the metal. Slag from the entire series of heats and metal was weighed, crushed, and tested. The results are presented in table 2.

The calculation shows that the total extraction of metals from the catalyst and intermediate products into the collector is: platinum - 98.1%; gold - 65.8%, silver - 94.3%, palladium - 55.0%. The platinum content in industrial products and production waste can be neglected. Then the recovery of platinum from the catalyst will be at least 98%.

The recovery was calculated for each metal as the ratio of the mass of metal in the collector to the mass of metal loaded on the heat, expressed as a percentage.

Example 2

Methodically, the melting was carried out, as in example 1, but instead of glass, pure river sand was added in the same amount. Slag acquired the required viscosity at a temperature of 1720 ° C. Extraction of metals from the catalyst, waste and industrial products into the collector amounted to: platinum - 98.1%; gold - 75.0%, silver - 95.6%, palladium - 58.5%. The recovery of platinum from the catalyst was at least 98%.

Claims (2)

1. A method of extracting platinum metals from spent catalysts on alumina supports, comprising batching spent catalysts with fluxes, smelting the resulting mixture onto a metal collector at a temperature of 1500 ÷ 1800 ° C in several stages with discharge after each stage of slag formed and melting another portion of the mixture on the collector from the previous smelting with the release of an alloy of platinum metals with a collector, characterized in that waste products and intermediate products of refining production are used as fluxes, toyaschie from slags, dusts ventilation and salts by evaporating the mother liquors, with a ratio, by weight. including: spent catalysts: slags: dust of ventilation systems: salts from evaporation of the mother liquor = 1: 0.5 ÷ 1.5: not more than 0.3: not more than 0.3. 2. The method according to p. 1, characterized in that the ratio of the mass of the collector and the total mass of spent catalysts with intermediate products of refining production is calculated to ensure the concentration of noble metals in the collector after melting is not higher than 15 wt. % for each metal.