RU2618024C1 - Method of extracting cerium - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method comprises breakage of iron-potassium catalyst waste, calcining the crushed catalyst at a temperature of 650-800°C for 3-6 hours and its subsequent cooling to room temperature, the dissolution of the calcined catalyst in concentrated hydrochloric acid in a ratio of catalyst: acid = 1:8-1:10, heating the resultant solution to boiling, and holding at reflux temperature for 30-120 minutes, extract solution for crystallisation of cerium dioxide for 3-12 hours at negative temperatures down to minus 20°C, obtaining a precipitate, separating the precipitate from the stock solution by decanting and filtering, washing the precipitate on the filter from an iron compound, drying the precipitate to constant weight with obtaining cerium.

EFFECT: increased yield of cerium.

1 dwg, 1 tbl, 6 ex

Description

The present invention relates to the chemical industry, and in particular to a method for processing spent iron-potassium catalysts for the dehydrogenation of olefinic hydrocarbons or other materials of a similar composition with the extraction of a valuable component from them - cerium. The obtained cerium dioxide can be used either in the production of iron-potassium catalysts as starting materials, or, as an independent reagent, in other industries.

Spent catalysts are multi-ton industrial waste, often containing substances that have a strong toxic effect on the environment. Such substances include oxides of many transition and rare earth elements. Most of the spent catalysts are subjected to simple disposal, which is dangerous and disadvantageous from both an environmental and economic point of view. Spent catalysts are valuable secondary raw materials, which leads to the inefficiency of their simple disposal; In addition, for the neutralization (reduction of toxicity of waste) of many catalysts, special technologies are needed, as well as specially equipped landfills, the equipment costs of which are very high. All this indicates that the recycling of spent catalysts, or recycling, is an urgent task.

Modern catalysts for the dehydrogenation of olefin hydrocarbons in chemical and phase composition can be attributed to the most complex in the processes of organic synthesis. Their main component is α-Fe ₂ O ₃ , the initial content of which is 55-85% of the mass. Another mandatory component is any potassium compound (K ₂ O, K ₂ CO ₃ ), the concentration of which is 2-20% of the mass, in terms of K ₂ O. Oxides of transition and rare-earth elements - molybdenum - are also used as promoters. 2.5%, tungsten, vanadium, manganese, cerium (5-60% of the mass in the form of carbonates, oxides, nitrates and hydroxides) and nickel. The most expensive of these promoters is cerium, since its compound accounts for about 55% of the cost of the catalyst, so the primary task is to extract this particular component.

A known method for the separation of cerium [RF Application 2000122097 A, IPC ⁷ C01F 17/00, G21C 56/00, G21C 19/46, publ. 08/20/2002], in which the separation is carried out from solutions of irradiated materials, including extraction of cerium (IV) or berkelium (IV) with a D2EGFK solution and reextraction with nitric acid solutions. Before re-extraction of cerium or berkelium, simple saturated alcohols are introduced into the organic phase to a concentration that ensures complete recovery of cerium or berkelium, then they are re-extracted with a solution of nitric acid (~ 2 mol / L) that does not contain a reducing agent. The disadvantages of this method are the use of organic solvents that are toxic, and the inability to use the method due to the different nature of the recoverable elements from the mixture of ions in the catalyst in accordance with the invention.

A known method for the allocation of cerium [RU 2373299 C1, IPC C22B 59/00, B03D 1/00, publ. November 20, 2009], which relates to the production of pure rare-earth metals (REM) or their oxides from poor or man-made materials using the ion flotation method. A method for extracting cerium and yttrium ions from a solution involves ion flotation using a surfactant as a collector. Sodium dodecyl sulfate at a concentration corresponding to the stoichiometric reaction is used as a collector: Me + 3 + 3DS- = Me [DS-] 3, where Me + 3 is the cerium or yttrium cation, DS is the dodecyl sulfate ion. Moreover, for selective extraction of yttrium and separation of yttrium and cerium ions, ion flotation is carried out at pH = 5. The technical result is to increase the percentage of extraction and separation of cerium and yttrium ions.

The closest analogue to the claimed invention is the Cerium extraction method, RF patent No. 2495147, IPC С22В 59/00, С22В 3/10, B01J 23/10, published October 10, 2013, in which cerium is extracted from spent iron-potassium olefinic hydrocarbon dehydrogenation catalysts. In the specified method, the extraction of cerium is carried out as follows:

- spend grinding the spent catalyst;

- the crushed catalyst is calcined at a temperature of 650-800 ° C for 3-6 hours;

- after calcination, the catalyst is cooled to room temperature;

- then carry out the extraction of the cerium compounds, for which:

- spend the dissolution of the calcined catalyst in concentrated hydrochloric acid;

- heat the solution to a boil and maintain the solution at the boiling point (100-110 ° C) for 30-120 minutes;

- spend the exposure of the solution for crystallization of cerium dioxide for 3-12 hours at a temperature of 0- + 20 ° C;

- after receiving the precipitate, it is separated from the mother liquor by filtration, draining the solution from the surface of the precipitate onto the filter with a pore size of the filter material of not more than 2 microns;

- the filter cake is washed from the iron compound and dried to constant weight to obtain cerium dioxide.

For dissolution take concentrated hydrochloric acid in the ratio of catalyst: acid, equal to 1: 8-1: 10.

The described method provides only the incomplete extraction of cerium due to the high degree of solubility of cerium dioxide at a temperature of 0- + 20 ° C during its crystallization and the departure of this part together with the mother liquor during filtration.

The objective of the invention is to increase the degree of extraction of cerium as an expensive component from spent iron-potassium catalysts for the dehydrogenation of olefinic hydrocarbons to obtain high-purity cerium compounds.

The technical result is an increase in the yield of cerium due to a decrease in the solubility of cerium dioxide with a decrease in the crystallization temperature.

The problem is solved, and the technical result is achieved by the claimed method of extracting cerium from spent iron-potassium catalysts for the dehydrogenation of olefinic hydrocarbons, in which

- spend grinding the spent catalyst;

- the crushed catalyst is calcined at a temperature of 650-800 ° C for 3-6 hours;

- after calcination, the catalyst is cooled to room temperature;

- spend the dissolution of the calcined catalyst in concentrated hydrochloric acid;

- heat the solution to a boil and maintain the solution at the boiling point (100-110 ° C) for 30-120 minutes;

- spend the exposure of the solution for crystallization of cerium dioxide for 3-12 hours;

- after receiving the precipitate, it is separated from the mother liquor by filtration, draining the solution from the surface of the precipitate to the filter (decantation) with a pore size of the filter material of not more than 2 microns;

- the filter cake is washed from the iron compound and dried to constant weight to obtain cerium dioxide.

For dissolution take concentrated hydrochloric acid in the ratio of catalyst: acid, equal to 1: 8-1: 10.

The difference between the invention and the prototype is the exposure of the dissolved catalyst in concentrated hydrochloric acid for crystallization of cerium dioxide at negative temperatures not lower than minus 20 ° C to obtain a precipitate of cerium dioxide.

It is desirable to carry out the filtration process at a crystallization temperature, but if this technical possibility is not available, it can be carried out at room temperature, but quickly, without allowing the solution to heat up and the precipitate to dissolve. To establish equilibrium, a long exposure is needed; in fact, decantation was carried out at crystallization temperature.

Due to the low temperature, the solubility of cerium dioxide in acid decreases and during crystallization a greater amount of it passes into the precipitate, thereby increasing the yield of cerium dioxide in the process of its extraction.

The method used the following products and reagents:

- spent iron-potassium catalysts for the dehydrogenation of olefinic hydrocarbons (isoamylenes in isoprene):

- S6-34, Basf, Germany;

- KDOM-08, Russia, TU 2173-134-5766801-2005;

- KDO, Russia, TU 2173-134-5766801-2005;

- KDOM, Russia, TU 2173-134-5766801-2005;

- LCD, Russia, TU 2173-163-05766801-2011;

- hydrochloric acid, class A, GOST 3118-77;

- distilled water, GOST 6709-726709-72.

A method of processing iron-potassium catalyst for the dehydrogenation of olefinic hydrocarbons with the extraction of cerium is carried out as follows.

In accordance with the proposed method, spent catalysts for the dehydrogenation of alkyl aromatic and olefin hydrocarbons for the dehydrogenation of isoamylenes to isoprene of a composition close to catalysts of the grades S6-34 (BASF, Germany), KDOM-08 (RF), KDOM (RF), KDO (RF), LCD are subject to processing (RF), which is a polydisperse mixture of whole, broken and sintered granules, as well as a powdery mass of black color with the following chemical composition after calcination, established by atomic absorption spectroscopy:

Used spent catalyst is pre-crushed on a disintegrator. It is desirable that the spent catalyst is milled to a fractional particle composition of not more than 0.2 mm, which leads to an acceleration of the dissolution process — the smaller the particle size, the larger their surface, and the faster the reaction.

Next, the crushed catalyst is calcined at a temperature of from 650 to 800 ° C. Annealing the spent catalyst is necessary to increase the difference in the ability of the oxide compounds that are part of the iron-potassium catalyst to dissolve in hydrochloric acid. During calcination, a reaction occurs of the conversion of magnetite Fe ₃ O ₄ - the main component of iron-potassium catalysts - into an acid-soluble form in accordance with the reaction equation:

4Fe ₃ O ₄ + O ₂ → 6Fe ₂ O ₃ .

Magnetite - Fe ₃ O _{4 is} slightly soluble in solutions of strong inorganic acids, in contrast to hematite Fe ₂ O ₃ .

In addition, when calcining the spent catalyst, Ce ₂ O ₃ is also oxidized in CeO ₂ , and the solubility of CeO ₂ in mineral acids is significantly lower than the solubility of Ce ₂ O ₃ .

Thus, the degree of solubility of iron compounds from cerium compounds is changed by the calcination operation to better separate them.

After calcination, the cerium compound is removed in the form of cerium dioxide, for which concentrated hydrochloric acid is poured into a heat-resistant flat-bottomed flask with a reflux condenser in the ratio catalyst: acid, kg / l, from 1: 8 to 1:10 and the prepared catalyst is poured. The catalyst is dissolved in concentrated hydrochloric acid by stirring at a temperature of 30-110 ° C for 5-30 minutes. In this case, the bulk of the iron-containing catalyst passes into the solution, and cerium dioxide is in the form of finely divided suspended particles. The heating of the solution is continued and the solution is kept at the boiling temperature (100-110 ° C) for 30-120 minutes, while the cerium dioxide precipitate crystallizes. After the time has passed, the solution is aged for the formation of cerium dioxide crystals for 3-12 hours at a temperature of 0--20 ° С. To form crystals of cerium dioxide, the solution is placed in a freezer with the specified minus temperature. It is possible to use another device or method that provides a given temperature. At this temperature, the solubility of CeO ₂ in mineral acids is significantly lower than at positive temperatures of the prototype 0- + 20 ° C, and a large part of the silicon dioxide, compared with the prototype, precipitates and crystallizes.

After receiving the precipitate, it is separated from the mother liquor by filtration - the solution is drained from the surface of the precipitate onto the filter with a pore size of the filter material of not more than 2 μm. The filter cake is washed with distilled water with a volume equal to the volume of hydrochloric acid, preferably while stirring the filter cake to better wash off the iron chloride. After washing the precipitate, moist cerium dioxide remains in it, which is sent for drying in an oven at a temperature of 105 ° C to constant weight to obtain a cerium-containing finished product - cerium dioxide. Exposure of the catalyst in hydrochloric acid at a temperature below minus 20 ° C can lead to crystallization of the main components of the mother liquor, for example, iron salts and their contamination with cerium dioxide.

The inventive method allows to extract from the spent catalysts for the dehydrogenation of olefinic hydrocarbons the most expensive component with a high yield and to obtain a product of high purity.

The yield (degree of recovery) of the product is considered as the ratio of the cerium dioxide content in the catalyst to the actually recovered cerium dioxide.

The purity of the obtained compounds is calculated from the results of their analysis by X-ray fluorescence or atomic absorption methods [GOST 23862.0-79. Rare earth metals and their oxides. General requirements for analysis methods. M .: IPK Publishing house of standards. 2003; International standard ISO 12677: 2003 “Chemical analysis of refractory products by X-ray fluorescence (XRF) - Fused cast bead method"; X-ray fluorescence chemical analysis of refractories (XRF); GOST 12364-84. Steel alloyed and high alloyed. Methods for the determination of cerium; GOST 23862.2-79. Rare earth metals and their oxides. Direct spectral method for the determination of impurities of rare earth oxides].

The invention is illustrated by examples of specific performance.

The table shows examples of the extraction of cerium from various spent catalysts for the dehydrogenation of olefinic hydrocarbons and the results of the extraction of cerium under various conditions.

Example 1 (prototype).

About 120 g of spent catalyst from Basf, Germany, grade S6-34, containing 9.60% by weight, cerium dioxide, was crushed in a disintegrator to a particle size not exceeding 0.20 mm. The crushed catalyst was calcined in a muffle furnace at a temperature of 650 ° C for 3 hours, after which the calcined catalyst was cooled to room temperature.

In a conical flat-bottomed flask with a reflux condenser, a cylinder of 800 ml of concentrated hydrochloric acid (35% by mass) was filled in, i.e. the ratio of acid volume to catalyst weight was 8: 1 ml / g. Then, a sample of a calcined catalyst weighing 100.00 g weighed on an analytical balance was poured into the same flask to an accuracy of 0.01 g. The catalyst was dissolved in concentrated hydrochloric acid by stirring with a magnetic stirrer at a temperature of 30 ° C for 30 minutes. Then, the solution was further heated to boiling (110 ° С) and the solution was kept at this temperature for 120 minutes, while cerium dioxide precipitated. After time, the solution with the precipitate was cooled to a temperature of + 20 ± 3 ° C and the solution was kept at this temperature to form cerium dioxide crystals for 6 hours.

After the exposure time, the solution was successively poured from the surface of the precipitate and the precipitate onto a filter with a pore size of the filter material not more than 2 μm. The filter cake was washed with distilled water with a volume of 800 ml, while the filter cake was stirred to better wash off the iron chloride. After washing, the precipitate was dried in an oven at a temperature of 105 ° C to constant weight for 3 hours.

After cooling the precipitate, which is cerium dioxide, it was weighed and its composition was analyzed. The mass of the obtained cerium dioxide precipitate was 7.75 g.

The content of elements in the catalyst and in the sediment was determined by x-ray fluorescence analysis. For analysis, the catalyst was ground and dried to constant mass, and the cerium dioxide composition was determined in the sample after drying. According to the results, 100 g of the initial catalyst sample contained 9.60 g of CeO ₂ , and the calcined residue obtained from it contained cerium dioxide in terms of oxides of 99.6% CeO ₂ and 0.4% Fe ₂ O ₃ , which characterizes the purity cerium dioxide. Thus, the purity of the product was 99.6%.

The yield is considered as the ratio of the cerium dioxide content of the catalyst to the actually recovered cerium dioxide. The yield calculation was carried out as follows.

From 100 g of catalyst, 7.75 g of cerium dioxide was obtained. The cerium dioxide content in the product is 99.6%, therefore, the mass of CeO ₂ is 7.75 * 0.996 = 7.72 g. The yield is: 7.72 * 100 / 9.60 = 80.4%.

The specified example of the extraction of cerium by the prototype was carried out for other catalysts KDOM, KDOM-08, KDO, at an annealing temperature of 650-800 ° C for 3-6 hours at a ratio of the weight of the catalyst to the volume of acid 1: 8-1: 10, at a temperature dissolution of the catalyst 30-110 ° C, boiling time 30-120 min with a crystallization temperature of 0- + 20 ° C for 3-12 hours. The cerium dioxide content in the catalyst was 7.1-11.4 g, the mass of cerium dioxide in the dried precipitate was 5.74-9.32 g, and the yield was 80.3-81.7%. This is reflected in the Table, example 1.

Example 2

Example 2 was carried out in accordance with example 1 with the following changes.

The catalyst was taken S6-34, the calcination temperature was 650 ° С during the calcination time of 3 hours, the ratio of the acid volume to the mass of the catalyst was 8: 1, the dissolution temperature was 30 ° С, the boiling time was 120 min, the crystallization temperature was -1 ° С, and the crystallization hold time 12 hours; the cerium dioxide content in the catalyst was 9.60 g, and the mass of cerium dioxide in the dried precipitate was 7.87 g. The yield of cerium dioxide was 82.0%.

The purity of the obtained cerium dioxide is confirmed by the X-ray diffraction pattern of CeO ₂ obtained from the spent catalyst, shown in the figure, which was compared with diffractometric data from [Crystallographic database WWW-Minkrist. http://database.iem.ac.ru/mincryst/rus/; Crystallography Open Database http://sdpd.univ-lemans.fr/cod/].

All peaks in this diffraction pattern belong to CeO ₂ , while they are almost identical to the data of the crystallographic database, not only the values of interplanar spacings, but also the relative intensities of the peaks, which indicates a high degree of purity of the obtained substance.

Example 3

Example 3 was carried out in accordance with example 1 with the following changes.

Catalyst KDOM-08, calcination temperature 700 ° С for 3 hours, the ratio of the mass of the catalyst to the volume of acid 1:10, the dissolution temperature 110 ° С, the boiling time 30 min, the crystallization temperature -10 ° С, the exposure time for crystallization 3 hours; the cerium dioxide content in the catalyst was 11.40 g, and the mass of cerium dioxide in the dried precipitate was 10.78 g. The yield of cerium dioxide was 94.6%.

Example 4

Example 4 was carried out in accordance with example 1 with the following changes.

KDO catalyst, calcination temperature 800 ° С for 3 hours, the ratio of acid volume to catalyst weight 8: 1, dissolution temperature 100 ° С, boiling time 60 min, crystallization temperature -20 ° С, holding time for crystallization 6 hours; the cerium dioxide content in the catalyst was 7.10 g, and the mass of cerium dioxide in the dried precipitate was 7.03 g. The yield of cerium dioxide was 99.0%.

Example 5

Example 5 was carried out in accordance with example 1 with the following changes.

KDOM catalyst, calcination temperature of 700 ° C for 6 hours, the ratio of acid volume to mass of catalyst 10: 1, dissolution temperature of 110 ° C, boiling time 120 min, crystallization temperature -10 ° C, holding time for crystallization 6 hours; the cerium dioxide content in the catalyst was 7.10 g, and the mass of cerium dioxide in the dried precipitate was 6.82 g. The yield of cerium dioxide was 96.1%.

Example 6

Example 6 was carried out in accordance with example 1 with the following changes.

LCD catalyst, calcination temperature 700 ° С for 3 hours, the ratio of acid volume to mass of catalyst 10: 1, dissolution temperature 30 ° С, boiling time 120 min, crystallization temperature -20 ° С, holding time for crystallization 12 hours; the cerium dioxide content in the catalyst was 9.20 g, and the mass of cerium dioxide in the dried precipitate was 9.06 g. The yield of cerium dioxide was 98.5%.

As can be seen from the examples and the Table to them, the percentage of cerium dioxide output has increased significantly, which confirms the implementation of the claimed technical result and the solution of the problem. The increase in cerium yield at negative temperatures during crystallization is explained by a decrease in the solubility of cerium dioxide in the mother liquor and a greater crystallization of its amount.

Claims (1)

A cerium extraction method in which the spent iron-potassium catalyst with cerium content is ground, the ground catalyst is calcined at a temperature of 650-800 ° C for 3-6 hours, after the end of calcination, the catalyst is cooled to room temperature, the calcined catalyst is dissolved in concentrated hydrochloric acid, heat the solution to a boil and hold the solution at the boiling point for 30-120 minutes, hold the solution for crystallization of cerium dioxide for 3-12 hours after receiving the precipitate, it is separated from the mother liquor by decantation and filtration, the filter cake is washed from the iron compound and dried to constant weight to obtain cerium dioxide, concentrated hydrochloric acid in the ratio catalyst: acid equal to 1: 8-1: 10 is taken for dissolution characterized in that the exposure of the dissolved catalyst in concentrated hydrochloric acid for crystallization of cerium dioxide is carried out at negative temperatures from minus 4 ° C to minus 20 ° C.

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