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INVENTION
Patent of the Russian Federation RU2111791

METHOD OF EXTRACT PLATINUM
FROM WORKED PLATINUM CONTAINING CATALYSTS
BASED ON ALUMINUM OXIDE

The name of the inventor: Spiridonov SE; Baybursky V.L .; Fadeeva IV; Astakhov VA; Tumasiev NN
The name of the patent holder: Nizhny Novgorod Oil Refining Research Center
Address for correspondence:
Date of commencement of the patent: 1997.06.17

The invention can be used in refining, namely, the extraction of platinum from spent platinum-containing catalysts based on alumina, in particular reforming and hydrogenation. The essence of the invention is as follows. The spent platinum-containing catalyst based on alumina is subjected to coke combustion in an oxygen-containing gas at 400-600 ° C. The catalyst is then treated with steam at 450-600 ^° C for 4-6 hours, with a water vapor pressure of 0.02-0.1 mPa and an air of 0.1-2.0 mPa. After this, the catalyst is leached at 150-180 ^° C, followed by the addition of a reducing agent, separating the precipitate from the sodium aluminate solution and isolating the final product by known methods. Moreover, aluminum or zinc with a particle size of 1-3 mm is used as the reducing agent, and the solution of sodium aluminate after separation of the platinum-containing precipitate is directed to synthesis of the zeolite. A new method of extracting platinum from spent platinum-containing catalysts based on aluminum oxide allows: - to increase the extraction of platinum to 99.0-99.5%; - increase the productivity of the process by approximately 2 times due to the increase in the filtration rate to 15.0 dm ³ / h · m ² (according to the prototype - 8.0 dm ³ / h · m ² ); - to dispose of solutions of sodium aluminate in a zeolite system. The developed method can be realized in industrial conditions without significant economic costs.

DESCRIPTION OF THE INVENTION

The invention relates to oil refining, namely, to methods for recovering platinum from spent platinum-containing catalysts based on alumina, in particular reforming and hydrogenation.

A method for extracting platinum from spent aluminum-platinum catalysts is known, the essence of which is that the alumoplatinum catalyst is treated with hot dilute sulfuric acid taken in excess to a stoichiometric amount at 102-112 ^° C and a ratio of T: H = 1: 10-20 with stirring in For 2-4 hours [1]. Alumina or alumina hydrate is introduced into the solution after separation of the slurry and after crystallization, crystalline aluminum sulfate is obtained. Slurries containing 30% platinum are calcined at 550 ^° C. and re-treated with sulfuric acid.

This method is based on acid leaching of platinum from waste aluminum-platinum catalysts. The use of a 10-20-fold excess of sulfuric acid leads to the formation of large quantities of acidic solutions containing aluminum sulfate, the utilization of which presents considerable difficulties.

The closest to the proposed process in terms of technical essence is the process for the recovery of rhenium and platinum from spent catalysts, in particular reforming catalysts, which, in addition to these metals, contain aluminum oxide as the main component [2]. This method is carried out by calcining coke in an oxygen-containing gas at 400-600 ^° C and treating the catalyst with concentrated alkali at 160-200 ^° C. A solution of sodium aluminate with a content of 100-200 g / l of Al ₂ O ₃ and 150-300 is obtained G / l Na ₂ O, platinum in metallic form remains in the sediment. For a more complete extraction of platinum from the sodium aluminate solution, a reducing agent, for example, metallic aluminum, hydrazine, formalin and / or ferrous iron, is introduced. The precipitate containing the metallic platinum is separated by filtration, washed and dried. The resulting precipitate is then treated with known methods to produce pure platinum or hexachloroplatinic acid.

Known conditions for carrying out the technological process of processing the spent catalyst make it possible to isolate platinum with an insufficiently high recovery rate, of the order of 98%.

In addition, a finely dispersed platinum-containing precipitate with a particle size of the order of 1 μm is obtained at the leaching stage, which makes it very difficult to separate it from the filtrate. The filtration rate at a pressure drop of 0.1 mPa is 8.0 dm ³ / h · m ² . Due to the fact that the filtration stage is limiting in the whole technological process, its insufficient speed leads to a significant increase in filtration time and significantly reduces its productivity.

The object of the invention is to provide a method for recovering platinum from spent platinum-containing alumina catalysts that would allow a high degree of platinum recovery to increase the productivity of the process by increasing the filtration rate in the separation step of the platinum-containing precipitate from the sodium aluminate solution.

This technical result is achieved by a method for extracting platinum from spent platinum-containing catalysts based on aluminum oxide, including burning coke in an oxygen-containing gas at 400-600 ^° C, working out the catalyst with alkali at 150-180 ^° C, then adding a reducing agent, separating the precipitate from the sodium aluminate solution And isolating the end product by known methods, after coke burning, the catalyst is treated with steam at 450-600 ^° C for 4-6 hours, the water vapor pressure being 0.02-0.1 mPa, and the air being 0.1-2 , 0 mPa.

As a reducing agent for platinum, aluminum or zinc with a particle size of 1-3 mm is used from the sodium aluminate solution. Moreover, the solution of sodium aluminate after separation of the platinum-containing precipitate can be directed to the synthesis of the zeolite.

The conducted researches showed that the selected optimal conditions for processing the spent platinum-containing catalyst based on aluminum oxide allow: to increase the extraction of platinum to 99.5; Increase the productivity of the process by increasing the filtration rate at the stage of separating the platinum-containing precipitate from the sodium aluminate solution. At the same time, the filtration rate increases to 15.0 dm ³ / h · m ² , i.e. In 2 times in comparison with the prototype. Such an increase in the filtration rate became possible due to the enlargement of the particles of the separated metallic platinum.

Carrying out the steaming step with a selected time interval of 4-6 hours at a temperature above 600 ^° C leads to a decrease in the solubility of the support in leaching, which reduces the degree of platinum release, and a temperature decrease below 450 ^° C. does not give the effect of coarsening the platinum-containing precipitate particles. In addition, an increase in processing time does not lead to an improvement in the process indicators.

The chosen ratio of water and air vapor pressure is optimal, as reducing it at the chosen temperature regime significantly reduces the processing efficiency, and the increase does not improve the process parameters by the extraction rate and the filtration rate.

The use of aluminum or zinc as a reducing agent with a particle size of less than 1 mm, does not give a complete separation of platinum from the sodium aluminate solution and can lead to losses of up to 1%. An increase in the particle size of more than 3 mm results in an increase in the time for carrying out the reduction step or the consumption of the reducing agent.

In addition, the proposed method with the selected optimal conditions makes it possible to use a solution of sodium aluminate after the separation of the platinum-containing precipitate in the synthesis of the zeolite, which contributes to an increase in the economics of the process as a whole.

Comparison of the claimed technical solution with the characteristics of the prototype allowed to establish compliance with its criterion "Novelty." Analysis of known technical solutions has shown that the distinguishing features of the proposed method correspond to the criterion of "essential differences".

The proposed method is carried out as follows. The spent platinum-containing catalyst based on alumina is subjected to treatment in an oxygen-containing gas at a temperature of 400-600 ^° C for burning coke. The catalyst is then treated with steam at 450-600 ^° C for 4-6 hours at a water vapor pressure of 0.02-0.1 mPa and air of 0.1-2.0 mPa. After such treatment, the catalyst is loaded into an autoclave filled with a concentrated alkali solution (300-350 g / l) and the mass is heated with stirring to 150-180 ^° C. The leaching process is carried out for 12-15 hours. At the end, a solution of sodium aluminate with a content of Al ₂ O _{3 of the} order of 150-200 g / l and Na ₂ O of the order of 200-250 g / l, while platinum is contained in the insoluble residue in the metallic form. In the resulting sodium aluminate solution, a reducing agent, aluminum or zinc, is introduced as a powder or chips with a particle size of 1-3 mm for a more complete extraction of platinum. The reduction process is carried out at 30-80 ^° C for 1.5 hours. After the reduction step, the platinum precipitate is separated by filtration at a pressure drop of 0.1 mPa. The resulting precipitate is washed with water and, together with the filter, is calcined at 700-750 ^° C.

The precipitate is then treated with concentrated sulfuric acid, separated on a filter and calcined at 750 ^° C. The platinum concentrate is dissolved in aqua regia and platinum is reprecipitated with a solution of ammonium chloride. The resulting precipitate of ammonium hexachloroplatinate is calcined until the production of spongy platinum.

The degree of extraction of platinum is about 99.5%.

Example 1 . The spent alumoplatinum reforming catalyst AP-56, containing, wt. %: Platinum 0.52, alumina-the rest, is treated in an oxygen-containing gas at 400-600 ^° C for coke burning. It is then treated with steam at 500 ^° C. for 5 hours. The water vapor pressure is then 0.1 mPa and the air is 1.0 mPa. A 1000 g sample of catalyst is charged and charged into an autoclave filled with a concentrated alkali solution (300-350 g / l) and the reaction mass is heated with stirring to 150-180 ^° C. The process is carried out for 12 hours. A solution of sodium aluminate with a content of Al ₂ O ₃ 220 g / l and Na ₂ O 250 g / l, platinum in metallic form in the precipitate. To complete the extraction of platinum from the sodium aluminate solution, aluminum is introduced with a particle size of 1.5 mm. The reduction of dissolved platinum is carried out at 50 ^° C. for 1 hour, after which the sodium aluminate solution is filtered at a pressure drop of 0.1 mPa and a filtration rate of 15.0 dm ³ / h · m ² . The filtration time of the solution is 20 hours. The resulting precipitate is washed with water and calcined at 700-750 ^° C. The precipitate is then treated with 46-48% sulfuric acid. The platinum-containing precipitate is separated on the filter and calcined at 750 ^° C. After that, the platinum concentrate is dissolved in aqua regia and platinum is reprecipitated with ammonium chloride. The resulting precipitate of ammonium hexachloroplatinate after calcination is calcined until a sponge platinum is obtained.

The degree of extraction of platinum from the spent reforming catalyst AP-56 is 99.5%. The productivity of the process, taking into account the filtration rate of 15.0 dm ³ / h, was 1.2 kg / day.

Example 2 . The spent aluminoplatinum hydrogenation catalyst AP-15, %: Platinum 0.15%, alumina-the rest, is treated similarly, as indicated in example 1. The water vapor pressure is 0.08 mPa and the air is 1.2 mPa. Zinc metal with a particle size of 3.0 mm is used as the reducing agent. The reduction of platinum from the sodium aluminate solution is carried out at 60 ^° C. The filtration rate of the platinum-containing precipitate is 16.0 dm ³ / h · m ² . Filtering time 20 h.

The degree of extraction of platinum from the spent catalyst of hydrogenation of AP-15 is 99.0%. The productivity of the process is 1.2 kg / day.

Example 3 (comparative) . The spent alumoplatinum reforming catalyst AP-56 containing wt.%: Platinum 0.52, alumina-the rest, is subjected to a coke-burning treatment similar to Example 1, but without steam treatment. The catalyst charge after calcination of coke in an amount of 1000 g is charged to the autoclave and leached according to the conditions of Example 1. The platinum-containing precipitate is separated on the filter at a filtration rate of 8.0 dm ³ / h · m ² . The filtration time was 43 hours. The remaining processing conditions and the isolation of platinum, as indicated in Example 1.

The degree of extraction of platinum from the spent reforming catalyst AP-56 is 98%. The productivity of the process, taking into account the filtration rate of 8.0 dm ³ / h · m ² , is 0.56 kg / day.

Analyzing the data obtained from the experimental studies (Examples 1-3), it can be concluded that additional processing of the spent reforming catalysts and hydrogenation with water vapor under the selected optimal conditions makes it possible to obtain a higher recovery of platinum 99.0-99.5% with increasing productivity Process approximately in 2 times.

Thus, the developed new method for extracting platinum from spent platinum-containing catalysts based on alumina made it possible to increase the extraction of platinum to 99.0-99.5%, to increase the productivity of the process by increasing the filtration rate to 15.0 dm ³ / h · m ² At the stage of separation of the platinum precipitate from the sodium aluminate solution; To utilize solutions of sodium aluminate in the synthesis of zeolites.

The developed method can be realized in industrial conditions without significant economic costs.

CLAIM

1. A method for recovering platinum from spent platinum-containing alumina catalysts, comprising calcining coke in an oxygen-containing gas at 400-600 ^° C, treating the catalyst with alkali at 150-180 ^° C followed by adding a reducing agent, separating the precipitate from the sodium aluminate solution and isolating Of the final product by known methods, characterized in that after calcination of the coke, the catalyst is treated with steam at 450-600 ^° C for 4-6 hours, the water vapor pressure being 0.02 to 0.1 mPa, and the air being 0.1 to 2 mPa , 0 mPa.

2. A method according to claim 1, characterized in that aluminum or zinc having a particle size of 1 to 3 mm is used as the reducing agent.

3. A method according to claim 1, characterized in that after the separation of the platinum-containing precipitate, the sodium aluminate solution is sent to synthesize the zeolite.

print version
Date of publication 14.03.2007gg

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