A method of obtaining a palladium from spent catalysts based on aluminum oxide

 

(57) Abstract:

The invention relates to the production of a noble metal catalyst recycling hydrometallurgical method. Treatment of the catalyst is carried out in 4 stages hydrochloric acid at a ratio of T:W = 1:0.6 for the first two stages and T:W = 1:05 on with subsequent portions addition of hydrogen peroxide at a ratio of H2O2: HCl = 1:10. And the first step of processing the hydrogen peroxide add 4 times with an interval of 10 min, and later, 2 times with an interval of 15 - 20 minutes Granules media 4 times washed with water at a ratio of T:W = 1:0,6, maintaining a contact time of 20 minutes Palladium restore from a solution of formic acid at pH 14. The method is fast enough to leaching 97 - 98.8% of the palladium contained in the catalyst, the minimum to break down the granules and to allocate chlorine and provides clearance from aluminum. 3 C.p. f-crystals, 1 table.

The invention relates to the field of production of precious metals refining catalysts by hydrometallurgical route.

In industrial catalysts noble metals (mainly palladium and platinum) deposited on a porous solid media - oxides of aluminum, silicon, silicates and d the th metal dissolution media, including grinding, sintering with the alkaline reagent, the leaching in the presence of the reducing agent and the recovery of precious metals from insoluble residue (U.S. Pat. RF N 2140999 BI N 31, 1999).

However, this method requires additional equipment for grinding, chatowania and sintering the mass of the catalyst and also leads to the formation of large volumes of a solution containing components of the carrier and reductant requiring treatment and disposal. The resulting concentrate of precious metals must also be processed because it contains significant amounts of impurities.

There is also known a method of leaching of precious metals with minimal dissolution of the carrier in the cell, when dissolved metals are recovered on a bulk coal cathode (U.S. Pat. RF N 2119964 BI N 28, 1998).

This method is quite energy intensive and time consuming. Besides, we have advanced to extract precious metals from the carbon cathode.

The known method of selective leaching of noble metal solutions containing complexing agents (cyanides, bromine compounds, and so on ) with subsequent sorption of metals orgplease, typically, toxic substances. Upon the dissolution of noble metals by this method produces solutions with a low concentration, which calls for a continuous circulation of the solution between the catalyst and sorbent and requires the appropriate hardware.

Moreover, additional procedures are required for the recovery of precious metals from sorbents.

Closest to the claimed technical solution is a method for palladium from spent catalysts based on aluminum oxide, comprising the treatment of the catalyst 10-25% hydrochloric acid with 8 to 12% hydrogen peroxide at a temperature of from 60oC to the boiling point, subsequent alkalization of the solution with ammonia to pH 9-10, filtering the precipitate and recovering palladium from solution (Abstract N LP, Refereed journal of Chemistry, 1984).

However, this method involves heating the pulp in the appropriate equipment, which results, as verified experimentally, not only to intense dissolution, but also the destruction of the granules media with the formation of fine, hard detachable precipitate of aluminum oxide, polluting recoverable palladium. The specified ratio of peroxide in the about and causes intense emission of gaseous chlorine. Alkalization of the solution to pH 9-10 does not provide transition only soluble aluminum in a soluble aluminate, which complicates the process of separation of a solution of palladium from the media because of the voluminous precipitate of aluminum hydroxide.

The technical objective of the proposed method is the maximum recovery of palladium from spent catalysts based on alumina and obtaining pure metal.

The problem is solved due to the fact that the catalyst is subjected to four treatment with hydrochloric acid at the ratio of the mass of catalyst and acid (T:W) of 1:0.6 for the first two stages and T:W=1:0.5 on the next, with portions added to the pulp of hydrogen peroxide so as to maintain the ratio of H2O2:HCl=1:10. In the first stage of processing of the catalyst, the hydrogen peroxide add 4 times with an interval of 10 min, and at subsequent stages, 2 times with an interval of 15...20 minutes

Granules of the carrier is washed with distilled water at a ratio of T:W=1: 0,6, maintaining a contact time of 20 minutes

Obtained at each stage of the processing solution is separated from the basics of the catalyst by decantation, neutralized with alkali to pH 14 and restore palladium ant to what Laney acid portions addition of hydrogen peroxide is sufficiently rapid and technically simple process does not require complicated equipment. The selected ratio of the mass of the catalyst and the volume of hydrochloric acid (T:W), as well as portions addition to the pulp of hydrogen peroxide provides an effective dissolution of palladium directly on the layer of catalyst and prevents the formation of large quantities of chlorine. This significantly reduces the consumption of reagents, and the resulting solution has a high concentration of palladium. While the destruction of the granules of the catalyst is minimal.

Washing the basis of the catalyst contact time 20 min allows you to extract the dissolved palladium of porous granules of aluminum oxide for 4 loop and thereby reduce the consumption of washing water.

Recovery of palladium in alkaline medium (pH 14) to prevent contamination of the metal component carrier, so as partially dissolved by acid treatment of the aluminum oxide forms in these conditions, the soluble aluminate.

The proposed method of producing palladium from spent catalysts implemented as follows.

Example 1. 500 g of the catalyst KP-G containing 1.8.2,0% palladium (TU 6-09-5514-89), were placed in a heat resistant glass and added 200 ml of distilled water for Zap is ercise hydrogen. After 10 min was added 30 ml of hydrogen peroxide and kept for 10 minutes Adding hydrogen peroxide was repeated 2 more times, after which the solution decantation in the intermediate tank. This was finished the first stage acid treatment.

The catalyst was filled with 300 ml of hydrochloric acid was added 30 ml of hydrogen peroxide. After 15 min was added 30 ml of hydrogen peroxide and after 15 min the solution decantation.

In the third stage acid treatment the catalyst was poured 250 ml of hydrochloric acid, which corresponds to T:W=1:0.5 and added 25 ml of hydrogen peroxide. After 20 min was added 25 ml of hydrogen peroxide and after 20 min the solution decantation.

The fourth stage acid treatment was carried out similarly to the third.

Then spent the washing of the pellet carrier. For this purpose, the granules were filled with 300 ml of distilled water (T:W=1:0.6) and after 20 min decantation of the solution. The water treatment was similarly repeated 3 more times.

Granules carrier was air-dried and analyzed for palladium content.

Solutions from the acid treatment and washing were combined, neutralized with alkali to pH 14 and added 10 ml of formic acid. The solution was boiled for 1. . .1,5 hours. Vosstanovlyu at t= 120...150oC.

In the resulting palladium was determined by the content of impurities by the method of spectral analysis. It was 0,023%, which corresponds to GOST 14836-82.

The mass of the obtained palladium and the residual content in the granules of media used to calculate the degree of extraction, which is constituted in this case by 98.7%.

The table below shows other examples of the implementation of the proposed method of obtaining palladium from spent catalyst KP-G

The proposed method of producing palladium was tested on the production line as a pilot method for processing catalyst KP, It allows you to process 160-180 kg of catalyst per month and get 2.5-3 kg of powdered palladium.

In this case the residual palladium content in the pellet carrier is 0,003...at 0.01%, which corresponds to the degree of metal extraction 97...98,8%.

Obtained in this way palladium corresponds to GOST 14836-82 and returned to production, which gives a significant economic effect.

This method allows the use of simple equipment, cheap and available reagents and consume a small amount of electricity. Moreover, it does not require retraining perk as process wastewater, represents an alkaline sodium aluminate solution, used for the disposal of acid solutions instead of the technical bases, and a small amount of chlorine that is released during the dissolution of palladium, which is readily absorbed in the trap with sodium thiosulfate solution or alkali.

1. A method of obtaining a palladium from spent catalysts based on aluminum oxide, comprising the treatment of the catalyst with hydrochloric acid with hydrogen peroxide and recovery of palladium from a solution, wherein the treatment is carried out in 4 stages when the ratio of the mass of the catalyst and the volume of acid T : W = 1 : 0.6 for the first two stages and T : W = 1 : 0.5 on the next, but the hydrogen peroxide added in portions, maintaining the ratio of N2ABOUT2: HCl is 1 : 10, with subsequent washing of the pellet carrier water.

2. The method according to p. 1, characterized in that the first stage of processing the hydrogen peroxide add 4 times with an interval of 10 min, and at subsequent stages, the hydrogen peroxide added 2 times with an interval of 15 - 20 minutes

3. The method according to p. 1, characterized in that the washing of the pellet carrier is conducted by 4-fold by treatment with water at a ratio of T : W = 1 : 0,6, the contact time of 20 minutes

4. Str is

 

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