KR20060030693A - Platinum Reduction Method in Platinum Regeneration Process - Google Patents

Abstract

The present invention relates to a method for reducing platinum in a platinum regeneration process, wherein sodium hydroxide is added to the ammonia complex of platinum and then reduced by adding hydrazine hydrate while maintaining the solution at a temperature of 50 ° C. or lower. .

Platinum, Spent Catalyst

Description

Reduction Method of Platinum in Platinum Regeneration Process

The present invention relates to a method for reducing platinum in a platinum regeneration process, and more particularly to a method for reducing platinum in a high yield in a stable state using hydrazine hydrate.

Background Art [0002] Many studies and developments have been made on a method for recovering platinum and platinum group metals contained in a refinery reforming catalyst or a waste catalyst for automobile exhaust purification. Catalysts used in various refineries to promote reforming reactions or to purify exhaust gases from automobiles contain a large amount of platinum group precious metals such as platinum, iridium, rhodium, and palladium, and these catalysts lose their activity as they are used. Finally, the metal supported on the catalyst is discarded, but the precious metal is expensive, so recovery and reuse of the catalyst is very important in terms of reducing the catalyst cost and utilizing the resources.

In general, recovering precious metals from spent catalysts include melting, aqua regia, and chlorine-containing hydrochloric acid. Among the most commonly used aqua regia, the spent catalyst is dissolved in aqua regia and ammonium chloride (NH ₄ Cl) In addition, it precipitates in the form of ammonia complex {(NH ₄ ) ₂ PtCl ₆ }, the reaction scheme is as follows.

H ₂ PtCl ₆ + NH ₄ Cl → (NH ₄ ) ₂ PtCl ₆ ↓ + 2HCl

The method of obtaining a platinum metal by filtering and washing this solid platinum complex and reducing it in the furnace at the temperature of about 800 degreeC was mainly used. However, such a reduction method requires more than 12 hours, preferably about 72 hours, which is not economical in terms of energy or time, and also causes a loss of platinum in the reduction process.

It is therefore an object of the present invention to provide a method for reducing platinum in a simple and economical manner in a platinum recovery process using the aqua regia method.

Another object of the present invention is to provide a method for reducing platinum in high yield in a stable state using hydrazine hydrate.

The object of the present invention is to reduce the platinum in the platinum regeneration process, characterized in that by adding a sodium hydroxide solution to the ammonia complex of platinum and then adding the hydrazine hydrate while maintaining the solution at a temperature below 50 ℃ Is achieved by.

Hereinafter, the present invention will be described in detail.

An aqueous sodium hydroxide solution is added to the ammonia complex of platinum {(NH ₄ ) ₂ [PtCl ₆ ]}. In this case, it is preferable to use a saturated solution in consideration of the treatment problem of the filtrate, and when a sodium hydroxide aqueous solution is added, the reduction reaction by the hydrazine hydrate in the future generates a lot of heat due to the exothermic reaction, so that the pre-cooled solution is gradually It is preferable to add. The amount of saturated sodium hydroxide solution added is preferably 1 kg or more per 200 g of the platinum complex.

Subsequently, hydrazine hydrate (NH ₂ NH ₂ H ₂ O) is added to carry out the reduction reaction. Since the reaction itself is an exothermic reaction, the temperature of the reaction solution is properly maintained below 50 ° C. using a cooling system so that the temperature of the reaction solution does not rise above 50 ° C.

The reaction vessel is attached with a cooling system by water or air to keep the reaction temperature below 50 ℃ continuously. If the temperature rises further, the subsequent reduction reaction is not stable, and if the solution boils, platinum may be lost.

If only the temperature is properly maintained as described above, the reduction reaction by the hydrazine hydrate proceeds very stably and has the advantage of recovering platinum in high yield.

Example 1

The automobile waste catalyst was pulverized, then dissolved in aqua regia, extracted, and an aqueous solution of ammonium chloride at a concentration of 17.7% was added to precipitate platinum in the form of an ammonia complex, followed by filtration and drying.

To 200 g of ammonia complex {(NH ₄ ) ₂ [PtCl ₆ ]} of platinum obtained in the above step, 1 kg of a saturated solution of sodium hydroxide was added. The reaction was continued for 20 minutes by adding 50 g of hydrazine hydrate (NH ₂ NH ₂ · H ₂ O) while maintaining the temperature of the solution at 40 ° C. using cooling water. Filtration, washing and drying gave platinum metal. The yield was 99.9%.

Example 2

The automobile waste catalyst was pulverized, then dissolved in aqua regia, extracted, and an aqueous solution of ammonium chloride at a concentration of 17.7% was added to precipitate platinum in the form of an ammonia complex, followed by filtration and drying.

To 200 g of ammonia complex {(NH ₄ ) ₂ [PtCl ₆ ]} of platinum obtained in the above step, 1 kg of a saturated solution of sodium hydroxide was added. The reaction was continued for 10 minutes by adding 50 g of hydrazine hydrate while maintaining the temperature of the solution at 45 ° C. with cooling water. Filtration, washing and drying gave platinum metal. The yield was 99.9%.

Example 3

The automobile waste catalyst was pulverized, then dissolved in aqua regia, extracted, and an aqueous solution of ammonium chloride at a concentration of 17.7% was added to precipitate platinum in the form of an ammonia complex, followed by filtration and drying.

To 200 g of ammonia complex {(NH ₄ ) ₂ [PtCl ₆ ]} of platinum obtained in the above step, 1 kg of a saturated solution of sodium hydroxide was added. The reaction was continued for 30 minutes by adding 50 g of hydrazine hydrate while maintaining the temperature of the solution at 50 ° C. with cooling water. Filtration, washing and drying gave platinum metal. The yield was 99.9%.

Comparative Example 1

To 200 g of ammonia complex of platinum {(NH ₄ ) ₂ [PtCl ₆ ]} was added 1 kg of a saturated solution of sodium hydroxide. The reaction was continued while slowly adding 50 g of hydrazine hydrate over 1 hour. As the temperature of the solution rose above 80 ° C., the solution overflowed or became violent. Hence, the yield of platinum metal obtained by filtration, washing and drying was 90.9%.

Comparative Example 2

The finely ground car waste catalyst was dissolved, extracted with aqua regia, and platinum was precipitated in the form of an ammonia complex by adding an aqueous ammonium chloride solution at a concentration of 17.7%, followed by filtration and drying.

200 g of the ammonia complex {(NH ₄ ) ₂ [PtCl ₆ ]} of platinum obtained in the above step was heated in a furnace at 800 ° C. for 12 hours. The yield of platinum metal was 99%.

In the platinum regeneration step of the present invention, there is a method in which the platinum reduction method can save time and energy by the reduction step compared to the known method, and recover platinum in a high yield by a stable reaction.

Claims (2)

A method for reducing platinum in a platinum regeneration process, comprising adding an aqueous sodium hydroxide solution to ammonia complex of platinum and then adding and reducing the hydrazine hydrate while maintaining a temperature of 50 ° C. or lower. The method of claim 1, wherein the aqueous sodium hydroxide solution is added in the form of a saturated solution.