CN116716483A - A method for efficient recycling of metallic palladium in spent palladium-containing catalysts - Google Patents

Abstract

The invention provides a method for efficiently recycling metallic palladium in palladium-containing waste catalyst, which includes: soaking the palladium-containing waste catalyst in a soaking liquid and filtering to obtain a first palladium-containing leachate, wherein the soaking liquid includes sulfuric acid and an oxidant; Then, the first palladium-containing leachate is enriched and filtered to obtain a second palladium-containing leachate; a reducing agent is added to the second palladium-containing leachate for reaction, filtered, washed, and dried to obtain a palladium product. The present invention uses chemical agents to leach, enrich and purify valuable palladium metal resources in palladium-containing waste catalysts, and finally can produce palladium products and aluminum-containing by-products with market value. This method can not only recycle spent palladium-containing catalysts to obtain high-purity palladium products, thereby improving the recycling rate of palladium-containing spent catalysts, but also does not produce any waste during production, that is, no secondary pollution, and can be to the complete recycling of palladium and aluminum, ultimately achieving the effects of environmental protection, greenness, energy saving and emission reduction, and clean production.

Description

A method for efficient recycling of metallic palladium in spent palladium-containing catalysts

Technical field

The present invention relates to the technical field of recovery and reuse of palladium resources in spent palladium-containing catalysts, and in particular, to a method for efficient recycling of metallic palladium in spent palladium-containing catalysts.

Background technique

Palladium (Pd), a platinum group metal element, shows good catalytic activity due to its unique physical and chemical properties, and is widely used as a catalyst in various fields such as petrochemistry, medicine, and new energy. In recent years, my country has been the world's largest consumer of platinum group metals. Palladium is currently the most consumed platinum group metal, and its demand is still very strong, especially in the application of chemical catalysts. However, domestic palladium metal resources are severely lacking, and a large amount of palladium metal still needs to be imported.

The deactivation of the palladium catalyst is mainly caused by the growth of palladium grains, which causes large changes in the specific surface area, coverage and poisoning of impurities. Due to palladium's good corrosion resistance, high temperature performance and stable electrical properties, the loss of palladium during the reaction process is not large, and the difference in palladium content between spent palladium catalysts and fresh catalysts is not large. The metal palladium content in spent palladium catalysts (approximately 1000-9000g/t) far exceeds the content in palladium ore (approximately 2-10g/t), and my country has a large amount of spent palladium catalysts to be processed every year, which makes the waste It is possible to more completely recover the palladium in the palladium catalyst. In addition, if the waste palladium catalyst is not processed in time, the palladium-containing waste catalyst will cause serious pollution to the surrounding environment and pose a certain threat to human health. Therefore, it is important to recover metallic palladium from the waste palladium catalyst. significance and huge economic benefits.

At present, the processes for recovering metal palladium from spent palladium catalysts include fire process, wet process, and combined fire-wet process. The pyrotechnic process requires large investment, high equipment requirements and long recovery cycle. The combined fire-wet process is cumbersome and difficult to achieve large-scale industrialization. The wet process has the characteristics of simple technology, low investment and short process, and has gradually become the most widely used method. The traditional wet process uses aqua regia (nitric acid + hydrochloric acid) for recovery. However, aqua regia itself is highly corrosive, and the chemical waste liquid produced during the recycling process will not only harm the environment, but the waste gas and nitrogen oxides in the waste liquid will also increase the processing costs of the company's environmental protection facilities. Therefore, it is of great significance to develop a metal palladium recovery technology that can efficiently recover metal palladium in spent palladium-containing catalysts while also achieving environmentally friendly and green effects.

Contents of the invention

The object of the present invention is to provide a method for efficient recycling of metal palladium in spent palladium-containing catalysts. This method uses a mixture of sulfuric acid and oxidant as a soaking liquid to soak the palladium-containing waste catalyst, and then enriches and purifies it to achieve recycling. Efficient recovery of palladium resources in palladium-containing spent catalysts can also achieve the goals of environmental protection, greenness, energy saving, emission reduction and clean production.

The present invention solves its technical problems by adopting the following technical solutions.

The present invention proposes a method for efficiently recycling metallic palladium in spent palladium-containing catalysts, which includes the following steps:

S1. Soak the palladium-containing waste catalyst in a soaking liquid and filter to obtain the first palladium-containing leachate, wherein the soaking liquid includes sulfuric acid and an oxidant;

S2. After the first palladium-containing leachate is enriched and filtered, the second palladium-containing leachate is obtained;

S3. Add a reducing agent to the second palladium-containing leach solution for reaction, filter, wash, and dry to obtain a palladium product.

The beneficial effects of the method for efficiently recycling and utilizing metal palladium in spent palladium-containing catalysts according to the embodiment of the present invention are:

The present invention adopts a green (wet) metallurgical method to recycle and process the palladium-containing waste catalysts that have failed during production in chemical plants, and uses chemical agents to leach, enrich and purify valuable palladium metal resources in the palladium-containing waste catalysts. Finally, It can produce palladium products and aluminum-containing by-products with market value. This method can not only recycle spent palladium-containing catalysts to obtain high-purity palladium products, thereby improving the recycling rate of palladium-containing spent catalysts, but also does not produce any waste during production, that is, no secondary pollution, and can be to the complete recycling of palladium and aluminum, ultimately achieving the effects of environmental protection, greenness, energy saving and emission reduction, and clean production.

The method of the present invention can also avoid the harm to people and the environment caused by the waste palladium catalyst being arbitrarily discarded and turned into solid waste, reduce the total amount of industrial solid waste, and at the same time achieve the purpose of recycling and reusing its resources. , to avoid the adverse consequences that the valuable palladium metal resources contained in it cannot be recycled sustainably, thereby achieving sustainable industrial development.

Description of the drawings

In order to explain the technical solutions of the embodiments of the present invention more clearly, the drawings required to be used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and therefore do not It should be regarded as a limitation of the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without exerting creative efforts.

Figure 1 is a flow chart for the efficient recovery and utilization of metal palladium in spent palladium-containing catalysts according to the present invention.

Detailed ways

In order to make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the examples, the conditions should be carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not indicated, they are all conventional products that can be purchased commercially.

The following is a detailed description of the method for efficiently recycling metal palladium in spent catalyst containing palladium according to the embodiment of the present invention.

Referring to Figure 1, an embodiment of the present invention provides a method for efficiently recycling metal palladium in spent palladium-containing catalysts, including the following steps:

S1. Soak the palladium-containing waste catalyst in a soaking liquid and filter to obtain the first palladium-containing leachate and aluminum-containing by-products, wherein the soaking liquid includes sulfuric acid and an oxidizing agent. The aluminum-containing by-products obtained by the present invention can be recycled and reused as building materials, aluminum-making and other raw materials, thereby improving resource utilization.

Further, in a preferred embodiment of the present invention, the step of soaking the palladium-containing waste catalyst in the soaking liquid is: first adding the palladium-containing waste catalyst to the sulfuric acid, and then adding the oxidant.

Further, in a preferred embodiment of the present invention, the molar concentration of sulfuric acid is 0.025-9 mol/L.

Further, in a preferred embodiment of the present invention, the usage ratio of the sulfuric acid and the palladium-containing spent catalyst is 0.5 to 200:1 (mL/g).

Further, in a preferred embodiment of the present invention, the oxidizing agent is selected from one of sodium hypochlorite, sodium chlorate, hydrogen peroxide, chlorine, ozone, oxygen, peracetic acid, and sodium percarbonate. Preferably, the volume ratio of sulfuric acid (or palladium-containing catalyst) and oxidant is 1-50.

Further, in a preferred embodiment of the present invention, the soaking time is 0.1 to 12 hours, and the soaking temperature is 50 to 100°C.

S2. After the first palladium-containing leachate is enriched and filtered, a second palladium-containing leachate is obtained.

Further, in a preferred embodiment of the present invention, the enrichment includes primary enrichment and secondary enrichment. The primary enrichment is heating and concentrating the first palladium-containing leachate. The temperature of the heating concentration is is 50~105℃.

Further, in a preferred embodiment of the present invention, the secondary enrichment uses an ammonium chloropalladate precipitation method to enrich the palladium-containing leachate after the primary enrichment. The enrichment step is:

(1) After adding a certain amount of ammonium chloride to the second palladium-containing leaching solution, add an appropriate amount of oxidant; filter, and wash the filter cake with saturated ammonium chloride, then add a certain amount of pure water to the filter cake, heat and boil for 1 to 10 hours, and cool Then, repeat step (1) at least three times to obtain a cooled solution.

(2) Add ammonia water to the above-mentioned cooled solution until the pH is 8 to 12. After filtering, add hydrochloric acid to the filtrate until the pH is 0.1 to 4. After filtering and washing, add ammonia water to dissolve the filter cake and adjust the pH to 8 to 8. 12. Repeat step (2) at least three times, add a reducing agent to the solution, filter, wash and dry to obtain sponge palladium.

Further, in a preferred embodiment of the present invention, the secondary enrichment adopts a combined method of dichlorodiammino-palladium method to enrich the palladium-containing leachate after the primary enrichment.

S3. Add a reducing agent to the second palladium-containing leach solution for reaction, filter, wash, and dry to obtain a palladium product. The sponge palladium product obtained by the palladium metal recovery method of the present invention can be used for the secondary manufacture of palladium catalysts, thereby improving the recovery and utilization rate of metal palladium. In addition, this palladium product can also be used in other fields, such as three-way catalysts for automobiles.

Further, in a preferred embodiment of the present invention, the reducing agent is selected from hydrazine hydrate, zinc powder, zinc flakes, iron powder, iron flakes, aluminum powder, aluminum flakes, copper powder, copper flakes, formic acid, formaldehyde, One of titanium trichloride and hypophosphorous acid.

The present invention adopts a green (wet) metallurgical method to recycle and process the palladium-containing waste catalysts that have failed during production in chemical plants, and uses chemical agents to leach, enrich and purify valuable palladium metal resources in the palladium-containing waste catalysts. Finally, It can produce palladium products and aluminum-containing by-products with market value. This method can recycle spent palladium-containing catalysts to obtain high-purity palladium products, thereby improving the recycling rate of palladium-containing spent catalysts, and does not produce any waste during production, that is, no secondary pollution, and can achieve The full recycling of palladium and aluminum ultimately achieves the effects of environmental protection, greenness, energy saving and emission reduction, and clean production.

The features and performance of the present invention will be described in further detail below with reference to examples.

Example 1

This embodiment provides a method for efficiently recycling metal palladium in spent palladium-containing catalysts, including the following steps:

(1) Add 35 mL of 3 mol/L sulfuric acid to 5 g of spent palladium-containing catalyst, where the liquid-to-solid ratio of sulfuric acid and spent palladium-containing catalyst is 7:1. Then add 5 mL of sodium hypochlorite solution with a mass fraction of 8%, heat in a water bath at 90°C for 30 minutes, cool and filter, to obtain the first palladium-containing leach solution and aluminum-containing by-products.

(2) The first palladium-containing leachate is heated and concentrated (primary enrichment), and then the palladium-containing leachate after the primary enrichment is subjected to secondary enrichment and filtration using the ammonium chloropalladate precipitation method to obtain the second palladium-containing leachate.

(3) Add an appropriate amount of reducing agent formic acid to the second palladium-containing leaching solution (the amount of formic acid is calculated by adding 1g of palladium to 3mL of formic acid), and stir continuously at room temperature until no palladium precipitates.

(4) After filtering the reduced leachate, washing with pure water, and drying, the target palladium product can be obtained.

Example 2

This embodiment provides a method for efficiently recycling metal palladium in spent palladium-containing catalysts, including the following steps:

(1) Add 40 mL of 6 mol/L sulfuric acid to 5 g of spent palladium-containing catalyst, where the liquid-to-solid ratio of sulfuric acid and spent palladium-containing catalyst is 8:1. Then add 4 mL of sodium hypochlorite solution with a mass fraction of 8%, heat in a water bath at 90°C for 30 minutes, cool and filter, to obtain the first palladium-containing leach solution and aluminum-containing by-products.

(2) The first palladium-containing leachate is heated and concentrated (primary enrichment), and then the palladium-containing leachate after the primary enrichment is subjected to secondary enrichment and filtration using a combined dichlorodiammino-palladium method to obtain the second palladium-containing leachate. Leachate.

(3) Add an appropriate amount of reducing agent formic acid to the second palladium-containing leaching solution (the amount of formic acid is calculated by adding 1g of palladium to 3mL of formic acid), and stir continuously at room temperature until no palladium precipitates.

(4) After filtering the reduced leachate, washing with pure water, and drying, the target palladium product can be obtained.

The above-described embodiments are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the invention is not intended to limit the scope of the claimed invention, but rather to represent selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention.

Claims (10)

1. The method for efficiently recycling the metal palladium in the palladium-containing spent catalyst is characterized by comprising the following steps of:

s1, soaking a palladium-containing dead catalyst in a soaking solution, and filtering to obtain a first palladium-containing leaching solution, wherein the soaking solution comprises sulfuric acid and an oxidant;

s2, enriching and filtering the first palladium-containing leaching solution to obtain a second palladium-containing leaching solution;

s3, adding a reducing agent into the second palladium-containing leaching solution for reaction, filtering, washing and drying to obtain a palladium product.

2. The method for efficiently recycling metallic palladium in a spent palladium-containing catalyst according to claim 1, wherein in the step S1, the step of immersing the spent palladium-containing catalyst in an immersion liquid is: the palladium-containing spent catalyst is added to the sulfuric acid before the oxidant.

3. The method for efficiently recycling metallic palladium in a spent palladium-containing catalyst according to claim 2, wherein in the step S1, the molar concentration of sulfuric acid is 0.025 to 9mol/L.

4. The method for efficiently recycling metallic palladium in a palladium-containing spent catalyst according to claim 3, wherein the ratio of the sulfuric acid to the palladium-containing spent catalyst is 0.5 to 200:1 (mL/g).

5. The method for efficiently recycling metallic palladium in a palladium-containing spent catalyst according to claim 1, wherein the oxidizing agent is one selected from the group consisting of sodium hypochlorite, sodium chlorate, hydrogen peroxide, chlorine, ozone, oxygen, peracetic acid, sodium percarbonate.

6. The method for efficiently recycling metallic palladium in a spent palladium-containing catalyst according to claim 1, wherein in the step S1, the soaking time is 0.1 to 12 hours and the soaking temperature is 50 to 100 ℃.

7. The method for efficiently recycling metallic palladium in a palladium-containing spent catalyst according to claim 1, wherein in the step S2, the enrichment includes a primary enrichment and a secondary enrichment, the primary enrichment is to heat-concentrate the first palladium-containing leaching solution, and the heat-concentrate temperature is 50-105 ℃.

8. The method for efficiently recycling metallic palladium in a spent palladium-containing catalyst according to claim 7, wherein in the step S2, the secondary enrichment is performed on the palladium-containing leaching solution after the primary enrichment by an ammonium chloropalladate precipitation method.

9. The method for efficiently recycling metallic palladium in a palladium-containing spent catalyst according to claim 7, wherein in the step S2, the secondary enrichment is performed on the palladium-containing leachate after the primary enrichment by adopting a dichloro-diamino palladium-sulfite combined method.

10. The method for efficiently recycling metallic palladium in a palladium-containing spent catalyst according to claim 1, wherein in the step S3, the reducing agent is one selected from hydrazine hydrate, zinc powder, zinc flakes, iron powder, iron flakes, aluminum powder, aluminum flakes, copper powder, copper flakes, formic acid, formaldehyde, titanium trichloride, hypophosphorous acid.