CN115212878A

CN115212878A - Method for preparing high-performance Pd-Ga2O3 catalyst by recycling waste palladium catalyst

Info

Publication number: CN115212878A
Application number: CN202210788721.8A
Authority: CN
Inventors: 唐文翔; 张驰; 曹艺嘉
Original assignee: Sichuan University
Current assignee: Sichuan University
Priority date: 2022-07-06
Filing date: 2022-07-06
Publication date: 2022-10-21

Abstract

The invention provides a method for recycling a waste palladium catalyst. The method comprises digesting the waste catalyst, adjusting the pH and Ga of the leachate ₂ O ₃ And capturing free noble metal. After the waste Pd catalyst is digested with aqua regia, obtaining a leaching solution and adjusting the pH value by using ammonia water; then the prepared Ga is mixed ₂ O ₃ Adding the solution to collect noble metal; the system is filtered and washed, and finally, the Pd-Ga with high catalytic methane oxidation performance is obtained through the drying and calcining steps ₂ O ₃ A catalyst. The invention greatly shortens the process of recycling the waste catalyst, and is a high-efficiency recycling process.

Description

Method for preparing high-performance Pd-Ga2O3 catalyst by recycling waste palladium catalyst

Technical Field

The invention belongs to the field of secondary resource recycling, and relates to a method for preparing high-performance Pd-Ga by recycling Pd in a waste catalyst ₂ O ₃ A method of preparing the catalyst.

Background

The palladium-based catalyst has important application in the fields of environmental management, fine chemical industry, energy chemical industry and the like. However, in the long-term use of the catalyst, the palladium active component loses its activity due to contamination by impurities or sintering, and thus needs to be replaced with a new catalytic material, thereby generating a spent catalyst. Although the palladium-based catalyst loses activity, the loss of Pd metal in the palladium-based catalyst is small, and the palladium-based catalyst has great recycling value. It is statistically estimated that about 80 million tons of waste catalysts containing a large amount of noble metals of the platinum group (Pt, pd, rh, etc.) and oxides thereof are generated every year in the world, and the recovery of the noble metals from the waste catalysts has become an important source of the noble metals.

The Recovery of Pd from Spent Catalyst generally involves two processes of enrichment and purification (Mariachiaria Miceli, patrizia Frontera, angela Malara. Recovery/Reuse of Heterogeneous Supported Catalyst [ J ]. Catalyst, 2021, 11, 591). Wherein, the enrichment is to improve the content of noble metal, and mainly separates the carrier and the active component of the waste catalyst; purification, i.e., increasing the purity of the precious metal, is primarily to separate the precious metal from other impurities, such as base metals, to obtain the high purity precious metal or its salts. Obviously, in order to realize the resource utilization of Pd in the waste catalyst, the operations of dissolving, enriching, purifying and the like are required to be carried out on the waste catalyst, the process flow is complex, and the used organic solvent is easy to cause environmental pollution.

Chinese patent CN108359809B uses ionic liquid as an extracting agent, and a high-purity palladium chloride product is obtained by treating a waste palladium catalyst through a wet recovery process. However, the ionic liquid used in the method greatly increases the cost of precious metal recovery, and the fluorine-containing raw material poses a challenge to subsequent wastewater treatment.

Chinese patent CN109852800B provides an extractant with very high palladium selectivity, which is one or a combination of more than two of sulfur-containing or phosphorus-containing organic ligand compounds. The provided palladium recovery method has the advantages of short flow, no sulfur, low nitrogen content and high palladium purity. But the cost of the organic solvent is high, and sulfur and phosphorus substances contained in the wastewater can be discharged after further treatment, so that the method is not suitable for large-scale production.

The invention is especially provided for solving a series of problems of long process flow, high raw material cost and the like of the existing recovery process of the waste palladium catalyst.

Disclosure of Invention

The invention aims to overcome the defects of complex process, great environmental pollution and the like of the existing waste palladium catalyst recovery process, provide a method for efficiently recovering Pd metal in the waste catalyst, and directly prepare the Pd metal into Pd-Ga with high catalytic activity ₂ O ₃ A catalyst.

In order to achieve the purpose, the invention adopts the following technical scheme:

(1) The catalyst containing Pd is digested to ensure that the Pd component is completely dissolved. Then filtering, and washing for a plurality of times by deionized water to ensure that the Pd component is basically present in the filtrate;

(2) Adjusting the pH of the filtrate to be close to neutral by using an alkaline solution;

(3) Ga prepared by itself ₂ O ₃ Adding the powder into the filtrate, and stirring at room temperature for 24h;

(4) Filtering the mixed solution, washing the mixed solution to be neutral by using deionized water, and then transferring the mixed solution to an oven for drying;

(5) The obtained filter cake is roasted in a muffle furnace to obtain fresh Pd-Ga ₂ O ₃ A catalyst.

Preferably, the digestion temperature in the step (1) is 250 ℃ and the digestion time is 60min.

Preferably, the digestion solution in step (1) is aqua regia.

Preferably, ammonia water is used at a concentration of 1mol/L for adjusting the pH in the step (2).

Preferably, ga in step (3) ₂ O ₃ The powder is prepared by precipitating gallium nitrate with ammonia water, and the calcining condition is 3 hours at 800 ℃.

Preferably, pd-Ga in step (5) ₂ O ₃ The calcination conditions of the catalyst were 500 ℃ for 2h.

Compared with the prior art, the invention has the following prominent substantive characteristics:

1. the recovery rate is high and reaches 97.91 percent;

2. the method has simple process, and only needs simple dissolving, filtering, pH adjustment of the filtrate and calcination operation in the process from the Pd-containing waste catalyst to the high-efficiency fresh catalyst;

3. the recovery method of the invention shortens the complex process flow from the waste Pd catalyst to the preparation of the new catalyst, and the obtained catalyst has good catalytic performance.

Drawings

FIG. 1 is a graph of the catalytic oxidation performance of methane of example 1.

Detailed Description

The invention is further described below by way of examples, which are intended to illustrate the invention, but the invention is not limited to the following examples

Example 1:

the palladium catalyst after industrial operation is crushed and ground, and calcined for 3 hours at 800 ℃ in an air atmosphere in order to remove impurities such as surface carbon. Weighing 10g of the treated powder, adding a proper amount of aqua regia solution to dissolve the powder, and transferring the solution into a digestion instrument. Filtering the filtrate after microwave digestion for 250-3 h, and adding 200ml of ammonia water in order to adjust the pH of the filtrate to be close to neutral. Weighing from prepared Ga ₂ O ₃ 1g of powder is added into the solution and stirred for dispersion. And after stirring at room temperature for 24 hours, filtering and washing the suspension, drying the obtained filter cake in an oven at 80 ℃ for 3 hours, and finally transferring the filter cake to a muffle furnace to calcine for 2 hours at 500 ℃.

And (3) testing and analyzing:

the catalyst prepared in example 1 was used as a sample to conduct a propane catalytic oxidation performance test. A sample of 100mg and sieved to 40-60 mesh was packed in the catalytic reaction bed with quartz wool. 1000ppm of methane gas and 4.5 percent of O2 are taken as raw material gas, and the volume space velocity is 60000 ml/(g) _cat H). The composition of the gas at the outlet of the reactor was determined by GC9790 II gas chromatography, manufactured by Furli.

The conversion rate of the example 1 to methane is shown in figure 1, the conversion rates of 100%, 90% and 50% of methane are respectively 431 ℃, 383 and 334 ℃, and the catalytic oxidation performance of the methane is high.

Claims

1. Recovery preparation of high-performance Pd-Ga from waste palladium catalyst ₂ O ₃ A method of catalyzing, comprising:

(1) Digesting the Pd-containing waste catalyst to ensure that the Pd component is completely transferred into the solution, then filtering, and washing for several times by using deionized water to ensure that the Pd component basically exists in the filtrate;

(2) Adjusting the pH of the filtrate to be close to neutrality by using an alkaline solution;

(3) Ga prepared by itself ₂ O ₃ Adding the powder to the filtrate at room temperatureStirring for 24 hours;

2. The method according to claim 1, characterized in that the digestion solution in step (1) is aqua regia.

3. The method according to claim 1, wherein the pH adjustment in the step (2) is carried out using aqueous ammonia having a concentration of 0.2 to 2 mol/L.

4. The method according to claim 1, wherein Ga in the step (3) ₂ O ₃ The powder is prepared by ammonia water precipitation of gallium nitrate, and the calcination condition is 3h at 800 ℃.

5. The method according to claim 1, wherein Pd-Ga in the step (5) ₂ O ₃ The calcination conditions of the catalyst were 500 ℃ for 2h.