WO2022233340A1 - Vocs combustion catalyst prepared from recycled waste ternary lithium-ion batteries, and preparation method therefor - Google Patents

Abstract

Disclosed in the present invention are a VOCs combustion catalyst prepared from recycled waste ternary lithium-ion batteries, and a preparation method therefor, which belong to the technical field of catalyst preparation. A CoMnNiOx composite oxide containing high oxygen defects is obtained by subjecting waste ternary lithium-ion batteries to the process of discharging → disassembling → mechanical exfoliation → acid dissolution of metal ions → filtration to remove insoluble impurities → salt formation and precipitation → alkali solution modification, such that efficient catalytic purification of VOCs is achieved.

Description

VOCs combustion catalyst prepared by recycling waste ternary lithium battery and preparation method thereof technical field

The invention relates to the technical field of catalyst preparation, in particular to a VOCs combustion catalyst prepared by recycling waste ternary lithium batteries and a preparation method thereof.

Background technique

Ternary lithium-ion batteries (TLIBs) are widely used in the consumer electronics market, electric vehicles and grid energy storage due to their advantages of high energy density, high storage capacity and good rate performance. In 2016, the total usage capacity of lithium-ion batteries (LIBs) in the world has reached 80GWh, which is about six million single cells, according to the statistics of Aviconi Energy. With the further increase in demand for electric vehicles, ternary lithium batteries will usher in a new wave of growth demand. However, the safe recycling and green disposal of waste ternary lithium batteries is still a key link in the development of the lithium battery industry.

Volatile organic compounds (VOCs) have received extensive attention from the government and the public due to their huge pollution emissions, severe environmental impacts and serious human health hazards. Among VOCs control technologies, catalytic oxidation is considered to be a technology with a wide range of applications due to its advantages of high efficiency, energy saving, and low toxic by-products. In recent years, transition metal oxides, such as Co ₃ O ₄ , MnO ₂ , and NiO, have shown promising potential in the catalytic oxidation of VOCs due to their excellent redox properties and good mobility of active oxygen. Since TLIBs have relatively high-priced Co and Ni elements, if the transition metal elements in TLIBs can be recycled to prepare composite oxide VOCs catalysts, then both the resource utilization of waste TLIBs and the pollution control of VOCs will be a problem. It has better environmental and economic benefits.

Although Chinese patent CN107694559B discloses a similar method of recycling waste TLIBs positive electrode material to prepare toluene degradation catalyst, only MnO ₂ with low economic value is recycled in this method, and Co and Ni elements cannot be effectively utilized. Usually, the recycled TLIBs cathode materials also contain metal elements such as Li and Al which are inert to the catalytic oxidation reaction, and oxygen vacancy defects are considered to be an important factor that can effectively promote the catalytic activity of composite oxides. Therefore, it is of great significance to easily and quickly remove inert metal elements and increase the defect content of composite oxides in the process of recycling waste LIBs cathode materials to prepare catalysts for improving the catalytic oxidation activity of VOCs.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is: to overcome the deficiencies of the prior art, to provide a VOCs combustion catalyst prepared by recycling waste ternary lithium batteries and a preparation method thereof. Acid-soluble metal ions → filtration to remove insoluble impurities → salt precipitation → alkaline solution modification process to obtain CoMnNiO _x composite oxides containing high oxygen defects, so as to achieve efficient catalytic purification of VOCs.

In a first aspect, the present invention provides a method for reusing waste ternary lithium batteries to prepare a VOCs combustion catalyst, comprising the following steps:

1) The waste ternary lithium battery is fully discharged, and the positive electrode material is separated and pulverized through shearing, screening, and mechanical peeling treatment;

2) adding the positive electrode material powder obtained in step 1) to the mixed solution of strong acid and hydrogen peroxide;

3) filtering the mixed solution obtained in step 2) to remove undissolved insoluble impurities to obtain the leachate of the positive electrode material;

4) adding carbonate solution to the leaching solution obtained in step 3) to promote the precipitation of transition metals Co ²⁺ , Mn ²⁺ and Ni ²⁺ , followed by filtering, washing, drying and calcining to obtain CoMnNiO _x composite oxide;

5) The CoMnNiO _x composite oxide obtained in step 4) is added to the alkaline solution, and after stirring treatment, a composite oxide catalyst with high oxygen deficiency is obtained.

The obtained composite oxide catalyst with high oxygen deficiency contains at least five metal elements of cobalt, manganese, nickel, aluminum and lithium. After the alkali treatment and modification in step 5), the three metal elements of cobalt, manganese and nickel account for all the metal elements. The molar proportion of the elements is at least 99%.

Considering that both Al and Li can be dissolved by the alkaline solution, and the oxides of Co, Mn, and Ni cannot react with the alkaline solution, the Al and Li elements in the composite oxide are obtained by the one-step precipitation method of alkaline solution etching. The defect-enhancing effect caused by the dissolution of Al and Li cations can greatly promote the catalytic oxidation activity of VOCs of the obtained composite oxides. Therefore, the composite oxides prepared by the alkaline solution post-treatment method have the advantages of good low-temperature activity, strong stability, and suitable for various types of VOCs reactions.

Preferably, in step 2), the strong acid is nitric acid, sulfuric acid or hydrofluoric acid.

Preferably, in step 2), the mixed solution is heated to 25-90°C.

Preferably, in step 4), the carbonate solution is sodium carbonate, sodium bicarbonate, ammonium carbonate, potassium carbonate, potassium bicarbonate or ammonium bicarbonate, and the concentration is 0.1-10 mol/L.

Preferably, in step 4), the calcination temperature is 200-600°C.

Preferably, in step 5), the alkali solution is sodium hydroxide or potassium hydroxide solution, and the concentration is 0.1-5mol/L.

Preferably, in step 5), the stirring temperature is 25-95°C.

In a second aspect, the present invention provides a VOCs combustion catalyst prepared by the above method.

Preferably, the VOCs combustion catalyst has a mesoporous structure of 5-80 nm and a specific surface area of 90-200 m ² /g.

The "catalytic oxidation" referred to in the present invention means that VOCs are oxidized by oxygen to carbon dioxide and water under the action of a catalyst, and do not show macroscopic flame combustion. In the catalytic oxidation of VOCs, the temperature corresponding to the conversion rate of the catalytic oxidation of the target VOCs is 10%, called "light-off temperature", and denoted as T ₁₀ ; the conversion rate of the target VOCs catalytic oxidation is 90%. The corresponding temperature The temperature is called "complete transformation temperature" and is recorded as T ₉₀ .

Compared with the prior art, the present invention has the following beneficial effects:

The present invention adopts waste ternary lithium electron positive electrode material to realize CoMnNiO _x composite oxide by reusing the transition metal element in it after a series of treatment processes. Among them, the catalyst prepared with carbonate as precipitant is more active than oxalic acid precipitant; in addition, the alkali treatment process achieves the increase of oxygen deficiency in the composite oxide, which is in typical VOCs pollutants such as acetone, ethyl acetate and propane. It exhibits excellent catalytic activity in the catalytic combustion reaction. The use of waste ternary lithium battery cathode materials to prepare high-performance VOCs catalysts not only realizes the recycling of waste lithium batteries, but also has excellent application prospects for VOCs catalytic combustion.

Description of drawings

Fig. 1 is the XRD pattern of the positive electrode material of ternary lithium battery and the _CoMnNiO composite oxide prepared by the present invention, wherein each curve represents from bottom to top: Li( _CoMnNi )O ternary obtained after mechanical disassembly, calcination and decarbonization Positive electrode material; the obtained positive electrode material was added to 1 mol/L sodium hydroxide solution, treated at 80°C for 4 h, filtered, washed and dried to obtain the positive electrode material-NaOH; the intermediate product prepared in Example 1; the product prepared in Example 2 Intermediate product; final product prepared in Example 2.

2 is a comparison of EPR results of oxygen vacancy characterization of CoMnNiO _x composite oxides before and after alkali treatment of the present invention, wherein the two curves represent the intermediate product prepared in Example 2 and the final product prepared in Example 2 from bottom to top.

Figure 3 shows the propane catalytic oxidation activity curves of catalysts at different treatment stages, in which the positive electrode material curve represents the Li(CoMnNi)O ₂ ternary positive electrode material obtained after mechanical disassembly, calcination and decarbonization; the positive electrode material-NaOH curve represents The obtained positive electrode material was added to 1 mol/L sodium hydroxide solution, treated at 80°C for 4 h, filtered, washed and dried to obtain the positive electrode material-NaOH; the CoMnNiO _x -oxalic acid curve represents the intermediate product in Example 1 ; the CoMnNiO _x -sodium carbonate curve represents the intermediate product in Example 2; the CoMnNiO _x -sodium carbonate-NaOH curve represents the final product in Example 2.

4 is a graph showing the activity curves of CoMnNiO _x composite oxides obtained by different precipitants for the catalytic oxidation of acetone, wherein the two curves from left to right represent the intermediate product prepared in Example 2 and the intermediate product prepared in Example 1, respectively.

Figure 5 shows the activity curves of the obtained CoMnNiO _x composite oxide for ethyl acetate catalytic oxidation before and after alkali treatment, wherein the two curves from left to right represent the final product prepared in Example 2 and the intermediate product prepared in Example 2 respectively.

Figure 6 is the nitrogen adsorption and desorption curve of the catalyst, wherein the CoMnNiO _x -oxalic acid curve represents the intermediate product in Example 1; the CoMnNiO _x -sodium carbonate curve represents the intermediate product in Example 2; CoMnNiO _x -sodium carbonate -The NaOH curve represents the final product in Example 2.

Fig. 7 is the pore size distribution diagram of the catalyst, wherein the CoMnNiO _x -oxalic acid curve represents the intermediate product in Example 1; the CoMnNiO _x -sodium carbonate curve represents the intermediate product in Example 2; CoMnNiO _x -sodium carbonate-NaOH The curve represents the final product in Example 2.

8 is a schematic structural diagram of a small-scale fixed-bed continuous flow reaction evaluation device of the present invention.

Detailed ways

The materials, reagents, etc. used in the following examples can be obtained from commercial sources unless otherwise specified.

Catalyst evaluation method used in the following examples:

When evaluating the catalytic oxidation performance of VOCs, a small fixed-bed continuous flow reaction evaluation device as shown in Figure 8 was used. The VOCs gas and oxygen entered the gas mixing device respectively, and then entered the quartz tube of the reaction furnace (model SK2-1-10K) after mixing. In the process, it contacts and reacts with the catalyst in the quartz tube, and the reacted gas enters the gas chromatograph for detection to obtain the catalytic oxidation conversion rate of VOCs gas.

During the test, the 40-60 mesh catalyst obtained by sieving 0.1g of tablets was put into a quartz tube (diameter 6mm), the reaction temperature was controlled by a temperature-programmed reaction furnace, and the VOCs gas was selected from three gases of propane, acetone or ethyl acetate. The concentrations were 2000 ppm, 1000 ppm and 1000 ppm, respectively, and the oxygen concentration was 20%. The space velocity was 18000 g·ml·h ⁻¹ .

Example 1

The waste ternary lithium battery is completely discharged, and the positive electrode material is separated and pulverized through shearing, screening and mechanical stripping treatment; the positive electrode material powder is added to the mixed solution of strong acid (nitric acid, sulfuric acid or hydrofluoric acid) and hydrogen peroxide and heated to 25-90° C. to promote the dissolution of metal ions in the positive electrode material; filter the mixed solution to remove undissolved insoluble impurities (conductive graphite, etc.) to obtain the leaching solution of the positive electrode material.

A 5 mol/L oxalic acid solution was continuously added dropwise to 150 mL of the positive electrode material leaching solution until flocculent precipitation occurred. Stir vigorously for 30 min, and then stand still for aging for 12 h. The obtained precipitate is filtered with suction, washed until neutral, and dried at 100°C overnight. Finally, the obtained powder was calcined in a muffle furnace at 300° C. for 3 hours in an air atmosphere to obtain a CoMnNiO _x composite metal oxide.

The obtained CoMnNiO _x composite metal oxide was added to a 1 mol/L sodium hydroxide solution, stirred at 80° C. for 4 hours, filtered, washed and dried to obtain an oxygen-deficient composite oxide, denoted as catalyst A. Catalyst A was used in the catalytic activity test of propane, acetone and ethyl acetate, respectively.

Example 2

The preparation method of the leaching solution of the positive electrode material is the same as that in Example 1.

5 mol/L sodium carbonate solution was continuously added dropwise to 150 mL of the positive electrode material leaching solution until the pH rose to 10. Stir vigorously for 30 min, and then stand still for aging for 12 h. The obtained precipitate is filtered with suction, washed until neutral, and dried at 100°C overnight. Finally, the obtained powder was calcined in a muffle furnace at 300° C. for 3 hours in an air atmosphere to obtain a CoMnNiO _x composite metal oxide.

The obtained CoMnNiO _x composite metal oxide was added to a 1 mol/L sodium hydroxide solution, stirred at 50°C for 8 hours, filtered, washed and dried to obtain an oxygen-deficient composite oxide, denoted as catalyst B. Catalyst B was used in the catalytic activity test of propane, acetone and ethyl acetate, respectively.

Example 3

The preparation method of the leaching solution of the positive electrode material is the same as that in Example 1.

A 5 mol/L ammonium carbonate solution was continuously added dropwise to 150 mL of the positive electrode material leaching solution until the pH rose to 10. Stir vigorously for 30 min, and then stand still for aging for 12 h. The obtained precipitate is filtered with suction, washed until neutral, and dried at 100°C overnight. Finally, the obtained powder was calcined in a muffle furnace at 300° C. for 3 hours in an air atmosphere to obtain a CoMnNiO _x composite metal oxide.

The obtained _CoMnNiOx composite metal oxide was added to a 1 mol/L potassium hydroxide solution, stirred at 80°C for 4 hours, filtered, washed and dried to obtain an oxygen-deficient composite oxide, denoted as catalyst C. Catalyst C was used in the catalytic activity test of propane, acetone and ethyl acetate, respectively.

Comparative Example 1

The preparation method of the leaching solution of the positive electrode material is the same as that in Example 1.

A 5 mol/L oxalic acid solution was continuously added dropwise to 150 mL of the positive electrode material leaching solution until flocculent precipitation occurred. Stir vigorously for 30 min, and then stand still for aging for 12 h. The obtained precipitate is filtered with suction, washed until neutral, and dried at 100°C overnight. Finally, the obtained powder was calcined in a muffle furnace at 300° C. for 3 hours in an air atmosphere to obtain a CoMnNiO _x composite metal oxide, which was denoted as catalyst R1. The catalyst R1 was used in the catalytic activity test of propane, acetone and ethyl acetate, respectively.

Comparative Example 2

The preparation method of the leaching solution of the positive electrode material is the same as that in Example 1.

5 mol/L sodium carbonate solution was continuously added dropwise to 150 mL of the positive electrode material leaching solution until the pH rose to 10. Stir vigorously for 30 min, and then stand still for aging for 12 h. The obtained precipitate is filtered with suction, washed until neutral, and dried at 100°C overnight. Finally, the obtained powder was calcined in a muffle furnace at 300° C. for 3 hours in an air atmosphere to obtain a CoMnNiO _x composite metal oxide, which was denoted as catalyst R2. The catalyst R2 was used in the catalytic activity test of propane, acetone and ethyl acetate, respectively.

The following table shows the catalytic degradation activities of VOCs of the catalysts prepared in Examples 1-3 and Comparative Examples 1-2

Table 1

From the catalytic oxidation results of Examples 1-3 and Comparative Examples 1-2, it can be seen that using carbonate as a precipitant has higher catalytic oxidation activity than using expensive oxalic acid, and the complete conversion temperature of VOCs is somewhat higher. reduce. At the same time, by modifying the obtained composite metal oxide by alkaline solution to remove metal cations such as Al and Li in the crystal, the oxygen defect content in the composite metal oxide can be greatly increased (as evidenced by the EPR results in Figure 2) , thereby further promoting the catalytic activity of the catalyst for VOCs, and the complete degradation temperature of VOCs can be further reduced by 10-20 °C. Therefore, we creatively used the preparation steps modified by carbonate and alkaline solution to recycle the cathode materials of waste ternary lithium batteries to obtain high-performance VOCs catalytic purification catalysts.

In addition, it can be seen from Figure 1 that in Example 2, the CoMnNiO _x composite oxide prepared by using sodium carbonate as a precipitant has a higher diffraction peak than the CoMnNiO _x composite oxide prepared by using oxalic acid as a precipitant in Example 1. It can be explained that the crystallinity of CoMnNiO _x -sodium carbonate prepared in Example 2 is lower, and it contains more oxygen vacancy defects. Similarly, CoMnNiO _x -sodium carbonate-NaOH after alkali treatment also has broad diffraction peaks, indicating that there are abundant oxygen vacancy defects.

It can be seen from Fig. 3 that: First, the activity comparison of the positive electrode material and the positive electrode material-NaOH shows that the catalyst activity after NaOH alkaline solution treatment is significantly improved. Secondly, by comparing the CoMnNiO _x -oxalic acid of Example 1, the CoMnNiO _x -sodium carbonate and CoMnNiO _x -sodium carbonate-NaOH of Example 2, it can be found that when sodium carbonate is used as a precipitant, the catalyst activity will be higher than the traditional oxalic acid precipitant. The activity is good, and the NaOH alkali treatment also further promotes the activity of the catalyst.

Figure 4 further confirms that the catalyst prepared using carbonate as precipitant is more active than oxalic acid precipitant. Figure 5 also further confirms that the alkali treatment can further improve the activity of the catalyst.

Figure 6 shows that the specific surface area of the VOCs combustion catalyst is 90-200 m ² /g, and Figure 7 shows that the catalyst has a mesoporous structure of 5-80 nm.

Although the present invention has been described in detail in conjunction with the preferred embodiments with reference to the accompanying drawings, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, those of ordinary skill in the art can make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions should all fall within the scope of the present invention/any Those skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should all be included within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (9)

The method for preparing VOCs combustion catalyst by reusing waste ternary lithium battery is characterized in that, comprising the following steps: 1) The waste ternary lithium battery is fully discharged, and the positive electrode material is separated and pulverized through shearing, screening, and mechanical peeling treatment; 2) adding the positive electrode material powder obtained in step 1) to the mixed solution of strong acid and hydrogen peroxide; 3) filtering the mixed solution obtained in step 2) to remove undissolved insoluble impurities to obtain the leachate of the positive electrode material; 4) adding carbonate solution to the leaching solution obtained in step 3) to promote the precipitation of transition metals Co ²⁺ , Mn ²⁺ and Ni ²⁺ , and then filtering, washing, drying and calcining to obtain CoMnNiO _x composite oxide; 5) The CoMnNiO _x composite oxide obtained in step 4) is added to the alkaline solution, and after stirring treatment, a composite oxide catalyst with high oxygen deficiency is obtained. The method of claim 1, wherein, in step 2), the strong acid is nitric acid, sulfuric acid or hydrofluoric acid. The method of claim 1, wherein, in step 2), the mixed solution is heated to 25-90°C. The method of claim 1, wherein in step 4), the carbonate solution is sodium carbonate, sodium bicarbonate, ammonium carbonate, potassium carbonate, potassium bicarbonate or ammonium bicarbonate, and the concentration is 0.1- 10mol/L. The method of claim 1, wherein, in step 4), the calcination temperature is 200-600°C. The method of claim 1, wherein, in step 5), the alkaline solution is sodium hydroxide or potassium hydroxide solution, and the concentration is 0.1-5mol/L. The method of claim 1, wherein, in step 5), the stirring temperature is 25-95°C. The VOCs combustion catalyst prepared by the method according to any one of claims 1-7 is utilized. The VOCs combustion catalyst according to claim 8, wherein the VOCs combustion catalyst has a mesoporous structure of 5-80 nm and a specific surface area of 90-200 m ² /g.

Images