A VOCs catalyst and its preparation method

Abstract

This invention belongs to the field of catalyst technology, specifically relating to a VOCs catalyst and its preparation method. Starting from the goals of high-value utilization of coal gasification fine slag and reducing catalyst preparation costs, this invention prepares a VOCs catalyst using halloysite nanotubes, after acidification, supported on decarbonized coal gasification fine slag, significantly improving the utilization efficiency of halloysite nanotubes. By introducing a complexing agent to capture active metal ions followed by reduction with a reducing agent, a metal-supported VOCs catalyst is prepared, reducing the particle size of the active component in the catalyst and improving its catalytic activity. Simultaneously, this provides a new approach for the high-value utilization of coal-based solid waste and the efficient utilization of halloysite.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a VOCs catalyst and its preparation method. Background Technology

[0002] Volatile organic compounds (VOCs) are common and complex organic pollutants found in both indoor and outdoor air. Currently, VOCs treatment methods mainly include recovery and degradation / oxidation methods. Recovery methods include membrane separation, condensation, adsorption, and absorption, while degradation / oxidation methods include thermal incineration, catalytic oxidation, photocatalytic degradation, and biodegradation. Catalytic oxidation technology, which can oxidize VOCs to CO2 and H2O at relatively low temperatures without producing other pollutants, is considered one of the most promising technologies. Catalysts are a key challenge in catalytic oxidation technology. Catalysts with good VOCs catalytic oxidation properties are generally noble metals (Pt, Pd, Au, and Rh, etc.). To reduce costs while improving the utilization rate of noble metals, supported catalysts are generally used in practical applications. Catalyst supports are mainly activated carbon, Al2O3, MgO, molecular sieves, and SiO2. However, these supports are generally expensive, and noble metal species are prone to agglomeration and detachment on their surfaces, which can reduce the catalytic activity of the catalyst.

[0003] With the rapid development of the modern coal chemical industry, a large amount of coal gasification slag is generated during coal gasification. The long-term storage of coal gasification slag seriously affects ecological and environmental safety, becoming one of the bottlenecks restricting the green and high-quality development of the modern coal chemical industry. Coal gasification slag contains two main components: amorphous microspheres and amorphous carbon. Among them, amorphous microspheres, due to their stable chemical properties, can serve as an effective alternative material to carriers such as Al2O3 and SiO2. Summary of the Invention

[0004] In view of this, the present invention provides a VOCs catalyst and its preparation method. The VOCs catalyst provided by the present invention uses acidified halloysite nanotubes supported on roasted coal gasification fine slag as a carrier, which has low cost and high catalytic activity.

[0005] This invention provides a method for preparing a VOCs catalyst, comprising the following steps: (1) Halloysite nanotubes and acidifying reagent are mixed and acidified to obtain acidified halloysite powder; the acidifying reagent is acetic acid solution; (2) The coal gasification fine slag is roasted to obtain ash; then the roasted ash is mixed with water and dispersant, and the resulting mixture is purified by removing the upper suspension to obtain decarbonized coal gasification fine slag. (3) The slurry obtained by mixing acidified halloysite nanotubes, decarbonized coal gasification fine slag, grinding aid and water is refined and ground to obtain catalyst support; (4) The aqueous dispersion of the catalyst support and the solution of the complexing agent are mixed for the second time to obtain a second mixed solution; (5) The second mixed solution and the soluble solution containing metal ions are mixed for a third time to obtain a third mixed solution; (6) The third mixed solution and the reducing agent are mixed for a fourth time to carry out a reduction reaction and obtain the VOCs catalyst.

[0006] Preferably, the calcination temperature is 800℃ and the time is 4 hours; the heating rate to the calcination temperature is 5℃ / min.

[0007] Preferably, the first mixing is a sequential ultrasonic treatment and a stirring treatment; the ultrasonic treatment has a power of 80~120 W; an ultrasonic time of 45~65 min; and an ultrasonic frequency of 30~40 kHz; the stirring treatment has a temperature of 50~70℃ and a time of 2~3 days. The second mixing process consists of a second ultrasonic treatment and a second stirring treatment performed sequentially; the power of the second ultrasonic treatment is 80~120 W; the time of the second ultrasonic treatment is 10~15 min; the frequency of the second ultrasonic treatment is 30~40 kHz; and the time of the second stirring treatment is 2.5~4.5 h. The third mixing process consists of a third ultrasonic treatment and a third stirring treatment performed sequentially; the power of the third ultrasonic treatment is 40~60 W; the time of the third ultrasonic treatment is 15~30 min; the frequency of the third ultrasonic treatment is 20~30 kHz; the temperature of the third stirring treatment is 25 ℃; and the time is 3~6 h.

[0008] Preferably, the concentration of the acetic acid solution is 1~6 mol / L; the solid-liquid ratio of the halloysite nanotubes to the acetic acid solution is 1g:10~200 mL.

[0009] Preferably, in step (2), the solid-liquid ratio of ash and water is 1g:10mL, the mass of the dispersant is 0.5~5% of the mass of ash, and the dispersant is sodium hexametaphosphate or sodium pyrophosphate.

[0010] More preferably, the calcined ash is treated with a dispersant to obtain a denser decarbonized coal gasification slag mainly composed of amorphous microspheres.

[0011] Preferably, in step (3), the mass ratio of the acidified halloysite nanotubes to the decarbonized coal gasification fine slag is 1:1, the ball milling speed for refining and grinding is 1200~1700 rpm, the solid content of the acidified halloysite nanotubes and the decarbonized coal gasification fine slag in the slurry is 20 wt%, and the refining and grinding time is 160~240 min; the grinding aid is one or more of sodium hexametaphosphate, octadecyltrimethylammonium bromide and acetamide, and the mass of the grinding aid is 0.5~3% of the total mass of the acidified halloysite nanotubes and the decarbonized coal gasification fine slag.

[0012] Preferably, the complexing agent is one or more of proline, glycine, aspartic acid, and arginine; the solvent in the solution of the complexing agent is ethanol and water; the volume ratio of ethanol to water is 3:2; and the molar ratio of the total moles of the complexing agent and the metal ions is 10:1.

[0013] More preferably, using small molecule organic compounds such as amino acids as complexing agents for metal ions to disperse the active components can improve the utilization rate of metal particles and enhance the catalytic activity of the catalyst.

[0014] Preferably, the metal ion includes one or more of Pd, Pt, Ru, and Rh ions; the reducing agent includes one or more of sodium borohydride, L-ascorbic acid, sodium D-isoascorbate, sodium citrate, and ammonium citrate.

[0015] Preferably, the molar ratio of the reducing agent to the total number of metal ions is 4:1; the reduction reaction is carried out at room temperature for 5-6 hours; in this invention, the reduction reaction can reduce metal ions to metal particles and load them onto a carrier.

[0016] More preferably, the reduction reaction is carried out in a fume hood; the steps of the reduction reaction are as follows: the solution of the reducing agent is pumped into the third mixed solution using a peristaltic pump and then stirred continuously for 5-6 hours.

[0017] In this invention, the reaction between a portion of the reducing agent (sodium borohydride) and the metal ions is exothermic and releases hydrogen gas, so the reduction reaction is carried out in a fume hood.

[0018] Preferably, after the reduction reaction, the process further includes centrifuging and washing the reduction system to remove excess reducing agent, complexing agent and other impurity ions, followed by vacuum drying to obtain the catalyst.

[0019] Preferably, the centrifugal washing involves washing with deionized water six times and then with anhydrous ethanol six times.

[0020] The present invention also provides a VOCs catalyst prepared by the preparation method described above, wherein the metal loading in the VOCs catalyst is 0.4~0.55 wt% and the metal particle size is less than 6 nm.

[0021] Compared with the prior art, the present invention has the following advantages: 1. This invention uses acidified halloysite nanotubes loaded onto roasted coal gasification slag as a carrier, which reduces the cost of the catalyst and provides a new approach to improving the high-value utilization of coal gasification slag.

[0022] 2. During the grinding process of decarbonized coal gasification fine slag mainly composed of amorphous microspheres and halloysite nanotubes, halloysite nanotubes are loaded onto the surface of amorphous microspheres, which greatly reduces the aggregation of halloysite nanotubes and increases the specific surface area and utilization rate of the carrier.

[0023] 3. This invention uses small amino acid molecules containing special groups as complexing agents to complex metal ions, achieving a "fixation" effect and ensuring uniform dispersion of the metal ions. Simultaneously, a peristaltic pump slowly pumps in a reducing agent to gently reduce the complexed metal ions into particles, improving metal utilization efficiency. Furthermore, the fixation by the complexing agent significantly enhances the dispersion of the metal particles.

[0024] The data from the examples show that the VOCs catalyst prepared by the present invention has excellent catalytic oxidation performance, and halloysite is uniformly dispersed on the surface of amorphous microspheres. The trapping of the complexing agent makes the reduced metal particles uniformly dispersed on the surface of halloysite with a particle diameter of less than 6 nm. The catalyst prepared in the examples can achieve complete catalytic oxidation of toluene at 170~180℃, and the VOCs catalyst has good thermal stability and water resistance. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the embodiments will be briefly described below.

[0026] Figure 1 SEM image of the catalyst support prepared in Example 1; Figure 2 TEM image of the VOCs catalyst prepared in Example 1; Figure 3 This is a photograph of the VOCs catalyst prepared in Example 1. Detailed Implementation

[0027] The present invention will now be described in more detail with reference to specific embodiments and accompanying drawings. These embodiments will help those skilled in the art to further understand the present invention. It is worth noting that the scope of protection of the present invention is limited to the catalyst synthesis approach; any modifications made under this synthetic approach fall within the scope of protection of the present invention.

[0028] Unless otherwise specified in this technical solution, the preparation method, equipment, materials, or composition are considered to be common technical features in existing public technologies and will not be specifically described in this invention.

[0029] Example 1 Three g of natural halloysite nanotubes were dispersed in 300 mL of a 4 mol / L acetic acid solution to obtain a first mixed solution. This first mixed solution was then sonicated for 60 min at a power of 80 W and a frequency of 30 kHz. The sonicated suspension was stirred at 60 °C for 3 days. After centrifugation and washing with deionized water until neutral, the halloysite suspension was dried in a vacuum drying oven. The dried halloysite powder was then ground to a fineness of 150-200 mesh.

[0030] The coal gasification fine slag was calcined at 800℃ (heating rate of 5℃ / min) for 4 hours. 20 g of the calcined coal gasification fine slag ash was dispersed in 200 mL of water, and 0.2 g of sodium hexametaphosphate was added and stirred. After stirring, the upper suspension was removed by siphoning through a silicone tube to obtain the decarbonized coal gasification fine slag at the bottom, which was mainly composed of amorphous microspheres.

[0031] 5 g of acidified halloysite nanotubes, 5 g of decarbonized coal gasification slag, 0.1 g of acetamide and 40 mL of water were mixed to obtain a slurry. The resulting slurry was then refined and ground to obtain a catalyst support. The refining and grinding speed was 1400 rpm and the grinding time was 220 min.

[0032] 2 g of catalyst support was dispersed in 20 mL of deionized water to obtain an aqueous dispersion of the catalyst support; 0.165 g of arginine was dissolved in 10 mL of a mixed solvent of ethanol and water (volume ratio of ethanol to water was 3:2) to obtain a complexing agent solution; the support dispersion and the complexing agent solution were mixed and subjected to ultrasonic treatment at a power of 100 W for 10 min at a frequency of 30 kHz, and the mixture was stirred vigorously for 3 h after ultrasonic treatment to ensure uniform mixing.

[0033] Take 6.3 mL of Pd(NO3)2 solution (obtained by dissolving 200 mg Pd(NO3)2·2H2O in 50 mL of water) and add it to the second mixed solution for ultrasonic treatment. The ultrasonic treatment time is 30 min, the ultrasonic power is 50 W, the ultrasonic frequency is 30 kHz, and the ultrasonic suspension is stirred for 6 h at a stirring temperature of 25 ℃.

[0034] Dissolve 0.0749 g of anhydrous D-isoascorbate sodium in 10 mL of deionized water and pump it into the third mixed solution using a peristaltic pump at a flow rate of 1 mL / min. Perform the experiment in a fume hood. Continue stirring the mixed solution containing anhydrous D-isoascorbate sodium at room temperature for 6 h (Pd). 2+ +2NaC6H7O6→Pd 0 +2Na + +2C6H6O6+2H + The precipitate was washed six times by centrifugation with deionized water and anhydrous ethanol, and the precipitate was placed in a vacuum drying oven at 60 °C for 12 h to obtain the VOCs catalyst.

[0035] Example 2 Three g of natural halloysite nanotubes were dispersed in 200 mL of a 1 mol / L acetic acid solution to obtain a first mixed solution. This first mixed solution was then sonicated for 45 min at a power of 80 W and a frequency of 30 kHz. The sonicated suspension was stirred at 50 °C for 2 days. After centrifugation and washing with deionized water until neutral, the halloysite suspension was dried in a vacuum drying oven. The dried halloysite powder was then ground to a fineness of 150-200 mesh to obtain acidified halloysite powder.

[0036] The coal gasification fine slag was calcined at 800℃ (heating rate of 5℃ / min) for 4 hours. 20 g of the ash obtained after calcination of the coal gasification fine slag was dispersed in 200 mL of water, and 0.4 g of sodium hexametaphosphate was added and stirred. After stirring, the upper suspension was removed by siphoning through a silicone tube to obtain the decarbonized coal gasification fine slag at the bottom, which was mainly composed of amorphous microspheres.

[0037] 10 g of acidified halloysite nanotubes, 10 g of decarbonized coal gasification slag, 0.1 g of sodium hexametaphosphate and 80 mL of water were mixed, and the resulting slurry was refined and ground to obtain the catalyst support. The grinding speed was 1200 rpm and the grinding time was 160 min.

[0038] 2 g of catalyst support was dispersed in 20 mL of deionized water to obtain a support dispersion. 0.0385 g of glycine was dissolved in 10 mL of a mixed solvent of ethanol and water (volume ratio of ethanol to water was 3:2) to obtain a complexing agent aqueous solution. The support dispersion and the complexing agent aqueous solution were mixed and subjected to ultrasonic treatment at a power of 120 W for 15 min at a frequency of 30 kHz. After ultrasonic treatment, the mixture was stirred vigorously for 2.5 h to ensure uniform mixing.

[0039] 4.32 mL of PtCl4 aqueous solution (obtained by dissolving 200 mg PtCl4 in 50 mL of water) was added to the second mixed solution and sonicated for 15 min at a power of 40 W and a frequency of 30 kHz. The sonicated suspension was then stirred for 3 h at a temperature of 25 °C.

[0040] Dissolve 0.036 g of L-ascorbic acid in 10 mL of deionized water and pump it into the third mixed solution using a peristaltic pump at a flow rate of 1 mL / min. Perform the experiment in a fume hood. Stir the mixed solution with added L-ascorbic acid at room temperature for 5 h (PtCl4 + 2C6H8O6 → Pt 0 +4Cl - +2C6H6O6+4H + The precipitate was washed six times by centrifugation with deionized water and anhydrous ethanol, and the precipitate was placed in a vacuum drying oven at 60 °C for 12 h to obtain the VOCs catalyst.

[0041] Example 3 Three g of natural halloysite nanotubes were dispersed in 200 mL of a 6 mol / L acetic acid solution to obtain a first mixed solution. This first mixed solution was then sonicated for 65 min at a power of 120 W and a frequency of 40 kHz. The sonicated suspension was stirred at 70 °C for 3 days. After centrifugation and washing with deionized water until neutral, the halloysite suspension was dried in a vacuum drying oven. The dried halloysite powder was then ground to a fineness of 150-200 mesh.

[0042] The coal gasification fine slag was calcined at 800℃ (heating rate of 5℃ / min) for 4 hours. 20 g of the ash obtained after calcination of the coal gasification fine slag was dispersed in 200 mL of water, and 0.6 g of sodium hexametaphosphate was added and stirred. After stirring, the upper suspension was removed by siphoning through a silicone tube to obtain the decarbonized coal gasification fine slag at the bottom, which was mainly composed of amorphous microspheres.

[0043] 15 g of acidified halloysite nanotubes, 15 g of decarbonized coal gasification slag, 0.3 g of octadecyltrimethylammonium bromide and 120 mL of water were mixed, and the resulting slurry was refined and ground to obtain the catalyst support. The grinding speed was 1700 rpm and the grinding time was 180 min.

[0044] 2 g of catalyst support was dispersed in 20 mL of deionized water to obtain a support dispersion. 0.129 g of aspartic acid was dissolved in 10 mL of ethanol / water solution (volume ratio of ethanol to water was 3:2) to obtain a complexing agent aqueous solution. The support dispersion and the complexing agent aqueous solution were mixed and subjected to ultrasonic treatment at a power of 120 W for 15 min at a frequency of 40 kHz. After ultrasonic treatment, the mixture was stirred vigorously for 4.5 h to ensure uniform mixing.

[0045] 7.9 mL of Rh(NO3)3 solution (obtained by dissolving 200 mg Rh(NO3)3·2H2O in 50 mL of water) was added to the second mixed solution and sonicated for 15 min at a power of 40 W and a frequency of 30 kHz. The sonicated suspension was then stirred for 3 h at a temperature of 25 °C.

[0046] 0.0147 g of sodium borohydride was dissolved in 10 mL of deionized water and pumped into the third mixed solution using a peristaltic pump at a flow rate of 1 mL / min. The experiment was conducted in a fume hood. The mixed solution with added sodium borohydride was stirred continuously at room temperature for 5 h. The precipitate was washed 6 times each with deionized water and anhydrous ethanol by centrifugation. The precipitate was then placed in a vacuum drying oven at 60 ℃ for 12 h to obtain the VOCs catalyst.

[0047] Example 4 Three g of natural halloysite nanotubes were dispersed in 200 mL of a 3 mol / L acetic acid solution to obtain a first mixed solution. This first mixed solution was then sonicated for 60 min at a power of 80 W and a frequency of 30 kHz. The sonicated suspension was stirred at 55 °C for 3 days. After centrifugation and washing with deionized water until neutral, the halloysite suspension was dried in a vacuum drying oven. The dried halloysite was then ground to a fineness of 150–200 mesh to obtain acidified halloysite powder.

[0048] The coal gasification fine slag was calcined at 800℃ (heating rate of 5℃ / min) for 4 hours. 20 g of the ash obtained after calcination of the coal gasification fine slag was dispersed in 200 mL of water, and 0.2 g of sodium hexametaphosphate was added and stirred. After stirring, the upper suspension was removed by siphoning through a silicone tube to obtain the decarbonized coal gasification fine slag at the bottom, which was mainly composed of amorphous microspheres.

[0049] 15 g of acidified halloysite nanotubes, 15 g of decarbonized coal gasification slag, 0.75 g of sodium hexametaphosphate, and 120 mL of water were mixed, and the resulting slurry was refined and ground to obtain the catalyst support. The refining and grinding speed was 1500 rpm, and the grinding time was 170 min.

[0050] 2 g of catalyst support was dispersed in 20 mL of deionized water to obtain a support dispersion. 0.0763 g of proline was dissolved in 10 mL of ethanol / water solution (ethanol to water volume ratio of 3:2) to obtain a complexing agent aqueous solution. The support dispersion and complexing agent aqueous solution were mixed and then subjected to ultrasonic treatment at a power of 90 W, a time of 15 min, and a frequency of 35 kHz. After ultrasonication, the mixture was vigorously stirred for 4.5 h to ensure homogeneity.

[0051] Take 2.2 mL of Pd(NO3)2 solution (obtained by dissolving 200 mg Pd(NO3)2·2H2O in 50 mL of water) and 2.8 mL of PtCl4 solution (obtained by dissolving 200 mg PtCl4 in 50 mL of water) and add them to the second mixed solution for ultrasonic treatment. The ultrasonic treatment time is 20 min, the ultrasonic power is 50 W, and the ultrasonic frequency is 25 kHz. The suspension after ultrasonication is stirred for another 4 h.

[0052] Dissolve 0.01 g of sodium borohydride in 10 mL of deionized water and pump it into the third mixed solution using a peristaltic pump at a flow rate of 1 mL / min. The experiment was conducted in a fume hood. The mixed solution with added sodium borohydride was stirred continuously at room temperature for 6 h. The mixed solution was then washed 6 times each with deionized water and anhydrous ethanol by centrifugation. The precipitate was placed in a vacuum drying oven and kept at 60 °C for 12 h to obtain the VOCs catalyst.

[0053] Comparative Example 1 Three g of natural halloysite nanotubes were dispersed in 200 mL of a 1 mol / L acetic acid solution to obtain a first mixed solution. This first mixed solution was then sonicated for 50 min at a power of 80 W and a frequency of 30 kHz. The sonicated suspension was stirred at 60 °C for 2 days. After centrifugation and washing with deionized water until neutral, the halloysite suspension was dried in a vacuum drying oven. The dried halloysite powder was then ground to a fineness of 150-200 mesh.

[0054] The coal gasification fine slag was calcined at 800℃ for 4 hours. 20 g of the ash obtained after calcination was dispersed in 200 mL of water, and 0.1 g of sodium hexametaphosphate was added. After stirring, the upper suspension was removed by siphoning through a silicone tube to obtain the decarbonized coal gasification fine slag at the bottom, which was mainly composed of amorphous microspheres.

[0055] A slurry was prepared by mixing 20 g of acidified halloysite nanotubes, 20 g of decarbonized coal gasification slag, 1.2 g of sodium hexametaphosphate, and 160 mL of water. The slurry was then refined and ground to obtain a refined catalyst support. The grinding speed was 1400 rpm, and the grinding time was 240 min.

[0056] 2 g of catalyst support was dispersed in 20 mL of deionized water. 1.5 mL of Pd(NO3)2 solution (obtained by dissolving 200 mg Pd(NO3)2·2H2O in 50 mL of water), 1.9 mL of PtCl4 solution (obtained by dissolving 200 mg PtCl4 in 50 mL of water), and 2.5 mL of Rh(NO3)3 solution (obtained by dissolving 200 mg Rh(NO3)3·2H2O in 50 mL of water) were added to the suspension, and the mixture was sonicated for 15 min at a power of 60 W and a frequency of 30 kHz. The sonicated suspension was then stirred for 6 h.

[0057] Dissolve 0.0115 g of sodium borohydride in 10 mL of deionized water and slowly add it to the above suspension containing metal ions. This step is performed in a fume hood. The mixture with added sodium borohydride is stirred continuously for 6 h. The mixture is then washed 6 times each with deionized water and anhydrous ethanol by centrifugation. The precipitate is placed in a vacuum drying oven and kept at 60 °C for 12 h to obtain the VOCs catalyst.

[0058] Performance testing For Examples 1-4 and Comparative Example 1, the temperature at which toluene conversion rates were 50%, 90%, and 100% was mainly detected. The testing instrument was a gas chromatograph (GC, GC-2014C) equipped with a flame ionization detector (FID). The test results are shown in Table 1.

[0059] Table 1. Catalytic performance of VOCs catalysts obtained in Examples 1-4 and Comparative Example 1

[0060] Table 1 shows that the closer the catalyst synthesis conditions are to the optimal conditions (Example 1), the better the catalytic performance of the catalyst.

[0061] Figure 1 The image shows a SEM image of halloysite-supported calcined coal gasification fine slag prepared in Example 1. Figure 1 It can be clearly observed that halloysite nanotubes are uniformly dispersed and loaded on the surface of amorphous microspheres, which indicates that the fine slag from decarbonized coal gasification has a good dispersing effect on halloysite nanotubes.

[0062] Figure 2 This is a TEM image of the VOCs catalyst prepared in Example 1. From... Figure 2 It can be clearly observed that the active Pd particles on the catalyst surface have a particle size of <6 nm, which is more uniformly dispersed and beneficial to improving the utilization rate of Pd.

[0063] Figure 3 Here is a photograph of the VOCs catalyst prepared in Example 1. Figure 3 It can be seen that the catalyst is a grayish-blue powder, proving that the reducing agent has a positive effect on Pd. 2+ The process has been restored.

[0064] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a VOCs catalyst, characterized in that, Includes the following steps: (1) Halloysite nanotubes and acidifying reagent are mixed and acidified to obtain acidified halloysite powder; the acidifying reagent is acetic acid solution; (2) The coal gasification fine slag is roasted to obtain ash; then the roasted ash is mixed with water and dispersant, and the resulting mixture is purified by removing the upper suspension to obtain decarbonized coal gasification fine slag. (3) The acidified halloysite nanotubes, decarbonized coal gasification fine slag, grinding aid and water are mixed, and the resulting slurry is refined and ground to obtain the catalyst support; (4) The aqueous dispersion of the catalyst support and the solution of the complexing agent are mixed for the second time to obtain a second mixed solution; (5) The second mixed solution and the soluble solution containing metal ions are mixed for a third time to obtain a third mixed solution; (6) The third mixed solution and the reducing agent are mixed for a fourth time to carry out a reduction reaction and obtain the VOCs catalyst.

2. The preparation method according to claim 1, characterized in that, The calcination temperature is 800℃ and the time is 4 hours; the heating rate to the calcination temperature is 5℃ / min.

3. The preparation method according to claim 1, characterized in that, The first mixing process consists of a first ultrasonic treatment and a first stirring treatment performed sequentially; the power of the first ultrasonic treatment is 80~120 W; the first ultrasonic treatment time is 45~65 min; the frequency of the first ultrasonic treatment is 30~40 kHz; the temperature of the first stirring treatment is 50~70℃; and the time is 2~3 days. The second mixing process consists of a second ultrasonic treatment and a second stirring treatment performed sequentially; the power of the second ultrasonic treatment is 80~120 W; the time of the second ultrasonic treatment is 10~15 min; the frequency of the second ultrasonic treatment is 30~40 kHz; and the time of the second stirring treatment is 2.5~4.5 h. The third mixing process consists of a third ultrasonic treatment and a third stirring treatment performed sequentially; the power of the third ultrasonic treatment is 40~60 W; the time of the third ultrasonic treatment is 15~30 min; the frequency of the third ultrasonic treatment is 20~30 kHz; the temperature of the third stirring treatment is 25 ℃; and the time is 3~6 h.

4. The preparation method according to claim 1, characterized in that, The concentration of the acetic acid solution is 1~6 mol / L, and the solid-liquid ratio of the halloysite nanotubes and the acidifying reagent is 1g:10~200 mL.

5. The preparation method according to claim 1, characterized in that, In step (2), the solid-liquid ratio of ash and water is 1g:10mL, the mass of the dispersant is 0.5~5% of the mass of ash, and the dispersant is sodium hexametaphosphate or sodium pyrophosphate.

6. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of the acidified halloysite nanotubes to the decarbonized coal gasification fine slag is 1:1, the ball milling speed for refining and grinding is 1200~1700 rpm, the solid content of the acidified halloysite nanotubes and the decarbonized coal gasification fine slag in the slurry is 20 wt%, and the refining and grinding time is 160~240 min; the grinding aid is one or more of sodium hexametaphosphate, octadecyltrimethylammonium bromide and acetamide, and the mass of the grinding aid is 0.5~3% of the total mass of the acidified halloysite nanotubes and the decarbonized coal gasification fine slag.

7. The preparation method according to claim 1, characterized in that, The complexing agent is one or more of proline, glycine, aspartic acid, and arginine; the solvent in the solution of the complexing agent is ethanol and water; the volume ratio of ethanol to water is 3:2; and the molar ratio of the total molar number of the complexing agent to the total molar number of the metal ions is 10:

1.

8. The preparation method according to claim 7, characterized in that, The metal ions include one or more of Pd, Pt, Ru, and Rh ions; the reducing agent includes one or more of sodium borohydride, L-ascorbic acid, sodium D-isoascorbate, sodium citrate, and ammonium citrate.

9. The preparation method according to claim 7, characterized in that, The molar ratio of the reducing agent to the total number of metal ions is 4:1; the reduction reaction is carried out at room temperature for 5-6 hours.

10. The VOCs catalyst prepared by the preparation method according to any one of claims 1 to 9, characterized in that, The metal loading in the VOCs catalyst is 0.4~0.55 wt%; the particle size of the metal is <6 nm.

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