Coal gasification slag-based supported NaA type zeolite catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of solid waste recycling and high-value utilization and catalysis, and particularly relates to a preparation method and application of a coal gasification slag-based supported NaA type zeolite catalyst. According to the invention, through adsorption of heavy metal ions and combination of calcination treatment, a metal oxide or a metal simple substance is successfully loaded on NaA type zeolite. The introduction of the metal active component significantly improves the catalytic performance of the catalyst, and especially shows excellent activity in the catalytic reduction reaction of p-nitrophenol.

Description

Technical Field

[0001] The present invention belongs to the technical fields of solid waste resource utilization and high-value utilization, and catalysis, and particularly relates to a gasification slag-based supported NaA zeolite catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] Gasification slag is a by-product generated during the gasification process. Its main components include silicon (Si) and carbon (C), and it is a heterogeneous industrial solid waste. In recent years, researchers have widely focused on using the effective component silicon in gasification slag to prepare excellent-performance NaA zeolite adsorbent materials and applying them to the removal of heavy metal ions. The adsorption method has become the preferred method for water treatment technology due to its advantages such as high efficiency, simple operation, and easy regeneration. However, traditional research often ignores the risk of heavy metal ions being released into the environment during the use of the adsorbent. Therefore, the reuse problem of waste zeolite adsorbents has gradually attracted the attention of scholars. Zeolite adsorbents containing heavy metal ions belong to hazardous solid wastes and may cause serious secondary pollution. Currently, the main treatment methods for waste adsorbents include incinerating carbonaceous adsorbents or landfilling after solidification / stabilization, but these methods consume a large amount of lime and cement and may cause further environmental pollution.

[0003] p-Nitrophenol is a highly toxic and difficult-to-degrade nitrophenol compound, and its benzene ring contains -NO2 and -OH groups in the para position. Once it enters the water body, p-nitrophenol will cause great harm to the survival, growth, and reproduction of aquatic organisms. Therefore, catalytically degrading it into low-toxicity compounds is of great significance. In the present invention, through the phase transformation process of gasification slag, the silicon therein is converted into a NaA zeolite adsorbent material with excellent adsorption performance, and waste NaA zeolite materials that adsorb heavy metal ions (such as Fe 3+ 、Co 2+ 、Ni² + 、Cu 2+ and Zn 2+ etc.) are selected to construct AMO x -NAZ and AM0-NAZ (AM = Fe, Cu, Co, Zn, Ni, etc.) active functional materials to realize the resourceful reuse of waste NaA zeolite materials.

[0004] This method not only solves the secondary pollution problem of waste zeolite adsorbents but also provides a new way for the high-value utilization of gasification slag. By converting waste adsorbents into catalytically active functional materials, the present invention not only reduces the potential harm to the environment but also provides an efficient solution for the catalytic degradation of toxic pollutants such as p-nitrophenol, which has important environmental and economic significance. Summary of the Invention

[0005] Aiming at the problems existing in the prior art, the present invention provides a coal gasification slag-based supported NaA zeolite catalyst, its preparation method and application.

[0006] The present invention is realized through the following technical solutions: The present invention provides a preparation method of a coal gasification slag-based supported NaA zeolite catalyst, including the following steps: (1) Place the coal gasification slag in an oven to dry the moisture, grind it with a ball mill, and then sieve it. Dry the sieved sample, ultrasonically disperse the dried coal gasification slag evenly in a 1 mol / L dilute hydrochloric acid solution, and then magnetically stir it under water bath conditions and perform solid-liquid separation; the purpose of this step is to dissolve metal oxides (such as iron oxide) and impurities in the coal gasification slag, remove impurities, and improve the purity of silicon and aluminum.

[0007] (2) Add the solid filter residue after solid-liquid separation in step (1) to a sodium hydroxide solution with a concentration of 2.5 mol / L, magnetically stir at room temperature, and then obtain pure silicon solution through centrifugal separation; the purpose of this step is to convert silicon and aluminum in the solid filter residue into soluble sodium silicate and sodium aluminate. Its function is to extract the silicon solution and provide a silicon source for the subsequent synthesis of NaA zeolite.

[0008] (3) Mix and stir the silicon solution in step (2) with sodium aluminate at room temperature. After mixing evenly, transfer it to a stainless steel hydrothermal autoclave for hydrothermal reaction to finally obtain pure-phase NaA zeolite, named NAZ; the purpose of this step is that the silicon solution (mainly composed of sodium silicate) reacts with sodium aluminate under hydrothermal conditions to form the crystal structure of NaA zeolite through polycondensation and rearrangement.

[0009] (4) Dissolve the heavy metal salt in deionized water to prepare a heavy metal salt solution. Add the NaA zeolite obtained in step (3) to the heavy metal salt solution, stir, and then collect the NaA zeolite material adsorbed with heavy metal ions, and rinse and store it with deionized water; (5) Place the NaA zeolite adsorbed with heavy metal ions obtained in step (4) in an alumina crucible, calcine it and keep it warm for the corresponding time, and collect the obtained sample.

[0010] Further, in step (1), for every 1 g of coal gasification slag, 20 mL of dilute hydrochloric acid solution is corresponding; the temperature of the water bath is 85 °C.

[0011] Water bath heating can provide a uniform and stable temperature environment, avoiding local overheating or uneven reaction. The temperature of 85 °C can effectively promote the reaction of components such as silicon and aluminum in the coal gasification slag with dilute hydrochloric acid, making them fully dissolve or disperse. Too high a temperature will cause side reactions.

[0012] The role of dilute hydrochloric acid is to dissolve metal oxides and other soluble components in coal gasification slag. The ratio of 1g coal gasification slag to 20mL dilute hydrochloric acid solution can ensure that the effective components in the coal gasification slag are fully in contact with the acid, avoiding incomplete reaction due to insufficient acid. Too much acid will increase the difficulty of subsequent treatment. The concentration of 1mol / L dilute hydrochloric acid is moderate, which can effectively dissolve metal oxides in coal gasification slag, and will not cause excessive corrosion or produce too many by-products due to excessive acid concentration.

[0013] Furthermore, in step (2), 40 mL of sodium hydroxide solution is used for every 2 g of the filter residue obtained in step (1). Too much sodium hydroxide solution will increase the side reaction and affect the purity of the silicon liquid; insufficient sodium hydroxide will cause the silicon in the filter residue to fail to fully dissolve, reduce the extraction efficiency of silicon, and further affect the subsequent synthesis of NaA zeolite.

[0014] Furthermore, in step (3), the amount of sodium aluminate added is limited to 2 g of sodium aluminate per 40 mL of the silicon liquid obtained in step (2), the hydrothermal temperature is 90° C., and the hydrothermal time is 18 h.

[0015] The amount of sodium aluminate added is limited to ensure that the molar ratio of silicon to aluminum is close to the theoretical value of NaA zeolite (Si / Al ≈ 1), thereby avoiding the formation of impurities. The hydrothermal reaction is carried out at 90°C, providing a suitable temperature and pressure environment to promote the dissolution, rearrangement and crystallization of aluminosilicates to form NaA zeolite. The reaction time of 18 hours ensures that the crystallization process is fully completed, and NaA zeolite with high crystallinity and high purity is obtained.

[0016] Furthermore, in step (4), the heavy metal salt is one of copper nitrate trihydrate, cobalt nitrate hexahydrate, nickel nitrate hexahydrate, iron nitrate nonahydrate and zinc nitrate hexahydrate, the heavy metal ion concentration is 40 mg / L, and the addition ratio of the NaA type zeolite material and the heavy metal salt solution is limited to 1 mg:1 mL.

[0017] Furthermore, the calcination atmosphere in step (5) is calcined in an air atmosphere to obtain the NaA type zeolite loaded with metal oxides, the calcination temperature is 500-600°C, and the insulation time is 4-8h.

[0018] Furthermore, the calcination atmosphere in step (5) is H2 / Ar (5 vol% H2) mixed atmosphere to obtain NaA type zeolite loaded with metal element, the calcination temperature is 500-600°C, and the insulation time is 4-8h.

[0019] The invention also provides a coal gasification slag-based supported NaA zeolite catalyst prepared by the preparation method.

[0020] The present invention also provides application of the coal gasification slag-based supported NaA zeolite catalyst in catalytic reduction of p-nitrophenol.

[0021] Compared with the prior art, the present invention has the following technical effects: (1) The present invention uses coal gasification slag as raw material and converts it into high-value-added NaA zeolite (NAZ) through acid treatment, alkali dissolution, hydrothermal synthesis and other steps. This not only realizes the high-value-added utilization of effective components of coal gasification slag, but also applies it to the adsorption and removal of heavy metal ions, thus realizing waste treatment and resource utilization of coal gasification slag, which is in line with the concepts of green chemistry and sustainable development.

[0022] (2) The present invention adopts conventional chemical treatment and hydrothermal synthesis methods, with mild process conditions, simple operation, and easy industrial production. Using coal gasification slag as raw material significantly reduces the preparation cost of zeolite catalysts and avoids the high cost problem of high-purity silicon and aluminum sources in traditional zeolite synthesis.

[0023] (3) The present invention successfully loads metal oxides or metal elements onto NaA zeolite by adsorbing heavy metal ions and combining calcination treatment. The introduction of metal active components significantly improves the catalytic performance of the catalyst, especially in the catalytic reduction reaction of p-nitrophenol, showing excellent activity.

[0024] (4) The metal-loaded NaA zeolite catalyst has a high specific surface area, rich pore structure and uniformly dispersed active sites, which can effectively adsorb reactants and provide sufficient catalytic active centers. In the catalytic reduction reaction of p-nitrophenol, the catalyst can efficiently reduce p-nitrophenol to p-aminophenol with a fast reaction rate and high conversion rate.

[0025] (5) By adjusting the calcination atmosphere (air or H2 / Ar mixed gas), NaA zeolite catalysts loaded with metal oxides or metal elements can be prepared respectively. This flexibility enables the catalyst to adapt to different catalytic reaction requirements and expands its application range. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is the X-ray diffraction pattern of the NaA type zeolite material powder obtained in step 3; Figure 2 This is a scanning electron microscope image of the NaA type zeolite material powder obtained in step 3; Figure 3 The adsorbed metal ion Cu was calcined in a H2 / Ar (5 vol% H2) mixed atmosphere obtained in step 5. 2+ X-ray diffraction pattern of NaA type zeolite material powder; Figure 4 This is the result diagram of the effect of the amount of catalyst added on the catalytic performance; Figure 5 Graph of the influence of the concentration of p-nitrophenol solution on the catalytic performance; Figure 6 Graph of the influence of the mass of sodium borohydride on the catalytic performance. Specific embodiments

[0027] The present invention will be further described below in conjunction with embodiments, but the present invention is not limited to the following embodiments.

[0028] In the following examples, the coal gasification slag is provided by a coal chemical enterprise in Shandong.

[0029] Table 1. Ultimate analysis of coal gasification slag ad / % C H N O 46.57 0.89 0.20 52.34 Table 2. Proximate analysis of coal gasification slag ad / % <![CDATA[K2O]]> <![CDATA[SiO2]]> <![CDATA[SO3]]> <![CDATA[Al2O3]]> CaO <![CDATA[Fe2O3]]> MgO <![CDATA[P2O5]]> <![CDATA[TiO2]]> <![CDATA[Na2O]]> 1.05 41.52 2.10 19.76 18.70 10.40 1.88 0.4 0.82 3.37 Example 1 (1) Place 8 g of coal gasification slag in an oven and dry the moisture at 100 °C for 8 h. Grind it in a ball mill for 1 - 2 h at a rotation speed of 300 - 500 r / min. After grinding, sieve it through a 200-mesh sieve. Take 4 g of the sieved coal gasification slag multiple times and put it into 80 mL of 1 mol / L dilute hydrochloric acid solution, and disperse it evenly by ultrasonic treatment. Stir magnetically at 85 °C in a water bath for 2 h, and then separate the solid and liquid to obtain the filter residue; (2) Add 2 g of the filter residue obtained in step (1) to 40 mL of 2.5 mol / L sodium hydroxide solution, disperse it evenly by ultrasonic treatment, stir magnetically at room temperature for 6 h, and then obtain relatively pure silicon solution by centrifugal separation; (3) Mix and stir the silicon solution (40 mL) obtained by centrifugation in step (2) with 2 g of sodium aluminate at room temperature. After mixing evenly, transfer it to a stainless steel hydrothermal autoclave and keep it at 90 °C for 18 h to finally obtain pure-phase NaA zeolite "NAZ"; (4) Dissolve copper nitrate trihydrate in deionized water to prepare a corresponding heavy metal ion solution with a concentration of 40 mg / L. Add 60 mg of NaA zeolite obtained in step (3) to 60 mL of the heavy metal ion solution, stir at 25 °C for 2 h, and then collect the NaA zeolite "Cu 2+ -NAZ" that adsorbs heavy metal ions Cu 2+ , rinse it with deionized water, and store it for subsequent experiments; (5) Place the NaA zeolite material (Cu 2+ -NAZ) that adsorbs heavy metal ions Cu 2+ obtained in step (4) in an alumina crucible, calcine it at 550 °C and keep it warm for 6 h in a mixed atmosphere of H2 / Ar (5 vol% H2), and collect the relevant sample "Cu-NAZ" at room temperature.

[0030] Figure 1 It is the X-ray diffraction pattern of the NaA zeolite material powder obtained in Step 3. It can be seen that the diffraction peaks at 2θ = 7.3°, 10.3°, 12.5°, 16.1°, 21.8°, 24.1°, 26.2°, 27.1°, 29.9° and 34.4° correspond to the (200), (220), (222), (420), (600), (622), (640), (642), (820) and (664) crystal planes of NaA zeolite respectively (JCPDS card number 89-5423).

[0031] Figure 2 It is the scanning electron microscope image of the NaA zeolite material powder obtained in Step 3. It can be seen that the NaA zeolite presents a uniform rhombic block shape, and its size is about 1.5 μm.

[0032] Figure 3 It is the X-ray diffraction pattern of the NaA zeolite material powder calcined in the H2 / Ar (5 vol% H2) mixed atmosphere obtained in Step 5 and adsorbed with metal ion Cu 2+ ; this pattern shows the characteristic diffraction peaks of the Cu (JCPDS card No. 89-2838) phase, and 2θ = 43.5°, 50.5° and 74.2° correspond to the (111), (200) and (220) crystal planes of Cu respectively.

[0033] Example 2 The difference between Example 2 and Example 1 is that the calcination temperature is 500 °C and the heat preservation time is 6 h.

[0034] Example 3 The difference between Example 3 and Example 1 is that the calcination temperature is 600 °C and the heat preservation time is 6 h.

[0035] Example 4 The difference between Example 4 and Example 1 is that the calcination atmosphere in Step (5) is calcination at 550 °C in air atmosphere and heat preservation for 6 h, and the collected sample "CuO-NAZ" is obtained.

[0036] Example 5 The difference between Example 5 and Example 4 is that the calcination atmosphere in Step (5) is calcination at 500 °C in air atmosphere and heat preservation for 6 h, and the collected sample "CuO-NAZ" is obtained.

[0037] Example 6 The difference between Example 6 and Example 4 is that the calcination atmosphere in Step (5) is calcination at 600 °C in air atmosphere and heat preservation for 6 h, and the collected sample "CuO-NAZ" is obtained.

[0038] Example 7 The difference between Example 7 and Example 1 is that the calcination holding time is 4 hours, and the other conditions are exactly the same.

[0039] Example 8 The difference between Example 8 and Example 1 is that the calcination holding time is 8 hours, and the other conditions are exactly the same.

[0040] Example 9 The difference between Example 9 and Example 1 is that the metal salt is cobalt nitrate hexahydrate, and the other conditions are exactly the same.

[0041] Example 10 The difference between Example 10 and Example 1 is that the metal salt is nickel nitrate hexahydrate, and the other conditions are exactly the same.

[0042] Example 11 The difference between Example 11 and Example 1 is that the metal salt is iron nitrate nonahydrate, and the other conditions are exactly the same.

[0043] Example 12 The difference between Example 12 and Example 1 is that the metal salt is zinc nitrate hexahydrate, and the other conditions are exactly the same.

[0044] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the calcination temperature is 400 °C and the holding time is 6 h.

[0045] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the calcination temperature is 700 °C and the holding time is 6 h.

[0046] Comparative Example 3 Comparative Example 3 is the NaA zeolite without calcination for adsorbing heavy metal ion Cu 2+

[0047] Comparative Example 4 The difference between Comparative Example 4 and Example 4 is that the calcination atmosphere in step (5) is calcination at 400 °C in air atmosphere and holding for 6 h, and the sample "CuO-NAZ" is collected.

[0048] Comparative Example 5 The difference between Comparative Example 5 and Example 4 is that the calcination atmosphere in step (5) is calcination at 700 °C in air atmosphere and holding for 6 h, and the sample "CuO-NAZ" is collected.

[0049] Comparative Example 6 The difference between Comparative Example 6 and Example 1 is that the calcination holding time is 10 hours, and the other conditions are exactly the same.

[0050] ​Comparative Example 7 The difference between Comparative Example 7 and Example 1 is that the calcination holding time is 2 hours, and the other conditions are exactly the same.

[0051] Examples 1-3 and Comparative Examples 1-3 explored the effect of calcination temperature on the catalytic performance of the material. 60 mg of the zeolite materials obtained in Examples 1-3 and Comparative Examples 1-3 were added to 60 mL of a p-nitrophenol solution (20 mg / L) containing 10 mg of sodium borohydride for catalytic reduction. The results are shown in Table 3.

[0052] Table 3. Comparison of the catalytic performance of the materials in Examples 1-3 and Comparative Examples 1-3 Calcination temperature Reduction rate (%) 550 (Example 1) 93 500 (Example 2) 75 600 (Example 3) 94 700 (Comparative Example 1) 93 400 (Comparative Example 2) 56 0 (Comparative Example 3) 0.5 The reasons are as follows: When the calcination temperature is lower than 550 °C in Example 1, the heavy metal Cu 2+ ions loaded on the NaA zeolite cannot be completely converted into elemental Cu. Therefore, the calcination temperature is set above 550 °C. The lower the calcination temperature, the lower the conversion rate of elemental Cu, and thus the reduction rate of p-nitrophenol is greatly reduced.

[0053] Examples 4-6 and Comparative Examples 4, 5 explored the effect of calcination temperature on the catalytic performance during calcination in an air atmosphere. The results are shown in Table 4.

[0054] Table 4. Comparison of the catalytic performance of the materials in Examples 4-6 and Comparative Examples 4, 5 Atmosphere / Temperature Reduction rate (%) Air 550 (Example 4) 90 Air 500 (Example 5) 82 Air 600 (Example 6) 90 Air 400 (Comparative Example 4) 73 Air 700 (Comparative Example 5) 89 The reasons are as follows: When calcining the Cu 2+ ions loaded on the NaA zeolite in an air atmosphere, CuO is finally obtained due to the participation of oxygen in the air. The calcination temperature at which the Cu 2+ ions are completely converted into CuO in situ also needs to be higher than 550 °C. However, the electron transfer ability of the CuO obtained in an air atmosphere is lower than that of elemental Cu, so the catalytic activity is reduced.

[0055] Examples 1 and Examples 7-8, Comparative Examples 6-7 explored the effect of holding time on the catalytic performance of the material. 60 mg of the zeolite materials obtained in Examples 1, 7-8 and Comparative Examples 6-7 were added to 60 mL of a p-nitrophenol solution (20 mg / L) containing 10 mg of sodium borohydride for catalytic reduction. The results are shown in Table 5.

[0056] Table 5. Comparison of the catalytic performance of the materials in Examples 1, 7-8 and Comparative Examples 6-7 Heat preservation time (h) Removal rate (%) 6 (Example 1) 93 4 (Example 7) 92 8 (Example 8) 90 10 (Comparative Example 6) 85 2 (Comparative Example 7) 80 The reasons are as follows: When the heat preservation time is set in the range of 4 - 8 h, the size distribution of elemental Cu mainly concentrates in the range of 5 - 10 nm. Such particle size ensures that elemental Cu has a large specific surface area and high catalytic reduction activity. When the heat preservation time is extended to 10 h, the particle size of elemental Cu grows, the specific surface area decreases, and the risk of oxidation increases, resulting in its low catalytic activity. However, if the heat preservation time is too short, such as 2 h, the Cu particles do not grow to a suitable size, and the too-small size causes a large amount of aggregation, reducing the catalytic activity.

[0057] Examples 1, 9 - 12 explored the influence of different metal salts. 60 mg of the zeolite materials obtained in Examples 1, 9 - 12 were added to 60 mL of p-nitrophenol solution (20 mg / L) containing 10 mg of sodium borohydride for catalytic reduction, and the results are shown in Table 6.

[0058] Table 6. Comparison of the catalytic performance of the materials in Examples 1, 9 - 12 Metal type Removal rate (%) Cu (Example 1) 93 Co (Example 9) 95 Ni (Example 10) 95 Fe (Example 11) 75 Zn (Example 12) 78 The reasons are as follows: Valuable metal elements Co, Ni, and Cu have higher electron transfer efficiency compared with metal Fe and Zn, which accelerates the conversion of p-nitrophenol to p-aminophenol. For elemental Co, Ni, and Cu with high catalytic efficiency, elemental Cu with lower cost is used as a suitable catalyst.

[0059] On the basis of the above analysis, further exploration was carried out on the influence of the catalyst addition amount, the concentration of p-nitrophenol solution, and the mass of sodium borohydride on the catalytic performance.

[0060] Exploration of the influence of the catalyst addition amount on the catalytic performance Weigh 50, 60, and 70 mg of the catalyst prepared in Example 1 and add them to 60 mL of p-nitrophenol solution (20 mg / L) containing 10 mg of sodium borohydride for catalytic reduction. The results are shown in Figure 4 , from Figure 4 it can be seen that when the catalyst addition amount is 50 mg and the reduction time is 30 min, its reduction efficiency is 97.7%. With the increase of the catalyst addition amount, the reduction efficiency of p-nitrophenol is inhibited. Due to the addition of excessive catalyst, agglomeration occurs among the catalysts in the system, so that the active surface is not exposed too much, and the catalytic performance is greatly reduced.

[0061] Exploration of the influence of the concentration of p-nitrophenol solution on the catalytic performance Weigh 3 portions of 60 mg of the catalyst prepared in Example 1 and add them to 60 mL of p-nitrophenol solutions with concentrations of 5 mg / L, 10 mg / L, and 20 mg / L containing 10 mg of sodium borohydride for catalytic reduction. The results are shown in Figure 5, The results show that with the increase of the initial concentration of p-NP, the catalytic reduction efficiency of the catalyst decreases to a certain extent, which may be due to the excessive occupation of the active sites on the catalyst surface. When the initial concentration of p-NP is 20 ppm (60 mg catalyst, 10 mg sodium borohydride, 60 mL solution volume), the reduction efficiency is 97.5%.

[0062] Investigate the effect of the mass of sodium borohydride on the catalytic performance Weigh 3 portions of 60 mg of the catalyst prepared in Example 1 and add them to 60 mL of a 20 mg / L p-nitrophenol solution containing 10 mg, 30 mg, and 60 mg of sodium borohydride for catalytic reduction. The results are shown in Figure 6 , The results show that with the increase of the amount of sodium borohydride used, the reduction rate of p-nitrophenol continuously increases. The increase in the amount of sodium borohydride used provides more hydride ions for the system, so the reduction efficiency is greatly improved.

Claims

1. A preparation method of a coal gasification slag-based supported NaA zeolite catalyst, characterized in that: The following steps are involved: (1) Dry the coal gasification slag to remove moisture, grind and sieve it with a ball mill, and dry it. Ultrasonic disperse the dried coal gasification slag in a 1 mol / L dilute hydrochloric acid solution, and then separate the solid and liquid by magnetic stirring in a water bath; (2) The solid residue after solid-liquid separation in step (1) is added to a sodium hydroxide solution with a concentration of 2.5 mol / L, magnetically stirred at room temperature, and then centrifuged to obtain pure silicon liquid; (3) mixing the silicon liquid and sodium aluminate in step (2) at room temperature, stirring and mixing them evenly to carry out a hydrothermal reaction, and finally obtaining a pure phase NaA type zeolite, named NAZ; (4) dissolving a heavy metal salt in deionized water to prepare a heavy metal salt solution, adding the NaA zeolite obtained in step (3) to the heavy metal salt solution, stirring, then collecting the NaA zeolite material adsorbing heavy metal ions, and rinsing with deionized water for storage; (5) calcining the NaA zeolite adsorbing heavy metal ions obtained in step (4), keeping it warm for a corresponding period of time, and collecting the obtained sample.

2. The preparation method of the gasification slag-based supported NaA zeolite catalyst according to claim 1, characterized in that: In step (1), 1 g of coal gasification slag corresponds to 20 mL of dilute hydrochloric acid solution; the temperature of the water bath is 85°C.

3. The preparation method of the gasification slag-based supported NaA zeolite catalyst according to claim 1, characterized in that: In step (2), every 2 g of the filter residue obtained in step (1) corresponds to 40 mL of sodium hydroxide solution.

4. The preparation method of the coal gasification slag-based supported NaA zeolite catalyst according to claim 1, wherein: In step (3), the amount of sodium aluminate added is limited to 2 g of sodium aluminate per 40 mL of the silicon liquid obtained in step (2), the hydrothermal temperature is 90° C., and the hydrothermal time is 18 h.

5. The preparation method of the coal gasification slag-based supported NaA zeolite catalyst according to claim 1, characterized in that: In step (4), the heavy metal salt is one of copper nitrate trihydrate, cobalt nitrate hexahydrate, nickel nitrate hexahydrate, iron nitrate nonahydrate and zinc nitrate hexahydrate, the heavy metal ion concentration is 40 mg / L, and the addition ratio of NaA type zeolite material and heavy metal salt solution is limited to 1 mg:1 mL.

6. The preparation method of the gasification slag-based supported NaA zeolite catalyst according to claim 1, characterized in that: The calcination atmosphere in step (5) is to calcine in an air atmosphere to obtain the NaA type zeolite loaded with metal oxides, the calcination temperature is 500-600°C, and the insulation time is 4-8h.

7. The preparation method of the coal gasification slag-based supported NaA zeolite catalyst according to claim 1, characterized in that: The calcination atmosphere in step (5) is to calcine the NaA type zeolite loaded with metal element in a H2 / Ar mixed atmosphere, wherein hydrogen accounts for 5% of the total volume of the mixed atmosphere and the remaining 95% is argon. The calcination temperature is 500-600°C and the insulation time is 4-8h.

8. A coal gasification slag-based supported NaA zeolite catalyst prepared by the preparation method according to any one of claims 1 to 7.

9. Use of a coal gasification slag-based supported NaA zeolite catalyst prepared by the preparation method according to any one of claims 1 to 7 in the catalytic reduction of p-nitrophenol.

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