A porous cordierite-based low-temperature denitration catalyst prepared from gasification slag, its preparation method and application

Abstract

This invention discloses a method for preparing a porous cordierite-based low-temperature denitrification catalyst using gasification slag as raw material, along with its application. The method involves adding a curing agent to the gasification slag and calcining it to eliminate interference from harmful elements such as arsenic, lead, and cadmium. The gasification slag is then used to prepare a porous cordierite support. Active components and co-catalysts are grown on the catalyst surface via impregnation. Finally, the finished catalyst is prepared through calcination. The catalyst synthesized by this invention exhibits high structural strength and a large specific surface area, maintaining high denitrification efficiency even at low temperatures. Simultaneously, it achieves high-value-added reuse of the gasification slag, possessing significant economic value and broad market application prospects.

Description

Technical Field

[0001] This invention relates to a method for preparing a porous cordierite-based low-temperature denitrification catalyst using gasification slag as raw material, belonging to the field of air pollution control and waste treatment. Background Technology

[0002] my country is rich in coal but poor in oil and natural gas, so it utilizes coal-to-oil technology to supply industrial fuel, residential gas, and metallurgical reducing gas. During the coal gasification stage, the organic matter in the coal undergoes a series of chemical reactions with the gasifying agent (such as steam / air or oxygen), converting solid coal into combustible gases containing CO, H2, and CH4, and non-combustible gases such as CO2 and N2, leaving behind a large amount of residue, known as gasification slag. A 75t / h boiler can emit 200t of gasification slag per day. With the continuous development of the coal slag gasification industry, a large amount of gasification slag has accumulated. Gasification slag contains heavy metals such as arsenic, mercury, lead, and cadmium, posing potential risks to human health and the environment.

[0003] Currently, the main methods for treating gasification slag are its use as a cement raw material, in the preparation of ceramsite, concrete wall materials, and bricks. For example, patent CN116444235A discloses a method for preparing concrete using gasification slag, fly ash, and coal gangue as raw materials, achieving a concrete strength of C50 or higher. Another example is patent CN102276225B, which uses fluidized bed slag, blast furnace slag, steel slag, coal slag, yellow phosphorus slag, and gasification slag as raw materials, and processes pretreatment, mixing, static pressing, stacking, and steam curing to obtain non-fired bricks. These non-fired bricks have high strength, are frost-resistant, and do not react with alkalis. The main use of gasification slag is as a raw material for cement production. GB / T1596-2017 specifies the loss on ignition and sulfur content of gasification slag. The above-mentioned treatment methods cannot fully realize the value of gasification slag, and with the decline of the domestic cement industry, there is an urgent need to find a safe and high-value-added disposal solution. The main components of gasification slag are SiO2, Al2O3, and CaO, making it an excellent carrier material. Utilizing gasification slag to synthesize carriers and applying them to the field of denitrification is a potential direction. Summary of the Invention

[0004] The purpose of this invention is to solve the problem of the lack of high-value-added reuse solutions for gasification slag. Another purpose of this invention is to provide a method for preparing a low-temperature denitrification catalyst.

[0005] The objective of this invention can be achieved through the following technical solution: This solution selects gasification slag as the carrier raw material. The residual carbon in the gasification slag gives it a high calorific value, and the oxidation of carbon leaves numerous micropores in their original positions, resulting in a large specific surface area. However, the presence of heavy metal impurities such as arsenic, lead, and cadmium in the gasification slag can affect its denitrification performance, thus requiring pretreatment. In this solution, the gasification slag is mixed with a curing agent and calcined at high temperature to allow the curing agent to combine with impurities such as lead, cadmium, and arsenic in the gasification slag to form a solid solution, reducing the impact of these impurities on denitrification performance. Then, a series of pore-forming agents, binders, and modifiers are added, and a porous cordierite carrier is synthesized through calcination. Compared with traditional cordierite with low specific surface area, the cordierite synthesized by this method not only has high strength but is also rich in micropores and macropores, overcoming the problem of low specific surface area in conventional cordierite; simultaneously, its surface is rich in acidic sites, which is beneficial for capturing NH3, making it an excellent denitrification catalyst carrier. Finally, the active components and co-catalysts are loaded by impregnation and then cured by calcination to obtain the finished catalyst.

[0006] A method for preparing a porous cordierite-based low-temperature denitration catalyst using gasification slag as raw material is disclosed. The catalyst uses gasification slag as raw material, which is pretreated to form a porous cordierite support. Then, an active component and a co-catalyst are loaded onto the surface and pores of the support using an impregnation method. Finally, the active component and co-catalyst are calcined to fix them. The active component is La₂O₃, and the co-catalyst is MoO₃. Based on the mass of the support, the mass percentage of the active component is 5-8%, and the mass percentage of the co-catalyst is 2-5%.

[0007] The specific synthesis steps are as follows:

[0008] (1) The vaporized slag and the curing agent are put into a grinding mill for grinding, and the screened powder is then roasted;

[0009] (2) Mix the powder obtained in step (1) with the pore-forming agent, binder and magnesium source evenly, dissolve the cerium source and zirconium source in deionized water, then mix the two evenly, knead and extrude to form a mold, and then calcine at 1000~1200℃.

[0010] (3) Dissolve the active component precursor and the co-catalyst precursor in deionized water to prepare a mixed solution, and then immerse the formed support in the mixed solution for equal volume impregnation.

[0011] (4) After thoroughly drying the solid obtained in step (3), impregnate it twice with an equal volume of ammonia solution;

[0012] (5) After thoroughly drying the solid obtained in step (4), calcinate it at 500~550℃ to obtain the finished catalyst.

[0013] In the above method: the curing agent in step (1) is a mixture of ferrous sulfate, bismuth nitrate and tin sulfate. The molar amount of ferrous sulfate added is 3 to 5 times the molar amount of arsenic in the gasification slag, the molar amount of bismuth nitrate added is 3 to 5 times the molar amount of lead in the gasification slag, and the molar amount of tin sulfate added is 3 to 5 times the molar amount of cadmium in the gasification slag.

[0014] In the above method: the particle size after grinding in step (1) is below 100 mesh; the calcination temperature in step (1) is 800~1000℃, the calcination time is 5~8h, and the calcination environment is an air atmosphere.

[0015] In the above method: the pore-forming agent in step (2) is flour or starch, and the mass of the pore-forming agent added is 30-60% of the mass of the powder obtained in step (1);

[0016] The binder mentioned in step (2) is polyethylene oxide (PEO), carboxymethyl cellulose (CMC), or polyvinyl alcohol (PVA), and the mass of the binder added is 3-5% of the mass of the powder obtained in step (1);

[0017] The magnesium source mentioned in step (2) is magnesium nitrate or magnesium chloride, and the molar amount of magnesium source added is 100-150% of the molar amount of aluminum in the gasification slag;

[0018] The cerium source mentioned in step (2) is cerium nitrate or cerium chloride, and the molar amount of cerium source added is 6-10% of the molar amount of aluminum in the vaporized slag;

[0019] The zirconium source mentioned in step (2) is zirconium oxychloride or zirconium nitrate, and the mass of the zirconium source added is 2 to 5% of the powder obtained in step (1).

[0020] In the above method: the extrusion molding shape in step (2) is a column with a diameter of 3~6mm, and the extrusion pressure is 2~5Mpa;

[0021] The roasting temperature in step (2) is 1000~1200℃, the roasting time is 3~5h, and the roasting environment is an empty atmosphere.

[0022] In the above method: the active component precursor in step (3) is a lanthanum nitrate or chloride, and the co-catalyst precursor is ammonium tetramolybdate or ammonium heptamolybdate;

[0023] The concentration of the ammonia solution in step (4) is 15-25%;

[0024] The roasting temperature in step (5) is 500~550℃, the roasting time is 6~12h, and the roasting environment is an empty atmosphere.

[0025] A porous cordierite-based low-temperature denitration catalyst prepared from gasification slag is disclosed. The catalyst is prepared by the method described above.

[0026] In the technical solution of this invention, the catalyst prepared by the method is used in low-temperature denitrification.

[0027] Furthermore, the application temperature is 120~180℃, and the operating environment has SO2≤35mg and H2O≤8%.

[0028] Beneficial effects:

[0029] (1) The low-temperature denitrification catalyst was prepared by selecting gasification slag as raw material, which solved the problem of large-scale accumulation of gasification slag and realized its high-value-added resource reuse. Since the residual organic matter in the gasification slag has a high calorific value, energy consumption can be reduced in the pretreatment stage. At the same time, the micropores left after the organic matter volatilizes increase the specific surface area of ​​the carrier.

[0030] (2) The gasification slag contains heavy metal impurities such as arsenic, lead, and cadmium. By introducing a curing agent, the heavy metal impurities are transformed into solid solutions or stable compounds, thus avoiding the influence of heavy metal impurities on denitrification performance. The curing agent is a mixture of iron, tin, and bismuth compounds, which itself has certain denitrification performance. Excess curing agent can act as an active component to improve the denitrification catalytic activity.

[0031] (3) Using flour or starch as a pore-forming agent, it is mixed with pretreated vaporized slag powder and additives, kneaded into shape, and then calcined to prepare cordierite carrier. Flour or starch has strong plasticity, which is conducive to kneading into a ball and uniform dispersion of each component. At the same time, at high temperature, flour and starch will oxidize and leave pores in their original positions, so that the cordierite carrier has a multi-level pore structure, which increases the specific surface area.

[0032] (4) Introducing cerium salt and zirconium salt during the preparation of cordierite support can promote the formation of cordierite crystal form, and excess cerium oxide can improve catalytic activity as an active component; zirconium salt can improve the surface acidity of the support and improve the support's ability to capture NH3.

[0033] (5) Porous cordierite was prepared by vaporization slag, which not only solved the problem of small specific surface area of ​​cordierite, but also had strong compressive strength.

[0034] (6) The synthesized denitrification catalyst has high denitrification activity in the temperature range of 120~180℃, and the denitrification efficiency can reach more than 95% in the temperature range of 150~180℃. Moreover, the denitrification catalyst has strong resistance to water sulfur poisoning.

[0035] The catalyst has readily available raw materials, a simple process, low cost, extremely high denitrification performance at low temperatures, and excellent resistance to water sulfur poisoning. It also solves the problems of large-scale accumulation of gasification slag and lack of high-value-added reuse solutions, thus possessing high economic value and broad market application prospects. Attached Figure Description

[0036] AppendixFigure 1 Detailed implementation method and denitrification performance diagram;

[0037] Appendix Figure 2 Detailed implementation method: SO2 / SO3 conversion rate diagram;

[0038] Appendix Figure 3 Detailed implementation method: Denitrification performance diagram of water sulfur poisoning test. Detailed Implementation

[0039] The following examples further illustrate the method for preparing a porous cordierite-based low-temperature denitrification catalyst using gasification slag as raw material according to the present invention. The examples are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following examples.

[0040] Unless otherwise specified, the experimental methods described in the following examples are conventional methods in the art, and the experimental apparatus and raw materials are commercially available unless otherwise specified. The gasification slag was purchased from Inner Mongolia Xinjiuchangyuan Environmental Protection Technology Co., Ltd., and its specific composition is as follows:

[0041] content 46.53 25.79 8.74 12.88 1.42 0.76 0.51

[0042] Denitrification performance test: The catalyst was crushed, and 2 ml of 20-40 mesh particles were screened and transferred to the center of the quartz reactor. The catalyst was fixed on both sides with quartz wool. Simulated NOx gas (NO (600ppm), NH3 (600ppm), O2 (6vol%), SO2 (13ppm), N2 as carrier gas) was introduced into one end of the quartz reactor, and the GHSV was 5000h. -1 The other end is connected to a flue gas analyzer to detect the concentrations of NO and SO2 in the exhaust gas. The temperature of the quartz reactor is controlled at 120~180℃, and the exhaust gas concentration is detected every 10℃ for 30 minutes.

[0043] Sulfur poisoning test: The catalyst was crushed, and 2 ml of 20-40 mesh particles were screened and transferred to the center of the quartz reactor. The catalyst was fixed on both sides with quartz wool. Simulated NOx gas (NO (600ppm), NH3 (600ppm), O2 (6vol%), SO2 (13ppm), H2O (8vol%), N2 as carrier gas, GHSV for 5000h) was introduced at one end of the quartz reactor. -1 The other end is connected to a flue gas analyzer to detect the concentrations of NO and SO2 in the exhaust gas. The temperature of the quartz reactor is controlled at 160℃ for 10 hours, and the exhaust gas concentration is detected every hour.

[0044] ;

[0045] .

[0046] <![CDATA[La2O3]]> 5% 6% 3% 4% 5% <![CDATA[MoO3]]> 3% 2% 4% 5% 3%

[0047] Example 1

[0048] Catalyst preparation: 100g of gasification slag, 15.8078g of FeSO4·7H2O, 7.1169g of Bi(NO3)3·5H2O, and 4.8725g of SnSO4 were weighed and ground in a pulverizer. The powder was then sieved to below 100 mesh for later use. The powder was transferred to a muffle furnace and calcined at 900℃ for 8 hours, yielding a total of 104.7261g of intermediate. The powder intermediate was mixed evenly with 62.8357g of starch, 3.1418g of CMC, and 109.1318g of MgCl2. Simultaneously, 41.4761g of Ce(NO3)3·6H2O and 3.1418g of Zr(NO3)4·5H2O were dissolved in 100g of deionized water to prepare a mixed solution. The two solutions were then mixed and kneaded evenly. After slight drying, the mixture was extruded into columnar catalysts with a diameter of 3mm using an extruder at a pressure of 5MPa. After thoroughly drying the columnar catalyst, it was transferred to a muffle furnace and calcined at 1200℃ for 5 hours to obtain a total of 92.7468 g of columnar cordierite support. The water absorption rate of the columnar cordierite support was 64.53% as determined by a water absorption test. 12.3252 g of La(NO3)3·6H2O and 5.6880 g of (NH4)6Mo7O were then added. 24 • 4H₂O was dissolved in 59.8495g of deionized water to prepare a mixed solution. Then, columnar cordierite support was immersed in the mixed solution for equal-volume impregnation. After impregnation, the support was thoroughly dried, and then immersed in 60ml of 20% ammonia solution for a second equal-volume impregnation. After this, it was dried and then transferred to a muffle furnace for calcination at 520℃ for 12h to obtain the finished catalyst.

[0049] Example 2

[0050] Catalyst preparation: 100g of gasification slag, 26.3464g of FeSO4·7H2O, 5.3376g of Bi(NO3)3·5H2O, and 3.8980g of SnSO4 were weighed and ground in a pulverizer. The powder was then sieved to below 100 mesh for later use. The powder was transferred to a muffle furnace and calcined at 800℃ for 8 hours, yielding a total of 102.6653g of intermediate. The powder intermediate was mixed evenly with 41.0661g of flour, 3.0800g of PVA, and 90.9432g of MgCl2. Simultaneously, 21.3530g of CeCl3·7H2O and 2.0533g of ZrOCl2·8H2O were dissolved in 100g of deionized water to prepare a mixed solution. The two solutions were then mixed and kneaded evenly. After slight drying, the mixture was extruded into 5mm diameter columnar catalysts using an extruder at a pressure of 2MPa. After thoroughly drying the columnar catalyst, it was transferred to a muffle furnace and calcined at 1100℃ for 3 hours to obtain a total of 94.5316 g of columnar cordierite support. The water absorption rate of the columnar cordierite support was measured to be 62.66%. 12.9289 g of LaCl3·7H2O and 5.7974 g of (NH4)6Mo7O were then added. 24 • 4H₂O was dissolved in 59.2335g of deionized water to prepare a mixed solution. Then, columnar cordierite support was immersed in the mixed solution for equal-volume impregnation. After impregnation, the support was thoroughly dried, and then immersed in 60ml of 15% ammonia solution for a second equal-volume impregnation. After this, it was dried and then transferred to a muffle furnace for calcination at 550℃ for 10h to obtain the finished catalyst.

[0051] Example 3

[0052] Catalyst preparation: 100g of gasification slag, 15.8078g of FeSO4·7H2O, 8.8961g of Bi(NO3)3·5H2O, and 2.9235g of SnSO4 were weighed and ground in a pulverizer. The powder was then sieved to below 100 mesh for later use. The powder was transferred to a muffle furnace and calcined at 1000℃ for 6 hours, yielding a total of 98.7882g of intermediate. The powdered intermediate was mixed evenly with 29.6365g of flour, 4.9394g of CMC, and 367.3789g of Mg(NO3)2·6H2O. Simultaneously, 33.1808g of Ce(NO3)3·6H2O and 3.9515g of ZrOCl2·8H2O were dissolved in 100g of deionized water to prepare a mixed solution. The two solutions were then mixed and kneaded evenly. After slight drying, the mixture was extruded into 6mm diameter columnar catalysts using an extruder at a pressure of 4MPa. After thoroughly drying the columnar catalyst, it was transferred to a muffle furnace and calcined at 1000℃ for 3 hours to obtain a total of 91.6479 g of columnar cordierite support. The water absorption rate of the columnar cordierite support was 61.37% as determined by a water absorption test. 17.0508 g of La(NO3)3·6H2O and 3.1704 g of (NH4)2Mo4O were then added. 13 • 2H₂O was dissolved in 56.2443g of deionized water to prepare a mixed solution. Then, columnar cordierite support was immersed in the mixed solution for equal-volume impregnation. After impregnation, the support was thoroughly dried, and then immersed in 60ml of 20% ammonia solution for a second equal-volume impregnation. After this, it was dried and then transferred to a muffle furnace for calcination at 500℃ for 6h to obtain the finished catalyst.

[0053] Example 4

[0054] Catalyst preparation: 100g of vaporization slag, 21.0771g of FeSO4·7H2O, 8.8961g of Bi(NO3)3·5H2O, and 3.8980g of SnSO4 were weighed and ground in a pulverizer. The powder was then screened to a mesh size of less than 100 mesh for later use. The powder was transferred to a muffle furnace and calcined at 800℃ for 5 hours, yielding a total of 102.9473g of intermediate. The powder intermediate was mixed evenly with 51.4737g of starch, 4.1179g of PEO, and 244.9190g of Mg(NO3)2·6H2O. Simultaneously, 32.0295g of CeCl3·7H2O and 5.1474g of Zr(NO3)4·5H2O were dissolved in 100g of deionized water to prepare a mixed solution. The two solutions were then mixed and kneaded evenly. After slight drying, the mixture was extruded into columnar catalysts with a diameter of 4mm using an extruder at a pressure of 3MPa. After thoroughly drying the columnar catalyst, it was transferred to a muffle furnace and calcined at 1100℃ for 4 hours to obtain a total of 94.3357 g of columnar cordierite support. The water absorption rate was tested and found to be 63.81%. 17.2028 g of LaCl3·7H2O and 2.1756 g of (NH4)2Mo4O were then added. 13 • 2H₂O was dissolved in 60.1956g of deionized water to prepare a mixed solution. Then, columnar cordierite support was immersed in the mixed solution for equal-volume impregnation. After impregnation, the support was thoroughly dried, and then immersed in 60ml of 15% ammonia solution for a second equal-volume impregnation. After this, it was dried and then transferred to a muffle furnace for calcination at 540℃ for 8 hours to obtain the finished catalyst.

[0055] Comparative Example 1

[0056] Catalyst preparation: 100g of gasification slag was weighed, ground, and screened to a fineness below 100 mesh for later use. The powder was mixed evenly with 60.0000g of starch, 3.0000g of CMC, and 109.1318g of MgCl2. Simultaneously, 41.4761g of Ce(NO3)3·6H2O and 3.0000g of Zr(NO3)4·5H2O were dissolved in 100g of deionized water to prepare a mixed solution. The two solutions were then mixed and kneaded evenly. After slight drying, the mixture was extruded into columnar catalysts with a diameter of 3mm using an extruder at a pressure of 5MPa. After thoroughly drying the columnar catalysts, they were calcined in a muffle furnace at 1200℃ for 5h to obtain 94.4873g of columnar cordierite support. The water absorption rate of the columnar cordierite support was 64.53% as determined by the water absorption test. 12.2091g La(NO3)3·6H2O and 5.6344g (NH4)6Mo7O 24• 4H₂O was dissolved in 58.6245g of deionized water to prepare a mixed solution. Then, columnar cordierite support was immersed in the mixed solution for equal-volume impregnation. After impregnation, the support was thoroughly dried, and then immersed in 60ml of 20% ammonia solution for a second equal-volume impregnation. After this, it was dried and then transferred to a muffle furnace for calcination at 520℃ for 12h to obtain the finished catalyst.

[0057] Comparative results: Compared with Example 1, the denitrification performance of the catalyst decreased significantly without curing treatment.

Claims

1. A method for preparing a porous cordierite-based low-temperature denitration catalyst using gasification slag as raw material, characterized in that: This catalyst uses gasification slag as raw material, which is pretreated to prepare a porous cordierite support. Then, an active component and a co-catalyst are loaded onto the surface and pores of the support using an impregnation method. Finally, the active component and the co-catalyst are fixed by calcination. The active component is La2O3, and the co-catalyst is MoO3. Based on the mass of the support, the mass percentage of the active component is 5-8%, and the mass percentage of the co-catalyst is 2-5%. The specific synthesis steps are as follows: (1) The vaporized slag and the curing agent are put into a grinding mill for grinding, and the screened powder is then roasted; (2) Mix the powder obtained in step (1) with the pore-forming agent, binder and magnesium source evenly, dissolve the cerium source and zirconium source in deionized water, then mix the two evenly, knead and extrude to form a mold, and then calcine at 1000~1200℃. (3) Dissolve the active component precursor and the co-catalyst precursor in deionized water to prepare a mixed solution, and then immerse the formed support in the mixed solution for equal volume impregnation. (4) After thoroughly drying the solid obtained in step (3), impregnate it twice with an equal volume of ammonia solution; (5) After thoroughly drying the solid obtained in step (4), calcinate it at 500~550℃ to obtain the finished catalyst.

2. The preparation method according to claim 1, characterized in that: The curing agent in step (1) is a mixture of ferrous sulfate, bismuth nitrate and tin sulfate. The molar amount of ferrous sulfate added is 3 to 5 times the molar amount of arsenic in the gasification slag, the molar amount of bismuth nitrate added is 3 to 5 times the molar amount of lead in the gasification slag, and the molar amount of tin sulfate added is 3 to 5 times the molar amount of cadmium in the gasification slag.

3. The preparation method according to claim 1, characterized in that: After grinding in step (1), the particle size is below 100 mesh; the calcination temperature in step (1) is 800~1000℃, the calcination time is 5~8h, and the calcination environment is an air atmosphere.

4. The preparation method according to claim 1, characterized in that: The pore-forming agent in step (2) is flour or starch, and the mass of the pore-forming agent added is 30-60% of the mass of the powder obtained in step (1). The binder mentioned in step (2) is polyethylene oxide (PEO), carboxymethyl cellulose (CMC), or polyvinyl alcohol (PVA), and the mass of the binder added is 3-5% of the mass of the powder obtained in step (1); The magnesium source mentioned in step (2) is magnesium nitrate or magnesium chloride, and the molar amount of magnesium source added is 100-150% of the molar amount of aluminum in the gasification slag; The cerium source mentioned in step (2) is cerium nitrate or cerium chloride, and the molar amount of cerium source added is 6-10% of the molar amount of aluminum in the vaporized slag; The zirconium source mentioned in step (2) is zirconium oxychloride or zirconium nitrate, and the mass of the zirconium source added is 2 to 5% of the powder obtained in step (1).

5. The preparation method according to claim 1, characterized in that: The extrusion molding shape described in step (2) is a column with a diameter of 3~6mm and an extrusion pressure of 2~5Mpa; The roasting temperature in step (2) is 1000~1200℃, the roasting time is 3~5h, and the roasting environment is an empty atmosphere.

6. The preparation method according to claim 1, characterized in that: The active component precursor in step (3) is a lanthanum nitrate or chloride, and the co-catalyst precursor is ammonium tetramolybdate or ammonium heptamolybdate; The concentration of the ammonia solution in step (4) is 15-25%; The roasting temperature in step (5) is 500~550℃, the roasting time is 6~12h, and the roasting environment is an empty atmosphere.

7. A porous cordierite-based low-temperature denitrification catalyst prepared from gasification slag, characterized in that the catalyst is prepared by the method described in any one of claims 1 to 7.

8. The application of the catalyst prepared by the method of claim 1 in low-temperature denitrification.

9. The application according to claim 8, characterized in that, The application temperature is 120~180℃, and the SO2 content in the operating environment is ≤35mg and the H2O content is ≤8%.

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