Monolithic Low-Temperature Water- and Sulfur-Resistant CO Oxidation Catalyst and Its Preparation Method

Abstract

This invention discloses an integral low-temperature water- and sulfur-resistant CO oxidation catalyst and its preparation method, comprising the following steps: preparing an aqueous solution of a mixed precursor of Sn salt and Zr salt, wherein the mass concentration of Sn salt is 5-20% and the mass concentration of Zr salt is 5-20%; impregnating a porous TiO2 support in the aqueous solution of the mixed precursor and then subjecting it to a first drying and calcination to obtain a pretreated support; preparing a mixed solution of Pt precursor and surfactant, then impregnating the pretreated support in the solution and subjecting it to a second drying and calcination to obtain the CO oxidation catalyst. This catalyst has good low-temperature CO oxidation activity and water and sulfur resistance, and is suitable for complex working conditions such as dust and sulfur content.

Description

Technical Field

[0001] This invention belongs to the field of environmental catalytic materials and environmental protection technology, and relates to an integral, low-temperature, water- and sulfur-resistant CO oxidation catalyst and its preparation method. The catalyst described in this invention is suitable for the removal of CO from sintering flue gas in the iron and steel industry. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] The steel industry is closely related to human life, but it is also a major cause of industrial pollution. The sintering process is a significant source of pollutants in the steel industry, characterized by large emissions, complex composition, and low flue gas temperature (120–180°C). Pollutants generated include NO. x For particulate matter, NOx, and SO2, the national emission standards have been strict, but the requirements for CO emissions are not yet clear. The initial concentration of CO in sintering flue gas is generally between 8000 and 10000 mg / m³. 3 The total annual CO emissions from steel sintering machines across the country reach 50 to 60 million tons, posing a serious threat not only to the natural environment and human health, but also to the enormous waste of energy caused by the incomplete combustion of fuel.

[0004] To reduce CO emissions from sintering flue gas, efforts are made in two ways: firstly, reducing CO emissions at the source and controlling the process; secondly, end-of-pipe treatment technologies, such as oxidizing CO to CO2. Currently, known CO catalysts are mainly used after the denitrification stage, requiring low dust content in the flue gas (0–5 mg / m³). 3 Most require dust-free flue gas and low sulfur dioxide concentration (0-20 mg / m³). 3 The flue gas temperature is typically 220-400℃, requiring not only additional heating treatment but also further treatment at the CO outlet to address excessive NO emissions. x The equipment manufacturing and operating costs are relatively high.

[0005] Meanwhile, with the implementation of ultra-low emission standards in the steel industry (NOx) x Emission limit 50 mg / m³ 3 The sintering flue gas SCR denitrification process has high costs and high energy consumption because the flue gas temperature is low and it requires heating with blast furnace gas or the use of expensive low-temperature denitrification catalysts. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide an integral, low-temperature, water- and sulfur-resistant CO oxidation catalyst and its preparation method.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing an integral, low-temperature, water- and sulfur-resistant CO oxidation catalyst, comprising the following steps:

[0009] Prepare an aqueous solution of mixed precursors of Sn salt and Zr salt, wherein the mass concentration of Sn salt is 5-20% and the mass concentration of Zr salt is 5-20%.

[0010] After the porous TiO2 support is impregnated in the aqueous solution of the mixed precursor, it is subjected to a first drying and calcination to obtain a pretreated support.

[0011] A mixed solution of Pt precursor and surfactant was prepared, and then the pretreated support was impregnated in it and subjected to a second drying and calcination to obtain the CO oxidation catalyst.

[0012] Pretreatment of the support with Sn and Zr can promote Pt dispersion and reduce Pt crystal size. The Sn-Zr-Ti interaction can provide more lattice oxygen for Pt, improve Pt oxidation performance, and enhance its resistance to water and sulfur. It can also prevent some Pt ​​active sites from being covered, which would lead to a decrease in catalyst activity at low temperatures. On the other hand, the addition of Zr is beneficial to increase the acidic sites of the support, promote the stability of the support structure, and inhibit the poisoning of alkali metals and alkaline earth metals in flue gas fly ash.

[0013] The interaction between porous TiO2 and Sn-Zr has two main effects: first, it provides more lattice oxygen to Pt, improving the catalytic activity of CO at low temperatures; second, it increases acidic sites, reduces SO2 adsorption and oxidation, and improves the catalyst's sulfur resistance.

[0014] Surfactants can promote the dispersion of precious metals and inhibit their aggregation.

[0015] In some embodiments, the porous TiO2 is extruded porous TiO2, and its cross-section has 10-50 pores.

[0016] Preferably, the porous TiO2 has a water absorption rate of 30%-60% and a specific surface area ≥150m². 2 / g.

[0017] In some embodiments, the Sn salt is selected from stannous chloride, stannous chloride, or sodium stannate.

[0018] In some embodiments, the Zr salt is selected from at least one of zirconium chloride, zirconium oxychloride, or zirconium nitrate.

[0019] In some embodiments, the surfactant is selected from at least one of polyvinylpyrrolidone, sodium polyacrylate, polyethylene glycol, or polypropylene glycol.

[0020] Preferably, the mass concentration of the surfactant is 0.5% to 1.5%.

[0021] In some embodiments, the temperature for the first drying is 80–120°C and the time is 15–30 min, and the temperature for calcination is 450–550°C and the time is 2–5 h.

[0022] In some embodiments, the second drying temperature is 80–120°C and the time is 15–30 min, and the calcination temperature is 450–550°C and the time is 2–5 h.

[0023] Secondly, the present invention provides an integral low-temperature water- and sulfur-resistant CO oxidation catalyst, which is prepared by the aforementioned preparation method.

[0024] In some embodiments, the monolithic low-temperature water- and sulfur-resistant CO oxidation catalyst includes a porous TiO2 support and an oxide promoter Sn supported thereon. x Zr 1-x O2 and active component Pt, wherein the mass percentage of Pt is 0.01% to 0.5%, and Sn x Zr 1-x The mass percentage of O2 is 1% to 20%, where 0 ≤ x ≤ 1.

[0025] The beneficial effects achieved by one or more embodiments of the present invention described above are as follows:

[0026] The catalyst possesses excellent low-temperature CO oxidation activity and resistance to water and sulfur, making it suitable for complex operating conditions such as dust and sulfur content. Therefore, the CO catalytic device using this CO oxidation catalyst can be placed before the SCR denitrification process unit to form a CO+SCR combined flue gas removal process. On the one hand, the heat energy generated by CO oxidation can increase the operating temperature of the SCR process, which is beneficial to improving the denitrification efficiency of the SCR catalyst. On the other hand, some NO in the flue gas is oxidized by the CO catalyst to generate NO2, which is beneficial to promoting the rapid SCR reaction and the decomposition of ammonium bisulfate deposited on the surface of the SCR catalyst, thereby improving the denitrification efficiency and service life. This achieves low-cost, energy-saving, and emission-reducing removal of CO and NO from steel sintering flue gas. Attached Figure Description

[0027] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0028] Figure 1 These are the catalytic oxidation CO efficiency curves of the catalysts in Examples 1-3 and Comparative Examples 1-5 of this invention.

[0029] Figure 2 This is the efficiency curve of NO oxidation catalytically produced by the catalyst in Example 1 of the present invention.

[0030] Figure 3 This is Example 1 of the present invention, showing the stability curves of the catalysts for the catalytic oxidation of CO in Comparative Examples 1, 3, and 4.

[0031] Figure 4 The figures show the catalytic oxidation efficiency curves of CO before and after catalyst wear in Example 1 of this invention. Detailed Implementation

[0032] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0033] The present invention will be further described below with reference to the embodiments.

[0034] Example 1

[0035] The catalyst preparation steps are as follows:

[0036] Weigh 4150g of distilled water, add 500g of tin tetrachloride pentahydrate and 350g of zirconium oxychloride octahydrate in sequence, and stir until fully dissolved to obtain a mixed solution;

[0037] A TiO2 support with 20 pores in the cross section and a size of 150*150*500mm was immersed in the above mixture for 2 minutes, and then dried at 100℃ for 30 minutes and calcined at 500℃ for 3 hours to obtain a pretreated support.

[0038] Weigh 4875g of distilled water, add 50g of polyvinylpyrrolidone and 75g of chloroplatinic acid in sequence, and stir thoroughly to obtain a mixed solution.

[0039] The pretreated carrier was immersed in the mixture for 2 minutes, and then dried at 100°C for 30 minutes and calcined at 500°C for 3 hours to obtain the catalyst sample of this embodiment.

[0040] Example 2

[0041] The catalyst preparation steps are as follows:

[0042] Weigh 4100g of distilled water, add 500g of stannous chloride and 300g of zirconium chloride in sequence, and stir until fully dissolved to obtain a mixed solution;

[0043] A TiO2 support with 30 holes in the cross section and a size of 150*150*500mm was immersed in the above mixture for 2 minutes, and then dried at 100℃ for 30 minutes and calcined at 500℃ for 3 hours to obtain a pretreated support.

[0044] Weigh 4875g of distilled water, add 50g of polyvinylpyrrolidone and 70g of chloroplatinic acid in sequence, and stir thoroughly to obtain a mixed solution.

[0045] The pretreated carrier was immersed in the mixture for 2 minutes, and then dried at 100°C for 30 minutes and calcined at 500°C for 3 hours to obtain the catalyst sample of this embodiment.

[0046] Example 3

[0047] The catalyst preparation steps are as follows:

[0048] Weigh 4200g of distilled water, add 500g of stannous chloride and 400g of zirconium nitrate in sequence, and stir until fully dissolved to obtain a mixed solution;

[0049] A TiO2 support with 50 holes in the cross section and a size of 150*150*500mm was immersed in the above mixture for 2 minutes, and then dried at 100℃ for 30 minutes and calcined at 500℃ for 3 hours to obtain a pretreated support.

[0050] Weigh 4900g of distilled water, add 50g of sodium polyacrylate and 70g of chloroplatinic acid in sequence, and stir thoroughly to obtain a mixed solution;

[0051] The pretreated carrier was immersed in the mixture for 2 minutes, and then dried at 100°C for 30 minutes and calcined at 500°C for 3 hours to obtain the catalyst sample of this embodiment.

[0052] Comparative Example 1

[0053] The catalyst preparation steps are as follows:

[0054] Weigh 4875g of distilled water, add 50g of polyvinylpyrrolidone and 75g of chloroplatinic acid in sequence, and stir thoroughly to obtain a mixed solution.

[0055] A TiO2 support with 20 pores in the cross section and a size of 150*150*500mm was immersed in the above mixture for 2 minutes, and then dried at 100℃ for 30 minutes and calcined at 500℃ for 3 hours to obtain the catalyst sample of this embodiment.

[0056] Comparative Example 2

[0057] The difference from Example 1 is that the porous TiO2 support is replaced with a cordierite support, while everything else is the same as in Example 1.

[0058] Comparative Example 3

[0059] The difference from Example 1 is that only a solution of tin tetrachloride pentahydrate is used to impregnate and modify the TiO2 support, and zirconium oxychloride octahydrate is omitted. However, the molar concentration of tin tetrachloride pentahydrate is the same as that of the mixed solution of tin tetrachloride pentahydrate and zirconium oxychloride octahydrate in Example 1. Everything else is the same as in Example 1.

[0060] Comparative Example 4

[0061] The difference from Example 1 is that only a solution of zirconium oxychloride octahydrate is used to impregnate and modify the TiO2 support, omitting tin tetrachloride pentahydrate, but the molar concentration of zirconium oxychloride octahydrate is the same as that of the mixed solution of tin tetrachloride pentahydrate and zirconium oxychloride octahydrate in Example 1. Everything else is the same as in Example 1.

[0062] Comparative Example 5

[0063] The difference from Example 1 is that the surfactant polyvinylpyrrolidone is omitted, while everything else is the same as in Example 1.

[0064] The catalytic performance of the catalysts prepared in Examples 1-3 and Comparative Examples 1-5 was tested. The specific test procedures and conditions are as follows:

[0065] Catalyst activity evaluation was conducted in a continuous flow fixed-bed reactor. The monolithic catalyst, wrapped in quartz cotton cloth, was placed in the center of the reactor. The catalyst was a 5*5 pore honeycomb structure. The composition of the reaction gas was 8000 mg / m³. 3 CO, 500 mg / m 3 SO2, 500mg / m³ 3 NO, 10% H2O, with N2 as the balance gas, and a volumetric hourly space velocity (VHSV) of 15000 h⁻¹ -1 The activity evaluation temperature range is 150-220℃.

[0066] CO catalysis results are as follows: Figure 1 As shown, the catalysts prepared in Examples 1-3 exhibit similar catalytic activities, all superior to those in Comparative Examples 1-5. The catalyst in Example 1 demonstrates the best catalytic oxidation activity, achieving a complete CO conversion temperature (T98) of 178°C. This indicates that the monolithic, low-temperature, water- and sulfur-resistant CO catalyst prepared by the method of this invention exhibits excellent CO catalytic activity in water- and sulfur-containing environments. Furthermore, the outlet gas temperature is approximately 25°C higher than the inlet gas temperature, indicating that after purification by the CO removal process, the CO catalytic oxidation reaction can provide a large amount of heat energy for subsequent SCR removal, significantly reducing the heating costs for enterprises in this process and achieving energy conservation and carbon reduction.

[0067] The catalytic NO results of Example 1 are as follows: Figure 2 As shown, by Figure 2 It can be seen that the catalyst prepared in Example 1 can oxidize NO to NOx. When the reaction temperature is 180℃, the NO conversion rate is 52.6% and the NO2 concentration is 251 mg / m³. 3 The ratio of NO to NO2 is approximately 1:1, which is the optimal ratio for rapid SCR reaction.

[0068] The catalytic stability of the catalysts prepared in Example 1 and Comparative Examples 1, 3, and 4 was tested. The specific test procedures and conditions are as follows:

[0069] Catalyst activity evaluation was conducted in a continuous flow fixed-bed reactor. The monolithic catalyst, wrapped in quartz cotton cloth, was placed in the center of the reactor. The catalyst was a 5*5 pore honeycomb type. In Example 1, the reactor temperature was set to 180°C, while in Comparative Examples 1, 3, and 4, the reactor temperature was set to 200°C. The reaction gas composition was 8000 mg / m³. 3 CO, 500 mg / m 3 SO2, 500mg / m³ 3 NO, 10% H2O, with N2 as the balance gas, and a volumetric hourly space velocity (VHSV) of 15000 h⁻¹ -1 .

[0070] The catalyst's water and sulfur resistance stability was tested for 100 hours, and the CO catalytic results are as follows: Figure 3 As shown, the results indicate that the catalyst prepared in Example 1 has better catalytic stability than Comparative Examples 1, 3, and 4. In particular, in the 100-h stability test at 180°C, the catalyst prepared in Example 1 showed only a 2% decrease in CO catalytic activity (CO conversion rate decreased from 100% to 98%). This demonstrates that the monolithic low-temperature water- and sulfur-resistant CO catalyst prepared by the method of this invention can effectively maintain the stability and durability of the catalyst while maintaining high activity, thereby reducing the pollution control costs for enterprises.

[0071] The catalyst prepared in Example 1 was subjected to wear rate testing. The specific testing process and conditions are as follows:

[0072] A 60*60*70mm catalyst sample was placed in an oven and dried at 105±2℃ for 2 hours. After drying, the sample was placed in a desiccator to cool to room temperature, and its mass (accurate to 0.01g) was recorded as m1. The sample was wrapped in a sponge and placed in the sample chamber, with the outer wall of the sample completely sealed to the chamber wall, allowing air and abrasive to flow completely through the sample channel. The standard wind speed in the catalyst channel was controlled and adjusted to 14±0.5m / s, the diameter of the duct entering the sample chamber was 65mm, and the abrasive content (dry high-hardness quartz sand with a particle size of 0.300~0.425mm) was 50±5g / m. The test was stopped after 2 hours. The sample was removed, placed in an oven, and dried at 105±2℃ for 2 hours. After drying, the sample was placed in a desiccator to cool to room temperature, and its mass was recorded as m2. The abrasion rate was then calculated using the formula (m1-m2) / m1*100.

[0073] The catalyst sample of Example 1 was subjected to wear test using the above method, and the wear rate of the sample was only 0.13%.

[0074] Activity tests were performed on the worn samples of Example 1, using the same methods as Examples 1-3 and Comparative Examples 1-5. The CO catalysis results are as follows: Figure 4 As shown, the catalytic CO activity of the worn sample did not decrease significantly. At a reaction temperature of 180℃, the CO conversion rate was still above 98%, demonstrating good wear resistance and fully meeting the needs of dust-containing CO removal from sintering flue gas in the steel industry.

[0075] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an integral, low-temperature, water- and sulfur-resistant CO oxidation catalyst, characterized in that: Includes the following steps: Prepare an aqueous solution of a mixed precursor of Sn salt and Zr salt, wherein the mass concentration of Sn salt is 5-20% and the mass concentration of Zr salt is 5-20%. After the porous TiO2 support is impregnated in the aqueous solution of the mixed precursor, it is subjected to a first drying and calcination to obtain a pretreated support; the temperature of the first drying is 80~120℃ and the time is 15~30min, the temperature of the calcination is 500~550℃ and the calcination time is 2~3h. A mixed solution of Pt precursor and surfactant is prepared, and then the pretreated support is impregnated in it and subjected to a second drying and calcination to obtain the CO oxidation catalyst. The second drying temperature is 80~120℃ and the time is 15~30min, and the calcination temperature is 500~550℃ and the calcination time is 2~3h. The porous TiO2 is extruded porous TiO2 with 10-50 pores in its cross-section; the water absorption rate of the porous TiO2 is 30%-60%, and the specific surface area is ≥150m². 2 / g; Interaction between porous TiO2 and Sn-Zr.

2. The preparation method of the monolithic low-temperature water- and sulfur-resistant CO oxidation catalyst according to claim 1, characterized in that: Sn salts are selected from one of stannous chloride, stannous chloride, or sodium stannate.

3. The preparation method of the monolithic low-temperature water- and sulfur-resistant CO oxidation catalyst according to claim 1, characterized in that: The Zr salt is selected from at least one of zirconium chloride, zirconium oxychloride, or zirconium nitrate.

4. The preparation method of the monolithic low-temperature water- and sulfur-resistant CO oxidation catalyst according to claim 1, characterized in that: The surfactant is selected from at least one of polyvinylpyrrolidone, sodium polyacrylate, polyethylene glycol, or polypropylene glycol.

5. The preparation method of the monolithic low-temperature water- and sulfur-resistant CO oxidation catalyst according to claim 4, characterized in that: The surfactant has a mass concentration of 0.5% to 1.5%.

6. A monolithic, low-temperature, water- and sulfur-resistant CO oxidation catalyst, characterized in that: It is prepared by any one of the preparation methods described in claims 1-5.

7. The monolithic low-temperature water- and sulfur-resistant CO oxidation catalyst according to claim 6, characterized in that: Includes a porous TiO2 support and an oxide additive Sn supported thereon. x Zr 1-x O2 and active component Pt, wherein the mass percentage of Pt is 0.01%~0.5%, and Sn x Zr 1-x The mass percentage of O2 is 1% to 20%, where 0 ≤ x ≤ 1.

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