Preparation method of water-resistant sulfur-resistant ultralow-temperature CO oxidation catalyst

Abstract

The invention discloses a preparation method of a water-resistant sulfur-resistant ultralow-temperature CO oxidation catalyst. The preparation method comprises the following steps: firstly, preparing an alpha-SiO2 carrier with a rich (101) crystal face by adopting a hydrothermal method; afterwards, an inorganic anchoring-organic grafting strategy is combined, an HF solution is used for conducting functionalization treatment on the surface of alpha-SiO2, methyl silicon trichloride is introduced, a Si-F-O-C-Si bonding structure is constructed, and the precious metal is accurately loaded on the bonding structure by means of a precursor in an organic grafting mode. The Si-F-O-C-Si bond not only regulates the surface electronic structure of alpha-SiO2 and inhibits the adsorption of SO2 on the active site of noble metal, but also can reduce SO2 by carbon atoms to prevent the oxidation process of SO2 on active lattice oxygen on the surface of the carrier; meanwhile, the F-O bond can rapidly provide reactive oxygen species for the Pt site, and CO oxidation reaction is promoted. Based on the design of the water-resistant and sulfur-resistant system, the prepared noble metal-based C-F-alpha-SiO2 catalyst shows excellent CO oxidation activity at the temperature of 80-110 DEG C.

Description

Technical Field

[0001] This invention belongs to the field of atmospheric pollutant removal technology, and specifically relates to a method for preparing a water- and sulfur-resistant ultra-low temperature CO oxidation catalyst. Background Technology

[0002] Carbon monoxide (CO) is one of the main pollutants emitted during industrial production. It can enter the lungs through the respiratory tract, causing diseases such as bronchitis and emphysema, seriously endangering human health. In recent years, emission standards have become increasingly stringent to reduce CO pollution. Catalytic oxidation of CO has long been the dominant CO removal technology globally, widely used in the treatment of waste gas from both mobile sources (such as automobiles and diesel vehicles) and stationary sources (such as the steel, coking, and cement industries). Currently, noble metal (such as Pt, Pd, and Au) based catalysts remain the mainstream catalysts for CO catalytic oxidation. However, the waste gas emitted by most industries currently contains H2O and SO2. Noble metal-based catalysts are susceptible to H2O and SO2 poisoning under low-temperature conditions, severely limiting their practical application. The poisoning mechanism mainly involves SO2 being oxidized to SO3 by the active lattice oxygen on the support surface, which then reacts with H2O to form H2SO4. This H2SO4 causes sulfation of the support surface, forming sulfates, which hinder the migration of active lattice oxygen to the noble metal active sites, ultimately leading to a significant decrease in the catalyst's CO oxidation performance.

[0003] To improve the water and sulfur resistance of noble metal-based CO catalysts, researchers have conducted extensive and in-depth studies in recent years. For example, Chinese patent application CN114950469A reports a CO catalyst with cobalt, cerium, and manganese oxides as active components, which performs well under conditions of 130 °C, 20 vol% H₂O, 500 ppm SO₂, 1 vol% CO, and a space velocity of 20,000 h⁻¹. -1 Under the specified reaction conditions, its CO conversion rate can reach approximately 90%. Furthermore, according to publicly available literature (Angew. Chem. Int. Ed. 2023, 62, e202310191), the Pd / TiO2-400 catalyst, under conditions of 120℃, 10 vol% H2O, 100 ppm SO2, 1 vol% CO, and a space velocity of 20000 h⁻¹, achieves a CO conversion rate of approximately 90%. -1 Under these conditions, the CO conversion rate remained around 96% after 100 hours of continuous operation. However, the catalyst's water and sulfur resistance decreased sharply below 120°C. Many real-world industrial environments present low-temperature, high-humidity, and high-sulfur scenarios: for example, the exhaust gas temperature during a cold start of a diesel generator can drop as low as 100°C; and the temperature of flue gas from waste incineration, steel, and cement industries after wet desulfurization is generally below 100°C. Such conditions typically require additional heating to meet the operational requirements of the precious metal catalyst, increasing treatment costs.

[0004] Therefore, in order to effectively reduce the cost of CO removal in industrial processes, it is urgent to develop noble metal-based CO oxidation catalysts with excellent catalytic activity and water and sulfur resistance at ultra-low temperatures (<120℃) to meet the current severe environmental protection and practical application requirements. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a water- and sulfur-resistant ultra-low temperature CO oxidation catalyst, so as to solve the problem of insufficient water resistance and sulfur resistance of existing noble metal-based CO oxidation catalysts under ultra-low temperature conditions, and thus promote the industrial application of this catalyst in harsh ultra-low temperature environments.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a water- and sulfur-resistant ultra-low temperature CO oxidation catalyst includes the following steps:

[0008] (1) Mix silicon source, alkali source, template agent and water evenly, place in a reaction vessel lined with polytetrafluoroethylene, crystallize at 150-180℃ for 1-6 days, filter, dry and calcine the crystallized product to obtain α-SiO2.

[0009] (2) α-SiO2 was placed in HF solution for functionalization treatment, and then washed, filtered and dried to obtain product A;

[0010] (3) React product A with methyl silicon trichloride solution, then wash and dry to obtain product B;

[0011] (4) The product B is mixed with the noble metal precursor solution and grafted. Then it is dried and calcined to obtain the noble metal-based CF-α-SiO2 catalyst.

[0012] In step (1), the amounts of silicon source, alkali source, template agent and water added meet the following molar ratio conditions: 1SiO2 / 0.01~2Na2O / 0.01~1.5 template agent / 60-100H2O.

[0013] In step (1), the silicon source is one or a mixture of several of silica sol, kaolin, amorphous SiO2, and sodium metasilicate; the alkali source is a 0.5 mol / L NaOH solution; and the template agent is one or a mixture of glucose, tetraethylammonium hydroxide, adamantane, cyclohexylamine, and tetraethylammonium bromide.

[0014] In step (1), the roasting temperature is 750-850℃ and the time is 5.5-6.5h.

[0015] In step (2), the ratio of α-SiO2 to HF solution is 3g:2.25~9mL.

[0016] In step (2), the temperature of the functionalization treatment is 60-100℃, the time is 2-6h, and the drying temperature is 75-85℃.

[0017] In step (3), the ratio of product A to methyltrichlorosilane is 1g:0.2-3mL.

[0018] In step (3), the reaction temperature is 25-60℃, the reaction time is 15-45 min, and the drying temperature is 45-80℃.

[0019] In step (4), the noble metal precursor is one or a mixture of several of the following: chloroplatinic acid, platinum nitrate, tetraammineplatinum nitrate, chloropalladium acid, palladium nitrate, palladium acetate, ammonium tetrachloroaurate, and chloroauric acid.

[0020] In step (4), the mass ratio of product B to the noble metal precursor solution is 1:0.001 to 0.5.

[0021] In step (4), the grafting reaction is carried out at a temperature of 60-80°C for 6-12 hours.

[0022] In step (4), the drying temperature is 55-65℃, the calcination temperature is 400-600℃, and the time is 3-8h.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1. The noble metal-based CF-α-SiO2 catalyst prepared in this invention uses α-SiO2 with a (101) crystal plane as a support and combines an inorganic anchoring-organic grafting strategy to construct a synergistic water- and sulfur-resistant system on this crystal plane. This system can effectively prevent the oxidation of SO2 on the active lattice oxygen on the support surface and its reaction with H2O to generate H2SO4. Compared with the prior art, this strategy more comprehensively and efficiently solves the problem of easy deactivation of noble metal-based CO oxidation catalysts under the coexistence of H2O and SO2.

[0025] 2. Compared with existing low-temperature, water- and sulfur-resistant CO oxidation catalysts, the noble metal-based CF-α-SiO2 catalyst synthesized by this method exhibits a significant component synergistic effect. After stepwise treatment with HF and methyltrichlorosilane, the α-SiO2(101) crystal facet forms a rich Si-FOC-Si bond structure, and noble metals (such as Pt) can be precisely loaded onto these bond sites through organic grafting. Among them, C atoms have a reducing effect on SO2, inhibiting the oxidation of SO2 on the active lattice oxygen on the support surface; while FO bonds can rapidly provide active oxygen species for Pt sites, promoting the oxidation reaction of CO on Pt. In addition, the formation of Si-FOC-Si bonds changes the surface electronic structure of the α-SiO2(101) crystal facet, which helps to suppress the adsorption of H2O and SO2 on the catalyst surface. Therefore, this catalyst system exhibits excellent ultra-low temperature water and sulfur resistance performance.

[0026] 3. The noble metal-based CF-α-SiO2 catalyst prepared by this method has excellent water and sulfur resistance, and the CO removal rate can reach more than 98.5% at 80-110℃. Attached Figure Description

[0027] Figure 1 The images shown are XRD patterns of the products in Embodiments 1-4 of this invention.

[0028] Figure 2 This is an FESEM image of the product of Embodiment 1 of the present invention.

[0029] Figure 3 The images show the water and sulfur resistance performance evaluation of the products of Example 1 and Comparative Examples 1 and 2 of this invention. Detailed Implementation

[0030] Example 1

[0031] A method for preparing a water- and sulfur-resistant ultra-low temperature CO oxidation catalyst includes the following steps:

[0032] (1) Dissolve 6.2g sodium metasilicate, 3.6mL NaOH (0.5mol / L) and 0.86g glucose in 80mL deionized water, stir at room temperature for 6h, and then transfer to a stainless steel reactor lined with polytetrafluoroethylene. Crystallize at 165℃ for 2d. After filtration and drying, the crystallized product is calcined at 800℃ for 6h to obtain α-SiO2.

[0033] (2) Weigh 3g of α-SiO2, add 5mL of HF solution, treat at 60℃ for 2h, then wash, filter, and dry at 80℃ to obtain product A.

[0034] (3) Add 1.5 mL of methyl silicon trichloride solution to 1 g of product A, react at 60 °C for 30 min, and then dry at 60 °C to obtain product B.

[0035] (4) Add 10 mL of chloroplatinic acid solution with a content of 0.1% to 1 g of product B, continue stirring at 80 °C for 12 h, then filter, wash, dry at 60 °C for 12 h, and calcine at 600 °C for 6 h to obtain Pt / CF-α-SiO2 catalyst.

[0036] Example 2

[0037] A method for preparing a water- and sulfur-resistant ultra-low temperature CO oxidation catalyst includes the following steps:

[0038] (1) Dissolve 6.2g sodium metasilicate, 3.6mL NaOH (0.5mol / L) and 1.69g tetraethylammonium hydroxide in 70mL deionized water, stir at room temperature for 3h, and then transfer to a stainless steel reactor lined with polytetrafluoroethylene. Crystallize at 160℃ for 2d. After filtration and drying, the crystallized product is calcined at 800℃ for 6h to obtain α-SiO2.

[0039] (2) Weigh 3g of α-SiO2, add 3mL of HF solution, treat at 70℃ for 2h, then wash, filter, and dry at 80℃ to obtain product A.

[0040] (3) Add 2 mL of methyl silicon trichloride solution to 1 g of product A, react at 60 °C for 45 min, and then dry at 60 °C to obtain product B.

[0041] (4) Add 10 mL of a 0.1% Pt tetraammineplatinum nitrate solution to 1 g of product B, stir at 60 °C for 6 h, then filter, wash, and dry at 60 °C for 12 h. Then calcine at 500 °C for 3 h to obtain the Pt / CF-α-SiO2 catalyst.

[0042] Example 3

[0043] A method for preparing a water- and sulfur-resistant ultra-low temperature CO oxidation catalyst includes the following steps:

[0044] (1) Dissolve 6.2g sodium metasilicate, 3.6mL NaOH (0.5mol / L) and 0.86g glucose in 80mL deionized water, stir at room temperature for 6h, and then transfer to a stainless steel reactor lined with polytetrafluoroethylene. Crystallize at 165℃ for 2d. After filtration and drying, the crystallized product is calcined at 800℃ for 6h to obtain α-SiO2.

[0045] (2) Weigh 1g of α-SiO2, add 3mL of HF solution, treat at 65℃ for 3h, then wash, filter, and dry at 80℃ to obtain product A.

[0046] (3) Add 2.5 mL of methyl silicon trichloride solution to 1 g of product A, react at 60 °C for 25 min, and then dry at 60 °C to obtain product B.

[0047] (4) Add 10 mL of palladium acetate solution with a Pd content of 0.1% to 1 g of product B, continue stirring at 60 °C for 8 h, then filter, wash, and dry at 60 °C for 12 h. Then calcine at 550 °C for 5 h to obtain Pd / CF-α-SiO2 catalyst.

[0048] Example 4

[0049] A method for preparing a water- and sulfur-resistant ultra-low temperature CO oxidation catalyst includes the following steps:

[0050] (1) Dissolve 6.2g sodium metasilicate, 3.6mL NaOH (0.5mol / L) and 0.86g glucose in 80mL deionized water, stir at room temperature for 6h, and then transfer to a stainless steel reactor lined with polytetrafluoroethylene. Crystallize at 165℃ for 2d. After filtration and drying, the crystallized product is calcined at 800℃ for 6h to obtain α-SiO2.

[0051] (2) Weigh 2g of α-SiO2, add 1.5mL of HF solution, treat at 80℃ for 3h, then wash, filter, and dry at 80℃ to obtain product A.

[0052] (3) Add 2 mL of methyl silicon trichloride solution to 1 g of product A, react at 50 °C for 45 min, and then dry at 60 °C to obtain product B.

[0053] (4) Add 10 mL of chloroauric acid solution with an Au content of 0.1% to 1 g of product B, continue stirring at 70 °C for 6 h, then filter, wash, and dry at 60 °C for 12 h. Then calcine at 550 °C for 3 h to obtain Au / CF-α-SiO2 catalyst.

[0054] Comparative Example 1

[0055] Compared with Example 1, Comparative Example 1 did not react with methyltrisilicon chloride solution, and all other steps were the same as in Example 1.

[0056] Comparative Example 2

[0057] Compared with Example 1, Comparative Example 2 did not perform HF pretreatment, but all other method steps were the same as in Example 1.

[0058] (1) Catalyst XRD determination

[0059] The products of Examples 1-4 were characterized by XRD using a Rigaku D / max Ultima X-ray diffractometer, and the results are as follows: Figure 1 As shown. Compared with the standard XRD card of α-SiO2 (PDF#46-1045), the XRD characteristic diffraction peak positions of the products of Examples 1 to 4 are exactly the same, indicating that the synthesis method based on the present invention can successfully synthesize the products of Examples 1 to 4.

[0060] (2) Catalyst SEM determination

[0061] The morphology of the product from Example 1 was characterized using a Regulus 8100 high-resolution field emission scanning electron microscope. The results are as follows: Figure 2 As shown. The product of Example 1 exhibits an olive shape with a length of approximately 1-2 μm. This morphology will facilitate the exposure of more (101) crystal planes, creating favorable conditions for the formation of Si-FOC-Si bonds. (3) Catalyst water and sulfur resistance test

[0062] The products prepared in Example 1 and Comparative Examples 1-2 were tested for water and sulfur resistance in a fixed-bed reactor. The catalyst dosage was 0.2 g, and the reaction mixture consisted of SO2 (1000 ppm), CO (3 vol%), H2O (20 vol%), and O2 (5 vol%), with N2 as the equilibrium gas. The reaction temperature was 100 °C, and the reaction space velocity was 100,000 h⁻¹. -1 .

[0063] The formulas for calculating CO conversion rate in Example 1 and Comparative Examples 1-2 are as follows:

[0064]

[0065] Figure 3 The results show the evaluation of the water and sulfur resistance of the products from Example 1 and Comparative Examples 1 and 2. In the presence of both H2O and SO2, the CO conversion rate of the product from Example 1 was approximately 98.5% after 350 hours of testing. In contrast, the CO conversion rates of the products from Comparative Examples 1 and 2 were 36.5% and 55.6%, respectively. These results indicate that the formation of Si-FOC-Si bonds in the Pt / CF-α-SiO2 catalyst provides excellent water and sulfur resistance for the Pt sites.

Claims

1. A method for producing a water- and sulfur-tolerant ultra-low temperature CO oxidation catalyst, characterized by, The method comprises the following steps: (1) mixing a silicon source, an alkali source, a template agent and water uniformly, placing them in a reaction kettle with a polytetrafluoroethylene liner, and crystallizing at 150-180℃ for 1-6 days to obtain α-SiO2 by suction filtration, drying and calcination; (2) functionalizing the α-SiO2 in an HF solution, and then washing, suction filtering and drying to obtain product A; (3) reacting the product A with a methyltrichlorosilane solution, and then washing and drying to obtain product B; (4) mixing the product B with a noble metal precursor solution, performing grafting reaction, and then drying and calcining to obtain a noble metal-based C-F-α-SiO2 catalyst.

2. The preparation method of a water-resistant and sulfur-resistant ultra-low temperature CO oxidation catalyst according to claim 1, characterized in that, In step (1), the silicon source is one or a mixture of several of silica sol, kaolin, amorphous SiO2 and sodium metasilicate; the alkali source is a 0.5 mol / L NaOH solution; the template agent is one or a mixture of several of glucose, tetraethylammonium hydroxide, adamantylammonium, cyclohexylamine and tetraethylammonium bromide; and the silicon source, alkali source, template agent and water are added in a molar ratio of 1 SiO2 / 0.01-2 Na2O / 0.01-1.5 template agent / 60-100 H2O.

3. The method for preparing a water-resistant and sulfur-resistant ultra-low temperature CO oxidation catalyst according to claim 1, characterized by, In step (1), the calcination temperature is 750-850℃, and the calcination time is 5.5-6.5 h.

4. The method for preparing a water-resistant and sulfur-resistant ultra-low temperature CO oxidation catalyst according to claim 1, characterized by, In step (2), the functionalization temperature is 60-100℃, the functionalization time is 2-6 h, and the drying temperature is 75-85℃.

5. The method for preparing a water-resistant and sulfur-resistant ultra-low temperature CO oxidation catalyst according to claim 1, characterized by, In step (3), the reaction temperature is 25-60℃, the reaction time is 15-45 min, and the drying temperature is 45-80℃.

6. The method for preparing a water-resistant and sulfur-resistant ultra-low temperature CO oxidation catalyst according to claim 1, characterized by, In step (4), the noble metal precursor is one or a mixture of several of chloroplatinic acid, platinum nitrate, tetraammineplatinum nitrate, chloropalladic acid, palladium nitrate, palladium acetate, ammonium tetrachloroaurate and chloroauric acid.

7. The method for preparing a water-resistant sulfur-resistant ultra-low temperature CO oxidation catalyst according to claim 1, characterized by, In step (4), the grafting reaction temperature is 60-80℃, and the grafting reaction time is 6-12 h.

8. The preparation method of a water-resistant and sulfur-resistant ultra-low temperature CO oxidation catalyst according to claim 1, characterized in that, In step (4), the drying temperature is 55-65℃, and the calcination temperature is 400-600℃, and the calcination time is 3-8 h.

9. The method for preparing a water-resistant sulfur-resistant ultra-low temperature CO oxidation catalyst according to claim 1, characterized by, In step (2), the ratio of the α-SiO2 to the HF solution is 3 g:2.25-9 mL; in step (3), the ratio of the product A to the methyltrichlorosilane is 1 g:0.2-3 mL; and in step (4), the mass ratio of the product B to the noble metal precursor solution is 1:0.001-0.

5.

10. A noble metal-based C-F-α-SiO2 catalyst prepared by the method according to any one of claims 1-9.

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