Water-resistant catalytic oxidation catalyst and preparation method thereof

Abstract

The preparation method comprises the following steps: (1) uniformly mixing a TS-1 molecular sieve, tetrachlorosilane and acetone, carrying out a reflux reaction at 70-80 DEG C, filtering, washing and drying to obtain a modified TS-1 molecular sieve; (2) mixing the modified TS-1 molecular sieve with a binder, a dispersing agent and water in proportion to prepare slurry, immersing a honeycomb carrier in the slurry in the step (1), and purging, drying and roasting to obtain a coated carrier; and (3) immersing the coated carrier in an active metal solution, purging, drying and roasting to obtain the monolithic catalyst. The catalyst prepared by the invention has excellent water resistance, and can still keep higher catalytic activity and stability after long-term operation under high water vapor content.

Description

Technical Field

[0001] The present invention belongs to the technical field of air pollution control, and particularly relates to a water-resistant catalytic oxidation catalyst and a preparation method thereof. Background Art

[0002] VOCs (volatile organic compounds) are one of the main air pollutants and are important reactants involved in the formation of photochemical smog and haze. The catalytic oxidation (combustion) method is an efficient VOCs treatment technology, and its core is the catalytic oxidation catalyst. In addition to being affected by factors such as reaction temperature and space velocity, the water vapor content in the waste gas has a significant impact on the performance of the catalyst. Industrial VOCs waste gas contains a certain amount of water vapor, and the catalytic oxidation catalyst is required to have a certain water resistance.

[0003] CN106466606A discloses an organic waste gas catalytic combustion catalyst resistant to water vapor and sulfur poisoning and a preparation method thereof. The catalytic combustion catalyst is composed of the following components in mass percentage: TiO2 70-93%, SiO2 3-10%, CeO2 3-10%, and CuO 1-10%. The preparation method of the catalyst is as follows: Mix metatitanic acid, the precursor of SiO2, and the precursor of CeO2 evenly by stirring, dry at 100-150°C for 8-12 hours, and calcine at 400-600°C for 3-5 hours to obtain a catalyst support; after grinding the support into powder, impregnate it in the precursor solution of CuO, and then dry at 100-150°C for 8-12 hours and calcine at 400-600°C for 3-5 hours to obtain an organic waste gas catalytic combustion catalyst resistant to water vapor and sulfur poisoning. However, the actual application effect of the prepared catalyst in resisting water vapor and sulfur poisoning is not provided in this invention.

[0004] CN102580734A discloses a monolithic palladium catalyst for catalytic combustion of acrylic waste gas with high water content and a preparation method thereof. The rare earth oxide-modified activated alumina, cerium oxide, and trace precious metal palladium are loaded onto the surface of a cordierite honeycomb ceramic support by a one-time vacuum coating method to prepare a monolithic palladium catalyst, and then the catalyst is used to treat the acrylic waste gas with high water content and the methyl methacrylate tail gas by catalytic combustion. The process conditions of catalytic combustion in this method require the water content to be lower than 25%, and the application range is limited.

[0005] CN111921554A discloses a Pd-based catalyst for catalytic oxidation of methane under aqueous conditions and a preparation method thereof. The Pd-based catalyst is PdO-MO / NO@HZ; wherein, NO@HZ is a hydrophobic core-shell structure, NO is the shell, and HZ is the core; MO and NO are different metal oxides, and HZ is a molecular sieve. The Pd-based catalyst is used for catalytic oxidation of methane under aqueous conditions. In the presence of water vapor, the catalyst still has good catalytic activity and stability, effectively improving the water resistance of the catalyst and enhancing the performance of the catalyst. The tested aqueous condition is only 6%, and the water content is relatively low.

[0006] In some existing processes, the water vapor content in some organic waste gases is as high as more than 25%. For example, the process flue gas during the ethylene cracking process is a type of organic waste gas with a relatively high water vapor content, and its water vapor content can reach 30%. For catalysts with poor water resistance, long-term operation under such conditions will seriously shorten the service life of the catalyst. Therefore, it is of great value to research and develop catalysts with higher water resistance performance. Summary of the Invention

[0007] Aiming at the deficiencies of the prior art, the present invention provides a water-resistant catalytic oxidation catalyst and a preparation method thereof. The catalyst prepared by the present invention has excellent water resistance performance and can still maintain high catalytic activity and stability after long-term operation under high water vapor content.

[0008] The first aspect of the present invention provides a preparation method of a water-resistant catalytic oxidation catalyst, which includes the following steps:

[0009] (1) Mix TS-1 molecular sieve, tetrachlorosilane, and acetone, and carry out a reflux reaction at 70-80 °C. After filtration, washing, and drying, a modified TS-1 molecular sieve is obtained;

[0010] (2) Mix the modified TS-1 molecular sieve with a binder, a dispersant, and water in proportion to prepare a slurry. Immerse the honeycomb carrier in the slurry of step (1), and after purging, drying, and calcination, a coated carrier is obtained;

[0011] (3) Immerse the coated carrier in an active metal solution, and after purging, drying, and calcination, a monolithic catalyst is obtained.

[0012] In the method of the present invention, the specific surface area of the TS-1 molecular sieve in step (1) is 400-450 m 2 / g, and the pore volume is 0.39-0.41 cm 3 / g. It can be prepared by hydrothermal synthesis or obtained by commercial purchase.

[0013] In the method of the present invention, in step (1), TS-1 molecular sieve, tetrachlorosilane and acetone are mixed in a mass ratio of 1:20 - 30:10 - 20. After mixing evenly, the mixture is refluxed at 70 - 80 °C for 6 - 10 h. After the reaction ends, it is filtered, washed with ethanol until no chloride ions are detected, and dried at 100 - 120 °C for 2 - 5 h to obtain the modified TS-1 molecular sieve.

[0014] In the method of the present invention, in step (2), the binder is an organic binder, such as at least one of methyl cellulose, hydroxypropyl methyl cellulose, etc.

[0015] In the method of the present invention, in step (2), the dispersant is an organic solvent, such as at least one of polyacrylic acid, acetone, etc.

[0016] In the method of the present invention, in step (2), the modified TS-1 molecular sieve, binder, dispersant, and water are mixed in a mass ratio of 15 - 30:1 - 3:1:100. The composite slurry can be prepared by methods such as beating and ball milling.

[0017] In the method of the present invention, in step (2), the mesh number of the honeycomb carrier is 200 - 400 mesh, and a cordierite honeycomb ceramic carrier is preferably used.

[0018] In the method of the present invention, in step (2), the honeycomb carrier is immersed in the slurry for 1 - 2 min. After taking it out, the residual liquid is blown off, dried at 100 - 120 °C for 4 - 6 h, and calcined at 500 - 550 °C for 1 - 3 h to obtain the carrier coated with the modified TS-1 molecular sieve coating.

[0019] In the method of the present invention, in step (3), the active metal is Pt, and preferably also includes one or more of Pd, Au, and Ir. Among them, the concentration of Pt is 2.5 - 5 g / L, and the mixed concentration of one or more of Pd, Au, and Ir is 0.1 - 0.5 times the concentration of Pt.

[0020] In the method of the present invention, in step (3), the active metal solution is its soluble salt, preferably a chlorine-containing compound or nitrate, such as chloroplatinic acid, platinum nitrate, palladium chloride, palladium nitrate, chloroauric acid, chloroiridic acid, etc., and is specifically selected according to the active metal.

[0021] In the method of the present invention, in step (3), the coated carrier is immersed in the active metal solution for 2 - 5 min. After taking it out, the residual liquid is blown off, dried at 100 - 120 °C for 4 - 6 h, and calcined at 450 - 500 °C for 1 - 2 h.

[0022] In the second aspect of the present invention, a water-resistant catalytic oxidation catalyst is also provided, which is prepared by the above method of the present invention. Calculated as a monolithic catalyst, the content of the modified TS-1 molecular sieve coating is 3% - 8%, and the content of the active metal is 0.05% - 0.2%.

[0023] The third aspect of the present invention also provides an application of the water-resistant catalytic oxidation catalyst prepared by the present invention as described above.

[0024] In the application of the present invention, in the waste gas to be treated, the concentration of total non-methane hydrocarbons ≤ 6000 mg / m 3 , and the water vapor content ≤ 35%.

[0025] In the application of the present invention, the catalytic oxidation conditions are: reaction space velocity 1000 - 30000 h -1 , and reaction temperature 200 - 450 °C.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The present invention prepares a catalyst with modified TS-1 molecular sieve as the main coating component. While achieving efficient loading of active metals, it improves the water resistance of the catalyst, enabling the catalyst to maintain high catalytic activity and stability at high water vapor content and relatively low reaction temperature.

[0028] (2) Using tetrachlorosilane and acetone to modify TS-1 molecular sieve synergistically improves the hydrophobicity while having excellent binding force, resulting in good long-term operation stability of the catalyst under high water content conditions.

[0029] (3) While using modified TS-1 molecular sieve, Pt is selected as the main active component, which can inhibit the loss of active sites caused by the migration and aggregation of Pt under high water vapor, ensuring that the catalyst has good catalytic activity and stability. Specific Embodiments

[0030] The technical solution and its implementation effect of the present invention will be further described below through examples. The examples are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given. However, the protection scope of the present invention is not limited to the following examples.

[0031] In the following examples, the experimental methods, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all purchased from conventional biochemical reagent stores.

[0032] The specific surface area of the TS-1 molecular sieve used in the examples of the present invention is about 400 m 2 / g, and the pore volume is 0.4 cm 3 / g, which is obtained by purchase.

[0033] In the embodiments of the present invention, the specific surface area and pore volume are obtained by analyzing the adsorption and desorption curves tested by an N2 sorptometer. The total hydrocarbon concentration in the waste gas is detected by a non-methane total hydrocarbon analyzer (J.U.M.3-900). The conversion rate of non-methane total hydrocarbon is calculated by the following formula:

[0034]

[0035] Example 1

[0036] (1) Mix TS-1 molecular sieve, tetrachlorosilane, and acetone in a mass ratio of 1:20:20, reflux and react at 75 °C for 6 h. After filtration, wash with ethanol until no chloride ions are detected, and dry at 100 °C for 5 h to obtain modified TS-1 molecular sieve.

[0037] (2) Mix the modified TS-1 molecular sieve material with methylcellulose, acetone, and water in a ratio of 30:1:1:100 to form a slurry. Immerse a 200-mesh cordierite honeycomb ceramic carrier in the slurry, impregnate for 2 min, blow off the residual liquid, dry at 110 °C for 5 h, and calcine at 525 °C for 2 h to obtain a carrier coated with a modified TS-1 molecular sieve coating.

[0038] (3) Immerse the coated carrier in a mixed solution of chloroplatinic acid and palladium chloride, where the concentration of Pt is 4.5 g / L and the ratio of Pt to Pd is 1:0.25. Immerse for 3 min, blow off the residual liquid, dry at 100 °C for 6 h, and calcine at 475 °C for 1.5 h to obtain a monolithic catalyst.

[0039] Calculated by the total mass of the catalyst, the content of the modified TS-1 molecular sieve coating is 7.52%, and the content of the active metal component is 0.181%.

[0040] Example 2

[0041] (1) Mix TS-1 molecular sieve, tetrachlorosilane, and acetone in a mass ratio of 1:25:15, reflux and react at 80 °C for 6 h. After filtration, wash with ethanol until no chloride ions are detected, and dry at 100 °C for 5 h to obtain modified TS-1 molecular sieve.

[0042] (2) Mix the modified TS-1 molecular sieve material with methylcellulose, acetone, and water in a ratio of 20:2:1:100 to form a slurry. Immerse a 200-mesh cordierite honeycomb ceramic carrier in the slurry, impregnate for 2 min, blow off the residual liquid, dry at 120 °C for 3 h, and calcine at 550 °C for 2 h to obtain a carrier coated with a modified TS-1 molecular sieve coating.

[0043] (3) Immerse the coated carrier in a mixed solution of chloroplatinic acid and palladium chloride, where the concentration of Pt is 2.5 g / L and the ratio of Pt to Pd is 1:0.5. Immerse for 3 min, purge the residual liquid, dry at 100 °C for 6 h, and calcine at 500 °C for 2 h to obtain the monolithic catalyst.

[0044] Based on the total mass of the catalyst, the content of the modified TS-1 zeolite coating is 6.85%, and the content of the active metal component is 0.157%.

[0045] Example 3

[0046] (1) Mix TS-1 zeolite, tetrachlorosilane, and acetone in a mass ratio of 1:30:10, reflux at 70 °C for 10 h, filter, wash with ethanol until no chloride ions are detected, and dry at 120 °C for 2 h to obtain the modified TS-1 zeolite.

[0047] (2) Mix the modified TS-1 zeolite material with methylcellulose, acetone, and water in a ratio of 15:3:1:100 to form a slurry. Immerse a 200-mesh cordierite honeycomb ceramic carrier in the slurry, immerse for 2 min, purge the residual liquid, dry at 100 °C for 5 h, and calcine at 500 °C for 3 h to obtain the carrier coated with the modified TS-1 zeolite coating.

[0048] (3) Immerse the coated carrier in a mixed solution of chloroplatinic acid and palladium chloride, where the concentration of Pt is 3.5 g / L and the ratio of Pt to Pd is 1:0.15. Immerse for 3 min, purge the residual liquid, dry at 100 °C for 4 h, and calcine at 450 °C for 2 h to obtain the monolithic catalyst.

[0049] Based on the total mass of the catalyst, the content of the modified TS-1 zeolite coating is 6.14%, and the content of the active metal component is 0.151%.

[0050] Example 4

[0051] The preparation method is the same as that of Example 1, except that in step (2), the binder is hydroxypropyl methylcellulose, and finally a monolithic catalyst is obtained.

[0052] Example 5

[0053] The preparation method is the same as that of Example 1, except that in step (2), the dispersant is polyacrylic acid, and finally a monolithic catalyst is obtained.

[0054] Example 6

[0055] The preparation method is the same as that of Example 1, except that in preparation step (3), the noble metals are Pt and Au. Finally, a monolithic catalyst is obtained.

[0056] Example 7

[0057] The preparation method is the same as that of Example 1, except that in the preparation step (3), the noble metals are Pt and Ir. An integral catalyst is finally prepared.

[0058] Example 8

[0059] The preparation method is the same as that of Example 1, except that in the preparation step (3), the noble metal is Pt. An integral catalyst is finally prepared.

[0060] Comparative Example 1

[0061] The preparation method is the same as that of Example 1, except that in the preparation step (1), methyl silicone oil is used instead of tetrachlorosilane, and an integral catalyst is finally prepared.

[0062] Comparative Example 2

[0063] The preparation method is the same as that of Example 1, except that acetone is not used in the preparation step (1), and an integral catalyst is finally prepared.

[0064] Comparative Example 3

[0065] The preparation method is the same as that of Example 1, except that step (1) is cancelled, and the molecular sieve used in step (2) is directly the unmodified TS-1 molecular sieve, and an integral catalyst is finally prepared.

[0066] Comparative Example 4

[0067] The preparation method is the same as that of Example 1, except that the TS-1 molecular sieve used in step (1) is replaced by ZSM-5 molecular sieve (specific surface area 420m 2 / g, pore volume 0.4cm 3 / g), and an integral catalyst is finally prepared.

[0068] Comparative Example 5

[0069] The preparation method is the same as that of Example 1, except that in the preparation step (3), the active metal is Pd, and an integral catalyst is finally prepared.

[0070] Test Example

[0071] In the ethylene cracking process of the petrochemical industry, the process coke burning gas is a type of VOCs waste gas with a relatively high water vapor content. The organic substances are mainly benzene and n-hexane. The water vapor content is about 30%, and the non-methane total hydrocarbon concentration at the reaction inlet is 3000mg / m 3 . The test conditions are: reaction space velocity 20000h -1 , reaction temperature 280°C.

[0072] Table 1 Removal effects of Examples and Comparative Examples

[0073]

[0074]

Claims

1. A preparation method of a water-resistant catalytic oxidation catalyst, characterized in that It includes the following steps: (1) Mix TS-1 molecular sieve, tetrachlorosilane, and acetone, and reflux at 70-80 °C. After filtration, washing, and drying, the modified TS-1 molecular sieve is obtained; (2) Mix the modified TS-1 molecular sieve with a binder, a dispersant, and water in proportion to prepare a slurry. Immerse the honeycomb carrier in the slurry of step (1), and obtain the coated carrier after purging, drying, and calcination; (3) Immerse the coated carrier in the active metal solution, and obtain the monolithic catalyst after purging, drying, and calcination.

2. The method according to claim 1, characterized in that: Step (1) The specific surface area of the TS-1 molecular sieve is 400-450 m 2 / g, and the pore volume is 0.39-0.41 cm 3 / g.

3. The method according to claim 1 or 2, characterized in that: In step (1), the TS-1 molecular sieve, tetrachlorosilane, and acetone are mixed in a mass ratio of 1:20-30:10-20.

4. The method according to claim 1, characterized in that: After mixing in step (1), reflux at 70-80 °C for 6-10 h.

5. The method according to claim 1, characterized in that: After the reflux reaction, filter, wash with ethanol until no chloride ions are detected, and dry at 100-120 °C for 2-5 h to obtain the modified TS-1 molecular sieve.

6. The method according to claim 1, characterized in that: In step (2), the binder is an organic binder, preferably at least one of methylcellulose and hydroxypropyl methylcellulose.

7. The method according to claim 1, characterized in that: In step (2), the dispersant is an organic solvent, preferably at least one of polyacrylic acid and acetone.

8. The method according to claim 1, characterized in that: In step (2), the modified TS-1 molecular sieve, binder, dispersant, and water are mixed in a mass ratio of 15-30:1-3:1:

100.

9. The method according to claim 1, characterized in that: In step (2), the mesh number of the honeycomb carrier is 200-400 mesh, and a cordierite honeycomb ceramic carrier is preferred.

10. The method according to claim 1, characterized in that: In step (2), the immersion time of the honeycomb carrier in the slurry is 1-2 min; after taking out, blow off the residual liquid, dry at 100-120 °C for 4-6 h, and calcine at 500-550 °C for 1-3 h.

11. The method according to claim 1, characterized in that: In step (3), the active metal is Pt, preferably further includes one or more of Pd, Au, and Ir, where the concentration of Pt is 2.5-5 g / L, and the mixed concentration of one or more of Pd, Au, and Ir is 0.1-0.5 times the concentration of Pt.

12. The method according to claim 1 or 11, characterized in that: In step (3), the active metal is its soluble salt, preferably a chlorine-containing compound or a nitrate.

13. The method according to claim 1, characterized in that: In step (3), the immersion time of the coated carrier in the active metal solution is 2-5 min; after taking out, blow off the residual liquid, dry at 100-120 °C for 4-6 h, and calcine at 450-500 °C for 1-2 h.

14. A water-resistant catalytic oxidation catalyst, characterized in that It is prepared by the method described in any one of claims 1-13.

15. The catalyst according to claim 14, characterized in that: Based on the monolithic catalyst, the content of the modified TS-1 molecular sieve coating is 3%-8%, and the content of the active metal is 0.05%-0.2%.

16. The application of the catalyst prepared by the method according to any one of claims 1-13 or the catalyst according to any one of claims 14-15, characterized in that: In the waste gas to be treated, the concentration of total non-methane hydrocarbons ≤ 6000 mg / m 3 , and the water vapor content ≤ 35%.

17. The application according to claim 16, characterized in that: The catalytic oxidation conditions are as follows: the reaction space velocity is 1000 - 30000 h -1 , and the reaction temperature is 200 - 450 °C.

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