Sulfate radical-containing SCR catalyst carrier material and preparation method thereof
By introducing sulfate and silane coatings into the anatase-type titanium dioxide SCR catalyst, the high-temperature sintering, anti-sulfur poisoning and hydrothermal stability of the catalyst are solved, and the activity and life of the catalyst are improved.
Patent Information
- Application Number
- CN202510415033.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-03
- Publication Date
- 2025-07-29
AI Technical Summary
The existing anatase titanium dioxide-based SCR catalysts are prone to sintering at high temperatures, have weak anti-sulfur poisoning ability, poor NH3 capture ability and insufficient hydrothermal stability, resulting in a shortening of the catalyst life.
By introducing sulfate into the anatase-type titanium dioxide SCR support material, modification is performed using generator gas to increase the acidic site density and sulfur resistance of the catalyst, and a silane coating is formed in the pores to improve the stability of the catalyst and water aging resistance.
It enhances the activity of the catalyst and anti-sulfur poisoning ability, extends the service life of the catalyst, and improves the denitrification efficiency in high humidity and high sulfur environments.
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical fields of waste gas treatment and catalysts, and particularly relates to a sulfate-containing SCR catalyst support material and a preparation method thereof. Background Art
[0002] An SCR catalyst (Selective Catalytic Reduction Catalyst) is a key environmental protection material used to reduce nitrogen oxides (NO x ) emissions in industrial waste gas and vehicle exhaust. Through a catalytic reduction reaction, harmful NO x is converted into harmless nitrogen and water.
[0003] The mainstream support material of SCR catalysts is anatase titanium dioxide. Due to its microporous and mesoporous crystal structures, it has a very high specific surface area, which can effectively promote the diffusion and adsorption of reactants in the denitrification process. Anatase titanium dioxide usually also doped with tungsten (WO3) or molybdenum (MoO3) to enhance thermal stability. The active component is mainly a vanadium-based catalyst, mainly vanadium pentoxide (V2O5), which is combined with WO3 / TiO2 and has high efficiency in catalysis at 300-400 °C, but there are problems of vanadium toxicity and high-temperature deactivation. The active component can also be some non-vanadium-based catalysts, such as Fe2O3, CuO, MnOx, etc., which are loaded on TiO2 or Al2O3 for low-temperature scenarios around 150 °C.
[0004] However, the existing SCR catalysts with anatase titanium dioxide as the support material still have the following problems: (1) Active components (such as V2O 5、 WO3, etc.) are prone to sintering and agglomeration deactivation at high temperatures; (2) The sulfur resistance poisoning ability is weak. SO2 is oxidized to SO3 on the catalyst surface and reacts with NH3 to form ammonium bisulfate (NH4HSO4), covering the active sites and blocking the pores of the catalyst; (3) The ability to capture NH3 is poor, and ammonia slip is likely to occur; (4) It is sensitive to hydrothermal aging. In a flue gas environment with high humidity (>10% H2O) and high temperature (>400 °C), anatase TiO2 is prone to sintering and the porosity decreases, resulting in a shortened catalyst life.
[0005] In order to solve the above technical problems, the inventor hopes to propose an improvement plan for the existing SCR catalyst to overcome the deficiencies of the existing SCR catalyst to a certain extent. Summary of the Invention
[0006] (1) Technical Problems to be Solved
[0007] In view of the above-mentioned disadvantages and deficiencies of the prior art, the present invention provides a sulfate-containing SCR catalyst support material and a preparation method thereof. The anatase-type titanium dioxide SCR support material is modified by producer gas to increase the sulfate content in the support material, thereby reducing the ammonia slip of the catalyst, stabilizing the active components of the catalyst, enhancing the sulfur poisoning resistance and water stability of the catalyst, and is of great significance for improving the catalytic activity of the SCR catalyst and extending the service life of the SCR catalyst.
[0008] (II) Technical solution
[0009] In the first aspect, the present invention provides a preparation method of a sulfate-containing SCR catalyst support material, wherein the support material is anatase-type titanium dioxide; the preparation method of the support material includes:
[0010] S1. Prepare a calcination precursor of anatase-type titanium dioxide by the sulfuric acid method; specifically include: using ilmenite or titanium slag as raw materials, reacting with concentrated sulfuric acid at 200-220 °C to generate titanyl sulfate, diluting the titanyl sulfate solution to pH = 1.5-2.0, and hydrolyzing at 80-90 °C to generate metatitanic acid. The metatitanic acid is washed and dried to obtain a calcination precursor of anatase-type titanium dioxide;
[0011] S2. Carry out temperature-controlled calcination on the calcination precursor, the calcination temperature is 400-780 °C, producer gas is introduced during the calcination process, and calcination is carried out for 4-9 h under aerobic conditions. After the calcination is completed, the obtained anatase-type titanium dioxide, that is, the sulfate-containing SCR catalyst support material, is obtained.
[0012] When preparing the calcination precursor of anatase-type titanium dioxide in S1, the calcination precursor already contains a certain amount of sulfate, but the sulfate content and density are not high enough; in S2, the anatase TiO2 support material is functionally modified by producer gas (containing components such as CO, H2, H2S, etc.), and sulfate (SO4 2- ) is controllably introduced onto the surface of the support material to increase the density of acidic sites and sulfur resistance of the SCR catalyst. Hydrogen sulfide gas (H2S) in the producer gas can better enter into the micropores and mesopores of anatase-type titanium dioxide during the calcination process of the catalyst support material, form sulfur dioxide (SO2) under oxygen-rich conditions, and further convert into sulfate (SO4 2- ), supplementing the sulfate content in the catalyst support material. H2S in the producer gas is oxidized on the surface of the support material to generate SO3, which reacts with TiO2 to generate titanium sulfate (Ti(SO4)2), while CO / H2 acts as a reducing agent to inhibit the over-oxidation of the support material. CO in the gas reacts with the surface oxygen of TiO2 to generate CO2, inducing the formation of oxygen vacancies in TiO2 and promoting the adsorption of SO3 and the stabilization of sulfate.
[0013] According to a preferred embodiment of the present invention, in S2, the calcination conditions are calcination at 600 - 780 °C for 5 - 7 h. During the calcination process, 3 - 5 wt% ammonium sulfate is added as a mineralizing agent for crystal form control.
[0014] According to a preferred embodiment of the present invention, in S2, producer gas is continuously injected into the calcination chamber of the calcination precursor. H2S enters the pores of titanium dioxide and undergoes oxidation to generate sulfur dioxide (SO2), which further reacts with TiO2 to form titanium sulfate (Ti(SO4)2). Calculated based on 1 m of the calcination chamber 3 the feeding rate is 3000 - 5000 m 3 / h.
[0015] According to a preferred embodiment of the present invention, in S2, before calcination, the calcination precursor is loaded with 1 - 3% CeO2 or WO3 or a combination of both (Ce / W molar ratio 1:2) by the impregnation method. These metal oxides can serve as catalytic active centers for H2S oxidation to promote the conversion of H2S into sulfate radicals (SO4 2- ); CeO2 - WO3 can also form a stable structure of Ce(SO4)2 - WO4 with sulfate radicals to form a "sulfate radical protective cover" to inhibit the decomposition and escape of high - temperature sulfates. 2- According to a preferred embodiment of the present invention, after S2, it further includes impregnating anatase titanium dioxide into an anhydrous ethanol solution of tetraethyl orthosilicate (TEOS) or hexamethyldisilazane (HMDS) with a concentration of 1 - 5%. After impregnation, it is treated by supercritical CO2 (50 °C, 10 MPa). The high diffusivity of supercritical CO2 is utilized to promote the uniform hydrolysis and condensation of silane in the pores, generating a hydrophobic nano - SiO2 coating in the pores to reduce the desorption of H2O from sulfate radicals and improve the anti - water aging performance of the SCR catalyst.
[0016] In a second aspect, the present invention provides a sulfate - containing SCR catalyst support material prepared by any of the above - mentioned methods. The sulfate content in the support material is 1.7 - 2.5 wt%; the BET is 120 - 160 m
[0017] / g. 2 / g.
[0018] (III) Beneficial effects
[0019] The present invention uses producer gas to functionalize and modify the calcined precursor, which not only solidifies the sulfate radicals contained in the calcined precursor of anatase titanium dioxide, but also increases the filling amount of sulfate radicals inside the micropores and mesopores of the SCR catalyst support material. Thus, the catalytic activity and service life of the SCR catalyst are improved in the following aspects: (1) enhancing the surface acidity of the catalyst, promoting the adsorption of basic gases such as ammonia (NH3), and improving the SCR reaction efficiency. (2) stabilizing the active components (V2O5, WO3, etc.) in the catalyst, preventing their sintering, agglomeration or loss at high temperatures, and extending the service life of the SCR catalyst. (3) improving the sulfur poisoning resistance of the catalyst, reducing the poisoning of the catalyst by SO2, and ensuring its high-efficiency desulfurization in sulfur-containing flue gas. (4) improving the surface structure of the catalyst, increasing the active sites of the catalyst, and enhancing the catalytic performance of the catalyst. (5) improving the water resistance stability of the catalyst.
[0020] The present invention utilizes producer gas (containing components such as CO, H2, H2S, etc.) to functionalize and modify the anatase TiO2 support material, realizes the resource utilization of producer gas, fixes the H2S in the producer gas, reduces the burden on the subsequent treatment of producer gas, and also reduces the modification cost of the SCR catalyst support material. At the same time, CO and H2 in the producer gas are reducing gases, which can inhibit the over-oxidation of the support material, and maintain an appropriate content of sulfate radicals, porosity and BET value. An appropriate content of sulfate radicals can increase the surface acidic sites and density of the support material, and inhibit the transformation of anatase to rutile phase. However, an excessive content of sulfate radicals may lead to the blockage of the pores of the support material, a decrease in specific surface area, and the release of SO3 at high temperatures, resulting in equipment corrosion and pollution. Specific embodiments
[0021] In order to better explain the present invention for easy understanding, the present invention will be described in detail below in conjunction with specific embodiments. When the meaning of "%" is not clearly stated in the embodiments of the present invention, "%" all represents mass percentage.
[0022] Example 1
[0023] This example provides a preparation method of an SCR catalyst support material containing sulfate radicals, and the steps are as follows: (1) Using ilmenite as a raw material, reacting with concentrated sulfuric acid at 200 °C to generate titanyl sulfate, diluting the titanyl sulfate solution to pH = 2.0, and hydrolyzing it at 90 °C to generate metatitanic acid. The metatitanic acid is washed and dried to obtain a calcined precursor of anatase titanium dioxide.
[0024] (2) Put the calcined precursor into 1m 3Calcination was carried out in a box furnace (the calcined precursor accounted for 1 / 10 of the volume of the box furnace). During the calcination process, 3 wt% (based on the mass of the calcined precursor) of ammonium sulfate was added as a mineralizing agent for crystal form control. The calcination conditions were calcination at 660 - 680 °C for 5 h. During the calcination process, producer gas was continuously introduced at a rate of 4000 m 3 / h. After the calcination, anatase-type titanium dioxide was obtained. Its anatase phase purity reached 98.5% (XRD analysis), the sulfate loading was stably at 1.78 wt%, and the BET was 126 m 2 / g.
[0025] Example 2
[0026] This example provides a method for preparing a sulfate-containing SCR catalyst support material, and the steps are as follows:
[0027] (1) Using titanium slag as a raw material, it reacts with concentrated sulfuric acid at 220 °C to form titanyl sulfate. The titanyl sulfate solution is diluted to pH = 1.5 and hydrolyzed at 90 °C to form metatitanic acid. The metatitanic acid is washed and dried to obtain a calcined precursor of anatase-type titanium dioxide.
[0028] (2) The calcined precursor is loaded with a 3% CeO2-WO3 combination by the impregnation method (loading the soluble salts of the precursors of CeO2 and WO3, which become oxides after calcination). The Ce / W molar ratio is 1:2. After impregnation, it is dried to obtain a calcined precursor.
[0029] (3) The calcined precursor is placed in a 1 m 3 box furnace for calcination (the calcined precursor accounts for 1 / 10 of the volume of the box furnace). During the calcination process, 2 wt% (based on the mass of the calcined precursor) of ammonium sulfate is added as a mineralizing agent for crystal form control. The calcination conditions are calcination at 600 - 620 °C for 6 h. During the calcination process, producer gas is continuously introduced at a rate of 4500 m 3 / h. After the calcination, anatase-type titanium dioxide is obtained. Its anatase phase purity reaches 98.7% (XRD analysis), the sulfate loading is stably at 2.1 wt%, and the BET is 121 m 2 / g.
[0030] Example 3
[0031] This example is based on Example 1. The anatase-type titanium dioxide obtained after calcination is further impregnated with a 2.5% anhydrous ethanol solution of TEOS. After impregnation, it is treated by supercritical CO2 (50 °C, 10 MPa). The high diffusivity of supercritical CO2 is utilized to promote the uniform hydrolysis and condensation of silane in the pores, and a hydrophobic nano-SiO2 coating is formed in the pores.
[0032] Example 4
[0033] Based on Example 2, in this example, the anatase titanium dioxide obtained after calcination was further impregnated with an anhydrous ethanol solution of 2.0% HMDS. After impregnation, it was treated by supercritical CO2 (50 °C, 10 MPa). The high diffusivity of supercritical CO2 was utilized to promote the uniform hydrolysis and condensation of silane in the pores, and a hydrophobic nano-SiO2 coating was formed in the pores.
[0034] Comparative Example 1
[0035] A preparation method of an SCR catalyst support material was prepared in this comparative example, and the steps are as follows:
[0036] (1) Using ilmenite as a raw material, it reacts with concentrated sulfuric acid at 200 °C to generate titanyl sulfate. The titanyl sulfate solution is diluted to pH = 2.0 and hydrolyzed at 90 °C to form metatitanic acid. The metatitanic acid is washed and dried to obtain a calcination precursor of anatase titanium dioxide.
[0037] (2) The calcination precursor was placed in a box furnace of 1 m 3 for calcination. During the calcination process, 3 wt% (based on the mass of the calcination precursor) of ammonium sulfate was added as a mineralizing agent for crystal form control. The calcination conditions were calcination at 660 - 680 °C for 5 h. After the calcination was completed, anatase titanium dioxide was obtained. Its anatase phase purity reached 99.3% (XRD analysis), the sulfate radical loading was stably at 1.07 wt%, and the BET was 152 m 2 / g.
[0038] Compared with Example 1, in Comparative Example 1, producer gas was not introduced into the calcination chamber during the calcination process. After calcination, the content of sulfate radicals in the prepared anatase titanium dioxide was only about 60% of that in Example 1. However, by continuously charging producer gas for auxiliary calcination during the calcination in step (2), the sulfate radical loading in the support material can be greatly increased.
[0039] Example 5
[0040] In the following manner, different SCR catalyst support materials in Examples 1 - 4 and Comparative Example 1 were used to load active components to prepare a usable SCR catalyst:
[0041] (1) The catalyst support material was impregnated in an ammonium metatungstate solution with a concentration of 10 wt%, a liquid-solid ratio of 1.2:1. After vacuum-assisted penetration for 10 minutes, it was taken out and rotary evaporated and dried at 60 °C for 4 hours to form a uniform WO3 pre-coating;
[0042] (2) Using the spray impregnation method, an ammonium metavanadate-oxalic acid solution was sprayed onto the surface of the WO3 / support material at a rate of 0.1 mL / min; the humidity was controlled at 50 - 60% to avoid the migration and agglomeration of V components.
[0043] (3) After impregnation, the carrier material was transferred to a microwave reactor (2.45 GHz, 300 W) and irradiated for 5 minutes to direct the V-W precursor to anchor at the surface defect sites of TiO2.
[0044] (4) It was heated to 550 °C at a heating rate of 3 °C / min and held for 2 hours in an air atmosphere to decompose the vanadium / tungsten precursor into oxides (NH4VO3 → V2O5, ammonium metatungstate → WO3), and the SCR catalyst was prepared. Among them, the loading amount of vanadium pentoxide was 1 wt%, and the loading amount of tungsten trioxide was 5 wt%.
[0045] According to the above method, five SCR catalysts were obtained respectively according to the different SCR carrier materials used in Examples 1-4 and Comparative Example 1, and named SCR-S1, SCR-S2, SCR-S3, SCR-S4, and SCR-D1.
[0046] Compare the ammonia adsorption amounts of the above different catalysts under static conditions, and the initial (catalytic temperature 300 °C, space velocity 15000 h -1 ) and after running for 50 h of NO x conversion rates in the flue gas of 200 ppm SO2 and high humidity (15% H2O). The catalytic activity decline rates after running for 50 h in the above environment were recorded in Table 1 respectively.
[0047] Table 1: Catalytic performance of SCR catalysts prepared with the same active components and different carrier materials
[0048]
[0049] Among them, the ammonia adsorption amount is the saturated amount of ammonia statically adsorbed by each g of the SCR catalyst at room temperature (25 °C, 1 atm NH3, 4-hour equilibrium), and the unit is mmol / g. The 50-h catalytic activity decline rate is used to characterize the water resistance and sulfur poisoning resistance of the catalyst, and the calculation method is:
[0050] Unit time decline rate = (X0 - X t ) / (X0 * t) × 100% / h; X0: initial NO x conversion rate; X t : NO x conversion rate after running time t (50 h).
[0051] From the above comparison, it can be seen that the SCR catalysts (SCR-S1, SCR-S2) prepared from the SCR catalyst support materials prepared in Examples 1-2 of the present invention after loading the active components, compared with the SCR catalyst (SCR-D1) prepared from the support material of Comparative Example 1, the ammonia adsorption amount of the former has been greatly improved. This proves that when preparing the anatase titanium dioxide support material, introducing producer gas for modification can increase the density of acidic sites in the catalyst and thus improve the capture ability for basic gases. And for the SCR catalysts (SCR-S3, SCR-S4) prepared from the SCR catalyst support materials in Examples 3-4 after loading the active components, the NH3 adsorption amount is further increased due to the hydrophobic nano-SiO2 coating. After operating in an environment of 200 ppm SO2 and high humidity, the SCR catalysts (SCR-S1, SCR-S2) prepared from the SCR catalyst support materials prepared in Examples 1-2 after loading the active components, compared with the SCR catalyst (SCR-D1) prepared from the support material of Comparative Example 1, the water aging resistance and sulfur poisoning resistance of the former have been significantly improved. For (SCR-S3, SCR-S4) obtained by introducing the SiO2 coating into the pores during the preparation of the anatase titanium dioxide support material in Examples 3-4, although the initial catalytic activity is reduced to a certain extent relative to SCR-S1 and SCR-S2, the catalytic activity decline rate after operating for 50 h in an environment of 200 ppm SO2 and high humidity is significantly less than that of the catalysts SCR-S1 and SCR-S2; this shows that the formation of the nano-SiO2 coating on the inner wall of the catalyst support material helps to slow down the aging effect of water on the catalyst and improve the water resistance of the catalyst, which is of great significance for extending the service life of the SCR catalyst.
[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements, or in the case where the technical features in the above embodiments do not conflict with each other, can be combined in the manner described in the embodiments, and these modifications, replacements or combinations do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A preparation method of an SCR catalyst support material containing sulfate radicals, characterized in that, The carrier material is anatase titanium dioxide; the preparation method of the carrier material includes: S1. Prepare a calcination precursor of anatase titanium dioxide by the sulfuric acid method; specifically, use ilmenite or titanium slag as the raw material, react with concentrated sulfuric acid at 200 - 220 °C to generate titanyl sulfate, dilute the titanyl sulfate solution to pH = 1.5 - 2.0, hydrolyze at 80 - 90 °C to generate metatitanic acid, and after washing and drying the metatitanic acid, obtain the calcination precursor of anatase titanium dioxide; S2. Carry out temperature-controlled calcination on the calcination precursor, the calcination temperature is 400 - 780 °C, blast furnace gas is introduced during the calcination process, and calcination is carried out for 4 - 9 h under aerobic conditions. After the calcination is completed, the obtained anatase titanium dioxide, that is, the SCR catalyst carrier material containing sulfate radicals, is obtained.
2. The preparation method according to claim 1, characterized in that, In S2, the calcination conditions are calcination at 600 - 780 °C for 5 - 7 h, and during the calcination process, 3 - 5 wt% ammonium sulfate is added as a mineralizer for crystal form control.
3. The preparation method according to claim 1, characterized in that, In S2, the producer gas is injected into the calcination chamber of the calcined precursor in a continuous manner. Calculated based on 1 m of the calcination chamber 3 the feeding rate is 3000 - 5000 m 3 / h.
4. The preparation method according to claim 1, characterized in that, In S2, before calcination, the calcination precursor is loaded with 1 - 3% CeO2 or WO3 or a combination of both by the impregnation method.
5. The preparation method according to claim 1, characterized in that, After S2, it also includes impregnating the anatase titanium dioxide into an anhydrous ethanol solution of tetraethyl orthosilicate TEOS or hexamethyldisilazane HMDS with a concentration of 1 - 5%. After impregnation, it is treated by supercritical CO2, and the high diffusivity of supercritical CO2 is used to promote the uniform hydrolysis and condensation of silane in the pores, and a hydrophobic nano-SiO2 coating is generated in the pores.
6. A sulfate-containing SCR catalyst support material prepared by the preparation method according to any one of claims 1-5, wherein the sulfate content in the support material is 1.7-2.5 wt%; BET is 120-160 m 2 / g.