Preparation method, product and application of low-temperature anti-poisoning composite Mn-based catalyst

Abstract

The invention relates to the technical field of catalysts, in particular to a preparation method, a product and application of a low-temperature anti-poisoning composite Mn-based catalyst. The preparation method of the low-temperature anti-poisoning composite Mn-based catalyst comprises the following steps: dissolving precursor substances respectively containing L, Mn and N in water to obtain a homogeneous solution; adding the homogeneous solution into the Si source solution, controlling the pH value of a reaction system to be alkaline, and aging; and carrying out suction filtration and washing on the aged mixed solution, and then drying and calcining to obtain the low-temperature anti-poisoning composite Mn-based catalyst. L is at least one of Cu, Ni and Co; n is Al and / or Fe. The low-temperature anti-poisoning composite Mn-based catalyst prepared by using the method disclosed by the invention not only can efficiently catalyze and reduce nitrogen oxides in flue gas at low temperature, but also has very good low-temperature anti-poisoning performance.

Description

Technical Field

[0001] The present invention relates to the field of catalyst technology, and in particular to a preparation method, product and application of a low-temperature anti-poisoning composite Mn-based catalyst. Background Art

[0002] Among the current denitrification technologies, low-temperature selective catalytic reduction (LT-SCR) technology has great application potential in industrial flue gas denitrification. The catalyst is the core of this technology and can be divided into low-temperature catalysts and medium- and low-temperature catalysts.

[0003] Selective Catalytic Reduction (SCR) is a process that reduces NO by adding an external reducing agent. x The method of treating flue gas by converting it into N2. However, some substances (SO2, water vapor, etc.) carried in the flue gas will be deposited on the catalyst, causing the catalyst to deactivate and reduce the denitration rate. Therefore, while improving the denitration efficiency, improving the SO2 resistance of NH3-SCR catalysts is of great significance in industrial applications. Generally speaking, there are three main SO2 poisoning mechanisms of NH3-SCR catalysts: (1) ammonium bisulfate covers the active sites; (2) the adsorption of active components is inhibited by sulfate components (cutting off the Langmuir-Hinshelwood (LH) mechanism); (3) the redox ability is lost after the sulfate components are formed. In addition, water will cause catalyst deactivation by changing the surface acidity of the SCR catalyst and competing with NH3 for adsorption centers. The formation of hydroxyl groups (-OH) with water bonds at the active sites can directly weaken the adsorption of NH3 and the conversion of intermediate substances. Therefore, in the development of NH3-SCR catalysts, water and sulfur resistance are one of the research focuses.

[0004] In current research, LT-SCR catalysts include transition metals such as Mn, Co, Ce, Fe, Cu, and precious metals such as Ag and Pt. Among them, Cu-based, Fe-based, and Mn-based catalysts are widely used. Mn-based catalysts are considered to be one of the catalysts with excellent low-temperature activity, such as MnO x / TiO2、MnO x / Al2O3 and Ni(Co)-MnO x -CeO2 and other catalysts. Mn-based catalysts are considered to have good redox ability and high activity per unit area. However, low-temperature SCR catalysts are generally plagued by problems such as SO2 and water vapor poisoning. Therefore, improving the anti-poisoning performance of the catalyst is an important problem in its practical application. Summary of the invention

[0005] Based on the above content, the present invention provides a preparation method, product and application of a low-temperature anti-poisoning composite Mn-based catalyst.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention is a method for preparing a low-temperature anti-poisoning composite Mn-based catalyst, comprising the following steps:

[0008] Step 1, dissolving precursor substances containing L, Mn and N respectively in water to obtain a homogeneous solution;

[0009] Step 2, adding the homogeneous solution to the Si source solution and controlling the pH of the reaction system to be alkaline, and aging;

[0010] Step 3, filtering and washing the aged mixed solution, and then drying it to obtain a hydrotalcite-like material containing L, N, Mn and SiO2;

[0011] Step 4, calcining the hydrotalcite-like material containing L, N, Mn and SiO2 to obtain the low-temperature anti-poisoning composite Mn-based catalyst;

[0012] The L is at least one of Cu, Ni and Co; and the N is Al and / or Fe.

[0013] The second technical solution of the present invention is a low-temperature anti-poisoning composite Mn-based catalyst prepared by the above-mentioned preparation method.

[0014] The third technical solution of the present invention is that the above-mentioned low-temperature anti-poisoning composite Mn-based catalyst is used in the selective catalytic reduction of NO in flue gas. x Application in.

[0015] The present invention discloses the following technical effects:

[0016] The present invention provides a method for preparing a highly efficient Mn-based catalyst that can be used for low-temperature anti-poisoning SCR technology, wherein a layered hydrotalcite-like substance is compounded with a SiO2 precursor and calcined under high-temperature oxygen-limited conditions to prepare a nano-metal composite material (SiO2(v) / L) with excellent anti-poisoning performance. w Mn x N y O z ). SiO2 was added as an auxiliary component in the preparation process of hydrotalcite-like materials to obtain SiO2(v) / L w Mn x N y O zThe catalyst can not only improve the N2 selectivity and stability of the catalyst, but also improve the nitrogen oxide removal rate under the coexistence of SO2+H2O through the bonding between Si and -OH in water molecules and the higher adsorption capacity for SO2, thereby enhancing the anti-poisoning performance of the catalyst and reducing the cost of industrial flue gas treatment.

[0017] The present invention SiO2(v) / L w Mn x N y O z The material can be synthesized in one step to prepare SiO2, active components (MnO x ) and other auxiliary components (L and N) composed of metal nanoparticles (i.e., low-temperature anti-poisoning composite Mn-based catalysts), which can be highly dispersed at the atomic level, can effectively reduce clustering, expose more active sites, produce more active species, and improve the activity of the catalyst as well as N2 selectivity and anti-poisoning performance.

[0018] The catalyst of the present invention effectively promotes the removal of NO in industrial flue gas. x The composite material combines the advantages of SiO2 and hydrotalcite-derived metal oxides to produce more surface active oxygen, abundant surface acid sites and better redox performance, which can effectively promote the denitrification of low-temperature industrial flue gas and solve the problem of catalyst poisoning.

[0019] The low-temperature anti-poisoning composite Mn-based catalyst prepared by the method of the present invention can not only efficiently catalyze and reduce nitrogen oxides in flue gas at low temperatures, but also has good low-temperature anti-poisoning performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 a is an X-ray diffraction spectrum, which is Co before calcination in Comparative Example 1 0.5 Mn 1.5 Fe1-LDH hydrotalcite, Co before calcination in Example 1 0.5 Mn 1.5 Fe1-LDH-SiO2 material, Co after calcination in comparative example 1 0.5 Mn 1.5 Fe1O zCatalyst, Example 1 calcined SiO2(0.5) / Co 0.5 Mn 1.5 Fe1O z Catalyst, Comparative Example 2: calcined Co-Mn-Fe / SiO2 catalyst prepared by a loading method (i.e., 15 wt% Co-Mn-Fe / SiO2 catalyst); Figure 1 b is SiO2(0.5) / Co after calcination in Example 1 0.5 Mn 1.5 Fe1O z TEM-EDS images of the catalyst. DETAILED DESCRIPTION

[0022] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0023] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0024] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0025] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0026] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0027] The "%" described in the present invention, unless otherwise specified, refers to mass percentage.

[0028] The "room temperature" described in the present invention, unless otherwise specified, refers to 20-30°C.

[0029] The first aspect of the present invention provides a method for preparing a low-temperature anti-poisoning composite Mn-based catalyst, comprising the following steps:

[0030] Step 1, dissolving precursor substances containing L, Mn and N respectively in water to obtain a homogeneous solution;

[0031] Step 2, adding the homogeneous solution to the Si source solution and controlling the pH of the reaction system to be alkaline, and aging;

[0032] Step 3, filtering and washing the aged mixed solution, and then drying it to obtain a hydrotalcite-like material containing L, N, Mn and SiO2;

[0033] Step 4, calcining the hydrotalcite-like material containing L, N, Mn and SiO2 to obtain the low-temperature anti-poisoning composite Mn-based catalyst;

[0034] The L is at least one of Cu, Ni and Co; and the N is Al and / or Fe.

[0035] In some embodiments of the present invention, the molar ratio of L, Mn, N to Si in the Si source solution is (0.5-2):(0.5-2):1:(0.4-0.6).

[0036] The concentrations of the homogeneous solution and the Si source solution have no effect on the catalytic performance of the prepared low-temperature anti-poisoning composite Mn-based catalyst. Therefore, the present invention does not impose any particular limitation on the concentrations of the homogeneous solution and the Si source solution.

[0037] In some embodiments of the present invention, the pH of the reaction system is controlled to be 8 to 12, and more preferably 9.5 to 10.5.

[0038] In some embodiments of the present invention, the Si source solution is prepared by dissolving Na2CO3 and Na2SiO2·9H2O in deionized water.

[0039] In some embodiments of the present invention, the molar ratio of Na2CO3 to Na2SiO2·9H2O is (3.3-5):1.

[0040] Step 2 is carried out at room temperature under the condition of being isolated from air and aerated with nitrogen, and the aging time is greater than 10 hours.

[0041] In step 3, the process of filtering and washing the aged mixed solution is specifically as follows: under the condition of filtering, repeatedly washing the mixed solution with deionized water until the pH value of the filtrate is 6-7, and when the filtrate is almost dried up, washing it once with anhydrous ethanol, and drying it to obtain a precipitate; placing the obtained precipitate in a container filled with anhydrous ethanol, and vigorously stirring it at room temperature, and then filtering it, and repeatedly washing the filter cake with anhydrous ethanol.

[0042] In some embodiments of the present invention, the calcination is specifically calcined at 350-600° C. for 4-5 hours under oxygen-limited conditions. More preferably, it is 350-450° C. The calcination is carried out in a muffle furnace, and the initial atmosphere of the calcination is an air atmosphere, but the amount of air is insufficient in the later stage of combustion. Therefore, the calcination atmosphere in the muffle furnace is called oxygen-limited conditions.

[0043] The second aspect of the present invention provides a low-temperature anti-poisoning composite Mn-based catalyst prepared by the above-mentioned preparation method.

[0044] In some embodiments of the present invention, the chemical composition is SiO2(v) / L w Mn x N y O z ; Wherein, L is at least one of Cu, Ni and Co; N is Al and / or Fe; v, w, x, y are the molar fractions of SiO2, L, Mn and N respectively, v is 0.3-0.7, w is 0.5-2, x is 0.5-2, y is 1, and w / y is 1 / 2-2 / 1, x / y is 1 / 2-2 / 1. More preferably, L and N are Co and Fe respectively, w / y is 1 / 2-3 / 2, x / y is 1 / 2-3 / 2; more preferably, L and N are Co and Fe respectively, v=0.5, w=0.5, x=1.5, y=1.

[0045] The present invention does not impose any particular limitation on the value range of z in the catalyst. In the present invention, the valence state of the metal in the low-temperature anti-poisoning composite Mn-based catalyst is a mixed form of multiple valence states, and Z represents the corresponding amount of O.

[0046] In some embodiments of the present invention, the Mn in the low-temperature anti-poisoning composite Mn-based catalyst is Mn 2+ , Mn 3+ and Mn 4+ It exists in 2 or 3 mixed valence forms.

[0047] The third aspect of the present invention provides a method for selective catalytic reduction of NO in flue gas by using the above-mentioned low-temperature anti-poisoning composite Mn-based catalyst. x Application in.

[0048] In a preferred embodiment of the present invention, the selective catalytic reduction of NO in flue gasx The reaction temperature range is 100-300°C; more preferably 150-300°C; more preferably 200°C.

[0049] The present invention improves the overall denitration performance of the catalyst by improving the structural properties of the catalyst and strengthening the electron transfer between metals. The overall denitration performance includes NO x Removal rate, N2 selectivity, and anti-poisoning.

[0050] The technical solutions described in the present invention, unless otherwise specified, are all conventional solutions in the art, and the reagents or raw materials used, unless otherwise specified, are purchased from commercial channels or have been disclosed.

[0051] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0052] Example 1: SiO2(0.5) / Co 0.5 Mn 1.5 Fe1O z Method for preparing catalyst

[0053] (1) Dissolve 8.715 mL of 50% Mn(NO3)2 solution, 3.6379 g of Co(NO3)2·6H2O and 10.1 g of Fe(NO3)3·9H2O in 100 mL of deionized water to obtain a stable, transparent homogeneous solution.

[0054] (2) At room temperature, nitrogen aeration and vigorous stirring, the above homogeneous solution was added dropwise into a 100 mL mixed solution containing 5.2995 g Na2CO3 and 3.55 g Na2SiO2·9H2O, and the pH value of the system was maintained at 10 with 4 mol / L NaOH solution. After the addition, aging was continued for 12 h.

[0055] (3) After aging, the aged mixed solution is filtered and repeatedly washed with deionized water until the pH value of the filtrate is 6-7 (measured by pH test paper). When the filtrate is almost dry, it is washed once with anhydrous ethanol and dried to obtain a precipitate. The obtained precipitate is placed in a beaker containing 200-300 mL of anhydrous ethanol, vigorously stirred for 1-2 hours at room temperature, and then filtered. The filter cake is repeatedly washed with anhydrous ethanol. The obtained filter cake is placed in a 60°C blast oven, dried overnight, and then ground into a powder state to obtain Co 0.5 Mn 1.5 Fe1-LDH-SiO2 material.

[0056] (4) The dried powder was placed in a muffle furnace and calcined under oxygen-limited conditions. After calcination at 400°C for 5 hours, SiO2(0.5) / Co was obtained.0.5 Mn 1.5 Fe1O z catalyst.

[0057] The SiO2(0.5) / Co prepared in Example 1 0.5 Mn 1.5 Fe1O z The catalyst was subjected to XPS analysis, and the results showed that the Mn in the catalyst was Mn 2+ , Mn 3+ and Mn 4+ A mixed form of three valence states, and Mn 2+ and Mn 3+ Accounting for 74.6%, Mn 4+ Proper amount of Mn 4+ The species contribute to the catalyst's excellent denitrification performance and N2 selectivity.

[0058] Comparative Example 1: Co 0.5 Mn 1.5 Fe1O z Method for preparing catalyst

[0059] (1) Dissolve 8.715 mL of Mn(NO3)2, 3.6379 g of Co(NO3)2·6H2O, and 10.1 g of Fe(NO3)3·9H2O in 100 mL of deionized water to obtain a stable, transparent, homogeneous solution.

[0060] (2) At room temperature, nitrogen aeration and vigorous stirring, the above homogeneous solution was added dropwise into a 100 mL solution containing 5.2995 g Na2CO3, and the pH value of the system was maintained at 10 with a 4 mol / L NaOH solution. After the addition was completed, the mixture was aged for 12 h.

[0061] (3) After aging, the aged mixed solution is filtered and repeatedly washed with deionized water until the pH value of the filtrate is 6-7 (measured by pH test paper). When the filtrate is almost dry, it is washed once with anhydrous ethanol and dried to obtain a precipitate. The obtained precipitate is placed in a beaker containing 200-300 mL of anhydrous ethanol, vigorously stirred for 1-2 hours at room temperature, and then filtered. The filter cake is repeatedly washed with anhydrous ethanol. The obtained filter cake is placed in a 60°C blast oven, dried overnight, and then ground into a powder state to obtain Co 0.5 Mn 1.5 Fe1-LDH type hydrotalcite.

[0062] (4) The dried powder was placed in a muffle furnace and calcined at 400°C for 5 hours to obtain Co 0.5 Mn 1.5 Fe1O zThe catalyst was used as a control catalyst. (That is, the only difference from Example 1 is that 3.55 g of Na2SiO2·9H2O in the mixed solution was omitted in step (2))

[0063] Co prepared in Comparative Example 1 0.5 Mn 1.5 Fe1O z The catalyst was subjected to XPS analysis, and the results showed that the Mn in the catalyst was Mn 2+ , Mn 3+ and Mn 4+ A mixed form of three valence states, and Mn 2+ and Mn 3+ Accounting for 76.2%, Mn 4+ It accounts for 23.8%.

[0064] Comparative Example 2: Preparation method of 15wt% Co-Mn-Fe / SiO2 catalyst

[0065] A 15wt% Co-Mn-Fe / SiO2 catalyst was prepared by a conventional loading method: 0.488g Co(NO3)2·6H2O, 0.3025g Fe(NO3)3·9H2O and 0.651mL Mn(NO3)2 were dissolved in 10mL deionized water to obtain a transparent homogeneous solution. 5mL of the prepared solution was loaded onto a 4g SiO2 carrier by an impregnation method, placed in an 80°C forced air drying oven, dried for 12 hours, and the dried powder was placed in a muffle furnace and calcined at 500°C for 4h under oxygen-limited conditions to obtain a 15wt% Co-Mn-Fe / SiO2 catalyst as another control catalyst.

[0066] XPS analysis of the 15wt% Co-Mn-Fe / SiO2 catalyst prepared in Comparative Example 2 showed that the Mn in the catalyst was Mn 2+ , Mn 3+ and Mn 4+ A mixed form of three valence states, and Mn 2+ and Mn 3+ Accounting for 92.8%, Mn 4+ It accounts for 7.2%.

[0067] Effect verification example 1: Catalyst activity test method

[0068] The catalytic performance test was carried out in a fixed bed microreactor (diameter d = 6 mm) at normal pressure, with a test temperature range of 100-300°C. The sample size was 0.15 g, and the gas composition of the simulated flue gas was: 500 ppm NO x , 500ppmNH3, 5%O2, Ar as balance gas. NO in the gas composition before and after the reaction xThe samples were analyzed online using a 2.4 M Gas Cell (Parker Technologies) and a Bruker INVENIO S analyzer (Bruker Optics).

[0069] Effect verification example 2: CoMnFeO with different molar ratios x Testing of the effect of catalyst activity

[0070] The method in Example 1 was used to prepare hydrotalcite-like materials with different proportions, different metals L, and different metals N, wherein the molar ratio of (Co+Mn) / Fe was 1 to 4, the molar ratio of Co / Mn was 1:3, 1:1, and 3:1, L was Ni or Cu, and N was Al; the hydrotalcite-like materials were calcined at high temperature (calcination temperature was 400°C) to obtain the corresponding catalyst (i.e., the only difference from Example 1 was that the molar ratio of (Co+Mn) / Fe was adjusted to 1 to 4; or, the molar ratio of Co / Mn was 1:3, 1:1, and 3:1; or, the metal L was replaced by Co with Ni or Cu; or, the metal N was replaced by Fe with Al) and used to treat laboratory simulated flue gas, and then the catalyst performance was determined by the activity test method in Effect Verification Example 1. The test results (as shown in Tables 1-4) show that the catalysts prepared with different molar ratios of (Co+Mn) / Fe and Co / Mn in the hydrotalcite-like materials are effective in treating NO in flue gas. x Different catalytic properties were shown in the process. The catalysts prepared with the molar ratios of (Co+Mn) / Fe and Co / Mn of 2:1 and 1:3 respectively and metals of Co and Fe had the best catalytic performance. When the test temperature was 200°C, Co1Mn1Fe1O z and Co 0.5 Mn 1.5 Fe1O z NO x The conversion rates reached 95.4% and 99.8% respectively.

[0071] Table 1 Effect of different molar ratios of (Co+Mn) / Fe on catalyst activity (calcination temperature is 400℃, test temperature is 200℃)

[0072]

[0073] Table 2 Effect of different molar ratios of Co / Mn on catalyst activity (calcination temperature is 400°C, test temperature is 200°C)

[0074]

[0075] Table 3 Effect of different metal L on catalyst performance (calcination temperature is 400℃, test temperature is 200℃)

[0076] Different metals (Co, Ni, Cu) <![CDATA[Co 0.5 Mn 1.5 Fe1O z ]]> <![CDATA[Ni 0.5 Mn 1.5 Fe1O z ]]> <![CDATA[Cu 0.5 Mn 1.5 Fe1O z ]]> <![CDATA[NO x Conversion rate (%)]]> 99.92 92.46 90.18

[0077] Table 4 Effect of different metal N on catalyst performance (calcination temperature is 400℃, test temperature is 200℃)

[0078] Different metal N (Fe, Al) <![CDATA[Co 0.5 Mn 1.5 Fe1O z ]]> <![CDATA[Co 0.5 Mn 1.5 Al1O z ]]> <![CDATA[NO x Conversion rate (%)]]> 99.92 98.79

[0079] Effect verification example 3: Test on the effect of calcination temperature and space velocity on catalyst activity

[0080] The effects of calcination temperature and gas space velocity (GHSV) on catalyst activity are crucial. Different calcination temperatures and GHSV have different effects on the occurrence of redox reactions in the catalyst and the adsorption capacity of gas components. Therefore, in order to determine an optimal calcination temperature and GHSV, the catalyst Co 0.5 Mn 1.5 Fe1O z At different calcination temperatures (calcination temperature is 350-600°C, that is, the only difference from Example 1 is that the calcination temperature is 350°C, 500°C, 600°C, and the other steps and parameters are the same as Example 1; the test temperature is 200°C) and GHSV (80,000 and 120,000h -1 ) was used to treat laboratory simulated flue gas, and then the activity test method in effect verification example 1 was used to determine the catalyst performance. The test results are shown in Table 5-6, indicating that Co 0.5 Mn 1.5 Fe1O z The optimum calcination temperature of the catalyst is 400°C and the GHSV is 80,000h -1 .

[0081] Table 5 Effect of calcination temperature on catalyst activity

[0082]

[0083] Table 6 Effect of space velocity on catalyst activity

[0084]

[0085] Effect verification example 4: Co 0.5 Mn 1.5 Fe1O z Activity test of different molar amounts of SiO2 at different test temperatures

[0086] A new type of hydrotalcite-like composite material loaded with SiO2 was prepared by the method in Example 1 and Comparative Examples 1 and 2, wherein the molar ratio of SiO2 was adjusted to 0.4-0.6 (i.e., the molar ratio of SiO2 to Fe was 0.4-0.6) by the method in Example 1; the composite material was calcined at high temperature (calcination temperature was 400°C) to obtain the corresponding catalyst (i.e., the only difference from Example 1 was that the molar ratio of SiO2 / Fe was 0.4-0.6, and the remaining steps and parameters were the same as those in Example 1) and used to treat laboratory simulated flue gas, and then the catalyst performance was determined by the activity test method in Effect Verification Example 2. The effect of temperature is crucial in the catalyst activity test, and different test temperatures have different effects on the occurrence of redox reactions in the catalyst and the adsorption capacity of gas components. Therefore, Co 0.5 Mn 1.5 Fe1O z 、SiO2(0.4) / Co 0.5 Mn 1.5 Fe1O z 、SiO2(0.5) / Co 0.5 Mn 1.5 Fe1O z 、SiO2(0.6) / Co 0.5 Mn 1.5 Fe1O z , 15wt% Co-Mn-Fe / SiO2 catalyst was used to treat laboratory simulated flue gas at different test temperatures (calcination temperature was 400℃, test temperature was 100-300℃). The test results (as shown in Table 7) show that the catalysts prepared with different molar amounts of SiO2 in the composite material have good performance in treating NO in flue gas. x Different catalytic properties were shown in the process. When the test temperature was 200℃, Co 0.5 Mn 1.5 Fe1O z 、SiO2(0.4) / Co 0.5 Mn 1.5 Fe1O z 、SiO2(0.5) / Co 0.5 Mn 1.5 Fe1O z 、SiO2(0.6) / Co 0.5 Mn 1.5 Fe1O z Catalyst NO x The conversion rates were 99.92%, 97.29%, 99.28% and 98.04% respectively. The SiO2(0.5) / Co 0.5 Mn 1.5 Fe1O zThe catalyst has the best catalytic performance. 15wt% Co-Mn-Fe / SiO2 prepared by the loading method has the best catalytic performance. x The removal rate is 54.5% at the same test temperature. By comparison, it can be concluded that the catalyst of the present invention has higher activity.

[0087] High N2 selectivity can effectively avoid the production of secondary pollutants (N2O). The test results (Table 8) show that SiO2(0.5) / Co 0.5 Mn 1.5 Fe1O z It exhibits excellent N2 selectivity in the process of treating flue gas. At 200°C, the N2 selectivity can reach 85.52%. The N2 selectivity of 15wt% Co-Mn-Fe / SiO2 prepared by the loading method is only 72.42% at the same test temperature. By comparison, it is shown that the catalyst of the present invention has higher N2 selectivity.

[0088] Table 7Co 0.5 Mn 1.5 Fe1O z , 15wt%Co-Mn-Fe / SiO2 and SiO2(v) / Co 0.5 Mn 1.5 Fe1O z Denitrification activity of catalyst (test temperature is 100~300℃)

[0089]

[0090] Table 8Co 0.5 Mn 1.5 Fe1O z , 15wt%Co-Mn-Fe / SiO2 and TiO2(0.5) / Co 0.5 Mn 1.5 Fe1O z N2 selectivity of catalyst (test temperature 100~300℃)

[0091]

[0092] Effect verification example 5: Test of the sulfur and water resistance of the catalyst

[0093] Low-temperature composite Mn-based SCR catalysts often have good reaction activity in flue gas without SO2 and / or H2O. However, in actual working conditions, the SCR device is usually installed after the desulfurization and dust removal device, and the flue gas still contains SO2 and H2O. Under such conditions, the catalyst is easily poisoned and deactivated. Therefore, the requirements for the catalyst's sulfur and water resistance are essential. 0.5 Mn 1.5Fe1O z The sulfur and water resistance of the catalyst were compared with that of 15wt% Co-Mn-Fe / SiO2 prepared by the loading method and Co derived from hydrotalcite. 0.5 Mn 1.5 Fe1O z The catalysts were compared as follows:

[0094] The sulfur resistance test of the catalyst was carried out in a fixed bed microreactor (diameter d = 6 mm) at normal pressure. The sample amount was 0.15 g, the gas flow rate was 200 mL / min, the test temperature was 100-300 ° C, the test time was 1 h, and the gas composition of the simulated flue gas was: 500 ppm NO x , 500ppmNH3, 100ppm SO2, 5%H2O, 5%O2, Ar as balance gas. NO in the gas composition before and after the reaction x The samples were analyzed online using a 2.4M Gas Cell (Parker Technologies) and a BRUKER INVENIO S analyzer (Bruker Optics).

[0095] SiO2(0.5) / Co prepared by the method of Example 1 and Comparative Examples 1 and 2 0.5 Mn 1.5 Fe1O z 、Co 0.5 Mn 1.5 Fe1O z , 15wt% Co-Mn-Fe / SiO2 catalyst (calcined at 400°C) was used to treat laboratory simulated flue gas, and then the sulfur resistance of the catalyst was determined by the above sulfur resistance test method. The test results are shown in Table 9, which show that compared with the 15wt% Co-Mn-Fe / SiO2 prepared by the loading method in Comparative Example 2 and the Co derived from hydrotalcite in Comparative Example 1, 0.5 Mn 1.5 Fe1O z Compared with the catalyst, the SiO2(0.5) / Co prepared in Example 1 0.5 Mn 1.5 Fe1O z The catalysts showed good SO2 resistance at 200℃. In the presence of 100ppm SO2, 15wt% Co-Mn-Fe / SiO2 and Co 0.5 Mn 1.5 Fe1O z NO x The conversion rates were 45.66% and 87.42% respectively. Compared with the case without SO2, NO x The conversion rates decreased by 8.84% and 10.74%, respectively. 0.5 Mn1.5 Fe1O z Catalyst, in the presence of 100ppm SO2, at 200℃ NO x The conversion rate was 95.7%, which was only 3.58% lower than that in the absence of SO2. It can be seen that SO2 has a great influence on the activity of the catalyst prepared by the supported method and the hydrotalcite-like catalyst. 0.5 Mn 1.5 Fe1O z Catalyst, the effect of SO2 on the catalyst is relatively weak.

[0096] Table 9Co 0.5 Mn 1.5 Fe1O x 、SiO2(0.5) / Co 0.5 Mn 1.5 Fe1O x and 15wt% Co-Mn-Fe / SiO2's sulfur resistance (test temperature 100~300℃)

[0097]

[0098] Similarly, the SiO2(0.5) / Co prepared by the methods of Example 1 and Comparative Examples 1 and 2 0.5 Mn 1.5 Fe1O z 、Co 0.5 Mn 1.5 Fe1O z , 15wt% Co-Mn-Fe / SiO2 catalyst (calcined at 400°C) was tested for its water resistance using the above water resistance test method. The test results are shown in Table 10, indicating that SiO2(0.5) / Co 0.5 Mn 1.5 Fe1O z The catalyst has excellent water resistance, which is much higher than that of 15wt% Co-Mn-Fe / SiO2 prepared by the supported method and Co derived from hydrotalcite. 0.5 Mn 1.5 Fe1O z Catalyst, in the presence of 5% H2O, SiO2(0.5) / Co 0.5 Mn 1.5 Fe1O z Catalyst NO x The conversion rate was 97.88% at 200℃, which was only reduced by 1.4%. However, the 15wt% Co-Mn-Fe / SiO2 and Co 0.5 Mn 1.5 Fe1O z NOx The conversion rates were 47.11% and 88.94%, respectively. Compared with the condition without H2O, NO x The conversion rates decreased by 7.39% and 10.98%, respectively. It can be seen that H2O has a greater effect on the activity of the catalyst prepared by the supported method and the hydrotalcite-like catalyst, while H2O has a greater effect on the activity of SiO2(0.5) / Co 0.5 Mn 1.5 Fe1O z The effect on the activity of the catalyst is relatively small.

[0099] Table 10Co 0.5 Mn 1.5 Fe1O x 、SiO2(0.5) / Co 0.5 Mn 1.5 Fe1O x and 15wt% Co-Mn-Fe / SiO2 water resistance (test temperature 100~300℃)

[0100]

[0101] In actual industrial flue gas, SO2 and H2O exist simultaneously. Therefore, for SiO2(0.5) / Co prepared by the methods of Example 1 and Comparative Examples 1 and 2, 0.5 Mn 1.5 Fe1O z 、Co 0.5 Mn 1.5 Fe1O z , 15wt% Co-Mn-Fe / SiO2 catalyst (calcination temperature is 400℃) was tested for its sulfur and water resistance using the above test method. The test results are shown in Table 11. The results show that compared with 15wt% Co-Mn-Fe / SiO2 prepared by the support method and Co derived from hydrotalcite 0.5 Mn 1.5 Fe1O z Catalyst, SiO2(0.5) / Co 0.5 Mn 1.5 Fe1O z Catalysts with excellent NO x Conversion rate, in the presence of 100ppm SO2+5%H2O, at 200℃ SiO2(0.5) / Co 0.5 Mn 1.5 Fe1O z The NOx conversion rate of the catalyst was 93.55%, which was reduced by 5.73%. 0.5 Mn 1.5 Fe1O zCatalyst NO x The conversion rates were 39.06% and 81.08%, respectively, which were 15.44% and 18.54% lower than those without SO2 and water. It can be seen that SO2 and water have a greater impact on the catalyst prepared by the supported method and the hydrotalcite-like catalyst, while SO2 and water have a greater impact on SiO2(0.5) / Co 0.5 Mn 1.5 Fe1O z The influence on the activity of the catalyst is relatively weak, which shows that the catalyst prepared by the present invention improves the anti-poisoning performance while ensuring a high catalytic activity.

[0102] Table 11Co 0.5 Mn 1.5 Fe1O x 、SiO2(0.5) / Co 0.5 Mn 1.5 Fe1O x and 15wt% Co-Mn-Fe / SiO2's SO2+H2O resistance (test temperature 100~300℃)

[0103]

[0104] Figure 1 a is an X-ray diffraction spectrum, which is Co before calcination in Comparative Example 1 0.5 Mn 1.5 Fe1-LDH hydrotalcite, Co before calcination in Example 1 0.5 Mn 1.5 Fe1-LDH-SiO2 material, Co after calcination in comparative example 1 0.5 Mn 1.5 Fe1O z Catalyst, Example 1 calcined SiO2(0.5) / Co 0.5 Mn 1.5 Fe1O z Catalyst, Comparative Example 2: calcined Co-Mn-Fe / SiO2 catalyst prepared by a loading method (i.e., 15 wt% Co-Mn-Fe / SiO2 catalyst); Figure 1 b is SiO2(0.5) / Co after calcination in Example 1 0.5 Mn 1.5 Fe1O z TEM-EDS images of the catalyst.

[0105] Depend on Figure 1 From a, we can see that after the introduction of Si species, relative to Co 0.5 Mn 1.5 Fe1-LDH hydrotalcite, Co 0.5 Mn 1.5The intensity of the hydrotalcite-like characteristic peak of Fe1-LDH-SiO2 material is significantly reduced, and the characteristic peak of SiO2 species appears, indicating that Co 0.5 Mn 1.5 The Fe1-LDH-SiO2 composite material was successfully prepared. After calcination at 400℃ for 5h under oxygen-limited conditions, the Co-Mn-Fe / SiO2 catalyst showed characteristic peaks of SiO2 and MnO2, and Co 0.5 Mn 1.5 Fe1O z The characteristic peak of MnO2 species appears, SiO2(0.5) / Co 0.5 Mn 1.5 Fe1O z The characteristic peaks of SiO2, MnO2 and weak FeSiO3 appeared. The electron transfer between multiple metal components helped to improve the overall catalytic performance. In addition, the TEM-EDS element dispersion analysis found that SiO2(0.5) / Co 0.5 Mn 1.5 Fe1O z The metal elements are evenly distributed and highly dispersed.

[0106] The present invention combines SiO2 and Co 0.5 Mn 1.5 Fe1-LDH hydrotalcite composite introduces a variety of metal elements into the LDH layer. By utilizing the layered structure and the bonding between metals, it effectively avoids the problems of limited loading of active components and easy agglomeration of metal particles in the preparation by the loading method. It can introduce a variety of metals in a large range. After calcination, highly dispersed MnO x Active components and auxiliary components improve the activity and N2 selectivity of the catalyst. In addition, the layered structure and high specific surface area of ​​LDH enable it to be used as a carrier to efficiently load SiO2 species, thereby improving the anti-poisoning ability of the catalyst.

[0107] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a low-temperature anti-poisoning composite Mn-based catalyst, It is characterized in that The following steps are involved: Step 1, dissolving precursor substances containing L, Mn and N respectively in water to obtain a homogeneous solution; Step 2, adding the homogeneous solution to the Si source solution and controlling the pH of the reaction system to be alkaline, and aging; Step 3: The aged mixed solution is filtered and washed, and then dried to obtain a mixture containing L, N, Mn and SiO 2 Hydrotalcite-like materials; Step 4, calcining the mixture containing L, N, Mn and SiO 2 The hydrotalcite-like material is used to obtain the low-temperature anti-poisoning composite Mn-based catalyst; The L is at least one of Cu, Ni and Co; and the N is Al and / or Fe.

2. The method for preparing the low-temperature anti-poisoning composite Mn-based catalyst according to claim 1, It is characterized in that The molar ratio of the L, Mn, N to Si in the Si source solution is (0.5-2):(0.5-2):1:(0.4-0.6).

3. The method for preparing the low-temperature anti-poisoning composite Mn-based catalyst according to claim 1, It is characterized in that The pH of the reaction system was controlled to be 8-12.

4. The method for preparing the low-temperature anti-poisoning composite Mn-based catalyst according to claim 1, It is characterized in that The Si source solution was prepared by 2 CO 3 and Na 2 SiO 2 9H 2 O was dissolved in deionized water.

5. The method for preparing the low-temperature anti-poisoning composite Mn-based catalyst according to claim 4, It is characterized in that The Na 2 CO 3 and Na 2 SiO 2 9H 2 The molar ratio of O is (3.3~5):

1.

6. The method for preparing the low-temperature anti-poisoning composite Mn-based catalyst according to claim 1, It is characterized in that The calcination is specifically performed at 350-600° C. for 4-5 hours.

7. A low-temperature poisoning-resistant composite Mn-based catalyst prepared according to the preparation method according to any one of claims 1 to 6.

8. The low-temperature anti-poisoning composite Mn-based catalyst according to claim 7, It is characterized in that The chemical composition is SiO 2 (v) / L w Mn x N y O z ; Wherein, L is at least one of Cu, Ni and Co; N is Al and / or Fe; v, w, x, y are SiO 2 , L, Mn, and N, v is 0.3-0.7, w is 0.5-2, x is 0.5-2, y is 1, and w / y is 1 / 8-2 / 1, and x / y is 1 / 8-2 / 1.

9. The low-temperature anti-poisoning composite Mn-based catalyst according to claim 7, It is characterized in that The Mn in the low-temperature anti-poisoning composite Mn-based catalyst is Mn 2+ , Mn 3+ and Mn 4+ It exists in 2 or 3 mixed valence forms.

10. The low temperature anti-poisoning composite Mn-based catalyst according to any one of claims 7 to 9 is used for selective catalytic reduction of NO in flue gas x Application in.

Images