Thallium poisoning-resistant denitration catalyst as well as preparation method and application thereof

Abstract

The invention provides a thallium poisoning-resistant denitration catalyst as well as a preparation method and application thereof. The catalyst comprises a catalyst active component and a carrier, wherein the active component comprises a main active component, a secondary active component A and a secondary active component B; the main active component is V2O5; the secondary active component A is WO3 and / or MoO3; the secondary active component B is CeO2 and / or Fe2O3; the carrier is molecular sieve modified TiO2. According to the present invention, the efficient denitration effect of the high-content thallium poisoning resistance catalyst is achieved, the application range of the denitration technology is easily widened so as to meet the increasingly severe environmental protection emission pressure and the increasingly severe environmental protection emission index, and the catalyst can provide the strong denitration conversion ability while the cost is reduced and the service life is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalysts, in particular to a thallium poisoning resistant denitration catalyst and a preparation method and application thereof. BACKGROUND

[0002] At present, the selective catalytic reduction denitration technology (NH3-SCR) with ammonia as a reducing agent in industrial kiln is the most mature and efficient ultra-low emission denitration technology. The first cement kiln SCR denitration project in China was put into operation in 2018, and subsequently the number of SCR projects in the cement industry increased rapidly. However, thallium poisoning was also observed in some projects during operation. Thallium compounds contained in dust are prone to physical or chemical reactions with denitration catalysts, and are enriched on the catalysts, with an enrichment content distribution of 1% to 9%. According to research, when the thallium loading exceeds 3%, the activity of the denitration catalyst decreases significantly, and when the thallium loading exceeds 6%, the denitration catalyst has almost no denitration activity. Thallium elements are easy to combine with active components, reduce the redox capacity of active sites, and easily cover the surface acid sites of the catalyst, resulting in a decrease in the adsorption capacity of the catalyst for the reducing agent NH3 and a reduction in the activity of the catalyst.

[0003] In the prior art, although the thallium-resistant catalyst has been improved, there are still the following problems: insufficient thallium resistance limit; easy plugging of active sites; complex preparation method, difficult to large-scale promotion, and the like. Therefore, it is of great significance to develop a denitration catalyst resistant to high thallium poisoning for improving the service life of the catalyst and promoting the high-quality development of the industry with ultra-low emission. SUMMARY

[0004] The present application aims to at least partially solve one of the problems in the prior art. To this end, one object of the present application is to provide a thallium poisoning resistant denitration catalyst and a preparation method and application thereof.

[0005] In a first aspect, the present application provides a thallium poisoning resistant denitration catalyst, which comprises a catalyst active component and a carrier, wherein the active component comprises a main active component, a secondary active component A and a secondary active component B. The main active component is V2O5. The secondary active component A is WO3 and / or MoO3. The secondary active component B is CeO2 and / or Fe2O3. The carrier is a molecular sieve modified TiO2.

[0006] According to the thallium poisoning resistant denitration catalyst provided by the present application, the carrier used is a molecular sieve modified TiO2. This molecular sieve modified multi-level pore structure (mesopore-macropore hierarchical structure) design provides high specific surface area for enrichment of thallium elements and promotes the adsorption of NO xThe macropore can accelerate mass transfer, reduce the accumulation of thallium in the pore, and be beneficial to the selective enrichment of thallium elements, improve the thallium poisoning resistance of the catalyst, and prolong the service life of the catalyst. In addition, the specific secondary active component A and the secondary active component B replace a part of the primary active component V2O5, and through coupling of the surface acid center and the redox active site of the catalyst, the synergistic effect between the components is achieved. Specifically, the catalyst is modified by simultaneously utilizing W / Mo acid sites and comprehensive regulation of Ce / Fe redox sites, and the two components play a synergistic role to accelerate the redox cycle of vanadium on the surface of the catalyst, stabilize the carrier and inhibit sulfatization, promote the denitration reaction activity of the catalyst in flue gas with high thallium content, realize the high-efficiency denitration effect of the thallium poisoning resistant catalyst, and is beneficial to widening the application range of the denitration technology, thereby meeting the increasingly severe environmental protection emission pressure and indicators. The catalyst provided by the application can reduce the cost, prolong the service life, and have strong denitration conversion capacity.

[0007] In some embodiments of the application, the mass percentage of the primary active component is 2-5%, preferably 3-4%, based on the total mass of the catalyst. For example, the mass percentage of the primary active component is 2%, 3%, 4%, 5%, or a range between any two of the above-mentioned values. Controlling the mass percentage of the primary active component in the above range can optimize the active site distribution, regulate the surface electronic structure, reduce the cost, and realize the synergistic improvement of activity and selectivity.

[0008] In some embodiments of the application, the total mass percentage of the secondary active component A and the secondary active component B is 3-15%, based on the total mass of the catalyst. For example, the mass percentage is 3%, 5%, 7%, 9%, 11%, 13%, 15%, or a range between any two of the above-mentioned values. Controlling the total mass percentage of the secondary active component A and the secondary active component B in the above range can regulate the surface acidity of the catalyst and stabilize the structure, and realize the significant improvement of the activity, selectivity and stability of the catalyst.

[0009] In some embodiments of the application, the mass percentage of the secondary active component A is 1.5-13.5%, preferably 3-8%, based on the total mass of the catalyst.

[0010] In some embodiments of the application, the mass percentage of the secondary active component B is 1.5-13.5%, preferably 3-8%, based on the total mass of the catalyst.

[0011] In some embodiments of the present application, the mass ratio of the less active component A to the less active component B is (1-9):(9-1), preferably (4-6):(6-4). For example, the mass ratio is 1:1, 1:3, 1:5, 1:7, 1:9, 9:1, 7:1, 5:1, 3:1, etc. By controlling the mass ratio of the less active component A to the less active component B within the above range, the synergy of the acid sites and the redox sites of the catalyst can be better controlled, which is beneficial to the improvement of the activity and selectivity of the catalyst.

[0012] In some embodiments of the present application, the mass percentage of the less active component A is 3-8%, and the mass percentage of the less active component B is 3-8%, based on the total mass of the catalyst.

[0013] More preferably, the mass percentage of the less active component A in the catalyst is 6%; the mass percentage of the less active component B in the catalyst is 6%; the mass percentage of the main active component in the catalyst is 3%; the mass percentage of ZSM-5 in the carrier in the catalyst is 8%.

[0014] In some embodiments of the present application, the mass percentage of the molecular sieve is 5-15%, preferably 7-10%, and more preferably 8%, based on the total mass of the catalyst. The mass percentage of the molecular sieve is 5%, 7%, 9%, 11%, 13%, 15%, etc., or a range between any two of the above values. Controlling the mass percentage of the molecular sieve within the above range can appropriately increase the specific surface area and pore size of the catalyst without reducing the stability and strength of the catalyst.

[0015] In some embodiments of the present application, the molecular sieve is selected from at least one of ZSM-5, Y-type molecular sieve or mordenite.

[0016] In some embodiments of the present application, the silicon-aluminum ratio of the molecular sieve is 10-100, preferably 20-60.

[0017] In some embodiments of the present application, the TiO2 is anatase.

[0018] In some embodiments of the present application, the content of thallium element enriched in the catalyst is 1-9%, preferably 2-8%. The catalyst provided by the present application can realize the enrichment of high content of thallium element and still has excellent denitration conversion capacity.

[0019] In some embodiments of the present application, when the content of thallium element enriched in the catalyst is 3%, the NO x conversion rate is not less than 95%.

[0020] In some embodiments of the present application, when the content of thallium element in the catalyst is 8%, the NO x The conversion rate is not less than 80%.

[0021] In a second aspect of the present application, the present application provides a method for preparing the anti-thallium poisoning denitration catalyst, comprising: (1) mixing TiO2 powder with molecular sieve, ball milling, drying and high-temperature calcination to obtain molecular sieve modified TiO2 molecular sieve; (2) impregnating the molecular sieve modified TiO2 molecular sieve into a precursor solution of the secondary active component B, and then drying and calcining to obtain a secondary active component B loaded catalyst; (3) impregnating the secondary active component B loaded catalyst into a precursor solution of the secondary active component A, and then drying and calcining to obtain a secondary active component loaded catalyst; (4) impregnating the secondary active component loaded catalyst into a precursor solution of the primary active component, and then drying and calcining to obtain the anti-thallium poisoning denitration catalyst.

[0022] According to the above method for preparing the catalyst provided by the present application, the active components are sequentially loaded on the catalyst carrier in the order of molecular sieve modified carrier, secondary active component B, secondary active component A and primary active component, which is helpful for the combination between the carrier and the active metal, and at the same time, the active components provide optimal active sites on the outermost surface of the catalyst, and the secondary active components play a synergistic role, thereby improving the denitration activity and anti-poisoning performance of the catalyst.

[0023] In some embodiments of the present application, in step (1), the temperature of the high-temperature calcination is 450-550°C, and the time is 1h-3h.

[0024] In some embodiments of the present application, in step (2), the configuration process of the precursor solution of the secondary active component B is: weighing a certain amount of cerium precursor or iron precursor and dissolving it in deionized water. The cerium precursor is cerium nitrate, and the iron precursor is iron nitrate.

[0025] In some embodiments of the present application, in step (3), the configuration process of the precursor solution of the secondary active component A is: weighing a certain amount of tungsten precursor or molybdenum precursor and dissolving it in deionized water. The tungsten precursor is ammonium metatungstate, and the molybdenum precursor is ammonium metatungstate.

[0026] In some embodiments of the present application, in step (4), the configuration process of the precursor solution of the primary active component is: dissolving vanadium precursor in oxalic acid solution. The vanadium precursor is ammonium metavanadate.

[0027] In some embodiments of the present application, the temperature of the precursor solution in steps (2) and (3) is independently room temperature.

[0028] In some embodiments of the present application, in step (4), the temperature for dissolving the precursor is 50-70℃, such as 50℃, 60℃, 65℃ or 70℃, but not limited to the listed values, and other values not listed in the range are also applicable.

[0029] In some embodiments of the present application, in steps (2)-(4), the temperature for calcination is independently 450-550℃, and the time is 3h-6h. For example, 450℃, 480℃, 500℃, 520℃ or 550℃, and 3h, 4h, 4.5h, 4.8h, 5.5h or 5.8h, but not limited to the listed values, and other values not listed in the range are also applicable.

[0030] In some embodiments of the present application, in steps (2)-(4), the temperature for drying is independently 100-120℃. For example, 100℃, 106℃, 110℃, 115℃, 118℃ or 120℃, but not limited to the listed values, and other values not listed in the range are also applicable.

[0031] In a third aspect of the present application, the above anti-thallium poisoning denitration catalyst is applied to the flue gas NOx with high thallium content in industrial furnaces. x In the treatment.

[0032] The present application has at least the following technical effects: (1) The vanadium-based catalyst provided by the present application adopts a molecular sieve modified multi-level pore structure design. The mesopores provide high specific surface area to enrich thallium elements and promote the adsorption of NOx, and the macropores accelerate mass transfer and reduce the accumulation of thallium in the pores, thereby improving the anti-thallium poisoning performance of the catalyst and prolonging the service life of the catalyst. x

[0033] (2) The mutual synergistic effect between the secondary active component A and the secondary active component B in the present application accelerates the redox cycle of vanadium on the surface of the catalyst, stabilizes the carrier and inhibits sulfatization, and can promote the denitration reaction activity of the catalyst in flue gas with high thallium content.

[0034] (3) The denitration catalyst prepared by the present application has an anti-thallium poisoning ability that is more than 60% higher than that of existing catalysts, ensuring a high denitration efficiency, reducing operating costs, and having great economic value. DETAILED DESCRIPTION

[0035] ​All other embodiments obtained by those of ordinary skill in the art without creative effort based on the embodiments of the present application fall within the scope of protection of the present application. The present application is described below with reference to specific embodiments, and it should be noted that these embodiments are merely descriptive and do not limit the present application in any way.

[0036] For the sake of brevity of expression, the names of catalysts in the following embodiments are in abbreviated form, and the composition of the catalysts is represented as xV-aAbB / cZSM-5@Ti, wherein x represents the percentage content of the main active component V2O5, A represents the secondary active component A, a represents the percentage content of the secondary active component A, B represents the secondary active component B, b represents the percentage content of the secondary active component B, and c represents the percentage content of the molecular sieve ZSM-5. The total mass of the catalysts in the following embodiments is 10 g.

[0037] Embodiment 1 The present embodiment provides a high-content thallium poisoning resistant denitration catalyst, which has a composition of 3V-6W6Ce / 8ZSM-5@Ti.

[0038] The present embodiment also provides a preparation method of the above-mentioned catalyst, comprising the following steps: Step one: molecular sieve ZSM-5 pretreatment of the carrier, 7.7 g of TiO2 powder is mixed with 0.8 g of molecular sieve ZSM-5, after ball milling and drying, calcination at 500℃ for 2h to form a ZSM-5@TiO2 carrier; Step two: 1.5134 g of cerium nitrate is dissolved in 20 ml of deionized water, and the above-mentioned ZSM-5@TiO2 carrier is added, and after magnetic stirring for 4 h, it is dried at 110℃ and calcined at 500℃ for 4 h to obtain CeO2 / ZSM-5@TiO2; Step three: 0.6375 g of ammonium metatungstate is dissolved in 20 ml of deionized water, and the product obtained in step two is added, and after magnetic stirring for 4 h, it is dried at 110℃ and calcined at 500℃ for 4 h to obtain WO3-CeO2 / ZSM-5@TiO2; Step four: 0.8310 g of oxalic acid is dissolved in 20 ml of deionized water to prepare an oxalic acid solution, and 0.3856 g of ammonium metavanadate is dissolved in the oxalic acid solution, and the product obtained in step three is added, and after magnetic stirring for 4 h, it is dried at 110℃ and calcined at 500℃ for 4 h to obtain a 3V-6W6Ce / 8ZSM-5@Ti catalyst.

[0039] Embodiment 2 The present embodiment provides a vanadium-based denitration catalyst based on fast SCR reaction, which has a composition of 3V-3Mo3Fe / 5ZSM-5@Ti.

[0040] Step one: ZSM-5 molecular sieve pretreatment of the carrier, 8.6 g of TiO2 powder was mixed with 0.5 g of ZSM-5 molecular sieve, after ball milling and drying, calcination at 500℃ for 2h, forming ZSM-5@TiO2 carrier; Step two: 1.5179 g of iron nitrate was dissolved in 20 ml of deionized water, and the above ZSM-5@TiO2 carrier was added, and after magnetic stirring and impregnation for 4 h, it was dried at 110℃ and calcined at 500℃ for 4 h to obtain Fe2O3 / ZSM-5@TiO2; Step three: 0.4085 g of ammonium molybdate was dissolved in 20 ml of deionized water, and the product obtained in step two was added, and after magnetic stirring and impregnation for 4 h, it was dried at 110℃ and calcined at 500℃ for 4 h to obtain MoO3-Fe2O3 / ZSM-5@TiO2; Step four: 0.8310 g of oxalic acid was dissolved in 20 ml of deionized water to prepare an oxalic acid solution, 0.3856 g of ammonium metavanadate was dissolved in the oxalic acid solution, and the product obtained in step three was added, and after magnetic stirring and impregnation for 4 h, it was dried at 110℃ and calcined at 500℃ for 4 h to obtain 3V-3Mo3Fe / 5ZSM-5@Ti catalyst.

[0041] Comparative Example 1 The difference between the catalyst of Comparative Example 1 and the catalyst of Example 1 is only that the catalyst of Comparative Example 1 does not contain ZSM-5 molecular sieve and the secondary active components WO3 and CeO2, that is, the composition is abbreviated as 3V / Ti.

[0042] Comparative Example 2 The difference between the catalyst of Comparative Example 2 and the catalyst of Example 1 is only that the catalyst of Comparative Example 2 does not contain the secondary active components WO3 and CeO2, but only contains the corresponding primary active component, that is, the composition is abbreviated as 3V / 8ZSM-5@Ti.

[0043] Comparative Example 3 The difference between the catalyst of Comparative Example 3 and the catalyst of Example 1 is only that the catalyst of Comparative Example 3 replaces the secondary active component CeO2 with an equal amount of WO3, and does not contain ZSM-5 molecular sieve, that is, the composition is abbreviated as 3V-12W / Ti.

[0044] Comparative Example 4 The difference between the catalyst of Comparative Example 4 and the catalyst of Example 1 is only that the catalyst of Comparative Example 4 replaces the secondary active component WO3 with an equal amount of CeO2, and does not contain ZSM-5 molecular sieve, that is, the composition is abbreviated as 3V-12Ce / Ti.

[0045] Comparative Example 5 The catalyst of Comparative Example 5 differs from the catalyst of Example 1 only in that the less active component CeO2 in the catalyst of Comparative Example 5 is replaced with an equal amount of WO3, i.e. the composition is abbreviated as 3V-12W / 8ZSM-5@Ti catalyst.

[0046] Comparative Example 6 The catalyst of Comparative Example 6 differs from the catalyst of Example 1 only in that the less active component WO3 in the catalyst of Comparative Example 6 is replaced with an equal amount of CeO2, i.e. the composition is abbreviated as 3V-12Ce / 8ZSM-5@Ti catalyst.

[0047] Comparative Example 7 The catalyst of Comparative Example 7 differs from the catalyst of Example 1 only in that the catalyst of Comparative Example 7 does not contain the molecular sieve ZSM-5, i.e. the composition is abbreviated as 3V-6W6Ce / Ti.

[0048] The performance of the catalysts of the examples and comparative examples was determined.

[0049] The denitration catalyst prepared in Example 1 was loaded with 3% and 8% thallium respectively, the denitration catalyst prepared in Example 2 was loaded with 3% and 6% thallium respectively, the denitration catalyst prepared in Comparative Example 1 was loaded with 3% and 8% thallium respectively, and the denitration catalyst prepared in Comparative Examples 2 to 7 was loaded with 3% thallium respectively. The catalysts and thallium nitrate were mixed in an aqueous solution in a ratio, impregnated and stirred for 4 h, and then dried at 105°C for 4 h after rotary evaporation. After calcination at 500°C for 4 h, they were used for activity evaluation respectively. The test conditions were: NO 400 ppm, NH3400 ppm, O2 volume concentration 3%, SO2200 ppm, N2 as the balance gas, space velocity 120000 h-1, and reaction temperature 300°C. The test results are shown in Table 1. -1

[0050] Table 1

[0051] ​From the results of Table 1, it can be seen that the denitration catalysts prepared in Examples 1-2 are significantly better than the denitration catalysts prepared in Comparative Examples 1-7. The thallium resistance of the denitration catalysts prepared in Examples 1-2 is improved more significantly, and the thallium resistance denitration efficiency of Examples 1-2 is increased by about 40-80% than that of Comparative Examples 1-7; it can be seen that after the synergistic effect of the molecular sieve modified carrier pore size distribution and the secondary active component, the denitration efficiency and thallium resistance of the denitration catalyst are significantly improved. In Example 1, it is significantly better than Comparative Example 1 without adding a secondary active component and a molecular sieve modified carrier, and Comparative Example 2 without adding a secondary active component. When the thallium content is increased to 8%, for Example 1 and Comparative Example 1, the denitration efficiency of Example 1 decreases less, while the conventional vanadium-based denitration catalyst of Comparative Example 1 has a significant thallium poisoning problem because of the high thallium content, and it almost cannot perform denitration, which further illustrates that the catalyst of the present application is suitable for high thallium content conditions, effectively overcomes the thallium poisoning problem, and has excellent denitration efficiency. In Example 1, it is significantly better than Comparative Example 4 which only adds one secondary active component without adding a molecular sieve, Comparative Examples 5 and 6 which only add one secondary active component, and Comparative Example 7 which does not add a molecular sieve. The results show that the catalyst of the present application can obtain better removal effect when two secondary active components and a molecular sieve modified carrier are added at the same time and act with the main active component, and the denitration efficiency of the molecular sieve modified carrier and the secondary active component only shows much lower denitration efficiency than that of the present application.

[0052] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A thallium-poisoning-resistant denitrification catalyst, characterized in that: It includes catalyst active components and a carrier, wherein the active components include a main active component, a secondary active component A and a secondary active component B; The main active component is V2O5; The secondary active component A is WO3 and / or MoO3; The secondary active component B is CeO2 and / or Fe2O3; The carrier is molecular sieve modified TiO2.

2. The catalyst according to claim 1, characterized in that Based on the total mass of the catalyst, the mass proportion of the main active component is 2-5%, preferably 3-4%.

3. The catalyst according to claim 1, characterized in that Based on the total mass of the catalyst, the total mass of the secondary active component A and the secondary active component B accounts for 3-15%; and / or, based on the total mass of the catalyst, the mass proportion of the secondary active component A is 1.5-13.5%, preferably 3-8%; And / or, based on the total mass of the catalyst, the mass proportion of the secondary active component B is 1.5-13.5%, preferably 3-8%.

4. The catalyst according to claim 1, characterized in that The mass ratio of the secondary active component A to the secondary active component B is (1-9): (9-1), preferably (4-6): (6-4).

5. The catalyst according to any one of claims 1 to 4, characterized in that Based on the total mass of the catalyst, the mass proportion of the molecular sieve is 5-15%, preferably 7-10%.

6. The catalyst according to any one of claims 1 to 4, characterized in that The molecular sieve is at least one of ZSM-5, Y-type molecular sieve or mordenite; Preferably, the silicon to aluminum ratio of the molecular sieve is in the range of 10-100, preferably 20-60.

7. The catalyst according to any one of claims 1 to 4, characterized in that The catalyst can be enriched with thallium in an amount of 1-9%, preferably 2-8%; And / or, when the content of thallium element enriched in the catalyst is 3%, NO x The conversion rate is not less than 95%; And / or, when the content of thallium element enriched in the catalyst is 8%, NO x The conversion rate is not less than 80%.

8. A method for preparing the thallium-poisoning-resistant denitration catalyst according to any one of claims 1 to 7, characterized in that: include: (1) TiO2 powder is mixed with molecular sieve, ball-milled, dried and then calcined at high temperature to obtain molecular sieve-modified TiO2 molecular sieve; (2) adding the molecular sieve modified TiO2 molecular sieve into the precursor solution of the secondary active component B for impregnation, and then drying and calcining to obtain the secondary active component B supported catalyst; (3) adding the secondary active component B supported catalyst into the precursor solution of the secondary active component A and impregnating the solution, followed by drying and calcining to obtain the secondary active component supported catalyst; (4) The secondary active component-loaded catalyst is added to the precursor solution of the main active component and impregnated, and then dried and calcined to obtain a thallium-poisoning-resistant denitrification catalyst.

9. The method according to claim 8, wherein in step (1), the high-temperature calcination temperature is 450-550°C and the time is 1 hour to 3 hours; And / or, in steps (2)-(4), the calcination temperature is independently 450-550°C and the calcination time is 3h-6h; And / or, in steps (2)-(4), the drying temperature is independently 100-120°C.

10. The thallium-poisoning-resistant denitration catalyst according to any one of claims 1 to 7 is used for treating NO in flue gas with high thallium content in industrial furnaces. x Application in governance.

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