Alkali metal poisoning resistant SCR catalyst and preparation method thereof

Abstract

The invention discloses an alkali metal poisoning resistant SCR catalyst and a preparation method thereof.The SCR catalyst is prepared by compositely doping Ce, Nb and Bi metal oxides through an impregnation method on the basis of a vanadium-based catalyst VWTi, and in the SCR catalyst finished product, the mass percent of V2O5 is 0.9%-1%, the mass percent of WO3 is 8.2%-8.6%, the mass percent of Nb2O5 is 1%-1.8%, the mass percent of CeO2 is 3.3%-4.7%, the mass percent of Bi2O3 is 0.2%-1.7%, the mass percent of B2O3 is 0.2%-1.7%, the mass percent of B2O3 is 0.2%-1.7%, and the balance is a solvent. The mass percent of TiO2 is the balance; aiming at the inactivation problem of a traditional VWTi catalyst under the alkali metal poisoning condition, the alkali metal poisoning resistance of the SCR catalyst is enhanced by optimizing the acidity and oxidation reduction performance of the SCR catalyst, the activity and stability of the SCR catalyst are improved, the SCR catalyst can still keep good catalytic activity under 1% KCl load, and compared with the prior art, the SCR catalyst has the advantages that the catalytic activity of the SCR catalyst is improved, and the catalytic activity of the SCR catalyst is improved. The activity of a commercial VWTi catalyst is less than 20% at 350 DEG C under the load of 1% KCl.

Description

Technical Field

[0001] The invention relates to a catalyst and a preparation technology thereof, in particular to an alkali metal poisoning resistant SCR catalyst and a preparation method thereof. Background Art

[0002] Nitrogen oxides (NO x ) is one of the key substances that cause atmospheric pollution, photochemical smog and greenhouse effect. With the acceleration of industrialization, NO2 emitted by coal-fired power plants, industrial boilers, etc. x It poses a serious threat to the environment and human health. x my country has promulgated a number of laws, regulations and standards to limit NO emissions from industrial emissions. x content.

[0003] Among the various denitrification technologies, Selective Catalytic Reduction (SCR) technology is the most efficient and mature denitrification technology. SCR technology uses a reducing agent (such as ammonia NH3 or urea) to react with NO under the action of a catalyst. x A reaction occurs, producing harmless nitrogen (N2) and water (H2O).

[0004] However, the activity of the catalyst will directly affect the denitrification efficiency of SCR technology. my country has a large amount of coal resources. During the coal combustion process, the alkali metal elements (such as sodium Na and potassium K) in the coal will enter the catalyst with the emission of flue gas, causing catalyst poisoning, which will reduce the activity of the catalyst. The current mainstream vanadium tungsten titanium (VWTi) catalyst will be deactivated due to alkali metal poisoning during use, which will cause inconvenience in industrial production. If it is not replaced in time, it will cause continuous pollution to the environment.

[0005] To solve this problem, researchers have developed a variety of catalysts that are resistant to alkali metal poisoning. For example, a cerium-manganese-based denitrification catalyst with publication number CN116637614A has a GHSV of 120,000 h -1 , 500ppm NH3, 500ppm NO, 5% O2, the denitrification efficiency is maintained at more than 80% in the range of 250-350℃, but its anti-alkali metal poisoning effect is still not ideal, and the catalyst activity decreases by an average of 10% under a Na loading of only 200μmol / g. For another example, a V,Fe / MoO3-molecular sieve-TiO2 catalyst with publication number CN117654602A has a denitrification efficiency of more than 80% in the range of 250-350℃. + Under ion poisoning, the catalyst can still maintain more than 95% catalytic activity at 300°C, but its test environment is too loose, with a space velocity of only 50,000h -1For example, the HZSM-5 based molecular sieve catalyst with publication number CN114433195A has a GHSV of 120,000 h -1 , 500ppm NH3, 500ppm NO, 5% O2, the denitrification efficiency reached more than 90% at 350℃, but only 200μmol / g Na + Under the ion poisoning amount, the activity drops to below 90%. For example, a catalyst for denitration resistant to alkali metal poisoning with publication number CN111330609A has a GHSV of 120,000 h -1 , 500ppm NH3, 500ppm NO, 300ppm SO2, and 350℃, the activity was 80.1% to 93.6%, and after loading with 0.5% Na2O and 0.8% K2O, the activity dropped to 72.7% to 81.2%.

[0006] In summary, most of the alkali metal poisoning-resistant SCR catalysts currently under development have poor alkali metal poisoning resistance and cannot achieve ideal results under harsh experimental conditions at high space velocities. At the same time, due to many reasons such as catalyst selectivity, cost, activity at a specific temperature, etc., there are almost no catalysts that can replace the VWTi catalyst and are truly put into industrial production.

[0007] As a commercial catalyst, VWTi catalyst has a high denitrification efficiency, but its activity will decrease significantly under the influence of alkali metal poisoning. + The activity will be reduced by 30% under ion poisoning. Usually, doping VWTi catalysts with transition metals and other elements can effectively improve the catalyst's resistance to alkali metal poisoning. Ce, as a common element in doped modified catalysts, can effectively improve the catalyst's resistance to alkali metal poisoning. However, in actual applications, the VWTi catalysts made by some processes will have their catalytic activity reduced due to the addition of Ce. Therefore, the development of a catalyst with excellent resistance to alkali metal poisoning is still a problem that needs to be solved urgently. Summary of the invention

[0008] The technical problem to be solved by the present invention is to provide an alkali metal poisoning resistant SCR catalyst for an alkali metal-rich flue gas environment and a preparation method thereof. The catalyst has strong alkali metal poisoning resistance, high activity and high stability.

[0009] The technical solution adopted by the present invention to solve the above technical problems is: an alkali metal poisoning resistant SCR catalyst, characterized in that the carrier of the SCR catalyst is TiO2, the active components include V2O5 and WO3, and the doping components include Nb2O5, CeO2 and Bi2O3.

[0010] The mass percentage of V2O5 in the SCR catalyst is 0.9-1%, the mass percentage of WO3 is 8.2-8.6%, the mass percentage of Nb2O5 is 1-1.8%, the mass percentage of CeO2 is 3.3-4.7%, the mass percentage of Bi2O3 is 0.2-1.7%, and the mass percentage of TiO2 is the balance. By precisely controlling the mass percentages of V2O5 (vanadium pentoxide) and WO3 (tungsten trioxide), the activity and selectivity of the SCR catalyst can be improved; by precisely controlling the mass percentages of the doping components Nb2O5 (niobium oxide), CeO2 (cerium oxide) and Bi2O3 (bismuth oxide), the performance of the SCR catalyst can be optimized so that it can maintain a high denitration efficiency under different working conditions.

[0011] A method for preparing an alkali metal poisoning resistant SCR catalyst is characterized by comprising the following preparation steps:

[0012] Step A: preparing a mixed precursor solution of vanadium and tungsten;

[0013] Step B: impregnating a mixed precursor solution of vanadium and tungsten on a titanium dioxide carrier, stirring dry in a water bath, and then calcining at high temperature;

[0014] Step C: preparing niobium, cerium and bismuth salt solutions;

[0015] Step D: impregnating the product obtained in step B with a solution of niobium, cerium and bismuth salts, stirring to dryness in a water bath and then calcining at high temperature;

[0016] Step E: Grind the product obtained in step D to a certain mesh size to obtain a finished SCR catalyst, in which the mass percentage of V2O5 is 0.9-1%, the mass percentage of WO3 is 8.2-8.6%, the mass percentage of Nb2O5 is 1-1.8%, the mass percentage of CeO2 is 3.3-4.7%, the mass percentage of Bi2O3 is 0.2-1.7%, and the mass percentage of TiO2 is the remainder.

[0017] The specific process of step A is as follows: dissolving ammonium metatungstate in deionized water and stirring evenly at room temperature; then adding oxalic acid and ammonium metavanadate, and ultrasonically oscillating until the added oxalic acid and ammonium metavanadate are completely dissolved; then heating the obtained light yellow solution in a water bath while stirring until the solution turns dark blue; finally, adding ethylene glycol to the dark blue solution and stirring evenly to obtain a mixed precursor solution of vanadium and tungsten.

[0018] The molar ratio of the added amount of oxalic acid and ammonium metavanadate is 2:1 or 3:1, the water bath temperature is 60-80°C, and the molar ratio of the added amount of ethylene glycol to the total amount of metal ions in the dark blue solution is 1.5:1.

[0019] The specific process of step B is: adding titanium dioxide powder as a carrier to the mixed precursor solution of vanadium and tungsten, and stirring evenly at room temperature; then standing at a certain temperature for a period of time and stirring dry in a water bath; and then drying and high-temperature calcining the product obtained after stirring dry in the water bath.

[0020] The specific process of step C is: dissolving niobium salt, cerium salt and bismuth salt in deionized water, and stirring evenly at room temperature; then adding citric acid to the obtained solution, stirring evenly, to obtain a niobium, cerium and bismuth salt solution.

[0021] The niobium salt is selected from niobium oxalate; the cerium salt is selected from one or more of cerium nitrate, cerium carbonate, and cerium sulfate; the bismuth salt is selected from one or more of bismuth nitrate and bismuth sulfate; the concentration of niobium in the niobium, cerium and bismuth salt solutions is 0.020-0.040 mol / L, the concentration of cerium is 0.050-0.080 mol / L, and the concentration of bismuth is 0.003-0.020 mol / L; the molar ratio of the amount of citric acid added to the total amount of metal ions in the solution is 1.5:1 or 2:1.

[0022] The specific process of step D is: adding the product obtained in step B to the niobium, cerium and bismuth salt solutions, and stirring evenly at room temperature; then standing at a certain temperature for a period of time and stirring dry in a water bath; and then drying and high-temperature calcining the product obtained after stirring dry in the water bath.

[0023] In the specific process of step B and step D, the standing temperature is 40-60° C., the standing time is 2-6 hours, the temperature of water bath drying is 60-80° C., the calcination temperature is 450° C.-500° C., and the calcination time is 5 hours.

[0024] Compared with the prior art, the advantages of the present invention are:

[0025] The present invention proposes an SCR catalyst for alkali metal-rich flue gas environment based on vanadium-based catalyst VWTi, modified with three metal elements of Ce, Nb and Bi, and a preparation method thereof. Ce and Nb doping can improve the SCR catalyst's resistance to alkali metal poisoning, and Bi doping can improve the SCR catalyst's activity. By loading a certain proportion of Nb, Ce and Bi metal components on the vanadium-based catalyst, not only can a better catalytic effect be obtained, but also the practical problem of the weak resistance of vanadium-based catalyst to alkali metal poisoning is improved, and through the synergistic effect between metals, it has a more excellent performance improvement. Compared with existing catalysts, it has higher catalytic activity and stronger resistance to alkali metal poisoning. Its performance is mainly achieved through the following aspects:

[0026] 1) The addition of Ce (cerium) element introduces a certain amount of Ce into the SCR catalyst 3+ ions, which can promote V5+ The reduction of VWTi and the generation of oxygen vacancies on the surface of the SCR catalyst improve the redox ability of the SCR catalyst; and due to the addition of Ce, the degree of alkali metal ions binding to V on the surface of the SCR catalyst is alleviated, and the SCR catalyst's resistance to alkali metal poisoning is improved. However, Ce doping on VWTi made by some processes will cause the SCR catalyst to agglomerate to varying degrees, reduce the specific surface area of ​​the SCR catalyst, and affect its catalytic performance.

[0027] The addition of Nb (niobium) element can further increase the oxygen vacancies on the surface of SCR catalyst, improve the acidity and redox performance of SCR catalyst; at the same time, it can promote the VO x The interaction between species leads to the improvement of electron transfer ability, thus increasing the activity. In addition, the addition of Nb helps to inhibit the formation of stable nitrate or nitrite products from NO2 in the presence of K.

[0028] In summary, by doping Nb (niobium) and Ce (cerium) elements in the SCR catalyst, the tolerance of the SCR catalyst to alkali metal elements (such as sodium and potassium) is improved. The doping of Nb (niobium) and Ce (cerium) elements helps to reduce the poisoning effect of alkali metals on the activity of the SCR catalyst and improves the SCR catalyst's resistance to alkali metal poisoning.

[0029] 2) The doping of Bi (bismuth) element increases the pore size on the surface of the SCR catalyst, further improves the redox performance, and can still maintain the SCR catalyst surface V after K poisoning. 5+ The high proportion of Ce and Nb can make the SCR catalyst surface V 5+ The addition of trace Bi elements can counteract the effect of SCR catalyst particle agglomeration caused by Ce addition and further enhance the catalytic activity of the SCR catalyst.

[0030] 3) By adding ethylene glycol to the dark blue mixed precursor solution of vanadium and tungsten, V and W are evenly loaded on the catalyst, and the reducing properties of ethylene glycol are used to enrich the formation of oxygen vacancies on the catalyst surface and optimize the catalyst activity performance; by using citric acid to assist in the metal doping process, the distribution of metal doping in the catalyst is more uniform, and it will not be deposited on the catalyst surface in large quantities.

[0031] 4) The preparation method of the SCR catalyst includes the steps of solution preparation, impregnation, calcination, etc. These steps are relatively simple and easy to operate, which helps to reduce production costs and improve yields, and has high practical application value. At the same time, these steps can ensure that the active components and doping elements are evenly distributed on the carrier titanium dioxide, thereby improving the overall performance of the SCR catalyst.

[0032] 5) Through the high-temperature calcination step, the thermal stability of the SCR catalyst can be enhanced, so that it can maintain good activity even at high temperatures; by grinding to a certain mesh size, the mechanical strength of the SCR catalyst can be improved, making it more durable in practical applications.

[0033] 6) Potassium chloride is loaded on the SCR catalyst of the present invention by an impregnation method to obtain an alkali metal poisoned SCR catalyst to simulate a poisoning environment. The SCR catalyst of the present invention is heated at 350°C and a space velocity of 200,000 h -1 Under the condition of NO x The conversion rate can reach more than 95%, and its conversion rate can still be maintained at more than 80% when 1% KCl is loaded, indicating that the SCR catalyst of the present invention can be used under the condition of flue gas rich in alkali metals. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is the SEM electron microscope image of the fresh catalyst 1-BiNbCe of Example 1. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below with reference to the accompanying drawings.

[0036] The present invention provides a method for preparing an alkali metal poisoning resistant SCR catalyst, which comprises the following preparation steps:

[0037] Step A: preparing a mixed precursor solution of vanadium and tungsten.

[0038] The specific steps are as follows: dissolving ammonium metatungstate in deionized water and stirring evenly at room temperature; then adding oxalic acid and ammonium metavanadate, and ultrasonically oscillating until the added oxalic acid and ammonium metavanadate are completely dissolved; then heating the obtained light yellow solution in a water bath while stirring until the solution turns dark blue; finally, adding ethylene glycol to the dark blue solution and stirring evenly to obtain a mixed precursor solution of vanadium and tungsten.

[0039] Preferably, the molar ratio of oxalic acid and ammonium metavanadate added is 2:1 or 3:1, the water bath temperature is 60-80° C., and the molar ratio of ethylene glycol added to the total amount of metal ions in the dark blue solution is 1.5:1.

[0040] Step B: impregnate a mixed precursor solution of vanadium and tungsten onto a titanium dioxide carrier, stir dry in a water bath, and then calcine at high temperature.

[0041] The specific steps are: adding titanium dioxide powder as a carrier to a mixed precursor solution of vanadium and tungsten, and stirring evenly at room temperature; then standing at a certain temperature for a period of time and stirring dry in a water bath; and then drying and high-temperature calcining the product obtained after stirring dry in the water bath.

[0042] Preferably, the standing temperature is 40-60° C., the standing time is 2-6 h, the temperature of water bath drying is 60-80° C., the calcination temperature is 450° C.-500° C., and the calcination time is 5 h.

[0043] Step C: preparing niobium, cerium and bismuth salt solutions.

[0044] The specific steps are: dissolving niobium salt, cerium salt and bismuth salt in deionized water and stirring evenly at room temperature; then adding citric acid to the obtained solution and stirring evenly to obtain niobium, cerium and bismuth salt solutions.

[0045] It is further defined that the niobium salt is selected from niobium oxalate; the cerium salt is selected from one or more of cerium nitrate, cerium carbonate, and cerium sulfate; and the bismuth salt is selected from one or more of bismuth nitrate and bismuth sulfate.

[0046] It is further defined that the concentration of niobium in the niobium, cerium and bismuth salt solution is 0.020-0.040 mol / L, the concentration of cerium is 0.050-0.080 mol / L, and the concentration of bismuth is 0.003-0.020 mol / L.

[0047] Preferably, the molar ratio of the amount of citric acid added to the total amount of metal ions in the solution is 1.5:1 or 2:1.

[0048] Step D: impregnate the product obtained in step B with the niobium, cerium and bismuth salt solutions, stir dry in a water bath and then calcine at high temperature.

[0049] The specific steps are: adding the product obtained in step B to the niobium, cerium and bismuth salt solutions, and stirring evenly at room temperature; then standing at a certain temperature for a period of time and stirring dry in a water bath; and then drying and high-temperature calcining the product obtained after stirring dry in the water bath.

[0050] Preferably, the standing temperature is 40-60° C., the standing time is 2-6 h, the temperature of water bath drying is 60-80° C., the calcination temperature is 450° C.-500° C., and the calcination time is 5 h.

[0051] Step E: Grind the product obtained in step D to a certain mesh size to obtain a finished SCR catalyst.

[0052] The carrier of the alkali metal poisoning resistant SCR catalyst prepared by the above preparation method is TiO2, the active components include V2O5 and WO3, the doping components include Nb2O5, CeO2 and Bi2O3, the mass percentage of V2O5 is 0.9-1%, the mass percentage of WO3 is 8.2-8.6%, the mass percentage of Nb2O5 is 1-1.8%, the mass percentage of CeO2 is 3.3-4.7%, the mass percentage of Bi2O3 is 0.2-1.7%, and the mass percentage of TiO2 is the remainder.

[0053] Specific comparative examples and embodiments are provided below for detailed description.

[0054] Comparative Example 1:

[0055] The P25 (TiO2) powder carrier was dried in an oven at 110°C for 4 hours; 0.96g of ammonium metatungstate was added to 60ml of deionized water and stirred until completely dissolved; 0.20g of oxalic acid and 0.13g of ammonium metavanadate were added, and the mixture was stirred after oscillation for 5 minutes until it was completely dissolved to obtain a light yellow solution; the mixture was placed in an 80°C water bath and heated and stirred for more than 30 minutes, and the solution color was dark blue; 0.47g of ethylene glycol was added and stirred evenly to obtain a mixed precursor solution of vanadium and tungsten. 9g of P25 powder was added to the mixed precursor solution of vanadium and tungsten, and after a brief stirring, the mixture was placed in a 60°C water bath and immersed for 2 hours, and then stirred dry in an 80°C water bath. The obtained product was placed in an oven at 110°C and dried overnight, and then taken out and calcined at 500°C for 5 hours, and finally ground to 40-60 mesh to obtain the finished product, named 1-VWTi.

[0056] The alkali metal loading process is as follows: 0.1g of KCl is dissolved in 20ml of deionized water, stirred and shaken until the solution is completely dissolved, 9.9g of 1-VWTi is added, and after a brief stirring, it is placed in a 60°C water bath for 2h, and then stirred dry in an 80°C water bath. The obtained product is placed in a 110°C oven to dry overnight, taken out and calcined at 500°C for 5h, and finally ground to 40-60 mesh to obtain the finished product.

[0057] Comparative Example 2:

[0058] A honeycomb commercial VWTi catalyst was purchased, ground to 40-60 mesh, and named 2-VWTi.

[0059] The alkali metal loading process is as follows: 0.1g of KCl is dissolved in 20ml of deionized water, stirred and shaken until the solution is completely dissolved, 9.9g of 2-VWTi is added, and after a brief stirring, it is placed in a 60°C water bath for 2h, and then stirred dry in an 80°C water bath. The obtained product is placed in a 110°C oven to dry overnight, taken out and calcined at 500°C for 5h, and finally ground to 40-60 mesh to obtain the finished product.

[0060] Embodiment 1:

[0061] The present embodiment provides an alkali metal poisoning resistant SCR catalyst (VWTi catalyst doped and modified with Ce, Nb, and Bi metals) and a preparation method thereof, wherein the mass percentage of the active component V2O5 in the catalyst is 0.9%, the mass percentage of WO3 is 8.5%, the mass percentage of the doping component Nb2O5 is 1.4%, the mass percentage of CeO2 is 3.9%, the mass percentage of Bi2O3 is 0.6%, and the mass percentage of TiO2 is the remainder.

[0062] The specific implementation method includes the following steps:

[0063] The P25 (TiO2) powder carrier was dried in an oven at 110°C for 4 hours; 0.96g of ammonium metatungstate was added to 60ml of deionized water and stirred until completely dissolved; 0.20g of oxalic acid and 0.13g of ammonium metavanadate were added, and ultrasonic oscillation was performed for 5 minutes and then stirred until completely dissolved to obtain a light yellow solution; it was placed in an 80°C water bath and heated and stirred for more than 30 minutes, and the solution color was dark blue; 0.47g of ethylene glycol was added and stirred evenly to obtain a mixed precursor solution of vanadium and tungsten. 9g of P25 powder was added to the mixed precursor solution of vanadium and tungsten, and after a brief stirring, it was placed in a 60°C water bath and immersed for 2 hours, and then stirred dry in an 80°C water bath. The obtained product was placed in an oven at 110°C and dried overnight, and then taken out and calcined at 500°C for 5 hours, and then ground into powder to obtain a phased product 1.

[0064] Take 0.59g C 10 H5B 20 , 0.80gCe(SO4)2, 0.11g Bi2(SO4)3·5H2O were dissolved in 40ml deionized water, stirred and shaken until the solution was completely dissolved, 0.11g citric acid was added, stirred evenly to obtain niobium, cerium and bismuth salt solutions, 10g of the interim product 1 was added, and after a brief stirring, it was placed in a 60℃ water bath pot and immersed for 2h, and then stirred dry in an 80℃ water bath. The obtained product was placed in a 110℃ oven and dried overnight, and then taken out and calcined at 500℃ for 5h, and finally ground to 40-60 mesh to obtain the finished SCR catalyst, named 1-BiNbCe.

[0065] Figure 1 The SEM electron microscope image of the fresh catalyst 1-BiNbCe of Example 1 is given. Figure 1 It can be seen that the catalyst surface of the present invention is granular, the particle size is uniform and clearly dispersed, the catalyst void structure is formed by the accumulation of catalyst particles, which is consistent with the characteristics of supported VWTi catalysts, and metal doping does not change the catalyst morphology.

[0066] The alkali metal loading process is as follows: 0.1g of KCl is dissolved in 20ml of deionized water, stirred and shaken until the solution is completely dissolved, 9.9g of 1-BiNbCe is added, and after a brief stirring, it is placed in a 60°C water bath for 2h, and then stirred dry in an 80°C water bath. The obtained product is placed in a 110°C oven to dry overnight, taken out and calcined at 500°C for 5h, and finally ground to 40-60 mesh to obtain the finished product.

[0067] Embodiment 2:

[0068] This embodiment provides an alkali metal poisoning resistant SCR catalyst (VWTi catalyst doped with Ce, Nb, and Bi) and a preparation method thereof, wherein the mass percentage of the active component V2O5 in the catalyst is 0.9%, the mass percentage of WO3 is 8.2%, the mass percentage of the doping component Nb2O5 is 1.8%, the mass percentage of CeO2 is 4.7%, the mass percentage of Bi2O3 is 1.7%, and the mass percentage of TiO2 is the remainder. Except for the addition amount of each component and the corresponding addition amount of citric acid, this embodiment adopts the same preparation method and parameters as Example 1.

[0069] The specific implementation method includes the following steps:

[0070] The P25 (TiO2) powder carrier was dried in an oven at 110°C for 4 hours; 0.96g of ammonium metatungstate was added to 60ml of deionized water and stirred until completely dissolved; 0.20g of oxalic acid and 0.13g of ammonium metavanadate were added, and ultrasonic oscillation was performed for 5 minutes and then stirred until completely dissolved to obtain a light yellow solution; it was placed in an 80°C water bath and heated and stirred for more than 30 minutes, and the solution color was dark blue; 0.47g of ethylene glycol was added and stirred evenly to obtain a mixed precursor solution of vanadium and tungsten. 9g of P25 powder was added to the mixed precursor solution of vanadium and tungsten, and after a brief stirring, it was placed in a 60°C water bath and immersed for 2 hours, and then stirred dry in an 80°C water bath. The obtained product was placed in an oven at 110°C and dried overnight, and then taken out and calcined at 500°C for 5 hours, and then ground into powder to obtain a phased product 1.

[0071] Take 0.81g C 10 H5B 20, 1.00g Ce(SO4)2, 0.28g Bi2(SO4)3·5H2O were dissolved in 40ml deionized water, stirred and shaken until the solution was completely dissolved, 0.13g citric acid was added, stirred evenly to obtain niobium, cerium and bismuth salt solutions, 10g of the interim product 1 was added, stirred briefly and evenly, and then placed in a 60℃ water bath pot for 2h, and then stirred dry in an 80℃ water bath. The obtained product was placed in a 110℃ oven to dry overnight, taken out and calcined at 500℃ for 5h, and finally ground to 40-60 mesh to obtain the finished SCR catalyst, named 2-BiNbCe.

[0072] The alkali metal loading process is as follows: 0.1g of KCl is dissolved in 20ml of deionized water, stirred and shaken until the solution is completely dissolved, 9.9g of 2-BiNbCe is added, and after a brief stirring, it is placed in a 60°C water bath for 2h, and then stirred dry in an 80°C water bath. The obtained product is placed in a 110°C oven to dry overnight, taken out and calcined at 500°C for 5h, and finally ground to 40-60 mesh to obtain the finished product.

[0073] Embodiment 3:

[0074] This embodiment provides an alkali metal poisoning resistant SCR catalyst (VWTi catalyst doped with Ce, Nb, and Bi metals) and a preparation method thereof, wherein the mass percentage of the active component V2O5 in the catalyst is 1%, the mass percentage of WO3 is 8.6%, the mass percentage of the doping component Nb2O5 is 1%, the mass percentage of CeO2 is 3.3%, the mass percentage of Bi2O3 is 0.2%, and the mass percentage of TiO2 is the remainder. Except for the addition amount of each component and the corresponding addition amount of citric acid, this embodiment adopts the same preparation method and parameters as Example 1.

[0075] The specific implementation method includes the following steps:

[0076] The P25 (TiO2) powder carrier was dried in an oven at 110°C for 4 hours; 0.96g of ammonium metatungstate was added to 60ml of deionized water and stirred until completely dissolved; 0.20g of oxalic acid and 0.13g of ammonium metavanadate were added, and ultrasonic oscillation was performed for 5 minutes and then stirred until completely dissolved to obtain a light yellow solution; it was placed in an 80°C water bath and heated and stirred for more than 30 minutes, and the solution color was dark blue; 0.47g of ethylene glycol was added and stirred evenly to obtain a mixed precursor solution of vanadium and tungsten. 9g of P25 powder was added to the mixed precursor solution of vanadium and tungsten, and after a brief stirring, it was placed in a 60°C water bath and immersed for 2 hours, and then stirred dry in an 80°C water bath. The obtained product was placed in an oven at 110°C and dried overnight, and then taken out and calcined at 500°C for 5 hours, and then ground into powder to obtain a phased product 1.

[0077] Take 0.43g C10 H5B 20 , 0.66g Ce(SO4)2, 0.04g Bi2(SO4)3·5H2O were dissolved in 40ml deionized water, stirred and shaken until the solution was completely dissolved, 0.10g citric acid was added, stirred evenly to obtain niobium, cerium and bismuth salt solutions, 10g of the interim product 1 was added, and after a brief stirring, it was placed in a 60℃ water bath pot for 2h, and then stirred dry in an 80℃ water bath. The obtained product was placed in a 110℃ oven to dry overnight, taken out and calcined at 500℃ for 5h, and finally ground to 40-60 mesh to obtain the finished SCR catalyst, named 3-BiNbCe.

[0078] The alkali metal loading process is as follows: 0.1g of KCl is dissolved in 20ml of deionized water, stirred and shaken until the solution is completely dissolved, 9.9g of 3-BiNbCe is added, and after a brief stirring, it is placed in a 60°C water bath for 2h, and then stirred dry in an 80°C water bath. The obtained product is placed in a 110°C oven to dry overnight, taken out and calcined at 500°C for 5h, and finally ground to 40-60 mesh to obtain the finished product.

[0079] Embodiment 4:

[0080] This embodiment provides an alkali metal poisoning resistant SCR catalyst (VWTi catalyst doped with Ce, Nb, and Bi) and a preparation method thereof, wherein the mass percentage of the active component V2O5 in the catalyst is 0.9%, the mass percentage of WO3 is 8.5%, the mass percentage of the doping component Nb2O5 is 1.4%, the mass percentage of CeO2 is 3.9%, the mass percentage of Bi2O3 is 0.6%, and the mass percentage of TiO2 is the remainder. Different from Example 1, the standing temperature during the impregnation process in this embodiment is 40°C, the standing time is 6h, the water bath stirring temperature is 60°C, and the molar ratio of citric acid to metal ions when loading metal doping is 2:1.

[0081] The specific implementation method includes the following steps:

[0082] The P25 (TiO2) powder carrier was dried in an oven at 110°C for 4 hours; 0.96g of ammonium metatungstate was added to 60ml of deionized water and stirred until completely dissolved; 0.20g of oxalic acid and 0.13g of ammonium metavanadate were added, and ultrasonic oscillation was performed for 5 minutes and then stirred until completely dissolved to obtain a light yellow solution; it was placed in an 80°C water bath and heated and stirred for more than 30 minutes, and the solution color was dark blue; 0.47g of ethylene glycol was added and stirred evenly to obtain a mixed precursor solution of vanadium and tungsten. 9g of P25 powder was added to the mixed precursor solution of vanadium and tungsten, and after a brief stirring, it was placed in a 40°C water bath and immersed for 6 hours, and then stirred dry in a 60°C water bath. The obtained product was placed in an oven at 110°C and dried overnight, and then taken out and calcined at 500°C for 5 hours, and then ground into powder after being taken out to obtain a phased product 1.

[0083] Take 0.59g C 10 H5B 20 , 0.80g Ce(SO4)2, 0.11g Bi2(SO4)3·5H2O were dissolved in 40ml deionized water, stirred and shaken until the solution was completely dissolved, 0.15g citric acid was added, stirred evenly to obtain niobium, cerium and bismuth salt solutions, 10g of the interim product 1 was added, and after a brief stirring, it was placed in a 40℃ water bath pot and immersed for 6h, and then stirred dry in a 60℃ water bath. The obtained product was placed in a 110℃ oven and dried overnight, and then taken out and calcined at 500℃ for 5h, and finally ground to 40-60 mesh to obtain the finished SCR catalyst, named 4-BiNbCe.

[0084] The alkali metal loading process is as follows: 0.1g of KCl is dissolved in 20ml of deionized water, stirred and shaken until the solution is completely dissolved, 9.9g of 4-BiNbCe is added, and after a brief stirring, it is placed in a 40°C water bath for 6h, and then stirred dry in a 60°C water bath. The obtained product is placed in a 110°C oven to dry overnight, taken out and calcined at 500°C for 5h, and finally ground to 40-60 mesh to obtain the finished product.

[0085] Embodiment 5:

[0086] This embodiment provides an alkali metal poisoning resistant SCR catalyst (VWTi catalyst doped with Ce, Nb, and Bi) and a preparation method thereof, wherein the mass percentage of the active component V2O5 in the catalyst is 0.9%, the mass percentage of WO3 is 8.5%, the mass percentage of the doping component Nb2O5 is 1.4%, the mass percentage of CeO2 is 3.9%, the mass percentage of Bi2O3 is 0.6%, and the mass percentage of TiO2 is the remainder. Different from Example 1, the temperature of the high temperature calcination process in this embodiment is 450°C, and the molar ratio of the amount of oxalic acid added to ammonium metavanadate is 3:1.

[0087] The specific implementation method includes the following steps:

[0088] The P25 (TiO2) powder carrier was dried in an oven at 110°C for 4 hours; 0.96g of ammonium metatungstate was added to 60ml of deionized water and stirred until completely dissolved; 0.30g of oxalic acid and 0.13g of ammonium metavanadate were added, and ultrasonic oscillation was performed for 5 minutes and then stirred until completely dissolved to obtain a light yellow solution; it was placed in an 80°C water bath and heated and stirred for more than 30 minutes, and the solution color was dark blue; 0.47g of ethylene glycol was added and stirred evenly to obtain a mixed precursor solution of vanadium and tungsten. 9g of P25 powder was added to the mixed precursor solution of vanadium and tungsten, and after a brief stirring, it was placed in a 60°C water bath and immersed for 2 hours, and then stirred dry in an 80°C water bath. The obtained product was placed in an oven at 110°C and dried overnight, and then taken out and calcined at 450°C for 5 hours, and then ground into powder to obtain a phased product 1.

[0089] Take 0.59g C 10 H5B 20 , 0.80g Ce(SO4)2, 0.11g Bi2(SO4)3·5H2O were dissolved in 40ml deionized water, stirred and shaken until the solution was completely dissolved, 0.11g citric acid was added, stirred evenly to obtain niobium, cerium and bismuth salt solutions, 10g of the interim product 1 was added, stirred briefly and evenly, and then placed in a 60℃ water bath pot for 2h, and then stirred dry in an 80℃ water bath. The obtained product was placed in a 110℃ oven and dried overnight, taken out and calcined at 450℃ for 5h, and finally ground to 40-60 mesh to obtain the finished SCR catalyst, named 5-BiNbCe.

[0090] The alkali metal loading process is as follows: 0.1g of KCl is dissolved in 20ml of deionized water, stirred and shaken until the solution is completely dissolved, 9.9g of 5-BiNbCe is added, and after a brief stirring, it is placed in a 60°C water bath for 2h, and then stirred dry in an 80°C water bath. The obtained product is placed in a 110°C oven to dry overnight, taken out and calcined at 450°C for 5h, and finally ground to 40-60 mesh to obtain the finished product.

[0091] The activity test was conducted on the fresh catalysts 1-VWTi and 2-VWTi of the two comparative examples and the fresh catalysts 1-BiNbCe, 2-BiNbCe, 3-BiNbCe, 4-BiNbCe and 5-BiNbCe of the five examples: 0.3 g of fresh catalyst sample with a mesh size of 40 to 60 was placed in a quartz tube for activity test. The reaction conditions of this test example were 550 ppm NO, 550 ppm NH3, 5.6% O2, and the rest was N2. The total gas flow rate was 1 L / min, and the reaction space velocity was 200,000 h -1 , the test temperature is 250℃~450℃.

[0092] Table 1 shows the reaction conditions: 550ppm NO, 550ppm NH3, 5.6% O2, the rest N2, the total gas flow rate is 1L / min, the reaction space velocity is 200,000h -1 The NO conversion rates of the fresh catalysts 1-VWTi and 2-VWTi of the two comparative examples and the fresh catalysts 1-BiNbCe, 2-BiNbCe, 3-BiNbCe, 4-BiNbCe and 5-BiNbCe of the five embodiments were tested at temperatures of 250°C, 300°C, 350°C, 400°C and 450°C respectively.

[0093] Table 1 Comparison of NO conversion of fresh catalysts 1-VWTi, 2-VWTi of two comparative examples and fresh catalysts 1-BiNbCe, 2-BiNbCe, 3-BiNbCe, 4-BiNbCe, 5-BiNbCe of five examples

[0094]

[0095] It can be seen from Table 1 that the catalytic activities of the fresh catalysts 1-BiNbCe, 2-BiNbCe, 3-BiNbCe, 4-BiNbCe and 5-BiNbCe of the five embodiments are significantly higher than those of the fresh catalysts of the comparative examples, among which the catalytic performances of the two catalysts 1-BiNbCe and 4-BiNbCe are better than those of 2-BiNbCe, 3-BiNbCe and 5-BiNbCe. Under the experimental conditions, the NO conversion rate is stably maintained at 100% in the temperature range of 350°C to 450°C.

[0096] The fresh catalysts 1-VWTi and 2-VWTi of the two comparative examples and the fresh catalysts 1-BiNbCe, 2-BiNbCe, 3-BiNbCe, 4-BiNbCe and 5-BiNbCe of the five examples were tested for activity after being poisoned with KCl: 0.3 g of the poisoned catalyst sample was taken, with a mesh size of 40 to 60, and placed in a quartz tube for activity testing. The reaction conditions of this test example were 550 ppm NO, 550 ppm NH3, 5.6% O2, and the rest was N2. The total gas flow rate was 1 L / min, and the reaction space velocity was 200,000 h -1 , the test temperature is 250℃~450℃.

[0097] Table 2 shows the reaction conditions: 550ppm NO, 550ppm NH3, 5.6% O2, the rest N2, the total gas flow rate is 1L / min, the reaction space velocity is 200,000h -1The NO conversion rates of the fresh catalysts 1-VWTi and 2-VWTi of the two comparative examples and the fresh catalysts 1-BiNbCe, 2-BiNbCe, 3-BiNbCe, 4-BiNbCe and 5-BiNbCe of the five embodiments after KCl poisoning were tested at temperatures of 250°C, 300°C, 350°C, 400°C and 450°C respectively.

[0098] Table 2 Comparison of NO conversion of fresh catalysts 1-VWTi, 2-VWTi of two comparative examples and fresh catalysts 1-BiNbCe, 2-BiNbCe, 3-BiNbCe, 4-BiNbCe, 5-BiNbCe of five examples after KCl poisoning

[0099]

[0100] It can be seen from Table 2 that the catalytic activities of the fresh catalysts 1-BiNbCe, 2-BiNbCe, 3-BiNbCe, 4-BiNbCe and 5-BiNbCe of the five embodiments after KCl poisoning are significantly higher than those of the catalysts of the comparative examples after poisoning, among which the catalytic performances of the two catalysts 1-BiNbCe and 4-BiNbCe are better than those of 2-BiNbCe, 3-BiNbCe and 5-BiNbCe. Under the experimental conditions, the NO conversion rate reaches more than 90% at 350°C, the catalyst activity reaches a peak at 400°C, and the NO conversion rate reaches 100%.

[0101] Stability test of 1-BiNbCe, 2-BiNbCe, 3-BiNbCe, 4-BiNbCe and 5-BiNbCe catalyst samples: 0.3g catalyst sample, mesh size of 40-60, was placed in a quartz tube for activity test. The reaction conditions of this test case were 550ppm NO, 550ppm NH3, 5.6% O2, and the rest was N2. The total gas flow rate was 1L / min, and the reaction space velocity was 200,000h -1 The test temperature was 350°C, and the NO conversion rates were recorded at 10h, 30h, 60h, 120h and 200h respectively.

[0102] Table 3 shows the reaction conditions: 550ppm NO, 550ppm NH3, 5.6% O2, the rest N2, the total gas flow rate is 1L / min, the reaction space velocity is 200,000h -1 The NO conversion rates of 1-BiNbCe, 2-BiNbCe, 3-BiNbCe, 4-BiNbCe and 5-BiNbCe at 10h, 30h, 60h, 120h and 200h were tested at a temperature of 350℃.

[0103] Table 3 Comparison of NO conversion of 1-BiNbCe, 2-BiNbCe, 3-BiNbCe, 4-BiNbCe, and 5-BiNbCe at 10 h, 30 h, 60 h, 120 h, and 200 h

[0104]

[0105] It can be seen from Table 3 that the catalytic activities of the fresh catalysts 1-BiNbCe, 2-BiNbCe, 3-BiNbCe, 4-BiNbCe and 5-BiNbCe of the five embodiments are stable, and the catalyst stability is guaranteed.

Claims

1. An alkali metal poisoning resistant SCR catalyst, characterized in that The carrier of the SCR catalyst is TiO2, the active components include V2O5 and WO3, and the doping components include Nb2O5, CeO2 and Bi2O3.

2. The alkali metal poisoning resistant SCR catalyst according to claim 1, characterized in that The mass percentage of V2O5 in the SCR catalyst is 0.9-1%, the mass percentage of WO3 is 8.2-8.6%, the mass percentage of Nb2O5 is 1-1.8%, the mass percentage of CeO2 is 3.3-4.7%, the mass percentage of Bi2O3 is 0.2-1.7%, and the mass percentage of TiO2 is the remainder.

3. A method for preparing the alkali metal poisoning resistant SCR catalyst according to claim 2, characterized in that The method comprises the following preparation steps: Step A: preparing a mixed precursor solution of vanadium and tungsten; Step B: impregnating a mixed precursor solution of vanadium and tungsten on a titanium dioxide carrier, stirring dry in a water bath, and then calcining at high temperature; Step C: preparing niobium, cerium and bismuth salt solutions; Step D: impregnating the product obtained in step B with a solution of niobium, cerium and bismuth salts, stirring to dryness in a water bath and then calcining at high temperature; Step E: Grind the product obtained in step D to a certain mesh size to obtain a finished SCR catalyst, in which the mass percentage of V2O5 is 0.9-1%, the mass percentage of WO3 is 8.2-8.6%, the mass percentage of Nb2O5 is 1-1.8%, the mass percentage of CeO2 is 3.3-4.7%, the mass percentage of Bi2O3 is 0.2-1.7%, and the mass percentage of TiO2 is the remainder.

4. The method for preparing an alkali metal poisoning resistant SCR catalyst according to claim 3, characterized in that The specific process of step A is as follows: dissolving ammonium metatungstate in deionized water and stirring evenly at room temperature; then adding oxalic acid and ammonium metavanadate, and ultrasonically oscillating until the added oxalic acid and ammonium metavanadate are completely dissolved; then heating the obtained light yellow solution in a water bath while stirring until the solution turns dark blue; finally, adding ethylene glycol to the dark blue solution and stirring evenly to obtain a mixed precursor solution of vanadium and tungsten.

5. The method for preparing an alkali metal poisoning resistant SCR catalyst according to claim 4, characterized in that The molar ratio of the added amount of oxalic acid and ammonium metavanadate is 2:1 or 3:1, the water bath temperature is 60-80°C, and the molar ratio of the added amount of ethylene glycol to the total amount of metal ions in the dark blue solution is 1.5:

1.

6. The method for preparing an alkali metal poisoning resistant SCR catalyst according to claim 3, characterized in that The specific process of step B is: adding titanium dioxide powder as a carrier to the mixed precursor solution of vanadium and tungsten, and stirring evenly at room temperature; then standing at a certain temperature for a period of time and stirring dry in a water bath; and then drying and high-temperature calcining the product obtained after stirring dry in the water bath.

7. The method for preparing an alkali metal poisoning resistant SCR catalyst according to claim 3, characterized in that The specific process of step C is: dissolving niobium salt, cerium salt and bismuth salt in deionized water, and stirring evenly at room temperature; then adding citric acid to the obtained solution, stirring evenly, to obtain a niobium, cerium and bismuth salt solution.

8. The method for preparing an alkali metal poisoning resistant SCR catalyst according to claim 7, characterized in that The niobium salt is selected from niobium oxalate; the cerium salt is selected from one or more of cerium nitrate, cerium carbonate, and cerium sulfate; the bismuth salt is selected from one or more of bismuth nitrate and bismuth sulfate; the concentration of niobium in the niobium, cerium and bismuth salt solutions is 0.020-0.040 mol / L, the concentration of cerium is 0.050-0.080 mol / L, and the concentration of bismuth is 0.003-0.020 mol / L; the molar ratio of the amount of citric acid added to the total amount of metal ions in the solution is 1.5:1 or 2:

1.

9. The method for preparing an alkali metal poisoning resistant SCR catalyst according to claim 6, characterized in that The specific process of step D is: adding the product obtained in step B to the niobium, cerium and bismuth salt solutions, and stirring evenly at room temperature; then standing at a certain temperature for a period of time and stirring dry in a water bath; and then drying and high-temperature calcining the product obtained after stirring dry in the water bath.

10. The method for preparing an alkali metal poisoning resistant SCR catalyst according to claim 9, characterized in that In the specific process of step B and step D, the standing temperature is 40-60° C., the standing time is 2-6 hours, the temperature of water bath drying is 60-80° C., the calcination temperature is 450° C.-500° C., and the calcination time is 5 hours.

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