A close-coupled SCR catalyst and its preparation method and application

Abstract

The present invention relates to the technical field of catalysts, and discloses a close-coupled SCR catalyst and a preparation method and application thereof, wherein the catalyst comprises a molecular sieve and indium oxide; the indium oxide is loaded on the surface of the molecular sieve in the form of particles; the indium oxide is A x In 1‑x O y , wherein A is one or more selected from Ce, La, Pr, Nb, Ga, Ni, Gd, Zn, Cr, Sr, and Zr; In is indium; O is oxygen; 0≤x<1, and y is determined by the chemical formula balancing method of indium oxide. The catalyst obtained by the present invention not only effectively improves the catalyst's resistance to hydrocarbon poisoning, solves the problem of catalyst deactivation due to hydrocarbon poisoning in the ccSCR system, but also improves the catalyst's low-temperature activity, broadens the active temperature window and N 2 Selective.

Description

Technical Field

[0001] The present invention relates to the field of catalyst technology, and in particular to a close-coupled SCR catalyst and a preparation method and application thereof. Background Art

[0002] Exhaust gas from fossil fuel combustion is the main source of nitrogen oxides in the atmosphere, of which mobile sources account for about 40%. As emission regulations become more stringent, it is difficult to meet ultra-low NO emissions during cold start using only traditional SCR catalysts. x The close-coupled selective catalytic reduction (ccSCR) technology is an effective solution to low-temperature NO x The technology of emission. The characteristic of this technology is to install the ccSCR catalyst at the forefront of the aftertreatment system to solve the low-temperature NOx emission problem. There are a lot of unburned hydrocarbons (HC) in the exhaust components of diesel engines. The exhaust temperature range of the cold cycle is about 150℃-400℃, which makes the ccSCR catalyst directly exposed to a large amount of unburned HC exhaust components. The catalyst cannot completely oxidize HC at this exhaust temperature, causing HC to cover the catalyst surface and form carbon deposits, causing the catalyst to deactivate.

[0003] Existing technicians have modified the catalyst, including doping the catalyst, but found that although the redox performance, oxygen storage capacity, SO2 resistance and HC resistance of the catalyst can be improved, due to the differences in the coordination between the selected doping material and the catalyst, the ability of the currently obtained catalyst to improve the resistance to hydrocarbon poisoning is limited, and the active temperature window of the doped catalyst is narrow, which limits its application in the post-treatment system. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a close-coupled SCR catalyst and a preparation method and application thereof. The catalyst obtained by the present invention not only effectively improves the catalyst's resistance to hydrocarbon poisoning, solves the problem of catalyst deactivation due to hydrocarbon poisoning in the ccSCR system, but also can improve the catalyst's low-temperature activity, broaden the active temperature window and N2 selectivity.

[0005] The present invention provides a close-coupled SCR catalyst, which comprises a molecular sieve and indium oxide; the indium oxide is loaded on the surface of the molecular sieve in the form of particles;

[0006] The indium oxide is A x In 1-x O y, wherein A is one or more selected from Ce (cerium), La (lanthanum), Pr (praseodymium), Nb (niobium), Ga (gallium), Ni (nickel), Gd (gadolinium), Zn (zinc), Cr (chromium), Sr (strontium), and Zr (zirconium); In is indium; O is oxygen; 0≤x<1, and y is determined by the method of balancing the chemical formula of indium oxide.

[0007] Furthermore, the average pore size of the molecular sieve is no greater than 1 nm.

[0008] Furthermore, the average particle size of the indium oxide is 2nm-50nm.

[0009] Furthermore, the molecular sieve contains active components, and the molecular sieve structure is selected from one of CHA, AEI, LTA, MFI, BEA, mullite, MOR, KFI, MCM, FER, and OFF.

[0010] Furthermore, the active components include one or more of Cu (copper), Fe (iron), Co (cobalt), Mn (manganese), Pd (palladium), Rh (rhodium), and Ce (cerium).

[0011] The present invention also provides a method for preparing the close-coupled SCR catalyst, which includes Scheme I and Scheme II:

[0012] Scheme I, indium oxide A in the catalyst x In 1-x O y When x is 0:

[0013] Dissolving an indium precursor in a reagent, adjusting the pH value of the dissolved solution to 5-10, performing solid-liquid separation, washing, drying, and calcining to form indium oxide, and ball-milling the indium oxide and the molecular sieve to obtain a tightly coupled SCR catalyst;

[0014] Scheme II, indium oxide A in the catalyst x In 1-x O y In the case of 0<x<1:

[0015] The indium precursor is dissolved in the reagent, and then the second metal element precursor is added to dissolve, the pH value of the dissolved solution is adjusted to 5-10, the solid-liquid separation, washing, drying, and roasting are performed to form indium oxide, and the indium oxide and the molecular sieve are ball-milled to obtain a tightly coupled SCR catalyst.

[0016] Furthermore, the reagents include deionized water and alcohol reagents; the alcohol reagents include one or more of methanol, ethanol, propanol, isopropanol, and ethylene glycol.

[0017] Furthermore, the pH value of the alcohol reagent is 1-5.

[0018] Those skilled in the art can adjust the pH value of the alcohol reagent by adding nitric acid, hydrochloric acid, sulfuric acid, citric acid, or malic acid.

[0019] Furthermore, the coordinating anions of the indium precursor include one or more of nitrate, hydrochloride, sulfate, selenite, and selenate.

[0020] Further, the second metal element precursor includes one or more of cerium nitrate, cerium acetate, cerium sulfate, lanthanum nitrate, niobium oxalate, ammonium niobate oxalate hydrate, praseodymium nitrate, gallium nitrate, nickel nitrate, nickel acetate, gadolinium nitrate, zinc nitrate, zinc acetate, chromium acetate, strontium oxalate, and zirconium nitrate.

[0021] Further, in Scheme II, the molar ratio of the second metal element precursor to the indium precursor is determined based on the molar ratio of the In element and the active element in the second metal element precursor according to the molecular formula of indium oxide;

[0022] The active elements are Ce in cerium nitrate, Ce in cerium acetate, Ce in cerium sulfate, La in lanthanum nitrate, Nb in niobium oxalate, Nb in ammonium niobate oxalate hydrate, Pr in praseodymium nitrate, Ni in nickel nitrate, Ni in nickel acetate, Gd in gadolinium nitrate, Zn in zinc nitrate, Zn in zinc acetate, Sr in strontium oxalate, Zr in zirconium nitrate, Ga in gallium nitrate, and Cr in chromium acetate.

[0023] Furthermore, the molar concentration of the indium precursor in the reagent is 0.1 mol / L-1 mol / L.

[0024] Further, in the II scheme, when the second metal element precursor is added for dissolution, the technicians in this field can increase the temperature during dissolution to dissolve the second metal element precursor, or stir during the dissolution process to promote the dissolution of the second metal element precursor. Preferably, the temperature during dissolution is 20°C-60°C.

[0025] Furthermore, when the pH value of the solution after adjustment is between 5 and 10, a mixed solution of an alkaline agent and ethanol is used, wherein the volume ratio of the alkaline agent to the ethanol is 1:1.

[0026] Furthermore, the alkaline reagent includes one or more of sodium hydroxide, potassium hydroxide, and ammonia water.

[0027] Furthermore, the pH value of the alkaline reagent is 10-14.

[0028] Furthermore, after adjusting the pH value of the dissolved solution to 5-10, the solution is mixed evenly and allowed to stand.

[0029] Furthermore, those skilled in the art should understand that there are many ways to mix uniformly, which are not limited in the present invention. As an example, stirring is adopted and the stirring is performed for 0.5h-2h.

[0030] Furthermore, the standing time is 1h-6h.

[0031] Furthermore, the specific method of washing is: washing with ethanol and deionized water in sequence until the washed substance is neutral.

[0032] A person skilled in the art can judge whether the washed substance is neutral by placing the washed substance in deionized water and detecting the pH value of the deionized water.

[0033] Furthermore, the drying temperature is 70°C-100°C.

[0034] It should be understood by those skilled in the art that drying is to remove the residual moisture after washing, and therefore, the drying time can be determined based on whether the product has a constant weight.

[0035] Furthermore, the calcination temperature is 500° C.-600° C., and the calcination time is 2 h-8 h.

[0036] Furthermore, the ball milling is dry milling or wet milling.

[0037] Furthermore, during the dry grinding, the mass ratio of indium oxide to molecular sieve is 1:(1-20).

[0038] Furthermore, during the dry grinding, the ball-to-material ratio is (2-6):1, the ball grinding time is 5min-20min, the rotation speed is 100r / min-200r / min, and the average particle size of the ball is 3mm-12mm.

[0039] Furthermore, during the wet grinding, the mass ratio of indium oxide to molecular sieve is 1:(1-20), and deionized water is added during the wet grinding, and the mass of the added deionized water is 1 to 6 times the total mass of the indium oxide and the molecular sieve.

[0040] Furthermore, during the wet grinding, the ball-to-material ratio is (2-6):1, the ball grinding time is 5min-20min, the rotation speed is 100r / min-200r / min, and the average particle size of the ball is 3mm-12mm.

[0041] The present invention also provides the use of the close-coupled SCR catalyst to reduce hydrocarbon poisoning in the process of catalyzing nitrogen oxides.

[0042] Furthermore, the temperature of the catalyst application environment is between 150°C and 400°C.

[0043] Furthermore, the temperature of the catalyst application environment is between 250°C and 400°C.

[0044] The embodiments of the present invention have the following technical effects:

[0045] 1. The catalyst of the present invention not only effectively improves the catalyst's resistance to hydrocarbon poisoning, solves the problem of catalyst deactivation due to hydrocarbon poisoning in the ccSCR system, but also improves the catalyst's low-temperature activity, broadens the active temperature window and N2 selectivity; the catalyst can significantly improve the catalyst's catalytic activity, especially at a temperature of 250°C-400°C.

[0046] 2. In the catalyst of the present invention, the molecular sieve is used as the basis for loading to carry out the SCR reaction and convert nitrogen oxides. The indium oxide loaded on the surface of the molecular sieve can provide acidic sites and oxidize hydrocarbons to form intermediates of the SCR reaction, thereby reducing the deposition of hydrocarbons on the surface of the catalyst, which not only avoids the occurrence of catalyst poisoning, but also improves the activity of the catalyst, N2 selectivity and broadens the active temperature window.

[0047] 3. In order to further avoid hydrocarbon poisoning of the catalyst in the present invention, the average pore size of the molecular sieve and the particle size of the indium oxide are further limited in the present invention, effectively preventing the indium oxide from entering the molecular sieve pores to occupy the active sites, so that the indium oxide is only loaded on the surface of the molecular sieve, so that the hydrocarbons can be completely oxidized on the catalyst surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0049] Figure 1 This is a microscopic morphology of indium oxide in Example 1 provided in the embodiments of the present invention.

[0050] Figure 2 It is a microscopic morphology diagram provided in Comparative Example 1 of the present invention.

[0051] Figure 3 This is a microscopic morphology of the catalyst provided in Example 1 of the present invention.

[0052] Figure 4It is a graph showing the catalytic activity test results of the catalysts of the examples of the present invention and the comparative examples.

[0053] Figure 5 It is a diagram showing the results of by-product generation in the catalysts of the embodiments of the present invention and the comparative examples.

[0054] Figure 6 It is a graph showing the catalytic activity test results of the catalyst provided in the embodiment of the present invention.

[0055] Figure 7 is the element distribution diagram of Example 3 of the present invention, wherein Figure 7 a is the element distribution diagram of the catalyst. Figure 7 b is the distribution diagram of O element. Figure 7 In the figure, c is the Al element distribution diagram. Figure 7 In the figure d, it is the distribution diagram of Si element. Figure 7 e is the distribution diagram of In element, Figure 7 In f, it is the distribution diagram of Ce element.

[0056] Figure 8 It is a graph showing the catalytic activity test results of the catalysts of the examples of the present invention and the comparative examples.

[0057] Fig. 9 A graph showing the catalytic activity test results of the catalyst provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0058] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0059] In a first aspect, some embodiments of the present invention provide a close-coupled SCR catalyst, the catalyst comprising a molecular sieve and indium oxide; the indium oxide is supported on the surface of the molecular sieve in the form of particles;

[0060] The indium oxide is A x In 1-x O y , wherein A is one or more selected from Ce, La, Pr, Nb, Ga, Ni, Gd, Zn, Cr, Sr, and Zr; In is indium; O is oxygen; 0≤x<1, and y is determined by the method of balancing the chemical formula of indium oxide.

[0061] In the catalyst of the present invention, the molecular sieve mainly performs SCR reaction to convert nitrogen oxides. The indium oxide in the catalyst can not only provide acid sites, but also oxidize hydrocarbons to form intermediate products of the SCR reaction, thereby reducing the deposition of hydrocarbons on the surface of the catalyst. Indium oxide not only avoids the occurrence of catalyst poisoning, but also improves the activity of the catalyst, N2 selectivity and widens the active temperature window.

[0062] In some embodiments, the average pore size of the molecular sieve is no greater than 1 nm; and the average particle size of the indium oxide is 2 nm-50 nm.

[0063] In the present invention, in order to promote the catalyst to reduce hydrocarbon poisoning of the catalyst on the basis of converting nitrogen oxides, the average pore size of the molecular sieve and the average particle size of the indium oxide are further limited, so that the indium oxide is loaded on the surface of the molecular sieve to prevent the indium oxide from entering the molecular sieve, thereby facilitating the successful conversion of hydrocarbons by the indium oxide on the surface of the molecular sieve, and successfully preventing the occurrence of catalyst poisoning.

[0064] In some embodiments, the molecular sieve contains active components, and the molecular sieve structure is selected from one of CHA, AEI, LTA, MFI, BEA, mullite, MOR, KFI, MCM, FER, and OFF.

[0065] In some embodiments, the active component includes one or more of Cu (copper), Fe (iron), Co (cobalt), Mn (manganese), Pd (palladium), Rh (rhodium), and Ce (cerium).

[0066] In a second aspect, some embodiments of the present invention further provide a method for preparing the close-coupled SCR catalyst, the method comprising Scheme I and Scheme II:

[0067] Scheme I, indium oxide A in the catalyst x In 1-x O y When x is 0:

[0068] Dissolving an indium precursor in a reagent, adjusting the pH value of the dissolved solution to 5-10, performing solid-liquid separation, washing, drying, and calcining to form indium oxide, and ball-milling the indium oxide and the molecular sieve to obtain a tightly coupled SCR catalyst;

[0069] Scheme II, indium oxide A in the catalyst x In 1-x O y In the case of 0<x<1:

[0070] The indium precursor is dissolved in the reagent, and then the second metal element precursor is added to dissolve, the pH value of the dissolved solution is adjusted to 5-10, the solid-liquid separation, washing, drying, and roasting are performed to form indium oxide, and the indium oxide and the molecular sieve are ball-milled to obtain a tightly coupled SCR catalyst.

[0071] In the method of the present invention, the particle size of the indium oxide can be regulated by adjusting the pH of the solution, so that the particle size of the indium oxide cannot enter the molecular sieve, and the indium oxide has sufficient catalytic area, which is conducive to the rapid conversion of hydrocarbons. On this basis, the indium oxide compound is mixed with the molecular sieve by ball milling, which is conducive to the uniform loading of the indium oxide compound on the surface of the molecular sieve.

[0072] In some embodiments, the reagents include deionized water and alcohol reagents; the alcohol reagents include one or more of methanol, ethanol, propanol, isopropanol, and ethylene glycol.

[0073] In some embodiments, the pH value of the alcohol reagent is 1-5.

[0074] In some embodiments, the second metal element precursor includes one or more of cerium nitrate, cerium acetate, cerium sulfate, lanthanum nitrate, niobium oxalate, ammonium niobate oxalate hydrate, praseodymium nitrate, gallium nitrate, nickel nitrate, nickel acetate, gadolinium nitrate, zinc nitrate, zinc acetate, chromium acetate, strontium oxalate, and zirconium nitrate.

[0075] In some embodiments, in the II scheme, the molar ratio of the second metal element precursor to the indium precursor is determined based on the molar ratio of the In element in the indium precursor and the active element in the second metal element precursor according to the molecular formula of indium oxide;

[0076] The active elements are Ce in cerium nitrate, Ce in cerium acetate, Ce in cerium sulfate, La in lanthanum nitrate, Nb in niobium oxalate, Nb in ammonium niobate oxalate hydrate, Pr in praseodymium nitrate, Ni in nickel nitrate, Ni in nickel acetate, Gd in gadolinium nitrate, Zn in zinc nitrate, Zn in zinc acetate, Sr in strontium oxalate, Zr in zirconium nitrate, Ga in gallium nitrate, and Cr in chromium acetate.

[0077] In some embodiments, the molar concentration of the indium precursor in the reagent is 0.1 mol / L-1 mol / L.

[0078] In some embodiments, when the pH value of the solution after adjustment is between 5 and 10, a mixed solution of an alkaline agent and ethanol is used, wherein the volume ratio of the alkaline agent to the ethanol is 1:1.

[0079] In some embodiments, the alkaline reagent includes one or more of sodium hydroxide, potassium hydroxide, and ammonia water.

[0080] In some embodiments, the pH value of the alkaline reagent is 10-14.

[0081] In the present invention, the growth rate of indium oxide can be controlled by adjusting the pH value of the alkaline reagent. Within this range, the uniformity of each element in the generated indium oxide can be achieved.

[0082] In some embodiments, after adjusting the pH value of the dissolved solution to 5-10, the solution is mixed evenly and allowed to stand.

[0083] In the present invention, the precipitate is aged by standing still, which helps to generate complete crystalline particles. Meanwhile, the aging process also helps the crystalline particles to separate from the impurity ions adsorbed on the surface.

[0084] In some embodiments, the standing time is 1 h-6 h.

[0085] In some embodiments, the specific method of washing is: washing with ethanol and deionized water in sequence until the washed substance is neutral.

[0086] In some embodiments, the drying temperature is 70°C-100°C.

[0087] In some embodiments, the calcination temperature is 500° C.-600° C., and the calcination time is 2 h-8 h.

[0088] In some embodiments, the ball milling is dry milling or wet milling.

[0089] In some embodiments, during the dry grinding, the mass ratio of indium oxide to molecular sieve is 1:(1-20).

[0090] In some embodiments, during the dry grinding, the ball-to-material ratio is (2-6):1, the ball grinding time is 5 min-20 min, the rotation speed is 100 r / min-200 r / min, and the average particle size of the ball is 3 mm-12 mm.

[0091] In some embodiments, during wet grinding, the mass ratio of indium oxide to molecular sieve is 1:(1-20), and deionized water is added during wet grinding, and the mass of deionized water added is 1 to 6 times the total mass of indium oxide and molecular sieve.

[0092] In some embodiments, during the wet grinding, the ball-to-material ratio is (2-6):1, the ball grinding time is 5 min-20 min, the rotation speed is 100 r / min-200 r / min, and the average particle size of the ball is 3 mm-12 mm.

[0093] In a third aspect, some embodiments of the present invention also provide the use of the close-coupled SCR catalyst to reduce hydrocarbon poisoning in the process of catalyzing nitrogen oxides.

[0094] The following is described in conjunction with some specific embodiments:

[0095] Embodiment 1:

[0096] Preparation of indium oxide: Take 55mL of deionized water, add 1.8g of indium nitrate to it, and stir to dissolve. Then, add 26g of cerium nitrate, stir until dissolved, and add ammonia water (pH=12) dropwise to the mixture to make the pH value of the solution about 8.5. Then, continue stirring for 1h to age it. Finally, filter, wash with ethanol and deionized water in turn until the washed material is neutral, dry it with air at 70℃, and roast it at 600℃ for 6h to obtain indium oxide Ce. 0.9 In 0.1 O5, such as Figure 1 As shown, Figure 1 The microscopic morphology of indium oxide;

[0097] The obtained indium oxide and Cu-SSZ-13 molecular sieve are ball-milled and mixed in a mass ratio of 1:4 to obtain a catalyst, wherein a dry milling method is adopted, the ball-to-material ratio is 4:1, the ball milling time is 10 minutes, the rotation speed is 150r / min, and the average particle size of the ball is 8mm; the average pore size of the Cu-SSZ-13 molecular sieve is 0.38nm.

[0098] Embodiment 2:

[0099] The method for preparing Example 2 is the same as that of Example 1, but the added mass of indium nitrate in Example 2 is 0.9 g, and indium oxide Ce is obtained. 0.95 In 0.05 O5.

[0100] Embodiment 3:

[0101] The method for preparing Example 3 is the same as that of Example 1, but the added mass of indium nitrate in Example 3 is 9 g, and indium oxide Ce is obtained. 0.5 In 0.5 O5.

[0102] Embodiment 4:

[0103] The method for preparing Example 4 is the same as that of Example 1, but in Example 4, indium oxide and Cu-SSZ-13 molecular sieve are ball-milled and mixed at a mass ratio of 1:19.

[0104] Embodiment 5:

[0105] The method for preparing Example 5 is the same as that of Example 1, but in Example 5, indium oxide and Cu-SSZ-13 molecular sieve are ball-milled and mixed at a mass ratio of 1:9.

[0106] Embodiment 6:

[0107] The method for preparing Example 6 is the same as that of Example 1, but in Example 6, indium oxide and Cu-SSZ-13 molecular sieve are ball-milled and mixed at a mass ratio of 2:3.

[0108] Embodiment 7:

[0109] Take 55mL of deionized water, add 1.8g of indium nitrate and 6.5g of ammonium niobate oxalate hydrate, and stir to dissolve. Then, add 26g of cerium nitrate and stir until dissolved. Add ammonia water dropwise to the mixture to make the pH value of the solution about 8.5. Then, continue stirring for 1h to age it. Finally, filter, wash with ethanol and deionized water in turn until the washed material is neutral, dry it with air at 70℃, and roast it at 600℃ for 6h to make indium oxide Ce. 0.7 Nb 0.2 In 0.1 O 10 Indium oxide and Cu-SSZ-13 molecular sieve were ball-milled in a mass ratio of 1:4 to obtain a catalyst, wherein a dry milling method was adopted, the ball-to-material ratio was 4:1, the ball milling time was 10 minutes, the rotation speed was 150 r / min, and the average particle size of the ball was 8 mm.

[0110] Embodiment 8:

[0111] The method for preparing Example 8 is the same as that of Example 1, but in Example 8, indium oxide and Cu-AEI molecular sieve are ball-milled and mixed at a mass ratio of 1:4. The average pore size of the Cu-AEI molecular sieve is 0.38 nm.

[0112] Embodiment 9:

[0113] Take 55mL of deionized water, add 18g of indium nitrate to it, and stir to dissolve. Subsequently, add ammonia water dropwise to the mixture to make the pH value of the solution about 8.5. Then, continue stirring for 1h to age it. Finally, filter, wash, blow dry at 70℃, and calcine at 600℃ for 6h to obtain indium oxide In2O3. The indium oxide and Cu-SSZ-13 molecular sieve are ball-milled and mixed in a mass ratio of 1:4 to obtain a catalyst.

[0114] Comparative Example 1:

[0115] Commercial Cu-SSZ-13 powder catalyst, Si / Al=10, the average pore size of Cu-SSZ-13 molecular sieve is 0.38nm, Cu content = 2.6wt%, such as Figure 2 As shown, Figure 2 This is the microscopic morphology of Comparative Example 1.

[0116] Comparative Example 2:

[0117] Take 55mL of deionized water, add 26g of cerium nitrate thereto, and stir until dissolved. Subsequently, ammonia water is added dropwise to the mixed solution to make the solution pH value about 8.5. Then, continue stirring for 1h to age it. Filter, wash with ethanol and deionizer in turn until the washed substance is neutral, dry with 70°C blast drying, and roast at 600°C for 6h to obtain CeO2. CeO2 and Cu-SSZ-13 molecular sieve are ball-milled and mixed in a mass ratio of 1:4 to obtain the catalyst of Comparative Example 2. Among them, the dry grinding method is adopted, the ball-to-material ratio is 4:1, the ball milling time is 10min, the rotation speed is 150r / min, and the average particle size of the ball is 8mm.

[0118] Comparative Example 3:

[0119] Cu-AEI molecular sieve catalyst, Si / Al=8, average pore size 0.38nm, Cu content = 2.4wt%.

[0120] Comparative Example 4:

[0121] The method for preparing Comparative Example 4 is the same as that of Example 1, but Ce in Comparative Example 4 is 0.9 In 0.1 The mixing method of O5 and Cu-SSZ-13 molecular sieve is to mix the materials uniformly through mechanical stirring.

[0122] Comparative Example 5:

[0123] Take 45g of deionized water, add 26g of cerium nitrate and 0.9g of indium nitrate thereto, and stir to dissolve. Then add 20g of Cu-SSZ-13 molecular sieve, raise the temperature to 80°C, and stir for 6h. Finally, filter, wash, blow dry at 70°C, and calcine at 600°C for 6h to obtain Comparative Example 5, in which indium ions are loaded inside the molecular sieve.

[0124] The present invention also tests the obtained embodiments and comparative examples.

[0125] Catalytic activity test method: The catalyst anti-HC performance test in NH3-SCR reaction uses the following simulated gas composition: 500ppm NO, 500ppm NH3, 800ppm C3H6, 8%vol O2, N2 as balance gas, total flow rate of 1000mL / min, reaction space velocity of 200000h -1 .

[0126] Results and analysis:

[0127] Through the method of the present invention, a catalyst is successfully obtained, such as Figure 3 In the catalyst of the present invention, the molecular sieve is not only used to convert nitrogen oxides, but also used to load indium oxides, which can provide acidic sites and oxidize hydrocarbons to form intermediate products of SCR reactions, thereby reducing the surface load of hydrocarbons on the catalyst, which not only avoids the occurrence of catalyst poisoning, but also improves the activity of the catalyst, N2 selectivity and widens the active temperature window, especially when the catalytic reaction temperature of the catalyst is lower than 400°C.

[0128] exist Figure 4 In the comparison between Example 1 to Example 3 and Comparative Example 1, it is found that compared with Comparative Example 1, Examples 1 to Example 3 all have better catalytic activity, especially when the catalyst is between 250°C and 400°C. When there are fewer hydrocarbons deposited on the surface of the catalyst, the catalytic activity of the catalyst is less affected. As the deposited hydrocarbons increase, the catalytic activity of the catalyst decreases significantly, as shown in Comparative Example 1; and the anti-hydrocarbon effect of Examples 1 to Example 3 in the present invention is significant, so it has always had good catalytic activity. Therefore, indium oxide can enhance the catalyst's resistance to hydrocarbon poisoning. Further comparison of Examples 1 to Example 3 shows that as the In / Ce molar ratio increases, the catalyst exhibits better resistance to hydrocarbons, but when it is further improved, the catalytic activity of the catalyst at high temperatures decreases. Therefore, it is further preferred that the In / Ce molar ratio is 1-19.

[0129] The N2O generation of the catalysts of Examples 1 to 3 was further compared with that of Comparative Example 1 during the hydrocarbon resistance test. Figure 5 As shown. Figure 5 It can be found that compared with Comparative Example 1, Examples 1 to 3 generate very little byproduct N2O, which shows that the catalyst of the present invention does not generate more byproducts when used. Further comparison of Examples 1 to 3 shows that as the In / Ce molar ratio in the indium oxide compound increases, the amount of byproduct N2O generated by the catalyst in the range of 300°C-450°C is significantly reduced. In summary, it is further preferred that the indium oxide is Ce 0.95 In 0.05 O5.

[0130] like Figure 6As shown, Example 1 was compared with Example 4-Example 6, and the mass ratio of indium oxide to molecular sieve was 1:4, 1:19, 1:9, and 2:3, respectively. Catalysts obtained from different examples were tested for catalytic activity. With the increase of indium oxide, the performance of the catalyst against hydrocarbons will be improved, so the catalyst exhibits better catalytic activity. As verified by comparing Example 4 with Example 1 and Example 5, Example 1 has better catalytic activity at 250°C-400°C. In Example 1, when the mass ratio of indium oxide to molecular sieve is 1:4, its NO x The conversion rate reaches 80% at 218°C; however, as the indium oxide further increases, the catalytic activity of the catalyst decreases, as verified by comparison of Examples 4 to 6. Therefore, it is further preferred that the mass ratio of indium oxide to molecular sieve is 1:(1-20).

[0131] Figure 7 This is a SEM mapping image of the surface of the material in Example 3. Figure 7 As can be seen in a, the white square is the crystal surface of SSZ-13 molecular sieve, which is mainly composed of Si, Al, O, In, and Ce. It can be seen that through the method of the present invention, indium oxide is successfully and evenly loaded on the surface of the molecular sieve.

[0132] Figure 8 The catalytic performance test results of the catalysts obtained from Example 1 and Comparative Examples 1 to 5 are as follows. Figure 8 It can be found that Example 1 of the present invention has good catalytic activity at 250°C-400°C, which is significantly better than Comparative Examples 1-5. The catalytic activity of the powder catalyst sample of Comparative Example 5, that is, the catalytic activity of the powder catalyst sample of Comparative Example 5, in which the In element and Ce are loaded in the Cu-SSZ-13 in an ion state by the ion exchange method, is as follows: Figure 8 It can be seen that when In and Ce exist in the molecular sieve pore structure in an ionic state, the catalytic activity of the catalyst decreases significantly at 350°C-400°C. It can be seen that this method cannot improve the catalyst's resistance to hydrocarbon poisoning. x When the conversion rate is lower than 240℃ or higher than 400℃, the NO x The conversion rate is significantly lower than that in Example 1.

[0133] Fig. 9 The catalytic activity test results of the catalysts were obtained from Example 1 and Example 7-Example 9. Fig. 9 It is found that the catalytic activity of Example 1, Example 7 and Example 8 is significantly better than that of Example 9, which shows that the addition of Ce element and / or Nb element can improve the catalytic activity of the catalyst at high temperature.x In 1-x O y , where 0<x<1.

[0134] It should be noted that the terms used in the present invention are only for describing specific embodiments, rather than limiting the scope of the present application. As shown in the present specification, unless the context clearly indicates an exception, the words "one", "a", "a kind of" and / or "the" do not specifically refer to the singular, but may also include the plural. The terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method or device. In the absence of more restrictions, the elements defined by the sentence "include one..." do not exclude the presence of other identical elements in the process, method or device including the elements.

[0135] It should also be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. Unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", etc. should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0136] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A close-coupled SCR catalyst, characterized in that: The catalyst comprises a molecular sieve and indium oxide; the indium oxide is loaded on the surface of the molecular sieve in the form of particles; The indium oxide is A x In 1-x O y , wherein A is one or more selected from Ce and Nb; In is indium; O is oxygen; 0<x<1, y is determined by the method of balancing the chemical formula of indium oxide; The catalyst uses NH3 as a reducing agent; Indium Oxide A in Catalyst x In 1-x O y In the case of 0<x<1: The preparation method of the catalyst comprises: dissolving an indium precursor in a reagent, adding a second metal element precursor to dissolve, adjusting the pH value of the dissolved solution to 5-10, solid-liquid separation, washing, drying, roasting, forming indium oxide, ball milling the indium oxide and molecular sieve to obtain a tightly coupled SCR catalyst; The mass ratio of indium oxide to molecular sieve is 1:(1-20).

2. The catalyst according to claim 1, characterized in that The average pore size of the molecular sieve is not greater than 1 nm; The average particle size of the indium oxide is 2nm-50nm.

3. The method for preparing the close-coupled SCR catalyst according to any one of claims 1 to 2, characterized in that: The preparation method comprises: The indium precursor is dissolved in the reagent, and then the second metal element precursor is added to dissolve, the pH value of the dissolved solution is adjusted to 5-10, the solid-liquid separation, washing, drying, and roasting are performed to form indium oxide, and the indium oxide and the molecular sieve are ball-milled to obtain a tightly coupled SCR catalyst.

4. The preparation method according to claim 3, characterized in that: The reagents include deionized water and alcohol reagents; the alcohol reagents include one or more of methanol, ethanol, propanol, isopropanol, and ethylene glycol; The coordinating anions of the indium precursor include one or more of nitrate, hydrochloride, sulfate, selenite, and selenate; The second metal element precursor includes one or more of cerium nitrate, cerium acetate, cerium sulfate, niobium oxalate, and ammonium niobate oxalate hydrate.

5. The preparation method according to claim 4, characterized in that: Determine the molar ratio of the second metal element precursor to the indium precursor based on the molar ratio of the In element and the active element in the second metal element precursor according to the molecular formula of indium oxide; The active element is the Ce element in cerium nitrate, the Ce element in cerium acetate, the Ce element in cerium sulfate, the Nb element in niobium oxalate, and the Nb element in ammonium niobate oxalate hydrate.

6. The preparation method according to claim 3, characterized in that: The molar concentration of the indium precursor in the reagent is 0.1 mol / L-1 mol / L; When the pH value of the solution after adjustment is between 5 and 10, a mixed solution of an alkaline agent and ethanol is used, wherein the volume ratio of the alkaline agent to the ethanol is 1:1; After adjusting the pH value of the dissolved solution to 5-10, mix evenly and let stand.

7. The preparation method according to claim 6, characterized in that: The standing time is 1h-6h.

8. The preparation method according to claim 3, characterized in that: The specific method of washing is: washing with ethanol and deionized water in sequence until the washed substance is neutral; The drying temperature is 70°C-100°C; The calcination temperature is 500° C.-600° C., and the calcination time is 2 h-8 h.

9. The preparation method according to claim 3, characterized in that: The ball milling is dry milling or wet milling; During the dry grinding, the mass ratio of indium oxide to molecular sieve is 1:(1-20); During the dry grinding, the ball-to-material ratio is (2-6):1, the ball grinding time is 5min-20min, the rotation speed is 100r / min-200r / min, and the average particle size of the ball is 3mm-12mm; During the wet grinding, the mass ratio of indium oxide to molecular sieve is 1:(1-20), and deionized water is added during the wet grinding, and the mass of the added deionized water is 1 to 6 times the total mass of the indium oxide and the molecular sieve; During the wet grinding, the ball-to-material ratio is (2-6):1, the ball grinding time is 5 min-20 min, the rotation speed is 100 r / min-200 r / min, and the average particle size of the ball is 3 mm-12 mm.

10. Use of the close-coupled SCR catalyst according to any one of claims 1 to 2 to reduce hydrocarbon poisoning in a process of catalyzing nitrogen oxides.

Images