Nitrous oxide adsorption decomposition catalyst, method of making and catalyst structure

Abstract

The application relates to a preparation method of a nitrous oxide adsorption and decomposition catalyst, a preparation method and a catalyst structure, which comprises the following steps: adding a silicon source and an aluminum source into a lye, mixing and stirring to obtain an A solution; adding a crystal seed with a MOR topological structure into the A solution, stirring to obtain a B solution; placing the B solution into a high-pressure reaction kettle to perform reaction, drying the obtained product after washing to obtain a MOR molecular sieve; modifying the MOR molecular sieve through an inorganic cation to obtain a modified MOR molecular sieve; treating the modified MOR molecular sieve through an ion exchange method or an impregnation method to obtain a Fe-MOR molecular sieve; and treating the Fe-MOR molecular sieve through an impregnation method to obtain a M / Fe-MOR catalyst, wherein M is a noble metal. The application can solve the problems that the catalyst has a high activation temperature for N2O and the conversion rate efficiency of N2O catalytic decomposition into N2 and O2 is low in the prior art.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tail gas treatment catalysts, in particular to a nitrous oxide adsorption and decomposition catalyst, a preparation method and a catalyst structure. BACKGROUND

[0002] High air-fuel ratio diesel vehicles are the main source of NO x emissions. Whether it is the removal of NO x in diesel vehicle exhaust represented by NH3-SCR, or the technology of selective catalytic reduction of clean hydrogen gas (H2-SCR) NO x in recent years, a large amount of N2O will be produced, and at the same time, these two NO x removal technology routes cannot directly decompose N2O.

[0003] With the strengthening of automobile exhaust emission limits and the reduction of automobile exhaust temperature (150℃ challenge), N2O gas is contained in the exhaust of diesel engines during cold start, and a large amount of N2O is generated after the exhaust passes through the aftertreatment device. The host factory uses ammonia as fuel, which is mixed with diesel fuel for combustion. The ammonia-diesel engine reduces carbon emissions and reduces NO x emissions compared to pure diesel engines, but the formation of N2O is one of the main problems in ammonia combustion. For every 10% increase in ammonia mixing, the original N2O increases by 50ppm.

[0004] At present, the main methods for removing N2O are catalytic decomposition, thermal decomposition, reduction flame treatment, etc. Among them, the catalytic decomposition method directly catalytically decomposes N2O into N2 and O2 under the action of a catalyst. This method is simple to operate and has low operating costs, but the activation temperature is above 400℃, and the conversion efficiency of N2O catalytic decomposition into N2 and O2 is low. SUMMARY

[0005] The embodiments of the present application provide a nitrous oxide adsorption and decomposition catalyst, a preparation method and a catalyst structure to solve the problems of high activation temperature of the catalyst for N2O and low conversion efficiency of N2O catalytic decomposition into N2 and O2 in the related art.

[0006] In a first aspect, a preparation method of a nitrous oxide adsorption and decomposition catalyst is provided, which includes the following steps:

[0007] A silicon source and an aluminum source are added to a lye, mixed and stirred to obtain an A solution;

[0008] Seed crystals with a MOR topological structure are added to the A solution, and stirred to obtain a B solution;

[0009] The B solution is placed in a high-pressure reaction kettle for reaction, and the obtained product is washed and dried to obtain a MOR molecular sieve;

[0010] The MOR molecular sieve is modified by inorganic cations to obtain a modified MOR molecular sieve;

[0011] The modified MOR molecular sieve is treated by ion exchange or impregnation to obtain a Fe-MOR molecular sieve;

[0012] The Fe-MOR molecular sieve is treated by impregnation to obtain a M / Fe-MOR catalyst, wherein M is a noble metal.

[0013] In some embodiments, the alkali solution includes one or more of sodium hydroxide solution and potassium hydroxide solution.

[0014] In some embodiments, the mass fraction of the alkali solution is 40% to 70%.

[0015] In some embodiments, the molar ratio of the silicon source and the aluminum source is 6 to 18:1.

[0016] And / or, the silicon source includes one or more of silica sol, tetraethyl orthosilicate and methyl orthosilicate.

[0017] And / or, the aluminum source includes one or more of sodium aluminate, aluminum isopropoxide and aluminum nitrate.

[0018] And / or, the seed crystal includes one or more of natural mordenite and Y-type molecular sieve.

[0019] And / or, the mass of the seed crystal is 1% to 5% of the mass of the silicon source.

[0020] And / or, the reaction conditions in the high-pressure reaction kettle are: the reaction pressure is 0.9 MPa to 1.2 MPa, the reaction temperature is 80 to 120°C, and the reaction time is 12 to 36 hours.

[0021] And / or, the drying temperature is 60 to 100°C, and the drying time is 4 to 8 hours.

[0022] The inorganic cations include one or more of sodium ions Na + and calcium ions Ca 2+ .

[0023] And / or, the molar ratio of the ion source of the inorganic cations to the MOR molecular sieve is 1:10 to 20.

[0024] And / or, the MOR molecular sieve is modified by inorganic cations to obtain a modified MOR molecular sieve, including: adding the MOR molecular sieve to an ion source solution of inorganic cations, stirring and mixing, and freeze-drying to obtain a modified MOR molecular sieve, wherein the molar concentration of the ion source solution is 0.5 to 2 mol / L, and the freezing temperature is -25°C to -40°C.

[0025] The noble metal includes one or more of Rh, Ru, Pt and Pd.

[0026] In some embodiments, the modified MOR molecular sieve is treated by ion exchange method or impregnation method to obtain the Fe-MOR molecular sieve, specifically comprising the following steps:

[0027] The iron source and the modified MOR molecular sieve are dissolved in a solvent;

[0028] After stirring and mixing at room temperature, filtering and washing for several times, and drying at 60-80℃, the Fe-MOR molecular sieve is obtained.

[0029] In some embodiments, the iron source includes one or more of ferric chloride, ferric nitrate and ferric sulfate;

[0030] And / or, the solvent includes one or more of distilled water and deionized water;

[0031] And / or, the molar ratio of the iron source to the modified MOR molecular sieve is 1:10-20.

[0032] In some embodiments, the Fe-MOR molecular sieve is treated by impregnation method to obtain the M / Fe-MOR catalyst, specifically comprising the following steps:

[0033] The noble metal solution and the Fe-MOR molecular sieve are stirred and mixed at room temperature, and vacuum freeze-dried to obtain the M / Fe-MOR catalyst.

[0034] In some embodiments, the noble metal solution and the Fe-MOR molecular sieve are stirred and mixed for 4-6h;

[0035] And / or, the freezing temperature is-25℃ to-40℃;

[0036] And / or, the mass of the noble metal salt in the noble metal solution is 0.5%-4% of the mass of the Fe-MOR molecular sieve.

[0037] In the second aspect, a nitrous oxide adsorption and decomposition catalyst is provided, which is prepared by the preparation method of the nitrous oxide adsorption and decomposition catalyst according to any one of the above.

[0038] In the third aspect, a catalyst structure is provided, which includes the nitrous oxide adsorption and decomposition catalyst according to the above.

[0039] The technical scheme provided in the present application has the following beneficial effects:

[0040] The embodiment of the present application provides a nitrous oxide adsorption and decomposition catalyst, a preparation method and a catalyst structure, a MOR molecular sieve is prepared first, then inorganic cations are used for modifying the MOR molecular sieve, and the adsorption capacity of nitrous oxide N2O is greatly improved. Then, a Fe-based molecular sieve Fe-MOR molecular sieve is obtained through ion exchange or impregnation, and the Fe-based molecular sieve has a decomposition N2O activation temperature of 400 DEG C or above, and has poor low-temperature activity. Therefore, a noble metal M is continuously impregnated through the impregnation method, and the M / Fe-MOR catalyst obtained can be stored in the catalyst through the adsorption effect of the molecular sieve at a temperature of less than 200 DEG C, and has low-temperature activity starting from 200 DEG C, and the T90 temperature is 230 DEG C. It can be seen that the M / Fe-MOR catalyst not only improves the low-temperature activity of N2O decomposition and has high conversion efficiency, but also reduces the generation of N2O by doping Fe, thereby reducing the amount of noble metal, and greatly reducing the cost of the catalyst.

[0041] The present application can form a catalyst structure through a layered partition coating process with other types of molecular sieves, couple the N2O decomposition catalyst with other catalysts, and obtain a high-efficiency NO x decomposition catalyst. BRIEF DESCRIPTION OF DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0043] Figure 1 The MOR molecular sieve XRD diagram provided by the embodiment of the present application;

[0044] Figure 2 The M / Fe-MOR catalyst SEM diagram obtained by using the conventional drying process provided by the embodiment of the present application;

[0045] Figure 3 The M / Fe-MOR catalyst SEM diagram obtained by using the freeze-drying process provided by the embodiment of the present application;

[0046] Figure 4 The catalyst structure schematic diagram of a NH3-SCR system provided by the embodiment of the present application;

[0047] Figure 5 The catalyst structure schematic diagram of another NH3-SCR system provided by the embodiment of the present application;

[0048] Figure 6 The catalyst structure schematic diagram of a H2-SCR system provided by the embodiment of the present application;

[0049] Figure 7 Another H2-SCR system catalyst structure schematic diagram provided by the embodiment of the application.

[0050] In the figure: 1, DeN2O catalyst; 2, Fe-based molecular sieve; 3, Cu-based molecular sieve; 4, ASC catalyst; 5, H2-SCR catalyst. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical scheme and advantages of the embodiments of the application clearer, the technical scheme of the embodiments of the application will be described clearly and completely below in combination with the drawings in the embodiments of the application. Obviously, the described embodiments are part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the application.

[0052] The embodiment of the application provides a preparation method of a nitrous oxide adsorption and decomposition catalyst, which comprises the following steps:

[0053] 101: A silicon source and an aluminum source are added into a lye, mixed and stirred to obtain an A solution.

[0054] The lye has two functions, one is to dissolve the aluminum source and the silicon source, and the other is to provide an alkaline environment for preparing the MOR type molecular sieve.

[0055] The lye has multiple choices, which can be determined according to actual needs. For example, the lye comprises one or more of sodium hydroxide solution and potassium hydroxide.

[0056] The concentration of the lye also has multiple choices, which can be determined according to actual needs. For example, the mass fraction of the lye is 40% to 70%.

[0057] The addition amount of the silicon source and the aluminum source also has multiple choices, which can be determined according to actual needs. For example, the molar ratio of the silicon source to the aluminum source is 6 to 18:1.

[0058] The nucleation and growth of the zeolite molecular sieve crystal are directly carried out in the solution. The silicon source and the aluminum source generate active species silicoaluminate ions in the solution, then condensation occurs, the structure unit required by the zeolite molecular sieve is slowly formed, and then the zeolite molecular sieve is further generated. A certain crystal type of molecular sieve has a certain pore structure and a silicon-aluminum ratio, but if the silicon-aluminum ratio exceeds the range or the synthesis conditions change, the crystal type will be affected, and the desired MOR molecular sieve cannot be obtained. Therefore, if the silicon-aluminum ratio is not in the range of 6 to 18:1, different crystal types of molecular sieves will be obtained.

[0059] The silicon source also has multiple choices, which can be determined according to actual needs, such as, as an example, the silicon source includes one or more of silica sol, tetraethyl orthosilicate Si (OC2H5) 4 and tetramethyl orthosilicate Si (OCH3) 4. Among them, in the silica sol, the mass fraction of SiO2 is 40%.

[0060] The aluminum source also has multiple choices, which can be determined according to actual needs, such as, as an example, the aluminum source includes one or more of aluminum triisopropoxide Al (i-OC3H7) 3, sodium aluminate NaAlO2 and aluminum nitrate Al (NO3) 3.

[0061] 102: Add seeds with MOR topological structure to the A solution, stir to obtain a B solution.

[0062] From the perspective of synthesis principle, adding seeds can shorten the required time for synthesis, and also improve the selectivity of the target crystal phase (such as the molecular sieve of MOR crystal form required in the present application), avoiding the generation of impurities.

[0063] The seeds have multiple choices, which can be determined according to actual needs, such as, as an example, the seeds include one or more of natural mordenite and Y-type molecular sieve; both the natural mordenite and the Y-type molecular sieve need to have MOR topological structure.

[0064] The amount of seeds added can also be determined according to actual needs, such as, as an example, the mass of the seeds is 1% to 5% of the mass of the silicon source; when it is lower than 1%, the seeds are difficult to function (shorten the time and improve the selectivity of the target crystal form), and when it is higher than 5%, the improvement is not great, which will waste the seeds and increase the cost.

[0065] 103: Put the B solution into a high-pressure reaction kettle for reaction, wash and dry the obtained product to obtain a MOR molecular sieve. Figure 1 It can also be confirmed from the MOR molecular sieve that the molecular sieve is of MOR crystal form.

[0066] The reaction conditions in the high-pressure reaction kettle are as follows: the reaction pressure is 0.9 MPa to 1.2 MPa, the reaction temperature is 80 to 120℃, the reaction time is 12 to 36 h; the drying temperature is 60 to 100℃, and the drying time is 4 to 8 h;

[0067] 104: Modify the MOR molecular sieve by inorganic cations to obtain a modified MOR molecular sieve.

[0068] Specifically, step 104 includes the following steps:

[0069] The MOR molecular sieve was added to an inorganic cation source solution, stirred and mixed, and then freeze-dried to obtain a modified MOR molecular sieve. The molar concentration of the ion source solution was 1 mol / L, and the freezing temperature was -25℃ to -40℃.

[0070] The inorganic cations include sodium ions (Na). + and calcium ions Ca 2+ One or more of the following; sodium ions (Na) + It can exist in the form of NaCl, calcium ions Ca 2+ It can exist in the form of CaCl2.

[0071] The molar ratio of the inorganic cation source to the MOR molecular sieve is 1:10 to 20.

[0072] Step 104 modifies the MOR molecular sieve using inorganic cations, which greatly improves the adsorption capacity of nitrous oxide (N₂O).

[0073] The saturated adsorption capacity of nitrous oxide by modified MOR molecular sieves was tested using a fluidized bed reactor. The results showed that:

[0074] The saturated adsorption capacity of the unmodified MOR molecular sieve is 0.2 mmol / g.

[0075] Calcium ions (Ca) 2+ The modified MOR molecular sieve has a saturated adsorption capacity of 0.36 mmol / g.

[0076] Sodium ion Na + The modified MOR molecular sieve has a saturated adsorption capacity of 0.27 mmol / g.

[0077] Compared to unmodified MOR molecular sieves, the saturated adsorption capacity is significantly improved.

[0078] This is due to calcium ions (Ca). 2+ and sodium ions Na + The interaction between the molecular sieve and the molecular sieve framework determines the cyclic strength of the molecular sieve (that is, the degree of change in the length of chemical bonds), which in turn determines the adsorption capacity of N2O.

[0079] 105: The modified MOR molecular sieve is treated by ion exchange or impregnation to obtain Fe-MOR molecular sieve.

[0080] In step 105, Fe is loaded onto the modified MOR molecular sieve via ion exchange or impregnation, in the treatment of NO. x In the process, compared with Cu-based molecular sieves, Fe-based molecular sieves can reduce the generation of the byproduct N2O. At the same time, Fe-based molecular sieves can decompose a portion of N2O at temperatures above 400℃.

[0081] Step 105 specifically includes the following steps:

[0082] The iron source and the modified MOR molecular sieve are dissolved in a solvent;

[0083] At room temperature, the mixture is stirred, filtered, and washed several times, and then dried at 60℃~80℃ to obtain Fe-MOR molecular sieve.

[0084] The iron source includes one or more of ferric chloride, ferric nitrate and ferric sulfate;

[0085] The solvent includes one or more of distilled water and deionized water;

[0086] The molar ratio of the iron source to the modified MOR molecular sieve is 1:10 to 20.

[0087] 106: The Fe-MOR molecular sieve is treated by impregnation to obtain M / Fe-MOR catalyst, which is denoted as DeN2O catalyst, where M is a noble metal.

[0088] Step 106 specifically includes the following steps:

[0089] At room temperature, the noble metal solution is stirred and mixed with the Fe-MOR molecular sieve for 4 to 6 hours, and then freeze-dried under vacuum at a temperature of -25°C to -40°C to obtain the M / Fe-MOR catalyst.

[0090] Freeze-drying can uniformly disperse precious metals in the molecular sieve framework. In conventional drying, precious metal ions migrate with the evaporation of water, leading to agglomeration of precious metals, which ultimately affects the activity of the catalyst.

[0091] See Figure 2 As shown, Figure 2 The conventional drying process was used, and it was clearly visible that multiple agglomerations occurred.

[0092] See Figure 3 As shown, Figure 3 The freeze-drying process was used, and it was clearly observed that no agglomeration occurred, and the precious metals were uniformly dispersed in the molecular sieve framework.

[0093] The precious metals include one or more of Rh, Ru, Pt, and Pd. The precious metals may exist in the form of precious metal salts, such as rhodium sulfate, ruthenium chloride, platinum nitrate, platinum acetate, palladium sulfate, and palladium nitrate.

[0094] The mass of the noble metal salt in the noble metal solution is 0.5% to 4% of the mass of the Fe-MOR molecular sieve. When the mass of the noble metal salt is less than 0.5%, the catalyst usage is insufficient to meet the catalytic demand, and when the mass of the noble metal salt is more than 4%, the noble metal is prone to agglomeration, thereby affecting the catalytic activity.

[0095] In the embodiment of the application, the MOR molecular sieve is first prepared, and then the MOR molecular sieve is modified by using inorganic cations, thereby greatly improving the adsorption capacity of dinitrogen monoxide N2O. Then, the Fe-based molecular sieve Fe-MOR molecular sieve is obtained by ion exchange or impregnation, and the Fe-based molecular sieve has a decomposition N2O activation temperature of 400℃ or higher and poor low-temperature activity. Therefore, the noble metal M is further impregnated by using the impregnation method to obtain the M / Fe-MOR catalyst, which can be stored in the catalyst by the adsorption of the molecular sieve at a temperature of less than 200℃, and has low-temperature activity starting from 200℃, and the T90 temperature is 230℃. It can be seen that the M / Fe-MOR catalyst not only improves the low-temperature activity of N2O decomposition and has high conversion efficiency, but also reduces the generation of N2O by Fe doping, thereby reducing the usage of noble metals and greatly reducing the cost of the catalyst.

[0096] In summary, the M / Fe-MOR catalyst of the application integrates the functions of N2O adsorption, high-temperature N2O decomposition, and low-temperature noble metal N2O decomposition, thereby greatly reducing the emission of N2O.

[0097] The embodiment of the application also provides a dinitrogen monoxide adsorption and decomposition catalyst prepared by using the preparation method of the dinitrogen monoxide adsorption and decomposition catalyst.

[0098] The embodiment of the application also provides a catalyst structure comprising the dinitrogen monoxide adsorption and decomposition catalyst.

[0099] Specifically, the catalyst structure of the application has various forms.

[0100] For example, as an example, the catalyst structure of the application is a catalyst structure of an NH3-SCR system.

[0101] Reference is made to Figure 4As shown, the catalyst structure of the NH3-SCR system is layered and zoned coating. The first layer is the nitrogen dioxide adsorption and decomposition catalyst of the application, that is, DeN2O catalyst 1, which can adsorb N2O at low temperature and directly decompose at the active temperature, with a decomposition efficiency of 100%. The second layer and the third layer are first zoned and then layered and zoned coating. Specifically, there are Fe-based molecular sieve 2 and two regions of Cu-based molecular sieve 3 on the DeN2O catalyst 1, and the Fe-based molecular sieve 2, the Cu-based molecular sieve 3 and the Cu-based molecular sieve 3 are sequentially distributed from one end of the DeN2O catalyst 1 to the other end, and the ASC catalyst 4 is coated on the Cu-based molecular sieve 3 at the edge. The Fe-based molecular sieve 2 can treat NO x while reducing N2O generation, but the active temperature is relatively high, so the zoned coating of the Cu-based molecular sieve 3 improves the low-temperature activity. In addition, the ASC catalyst 4 oxidizes the ammonia that is not completely reacted, and further treats the NO x after ammonia oxidation by the Cu-based molecular sieve 3, and finally decomposes N2O by the first layer of DeN2O catalyst 1. The ASC catalyst 4 is a Pt noble metal supported on a metal oxide, wherein the metal oxide specifically refers to a composite oxide composed of one or more than two combinations of cobalt oxide, aluminum oxide, silicon oxide, cerium oxide, and zirconium oxide. Preferably, the composite oxide is composed of one or more than two combinations of aluminum oxide, cerium oxide, and zirconium oxide.

[0102] Referring to Figure 5 As shown, the catalyst structure of the NH3-SCR system is layered and zoned coating. The first layer is the nitrogen dioxide adsorption and decomposition catalyst of the application, that is, DeN2O catalyst 1, which can adsorb N2O at low temperature and directly decompose at the active temperature, with a decomposition efficiency of 100%. The second layer and the third layer are first zoned and then layered and zoned coating. Specifically, there are Fe-based molecular sieve 2 and two regions of Cu-based molecular sieve 3 on the DeN2O catalyst 1, and the Fe-based molecular sieve 2, the Cu-based molecular sieve 3 and the Cu-based molecular sieve 3 are sequentially distributed from one end of the DeN2O catalyst 1 to the other end, and the ASC catalyst 4 is coated on the Cu-based molecular sieve 3 at the edge. The Fe-based molecular sieve 2 can treat NO x while reducing N2O generation, but the active temperature is relatively high, so the zoned coating of the Cu-based molecular sieve 3 improves the low-temperature activity. In addition, the ASC catalyst 4 oxidizes the ammonia that is not completely reacted, and further treats the NO x after ammonia oxidation by the Cu-based molecular sieve 3, and finally decomposes N2O by the first layer of DeN2O catalyst 1. The ASC catalyst 4 is a Pt noble metal supported on a metal oxide, wherein the metal oxide specifically refers to a composite oxide composed of one or more than two combinations of cobalt oxide, aluminum oxide, silicon oxide, cerium oxide, and zirconium oxide. Preferably, the composite oxide is composed of one or more than two combinations of aluminum oxide, cerium oxide, and zirconium oxide.

[0103] For another example, the catalyst structure of the application is the catalyst structure of the H2-SCR system.

[0104] Referring to Figure 6 As shown in the figure, the catalyst structure of the H2-SCR system is layered coating, the first layer is the nitrogen monoxide adsorption and decomposition catalyst of the application, that is, DeN2O catalyst 1, which can adsorb N2O at low temperature and directly decompose after reaching the active temperature, with a decomposition efficiency of 100%. The second layer is H2-SCR catalyst 5 coated on the DeN2O catalyst 1, mainly composed of noble metal supported metal oxide. The noble metal is one or several of Pt, Pd, Ru and Ir. The metal oxide is one or a combination of two or more of titanium dioxide, zirconium dioxide, tin dioxide, silicon dioxide, aluminum oxide and cerium dioxide. The loading method is one of coprecipitation, impregnation and sol-gel.

[0105] Referring to Figure 7 As shown in the figure, the catalyst structure of the H2-SCR system is layered coating, the first layer is the nitrogen monoxide adsorption and decomposition catalyst of the application, that is, DeN2O catalyst 1, which can adsorb N2O at low temperature and directly decompose after reaching the active temperature, with a decomposition efficiency of 100%. The second layer is H2-SCR catalyst 5 coated on the DeN2O catalyst 1, mainly composed of noble metal supported metal oxide. The noble metal is one or several of Pt, Pd, Ru and Ir. The metal oxide is one or a combination of two or more of titanium dioxide, zirconium dioxide, tin dioxide, silicon dioxide, aluminum oxide and cerium dioxide. The loading method is one of coprecipitation, impregnation and sol-gel.

[0106] Example 1

[0107] A preparation method of a nitrogen monoxide adsorption and decomposition catalyst, comprising the following steps:

[0108] 101: Add a silicon source and an aluminum source to a lye, mix and stir to obtain an A solution.

[0109] The lye is a sodium hydroxide solution.

[0110] The mass fraction of the sodium hydroxide solution is 40%.

[0111] The molar ratio of the silicon source to the aluminum source is 6:1.

[0112] The silicon source is silica sol.

[0113] The aluminum source is aluminum triisopropylate.

[0114] 102: Add a seed crystal with MOR topological structure to the A solution and stir to obtain a B solution.

[0115] The seed crystal is natural mordenite.

[0116] The mass of the seed crystal is 1% of the mass of the silicon source;

[0117] 103: The B solution is placed in a high-pressure reaction kettle for reaction, and the obtained product is washed and dried to obtain a MOR molecular sieve.

[0118] The reaction conditions in the high-pressure reaction kettle are as follows: the reaction pressure is 0.9 MPa, the reaction temperature is 80°C, and the reaction time is 12 h; the drying temperature is 60°C, and the drying time is 4 h;

[0119] 104: The MOR molecular sieve is modified by an inorganic cation to obtain a modified MOR molecular sieve.

[0120] Specifically, step 104 includes the following steps:

[0121] The MOR molecular sieve is added to an ion source solution of an inorganic cation, stirred and mixed, and freeze-dried to obtain a modified MOR molecular sieve, wherein the molar concentration of the ion source solution is 1 mol / L, and the freezing temperature is -25°C.

[0122] The inorganic cation is calcium ion Ca 2+ ; and the ion source is calcium chloride.

[0123] The molar ratio of the ion source of the inorganic cation to the MOR molecular sieve is 1:10.

[0124] The modified MOR molecular sieve is tested for the adsorption capacity of saturated laughing gas by using a fluidized bed, and the adsorption capacity of the Ca-modified MOR molecular sieve is 0.36 mmol / g.

[0125] 105: The modified MOR molecular sieve is treated by ion exchange or impregnation to obtain a Fe-MOR molecular sieve.

[0126] Specifically, step 105 includes the following steps:

[0127] The iron source and the modified MOR molecular sieve are dissolved in a solvent.

[0128] At room temperature, the mixture is stirred, filtered and washed several times, and then dried at 60°C to obtain a Fe-MOR molecular sieve.

[0129] The iron source is ferric chloride;

[0130] The solvent is distilled water;

[0131] The molar ratio of the iron source to the modified MOR molecular sieve is 1:10.

[0132] 106: treating the Fe-MOR molecular sieve by the impregnation method to obtain a M / Fe-MOR catalyst, and denoted as DeN2O catalyst, wherein M is a noble metal.

[0133] The step 106 specifically comprises the following steps:

[0134] The noble metal solution is mixed with the Fe-MOR molecular sieve by stirring at room temperature for 4-6 h, and vacuum freeze-drying is performed at a freezing temperature of -25°C to obtain the M / Fe-MOR catalyst.

[0135] The noble metal is Rh.

[0136] The mass of the noble metal salt in the noble metal solution is 0.5% of the mass of the Fe-MOR molecular sieve.

[0137] The Fe-based molecular sieve has a decomposition N2O activation temperature of 400°C or higher, and has poor low-temperature activity. The Rh / Fe-MOR catalyst obtained by the impregnation method has low-temperature activity starting at 200°C, and the T90 temperature is 230°C. This new catalyst not only improves the low-temperature activity of N2O decomposition, but also greatly reduces the cost of the catalyst.

[0138] The Rh / Fe-MOR catalyst prepared above is used to design the catalyst structure of an NH3-SCR system, and the catalyst structure of the NH3-SCR system is a layered and zoned coating, as shown in Figure 4 The first layer is the Rh / Fe-MOR catalyst, i.e., the DeN2O catalyst 1, which can adsorb N2O at low temperature during cold start and directly decompose after reaching the active temperature, with an efficiency of 95% or higher. The second and third layers are zoned and then layered and zoned coating, and the specific operation is that the Rh / Fe-MOR catalyst is coated with a Fe-SSZ13 molecular sieve catalyst, i.e., a Fe-based molecular sieve 2, in the front 40% region, a Cu-SSZ13 molecular sieve catalyst, i.e., a Cu-based molecular sieve 3, in the middle 40% region, and a Cu-SSZ13 molecular sieve catalyst, i.e., a Cu-based molecular sieve 3, in the second layer in the rear 20% region, and a Pt / Al2O3 molecular sieve catalyst, i.e., an ASC catalyst 4, in the third layer.

[0139] Example 2

[0140] A preparation method of a dinitrogen monoxide adsorption and decomposition catalyst, comprising the following steps:

[0141] 101: adding a silicon source and an aluminum source into a lye, and mixing and stirring to obtain an A solution.

[0142] The lye is a sodium hydroxide solution.

[0143] The mass fraction of the sodium hydroxide solution is 70%.

[0144] The molar ratio of the silicon source and the aluminum source is 18:1.

[0145] The silicon source is a silica sol.

[0146] The aluminum source is aluminum triisopropoxide.

[0147] 102: Seed crystals with MOR topology are added to the A solution, and stirring is performed to obtain a B solution.

[0148] The seed crystals are natural mordenite.

[0149] The mass of the seed crystals is 5% of the mass of the silicon source.

[0150] 103: The B solution is placed in a high-pressure reaction kettle for reaction, and the obtained product is washed and dried to obtain a MOR molecular sieve.

[0151] The reaction conditions in the high-pressure reaction kettle are as follows: the reaction pressure is 1.2 MPa, the reaction temperature is 120 DEG C, the reaction time is 36 h, the drying temperature is 100 DEG C, and the drying time is 8 h.

[0152] 104: The MOR molecular sieve is modified by an inorganic cation to obtain a modified MOR molecular sieve.

[0153] Specifically, step 104 includes the following steps:

[0154] The MOR molecular sieve is added to an ion source solution of an inorganic cation, stirring is performed, and freeze-drying is performed to obtain a modified MOR molecular sieve, wherein the molar concentration of the ion source solution is 1 mol / L, and the freezing temperature is -40 DEG C.

[0155] The inorganic cation is calcium ion Ca 2+ ; and the ion source is calcium chloride.

[0156] The molar ratio of the ion source of the inorganic cation to the MOR molecular sieve is 1:20.

[0157] The modified MOR molecular sieve is tested for the laughing gas saturation adsorption capacity by using a flow bed, and the saturation adsorption capacity of the Ca-modified MOR molecular sieve is 0.36 mmol / g.

[0158] 105: The modified MOR molecular sieve is treated by an ion exchange method or an impregnation method to obtain a Fe-MOR molecular sieve.

[0159] Specifically, step 105 includes the following steps:

[0160] An iron source and the modified MOR molecular sieve are dissolved in a solvent.

[0161] After stirring and mixing at room temperature, filtering and washing several times, and drying at 80℃, the Fe-MOR molecular sieve is obtained.

[0162] The iron source is ferric chloride;

[0163] The solvent is distilled water;

[0164] The molar ratio of the iron source to the modified MOR molecular sieve is 1:20.

[0165] 106: The Fe-MOR molecular sieve is treated by an impregnation method to obtain an M / Fe-MOR catalyst, denoted as a DeN2O catalyst, wherein M is a noble metal.

[0166] The step 106 specifically includes the following steps:

[0167] The noble metal solution and the Fe-MOR molecular sieve are stirred and mixed at room temperature for 6h, and vacuum freeze-drying is performed at a freezing temperature of -40℃ to obtain the M / Fe-MOR catalyst.

[0168] The noble metal is Rh.

[0169] The mass of the noble metal salt in the noble metal solution is 4% of the mass of the Fe-MOR molecular sieve.

[0170] The Fe-based molecular sieve has a decomposition N2O activation temperature of above 400℃, and has poor low-temperature activity. The Rh / Fe-MOR catalyst obtained by the impregnation method has low-temperature activity starting at 200℃, and the T90 temperature is 230℃. This new type of catalyst not only improves the low-temperature activity of N2O decomposition, but also greatly reduces the cost of the catalyst.

[0171] The Rh / Fe-MOR catalyst prepared above is used to design the catalyst structure of an NH3-SCR system, which is coated in layers and zones, as shown in Figure 5 The first layer is the Rh / Fe-MOR catalyst, i.e., the DeN2O catalyst 1, which can adsorb N2O at low temperature during cold start and directly decompose after reaching the active temperature, with an efficiency of above 95%. The second layer is coated with a Fe-SSZ13 molecular sieve catalyst, i.e., a Fe-based molecular sieve 2. The third layer is coated with a Cu-SSZ13 molecular sieve catalyst, i.e., a Cu-based molecular sieve 3, in the front 80% area, and a Pt / Al2O3 molecular sieve catalyst, i.e., an ASC catalyst 4, in the rear 20% area.

[0172] The catalyst structure of the NH3-SCR system prepared in the above embodiment 1 and embodiment 2 is tested, and the test conditions and test results are shown as follows.

[0173] SGB small sample test conditions:

[0174] 1. Inlet side atmosphere 1: NO 500ppm, N20 20ppm, C3H6 100ppm, CO 300ppm, H20 10%, O210%.

[0175] 2. Inlet side atmosphere 2: NO 500ppm, N20 200ppm, C3H6 100ppm, CO 300ppm, H20 10%, O210%.

[0176] 3. Inlet side space velocity: 30000 / h.

[0177] 4. Outlet side detection: N20 amount, NH3 amount, NOx amount.

[0178] 5. Test temperature group 1: 100C, 200C, 230C, 400C, 500C, 600C.

[0179] Among them, the conversion efficiency is calculated by using in-situ infrared test of gas concentration before and after conversion.

[0180]

[0181] In the above formula, X N2O is the conversion efficiency of N20, [N20] inlet is the concentration of N20 before conversion, [N20] outlet is the concentration of N20 after conversion.

[0182] Table 1

[0183]

[0184] From the above data, at 100C, the N20 conversion efficiency has reached more than 83%, and at 200C, the N20 conversion efficiency has reached more than 90%, so it can be seen that the present application has very high low-temperature activity and conversion efficiency.

[0185] And at 400C, the N20 conversion efficiency has reached 98%, which shows that at high temperature, Fe-based molecular sieve 2, Cu-based molecular sieve 3 and ASC catalyst 4 also participate in N20 conversion.

[0186] For example 1, at high temperature, Fe-based molecular sieve 2 can treat NO x while reducing N20 generation, ASC catalyst 4 oxidizes ammonia that is not completely reacted, and further treats the ammonia-oxidized NO x by Cu-based molecular sieve 3, and finally decomposes N20 by the first layer of DeN20 catalyst 1.

[0187] For Example 2, the Fe-based molecular sieve 2 can treat NO at high temperature x while reducing N2O generation, the ASC catalyst 4 oxidizes the incompletely reacted ammonia and further treats the ammonia-oxidized NO by the Fe-based molecular sieve 2 x and finally decomposes N2O by the first layer of DeN2O catalyst.

[0188] In the description of the present application, it should be noted that the terms "upper", "lower", and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, and it can be the internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0189] It should be noted that in the present application, relational terms such as "first" and "second" and the like are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or device. Without more limitations, the element defined by the statement "including a" does not exclude the presence of another identical element in the process, method, article or device including the element.

[0190] The above is only a specific embodiment of the present application, which enables those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features applied herein.

Claims

1. A method for preparing a nitrous oxide adsorption-decomposition catalyst, characterized in that, It includes the following steps: Add silicon source and aluminum source to alkaline solution, mix and stir to obtain solution A; Add seed crystals with a MOR topological structure to solution A, stir, and obtain solution B; The B solution was placed in a high-pressure reactor for reaction, and the resulting product was washed and dried to obtain MOR molecular sieve. The MOR molecular sieve was modified by inorganic cations to obtain a modified MOR molecular sieve. The modified MOR molecular sieve is treated by ion exchange or impregnation to obtain Fe-MOR molecular sieve. The Fe-MOR molecular sieve was treated by impregnation to obtain an M / Fe-MOR catalyst, wherein M is a noble metal; The inorganic cation is calcium ion (Ca). 2+ Or calcium ions (Ca) 2+ and sodium ions Na + .

2. The method for preparing the nitrous oxide adsorption and decomposition catalyst according to claim 1, characterized in that: The alkaline solution includes one or more of sodium hydroxide solution and potassium hydroxide solution.

3. The method for preparing the nitrous oxide adsorption and decomposition catalyst as described in claim 2, characterized in that: The mass fraction of the alkaline solution is 40% to 70%.

4. The preparation method of the nitrous oxide adsorption and decomposition catalyst according to claim 1, characterized in that: The molar ratio of the silicon source to the aluminum source is 6~18:1; And / or, the silicon source includes one or more of silica sol, tetraethyl orthosilicate and methyl orthosilicate; And / or, the aluminum source includes one or more of sodium aluminate, aluminum triisopropoxide, and aluminum nitrate; And / or, the seed crystals include one or more of natural mordenite and Y-type molecular sieves; And / or, the mass of the seed crystal is 1% to 5% of the mass of the silicon source; And / or, the reaction conditions in the high-pressure reactor are: reaction pressure of 0.9 MPa to 1.2 MPa, reaction temperature of 80 to 120°C, and reaction time of 12 to 36 h; And / or, the drying temperature is 60~100℃, and the drying time is 4~8h; And / or, the molar ratio of the ion source of the inorganic cation to the MOR molecular sieve is 1:10~20; And / or, modifying the MOR molecular sieve with inorganic cations to obtain modified MOR molecular sieve, comprising: adding the MOR molecular sieve to an ion source solution of inorganic cations, stirring and mixing, and freeze-drying to obtain modified MOR molecular sieve, wherein the molar concentration of the ion source solution is 0.5~2 mol / L, and the freezing temperature is -25℃~-40℃; The precious metals include one or more of Rh, Ru, Pt and Pd.

5. The method for preparing the nitrous oxide adsorption and decomposition catalyst according to claim 1, characterized in that, The modified MOR molecular sieve is treated by ion exchange or impregnation to obtain Fe-MOR molecular sieve, specifically including the following steps: The iron source and the modified MOR molecular sieve are dissolved in a solvent; At room temperature, the mixture is stirred, filtered, and washed several times, and then dried at 60℃~80℃ to obtain Fe-MOR molecular sieve.

6. The method for preparing the nitrous oxide adsorption and decomposition catalyst as described in claim 5, characterized in that: The iron source includes one or more of ferric chloride, ferric nitrate and ferric sulfate; And / or, the solvent includes one or more of distilled water and deionized water; And / or, the molar ratio of the iron source to the modified MOR molecular sieve is 1:10~20.

7. The method for preparing the nitrous oxide adsorption and decomposition catalyst according to claim 1, characterized in that, The Fe-MOR molecular sieve is treated by impregnation to obtain the M / Fe-MOR catalyst, specifically including the following steps: At room temperature, the noble metal solution is stirred and mixed with the Fe-MOR molecular sieve, and then freeze-dried under vacuum to obtain the M / Fe-MOR catalyst.

8. The method for preparing the nitrous oxide adsorption and decomposition catalyst as described in claim 7, characterized in that: The noble metal solution was stirred and mixed with the Fe-MOR molecular sieve for 4-6 hours; And / or, the freezing temperature is -25℃ to -40℃; And / or, the mass of the noble metal salt in the noble metal solution is 0.5% to 4% of the mass of the Fe-MOR molecular sieve.

9. A nitrous oxide adsorption-decomposition catalyst, characterized in that: It is prepared by the method for preparing the nitrous oxide adsorption decomposition catalyst as described in any one of claims 1 to 8.

10. A catalyst structure, characterized in that: It includes the nitrous oxide adsorption and decomposition catalyst as described in claim 9.

Images