Manganese-based catalyst for purifying exhaust gas of motor vehicle, and preparation method and application thereof

Abstract

The application relates to the field of motor vehicle exhaust treatment, in particular to a manganese-based catalyst for motor vehicle exhaust purification and a preparation method and application thereof, the preparation method comprising the following steps: S1, mixing a transition metal salt with a manganese-based active phase, carrying out ultrasonic chemical precipitation treatment, washing and drying to obtain a precursor; and S2, calcining the obtained precursor at 300-800 DEG C to obtain a manganese-based catalyst containing a transition metal oxide. The manganese-based catalyst is prepared by using an ultrasonic chemical precipitation method to prepare a precursor, and the catalyst obtained after calcination, and the transition metal oxide is uniformly precipitated around the manganese-based active phase. The crystal lattices of the two are adapted, a large amount of inert crystal lattice oxygen can be converted into active crystal lattice oxygen, high-efficiency CO and HC oxidation can be realized at low temperature, a large amount of adjacent oxygen vacancies generated after the oxidation can realize high-selectivity reduction of NO into N2 at low temperature, and the reaction path of NO is accurately controlled.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of motor vehicle exhaust treatment, in particular to a manganese-based catalyst for motor vehicle exhaust purification and a preparation method and application thereof. BACKGROUND

[0002] In the foreseeable future, internal combustion engines will still be one of the main modes of transportation. However, nitrogen oxides (NO), carbon monoxide (CO) and hydrocarbons (HC) emitted by internal combustion engines can cause human respiratory and nervous system diseases, which has prompted a continuous increase in demand for high-performance three-way catalysts. Currently commercially available three-way catalysts mainly include the following two types:

[0003] 1) noble metal-based catalysts, noble metal active sites mainly act as adsorption and activation centers for O2, CO and NO, however, this mechanism has a trade-off between CO / HC oxidation rate and NO reduction rate, and N2O is easily generated under low temperature conditions. To solve this limitation, it is usually necessary to increase the reaction temperature to increase the turnover frequency of individual active sites, but this results in poor performance of most commercial three-way catalysts below 350℃.

[0004] 2) transition metal-based catalysts, the oxidation process thereof uses lattice oxygen as the oxidation site for HC / CO, and the oxygen vacancies generated after the reaction can act as adsorption and activation sites for NO, and the lattice oxygen is regenerated through the oxidation process. This cyclic evolution process effectively avoids the competition between HC / CO oxidation and NO reduction. However, this process largely depends on the activity of lattice oxygen under low temperature conditions.

[0005] Currently, research on the activation of lattice oxygen under low temperature conditions has been widely carried out, mainly through strategies such as metal doping and surface loading. However, due to the lack of precise control of lattice oxygen activation, the formation structure of oxygen vacancies and the diversification of NO adsorption and conversion paths, it still faces challenges for transition metal-based three-way catalysts to achieve high selectivity for NO reduction at low temperatures. Under normal circumstances, when a single NO molecule is adsorbed on an isolated oxygen vacancy on a transition metal oxide, it can couple with NO in the gas phase through the N≡N bond to form N2O, which is the least desirable but most likely result. In addition, the adsorbed NO can also be oxidized to NO2 by adjacent lattice oxygen, deviating from the expected behavior.

[0006] Therefore, it is necessary to provide a technical solution to solve the above problems. SUMMARY

[0007] One of the purposes of the present application is to provide a preparation method of a manganese-based catalyst for motor vehicle exhaust purification to solve the problem that current transition metal three-way catalysts cannot regulate the reaction path of NO, and the result of NO reduction often deviates from the expectation, in view of the deficiencies of the prior art.

[0008] To achieve the above object, the present application adopts the following technical solutions:

[0009] A preparation method of a manganese-based catalyst for motor vehicle exhaust purification, comprising the following steps:

[0010] S1, mixing a transition metal salt with a manganese-based active phase, treating by ultrasonic chemical precipitation method, washing, and drying to obtain a precursor;

[0011] S2, calcining the precursor obtained in step S1 at 300-800 ℃ to obtain a manganese-based catalyst containing transition metal oxides.

[0012] Preferably, the manganese-based active phase is at least one of MnO2, Mn2O3, and Mn3O4; and the transition metal salt is selected from one or more of soluble cobalt salt, soluble germanium salt, soluble copper salt, soluble nickel salt, and soluble iron salt.

[0013] Preferably, the mass of the transition metal oxides is 5%-60% of the mass of the manganese-based catalyst.

[0014] Preferably, in step S1, the treatment step of the ultrasonic chemical precipitation method is: under ultrasonic conditions, adding a precipitant until the pH value of the system is 9-12; then continuing ultrasonic treatment, washing, and drying to obtain the precursor.

[0015] Preferably, in step S1, the preparation step of the manganese-based active phase is: calcining a manganese source and dispersing it in a solvent together with a dispersant, ultrasonic treatment in an ice water bath, washing, and drying to obtain the manganese-based active phase.

[0016] Preferably, the manganese source is manganese carbonate; the dispersant is polyvinylpyrrolidone; and the mass ratio of the manganese-based active phase to the dispersant is (1-50):1.

[0017] Preferably, it further comprises loading the manganese-based catalyst containing transition metal oxides obtained in step S2 into a carrier to obtain a monolithic manganese-based catalyst.

[0018] Preferably, the carrier is a honeycomb ceramic with pores; and the loading step is:

[0019] S3, adding the etched honeycomb ceramic into an aqueous solution containing a binder to obtain a carrier mixture;

[0020] S4, dispersing the manganese-based catalyst containing transition metal oxides into the carrier mixture, stirring and soaking, drying, and calcining to obtain the monolithic manganese-based catalyst.

[0021] Preferably, in step S4, the soaking time is 10-14 hours, and the calcination temperature is 300-800℃; after step S4, the step is repeated to increase the loading, and the number of repetitions is 1-5 times.

[0022] The second object of the present application is to provide a manganese-based catalyst for purifying exhaust gas of a motor vehicle, which is prepared by the method for preparing a manganese-based catalyst for purifying exhaust gas of a motor vehicle.

[0023] The manganese-based catalyst of the present application is prepared by an ultrasonic chemical precipitation method, and the transition metal oxide in the catalyst is uniformly deposited around the manganese-based active phase. The transition metal oxide of this structure can adapt to the crystal lattice of the manganese-based active phase, can promote the tensile strain of the manganese-based active phase at the phase boundary, and further promote the transfer of electrons from the transition metal oxide to the manganese-based active phase, thereby converting a large amount of inert lattice oxygen into active lattice oxygen, so as to realize efficient oxidation of CO, HC (such as C3H6, C3H8, etc.) at low temperature. After the oxidation and combustion of CO and HC, a large number of adjacent oxygen vacancies are generated in the manganese-based active phase. Unlike isolated oxygen vacancies, a large number of adjacent oxygen vacancies can adjust the reduction path of NO. After two NO molecules are co-adsorbed on adjacent oxygen vacancies, they are converted into N2, realizing the high selectivity of NO to N2 at low temperature, rather than deviating from the expected result to obtain N2O or NO2. The present application solves the problem that the reaction path of NO cannot be controlled in the current transition metal ternary catalyst, and the reduction result of NO often deviates from the expected result. At the same time, the present application ensures the complete catalytic combustion of CO, C3H6, and C3H8 at low temperature, and has good effect on exhaust gas purification. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The propane conversion rate of the catalysts of Example 1 and Comparative Examples 1-3 at different temperature points.

[0025] Figure 2 The propane conversion rate of the catalysts of Example 1 and Comparative Examples 1-3 at different temperature points.

[0026] Figure 3 The propane conversion rate of the catalysts of Example 1 and Comparative Examples 1-3 at different temperature points.

[0027] Figure 4 The propane conversion rate of the catalysts of Example 1 and Comparative Examples 1-3 at different temperature points.

[0028] Figure 5 The propane conversion rate of the catalysts of Example 1 and Comparative Examples 1-3 at different temperature points.

[0029] Figure 6The figure of the gas purification stability test results of the catalyst of the present application comparative example 1 at different temperatures.

[0030] Figure 7 The figure of the gas purification stability test results of the catalyst of the present application example 1 at different temperatures.

[0031] Figure 8 The propane conversion rate of the catalyst of the present application examples 2-4 at different temperature points.

[0032] Figure 9 The propylene conversion rate of the catalyst of the present application examples 2-4 at different temperature points.

[0033] Figure 10 The carbon monoxide conversion rate of the catalyst of the present application examples 2-4 at different temperature points.

[0034] Figure 11 The nitrogen monoxide conversion rate of the catalyst of the present application examples 2-4 at different temperature points.

[0035] Figure 12 The nitrogen conversion rate of the catalyst of the present application examples 2-4 at different temperature points.

[0036] Figure 13 The propane conversion rate of the catalyst of the present application examples 5-10 at different temperature points.

[0037] Figure 14 The propylene conversion rate of the catalyst of the present application examples 5-10 at different temperature points.

[0038] Figure 15 The carbon monoxide conversion rate of the catalyst of the present application examples 5-10 at different temperature points.

[0039] Figure 16 The nitrogen monoxide conversion rate of the catalyst of the present application examples 5-10 at different temperature points.

[0040] Figure 17 The nitrogen conversion rate of the catalyst of the present application examples 5-10 at different temperature points. DETAILED DESCRIPTION

[0041] In order to make the technical solutions and advantages of the present application clearer, the present application and its beneficial effects are described in further detail below, but the embodiments of the present application are not limited thereto.

[0042] The present application provides a preparation method of a manganese-based catalyst for motor vehicle exhaust purification, comprising the following steps:

[0043] S1, mix the transition metal salt with the manganese-based active phase, treat by ultrasonic chemical precipitation method, wash, dry to obtain a precursor;

[0044] S2, calcining the precursor obtained in step S1 at 300-800℃ to obtain a manganese-based catalyst containing transition metal oxides.

[0045] The ultrasonic chemical precipitation method first disperses transition metal salts around the manganese-based active phase by ultrasonic mixing, then converts the transition metal salts into precipitates by chemical precipitation, and then decomposes and converts the precipitates into transition metal oxides by calcination, which are dispersed around the manganese-based active phase. Compared with the direct mixing of two powders, the lattice compatibility of the transition metal oxides and the manganese-based active phase is excellent, which can cause the manganese-based active phase at the phase boundary to be stretched and strained, thereby activating the lattice oxygen, realizing the efficient catalytic combustion of CO, C3H6 and C3H8 at low temperature; and after the oxidation combustion of CO and HC, a large number of adjacent oxygen vacancies are generated in the manganese-based active phase of this structure, which can adjust the reduction path of NO, lay the foundation for high selectivity NO reduction, and make NO be reduced to N2 at low temperature with high selectivity, rather than deviating from the expected N2O or NO2. The manganese-based catalyst prepared by the present application can realize the complete catalytic combustion of CO, C3H6 and C3H8 and the 100% reduction of NO to N2 at a low temperature of 250℃, and has no performance decay after 100 hours of reaction at 600℃, with high stability.

[0046] In addition, compared with traditional noble metal catalysts (such as palladium-based ternary catalysts), the manganese-based catalyst of the present application has better purification effect, does not need to rely on high reaction temperature to realize high selective reduction of NO, does not need to balance the contradiction between CO / HC oxidation rate and NO reduction rate, but CO / HC oxidation helps NO high selective reduction, CO / HC / NO conversion rate is high, and operation stability is stronger. In addition, the preparation method of the present application is also simpler, convenient to operate, and has lower use cost of noble metal.

[0047] Specifically, the calcination temperature in step S2 can be 300-400℃, 400-500℃, 500-600℃, 600-700℃ or 700-800℃. Specifically, it can be adjusted according to the different temperatures at which the precipitates are calcined and decomposed into transition metal oxides.

[0048] In some embodiments, the manganese-based active phase is at least one of MnO2, Mn2O3 and Mn3O4.

[0049] In some embodiments, the transition metal salt is selected from one or more of soluble cobalt salt, soluble germanium salt, soluble copper salt, soluble nickel salt and soluble iron salt, and the corresponding generated transition metal oxide can be any one of Co3O4, CeO2, CuO, NiO and Fe2O3.

[0050] In some embodiments, the mass of the transition metal oxide is 5% to 60% of the mass of the manganese-based catalyst; specifically, the mass of the transition metal oxide is 5% to 10%, 10% to 20%, 20% to 30%, 30% to 40%, 40% to 50%, or 50% to 60% of the mass of the manganese-based catalyst. Correspondingly, the mass of the manganese-based active phase is 40% to 95% of the mass of the manganese-based catalyst. Controlling the mass of the manganese-based active phase and the transition metal oxide within the above range ensures that the manganese-based active phase has sufficient adjacent oxygen vacancies to precisely regulate the reduction path of NO, and a certain amount of transition metal oxide can obtain more active lattice oxygen, ensuring the smooth progress of the oxidation reaction at low temperature. Preferably, the mass of the transition metal oxide is 20% to 40% of the mass of the manganese-based catalyst.

[0051] In some embodiments, in step S1, the treatment step of the ultrasonic chemical precipitation method is as follows: under ultrasonic conditions, a precipitant is added, and the addition is stopped when the pH value of the system is 9 to 12; then the ultrasonic treatment is continued, and after washing and drying, the precursor is obtained.

[0052] During the ultrasonic process, the precipitant is added dropwise, which can make the transition metal uniformly precipitate in the form of a precipitate around the manganese-based active phase. The precipitate is generally a hydroxide, and the precipitant can be a 25 wt% aqueous solution of tetramethylammonium hydroxide. Of course, different precipitates can also be added to form other forms of precipitates, but the subsequent calcination and decomposition process should be considered. After adding enough precipitant, the ultrasonic treatment is continued for a period of time, and the continued ultrasonic treatment time can be 2 to 5 hours to ensure sufficient precipitation of the transition metal. During the ultrasonic process, stirring can be performed simultaneously.

[0053] In some embodiments, in step S1, the preparation step of the manganese-based active phase is as follows: after calcination, the manganese source is dispersed in a solvent together with a dispersant, ultrasonic treatment is performed in an ice water bath, washing and drying are performed, and then the manganese-based active phase is obtained.

[0054] The manganese source can be manganese carbonate; and the dispersant can be polyvinylpyrrolidone. Different oxides can be obtained by calcining the manganese source at different calcination temperatures. The calcination temperature is adjusted according to the specific manganese-based active phase required to be selected, for example, Mn2O3 is used as the manganese-based active phase, and calcination can be performed at 650 ℃.

[0055] The manganese oxide obtained after calcination is a large particle formed by aggregation of a large number of small particles, and the large particle is not conducive to subsequent mixing with the transition metal salt. Therefore, a dispersing agent is added after calcination and dispersion is performed with ultrasonic to obtain a small particle manganese-based active phase. The ultrasonic is performed under an ice water bath to avoid the dispersion effect of the manganese-based active phase being affected by overheating of water during the ultrasonic process. Then, the dispersing agent is washed away to obtain a clean small particle manganese oxide as the manganese-based active phase. Specifically, the mass ratio of the manganese-based active phase to the dispersing agent can be (1-50):1.

[0056] In some embodiments, the preparation method of the catalyst further comprises loading the manganese-based catalyst containing the transition metal oxide obtained in step S2 into a carrier to obtain a monolithic manganese-based catalyst.

[0057] Compared with using the obtained powder manganese-based catalyst containing the transition metal oxide as a tail gas purification catalyst, the catalyst is first loaded into a carrier and then used in the form of a monolithic manganese-based catalyst for catalytic reaction, and the tail gas purification effect is better and the stability is stronger. The carrier is a honeycomb ceramic with pores, and the pores are more conducive to the adhesion of the catalyst.

[0058] Specifically, the loading step is:

[0059] S3, adding the etched honeycomb ceramic into an aqueous solution containing a binder to obtain a carrier mixture;

[0060] S4, dispersing the manganese-based catalyst containing the transition metal oxide into the carrier mixture, stirring and soaking, drying, and calcining to obtain a monolithic manganese-based catalyst.

[0061] The etching of the honeycomb ceramic can be performed using dilute nitric acid to obtain a honeycomb ceramic with a large number of pores. The addition of a certain amount of binder is more conducive to the adhesion of the catalyst. After soaking and drying, the catalyst is further calcined to further strengthen the adhesion of the catalyst, ensure the catalytic effect of the oxidation and reduction of the tail gas, and also facilitate the recycling and reuse.

[0062] Preferably, in step S4, the soaking time is 10-14 hours, and the calcination temperature is 300-800 ℃.

[0063] In some embodiments, the step S4 is repeated after the above step S4 to increase the loading amount, and the number of repetitions is 1-5 times. After multiple loadings, the catalyst content is increased, which can more efficiently catalyze and treat more motor vehicle tail gas.

[0064] The application and its beneficial effects will be further described in detail below with reference to specific embodiments and the accompanying drawings of the specification, but the embodiments of the application are not limited thereto.

[0065] Example 1

[0066] A method for preparing a manganese-based catalyst for purifying exhaust gas of a motor vehicle, comprising the following steps:

[0067] (1) calcining 5 g of MnCO3 powder in a muffle furnace at a heating rate of 3 °C / min at 650 °C for 3 hours;

[0068] (2) taking 2 g of the calcined powder obtained in step (1) and 100 mg of a dispersant, polyvinylpyrrolidone (PVP), and dispersing them in 100 mL of deionized water, then stirring the mixture and ultrasonically treating it in an ice water bath for 3 hours;

[0069] (3) washing the product obtained in step (2) several times with deionized water and vacuum drying it at 60 °C to obtain a powder Mn2O3 catalyst as a manganese-based active phase;

[0070] (4) dispersing 3.6258 g of Co(NO3)2·6H2O in 100 mL of deionized water containing 2 g of Mn2O3 powder, mixing, stirring and ultrasonically treating for 30 minutes until the nitrate is completely dissolved;

[0071] (5) while maintaining stirring and ultrasonic treatment, adding 25 wt% of a tetramethylammonium hydroxide aqueous solution dropwise to the solution obtained in step (4) until the pH of the solution is adjusted to 10, and then continuing stirring and ultrasonic treatment for 3 hours; and then washing the product several times with deionized water and vacuum drying it at 60 °C to obtain a precursor;

[0072] (6) calcining the precursor obtained in step (5) at 650 °C for 6 hours to obtain a powder Co3O4 / Mn2O3 catalyst, the mass of Co3O4 being about 33.3% of the total mass of the catalyst;

[0073] (7) preparation of a carrier: etching a honeycomb ceramic (diameter 30 mm * length 50 mm) with dilute nitric acid at a concentration of 0.1 mol / L, and then adding it to an aqueous solution containing 300 mg of a binder, pseudoboehmite, to obtain a carrier mixture;

[0074] (8) taking 3 g of the powder Co3O4 / Mn2O3 catalyst and dispersing it in the carrier mixture, and soaking it in the solution while continuously stirring the solution for 12 hours; and then drying it at 80 °C for 12 hours, and then calcining it at 650 °C for 6 hours to obtain a first loaded catalyst;

[0075] (9) The first loaded catalyst is dispersed again into the support mixed solution and soaked for 12 hours under continuous stirring of the solution; then dried at 80 °C for 12 hours and calcined at 650 °C for 6 hours to obtain the second loaded catalyst, and the same loading is repeated for 2 more times to increase the deposition amount of Co3O4 / Mn2O3, and the preparation of the whole Co3O4 / Mn2O3 catalyst is completed.

[0076] Example 2

[0077] A method for preparing a manganese-based catalyst for purification of motor vehicle exhaust, comprising the following steps:

[0078] (1) 5 g of MnCO3 powder is calcined in a muffle furnace at a heating rate of 3 °C / min at 650 °C for 3 hours;

[0079] (2) 2 g of the calcined powder obtained in step (1) and 100 mg of dispersant polyvinylpyrrolidone (PVP) are dispersed in 100 mL of deionized water, then the mixture is stirred and ultrasonically treated in an ice water bath for 3 hours;

[0080] (3) The mixture obtained in step (2) is washed with deionized water several times, and vacuum dried at 60 °C to obtain a powder Mn2O3 catalyst as a manganese-based active phase;

[0081] (4) 3.6258 g of Co(NO3)2·6H2O is dispersed in 100 mL of deionized water containing 2 g of Mn2O3 powder, mixed, stirred and ultrasonically treated for 30 minutes until the nitrate is completely dissolved;

[0082] (5) While maintaining stirring and ultrasonic treatment, 25wt% of a tetramethylammonium hydroxide aqueous solution is added dropwise to the solution obtained in step (4) until the pH value of the solution is adjusted to 10, and then stirring and ultrasonic treatment are continued for 3 hours; then the product is washed with deionized water several times and vacuum dried at 60 °C to obtain a precursor;

[0083] (6) The precursor obtained in step (5) is calcined at 650 °C for 6 hours to obtain a powder Co3O4 / Mn2O3 catalyst, and the mass of Co3O4 is 33.3% of the total mass of the catalyst. The powder catalyst is used for purification of motor vehicle exhaust without loading.

[0084] Example 3

[0085] Different from example 2, the mass of the transition metal salt added is 0.3817 g; and the mass of Co3O4 obtained is 5% of the total mass of the catalyst.

[0086] The rest is the same as Example 2, which will not be repeated here.

[0087] Example 4

[0088] Different from Example 2 is the mass of the transition metal salt added, which is 10.8874 g; the mass of the obtained Co3O4 is 60% of the total mass of the catalyst.

[0089] The rest is the same as Example 2, which will not be repeated here.

[0090] Example 5

[0091] Different from Example 1 is that the transition metal salt of this embodiment is 2.5228 g of Ce(NO3)2·6H2O, and the catalyst obtained after mixing with Mn2O3 is a powder CeO2 / Mn2O3 catalyst; the same as the loading step of Example 1 is carried out for loading, and a whole type CeO2 / Mn2O3 catalyst is obtained.

[0092] The rest is the same as Example 1, which will not be repeated here.

[0093] Example 6

[0094] A preparation method of a manganese-based catalyst for purifying exhaust gas of a motor vehicle, comprising the following steps:

[0095] (1) 5 g of MnCO3 powder is calcined at 650 °C for 3 hours in a muffle furnace at a heating rate of 3 °C / min;

[0096] (2) 2 g of the calcined powder obtained in step (1) and 2 g of the dispersant polyvinylpyrrolidone (PVP) are dispersed in 100 mL of deionized water, then the mixture is stirred and ultrasonically treated in an ice water bath for 3 hours;

[0097] (3) The mixture obtained in step (2) is washed with deionized water several times, and vacuum dried at 60 °C to obtain a powder Mn2O3 catalyst as a manganese-based active phase;

[0098] (4) 2.5297 g of Fe(NO3)3·6H2O is dispersed in 100 mL of deionized water containing 2 g of Mn2O3 powder for mixing, stirring and ultrasonic treatment for 30 minutes until the nitrate is completely dissolved;

[0099] (5) While maintaining stirring and ultrasonic treatment, 25wt% of a tetramethylammonium hydroxide aqueous solution is added dropwise to the solution obtained in step (4) until the pH value of the solution is adjusted to 9, and then the stirring and ultrasonic treatment is continued for 3 hours; and then the product is washed with deionized water several times, and vacuum dried at 60 °C to obtain a precursor;

[0100] (6) calcining the precursor obtained in step (5) at 500 °C for 6 hours to obtain a powder Fe2O3 / Mn2O3 catalyst, the mass of Fe2O3 being 33.3% of the total mass of the catalyst;

[0101] (7) Preparation of the support: etching a honeycomb ceramic (diameter 30 mm * length 50 mm) with dilute nitric acid at a concentration of 0.1 mol / L, then adding it to an aqueous solution containing 300 mg of binder pseudo-boehmite, to obtain a support mixture;

[0102] (8) dispersing 3 g of the powder Fe2O3 / Mn2O3 catalyst in the support mixture and leaving it to soak for 12 hours with constant stirring of the solution; then drying at 80 °C for 12 hours and calcining at 500 °C for 6 hours to obtain a first supported catalyst;

[0103] (9) dispersing the first supported catalyst again in the support mixture and leaving it to soak for 12 hours with constant stirring of the solution; then drying at 80 °C for 12 hours and calcining at 500 °C for 6 hours to obtain a second supported catalyst, and repeating the loading again twice in the same way to increase the amount of Fe2O3 / Mn2O3 deposited, to complete the preparation of the bulk Fe2O3 / Mn2O3 catalyst.

[0104] Example 7

[0105] A method for preparing a manganese-based catalyst for the purification of motor vehicle exhaust gases, comprising the following steps:

[0106] (1) calcining 8 g of MnCO3 powder in a muffle furnace at a heating rate of 3 °C / min at 650 °C for 3 hours;

[0107] (2) dispersing 5 g of the calcined powder obtained in step (1) and 100 mg of dispersant polyvinylpyrrolidone (PVP) in 100 mL of deionized water, then stirring the mixture and ultrasonically treating it in an ice water bath for 3 hours;

[0108] (3) washing the mixture obtained in step (2) with deionized water several times and drying it under vacuum at 60 °C to obtain a powder Mn2O3 catalyst as the manganese-based active phase;

[0109] (4) dispersing 3.0366 g of Cu(NO3)2·6H2O in 100 mL of deionized water containing 2 g of Mn2O3 powder, mixing, stirring and ultrasonically treating for 30 minutes until the nitrate is completely dissolved;

[0110] (5) while maintaining stirring and ultrasonic treatment, 25 wt% of a tetramethylammonium hydroxide aqueous solution was added dropwise to the solution obtained in step (4) until the pH value of the solution was adjusted to 12, and then stirring and ultrasonic treatment were continued for 3 hours; the product was then washed several times with deionized water and dried under vacuum at 60 °C to obtain a precursor;

[0111] (6) the precursor obtained in step (5) was calcined at 300 °C for 6 hours to obtain a powder CuO / Mn2O3 catalyst, the mass of CuO being 33.3% of the total mass of the catalyst;

[0112] (7) preparation of a carrier: a honeycomb ceramic (diameter 30 mm*length 50 mm) was etched with dilute nitric acid with a concentration of 0.1 mol / L, and then added to an aqueous solution containing 300 mg of binder pseudo-boehmite to obtain a carrier mixture;

[0113] (8) 3 g of the powder CuO / Mn2O3 catalyst was dispersed into the carrier mixture, and soaked for 12 hours under continuous stirring of the solution; then dried at 80 °C for 12 hours, and then calcined at 300 °C for 6 hours to obtain a first loaded catalyst;

[0114] (9) the first loaded catalyst was dispersed again into the carrier mixture, and soaked for 12 hours under continuous stirring of the solution; then dried at 80 °C for 12 hours, and then calcined at 300 °C for 6 hours to obtain a second loaded catalyst, and the same loading was repeated for a third time to increase the deposition amount of CuO / Mn2O3, and the preparation of the whole CuO / Mn2O3 catalyst was completed.

[0115] Example 8

[0116] A method for preparing a manganese-based catalyst for purifying exhaust gas of a motor vehicle, comprising the following steps:

[0117] (1) 5 g of MnCO3 powder was calcined in a muffle furnace at a heating rate of 3 °C / min at 650 °C for 3 hours;

[0118] (2) 2.5 g of the calcined powder obtained in step (1) and 100 mg of a dispersant, polyvinylpyrrolidone (PVP), were dispersed in 100 mL of deionized water, and then the mixture was stirred and ultrasonically treated in an ice water bath for 3 hours;

[0119] (3) the mixture obtained in step (2) was washed several times with deionized water and dried under vacuum at 60 °C to obtain a powder Mn2O3 catalyst as a manganese-based active phase;

[0120] (4) 3.8931 g of Ni(NO3)2-6H2O was dispersed in 100 mL of deionized water containing 2 g of Mn2O3 powder, mixed, stirred and ultrasonically treated for 30 minutes until the nitrate was completely dissolved;

[0121] (5) While maintaining stirring and ultrasonic treatment, 25wt% of a tetramethylammonium hydroxide aqueous solution was added dropwise to the solution obtained in step (4) until the pH value of the solution was adjusted to 10, and then stirring and ultrasonic treatment was continued for 3 hours; then the product was washed several times with deionized water and dried under vacuum at 60°C to obtain a precursor;

[0122] (6) The precursor obtained in step (5) was calcined at 800°C for 6 hours to obtain a powder NiO / Mn2O3 catalyst, the mass of NiO being 33.3% of the total mass of the catalyst;

[0123] (7) Preparation of the carrier: the honeycomb ceramic (diameter 30 mm*length 50 mm) was etched with dilute nitric acid with a concentration of 0.1 mol / L, and then added to an aqueous solution containing 300 mg of binder pseudo-boehmite to obtain a carrier mixture;

[0124] (8) 3 g of the powder NiO / Mn2O3 catalyst was dispersed into the carrier mixture, and soaked for 12 hours under constant stirring of the solution; then dried at 80°C for 12 hours, and then calcined at 800°C for 6 hours to obtain a first loaded catalyst;

[0125] (9) The first loaded catalyst was again dispersed into the carrier mixture, and soaked for 12 hours under constant stirring of the solution; then dried at 80°C for 12 hours, and then calcined at 800°C for 6 hours to obtain a second loaded catalyst, and the same loading was repeated four times to increase the deposition amount of NiO / Mn2O3, and the preparation of the whole NiO / Mn2O3 catalyst was completed.

[0126] Example 9

[0127] A method for preparing a manganese-based catalyst for purifying exhaust gas of a motor vehicle, comprising the following steps:

[0128] (1) 5 g of MnCO3 powder was calcined in a muffle furnace at a heating rate of 3°C / min at 450°C for 3 hours;

[0129] (2) 2 g of the calcined powder obtained in step (1) and 100 mg of a dispersant, polyvinylpyrrolidone (PVP), were dispersed in 100 mL of deionized water, and then the mixture was stirred and ultrasonically treated in an ice water bath for 3 hours;

[0130] (3) The mixture obtained in step (2) is washed with deionized water several times and dried at 60 °C under vacuum to obtain a powder MnO2catalyst as a manganese-based active phase;

[0131] (4) 3.6258 g of Co(N03)2-6H2O is dispersed in 100 mL of deionized water containing 2 g of MnO2powder, mixed, stirred and ultrasonically treated for 30 minutes until the nitrate is completely dissolved;

[0132] (5) While maintaining stirring and ultrasonic treatment, 25 wt% of a tetramethylammonium hydroxide aqueous solution is added dropwise to the solution obtained in step (4) until the pH of the solution is adjusted to 10, and then stirring and ultrasonic treatment are continued for 3 hours; and then the product is washed with deionized water several times and dried at 60 °C under vacuum to obtain a precursor;

[0133] (6) The precursor obtained in step (5) is calcined at 450 °C for 6 hours to obtain a powder Co3O4 / MnO2catalyst, the mass of Co3O4being 33.3% of the total mass of the catalyst;

[0134] (7) Preparation of the carrier: a honeycomb ceramic (diameter 30 mm * length 50 mm) is etched with dilute nitric acid with a concentration of 0.1 mol / L, and then added to an aqueous solution containing 300 mg of binder pseudo-boehmite to obtain a carrier mixture;

[0135] (8) 3 g of the powder Co3O4 / MnO2catalyst is dispersed into the carrier mixture, and soaked for 12 hours under constant stirring of the solution; and then dried at 80 °C for 12 hours, and then calcined at 650 °C for 6 hours to obtain a first loaded catalyst;

[0136] (9) The first loaded catalyst is dispersed again into the carrier mixture, and soaked for 12 hours under constant stirring of the solution; and then dried at 80 °C for 12 hours, and then calcined at 650 °C for 6 hours to obtain a second loaded catalyst, and the same loading is repeated twice again to increase the deposition amount of Co3O4 / MnO2, and the preparation of the overall Co3O4 / MnO2catalyst is completed.

[0137] Example 10

[0138] A method for preparing a manganese-based catalyst for purifying exhaust gas of a motor vehicle, comprising the following steps:

[0139] (1) 5 g of MnCO3powder is calcined in a muffle furnace at a heating rate of 3 °C / min at 850 °C for 3 hours;

[0140] (2) Take 2 g of the calcined powder obtained in step (1) and 100 mg of the dispersant polyvinylpyrrolidone (PVP) and disperse them in 100 mL of deionized water, then stir the mixture and ultrasonically treat it in an ice water bath for 3 hours;

[0141] (3) Wash the mixture obtained in step (2) with deionized water several times and dry it at 60°C under vacuum to obtain the powder Mn304 catalyst as the manganese-based active phase;

[0142] (4) Disperse 3.6258 g of Co(N03)2-6H20 in 100 mL of deionized water containing 2 g of the Mn304 powder, mix, stir and ultrasonically treat for 30 minutes until the nitrate is completely dissolved;

[0143] (5) While maintaining stirring and ultrasonic treatment, add dropwise to the solution obtained in step (4) 25 wt% of a tetramethylammonium hydroxide aqueous solution until the pH of the solution is adjusted to 10, then continue stirring and ultrasonic treatment for 3 hours; then wash the product with deionized water several times and dry it at 60°C under vacuum to obtain the precursor;

[0144] (6) Calcine the precursor obtained in step (5) at 450°C for 6 hours to obtain the powder Co304 / Mn304 catalyst, the mass of Co304 being 33.3% of the total mass of the catalyst;

[0145] (7) Preparation of the carrier: etch the honeycomb ceramic (diameter 30 mm*length 50 mm) with dilute nitric acid at a concentration of 0.1 mol / L, then add it to an aqueous solution containing 300 mg of the binder pseudoboehmite to obtain a carrier mixture;

[0146] (8) Disperse 3 g of the powder Co304 / Mn304 catalyst into the carrier mixture and immerse it in the solution while continuously stirring for 12 hours; then dry it at 80°C for 12 hours and calcine it at 650°C for 6 hours to obtain the first loaded catalyst;

[0147] (9) Disperse the first loaded catalyst again into the carrier mixture and immerse it in the solution while continuously stirring for 12 hours; then dry it at 80°C for 12 hours and calcine it at 650°C for 6 hours to obtain the second loaded catalyst, and similarly repeat the loading 2 more times to increase the amount of Co304 / Mn304 deposited and complete the preparation of the monolithic Co304 / Mn304 catalyst.

[0148] Comparative Example 1

[0149] Different from Example 1, the manganese-based catalyst of this comparative example does not add transition metal oxides, but directly loads the prepared powder Mn2O3 catalyst into the carrier to obtain a monolithic Mn2O3 catalyst.

[0150] The rest is the same as Example 1, which will not be repeated here.

[0151] Comparative Example 2

[0152] Different from Example 1, the tail gas purification catalyst of this comparative example does not use a manganese-based system, but directly loads the prepared powder Co3O4 catalyst into the carrier to obtain a monolithic Co3O4 catalyst.

[0153] The preparation of the powder Co3O4 catalyst is as follows:

[0154] (1) 5 g of Co(NO3)2·6H2O was dispersed in 100 mL of deionized water, stirred and ultrasonically treated for 30 minutes until the nitrate was completely dissolved;

[0155] (2) While maintaining stirring and ultrasonic treatment, 25wt% of a tetramethylammonium hydroxide aqueous solution was added dropwise to the solution obtained in step (1) until the pH value of the solution was adjusted to 10, and then stirring and ultrasonic treatment was continued for 3 hours. Then the product was washed several times with deionized water and vacuum dried at 60°C to obtain a precursor;

[0156] (3) The precursor obtained in step (2) was calcined at 650°C for 6 hours to obtain a powder Co3O4 catalyst.

[0157] The rest is the same as Example 1, which will not be repeated here.

[0158] Comparative Example 3

[0159] Different from Example 1, the preparation of the powder Co3O4 / Mn2O3 catalyst is as follows:

[0160] (1) 5 g of MnCO3 powder was calcined in a muffle furnace at a heating rate of 3°C / min at 650°C for 3 hours;

[0161] (2) 2 g of the calcined powder obtained in step (1) and 100 mg of a dispersant, polyvinylpyrrolidone (PVP), were dispersed in 100 mL of deionized water, then the mixture was stirred and ultrasonically treated in an ice water bath for 3 hours;

[0162] (3) The mixture obtained in step (2) was washed with deionized water several times, and vacuum dried at 60°C to obtain a powder Mn2O3;

[0163] (4) Disperse 5 g Co(NO3)2‧6H2O in 100 mL of deionized water, stir and sonicate for 30 minutes until the nitrate is completely dissolved;

[0164] (5) While maintaining stirring and ultrasonic treatment, add 25wt% tetramethylammonium hydroxide aqueous solution dropwise to the solution obtained in step (4) until the pH value of the solution is adjusted to 10, and then continue stirring and ultrasonic treatment for 3 hours; then wash the product several times with deionized water, dry it under vacuum at 60 °C, and then calcine it at 400 °C for 3 hours to obtain powdered Co3O4;

[0165] (6) A powdered Co3O4+Mn2O3 catalyst was prepared by mechanically mixing and grinding 1 g Co3O4 powder and 2 g Mn2O3 powder.

[0166] The rest is the same as in Example 1, and will not be repeated here.

[0167] The catalysts obtained in Examples 1-10 and Comparative Examples 1-3 were subjected to gas purification tests. These catalytic activity experiments were conducted in a fixed-bed reactor with the following initial gas concentrations: 0.1 vol% propane, 0.1 vol% propylene, 2 vol% carbon monoxide, 0.05 vol% nitric oxide, 2 vol% oxygen, and 5 vol% water. Nitrogen was used as the carrier gas, and the volumetric hourly space velocity (VHSV) was 50,000 h⁻¹. -1 The activity test temperature is 100~400 ℃, and the stability test temperature is 650 ℃.

[0168] Test results are as follows Figures 1-17 As shown.

[0169] Depend on Figures 1-5 As can be seen, the catalyst prepared in Example 1 of this invention achieves complete conversion of multiple components in motor vehicle exhaust gas at 250 °C and achieves 100% nitrogen selectivity. Compared with the original Mn2O3 catalyst of Comparative Example 1, or compared with the catalyst mainly composed of transition metals in Comparative Example 2, the catalyst of this invention effectively reduces the conversion temperature of CO, H2O, and NO, and can achieve 100% conversion at 250 °C. Compared with the catalyst of Comparative Example 3, the preparation method of this invention yields a unique structure with high lattice compatibility between the transition metal oxide and the manganese-based active phase, which can convert the inert lattice oxygen of the manganese-based active phase into active lattice oxygen, laying the foundation for subsequent CO, H2O, and NO conversion, achieving the goal of precisely controlling the NO reaction pathway, thereby obtaining a 100% conversion effect at a lower temperature.

[0170] Depend on Figures 6-7It can be seen that the catalyst prepared in Example 1 of the present application has more excellent stability than the original Mn2O3 catalyst prepared in Comparative Example 1, and the performance does not attenuate after 100 hours of reaction at 650 DEG C.

[0171] By Figures 8-12 It can also be seen that the catalysts prepared in Examples 2-4 of the present application all have excellent activity, indicating that the preparation method of the present application is suitable for the mixed preparation of transition metal oxides and manganese-based active phases in different proportions, and the obtained catalysts can regulate the reaction path of NO, make it 100% reduction to N2, and at the same time ensure the complete catalytic combustion of CO / HC at low temperature.

[0172] By Figures 13-17 It can also be seen that the catalysts prepared in Examples 5-10 of the present application all have excellent activity, indicating that the preparation method of the present application is suitable for the mixed preparation of transition metal oxides and manganese-based active phases, and the obtained catalysts can regulate the reaction path of NO, make it 100% reduction to N2, and at the same time ensure the complete catalytic combustion of CO / HC at low temperature.

[0173] According to the disclosure and teaching of the above description, those skilled in the art of the present application can also make changes and modifications to the above embodiments. Therefore, the present application is not limited to the above specific embodiments, and any obvious improvements, replacements or modifications made by those skilled in the art on the basis of the present application all fall within the protection scope of the present application. In addition, although some specific terms are used in the present specification, these terms are only for convenience of explanation and do not constitute any limitation on the present application.

Claims

1. A method for producing a manganese-based catalyst for purification of exhaust gas of a motor vehicle, characterized by, The method comprises the following steps: S1, mixing a transition metal salt with a manganese-based active phase, treating by ultrasonic chemical precipitation method, washing, drying to obtain a precursor; the treatment step of the ultrasonic chemical precipitation method is: under ultrasonic condition, adding a precipitant, stopping adding when the pH value of the system is 9-12; then continuing ultrasonic treatment, washing, drying to obtain the precursor; S2, calcining the precursor obtained in step S1 at 300-800 ℃ to obtain a manganese-based catalyst containing transition metal oxides, the manganese-based catalyst being a ternary catalyst; the mass of the transition metal oxides being 5%-60% of the mass of the manganese-based catalyst; In step S1, the preparation step of the manganese-based active phase is: calcining a manganese source manganese carbonate, dispersing the manganese carbonate in a solvent together with a dispersant polyvinylpyrrolidone, treating by ultrasonic in an ice water bath, washing, drying to obtain the manganese-based active phase; the mass ratio of the manganese-based active phase to the dispersant being (1-50):1; The manganese-based active phase is Mn2O3; the transition metal salt is selected from one or more of soluble cobalt salt, soluble cerium salt, soluble copper salt, soluble nickel salt, and soluble iron salt.

2. The method of producing a manganese-based catalyst for purifying exhaust gas of a motor vehicle according to claim 1, characterized by, The method further comprises loading the manganese-based catalyst containing transition metal oxides obtained in step S2 in a carrier to obtain a monolithic manganese-based catalyst.

3. The method of producing a manganese-based catalyst for purifying exhaust gas of a motor vehicle according to claim 2, wherein The carrier is a honeycomb ceramic with pores; the loading step is: S3, adding the etched honeycomb ceramic into an aqueous solution containing a binder to obtain a carrier mixture; S4, dispersing the manganese-based catalyst containing transition metal oxides in the carrier mixture, stirring and soaking, drying, and calcining to obtain the monolithic manganese-based catalyst.

4. The method of producing a manganese-based catalyst for purifying exhaust gas of a motor vehicle according to claim 3, wherein In step S4, the soaking time is 10-14 hours, and the calcining temperature is 300-800 ℃.

5. A manganese-based catalyst for purification of exhaust gas of a motor vehicle, characterized in that, The manganese-based catalyst for purifying exhaust gas of a motor vehicle is prepared by the method according to any one of claims 1-4.

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