Manganese-based catalyst for purifying tail gas of motor vehicle as well as preparation method and application of manganese-based catalyst

Abstract

The invention relates to the field of motor vehicle tail gas treatment, in particular to a manganese-based catalyst for motor vehicle tail gas purification and a preparation method and application thereof.The preparation method comprises the following steps that S1, transition metal salt and a manganese-based active phase are mixed, treated through an ultrasonic chemical precipitation method, washed and dried, and then a precursor is obtained; and S2, calcining the obtained precursor at 300-800 DEG C to obtain the manganese-based catalyst containing the transition metal oxide. According to the manganese-based catalyst disclosed by the invention, the precursor is prepared by adopting an ultrasonic chemical precipitation method, the transition metal oxide is uniformly precipitated around the manganese-based active phase, crystal lattices of the transition metal oxide and the manganese-based active phase are matched, and a large amount of inert crystal lattice oxygen can be converted into active crystal lattice oxygen, so that high-efficiency CO and HC oxidation is realized at low temperature; and then a large number of adjacent oxygen vacancies are generated, so that NO is highly selectively reduced into N2 at low temperature, and the reaction path of NO is precisely regulated and controlled.

Description

Technical Field

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

[0002] In the foreseeable future, internal combustion engines will remain 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 led to a continued increase in demand for high-performance three-way catalysts. Currently, commercially available three-way catalysts mainly include the following two types:

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

[0004] 2) For transition metal-based catalysts, the lattice oxygen is used as the oxidation site for HC / CO during the oxidation process. The oxygen vacancies generated after the reaction can be used as the 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 depends largely on the activity of lattice oxygen under low temperature conditions.

[0005] At present, research on lattice oxygen activation 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 over lattice oxygen activation, the formation structure of oxygen vacancies and the diversity of NO adsorption and conversion pathways, transition metal-based three-way catalysts still face challenges in achieving highly selective NO reduction at low temperatures. Typically, when a single NO molecule is adsorbed on an isolated oxygen vacancy on a transition metal oxide, it may couple with NO in the gas phase through an N≡N bond to form N2O, which is the least ideal but most likely outcome. In addition, the adsorbed NO may also be oxidized to NO2 by adjacent lattice oxygen, deviating from the expected behavior.

[0006] In view of this, it is indeed necessary to provide a technical solution to the above problems. Summary of the invention

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

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A method for preparing a manganese-based catalyst for purifying exhaust gas from a motor vehicle comprises the following steps:

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

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

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

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

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

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

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

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

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

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

[0020] S4, dispersing the manganese-based catalyst containing transition metal oxide in the carrier mixed liquid, stirring and soaking, drying and calcining to obtain a monolithic manganese-based catalyst.

[0021] Preferably, in step S4, the soaking time is 10 to 14 hours, and the calcination temperature is 300 to 800° C.; after step S4, the step is repeated 1 to 5 times to increase the loading amount.

[0022] A second object of the present invention is to provide a manganese-based catalyst for purifying exhaust gas of motor vehicles, characterized in that it is prepared by the preparation method of the manganese-based catalyst for purifying exhaust gas of motor vehicles described above.

[0023] The beneficial effects of the present invention are as follows: the manganese-based catalyst of the present invention adopts an ultrasonic chemical precipitation method to prepare a precursor, and a catalyst is obtained after calcination. The transition metal oxide in the catalyst is uniformly precipitated around the manganese-based active phase. The transition metal oxide of this structure can adapt to the lattice of the manganese-based active phase, and can promote the tensile strain of the manganese-based active phase at the phase boundary, thereby promoting 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, thereby realizing efficient oxidation of CO and HC (such as C3H6, C3H8, etc.) at low temperature; and CO After oxidative combustion, HC will cause the manganese-based active phase to generate a large number of adjacent oxygen vacancies. Unlike isolated oxygen vacancies, a large number of adjacent oxygen vacancies can adjust the reduction path of NO. The adjacent oxygen vacancies adsorb two NO molecules and convert them into N2, thereby achieving highly selective reduction of NO to N2 at low temperature, rather than deviating from the expected N2O or NO2. This solves the problem that the current transition metal ternary catalyst cannot regulate the reaction path of NO and the NO reduction results often deviate from expectations. At the same time, it ensures the complete catalytic combustion of CO, C3H6, and C3H8 at low temperatures, which has a good effect on exhaust gas purification. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The propane conversion rates of the catalysts in Example 1 of the present invention and Comparative Examples 1 to 3 at different temperature points are shown.

[0025] Figure 2 The propylene conversion rates of the catalysts in Example 1 of the present invention and Comparative Examples 1 to 3 at different temperatures.

[0026] Figure 3 The carbon monoxide conversion rates of the catalysts in Example 1 of the present invention and Comparative Examples 1 to 3 at different temperature points are shown.

[0027] Figure 4 The nitric oxide conversion rates of the catalysts in Example 1 of the present invention and Comparative Examples 1 to 3 at different temperature points are shown.

[0028] Figure 5 The nitrogen conversion rates of the catalysts in Example 1 of the present invention and Comparative Examples 1 to 3 at different temperatures are shown.

[0029] Figure 6This is a graph showing the gas purification stability test results of the catalyst of Comparative Example 1 of the present invention at different temperatures.

[0030] Figure 7 This is a graph showing the gas purification stability test results of the catalyst of Example 1 of the present invention at different temperatures.

[0031] Figure 8 The propane conversion rates of the catalysts in Examples 2 to 4 of the present invention at different temperatures are shown.

[0032] Fig. 9 The propylene conversion rates of the catalysts in Examples 2 to 4 of the present invention at different temperatures are shown.

[0033] Fig.10 The carbon monoxide conversion rates of the catalysts of Examples 2 to 4 of the present invention at different temperature points.

[0034] Fig.11 The nitric oxide conversion rates of the catalysts of Examples 2 to 4 of the present invention at different temperature points are shown.

[0035] Fig.12 The nitrogen conversion rates of the catalysts in Examples 2 to 4 of the present invention at different temperatures are shown.

[0036] Fig.13 The propane conversion rates of the catalysts in Examples 5 to 10 of the present invention at different temperatures are shown.

[0037] Fig.14 The propylene conversion rates of the catalysts in Examples 5 to 10 of the present invention at different temperatures are shown.

[0038] Fig.15 The carbon monoxide conversion rates of the catalysts of Examples 5 to 10 of the present invention at different temperature points.

[0039] Fig.16 The nitrogen monoxide conversion rates of the catalysts of Examples 5 to 10 of the present invention at different temperature points are shown.

[0040] Fig.17 The nitrogen conversion rates of the catalysts in Examples 5 to 10 of the present invention at different temperatures are shown. DETAILED DESCRIPTION

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

[0042] The present invention provides a method for preparing a manganese-based catalyst for purifying exhaust gas from a motor vehicle, comprising the following steps:

[0043] S1. Mixing the transition metal salt and the manganese-based active phase, treating them by ultrasonic chemical precipitation method, washing, and drying to obtain a precursor;

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

[0045] The ultrasonic chemical precipitation method first uses ultrasonic mixing to disperse the transition metal salt around the manganese-based active phase, and then converts the transition metal salt into a precipitate after chemical precipitation. The precipitate can be decomposed and converted into a transition metal oxide after calcination and dispersed around the manganese-based active phase. Compared with the direct mixing of two powders, this combination structure has excellent lattice adaptability between the transition metal oxide and the manganese-based active phase, which can promote tensile strain of the manganese-based active phase at the phase boundary, thereby activating the lattice oxygen and realizing efficient catalytic combustion of CO, C3H6, and C3H8 at low temperatures; and after oxidative combustion of CO and HC, the manganese-based active phase of this structure will generate a large number of adjacent oxygen vacancies, which can regulate the reduction path of NO, laying the foundation for achieving highly selective NO reduction, allowing NO to be highly selectively reduced to N2 at low temperatures, rather than deviating from the expected N2O or NO2. The manganese-based catalyst prepared by the present invention can achieve complete catalytic combustion of CO, C3H6, and C3H8 and 100% reduction of NO to N2 at a low temperature of 250°C, and has no performance decay after reacting at 600°C for 100 hours, and has high stability.

[0046] In addition, compared with traditional noble metal catalysts (such as palladium-based three-way catalysts), the manganese-based catalyst of the present invention has better purification effect, does not need to rely on high reaction temperature to achieve high selective reduction of NO, does not need to weigh 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 invention is also simpler, easy to operate, and reduces the use cost of noble metals.

[0047] Specifically, the calcination temperature in step S2 may be 300-400°C, 400-500°C, 500-600°C, 600-700°C or 700-800°C, and may be adjusted according to the temperature at which the precipitate is 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 transition metal salts of soluble cobalt salts, soluble germanium salts, soluble copper salts, soluble nickel salts, and soluble iron salts, and the corresponding transition metal oxide generated may 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, on the one hand, ensures that the manganese-based active phase has enough adjacent oxygen vacancies to accurately control the reduction path of NO, and on the other hand, 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 processing steps of the ultrasonic chemical precipitation method are: adding a precipitant under ultrasonic conditions, and stopping the addition when the pH value of the system is 9-12; then continuing ultrasonic treatment, washing, and drying to obtain a precursor.

[0052] The precipitant is added dropwise during the ultrasonic process, so that the transition metal can be uniformly precipitated around the manganese-based active phase in the form of a precipitate. The precipitate is generally a hydroxide, and the precipitant can be a 25wt% tetramethylammonium hydroxide aqueous solution. 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 sufficient precipitant is added dropwise, the ultrasonic process is continued for a period of time, and the ultrasonic time can be continued for 2 to 5 hours to ensure sufficient precipitation of the transition metal. The ultrasonic process can be accompanied by stirring at the same time.

[0053] In some embodiments, in step S1, the preparation steps of the manganese-based active phase are: calcining a manganese source and dispersing it in a solvent together with a dispersant, ultrasonically treating it in an ice-water bath, washing it, and drying it to obtain the manganese-based active phase.

[0054] Wherein, the manganese source can be manganese carbonate; the dispersant can be polyvinyl pyrrolidone. The manganese source can obtain different oxides at different calcination temperatures. The calcination temperature is adjusted according to the specific manganese-based active phase selected. For example, if Mn2O3 is used as the manganese-based active phase, the calcination can be performed at 650°C.

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

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

[0057] Compared with using the obtained powdered manganese-based catalyst containing transition metal oxide as an exhaust gas purification catalyst, the catalyst is first loaded on a carrier and then catalytically reacted in the form of a monolithic manganese-based catalyst, which has a better exhaust gas purification effect and stronger stability. Among them, the carrier is a honeycomb ceramic with pores, and the pores are more conducive to the adhesion of the catalyst thereto.

[0058] Specifically, the loading steps are:

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

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

[0061] Dilute nitric acid can be used to etch honeycomb ceramics to obtain honeycomb ceramics with a large number of pores. At the same time, adding a certain amount of binder is more conducive to the adhesion of the catalyst thereto. After soaking and drying, calcination treatment is required to further enhance the firmness of the catalyst load, ensure the catalytic effect on the oxidation and reduction of exhaust gas, and also make it more conducive to recycling and reuse.

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

[0063] In some embodiments, the above step S4 is repeated to increase the loading amount, and the number of repetitions is 1 to 5. After multiple loadings, the catalyst content is increased, and more motor vehicle exhaust can be catalytically treated more efficiently.

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

[0065] Example 1

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

[0067] (1) 5 g of MnCO powder was calcined at 650 °C for 3 h in a muffle furnace at a heating rate of 3 °C / min;

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

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

[0070] (4) 3.6258 g of Co(NO3)2·6H2O was dispersed in 100 mL of deionized water containing 2 g of Mn2O3 powder, mixed, stirred and ultrasonicated for 30 min until the nitrate was completely dissolved;

[0071] (5) while maintaining stirring and ultrasonic treatment, adding 25 wt % 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 continuing stirring and ultrasonic treatment for 3 hours; then washing the product with deionized water several times, and vacuum drying 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 powdered Co3O4 / Mn2O3 catalyst, wherein the mass of Co3O4 is approximately 33.3% of the total mass of the catalyst;

[0073] (7) Preparation of carrier: A honeycomb ceramic (diameter 30 mm*length 50 mm) was etched with 0.1 mol / L dilute nitric acid, and then added into an aqueous solution containing 300 mg of pseudo-boehmite as a binder to obtain a carrier mixed solution;

[0074] (8) 3 g of powdered Co3O4 / Mn2O3 catalyst was dispersed into the carrier mixed solution and immersed in the solution for 12 hours while the solution was continuously stirred; then dried at 80°C for 12 hours, and then calcined at 650°C for 6 hours to obtain the first supported catalyst;

[0075] (9) The first loaded catalyst was dispersed again in the carrier mixed solution and immersed in the solution for 12 hours while the solution was continuously stirred; then dried at 80°C for 12 hours, and then calcined at 650°C for 6 hours to obtain the second loaded catalyst. The loading was repeated twice to increase the deposition amount of Co3O4 / Mn2O3, thereby completing the preparation of the integral Co3O4 / Mn2O3 catalyst.

[0076] Example 2

[0077] A method for preparing a manganese-based catalyst for purifying exhaust gas from a motor vehicle comprises the following steps:

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

[0079] (2) dispersing 2 g of the calcined powder obtained in step (1) and 100 mg of a dispersant polyvinylpyrrolidone (PVP) in 100 mL of deionized water, and then stirring the mixture and ultrasonically treating it in an ice water bath for 3 hours;

[0080] (3) washing the mixture obtained in step (2) with deionized water for several times, and vacuum drying at 60° C. to obtain a powdered Mn2O3 catalyst as a manganese-based active phase;

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

[0082] (5) while maintaining stirring and ultrasonic treatment, adding 25 wt % 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 continuing stirring and ultrasonic treatment for 3 hours; then washing the product with deionized water several times, and vacuum drying 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 powdered Co3O4 / Mn2O3 catalyst, wherein the mass of Co3O4 is 33.3% of the total mass of the catalyst. The powdered catalyst is used to purify motor vehicle exhaust without loading.

[0084] Example 3

[0085] The difference from Example 2 is that the mass of the transition metal salt added is 0.3817 g; the mass of the obtained Co3O4 is 5% of the total mass of the catalyst.

[0086] The rest is the same as in Example 2 and will not be described again here.

[0087] Example 4

[0088] The difference from Example 2 is that the mass of the added transition metal salt 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 in Example 2 and will not be described again here.

[0090] Example 5

[0091] The difference from Example 1 is that the transition metal salt in this example is 2.5228 g of Ce(NO3)2·6H2O, and the catalyst obtained after mixing with Mn2O3 is a powdered CeO2 / Mn2O3 catalyst; similarly, the loading steps of Example 1 are followed to obtain an integral CeO2 / Mn2O3 catalyst.

[0092] The rest is the same as in Example 1 and will not be described again here.

[0093] Example 6

[0094] A method for preparing a manganese-based catalyst for purifying exhaust gas from a motor vehicle comprises the following steps:

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

[0096] (2) dispersing 2 g of the calcined powder obtained in step (1) and 2 g of a dispersant polyvinyl pyrrolidone (PVP) in 100 mL of deionized water, and then stirring the mixture and ultrasonically treating it in an ice water bath for 3 hours;

[0097] (3) washing the mixture obtained in step (2) with deionized water for several times, and vacuum drying at 60° C. to obtain a powdered Mn2O3 catalyst as a manganese-based active phase;

[0098] (4) 2.5297 g of Fe(NO3)3·6H2O was dispersed in 100 mL of deionized water containing 2 g of Mn2O3 powder, mixed, stirred and ultrasonicated for 30 min until the nitrate was completely dissolved;

[0099] (5) while maintaining stirring and ultrasonic treatment, adding 25 wt % tetramethylammonium hydroxide aqueous solution dropwise to the solution obtained in step (4) until the pH value of the solution is adjusted to 9, and then continuing stirring and ultrasonic treatment for 3 hours; then washing the product with deionized water several times, and vacuum drying 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 powdered Fe2O3 / Mn2O3 catalyst, wherein the mass of Fe2O3 is 33.3% of the total mass of the catalyst;

[0101] (7) Preparation of carrier: A honeycomb ceramic (diameter 30 mm*length 50 mm) was etched with 0.1 mol / L dilute nitric acid, and then added into an aqueous solution containing 300 mg of pseudo-boehmite as a binder to obtain a carrier mixed solution;

[0102] (8) 3 g of powdered Fe2O3 / Mn2O3 catalyst was dispersed into the carrier mixed solution and immersed for 12 hours while the solution was continuously stirred; then dried at 80°C for 12 hours, and then calcined at 500°C for 6 hours to obtain the first supported catalyst;

[0103] (9) The first loaded catalyst was dispersed again in the carrier mixed solution and immersed for 12 hours while the solution was continuously stirred; then dried at 80°C for 12 hours, and then calcined at 500°C for 6 hours to obtain the second loaded catalyst. The loading was repeated twice to increase the amount of Fe2O3 / Mn2O3 deposited, thereby completing the preparation of the integral Fe2O3 / Mn2O3 catalyst.

[0104] Example 7

[0105] A method for preparing a manganese-based catalyst for purifying exhaust gas from a motor vehicle comprises the following steps:

[0106] (1) 8 g of MnCO powder was calcined at 650 °C for 3 h in a muffle furnace at a heating rate of 3 °C / min;

[0107] (2) dispersing 5 g of the calcined powder obtained in step (1) and 100 mg of a dispersant polyvinyl pyrrolidone (PVP) in 100 mL of deionized water, and 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 for several times, and vacuum drying at 60° C. to obtain a powdered Mn2O3 catalyst as a manganese-based active phase;

[0109] (4) 3.0366 g of Cu(NO3)2·6H2O was dispersed in 100 mL of deionized water containing 2 g of Mn2O3 powder, mixed, stirred and ultrasonicated for 30 min until the nitrate was completely dissolved;

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

[0111] (6) calcining the precursor obtained in step (5) at 300° C. for 6 hours to obtain a powdered CuO / Mn2O3 catalyst, wherein the mass of CuO is 33.3% of the total mass of the catalyst;

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

[0113] (8) 3 g of powdered CuO / Mn2O3 catalyst was dispersed into the carrier mixed solution and immersed for 12 hours while the solution was continuously stirred; then dried at 80°C for 12 hours, and then calcined at 300°C for 6 hours to obtain the first supported catalyst;

[0114] (9) The first loaded catalyst was dispersed again in the carrier mixed solution and immersed for 12 hours while the solution was continuously stirred; then dried at 80°C for 12 hours, and then calcined at 300°C for 6 hours to obtain the second loaded catalyst. The loading was repeated twice to increase the deposition amount of CuO / Mn2O3, thereby completing the preparation of the integral CuO / Mn2O3 catalyst.

[0115] Example 8

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

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

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

[0119] (3) washing the mixture obtained in step (2) with deionized water for several times, and vacuum drying at 60° C. to obtain a powdered 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 ultrasonicated for 30 min until the nitrate was completely dissolved;

[0121] (5) while maintaining stirring and ultrasonic treatment, adding 25 wt % 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 continuing stirring and ultrasonic treatment for 3 hours; then washing the product with deionized water several times, and vacuum drying at 60° C. to obtain a precursor;

[0122] (6) calcining the precursor obtained in step (5) at 800° C. for 6 hours to obtain a powdered NiO / Mn2O3 catalyst, wherein the mass of NiO accounts for 33.3% of the total mass of the catalyst;

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

[0124] (8) 3 g of powdered NiO / Mn2O3 catalyst was dispersed into the carrier mixed solution and immersed for 12 hours while the solution was continuously stirred; then dried at 80°C for 12 hours, and then calcined at 800°C for 6 hours to obtain the first supported catalyst;

[0125] (9) The first loaded catalyst was dispersed again in the carrier mixed solution and immersed for 12 hours while the solution was continuously stirred; then dried at 80°C for 12 hours, and then calcined at 800°C for 6 hours to obtain the second loaded catalyst. The loading was repeated 4 times to increase the amount of NiO / Mn2O3 deposited, thereby completing the preparation of the integral NiO / Mn2O3 catalyst.

[0126] Example 9

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

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

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

[0130] (3) washing the mixture obtained in step (2) with deionized water for several times, and vacuum drying at 60° C. to obtain a powdered MnO2 catalyst as a manganese-based active phase;

[0131] (4) 3.6258 g of Co(NO3)2·6H2O was dispersed in 100 mL of deionized water containing 2 g of MnO2 powder, mixed, stirred and ultrasonicated for 30 min until the nitrate was completely dissolved;

[0132] (5) while maintaining stirring and ultrasonic treatment, adding 25 wt % 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 continuing stirring and ultrasonic treatment for 3 hours; then washing the product with deionized water several times, and vacuum drying at 60° C. to obtain a precursor;

[0133] (6) calcining the precursor obtained in step (5) at 450° C. for 6 hours to obtain a powdered Co3O4 / MnO2 catalyst, wherein the mass of Co3O4 is 33.3% of the total mass of the catalyst;

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

[0135] (8) 3 g of powdered Co3O4 / MnO2 catalyst was dispersed into the carrier mixed solution and immersed in the solution for 12 hours while the solution was continuously stirred; then dried at 80°C for 12 hours, and then calcined at 650°C for 6 hours to obtain the first supported catalyst;

[0136] (9) The first loaded catalyst was dispersed again in the carrier mixed solution and immersed in the solution for 12 hours while the solution was continuously stirred; then dried at 80°C for 12 hours, and then calcined at 650°C for 6 hours to obtain the second loaded catalyst. The loading was repeated twice to increase the deposition amount of Co3O4 / MnO2, thereby completing the preparation of the integral Co3O4 / MnO2 catalyst.

[0137] Example 10

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

[0139] (1) 5 g of MnCO powder was calcined at 850 °C for 3 h in a muffle furnace at a heating rate of 3 °C / min;

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

[0141] (3) washing the mixture obtained in step (2) with deionized water for several times, and vacuum drying at 60° C. to obtain a powdered Mn3O4 catalyst as a manganese-based active phase;

[0142] (4) 3.6258 g of Co(NO3)2·6H2O was dispersed in 100 mL of deionized water containing 2 g of Mn3O4 powder, mixed, stirred and ultrasonicated for 30 min until the nitrate was completely dissolved;

[0143] (5) while maintaining stirring and ultrasonic treatment, adding 25 wt % 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 continuing stirring and ultrasonic treatment for 3 hours; then washing the product with deionized water several times, and vacuum drying at 60° C. to obtain a precursor;

[0144] (6) calcining the precursor obtained in step (5) at 450° C. for 6 hours to obtain a powdered Co3O4 / Mn3O4 catalyst, wherein the mass of Co3O4 is 33.3% of the total mass of the catalyst;

[0145] (7) Preparation of carrier: A honeycomb ceramic (diameter 30 mm*length 50 mm) was etched with 0.1 mol / L dilute nitric acid, and then added into an aqueous solution containing 300 mg of pseudo-boehmite as a binder to obtain a carrier mixed solution;

[0146] (8) 3 g of powdered Co3O4 / Mn3O4 catalyst was dispersed into the carrier mixed solution and immersed in the solution for 12 hours while the solution was continuously stirred; then dried at 80°C for 12 hours, and then calcined at 650°C for 6 hours to obtain the first supported catalyst;

[0147] (9) The first loaded catalyst was dispersed again in the carrier mixed solution and immersed for 12 hours while the solution was continuously stirred; then dried at 80°C for 12 hours, and then calcined at 650°C for 6 hours to obtain the second loaded catalyst. The loading was repeated twice to increase the deposition amount of Co3O4 / Mn3O4, thereby completing the preparation of the integral Co3O4 / Mn3O4 catalyst.

[0148] Comparative Example 1

[0149] Different from Example 1, the manganese-based catalyst in this comparative example does not add transition metal oxides, and the prepared powdered Mn2O3 catalyst is directly loaded on the carrier to obtain a monolithic Mn2O3 catalyst.

[0150] The rest is the same as in Example 1 and will not be described again here.

[0151] Comparative Example 2

[0152] Different from Example 1, the catalyst for exhaust gas purification in this comparative example does not adopt a manganese-based system, but directly loads the prepared powdered Co3O4 catalyst on a carrier to obtain a monolithic Co3O4 catalyst.

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

[0154] (1) Disperse 5 g of Co(NO3)2·6H2O in 100 mL of deionized water, stir and ultrasonicate for 30 min until the nitrate is completely dissolved;

[0155] (2) while maintaining stirring and ultrasonic treatment, adding 25 wt % tetramethylammonium hydroxide aqueous solution dropwise to the solution obtained in step (1) until the pH value of the solution is adjusted to 10, and then continuing stirring and ultrasonic treatment for 3 hours; then washing the product with deionized water several times, and vacuum drying 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 powdered Co3O4 catalyst.

[0157] The rest is the same as in Example 1 and will not be described again here.

[0158] Comparative Example 3

[0159] The difference from Example 1 is the preparation of powdered Co3O4 / Mn2O3 catalyst, the preparation steps are as follows:

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

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

[0162] (3) washing the mixture obtained in step (2) with deionized water for several times, and vacuum drying at 60° C. to obtain powdered Mn2O3;

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

[0164] (5) while maintaining stirring and ultrasonic treatment, adding 25 wt% tetramethylammonium hydroxide aqueous solution to the solution obtained in step (4) dropwise until the pH value of the solution is adjusted to 10, and then continuing stirring and ultrasonic treatment for 3 hours; then washing the product with deionized water several times, and vacuum drying at 60° C., and then calcining at 400° C. for 3 hours to obtain powdered Co3O4;

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

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

[0167] Gas purification test was performed on the catalysts obtained in Examples 1 to 10 and Comparative Examples 1 to 3. The catalytic activity test was performed in a fixed bed reactor. The initial gas concentration was: 0.1 vol% propane, 0.1 vol% propylene, 2 vol% carbon monoxide, 0.05 vol% nitric oxide, 2 vol% oxygen, 5 vol% water, nitrogen as carrier gas, and the volume space velocity was 50000 h -1 The activity test temperature is 100-400°C, and the stability test temperature is 650°C.

[0168] Test results such as Figures 1 to 17 shown.

[0169] Depend on Figures 1 to 5 It can be seen that the catalyst prepared in Example 1 of the present invention achieves complete conversion of multiple components in motor vehicle exhaust at 250°C and achieves 100% nitrogen selectivity. Compared with the original Mn2O3 catalyst of Comparative Example 1, or compared with the transition metal-based catalyst of Comparative Example 2, the catalyst of the present invention effectively reduces the conversion temperature of CO, HO, and NO, and can achieve 100% conversion at 250°C. Compared with the catalyst of Comparative Example 3, the preparation method of the present invention can obtain a unique structure, and the lattice adaptability of the transition metal oxide and the manganese-based active phase is high, which can convert the inert lattice oxygen of the manganese-based active phase into active lattice oxygen, laying the foundation for the subsequent conversion of CO, HO, and NO, and achieving the purpose of accurately controlling the NO reaction path, thereby obtaining a 100% conversion effect at a lower temperature.

[0170] Depend on Figures 6-7 It can be seen that the catalyst prepared in Example 1 of the present invention has better stability than the original Mn2O3 catalyst prepared in Comparative Example 1, and its performance does not decay after reacting at 650°C for 100 hours.

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

[0172] Depend on Figures 13 to 17It can also be seen that the catalysts prepared in Examples 5 to 10 of the present invention all have excellent activity, indicating that the preparation method of the present invention 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 to allow it to be 100% reduced to N2, while ensuring complete catalytic combustion of CO / HC at low temperatures.

[0173] According to the disclosure and teaching of the above description, those skilled in the art to which the present invention belongs can also change and modify the above embodiment. Therefore, the present invention is not limited to the above specific embodiment, and any obvious improvement, replacement or modification made by those skilled in the art on the basis of the present invention belongs to the protection scope of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims

1. A method for preparing a manganese-based catalyst for purifying exhaust gas from a motor vehicle, characterized in that: The following steps are involved: S1. Mixing the transition metal salt and the manganese-based active phase, treating them by ultrasonic chemical precipitation method, washing, and drying to obtain a precursor; S2. calcining the precursor obtained in step S1 at 300-800° C. to obtain a manganese-based catalyst containing a transition metal oxide.

2. The method for preparing a manganese-based catalyst for purifying exhaust gas of a motor vehicle according to claim 1, characterized in that: The manganese-based active phase is at least one of MnO2, Mn2O3, and Mn3O4; the transition metal salt is selected from one or more of soluble cobalt salts, soluble germanium salts, soluble copper salts, soluble nickel salts, and soluble iron salts.

3. The method for preparing a manganese-based catalyst for purifying exhaust gas of a motor vehicle according to claim 1 or 2, characterized in that: The mass of the transition metal oxide is 5% to 60% of the mass of the manganese-based catalyst.

4. The method for preparing a manganese-based catalyst for purifying exhaust gas of a motor vehicle according to claim 1 or 2, characterized in that: In step S1, the processing steps of the ultrasonic chemical precipitation method are: adding a precipitant under ultrasonic conditions, and stopping the addition when the pH value of the system is 9-12; then continuing ultrasonic treatment, washing, and drying to obtain a precursor.

5. The method for preparing a manganese-based catalyst for purifying exhaust gas of a motor vehicle according to claim 1 or 2, characterized in that: In step S1, the preparation steps of the manganese-based active phase are: calcining a manganese source and dispersing it in a solvent together with a dispersant, ultrasonically treating it in an ice-water bath, washing it, and drying it to obtain the manganese-based active phase.

6. The method for preparing a manganese-based catalyst for purifying exhaust gas of a motor vehicle according to claim 5, characterized in that: The manganese source is manganese carbonate; the dispersant is polyvinyl pyrrolidone; and the mass ratio of the manganese-based active phase to the dispersant is (1-50):

1.

7. The method for preparing a manganese-based catalyst for purifying exhaust gas of a motor vehicle according to claim 1, characterized in that: The method also includes loading the manganese-based catalyst containing transition metal oxide obtained in step S2 into a carrier to obtain a monolithic manganese-based catalyst.

8. The method for preparing a manganese-based catalyst for purifying exhaust gas of a motor vehicle according to claim 7, characterized in that: The carrier is a honeycomb ceramic with pores; the loading steps are: S3, adding the etched honeycomb ceramic into an aqueous solution containing a binder to obtain a carrier mixed solution; S4, dispersing the manganese-based catalyst containing transition metal oxide in the carrier mixed liquid, stirring and soaking, drying and then calcining to obtain a monolithic manganese-based catalyst.

9. The method for preparing a manganese-based catalyst for purifying exhaust gas of a motor vehicle according to claim 8, characterized in that: In step S4, the soaking time is 10 to 14 hours, and the calcination temperature is 300 to 800°C.

10. A manganese-based catalyst for purifying exhaust gas from a motor vehicle, characterized in that: The catalyst is prepared by the method for preparing a manganese-based catalyst for purifying exhaust gas of motor vehicles as described in any one of claims 1 to 9.

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