CN113559850B - Manganese-based composite oxide catalyst and preparation method and application thereof - Google Patents
Manganese-based composite oxide catalyst and preparation method and application thereof Download PDFInfo
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Abstract
The invention relates to a manganese-based composite oxide catalyst, a preparation method and application thereof. The composite oxide catalyst of the present invention is prepared from Mn of the formula (x)2O3/(1‑x)AMn2O5Wherein A is one or more of Sm, La, Y, Sr, Ce, Ba, Ca, Gd, Nd and Pr, and x is not equal to 0. Composite oxide bond AMn of the present invention2O5Excellent thermal stability and NO oxidation property and Mn2O3The catalyst has strong oxidizing property and excellent thermal stability, and can realize the performance of simultaneously and efficiently removing various pollutants such as HC (hydrocarbon), CO (carbon monoxide) and NO (nitrogen monoxide) by one catalyst in the purification of the tail gas of the diesel vehicle.
Description
Technical Field
The invention belongs to the technical field of air pollution control, relates to a manganese-based composite oxide catalyst for diesel vehicle tail gas treatment, and a preparation method and application thereof, and particularly relates to synergistic purification of HC (hydrocarbon), CO (carbon monoxide) and NO (nitrogen monoxide) in diesel vehicle tail gas.
Background
The automobile is an important component of modern society, and the automobile industry develops rapidly along with rapid economic development and urbanization process. The source of automotive power is primarily the combustion of fossil fuels (e.g., gasoline, diesel, etc.). The pollutants generated from the tail gas of fossil fuel automobiles are mainly Nitrogen Oxides (NO)x) Carbon monoxide (CO), Hydrocarbons (HC), Particulate Matter (PM), and the like. Diesel vehicle NOxThe emission amount exceeds 80% of the total emission amount of the automobile, and the PM emission amount exceeds 90%.
Pollutants emitted from automobiles are a major source of air pollution, and diesel vehicles make the greatest contribution among mobile sources. In pollutants discharged by motor vehicle exhaust, CO directly harms human health, and poisoning symptoms can occur after the pollutants are inhaled, even death occurs. HC and NOxIs an important source for generating acid rain and photochemical smog, and generates O through a series of chemical reactions under the action of sunlight3Further forming photochemical smog which causes serious harm to the environment and human body.
Currently, to meet emission standards, diesel aftertreatment technology requires DOC (diesel oxidation catalyst), DPF (diesel particulate filter), SCR (selective catalytic reduction), and ASC (ammonia slip catalyst) coupling to achieve emission standards. Wherein CO and HC are removed in DOC module, PM is removed in DPF module, NOx is removed in SCR catalyst by adding urea, and excess NH3By passingThe ASC module is removed. Oxidation of NO to NO, given that NO is the major constituent of direct emissions downstream of diesel engines2Is a key step for reducing NO and PM in the tail gas of the diesel engine to the maximum extent. Due to NO2Has a specific gravity of O2Higher oxidation ability, which can improve the oxidation ability of HCs in DOC and PM in DPF. In order to reduce the NO produced by the engine, a DOC module is usually installed in the exhaust aftertreatment line downstream of the engine before the DPF module, converting some amount of NO to NO while removing CO and HC2. This places stringent requirements on the thermal stability and catalytic oxidation activity of the DOC material.
The DOC system consists of a shell, a vibration damping layer, a base body and a catalyst. The catalyst is the DOC core part and is the main performance index of the DOC. At present, the commercial DOC catalyst is mainly prepared by loading noble metals such as platinum (Pt), palladium (Pd) and the like on oxides, and has excellent catalytic performance, but the resource storage amount is small, and the price is high. In view of the pursuit of fuel economy and the cost of aftertreatment devices, it is necessary to develop a low-cost catalyst having good efficiency and stability. The transition/rare earth metal oxide has certain catalytic oxidation capacity to CO, NO and HC, and is concerned by researchers due to the advantages of abundant reserves and low cost.
Manganese-based mullite of the formula AMn2O5The material has excellent oxidation performance and extremely high thermal stability, is a material with high-efficiency catalytic activity for catalytic oxidation of NO and CO, and becomes a mixed oxide system which is researched more in the field of control of tail gas of motor vehicles at present. At AMn2O5In the structure, the A-site ion mainly acts to stabilize the structure of the composite oxide and can control the valence state and the dispersion state of the Mn element. In addition, AMn2O5The catalytic performance is due to its unique Mn-Mn dimer active site.
Citation 1 discloses a mullite-type composite oxide catalyst for the oxidation of nitric oxide, which has a general chemical formula A1-xA'xB'yO5Wherein A and A' are each independently one of a rare earth metal or an alkaline earth metal element, the rare earth metal element may beLa, Ce, Nd, Gd and Sm, and the alkaline earth metal elements can be Mg, Ca, Sr and Ba; b and B' are each independently a transition metal element, which may be Fe, Co, Mn, Ni, Ti, and Cr. In addition, citation 1 studies the catalytic performance of the mullite-type composite oxide catalyst on nitric oxide, and proves that the mullite-type composite oxide catalyst and Pt/γ -Al2O3Compared with the nitric oxide conversion rate, the conversion rate is obviously improved.
In addition, in order to improve the catalytic activity, modified manganese-based mullite and a manganese-based mullite composite have been studied. For example, cited reference 3 discloses Ag-modified manganese-based mullite.
Although the catalysts can improve the activity of the manganese-based mullite catalyst to a certain extent, the performance optimization still has room for further improvement.
Cited documents:
cited document 1: CN104624184A
Cited document 2: CN110433794A
Cited document 3: CN110013849A
Disclosure of Invention
Problems to be solved by the invention
Aiming at the mullite catalyst (AMn) which is expected to replace noble metal and applied to the DOC field of motor vehicle tail gas2O5) The catalytic performance of the catalyst mainly depends on the A site element and the synthesis method, and the exposure of the B site Mn element is directly and positively correlated with the catalytic oxidation activity of the catalyst. Therefore, how to increase the content of the surface active sites of the mullite is to improve the content of the surface active sites of the mullite on the premise of keeping the bulk phase structure of the mullite unchangedHigh catalytic oxidation performance and key for further industrial application.
Means for solving the problems
After long-term intensive research by the inventors, it is found that the technical problems can be solved by implementing the following technical scheme:
1. a manganese-based composite oxide catalyst, characterized in that the manganese-based composite oxide is represented by the following formula:
(x)Mn2O3/(1-x)AMn2O5
wherein A is one or more of Sm, La, Y, Sr, Ce, Ba, Ca, Gd, Nd and Pr, and x is not equal to 0.
2. The manganese-based composite oxide catalyst according to the above 1, wherein x is in the range of 0.01 to 0.5, preferably in the range of 0.05 to 0.3.
3. The manganese-based composite oxide catalyst according to the above 1 or 2, wherein the BET specific surface area of the manganese-based composite oxide is 15 to 30m2(ii)/g, the average pore diameter is 30 to 60 nm.
4. The manganese-based composite oxide catalyst according to any one of the above 1 to 3, wherein, in the amount of the catalyst: 0.1g, particle size: 40-60 meshes, flue gas concentration: NO 500ppm, O2Concentration: 10vol.%, N2: balance, total gas amount: 200mL min-1And airspeed: 120000h-1Under the conditions of (a) under (b),
t of the manganese-based composite oxide catalyst80-NOIs below 260 ℃ in which T80-NOIs the temperature at which the NO conversion is 80%.
5. A method for producing the manganese-based composite oxide catalyst according to any one of the above 1 to 4, characterized by comprising a step of mixing a soluble A salt and a soluble manganese salt at a molar ratio of A: Mn (1-x):2 to obtain a mixture.
6. The production method according to the above 5, which comprises a step of adding a complexing agent to the mixture.
7. The production method according to 5 or 6 above, further comprising a step of subjecting the mixture to hydrothermal treatment, coprecipitation, or formation of a solvent gel.
8. The production method according to the above 6, wherein the complexing agent is citric acid.
9. The production method according to any one of the above 5 to 8, wherein the soluble A salt is a nitrate, an acetate or a chloride of A, and the soluble manganese salt is a divalent manganese salt or a heptavalent manganese salt.
10. Use of the manganese-based composite oxide catalyst according to any one of the above 1 to 4 for simultaneously removing hydrocarbons, carbon monoxide and nitrogen monoxide in a diesel vehicle exhaust gas with high efficiency.
ADVANTAGEOUS EFFECTS OF INVENTION
Through the implementation of the technical scheme, the invention can obtain the following technical effects:
(1) the manganese-based composite oxide catalyst of the present invention incorporates AMn2O5Excellent thermal stability and NO oxidation properties of mullite structure and Mn2O3The catalyst has the advantages of low ignition temperature, high conversion efficiency, good high temperature resistance, excellent water resistance, low price and the like in the purification of the tail gas of the diesel vehicle, and can realize the performance of efficiently removing various pollutants such as HC (hydrocarbon), CO (carbon monoxide), NO (nitrogen monoxide) and the like by one catalyst.
(2) Manganese-based composite oxide (x) Mn of the present invention2O3/(1-x)AMn2O5(x ≠ 0) as compared to mullite oxide AMn2O5And Mn2O3The temperature required for reaching the same catalytic activity is reduced, and the energy is saved and the consumption is reduced.
(3) The synthesis process is simple, the operation cost is low, the industrial application is easy, and the method has a high market popularization prospect.
Drawings
FIG. 1 is Sm0.5Mn2O5、Sm0.7Mn2O5、Sm0.9Mn2O5、SmMn2O5And Mn2O3XRD pattern of (a).
FIG. 2 Sm0.5Mn2O5、Sm0.7Mn2O5、Sm0.9Mn2O5、SmMn2O5And Mn2O3Graph of NO conversion.
FIG. 3 is Sm0.9Mn2O5And SmMn2O5(NO + CO + C)3H6) And (4) a conversion rate chart.
FIG. 4 Sm0.9Mn2O5(NO + CO + C) Stable at 300 ℃ for 50 hours3H6) And (4) a conversion rate chart.
Detailed Description
The present invention will be described in detail below. The technical features described below are explained based on typical embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples. It should be noted that:
in the present specification, the numerical range represented by "numerical value a to numerical value B" means a range including the end point numerical value A, B.
In the present specification, the numerical ranges indicated by "above" or "below" mean the numerical ranges including the numbers.
In the present specification, the meaning of "may" includes both the meaning of performing a certain process and the meaning of not performing a certain process.
As used herein, the term "optional" or "optional" is used to indicate that certain substances, components, performance steps, application conditions, and the like are used or not used.
In the specification, the unit names used are all international standard unit names.
In the present specification, the term "plurality" means two or more than two unless otherwise specified.
In the present specification, reference to "some particular/preferred embodiments," "other particular/preferred embodiments," "embodiments," and the like, means that a particular element (e.g., feature, structure, property, and/or characteristic) described in connection with the embodiment is included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it is to be understood that the described elements may be combined in any suitable manner in the various embodiments.
< first aspect >
A first aspect of the invention provides a manganese-based composite oxide catalyst. The manganese-based composite oxide catalyst provided by the invention has more Mn active sites on the premise of keeping excellent thermal stability, and can greatly improve the synergistic catalytic oxidation capacity of CO, HC and NO.
Catalyst composition
The manganese-based composite oxide catalyst of the present invention can be represented by the following formula:
(x)Mn2O3/(1-x)AMn2O5
wherein A is one or more of Sm, La, Y, Sr, Ce, Ba, Ca, Gd, Nd and Pr, and x is not equal to 0. As is clear from the above formula, the manganese-based composite oxide of the present invention has AMn2O5Mullite and Mn2O3Two structures are provided.
In the present invention, for the convenience of description, Mn of the above formula (x)2O3/(1-x)AMn2O5Can also be written as A1-xMn2O5. Note that since "O" in the composite oxide is adjustable, "x" is mainly used to define the ratio of a to Mn.
According to the study by the present inventors, it has been found that the value of x in the manganese-based composite oxide of the present invention is preferably in the range of 0 or more and 0.5 or less, more preferably in the range of 0.01 to 0.5, and still more preferably in the range of 0.05 to 0.3.
The M element in the manganese-based composite oxide of the present invention may be one or more elements selected from Sm, La, Y, Sr, Ce, Ba, Ca, Gd, Nd, Pr. When M is two or more of the above elements, the element ratio between them is not particularly limited, and compounding may be carried out as needed.
Other ingredients
In some preferred embodiments of the present invention, no other metal elements other than element a and element Mn may be substantially included in the catalyst of the present invention. By "not substantially included" in the context of the present invention is meant that the materials or components comprising the materials are not introduced as raw materials in forming or making the catalysts of the present invention.
In other specific embodiments, other metal elements may be added as necessary in addition to the above-mentioned components of the catalyst of the present invention without affecting the technical effect of the present invention. Other metallic elements that may be used include one or more of tungsten, copper, nickel, and rare earth elements. And the total content of these additional metal elements is 1 mol% or less, preferably 0.8 mol% or less, for example 0.2 mol% or less, based on the total number of moles of metal elements in the catalyst.
Further, the catalyst of the present invention may be a supported catalyst or an unsupported catalyst. The carrier is not particularly limited and may be a carrier commonly used in the art, such as cordierite, a metal oxide carrier (e.g., alumina, titania, etc.), carbon black, a molecular sieve, hydrotalcite, natural zeolite, ash in a fluidized bed, etc., and a typical carrier may be one of cordierite, alumina, a molecular sieve, or hydrotalcite.
Catalyst crystal structure
As described above, the manganese-based composite oxide catalyst of the present invention has AMn2O5Mullite and Mn2O3Two structures are provided. The following description will specifically discuss an example in which A is Sm.
FIG. 1 shows a manganese-based composite oxide Sm prepared in subsequent example 10.9Mn2O5(i.e., (x) Mn)2O3/(1-x)AMn2O5Where x ═ 0.1) XRD pattern. It can be seen that Sm0.9Mn2O5Simultaneously possess SmMn2O5And Mn2O3Showing Sm0.9Mn2O5With AMn2O5Mullite and Mn2O3Two structures are provided.
Manganese-based composite oxide Sm prepared in subsequent examples 2 and 3 shown in FIG. 10.7Mn2O5(i.e., (x) Mn)2O3/(1-x)AMn2O5Where x is 0.3) and Sm0.5Mn2O5(i.e., (x) Mn)2O3/(1-x)AMn2O5Where x ═ 0.5) also showed the same diffraction peaks, indicating Sm0.7Mn2O5And Sm0.5Mn2O5Also has AMn at the same time2O5Mullite and Mn2O3Two structures are provided. Also, as can be seen from FIG. 1, Mn increases with the value of x2O3The intensity of the diffraction peak gradually increased.
The manganese-based composite oxide catalyst of the present invention incorporates AMn2O5Mullite and Mn2O3The catalyst has the advantages of two structures, so that the catalyst has the advantages of low ignition temperature, high conversion efficiency, good high-temperature resistance, excellent water resistance, low price and the like in the tail gas purification of the diesel vehicle, and can realize the performance of efficiently removing various pollutants such as HC (hydrocarbon), CO (carbon monoxide), NO (nitrogen monoxide) and the like by one catalyst.
Specific surface area
The change in specific surface area of the manganese-based composite oxide catalyst with the composition will be described below.
Manganese-based composite oxide catalyst (x) Mn of the present invention2O3/(1-x)AMn2O5The BET specific surface area of (A) is 15 to 30m2(ii)/g, the average pore diameter is 30 to 60 nm.
Manganese-based composite oxide catalyst (x) Mn2O3/(1-x)AMn2O5AMn prepared under the same conditions2O5In contrast, the specific surface area and pore volume increased nearly by a factor of two. This is the manganese-based composite oxide catalyst (x) Mn of the present invention2O3/(1-x)AMn2O5One of the reasons why the catalytic performance is excellent.
In addition, water affects the catalytic performance of the catalyst, and the catalyst of the present invention has excellent water resistance.
< second aspect >
A second aspect of the invention provides a method for producing a manganese-based composite oxide. The method for producing the manganese-based composite oxide of the present invention is not particularly limited, and it can be produced using production methods known in the art, such as hydrothermal synthesis, coprecipitation, sol-gel method, and the like, as long as the crystal structure, BET specific surface area, and the like of the produced composite oxide are within the above-described range of the present invention.
Manganese-based composite oxide (x) Mn in the invention2O3/(1-x)AMn2O5The preparation method comprises the step of mixing the soluble A salt and the soluble manganese salt according to the molar ratio of A: Mn (1-x): 2. Thereafter, the mixture including the two salts may be subjected to further steps such as hydrothermal treatment, coprecipitation, or formation of a solvent gel, thereby obtaining the manganese-based composite oxide a1-xMn2O5。
The following description will be made by taking a sol-gel method as an example.
Preparation of manganese-based composite oxide A by sol-gel method1-xMn2O5The method mainly comprises the following steps: mixing soluble A salt and soluble manganese salt according to the molar ratio of A: Mn (1-x):2 to obtain a mixed solution; heating the mixed solution to form a sol; then drying and roasting are carried out.
In embodiments of the invention, the soluble a salt may be a nitrate, acetate, chloride, etc. of a. The soluble manganese salt at least comprises divalent manganese salt and heptavalent manganese salt.
The element a in the manganese-based composite oxide of the present invention may be one or more selected from Sm, La, Y, Sr, Ce, Ba, Ca, Gd, Nd, and Pr. When a is two or more of the above elements, the element ratio therebetween is not particularly limited, and compounding may be performed as necessary.
According to the study of the present inventors, it has been found that the value of x in the manganese-based composite oxide of the present invention may be 0.01 to 0.5, preferably 0.05 to 0.3.
In some embodiments of the present invention, a complexing agent may be added to the mixed solution of the soluble a salt and the soluble manganese salt in order to uniformly mix the metal ions. Examples of complexing agents may include citric acid and the like.
When the gel is formed by heating, the heating is preferably carried out in a water bath, and the heating temperature can be 40-100 ℃, and preferably 60-80 ℃.
The drying method is not particularly limited, and the product may be dried in an atmospheric environment using equipment generally used in the art. The drying temperature may be 80 to 150 ℃ in some embodiments, and is preferably 100 to 120 ℃; the drying time is not limited, and may be, for example, 8 to 24 hours, preferably 10 to 18 hours, and more preferably 12 to 15 hours.
The method of calcination is not particularly limited, and the product can be calcined in an atmospheric environment using equipment that is usual in the art. The roasting temperature can be 400-1000 ℃, preferably 500-800 ℃. The roasting time can be 8-24 h, preferably 10-16 h.
< third aspect >
In a third aspect of the present invention, there is provided use of the above manganese-based composite oxide catalyst for purification of CO, CH and NO in automobile exhaust.
The HC is not particularly limited, and specifically includes hydrocarbons (alkanes, alkenes, alkynes, cyclic hydrocarbons, aromatic hydrocarbons), ketones, esters, alcohols, ethers, aldehydes, acids, epoxy compounds, and the like.
The conditions for the catalytic performance test are not particularly limited, and test conditions common in the art may be used. In some specific embodiments, the test conditions and resulting catalytic performance are as follows.
When the smoke is NO, the experimental conditions are as follows:
the catalyst dosage is as follows: 0.1g, particle size: 40-60 meshes, flue gas concentration: NO 500ppm, O2Concentration: 10vol.%, N2: balance, total gas amount: 200mL min-1And airspeed: 120000h-1，
Under the above conditions, the manganese-based composite oxide catalyst A of the present invention1-xMn2O5T of80-NOAt 260 ℃ or lower under the same conditions, SmMn2O5T of80-NOAt 325 ℃ where T80-NOIs the temperature at which the NO conversion is 80%. Lower temperatures indicate better catalytic performance of the catalyst. Therefore, the catalytic effect of the composite oxide catalyst of the present invention is very surprising.
When the flue gas is NO, CO and C3H6For the three, the experimental conditions were:
the dosage of the catalyst is as follows: 0.1g, particle size: 40-60 meshes, flue gas concentration: NO 500ppm, CO 1%, C3H6 2000ppm，O2Concentration: 10vol.%, N2: balance, total gas amount: 200mL min-1And airspeed: 120000h-1，
Under the above conditions, the manganese-based composite oxide catalyst of the present invention and SmMn at a temperature of 300 ℃ are obtained2O5Both enable CO and C3H6Substantially all of the conversion; however, at a temperature of 300 ℃, the conversion rate of NO of the manganese-based composite oxide catalyst is higher than SmMn2O5。
Thus, the manganese-based composite oxide catalyst A of the present invention1-xMn2O5For NO + CO + C3H6The catalytic oxidation performance of the three is also obviously superior to SmMn2O5。
Examples
The present invention will be described below with reference to specific examples.
First, the structure and performance characterization of the catalyst will be explained.
(1) Crystal structure
The XRD data of all samples in the present invention were tested on a Rigaku X-ray diffractometer with a Cu ka radiation source (λ ═ 0.15405nm) at a voltage of 40kV and a current of 200 mA.
(2) BET specific surface area test
The BET specific surface area was obtained by nitrogen adsorption-desorption on a Quantachrome Autosorb-1MP apparatus at liquid nitrogen temperature (-196 ℃ C.).
(3) Testing of catalytic Performance (stability test included in the testing procedure)
The catalytic performance test steps of the invention are as follows:
the catalytic oxidation reaction was carried out in a continuous-flow microreactor made from quartz tubes (id ═ 6 mm). Reaction mixture (500ppm NO + 10% O)2+N2(balance), or 500ppm NO + 1% CO +2000ppm C3H6+10％O2+N2(remainder)) the total flow rate was 200mL min-1GHSV of 120,000mL g-1h-1. The concentrations of reactants and products were monitored on-line by a Gasmet DX4000 gas analyzer. The conversion was calculated as the NO conversion (X) according to the following formulaNOAnd (%):
wherein, CinAnd CoutThe concentrations of NO corresponding to the inlet and outlet, respectively.
Example 1
0.9 2 5Preparation of composite oxide SmMnO
0.09mol of Sm (NO)3)3·6H2O、0.2mol Mn(NO3)2And 0.29mol citric acid in a beaker and 1L deionized water was added. Steaming in 80 deg.C water bath to obtain sol, air drying, and drying at 120 deg.C for 12 hr. Then, the mixture was baked at 500 ℃ and 800 ℃ for 10 hours, respectively. Thus, a composite oxide Sm was obtained0.9Mn2O5。
FIG. 1 shows a composite oxide Sm0.9Mn2O5XRD pattern of (a). As shown in FIG. 1, the composite oxide Sm is0.9Mn2O5Mainly SmMn2O5And Mn2O3And (4) forming.
Comparative example 1
2 5Preparation of oxide SmMnO
Except that "0.09 mol of Sm (NO) in example 13)3·6H2O' is changed to "0.1 mol Sm (NO)3)3·6H2SmMn was prepared in the same manner as in example 1 except that O ″2O5(i.e., Sm1.0Mn2O5Or simply SMO).
Comparison of example 1 with comparative example 1
For SmMn prepared in comparative example 12O5And composite oxide Sm prepared in example 10.9Mn2O5The BET nitrogen adsorption specific surface area measurements were made, respectively, and the results are shown in table 1 below.
TABLE 1Sm0.9Mn2O5And SmMn2O5Specific surface area
| Catalyst and process for producing the same | Specific surface area (m)2 g-1) |
| Sm0.9Mn2O5 | 22.22 |
| SmMn2O5 | 11.39 |
As shown in Table 1, it is found that the metal complex reacts with SmMn2O5In contrast, the composite oxide Sm0.9Mn2O5Is increased by nearly one time.
In order to examine the composite oxide catalyst Sm0.9Mn2O5With SmMn2O5For NO and (NO + CO + C), respectively3H6) Catalytic performance tests were performed. The results are shown in FIGS. 2 and 3, respectively.
As can be seen from FIG. 2, the composite oxide Sm was found to be present at a NO conversion of 80%0.9Mn2O5The temperature at this time was only 235 ℃; and Sm1.0Mn2O5(i.e., SmMn)2O5) The temperature at this time was 325 ℃. As can be seen from this, the composite oxide catalyst Sm of the present invention0.9Mn2O5The above effects of (a) are very surprising.
Composite oxide catalyst Sm0.9Mn2O5For NO + CO + C3H6The synergistic purification effect of the three is shown in fig. 3.
As shown in FIG. 3, when the temperature was 300 ℃ compared to SmMn2O5，Sm0.9Mn2O5The catalyst can be used for mixing CO and C3H6Both are converted substantially completely; and, Sm0.9Mn2O5The NO conversion rate of the catalyst is 76 percent and is better than SmMn2O5(NO conversion 54%).
Thus, the composite oxide catalyst Sm of the present invention0.9Mn2O5For NO + CO + C3H6The catalytic oxidation performance of the three is obviously superior to SmMn2O5。
Composite oxide catalyst Sm0.9Mn2O5For NO + CO + C3H6The thermal stability effect of the three synergistic purifications is shown in figure 4. From FIG. 4, it can be found that the composite oxide catalyst Sm0.9Mn2O5Has excellent thermal stability at 300 ℃.
Example 2
0.7 2 5Preparation of composite oxide SmMnO
0.07mol of Sm (NO)3)3·6H2O、0.2mol Mn(NO3)2And 0.27mol citric acid in a beaker and 1L deionized water was added. Steaming in 80 deg.C water bath to obtain sol, taking out, air drying, and drying at 120 deg.C for 12 hr. Then, the mixture was calcined at 500 ℃ and 800 ℃ for 10 hours, respectively. Thus, a composite oxide Sm was obtained0.7Mn2O5。
FIG. 1 shows a composite oxide Sm0.7Mn2O5XRD pattern of (a). As shown in FIG. 1, the composite oxide Sm is0.7Mn2O5Mainly SmMn2O5And Mn2O3And (4) forming.
Sm0.7Mn2O5The NO catalytic oxidation performance results of the catalyst are shown in fig. 2. More specifically, as can be seen from FIG. 2, when the NO conversion reaches up to 80%, the composite oxide Sm0.7Mn2O5The temperature at this time was 255 ℃; and SmMn2O5The temperature at this time was 325 ℃. Composite oxide catalyst Sm0.7Mn2O5The above effects of (a) are very surprising.
Example 3
0.5 2 5Preparation of composite oxide SmMnO
0.05mol of Sm (NO)3)3·6H2O、0.2mol Mn(NO3)2And 0.25mol citric acid in a beaker and 1L deionized water was added. Steaming in 80 deg.C water bath to obtain sol, taking out, air drying, and drying at 120 deg.C for 12 hr. Then, the mixture was calcined at 500 ℃ and 800 ℃ for 10 hours, respectively. Thus, a composite oxide Sm was obtained0.5Mn2O5。
FIG. 1 shows a composite oxide Sm0.5Mn2O5XRD pattern of (a). As shown in FIG. 1, the composite oxide Sm is0.5Mn2O5Mainly SmMn2O5And Mn2O3And (4) forming.
Sm0.5Mn2O5The NO catalytic oxidation performance results for the catalyst are shown in fig. 2. Sm when the NO conversion rate reaches 80 percent0.5Mn2O5The temperature at this time was 255 ℃; and SmMn2O5The temperature at this time was 325 ℃. Composite oxide catalyst Sm0.5Mn2O5The above effects of (a) are very surprising.
Industrial applicability
The manganese-based composite oxide catalyst can realize the performance of simultaneously and efficiently removing various pollutants such as HC (hydrocarbon), CO (carbon monoxide) and NO (nitrogen monoxide) by one catalyst in the tail gas purification of diesel vehicles, thereby being beneficial to popularization and application.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A manganese-based composite oxide catalyst, characterized in that said manganese-based composite oxide is represented by the following formula:
(x)Mn2O3/(1-x)AMn2O5
wherein A is one or more of Sm, La, Y, Sr, Ce, Ba, Ca, Gd, Nd and Pr, x is in the range of 0.01-0.5,
the BET specific surface area of the manganese-based composite oxide catalyst is 15-22.22 m/g;
the preparation method of the manganese-based composite oxide catalyst comprises the step of mixing a soluble A salt and a soluble manganese salt in a molar ratio of A: Mn (1-x):2 to obtain a mixture.
2. The manganese-based composite oxide catalyst according to claim 1, wherein x is in the range of 0.05 to 0.3.
3. The manganese-based composite oxide catalyst according to claim 1 or 2, wherein the average pore diameter of the manganese-based composite oxide is 30 to 60 nm.
4. The manganese-based composite oxide catalyst according to claim 1 or 2, characterized in that the molar ratio of the catalyst amount: 0.1g, particle size: 40-60 meshes, flue gas concentration: NO 500ppm, O2Concentration: 10vol.%, N2: balance, total gas amount: 200mL min-1The space velocity: 120000h-1Under the conditions of (a) under (b),
t of the manganese-based composite oxide catalyst80-NOIs below 260 ℃ in which T80-NOIs the temperature at which the NO conversion is 80%.
5. A method for producing a manganese-based composite oxide catalyst according to any one of claims 1 to 4, characterized in that it comprises a step of mixing a soluble A salt and a soluble manganese salt in a molar ratio of A: Mn (1-x):2 to obtain a mixture.
6. The method of claim 5, including the step of adding a complexing agent to the mixture.
7. The method according to claim 5 or 6, further comprising a step of subjecting the mixture to hydrothermal treatment, coprecipitation, or sol gel formation.
8. The method according to claim 6, wherein the complexing agent is citric acid.
9. The method according to claim 5 or 6, wherein the soluble A salt is a nitrate, acetate or chloride of A, and the soluble manganese salt is a divalent manganese salt or a heptavalent manganese salt.
10. Use of the manganese-based composite oxide catalyst according to any one of claims 1 to 4 for simultaneous removal of hydrocarbons, carbon monoxide and nitrogen monoxide in diesel exhaust.
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| CN113559850B (en) * | 2021-07-13 | 2022-07-08 | 清华大学 | Manganese-based composite oxide catalyst and preparation method and application thereof |
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