Modified Mn2O3 / DPF monolithic catalyst with different potassium contents and preparation method thereof
By constructing modified Mn2O3 catalysts with different potassium contents in situ on DPF, the problem of purifying particulate matter in diesel engine exhaust gas was solved, achieving efficient catalytic combustion and cost reduction.
Patent Information
- Application Number
- CN202510840185.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-23
- Publication Date
- 2025-11-07
AI Technical Summary
In existing technologies, it is difficult to effectively remove particulate matter from diesel engine exhaust, and the exposure of catalyst active sites is uncontrollable, with low utilization rate, poor coating adhesion, and complex processes.
Modified Mn2O3 catalysts with different potassium contents were constructed in situ on DPF using a hydrothermal method. By adjusting the molar ratio of potassium nitrate to manganese acetate, irregular prismatic and pyramidal Mn2O3 structures were formed, thereby improving the contact efficiency and activity between the catalyst and soot particles.
It achieves complete removal of soot particles below 450℃, reduces catalyst consumption, simplifies the process, and improves catalyst activity and adhesion.
Smart Images
Figure CN120900618A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application discloses a kind of different potassium content modified Mn2O3 / DPF monolithic catalyst and preparation method thereof, and relates to the technical field of catalyst preparation. BACKGROUND
[0002] Compared with gasoline engine, diesel engine has high thermal efficiency, good durability, high economic feasibility and other advantages, and has been widely applied to heavy transport, industrial and agricultural machinery and ship fields etc.. However, the exhaust of diesel engine can cause great harm to the natural environment and human health. The pollutants contained in diesel engine exhaust include carbon monoxide (CO), nitrogen oxides (NOx), hydrocarbons (HC), soot particles (PM) and a small amount of other pollutants such as SOx, heavy metal ions, etc. Among them, particulate matter (PM) is the most serious and most difficult to eliminate pollutant, soot is roughly composed of two parts, one part is mainly insoluble substances composed of carbon particles (dry soot 40%~50%), sulfate (5%~10%), and ash particles. The other part is mainly soluble particles (35%~45%) composed of incomplete combustion of fuel, oil and intermediates or suspended particles (aerosol).
[0003] In the aspect of catalyst, manganese-based oxide catalyst in transition metal oxide is widely used in the research of catalytic combustion of soot due to its excellent redox performance. The valence electron configuration of manganese is 3d54s2, and the particularity of its valence electron configuration promotes it to form various valence state oxides, such as MnO2, Mn2O3 and Mn3O4, and various oxidation states can be converted to each other. Alkali metal has good thermal conductivity, and its melting characteristics at high temperature lead to strong surface fluidity, which makes the addition of alkali metal can improve the contact state of soot particles and catalyst. Studies have shown that the activity of catalyst can be improved by modifying manganese oxide catalyst with alkali metal. Therefore, the manganese oxide catalyst modified by alkali metal has strong application potential by coating on the surface of exhaust aftertreatment filter;
[0004] For the elimination of diesel soot particles, people focus on developing various technologies to control the emission of these pollutants, and implement more stringent soot emission regulations to promote the development of various strategies. At present, researchers mainly control the emission of soot particles in diesel exhaust through three means: improving fuel quality, improving engine structure and exhaust aftertreatment. The clean diesel technology and engine improvement technology are in-machine purification, and the exhaust aftertreatment technology belongs to out-of-machine purification. Due to the limitations of existing technical means, it is difficult to effectively eliminate soot particles by only the first two methods. Therefore, diesel vehicle catalytic aftertreatment technology is a necessary means for efficient purification of soot particles in motor vehicle exhaust, and the challenge faced by the technology research is how to design and prepare a high-performance catalyst and efficiently coat it on the filter surface.
[0005] However, in terms of catalyst coating, the current mainstream coating method in the industry is to first prepare a powder catalyst, then mix the powder catalyst, aluminum sol and binder to form a slurry, and finally use a coating machine to coat the slurry on the DPF, followed by drying, calcination and other processes to obtain a DPF containing a monolithic catalyst (CDPF). However, this coating method often brings some unavoidable problems, such as uncontrollable exposure of active sites of the catalyst, low utilization rate of the catalyst, poor adhesion of the coating leading to shedding over time, complex process and equipment, etc. Therefore, it is of important application prospect to provide a method for in-situ growth of active components on a DPF carrier. SUMMARY
[0006] In view of this, the present application provides a Mn2O3 / DPF monolithic catalyst with different potassium content and a preparation method thereof. By adjusting the content of potassium nitrate, the performance of the catalyst is improved, thereby achieving the purpose of improving the activity of the catalyst.
[0007] The technical scheme provided by the present application is a Mn2O3 / DPF monolithic catalyst with different potassium content, which is composed of DPF and Mn2O3 catalyst. The catalyst has irregular prismatic and pyramidal morphology under different potassium nitrate addition amounts.
[0008] Preferably, the size of the Mn2O3 catalyst with irregular prismatic and pyramidal morphology is 2-4 μm.
[0009] The present application also provides a preparation method of the catalyst, which comprises: using aqueous solutions of manganese acetate, urea and different amounts of potassium nitrate as raw materials, and constructing Mn2O3 on DPF in-situ by hydrothermal method to obtain catalysts with different performances, which are denoted as K / Mn-x:y / DPF, wherein x:y represents the molar ratio of potassium nitrate to manganese acetate.
[0010] Preferably, the in-situ construction of Mn2O3 on DPF in the aqueous solution of manganese acetate, urea and potassium nitrate by hydrothermal method is denoted as K / Mn / DPF, which comprises:
[0011] 1) pretreatment of DPF;
[0012] 2) mixing the pretreated DPF with potassium nitrate, manganese acetate and urea, and placing the obtained mixed solution into a reaction kettle, sealing the reaction kettle and then transferring it to a constant temperature condition of 100-160℃ for reaction for 6-18h;
[0013] After the reaction is completed, the reacted material is taken out after cooling to room temperature, washed and the excess liquid on the material is removed;
[0014] The obtained sample is then sequentially subjected to drying and calcination, and finally the monolithic catalyst K / Mn / DPF is obtained.
[0015] Preferably, the method for pretreating DPF comprises cutting, washing and drying in sequence, wherein the washing process is sequentially performed according to the washing sequence of ultrapure water, ethanol and ultrapure water.
[0016] Preferably, the added amount of urea is 4.18g, the added amount of manganese acetate is 2.45g, and the added amount of potassium nitrate is 0-2.02g.
[0017] Preferably, the drying and calcination conditions are that the sample is placed in a constant temperature condition of 60-100℃ for drying for 8-10h, and finally calcined at 350-750℃ for 3-5h.
[0018] Preferably, the heating rate during calcination is 1-5℃ / min.
[0019] The present application provides a preparation method of a modified Mn2O3 / DPF monolithic catalyst with different potassium contents, which grows active components on DPF by physical and chemical methods. Since the catalytic combustion of soot particles is a deep oxidation reaction of gas-solid-solid three phases, the contact between the catalyst and soot particles is a very critical factor. Compared with the powder catalyst coated with the same weight, the in-situ construction of some special morphologies on DPF in the present application can expose more area to contact with soot, thereby further improving the combustion efficiency of soot particles. At the same time, through the in-situ construction method, the consumption of catalyst can be greatly reduced under the same thickness of coating, thereby being beneficial to cost saving.
[0020] The application uses urea, manganese acetate and potassium nitrate as raw materials, and constructs modified Mn2O3 / DPF monolithic catalysts with different potassium contents on the surface and in the pores of DPF in-situ by a hydrothermal method, so as to improve the activity of the catalyst by regulating the content of potassium.
[0021] It should be understood that the foregoing general description and the following detailed description are only exemplary and explanatory and are not restrictive of the disclosure. BRIEF DESCRIPTION OF DRAWINGS
[0022] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and serve to explain the principles of the application, together with the description.
[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, for those skilled in the art, other drawings can also be obtained based on these drawings without creative labor.
[0024] Figure 1 The scanning electron microscope photos of DPF provided for the disclosed embodiment 1 of the present application;
[0025] Figure 2 The scanning electron microscope photos of K / Mn-x:y / DPF monolithic catalysts provided for the disclosed embodiment 1 of the present application; Fig. a and b are SEM photos of Mn / DPF; Fig. c and d are SEM photos of K / Mn1:4 / DPF; Fig. e and f are SEM photos of K / Mn1:2 / DPF; Fig. g and h are SEM photos of K / Mn1:1 / DPF; Fig. i and j are SEM photos of K / Mn2:1 / DPF;
[0026] Figure 3 The XRD graphs of K / Mn-x:y / DPF monolithic catalyst (A) and powder (B) in a hydrothermal kettle provided for the disclosed embodiment 1 of the present application;
[0027] Figure 4 The SEM (a), EDS mapping images (b-g) and EDS spectrum (h) of K / Mn-1:1 / DPF catalyst provided for the disclosed embodiment 1 of the present application. DETAILED DESCRIPTION
[0028] The exemplary embodiments will be described in detail herein with reference to the attached drawings. In the following description, like reference numerals refer to like elements throughout the description. The following exemplary embodiments described herein represent illustrations of systems consistent with aspects of the present disclosure as detailed in the appended claims. No limitation on the scope of the present disclosure is intended by these descriptions.
[0029] In order to solve the problems of uncontrollable exposure of active sites of diesel soot particle catalyst, low utilization rate of catalyst, poor adhesion of coating, complex process and equipment, etc., the embodiment provides a preparation method of a different potassium content modified Mn2O3 / DPF monolith, which comprises: in a manganese acetate, urea and potassium nitrate aqueous solution, Mn2O3 is constructed on the DPF in situ by a hydrothermal method to obtain the monolith catalyst, which is denoted as K / Mn / DPF, and by adjusting the molar ratio of potassium nitrate to manganese acetate, catalysts with different performances can be obtained, which are denoted as K / Mn-x:y / DPF, wherein x:y represents the molar ratio of potassium nitrate to manganese acetate.
[0030] Specifically, the method comprises the following steps:
[0031] 1) pretreating the DPF;
[0032] The method for pretreating the DPF comprises the following steps in sequence: cutting, cleaning, and then drying; wherein the cleaning process is performed in the order of ultrapure water, ethanol and ultrapure water.
[0033] In specific implementation, the DPF can be cut into small cubes with uniform size, and the edge burrs are polished to be smooth. Then the small cubes are cleaned in the order of ultrapure water, ethanol and ultrapure water.
[0034] Finally, the residual liquid is blown off with an ear cleaning ball, and the DPF is dried in an oven overnight and stored in a storage box.
[0035] After the above steps, the impurities on the inner and outer surfaces of the carrier are removed, and the in-situ construction of Mn2O3 and catalyst on the surface and inside the pores is facilitated.
[0036] 2) the pretreated DPF and a mixed solution of different amounts of potassium nitrate, manganese acetate and urea are respectively placed in a reaction kettle, the reaction kettle is sealed, and a hydrothermal reaction is performed; after the reaction is completed, the sample after the reaction is taken out after cooling to room temperature, and the sample is washed, dried and calcined, the molar ratio of potassium nitrate to manganese acetate is adjusted, and catalysts with different performances are obtained, which are denoted as K / Mn-x:y / DPF, wherein the different performances referred to by the present application are different catalytic activities,
[0037] The molar ratio of potassium nitrate to manganese acetate is adjusted, and the manganese-based oxides synthesized under different potassium nitrate concentrations are all Mn2O3.
[0038] The specific operation method is as follows: first, different amounts of potassium nitrate, 2.45 g of manganese acetate and 4.18 g of urea are weighed and configured into a mixed solution and transferred to a hydrothermal reaction kettle. Subsequently, the pretreated DPF is placed in the reaction kettle, which is sealed and transferred to an oven at 100-160℃ constant temperature for 6-18h. After the reaction is completed, the cooled catalyst is taken out, washed with a large amount of deionized water, and the excess liquid is blown dry with an ear cleaning ball. The sample is placed in a 60-100℃ oven for drying for 8-10h, and finally calcined at 350-750℃ for 3-5h.
[0039] The mass of potassium nitrate in step 3) is 0-2.02g, not including 0g; the heating rate during calcination is 1-5℃ / min.
[0040] The catalysts with different properties are as follows: the manganese-based oxides synthesized under different potassium nitrate concentrations are all Mn2O3.
[0041] The embodiment also provides a modified Mn2O3 catalyst with different potassium contents prepared by the above method, and the catalyst is composed of a DPF and a modified Mn2O3 catalyst with different potassium contents. The catalyst has irregular prismatic and pyramidal morphologies under different potassium nitrate concentrations.
[0042] The size of the Mn2O3 catalyst with irregular prismatic and pyramidal morphologies is 3-8μm.
[0043] The modified Mn2O3 catalyst with different potassium contents provided by the present application can be used in the catalytic combustion reaction of soot particles, and all the catalysts can completely remove soot particles below 450℃.
[0044] The present application will be further explained and described in conjunction with specific examples, but is not used to limit the protection scope of the present application.
[0045] Example 1
[0046] Pretreatment of DPF carrier
[0047] First, the DPF is cut into small cubes with a length x width x height of 1.9cm x 1.9cm x 1.9cm, and the edges are polished with sandpaper to make them flat and smooth. Then the small cubes are sequentially washed with ultrapure water, ethanol and ultrapure water. Finally, the residual liquid is blown off with an ear cleaning ball, placed in a 80-120℃ oven to dry overnight and stored in a storage box.
[0048] Preparation of K / Mn-x:y / DPF
[0049] First, 0-2.02 g of potassium nitrate (not including 0), 2.45 g of manganese acetate and 4.18 g of urea are weighed according to the molar ratio of manganese acetate, and a mixed solution is prepared and transferred to a hydrothermal reactor, respectively. Then, the pretreated DPF is placed in the reactor, and the material should be in a suspended state during the hydrothermal reaction. After sealing, it is transferred to an oven at 100-160°C for 6-18h. After the reaction is completed, the cooled catalyst is taken out, washed with a large amount of deionized water, and the excess liquid is blown dry with an ear cleaning ball. The sample is placed in a 60-100°C oven for 8-10h, and finally calcined at 350-750°C for 3-5h to obtain K / Mn-x:y / DPF.
[0050] Figure 2 For the scanning electron microscope photo of K / Mn-x:y / DPF, it can be seen that the prepared Mn2O3 catalyst is uniformly loaded on the DPF in the form of irregular pyramids or prisms (compared with Figure 1 Comparison), the size of the irregular prisms and pyramids of Mn2O3 catalyst is 3-8μm, and no bare DPF is observed. The structure composed of irregular prisms and pyramids can better trap soot and improve the contact efficiency of the catalyst and soot, thereby more effectively catalyzing the oxidation of soot particles.
[0051] Figure 3 The XRD results of the K / Mn-x:y / DPF bulk catalysts synthesized under different potassium nitrate concentrations and the powders in their respective hydrothermal reactors (labeled as K / Mn-x:y-p) are calcined together. As can be seen from the figure, the K / Mn-x:y / DPF catalysts prepared under different potassium nitrate content conditions all have obvious Mg2Al4Si5O 18 diffraction peaks of DPF structure, while the powders calcined together show obvious Mn2O3 diffraction peaks. More specifically, Figure 3 A shows that the structure of DPF is Mg2Al4Si5O 18 , Figure 3 B is because the instrument sensitivity is limited, the diffraction peak of DPF structure is too strong, and the structure of the catalyst cannot be detected, so the powders calcined together are tested by XRD, and it is proved that the addition of different K cannot change the crystal structure of the catalyst;
[0052] Comparative Example 1
[0053] The catalyst Mn / DPF is prepared, and the other preparation steps are the same as in Example 1, except that when preparing the mixed solution, 2.45 g of manganese acetate and 4.18 g of urea are weighed and prepared into a mixed solution, and no potassium nitrate is added, to obtain the catalyst Mn / DPF;
[0054] Table 1 Raw material ratio of K / Mn-x:y / DPF catalyst prepared at different concentrations of potassium nitrate
[0055]
[0056] As shown in FIG. 6, the K / Mn-1:1 / DPF catalyst was subjected to EDS analysis by scanning electron microscopy, and the element distribution on the monolithic catalyst was observed. The observation results are shown in FIG. 7. In FIG. 7a, it can be seen that the alkali metal K-modified Mn2O3 catalyst is distributed in the shape of irregular prisms or pyramids on the cordierite carrier. From the EDS-mapping results, it can be seen that the carrier of the catalyst is a composite oxide composed of Mg, Al and Si, which matches the composition of the DPF raw material cordierite ceramic. At the same time, no obvious bare carrier was observed, which indicates that this hydrothermal method can be used to synthesize Mn2O3 catalyst on the DPF carrier more uniformly. In addition, as shown in FIG. 7f, the K element is uniformly distributed on the monolithic catalyst, which ensures that the K element improves the mobility of the catalyst and promotes the generation of more oxygen vacancies on the surface of the catalyst to improve the activity of the catalyst. Figure 4 Figure 4 Figure 4 Figure 4
[0057] Example 2
[0058] Evaluation method of catalyst activity: gas chromatography detection system was used, and the catalyst was in a fixed bed mode; specific steps: first, carbon soot was weighed according to the weight ratio of active component to carbon soot of 10:1, 4-10 ml of anhydrous ethanol was added, and ultrasonic oscillation was performed at 60-100 Hz for 10-20 min, so that the carbon soot could be uniformly dispersed. Then, the prepared K / Mn-x:y / DPF catalyst was fully immersed and the excess liquid was blown dry with ear cleaning balls. Finally, the sample was placed in a 40-90°C oven for drying for 6-10 h. The K / Mn-x:y / DPF mixed with carbon soot was wrapped with quartz wool and loaded into a 32 mm quartz reaction tube. The gas flow was controlled at 50 mL / min, the volume content of NO in the gas was 2000 ppm, the volume content of O2 was 10%, and the balance was Ar; the heating rate was controlled at about 2°C / min.
[0059] Evaluation method: the oxidation ability of the catalyst was represented by the combustion temperature of the carbon soot particles, wherein the ignition temperature (T 10 ), the temperature corresponding to the maximum combustion rate (T 50 ) and the burnout temperature (T 90 ), respectively, which are calculated by integrating the curves of CO2 and CO produced by the combustion of carbon black in the programmed temperature oxidation reaction, and the temperature points corresponding to 10%, 50%, and 90% of the sum of the integral areas of CO2 and CO are T 10 , T 50 , and T 90 , respectively. SCO2 m represents the CO2 selectivity of the catalyst corresponding to the maximum combustion rate of carbon smoke. The results of catalytic combustion of carbon smoke particles on the pure DPF carrier are shown in Table 2. As can be seen from the table, in the absence of a catalyst, the combustion temperature of pure carbon smoke is high, indicating that the K / Mn-x:y / DPF catalyst prepared in the present application has high catalytic activity for the catalytic combustion of carbon smoke particles.
[0060] Table 2 Catalytic combustion activity of pure DPF carrier and prepared catalysts
[0061]
[0062] As can be seen from Table 2, K / Mn-1:1 / DPF shows the best activity, with T 10 , T 50 , T 90 values and CO2 selectivity of 281℃, 344℃, 391℃, and 99.6%, respectively. The high activity of the catalyst can be attributed to the porous structure brought by the irregular prismatic and pyramidal stacking, the higher valence of manganese species, and the higher content of active oxygen species.
[0063] The above description is only preferred embodiments of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the technical principles of the present application, a number of improvements and modifications can be made, and these changes and modifications should be considered as the protection scope of the present application.
Claims
1. A modified Mn203 / DPF monolithic catalyst with different potassium content, characterized in that, The catalyst is composed of DPF and Mn2O3 catalyst, and the morphology of the catalyst with different potassium nitrate addition amounts includes irregular prisms and pyramids.
2. The modified Mn203 / DPF monolithic catalyst with different potassium content according to claim 1, characterized in that, The size of the Mn2O3 catalyst with irregular prisms and pyramids is 2-4 μm.
3. Process for the preparation of the catalyst according to any one of claims 1-2, characterized in that, The method comprises the following steps: Mn2O3 is in-situ constructed on DPF by using a hydrothermal method with aqueous solution of manganese acetate, urea and different amounts of potassium nitrate as raw materials to obtain catalysts with different properties, which are recorded as K / Mn-x:y / DPF, and x:y represents the molar ratio of potassium nitrate to manganese acetate.
4. The method of claim 3, wherein the catalyst is prepared by the steps of: The method comprises the following steps: 1) pretreating DPF; 2) mixing the pretreated DPF with different amounts of potassium nitrate, manganese acetate and urea to obtain a mixed solution, placing the mixed solution in a reaction kettle, sealing the reaction kettle, and then transferring the reaction kettle to a constant temperature condition of 100-160 ℃ for reaction for 6-18 h; after the reaction is completed, the material after reaction is taken out after being cooled to room temperature, and the material is washed and the excess liquid on the material is removed; then the obtained sample is sequentially subjected to drying and calcination to finally obtain the monolithic catalyst recorded as K / Mn-x:y / DPF.
5. The method of claim 4, wherein the catalyst is prepared by the steps of: The method for pretreating DPF comprises the following steps in sequence: cutting, cleaning and drying; and the cleaning process comprises the following steps in sequence: cleaning with ultrapure water, cleaning with ethanol and cleaning with ultrapure water.
6. The method of claim 4, wherein the catalyst is prepared by the steps of: The addition amount of urea is 4.18 g, the addition amount of manganese acetate is 2.45 g, and the addition amount of potassium nitrate is 0-2.02 g, and 0 g is not included.
7. The method of claim 4, wherein the catalyst is prepared by the steps of: The drying and calcination conditions are that the sample is placed in a constant temperature condition of 60-100 ℃ for drying for 8-10 h, and finally calcination is performed at 350-750 ℃ for 3-5 h.
8. The method of claim 7, wherein the catalyst is prepared by a method comprising: The heating rate during calcination is 1-5 ℃ / min.