Metal oxide catalyst for soot combustion of tail gas of diesel vehicle and preparation method of metal oxide catalyst

Abstract

The invention discloses a metal oxide catalyst for soot combustion of diesel vehicle tail gas and a preparation method thereof, the catalyst is characterized in that an active component MnOx is loaded on a carrier CuaAlb-LDO, x is the number of oxygen, the mass percentage of Mn to the carrier CuaAlb-LDO is 1-10%, the carrier CuaAlb-LDO is a metal oxide which is derived by roasting a hydrotalcite precursor CuaAlb-LDH and contains a defect structure, and the active component MnOx is an active component MnOx. Wherein the molar ratio of Cu to Al is a: b = (1-2): (1-4). The catalyst can significantly improve the combustion reaction activity of soot in the tail gas of a diesel vehicle and has good cycle stability, especially under the condition of NOx atmosphere, the catalytic activity is further improved, and T50 is only 327 DEG C. And meanwhile, the catalyst has the advantages of greenness, environmental protection, low cost, simple process, high activity, good stability and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental catalysis, and in particular relates to a metal oxide catalyst for combustion of diesel vehicle exhaust soot and a preparation method thereof. Background Art

[0002] Diesel engines have the advantages of high thermal efficiency and sufficient power, and have become the first choice for heavy machinery and light trucks. Since the exhaust gas emitted by diesel engines contains environmental pollutants such as soot particles (PM), diesel particulate filters (DPF) are usually used to filter soot particles. However, the collected carbon black particles generally require a temperature greater than 600°C to burn, while the exhaust gas temperature is only 150-400°C. Therefore, most existing particulate filter systems use catalysts to allow carbon black particles to burn at relatively low exhaust gas temperatures.

[0003] At present, there are many catalyst systems for soot combustion, including precious metal catalysts, metal oxide catalysts, and three-dimensional composite material catalysts.

[0004] Xiong et al. reported three-dimensional ordered macroporous (3DOM) Al 2 O 3 Loaded core-shell structure Pt@MnO x Nanoparticle catalyst (3DOM-Pt@MnO x / Al 2 O 3 ), at 5% O 2 The T of the most active sample for catalytic soot combustion under 750ppm NO atmosphere 50 351℃, T 90 is 392 ℃ (Chinese Chemical Letters 32 (2021) 1447–1450).

[0005] The Chinese invention patent with the announcement number CN106669669B discloses "a low-loaded precious metal type soot combustion catalyst and its preparation method and application", and the preferred catalyst precious metal Pt and its carrier MnO x The mass ratio is 1%, and in 10% O 2 The T of the sample catalyzing soot combustion under 500ppm NO atmosphere is 90 is 390 ℃.

[0006] Wang et al. prepared MnCuO by template method. x / 3DOM-m SiO 2 Catalyst, under loose contact conditions, 10% O 2 and 2000ppm NO atmosphere, T 50is 405℃ (Catalysis Today, 2021, 364: 21-34).

[0007] The Chinese invention patent application with publication number CN1775350A discloses a method for “combustion of diesel exhaust soot and NO x Storage-reduction bimetallic catalyst and preparation method", the catalyst is based on Mg-Al hydrotalcite composite oxide loaded with Pt and K, and the auxiliary active component is Cu. The preferred catalyst with the best activity is 1Pt / 6.5K / 3Cu / MgAlO, in 5%O 2 The temperature T at which the soot combustion rate of the catalyst is fastest under 1000ppm NO atmosphere is m It is 268.1℃, and has excellent soot combustion activity.

[0008] It can be seen that although the catalyst systems for the combustion of diesel vehicle exhaust soot recorded in the prior art have their own characteristics, they still have problems such as low reaction activity, complex preparation process and / or high cost. Summary of the invention

[0009] The present invention aims to solve the above problems existing in the prior art and provides a metal oxide catalyst for combustion of diesel vehicle exhaust soot and a preparation method thereof.

[0010] The technical solution of the present invention is: a metal oxide catalyst for the combustion of diesel exhaust soot, on a carrier Cu a Al b -LDO is loaded with active component MnO x , where x is the number of oxygen, Mn and the carrier Cu a Al b -LDO has a mass percentage of 1-10%, and the carrier Cu a Al b -LDO is a hydrotalcite precursor Cu a Al b -LDH is derived by calcination and contains a metal oxide with a defective structure, wherein the molar ratio of Cu to Al is a:b=1-2:1-4.

[0011] The preferred Mn and Cu carrier a Al b -The mass percentage of LDO is 3%.

[0012] The preferred molar ratio of Cu to Al is a:b=1:2.

[0013] A method for preparing the above-mentioned metal oxide catalyst for combustion of diesel vehicle exhaust soot is carried out in the following steps: Step 1. Cu(NO3 ) 2 Solution and Al(NO 3 ) 3 The solution is prepared into a mixed salt solution with a concentration of 0.8-2.0 mol / L according to the molar ratio of Cu to Al of 1-2:1-4. 2 CO 3 Prepare Na in a molar ratio of 2:1 + A mixed alkaline solution with a concentration of 4.8 mol / L; Step 2. Add the mixed salt solution and the mixed alkali solution at a volume ratio of 1:1 into a container containing deionized water at room temperature at a rate of 1 mL / min, stir magnetically and control the pH value to 11-12; after the addition is completed, stir and age at 50 °C for 10 h; wash the mixture to pH = 7, filter and separate, and vacuum dry at 120 °C to obtain the hydrotalcite precursor Cu a Al b -LDH; Step 3: Use a deposition precipitation method or an impregnation method to load the manganese salt on the hydrotalcite precursor Cu a Al b -LDH, the manganese in the manganese salt and the carrier Cu a Al b -The mass percentage of LDO is 1-10%; Step 4. The hydrotalcite precursor Cu loaded with manganese compound a Al b -LDH was ground and the ground powder was calcined at 600 °C for 4 h to obtain the metal oxide catalyst MnO x / Cu a Al b -LDO.

[0014] The preferred deposition precipitation method of step 3 is to weigh a manganese salt and dissolve it in deionized water, and then drop the manganese salt solution into a container containing Cu a Al b -LDH in a beaker, and drop an alkaline solution used as a precipitant to control the pH to 8. After the dropwise addition is completed, let it stand for 12 to 24 hours and dry at 80°C. The alkaline solution used as a precipitant is NaOH, Na 2 CO 3 , KOH, K 2 CO 3 NH 3 ·H 2 O、NH 4 (CO 3 ) 2 Any one or both of .

[0015] The preferred immersion method of step 3 is to weigh a manganese salt and dissolve it in deionized water, and then drop the manganese salt solution into a container containing Cu a Al b -LDH in a beaker, let stand for 12-24 h after adding, and dry at 80 °C.

[0016] Preferably, the manganese salt is nitrate or acetate.

[0017] The metal oxide catalyst for diesel vehicle exhaust carbon soot combustion prepared by the present invention is based on a hydrotalcite precursor Cu a Al b -LDH is calcined and derived from a metal oxide with a defective structure as a carrier, and the active component MnO is loaded on the carrier. x By limiting the molar ratio of Cu to Al in the carrier and the loading amount of Mn in the active component, the combustion activity of diesel exhaust soot can be significantly improved and has good cycle stability, especially in NO x Under the atmosphere conditions, the catalytic activity is further improved, T 50 Only 327 ℃. No precious metals are required, and it has the advantages of being green and environmentally friendly, low cost, simple process, high activity and good stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The catalysts prepared in Examples 1 and 2 of the present invention and the 3% MnO prepared in Example 3 are x / Cu 1 Al 2 -XRD diffraction pattern of LDO(Na) catalyst.

[0019] Figure 2 It is the XRD diffraction pattern of the catalyst prepared in the comparative example of the present invention.

[0020] Figure 3 It is an activity evaluation diagram of the catalysts prepared in the comparative example and Examples 1 and 2 of the present invention.

[0021] Figure 4 This is an activity evaluation graph of the catalyst prepared in Example 3 of the present invention.

[0022] Figure 5 3% MnO prepared in Example 3 of the present invention x / Cu 1 Al 2 -Activity evaluation diagram of LDO(Na) catalyst under different reaction atmospheres.

[0023] Figure 6 3% MnO prepared in Example 3 of the present invention x / Cu 1 Al 2-LDO(Na) catalyst stability test results. DETAILED DESCRIPTION Example 1

[0024] Step 1. Weigh 1.933 g Cu(NO 3 ) 2 ·3H 2 O, 6.002 g Al(NO 3 ) 3 9H 2 O was dissolved in 20 mL of deionized water to prepare a 1.2 mol / L mixed salt solution; 1.92 g of NaOH, 2.54 g of Na 2 CO 3 Dissolve in 20 mL of deionized water to prepare Na + A mixed alkaline solution with a concentration of 4.8 mol / L; Step 2. At room temperature, the mixed salt solution and the mixed alkali solution were added dropwise at a volume ratio of 1:1 into a container containing 10 ml of deionized water at a rate of 1 mL / min, and the pH value was controlled to be 11-12 by magnetic stirring; after the addition was completed, the mixture was stirred and aged at 50°C for 10 h; the mixture was washed to pH = 7, filtered and separated, and vacuum dried at 120°C for 2-5 h to obtain the hydrotalcite precursor Cu 1 Al 2 -LDH; Step 3. Prepare 0.055 mol / L Mn(NO 3 ) 2 (50 wt%) solution, prepare 1 mol / L NH 3 ·H 2 O solution as a precipitant, weigh 500 mg Cu 1 Al 2 -LDH was dispersed in 20 mL of deionized water and 10 mL of Mn(NO 3 ) 2 (50wt%) solution and dropwise addition of NH 3 ·H 2 O solution was controlled to pH = 8, and after the addition was completed, it was allowed to stand for 24 h, and then evaporated and dried at 80 °C with stirring to obtain a hydrotalcite precursor Mn(OH) 2 / Cu 1 Al 2 -LDH; Step 4. Prepare a hydrotalcite precursor Mn(OH) loaded with manganese hydroxide. 2 / Cu 1 Al 2 -LDH was ground and the ground powder was calcined at 600℃ for 4h to obtain 3% MnOx / Cu 1 Al 2 -LDO(NH 3 ·H 2 O) of metal oxide catalysts.

[0025] Embodiment 2: Steps 1 and 2 are the same as in Example 1; Step 3. Prepare 0.055 mol / L Mn(NO 3 ) 2 (50 wt%) solution, weigh 500 mg Cu 1 Al 2 -LDH was dispersed in 20 mL of deionized water and 10 ml of Mn(NO 3 ) 2 (50 wt%) solution, after addition, let stand for 24 h, and evaporate to dryness at 80 °C with stirring; Step 4. The hydrotalcite precursor Mn(NO 3 ) 2 / Cu 1 Al 2 -LDH was ground and the ground powder was calcined at 600℃ for 4h to obtain 3% MnO x / Cu 1 Al 2 -LDO (imp) catalyst.

[0026] Embodiment 3: Step 1. Weigh Cu(NO) in a molar ratio of Cu to Al of 1:1, 2:3, 1:2, 1:3, and 1:4. 3 ) 2 ·3H 2 O and Al(NO 3 ) 3 9H 2 O, dissolved in deionized water to prepare a mixed salt solution with a concentration of 0.8-2.0 mol / L; prepare NaOH and Na 2 CO 3 A mixed alkaline solution with a molar ratio of 2:1 and a concentration of 4.8 mol / L; Step 2. At room temperature, the mixed salt solution and the mixed alkali solution were added to a container containing 10 ml of deionized water at a volume ratio of 1:1 at a rate of 1 mL / min, and the pH value was controlled to be 11-12 by magnetic stirring; after the addition was completed, the mixture was stirred and aged at 50°C for 10 h; the mixture was washed to pH = 7, filtered and separated, and vacuum dried at 120°C for 2-5 h to obtain hydrotalcite precursor Cu 1 Al 1 -LDH, Cu2 Al 3 -LDH, Cu 1 Al 2 -LDH, Cu 1 Al 3 -LDH, Cu 1 Al 4 -LDH; Step 3. Weigh 500 mg Cu 1 Al 1 -LDH, Cu 2 Al 3 -LDH, Cu 1 Al 2 -LDH, Cu 1 Al 3 -LDH, Cu 1 Al 4 -LDH was dispersed in 20 mL of deionized water and 10 mL of 0.055 mol / L Mn(NO 3 ) 2 (50 wt%) solution, add a mixed alkali solution (NaOH and Na 2 CO 3 The molar ratio was 2:1, and the concentration was 1.2 mol / L) and the pH was controlled to 8. After the addition was completed, the mixture was allowed to stand for 24 h and then evaporated and dried at 80 °C to obtain the hydrotalcite precursor Mn(OH) loaded with manganese hydroxide. 2 / Cu 1 Al 1 -LDH, Mn(OH) 2 / Cu 1 Al 2 -LDH, Mn(OH) 2 / Cu 2 Al 3 -LDH, Mn(OH) 2 / Cu 1 Al 3 -LDH, Mn(OH) 2 / Cu 1 Al 4 -LDH; Step 4. Grind the hydrotalcite precursor loaded with manganese hydroxide respectively, and calcine the ground powder at 600℃ for 4h to obtain five catalysts, which are named as: 3%MnO x / Cu 1 Al 1 -LDO(Na), 3%MnO x / Cu 2 Al 3 -LDO(Na), 3%MnOx / Cu 1 Al 2 -LDO(Na), 3%MnO x / Cu 1 Al 3 -LDO(Na), 3%MnO x / Cu 1 Al 4 -LDO(Na).

[0027] 3% MnO prepared in Examples 1, 2 and 3 of the present invention x / Cu 1 Al 2 -XRD diffraction pattern of LDO(Na) catalyst Figure 1 As shown. Characteristic diffraction peaks corresponding to copper-aluminum hydrotalcite appear at 2θ=11.7°, 23.5°, 32.7°, 35.5°, and 40.3°, which are respectively attributed to the (003), (006), (302), (21-1), and (311) crystal planes (PDF#46-0099), indicating that the hydrotalcite structure material was successfully synthesized. After calcination at 600 °C, the hydrotalcite precursor was transformed into a composite oxide. The diffraction peaks at 2θ=35.6°, 38.8°, 48.8°, 58.4°, and 66.2° in the figure correspond to the (002), (111), (200), (-202), (202), and (-311) crystal planes of CuO (PDF#45-0937). It can be found that MnO is loaded in different ways. x The relative intensities of the strongest and second strongest peaks of CuO obtained are different, that is, different methods introduce MnO x , the degree of modification of the CuO unit cell structure is different.

[0028] Comparative Example: Prepare 0.055 mol / L Mn(NO 3 ) 2 (50 wt%) solution, prepare 0.024 mol / L Cu(NO 3 ) 2 ·3H 2 O solution. Weigh 500 mg γ-Al 2 O 3 , dispersed in 20 mL of deionized water, and 10 ml of Mn(NO 3 ) 2 (50 wt%) solution and 10 ml Cu(NO 3 ) 2The solution was added dropwise, allowed to stand for 24 h, dried at 80 °C, ground, and calcined at 600 °C for 4 h. The resulting catalyst was named 3% MnO x 3% CuO x / γ-Al 2 O 3 The catalyst containing 3 wt% Cu or 3 wt% Mn was prepared by the same method and named as 3% CuO x / γ-Al 2 O 3 (imp), 3% MnO x / γ-Al 2 O 3 (imp).

[0029] The XRD diffraction pattern of the catalyst prepared in the comparative example is as follows: Figure 2 As shown. The diffraction peaks at 2θ = 31.9°, 37.6°, 39.5°, 45.8°, 60.5°, and 66.8° correspond to γ-Al 2 O 3 (220), (311), (222), (400), (511), (440) crystal planes (γ-Al 2 O 3 ,PDF#29-0063). In addition to the detection of γ-Al 2 O 3 Crystalline phase, no other diffraction peaks were detected, indicating that the MnO loaded by the impregnation method x , CuO x In γ-Al 2 O 3 The surface is highly dispersed.

[0030] experiment: Carbon smoke catalytic combustion activity test experiment (applicable to both comparative examples and examples) The soot particles used in the present invention are Printex-U samples produced by Degussa. The activity of the catalyst is evaluated by temperature-programmed oxidation TPO (Temperature-programmed oxidation). The reaction product is detected by Agilent GC-6890N gas chromatograph. The reaction tube adopts a quartz tube with an inner diameter of 6 mm, which is heated by an external electric furnace. Weigh 80 mg of catalyst sample and 20 mg of soot particles, mix and grind them thoroughly in an agate mortar for 20 min to form a close contact between the catalyst and the soot particles. In order to avoid high temperature during the heating process, 250 mg of quartz sand is added to the mixture of soot and catalyst for dilution. Then, the mixture is fixed in the constant temperature section of the fixed bed quartz reactor by two quartz cotton balls, and heated in the range of 200-600 ° C, with a heating rate of 1 ° C / min. The catalyst is heated at 5% O 2 and 750ppm NO / N 2 The reaction was carried out under the atmosphere. The temperature (T 50 ) represents the active temperature of the catalyst, and the temperature at which the carbon black conversion rate is 10% (T 10 ) represents the ignition temperature of carbon black, and the temperature at which the carbon black conversion rate is 90% (T 90 ) represents the burnout temperature of carbon black, carbon black is oxidized to generate CO 2 The temperature at which the concentration is maximum is T m .

[0031] 2. Activity evaluation of catalysts prepared in comparative examples and examples 1 and 2 The results of the activity test of the catalysts prepared in the comparative example and examples 1 and 2 in the soot combustion reaction are as follows: Figure 3 Compared with the samples prepared in the comparative example, the catalyst activity prepared in Examples 1 and 2 of the present invention is significantly improved. x 3% CuO x / γ-Al 2 O 3 (imp) Sample T 50 is 462 ℃. In comparison, the 3% MnO prepared in Example 2 x / CuAl-LDO(imp) T 50 The temperature of the composite oxide prepared by deriving the hydrotalcite precursor is reduced by 74 °C, which shows the advantages of the method for preparing the composite oxide by deriving the hydrotalcite precursor disclosed in the present invention. x / Cu 1 Al 2 -LDO(NH 3 ·H 2 O) catalyst, the activity is further improved, T 50Reduce to 375°C.

[0032] III. Activity evaluation of the catalyst prepared in Example 3 The results of the activity test of the catalyst prepared in Example 3 in the soot combustion reaction are as follows: Figure 4 shown. Figure 4 The results show that the Cu / Al molar ratio of the prepared catalyst has little effect on the soot combustion reaction activity, and the sample with a Cu / Al molar ratio of 1:2 has the best activity. x / Cu 1 Al 2 -LDO(Na) has a faster soot combustion rate. 2 and 750ppm NO atmosphere, T 10 The temperature is only 288°C, T 50 355℃, T 90 It is 387℃.

[0033] 4. 3% MnO prepared in Example 3 x / Cu 1 Al 2 -LDO (Na) catalyst catalytic soot combustion activity test under different reaction atmospheres The test atmosphere includes: 1%O 2 Atmosphere (gas composition: 1%O 2 / N 2 50 ml / min) or 20% O 2 Atmosphere (gas composition: air 50ml / min) or 5% O 2 and 750ppm NO / N 2 Atmosphere (gas composition: air 20 mL / min, 1500ppm NO / Ar 40 mL / min, N 2 20 mL / min) or 0.5% O 2 and 750ppm NO / N 2 Atmosphere (gas composition: 1%O 2 / N 2 30 mL / min, 1500ppm NO / Ar 30 mL / min) or 10%O 2 and 5000ppm NO atmosphere (gas composition: air 30 mL / min, 1% NO / N 2 30 mL / min).

[0034] 3% MnO prepared in Example 3 x / Cu 1 Al 2-LDO(Na) catalyst activity test results under different reaction atmospheres Figure 5 As shown in Table 1. The results show that: x / Cu 1 Al 2 -LDO(Na) catalyst in 20% O 2 Excellent soot combustion activity in atmosphere, T 50 362 ℃ (La prepared by Fang et al. 0.8 K 0.2 FeO 3-δ Nanotube catalyst in 20%O 2 In the atmosphere, T 50 405 °C, Applied Catalysis B: Environmental, 2018, 236: 184-194; LaMn prepared by Da et al. 0.7 Pt 0.3 O 3 Catalyst, in 10% O 2 In the atmosphere, T 50 384 °C, Catalysis Today (2018) 327, 73-80). The catalyst prepared by the present invention has a high x The activity was better in the presence of 5% O 2 and 750ppm NO atmosphere, T 50 is 355°C, and NO x The higher the concentration, the faster the reaction rate, which is better than the results reported in the literature (MnO prepared by Wang et al. x -900 catalyst at 10% O 2 and 1000ppm NO atmosphere, T 50 360 ℃, Catal. Sci. Technol., 2024, 14, 6278-6285; PrMnO prepared by Liu et al. 3 The catalyst was in 5% O 2 and 1000ppm NO atmosphere, T 50 360°C, Separation and Purification Technology 354 (2025) 129227). In addition, the catalyst prepared by the present invention has a T 50 The temperature is 418 °C and 20% O 2 The temperature difference under 1% O atmosphere is only 56 °C, which is comparable to some precious metal catalysts in the literature (1% Pt / CZ-im catalyst prepared by Yao et al. 2 In the atmosphere, T50 is 394°C, Fuel 334 (2023) 126782).

[0035] Table 1

[0036] 5. 3% MnO prepared in Example 3 of the present invention x / Cu 1 Al 2 - Cyclic stability of LDO(Na) catalyst for diesel exhaust soot combustion Take 3% MnO prepared in Example 3 of the present invention x / Cu 1 Al 2 -LDO(Na) catalyst was subjected to five cycles of reaction evaluation according to the method of Experiment 1. The catalytic performance was as follows Figure 6 The results show that the characteristic temperature does not change significantly with the increase in the number of cycles, indicating that the catalyst has not been significantly deactivated after five cycles.

Claims

1. A metal oxide catalyst for combustion of diesel exhaust soot, characterized in that: On the carrier Cu a Al b -LDO is loaded with active component MnO x , where x is the number of oxygen, Mn and the carrier Cu a Al b -LDO has a mass percentage of 1-10%, and the carrier Cu a Al b -LDO is a hydrotalcite precursor Cu a Al b -LDH is derived by calcination and contains a metal oxide with a defective structure, wherein the molar ratio of Cu to Al is a:b=1-2:1-4.

2. The metal oxide catalyst for combustion of diesel exhaust soot according to claim 1, characterized in that: Mn and Support Cu a Al b -The mass percentage of LDO is 3%.

3. The metal oxide catalyst for combustion of diesel exhaust soot according to claim 2, characterized in that: The molar ratio of Cu to Al is a:b=1:

2.

4. A method for preparing a metal oxide catalyst for combustion of diesel vehicle exhaust soot as claimed in claim 1, 2 or 3, characterized in that Follow the steps below: Step 1. Prepare a mixed salt solution with a concentration of 0.8-2.0 mol / L by mixing Cu(NO3)2 solution and Al(NO3)3 solution at a molar ratio of Cu to Al of 1-2:1-4, and prepare a NaOH and Na2CO3 solution at a molar ratio of 2:

1. + A mixed alkaline solution with a concentration of 4.8 mol / L; Step 2. Add the mixed salt solution and the mixed alkali solution at a volume ratio of 1:1 into a container containing deionized water at room temperature at a rate of 1 mL / min, stir magnetically and control the pH value to 11-12; after the addition is completed, stir and age at 50 °C for 10 h; wash the mixture to pH = 7, filter and separate, and vacuum dry at 120 °C to obtain the hydrotalcite precursor Cu a Al b -LDH; Step 3: Use a deposition precipitation method or an impregnation method to load the manganese salt on the hydrotalcite precursor Cu a Al b -LDH, the manganese in the manganese salt and the carrier Cu a Al b -The mass percentage of LDO is 1-10%; Step 4. The hydrotalcite precursor Cu loaded with manganese compound a Al b -LDH was ground and the ground powder was calcined at 600 °C for 4 h to obtain the metal oxide catalyst MnO x / Cu a Al b -LDO.

5. The method for preparing a metal oxide catalyst for combustion of diesel vehicle exhaust soot according to claim 4, characterized in that The deposition precipitation method in step 3 is to weigh a manganese salt and dissolve it in deionized water, and then drop the manganese salt solution into a container containing Cu a Al b -LDH in a beaker, and drop an alkaline solution used as a precipitant to control the pH to 8. After the dropwise addition is completed, let it stand for 12 to 24 hours and dry at 80°C. The alkaline solution used as a precipitant is any one or two of NaOH, Na2CO3, KOH, K2CO3, NH3·H2O, and NH4(CO3)2.

6. The method for preparing a metal oxide catalyst for combustion of diesel vehicle exhaust soot according to claim 4, characterized in that The immersion method in step 3 is to weigh a manganese salt and dissolve it in deionized water, and then drop the manganese salt solution into a container containing Cu a Al b -LDH in a beaker, let stand for 12-24 h after adding, and dry at 80 °C.

7. The method for preparing a metal oxide catalyst for combustion of diesel vehicle exhaust soot according to claim 4, characterized in that: The manganese salt is nitrate or acetate.

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