A flue gas NO x High-efficiency MnO2@Co3O4 composite catalyst treated with NH4Cl2 and its preparation method

Abstract

The invention discloses a flue gas NO x The high-efficiency MnO2@Co3O4 composite catalyst and its preparation method are prepared by hydrothermal method, combined with ion implantation of cobalt ions, and then heat treatment. By controlling process parameters such as ion implantation and oxygen partial pressure, the window temperature of 90-350℃ and catalytic conversion efficiency of more than 90% at 200-250℃ are obtained, and good catalytic activity is also shown at low and high temperatures. The structure of the MnO2@Co3O4 composite catalyst is that Co3O4 nanoparticles are loaded on the surface of MnO2 nanospheres, and the specific surface area of ​​the MnO2@Co3O4 composite catalyst is 115-135m 2 ·g ‑1 The loading rate of Co3O4 nanoparticles is 30-40%, which has a large specific surface area and many catalytic active sites, which is beneficial to improve the catalytic activity. x The tail gas has good catalytic activity and can also effectively reduce the catalytic cost.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, in particular to a flue gas NO x A highly efficient manganese-cobalt-based catalyst treated with a catalyst and a preparation method thereof. Background Art

[0002] Nitrogen oxides (NO) x It is one of the main causes of air pollutants, and with the development of industrialization, especially with the sharp increase in energy consumption such as coal and oil, the NO x The increasing pressure will also cause damage to the atmospheric environment. x The treatment of NO is still mainly based on selective catalytic reduction (SCR); therefore, a large number of catalyst types have been developed. Among them, precious metal platinum, palladium, gold and their alloy catalysts have a great effect on NO x It has excellent catalytic efficiency, but its high material cost and the susceptibility to catalyst poisoning and failure also limit its practical application. Transition metal oxide type catalysts not only have advantages in cost but also have breakthroughs in catalytic efficiency, making them an alternative catalyst.

[0003] Chinese patent CN 104475084 A provides a method for preparing a low-temperature, high-efficiency denitration catalyst MnO2. The MnO2 catalyst prepared by this method has a large specific surface area, absorbs a lot of oxygen, and has a high nitrogen oxide removal rate. It also has good stability. After denitration treatment, the mesoporous structure remains stable, and the selective catalytic reduction activity at low temperatures is higher.

[0004] Chinese patent CN 111266104 A provides a composite manganese oxide comprising MnO2 nanowires and MnO2 blocks; the MnO2 blocks are supported on the MnO2 nanowires, and the crystal structures of the MnO2 nanowires and the MnO2 blocks are both α-phase. Experimental results show that the composite manganese oxide of the present invention has a good catalytic effect on NO x In the simulated exhaust gas, the temperature window corresponding to a catalytic conversion rate of 90% is 94-332°C, and the window width is 238°C. Efficient catalytic conversion of NO can be achieved at low temperatures, and the operating temperature is much lower than that of commercial catalysts.

[0005] The journal article "Study on the Activity of Co-modified α-MnO2 Catalyst for Simultaneous Denitrification and Dechlorobenzene at Low Temperature" uses a one-step hydrothermal method to prepare α-MnO2 and Co-modified α-MnO2 catalyst (MnCo β O x, β is the molar ratio of Co to Mn), the activity of the catalyst for single denitrification, single denitrification of chlorobenzene, and simultaneous denitrification and denitrification of chlorobenzene was tested by NH3 selective catalytic reduction (NH3-SCR) and chlorobenzene (CB) catalytic oxidation reaction (CBCO), and the stability of the catalyst was investigated. The results showed that: MnCo with β = 1.0 1.0 O x The catalyst has the best catalytic performance. The catalytic activity is significantly improved in the temperature range of 150-250℃. The NO conversion rate and CB removal efficiency increase by about 19% and 12% respectively. When NH3, NO and CB are introduced at the same time, MnCo 1.0 O x The NO conversion rate and CB removal efficiency of the catalyst reached 94% and 82% respectively within 200-300℃, and it was found that the presence of CB could inhibit the catalytic reduction reaction of NO, while the presence of NH3 and NO could improve the catalytic removal efficiency of CB. The stability test results at 250℃ showed that MnCo 1.0 O x The catalyst can still maintain good activity after 12 hours of continuous reaction, with NO conversion rate and CB removal efficiency close to 100% and above 80%, respectively.

[0006] Non-metal oxide complexes have also been a research hotspot in recent years. However, due to the complex influences on catalytic activity; for example, the structure, composition, and preparation process of the oxides all have a significant impact on catalytic performance. Therefore, how to find non-metal oxide complex catalyst materials is also a research focus and difficulty. Summary of the Invention

[0007] Based on the needs and defects in the prior art, the present invention discloses a high-efficiency manganese-cobalt-based catalyst for flue gas NOx treatment and a preparation method thereof, which can efficiently catalyze NOx at low temperatures. x The catalytic efficiency of the reaction at low temperature is as high as 87.5%; and the manganese-based catalyst also has good stability, which can effectively extend the service life of the catalyst and reduce the frequency of catalyst replacement.

[0008] In order to solve the above problems and achieve the effects thereof, the specific technical solutions provided by the present invention are as follows:

[0009] A method for preparing a high-efficiency MnO2@Co3O4 composite catalyst for treating flue gas NOx comprises the following steps:

[0010] (1) Pour 80-90 parts of MnCl2·4H2O and 250-270 parts of sodium oleate into a mixed solvent consisting of anhydrous ethanol, n-hexane and deionized water; heat to 70-75°C and react for 3-4 hours while stirring;

[0011] (2) filtering the reaction solution of step (1) to obtain the manganese oleate organic phase, and rotary evaporating to obtain a manganese oleate solid;

[0012] (3) dissolving manganese oleate in octadecenoic acid, heating to 115-125°C and reacting for 2-3 hours; continuing to heat to 310-330°C and reacting for 2-3 hours; cooling and filtering to obtain nano-MnO particles;

[0013] (4) placing the container containing the nano-MnO particles in an ion implantation device, and controlling the base to vibrate and thereby drive the nano-MnO particles to vibrate; turning on the power supply to implant cobalt ions into the nano-MnO particles;

[0014] (5) The particles obtained in step (4) were heat treated at 300-350° C. for 2-3 h in an oxygen and argon environment to obtain a MnO 2 @Co 3 O 4 composite catalyst.

[0015] Furthermore, the particle size distribution range of the nano-MnO particles in step (4) is 20 to 30 nm.

[0016] Furthermore, the dose of ion implantation in step (4) is (5-8)×10 -17 ions·cm -2 , the ion injection time is 3 to 4 hours.

[0017] During the ion implantation process, cobalt ions enter the surface of nano-MnO particles. By controlling the ion implantation dose and time, the content ratio of cobalt and manganese can be controlled; and the distribution of cobalt ions on the surface of nano-MnO particles can also be controlled. The research process found that the content ratio of cobalt and manganese and the coating ratio of Co3O4 also have a significant effect on the activity of the catalyst. Therefore, the ion implantation dose is (5-8)×10 -17 ions·cm -2 , ion injection time of 3 to 4 hours is beneficial to improving catalytic activity.

[0018] Furthermore, in step (5), the mixing ratio of oxygen to argon is 1:(10-20). Since the nanoparticle components formed during the ion implantation process include MnO, Co, and manganese cobalt oxide. In order to further obtain the MnO2@Co3O4 composite catalyst, it is necessary to further perform heat treatment in an oxygen atmosphere. The present application preferably uses a mixed gas of oxygen and argon as the oxygen source, and it is found that a lower oxygen partial pressure is more conducive to improving the catalytic activity of the MnO2@Co3O4 composite catalyst.

[0019] A flue gas NO xThe treated high-efficiency MnO2@Co3O4 composite catalyst is prepared by the above preparation method. The structure of the MnO2@Co3O4 composite catalyst is that Co3O4 nanoparticles are loaded on the surface of MnO2 nanospheres.

[0020] Furthermore, the particle size distribution range of the MnO2@Co3O4 composite catalyst is 25 to 35 nm.

[0021] Furthermore, the atomic ratio of Mn to Co in the MnO2@Co3O4 composite catalyst is (3-5):1.

[0022] Furthermore, the specific surface area of ​​the MnO2@Co3O4 composite catalyst is 115-135m 2 ·g -1 .

[0023] Furthermore, the particle size of the Co3O4 nanoparticles is 5 to 10 nm, and the loading rate of the Co3O4 nanoparticles is 30 to 40%.

[0024] By comparison, it was found that the particle size distribution of the nano-MnO particles obtained in step (4) was 20-30 nm; and after ion implantation and heat treatment, the particle size of the catalyst particles tended to increase.

[0025] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0026] (1) This application first uses a hydrothermal method to prepare nano-MnO particles, combined with ion implantation of cobalt ions and subsequent heat treatment. By controlling process parameters such as ion implantation and oxygen partial pressure, a MnO2@Co3O4 composite catalyst is prepared. The cobalt-manganese content ratio and the Co3O4 coating ratio have a significant effect on the catalyst activity. Controlling the ion implantation dose and time can control the cobalt-manganese content ratio; the distribution of cobalt ions on the surface of the nano-MnO particles can also be controlled.

[0027] (2) The structure of the MnO2@Co3O4 composite catalyst material prepared by the present invention is that Co3O4 nanoparticles are loaded on the surface of MnO2 nanospheres. It has a high specific surface area, a stable structure, and excellent catalytic performance. It has good conversion efficiency for nitrogen oxides under temperature conditions of 90 to 350°C.

[0028] (3) The preparation method of the present invention is simple, the process parameters are controllable, and it is also conducive to the expansion of the industry; it has good application prospects in the catalysis of flue gas nitrogen oxides. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1The scanning electron microscope images of the MnO2@Co3O4 composite catalysts prepared in Examples 1 to 5 are shown;

[0030] Figure 2 The catalytic efficiency curves of the MnO2@Co3O4 composite catalysts prepared in Examples 1 to 5 and Comparative Examples 1 to 4 for NOx simulated exhaust gas are shown. DETAILED DESCRIPTION

[0031] To make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0032] Example 1

[0033] A flue gas NO x The preparation method of the treated high-efficiency MnO2@Co3O4 composite catalyst comprises the following steps:

[0034] (1) Pour 80 parts of MnCl2·4H2O and 250 parts of sodium oleate into a mixed solvent consisting of anhydrous ethanol, n-hexane, and deionized water; heat to 70°C and react for 3 hours while stirring;

[0035] (2) filtering the reaction solution of step (1) to obtain the manganese oleate organic phase, and rotary evaporating to obtain a manganese oleate solid;

[0036] (3) dissolving manganese oleate in octadecenoic acid, heating to 115°C and reacting for 2 h; then heating to 310°C and continuing to react for 2 h; cooling and filtering to obtain nano-MnO particles;

[0037] (4) The vessel containing the nano-MnO particles is placed in the ion implantation device, and the base is controlled to vibrate to drive the nano-MnO particles to vibrate; the power is turned on to implant cobalt ions into the nano-MnO particles; the ion implantation dose is 5×10 -17 ions·cm -2 , the ion injection time is 3h.

[0038] (5) The particles obtained in step (4) were heat treated at 300° C. for 2 h in an oxygen and argon environment to obtain a MnO 2 @Co 3 O 4 composite catalyst, wherein the mixing ratio of oxygen to argon was 1:10.

[0039] Example 2

[0040] A flue gas NO x The preparation method of the treated high-efficiency MnO2@Co3O4 composite catalyst comprises the following steps:

[0041] (1) Pour 90 parts of MnCl2·4H2O and 270 parts of sodium oleate into a mixed solvent consisting of anhydrous ethanol, n-hexane, and deionized water; heat to 75°C and react for 4 hours while stirring;

[0042] (2) filtering the reaction solution of step (1) to obtain the manganese oleate organic phase, and rotary evaporating to obtain a manganese oleate solid;

[0043] (3) dissolving manganese oleate in octadecenoic acid, heating to 125°C and reacting for 3 h; then heating to 330°C and continuing to react for 3 h; cooling and filtering to obtain nano-MnO particles;

[0044] (4) Place the container containing the nano-MnO particles in the ion implantation device, and control the base to vibrate and drive the nano-MnO particles to vibrate; turn on the power supply and implant cobalt ions into the nano-MnO particles; the ion implantation dose is 8×10 -17 ions·cm -2 , the ion injection time is 4h.

[0045] (5) The particles obtained in step (4) were heat treated at 350° C. for 3 h in an oxygen and argon environment to obtain a MnO 2 @Co 3 O 4 composite catalyst, wherein the mixing ratio of oxygen to argon was 1:20.

[0046] Example 3

[0047] A flue gas NO x The preparation method of the treated high-efficiency MnO2@Co3O4 composite catalyst comprises the following steps:

[0048] (1) Pour 85 parts of MnCl2·4H2O and 260 parts of sodium oleate into a mixed solvent consisting of anhydrous ethanol, n-hexane, and deionized water; heat to 80°C and react for 3.5 hours while stirring;

[0049] (2) filtering the reaction solution of step (1) to obtain the manganese oleate organic phase, and rotary evaporating to obtain a manganese oleate solid;

[0050] (3) dissolving manganese oleate in octadecenoic acid, heating to 120°C and reacting for 2.5 hours; then heating to 320°C and reacting for 2.5 hours; cooling and filtering to obtain nano-MnO particles;

[0051] (4) The vessel containing the nano-MnO particles is placed in the ion implantation device, and the base is controlled to vibrate to drive the nano-MnO particles to vibrate; the power is turned on to implant cobalt ions into the nano-MnO particles; the ion implantation dose is 6×10 -17 ions·cm -2 , the ion injection time is 3.5h.

[0052] (5) The particles obtained in step (4) were heat treated at 330° C. for 2.5 h in an oxygen and argon environment to obtain a MnO 2 @Co 3 O 4 composite catalyst, wherein the mixing ratio of oxygen to argon was 1:15.

[0053] Example 4

[0054] A flue gas NO x The preparation method of the treated high-efficiency MnO2@Co3O4 composite catalyst comprises the following steps:

[0055] (1) Pour 80 parts of MnCl2·4H2O and 270 parts of sodium oleate into a mixed solvent consisting of anhydrous ethanol, n-hexane, and deionized water; heat to 75°C and react for 3 hours while stirring;

[0056] (2) filtering the reaction solution of step (1) to obtain the manganese oleate organic phase, and rotary evaporating to obtain a manganese oleate solid;

[0057] (3) dissolving manganese oleate in octadecenoic acid, heating to 115°C and reacting for 2.5 hours; then heating to 310°C and continuing the reaction for 3 hours; cooling and filtering to obtain nano-MnO particles;

[0058] (4) The vessel containing the nano-MnO particles is placed in the ion implantation device, and the base is controlled to vibrate to drive the nano-MnO particles to vibrate; the power is turned on to implant cobalt ions into the nano-MnO particles; the ion implantation dose is 7×10 -17 ions·cm -2 , the ion injection time is 3h.

[0059] (5) The particles obtained in step (4) were heat-treated at 300° C. for 3 h in an oxygen and argon environment to obtain a MnO 2 @Co 3 O 4 composite catalyst, wherein the mixing ratio of oxygen to argon was 1:17.

[0060] Example 5

[0061] A flue gas NO x The preparation method of the treated high-efficiency MnO2@Co3O4 composite catalyst comprises the following steps:

[0062] (1) Pour 90 parts of MnCl2·4H2O and 250 parts of sodium oleate into a mixed solvent consisting of anhydrous ethanol, n-hexane, and deionized water; heat to 70°C and react for 4 hours while stirring;

[0063] (2) filtering the reaction solution of step (1) to obtain the manganese oleate organic phase, and rotary evaporating to obtain a manganese oleate solid;

[0064] (3) dissolving manganese oleate in octadecenoic acid, heating to 125°C and reacting for 2 h; then heating to 320°C and continuing to react for 2 h; cooling and filtering to obtain nano-MnO particles;

[0065] (4) The vessel containing the nano-MnO particles is placed in the ion implantation device, and the base is controlled to vibrate to drive the nano-MnO particles to vibrate; the power is turned on to implant cobalt ions into the nano-MnO particles; the ion implantation dose is 6×10 -17 ions·cm -2 , the ion injection time is 2h.

[0066] (5) The particles obtained in step (4) were heat treated at 340° C. for 2 h in an oxygen and argon environment to obtain a MnO 2 @Co 3 O 4 composite catalyst, wherein the mixing ratio of oxygen to argon was 1:13.

[0067] In order to investigate the influence of certain factors on the MnO2@Co3O4 composite catalyst, the applicant used Example 3 as a benchmark and controlled the single factor variables respectively.

[0068] Comparative Example 1

[0069] The only difference from Example 3 is that the ion implantation dose used in step (4) of Comparative Example 1 is 4×10 - 17 ions·cm -2 .

[0070] Comparative Example 2

[0071] The only difference from Example 3 is that the ion implantation dose used in step (4) of Comparative Example 2 is 9×10 - 17 ions·cm -2 .

[0072] Comparative Example 3

[0073] The only difference from Example 3 is that in step (5), the mixing ratio of oxygen to argon used in Example 3 is 1:5.

[0074] Comparative Example 4

[0075] The only difference from Example 3 is that in Comparative Example 4, the mixing ratio of oxygen to argon is 1:30 in step (5).

[0076] The morphology of the MnO2@Co3O4 composite catalysts prepared in Examples 1 to 5 was characterized. Figure 1 As shown, the structure of the MnO2@Co3O4 composite catalyst prepared in this application is that Co3O4 nanoparticles are loaded on the surface of MnO2 nanospheres.

[0077] The physical and chemical properties of the catalysts prepared in Examples 1 to 5 and Comparative Examples 1 to 4 were measured, and the specific test results are shown in Table 1 below.

[0078] (1) The surface morphology of the MnO2@Co3O4 composite catalyst was observed using a scanning electron microscope, and the particle size of the MnO2@Co3O4 composite catalyst was obtained.

[0079] (2) Use a metal element analyzer to measure the content ratio of Mn and Co.

[0080] (3) The BET method was used to determine the specific surface area of ​​the MnO2@Co3O4 composite catalyst.

[0081] (4) The loading rate of Co3O4 nanoparticles was measured and calculated by ICP-AES method.

[0082] (5) NO x The catalytic activity test was performed as follows: 0.5 g of MnO2@Co3O4 composite catalyst was weighed and placed in a quartz tube at 15000 mL·g -1 ·h -1 The flow rate of the simulated NO x Mixed gas (800 ppm NO, 10 vol.% O2, remaining N2); the pollutant gas concentration at the outlet is detected by an analytical instrument; the data is fitted into a catalytic efficiency curve.

[0083] Table 1

[0084]

[0085] from Figure 1 From the scanning electron microscope images of the MnO2@Co3O4 composite catalyst, it can be observed that the structure of the MnO2@Co3O4 composite catalyst prepared in Examples 1 to 5 is that Co3O4 nanoparticles are loaded on the surface of MnO2 nanospheres; the particle size distribution range of the MnO2@Co3O4 composite catalyst is 25 to 35 nm, and the particle size of the Co3O4 nanoparticles is 5 to 10 nm.

[0086] from Figure 2 It can be seen that the catalytic materials prepared in Examples 1 to 5 have a NO x The conversion rate is as high as over 90%, and it still has good catalytic activity at low and high temperatures.

[0087] The test data in Table 1 also show that the catalyst activities of Comparative Examples 1 and 2 are lower than those of Example 3. This indicates that the ion implantation process parameters significantly affect the Co₃O₄ nanoparticle loading rate and the activity of the MnO₂@Co₃O₄ composite catalyst. A lower cobalt ion implantation dose indicates less cobalt deposited on the MnO₂ particle surface, resulting in a lower Co atomic ratio and a corresponding decrease in the Co₃O₄ nanoparticle loading rate. Furthermore, the catalytic activity of the MnO₂@Co₃O₄ composite catalyst decreased by 10% compared to Example 3. A higher cobalt ion implantation dose indicates more cobalt deposited on the MnO₂ particle surface, resulting in an increase in the Co atomic ratio and a corresponding increase in the Co₃O₄ nanoparticle loading rate. However, the catalytic activity of the MnO₂@Co₃O₄ composite catalyst still decreased compared to Example 3, and the degree of decrease was greater than that of Comparative Example 1. In other words, optimal catalytic activity can only be achieved when the Mn:Co atomic ratio and Co₃O₄ nanoparticle loading rate are appropriately selected.

[0088] Comparative Example 4 differs from Example 3 in that an oxygen to argon mixing ratio of 1:30 is used. While the activity of the MnO2@Co3O4 composite catalyst is affected, the effect is minor. Conversely, in Comparative Example 3, where an oxygen to argon mixing ratio of 1:5 is used, the catalytic activity decreases significantly, by 5% compared to Example 3. This suggests that a lower oxygen partial pressure is more conducive to improving the catalytic activity of the MnO2@Co3O4 composite catalyst.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A flue gas NO x The method for preparing the treated MnO2@Co3O4 composite catalyst is characterized in that: The steps include: (1) Pour 80-90 parts of MnCl2·4H2O and 250-270 parts of sodium oleate into a mixed solvent consisting of anhydrous ethanol, n-hexane and deionized water; heat to 70-75°C and react for 3-4 hours while stirring; (2) filtering the reaction solution of step (1) to obtain the manganese oleate organic phase, and rotary evaporating to obtain a manganese oleate solid; (3) dissolving manganese oleate in octadecenoic acid, heating to 115-125°C and reacting for 2-3 hours; continuing to heat to 310-330°C and reacting for 2-3 hours; cooling and filtering to obtain nano-MnO particles; (4) placing the container containing the nano-MnO particles in an ion implantation device, and controlling the base to vibrate and thereby drive the nano-MnO particles to vibrate; turning on the power supply to implant cobalt ions into the nano-MnO particles; (5) heat treating the particles obtained in step (4) at 300-350° C. for 2-3 h in an oxygen and argon environment to obtain a MnO2@Co3O4 composite catalyst; The dose of ion implantation in step (4) is (5-8)×10 -17 ions·cm -2 , ion injection time is 3 to 4 hours; The mixing ratio of oxygen to argon in step (5) is 1:(10-20).

2. Flue gas NO according to claim 1 x The method for preparing the treated MnO2@Co3O4 composite catalyst is characterized in that: The particle size distribution range of the nano-MnO particles in step (4) is 20 to 30 nm.

3. A flue gas NO x The treated MnO2@Co3O4 composite catalyst is characterized in that: Prepared according to any one of claims 1 to 2.

4. Flue gas NO according to claim 3 x The treated MnO2@Co3O4 composite catalyst is characterized in that: The particle size distribution range of the MnO2@Co3O4 composite catalyst is 25-35 nm.

5. Flue gas NO according to claim 3 x The treated MnO2@Co3O4 composite catalyst is characterized in that: The atomic ratio of Mn to Co in the MnO2@Co3O4 composite catalyst is (3-5):

1.

6. Flue gas NO according to claim 3 x The treated MnO2@Co3O4 composite catalyst is characterized in that: The specific surface area of ​​the MnO2@Co3O4 composite catalyst is 115-135m 2 ·g -1 .

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