SCR-CO catalytic oxidation bifunctional catalyst prepared based on waste denitration catalyst and hydrotalcite and preparation method of SCR-CO catalytic oxidation bifunctional catalyst

Abstract

The invention aims to provide an SCR-CO catalytic oxidation bifunctional catalyst prepared on the basis of a waste denitration catalyst and hydrotalcite and a preparation method of the SCR-CO catalytic oxidation bifunctional catalyst, and belongs to the technical field of industrial solid waste resource utilization and air pollution control. A hydrotalcite precursor is loaded on the surface of the composite material by adopting a mechanical mixing-calcining method for compounding; according to the method, efficient utilization of active components in the waste catalyst is realized, resource utilization of hazardous wastes is realized, and a highly dispersed metal oxide complex is formed after calcination by utilizing a unique layered structure and adjustable alkaline sites of hydrotalcite. The prepared catalyst not only retains excellent NH3-SCR denitration activity, but also shows excellent CO low-temperature catalytic oxidation performance due to the synergistic effect of alkaline sites introduced by hydrotalcite and transition metal ions. The method realizes resource utilization of hazardous wastes, is flexible in preparation method and easy to industrialize, and innovatively develops the bifunctional catalyst.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of industrial solid waste resource utilization and air pollution control, and particularly relates to an SCR-CO catalytic oxidation bifunctional catalyst prepared based on waste denitration catalyst and hydrotalcite and a preparation method thereof. BACKGROUND

[0002] China mainly uses coal as the main energy structure, and a large amount of nitrogen oxides (NO x ) is discharged into the atmosphere every year, which is one of the main air pollutants. The selective catalytic reduction (SCR) technology is the mainstream technology for industrial flue gas denitration at present, and the core is the V2O5-WO3-TiO2 series catalyst. However, the catalyst will be deactivated due to loss of active components, poisoning, and structure collapse after being used for 3-5 years, and a large amount of waste denitration catalyst will be produced. At present, the waste denitration catalyst is mainly landfilled or simply regenerated, which not only wastes resources but also has the risk of heavy metal pollution. Therefore, how to realize the high-value resource utilization of the waste denitration catalyst has become a difficult problem in the industry.

[0003] At the same time, in addition to NO x , the industrial flue gas also often contains CO and other reducing pollutants. The existing treatment technology needs to use SCR denitration catalyst and CO oxidation catalyst respectively, which has the problems of large equipment investment, complex process, and high energy consumption. Therefore, it is of great economic and environmental value to develop a bifunctional catalyst that can simultaneously realize SCR denitration and CO catalytic oxidation, and can reduce the cost by using waste denitration catalyst.

[0004] In the prior art, CN105481007A discloses a resource treatment process for waste denitration catalyst based on strong alkali leaching. The catalyst is treated by leaching with a strong alkali solution, and after solid-liquid separation, a filter liquor containing vanadium and tungsten and a titanium white powder crude product are obtained. Specifically, the process uses a multi-stage precipitation method to separate ammonium metavanadate and sodium tungstate from the filter liquor, and at the same time, the titanium white powder filter residue is treated by a water washing process. However, the technical scheme has the following technical defects: first, the process flow involves multiple separation units (including alkali leaching, precipitation, filtration, washing, etc.), which leads to high overall energy consumption and limited production efficiency; second, the sodium-containing wastewater and alkaline waste residue generated in the leaching process are easy to cause secondary environmental pollution; and more importantly, the purity of the titanium white powder product obtained by the prior art is usually lower than 90% (verified by XRD and BET characterization), which cannot meet the technical requirements of TiO2 purity ≥ 95% in high-end application fields such as coatings and plastics.

[0005] At present, there is no report on the preparation of a bifunctional catalyst with both SCR and CO oxidation functions by compounding waste SCR catalyst and hydrotalcite. Coupling these two materials not only realizes the high-value resource utilization of waste, but also creates comprehensive performance that cannot be achieved by a single catalyst through the synergistic effect between components. Summary of the Invention

[0006] This invention addresses the problems of difficulty in recovering spent denitrification catalysts, complex recovery processes, and the risk of secondary pollution in existing technologies. It provides a bifunctional SCR-CO catalytic oxidation catalyst based on spent denitrification catalysts and hydrotalcite, along with its preparation method. This method features a simple process flow and low cost, and the resulting catalyst exhibits a significant synergistic effect, capable of treating catalysts containing NO. x Complex flue gas containing CO.

[0007] The present invention adopts the following technical solution: A bifunctional SCR-CO catalytic oxidation catalyst prepared from spent denitrification catalyst and hydrotalcite, wherein the catalyst is prepared from spent denitrification catalyst and hydrotalcite, and simultaneously possesses the ability to selectively reduce NO by NH3. x The reaction involves catalytic oxidation of CO; the selective catalytic reduction active layer is provided with V, W, and Ti elements from spent denitrification catalyst, and at least two of the elements Mg, Al, Cu, Co, Mn, and Fe provided by hydrotalcite.

[0008] Furthermore, the waste denitrification catalyst is a waste V2O5-WO3-TiO2 catalyst generated from coal-fired plants, steel plants, etc., wherein the mass content of V2O5 is 1-5% and the mass content of WO3 is 5-10%.

[0009] Furthermore, the hydrotalcite is magnesium aluminum hydrotalcite, and the waste denitrification catalyst is a honeycomb catalyst or a plate catalyst.

[0010] A method for preparing a bifunctional SCR-CO catalytic oxidation catalyst based on waste denitrification catalyst and hydrotalcite includes the following steps: S1. Magnesium aluminum hydrotalcite is mixed with carbon powder or graphite powder in a certain proportion and then calcined to obtain magnesium aluminum spinel. S2, Pretreatment of waste denitrification catalyst; S3. Mechanically mix magnesium aluminum spinel, pretreated waste denitrification catalyst and binder in proportion to obtain a mixture; S4. After drying the mixture, it is calcined to obtain a bifunctional catalyst.

[0011] Furthermore, the mass ratio of the magnesium aluminum hydrotalcite to carbon powder or graphite powder in S1 is 1:0.5-2.

[0012] Furthermore, the carbon powder or graphite powder mentioned in S1 has a particle size of 200 mesh, a calcination temperature of 1100-1300℃, and a calcination time of 2-5h.

[0013] Furthermore, the roasting time is 3 hours.

[0014] Furthermore, the pretreatment method for the waste denitrification catalyst described in S2 is as follows: the waste denitrification catalyst is crushed, cleaned, and ground; it is washed with deionized water and dried to remove soluble poisons physically adsorbed on the surface.

[0015] Furthermore, the particle size of the pretreated waste denitrification catalyst is 100-600 mesh.

[0016] Furthermore, the particle size of the pretreated waste denitrification catalyst is 200-500 mesh.

[0017] Furthermore, the mass ratio of the magnesium aluminum spinel, the pretreated waste denitrification catalyst, and the binder in S3 is 3:15:2.

[0018] Furthermore, the binder described in S3 includes at least one of silica sol, aluminum sol, or polyvinyl alcohol.

[0019] Furthermore, the mechanical mixing time described in S3 is 20-60 min, and the mixing speed is 200-500 rpm.

[0020] Furthermore, the drying temperature gradient described in S4 is as follows: first, the temperature is increased to 80℃ at a rate of 5-10℃ / min and held for 1 hour, then the temperature is increased to 120℃ at a rate of 10-15℃ / min and held for 2 hours.

[0021] Furthermore, the calcination temperature described in S4 is 500℃, and the calcination time is 1-8h.

[0022] Furthermore, the roasting time described in S4 is 5 hours.

[0023] The bifunctional catalyst is used to simultaneously treat nitrogen oxides and volatile organic compounds in flue gas.

[0024] The beneficial effects of this invention are as follows: 1. This invention uses industrial hazardous solid waste (waste denitrification catalyst) as the main raw material and achieves low-cost preparation of bifunctional catalysts through directional conversion. The cost is reduced by more than 60% compared with traditional precious metal catalysts, which meets the requirements of green circular economy.

[0025] 2. This invention innovatively constructs a synergistic catalytic system for SCR denitrification and CO oxidation. The alkaline sites generated by the calcination of hydrotalcite promote NH3 adsorption and activation, thereby achieving NO… x Simultaneous and efficient removal of CO (200-400℃) and CO (160-220℃).

[0026] 3. The catalyst obtained by the present invention is suitable for high-precision industrial equipment, achieving a balance between flexibility and economy in technology promotion. Attached Figure Description

[0027] Figure 1 The bifunctional catalyst prepared in the embodiments of the present invention and the product of the comparative example show NO in simulated flue gas. x A graph showing the conversion rate as a function of temperature; Figure 2 This is a graph showing the change of CO with temperature in simulated flue gas for the bifunctional catalyst prepared in the embodiments of the present invention and the product of the comparative example. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. The embodiments provide detailed implementation methods and specific operation processes, but the scope of protection of the present invention is not limited to the following embodiments.

[0029] Example A method for preparing a bifunctional SCR-CO catalytic oxidation catalyst based on waste denitrification catalyst and hydrotalcite includes the following steps: S1. Mix magnesium aluminum hydrotalcite (Mg / Al molar ratio 3:1) and 200 mesh graphite powder at a mass ratio of 1:1, calcine at 1200℃ in a muffle furnace for 3 hours, and obtain magnesium aluminum spinel after natural cooling. S2. Take the waste honeycomb SCR catalyst (3% V2O5 and 8% WO3) from the coal-fired power plant, crush it with a jaw crusher and then ball mill it to a particle size of 200 mesh. Wash it three times with deionized water to remove surface impurities and dry it at 105℃ for 12 hours to obtain the pretreated waste honeycomb SCR catalyst. S3. Magnesium aluminum spinel, pretreated waste honeycomb SCR catalyst and silica sol binder are placed in a V-type mixer at a mass ratio of 3:15:2 and mixed at 300 rpm for 40 minutes to obtain a mixture. S4. Spread the mixture evenly on the oven tray, heat it to 80℃ at 5℃ / min and keep it at that temperature for 1 hour, then heat it to 120℃ at 10℃ / min and keep it at that temperature for 2 hours; finally, transfer it to a muffle furnace and calcine it at 500℃ for 5 hours. After natural cooling, the bifunctional catalyst product is obtained.

[0030] Performance testing The catalyst prepared above was tableted, sieved to 40-60 mesh, and evaluated in a fixed-bed reactor. The reaction gas composition was: 500 ppm NO, 500 ppm NH3, 1% CO, 5% O2, with N2 as the balance gas. The space velocity was 50,000 h⁻¹. -1 The temperature range is 150-400℃, and tests are conducted at 50℃ intervals.

[0031] Comparative Example S1. Copper-cobalt hydrotalcite (Cu / Co molar ratio 2:1) and 200-mesh carbon powder are mixed at a mass ratio of 1:1.5, heated to 1100℃ in a muffle furnace at 10℃ / min, calcined for 5 hours, and then naturally cooled to obtain copper-cobalt spinel. This combination introduces transition metals and enhances redox activity.

[0032] S2. Pretreatment of spent denitrification catalyst: The spent catalyst was selected from a steel plant plate SCR catalyst (4% V2O5 and 6% WO3 by mass), ground to a particle size of 300 mesh, washed three times with deionized water to remove surface impurities, and dried at 105℃ for 12 hours.

[0033] S3, Mechanical Hybrid Weigh the raw materials according to a spinel: pretreated waste catalyst: binder mass ratio of 4:15:2. Use aluminum sol (30% solid content) as the binder, mix at 400 rpm for 30 minutes.

[0034] S4. Drying and roasting The drying gradient is the same as in Example 1; the calcination conditions are 500°C for 3 hours (heating rate 10°C / min) to shorten the process time.

[0035] Performance testing The catalyst prepared above was tableted, sieved to 40-60 mesh, and evaluated in a fixed-bed reactor. The reaction gas composition was: 500 ppm NO, 500 ppm NH3, 1% CO, 5% O2, with N2 as the balance gas. The space velocity was 50,000 h⁻¹. -1 The temperature range is 150-400℃, and tests are conducted at 50℃ intervals.

[0036] The test results are as follows: Figure 1 and Figure 2 As shown.

[0037] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be defined by the appended claims.

Claims

1. A bifunctional SCR-CO catalytic oxidation catalyst prepared from waste denitrification catalyst and hydrotalcite, characterized in that: The catalyst is prepared from spent denitrification catalyst and hydrotalcite, and also has the ability to selectively reduce NO by NH3. x The selective catalytic reduction active layer is provided with V, W, and Ti elements from spent denitrification catalyst, and at least two of the following elements: Mg, Al, Cu, Co, Mn, and Fe elements provided by hydrotalcite. The waste denitrification catalyst is a waste V2O5-WO3-TiO2 catalyst generated from coal-fired plants and steel plants, wherein the mass content of V2O5 is 1-5% and the mass content of WO3 is 5-10%. The hydrotalcite is magnesium aluminum hydrotalcite, and the waste denitrification catalyst is a honeycomb catalyst or a flat plate catalyst.

2. A method for preparing a bifunctional SCR-CO catalytic oxidation catalyst based on waste denitrification catalyst and hydrotalcite as described in claim 1, characterized in that: Includes the following steps: S1. Magnesium aluminum hydrotalcite is mixed with carbon powder or graphite powder in a certain proportion and then calcined to obtain magnesium aluminum spinel. S2, Pretreatment of waste denitrification catalyst; S3. Mechanically mix magnesium aluminum spinel, pretreated waste denitrification catalyst and binder in proportion to obtain a mixture; S4. After drying the mixture, it is calcined to obtain a bifunctional catalyst.

3. The method for preparing a bifunctional SCR-CO catalytic oxidation catalyst based on waste denitrification catalyst and hydrotalcite according to claim 2, characterized in that: The mass ratio of magnesium aluminum hydrotalcite to carbon powder or graphite powder in S1 is 1:0.5-2; The carbon powder or graphite powder has a particle size of 200 mesh, a calcination temperature of 1100-1300℃, and a calcination time of 2-5 hours.

4. The method for preparing a bifunctional SCR-CO catalytic oxidation catalyst based on waste denitrification catalyst and hydrotalcite according to claim 2, characterized in that: The pretreatment method for the spent denitrification catalyst described in S2 is as follows: the spent denitrification catalyst is crushed, cleaned, and ground; it is washed with deionized water and dried to remove soluble poisons physically adsorbed on the surface; The particle size of the pretreated waste denitrification catalyst is 100-600 mesh.

5. The method for preparing a bifunctional SCR-CO catalytic oxidation catalyst based on waste denitrification catalyst and hydrotalcite according to claim 2, characterized in that: The mass ratio of magnesium aluminum spinel, pretreated waste denitrification catalyst, and binder in S3 is 3:15:

2.

6. The method for preparing a bifunctional SCR-CO catalytic oxidation catalyst based on waste denitrification catalyst and hydrotalcite according to claim 2, characterized in that: The binder described in S3 includes at least one of silica sol, aluminum sol, or polyvinyl alcohol.

7. The method for preparing a bifunctional SCR-CO catalytic oxidation catalyst based on waste denitrification catalyst and hydrotalcite according to claim 2, characterized in that: The mechanical mixing time described in S3 is 20-60 min, and the mixing speed is 200-500 rpm.

8. The method for preparing a bifunctional SCR-CO catalytic oxidation catalyst based on waste denitrification catalyst and hydrotalcite according to claim 2, characterized in that: The drying temperature gradient described in S4 is as follows: first, heat the temperature to 80℃ at a rate of 5-10℃ / min and hold for 1 hour, then heat the temperature to 120℃ at a rate of 10-15℃ / min and hold for 2 hours.

9. The method for preparing a bifunctional SCR-CO catalytic oxidation catalyst based on waste denitrification catalyst and hydrotalcite according to claim 2, characterized in that: The roasting temperature described in S4 is 500℃, and the roasting time is 1-8h.

10. A bifunctional catalyst as described in claim 1, used for the simultaneous treatment of nitrogen oxides and volatile organic compounds in flue gas.

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