Method for preparing denitration catalyst and molecular sieve from electrolytic manganese residues and mineralizing CO2

Abstract

The invention belongs to the technical field of solid waste resource utilization and air pollution control, and particularly relates to a method for preparing a denitration catalyst and a molecular sieve from electrolytic manganese residues and mineralizing CO2. The method comprises the following steps: firstly, leaching electrolytic manganese residues by using oxalic acid to form ferromanganese leaching liquid and leaching residues which are rich in ferromanganese elements; and adding ammonia water into the ferromanganese leaching solution, filtering, washing and roasting to obtain the iron-manganese-based SCR denitration catalyst. The leaching residues are subjected to alkali fusion and water leaching, and a silicon-aluminum leaching solution rich in aluminosilicate and semi-hydrated gypsum filter residues are obtained; and finally, synthesizing the A-type molecular sieve from the silicon-aluminum leachate through a hydrothermal reaction, and meanwhile, using semi-hydrated gypsum filter residues for mineral storage of CO2. According to the method, various components in the electrolytic manganese residues are fully utilized, high additional value and multi-stage utilization of the electrolytic manganese residues are achieved, emission reduction of NOx and CO2 is achieved, and a new method is provided for high-value utilization of the electrolytic manganese residues.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid waste resource utilization and air pollution control, and specifically relates to a method for preparing a denitration catalyst and a molecular sieve and mineralizing CO2 by using electrolytic manganese slag. Background Art

[0002] Electrolytic manganese slag is a byproduct of electrolytic manganese metal production. It's estimated that for every ton of manganese metal produced, approximately 8 to 12 tons of slag are generated. As a major manganese metal producer, China accounts for 98% of the world's total, with approximately 13 million tons of slag added annually, creating a massive stockpile. However, the common practice of damming and stockpiling slag can cause severe secondary pollution to surrounding soil and groundwater. The massive accumulation of slag is hindering the further development of my country's manganese metal industry, and the resourceful utilization of slag has become a pressing issue for the industry.

[0003] The content of SiO2, Fe2O3, Al2O3 and MnO in electrolytic manganese slag exceeds 40%, among which Al2O3 and SiO2 are the main raw materials for synthesizing molecular sieves, MnO x and Fe2O3 can be used as active components of NH3-SCR catalyst for nitrogen oxides (NO x ) emission reduction. Furthermore, electrolytic manganese slag also contains a large amount of calcium sulfate (CaSO4), which is usually present in the form of CaO and SO3. This can be used to mineralize and store carbon dioxide (CO2), thereby reducing CO2 emissions. Therefore, if electrolytic manganese slag can be used as a raw material to mineralize CO2 and prepare NH3-SCR catalysts and molecular sieves, it can not only reduce the waste of valuable elements such as Mn, Fe, Al, and Si, increase product added value, but also achieve the goal of "treating waste with waste."

[0004] Some scholars have conducted research on the resource utilization of electrolytic manganese slag. For example, the invention patent with publication number CN113698123B discloses a method for the resource utilization of electrolytic manganese slag to produce high-performance concrete additives. The method uses electrolytic manganese slag washed with non-polluted water or electrolytic manganese cathode liquid, then allowed to settle, filtered, and mixed with calcium hydroxide and calcium oxide clinker for use as a concrete additive. This patent only uses electrolytic manganese slag as a concrete additive, and the added value of the product is low. The invention patent with publication number CN114644343B proposes a method for preparing pure phase X-type zeolite from electrolytic manganese slag. The method obtains pure phase X-type zeolite by acid leaching, alkali melting, and hydrothermal crystallization of electrolytic manganese slag. This patent only considers the valuable elements Si and Al in the electrolytic manganese slag, but ignores the elements Fe, Mn, etc.

[0005] Therefore, developing a new process that uses electrolytic manganese slag as raw material to simultaneously prepare SCR denitrification catalysts and molecular sieves and realize CO2 mineralization is of great significance for achieving high-value utilization of electrolytic manganese slag. Summary of the Invention

[0006] In view of this, one of the objects of the present invention is to provide a method for simultaneously preparing a denitration catalyst, a type A molecular sieve and mineralizing CO2 using electrolytic manganese slag. This method combines the preparation of SCR denitration catalyst, CO2 mineralization and molecular sieve synthesis, thereby achieving high added value and multi-stage utilization of electrolytic manganese slag.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for simultaneously preparing a denitration catalyst and a type A molecular sieve and mineralizing CO2 using electrolytic manganese slag comprises the following steps:

[0009] 1) leaching the electrolytic manganese slag with an oxalic acid solution, and filtering to obtain a ferromanganese leachate and leaching slag rich in iron and manganese elements;

[0010] 2) adding aqueous ammonia to the ferromanganese leaching solution obtained in step 1), reacting until complete precipitation, stirring, aging, filtering, washing, and calcining to obtain an iron-manganese-based SCR denitration catalyst;

[0011] 3) The leached residue obtained in step 1) is subjected to sodium treatment, roasting, leaching, and filtering to obtain a silicon-aluminum leachate rich in silicon and aluminum elements and a hemihydrate gypsum filter residue;

[0012] 4) adding a directing agent to the silicon-aluminum leachate obtained in step 3) to prepare a type A molecular sieve through a hydrothermal reaction;

[0013] 5) adding ammonia water to the hemihydrate gypsum filter residue obtained in step 3) and introducing CO2 to generate calcium carbonate, thereby achieving CO2 mineralization.

[0014] Furthermore, in step 1), the particle size of the electrolytic manganese slag raw material is ≤100 μm.

[0015] Furthermore, in step 1), the concentration of the oxalic acid is 0.1-1.0 mol / L, the liquid-to-solid ratio of the oxalic acid solution to the electrolytic manganese slag is 1-10, and the stirring time is 30-120 min.

[0016] Preferably, the oxalic acid concentration is 0.1 mol / L, the liquid-to-solid ratio of the oxalic acid solution to the electrolytic manganese slag is 10, and the stirring time is 30 min.

[0017] Furthermore, in step 2), the mass fraction of the ammonia water is 20% to 30%; the stirring time is 2 to 3 hours, the aging time is 10 to 24 hours; the roasting temperature is 400-600° C., and the roasting time is 200-300 minutes.

[0018] Preferably, in step 2), the mass fraction of the ammonia water is 25%.

[0019] Preferably, in step 2), the stirring time is 3 h and the aging time is 10 h.

[0020] Preferably, in step 2), the calcination temperature is 500° C. and the calcination time is 240 min.

[0021] Furthermore, in step 3), the sodium roasting is performed by mixing the leaching residue obtained in step 1) with sodium hydroxide and then roasting; the mass ratio of the leaching residue to the sodium hydroxide is 1:1 to 1:4, the roasting temperature is 500 to 900° C., and the roasting time is 30 to 240 minutes.

[0022] Preferably, in step 3), the mass ratio of the leaching residue to the sodium hydroxide is 1:1.

[0023] Preferably, in step 3), the calcination temperature is 900° C. and the calcination time is 30 min.

[0024] Furthermore, in step 3), the leaching temperature is 25-100° C., and the leaching time is 30-120 min.

[0025] Preferably, in step 3), the leaching temperature is 25° C. and the leaching time is 30 min.

[0026] Furthermore, in step 3), the leaching comprises: dissolving the roasted product in deionized water and stirring for leaching.

[0027] Preferably, the liquid-to-solid ratio of the calcined product to the deionized water is 1:1 to 4:1, most preferably 1:1.

[0028] Furthermore, in step 4), the directing agent is prepared by dissolving sodium hydroxide, aluminum hydroxide and sodium silicate in water; and the molar ratio of silicon to aluminum in the directing agent is 1:1 to 1:4.

[0029] Preferably, the molar ratio of silicon to aluminum in the directing agent is 1:1.

[0030] Furthermore, in step 4), the volume ratio of the directing agent to the silicon-aluminum leaching solution is 1:10 to 1:30, the hydrothermal temperature is 80 to 120° C., and the hydrothermal time is 4 to 24 hours.

[0031] Preferably, the volume ratio of the directing agent to the silicon-aluminum leaching solution is 1:10, the hydrothermal temperature is 120° C., and the hydrothermal time is 4 hours.

[0032] A second object of the present invention is to provide an iron-manganese-based SCR denitration catalyst prepared by the above method, which has good low-temperature activity and catalytic activity within the range of 100 to 275°C.

[0033] The third object of the present invention is to provide a type A molecular sieve prepared by the above method.

[0034] Furthermore, the type A molecular sieve comprises the following XRD diffraction peaks (2θ): 7.1°, 10.1°, 12.4°, 16.1°, 17.6°, 20.4°, 21.6°, 22.8°, 24.0°, 25.4°, 26.2°, 27.2°, 29.1°, 29.9°, 30.9°, 32.1°, 34.2°, 35.8°, and 37.9°.

[0035] A fourth object of the present invention is to provide an application of the aforementioned iron-manganese-based SCR denitration catalyst in NH3-SCR reaction, nitrogen oxide emission reduction and / or low-temperature denitration in coal-fired power plants.

[0036] The beneficial effects of the present invention are:

[0037] 1. The present invention establishes a new process that uses industrial solid waste electrolytic manganese slag as raw material to combine the preparation of SCR denitration catalysts, CO2 mineralization, and molecular sieve synthesis. The process first uses oxalic acid to leach electrolytic manganese slag to form a ferromanganese leachate and leach residue rich in manganese iron elements; ammonia water is added to the ferromanganese leachate, and after filtering, washing, and roasting, an iron-manganese-based SCR denitration catalyst is obtained; the leach residue is alkali-fused and water-leached to obtain a silicoaluminate-rich silicoaluminate leachate and a semi-hydrated gypsum filter residue; finally, a type A molecular sieve is synthesized from the silicoaluminate leachate through a hydrothermal reaction, and the semi-hydrated gypsum filter residue is used for mineral storage of CO2. This process has mild reaction conditions, simple operation, low production cost, significant economic benefits, and is environmentally friendly, with great prospects for industrial application.

[0038] 2. The method of the present invention makes full use of various components in electrolytic manganese slag, realizes its high added value and multi-level utilization, and is used for NO x and CO2 emission reduction, which provides a new method for high-value utilization of large amounts of industrial solid waste.

[0039] 3. The iron-manganese based SCR denitration catalyst prepared in the present invention has good low temperature activity within 100-275°C, especially in Example 1, in the entire reaction temperature range, NO x The conversion rate is maintained above 90%, and the catalyst has good catalytic activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 The process flow chart of the method for high value-added and multi-stage utilization of electrolytic manganese slag of the present invention is as follows;

[0041] Figure 2 Activity diagram of the iron-manganese-based SCR denitration catalyst prepared in Examples 1 to 3;

[0042] Figure 3 This is the XRD pattern of the type A molecular sieve prepared in Examples 1 to 3. DETAILED DESCRIPTION

[0043] The technical solutions of the present invention will be further described in detail below with reference to specific embodiments. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Therefore, all other embodiments derived by those skilled in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0044] The composition and content of the electrolytic manganese slag raw material used in the present invention are shown in Table 1.

[0045] Table 1. Chemical composition of electrolytic manganese slag

[0046] Element <![CDATA[SiO2]]> <![CDATA[SO3]]> CaO <![CDATA[Fe2O3]]> <![CDATA[Al2O3]]> MnO MgO other wt.% 36.3 28.8 14.9 4.8 6.6 5.1 2.9 0.6

[0047] In the embodiment of the present invention, the pre-treatment of the electrolytic manganese slag includes: drying, crushing, and screening the electrolytic manganese slag to obtain electrolytic manganese slag with a particle size of less than 100 μm.

[0048] The process flow of the method for simultaneously preparing denitration catalyst, molecular sieve and mineralizing CO2 by using electrolytic manganese slag provided by the present invention is as follows: Figure 1 The main steps are as follows:

[0049] 1) leaching the electrolytic manganese slag with an oxalic acid solution, and filtering to obtain a ferromanganese leachate and leaching slag rich in iron and manganese elements;

[0050] 2) adding aqueous ammonia to the ferromanganese leaching solution obtained in step 1), precipitating, washing, and calcining to prepare an iron-manganese-based SCR denitration catalyst;

[0051] 3) The leached residue obtained in step 1) is subjected to sodium treatment, roasting, leaching, and filtering to obtain a silicon-aluminum leachate rich in silicon and aluminum elements and a hemihydrate gypsum filter residue;

[0052] 4) adding a directing agent to the silicon-aluminum leachate obtained in step 3) to prepare a type A molecular sieve through a hydrothermal reaction;

[0053] 5) adding ammonia water to the hemihydrate gypsum filter residue obtained in step 3) and introducing CO2 to generate calcium carbonate, thereby achieving CO2 mineralization.

[0054] Example 1. Method for simultaneously preparing denitrification catalyst, molecular sieve and mineralizing CO2 using electrolytic manganese slag

[0055] (1) 10 g of electrolytic manganese slag finely ground to less than 100 μm was added to 100 mL of 0.1 mol / L oxalic acid solution, stirred for 30 min, and filtered to obtain a ferromanganese leaching solution and leaching residue rich in iron and manganese elements;

[0056] (2) adding 25% by mass of ammonia water to the ferromanganese leaching solution obtained in step (1), reacting until complete precipitation, stirring for 3 hours, aging for 10 hours, filtering and washing, and calcining at 500° C. for 240 minutes to obtain an iron-manganese-based SCR denitration catalyst;

[0057] (3) uniformly mixing the leached residue obtained in step (1) with sodium hydroxide, with the mass ratio of the leached residue to the sodium hydroxide being 1:1, and calcining the mixture at 900° C. for 30 min to obtain a solid product;

[0058] (4) the solid product obtained in step (3) was leached with deionized water at 25° C. under magnetic stirring for 30 min at a liquid-to-solid ratio of 1:1, and solid-liquid separation was performed to obtain a silicon-aluminum leachate rich in silicon and aluminum elements and a hemihydrate gypsum filter residue;

[0059] (5) dissolving sodium hydroxide, aluminum hydroxide, and sodium silicate in water, controlling the molar ratio of silicon to aluminum to be 1:1, to obtain a directing agent;

[0060] (6) adding the directing agent prepared in step (5) to the silicon-aluminum leachate obtained in step (4), fully mixing and placing in a reactor, performing a hydrothermal reaction at a certain temperature, controlling the volume ratio of the directing agent to the silicon-aluminum leachate to be 1:10, the hydrothermal temperature to be 120° C., the hydrothermal time to be 4 h, and washing the solid product with deionized water to obtain a type A molecular sieve;

[0061] (7) adding ammonia water to the semi-hydrated gypsum filter residue obtained in step (4) and introducing CO2 to generate calcium carbonate, thereby achieving CO2 mineralization.

[0062] Example 2. Method for preparing denitrification catalyst, molecular sieve and mineralization of CO2 using electrolytic manganese slag

[0063] (1) 10 g of electrolytic manganese slag finely ground to less than 100 μm was added to 50 mL of 0.5 mol / L oxalic acid solution, stirred for 60 min, and filtered to obtain a ferromanganese leaching solution and leaching residue rich in iron and manganese elements;

[0064] (2) adding 25% by mass of ammonia water to the ferromanganese leaching solution obtained in step (1), reacting until complete precipitation, stirring for 2 hours, aging for 12 hours, filtering and washing, and calcining at 500° C. for 240 minutes to obtain an iron-manganese-based SCR denitration catalyst;

[0065] (3) uniformly mixing the leached residue obtained in step (1) with sodium hydroxide, with the mass ratio of the leached residue to the sodium hydroxide being 1:2, and calcining the mixture at 600° C. for 120 min to obtain a solid product;

[0066] (4) the solid product obtained in step (3) was leached with deionized water at 50° C. under magnetic stirring for 60 min at a liquid-to-solid ratio of 2:1, and solid-liquid separation was performed to obtain a silicon-aluminum leachate rich in silicon and aluminum elements and a hemihydrate gypsum filter residue;

[0067] (5) dissolving sodium hydroxide, aluminum hydroxide, and sodium silicate in water, controlling the silicon-aluminum molar ratio to be 1:2, to obtain a directing agent;

[0068] (6) adding the directing agent prepared in step (5) to the silicon-aluminum leachate obtained in step (4), fully mixing and placing in a reactor, performing a hydrothermal reaction at a certain temperature, controlling the volume ratio of the directing agent to the silicon-aluminum leachate to be 1:20, the hydrothermal temperature to be 100° C., the hydrothermal time to be 12 h, and washing the solid product with deionized water to obtain a type A molecular sieve;

[0069] (7) adding ammonia water to the semi-hydrated gypsum filter residue obtained in step (4) and introducing CO2 to generate calcium carbonate, thereby achieving CO2 mineralization.

[0070] Example 3. Method for simultaneously preparing denitrification catalyst, molecular sieve and mineralizing CO2 using electrolytic manganese slag

[0071] (1) 10 g of electrolytic manganese slag finely ground to less than 100 μm was added to 10 mL of 1.0 mol / L oxalic acid solution, stirred for 120 min, and filtered to obtain a ferromanganese leaching solution and leaching residue rich in iron and manganese elements;

[0072] (2) adding 25% by mass of ammonia water to the ferromanganese leaching solution obtained in step (1), reacting until complete precipitation, stirring for 2 hours, aging for 24 hours, filtering and washing, and calcining at 500° C. for 240 minutes to obtain an iron-manganese-based SCR denitration catalyst;

[0073] (3) uniformly mixing the leached residue obtained in step (1) with sodium hydroxide, with the mass ratio of the leached residue to the sodium hydroxide being 1:4, and calcining the mixture at 500° C. for 240 min to obtain a solid product;

[0074] (4) the solid product obtained in step (3) was leached with deionized water at 100° C. under magnetic stirring for 30 min at a liquid-to-solid ratio of 4:1, and solid-liquid separation was performed to obtain a silicon-aluminum leachate rich in silicon and aluminum elements and a hemihydrate gypsum filter residue;

[0075] (5) dissolving sodium hydroxide, aluminum hydroxide, and sodium silicate in water, controlling the silicon-aluminum molar ratio to be 1:4, to obtain a directing agent;

[0076] (6) adding the directing agent obtained in step (5) to the silicon-aluminum leachate obtained in step (4), fully mixing and placing in a reactor, performing a hydrothermal reaction at a certain temperature, controlling the volume ratio of the directing agent to the silicon-aluminum leachate to be 1:30, the hydrothermal temperature to be 80° C., the hydrothermal time to be 24 h, and washing the solid product with deionized water to obtain a type A molecular sieve;

[0077] (7) adding ammonia water to the semi-hydrated gypsum filter residue obtained in step (4) and introducing CO2 to generate calcium carbonate, thereby achieving CO2 mineralization.

[0078] Example 4

[0079] (1) Catalytic activity test of iron-manganese-based SCR catalyst

[0080] The performance of the iron-manganese-based SCR catalysts prepared in Examples 1 to 3 was tested. 0.2 g of the prepared catalyst was placed in a quartz tube reactor for activity testing. The reactor inlet contained 500 ppm NO, 500 ppm NH3, 5% O2, and the remainder N2. The total gas flow rate was 150 mL / min, and the test temperature was 100-275°C. The results are shown in Figure 2. Figure 2 As shown in the figure, the iron-manganese based SCR catalyst prepared by the present invention has good low temperature activity within 100-275°C, especially in Example 1, in the entire reaction temperature range, NO x The conversion rate is maintained above 90%, and the catalyst has good catalytic activity.

[0081] (2) XRD characterization of type A molecular sieve

[0082] XRD characterization test was performed on the type A molecular sieve prepared in Example 1 to Example 3. The results are as follows Figure 3 As shown, XRD diffraction peaks belonging to type 4A molecular sieve were observed at 7.1°, 10.1°, 12.4°, 16.1°, 17.6°, 20.4°, 21.6°, 22.8°, 24.0°, 25.4°, 26.2°, 27.2°, 29.1°, 29.9°, 30.9°, 32.1°, 34.2°, 35.8°, and 37.9°, indicating that type 4A molecular sieve was successfully prepared.

Claims

1. A method for simultaneously preparing a denitration catalyst and a type A molecular sieve and mineralizing CO2 using electrolytic manganese slag, characterized in that: The steps include: 1) leaching electrolytic manganese slag with oxalic acid solution, and filtering to obtain ferromanganese leaching solution and leaching slag rich in iron and manganese elements; 2) adding aqueous ammonia to the ferromanganese leaching solution obtained in step 1), reacting until complete precipitation, stirring, aging, filtering, washing, and roasting to obtain an iron-manganese-based SCR denitration catalyst; 3) The leached residue obtained in step 1) is subjected to sodium calcination, leaching and filtering to obtain a silicon-aluminum leaching solution rich in silicon and aluminum elements and a semi-hydrated gypsum filter residue; 4) adding a directing agent to the silicon-aluminum leaching solution obtained in step 3) to obtain a type A molecular sieve through a hydrothermal reaction; 5) adding ammonia water to the semi-hydrated gypsum residue obtained in step 3) and introducing CO2 to generate calcium carbonate, thereby achieving CO2 mineralization.

2. The method according to claim 1, characterized in that In step 1), the concentration of oxalic acid is 0.1-1.0 mol / L, the liquid-to-solid ratio of the oxalic acid solution to the electrolytic manganese slag is 1-10, and the stirring time is 30-120 min.

3. The method according to claim 1, characterized in that In step 2), the mass fraction of the ammonia water is 20% to 30%; the stirring time is 2 to 3 hours, the aging time is 10 to 24 hours; the roasting temperature is 400-600° C., and the roasting time is 200-300 minutes.

4. The method according to claim 1, characterized in that In step 3), the sodium roasting is to mix the leached residue obtained in step 1) with sodium hydroxide and then roast it; the mass ratio of the leached residue to the sodium hydroxide is 1:1 to 1:4, the roasting temperature is 500 to 900° C., and the roasting time is 30 to 240 minutes.

5. The method according to claim 1, characterized in that In step 3), the leaching temperature is 25-100° C. and the leaching time is 30-120 min.

6. The method according to claim 1, characterized in that In step 4), the directing agent is prepared by dissolving sodium hydroxide, aluminum hydroxide and sodium silicate in water; in the directing agent, the molar ratio of silicon to aluminum is 1:1 to 1:

4.

7. The method according to claim 1, characterized in that In step 4), the volume ratio of the directing agent to the silicon-aluminum leaching solution is 1:10-1:30, the hydrothermal temperature is 80-120° C., and the hydrothermal time is 4-24 hours.

8. An iron-manganese-based SCR denitration catalyst prepared by the method described in any one of claims 1 to 7.

9. A type molecular sieve prepared by the method according to any one of claims 1 to 7.

10. Use of the iron-manganese-based SCR denitration catalyst prepared according to claim 8 in NH3-SCR reaction, nitrogen oxide emission reduction and / or low-temperature denitration in coal-fired power plants.

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