Preparation method and application of a bimetallic composite catalytic material

Abstract

This invention discloses a method for preparing a bimetallic composite catalytic material and its application. The invention first obtains a bimetallic composite catalytic material by combining two transition metal elements, and then uses it to catalyze the oxidation of sulfite, achieving an oxidation rate of over 90%. Compared with non-catalytic oxidation, the oxidation efficiency of sulfite using the bimetallic composite catalytic material in this invention is increased by 20-35 times.

Description

Technical Field

[0001] This invention relates to the field of catalytic oxidation of sulfites, and more specifically to a method for preparing and applying a bimetallic composite catalytic material. Background Technology

[0002] Implementing flue gas desulfurization (FGD) projects is an effective means of strictly controlling SO2 emissions from fossil fuel industries. Typical FGD processes include limestone / lime absorption (calcium-based wet or semi-dry desulfurization processes), magnesium oxide, ammonia, and sodium alkali methods. These desulfurization methods can efficiently absorb SO2 from flue gas, but various desulfurizing agents generate sulfites as a byproduct after the desulfurization reaction. Because sulfites are physically and chemically unstable and easily decompose, direct utilization is difficult; they must be oxidized into stable sulfates for better disposal and utilization. Direct air oxidation of sulfites is time-consuming, energy-intensive, and costly.

[0003] Traditional ionic homogeneous catalysts exhibit good catalytic efficiency, but their practical application is limited due to the difficulty in recycling and reuse, and the generation of secondary pollution wastewater. Recent studies have shown that heterogeneous catalysts prepared by supporting transition metal elements (such as Co) on molecular sieves, activated carbon, or metal-organic frameworks (MOFs) can improve the oxidation rate of MgSO3 compared to non-catalytic oxidation, while also facilitating catalyst recycling and reducing metal pollution in wastewater. However, single-component metal catalysts still exhibit low efficiency when used for the oxidation of sulfites, especially the less soluble calcium sulfite. The interaction between the active component and the support is weak, leading to easy detachment or shielding by the support, resulting in a rapid decline in catalytic activity and inconvenient recovery, which is detrimental to oxidation cost control. Summary of the Invention

[0004] To address the technical problems of weak interaction between the active components and the support, easy detachment, low catalytic activity, and difficulty in recycling of conventional heterogeneous catalysts in sulfite oxidation reactions, this invention proposes a method for preparing and applying a bimetallic composite catalytic material. First, a bimetallic MOF material with transition metal interdoping is combined with gel microspheres to construct a catalyst gel microsphere, which is then used to catalyze the sulfite oxidation reaction, significantly improving the oxidation effect, stability, and recycling performance of sulfite.

[0005] The specific technical solution of the present invention is as follows:

[0006] A method for preparing a bimetallic composite catalytic material involves first combining a transition metal-doped bimetallic MOF material with a gel to form a gel microsphere of the bimetallic composite catalytic material. Then, the gel microsphere of the bimetallic composite catalytic material is added to a sulfite slurry, and oxygen-containing gas is introduced to mix and react until the oxidation reaction is complete.

[0007] Furthermore, the preparation method of the gel microspheres of the bimetallic composite catalytic material includes the following steps:

[0008] (1) Mix bimetallic MOFs material, polyvinyl alcohol and sodium alginate with water and stir to obtain liquid A;

[0009] (2) Dissolve boric acid in water and add an auxiliary agent to obtain solution B;

[0010] (3) Liquid A was added dropwise to solution B to obtain microspheres;

[0011] (4) After drying the microspheres, gel microspheres of bimetallic composite catalytic material are obtained.

[0012] Furthermore, bimetallic MOFs materials are metal-organic framework materials synthesized from soluble salts of any two different metal elements selected from transition metals Fe, Co, Ni, Mn, and Ce.

[0013] Furthermore, the molar ratio of the two transition metal elements in the bimetallic MOFs material is 0.1 to 10:1; the organic ligand used in the bimetallic MOFs material is any one of phthalic acid, isophthalic acid, and terephthalic acid.

[0014] Furthermore, in step (1), the amounts of bimetallic MOFs material, polyvinyl alcohol and sodium alginate are 1-20% of the mass of water, 1-20% and 0.5-12%, respectively.

[0015] Furthermore, in step (2), the mass concentration of boric acid is controlled at 5-27.5%; the auxiliary agent is one or two soluble chloride salts.

[0016] Further, step (3) is carried out under stirring conditions, with a stirring rate of 30 to 300 rpm; the diameter of the microspheres obtained is 2 mm to 10 mm.

[0017] Furthermore, the sulfite is calcium sulfite, magnesium sulfite, sodium sulfite, or ammonium sulfite, and the concentration of the sulfite slurry is 2-40%.

[0018] Furthermore, in the oxidation reaction, the amount of gel microspheres of the bimetallic composite catalyst is 5-80% of the total mass of sulfite.

[0019] Furthermore, the oxidation reaction takes 1 to 12 hours.

[0020] Furthermore, after the oxidation reaction is completed, the gel microspheres of the bimetallic composite catalyst are separated and recycled for the next batch of oxidation reactions. The separated oxidation product, sulfate, is further utilized.

[0021] The beneficial effects of this invention are as follows:

[0022] This invention incorporates bimetallic transition metal elements into an organic ligand framework with a network structure. This increases the number of catalytically active species and sites, and through the regulation of electron distribution and electron transfer between the metals, a synergistic effect of the active metals is generated, significantly increasing the chain oxidation rate of sulfite. Furthermore, a composite catalyst microsphere is constructed by combining a highly active bimetallic MOF catalyst with a gel possessing good flexibility and environmental compatibility. This allows reactants to fully contact, diffuse, and react within the composite catalyst, resulting in excellent catalytic performance during sulfite oxidation and significantly improved recycling performance and catalytic stability. Compared to non-catalytic oxidation, the sulfite oxidation efficiency using this catalyst is increased by 20–30 times, and after five recycling cycles, the catalytic efficiency decreases by less than 25%. Therefore, this invention applies bimetallic composite catalytic materials in the form of gel microspheres to the sulfite oxidation reaction, offering advantages such as high activity, high stability, and easy recovery. Even for calcium sulfite with low solubility, a high oxidation efficiency can be achieved, and the cost of sulfite oxidation treatment can be significantly reduced. Attached Figure Description

[0023] Figure 1 The image shows a sample of the gel microspheres of the prepared bimetallic composite catalytic material.

[0024] Figure 2 This is a SEM image of calcium sulfite before oxidation in Example 1.

[0025] Figure 3 This is a SEM image of the oxidation product from Example 1. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited thereto.

[0027] Example 1

[0028] Bimetallic MOF active materials were prepared by hydrothermal reaction using phthalic acid (15 mmol) and a mixed salt of manganese and copper (8 mmol of MnCl2 and 2 mmol of CuCl3·6H2O). The solid phase of the product was separated and dried in an oven to obtain Mn / Cu-MOF active materials.

[0029] 4 g (2 wt.%) of Mn / Cu-MOFs active material, 12 g (4 wt.%) of polyvinyl alcohol (PVA), and 4 g (1 wt.%) of sodium alginate (SA) were placed in a beaker containing 120 mL of water and stirred continuously to obtain a homogeneous liquid A. 25 g of boric acid was dissolved in 100 mL of water, and then 5 g of CaCl2 and 2 g of NaCl were added and mixed to obtain solution B. Liquid A was added dropwise to solution B, and the mixture was stirred for 12 h to obtain microspheres. The microspheres were then separated, washed with clean water, and dried in an oven for 8 h to obtain catalyst gel microspheres with a diameter of approximately 4 mm.

[0030] 30g of CaSO3 was added to a beaker containing 200ml of water. While stirring, the pH of the slurry was adjusted to no more than 8. Then, 22g of the prepared catalyst gel microspheres were added, and air was bubbled through at a rate of 0.3L / min. The reaction was stopped after 12 hours, and the catalyst gel microspheres were removed for use in the next batch. The reaction slurry was then filtered, and the separated solid product was dried in a 60℃ oven for 2 hours. The solid product sample was titrated with iodine standard solution and Na2S2O3 solution to calculate the CaSO3 content in the reaction product. Based on the initial CaSO3 content, the oxidation rate of CaSO3 to CaSO4 was calculated to be 98%. The oxidation product is mainly composed of calcium sulfate, has stable properties, and can be further used as a cement additive, gypsum building material, etc.

[0031] The oxidation process with the same dosage of calcium sulfite was repeated five times, and the catalyst gel microspheres collected from the first round of reaction were recycled for subsequent reactions with fresh CaSO3. After the fifth reaction, the oxidized solid product was separated and dried. The CaSO3 content was determined by iodometric titration, and the oxidation rate of CaSO3 to CaSO4 was calculated to be 84%. After repeating the operation five times, the catalyst activity loss was no more than 15%, indicating that its recycling performance was good.

[0032] Example 2

[0033] Bimetallic MOF active materials were prepared by hydrothermal reaction using phthalic acid (18 mmol) and a mixed salt of cobalt and nickel (4 mmol of Co(NO3)2 and 9 mmol of NiCl2·4H2O). The solid phase of the product was separated and dried in an oven to obtain Co / Ni-MOF active materials.

[0034] 2g of Co / Ni-MOFs active material, 4g of polyvinyl alcohol (PVA), and 1g of sodium alginate (SA) were placed in a beaker containing 120mL of water and stirred continuously to obtain a homogeneous liquid A. 23g of boric acid was dissolved in 100mL of water, and then 4g of CaCl2 was added and mixed to obtain solution B. Liquid A was added dropwise to solution B, and the mixture was stirred for 10 hours to obtain microspheres. The microspheres were then separated, washed with clean water, and dried in an oven for 9 hours to obtain catalyst gel microspheres with a diameter of approximately 5mm.

[0035] 15g of CaSO3 was added to a beaker containing 200ml of water. While stirring, the pH of the slurry was adjusted to no more than 8. Then, 8g of the prepared catalyst gel microspheres were added, and air was bubbled through at a rate of 0.3L / min. The reaction was stopped after 3 hours, and the catalyst gel microspheres were removed for use in the next batch. The reaction slurry was then filtered, and the separated solid product was dried in a 50℃ oven for 3 hours. The solid product sample was titrated with iodine standard solution and Na2S2O3 solution to calculate the CaSO3 content in the reaction product. Based on the initial CaSO3 content, the oxidation rate of CaSO3 to CaSO4 was calculated to be 94%. The oxidation product is mainly composed of calcium sulfate, has stable properties, and can be further used as a cement additive, gypsum building material, etc.

[0036] The oxidation process with the same dosage of calcium sulfite was repeated five times, and the catalyst gel microspheres collected from the first round of reaction were recycled for subsequent reactions with fresh CaSO3. After the fifth reaction, the oxidized solid product was separated and dried. The CaSO3 content was determined by iodometric titration, and the oxidation rate of CaSO3 to CaSO4 was calculated to be 81%. After repeating the operation five times, the catalyst activity loss was no more than 13%, indicating good recycling performance.

[0037] Example 3

[0038] Bimetallic MOF active materials were prepared by hydrothermal reaction using terephthalic acid (18 mmol) and a mixed salt of iron and manganese (12 mmol FeCl2·4H2O and 1 mmol MnCl2·4H2O). The solid phase of the product was separated and dried in an oven to obtain Fe / Mn-MOF active materials.

[0039] 5g of Fe / Mn-MOFs active material, 5g of polyvinyl alcohol (PVA), and 2g of sodium alginate (SA) were placed in a beaker containing 100mL of water and stirred continuously to obtain a homogeneous liquid A. 20g of boric acid was dissolved in 100mL of water, and 2g of NaCl was added and mixed to obtain solution B. Liquid A was added dropwise to solution B, and the mixture was stirred for 12 hours to obtain microspheres. The microspheres were then separated, washed three times with clean water, and dried in an oven for 12 hours to obtain catalyst gel microspheres with a diameter of approximately 3mm.

[0040] 10g of CaSO3 was added to a beaker containing 200ml of water. While stirring, the pH of the slurry was adjusted to no more than 8. Then, 6g of the prepared catalyst gel microspheres were added, and air was bubbled through at 0.4L / min. The reaction was stopped after 6 hours. The catalyst gel microspheres were then removed for the next batch of reaction. The reaction slurry was then filtered, and the separated solid product was dried in a 50℃ oven for 3 hours. The solid product sample was titrated with iodine standard solution and Na2S2O3 solution to calculate the CaSO3 content in the reaction product. Based on the initial CaSO3 content, the oxidation rate of CaSO3 to CaSO4 was calculated to be 96.5%. The oxidation product is mainly composed of calcium sulfate, has stable properties, and can be further used as a cement additive, gypsum building material, etc.

[0041] Example 4

[0042] Bimetallic MOF active materials were prepared by hydrothermal reaction using isophthalic acid (18 mmol) and a mixed salt of iron and cobalt (4 mmol FeCl2 and 10 mmol CoCl2·4H2O). The solid phase of the product was separated and dried in an oven to obtain Fe / Co-MOF active materials.

[0043] 4g of Fe / Co-MOFs active material, 5g of polyvinyl alcohol (PVA), and 2g of sodium alginate (SA) were placed in a beaker containing 120mL of water and stirred continuously to obtain a homogeneous liquid A. 24g of boric acid was dissolved in 100mL of water, and then 5g of CaCl2 was added and mixed to obtain solution B. Liquid A was added dropwise to solution B, and the mixture was stirred for 10 hours to obtain microspheres. The microspheres were then separated, washed with clean water, and dried in an oven for 10 hours to obtain catalyst gel microspheres with a diameter of approximately 5mm.

[0044] 20g of MgSO3 was added to a beaker containing 200ml of water. While stirring, the pH of the slurry was adjusted to no more than 9. Then, 8g of the prepared catalyst gel microspheres were added, and air was bubbled through at 0.6L / min. The reaction was stopped after 4 hours, and the catalyst gel microspheres were removed for the next batch of reaction. The reaction slurry was then sampled and titrated with iodine standard solution and Na2S2O3 solution to calculate the MgSO3 content in the reaction product. Based on the initial MgSO3 content, the oxidation rate of MgSO3 to MgSO4 was calculated to be 96%. The oxidation product was mainly composed of magnesium sulfate, which was stable and could be further separated into products through concentration, crystallization, and liquid-solid separation. The same dosage of magnesium sulfite oxidation was repeated 5 times. The catalyst gel microspheres from the first round of reaction were recycled for subsequent reactions with fresh MgSO3. After the 5th reaction, the oxidized solid product was separated and dried. The MgSO3 content was determined by iodometric titration, and the oxidation rate of MgSO4 was calculated to be 82%. After repeating the operation 5 times, the catalyst activity loss was no more than 13%, indicating that the catalyst has good recycling performance.

[0045] Example 5

[0046] Bimetallic MOF active materials were prepared by hydrothermal reaction using phthalic acid (12 mmol) and a mixed salt of copper and nickel (10 mmol CuCl2 and 1 mmol NiCl2·4H2O). The solid phase of the product was separated and dried in an oven to obtain Cu / Ni-MOF active materials.

[0047] 12g of Cu / Ni-MOFs active material, 6g of polyvinyl alcohol (PVA), and 3g of sodium alginate (SA) were placed in a beaker containing 120mL of water and stirred continuously to obtain a homogeneous liquid A. 23g of boric acid was dissolved in 100mL of water, and then 6g of MgCl2 was added and mixed to obtain solution B. Liquid A was added dropwise to solution B, and the mixture was stirred for 10 hours to obtain microspheres. The microspheres were then separated, washed with clean water, and dried in an oven for 12 hours to obtain catalyst gel microspheres with a diameter of approximately 5mm.

[0048] 40g of MgSO3 was added to a beaker containing 200ml of water. While stirring, the pH of the slurry was adjusted to no more than 9.5 using hydrochloric acid and sodium hydroxide. Then, 10g of the prepared catalyst gel microspheres were added, and air was bubbled through at a rate of 1L / min. The reaction was stopped after 5 hours, and the catalyst gel microspheres were removed for use in the next batch. Samples were then taken from the reaction slurry, and the reaction product samples were titrated with iodine standard solution and Na2S2O3 solution to calculate the MgSO3 content in the reaction product. Based on the initial MgSO3 content, the oxidation rate of MgSO3 to MgSO4 was calculated to be 98%. The oxidation product is mainly composed of magnesium sulfate, is stable, and can be further concentrated, crystallized, and separated into liquid and solid components for use as agricultural fertilizer.

[0049] Example 6

[0050] Bimetallic MOF active materials were prepared by hydrothermal reaction using isophthalic acid (12 mmol) and a mixed salt of manganese and nickel (4 mmol of MnCl2 and 10 mmol of NiCl2·4H2O). The solid phase of the product was separated and dried in an oven to obtain Mn / Ni-MOF active materials.

[0051] 10g of Mn / Ni-MOFs active material, 6g of polyvinyl alcohol (PVA), and 5g of sodium alginate (SA) were placed in a beaker containing 120mL of water and stirred continuously to obtain a homogeneous liquid A. 28g of boric acid was dissolved in 100mL of water, and then 4g of CaCl2 was added and mixed to obtain solution B. Liquid A was added dropwise to solution B, and the mixture was stirred for 10 hours to obtain microspheres. The microspheres were then separated, washed with clean water, and dried in an oven for 9 hours to obtain catalyst gel microspheres with a diameter of approximately 5mm.

[0052] Add 60g of Na₂SO₃ to a beaker containing 200ml of water. While stirring, adjust the pH of the slurry to no more than 8. Then add 5g of the prepared catalyst gel microspheres and purge with air at 0.4L / min. After reacting for 4 hours, stop the reaction and remove the catalyst gel microspheres for the next batch of reaction. Filter the reaction slurry, and sample the separated liquid product. Titrate the sample with iodine standard solution and Na₂S₂O₃ solution to calculate the Na₂SO₃ content in the reaction product. Based on the initial Na₂SO₃ content, the oxidation rate of Na₂SO₃ to Na₂SO₄ can be calculated to be 99.5%. The oxidation product, sodium sulfate, is stable and can be further separated through concentration, crystallization, and liquid-solid separation as a raw material for downstream products.

Claims

1. The application of a bimetallic composite catalytic material gel microsphere in the sulfite oxidation reaction, characterized in that, First, the bimetallic MOFs material with transition metal interdoping is combined with a gel to form a gel microsphere of bimetallic composite catalytic material. Then, the gel microsphere of bimetallic composite catalytic material is added to a sulfite slurry and oxygen-containing gas is introduced. The mixture is stirred and reacted until the oxidation reaction is completed. The preparation method of the gel microspheres of the bimetallic composite catalytic material includes the following steps: (1) Mix bimetallic MOFs material, polyvinyl alcohol and sodium alginate with water and stir to obtain liquid A; (2) Dissolve boric acid in water and add an auxiliary agent to obtain solution B; (3) Liquid A is added dropwise to solution B to obtain microspheres; (4) After drying the microspheres, gel microspheres of bimetallic composite catalytic material are obtained; The bimetallic MOFs material is a metal-organic framework material synthesized from soluble salts of any two different metal elements selected from transition metals Fe, Co, Ni, Mn, and Cu; the organic ligand used in the bimetallic MOFs material is any one of phthalic acid, isophthalic acid, and terephthalic acid.

2. The application according to claim 1, characterized in that, The molar ratio of the two transition metal elements in bimetallic MOF materials is 0.1 to 10:

1.

3. The application according to claim 1, characterized in that, In step (1), the amounts of bimetallic MOFs material, polyvinyl alcohol and sodium alginate are 1~20%, 1~20% and 0.5~12% of the mass of water, respectively.

4. The application according to claim 1, characterized in that, In step (2), the mass concentration of boric acid is controlled at 5-27.5%; the auxiliary agent is one or two soluble chloride salts.

5. The application according to claim 1, characterized in that, Step (3) is carried out under stirring conditions, with a stirring rate of 30~300 r / min; the microspheres obtained in step (4) have a diameter of 2 mm~10 mm.

6. The application according to claim 1, characterized in that, The sulfite is calcium sulfite, magnesium sulfite, sodium sulfite or ammonium sulfite, and the concentration of the sulfite slurry is 2-40%.

7. The application according to any one of claims 1 to 6, characterized in that, In the oxidation reaction, the amount of gel microspheres of the bimetallic composite catalyst is 5-80% of the total mass of sulfite.

8. The application according to any one of claims 1 to 6, characterized in that, The oxidation reaction takes 1 to 12 hours.

9. The application according to any one of claims 1 to 6, characterized in that, After the oxidation reaction is complete, the gel microspheres of the bimetallic composite catalyst are separated and recycled for the next batch of oxidation reaction. The separated oxidation product, sulfate, is further utilized.

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