Kilogram-level high-loading iron monatomic catalyst as well as preparation method and application of kilogram-level high-loading iron monatomic catalyst

Abstract

The invention discloses a kilogram-level high-loading-capacity iron monatomic catalyst as well as a preparation method and application thereof. The kilogram-level high-loading-capacity iron monatomic catalyst is prepared by taking high-stability graphite phase carbon nitride as a substrate. The catalyst not only has the characteristics of high single-batch yield (more than 1 kg), low synthesis cost (about 128 yuan / kg) and high iron atom loading capacity (about 6.1% by mass), but also keeps excellent catalytic activity, selectivity and stability. Wherein the activation efficiency of peroxymonosulfate (PMS) and the content and the selectivity of generated singlet oxygen (1O2) have outstanding advantages, and the efficient degradation of typical antibiotics (such as sulfamethoxazole, tetracycline, ciprofloxacin and levofloxacin) can still be realized after the compound is recycled for multiple times; the results show that the prepared kilogram-level high-load iron monatomic catalyst has good industrial production potential and new pollutant treatment application prospects.

Description

Technical Field

[0001] The invention belongs to the field of catalysts, and in particular relates to a kilogram-level high-load iron single-atom catalyst and a preparation method and application thereof. Background Art

[0002] Single atom catalysts (SACs) inherit the advantages of homogeneous catalysts and heterogeneous catalysts, and have the advantages of high atom utilization, high reactivity, low material cost, recyclability and greater stability. Iron is cheap and abundant in nature. Iron-based catalysts often have high durability, adjustability in acidic and alkaline media, and high methanol tolerance. The activation of peroxymonosulfate (PMS) by iron single atom catalysts (Fe SACs) to generate reactive oxygen species (ROS) in situ can effectively remove typical antibiotics, and thus are widely used in advanced oxidation processes (AOPs) in environmental remediation technology.

[0003] At present, the scale of iron single-atom catalysts prepared by various synthesis methods reported in the literature is usually only at the gram level or even the milligram level, which is far from meeting the requirements of factory production. Traditional preparation methods face technical bottlenecks such as amplification effect, waste liquid pollution, and expensive equipment, and cannot be produced in a single batch at the kilogram level. Among them, impregnation, ion exchange, hydrothermal treatment, co-precipitation and other methods lead to metal atom aggregation due to the amplification effect; selective etching and template loading produce a large amount of liquid waste and there are environmental pollution problems; mass separation-soft landing and atomic layer deposition methods are often hindered by expensive experimental equipment requirements and low production efficiency. In the existing reports on the large-scale preparation of iron single-atom catalysts, 10 grams or more of materials can be synthesized at one time, but their loading is less than 2% by mass. Therefore, the industrialization and commercialization of high-loaded iron single-atom catalysts needs to be accelerated.

[0004] To break through the technical bottleneck of industrialization and commercialization of high-loaded iron single-atom catalysts, first, it is necessary to be able to prepare at the kilogram level. The mass production process requires higher stability of the catalyst, and agglomeration must not occur during the preparation process; second, a simple and low-cost synthesis process is required, while ensuring that the synthesis process is green and environmentally friendly. This preparation method uses hydrogen bonds to allow the iron-containing precursor to undergo stable self-assembly, fix the iron atoms to prevent agglomeration during the subsequent pyrolysis process, and provide the possibility for the preparation of kilogram-level iron single-atom catalysts. In addition, in the synthesis process of a single batch of kilogram-level high-loaded iron single-atom catalysts, the solute ratio is reasonably reduced to reduce the amount of liquid and the generation of waste liquid. The precursor volume is reduced by static precipitation and filtration to facilitate pyrolysis. In this way, a simple and feasible synthesis process is successfully used to prepare kilogram-level high-loaded iron single-atom catalysts. Summary of the invention

[0005] The purpose of the present invention is to address the deficiencies of the prior art and provide a kilogram-level high-load iron single-atom catalyst and a preparation method and application thereof.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a kilogram-level high-load iron single-atom catalyst, comprising the following steps:

[0008] (1) dissolving 1 to 1.7 g of melamine in 48.5 to 200 ml of water to obtain solution A; then dissolving 0.5 to 0.82 g of cyanuric acid in 30 to 228 ml of water to obtain solution B;

[0009] (2) dissolving 0.432-0.452 g of an organic ligand and 0.485-0.5 g of a metal salt in 40-90 ml of water to obtain a solution C;

[0010] (3) Then, solution B and solution C are mixed evenly to obtain solution D;

[0011] (4) then mixing solution A and solution D evenly to obtain solution E;

[0012] (5) allowing solution E to settle for 8 to 24 hours, filtering solution E after settling and stratification, and drying the precipitated powder to obtain a precursor;

[0013] (6) The precursor obtained in step (5) is heated to 500-650 degrees Celsius and kept warm for 3-6 hours to obtain a kilogram-level high-load iron single-atom catalyst.

[0014] Furthermore, the organic ligand is oxalic acid.

[0015] Furthermore, the metal salt is ferric nitrate.

[0016] In a second aspect, the present invention provides a kilogram-level high-loading iron single-atom catalyst.

[0017] In a third aspect, the present invention provides an application of a kilogram-scale high-load iron single-atom catalyst in the degradation of typical antibiotics.

[0018] Furthermore, the typical antibiotic is sulfamethoxazole, tetracycline, ciprofloxacin or levofloxacin.

[0019] The beneficial effects of the present invention are:

[0020] 1) The iron single atom catalyst in the preparation process has strong stability, ensuring the isolated existence of iron atoms during pyrolysis;

[0021] 2) The synthesis process is simple and reasonable, suitable for scale-up, and has low preparation cost;

[0022] 3) The iron single-atom catalyst that can be produced by the present invention at the kilogram level has a loading and performance similar to that of the iron single-atom catalyst prepared in small batches in the laboratory at the gram level, ten-gram level, hundred-gram level, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Synchrotron radiation spectra of high-loaded iron single-atom catalysts at different scales;

[0024] Figure 2 This is a spherical aberration-corrected high-angle annular dark-field scanning transmission electron microscopy image of a kilogram-scale high-load iron single-atom catalyst;

[0025] Figure 3 A comparison of Fe content in high-loaded iron single-atom catalysts of different scales;

[0026] Figure 4 This is a cost analysis diagram for kilogram-scale high-loading iron single-atom catalysts;

[0027] Figure 5 A data comparison of the degradation of typical antibiotics by persulfate activated by high-loaded iron single-atom catalysts of different scales; Figure 6 A comparison of the degradation rates of high-loaded iron single-atom catalysts of different scales. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the present invention more clear, the present invention is further described in detail in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0029] The present invention adopts hydrogen bond self-assembly-high temperature pyrolysis scheme to prepare kilogram-level high-load iron single-atom catalyst. The method forms a metal-organic complex by coordination of organic ligands and metal ions, and then disperses and stabilizes the complex by the precursor formed by hydrogen bond self-assembly between melamine, cyanuric acid and complex molecules, wherein the important role of hydrogen bonds is to increase the melting point of melamine and fix the complex in the precursor, therefore, the scheme can solve the metal ion migration and atomic agglomeration caused by melamine melting during high temperature pyrolysis, thereby providing the possibility for kilogram-level preparation of iron single-atom catalyst. In addition, by rationally adjusting the solute ratio between the organic ligand and the metal solution, the synthesis processes such as static precipitation and suction filtration of the precursor solution are simplified, so that the kilogram-level production can be reduced while the preparation cost is reduced.

[0030] In a first aspect, the present invention provides a method for preparing a kilogram-level high-load iron single-atom catalyst, comprising the following steps:

[0031] (1) 1 to 1.7 g of melamine is dissolved in 48.5 to 200 ml of water to obtain a solution A having a solute ratio of 5 to 35 g / L; then 0.5 to 0.82 g of cyanuric acid is dissolved in 30 to 228 ml of water to obtain a solution B having a solute ratio of 2.2 to 27.3 g / L.

[0032] (2) 0.432-0.452 g of an organic ligand and 0.485-0.5 g of a metal salt are dissolved in 40-90 ml of water to obtain a solution C having a solute ratio of 10.2-23.8 g / L.

[0033] (3) Then, solution B and solution C are mixed evenly to obtain solution D.

[0034] (4) Then, solution A and solution D are mixed evenly to obtain solution E.

[0035] (5) The solution E is allowed to settle for 8 to 24 hours, and the solution E after settling is filtered, and the precipitated powder is dried to obtain a precursor.

[0036] (6) The precursor obtained in step (5) is heated to 500-650 degrees Celsius and kept warm for 3-6 hours to obtain a kilogram-level high-load iron single-atom catalyst.

[0037] The organic ligand is oxalic acid.

[0038] The metal salt is ferric nitrate.

[0039] In a second aspect, the present invention provides a kilogram-level high-loading iron single-atom catalyst.

[0040] In a third aspect, the present invention provides an application of a kilogram-scale high-load iron single-atom catalyst in the degradation of typical antibiotics.

[0041] The typical antibiotics are sulfamethoxazole, tetracycline, ciprofloxacin or levofloxacin.

[0042] Example 1

[0043] (1) 1.5 g of melamine was dissolved in 150 ml of water to obtain a solution A with a solute ratio of 10 g / L; then 0.8 g of cyanuric acid was dissolved in 180 ml of water to obtain a solution B with a solute ratio of 4.4 g / L.

[0044] (2) 432 mg of oxalic acid and 485 mg of ferric nitrate were dissolved in 45 ml of water to obtain a solution C having a solute ratio of 20.4 g / L.

[0045] (3) Then, solution B and solution C are mixed evenly to obtain solution D.

[0046] (4) Then, solution A and solution D are mixed evenly to obtain solution E.

[0047] (5) Solution E was allowed to stand and settle for 12 hours. At this time, solution E had been clearly stratified. The stratified solution E was filtered and the precipitated powder was dried to obtain a precursor.

[0048] (6) The precursor obtained in step (5) was heated to 550 degrees Celsius and kept warm for 4 hours to obtain 1 gram of a high-loading iron single atom catalyst, which was recorded as 1-Fe SAC.

[0049] Example 2

[0050] (1) 15 g of melamine was dissolved in 1.5 liters of water to obtain a solution A with a solute ratio of 10 g per liter; then 8 g of cyanuric acid was dissolved in 1.8 liters of water to obtain a solution B with a solute ratio of 4.4 g per liter.

[0051] (2) 4.32 g of oxalic acid and 4.85 g of ferric nitrate were dissolved in 0.45 liter of water to obtain a solution C having a solute ratio of 20.4 g / L.

[0052] (3) Then, solution B and solution C are mixed evenly to obtain solution D.

[0053] (4) Then, solution A and solution D are mixed evenly to obtain solution E.

[0054] (5) Solution E was allowed to stand and settle for 12 hours. At this time, solution E had been clearly stratified. The stratified solution E was filtered and the precipitated powder was dried to obtain a precursor.

[0055] (6) The precursor obtained in step (5) was heated to 550 degrees Celsius and kept warm for 4 hours to obtain 10 grams of high-loading iron single atom catalyst, recorded as 10-Fe SAC.

[0056] Example 3

[0057] (1) 150 g of melamine was dissolved in 10 liters of water to obtain a solution A with a solute ratio of 15 g per liter; then 93 g of cyanuric acid was dissolved in 9.3 liters of water to obtain a solution B with a solute ratio of 10 g per liter.

[0058] (2) 43.2 g of oxalic acid and 48.5 g of ferric nitrate were dissolved in 4.5 liters of water to obtain a solution C having a solute ratio of 20.4 g / L.

[0059] (3) Then, solution B and solution C are mixed evenly to obtain solution D.

[0060] (4) Then, solution A and solution D are mixed evenly to obtain solution E.

[0061] (5) Solution E was allowed to stand and settle for 12 hours. At this time, solution E had been clearly stratified. The stratified solution E was filtered and the precipitated powder was dried to obtain a precursor.

[0062] (6) The precursor obtained in step (5) was heated to 550 degrees Celsius and kept warm for 4 hours to obtain 100 grams of high-loading iron single atom catalyst, recorded as 100-Fe SAC.

[0063] Example 4

[0064] (1) 1500 g of melamine was dissolved in 50 liters of water to obtain a solution A having a solute ratio of 30 g / L; then 794 g of cyanuric acid was dissolved in 34 liters of water to obtain a solution B having a solute ratio of 23.4 g / L.

[0065] (2) 432 g of oxalic acid and 484.8 g of ferric nitrate were dissolved in 45 liters of water to obtain a solution C having a solute ratio of 20.4 g / L.

[0066] (3) Then, solution B and solution C are mixed evenly to obtain solution D.

[0067] (4) Then, solution A and solution D are mixed evenly to obtain solution E.

[0068] (5) Solution E was allowed to stand and settle for 12 hours. At this time, solution E had been clearly stratified. The stratified solution E was filtered and the precipitated powder was dried to obtain a precursor.

[0069] (6) The precursor obtained in step (5) was heated to 550 degrees Celsius and kept warm for 4 hours to obtain 1000 grams of high-loaded iron single-atom catalyst, recorded as 1000-Fe SAC.

[0070] Application Example 1 Degradation experiment of sulfamethoxazole by high-loaded iron single-atom catalysts at different scales

[0071] (1.1) A saturated aqueous solution of sulfamethoxazole was added to 8 100 ml beakers containing 50 ml of deionized water, respectively, so that the initial concentration of the sulfamethoxazole solution was 0.05 mmol per liter. Each of the three beakers was a set of parallel experiments, and the 1-Fe SAC, 10-Fe SAC, 100-Fe SAC and 1000-Fe SAC prepared in Examples 1-4 were added, followed by ultrasonic assisted dispersion and stirring on a magnetic stirrer. The activator PMS was added at a concentration of 0.5 mmol per liter.

[0072] (1.2) Start timing after adding the activator, use a syringe to take samples at 0, 1, 2, 3, 4, 5, 10 and 20 minutes, and separate the catalyst with a 0.22 micron water filter membrane before adding it to the liquid phase vial.

[0073] (1.3) Use high performance liquid chromatography to determine the concentration of parachlorophenol in the solution.

[0074] Application Example 2 Degradation of Tetracycline by High-Loaded Iron Single Atom Catalysts at Different Scales

[0075] (2.1) A saturated aqueous solution of tetracycline was added to eight 100 ml beakers containing 50 ml of deionized water, so that the initial concentration of the tetracycline solution was 0.05 mmol / L. Three beakers were used as a parallel experiment, and 1-Fe SAC, 10-Fe SAC, 100-Fe SAC and 1000-Fe SAC prepared in Examples 1 and 2 were added, respectively, and then ultrasonically dispersed and placed on a magnetic stirrer for stirring. The activator PMS was added at a concentration of 0.5 mmol / L.

[0076] (2.2) Start timing after adding the activator, use a syringe to take samples at 0, 1, 2, 3, 4, 5, 10, 20 and 30 minutes, and separate the catalyst with a 0.22 micron filter membrane before adding it to the liquid phase vial.

[0077] (2.3) The concentration of tetracycline in the solution was determined using high performance liquid chromatography.

[0078] Application Example 3 Degradation experiment of ciprofloxacin by high-loaded iron single atom catalysts at different scales

[0079] (3.1) A saturated aqueous solution of ciprofloxacin was added to 8 100 ml beakers containing 50 ml of deionized water, respectively, so that the initial concentration of the ciprofloxacin solution was 0.05 mmol / L. Three beakers were used as a parallel experiment, and the 1-Fe SAC, 10-Fe SAC, 100-Fe SAC and 1000-Fe SAC prepared in Examples 1-4 were added, followed by ultrasonic assisted dispersion and stirring on a magnetic stirrer. The activator PMS was added at a concentration of 0.5 mmol / L.

[0080] (3.2) Start timing after adding the activator, use a syringe to take samples at 0, 1, 2, 3, 4, 5, 10, 20 and 30 minutes, and separate the catalyst with a 0.22 micron filter membrane before adding it to the liquid phase vial.

[0081] (3.3) The concentration of ciprofloxacin in the solution was determined using high performance liquid chromatography.

[0082] Application Example 4 Degradation experiment of levofloxacin by high-loaded iron single atom catalysts at different scales

[0083] (4.1) The saturated aqueous solution of levofloxacin was added to 8 100 ml beakers containing 50 ml of deionized water, respectively, so that the initial concentration of the levofloxacin solution was 0.05 mmol per liter. Each three beakers formed a group of parallel experiments, and the 1-Fe SAC, 10-Fe SAC, 100-Fe SAC and 1000-Fe SAC prepared in Examples 1-4 were added respectively, and then ultrasonic assisted dispersion was performed, and the mixture was placed on a magnetic stirrer for stirring. The activator PMS was added at a concentration of 0.5 mmol per liter.

[0084] (4.2) Start timing after adding the activator, use a syringe to take samples at 0, 1, 2, 3, 4, 5, 10, 20 and 30 minutes, and separate the catalyst with a 0.22 micron filter membrane before adding it to the liquid phase vial.

[0085] (4.3) The concentration of levofloxacin in the solution was determined using high performance liquid chromatography.

[0086] like Figure 1 As shown in the synchrotron radiation spectrum, 1-Fe SAC, 10-Fe SAC, 100-Fe SAC and 1000-Fe SAC before calcination (precursor) and after calcination (finished catalyst), compared with the iron foil standard (Fe foil), have no iron-iron bonds, indicating that the iron metal has not agglomerated and its coordination state with nitrogen is similar to that of iron phthalocyanine (FePc). Figure 2 As shown, metal atom bright spots can be clearly seen in the spherical aberration-corrected high-angle annular dark-field scanning transmission electron microscopy image of the prepared 1000-Fe SAC, indicating that the iron atoms exist in the form of single atoms, proving the successful preparation of large-scale iron single-atom catalysts.

[0087] Figure 3 This indicates that the metal in the kilogram-level high-load iron single-atom catalyst prepared by the present invention has an ultra-high loading amount, wherein the iron content in 1000 grams of the iron single-atom catalyst is as high as 6.1% by mass. Figure 4 The actual product photos and cost analysis of high-loaded iron single-atom catalysts for small-batch and large-scale production are shown. The kilogram-level preparation cost is 128 yuan per kilogram, which is mainly composed of raw materials and electricity. The cost increase from gram level to kilogram level is not significant. Figure 5 As shown, the activation of persulfate by iron single-atom catalysts prepared at the gram to kilogram scale produces 1 O 2 Active species. Figure 6As shown, taking four typical antibiotics as examples, the kilogram-level high-load iron single-atom catalyst prepared by the present invention has good catalytic performance, and the activation rates of high-load iron single-atom catalysts of different preparation scales in the persulfate degradation system are basically the same, and the rate constants of the iron atom sites at a single site are similar, indicating that the production process has been successfully scaled up to achieve the goal of large-scale preparation of iron single-atom catalysts.

[0088] The present invention adopts hydrogen bond self-assembly-high temperature pyrolysis scheme to prepare kilogram-level high-load iron single-atom catalyst on a large scale. The method provided by the present invention forms a metal-organic complex by coordination of organic ligands and metal ions, and then disperses and stabilizes the complex by using the precursor formed by hydrogen bond self-assembly of melamine, cyanuric acid and the complex, wherein the important role of hydrogen bonds is to increase the melting point of melamine and fix the complex in the precursor, therefore, the scheme can solve the metal ion migration and atomic agglomeration caused by melamine melting during high temperature pyrolysis, thereby providing the possibility for large-scale preparation. In addition, by rationally adjusting the solute ratio of the organic ligand to the iron ion solution, the synthesis processes such as static precipitation and suction filtration of the precursor solution are simplified, so that it can be produced at the kilogram level while reducing the preparation cost. The advantages of the kilogram-level high-load iron single-atom catalyst prepared by the present invention are: 1. The single atom stability during the preparation process is strong, ensuring the isolated existence of the iron atom during pyrolysis; 2. The synthesis process is simple and reasonable, suitable for scale-up, and the preparation cost is low; 3. The method can produce a kilogram-level high-load iron single-atom catalyst with similar kilogram-level and gram-level loading and performance. This provides a new solution for the large-scale preparation of kilogram-level high-load iron single-atom catalysts and a new idea for the industrialization and commercialization of single-atom catalysts.

[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 method for preparing a kilogram-level high-load iron single-atom catalyst, characterized in that: The following steps are involved: (1) dissolving 1 to 1.7 g of melamine in 48.5 to 200 ml of water to obtain solution A; then dissolving 0.5 to 0.82 g of cyanuric acid in 30 to 228 ml of water to obtain solution B; (2) dissolving 0.432-0.452 g of an organic ligand and 0.485-0.5 g of a metal salt in 40-90 ml of water to obtain a solution C; (3) Then, solution B and solution C are mixed evenly to obtain solution D; (4) then mixing solution A and solution D evenly to obtain solution E; (5) allowing solution E to settle for 8 to 24 hours, filtering solution E after settling and stratification, and drying the precipitated powder to obtain a precursor; (6) The precursor obtained in step (5) is heated to 500-650 degrees Celsius and kept warm for 3-6 hours to obtain a kilogram-level high-load iron single-atom catalyst.

2. The method for preparing a kilogram-level high-load iron single-atom catalyst according to claim 1, characterized in that: The organic ligand is oxalic acid.

3. The method for preparing a kilogram-level high-load iron single-atom catalyst according to claim 1, characterized in that: The metal salt is ferric nitrate.

4. A kilogram-level high-load iron single-atom catalyst prepared by any method of claims 1-3.

5. Use of the kilogram-level high-load iron single-atom catalyst according to claim 4 in the degradation of typical antibiotics.

6. The use according to claim 5, characterized in that: The typical antibiotics are sulfamethoxazole, tetracycline, ciprofloxacin or levofloxacin.

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