Preparation method and application of copper-cobalt composite porous carbon supported carbon fiber cloth low-chlorine demercuration catalyst

Abstract

In view to the environmental problem of current atmospheric mercury pollution emission, the application discloses a preparation method and application of a copper-cobalt composite porous carbon loaded carbon fiber cloth low-chlorine mercury removal catalyst. The preparation of the low-chlorine mercury removal catalyst mainly comprises the following steps: 1) a copper-cobalt mixed solution is prepared, then an organic ligand and a carbon fiber cloth are added, and a hydrothermal reaction is carried out to prepare a copper-cobalt organic compound carbon fiber precursor; 2) the prepared precursor is subjected to high-temperature carbonization, and finally a copper-cobalt composite porous carbon low-chlorine mercury removal catalyst is obtained. The low-chlorine mercury removal adsorbent can be directly placed between flue gas dust removal and wet scrubbing purification, and more than 85% of elemental mercury in flue gas can be efficiently catalytically oxidized into oxidized mercury, and finally removed in the wet scrubbing process. In the aspect, by in-situ forming high-catalytic-activity copper-cobalt composite porous carbon on the carbon fiber cloth, the low-chlorine mercury removal material is prepared, which can be directly applied to the existing flue gas treatment device, and efficient removal of elemental mercury in flue gas is realized.

Description

Technical Field

[0001] This invention relates to a method for preparing and applying a copper-cobalt composite porous carbon supported carbon fiber cloth low-chlorine mercury removal catalyst, which is suitable for the treatment of mercury-containing flue gas generated in waste incineration, metal smelting, coal combustion and other fields, and belongs to the field of mercury pollution emission control and flue gas treatment. Background Technology

[0002] Mercury is a highly toxic, bioaccumulative, and long-distance migrating heavy metal pollutant that can cause serious harm to human health and the ecological environment. Relevant documents have clearly listed mercury as a major heavy metal pollutant, requiring key monitoring and emission limit control. Mercury pollution prevention and control has become a major public concern both domestically and internationally.

[0003] Non-ferrous metals, waste incineration, and coal combustion are the main sources of atmospheric mercury emissions in my country. Mercury typically exists in three forms in the flue gas from these industries: particulate mercury, elemental mercury, and mercury oxide. Due to the high stability, volatility, and poor water solubility of elemental mercury, its removal rate in traditional flue gas purification processes is very low, making elemental mercury the primary form of atmospheric mercury pollution. The mainstream strategies for removing elemental mercury can be divided into adsorption and catalytic oxidation. Catalytic oxidation has received widespread attention due to its low operating cost and low likelihood of secondary pollution. Chinese patent CN109529885B discloses a cobalt sulfide / biochar composite material and its preparation method, as well as its application as a catalyst for elemental mercury oxidation. Chinese patent CN110833830A discloses a method for preparing a mercury removal catalyst using natural mineral soil and waste residue. It utilizes materials such as red mud and montmorillonite to prepare a porous mercury removal catalyst, achieving the catalytic oxidation of mercury in low-temperature flue gas. However, the performance of the catalyst is easily affected by flue gas components, such as water vapor and sulfur dioxide. Furthermore, most catalysts require high concentrations of HCl to achieve stable catalytic mercury removal, which greatly limits their application. Therefore, developing a novel catalyst for the efficient catalytic oxidation of elemental mercury under complex flue gas compositions and low chlorine conditions is urgently needed. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the first objective of this invention is to provide a method for constructing a low-chlorine mercury removal material on a copper-cobalt composite porous carbon in situ supported on a carbon fiber cloth. In this composite material, copper and cobalt form heterojunction structures in various forms and are fixed on the carbon fiber cloth by porous carbon, exhibiting high dispersion and high activity, and demonstrating excellent catalytic oxidation performance for elemental mercury.

[0005] Another objective of this invention is to provide an application method for a copper-cobalt composite porous carbon supported carbon fiber cloth low-chlorine mercury removal catalyst, which can achieve efficient catalytic oxidation of elemental mercury in flue gas at a relatively low temperature and in a low-chlorine atmosphere; at the same time, the catalyst can still achieve a catalytic conversion efficiency of more than 85% for elemental mercury in an atmosphere containing high concentrations of sulfur dioxide and water vapor, and has excellent prospects for industrial application.

[0006] To achieve the above objectives, this invention provides a method for preparing a copper-cobalt composite porous carbon supported carbon fiber cloth low-chlorination mercury removal catalyst, which mainly includes the following three steps:

[0007] (1) Add a certain amount of copper sulfate and cobalt chloride to the solution to prepare a copper-cobalt mixed aqueous solution, wherein the proportion of copper ions to the total molar of metal is 0.1 to 0.3. Then add a certain amount of organic ligand to the mixed solution and stir the mixed solution until it is completely dissolved to obtain the mixed solution.

[0008] (2) Take a certain volume of the mixed solution and add a certain amount of carbon fiber mesh (CF). Then transfer the mixed solution to a closed hydrothermal reactor and react at 100-160℃ for 0.5-1.5 hours. After the reaction is complete, allow it to cool naturally to room temperature, filter, wash and dry to obtain copper-cobalt organic ligand supported carbon fiber mesh (represented by CuCo-MOF@C).

[0009] (3) The prepared copper-cobalt organic ligand-supported carbon fiber mesh was placed in a closed tube furnace and heated to 600–800 °C under an inert atmosphere, and held for 10–30 min to finally obtain a porous carbon-encapsulated copper-cobalt composite carbon fiber mesh low-chlorination mercury removal catalyst (using Cu). x Co y O z @C@CF indicates).

[0010] The preparation method of the copper-cobalt composite porous carbon supported carbon fiber cloth low-chlorination mercury removal catalyst of the present invention further includes the following preferred preparation schemes:

[0011] In the preferred preparation method, the total concentration of copper and cobalt ions in the prepared mixed solution is 80 mmol / L.

[0012] In the preferred preparation method, the added organic ligand is one or more of 2-methylimidazole, 2-nitroimidazole, 5-chlorobenzimidazole, benzotribenzoic acid, and mestribenzoic acid.

[0013] In the preferred preparation scheme, the molar ratio of the added organic ligand to the total amount of copper and cobalt is (5-10):1.

[0014] In the preferred preparation method, 1 to 3 g of carbon fiber mesh is added to every 100 mL of the prepared mixed solution.

[0015] In the preferred preparation method, the inert atmosphere during the high-temperature calcination process is one or more of nitrogen or argon.

[0016] In the preferred preparation method, the heating rate during the high-temperature calcination process is 5–10 °C / min.

[0017] This invention also provides a method for applying a copper-cobalt composite porous carbon supported carbon fiber cloth low-chlorine mercury removal catalyst, which is used to catalytically oxidize elemental mercury.

[0018] In the preferred application scheme, the application temperature of the low-chlorine mercury removal catalyst is 50–240℃.

[0019] In the preferred application scheme, the HCl concentration in the flue gas can be below 0.5 ppm.

[0020] In the preferred application scheme, the catalytic oxidation efficiency of elemental mercury by the low-chlorine mercury removal catalyst in a complex atmosphere containing sulfur dioxide and water vapor is above 85%.

[0021] The copper-cobalt composite porous carbon-supported carbon fiber cloth low-chlorination mercury removal catalyst of the present invention can achieve highly efficient catalytic oxidation of elemental mercury under complex low-chlorine atmospheres. The preparation principle is as follows: Under hydrothermal conditions, copper and cobalt in solution can form copper-cobalt metal-organic complexes (represented by CuCo-MOF) with organic ligands, which grow in situ on the surface of carbon fiber cloth (represented by CF), forming a copper-cobalt organic complex-supported carbon fiber cloth composite material (represented by CuCo-MOF@CF). During high-temperature carbonization, the copper-cobalt organic ligands supported on the carbon fiber mesh can form porous carbon-encapsulated copper-cobalt composites (CuCo-MOF@CF). x Co y O z The copper-cobalt composite oxide encapsulated within porous carbon forms a heterojunction structure. Furthermore, some copper is reduced to elemental copper, dispersed within the composite oxide. The carbon fiber mesh in the prepared mercury removal catalyst provides a support for the active catalyst components and facilitates direct application of the catalyst. The porous carbon encapsulated on the surface of the copper-cobalt oxide in the prepared mercury removal catalyst prevents agglomeration of the copper-cobalt oxide, improves the structural stability of the copper-cobalt oxide particles, and facilitates contact between the gas and the active components. The copper-cobalt composite in the prepared mercury removal catalyst contains CuO... x and CoO y Rich in Cu + / Cu 2+ Co 2+ / Co 3+ The variable valence electrons can form active chlorine under low chlorine atmosphere, thereby promoting the catalytic oxidation of mercury. At the same time, the presence of some elemental copper promotes the adsorption of gaseous mercury, creating favorable conditions for the efficient catalysis of mercury under low chlorine atmosphere.

[0022] Compared with the prior art, the advantages of the technical solution of the present invention are as follows:

[0023] 1. The preparation process of the mercury removal catalyst is stable and environmentally friendly, meeting the requirements of industrial production;

[0024] 2. The mercury removal catalyst has good catalytic performance and can maintain high efficiency in catalytic oxidation even in atmospheres with low chlorine, high sulfur dioxide, and high water vapor.

[0025] 3. The mercury removal catalyst can be directly applied to existing flue gas dust removal and wet scrubbing units without the need for additional equipment.

[0026] Specific implementation methods

[0027] The following examples are intended to further illustrate the present invention, but not to limit the scope of protection of the claims of the present invention.

[0028] Comparative Example 1:

[0029] Take 8 mmol of copper sulfate and add it to 100 mL of aqueous solution. Then add 50 mmol of 2-methylimidazole to the solution and stir until completely dissolved. Add 2 g of carbon fiber mesh to the mixture, sonicate for 10 min, and then transfer the mixture to a 200 mL sealed reactor. React hydrothermally at 120 °C for 1 h to obtain the Cu-MOF@C precursor. Place the prepared precursor in a tube furnace and heat it to 650 °C at a heating rate of 5 °C / min under a nitrogen atmosphere, and hold for 20 min to obtain the porous carbon-encapsulated copper-cobalt composite carbon fiber mesh catalyst CuO. x @C@CF.

[0030] Comparative Example 2:

[0031] Take 8 mmol of cobalt nitrate and add it to 100 mL of aqueous solution. Then add 50 mmol of 2-methylimidazole to the solution and stir until completely dissolved. Under the same conditions as Comparative Example 1, a porous carbon-encapsulated copper-cobalt composite carbon fiber mesh catalyst CoO can be obtained. x @C@CF.

[0032] Example 1:

[0033] Take 0.4 mmol of copper sulfate and 7.6 mmol of cobalt nitrate, respectively, and add them to 100 mL of aqueous solution. Then add 50 mmol of 2-methylimidazole to the solution and stir until completely dissolved. The remaining conditions are the same as in Comparative Example 1. achievable To porous carbon-encapsulated copper-cobalt composite carbon fiber mesh catalyst Cu 0 .05 Co 0.95 O z @C@DF .

[0034] Example 2:

[0035] 1.2 mmol of copper sulfate and 6.8 mmol of cobalt nitrate were added to 100 mL of aqueous solution, and then 50 mmol of 2-methylimidazole was added to the solution. The solution was stirred until completely dissolved. Under the same conditions as Comparative Example 1, a porous carbon-encapsulated copper-cobalt composite carbon fiber mesh catalyst, Cu, was obtained. 0.15 Co 0.85 O z @C@CF.

[0036] Example 3:

[0037] Take 4 mmol of copper sulfate and 4 mmol of cobalt nitrate, respectively, and add them to 100 mL of aqueous solution. Then add 50 mmol of 2-methylimidazole to the solution and stir until completely dissolved. Under the same conditions as Comparative Example 1, a porous carbon-encapsulated copper-cobalt composite carbon fiber mesh catalyst Cu can be obtained. 0.5 Co 0.5 O z @C@CF.

[0038] Application Example 1:

[0039] The application steps of the prepared catalyst for the catalytic oxidation removal of elemental mercury in flue gas are as follows: Take 20 mg of the prepared catalyst (Comparative Example 1, Comparative Example 2, Example 1 and Example 2), place the catalyst in a fixed-bed reactor, and introduce simulated flue gas (Hg) into the reactor. 0 Concentration of 800 μg / m 3 The concentrations were: O2 5%, SO2 2000 pppm, water vapor 5%, HCl 10 ppm, and the remainder N2; flow rate controlled at 0.8 L / min; and reaction temperature 150 °C. (Note: The last part, "Hg," appears to be an unrelated fragment and is omitted from the translation.) 0 The results of the catalytic oxidation study are shown in Table 1.

[0040] Table 1 Effects of different catalysts on Hg 0 Catalytic oxidation effect

[0041] <![CDATA[Comparative Example 1: CuO x @C@CF]]> 51.23％ <![CDATA[Comparative Example 2: CoO x @C@CF]]> 39.45％ <![CDATA[Example 1: Cu 0.05 Co 0.95 O z @C@CF]]> 63.21％ <![CDATA[Example 2: Cu 0.15 Co 0.85 O z @C@CF]]> 93.64％ <![CDATA[Example 3: Cu 0.5 Co 0.5 O z @C@CF]]> 81.13％

[0042] As shown in Table 1, the prepared copper-cobalt composite porous carbon-supported carbon fiber cloth catalyst exhibits significantly better catalytic oxidation performance for Hg0 than either the copper-cobalt composite porous carbon-supported carbon fiber catalyst alone or the cobalt-cobalt composite porous carbon-supported carbon fiber catalyst alone. This indicates that the bimetallic copper-cobalt composite has a synergistic effect, which is beneficial to the formation of catalytic active sites, thereby achieving Hg0 oxidation. 0 Highly efficient oxidation and removal. Furthermore, a comparison of Examples 1 and 2 revealed that the ratio of copper to cobalt in the bimetallic composite catalyst plays a crucial role in catalytic efficiency.

[0043] Application Example 2:

[0044] Take 20mg of the prepared Cu 0.15 Co 0.85 O z @C@CF catalyst, the catalyst is placed in a fixed-bed reactor and simulated flue gas (Hg) is introduced. 0 Concentration of 800 μg / m 3 (O2 concentration of 5%), flow rate controlled at 0.8 L / min, and reaction at 150 °C, to investigate the effect of different flue gas components on Hg. 0 The catalytic oxidation efficiency is shown in Table 2.

[0045] Table 2. Effects of different flue gas components on Hg 0 Effect of catalytic oxidation efficiency

[0046]

[0047]

[0048] Table 2 shows that increasing the concentrations of SO2 and H2O in the flue gas reduces the catalyst's effect on Hg. 0 The catalytic oxidation effect of the porous carbon-encapsulated copper-cobalt composite carbon fiber mesh catalyst was good, but at higher concentrations of SO2 and H2O (5000 ppm and 10%, respectively), the reaction with Hg was significantly reduced. 0 The catalytic efficiency is still above 85%, which indicates that Cu x Co y O z The C@CF composite catalyst can achieve Hg removal from flue gas containing high sulfur and high water vapor. 0 Catalytic oxidation. Typically, HCl in flue gas reacts with Hg... 0 Catalytic oxidation plays a crucial role in the synthesis of Cu. x Co y O z The @C@CF composite catalyst can react with Hg at 0.5 ppm HCl. 0 With an oxidation removal efficiency of 88.56%, the oxidation removal of mercury in a low-chlorine atmosphere can be achieved.

[0049] Application Example 3:

[0050] Take 20mg of the prepared Cu 0.15 Co 0.85 O z @C@CF catalyst, the catalyst is placed in a fixed-bed reactor and simulated flue gas (Hg) is introduced. 0 Concentration of 800 μg / m 3(O2 concentration 5%, SO2 concentration 2000ppm, HCl concentration 10ppm, water vapor concentration 5%, remainder N2) The effect of different reaction temperatures on Hg was investigated. 0 The catalytic oxidation efficiency is shown in Table 3.

[0051] Table 3 Effects of different reaction temperatures on Hg 0 Effect of catalytic oxidation efficiency

[0052] 50℃ 90.13％ 100℃ 91.33％ 150℃ 93.64％ 200℃ 94.75％ 250℃ 93.58 300℃ 85.32％ 350℃ 78.62％

[0053] Table 3 shows that, within the reaction temperature range of 50℃ to 250℃, the porous carbon-encapsulated copper-cobalt composite carbon fiber mesh catalyst has a significant effect on Hg. 0 The catalytic efficiency is still above 90%, which indicates that Cu x Co y O z @C@CF composite catalysts can achieve Hg at lower temperatures 0 Oxidative removal. Further increasing the reaction temperature, Hg... 0 The reduced oxidation removal efficiency may be due to decreased stability of catalytic oxidation sites on the catalyst surface at high temperatures.

Claims

1. The application of a copper-cobalt composite porous carbon supported carbon fiber cloth low-chlorination mercury removal catalyst, characterized in that, The preparation method of the copper-cobalt composite porous carbon supported carbon fiber cloth low-chlorination mercury removal catalyst includes the following steps: (1) Prepare a copper-cobalt mixed aqueous solution by mixing copper sulfate and cobalt chloride, then add an organic ligand and stir until completely dissolved to obtain a mixed solution; In step (1), the organic ligands are one or more of 2-methylimidazole, 2-nitroimidazole, 5-chlorobenzimidazole, benzoic acid, and mesitylecithic acid, and the molar ratio of the added organic ligands to the total amount of copper and cobalt is (5~10):

1. (2) Add the carbon fiber mesh to the above mixed solution and transfer it to a closed hydrothermal reactor. React at 100~160℃ for 0.5~1.5 hours. After the reaction is completed, cool naturally to room temperature, filter, wash and dry to obtain copper cobalt organic ligand supported carbon fiber mesh. (3) The prepared copper-cobalt organic ligand supported carbon fiber mesh was placed in a closed tube furnace and heated to 600~800℃ under an inert atmosphere and kept at that temperature for 10~30min to obtain a porous carbon-encapsulated copper-cobalt composite carbon fiber mesh mercury removal catalyst. The copper-cobalt composite porous carbon supported carbon fiber cloth low-chlorine mercury removal catalyst is used for the catalytic oxidation of gaseous elemental mercury in industrial flue gas; the application temperature is 50~250℃, and the HCl concentration in the flue gas is below 0.5ppm; the low-chlorine mercury removal catalyst has a catalytic oxidation efficiency of more than 85% for elemental mercury in complex flue gas containing sulfur dioxide and water vapor.

2. The application according to claim 1, characterized in that, In step (1), the total concentration of copper and cobalt ions in the copper-cobalt mixed aqueous solution is 80 mmol / L.

3. The application according to claim 1, characterized in that, In step (2), 1-3 g of carbon fiber mesh is added per 100 mL of mixed solution; in step (3), the inert atmosphere is one or more of nitrogen and argon, and the heating rate is 5-10 °C / min.

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