Preparation method of size-adjustable copper-iron catalyst

Abstract

The invention relates to the technical field of CO oxidation catalysts, in particular to a preparation method of a size-adjustable copper-iron catalyst. The method comprises the following steps: preparing a mixed solution from ferric chloride and ethanol and deionized water in a certain proportion, and mixing the mixed solution with sodium acetate; then, the mixture is subjected to a hydrothermal reaction in a reaction kettle, suction filtration and drying are performed, and the carrier is prepared. Mixing the carrier with an aqueous solution containing a certain amount of copper nitrate, and adding excessive sodium carbonate solution; performing suction filtration and drying to obtain an intermediate product; and finally, calcining the intermediate product to obtain the catalyst. The copper-iron catalyst does not need precious metal, is low in cost, simple in preparation method, controllable in condition and free of generation of strong acid and strong alkali waste liquid, and can be industrially applied on a large scale.

Description

Technical Field

[0001] This invention relates to the field of CO oxidation catalyst technology, and in particular to a method for preparing a size-tunable copper-iron catalyst. Background Technology

[0002] The steel industry is a crucial foundation of the national economy and a significant source of air pollutants. Major processes such as sintering, ironmaking, steelmaking, and coking generate large quantities of industrial waste gas containing CO. Highly efficient catalytic oxidation of CO can eliminate its extreme toxicity and achieve emission standards. Currently, CO catalytic oxidation technology, already applied to small mobile emission sources, is the most promising CO control technology for sintering flue gas. This technology utilizes the selective adsorption of CO by active sites on the catalyst surface, which then reacts with O2 to generate CO2, thus achieving CO purification. However, in practical applications, the cost of commercially available precious metal catalysts makes direct introduction into the treatment of smelting flue gas in the steel industry difficult. Traditional non-precious metal catalysts, especially Fe-based ones, lack sufficient efficiency and stability, making it difficult to meet the long-term stable operation requirements of the complex working conditions in the steel industry.

[0003] Although iron oxide catalysts are inexpensive, possess tunable redox properties, and have a strong ability to form oxygen vacancies, they suffer from high catalytic temperatures and low conversion efficiency. Currently, the most feasible modification method is to prepare CuO / Fe2O3 catalysts by supporting copper oxide. However, CuO / Fe2O3 catalysts exhibit low catalytic efficiency within the 200-300℃ range, making it difficult to meet emission standards for sintering flue gas. Further optimization of their low-temperature catalytic activity is needed to adapt them to the complex environment of actual sintering processes. Summary of the Invention

[0004] Based on the above, this invention provides a method for preparing a size-tunable copper-iron catalyst and a method for adjusting the size of the copper-iron catalyst to improve the catalytic activity of CO oxidation. This invention utilizes the size effect to adjust the CO catalytic oxidation activity of the copper-iron catalyst, thereby solving the problems of high cost, poor catalyst stability, and low catalytic efficiency within 200-300℃ of traditional catalysts. The catalyst prepared by this invention exhibits long-term stability in the CO catalytic oxidation reaction.

[0005] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of this invention is a method for preparing a size-tunable copper-iron catalyst, comprising the following steps: Iron salts and sodium acetate are mixed with the mixed solution to obtain a mixture; The mixture was subjected to a hydrothermal reaction, filtered, and dried to obtain a carrier; The carrier was added to an aqueous solution of copper salt, and an alkaline salt solution was added to make the pH of the system not less than 9.0. The reaction was carried out, filtered, and dried to obtain the intermediate product. The intermediate product was calcined to obtain the copper-iron catalyst; The mixed solution consists of ethanol and water; wherein the volume ratio of ethanol to water is 40:(3~4).

[0006] The second technical solution of the present invention is a copper-iron catalyst prepared by the above-mentioned preparation method.

[0007] The third technical solution of the present invention is the application of the above-mentioned copper-iron catalyst in the catalytic oxidation of CO.

[0008] The fourth technical solution of this invention is a method for adjusting the size of the aforementioned copper-iron catalyst, which controls the size of the copper-iron catalyst by adjusting the volume ratio of ethanol to water in the mixed solution. As the amount of water increases, the size of the copper-iron catalyst decreases.

[0009] This invention optimizes the catalytic performance by improving the strength of the metal-support interaction through the size effect of the support. The preparation method is simple, low-cost, and under controllable conditions, without generating strong acid or strong alkali waste liquids, and can be applied on a large scale in industry.

[0010] Compared with the prior art, the present invention has the following beneficial effects: ① Lower operating temperature range: A hydroxyl oxide support was constructed using a hydrothermal method, and then the CuO active component was highly dispersed as extremely small nanoparticles on the support via a deposition-precipitation method. The size effect of the copper-iron catalyst significantly increased the number of effective active sites, thereby effectively reducing the temperature range required for the reaction.

[0011] ② Environmental friendliness and sustainability: The method of this invention uses non-precious metals copper and iron as active components, avoiding the high cost and resource scarcity problems of traditional precious metal catalysts (such as Pt and Pd). The hydrothermal synthesis method for preparing the iron hydroxyl oxide support lowers the reaction temperature, thereby reducing energy consumption, making it a greener choice for the support. The deposition-precipitation method is used, and sodium carbonate is added to maintain a pH value greater than 9.0, resulting in Cu... 2+ It will almost completely precipitate on the surface of the iron oxide carrier in the form of basic copper carbonate or copper hydroxide. This improves the utilization rate of copper, reduces the discharge of wastewater containing heavy metals at the source, and lowers the cost and environmental risks of subsequent wastewater treatment. These are the low-pollution characteristics of the process, and they all meet the requirements of sustainable development.

[0012] ③ Significantly reduce the manufacturing cost of CO oxidation catalyst: By controlling the size, the dispersion of copper elements on the surface is improved, which effectively increases the number of surface active sites without increasing production costs, thereby fundamentally reducing the raw material cost required to achieve the same activity. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 The results show the CO catalytic activity test results of the catalysts prepared in Examples 1-3 and Comparative Examples 1-3 of this invention.

[0015] Figure 2 The images shown are SEM images of the catalysts prepared in Examples 1-3 of this invention; where a is Example 3, b is Example 2, and c is Example 1. Detailed Implementation

[0016] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0017] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0018] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0019] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This specification and embodiments are merely exemplary.

[0020] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0021] Unless otherwise specified, "room temperature" in this invention refers to 20-30℃.

[0022] The first aspect of this invention provides a method for preparing a size-tunable copper-iron catalyst, comprising the following steps: Iron salts and sodium acetate are mixed with the mixed solution to obtain a mixture; The mixture was subjected to a hydrothermal reaction, filtered, and dried to obtain a carrier; The carrier was added to an aqueous solution of copper salt, and an alkaline salt solution was added to make the pH of the system not less than 9.0. The reaction was carried out, filtered, and dried to obtain the intermediate product. The intermediate product was calcined to obtain the copper-iron catalyst; The mixed solution consists of ethanol and water; wherein the volume ratio of ethanol to water is 40:(3~4). Optionally, the volume ratio of ethanol to water is 40:3, 40:3.5, 40:4, or any value between the two aforementioned ratios.

[0023] In a preferred embodiment of the present invention, the iron salt is ferric chloride; the ratio of the iron salt to sodium acetate and the mixed solution is 1.09 g: 3.2 g: (42~45) mL.

[0024] In a preferred embodiment of the present invention, the hydrothermal reaction conditions are set as follows: 180~190℃ for 8~12h.

[0025] The carrier is iron hydroxyl oxide, which is converted into iron oxide after subsequent calcination.

[0026] In a preferred embodiment of the present invention, the copper salt aqueous solution is a 0.076-0.27 mol / L copper nitrate aqueous solution; the solid-liquid ratio of the carrier to the copper salt aqueous solution is 0.15-0.35 g / mL; and the alkaline salt solution is a 0.2-0.5 mol / L Na2CO3 solution.

[0027] In a preferred embodiment of the present invention, the reaction conditions for preparing the intermediate product are set as follows: stirring at room temperature for 1-2 hours. The present invention does not impose any particular limitation on the stirring speed; stirring speeds commonly used by those skilled in the art are adopted.

[0028] During the preparation of the intermediate product, an alkaline salt solution was continuously added dropwise throughout the reaction process to ensure that the system pH was not less than 9.0. Experimental verification showed that when the pH of the reaction system was greater than 9, the performance of the final catalyst did not significantly differ with increasing pH. Therefore, in the actual catalyst preparation process, when preparing the intermediate product, considering both cost and safety, it is sufficient to ensure that the pH of the reaction system is greater than 9, such as 9.1, 9.2, or 9.3.

[0029] In a preferred embodiment of the present invention, the calcination conditions are set as follows: calcination at 400~450℃ for 4~6 hours. Optionally, the calcination temperature can be 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, etc., and the calcination time can be 4 hours, 5 hours, 6 hours, etc. The heating rate during calcination is controlled at 5~10℃ / min, for example, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min. After calcination, a cooling step to room temperature at a cooling rate of 5~10℃ / min is included; optionally, the cooling rate after calcination can be 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min.

[0030] In preparing the carrier and intermediate product, the drying is carried out in an oven at 40-50°C for 12-20 hours. Optionally, the drying temperature can be 40°C, 45°C, 50°C, etc., and the drying time can be 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, etc.

[0031] A second aspect of this invention provides a copper-iron catalyst prepared using the above-described preparation method. The copper-iron catalyst prepared using this method has a copper oxide loading of 5 wt%. Experiments have verified that both excessively high and low copper oxide loadings affect the catalytic oxidation performance of the prepared catalyst for CO; the catalyst exhibits optimal catalytic oxidation performance for CO when the copper oxide loading is 5 wt%.

[0032] A third aspect of the present invention provides the application of the above-described copper-iron catalyst in the catalytic oxidation of CO.

[0033] The average size of the copper-iron catalyst of this invention is 80~240nm. Through experiments, this invention found that within this size range, the catalytic activity increases as the catalyst size decreases, but the catalytic activity begins to deteriorate as the catalyst size further decreases (below 80nm).

[0034] A fourth aspect of the present invention provides a method for adjusting the size of the aforementioned copper-iron catalyst, wherein the size of the copper-iron catalyst is controlled by adjusting the volume ratio of ethanol to water in the mixed solution. As the amount of water increases, the size of the copper-iron catalyst decreases.

[0035] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field, and the reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0036] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0037] Example 1 Step 1: Add 1.09 g of ferric chloride to a mixed solution consisting of 40.0 mL of ethanol and 3.0 mL of deionized water. Then add 3.2 g of sodium acetate to the mixture and mix.

[0038] Step 2: Transfer the mixture to a 100 mL autoclave and heat at 180 °C for 8 h to produce carrier powder. Then filter the powder and dry it in a drying oven at 50 °C for 12 h to obtain the hydroxyl oxygen carrier.

[0039] Step 3: Weigh 6.0 g of ferric hydroxyl oxide carrier and add it to a copper nitrate aqueous solution with a molar concentration of 0.27 mol / L. The concentration of the carrier in the copper nitrate aqueous solution is 0.35 g / mL.

[0040] Step 4: Add 0.5 mol / L Na₂CO₃ solution dropwise, ensuring the pH of the solution is greater than 9. Stir the mixture for 2 hours, then filter under vacuum and dry at 50°C for 20 hours to obtain the intermediate product.

[0041] Step 5: The intermediate product was calcined in a muffle furnace at a heating rate of 10℃ / min to 400℃ for 6 hours, and then cooled to room temperature at a cooling rate of 10℃ / min to obtain the copper-iron catalyst (CuO / Fe2O3 catalyst, denoted as 5-Cu / Fe(240)). The CuO loading in the copper-iron catalyst prepared in this example was 5wt% (the formula for calculating the copper oxide loading is...). ,in, This indicates the mass of copper salt that needs to be weighed. This indicates the total mass of the final catalyst. Indicates the molecular weight of copper salts. (Indicates the molecular weight of CuO) Scanning electron microscopy (SEM) revealed that the average size of the copper-iron catalyst prepared in this embodiment was 240 nm. Figure 2 As shown in c.

[0042] Example 2 The only difference from Example 1 is that in step 1, the amount of deionized water added is 3.5 mL; all other steps and parameters are the same as in Example 1. The obtained catalyst is denoted as 5-Cu / Fe(160). Scanning electron microscopy (SEM) shows that the average size of the copper-iron catalyst obtained in this example is 160 nm. Figure 2 As shown in b.

[0043] Example 3 The only difference from Example 1 is that in step 1, the amount of deionized water added is 4.0 mL; all other steps and parameters are the same as in Example 1. The obtained catalyst is denoted as 5-Cu / Fe(80). Scanning electron microscopy (SEM) shows that the average size of the copper-iron catalyst obtained in this example is 80 nm. Figure 2 As shown in Figure a.

[0044] Comparative Example 1 The only difference from Example 1 is that steps 3 and 4 are omitted; the remaining steps and parameters are the same as in Example 1; the copper-iron catalyst obtained is denoted as Fe-240.

[0045] Comparative Example 2 The only difference from Example 2 is that steps 3 and 4 are omitted; the remaining steps and parameters are the same as in Example 2; the obtained copper-iron catalyst is denoted as Fe-160.

[0046] Comparative Example 3 The only difference from Example 3 is that steps 3 and 4 are omitted; the remaining steps and parameters are the same as in Example 3; the obtained oxidation catalyst is denoted as Fe-80.

[0047] Catalyst activity detection The catalysts prepared in the examples and comparative examples were placed in fixed-bed reactors for catalytic activity testing.

[0048] Catalyst activity testing conditions: reaction temperature 30-300℃, reaction pressure atmospheric pressure, 5000ppmCO, 20%O2, N2 as equilibrium gas, gas flow rate 200ml / min. Catalyst dosage 0.3g. The catalyst CO catalytic activity test results are as follows: Figure 1 As shown.

[0049] The catalytic activity of a catalyst for CO is evaluated using CO conversion rate: XCO =(CO in -CO out ) / CO in 100%.

[0050] CO in CO out These represent the CO concentrations at the inlet and outlet of the fixed-bed reactor, respectively. For detailed catalytic activity detection results, please refer to [link to relevant documentation]. Figure 1 It can be observed that the CO conversion rate of all catalyst samples increases with increasing temperature, reaching over 90% at 220℃. At 250℃, the CO conversion rate of the 5-Cu / Fe(80) catalyst is almost 100%, while the CO conversion rates of the 5-Cu / Fe(160) and 5-Cu / Fe(240) catalysts reach 92%, and the CO conversion rate of the catalyst without CuO loading is only about 33%. The catalyst with a CuO loading of 5% and a size of 80nm exhibits the highest CO catalytic efficiency, reaching the optimal CO conversion rate. As the catalyst size decreases, the specific surface area increases significantly, the proportion of highly active sites increases, and the catalyst can more effectively adsorb and activate reactant molecules. It can also optimize the adsorption strength of the catalyst for reactant molecules, thereby significantly reducing the activation energy required for the reaction and making each active site react faster. At the same time, a wider and tighter contact interface can be formed between the small-sized iron oxide support and the highly dispersed CuO. This greatly improves the catalytic oxidation efficiency of CO.

[0051] This invention also tested the performance of the catalyst under the synergistic effect of 3 vol% H2O + 50 ppm SO2 (the test method is the same as described above for catalytic activity testing). Under such harsh conditions, the catalyst exhibited remarkable robustness. The CO conversion rate initially decreased to approximately 80%, but the activity remained stable at this level throughout continuous operation for over 200 hours, without significant degradation. In the presence of SO2 and H2O, the trend of CO conversion rate change of the catalyst prepared in this invention was significantly better than that of conventional catalysts, demonstrating excellent resistance to poisoning and long-term stability.

[0052] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a size-tunable copper-iron catalyst, characterized in that, Includes the following steps: Iron salts and sodium acetate are mixed with the mixed solution to obtain a mixture; The mixture was subjected to a hydrothermal reaction, filtered, and dried to obtain a carrier; The carrier was added to an aqueous solution of copper salt, and an alkaline salt solution was added to make the pH of the system not less than 9.

0. The reaction was carried out, filtered, and dried to obtain the intermediate product. The intermediate product was calcined to obtain the copper-iron catalyst; The mixed solution consists of ethanol and water; wherein the volume ratio of ethanol to water is 40:(3~4).

2. The preparation method according to claim 1, characterized in that, The iron salt is ferric chloride; the ratio of the iron salt to sodium acetate and the mixed solution is 1.09 g : 3.2 g : (42~45) mL.

3. The preparation method according to claim 1, characterized in that, The hydrothermal reaction conditions are set as follows: 180~190℃ for 8~12 hours.

4. The preparation method according to claim 1, characterized in that, The copper salt aqueous solution is a 0.076-0.27 mol / L copper nitrate aqueous solution; the solid-liquid ratio of the carrier to the copper salt aqueous solution is 0.15-0.35 g / mL; the alkaline salt solution is a 0.2-0.5 mol / L Na2CO3 solution.

5. The preparation method according to claim 1, characterized in that, The reaction conditions for preparing the intermediate product are as follows: stirring at room temperature for 1-2 hours.

6. The preparation method according to claim 1, characterized in that, The calcination conditions are set as follows: calcination at 400~450℃ for 4~6 hours.

7. A copper-iron catalyst prepared by the preparation method according to any one of claims 1 to 6.

8. The application of the copper-iron catalyst as described in claim 7 in the catalytic oxidation of CO.

9. A method for adjusting the size of the copper-iron catalyst according to claim 7, characterized in that, The size of the copper-iron catalyst can be controlled by adjusting the volume ratio of ethanol to water in the mixed solution.

Images