High specific surface area desulfurizer hydrated iron oxide and its preparation method

Abstract

The application discloses a high specific surface area desulfurizer hydrated iron oxide component and a preparation method thereof. First, an iron source ferrous salt and a precipitant are respectively dissolved completely by being heated to 40 DEG C, then the precipitant is put into the ferrous salt solution to carry out stirring and mixing reaction, pH is kept at 6.5-9.5, then small molecule organic alcohol, acid or amine substance is added, air is introduced to carry out oxidation reaction, finally, the material liquid is filtered, rinsed and dried, and the high specific surface area hydrated iron oxide desulfurizer active component is obtained. The preparation method of the high specific surface area hydrated iron oxide desulfurizer active component has the advantages of mild reaction condition, simple technological process, low production cost, non-toxic and non-pollution, and the specific surface area of the prepared hydrated iron oxide is greatly improved, the sulfur capacity is as high as 60.85%, and the method has good application prospect and potential practical value.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrogen sulfide removal, and particularly relates to a preparation method of an active component of a high specific surface area hydrated iron oxide desulfurizer. BACKGROUND

[0002] Hydrogen sulfide is a very toxic gas, which can seriously threaten human life and health. When the concentration of hydrogen sulfide exceeds 10 ppm, the human health will be affected, and when the hydrogen sulfide exceeds 600 ppm, the hydrogen sulfide can cause death. The sources of hydrogen sulfide are numerous, including industrial waste gas emission, utilization of fossil energy such as coal and oil, utilization of natural gas, biogas and so on, and release of digestion gas in sewage treatment plants and municipal solid waste landfills and so on. In China, the content of hydrogen sulfide in gas phase is strictly limited. In civil biogas or coal gas, the content of hydrogen sulfide should not exceed 20 mg / Nm 3 ; because hydrogen sulfide has serious corrosion to the transportation pipeline, reactor and so on, in some catalytic reactions, it will also cause poisoning of the catalyst, for example, in the Fischer-Tropsch synthesis process, a few ppm of hydrogen sulfide content in the synthesis gas will cause poisoning of the catalyst and reduce the service life of the catalyst. In the proton exchange membrane fuel cell, in order to protect the noble metal catalyst in the electrode material, the concentration of hydrogen sulfide in the gas should not exceed 0.1 ppm. Therefore, in industrial production, there are more stringent standards for the content of sulfur in the material. Therefore, it is necessary to remove hydrogen sulfide in the gas.

[0003] There are a large number of research works on hydrogen sulfide removal at home and abroad, and the main industrial application technologies include dry desulfurization, wet desulfurization and biological desulfurization. Considering the operation cost and desulfurization efficiency, the dry desulfurization is still more in industry. The most widely used in the dry desulfurization process is the metal oxide method, the basic principle of which is to use the physical or chemical adsorption of metal ions in the metal oxide to hydrogen sulfide to remove hydrogen sulfide in the gas, and then to regenerate by using air. Compared with other desulfurizers, the iron-based desulfurizer with iron oxide as the main active component has higher sulfur capacity and faster sulfuration reaction rate. The raw material of the iron-based desulfurizer is widely available, the desulfurizer is simple to prepare, the desulfurizer is convenient to load and unload, and can be used in a wide temperature range, so it has been widely applied. According to the desulfurization mechanism of the iron oxide desulfurizer, the effective active component in the iron-based desulfurizer at room temperature is hydrated iron oxide FeOOH or amorphous hydrated iron oxide (Fe2O3·xH2O). Therefore, the development of the iron oxide desulfurizer with large specific surface area, high activity, high sulfur capacity, not easy to deactivate and low cost has become a hot research field at present.

[0004] Invention patent 200810112428.X uses a soluble ferrous salt to knead a solid hydroxide to prepare an amorphous high-strength hydroxyl iron oxide desulfurizer. However, the product of this method is to be naturally dried in the air, which requires a high air environment, and the sulfur capacity of the prepared iron oxide is only 47%.

[0005] The reaction between iron oxide desulfurizer and H2S is a typical gas-solid catalytic reaction. It involves not only surface participation but also gas diffusion into the interior of the grains. Before diffusion into the inner layers of the particles, sufficient specific surface area is needed to provide opportunities for gas-solid contact, allowing more gas molecules to interact with the solid surface and thus accelerating the mass transfer rate. However, desulfurizers cannot maintain a large specific surface area indefinitely during use; during regeneration, some specific surface area is lost due to particle size increase. Therefore, increasing the specific surface area is crucial for improving the sulfur capacity of iron oxide desulfurization. Summary of the Invention

[0006] Therefore, the purpose of this invention is to provide a method for preparing the active component of a layered hydrated iron oxide desulfurizer with mild synthesis conditions, low production cost, and high specific surface area. Using this preparation process, the specific surface area can be increased to 211 m². 2 / g, and the finished product has a good lamellar crystal structure, thus solving the problems of low sulfur capacity, easy deactivation and poor regeneration ability caused by insufficient specific surface area of ​​iron oxide desulfurizer in industrial applications.

[0007] In a first aspect, the present invention provides a method for preparing a high specific surface area desulfurizing agent, hydrated iron oxide, characterized in that the hydrated iron oxide is obtained by the following preparation method: (1) using ferrous salt as an iron source, the ferrous salt is completely dissolved in water to form a ferrous salt solution, and the temperature is raised to 40°C under continuous stirring; (2) under continuous stirring, a large amount of precipitant solution is rapidly added to the solution system of step (1), the pH is adjusted to 6.5-9.5, and the temperature is maintained at 40°C; the precipitant is Na2CO3, K2CO3, ... (2) One or more of NH4HCO3, NaOH, KOH, NaHCO3 or NH3·H2O; (3) After the pH value of the mixture in step (2) is constant, add small molecule organic reagents containing polar functional groups such as -OH, -NH2, -COOH, and stir to mix evenly; (4) Pass compressed air through the mixture obtained in step (3) for rapid oxidation and aging; (5) Filter the slurry obtained in step (4), wash away the by-product soluble salts generated in the process, and obtain filter cake; (6) Dry the filter cake obtained in step (5) to obtain high specific surface area desulfurizing agent hydrated iron oxide material;

[0008] In some embodiments, in step (1), the concentration of ferrous ions in the ferrous salt solution is 0.1-4.0 mol / L; the ferrous salt is FeCl₂. 2· One or more of 4H2O, Fe(NO3)2·6H2O, FeSO4·7H2O, or ferrous acetate. In some specific embodiments, the ferrous salt is preferably FeSO4·7H2O.

[0009] In some embodiments, in step (2), the molar ratio of the precipitant to the ferrous salt is (0.2-2.0):1.

[0010] In some embodiments, the precipitant solution is 0.1-1 mol / L.

[0011] In some embodiments, the precipitant is Na2CO3.

[0012] In some embodiments, in step (3), the molar ratio of the small molecule organic reagent to the ferrous salt is 1:(50-90), and the small molecule organic reagent is one or more of acetic acid, ethanol, ethylene glycol, n-butanol, ethylenediamine, triethylamine, acetone or glycine, preferably n-butanol.

[0013] In some embodiments, in step (4), the oxidation and aging time is 3.0-6.0 h.

[0014] In some embodiments, in step (4), the air velocity is 10-360 m / s. 3 / h.

[0015] In some embodiments, in step (6), the filter cake drying temperature is 70-90°C.

[0016] In some specific embodiments, the hydrated iron oxide is obtained by the following preparation method: (1) ferrous sulfate solution is heated to 40°C under continuous stirring; (2) Na2CO3 solution is added rapidly and in large quantities to the solution system of step (1) under continuous stirring to adjust the pH to 6.5-9.5 and maintain the temperature at 40°C; (3) after the pH value of the mixture system of step (2) is constant, n-butanol containing small molecule organic reagent is added and stirred to make it evenly mixed; (4) the mixture system obtained in step (3) is passed through compressed air for rapid oxidation and aging; (5) the slurry obtained in step (4) is filtered to remove the by-product soluble salts generated during the process, and a filter cake is obtained. According to this embodiment, the high specific surface area desulfurizing agent hydrated iron oxide of the present invention has a maximum specific surface area of ​​211.22 m². 2 When applied to the desulfurization of gaseous H2S, the sulfur capacity can reach as high as 60.85%.

[0017] Secondly, the present invention provides a high specific surface area desulfurizing agent, hydrated iron oxide, prepared according to the aforementioned preparation method.

[0018] Compared with existing iron oxide desulfurizing agents, the advantages of the high specific surface area desulfurizing agent hydrated iron oxide and its preparation method described in this invention are as follows:

[0019] (1) The method for preparing high specific surface area desulfurizing agent hydrated iron oxide provided by the present invention is suitable for industrial-scale production because the reaction conditions involved are mild, the process is simple, the production cost is low, and it is non-toxic and pollution-free.

[0020] (2) The preparation method of the high specific surface area desulfurizing agent hydrated iron oxide described in this invention limits the temperature of the solution in steps (1) and (2) to precisely control it at 40°C. At this temperature, the high content of ferrous iron source and precipitant can be fully dissolved and mixed, avoiding the impact on production efficiency due to the low solubility of the precipitant. Moreover, with the assistance of a suitable air flow rate, it can make Fe 2+ Rapid oxidation to hydrated iron oxide will not cause the synthesized hydrated iron oxide to lose some active sites or generate magnetic Fe3O4 with very low desulfurization activity due to excessively low temperature or slow oxidation rate, nor will it reduce its desulfurization activity due to excessively high temperature destroying the structure of the formed hydrated iron oxide.

[0021] (3) The preparation method of the high specific surface area desulfurizing agent hydrated iron oxide described in this invention introduces small molecule polar organic reagents for the first time. The activity of the iron oxide desulfurizing agent depends primarily on the content of the active components. The highly active hydroxyl, amino, and carboxyl groups of the organic reagents undergo uniform physical or chemical adsorption with the surface of iron oxide, resulting in abundant surface hydroxyl or amino groups on the surface of the prepared iron oxide. This is beneficial to increase the surface activity of the hydrated iron oxide to provide more H2S adsorption sites, thereby improving the desulfurization efficiency and sulfur penetration capacity of the iron oxide. On the other hand, the addition of small molecule alcohols or amines tends to make the crystal structure of the hydrated iron oxide tend to develop towards an amorphous or incomplete crystal state, which is beneficial for desulfurization because the disordered amorphous state can provide more attachment sites, and the prepared iron oxide has a higher degree of hydration and a stronger affinity for H2S.

[0022] (4) The high specific surface area desulfurizing agent hydrated iron oxide described in this invention has a specific surface area of ​​up to 170.43-211.22 m². 2 When applied to the desulfurization of gaseous H2S, the sulfur capacity can reach as high as 60.85%. Attached Figure Description

[0023] Figure 1 The XRD patterns are of high specific surface area hydrated iron oxide and ordinary hydrated iron oxide in Example 1.

[0024] Figure 2 The image shows a comparison of scanning electron microscopy (SEM) images of high specific surface area hydrated iron oxide prepared in Example 1 and ordinary hydrated iron oxide. Detailed Implementation

[0025] In the following embodiments of the present invention, the crystal structure of the prepared high specific surface area hydrated iron oxide was tested using a Rigaku Corporation MiniFlex 600 X-ray diffractometer (Cu Kα rays, voltage 40kV, current 30mA); the specific surface area of ​​the prepared hydrated iron oxide was tested using a 3H-2000BET-A solid standard reference method; and the morphology of the prepared hydrated iron oxide was tested using a field emission scanning electron microscope (FE-SEM).

[0026] Example 1

[0027] 0.7m 3 A 0.3 mol / L ferrous sulfate solution was added to 2m 3 In the reaction vessel, the mixture was stirred and steam was introduced to raise the temperature to 40°C. Then, a 0.45 mol / L soda ash solution was added while stirring continuously, maintaining the temperature at 40°C. When the pH of the slurry reached 8.0, the addition of soda ash solution was stopped, and stirring was continued for 20 minutes. Next, 360 g of n-butanol was added, and stirring was continued for another 20 minutes. Afterward, air was introduced for oxidation at a flow rate of 80 m / s. 3 The reaction was carried out at a constant temperature of 40°C throughout the entire process. When the solution turned brownish-red, the air and steam were shut off, the solution was washed, filtered, and dried at 80°C.

[0028] Example 2

[0029] 0.7m 3 A 0.8 mol / L ferrous sulfate solution was added to 2m 3 In the reaction vessel, the mixture was stirred and steam was introduced to raise the temperature to 40°C. Then, a 0.45 mol / L soda ash solution was added while stirring continuously, maintaining the temperature at 40°C. When the pH of the slurry reached 7.5, the addition of soda ash solution was stopped, and stirring was continued for 20 minutes. Next, 312 g of acetic acid was added, and stirring was continued for another 20 minutes. Afterward, air was introduced for oxidation at a flow rate of 80 m / s. 3 The reaction was carried out at a constant temperature of 40°C throughout the entire process. When the solution turned brownish-red, the air and steam were shut off, the solution was washed, filtered, and dried at 80°C.

[0030] Example 3

[0031] 0.7m 3 A 0.8 mol / L ferrous sulfate solution was added to 2m 3In the reaction vessel, the mixture was stirred and steam was introduced to raise the temperature to 40°C. Then, a 0.45 mol / L soda ash solution was added while stirring continuously, maintaining the temperature at 40°C. When the pH of the slurry reached 7.5, the addition of soda ash solution was stopped, and stirring was continued for 20 minutes. Next, 392 g of ethylenediamine was added, and stirring was continued for another 20 minutes. Afterward, air was introduced for oxidation at a flow rate of 80 m / s. 3 The reaction was carried out at a constant temperature of 40°C throughout the entire process. When the solution turned brownish-red, the air and steam were shut off, the solution was washed, filtered, and dried at 80°C.

[0032] like Figure 1 As shown, the XRD patterns of the high specific surface area hydrated iron oxide prepared in Example 1 of this invention and ordinary hydrated iron oxide are obtained from... Figure 1 It is known that the characteristic diffraction peaks of ordinary iron oxide are sharper, indicating that its crystal form is more complete. High specific surface area hydrated iron oxide is closer to an amorphous state, with a low degree of crystallization and an incomplete crystal structure. This structure has a higher degree of hydration, which is more conducive to desulfurization.

[0033] like Figure 2 As shown, A and B are scanning electron microscope images of ordinary hydrated iron oxide and high specific surface area hydrated iron oxide prepared in Example 1 of the present invention, respectively. The images show that the high specific surface area hydrated iron oxide prepared in the present invention has more loose surface pores, indicating that it has better H2S adsorption performance. When applied to the desulfurization of gaseous H2S, the sulfur capacity can reach up to 60.85%.

[0034] Table 1. Specific surface area results of hydrated iron oxide prepared in Examples 1, 2, and 3 and in the literature "Study on the Desulfurization Activity of Iron Hydroxide Prepared by Different Methods":

[0035] Serial number Hydrated iron oxide sample Specific surface area (m 2 / g) 1 Literature value 55.49 2 Example 1 211.22 3 Example 2 195.34 4 Example 3 173.43

[0036] The data in Table 1 show that the specific surface area of ​​the hydrated iron oxide prepared after treatment with small molecule organic reagents was significantly improved.

[0037] In this invention, the experimental conditions of the examples are not limited to those described above. The numerical values ​​mentioned above are reference values ​​during the experiment and are only preferred embodiments of this invention. They are not intended to limit this invention. All modifications, substitutions, and improvements made in accordance with the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for producing a high specific surface area desulfurizer, hydrous iron oxide, characterized by, The hydrated iron oxide is obtained by the following preparation method: (1) using ferrous salt as iron source, the ferrous salt is completely dissolved in water to form a ferrous salt solution, and the temperature is increased to 40℃ under constant stirring; (2) under constant stirring, a large amount of precipitant solution is added into the solution system of step (1) rapidly, the pH is adjusted to 6.5-9.5, and the temperature is kept at 40℃; the precipitant is one or more of Na2CO3, K2CO3, NH4HCO3, NaOH, KOH, NaHCO3 or NH3·H2O; (3) after the pH value of the mixed system of step (2) is constant, a small molecule organic reagent containing polar functional groups -OH, -NH2, -COOH is added and stirred to mix uniformly; the molar ratio of the small molecule organic reagent to the ferrous salt is 1:(50-90), and the small molecule organic reagent is one or more of acetic acid, ethanol, ethylene glycol, n-butanol, ethylenediamine, triethylamine, acetone or glycine; (4) the mixed system obtained in step (3) is subjected to rapid oxidation and aging by introducing compressed air; (5) the slurry obtained in step (4) is filtered, and the byproduct soluble salt generated in the process is removed by washing to obtain a filter cake; (6) the filter cake obtained in step (5) is dried to obtain the high specific surface area desulfurizer hydrated iron oxide material.

2. The production method according to claim 1, characterized by, In the step (1), the concentration of ferrous ions in the ferrous salt solution is 0.1-4.0 mol / L; the ferrous salt is FeCl 2· 4H2O, Fe(NO3)2·6H2O, FeSO4·7H2O or ferrous acetate.

3. The production method according to claim 2, characterized by, The ferrous salt is FeSO4·7H2O.

4. The method of claim 1, wherein, In the step (2), the molar ratio of the precipitant to the ferrous salt is (0.2-2.0):1; and the precipitant solution is 0.1-1 mol / L.

5. The preparation method according to claim 1, characterized in that, The precipitant is Na2CO3.

6. The method of claim 1, wherein, The small molecule organic reagent is n-butanol.

7. The preparation method according to claim 1, characterized in that, In the step (4), the oxidation and aging time is 3.0-6.0 h.

8. The method of claim 1, wherein, In the step (4), the air flow rate is 10-360 m 3 / h.

9. The method of claim 1, wherein, In the step (6), the filter cake drying temperature is 70-90℃.

10. The method of claim 1, wherein, The hydrated iron oxide is obtained by the following preparation method: (1) the ferrous sulfate solution is heated to 40℃ under constant stirring; (2) under constant stirring, a large amount of Na2CO3 solution is added into the solution system of step (1) rapidly, the pH is adjusted to 6.5-9.5, and the temperature is kept at 40℃; (3) after the pH value of the mixed system of step (2) is constant, n-butanol, a small molecule organic reagent, is added and stirred to mix uniformly; (4) the mixed system obtained in step (3) is subjected to rapid oxidation and aging by introducing compressed air; (5) the slurry obtained in step (4) is filtered, and the byproduct soluble salt generated in the process is removed by washing to obtain a filter cake.

11. The high specific surface area desulfurizer hydrated iron oxide prepared by the preparation method of any one of claims 1-10.

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