Iron oxyhydroxide solid desulfurizer and preparation method thereof

Abstract

The invention discloses a ferric oxyhydroxide solid desulfurizer and a preparation method thereof, and belongs to the technical field of gas purification. The iron oxyhydroxide solid desulfurizing agent is prepared from an alpha-FeOOH nanorod, a modified carbon nano tube, gamma-Al2O3 and starch, wherein the modified carbon nanotubes are obtained by grafting polylactic acid after nitrogen plasma pretreatment. The preparation method of the FeOOH solid desulfurizer comprises the following steps: preparing a modified carbon nanotube, synthesizing an alpha-FeOOH nanorod under the assistance of ultrasonic waves, carrying out ball-milling molding on the components to obtain a wet green body, and carrying out segmented drying and nitrogen roasting on the wet green body. The circulating stability of the prepared iron oxyhydroxide desulfurizer is improved, and the requirement for long-term stable operation of industrial dry desulfurization can be met.

Description

A solid desulfurizing agent of iron hydroxyl oxide and its preparation method Technical Field

[0001] This invention relates to the field of gas purification technology, specifically to a solid desulfurizing agent of iron hydroxyl oxide and its preparation method. Background Technology

[0002] In the purification of industrial gases such as natural gas, refinery gas, and biogas, the removal of hydrogen sulfide is a crucial step in ensuring equipment safety, product quality, and environmental compliance. Dry desulfurization, due to its advantages of simple operation, high desulfurization precision, and no wastewater discharge, has become the mainstream technology for the deep removal of low-concentration H2S. Iron hydroxyl oxide (FeOOH), with its high specific surface area, abundant mesoporous structure, and strong chemisorption properties for H2S, is widely recognized as an ideal active component in dry desulfurization and is extensively used in the fine desulfurization of various industrial gases.

[0003] Traditional iron hydroxyl oxide desulfurizers often employ simple composite systems of FeOOH and a single support (such as γ-Al₂O₃ or activated carbon), prepared through physical mixing or impregnation molding. The bond between FeOOH and the support relies solely on van der Waals forces or weak electrostatic interactions, lacking stable chemical bonds. During the desulfurization-regeneration cycle, temperature fluctuations during regeneration roasting and the scouring and impact of bed airflow can easily cause FeOOH to detach from the support surface, leading to continuous loss of active sites and a decrease in desulfurization capacity. Simultaneously, the system lacks directional conductivity design, resulting in Fe… 2+ Oxidized to Fe 3+ The regeneration of FeOOH is inefficient, easily leading to crystal collapse and sintering. Furthermore, FeOOH itself is brittle, and its mechanical strength supported only by the carrier is weak, making it prone to pulverization and increasing bed pressure drop. In addition, the simple pore structure makes FeOOH prone to agglomeration and blockage, resulting in a sharp drop in desulfurization efficiency under high temperature and humidity conditions. While existing technologies attempt to improve performance by optimizing the FeOOH crystal form, increasing the carrier ratio, improving the molding process, or adding conventional additives, these methods only partially optimize single-cycle sulfur capacity or initial strength, failing to address core issues such as weak interfacial bonding, inefficient regeneration, and easily damaged structure. They also cannot overcome the problem of insufficient cyclic stability of ferric hydroxyl oxide desulfurizers.

[0004] Therefore, there is an urgent need for a solid ferric hydroxide desulfurizer and its preparation method to improve the cyclic stability of the ferric hydroxide desulfurizer and meet the requirements for long-term stable operation of industrial dry desulfurization. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this application provides a solid desulfurizing agent of ferric hydroxide and its preparation method. By introducing plasma functional groups into carbon nanotubes and modifying them through polymer grafting, the application achieves the performance goals of preventing the active components from falling off, preventing structural pulverization, and achieving high regeneration efficiency.

[0006] In a first aspect, this application provides a solid desulfurizing agent of iron hydroxyl oxide, comprising α-FeOOH nanorods, modified carbon nanotubes, γ-Al2O3 and starch;

[0007] The modified carbon nanotubes were obtained by grafting polylactic acid after plasma nitriding pretreatment.

[0008] Preferably, the mass ratio of the α-FeOOH nanorods, modified carbon nanotubes, γ-Al2O3 and starch is (70-85):(2-5):(1-20):(3-6).

[0009] In this context, by introducing polar functional groups such as amino and hydroxyl groups onto the surface of carbon nanotubes through nitrogen plasma treatment, Fe-OC and Fe-NC coordination bonds are formed with iron hydroxyl oxide nanorods. Simultaneously, a grafted flexible polylactic acid layer compensates for thermal expansion differences, significantly enhancing the interfacial bonding between α-FeOOH and carbon nanotubes. The modified three-dimensional tubular structure of the carbon nanotubes constructs a highly efficient conductive network, accelerating the Fe... 2+ To Fe 3+ Electron transfer shortens the regeneration cycle and reduces crystal structure damage caused by valence cycling, significantly improving regeneration stability. Meanwhile, the mesoporous structure of modified carbon nanotubes forms hierarchical channels with starch pore-forming agents, and its surface polar functional groups help α-FeOOH nanorods to be uniformly dispersed, exposing more desulfurization active sites, accelerating H2S mass transfer efficiency, and supporting the desulfurizer to achieve high initial sulfur capacity and long penetration time.

[0010] Preferably, the α-FeOOH nanorods have a diameter of 40-50 nm and a length of 200-300 nm.

[0011] In this case, the 40-50nm diameter and 200-300nm length provide a huge specific surface area, shorten the H2S diffusion path, and increase the contact probability of active sites; the α-type crystal structure has higher thermal and chemical stability than other crystal forms (β, γ), ensuring recyclability.

[0012] Preferably, the γ-Al2O3 has a pore volume of 0.8-1.0 cm³ / g and a particle size of 1-5 μm; the starch has a particle size of 50-100 μm.

[0013] In this case, 0.8-1.0cm 3The / g pore volume provides three-dimensional interconnected channels, promoting H2S molecule diffusion and product transport; it forms a hydrogen bond network with the hydroxyl groups on the α-FeOOH surface, enhancing interfacial bonding and improving structural stability; the 1-5μm particle size provides skeletal support, compensating for the brittleness of α-FeOOH and improving overall compressive strength. Soluble starch forms a soft template during ball milling, improving slurry plasticity and facilitating extrusion molding; it completely decomposes during calcination, forming micropores, increasing specific surface area and sulfur capacity; and it forms a network structure during the drying stage of the wet green body, improving wet green body strength and preventing cracking.

[0014] Secondly, this application provides a method for preparing a solid desulfurizing agent of iron hydroxyl oxide, comprising the following steps:

[0015] S1: Carbon nanotubes are pretreated by plasma nitriding, mixed with polylactic acid solution, ultrasonically assisted blending, melted at high temperature, cooled to room temperature, and then precipitated and dried to obtain modified carbon nanotubes.

[0016] S2: Fe(NO3)3 solution and NaOH solution were mixed in an ultrasonic reactor, pH was controlled, and after aging and drying, α-FeOOH nanorods were obtained;

[0017] S3: Mix α-FeOOH nanorods, modified carbon nanotubes, γ-Al2O3, and starch, add deionized water, ball mill to form a slurry, and extrude it through a die to obtain a wet preform;

[0018] S4: The wet blank is dried in sections, then calcined in a nitrogen atmosphere and cooled to room temperature to obtain a solid desulfurizing agent of iron hydroxyl oxide.

[0019] In this context, nitrogen plasma pretreatment replaces traditional chemical oxidation, avoiding the introduction of impurities and improving surface activity and grafting efficiency; ultrasound-assisted synthesis ensures uniform particle size and good dispersion of nanomaterials, significantly improving the utilization rate of active sites; segmented drying and nitrogen calcination processes prevent material deformation and activity loss, ensuring stable performance of the final product.

[0020] Preferably, in step S1, the parameters for plasma nitriding pretreatment are: power of 80-120W, time of 15-20min, vacuum degree of 3-5Pa, nitrogen purity of 99.99-99.995%, nitrogen flow rate of 90-110mL / min, and cavity pressure of 8-12Pa; the power for ultrasonic-assisted blending is 45-55W, and the time is 50-60min; the temperature for high-temperature melting is 150-160℃, and the time is 60-90min.

[0021] Preferably, in S1, the solvent of the polylactic acid solution is dichloromethane and o-dichlorobenzene in a volume ratio of 1:1, the concentration of the polylactic acid solution is 9-11 wt%, and the molecular weight of the polylactic acid is 50,000-100,000.

[0022] In this case, the concentration of polylactic acid solution can balance the solution viscosity and the grafting amount. If the concentration is too low, the grafting amount will be insufficient and an effective flexible buffer layer cannot be formed. If the concentration is too high, the solution viscosity will be too high, which is not conducive to uniform mixing with carbon nanotubes. A molecular weight of 50,000-100,000 ensures that the flexible layer formed after polylactic acid grafting has sufficient mechanical strength and elasticity, which can compensate for the difference in thermal expansion and avoid the defects of easy detachment of the flexible layer due to too low molecular weight and insufficient flexibility due to too high molecular weight.

[0023] Preferably, in step S2, the stirring speed of the ultrasonic reactor is 180-220 rpm, and the ultrasonic power is 90-110 W; the concentration of the Fe(NO3)3 solution is 0.48-0.52 mol / L; the concentration of the NaOH solution is 0.98-1.02 mol / L, and the volume ratio of Fe(NO3)3 solution to NaOH solution is 1:(1.8-2.4); the pH is controlled at 8.5-9.5; the aging temperature is 55-60℃, and the aging time is 18-24 h; the drying temperature is 78-82℃, and the drying time is 11-13 h.

[0024] Preferably, in step S3, the ball milling conditions are: the ball milling speed is 380-420 rpm, the ball milling time is 10-14 h; and the size of the die head is Φ1.8×(2.2-3.2) mm.

[0025] Preferably, in step S4, the nitrogen flow rate in the nitrogen atmosphere is 90-110 mL / min, and the heating rate is 5℃ / min; the segmented drying is: first drying at 75-85℃ for 10-14 h, and then drying at 115-125℃ for 5-7 h; the calcination temperature is 390-410℃, and the time is 1.5-2 h.

[0026] In this case, the surface moisture is gradually removed in the low-temperature stage of the stage and the internal moisture is completely removed in the high-temperature stage to avoid the internal stress caused by rapid evaporation of moisture, which leads to particle cracking. The nitrogen flow rate is 90-110 mL / min to maintain an inert atmosphere during the calcination process to prevent α-FeOOH from being oxidized to Fe2O3, which has no desulfurization activity. The temperature is increased slowly to reduce the damage of thermal stress to the product structure and ensure that the product has a regular pore structure and stable crystal morphology after calcination.

[0027] Beneficial technical effects:

[0028] This application introduces polar functional groups such as amino and hydroxyl groups onto the surface of carbon nanotubes through nitrogen plasma treatment, forming Fe-OC and Fe-NC coordination bonds with iron hydroxyl oxide nanorods. Simultaneously, a grafted polylactic acid flexible layer compensates for differences in thermal expansion, significantly enhancing the interfacial bonding between α-FeOOH and carbon nanotubes. The modified three-dimensional tubular structure of the carbon nanotubes constructs a highly efficient conductive network, accelerating the Fe... 2+ To Fe 3+ The electron transfer shortens the regeneration cycle and reduces crystal structure damage caused by valence state cycling, significantly improving regeneration stability. At the same time, the mesoporous structure of the modified carbon nanotubes forms hierarchical channels with the starch pore-forming agent, and its surface polar functional groups help the α-FeOOH nanorods to be uniformly dispersed, exposing more desulfurization active sites, accelerating H2S mass transfer efficiency, and supporting the desulfurizer to achieve high initial sulfur capacity and long penetration time, thus solving the problem of insufficient cycle stability of traditional hydroxyl iron oxide desulfurizers during long-term desulfurization. Attached Figure Description

[0029] Figure 1 is a process flow diagram of the preparation process of a hydroxyl iron oxide solid desulfurizer according to this application. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are some embodiments of this application, but not all embodiments.

[0031] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0032] Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0033] The present invention will be further described below with reference to embodiments, but is not limited thereto.

[0034] Example 1

[0035] This embodiment provides a solid desulfurizing agent of iron hydroxyl oxide, comprising α-FeOOH nanorods, modified carbon nanotubes, γ-Al2O3 and starch, in a mass ratio of 70:3:10:3.

[0036] The α-FeOOH nanorods have a diameter of 40 nm and a length of 200 nm.

[0037] The γ-Al2O3 has a pore volume of 0.8 cm³ / g and a particle size of 2 μm; the starch has a particle size of 50 μm.

[0038] As shown in Figure 1, this embodiment provides a method for preparing a solid desulfurizing agent of iron hydroxyl oxide, including the following steps:

[0039] S1: Carbon nanotubes were pretreated with 80W plasma nitriding for 15 min with the following parameters: vacuum degree 3 Pa, nitrogen purity 99.99%, nitrogen flow rate 90 mL / min, and cavity pressure 8 Pa. 9 wt.% polylactic acid solution was added and mixed. The mixture was ultrasonically assisted by 45W for 50 min, melted at 155℃ for 85 min, precipitated, and then vacuum dried at 80℃ to obtain modified carbon nanotubes.

[0040] S2: 0.48 mol / L Fe(NO3)3 solution and 0.98 mol / L NaOH solution were mixed in a 90W, 180rpm ultrasonic reactor, the pH was controlled at 8.5, aged at 55℃ for 20h, and dried at 78℃ for 11h to obtain α-FeOOH nanorods.

[0041] S3: α-FeOOH nanorods, modified carbon nanotubes, γ-Al2O3 and starch are mixed, deionized water is added, and the mixture is ball-milled at 420 rpm for 14 h to make a slurry. The slurry is then extruded through a Φ1.8×2.2 mm die to obtain a wet preform.

[0042] S4: The wet blank is dried in stages. First, it is dried at 75℃ for 14 hours, then at 115℃ for 7 hours, and then calcined at 390℃ for 1.5 hours in a nitrogen atmosphere (nitrogen flow rate 110mL / min, heating rate 5℃ / min). After cooling to room temperature, the solid desulfurizing agent of iron hydroxyl oxide is obtained.

[0043] Example 2

[0044] This embodiment provides a solid desulfurizing agent of iron hydroxyl oxide, comprising α-FeOOH nanorods, modified carbon nanotubes, γ-Al2O3 and starch in a mass ratio of 80:5:9:4.

[0045] The α-FeOOH nanorods have a diameter of 50 nm and a length of 250 nm.

[0046] The γ-Al2O3 has a pore volume of 1.0 cm³ / g and a particle size of 3 μm; the starch has a particle size of 70 μm.

[0047] As shown in Figure 1, this embodiment provides a method for preparing a solid desulfurizing agent of iron hydroxyl oxide, including the following steps:

[0048] S1: Carbon nanotubes were pretreated with 80W plasma nitriding for 15 min with the following parameters: vacuum degree 3 Pa, nitrogen purity 99.99%, nitrogen flow rate 90 mL / min, and cavity pressure 8 Pa. 9 wt.% polylactic acid solution was added and mixed. The mixture was ultrasonically assisted by 45W for 50 min, melted at 155℃ for 85 min, precipitated, and then vacuum dried at 80℃ to obtain modified carbon nanotubes.

[0049] S2: Mix 0.48 mol / L Fe(NO3)3 solution and 0.98 mol / L NaOH solution in a 100W, 180rpm ultrasonic reactor, control the pH to 9, age at 60℃ for 24h, and dry at 78℃ for 11h to obtain α-FeOOH nanorods.

[0050] S3: α-FeOOH nanorods, modified carbon nanotubes, γ-Al2O3 and starch are mixed, deionized water is added, and the mixture is ball-milled at 420 rpm for 14 h to make a slurry. The slurry is then extruded through a Φ1.8×2.2 mm die to obtain a wet preform.

[0051] S4: The wet blank is dried in stages. First, it is dried at 85℃ for 10 hours, then at 115℃ for 5 hours, and then calcined at 390℃ for 1.8 hours in a nitrogen atmosphere (nitrogen flow rate 110mL / min, heating rate 5℃ / min). After cooling to room temperature, the solid desulfurizing agent of iron hydroxyl oxide is obtained.

[0052] Example 3

[0053] This embodiment provides a solid desulfurizing agent of iron hydroxyl oxide, comprising α-FeOOH nanorods, modified carbon nanotubes, γ-Al2O3 and starch, in a mass ratio of 75:3:12:5.

[0054] The α-FeOOH nanorods have a diameter of 50 nm and a length of 250 nm.

[0055] The γ-Al2O3 has a pore volume of 1.0 cm³ / g and a particle size of 3 μm; the starch has a particle size of 70 μm.

[0056] As shown in Figure 1, this embodiment provides a method for preparing a solid desulfurizing agent of iron hydroxyl oxide, including the following steps:

[0057] S1: Carbon nanotubes were pretreated with 120W plasma nitriding for 15 min with the following parameters: vacuum degree 3 Pa, nitrogen purity 99.99%, nitrogen flow rate 110 mL / min, and cavity pressure 12 Pa. 11 wt.% polylactic acid solution was added and mixed. The mixture was ultrasonically assisted by 45W for 50 min, melted at 165℃ for 95 min, precipitated, and then vacuum dried at 80℃ to obtain modified carbon nanotubes.

[0058] S2: 0.48 mol / L Fe(NO3)3 solution and 0.98 mol / L NaOH solution were mixed in a 110W, 220rpm ultrasonic reactor, the pH was controlled at 9, aged at 55℃ for 18h, and dried at 78℃ for 11h to obtain α-FeOOH nanorods.

[0059] S3: α-FeOOH nanorods, modified carbon nanotubes, γ-Al2O3 and starch are mixed, deionized water is added, and the mixture is ball-milled at 420 rpm for 14 h to make a slurry. The slurry is then extruded through a Φ1.8×2.2 mm die to obtain a wet preform.

[0060] S4: The wet blank is dried in stages. First, it is dried at 75℃ for 14 hours, then at 115℃ for 7 hours, and then calcined at 410℃ for 2.0 hours in a nitrogen atmosphere (nitrogen flow rate 100mL / min, heating rate 5℃ / min). After cooling to room temperature, the solid desulfurizing agent of iron hydroxyl oxide is obtained.

[0061] Example 4

[0062] This embodiment provides a solid desulfurizing agent of iron hydroxyl oxide, comprising α-FeOOH nanorods, modified carbon nanotubes, γ-Al2O3 and starch in a mass ratio of 70:5:18:6.

[0063] The α-FeOOH nanorods have a diameter of 45 nm and a length of 260 nm.

[0064] The γ-Al2O3 has a pore volume of 0.9 cm³ / g and a particle size of 2 μm; the starch has a particle size of 70 μm.

[0065] As shown in Figure 1, this embodiment provides a method for preparing a solid desulfurizing agent of iron hydroxyl oxide, including the following steps:

[0066] S1: Carbon nanotubes were pretreated with 120W plasma nitriding for 20 min with the following parameters: vacuum degree 5 Pa, nitrogen purity 99.99%, nitrogen flow rate 110 mL / min, and cavity pressure 8 Pa. 9 wt.% polylactic acid solution was added and mixed. The mixture was ultrasonically assisted by 45W for 50 min, melted at 155℃ for 85 min, precipitated, and then vacuum dried at 80℃ to obtain modified carbon nanotubes.

[0067] S2: 0.48 mol / L Fe(NO3)3 solution and 0.98 mol / L NaOH solution were mixed in a 90W, 200rpm ultrasonic reactor, the pH was controlled at 9, aged at 60℃ for 24h, and dried at 78℃ for 11h to obtain α-FeOOH nanorods;

[0068] S3: α-FeOOH nanorods, modified carbon nanotubes, γ-Al2O3 and starch are mixed, deionized water is added, and the mixture is ball-milled at 420 rpm for 14 h to make a slurry. The slurry is then extruded through a Φ1.8×2.2 mm die to obtain a wet preform.

[0069] S4: The wet blank is dried in stages. First, it is dried at 85℃ for 14 hours, then at 120℃ for 6 hours, and then calcined at 400℃ for 2 hours in a nitrogen atmosphere (nitrogen flow rate 100mL / min, heating rate 5℃ / min). After cooling to room temperature, the solid desulfurizing agent of iron hydroxyl oxide is obtained.

[0070] Example 5

[0071] This embodiment provides a solid desulfurizing agent of iron hydroxyl oxide, comprising α-FeOOH nanorods, modified carbon nanotubes, γ-Al2O3 and starch, in a mass ratio of 80:5:18:5.

[0072] The α-FeOOH nanorods have a diameter of 50 nm and a length of 300 nm.

[0073] The γ-Al2O3 has a pore volume of 1.0 cm³ / g and a particle size of 5 μm; the starch has a particle size of 100 μm.

[0074] As shown in Figure 1, this embodiment provides a method for preparing a solid desulfurizing agent of iron hydroxyl oxide, including the following steps:

[0075] S1: Carbon nanotubes were pretreated with 120W plasma nitriding for 20 min with the following parameters: vacuum degree 4 Pa, nitrogen purity 99.99%, nitrogen flow rate 100 mL / min, and cavity pressure 10 Pa. 10.wt% polylactic acid solution was added and mixed. Ultrasonic blending was performed with a power of 55W for 50 min. The mixture was then melted at 155℃ for 95 min, precipitated, and vacuum dried at 80℃ to obtain modified carbon nanotubes.

[0076] S2: 0.48 mol / L Fe(NO3)3 solution and 0.98 mol / L NaOH solution were mixed in a 100W, 190rpm ultrasonic reactor, the pH was controlled at 9, aged at 60℃ for 24h, and dried at 78℃ for 11h to obtain α-FeOOH nanorods.

[0077] S3: α-FeOOH nanorods, modified carbon nanotubes, γ-Al2O3 and starch are mixed, deionized water is added, and the mixture is ball-milled at 420 rpm for 14 h to make a slurry. The slurry is then extruded through a Φ1.8×2.2 mm die to obtain a wet preform.

[0078] S4: The wet blank is dried in stages. First, it is dried at 80℃ for 13 hours, then at 120℃ for 7 hours, and then calcined at 390℃ for 2.2 hours in a nitrogen atmosphere (nitrogen flow rate 110 mL / min, heating rate 5℃ / min). After cooling to room temperature, the solid desulfurizing agent of iron hydroxyl oxide is obtained.

[0079] Example 6

[0080] This embodiment provides a solid desulfurizing agent containing iron hydroxyl oxide, comprising α-FeOOH nanorods, modified carbon nanotubes, γ-Al2O3, and starch in a mass ratio of 75:5:20:5.

[0081] The α-FeOOH nanorods have a diameter of 50 nm and a length of 200 nm.

[0082] The γ-Al2O3 has a pore volume of 1.0 cm³ / g and a particle size of 4 μm; the starch has a particle size of 60 μm.

[0083] As shown in Figure 1, this embodiment provides a method for preparing a solid desulfurizing agent of iron hydroxyl oxide, including the following steps:

[0084] S1: Carbon nanotubes were pretreated with 120W plasma nitriding for 20 min with the following parameters: vacuum degree 3 Pa, nitrogen purity 99.99%, nitrogen flow rate 90 mL / min, and cavity pressure 8 Pa. 9 wt.% polylactic acid solution was added and mixed. The mixture was ultrasonically assisted by 55W for 50 min, melted at 165℃ for 95 min, precipitated, and then vacuum dried at 80℃ to obtain modified carbon nanotubes.

[0085] S2: 0.48 mol / L Fe(NO3)3 solution and 0.98 mol / L NaOH solution were mixed in a 90W, 180rpm ultrasonic reactor, the pH was controlled at 8.5, aged at 60℃ for 24h, and dried at 78℃ for 11h to obtain α-FeOOH nanorods;

[0086] S3: α-FeOOH nanorods, modified carbon nanotubes, γ-Al2O3 and starch are mixed, deionized water is added, and the mixture is ball-milled at 420 rpm for 14 h to make a slurry. The slurry is then extruded through a Φ1.8×2.2 mm die to obtain a wet preform.

[0087] S4: The wet blank is dried in stages. First, it is dried at 85℃ for 12 hours, then at 120℃ for 6 hours, and then calcined at 400℃ for 2 hours in a nitrogen atmosphere (nitrogen flow rate 100mL / min, heating rate 5℃ / min). After cooling to room temperature, the solid desulfurizing agent of iron hydroxyl oxide is obtained.

[0088] Comparative Example 1

[0089] This comparative example provides a solid desulfurizing agent of hydroxyl iron oxide and its preparation method. The difference from Example 1 is that modified carbon nanotubes are not added in step S, and the other components and preparation method are the same as in Example 1.

[0090] Comparative Example 2

[0091] This comparative example provides a solid desulfurizing agent of ferric hydroxide and its preparation method. The difference from Example 1 is that in step S, the modified carbon nanotubes are replaced with unmodified carbon nanotubes, while the other components and preparation methods are the same as in Example 1.

[0092] Comparative Example 3

[0093] This comparative example provides a solid desulfurizing agent of hydroxyl iron oxide and its preparation method. The difference from Example 1 is that in step S, the modified carbon nanotubes are replaced with carbon nanotubes that have only undergone plasma nitriding treatment and have no polylactic acid grafting. The other components and preparation methods are the same as in Example 1.

[0094] The initial sulfur capacity, sulfur capacity retention rate (8 regenerations), compressive strength and anti-pulverization rate (%) of the hydroxyl iron oxide solid desulfurizers prepared in Examples 1-6 and Comparative Examples 1-3 of this application were tested and compared. The results are shown in Table 1.

[0095] Test method:

[0096] Initial sulfur capacity: The ratio of sulfur mass to the desulfurizer's own mass when the desulfurizer is saturated was determined by simulating an adsorption experiment of H2S-containing feed gas.

[0097] Sulfur capacity retention rate: After 8 adsorption-regeneration cycles, the percentage of the final sulfur capacity to the initial sulfur capacity is measured.

[0098] Compressive strength: The maximum compressive strength of the desulfurizing agent particles when they break is determined by mechanical testing, and the average value is taken.

[0099] Anti-pulverization rate: After the desulfurizer is treated with water for 2 hours, the percentage of the mass of unpulverized particles to the initial mass is measured.

[0100] Table 1. Performance test results of a solid desulfurizing agent of iron hydroxide in the examples and comparative examples.

[0101]

[0102] Examples 1-6 of this application introduce polar functional groups such as amino and hydroxyl groups onto the surface of carbon nanotubes through nitrogen plasma treatment, forming Fe-OC and Fe-NC coordination bonds with hydroxyl iron oxide nanorods. Simultaneously, a grafted polylactic acid flexible layer compensates for differences in thermal expansion, significantly enhancing the interfacial bonding force between α-FeOOH and carbon nanotubes. The modified three-dimensional tubular structure of the carbon nanotubes constructs a highly efficient conductive network, accelerating the Fe...2+ To Fe 3+ The electron transfer shortens the regeneration cycle and reduces crystal structure damage caused by valence state cycling, significantly improving regeneration stability. At the same time, the mesoporous structure of the modified carbon nanotubes forms hierarchical channels with the starch pore-forming agent, and its surface polar functional groups help the α-FeOOH nanorods to be uniformly dispersed, exposing more desulfurization active sites, accelerating H2S mass transfer efficiency, and supporting the desulfurizer to achieve high initial sulfur capacity and long penetration time, thus solving the problem of insufficient cycle stability of traditional hydroxyl iron oxide desulfurizers during long-term desulfurization.

[0103] In Comparative Example 1, the lack of carbon nanotubes resulted in a desulfurizing agent system that lacked a three-dimensional conductive network and a rigid supporting framework, thus failing to accelerate the Fe regeneration process. 2+ To Fe 3+ The electron transfer is difficult, and it is difficult to strengthen the interfacial bonding between α-FeOOH and γ-Al2O3. At the same time, there is no additional mesoporous structure to assist mass transfer, resulting in a significant decrease in the regeneration stability, mechanical strength and mass transfer efficiency of the desulfurizer. Comparative Example 2 uses unmodified carbon nanotubes with an inert graphite structure on the surface, which cannot form Fe-OC and Fe-NC coordination bonds with α-FeOOH. It relies solely on physical adsorption and is prone to interfacial peeling during cycling. Moreover, there is no flexible layer to compensate for the difference in thermal expansion, and the structural stress concentration easily leads to the shedding of active components and particle pulverization. Comparative Example 3 uses carbon nanotubes that have only undergone plasma nitriding treatment without polylactic acid grafting. Although polar functional groups can be introduced to form coordination bonds with α-FeOOH, the lack of a polylactic acid flexible buffer layer cannot compensate for the difference in thermal expansion between carbon nanotubes and α-FeOOH. Temperature fluctuations during cycling easily lead to interfacial peeling. At the same time, there is no flexible layer to assist in improving structural toughness, and the desulfurizer's anti-pulverization ability and regeneration stability are still not optimal.

[0104] It should be understood that the above are only some embodiments of the present invention. It should be pointed out that for those skilled in the art, other modifications and improvements can be made without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A solid desulfurizing agent containing iron hydroxyl oxide, characterized in that, It includes α-FeOOH nanorods, modified carbon nanotubes, γ-Al2O3 and starch; the modified carbon nanotubes are obtained by grafting polylactic acid after plasma nitriding pretreatment.

2. The hydroxyl iron oxide solid desulfurizer according to claim 1, characterized in that, The mass ratio of the α-FeOOH nanorods, modified carbon nanotubes, γ-Al2O3 and starch is (70-85):(2-5):(1-20):(3-6).

3. The hydroxyl iron oxide solid desulfurizer according to claim 1, characterized in that, The α-FeOOH nanorods have a diameter of 40-50 nm and a length of 200-300 nm.

4. The hydroxyl iron oxide solid desulfurizer according to claim 1, characterized in that, The γ-Al2O3 has a pore volume of 0.8-1.0 cm³ / g and a particle size of 1-5 μm; the starch has a particle size of 50-100 μm.

5. A method for preparing a solid desulfurizing agent of ferric hydroxide according to any one of claims 1-4, characterized in that, Includes the following steps: S1: Carbon nanotubes are pretreated by plasma nitriding, mixed with polylactic acid solution, ultrasonically assisted blending, melted at high temperature, cooled to room temperature, and then precipitated and dried to obtain modified carbon nanotubes. S2: Fe(NO3)3 solution and NaOH solution are mixed in an ultrasonic reactor, pH is controlled, and after aging and drying, α-FeOOH nanorods are obtained; S3: α-FeOOH nanorods, modified carbon nanotubes, γ-Al2O3 and starch are mixed, deionized water is added, ball milling is performed to form a slurry, and the slurry is extruded through a die to obtain a wet green body; S4: The wet green body is dried in sections, then calcined under a nitrogen atmosphere and cooled to room temperature to obtain a solid desulfurizing agent of iron hydroxyl oxide.

6. The method for preparing a solid desulfurizing agent of ferric hydroxide according to claim 5, characterized in that, In S1, the parameters for plasma nitriding pretreatment are as follows: power 80-120W, time 15-20min, vacuum degree 3-5Pa, nitrogen purity 99.99-99.995%, nitrogen flow rate 90-110mL / min, and cavity pressure 8-12Pa; the power for ultrasonic-assisted blending is 45-55W, and the time is 50-60min; the temperature for high-temperature melting is 150-160℃, and the time is 60-90min.

7. The method for preparing a solid desulfurizing agent of ferric hydroxide according to claim 5, characterized in that, In S1, the solvent of the polylactic acid solution is dichloromethane and o-dichlorobenzene in a volume ratio of 1:1, the concentration of the polylactic acid solution is 9-11 wt%, and the molecular weight of the polylactic acid is 50,000-100,000.

8. The method for preparing a solid desulfurizing agent of ferric hydroxide according to claim 5, characterized in that, In step S2, the stirring speed of the ultrasonic reactor is 180-220 rpm, and the ultrasonic power is 90-110 W; the concentration of the Fe(NO3)3 solution is 0.48-0.52 mol / L; the concentration of the NaOH solution is 0.98-1.02 mol / L, and the volume ratio of Fe(NO3)3 solution to NaOH solution is 1:(1.8-2.4); the pH is controlled at 8.5-9.5; the aging temperature is 55-60℃, and the aging time is 18-24 h; the drying temperature is 78-82℃, and the drying time is 11-13 h.

9. The method for preparing a solid desulfurizing agent of ferric hydroxide according to claim 5, characterized in that, In S3, the ball milling conditions are: the ball milling speed is 380-420 rpm, and the ball milling time is 10-14 h; the size of the die head is Φ1.8×(2.2-3.2) mm.

10. The method for preparing a solid desulfurizing agent of ferric hydroxide according to claim 5, characterized in that, In step S4, the nitrogen flow rate in the nitrogen atmosphere is 90-110 mL / min, and the heating rate is 5℃ / min; the segmented drying is: first drying at 75-85℃ for 10-14 h, and then drying at 115-125℃ for 5-7 h; the calcination temperature is 390-410℃, and the time is 1.5-2 h.

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