Iron oxyhydroxide desulfurizer and method for preparing the same

Abstract

The present application relates to the technical field of desulfurizer, and particularly relates to a kind of ferric oxyhydroxide desulfurizer and its preparation method.The present application aims to solve the problems of low particle mechanical strength, easy pulverization, bed pressure drop rising and unreasonable pore structure leading to insufficient sulfur capacity release in the deep purification of low-concentration hydrogen sulfide with existing desulfurizer.The preparation method comprises the following steps: taking ferric nitrate as iron source, generating ferric oxyhydroxide slurry through urea hydrolysis reaction, modifying and constructing surface anchoring sites through sodium citrate complexation; introducing hexadecyl trimethyl ammonium bromide and sodium salicylate micellar template to directionally construct mesoporous structure; then strengthening surface density through kneading, salt solution spraying and wet heat aging; finally, removing the template through hydrogen peroxide treatment.The obtained desulfurizer has high mechanical strength, low abrasion rate, excellent mesoporous structure and long low-concentration breakthrough life, and is suitable for low-concentration long-period scenarios such as city gas purification.

Description

Technical Field

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

[0002] Ferric hydroxyl oxide (FHO) desulfurizers, as core materials in dry desulfurization technology, are widely used in scenarios involving the deep removal of low-concentration hydrogen sulfide, such as urban gas purification and fuel cell intake protection. These applications require desulfurizers to possess extremely high leakage tolerance and stability, as the concentration of hydrogen sulfide in the intake air is often as low as ppm or even sub-ppm, and continuous operation for thousands of hours is required. However, traditional FHO desulfurizers exhibit significant drawbacks under long-term low-concentration conditions: their particle mechanical strength is generally insufficient, and they are prone to pulverization during loading and operation due to vibration and airflow erosion. The resulting fine powder migration gradually clogs the bed pores, causing a continuous increase in pressure drop, ultimately leading to increased system energy consumption or even forced shutdown.

[0003] A deeper problem lies in the fact that the pore structure design of traditional materials often focuses on high specific surface area, but this often results in micropores or a discrete pore size distribution. While microporous structures are beneficial for increasing the initial reaction rate, they are difficult to effectively diffuse the elemental sulfur or other solid products generated in the reaction. As the reaction proceeds, sulfides accumulate within the pores, gradually blocking mass transfer pathways and preventing the full utilization of internal active sites. This leads to a sharp decline in the desulfurizing agent's reaction rate in the later stages, with the actual sulfur capacity far below the theoretical value. This pore blockage effect is particularly pronounced in low-concentration, long-cycle operation, where the slow reaction rate makes it easier for products to accumulate locally, forming dead zones.

[0004] Current manufacturing processes aim to balance strength and pore structure, often employing strategies such as increasing binder dosage or introducing simple pore-forming agents (e.g., starch, wood flour). However, while high binder content can improve particle strength, it sacrifices pore volume and pore size, leading to increased mass transfer resistance. Simple pore-forming agents, while creating pores, suffer from poor channel connectivity and disordered distribution, failing to synergistically optimize diffusion and reaction kinetics. Furthermore, conventional molding processes such as tableting or extrusion often neglect densification of the particle surface, making it more prone to wear and pulverization during operation, accelerating bed pressure drop deterioration. These shortcomings collectively limit the technical ceiling of traditional desulfurizers under low concentration and high space velocity conditions, making it difficult to meet the comprehensive demands of modern industry for low pressure drop, long lifespan, and high sulfur release rate. Summary of the Invention

[0005] In view of this, the purpose of this invention is to propose a hydroxyl iron oxide desulfurizing agent and its preparation method, so as to solve the problems of existing hydroxyl iron oxide desulfurizing agents in the deep purification process of low concentration hydrogen sulfide, which are caused by low particle mechanical strength and easy pulverization leading to increased bed pressure drop, and unreasonable pore structure leading to retention of reaction products and insufficient release of sulfur capacity, making it difficult to meet the requirements of long-term operation.

[0006] To achieve the above objectives, the present invention provides a method for preparing an iron hydroxyl oxide desulfurizing agent, comprising the following steps: (1) Prepare an iron-containing precursor solution using ferric nitrate nonahydrate as the iron source; add urea to the iron-containing precursor solution, heat to 85-95℃ for hydrolysis reaction for 50-70 min, cool to 70℃, add complexing modification solution containing trisodium citrate dihydrate, complex modification for 20-40 min, cool to 65℃, and obtain modified slurry; (2) Prepare micelle mother liquor by mixing hexadecyltrimethylammonium bromide, sodium salicylate and deionized water. Add the micelle mother liquor to the modified slurry obtained in step (1) and react for 45-75 min. Filter, then wash with sodium chloride solution and dry to obtain modified iron hydroxyl oxide powder. (3) Modified iron hydroxyl oxide powder, bentonite, colloidal silica aqueous dispersion and deionized water are kneaded to obtain plastic wet material, which is then extruded and rolled into wet granules; sodium chloride solution is sprayed onto the surface of wet granules under tumbling condition, and then dried under wet heat aging at 50-70℃ for 4-10h to obtain intermediate granules; after being washed with deionized water, they are placed in hydrogen peroxide solution and treated at 50-60℃ for 60-150min, then washed and dried to obtain iron hydroxyl oxide desulfurizer.

[0007] Furthermore, based on 404 parts by weight of ferric nitrate nonahydrate, the amount of urea added is 160-200 parts, the amount of trisodium citrate dihydrate added is 5-25 parts, the amount of hexadecyltrimethylammonium bromide added is 12-24 parts, and the amount of sodium salicylate added is 8-18 parts; desulfurizing agent Furthermore, based on 500 parts by weight of modified iron hydroxyl oxide powder, the amount of sodium chloride solution added is 80-160 parts.

[0008] Preferably, the concentration of the sodium chloride solution is 15wt%-25wt%.

[0009] Preferably, the iron-containing precursor solution is prepared from 3000 parts of deionized water, 404 parts of ferric nitrate nonahydrate, 80-160 parts of sodium chloride and 60-150 parts of polyvinylpyrrolidone K30.

[0010] Preferably, the concentration of the sodium chloride washing solution is 1wt%-3wt% by mass.

[0011] Preferably, in the raw materials for preparing the plastic wet material, the mass ratio of modified ferric hydroxide powder, bentonite, colloidal silica aqueous dispersion and deionized water is 500:8-15:25-40:380-420.

[0012] Preferably, the silica content in the silica aqueous dispersion is 25wt%-35wt%.

[0013] Preferably, the concentration of the hydrogen peroxide solution is 0.5wt%-2wt%.

[0014] Preferably, the plastic wet material is obtained by kneading at room temperature for 10-20 minutes.

[0015] Preferably, the extrusion uses an extrusion plate with a pore size of 3mm, the spherical rotation speed is 700-900rpm, and the spherical rotation time is 8-12min.

[0016] Preferably, the damp heat aging is carried out in a closed damp heat aging chamber, and the moisture source is provided in a manner in which the particles do not come into direct contact with the water.

[0017] Furthermore, the present invention also provides a hydroxyl iron oxide desulfurizing agent, which is obtained by the preparation method of the hydroxyl iron oxide desulfurizing agent preparation method.

[0018] This invention effectively regulates the nucleation and growth process of primary iron hydroxyl oxide particles by introducing the synergistic effect of sodium chloride and polyvinylpyrrolidone K30 during the nucleation stage. The synergistic effect of the high ionic strength environment and the polymer adsorbent inhibits disordered agglomeration between particles, promoting the formation of a matrix structure with stronger cohesion and a more stable framework. This structural basis provides support for subsequent low-binder molding, significantly reducing the tendency of particles to pulverize during operation, thereby reducing the risk of increased bed pressure drop caused by fine powder migration and improving the mechanical durability and long-term operational stability of the desulfurizer.

[0019] A complexation modification of ferric hydroxide slurry was performed using trisodium citrate dihydrate to construct polycarboxylic acid anionic anchoring sites on its surface. This modification step resulted in a stable charge distribution on the material surface, laying the foundation for the directional adsorption of the template agent. The polycarboxylic acid sites effectively guided the micellar template to be uniformly fixed on the particle surface, preventing random encapsulation or local aggregation, thus forming well-connected mesoporous channels with a concentrated pore size distribution after template removal. This ordered pore structure facilitates the efficient diffusion of reactant gases and the timely removal of sulfur products, alleviating pore blockage problems and improving the sulfur release efficiency under low-concentration hydrogen sulfide conditions.

[0020] A composite micelle mother liquor composed of hexadecyltrimethylammonium bromide and sodium salicylate was used for template construction. Combined with a post-treatment sequence of sodium chloride solution spraying and hydrothermal aging, synergistic optimization of the particle surface and bulk structure was achieved. After directional fixation, the micelle template can form a permeable mesoporous network through oxidation removal, enhancing mass transfer capacity. Meanwhile, the dissolution-rearrangement-reconsolidation process induced by surface salt treatment and hydrothermal aging promotes the formation of a denser structure on the particle shell, effectively suppressing dust generation and migration during operation. This internally sparse and externally dense structural design maintains high mesopore volume while strengthening particle boundary strength, giving the desulfurizer both excellent diffusion kinetics and mechanical stability, thus enabling long-term, low-pressure-drop, and highly efficient operation in low-concentration, deep-purification scenarios. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0022] Example 1: The raw materials used in this embodiment are sourced as follows: Bentonite is from Sigma-Aldrich, catalog number 285234; colloidal silica aqueous dispersion is from Sigma-Aldrich, catalog number 420794, trade name LUDOX SM, with a silica content of 30wt%.

[0023] S1: Add 3000g of deionized water to a stirred reaction vessel, start stirring at 400rpm and control the temperature at 25℃; add 404g of ferric nitrate nonahydrate, 120g of sodium chloride, and 110g of polyvinylpyrrolidone K30 in sequence, and continue stirring for 30min; then let stand for 5min to remove large air bubbles, and obtain an iron-containing homogeneous precursor solution; then add 180g of urea, maintain stirring at 500rpm and raise the temperature to 90℃ within 20min, stir at 90℃ for 60min, and let it cool naturally to 70℃; dissolve 15g of trisodium citrate dihydrate in 200g of deionized water to prepare a complexing modification solution; slowly add the above complexing modification solution to the 70℃ slurry within 5min, and increase stirring to 600rpm to continue the reaction for 30min, and then lower the system temperature to 65℃ for later use; S2: Add 18g of hexadecyltrimethylammonium bromide and 12g of sodium salicylate to 300g of deionized water, stir at 60℃ for 30min, and let stand for 20min to obtain micelle mother liquor; slowly add the micelle mother liquor along the reactor wall to the slurry obtained in step S1 at 65℃ within 15min, maintaining stirring at 300rpm during the addition process, and after the addition is completed, maintain stirring at 65℃ and 300rpm for 60min, and then cool down to 40℃; filter to obtain a wet filter cake, then perform a displacement washing with sodium chloride washing solution (concentration 2wt%), and finally dry at 80℃ for 6h to obtain modified iron hydroxyl oxide powder; S3: Add 500g of modified iron hydroxide powder to a kneading device, followed by 10g of bentonite, 30g of colloidal silica aqueous dispersion (30wt% silica content), and 400g of deionized water. Knead for 15 minutes at room temperature to obtain a plastic wet material. Then, extrude the wet material into strips through a 3mm aperture extrusion plate, and roll it in a rotating disc at 800rpm for 10 minutes. Sieve to obtain wet particles with a particle size of 3mm-5mm. Add the particles to a rotating mixing drum and tumble at 30rpm. While tumbling, spray 120g of sodium chloride solution (20wt% concentration) evenly over 10 minutes. The wet granules were tumbled for 10 minutes to obtain a surface layer of salt-containing wet granules. These were then evenly spread on a tray, and 500g of deionized water was added to the bottom of a sealed humid heat aging chamber as a moisture source (the bottom of the tray containing the wet granules was 80mm from the liquid surface, and the thickness of the spread material was controlled at 15mm). The tray was then aged at 60℃ for 6 hours. After aging, the granules were dried at 80℃ for 6 hours to obtain dried intermediate granules. These granules were then rinsed three times in deionized water. Finally, they were treated in a hydrogen peroxide solution (1wt%) at 60℃ for 120 minutes, rinsed twice in deionized water, and dried at 80℃ for 6 hours to obtain hydroxyl iron oxide desulfurizer.

[0024] Example 2: The difference from Example 1 is as follows: In step S1, the amount of sodium chloride is 80g, the amount of polyvinylpyrrolidone K30 is 130g, and the amount of trisodium citrate dihydrate in the complexing modification solution is 10g; in step S2, the amount of hexadecyltrimethylammonium bromide is 16g, sodium salicylate is 12g, and deionized water is 280g; in step S3, the amount of bentonite is 8g, the amount of colloidal silica aqueous dispersion is 25g, the amount of deionized water is 380g, the rolling speed of the rolling disc is 850rpm, and the rolling time is 10min; the amount of sodium chloride solution sprayed is 140g with a concentration of 25wt%, and the aging temperature of the closed humid heat aging chamber is 65℃ for 8h. All other conditions are the same as in Example 1.

[0025] Example 3: The difference from Example 1 is as follows: In step S1, the amount of polyvinylpyrrolidone K30 used is 90g, and the amount of trisodium citrate dihydrate in the complexing modification solution is 25g; in step S2, the amount of hexadecyltrimethylammonium bromide used is 24g, sodium salicylate is 18g, and deionized water is 350g; in step S3, the amount of sodium chloride solution sprayed is 100g with a concentration of 15wt%, the aging temperature in the closed humid heat aging chamber is 55℃, and the aging time is 6h; the concentration of hydrogen peroxide solution is 1.5wt%. All other conditions are the same as in Example 1.

[0026] Example 4: The difference from Example 1 is as follows: In step S1, the amount of sodium chloride used is 160g, the amount of polyvinylpyrrolidone K30 used is 150g, and the amount of trisodium citrate dihydrate in the complexation modification solution is 20g; in step S2, the amount of sodium salicylate used is 10g; in step S3, the amount of bentonite used is 15g, the amount of colloidal silica aqueous dispersion used is 40g, the amount of deionized water used is 420g, the rolling speed of the rolling disc is 900rpm, and the rolling time is 12min; the amount of sodium chloride solution sprayed is 160g, the concentration is 25wt%, and the aging temperature of the closed humid heat aging chamber is 70℃, and the aging time is 10h. All other conditions are the same as in Example 1.

[0027] Example 5: The difference from Example 1 is as follows: in step S1, the amount of sodium chloride and polyvinylpyrrolidone K30 used is 100g; in step S2, the amount of hexadecyltrimethylammonium bromide used is 20g, sodium salicylate used is 14g, and deionized water used is 320g; in step S3, the concentration of hydrogen peroxide solution is 0.5wt%, and the treatment time of hydrogen peroxide solution is 150min. All other conditions are the same as in Example 1.

[0028] Example 6: The difference from Example 1 is as follows: In step S1, the amount of polyvinylpyrrolidone K30 used is 60g, and the amount of trisodium citrate dihydrate in the complexation modification solution is 5g; in step S2, the amount of hexadecyltrimethylammonium bromide used is 12g, sodium salicylate used is 8g, and deionized water used is 250g; in step S3, the amount of bentonite used is 12g, the amount of colloidal silica aqueous dispersion used is 35g, the rolling speed of the rolling disc is 700rpm, and the rolling time is 8min; the amount of sodium chloride solution sprayed is 80g, the concentration is 20wt%, the aging temperature of the sealed humid heat aging chamber is 50℃, and the aging time is 4h; the concentration of hydrogen peroxide solution is 2wt%, the hydrogen peroxide solution treatment temperature is 50℃, and the treatment time is 60min. All other conditions are the same as in Example 1.

[0029] Comparative Example 1: The difference from Example 1 is that sodium chloride is not added in step S1 (the amount of sodium chloride used is 0g), and the other conditions are the same as in Example 1.

[0030] Comparative Example 2: The difference from Example 1 is that polyvinylpyrrolidone K30 is not added in step S1 (the amount of polyvinylpyrrolidone K30 is 0g), and the other conditions are the same as in Example 1.

[0031] Comparative Example 3: The difference from Example 1 is that the complexing modification solution in step S1 does not contain trisodium citrate dihydrate. Instead of dissolving 15g of trisodium citrate dihydrate in 200g of deionized water to prepare the complexing modification solution, only 200g of deionized water is added, without adding trisodium citrate dihydrate. The other conditions are the same as in Example 1.

[0032] Comparative Example 4: The difference from Example 1 is that the micelle mother liquor in step S2 does not contain sodium salicylate. Instead of adding 18g of hexadecyltrimethylammonium bromide and 12g of sodium salicylate to 300g of deionized water, only 30g of hexadecyltrimethylammonium bromide is added to 300g of deionized water. The other conditions are the same as in Example 1.

[0033] Comparative Example 5: The difference from Example 1 is that the micelle mother liquor in step S2 does not contain hexadecyltrimethylammonium bromide. Instead of adding 18g of hexadecyltrimethylammonium bromide and 12g of sodium salicylate to 300g of deionized water, only 30g of sodium salicylate is added to 300g of deionized water. The other conditions are the same as in Example 1.

[0034] Comparative Example 6: The difference from Example 1 is that in step S3, 120g of sodium chloride solution (concentration 20wt%) was sprayed evenly onto the surface of wet particles within 10 minutes using a spray method, and 20g of deionized water was sprayed evenly onto the surface of wet particles within 10 minutes using a spray method. The other conditions are the same as in Example 1.

[0035] Sample Preparation: Hydroxyferric oxide desulfurizers were prepared according to their respective steps in Examples 1-6 and Comparative Examples 1-6. For particle mechanics and low-concentration breakthrough life tests, samples were sieved to obtain particles with a diameter of 3mm-5mm. For breakthrough sulfur capacity and specific surface area tests, samples were dried at 80℃ for 6 hours, then crushed and sieved to obtain particles with a diameter of 0.12mm-0.18mm. All samples were dried to constant weight at 80℃ before testing and cooled to 25℃ in a desiccator for later use. The breakthrough sulfur capacity test and calculation adopted the apparatus and data processing methods given in HG / T 5759-2020, and key conditions such as relevant test gas composition, space velocity, and packing volume were determined according to this standard.

[0036] Specific surface area and pore structure: Specific surface area was determined according to GB / T 19587-2017, and mesopore size distribution was calculated according to GB / T 21650.2-2008; 0.50 g of each sample powder was placed in the degassing station and degassed under vacuum at 200℃ for 6 h before being transferred to the analysis station for nitrogen adsorption-desorption testing at 77 K; the BET linear fitting interval was taken as relative pressure P / P0 = 0.05-0.30, and the specific surface area S was calculated. BET (m)2 / g); the mesopore volume V was calculated using the BJH method based on the desorption branch. meso (cm) 3 / g) and average mesopore diameter D p (nm).

[0037] Particle crushing resistance: The particle crushing resistance test was conducted according to HG / T 2782-2024. Forty particles with a particle size of 3mm-5mm were randomly selected and tested one by one on the particle crushing resistance tester. After the loading head contacted the sample, pressure was applied at a uniform loading speed of 5mm / min. The maximum load F when the particle first showed obvious crushing was recorded. i (N); Calculate the average crushing force F. avg =(∑F i ) / 40 (N / particle).

[0038] Abrasion rate: The abrasion rate was determined according to HG / T 2976-2011. The abrasion tester used had an inner diameter of 120 mm, a length of 150 mm, and one inner baffle (length 150 mm, height 18 mm). The grinding cylinder speed was 60 r / min, and the abrasion time was 30 min. 100.0 g of sample with a particle size of 3 mm-5 mm was placed into the grinding cylinder. After abrasion, the sample was removed and sieved using a metal wire woven mesh test sieve conforming to GB / T 6003.1 (sieve aperture 0.18 mm). The mass of the material passing through the sieve was weighed. f (g), according to A=m f Calculate the wear rate A (wt%) using 100.0×100%.

[0039] Breakthrough sulfur capacity (as S): The breakthrough sulfur capacity test was conducted according to the apparatus and calculation method given in HG / T 5759-2020. The apparatus used was a stainless steel reaction tube with an inner diameter of 6 mm. The sample loading volume was 1.0 mL (first fill a graduated cylinder with 0.12 mm-0.18 mm sample to the full volume of 1.0 mL, level it, and then weigh it to obtain the sample mass m). The reaction tube was filled with quartz sand at both the top and bottom to fix the bed and prevent entrainment. The reaction temperature was controlled at 25 °C using a constant temperature water bath. Nitrogen gas was first passed through at a space velocity of 1000 h⁻¹. -1 The system was purged for 30 minutes, and a micro-oxygen supply was initiated at a flow rate of 1 mL / min. Subsequently, the intake gas was switched to a mixture containing 3% hydrogen sulfide by volume, and the intake air velocity was maintained at 1000 h⁻¹. -1 The exhaust gas was collected at fixed time intervals, and the volume fraction of hydrogen sulfide in the exhaust gas was measured; when the volume fraction of hydrogen sulfide in the exhaust gas reached 1×10⁻⁶, the exhaust gas was tested. -4When breakthrough is detected, the test is stopped, and the cumulative gas volume V (L) is recorded. The breakthrough sulfur capacity w (wt%) is calculated according to w=c·V·M / (m·V0)×100%, where c is the volume fraction of hydrogen sulfide in the inlet gas (0.03 in this test), M is the molar mass of sulfur 32.06g / mol, and V0 is the molar volume of gas under standard conditions 22.4L / mol.

[0040] Low-concentration hydrogen sulfide breakthrough lifetime and bed pressure drop variation: A low-concentration breakthrough lifetime test was established according to the fixed-bed evaluation device configuration in HG / T 5759-2020. The reaction tube had an inner diameter of 25 mm and was filled with 50 mL of desulfurizing agent with a particle size of 3 mm-5 mm obtained in the examples / comparative examples (filling height approximately 100 mm). Both ends were leveled with quartz sand and limited with glass wool. The inlet gas was a mixture of hydrogen sulfide with a volume fraction of 500 ppm, oxygen with a volume fraction of 0.10%, and nitrogen as the balance gas. The test temperature was 25 °C, and the gas flow rate was 3.0 L / min (corresponding to a space velocity of approximately 3600 h⁻¹). -1 The inlet relative humidity was controlled at 60%; an online electrochemical hydrogen sulfide analyzer was used to continuously monitor the outlet hydrogen sulfide concentration, and differential pressure transmitters were connected to both ends of the reaction tube to record the bed pressure drop ΔP (Pa) in real time; the breakthrough time t was recorded when the outlet hydrogen sulfide concentration reached 1 ppm as the breakthrough criterion. break (h), and press W low =Q·60·t break ·C in ·M / (m bed ·V0) Calculate the low concentration sulfur capacity W low (mg S / g), where Q is the inlet volumetric flow rate (L / min), C in The inlet hydrogen sulfide volume fraction (in this experiment, it is taken as 5.0 × 10⁻⁶). -4 ), m bed The mass of the sample being filled (g).

[0041] The test results are recorded in Table 1.

[0042] Table 1 Test Results

[0043] As can be seen from the data in Table 1 of the embodiments, the hydroxyl iron oxide desulfurizer prepared by the present invention maintains a high level in terms of specific surface area and mesopore volume. The average mesopore size is concentrated in the mesopore scale, which is more conducive to gas diffusion. At the same time, the particle crushing resistance remains high and the wear rate is low. Under low concentration hydrogen sulfide conditions, the penetration life is long and the bed pressure drop rises relatively slowly. This trend indicates that the present invention achieves simultaneous optimization between pore structure construction and particle engineering stability: sodium chloride and polyvinylpyrrolidone K30 are introduced to synergistically regulate the nucleation stage, making it easier for the hydroxyl iron oxide matrix to form a more cohesive framework; subsequently, multi-carboxyl anchoring points are constructed on the surface through complexation modification with trisodium citrate dihydrate, making it easier for the micelle template formed by hexadecyltrimethylammonium bromide and sodium salicylate to be oriented and fixed, and to form interconnected mesopore channels after post-treatment removal; furthermore, with the addition of sodium chloride solution spraying and wet heat aging to induce surface dissolution-rearrangement-reconsolidation, a relatively dense shell is formed, inhibiting dust migration and channel blockage. Therefore, in low-concentration deep purification scenarios such as urban gas terminal purification and fuel cell front-end protection, it is possible to simultaneously achieve high available sulfur capacity release, long operating cycle and low pressure drop risk.

[0044] As can be seen from the data in Table 1 for Example 1 and Comparative Example 1, when sodium chloride is not added in step S1, the crushing resistance and wear control of the particles show significant adverse changes, accompanied by a faster increase in bed pressure drop and a shorter low-concentration penetration life. The main reason is that the lack of an ionic strength environment provided by sodium chloride during the nucleation / growth stage makes the primary particles more prone to uncontrolled agglomeration and accumulation of skeletal defects. Even with the subsequent formation of bentonite and colloidal silica aqueous dispersions, it is more difficult to compensate for the microcracks and fragile boundary areas caused by insufficient cohesion in the matrix, leading to increased frictional pulverization, intensified fine powder migration, and induced pressure drop during operation. Therefore, the synergistic regulation of sodium chloride and polyvinylpyrrolidone K30 in the nucleation stage is not a simple salting effect, but rather a fundamental support for the stability of particle engineering.

[0045] As can be seen from the data in Table 1 for Example 1 and Comparative Example 2, when polyvinylpyrrolidone K30 is not added in step S1, the pore structure index and mechanical stability weaken simultaneously, the wear rate increases and the penetration life is shortened more significantly. It is speculated that this is because polyvinylpyrrolidone K30 plays a crucial role in surface adsorption stability and steric hindrance dispersion during the nucleation and growth stages, inhibiting particle aggregation and promoting the formation of a more uniform framework connection. When it is absent, the nucleus growth and aggregation process becomes more disordered, making it difficult for the subsequent complexation modification of trisodium citrate dihydrate to form uniform anchoring points on the already highly roughened surface, further weakening the effective retention of the micelle template, resulting in simultaneous damage to mesoporous connectivity and structural strength.

[0046] As can be seen from the data in Table 1 for Example 1 and Comparative Example 3, when only the complexation modification of trisodium citrate dihydrate is removed, the crushing resistance of the particles can be maintained at a relatively usable level. However, the mesopore volume and average mesopore diameter show a shrinking trend, affecting the penetration sulfur capacity and the release of low-concentration usable sulfur capacity. The main reason is that the polycarboxyl coordination provided by trisodium citrate dihydrate can form stable anionic sites on the surface of iron hydroxide. These sites are the basis for the directional adsorption and stable retention of hexadecyltrimethylammonium bromide micelles. Without this anchoring, micelles are more prone to non-directional coating or local desorption. The pores formed after template removal are more likely to have insufficient connectivity or uncontrolled pore size distribution, leading to the reaction products being more easily retained in the pores and reducing the efficiency of subsequent sulfur capacity release. Therefore, the contribution of the surface anchoring step to the controllability of the mesoporous structure cannot be easily replaced.

[0047] As can be seen from the data in Table 1 for Example 1 and Comparative Examples 4 and 5, when the micelle mother liquor lacks sodium salicylate or hexadecyltrimethylammonium bromide, the effectiveness of mesoporous structure construction decreases significantly, leading to simultaneous adverse changes in breakthrough sulfur capacity and low-concentration breakthrough lifetime, accompanied by a decrease in pressure drop control capability. It is speculated that this is because hexadecyltrimethylammonium bromide provides the micelle framework, while sodium salicylate plays a role in regulating the micelle structure and stability in the system; the absence of either component will cause the template morphology and retention efficiency to deviate from the optimal window, resulting in reduced pore connectivity, narrower mass transfer channels, or increased clogging after the accumulation of sulfurization products. Especially under low-concentration long-term operating conditions, the impact of gradual pore blockage on subsequent rate maintenance is often underestimated; therefore, such differences can be amplified into significant differentiation in lifetime and pressure drop, demonstrating the synergistic necessity of the two-component template design.

[0048] As can be seen from the data in Table 1 for Example 1 and Comparative Example 6, when the sodium chloride solution spraying in step S3 is removed and replaced with deionized water spraying, although the specific surface area and mesopore volume show an upward trend and the breakthrough sulfur capacity can also maintain a high level, the particle crushing resistance decreases, the wear rate increases, and the final bed pressure drop increases significantly, and the low-concentration breakthrough life is shortened. The reason is that the sodium chloride solution spraying and wet heat aging jointly drive the surface dissolution-rearrangement-reconsolidation to form a relatively dense shell to inhibit dust migration. When this shell structure is missing, even if the internal pore structure is more open, the structural disturbance induced by running friction and sulfide products is more likely to trigger pulverization and fine powder carrying, resulting in a decrease in the effective porosity of the bed and a rapid increase in pressure drop, which in turn leads to earlier breakthrough. It can be seen that the present invention achieves a typical 1+1 greater than 2 by connecting the mesopores and the shell salt treatment to stabilize the particles through micelle templates: it ensures both the reaction / diffusion channels and long-term engineering stability, thereby simultaneously obtaining high usable sulfur capacity and low pressure drop life.

[0049] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A method for preparing a hydroxyl iron oxide desulfurizing agent, characterized in that, Includes the following steps: (1) Prepare an iron-containing precursor solution using ferric nitrate nonahydrate as the iron source; add urea to the iron-containing precursor solution, heat to 85-95℃ for hydrolysis reaction for 50-70 min, cool to 70℃, add complexing modification solution containing trisodium citrate dihydrate, complex modification for 20-40 min, cool to 65℃, and obtain modified slurry; (2) Prepare micelle mother liquor by mixing hexadecyltrimethylammonium bromide, sodium salicylate and deionized water. Add the micelle mother liquor to the modified slurry obtained in step (1) and react for 45-75 min. Filter, then wash with sodium chloride solution and dry to obtain modified iron hydroxyl oxide powder. (3) Modified iron hydroxide powder, bentonite, colloidal silica aqueous dispersion and deionized water are kneaded to obtain plastic wet material, which is then extruded and rolled into wet granules; sodium chloride solution is sprayed onto the surface of the wet granules while tumbling, and then dried after wet heat aging at 50-70℃ for 4-10h to obtain intermediate granules; after being washed with deionized water, they are placed in hydrogen peroxide solution and treated at 50-60℃ for 60-150min, then washed and dried to obtain iron hydroxide desulfurizer; Based on 404 parts by weight of ferric nitrate nonhydrate, the amount of urea added is 160-200 parts, the amount of trisodium citrate dihydrate added is 5-25 parts, the amount of hexadecyltrimethylammonium bromide added is 12-24 parts, and the amount of sodium salicylate added is 8-18 parts. Based on 500 parts by weight of modified iron hydroxide powder, the amount of sodium chloride solution added is 80-160 parts; the concentration of the sodium chloride solution is 15wt%-25wt%. The iron-containing precursor solution is prepared by mass fractions of 3000 parts deionized water, 404 parts ferric nitrate nonahydrate, 80-160 parts sodium chloride and 60-150 parts polyvinylpyrrolidone K30.

2. The method for preparing the ferric hydroxide desulfurizer according to claim 1, characterized in that, The concentration of the sodium chloride washing solution is 1wt%-3wt% by weight.

3. The method for preparing the ferric hydroxide desulfurizer according to claim 1, characterized in that, In the raw materials for preparing the plastic wet material, the mass ratio of modified hydroxyl iron oxide powder, bentonite, colloidal silica aqueous dispersion and deionized water is 500:8-15:25-40:380-420.

4. The method for preparing the ferric hydroxide desulfurizer according to claim 1, characterized in that, The silica aqueous dispersion contains 25wt%-35wt% silica.

5. The method for preparing the ferric hydroxide desulfurizer according to claim 1, characterized in that, The concentration of the hydrogen peroxide solution is 0.5wt%-2wt%.

6. The method for preparing the hydroxyl iron oxide desulfurizer according to claim 1, characterized in that, The plastic wet material is obtained by kneading at room temperature for 10-20 minutes.

7. The method for preparing the ferric hydroxide desulfurizer according to claim 1, characterized in that, The extrusion uses an extrusion plate with a 3mm aperture, the spherical rotation speed is 700-900rpm, and the spherical rotation time is 8-12min.

8. The method for preparing the ferric hydroxide desulfurizer according to claim 1, characterized in that, The damp heat aging is carried out in a closed damp heat aging chamber, and the moisture source is provided in a way that the particles do not come into direct contact with the water.

9. A hydroxyl iron oxide desulfurizing agent, characterized in that, It is obtained by the preparation method of the ferric hydroxide desulfurizer according to any one of claims 1-8.

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