Iron chelate desulfurizer

Abstract

The invention relates to the technical field of environmental catalysis and pollution treatment, in particular to a chelated iron desulfurizer. According to the desulfurizer, DOTA is used as a core chelating agent, an iron active center is accurately anchored to a shell layer of a polymer core-shell structure microsphere through a multi-step polymerization and functionalization process, and the design of solution-state complexing iron is assisted, so that the desulfurizer has both solid-phase localization and solution compensation, the capability of resisting poisoning of impurities such as cyanide and mercaptan is remarkably improved, and iron loss is reduced. The desulfurizer is high in desulfurization efficiency and large in sulfur capacity, can stably operate for a long period, shows excellent continuous activity and selectivity under the conditions of coexistence of various impurities and repeated regeneration, and has a good application prospect.

Description

Technical Field

[0001] This invention relates to the field of environmental catalysis and pollution control technology, and in particular to a chelated iron desulfurizing agent. Background Technology

[0002] Hydrogen sulfide, as an important industrial byproduct and environmental pollutant, is widely present in petrochemical, natural gas processing, wastewater treatment, and biomass gasification fields. Traditional desulfurization technologies mainly include physical absorption, chemical absorption, and biological desulfurization. Among them, liquid-phase oxidation has attracted widespread attention due to its advantages such as mild operation, good selectivity, and the ability to directly convert H2S into elemental sulfur.

[0003] Chelated iron desulfurization technology, as an important branch of liquid-phase oxidation, is based on the utilization of Fe... 3+ The oxidizing properties of the chelating agent oxidize sulfide to elemental sulfur, while simultaneously stabilizing iron ions through a chelating agent to prevent their hydrolysis and precipitation. Traditional chelating iron desulfurizers often use conventional chelating agents such as EDTA and NTA. Although these can stabilize iron ions to a certain extent, they face many challenges in practical industrial applications.

[0004] First, insufficient resistance to poisoning is a key bottleneck in existing technologies. Industrial waste gases commonly contain impurities such as cyanides, thiols, and heavy metal ions. These substances compete with chelating agents or iron ions for complexation, leading to the deactivation of active sites. Cyanides, in particular, possess extremely strong complexing abilities, capable of capturing iron ions to form more stable complexes, causing desulfurizers to rapidly lose their effectiveness. Thiols, on the other hand, form sulfur-iron bonds with iron ions, hindering normal oxidation reactions.

[0005] Secondly, iron loss seriously affects the economic efficiency and environmental friendliness of desulfurizing agents. Traditional chelating agents have relatively low stability constants, and iron ions are prone to hydrolysis and precipitation or loss through circulation during long-term operation, requiring frequent replenishment, increasing operating costs and introducing the risk of secondary pollution. This is especially true in alkaline environments, where Fe... 3+ It is highly susceptible to hydrolysis to form Fe(OH)3 precipitate, resulting in the loss of active components.

[0006] Third, selective oxidation is difficult to control. An ideal desulfurization process should selectively oxidize H2S to elemental sulfur, but in actual reactions, over-oxidation often occurs, forming byproducts such as sulfates and sulfites, which reduces sulfur recovery and increases the difficulty of subsequent separation. Existing technologies struggle to precisely control the reaction pathway and oxidation depth.

[0007] Fourth, mass transfer limitations affect reaction efficiency. H₂S has relatively low solubility in the liquid phase, making gas-liquid mass transfer the rate-determining step. Traditional homogeneous catalytic systems lack effective mass transfer enhancement methods, making it difficult to improve interfacial reaction efficiency.

[0008] Fifth, the applicable pH range is narrow. Existing chelated iron systems typically maintain good stability and activity within a specific pH range. pH fluctuations can lead to iron ion hydrolysis or chelating agent decomposition, affecting desulfurization efficiency. Actual industrial waste gas has complex compositions, making precise pH control difficult.

[0009] Sixth, its regeneration performance is limited. After the desulfurization reaction, Fe needs to be regenerated through oxidation. 2+ Re-oxidized to Fe 3+ Traditional systems have low regeneration efficiency and significant activity decay after multiple regenerations, affecting long-term stable operation.

[0010] Furthermore, existing technologies face challenges such as uneven distribution of active components, complex reactor design, and harsh operating conditions. In homogeneous catalytic systems, active centers are randomly dispersed, making it difficult to form high-density active regions. While immobilization technology can reduce iron loss, it often comes at the cost of sacrificing activity and mass transfer performance. Therefore, there is an urgent need to develop a novel chelated iron desulfurizing agent that integrates high stability, strong resistance to poisoning, low iron loss, and high selectivity to meet the demands of efficient desulfurization under complex operating conditions. This desulfurizing agent should possess a stable active center structure, an effective mass transfer enhancement mechanism, and excellent regeneration performance. Summary of the Invention

[0011] In view of this, the purpose of this invention is to provide a chelated iron desulfurizing agent to solve the problems of easy deactivation and severe iron loss of existing chelated iron desulfurizing agents under complex working conditions.

[0012] To achieve the above objectives, this invention provides a chelated iron desulfurizing agent, which is prepared from the following raw materials by weight: 8-12 parts of DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid), 1000 parts of deionized water, 12-16 parts of ferric chloride hexahydrate, 16-24 parts of anhydrous sodium carbonate, 8-12 parts of sodium bicarbonate, and 40-60 parts of macrocyclic functionalized core-shell composite microspheres loaded with iron active centers.

[0013] Preferably, the DOTA model is macrocyclics M-140.

[0014] Furthermore, the preparation steps of the macrocyclic functionalized core-shell composite microspheres loaded with iron active centers are as follows: S1: p-SCN-Bn-DOTA (S-2-(4-phenyl isothiocyanate)-1,4,7,10-tetraazacyclododecanetetraacetic acid), 2-aminoethyl methacrylate hydrochloride and N,N-diisopropylethylamine were added to N,N-dimethylformamide, stirred at 25°C for 12 h, and purified to obtain a polymerizable macrocyclic monomer; S2: Polyvinyl alcohol was added to deionized water and stirred for 30 min. Then 4-chloromethylstyrene, divinylbenzene, 2-hydroxyethyl methacrylate and azobisisobutyronitrile were added and stirred at 70 °C for 6 h. After purification, cross-linked polymer microspheres were obtained. S3: Add cross-linked polymer microspheres and trimethylamine aqueous solution to anhydrous ethanol, stir and react at 60℃ for 6-10 h, purify, and obtain quaternized functional microspheres; S4: Under nitrogen protection, quaternized functional microspheres were dispersed in anhydrous dichloromethane, and then triethylamine and 2-bromoisobutyryl bromide were added. The mixture was stirred at 25°C for 3-5 hours and purified to obtain functional microspheres with initiator groups on the surface. S5: N-isopropylacrylamide and polymerizable macrocyclic monomers were added to a mixed solution of deionized water and anhydrous ethanol and stirred for 15 min. Then, functional microspheres with initiator groups on the surface, copper chloride, copper dichloride and N,N,N',N'',N''-pentamethyldiethylenetriamine were added. Nitrogen gas was purged for oxygen removal for 30 min, and the mixture was stirred at 25 °C for 5-7 h. After purification, macrocyclic functionalized core-shell composite microspheres were obtained. S6: Disperse macrocyclic functionalized core-shell composite microspheres in deionized water, add ferric chloride hexahydrate, stir at 60℃ for 6 h, and purify to obtain macrocyclic functionalized core-shell composite microspheres loaded with iron active centers.

[0015] Preferably, in step S1, the weight ratio of p-SCN-Bn-DOTA, 2-aminoethyl methacrylate hydrochloride, N,N-diisopropylethylamine and N,N-dimethylformamide is 4-6:2.4-3.6:1.6-2.4:40-60.

[0016] Preferably, the p-SCN-Bn-DOTA in step S1 is macrocyclics B-205.

[0017] Preferably, the weight-average molecular weight of polyvinyl alcohol in step S2 is 120,000-140,000.

[0018] Preferably, in step S2, the weight ratio of polyvinyl alcohol, deionized water, 4-chloromethylstyrene, divinylbenzene, 2-hydroxyethyl methacrylate and azobisisobutyronitrile is 20:2000:140-180:35-45:8-12:1.6-2.4.

[0019] Preferably, in step S3, the weight ratio of cross-linked polymer microspheres, trimethylamine aqueous solution, and anhydrous ethanol is 100:160-240:160-240.

[0020] Preferably, the concentration of anhydrous ethanol in step S3 is 45 wt%.

[0021] Preferably, in step S4, the weight ratio of quaternized functional microspheres, anhydrous dichloromethane, triethylamine, and 2-bromoisobutyryl bromide is 60:500:15-25:30-50.

[0022] Preferably, in step S5, the weight ratio of N-isopropylacrylamide, polymerizable macrocyclic monomer, deionized water, anhydrous ethanol, functional microspheres with surface initiator groups, copper chloride, copper dichloride, and N,N,N',N'',N''-pentamethyldiethylenetriamine is 50-70:4-8:400:400:60:0.8-1.2:0.8-1.2:1.6-2.4.

[0023] Preferably, in step S6, the weight ratio of macrocyclic functionalized core-shell composite microspheres, deionized water, and ferric chloride hexahydrate is 100:1000:8-12.

[0024] The beneficial effects of this invention are: Significantly enhanced resistance to poisoning: The multidentate chelating environment constructed using the macrocyclic ligand DOTA forms a complex structure with a higher stability constant than traditional ligands such as EDTA and NTA. 3+ The ions are firmly bound within the coordination cage, effectively resisting competition for position from strong ligands such as cyanides and thiols. The quaternized shell provides a cationic microenvironment that further stabilizes the complex structure, significantly improving its tolerance under complex operating conditions.

[0025] Iron loss is significantly reduced: the active center is spatially localized through a core-shell composite microsphere structure, allowing for the storage of key Fe... 3 + The DOTA-Fe complex is immobilized within the polymer shell, fundamentally preventing the diffusion and loss of iron ions. Simultaneously, the introduction of the solution-phase DOTA-Fe complex serves as an "active reservoir," forming a dual guarantee mechanism of solid-phase localization and solution compensation. This ensures efficient interfacial reactions while minimizing the systemic loss of iron components, achieving a balance between economic efficiency and environmental friendliness.

[0026] Precise control of selective oxidation: The smart responsive shell of poly(N-isopropylacrylamide) can regulate the hydrophilic-hydrophobic balance of the local microenvironment according to the reaction environment, providing an optimized reaction environment for the selective oxidation of H2S to elemental sulfur. The selective enrichment effect of quaternary ammonium sites on anionic substrates makes the reaction more inclined to proceed along the desired pathway, effectively suppressing excessive oxidation side reactions, improving sulfur recovery rate and reducing by-product formation.

[0027] Significantly improved mass transfer efficiency: The core-shell structure design allows for a high-density distribution of active centers near the gas-liquid interface, greatly shortening the diffusion path of reactants. Quaternary ammonium functional groups contribute to the HS-H2O conversion. - S2O32- Electrostatic adsorption of anionic substrates creates a high-concentration reaction region at the interface, overcoming the problem of active component dispersion and dilution in traditional homogeneous systems. The swelling and contraction characteristics of the smart shell further optimize mass transfer resistance, achieving highly efficient gas-liquid interfacial reactions.

[0028] Excellent cycle stability: The solid-phase localized active center structure remains stable during regeneration, avoiding the problem of easy aggregation and deactivation of traditional homogeneous catalysts. The compensation mechanism of solution-phase complexed iron ensures timely replenishment of active components, and the synergistic effect of multiple stabilization measures enables the desulfurizer to maintain a high level of desulfurization performance after multiple cycles. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in this invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0030] Figure 1 The infrared spectra of the cross-linked polymer microspheres, quaternized functional microspheres, macrocyclic functionalized core-shell composite microspheres, and macrocyclic functionalized core-shell composite microspheres loaded with iron active centers in Example 2 of the present invention are shown. Detailed Implementation

[0031] 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.

[0032] Example 1: (1) 4g of S-2-(4-phenyl isothiocyanate)-1,4,7,10-tetraazacyclododecanetetraacetic acid (p-SCN-Bn-DOTA, model macrocyclics B-205), 2.4g of 2-aminoethyl methacrylate hydrochloride and 1.6g of N,N-diisopropylethylamine were added to 40g of N,N-dimethylformamide, stirred at 25°C for 12h, and after solvent removal under reduced pressure, washed with acetonitrile / water (9:1, v / v) and dried under vacuum to obtain a polymerizable macrocyclic monomer; (2) Add 20g of polyvinyl alcohol (model Mowiol 18-88, weight average molecular weight about 130,000) to 2000g of deionized water, stir at 600rpm for 30min, then add 140g of 4-chloromethylstyrene, 35g of divinylbenzene, 8g of 2-hydroxyethyl methacrylate and 1.6g of azobisisobutyronitrile, stir at 70℃ for 6h, filter, wash with anhydrous ethanol and deionized water until neutral, and vacuum dry to obtain cross-linked polymer microspheres; (3) 100g of cross-linked polymer microspheres and 160g of trimethylamine aqueous solution (concentration of 45wt%) were added to 240g of anhydrous ethanol, stirred at 60℃ for 6h, filtered, washed with anhydrous ethanol and deionized water until neutral, and dried under vacuum to obtain quaternized functional microspheres. (4) Under nitrogen protection, 60g of quaternized functional microspheres were dispersed in 500g of anhydrous dichloromethane, and then 15g of triethylamine and 30g of 2-bromoisobutyryl bromide were added. The mixture was stirred at 25°C for 3h, filtered, and washed successively with anhydrous dichloromethane, anhydrous ethanol and deionized water. The mixture was then dried under vacuum to obtain functional microspheres with initiator groups on the surface. (5) Add 50g of N-isopropylacrylamide and 4g of polymerizable macrocyclic monomer to a mixed solution of 400g of deionized water and 400g of anhydrous ethanol, stir for 15min, then add 60g of functional microspheres with initiator groups on the surface, 0.8g of copper chloride, 0.8g of copper dichloride and 1.6g of N,N,N',N'',N''-pentamethyldiethylenetriamine, purge with nitrogen to remove oxygen for 30min, stir at 25℃ for 5h, filter, wash with anhydrous ethanol and deionized water in sequence, and vacuum dry to obtain macrocyclic functionalized core-shell composite microspheres; (6) Disperse 100g of macrocyclic functionalized core-shell composite microspheres in 1000g of deionized water, add 8g of ferric chloride hexahydrate, stir at 60℃ for 6h, filter, wash with deionized water, and vacuum dry to obtain macrocyclic functionalized core-shell composite microspheres loaded with iron active centers. (7) Add 8g of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA, model macrocyclics M-140) to 1000g of deionized water, stir for 15min, then add 12g of ferric chloride hexahydrate, 16g of anhydrous sodium carbonate and 8g of sodium bicarbonate, stir for 30min, then add 40g of macrocyclic functionalized core-shell composite microspheres loaded with iron active centers, stir at 25℃ for 30min to obtain chelated iron desulfurizing agent.

[0033] Example 2: (1) 5g of S-2-(4-phenyl isothiocyanate)-1,4,7,10-tetraazacyclododecanetetraacetic acid (p-SCN-Bn-DOTA, model macrocyclics B-205), 3g of 2-aminoethyl methacrylate hydrochloride and 2g of N,N-diisopropylethylamine were added to 50g of N,N-dimethylformamide, stirred at 25°C for 12h, and after solvent removal under reduced pressure, washed with acetonitrile / water (9:1, v / v) and dried under vacuum to obtain a polymerizable macrocyclic monomer; (2) Add 20g of polyvinyl alcohol (model Mowiol 18-88, weight average molecular weight about 130,000) to 2000g of deionized water, stir at 600rpm for 30min, then add 160g of 4-chloromethylstyrene, 40g of divinylbenzene, 10g of 2-hydroxyethyl methacrylate and 2g of azobisisobutyronitrile, stir at 70℃ for 6h, filter, wash with anhydrous ethanol and deionized water until neutral, and vacuum dry to obtain cross-linked polymer microspheres; (3) 100g of cross-linked polymer microspheres and 200g of trimethylamine aqueous solution (concentration of 45wt%) were added to 200g of anhydrous ethanol and stirred at 60℃ for 8h. After filtration, the microspheres were washed with anhydrous ethanol and deionized water until neutral and then dried under vacuum to obtain quaternized functional microspheres. (4) Under nitrogen protection, 60g of quaternized functional microspheres were dispersed in 500g of anhydrous dichloromethane, and then 20g of triethylamine and 40g of 2-bromoisobutyryl bromide were added. The mixture was stirred at 25°C for 4h, filtered, and washed successively with anhydrous dichloromethane, anhydrous ethanol and deionized water. The mixture was then dried under vacuum to obtain functional microspheres with initiator groups on the surface. (5) Add 60g of N-isopropylacrylamide and 6g of polymerizable macrocyclic monomer to a mixed solution of 400g of deionized water and 400g of anhydrous ethanol, stir for 15min, then add 60g of functional microspheres with initiator groups on the surface, 1g of copper chloride, 1g of copper dichloride and 2g of N,N,N',N'',N''-pentamethyldiethylenetriamine, purge with nitrogen to remove oxygen for 30min, stir at 25℃ for 6h, filter, wash with anhydrous ethanol and deionized water in sequence, and vacuum dry to obtain macrocyclic functionalized core-shell composite microspheres; (6) Disperse 100g of macrocyclic functionalized core-shell composite microspheres in 1000g of deionized water, add 10g of ferric chloride hexahydrate, stir at 60℃ for 6h, filter, wash with deionized water, and vacuum dry to obtain macrocyclic functionalized core-shell composite microspheres loaded with iron active centers. (7) Add 10g of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA, model macrocyclics M-140) to 1000g of deionized water, stir for 15min, then add 14g of ferric chloride hexahydrate, 20g of anhydrous sodium carbonate and 10g of sodium bicarbonate, stir for 30min, then add 50g of macrocyclic functionalized core-shell composite microspheres loaded with iron active centers, stir at 25℃ for 30min to obtain chelated iron desulfurizing agent.

[0034] Example 3: (1) 6g of S-2-(4-phenyl isothiocyanate)-1,4,7,10-tetraazacyclododecanetetraacetic acid (p-SCN-Bn-DOTA, model macrocyclics B-205), 3.6g of 2-aminoethyl methacrylate hydrochloride and 2.4g of N,N-diisopropylethylamine were added to 60g of N,N-dimethylformamide, stirred at 25°C for 12h, and after solvent removal under reduced pressure, washed with acetonitrile / water (9:1, v / v) and dried under vacuum to obtain a polymerizable macrocyclic monomer; (2) Add 20g of polyvinyl alcohol (model Mowiol 18-88, weight average molecular weight about 130,000) to 2000g of deionized water, stir at 600rpm for 30min, then add 180g of 4-chloromethylstyrene, 45g of divinylbenzene, 12g of 2-hydroxyethyl methacrylate and 2.4g of azobisisobutyronitrile, stir at 70℃ for 6h, filter, wash with anhydrous ethanol and deionized water until neutral, and vacuum dry to obtain cross-linked polymer microspheres; (3) 100g of cross-linked polymer microspheres and 240g of trimethylamine aqueous solution (concentration of 45wt%) were added to 160g of anhydrous ethanol and stirred at 60℃ for 10h. After filtration, the microspheres were washed with anhydrous ethanol and deionized water until neutral and then dried under vacuum to obtain quaternized functional microspheres. (4) Under nitrogen protection, 60g of quaternized functional microspheres were dispersed in 500g of anhydrous dichloromethane, and then 25g of triethylamine and 50g of 2-bromoisobutyryl bromide were added. The mixture was stirred at 25°C for 5h, filtered, and washed successively with anhydrous dichloromethane, anhydrous ethanol and deionized water. The mixture was then dried under vacuum to obtain functional microspheres with initiator groups on the surface. (5) Add 70g of N-isopropylacrylamide and 8g of polymerizable macrocyclic monomer to a mixed solution of 400g of deionized water and 400g of anhydrous ethanol, stir for 15min, then add 60g of functional microspheres with initiator groups on the surface, 1.2g of copper chloride, 1.2g of copper dichloride and 2.4g of N,N,N',N'',N''-pentamethyldiethylenetriamine, purge with nitrogen to remove oxygen for 30min, stir at 25℃ for 7h, filter, wash with anhydrous ethanol and deionized water in sequence, and vacuum dry to obtain macrocyclic functionalized core-shell composite microspheres; (6) Disperse 100g of macrocyclic functionalized core-shell composite microspheres in 1000g of deionized water, add 12g of ferric chloride hexahydrate, stir at 60℃ for 6h, filter, wash with deionized water, and vacuum dry to obtain macrocyclic functionalized core-shell composite microspheres loaded with iron active centers. (7) Add 12g of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA, model macrocyclics M-140) to 1000g of deionized water, stir for 15min, then add 16g of ferric chloride hexahydrate, 24g of anhydrous sodium carbonate and 12g of sodium bicarbonate, stir for 30min, then add 60g of macrocyclic functionalized core-shell composite microspheres loaded with iron active centers, stir at 25℃ for 30min to obtain chelated iron desulfurizing agent.

[0035] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that in step (3), trimethylamine treatment is not performed to form benzyl quaternary ammonium sites (i.e., no quaternization functionalization is performed), and the other conditions are the same as in Example 2.

[0036] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that: in step (5), the polymerizable macrocyclic monomer S-2-(4-phenyl isothiocyanate)-1,4,7,10-tetraazacyclododecanetetraacetic acid is not added during shell polymerization, and only N-isopropylacrylamide is used as the shell monomer to construct the shell. The other conditions are the same as in Example 2.

[0037] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that in step (5), N-isopropylacrylamide was replaced with methyl methacrylate for shell polymerization, the total amount of monomers fed, the catalysis and time were kept the same, and the other conditions were the same as in Example 2.

[0038] Comparative Example 4: The difference between Comparative Example 4 and Example 2 is that: in step (6), the loading treatment of ferric chloride hexahydrate is not performed (the iron active center is not constructed in the solid phase), and the process directly proceeds to step (7) to prepare the solution complex iron system. The other conditions are the same as those in Example 2.

[0039] Comparative Example 5: The difference between Comparative Example 5 and Example 2 is that 1,4,7,10-tetraazacyclododecane-1,7-diacetic acid and its iron complex are not added in step (7), but only deionized water is used to maintain the same volume and stirring conditions (i.e. only the iron-supported active center is retained), and the other conditions are the same as in Example 2.

[0040] Comparative Example 6: The difference between Comparative Example 6 and Example 2 is that: in step (7), instead of adding anhydrous sodium carbonate and sodium bicarbonate buffer system, an equimolar sodium chloride solution is added, the total volume of the solution is kept consistent with the stirring conditions, and the other conditions are the same as in Example 2.

[0041] Performance testing: Infrared spectroscopy analysis: Fourier transform infrared spectrometry was used for analysis, and the results are as follows: Figure 1 As shown.

[0042] Hydrogen sulfide removal efficiency and breakthrough sulfur capacity: The desulfurization performance of each example and comparative example was investigated using a 1L bubble column (liquid volume 500mL) at (25±1)℃ and (50±5)% relative humidity. The inlet gas ratio was 0.50% hydrogen sulfide, 2.00% carbon dioxide, and the balance nitrogen, with a total flow rate of 1000mL / min. The total iron concentration of the desulfurizing agent in the liquid phase was 0.050mol / L, and the initial pH was 8.30. The hydrogen sulfide content at both the inlet and outlet was determined by iodometric titration. The removal rate was calculated after 60 minutes of stable operation. The breakthrough time was defined as the outlet reaching 5% of the inlet, and the sulfur capacity was calculated based on the sulfur absorbed per unit volume (as S). The results are shown in Table 1.

[0043] Selectivity of elemental sulfur: Elemental sulfur generated in the reaction was collected under the same conditions as the hydrogen sulfide removal efficiency and breakthrough sulfur capacity test. After filtration, it was vacuum dried at 50°C to constant weight. The amount of hydrogen sulfide removed was determined by iodometric titration, and the selectivity of elemental sulfur was calculated accordingly. The results are shown in Table 1.

[0044] Resistance to cyanide and mercaptan poisoning: Under the test conditions of hydrogen sulfide removal efficiency and breakthrough sulfur capacity, a sodium cyanide solution with a mass concentration of 10 mg / L was introduced by atomization and carried into the gas, and 20 mg / L ethanethiol was added to the liquid phase. After keeping other conditions unchanged, the removal rate was determined by iodometric titration after 60 min of stable operation. The results are shown in Table 1.

[0045] Cycle stability and regeneration performance: A single cycle was defined as 240 min of desulfurization, 30 min of air bubbling regeneration (500 mL / min), and 10 min of settling. Fifty cycles were continuously performed at the same temperature, pH and gas flow rate. The removal rate was determined by iodometric titration at the end of the 50 cycles. The results are shown in Table 1.

[0046] Table 1 Performance Test Results Data Analysis: As can be seen from the data in Examples 1-3 in Table 1, the chelated iron desulfurizer prepared by the present invention exhibits a stable and balanced desulfurization capacity throughout the entire process of gas-liquid absorption-interfacial oxidation-solid-liquid separation. Its removal efficiency, penetration persistence, sulfur load per unit volume, elemental sulfur yield, tolerance to the coexistence of cyanide and mercaptan, and activity retention after multiple cycles all reach a level that matches the requirements of the working conditions. This may be due to the following reasons: the core-shell composite microspheres localize the ferric active center in the shell layer near the gas-liquid interface, and the macrocyclic ligand stabilizes the ferric iron in the multidentate nitrogen-oxygen coordination environment, reducing the probability of hydrolysis and substitution by impurities; the cationic microenvironment constructed by benzyl quaternary ammonium enriches the anionic substrate, shortens the diffusion path and reduces mass transfer resistance; the poly-N-isopropylacrylamide shell regulates local solvation and microenvironment polarity, making hydrogen sulfide more inclined to selectively oxidize via the elemental sulfur pathway; at the same time, the complexed iron in the solution phase and the active center localized in the solid phase form a complementary "active pool", providing an active buffer and iron loss compensation between operation and regeneration, thereby supporting long-term stable operation.

[0047] As can be seen from the data in Table 1 for Example 2 and Comparative Example 1, Example 2 exhibits more complete and balanced performance in terms of removal efficiency, penetration persistence, sulfur capacity, elemental sulfur selectivity, resistance to impurity poisoning, and cycle stability. This is because Comparative Example 1, lacking the benzyl quaternary ammonium site, does not possess a stable cation microenvironment in its shell, making it difficult to form an interface enrichment for anionic substrates. This results in a decrease in the effective reaction volume fraction at the gas-liquid interface and an increase in mass transfer resistance. Simultaneously, the interfacial charge regulation is weakened, and the ability to suppress side reaction pathways decreases, resulting in a synergistic decline in selectivity and tolerance.

[0048] As can be seen from the data of Example 2 and Comparative Example 2 in Table 1, Example 2 is superior to the shell system containing only poly-N-isopropylacrylamide in many indicators. This is because without macrocyclic ligand sites, the shell lacks a multidentate chelating environment with a high stability constant. Trivalent iron is more easily hydrolyzed or competitively displaced by strong ligands such as cyanide and thiols, resulting in a decrease in the effective density and lifetime of the active center. At the same time, the frequency of iron-ligand reorganization near the interface increases, affecting the continuous activation and regeneration efficiency, and consequently reducing selectivity and cycle durability.

[0049] As can be seen from the data in Table 1 for Example 2 and Comparative Example 3, Example 2 has a greater advantage in mass transfer and selectivity correlation indicators, and its tolerance and cycling performance are more stable. This is because the methyl methacrylate shell is more hydrophobic and has a higher glass transition temperature, which reduces interfacial wettability and ion permeability, resulting in unfavorable diffusion, penetration, and local solvation of hydrogen sulfide and its ionic state in the shell; lacking a reversibly controllable hydrophilic-hydrophobic balance, the interfacial reaction is difficult to achieve efficient in-situ and local oxidation under mild conditions.

[0050] As can be seen from the data in Table 1 for Example 2 and Comparative Example 4, Example 2 is superior in terms of penetration persistence, sulfur capacity, and cycle retention. This is because Comparative Example 4 lacks solid-phase localized iron, resulting in insufficient density of active centers near the interface. It mainly relies on the bulk migration of complexed iron in the solution phase for replenishment, thus limiting the effective reaction rate at the interface. At the same time, the iron in the solution phase is more prone to loss and morphological fluctuations during cycling. Although it recovers briefly after regeneration, it is not in a steady state, resulting in a decrease in continuous output capacity and lifespan.

[0051] As can be seen from the data in Table 1 for Example 2 and Comparative Example 5, Example 2 performs better in terms of removal efficiency, penetration persistence, and activity at the cycle endpoint. This is because Comparative Example 5 relies solely on immobilized iron, and the system lacks a bulk "active reservoir" and compensation channels, limiting the regeneration and diffusion replenishment rate of active species after the interfacial reaction. In the presence of impurities, if local activity is temporarily passivated, the lack of rapid bulk refill leads to a temporary drop in efficiency and premature penetration.

[0052] As can be seen from the data in Table 1 for Example 2 and Comparative Example 6, Example 2 is more resilient in terms of selectivity, resistance to poisoning, and cycle stability. This is because, due to the lack of carbonate / bicarbonate buffer in Comparative Example 6, the system pH is more prone to drift, the hydrolysis and coordination rearrangement of ferric iron are intensified, and the pH of the interfacial microenvironment is difficult to maintain in a range favorable to the elemental sulfur pathway; at the same time, the lack of buffer amplifies the fluctuations in redox potential and coordination state, thus reducing the robustness against cyanide and thiols.

[0053] from Figure 1 It can be seen that, with the gradual progress of functionalization and coordination, the C-Cl characteristic peak (~702 cm⁻¹) of the cross-linked polymer microspheres to the quaternized functional microspheres increases. -1 The concentration of quaternary ammonium significantly decreased until it almost disappeared, and quaternary ammonium characteristic bands (1475, 1180, 1035 cm⁻¹) appeared. -1 In C, due to the grafting of N-isopropylacrylamide with a macrocyclic monomer, amide I / II (~1650 / 1540 cm⁻¹) -1 ) and COO - Double peaks (~1606 / 1411cm) -1 The presence of ν is obvious; further loading with Fe(III) followed by loading with iron-active centers in macrocyclic core-shell composite microspheres, COO⁻ as / ν s The peak has shifted as a whole (~1594 / 1396cm) -1 ) and at 580 / 495cm -1 The presence of Fe-O / Fe-N fingerprint peaks jointly verifies the phased completion of quaternization, shell grafting, and the construction of iron active centers.

[0054] 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 chelated iron desulfurizing agent, characterized in that, The product is prepared by weight from the following components: 8-12 parts DOTA, 1000 parts deionized water, 12-16 parts ferric chloride hexahydrate, 16-24 parts anhydrous sodium carbonate, 8-12 parts sodium bicarbonate and 40-60 parts macrocyclic functionalized core-shell composite microspheres loaded with iron active centers. The preparation steps of the macrocyclic functionalized core-shell composite microspheres loaded with iron active centers are as follows: S1: p-SCN-Bn-DOTA (S-2-(4-phenyl isothiocyanate)-1,4,7,10-tetraazacyclododecanetetraacetic acid), 2-aminoethyl methacrylate hydrochloride and N,N-diisopropylethylamine were added to N,N-dimethylformamide, stirred at 25°C for 12 h, and purified to obtain a polymerizable macrocyclic monomer; S2: Polyvinyl alcohol was added to deionized water and stirred for 30 min. Then 4-chloromethylstyrene, divinylbenzene, 2-hydroxyethyl methacrylate and azobisisobutyronitrile were added and stirred at 70 °C for 6 h. After purification, cross-linked polymer microspheres were obtained. S3: Add cross-linked polymer microspheres and trimethylamine aqueous solution to anhydrous ethanol, stir and react at 60℃ for 6-10 h, purify, and obtain quaternized functional microspheres; S4: Under nitrogen protection, quaternized functional microspheres were dispersed in anhydrous dichloromethane, and then triethylamine and 2-bromoisobutyryl bromide were added. The mixture was stirred at 25°C for 3-5 hours and purified to obtain functional microspheres with initiator groups on the surface. S5: N-isopropylacrylamide and polymerizable macrocyclic monomers were added to a mixed solution of deionized water and anhydrous ethanol and stirred for 15 min. Then, functional microspheres with initiator groups on the surface, copper chloride, copper dichloride and N,N,N',N'',N''-pentamethyldiethylenetriamine were added. Nitrogen gas was purged for oxygen removal for 30 min, and the mixture was stirred at 25 °C for 5-7 h. After purification, macrocyclic functionalized core-shell composite microspheres were obtained. S6: Disperse macrocyclic functionalized core-shell composite microspheres in deionized water, add ferric chloride hexahydrate, stir at 60℃ for 6 h, and purify to obtain macrocyclic functionalized core-shell composite microspheres loaded with iron active centers.

2. The chelated iron desulfurizer according to claim 1, characterized in that, The model number of the DOTA is macrocyclicsM-140.

3. The chelated iron desulfurizing agent according to claim 1, characterized in that, In step S1, the weight ratio of p-SCN-Bn-DOTA, 2-aminoethyl methacrylate hydrochloride, N,N-diisopropylethylamine, and N,N-dimethylformamide is 4-6:2.4-3.6:1.6-2.4:40-60.

4. The chelated iron desulfurizer according to claim 1, characterized in that, In step S1, the p-SCN-Bn-DOTA model is macrocyclics B-205.

5. The chelated iron desulfurizer according to claim 1, characterized in that, In step S2, the weight-average molecular weight of polyvinyl alcohol is 120,000-140,000.

6. The chelated iron desulfurizer according to claim 1, characterized in that, In step S2, the weight ratio of polyvinyl alcohol, deionized water, 4-chloromethylstyrene, divinylbenzene, 2-hydroxyethyl methacrylate, and azobisisobutyronitrile is 20:2000:140-180:35-45:8-12:1.6-2.

4.

7. The chelated iron desulfurizing agent according to claim 1, characterized in that, In step S3, the weight ratio of cross-linked polymer microspheres, trimethylamine aqueous solution, and anhydrous ethanol is 100:160-240:160-240; the concentration of anhydrous ethanol in step S3 is 45 wt%.

8. The chelated iron desulfurizing agent according to claim 1, characterized in that, In step S4, the weight ratio of quaternized functional microspheres, anhydrous dichloromethane, triethylamine, and 2-bromoisobutyryl bromide is 60:500:15-25:30-50.

9. The chelated iron desulfurizing agent according to claim 1, characterized in that, In step S5, the weight ratio of N-isopropylacrylamide, polymerizable macrocyclic monomer, deionized water, anhydrous ethanol, functional microspheres with surface initiator groups, copper monochloride, copper dichloride, and N,N,N',N'',N''-pentamethyldiethylenetriamine is 50-70:4-8:400:400:60:0.8-1.2:0.8-1.2:1.6-2.

4.

10. The chelated iron desulfurizing agent according to claim 1, characterized in that, In step S6, the weight ratio of macrocyclic functionalized core-shell composite microspheres, deionized water, and ferric chloride hexahydrate is 100:1000:8-12.

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