Chelated iron desulfurizer

Abstract

The present application relates to the field of environmental catalysis and pollution control technology, and particularly relates to a chelated iron desulfurizer. The desulfurizer takes DOTA as a core chelating agent, and through a multi-step polymerization and functionalization process, the iron active center is precisely anchored in the shell layer of the polymer core-shell structure microsphere, supplemented by the design of solution-state complex iron, which has both solid-phase localization and solution compensation, significantly improving the resistance to cyanide, mercaptan and other impurities poisoning capacity, and reducing iron loss. The desulfurizer has high desulfurization efficiency, large sulfur capacity, and can be stably operated for a long period. Under the conditions of coexistence of various impurities and repeated regeneration, the desulfurizer shows excellent sustained activity and selectivity, and has good application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of environmental catalysis and pollution control technology, and particularly relates to a chelated iron desulfurizer. BACKGROUND

[0002] Hydrogen sulfide, as an important industrial by-product and environmental pollutant, exists widely in the fields of petroleum chemical industry, natural gas treatment, wastewater treatment and biomass gasification. Traditional desulfurization technologies mainly include physical absorption method, chemical absorption method and biological desulfurization method, among which the liquid phase oxidation method is widely concerned due to its advantages of mild operation, good selectivity and direct conversion of H2S into elemental sulfur.

[0003] The chelated iron desulfurization technology, as an important branch of the liquid phase oxidation method, is to use the oxidizability of Fe 3+ to oxidize hydrogen sulfide into elemental sulfur, and to stabilize iron ions by chelating agents to prevent their hydrolysis and precipitation. Traditional chelated iron desulfurizers mostly use EDTA, NTA and other conventional chelating agents, which can stabilize iron ions to a certain extent, but face many challenges in actual industrial applications.

[0004] Firstly, the insufficient anti-poisoning ability is a key bottleneck of the existing technology. Impurities such as cyanide, mercaptans and heavy metal ions exist universally in industrial waste gas, which have competitive complexing ability with chelating agents or iron ions, leading to the deactivation of active centers. In particular, cyanide has a strong complexing ability, which can form a more stable complex with iron ions, causing the rapid failure of the desulfurizer. Mercaptans can form sulfur-iron bonds with iron ions, hindering the normal oxidation reaction.

[0005] Secondly, the iron loss seriously affects the economy and environmental protection of the desulfurizer. The stability constant of the traditional chelating agent is relatively low, and the iron ions are prone to hydrolysis and precipitation or loss with the circulation in the long-term operation, which requires frequent replenishment, increasing the operation cost and bringing the risk of secondary pollution. Especially in the alkaline environment, Fe 3+ is prone to hydrolysis to form Fe(OH)3 precipitate, resulting in the loss of active components.

[0006] Thirdly, the selective oxidation control is difficult. The ideal desulfurization process should selectively oxidize H2S into elemental sulfur, but in the actual reaction, over-oxidation often occurs to form by-products such as sulfates and sulfites, which reduces the sulfur recovery rate and increases the difficulty of subsequent separation. The existing technology is difficult to accurately control the reaction path and oxidation depth.

[0007] Fourthly, the mass transfer limitation affects the reaction efficiency. The solubility of H2S in the liquid phase is relatively low, and the gas-liquid mass transfer becomes the control step of the reaction rate. The traditional homogeneous catalytic system lacks effective mass transfer enhancement means, which is difficult to improve the interface reaction efficiency.

[0008] Fifth, the pH range is narrow. The existing chelated iron system usually maintains good stability and activity within a certain pH range. The pH fluctuation will lead to iron hydrolysis or chelator decomposition, affecting the desulfurization effect. The actual industrial waste gas composition is complex, and the pH is difficult to control accurately.

[0009] Sixth, the regeneration performance is limited. After the desulfurization reaction, Fe 2+ is re-oxidized to Fe 3+ . The regeneration efficiency of the traditional system is not high, and the activity decreases significantly after multiple regeneration, affecting the long-term stable operation.

[0010] In addition, the existing technology also faces problems such as uneven distribution of active components, complex reactor design, and harsh operating conditions. The active centers in the homogeneous catalytic system are randomly dispersed, making it difficult to form a high-density active area. Although the immobilization technology can reduce iron loss, it often sacrifices activity and mass transfer performance. Therefore, it is urgent to develop a new type of chelated iron desulfurizer with high stability, strong resistance to poisoning, low iron loss, and high selectivity to meet the high-efficiency desulfurization demand under complex working conditions. Such a desulfurizer should have a stable active center structure, an effective mass transfer strengthening mechanism, and excellent cyclic regeneration performance. SUMMARY

[0011] Therefore, the purpose of the present application is to provide a chelated iron desulfurizer to solve the problems of existing chelated iron desulfurizers that are easily deactivated and have severe iron loss under complex working conditions.

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

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

[0014] Further, the preparation steps of the macrocyclic functionalized core-shell structure composite microspheres loaded with iron active centers are as follows:

[0015] S1: p-SCN-Bn-DOTA (S-2-(4-isothiocyanate phenyl)-1,4,7,10-tetraazacyclododecane tetraacetic acid), 2-aminoethyl methacrylate hydrochloride, and N,N-diisopropyl ethylamine are added to N,N-dimethyl formamide, stirred at 25℃ for 12h, purified, and a polymerizable macrocyclic monomer is obtained;

[0016] S2: adding polyvinyl alcohol into deionized water, stirring for 30 min, then adding 4-chloromethylstyrene, divinylbenzene, 2-hydroxyethyl methacrylate and azobisisobutyronitrile, stirring for 6 h at 70℃, purifying to obtain crosslinked polymer microspheres;

[0017] S3: adding crosslinked polymer microspheres and aqueous trimethylamine into anhydrous ethanol, stirring for 6-10 h at 60℃, purifying to obtain quaternized functional microspheres;

[0018] S4: dispersing quaternized functional microspheres in anhydrous dichloromethane under nitrogen protection, then adding triethylamine and 2-bromoisobutyryl bromide, stirring for 3-5 h at 25℃, purifying to obtain functional microspheres with initiating groups on the surface;

[0019] S5: adding N-isopropyl acrylamide and polymerizable macrocyclic monomer into a mixed solution of deionized water and anhydrous ethanol, stirring for 15 min, then adding functional microspheres with initiating groups on the surface, cuprous chloride, cupric dichloride and N,N,N',N'',N''-pentamethyldiethylenetriamine, deoxygenating for 30 min under nitrogen, stirring for 5-7 h at 25℃, purifying to obtain macrocyclic functional core-shell structure composite microspheres;

[0020] S6: dispersing macrocyclic functional core-shell structure composite microspheres in deionized water, then adding ferric chloride hexahydrate, stirring for 6 h at 60℃, purifying to obtain macrocyclic functional core-shell structure composite microspheres loaded with iron active centers.

[0021] Preferably, the weight ratio of p-SCN-Bn-DOTA, 2-aminoethyl methacrylate hydrochloride, N,N-diisopropylethylamine and N,N-dimethylformamide in step S1 is 4-6:2.4-3.6:1.6-2.4:40-60.

[0022] Preferably, the model of p-SCN-Bn-DOTA in step S1 is macrocyclics B-205.

[0023] Preferably, the weight average molecular weight of polyvinyl alcohol in step S2 is 120000-140000.

[0024] Preferably, the weight ratio of polyvinyl alcohol, deionized water, 4-chloromethylstyrene, divinylbenzene, 2-hydroxyethyl methacrylate and azobisisobutyronitrile in step S2 is 20:2000:140-180:35-45:8-12:1.6-2.4.

[0025] Preferably, the weight ratio of crosslinked polymer microspheres, aqueous trimethylamine and anhydrous ethanol in step S3 is 100:160-240:160-240.

[0026] Preferably, the concentration of anhydrous ethanol in step S3 is 45wt%.

[0027] Preferably, the weight ratio of quaternary ammonium functional microspheres, anhydrous dichloromethane, triethylamine and 2-bromoisobutyryl bromide in step S4 is 60:500:15-25:30-50.

[0028] Preferably, the weight ratio of N-isopropyl acrylamide, polymerizable macrocyclic monomer, deionized water, anhydrous ethanol, surface-initiation-group-containing functional microspheres, cuprous chloride, cupric chloride and N,N,N',N'',N''-pentamethyldiethylenetriamine in step S5 is 50-70:4-8:400:400:60:0.8-1.2:0.8-1.2:1.6-2.4.

[0029] Preferably, the weight ratio of macrocyclic functional core-shell structure composite microspheres, deionized water and ferric chloride hexahydrate in step S6 is 100:1000:8-12.

[0030] The beneficial effects of the present application are:

[0031] Significant enhancement of anti-poisoning ability: The multi-dentate chelating environment constructed by macrocyclic ligand DOTA forms a complex structure with higher stability constant than traditional ligands such as EDTA and NTA. The pre-organization effect and multi-point coordination characteristics of macrocyclic ligand make Fe 3+ ions firmly bound in the coordination cage, effectively resisting the competition of strong ligands such as cyanide and thiol. The cationic microenvironment provided by the quaternary ammonium shell further stabilizes the complex structure, significantly improving the tolerance performance in complex working conditions.

[0032] Significant reduction of iron loss: The spatial localization of active centers is realized through the core-shell composite microsphere structure, and the key Fe 3 + -DOTA complex is immobilized in the polymer shell, which fundamentally prevents the diffusion loss of iron ions. At the same time, the solution-phase DOTA-Fe complex is introduced as an "active reservoir", forming a dual protection mechanism of solid-phase localization and solution compensation, which not only ensures the efficient progress of the interface reaction, but also maximizes the systematic loss of iron components, achieving the unity of economy and environmental protection.

[0033] Accurate control of selective oxidation: The poly-N-isopropyl acrylamide intelligent response shell can adjust the balance of hydrophilic and hydrophobic levels of the local microenvironment according to the reaction environment, providing an optimal 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 follow the desired path, effectively inhibiting over-oxidation side reactions, improving sulfur recovery rate and reducing byproduct generation.

[0034] Significant improvement of mass transfer efficiency: the core-shell structure design makes the active center high-density distribution near the gas-liquid interface, greatly shortening the diffusion path of the reactants. The electrostatic adsorption of quaternary ammonium functional groups to HS - , S2O3 2- , etc. Anion substrate forms a high-concentration reaction area at the interface, overcoming the problem of dilution of active components in traditional homogeneous systems. The swelling and shrinking properties of the intelligent shell further optimize the mass transfer resistance, realizing efficient gas-liquid interface reaction.

[0035] 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 complex iron ensures the timely replenishment of active components. The synergistic effect of multiple stabilization measures enables the desulfurizer to maintain high desulfurization performance after multiple cycles. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the present application or prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description.

[0037] Figure 1 The infrared spectra of the cross-linked polymer microspheres, quaternized functional microspheres, macrocyclic functional core-shell structure composite microspheres, and iron active center loaded macrocyclic functional core-shell structure composite microspheres in Example 2 of the present application. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the present application more clear and explicit, the following will further describe the present application in combination with specific embodiments.

[0039] Example 1:

[0040] (1) Add 4g S-2-(4-isothiocyanate phenyl)-1,4,7,10-tetraazacyclododecane tetraacetic acid (p-SCN-Bn-DOTA, type: macrocyclics B-205), 2.4g 2-aminoethyl methacrylate hydrochloride and 1.6g N,N-diisopropyl ethylamine into 40g N,N-dimethyl formamide, stir at 25℃ for 12h, remove the solvent under reduced pressure, wash with acetonitrile / water (9:1, v / v), and vacuum dry to obtain polymerizable macrocyclic monomer;

[0041] (2) 20 g of polyvinyl alcohol (type Mowiol 18-88, weight average molecular weight about 130000) was added into 2000 g of deionized water, stirred at 600 rpm for 30 min, then 140 g of 4-chloromethylstyrene, 35 g of divinylbenzene, 8 g of 2-hydroxyethyl methacrylate and 1.6 g of azobisisobutyronitrile were added, stirred at 70℃ for 6 h, filtered, washed with anhydrous ethanol and deionized water in turn until neutral, and vacuum dried to obtain crosslinked polymer microspheres;

[0042] (3) 100 g of crosslinked polymer microspheres and 160 g of trimethylamine aqueous solution (concentration of 45 wt%) were added into 240 g of anhydrous ethanol, stirred at 60℃ for 6 h, filtered, washed with anhydrous ethanol and deionized water in turn until neutral, and vacuum dried to obtain quaternized functional microspheres;

[0043] (4) 60 g of quaternized functional microspheres were dispersed in 500 g of anhydrous dichloromethane under nitrogen protection, then 15 g of triethylamine and 30 g of 2-bromoisobutyryl bromide were added, stirred at 25℃ for 3 h, filtered, washed with anhydrous dichloromethane, anhydrous ethanol and deionized water in turn, and vacuum dried to obtain functional microspheres with initiating groups on the surface;

[0044] (5) 50 g of N-isopropyl acrylamide and 4 g of polymerizable macrocyclic monomer were added into a mixed solution of 400 g of deionized water and 400 g of anhydrous ethanol, stirred for 15 min, then 60 g of functional microspheres with initiating groups on the surface, 0.8 g of copper(I) chloride, 0.8 g of copper(II) chloride and 1.6 g of N,N,N',N'',N''-pentamethyldiethylenetriamine were added, deoxygenated by nitrogen for 30 min, stirred at 25℃ for 5 h, filtered, washed with anhydrous ethanol and deionized water in turn, and vacuum dried to obtain macrocyclic functional core-shell structure composite microspheres;

[0045] (6) 100 g of macrocyclic functional core-shell structure composite microspheres were dispersed in 1000 g of deionized water, then 8 g of ferric chloride hexahydrate was added, stirred at 60℃ for 6 h, filtered, washed with deionized water, and vacuum dried to obtain macrocyclic functional core-shell structure composite microspheres loaded with iron active centers;

[0046] (7) 8 g of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA, type macrocyclics M-140) was added into 1000 g of deionized water, stirred for 15 min, then 12 g of ferric chloride hexahydrate, 16 g of anhydrous sodium carbonate and 8 g of sodium bicarbonate were added, stirred for 30 min, then 40 g of macrocyclic functional core-shell structure composite microspheres loaded with iron active centers were added, stirred at 25℃ for 30 min to obtain chelated iron desulfurizer.

[0047] Example 2:

[0048] (1) 5 g of S-2-(4-isothiocyanatophenyl)-1,4,7,10-tetraazacyclododecane tetraacetic acid (p-SCN-Bn-DOTA, type: macrocyclics B-205), 3 g of 2-aminoethyl methacrylate hydrochloride and 2 g of N,N-diisopropylethylamine were added into 50 g of N,N-dimethylformamide, stirred at 25 °C for 12 h, washed with acetonitrile / water (9:1, v / v) after removing the solvent under reduced pressure, and vacuum dried to obtain a polymerizable macrocyclic monomer;

[0049] (2) 20 g of polyvinyl alcohol (type: Mowiol 18-88, weight average molecular weight about 130000) was added into 2000 g of deionized water, stirred at 600 rpm for 30 min, and then 160 g of 4-chloromethylstyrene, 40 g of divinylbenzene, 10 g of 2-hydroxyethyl methacrylate and 2 g of azobisisobutyronitrile were added, stirred at 70 °C for 6 h, filtered, washed with anhydrous ethanol and deionized water in sequence until neutral, and vacuum dried to obtain crosslinked polymer microspheres;

[0050] (3) 100 g of crosslinked polymer microspheres and 200 g of trimethylamine aqueous solution (concentration: 45 wt%) were added into 200 g of anhydrous ethanol, stirred at 60 °C for 8 h, filtered, washed with anhydrous ethanol and deionized water in sequence until neutral, and vacuum dried to obtain quaternized functional microspheres;

[0051] (4) 60 g of quaternized functional microspheres were dispersed in 500 g of anhydrous dichloromethane under nitrogen protection, and then 20 g of triethylamine and 40 g of 2-bromoisobutyryl bromide were added, stirred at 25 °C for 4 h, filtered, washed with anhydrous dichloromethane, anhydrous ethanol and deionized water in sequence, and vacuum dried to obtain functional microspheres with initiating groups on the surface;

[0052] (5) 60 g of N-isopropylacrylamide and 6 g of polymerizable macrocyclic monomer were added into a mixed solution of 400 g of deionized water and 400 g of anhydrous ethanol, stirred for 15 min, and then 60 g of functional microspheres with initiating groups on the surface, 1 g of copper(I) chloride, 1 g of copper(II) chloride and 2 g of N,N,N',N'',N''-pentamethyldiethylenetriamine were added, deoxygenated by nitrogen for 30 min, stirred at 25 °C for 6 h, filtered, washed with anhydrous ethanol and deionized water in sequence, and vacuum dried to obtain macrocyclic functional core-shell structure composite microspheres;

[0053] (6) 100 g of macrocyclic functional core-shell structure composite microspheres were dispersed in 1000 g of deionized water, and then 10 g of ferric chloride hexahydrate was added, stirred at 60 °C for 6 h, filtered, washed with deionized water, and vacuum dried to obtain macrocyclic functional core-shell structure composite microspheres loaded with iron active centers;

[0054] (7) 10 g of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA, type: macrocyclics M-140) was added into 1000 g of deionized water, stirred for 15 min, and then 14 g of ferric chloride hexahydrate, 20 g of anhydrous sodium carbonate, and 10 g of sodium bicarbonate were added, stirred for 30 min, and then 50 g of macrocyclic functional core-shell structure composite microspheres loaded with iron active centers were added, stirred for 30 min at 25°C, to obtain a chelated iron desulfurizer.

[0055] Example 3:

[0056] (1) 6 g of S-2-(4-isothiocyanatophenyl)-1,4,7,10-tetraazacyclododecane tetraacetic acid (p-SCN-Bn-DOTA, type: macrocyclics B-205), 3.6 g of 2-aminoethyl methacrylate hydrochloride, and 2.4 g of N,N-diisopropylethylamine were added into 60 g of N,N-dimethylformamide, stirred at 25°C for 12 h, and then washed with acetonitrile / water (9:1, v / v) after solvent removal under reduced pressure, and vacuum dried to obtain a polymerizable macrocyclic monomer;

[0057] (2) 20 g of polyvinyl alcohol (type: Mowiol 18-88, weight average molecular weight about 130000) was added into 2000 g of deionized water, stirred at 600 rpm for 30 min, and then 180 g of 4-chloromethylstyrene, 45 g of divinylbenzene, 12 g of 2-hydroxyethyl methacrylate, and 2.4 g of azobisisobutyronitrile were added, stirred at 70°C for 6 h, filtered, and then washed with anhydrous ethanol and deionized water to neutral, and vacuum dried to obtain crosslinked polymer microspheres;

[0058] (3) 100 g of crosslinked polymer microspheres and 240 g of a trimethylamine aqueous solution (concentration: 45 wt%) were added into 160 g of anhydrous ethanol, and stirred at 60°C for 10 h, filtered, and then washed with anhydrous ethanol and deionized water to neutral, and vacuum dried to obtain quaternary ammonium functional microspheres;

[0059] (4) 60 g of quaternary ammonium functional microspheres were dispersed in 500 g of anhydrous dichloromethane under nitrogen protection, and then 25 g of triethylamine and 50 g of 2-bromoisobutyryl bromide were added, stirred at 25°C for 5 h, filtered, and then washed with anhydrous dichloromethane, anhydrous ethanol, and deionized water, and vacuum dried to obtain functional microspheres with an initiation group on the surface;

[0060] (5) 70 g of N-isopropyl acrylamide and 8 g of polymerizable macrocyclic monomer were added to a mixed solution of 400 g of deionized water and 400 g of anhydrous ethanol, stirred for 15 min, and then 60 g of surface-initiating group functional microspheres, 1.2 g of copper chloride, 1.2 g of copper dichloride, and 2.4 g of N,N,N',N'',N''-pentamethyldiethylenetriamine were added, deoxygenated by nitrogen for 30 min, stirred at 25°C for 7 h, filtered, washed with anhydrous ethanol and deionized water in turn, and vacuum dried to obtain macrocyclic functional core-shell structure composite microspheres;

[0061] (6) 100 g of macrocyclic functional core-shell structure composite microspheres were dispersed in 1000 g of deionized water, and then 12 g of iron chloride hexahydrate was added, stirred at 60°C for 6 h, filtered, washed with deionized water, and vacuum dried to obtain macrocyclic functional core-shell structure composite microspheres loaded with iron active centers.

[0062] (7) 12 g of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA, type: macrocyclics M-140) was added to 1000 g of deionized water, stirred for 15 min, and then 16 g of iron chloride hexahydrate, 24 g of anhydrous sodium carbonate, and 12 g of sodium bicarbonate were added, stirred for 30 min, and then 60 g of macrocyclic functional core-shell structure composite microspheres loaded with iron active centers were added, stirred at 25°C for 30 min to obtain chelated iron desulfurizer.

[0063] Comparative Example 1:

[0064] Comparative Example 1 and Example 2 differ in that in step (3), no trimethylamine treatment is performed to form benzyl quaternary ammonium sites (i.e., no quaternary ammonium functionalization is performed), and the remaining conditions are consistent with Example 2.

[0065] Comparative Example 2:

[0066] Comparative Example 2 and Example 2 differ in that in step (5), no polymerizable macrocyclic monomer S-2-(4-isothiocyanate phenyl)-1,4,7,10-tetraazacyclododecane tetraacetic acid is added during shell layer polymerization, and only N-isopropyl acrylamide is used as a shell layer monomer to construct the shell layer, and the remaining conditions are consistent with Example 2.

[0067] Comparative Example 3:

[0068] Comparative Example 3 and Example 2 differ in that in step (5), N-isopropyl acrylamide is replaced by methyl methacrylate for shell layer polymerization, and the total monomer feed amount, catalysis, and time remain consistent, and the remaining conditions are consistent with Example 2.

[0069] Comparative Example 4:

[0070] Comparative Example 4 differs from Example 2 in that no iron trichloride hexahydrate loading treatment is performed in step (6) (no solid-phase localized iron active center is constructed), and the solution complexing iron system is directly prepared in step (7). The other conditions are the same as those in Example 2.

[0071] Comparative Example 5:

[0072] Comparative Example 5 differs from Example 2 in that no 1,4,7,10-tetraazacyclododecane-1,7-diacetic acid and its iron complex are added in step (7), and only deionized water is used instead, while maintaining the same volume and stirring conditions (i.e., only the solid-supported iron active center is retained). The other conditions are the same as those in Example 2.

[0073] Comparative Example 6:

[0074] Comparative Example 6 differs from Example 2 in that no anhydrous sodium carbonate and sodium bicarbonate buffer system is added in step (7), and instead an equimolar ionic strength sodium chloride solution is added, while maintaining the same total volume and stirring conditions. The other conditions are the same as those in Example 2.

[0075] Performance test:

[0076] Infrared spectrum analysis: Fourier transform infrared spectrometer was used for analysis, and the results are shown in Table 1. Figure 1

[0077] Hydrogen sulfide removal efficiency and breakthrough sulfur capacity: The desulfurization performance of each example and each comparative example was investigated in a 1L bubble column (liquid volume 500mL) at (25±1)℃, relative humidity (50±5)%, with an inlet gas ratio of hydrogen sulfide volume fraction 0.50%, carbon dioxide 2.00%, and the balance nitrogen, total flow rate 1000mL / min, total iron concentration in the liquid phase of the desulfurizer 0.050mol / L, and initial pH 8.30. The inlet and outlet hydrogen sulfide contents were determined by iodimetry, stable operation was maintained for 60min, the removal rate was calculated, the breakthrough time was defined as when the outlet reached 5% of the inlet, and the sulfur capacity was calculated based on the sulfur (in S) absorbed per unit volume, and the results are shown in Table 1.

[0078] Elemental sulfur selectivity: The elemental sulfur generated under the same conditions as the hydrogen sulfide removal efficiency and breakthrough sulfur capacity test was collected, filtered, and vacuum dried at 50℃ to a constant weight to obtain the mass. The amount of removed hydrogen sulfide was determined by iodimetry, and the elemental sulfur selectivity was calculated accordingly, and the results are shown in Table 1.

[0079] Resistance to cyanide and mercaptan poisoning: Under the conditions of the hydrogen sulfide removal efficiency and breakthrough sulfur capacity test, a 10mg / L sodium cyanide solution was introduced into the gas by atomization and added into the liquid phase, and 20mg / L ethyl mercaptan was added, while maintaining other conditions unchanged. After stable operation for 60min, the removal rate was determined by iodimetry, and the results are shown in Table 1. ​

[0080] Cyclic stability and regeneration performance: A single cycle was defined as 240 min desulfurization, 30 min air bubbling regeneration (500 mL / min), and 10 min standing, and 50 cycles were continuously performed under the same temperature, pH, and gas flow. The removal rate was determined by iodometric method at the end of the 50th cycle, and the results are shown in Table 1.

[0081] Table 1 Performance test results

[0082]

[0083] Data analysis:

[0084] As can be seen from the data of Examples 1-3 in Table 1, the chelated iron desulfurizer prepared in the application exhibits stable and balanced desulfurization capacity in the whole process of gas-liquid absorption, interfacial oxidation, and solid-liquid separation. Its removal efficiency, penetration persistence, sulfur load per unit volume, elemental sulfur yield, and resistance to coexistence of cyanide and mercaptan all maintain activity after multiple cycles, all reaching a level matching the working conditions. This may be due to the fact that the core-shell composite microspheres localize the trivalent iron active center in the shell layer close to the gas-liquid interface, the macrocyclic ligand stabilizes the trivalent iron in the multi-dentate nitrogen-oxygen coordination environment, reducing the probability of hydrolysis and site competition by impurities; the cationic microenvironment constructed by the benzyl quaternary ammonium group enriches the anionic substrate, shortens the diffusion path, and reduces the mass transfer resistance; the poly-N-isopropyl acrylamide shell layer regulates local solvation and microenvironment polarity, making hydrogen sulfide more inclined to be selectively oxidized through the elemental sulfur path; at the same time, the complex iron in the solution phase and the localized active center in the solid phase form a complementary "active bank", providing active buffering and iron loss compensation between operation and regeneration, thereby supporting long-period stable operation.

[0085] As can be seen from the data of Example 2 and Comparative Example 1 in Table 1, Example 2 performs more completely and evenly in terms of removal efficiency, penetration persistence, sulfur capacity, elemental sulfur selectivity, and resistance to impurity poisoning and cyclic stability. This is because, after the absence of the benzyl quaternary ammonium group site in Comparative Example 1, the shell layer does not have a stable cationic microenvironment, making it difficult to form an interfacial enrichment of anionic substrates, resulting in a decrease in the effective reaction volume fraction at the gas-liquid interface and an increase in the mass transfer resistance; at the same time, the interface charge regulation is weakened, and the inhibition ability of the side reaction path is decreased, resulting in a coordinated decline in selectivity and resistance.

[0086] As can be seen from the data of Example 2 and Comparative Example 2 in Table 1, Example 2 is overall superior to the shell layer system containing only poly-N-isopropyl acrylamide, because without the macrocyclic ligand site, the shell layer lacks a multi-dentate chelation environment with high stability constant, and the trivalent iron is more likely to hydrolyze or be competitively coordinated by cyanide, mercaptan, and other strong ligands, 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 supply of activity and regeneration efficiency, and consequently reducing the selectivity and cyclic persistence.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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) appear; the ν as / ν s peak of COO⁻ is shifted (~1594 / 1396 cm -1 ) and Fe-O / Fe-N fingerprint peaks appear at 580 / 495 cm -1 , which together verify the completion of the quaternization, shell grafting and iron active center construction.

[0092] It should be understood by those of ordinary skill in the art that the above discussion of any of the embodiments is merely exemplary in nature and is not intended to suggest the scope of the application, which is indicated by the appended claims; the technical features among the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes of different aspects of the application as described above, which are not provided in details for the sake of brevity.

Claims

1. A chelated iron desulfurizer characterized by, Prepared from the following components: DOTA 8-12 parts, deionized water 1000 parts, ferric chloride hexahydrate 12-16 parts, anhydrous sodium carbonate 16-24 parts, sodium bicarbonate 8-12 parts and macrocyclically functionalized core-shell structure composite microspheres loaded with iron active centers 40-60 parts by weight; The preparation steps of the macrocyclically functionalized core-shell structure composite microspheres loaded with iron active centers are as follows: S1: p-SCN-Bn-DOTA, 2-aminoethyl methacrylate hydrochloride and N,N-diisopropyl ethylamine were added to N,N-dimethyl formamide, stirred at 25℃ for 12h, purified to obtain polymerizable macrocyclic monomer; S2: polyvinyl alcohol was added to deionized water, stirred for 30min, then 4-chloromethyl styrene, divinylbenzene, 2-hydroxyethyl methacrylate and azobisisobutyronitrile were added, stirred at 70℃ for 6h, purified to obtain crosslinked polymer microspheres; S3: crosslinked polymer microspheres and trimethylamine aqueous solution were added to anhydrous ethanol, stirred and reacted at 60℃ for 6-10h, purified to obtain quaternary ammonium functional microspheres; S4: quaternary ammonium functional microspheres were dispersed in anhydrous dichloromethane under nitrogen protection, then triethylamine and 2-bromoisobutyryl bromide were added, stirred at 25℃ for 3-5h, purified to obtain functional microspheres with surface initiation groups; S5: N-isopropyl acrylamide and polymerizable macrocyclic monomer were added to a mixed solution of deionized water and anhydrous ethanol, stirred for 15min, then functional microspheres with surface initiation groups, copper chloride, copper dichloride and N,N,N',N'',N''-pentamethyl diethylenetriamine were added, deoxygenated by nitrogen for 30min, stirred at 25℃ for 5-7h, purified to obtain macrocyclically functionalized core-shell structure composite microspheres; S6: macrocyclically functionalized core-shell structure composite microspheres were dispersed in deionized water, then ferric chloride hexahydrate was added, stirred at 60℃ for 6h, purified to obtain macrocyclically functionalized core-shell structure composite microspheres loaded with iron active centers.

2. The chelated iron desulfurizer of claim 1, wherein, The model of the DOTA is macrocyclics M-140.

3. The chelated iron desulfurizer of claim 1, wherein, The weight ratio of p-SCN-Bn-DOTA, 2-aminoethyl methacrylate hydrochloride, N,N-diisopropyl ethylamine and N,N-dimethyl formamide in step S1 is 4-6:2.4-3.6:1.6-2.4:40-60.

4. The chelated iron desulfurizer of claim 1, wherein, The model of p-SCN-Bn-DOTA in step S1 is macrocyclics B-205.

5. The chelated iron desulfurizer of claim 1, wherein, The weight average molecular weight of polyvinyl alcohol in step S2 is 120000-140000.

6. The chelated iron desulfurizer of claim 1, wherein, The weight ratio of polyvinyl alcohol, deionized water, 4-chloromethyl styrene, divinylbenzene, 2-hydroxyethyl methacrylate and azobisisobutyronitrile in step S2 is 20:2000:140-180:35-45:8-12:1.6-2.

4.

7. The chelated iron desulfurizer of claim 1, wherein, The weight ratio of crosslinked polymer microspheres, trimethylamine aqueous solution and anhydrous ethanol in step S3 is 100:160-240:160-240; the concentration of anhydrous ethanol in step S3 is 45wt%.

8. The chelated iron desulfurizer of claim 1, wherein, The weight ratio of the quaternary ammonium functional microspheres, anhydrous dichloromethane, triethylamine and 2-bromoisobutyryl bromide in the step S4 is 60:500:15-25:30-50.

9. The chelated iron desulfurizer of claim 1, wherein, The weight ratio of N-isopropyl acrylamide, polymerizable macrocyclic monomer, deionized water, anhydrous ethanol, surface-initiation-group-containing functional microspheres, cuprous chloride, cupric chloride and N,N,N',N'',N''-pentamethyldiethylenetriamine in the step S5 is 50-70:4-8:400:400:60:0.8-1.2:0.8-1.2:1.6-2.

4.

10. The chelated iron desulfurizer of claim 1, wherein, The weight ratio of the macrocyclic functional core-shell structure composite microspheres, deionized water and ferric chloride hexahydrate in the step S6 is 100:1000:8-12.

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