A complex iron desulfurizer and a preparation method thereof

Abstract

The present application relates to the field of environmental catalysis and pollution control technology, and particularly relates to a complex iron desulfurizer and a preparation method thereof. The desulfurizer is modified by double-path nano-silicon dioxide, and is grafted by alkoxysilane in acid and alkali environments, so that the system is endowed with high hydrophilicity and excellent dispersibility, and the colloidal stability and interfacial activity are significantly improved. Meanwhile, N-methyldiethanolamine and ten-water borax are combined to design a buffer shell, so that the pH and coordination stability of the active center of the complex iron are effectively maintained, and the anti-carbon dioxide interference and cycle life are improved. The desulfurizer has excellent performance in desulfurization efficiency, breakthrough time, volume sulfur capacity and multi-cycle, and can still maintain high efficiency under high carbon dioxide atmosphere, and has wide 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 complex iron desulfurizer and a preparation method thereof. BACKGROUND

[0002] With the acceleration of industrialization, the treatment of harmful gases containing hydrogen sulfide has become an important issue in the field of environmental protection. As a kind of efficient wet desulfurization process, the complex iron desulfurization technology is widely used in natural gas purification, coal gas desulfurization, biomass gas purification and other fields due to its mild reaction, good selectivity, renewable use and other advantages.

[0003] The traditional complex iron desulfurizer mainly uses trivalent iron ions and polybasic carboxylic acid chelating agents to form stable complexes, and through oxidation-reduction reaction, hydrogen sulfide is converted into elemental sulfur, and the activity is restored in the oxidation regeneration process. However, the existing technology has many deficiencies:

[0004] Firstly, the complex iron desulfurizer faces serious dispersion stability problems in practical application. Due to the insufficient surface charge density of complex iron particles, agglomeration and sedimentation easily occur in high ionic strength environment, resulting in a sharp decrease in active surface area and a significant decrease in desulfurization efficiency. Especially in the environment of composite gas containing high concentration of carbon dioxide, the pH fluctuation caused by carbon dioxide absorption will further aggravate the instability of complex iron, making the system easy to be deactivated.

[0005] Secondly, the low gas-liquid mass transfer efficiency is the key bottleneck restricting the improvement of desulfurization performance. The surface tension of the traditional desulfurizer is large, which is difficult to form effective gas-liquid contact interface, resulting in increased mass transfer resistance of hydrogen sulfide from gas phase to liquid phase. At the same time, in the gas-liquid contact equipment such as bubble column, due to the slow interface renewal rate, it is difficult to form fresh liquid film, which further reduces the mass transfer driving force and reaction rate.

[0006] Thirdly, the cyclic regeneration performance is unstable. In the multiple oxidation regeneration cycles, the active center of complex iron is easily disturbed by impurity ions, and the coordination environment changes, resulting in the decrease of oxidation-reduction reversibility. Especially in the absence of effective buffer system, the sharp fluctuation of pH value will cause the dissociation of complex or the formation of inactive polymerization state, which seriously affects the long-term use effect.

[0007] Fourthly, the existing modification strategy has limitations. Although some studies have tried to improve the desulfurizer performance by adding surfactants or dispersion stabilizers, these additives often bring side effects such as excessive foam and interface pollution. Simple chemical modification cannot meet the dual requirements of dispersion stability and mass transfer efficiency, and often appears the phenomenon of losing one to gain the other.

[0008] Fifth, the buffer system design is unreasonable. The traditional desulfurizer lacks effective pH buffering mechanism, and under the impact of carbon dioxide and other acid gases, the pH value is prone to sudden drop, which leads to unstable complex iron complex state, reduces the number of active sites, and significantly reduces the desulfurization capacity and reaction kinetics. The existing buffer system either lacks buffering capacity or competes with the complex iron system for coordination.

[0009] Based on the above technical status, it is urgent to develop a new type of complex iron desulfurizer preparation method, which solves the key technical problems such as poor dispersion stability, low mass transfer efficiency, and unstable circulation performance by reasonable component ratio, surface modification and process optimization, to meet the strict requirements of industrial application. SUMMARY

[0010] Therefore, the purpose of the present application is to provide a complex iron desulfurizer and a preparation method thereof, so as to prepare a complex iron desulfurizer with high dispersion stability and excellent gas-liquid mass transfer efficiency.

[0011] Based on the above purpose, the present application provides a complex iron desulfurizer, which contains the following components in 1600 parts of raw materials by weight: 54 parts of ferric chloride hexahydrate, 75-89 parts of ethylenediaminetetraacetic acid disodium dihydrate, 30-36 parts of citric acid monohydrate, 130-190 parts of sodium hydroxide solution, 5-9 parts of N-methyldiethanolamine, 15-23 parts of borax decahydrate, 0.8-1.2 parts of nano-silicon dioxide A, 0.8-1.2 parts of nano-silicon dioxide B, and the balance of deionized water.

[0012] Preferably, the concentration of the sodium hydroxide solution is 4wt%.

[0013] Further, the nano-silicon dioxide A is obtained by grafting triethoxysilylethyl-terminated polydimethylsiloxane and methoxypolyethylene glycol triethoxysilane on nano-silicon dioxide after high-temperature dehydroxylation in an alkaline environment.

[0014] Preferably, the weight ratio of the nano-silicon dioxide, triethoxysilylethyl-terminated polydimethylsiloxane and methoxypolyethylene glycol triethoxysilane is 10:0.3-0.6:0.15-0.3.

[0015] Preferably, the high-temperature dehydroxylation is treated at 350-450°C for 1.5-3h.

[0016] Preferably, the alkaline environment is constructed by triethylamine, anhydrous ethanol and deionized water in a weight ratio of 3-7:320-380:180-120.

[0017] Further, the nano-silica B is obtained by refluxing and re-hydroxylating nano-silica, and then grafting triethoxysilylethyl terminated polydimethylsiloxane and methoxypolyethylene glycol triethoxysilane in an acidic environment.

[0018] Preferably, the weight ratio of the nano-silica, triethoxysilylethyl terminated polydimethylsiloxane and methoxypolyethylene glycol triethoxysilane is 10:0.3-0.6:0.15-0.3.

[0019] Preferably, the refluxing and re-hydroxylating is refluxing and stirring in deionized water for 30-60 min.

[0020] Preferably, the acidic environment is constructed by glacial acetic acid, anhydrous ethanol and deionized water in a weight ratio of 3-7:320-380:180-120.

[0021] Preferably, the grafting condition is stirring at 25°C for 30-60 min, and then refluxing and stirring at 60°C for 3-5 h.

[0022] Preferably, the average particle size of the nano-silica is 50 nm.

[0023] Preferably, the weight average molecular weight of the triethoxysilylethyl terminated polydimethylsiloxane is 800-900.

[0024] Preferably, the weight average molecular weight of the methoxypolyethylene glycol triethoxysilane is 18000-22000.

[0025] Further, the present application also provides a preparation method of the complex iron desulfurizer, comprising the following steps:

[0026] (1) adding ferric chloride hexahydrate, part of ethylenediaminetetraacetic acid disodium salt dihydrate, citric acid monohydrate and part of sodium hydroxide solution into part of deionized water, stirring at 35-45°C for 25-40 min to obtain a complex intermediate solution;

[0027] (2) adding N-methyldiethanolamine, borax decahydrate and part of deionized water into the complex intermediate solution of step (1), stirring at 33-38°C for 20-30 min to obtain a buffer shell coated complex dispersion liquid;

[0028] (3) adding nano-silica A and nano-silica B into the buffer shell coated complex dispersion liquid of step (2), stirring at 33-38°C for 20-30 min to obtain a stable dispersion liquid;

[0029] (4) adding the remaining disodium ethylenediaminetetraacetate dihydrate and the remaining sodium hydroxide solution into the stable dispersion liquid of step (3), standing for 10-14 h at 25 °C, and then adding deionized water to obtain the complex iron desulfurizer.

[0030] Preferably, the weight ratio of the disodium ethylenediaminetetraacetate dihydrate in step (1) and the disodium ethylenediaminetetraacetate dihydrate in step (4) is 42-48:33-41.

[0031] Preferably, the weight ratio of the sodium hydroxide solution in step (1) and the sodium hydroxide solution in step (4) is 50-70:80-120.

[0032] The complex iron desulfurizer of the present application realizes significant improvement in dispersion stability, mass transfer efficiency and cyclic regeneration performance through innovative double-path nano-silica surface modification and step-by-step complexation process.

[0033] In terms of dispersion stability, a differentiated surface chemical environment is constructed by introducing nano-silica A treated by dehydroxylation and nano-silica B treated by rehydroxylation. Nano-silica A is co-grafted in an alkaline environment to form a high-density silanol group and an organic silicon segment on its surface, providing strong electrostatic repulsion and steric hindrance effect; nano-silica B is co-grafted in an acidic environment to retain a moderate hydroxyl density and form a continuous hydrophilic brush layer structure. The synergistic effect of the two modified nanomaterials enables the desulfurizer to maintain a high negative potential value, effectively inhibits van der Waals attraction between particles, significantly reduces the tendency of coalescence and sedimentation, and ensures long-term dispersion stability of the system.

[0034] In terms of mass transfer enhancement, the introduction of triethoxysilyl ethyl-terminated polydimethylsiloxane reduces the surface tension of the liquid film, promotes bubble rupture and interface renewal, and increases the gas-liquid contact area. At the same time, the hydrophilic segment formed by methoxypolyethylene glycol triethoxysilane enhances the wettability and flowability of the interface, reducing the mass transfer resistance. The synergistic modification of the two-component silane achieves a balance between "low surface energy liquid discharge" and "high wettability mass transfer", significantly improving the transfer efficiency of hydrogen sulfide from the gas phase to the liquid phase.

[0035] In terms of buffer stability, the buffer shell layer composed of N-methyldiethanolamine and borax decahydrate can effectively resist the pH shock caused by carbon dioxide absorption. When carbon dioxide dissolves and causes the pH of the system to drop, the buffer system rapidly releases hydroxide ions to maintain the pH stability of the microenvironment around the complex iron, preventing the dissociation and precipitation of the complex. This localized pH buffering mechanism ensures the stability of the coordination structure of the complex iron active center and maintains high catalytic activity.

[0036] In terms of reaction kinetics, the step-by-step complexing process avoids the problems of competitive coordination and non-target ligand occupying inner coordination sites by rhythm control of first semi-complexing, then buffering, and finally full complexing. The intermediate formed by preliminary complexing provides an orderly binding path for subsequent ligands, and finally forms an active complex with optimized coordination environment. This control strategy not only improves the complexing efficiency, but also enhances the redox reversibility of the complex.

[0037] In terms of cyclic regeneration performance, the surface-modified nanosilica as a carrier skeleton provides a stable loading environment for complexed iron, preventing the loss and aggregation of active components during regeneration. At the same time, the buffer shell maintains local pH stability during oxidation regeneration, ensuring Fe 3+ / Fe 2+ The reversibility of the redox reaction significantly improves the cyclic service life.

[0038] In terms of anti-interference ability, the multi-layer protection structure constructed by the double-path surface modification can effectively isolate the interference of impurity ions and reduce the poisoning phenomenon. Especially under high carbon dioxide concentration conditions, the presence of the buffer system enables the desulfurizer to maintain high activity, exhibiting excellent anti-interference performance.

[0039] In summary, through systematic material design and process innovation, the complexed iron desulfurizer has achieved comprehensive performance improvement in stability, efficiency and durability, providing reliable technical support for industrial application. BRIEF DESCRIPTION OF DRAWINGS

[0040] 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.

[0041] Figure 1 Viscosity-shear rate curves of the complexed iron desulfurizer prepared for Inventive Examples 1-3 and Comparative Examples 1-7;

[0042] Figure 2 Infrared spectra of the nanosilica, nanosilica A and nanosilica B in Inventive Example 2. DETAILED DESCRIPTION

[0043] 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.

[0044] Example 1:

[0045] (1) 10 g of nano-silica (average particle size 50 nm) was heated in a muffle furnace at 350 °C for 1.5 h, collected after cooling, and then dispersed in 320 g of absolute ethanol and 180 g of deionized water, ultrasonically treated for 20 min, and then 3 g of triethylamine, 0.3 g of triethoxysilyl ethyl terminated polydimethylsiloxane (weight average molecular weight 840, Gelest, DMS-XT11), and 0.15 g of methoxypolyethylene glycol triethoxysilane (weight average molecular weight 20000, Creative PEG Works, mPEG-Silane) were added, stirred at 25 °C for 30 min, and then stirred at 60 °C for 3 h, centrifuged, washed with absolute ethanol 3 times, and dried at 40 °C under vacuum for 6 h to obtain nano-silica A;

[0046] (2) 10 g of nano-silica (average particle size 50 nm) was added to 100 g of deionized water, stirred at reflux for 30 min, and then collected by centrifugation after cooling; the wet gel was then added to 320 g of absolute ethanol and 180 g of deionized water, ultrasonically treated for 20 min, and then 3 g of glacial acetic acid, 0.3 g of triethoxysilyl ethyl terminated polydimethylsiloxane (weight average molecular weight 840, Gelest, DMS-XT11), and 0.15 g of methoxypolyethylene glycol triethoxysilane (weight average molecular weight 20000, Creative PEG Works, mPEG-Silane) were added, stirred at 25 °C for 30 min, and then stirred at 60 °C for 3 h, centrifuged, washed with absolute ethanol 3 times, and dried at 40 °C under vacuum for 6 h to obtain nano-silica B;

[0047] (3) 54 g of ferric chloride hexahydrate, 42 g of disodium ethylenediaminetetraacetate dihydrate, 30 g of citric acid monohydrate, and 50 g of a 4 wt% sodium hydroxide solution were added to 850 g of deionized water, stirred at 35 °C for 25 min, and a complex intermediate solution was obtained;

[0048] (4) 5 g of N-methyldiethanolamine, 15 g of borax decahydrate, and 120 g of deionized water were added to the complex intermediate solution of step (3), stirred at 33 °C for 20 min, and a buffer shell-wrapped complex dispersion was obtained;

[0049] (5) 0.8 g of nano-silica A and 0.8 g of nano-silica B were added to the buffer shell-wrapped complex dispersion of step (4), respectively, and stirred at 33 °C for 20 min to obtain a stable dispersion;

[0050] (6) 33 g of disodium ethylenediaminetetraacetate dihydrate and 80 g of a 4 wt% sodium hydroxide solution were added to the stable dispersion of step (5), allowed to stand at 25 °C for 10 h, and then diluted to 1600 g with deionized water to obtain a complex iron desulfurizer.

[0051] Example 2:

[0052] (1) 10 g of nanosilica (average particle size 50 nm) was heated in a muffle furnace at 400 °C for 2 h, collected after cooling, and then dispersed in 350 g of absolute ethanol and 150 g of deionized water, ultrasonically treated for 30 min, and then 5 g of triethylamine, 0.4 g of triethoxysilyl ethyl terminated polydimethylsiloxane (weight average molecular weight 840, Gelest, DMS-XT11), and 0.2 g of methoxypolyethylene glycol triethoxysilane (weight average molecular weight 20000, Creative PEG Works, mPEG-Silane) were added, stirred at 25 °C for 45 min, and then stirred at 60 °C under reflux for 4 h, centrifuged, washed with absolute ethanol 3 times, and dried at 40 °C under vacuum for 8 h to obtain nanosilica A;

[0053] (2) 10 g of nanosilica (average particle size 50 nm) was added to 100 g of deionized water, stirred under reflux for 45 min, and then collected by centrifugation after cooling to obtain a wet gel, which was then dispersed in 350 g of absolute ethanol and 150 g of deionized water, ultrasonically treated for 30 min, and then 5 g of glacial acetic acid, 0.4 g of triethoxysilyl ethyl terminated polydimethylsiloxane (weight average molecular weight 840, Gelest, DMS-XT11), and 0.2 g of methoxypolyethylene glycol triethoxysilane (weight average molecular weight 20000, Creative PEG Works, mPEG-Silane) were added, stirred at 25 °C for 45 min, and then stirred at 60 °C under reflux for 4 h, centrifuged, washed with absolute ethanol 3 times, and dried at 40 °C under vacuum for 8 h to obtain nanosilica B;

[0054] (3) 54 g of ferric chloride hexahydrate, 45 g of disodium ethylenediaminetetraacetate dihydrate, 32 g of citric acid monohydrate, and 60 g of a 4 wt% sodium hydroxide solution were added to 800 g of deionized water, and stirred at 40 °C for 30 min to obtain a complex intermediate solution;

[0055] (4) 7 g of N-methyldiethanolamine, 19 g of borax decahydrate, and 100 g of deionized water were added to the complex intermediate solution of step (3), and stirred at 35 °C for 20 min to obtain a buffer shell-wrapped complex dispersion;

[0056] (5) 1 g of nanosilica A and 1 g of nanosilica B were respectively added to the buffer shell-wrapped complex dispersion of step (4), and stirred at 35 °C for 20 min to obtain a stable dispersion;

[0057] (6) To the stable dispersion of step (5), 37 g of disodium ethylenediaminetetraacetate dihydrate and 100 g of 4 wt% sodium hydroxide solution were added, and it was allowed to stand for aging at 25 °C for 12 h, and then it was diluted to 1600 g with deionized water to obtain a complex iron desulfurizer.

[0058] Example 3:

[0059] (1) 10 g of nanosilica (average particle size 50 nm) was heated in a muffle furnace at 450 °C for 3 h, and then collected after cooling, and dispersed in 380 g of anhydrous ethanol and 120 g of deionized water, and ultrasonically treated for 40 min, and then 7 g of triethylamine, 0.6 g of triethoxysilyl ethyl-terminated polydimethylsiloxane (weight average molecular weight 840, Gelest Corporation, DMS-XT11) and 0.3 g of methoxypolyethylene glycol triethoxysilane (weight average molecular weight 20000, Creative PEG Works Corporation, mPEG-Silane) were added, and after stirring at 25 °C for 60 min, it was stirred at 60 °C for 5 h, and then centrifuged, washed with anhydrous ethanol 3 times, and dried at 40 °C under vacuum for 10 h to obtain nanosilica A;

[0060] (2) 10 g of nanosilica (average particle size 50 nm) was added to 100 g of deionized water, and stirred at reflux for 60 min, and then after cooling, the wet gel was collected by centrifugation, and then dispersed in 380 g of anhydrous ethanol and 120 g of deionized water, and ultrasonically treated for 40 min, and then 7 g of glacial acetic acid, 0.6 g of triethoxysilyl ethyl-terminated polydimethylsiloxane (weight average molecular weight 840, Gelest Corporation, DMS-XT11) and 0.3 g of methoxypolyethylene glycol triethoxysilane (weight average molecular weight 20000, Creative PEG Works Corporation, mPEG-Silane) were added, and after stirring at 25 °C for 60 min, it was stirred at 60 °C for 5 h, and then centrifuged, washed with anhydrous ethanol 3 times, and dried at 40 °C under vacuum for 10 h to obtain nanosilica B;

[0061] (3) 54 g of ferric chloride hexahydrate, 48 g of disodium ethylenediaminetetraacetate dihydrate, 36 g of citric acid monohydrate and 70 g of 4 wt% sodium hydroxide solution were added to 750 g of deionized water, and stirred at 45 °C for 40 min to obtain a complex intermediate solution;

[0062] (4) To the complex intermediate solution of step (3), 9 g of N-methyldiethanolamine, 23 g of borax decahydrate and 80 g of deionized water were added, and stirred at 38 °C for 30 min to obtain a buffered shell-coated complex dispersion;

[0063] (5) Respectively, 1.2 g of nano-silica A and 1.2 g of nano-silica B were added into the buffer shell coated complex dispersion liquid of step (4), stirred at 38 °C for 30 min, to obtain a stable dispersion liquid;

[0064] (6) 41 g of disodium ethylenediaminetetraacetate dihydrate and 120 g of 4 wt% sodium hydroxide solution were added into the stable dispersion liquid of step (5), aged at 25 °C for 14 h, and then diluted to 1600 g with deionized water, to obtain a complex iron desulfurizer.

[0065] Comparative Example 1

[0066] The difference between Comparative Example 1 and Example 2 is that the surface organosilane co-grafting modification of nano-silica is not performed, and the addition of triethoxysilyl ethyl terminated polydimethylsiloxane and methoxypolyethylene glycol triethoxysilane in steps (1) and (2) of Example 2 is omitted, and the unmodified nano-silica is directly used in the subsequent step (5) dispersion process.

[0067] Comparative Example 2

[0068] The difference between Comparative Example 2 and Example 2 is that only polydimethylsiloxane single agent grafting is performed, and the addition of methoxypolyethylene glycol triethoxysilane is omitted, that is, only triethoxysilyl ethyl terminated polydimethylsiloxane is added in steps (1) and (2), and no methoxypolyethylene glycol triethoxysilane is added.

[0069] Comparative Example 3

[0070] The difference between Comparative Example 3 and Example 2 is that only methoxypolyethylene glycol triethoxysilane single agent grafting is performed, and the addition of triethoxysilyl ethyl terminated polydimethylsiloxane is omitted, that is, only methoxypolyethylene glycol triethoxysilane is added in steps (1) and (2), and no triethoxysilyl ethyl terminated polydimethylsiloxane is added.

[0071] Comparative Example 4

[0072] The difference between Comparative Example 4 and Example 2 is that the buffer shell design is not used, and the addition of N-methyldiethanolamine and borax decahydrate in step (4) is omitted, that is, no weak base buffer shell is formed on the outer layer of the complex intermediate liquid, and the nano-silica is directly added into the complex intermediate liquid without forming a buffer shell to perform step (5).

[0073] Comparative Example 5

[0074] Comparative Example 5 differs from Example 2 in that the order of complexation and pH plateau is changed, the order control of first half complexation, then buffering, then complexation in Step (3) and Step (4) is omitted, and ferric chloride hexahydrate, disodium ethylenediaminetetraacetate dihydrate, N-methyldiethanolamine, and borax decahydrate are added together into deionized water at room temperature and stirred for 50 min.

[0075] Comparative Example 6

[0076] Comparative Example 6 differs from Example 2 in that the silicon alcohol density regulation on the surface of silicon dioxide is changed, the 400°C dehydroxylation and reflux rehydroxylation operation is not performed, and the original nano-silicon dioxide powder is directly used for corresponding treatment in Step (1) and Step (2), and other conditions remain unchanged.

[0077] Comparative Example 7

[0078] Comparative Example 7 differs from Example 2 in that the catalytic conditions of hydrolysis-condensation of alkoxysilane are changed, and the base catalysis / acid catalysis conditions in Step (1) and Step (2) are interchanged, specifically, using glacial acetic acid acid catalysis in Step (1) and using triethylamine base catalysis in Step (2), and other conditions remain unchanged.

[0079] Performance test:

[0080] Dispersion stability: dilute the sample to 0.1wt% solid content with deionized water, use electrophoretic light scattering to determine the Zeta potential, test temperature 25°C, equilibrium time 120s, repeat 3 times to take the average, record the Zeta potential after 0h and 168h standing, and the results are shown in Table 1.

[0081] Viscosity-shear characteristics: according to GB / T 2794-2022; take the sample and stand for 30 min to defoam, load it into a rotary rheometer at 25.0±0.2°C constant temperature; pre-shear for 100s -1 After 60s, stand for 300s to balance; perform up-scan of shear rate from 0.1 to 100 -1 ; record the viscosity-shear rate curve, and the results are shown in Table 1. Figure 1

[0082] Desulfurization removal rate, breakthrough time, and sulfur capacity: use an organic glass bubble absorption column (inner diameter 30 mm, height 300 mm), working liquid volume 500mL; the inlet gas is a standard gas with a hydrogen sulfide volume fraction of 3000ppm, a carbon dioxide volume fraction of 5%, and the balance being nitrogen, total flow rate 1.0L·min -1 ​, temperature 30±1°C, normal pressure continuous operation, each of the inlet and outlet gas is provided with a sampling port, the inlet and outlet hydrogen sulfide concentrations are executed according to HJ 1388-2024, the sampling, color development, determination steps and quality control are carried out according to the standard, the breakthrough criterion is that the outlet hydrogen sulfide concentration / inlet hydrogen sulfide concentration≥5%, and the cyclic regeneration is as follows: after breakthrough, air is bubbled for regeneration (0.5vvm, 30min), after standing for 5min, it enters the next cycle, a total of 5 cycles, the desulfurization removal rate after 5 cycles is recorded, and the results are shown in Table 1.

[0083] Anti-carbon dioxide interference: the volume fraction of carbon dioxide in the inlet gas is increased from 5% to 15%, and the rest remains unchanged, continuous operation, each platform is maintained for 60min, and the pH (online electrode, 25°C calibration, NIST buffer calibration) and desulfurization removal rate after 60min are recorded.

[0084] Fourier transform infrared spectroscopy: tested by a Fourier transform infrared spectrometer, and the results are shown in Figure 2 .

[0085] Table 1 Performance test results

[0086] ;

[0087] Data analysis:

[0088] As can be seen from the data of Examples 1-3 in Table 1, the complex iron desulfurizer prepared in the application simultaneously presents stable and balanced excellent performance in dispersion stability, single cycle desulfurization efficiency, breakthrough time, volume sulfur capacity, cycle retention rate and carbon dioxide interference tolerance. This is mainly due to the pre-treatment of the surface silanol density of nano-silicon dioxide and the co-grafting of alkoxysilane through acid / alkali two routes, on the one hand, a uniform hydrophilic brush layer is constructed to reduce the adhesion between colloids and maintain a high Zeta potential, on the other hand, low surface energy fragments promote bubble membrane liquid discharge and interface renewal, so as to balance dispersion stability and gas-liquid mass transfer. The complexation stage adopts the rhythm of semi-complexation first, then buffering, and then complexation again, which not only avoids the pH drop caused by carbon dioxide absorption, but also reduces the occupation of non-target ligand to the inner coordination site, so as to maintain the activity and kinetic advantage in continuous bubbling and cyclic regeneration. Therefore, the desulfurizer prepared in the application can still maintain high level desulfurization and longer breakthrough under the condition of complex gas composition and multiple regeneration.

[0089] From the data of Example 2 and Comparative Example 1 in Table 1, it can be seen that the absolute value of the Zeta potential of Comparative Example 1 is significantly lower and decays more obviously over time; the removal rate of desulfurization, breakthrough time and volume sulfur capacity are all significantly lower, and the retention rate under the interference of recycling and carbon dioxide is also poorer. This may be due to the lack of synergy of triethoxysilylethyl-terminated polydimethylsiloxane and methoxypolyethylene glycol triethoxysilane, resulting in insufficient surface hydration layer and low surface energy liquid discharge effect, and the colloids are more likely to coalesce and settle, the interface update is inhibited, and the local pH and ionic strength fluctuation is amplified, which comprehensively weakens the mass transfer-reaction-regeneration link.

[0090] From the data of Example 2 and Comparative Example 2 in Table 1, it can be seen that the negative amplitude of the Zeta potential of Comparative Example 2 is lower and decays more over time; all performance indicators are lower than Example 2, and the decrease is more obvious under carbon dioxide conditions. This may be due to the lack of hydrophilic brush layer of methoxypolyethylene glycol triethoxysilane with only low surface energy fragments, resulting in insufficient hydration layer and electrostatic repulsion, leading to decreased dispersion stability and specific interface area; although there is a certain bubble membrane liquid discharge, the mass transfer benefit is offset by coalescence and settlement, resulting in simultaneous decrease of breakthrough and sulfur capacity.

[0091] From the data of Example 2 and Comparative Example 3 in Table 1, it can be seen that Comparative Example 3 performs relatively well in dispersion stability and long-term Zeta potential, but the desulfurization removal rate, breakthrough and sulfur capacity are still lower than Example 2, and there is still a gap under the interference of recycling and carbon dioxide. This may be due to the fact that the hydrophilic brush layer ensures dispersion, but the de-wetting and bubble membrane liquid discharge effect of triethoxysilylethyl-terminated polydimethylsiloxane is lacking, resulting in insufficient interface update and gas-liquid mass transfer; the activity is not fully utilized, limiting the breakthrough time and effective sulfur capacity.

[0092] From the data of Example 2 and Comparative Example 4 in Table 1, it can be seen that the Zeta potential of Comparative Example 4 decays more significantly over time, and the desulfurization, breakthrough and sulfur capacity are all significantly decreased, and the decline is particularly prominent under the interference of carbon dioxide. This may be due to the fact that the N-methyldiethanolamine / boron decahydrate buffer shell is not introduced, and the pH drop caused by carbon dioxide absorption cannot be inhibited, the iron-ethylenediaminetetraacetate complex is unstable, the inner coordination site is disturbed, the oxidation kinetics and regeneration closed loop are destroyed, resulting in the decline of the whole link of performance.

[0093] From the data of Example 2 and Comparative Example 5 in Table 1, it can be seen that Comparative Example 5 is lower than Example 2 in all indicators, and the long-term stability and recycling retention are also weaker. This may be due to the loss of process control of step-by-step pH control and step-by-step coordination, which is easy to form unfavorable coordination configuration and free anion competition, and the buffer shell is difficult to completely cover; as a result, the effective active site density and accessibility decrease, and the system is more sensitive to carbon dioxide and ionic strength fluctuation.

[0094] From the data of Example 2 and Comparative Example 6 in Table 1, it can be seen that the zeta potential and long-term stability of Comparative Example 6 are not as good as Example 2, and the desulfurization, breakthrough and sulfur capacity all decrease, and the cycle retention is moderately damaged. This is likely due to the absence of high-temperature dehydroxylation / rehydroxylation of the silanol density preset, resulting in uneven density and crosslinking state of the subsequent alkoxysilane grafting, producing a "mottled / exposed" surface and a discontinuous brush layer; the colloidal repulsion and interfacial effect are weakened, and the mass transfer and stability are simultaneously limited.

[0095] From the data of Example 2 and Comparative Example 7 in Table 1, it can be seen that the overall indicators of Comparative Example 7 are lower than those of Example 2, showing a synergistic decrease in dispersion stability, breakthrough and sulfur capacity, and the retention rate under carbon dioxide conditions is also affected. This is likely due to the acid / base catalytic exchange breaking the complementary arrangement of "crosslinking patches / islands" and "uniform brush layer", causing the two types of nanosilica to mismatch in morphology and grafting state, making it difficult to simultaneously achieve strong hydration stability and bubble membrane liquid discharge, resulting in a synergistic weakening of mass transfer-stability.

[0096] From Figure 1 it can be seen that Examples 1-3 and Comparative Examples 1-7 all show significant shear thinning with increasing shear rate: among them, Example 2 has the lowest viscosity and monotonically decreases in the range of 0.1-100 s -1 , and Examples 1 and 3 are slightly higher but also have no obvious upturn; in contrast, Comparative Example 2 has the highest overall viscosity and the most significant weak thickening at about 65-75 s -1 , Comparative Examples 1 and 4 also have a small upturn, Comparative Examples 5 and 7 have a moderate upturn, and Comparative Examples 3 and 6 remain basically monotonically thinning, indicating that double-silane co-grafting and buffer shell-stepwise complexation strategy not only improve dispersion stability but also inhibit high-shear abnormalities, thereby being more conducive to gas-liquid mass transfer and cycle stability.

[0097] From Figure 1 it can be seen that, compared with the original nanosilica, nanosilicas A and B both have obvious C-H stretching vibration peaks at 2962 / 2925 / 2854 cm -1 , and strong Si-CH3 deformation vibration peaks at 1260 cm -1 , proving that the organic silicon segment is successfully grafted; among them, the A sample has a higher peak intensity, and its 3745 / 3400 cm -1 (Si-OH / adsorbed water) is significantly weakened, indicating that the grafting is more complete under alkaline catalysis; the B sample still retains a certain OH bandwidth, and a weaker shoulder peak (C-O-C characteristic of PEG) appears at 1110 cm -1 , and a weak carbon shoulder peak of ~1716 cm -1 is detected, which is a hetero peak signal of residual acetic acid / acetic acid salt in the acid catalysis system. The three together maintain 1080 / 800 / 460 cm -1The Si-O-Si backbone features of the original sample are present, but the additional C-H / Si-CH3 bands and OH attenuations of A / B are an intuitive evidence of the success of the modification.

[0098] 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 imply limitations on the scope of the application; under the concept of the present application, 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 present application as described above, which are not provided in details for the sake of simplicity.

Claims

1. A complexed iron desulfurizer characterized by, The 1600 parts of raw materials contain the following components by weight: 54 parts of ferric chloride hexahydrate, 75-89 parts of disodium ethylenediaminetetraacetate dihydrate, 30-36 parts of citric acid monohydrate, 130-190 parts of sodium hydroxide solution, 5-9 parts of N-methyldiethanolamine, 15-23 parts of borax decahydrate, 0.8-1.2 parts of nano-silica A, 0.8-1.2 parts of nano-silica B, and the balance of deionized water; The nano-silica A is obtained by grafting triethoxysilyl ethyl-terminated polydimethylsiloxane and methoxypolyethylene glycol triethoxysilane on nano-silica after high-temperature dehydroxylation in an alkaline environment, and the weight ratio of the nano-silica, triethoxysilyl ethyl-terminated polydimethylsiloxane, methoxypolyethylene glycol triethoxysilane, and triethylamine is 10:0.3-0.6:0.15-0.3:3-7; The nano-silica B is obtained by grafting triethoxysilyl ethyl-terminated polydimethylsiloxane and methoxypolyethylene glycol triethoxysilane on nano-silica after rehydroxylation by reflux in an acidic environment, and the weight ratio of the nano-silica, triethoxysilyl ethyl-terminated polydimethylsiloxane, methoxypolyethylene glycol triethoxysilane, and glacial acetic acid is 10:0.3-0.6:0.15-0.3:3-7.

2. The complexed iron desulfurizer of claim 1, wherein, The concentration of the sodium hydroxide solution is 4wt%.

3. The complexed iron desulfurizer of claim 1, wherein, The high-temperature dehydroxylation is treated at 350-450°C for 1.5-3h.

4. The complexed iron desulfurizer of claim 1, wherein, The alkaline environment is constructed by triethylamine, anhydrous ethanol, and deionized water in a weight ratio of 3-7:320-380:180-120.

5. The complexed iron desulfurizer of claim 1, wherein, The rehydroxylation by reflux is refluxed and stirred in deionized water for 30-60min.

6. The complexed iron desulfurizer of claim 1, wherein, The acidic environment is constructed by glacial acetic acid, anhydrous ethanol, and deionized water in a weight ratio of 3-7:320-380:180-120.

7. The complexed iron desulfurizer of claim 1, wherein, The weight average molecular weight of the triethoxysilyl ethyl-terminated polydimethylsiloxane is 800-900.

8. The complexed iron desulfurizer of claim 1, wherein, The weight average molecular weight of the methoxypolyethylene glycol triethoxysilane is 18000-22000.

9. A process for the preparation of the complexed iron desulfurizer according to any one of claims 1-8, characterized in that, The method comprises the following steps: (1) ferric chloride hexahydrate, part of disodium ethylenediaminetetraacetate dihydrate, citric acid monohydrate, and part of sodium hydroxide solution are added to part of deionized water, and stirred at 35-45°C for 25-40min to obtain a complex intermediate solution; (2) N-methyldiethanolamine, borax decahydrate, and part of deionized water are added to the complex intermediate solution of step (1), and stirred at 33-38°C for 20-30min to obtain a buffer shell-wrapped complex dispersion liquid; (3) nano-silica A and nano-silica B are added to the buffer shell-wrapped complex dispersion liquid of step (2), and stirred at 33-38°C for 20-30min to obtain a stable dispersion liquid; (4) the remaining disodium ethylenediaminetetraacetate dihydrate and the remaining sodium hydroxide solution are added to the stable dispersion liquid of step (3), and left to stand at 25°C for 10-14h for curing, and then diluted with the remaining deionized water to obtain a complex iron desulfurizer.

10. The method of claim 9 wherein the complexed iron desulfurizer is prepared by the steps of: The weight ratio of the disodium ethylenediaminetetraacetate dihydrate in step (1) and the disodium ethylenediaminetetraacetate dihydrate in step (4) is 42-48:33-41; the weight ratio of the sodium hydroxide solution in step (1) and the sodium hydroxide solution in step (4) is 50-70:80-120.

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