Carbon dioxide and hydrogen sulfide selective separation material

Abstract

The present application relates to the technical field of gas purification and separation, and discloses a selective separation material for carbon dioxide and hydrogen sulfide, which is prepared from 15-25 parts of a hindered hydrazine salt active component, 5-15 parts of a dielectric regulation dissociation agent, 1-5 parts of a proton transfer agent and 55-79 parts of an inert poor water solvent, and preparation is performed by using a step-by-step strategy of pre-solvent activation, dissolution assistance and homogeneous complexing. The present application solves the problems of low solubility of a high-concentration hindered hydrazine salt in a poor water organic solvent and shielding of active sites by introducing a high-dielectric-constant regulating agent to construct a solvent separation ion pair environment. By using the synergistic effect of the large steric hindrance effect of a hindered hydrazine group and a poor water environment, carbon dioxide chemical absorption is strongly inhibited in thermodynamics and kinetics, while the high-efficiency proton transfer and capture capacity for hydrogen sulfide is retained. The material has a very high selectivity factor, excellent hydrogen sulfide absorption capacity and low regeneration energy consumption.

Description

Technical Field

[0001] This invention relates to the field of gas purification and separation technology, and in particular to materials for the selective separation of carbon dioxide and hydrogen sulfide. Background Technology

[0002] In natural gas purification, coal chemical, and oil refining industries, acidic feed gas typically contains both hydrogen sulfide and carbon dioxide. To meet the process requirements of subsequent Claus sulfur recovery units regarding the concentration of hydrogen sulfide in the feed gas, or to retain carbon dioxide for applications such as oil displacement and urea synthesis, highly selective desulfurization solvents are needed to deeply remove hydrogen sulfide from the mixed gas while reducing the co-absorption of carbon dioxide.

[0003] Current industrial desulfurization technologies primarily rely on hindered amine aqueous solution systems, such as N-methyldiethanolamine (MDEA). While these systems achieve a degree of selectivity by utilizing kinetic differences, they still suffer from insurmountable thermodynamic and engineering drawbacks in practical applications. Because water is both a solvent and a necessary reactant for carbon dioxide hydration, in water-rich environments, carbon dioxide readily hydrates to form bicarbonates or reacts with amines to form carbamates, making it difficult to further improve the selectivity factor, especially under high pressure or high acid load conditions, where the co-absorption of carbon dioxide increases. Furthermore, water's high specific heat capacity and high latent heat of vaporization result in enormous energy consumption during solvent regeneration, and the volatile nature of aqueous solutions leads to solvent loss and makes it difficult to maintain the water balance of the system.

[0004] To overcome the shortcomings of aqueous solution systems, the industry has attempted to use physical solvents (such as polyethylene glycol dimethyl ether) or water-poor mixed solvent systems. However, pure physical solvents rely on Henry's Law for absorption, and the solubility difference between hydrogen sulfide and carbon dioxide is limited, making it impossible to achieve high-precision chemical selectivity separation, and they also have low sulfur capacity. Introducing chemically active components (such as amine salts or alkali metal salts) into low-polarity organic solvents to construct water-poor chemical absorption systems faces serious compatibility and activity release challenges. Because conventional organic solvents (such as ethers and alcohols) have low dielectric constants, highly polar ionic active components are extremely difficult to dissociate in them, tending to exist as tight ion pairs or even solid aggregates. This strong electrostatic binding effect causes anionic active sites to be shielded by cations, preventing them from effectively participating in proton exchange reactions, resulting in a significant decrease in the hydrogen sulfide load of the absorbent, and even precipitation and stratification, making it difficult to meet the requirements of homogeneous stability and high absorption capacity for continuous industrial operation.

[0005] Therefore, the present invention provides a material for the selective separation of carbon dioxide and hydrogen sulfide to overcome the shortcomings of the prior art. Summary of the Invention

[0006] The purpose of this invention is to provide a material for selectively separating carbon dioxide and hydrogen sulfide, which solves the problems of low solubility of active components and severe ion association leading to decreased absorption capacity in water-poor organic systems, as well as poor carbon dioxide selectivity and high regeneration energy consumption in water-rich systems.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] In a first aspect, the present invention provides a material for the selective separation of carbon dioxide and hydrogen sulfide, employing the following technical solution:

[0009] A material for the selective separation of carbon dioxide and hydrogen sulfide, the material being prepared from raw materials comprising the following parts by weight:

[0010] 15 to 25 parts of hindered hydrazine salt active component;

[0011] 5 to 15 parts of dielectric modulator dissociation agent;

[0012] 1 to 5 parts of proton transfer agent;

[0013] 55 to 79 parts of inert, water-poor solvent.

[0014] By adopting the above technical solution, the present invention achieves highly efficient and selective capture of hydrogen sulfide through the synergistic effect of multiple components. Its core mechanism is as follows:

[0015] Dielectric regulation mechanism of solubilization and activity release:

[0016] In conventional low-polarity organic solvents, ionic active components tend to form close-contact ion pairs or precipitate directly in crystalline form, resulting in the shielding of anionic active sites by cations. This invention introduces a dielectric-controlled dissociation agent with a high dielectric constant. This component utilizes its strongly polar groups to specifically solvate and encapsulate alkali metal cations, weakening the electrostatic attraction between the cations and hindered hydrazine anions. This process transforms close-contact ion pairs into solvent-separated pairs, thereby allowing the hindered hydrazine anions to be stably dispersed as free ions in the water-poor system, restoring their chemical activity in capturing acidic gases.

[0017] Mechanisms of reaction pathway disruption in water-scarce environments:

[0018] The chemical absorption of carbon dioxide mainly relies on hydration reactions to form bicarbonate or on the formation of carbamates from amines. Both of these reactions are highly dependent on water molecules or limited by polar environments. This invention strictly controls the content of the proton transfer agent (water) to below 5 parts, creating a water-starved environment. Under this environment, the hydration reaction pathway of carbon dioxide is thermodynamically strongly suppressed; simultaneously, the unique sterically hindered N,N'-di-tert-butyl structure of the hindered hydrazine active component prevents its direct formation of carbamates from carbon dioxide. In contrast, the reaction of hydrogen sulfide with the active component is mainly based on a rapid proton transfer process, and is less affected by steric hindrance and water content. Therefore, this system maintains a high hydrogen sulfide absorption capacity while significantly reducing the solubility of carbon dioxide, achieving highly selective separation.

[0019] Low-energy regeneration mechanism:

[0020] The system is mainly composed of an inert, water-poor solvent, whose specific heat capacity and latent heat of vaporization are much lower than those of water. In addition, in a water-poor organic medium, the dissociation barrier of the products formed by the active component and hydrogen sulfide is lower, and hydrogen sulfide is more likely to escape during thermal regeneration, thereby reducing the thermal load of solvent regeneration.

[0021] Preferably, the hindered hydrazine salt active component is one or more of the alkali metal salt of N,N'-di-tert-butylhydrazine phosphonic acid or the alkali metal salt of N,N'-di-tert-butylhydrazine sulfonic acid; wherein the cation of the alkali metal salt is selected from potassium ions or sodium ions.

[0022] By employing the above technical solution, the N,N'-di-tert-butyl structure provides high steric hindrance, further reducing the reaction rate constant for the binding of carbon dioxide to the active center and enhancing kinetic selectivity. Simultaneously, the phosphonate or sulfonic acid groups, as strong electron-withdrawing groups, regulate the basicity of the hydrazine nitrogen atom, making it more suitable for the dissociation equilibrium of hydrogen sulfide.

[0023] Preferably, the dielectric modulating dissociation agent is selected from one or more of sulfolane or propylene carbonate; the proton transfer agent is deionized water.

[0024] By adopting the above technical solutions, sulfolane or propylene carbonate have high dielectric constants and good chemical stability, which can effectively penetrate into the interior of the salt lattice and promote the overcoming of lattice energy; deionized water, as the only proton shuttle carrier, can maintain the ion channel for acid-base reactions with a small amount of addition, without causing a large amount of carbon dioxide hydration.

[0025] Preferably, the inert, water-poor solvent is selected from one or more of polyethylene glycol dimethyl ether or tetraethylene glycol.

[0026] By adopting the above technical solution, polyethylene glycol dimethyl ether or tetraethylene glycol has a high boiling point, low vapor pressure and good chemical inertness. As a physical absorption medium, its physical solubility for acidic gases follows Henry's Law. It can be combined with chemically active components to achieve physical-chemical mixed absorption and reduce solvent evaporation loss during the regeneration process.

[0027] Preferably, the hindered hydrazine salt active component is prepared by the following method: N,N'-di-tert-butylhydrazine is dissolved in a haloalkane solvent, and phosphorus trichloride or chlorosulfonic acid is added dropwise at 0 to 5°C to obtain an intermediate; the intermediate is dissolved in an alcohol solvent, and an alkali metal hydroxide or carbonate is added to adjust the pH to 9.0 to 10.0, followed by crystallization and drying. More preferably, the haloalkane solvent is anhydrous dichloromethane; the alcohol solvent is selected from anhydrous ethanol or isopropanol.

[0028] By adopting the above technical solution, the substitution reaction site is effectively controlled by the low-temperature dropwise synthesis route, avoiding the occurrence of side reactions. In the salt formation stage, the use of alcohol solvents and precise control of pH value can obtain high-purity target salt crystals, which are convenient for subsequent compounding in organic solvent systems.

[0029] Secondly, the present invention provides a method for preparing the above-mentioned selective separation material for carbon dioxide and hydrogen sulfide, employing the following technical solution:

[0030] A method for preparing a material for selectively separating carbon dioxide and hydrogen sulfide includes the following steps:

[0031] S1. Pre-solventization activation: The hindered hydrazine salt active component is mixed with the dielectric modulating dissociation agent, and lattice penetration is carried out under heating and stirring conditions to obtain a pre-activated slurry.

[0032] S2, Dissolution aid: Add the proton transfer agent to the pre-activated slurry and stir until the solid is completely dissolved to obtain a high-concentration salt solution;

[0033] S3. Homogeneous compounding: The high-concentration salt solution is added to the inert, water-poor solvent and stirred until homogeneous to obtain the selective separation material for carbon dioxide and hydrogen sulfide.

[0034] By adopting the above technical solution, this invention employs a stepwise dissolution strategy to solve the problem of dissolving high-concentration salts in low-polarity solvents:

[0035] Lattice penetration stage (S1): High-concentration salts are extremely difficult to dissolve when directly added to an inert, water-poor solvent. In this method, the salt is first mixed with a high dielectric constant regulator and heated. The heat energy and the polarity of the dielectric agent are used to pre-wedge solvent molecules into the lattice structure of the salt, weakening the lattice energy and forming a swollen, pre-activated slurry.

[0036] Polar bridging stage (S2): A trace amount of proton transfer agent (water) is introduced as a co-solvent. Water molecules, with their extremely small size and strong hydrogen bonding ability, rapidly form a first solvation layer around the pre-solvated ions, completely destroying the remaining crystal lattice structure and forming a transparent, high-concentration mother liquor.

[0037] Metastable dispersion stage (S3): The ion clusters that have formed solvated shells are dispersed into a large amount of inert, water-poor solvent. Since the ions are encapsulated by dielectric agents and water molecules, the repulsion caused by direct contact with the inert solvent is avoided, thus forming a thermodynamically stable homogeneous system.

[0038] Preferably, in step S1, the heating and stirring conditions are: temperature 40 to 50°C, stirring speed 500 to 800 rpm, and time 30 to 60 minutes.

[0039] By adopting the above technical solution, the appropriate heating temperature provides activation energy, which accelerates the diffusion rate of dielectric agent molecules; the higher shear rate helps to break and disperse solid particles, increases the contact area, and ensures the pre-solventization effect.

[0040] Preferably, in step S2, the stirring time until the solid is completely dissolved is 10 to 50 minutes.

[0041] By adopting the above technical solution, the dissolution time is controlled to ensure that the system reaches dissolution equilibrium, avoiding microcrystal residue due to insufficient stirring time or local solvent evaporation due to excessive stirring time.

[0042] Preferably, in step S3, the conditions for uniform mixing are: temperature 20 to 30°C, stirring speed 200 to 400 rpm, and time 1 to 2 hours.

[0043] By adopting the above technical solution, the final compounding is carried out at room temperature and medium-low speed stirring to prevent the introduction of air bubbles or local overheating caused by vigorous stirring, thus ensuring the uniformity and stability of the final product.

[0044] In summary, the present invention has at least one of the following beneficial technical effects:

[0045] 1. This invention employs a sterically hindered hindered hydrazine salt combined with an inert, water-poor solvent to construct an absorption environment with low water activity. Since the hydration reaction of CO2 is highly dependent on water molecules, and the steric hindrance effect of the hindered hydrazine group prevents the formation of carbamates, this material restricts the CO2 absorption pathway in both thermodynamic and kinetic dimensions. Simultaneously, H2S can still react with the active base through rapid proton transfer, thus achieving an extremely high H2S / CO2 selectivity factor. This solves the problem of traditional aqueous solutions failing to achieve deep removal of hydrogen sulfide while retaining a high proportion of carbon dioxide.

[0046] 2. This invention introduces a dielectric-controlled dissociation agent with a high dielectric constant, utilizing its strong solvation effect to overcome the lattice energy of high-concentration hindered hydrazine salts in low-polarity ether solvents. This component effectively weakens the electrostatic attraction between anions and cations, transforming closely contacting ion pairs into solvent-separated ion pairs, fully releasing the shielded anion active sites, ensuring that the absorbent still possesses a high hydrogen sulfide loading capacity in non-aqueous systems with low water content, and avoiding high-concentration salt precipitation or stratification.

[0047] 3. The organic solvent system selected in this invention has a lower specific heat capacity and latent heat of vaporization than water, and the active component has a lower proton dissociation energy barrier in non-aqueous media, enabling rapid and complete desorption of hydrogen sulfide with low energy consumption during thermal regeneration. Furthermore, the high boiling point and chemical inertness of solvents such as polyethylene glycol dimethyl ether effectively suppress solvent evaporation loss and oxidative degradation during regeneration, ensuring the performance stability of the material in long-term, multiple absorption-desorption cycles. Detailed Implementation

[0048] The technical solutions of the present invention will be clearly and completely described below with reference to embodiments, comparative examples, and test examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] Preparation Examples 1-3:

[0050] Preparation Example 1: Synthesis of dipotassium N,N'-di-tert-butylhydrazine phosphonate (component A1)

[0051] In a reactor equipped with a stirrer, thermometer, and reflux condenser, the following operations are performed in sequence:

[0052] Intermediate synthesis: 100 parts by weight of anhydrous dichloromethane were added as a solvent, and the mixture was stirred and cooled to 0-5°C. 14.4 parts by weight of N,N'-di-tert-butylhydrazine (purity >98%) was added. 13.8 parts by weight of phosphorus trichloride were slowly added dropwise at low temperature over a period of 1 hour. After the addition was complete, the temperature was raised to 25°C and the reaction was carried out for 4 hours. Subsequently, 5 parts by weight of water were added to initiate a hydrolysis reaction for 1 hour. The solvent and byproducts were removed by vacuum distillation to obtain a viscous acidic intermediate.

[0053] Salt formation and purification: The above intermediate was redissolved in 50 parts by weight of anhydrous ethanol. A 20% potassium hydroxide ethanol solution was added dropwise with stirring to adjust the pH to 9.5-10.0. After standing and cooling, a white precipitate formed. The precipitate was filtered, washed three times with cold ethanol, and dried under vacuum to obtain dipotassium N,N'-di-tert-butylhydrazine phosphonate (component A1).

[0054] Preparation Example 2: Synthesis of potassium N,N'-di-tert-butylhydrazine sulfonate (component A2)

[0055] The following operations are performed in the reactor:

[0056] Intermediate synthesis: 100 parts by weight of anhydrous dichloromethane were added, and the temperature was lowered to 0-5°C. 14.4 parts by weight of N,N'-di-tert-butylhydrazine were added. 11.7 parts by weight of chlorosulfonic acid were slowly added dropwise. After the addition was complete, the reaction was carried out at 30°C for 5 hours. The solvent was removed under reduced pressure to obtain the sulfonic acid intermediate.

[0057] Salt formation and purification: The intermediate was dispersed in 60 parts by weight of isopropanol. Finely ground potassium carbonate powder (in excess) was slowly added until no bubbles were generated and the system was alkaline (pH>9). Unreacted inorganic salts were removed by filtration, the filtrate was concentrated and crystallized, and dried to obtain potassium N,N'-di-tert-butylhydrazine sulfonate (component A2) as the final product.

[0058] Preparation Example 3: Synthesis of disodium N,N'-di-tert-butylhydrazine phosphonate (component A3):

[0059] The operating procedure is basically the same as in Preparation Example 1, except for the salt formation and purification steps: the acidic intermediate is dissolved in 50 parts by weight of anhydrous ethanol, and then a 20% sodium hydroxide ethanol solution is added dropwise instead of potassium hydroxide solution to adjust the pH to 9.5 to 10.0. After filtration, washing, and drying, disodium N,N'-di-tert-butylhydrazine phosphonate (component A3) is obtained.

[0060] Examples 1-5: Example

[0061] This embodiment provides a material for the selective separation of carbon dioxide and hydrogen sulfide, the preparation method of which includes the following steps:

[0062] (1) Weigh 20 parts of dipotassium N,N'-di-tert-butylhydrazine phosphonate (component A1) and 10 parts of sulfolane, mix them in a mixing tank at 45°C and 600 rpm for 40 minutes to allow sulfolane to fully impregnate and penetrate the solid salt lattice to obtain a pre-activated slurry.

[0063] (2) Add 3 parts of deionized water to the above slurry and continue stirring for 20 minutes until the solid is completely dissolved to form a transparent high-concentration salt solution;

[0064] (3) Slowly inject the solution obtained in step (2) into 67 parts of polyethylene glycol dimethyl ether (NHD) and stir for 1.5 hours at 25°C and 300 rpm to obtain a homogeneous and transparent finished absorbent liquid.

[0065] Example 2:

[0066] This embodiment provides a material for the selective separation of carbon dioxide and hydrogen sulfide, designed to verify the effect of high content of dissociating agent on the system performance. Its preparation method includes the following steps:

[0067] (1) Weigh 15 parts of N,N'-di-tert-butylhydrazine phosphonate dipotassium (component A1) and 15 parts of sulfolane, mix them in a mixing tank at 50°C and 800 rpm for 60 minutes to carry out deep presolvation treatment;

[0068] (2) Add 3 parts of deionized water to the above mixture and stir for 20 minutes until completely dissolved;

[0069] (3) Add the obtained solution to 67 parts of polyethylene glycol dimethyl ether (NHD) and stir and mix evenly at 25°C to obtain the finished absorbent solution.

[0070] Example 3:

[0071] This embodiment provides a material for the selective separation of carbon dioxide and hydrogen sulfide, designed to verify its inhibitory effect on carbon dioxide absorption at extremely low water content. The preparation method includes the following steps:

[0072] (1) Weigh 25 parts of N,N'-di-tert-butylhydrazine phosphonate dipotassium (component A1) and 10 parts of sulfolane, and mix and stir at 40°C for 30 minutes;

[0073] (2) Add 1 part of deionized water very slowly and stir for 40 minutes to use the solubilizing effect of sulfolane to dissolve the high concentration of salt in the presence of trace amounts of water.

[0074] (3) Disperse the obtained high viscosity solution in 64 parts of polyethylene glycol dimethyl ether (NHD) and stir for 2 hours until the system is homogeneous to obtain the finished absorbent solution.

[0075] Example 4: This example provides a material for the selective separation of carbon dioxide and hydrogen sulfide, designed to verify the applicability of different anionic groups and different dielectric modifiers. Its preparation method includes the following steps:

[0076] (1) Weigh 20 parts of potassium N,N'-di-tert-butylhydrazine sulfonate (component A2) and 10 parts of propylene carbonate (PC), and mix and stir at 45°C for 40 minutes.

[0077] (2) Add 3 parts of deionized water and stir to dissolve;

[0078] (3) Inject the solution into 67 parts of tetraethylene glycol (TEG), stir and mix evenly at room temperature to obtain the finished absorbent solution.

[0079] Example 5: This example provides a material for the selective separation of carbon dioxide and hydrogen sulfide, designed to verify its applicability to different alkali metal cations. Its preparation method includes the following steps:

[0080] (1) Weigh 20 parts of N,N'-di-tert-butylhydrazine phosphonate disodium (component A3) and 12 parts of sulfolane, and mix and stir at 50°C for 50 minutes;

[0081] (2) Add 5 parts of deionized water (Note: Sodium salt has a slightly lower solubility, so increase the amount of water accordingly), and stir until dissolved;

[0082] (3) Add the solution to 63 parts of polyethylene glycol dimethyl ether (NHD), stir and mix evenly to obtain the finished absorbent solution.

[0083] Comparative Examples 1-5:

[0084] Comparative Example 1: The difference from Example 1 is that component B (sulfolane) was not added. Specifically, 10 parts of sulfolane were replaced with an equal amount of polyethylene glycol dimethyl ether (NHD), while the other raw materials and preparation steps remained the same.

[0085] Comparative Example 2: Compared with Example 1, the difference is that the solvent system was changed to a traditional aqueous solution. Specifically, 10 parts of sulfolane and 67 parts of polyethylene glycol dimethyl ether (NHD) were completely replaced with 77 parts of deionized water, that is, the total water content in the system was 80 parts. The other raw materials and preparation steps were the same.

[0086] Comparative Example 3: Compared with Example 1, the difference is that the core active component was replaced with a conventional alcohol amine. Specifically, 20 parts of component A1 (N,N'-di-tert-butylhydrazine dipotassium phosphonate) were replaced with an equal amount of N-methyldiethanolamine (MDEA), while the remaining raw materials and preparation steps were the same.

[0087] Comparative Example 4: Compared with Example 1, the difference is that the amount of component B (sulfolane) added is below a certain threshold. Specifically, the amount of sulfolane is reduced to 1 part, and the amount of polyethylene glycol dimethyl ether (NHD) is increased to 76 parts, while the other raw materials and preparation steps are the same.

[0088] Comparative Example 5: Compared with Example 1, the difference is that the core active component A1 was not added. Specifically, 20 parts of component A1 were replaced with an equal amount of polyethylene glycol dimethyl ether (NHD), i.e., a pure physical solvent system, while the other raw materials and preparation steps remained the same.

[0089] Test Example 1-3:

[0090] Test Example 1: Solution Phase Behavior and Stability Test

[0091] Experimental description:

[0092] This test aims to verify the compatibility and thermodynamic stability of the absorbent systems prepared in each embodiment and comparative example under different temperature conditions, and in particular to investigate the effect of dielectric modulators on the dissolution behavior of high-concentration hindered hydrazine salts in low-polarity solvents.

[0093] Experimental steps:

[0094] (1) Sample standing observation: The fresh absorbent samples prepared in Examples 1-5 and Comparative Examples 1 and 4 were placed in 100mL stoppered colorimetric tubes, sealed, and left to stand in a constant temperature water bath at 25±0.5℃ for 48 hours. The clarity of the solution was observed with the aid of a Tyndall effect laser pen, and the presence of suspended particles, turbidity, or bottom sediment was recorded.

[0095] (2) Temperature-dependent phase behavior test: The above sample was heated to 50°C and held for 2 hours to observe the dissolution state at high temperature; then cooled to 10°C at a rate of 1°C / min to observe whether crystals precipitate at low temperature.

[0096] (3) Kinematic viscosity determination: The kinematic viscosity of each homogeneous sample was determined at 25°C using an Ubbelohde viscometer in accordance with GB / T265-1988 standard. For heterogeneous samples (with precipitation or stratification), viscosity testing was not performed.

[0097] Experimental data:

[0098] The phase behavior observations and viscosity test results for each sample are detailed in Table 1.

[0099] Table 1. Phase stability and viscosity test data of each absorbent system

[0100] Sample number Component characteristics summary Appearance at 25℃ (48h) Temperature stability from 10 to 50℃ <![CDATA[Kinematic viscosity (25 °C, mm 2 / s)]]> Example 1 20%A1 + 10% Sulfolane Colorless and transparent liquid No crystals precipitated, remaining clear. 34.27 Example 2 15%A1 + 15% Sulfolane Colorless and transparent liquid No crystals precipitated, remaining clear. 28.15 Example 3 25%A1+1%water Slightly yellow transparent liquid No crystals precipitate, viscosity increases 43.62 Example 4 20% A2+TEG system Colorless and transparent liquid No crystals precipitated, remaining clear. 51.09 Example 5 20% A3 (sodium salt) Colorless and transparent liquid It appears slightly opalescent at 10℃, but becomes clear upon further heating. 37.84 Comparative Example 1 0% Sulfolane (without component B) Large amount of white flocculent precipitate Solid-liquid separation, unable to dissolve -- (Heterogeneous) Comparative Example 4 1% Sulfolane (Low B component) The liquid is cloudy with a small number of particles at the bottom. The water remains cloudy even at 50°C. -- (Heterogeneous)

[0101] Conclusion Analysis:

[0102] Based on the data in Table 1 and the technical mechanism of this invention, the following conclusions are drawn:

[0103] (1) Verification of the solubilization mechanism of the dielectric control component: In Examples 1-5, after the introduction of more than 10% of the dielectric control dissociation agent (sulfolane or propylene carbonate), a homogeneous and transparent stable solution was formed. In contrast, in Comparative Example 1, when this component was missing, the hindered hydrazine salt showed a large amount of precipitation in polyethylene glycol dimethyl ether (NHD); in Comparative Example 4, only 1% sulfolane was added, and the system was turbid.

[0104] This phenomenon confirms the solvation mechanism proposed in this invention: the low dielectric constant of low-polarity ether solvents such as NHD is insufficient to overcome the lattice energy of N,N'-di-tert-butylhydrazine phosphonate. The introduction of components with high dielectric constants >40 increases the polarity of the mixed solvent system, weakening the electrostatic attraction between cations and anions through solvation, thus enabling the salt components to be stably dispersed in the water-poor organic phase.

[0105] (2) Structural adaptability analysis: Example 3 remained clear even with extremely low water content (1%), indicating that the dielectric modifier dominated the salt dissolution process, eliminating the dependence on water in traditional processes. Example 4 shows that the system has good universality for sulfonates and tetraethylene glycol as the main solvents.

[0106] (3) Physical property evaluation: The kinematic viscosity of Examples 1 and 2 was controlled between 28 and 35 mm. 2 The value is within the range of / s, which is slightly higher than that of pure solvents but much lower than that of ionic liquids. This meets the requirements of industrial packed towers for fluid flowability and is beneficial to the gas-liquid mass transfer process.

[0107] Test Example 2: Static Absorption Performance and Selectivity Test

[0108] Experimental description:

[0109] This test uses a high-pressure gas-liquid balance vessel to determine the saturated absorption capacity of carbon dioxide and hydrogen sulfide in each absorbent system under simulated industrial conditions, and evaluates the separation performance of the materials by calculating the selectivity factor.

[0110] Experimental steps:

[0111] (1) Apparatus preparation: Use a 500mL stainless steel high-pressure reactor equipped with a magnetic stir coupler and a precision pressure sensor. Before the experiment, purge the system with nitrogen and check its airtightness.

[0112] (2) Feeding and balancing: Quantitatively inject 150 mL of the absorbent sample to be tested into the reactor. Turn on the heating mantle and stirring device, and set the temperature inside the reactor to be stable at 40 ± 0.1 ℃.

[0113] (3) Gas intake and absorption: Simulated raw material gas is rapidly introduced into the reactor using a mass flow controller until the total pressure inside the reactor reaches 2.0 MPa, at which point the gas intake is stopped. The molar composition of the simulated raw material gas is: H2S (1.04%) + CO2 (10.12%) + N2 (equilibrium gas).

[0114] (4) Data recording and analysis: Maintain a constant temperature of 40℃ and continuously stir, monitoring the pressure change inside the vessel. When the pressure fluctuation is less than 1 kPa within 30 minutes, it is considered to have reached a gas-liquid equilibrium state. Analyze the gas phase components online using a gas chromatograph, and calculate the equilibrium solubility (i.e., absorption load) of H2S and CO2 in the liquid phase using the principle of material balance.

[0115] Parameter calculation:

[0116] Absorption load: defined as the number of moles of gas absorbed per mole of active component (or total solvent). For physical solvent systems without active components, the load is calculated based on the volume of gas absorbed per unit volume of solvent.

[0117] Selectivity factor: The calculation formula is: (hydrogen sulfide liquid phase mole fraction / hydrogen sulfide gas phase mole fraction) divided by (carbon dioxide liquid phase mole fraction / carbon dioxide gas phase mole fraction)

[0118] Experimental data:

[0119] The static equilibrium absorption data for each embodiment and comparative example are recorded in Table 2.

[0120] Table 2. Acid gas equilibrium absorption performance data of each system under 40℃ and 2.0MPa conditions.

[0121] Sample number Hydrogen sulfide saturation load Carbon dioxide saturation load Hydrogen sulfide / carbon dioxide selectivity factor Example 1 0.684 0.032 198.5 Example 2 0.652 0.029 213.1 Example 3 0.597 0.015 345.8 Example 4 0.633 0.041 142.6 Example 5 0.581 0.035 158.3 Comparative Example 1 0.112 0.028 35.4 Comparative Example 2 0.745 0.482 13.6 Comparative Example 3 0.522 0.187 26.9 Comparative Example 4 0.283 0.031 82.5 Comparative Example 5 0.046 0.114 3.8

[0122] Conclusion Analysis

[0123] Based on the patterns shown in Table 2 and the dielectric modulation mechanism of this invention, the following analytical conclusions are drawn:

[0124] (1) Activation effect of dielectric dissociation on active sites: The hydrogen sulfide loading of Example 1 (0.684) was higher than that of Comparative Example 1 (0.112) and Comparative Example 4 (0.283). Comparative Example 1 lacked sulfolane, and the hindered hydrazine salt existed in the form of close ion pairs or solid precipitation. The lone pair electrons on the nitrogen atom were shielded by potassium ions, and hydrogen sulfide could not be effectively captured. Its absorbance was mainly contributed by the physical solvent. After introducing sufficient dielectric modifier in Example 1, the hydrogen sulfide loading was restored to the theoretical chemical absorption level, confirming that the high dielectric component successfully constructed solvent-separated ion pairs and released anionic active centers.

[0125] (2) Inhibitory effect of water-scarce environment on carbon dioxide: Comparing Example 1 and Comparative Example 2 (all-water system), although the hydrogen sulfide absorption of Comparative Example 2 was higher (0.745), its carbon dioxide load was as high as 0.482, resulting in a selectivity factor of only 13.6. This indicates that the hydration reaction of carbon dioxide cannot be avoided in a water-rich environment. In contrast, in Example 1, the carbon dioxide load was suppressed to an extremely low level of 0.032, and the selectivity was improved by about 14 times. In Example 3, the water content was further reduced to 1%, and the carbon dioxide load was reduced to 0.015, confirming that the starvation effect of the carbon dioxide reaction pathway can be achieved by controlling the trace water content.

[0126] (3) Matching of the special hindered structure with the solvent: Comparative Example 3 was tested using MDEA in the same solvent system, and its carbon dioxide load (0.187) was higher than that of Example 1. This indicates that even in a low-water environment, conventional alkanolamine molecules are more likely to form urethanes or bicarbonates with carbon dioxide than the special hindered hydrazine salt described in this invention. This invention achieves a separation effect superior to that of traditional hindered amines through the dual shielding of large sterically hindered anions and a water-poor medium.

[0127] (4) Comprehensive performance evaluation: Examples 1 to 5 all showed a high selectivity factor greater than 140 and maintained a high hydrogen sulfide absorption capacity, which verified the technical robustness of the ternary compound system under different formulation fine-tuning, and can meet the process requirements of deep desulfurization while retaining carbon dioxide.

[0128] Test Example 3: Low-pressure desorption and regeneration performance test

[0129] Experimental description:

[0130] This test aims to examine the desorption efficiency of the absorbent during thermal regeneration and its chemical stability in multiple absorption-desorption cycles. Example 1 (the solvent system of this invention) and Comparative Example 2 (an all-aqueous solvent system) were selected as comparative subjects.

[0131] Experimental steps:

[0132] (1) Preparation of rich liquid: The saturated rich liquid that reached gas-liquid equilibrium in test example 2 was taken as the initial sample, and its initial hydrogen sulfide load was measured.

[0133] (2) Negative pressure desorption: Transfer the rich liquid into a desorption vessel equipped with a reflux condenser. Adjust the system pressure to an absolute pressure of 20 kPa, turn on the oil bath heating, and rapidly raise the temperature of the liquid in the vessel to 100 ± 1 °C. Maintain this temperature and pressure conditions for 30 minutes to allow the dissolved gas to escape.

[0134] (3) Lean solution analysis: Samples were taken and cooled to determine the residual hydrogen sulfide load in the lean solution after desorption.

[0135] (4) Data calculation: Calculate the desorption rate according to the formula:

[0136] Desorption rate = Rich liquid load − Lean liquid load Rich liquid load × 100%.

[0137] (5) Cyclic test: Cool the regenerated lean solution to 40°C, and then introduce simulated gas to absorb until saturation. Repeat the above desorption steps for a total of 5 complete absorption-regeneration cycles, and record the desorption rate data for each cycle.

[0138] Experimental data:

[0139] The regeneration performance test results for each cycle are recorded in Table 3.

[0140] Table 3. Hydrogen sulfide desorption rate data of Example 1 and Comparative Example 2 during five cycles.

[0141] Loop count Example 1 Desorption rate (%) Comparative Example 2 Desorption Rate (%) 1 99.12 94.35 2 98.87 93.82 3 98.93 91.04 4 98.56 89.67 5 98.41 87.23

[0142] Conclusion Analysis:

[0143] Based on the data characteristics in Table 3 and the principles of gas-liquid mass transfer kinetics, the analysis is as follows:

[0144] (1) Analysis of differences in desorption depth: The desorption rate of Example 1 remained above 98.4% in each cycle, which was better than that of Comparative Example 2. From a thermodynamic perspective, Comparative Example 2 is an all-water system, with sulfide ions (HS-H2O) − ) and protonated organic bases (RH) + In water, the protons undergo strong solvation (hydration effect), forming a stable hydrated ion shell. The reverse reaction requires overcoming a high energy barrier to destroy the hydrated layer. However, Example 1 uses a water-poor organic solvent system where the active component exists as solvent ion pairs. The interaction between ions and solvent is weaker, and the reverse process of the proton transfer reaction (i.e., the release of H2S) is more likely to occur under thermal excitation, thus achieving more thorough regeneration.

[0145] (2) Cyclic stability evaluation: With the increase of the number of cycles, the desorption rate of Example 1 fluctuated very little (range <0.8%), showing excellent chemical and thermal stability. The high boiling point characteristics of polyethylene glycol dimethyl ether and sulfolane inhibited solvent volatilization and ensured the constant composition of the formulation. In contrast, the desorption rate of Comparative Example 2 showed a decreasing trend with each cycle, dropping to 87.23% by the fifth cycle. This is attributed to the fact that under negative pressure heating conditions, a large amount of water as a solvent vaporized and was lost, resulting in a decrease in the absorbent liquid level and a passive increase in salt concentration, which in turn caused local supersaturation precipitation or abnormal increase in viscosity, deteriorated the gas-liquid mass transfer interface, and ultimately led to a decline in regeneration performance.

[0146] (3) Energy consumption potential assessment: Example 1 can achieve almost complete desorption (>99%) within 30 minutes, and the specific heat capacity of the main solvent (about 2.1 J / (g⋅K)) is much lower than that of water (4.18 J / (g⋅K)), suggesting that the system can reduce the sensible heat load and latent heat load of the reboiler in industrial applications.

Claims

1. A material for the selective separation of carbon dioxide and hydrogen sulfide, characterized in that, The material is prepared from raw materials comprising the following parts by weight: The hindered hydrazine salt active component comprises 15 to 25 parts; the hindered hydrazine salt active component is one or more of the alkali metal salt of N,N'-di-tert-butylhydrazine phosphonic acid or the alkali metal salt of N,N'-di-tert-butylhydrazine sulfonic acid; wherein the cation of the alkali metal salt is selected from potassium ions or sodium ions; 5 to 15 parts of dielectric modulator / dissociator; wherein the dielectric modulator / dissociator is selected from one or more of sulfolane or propylene carbonate; 1 to 5 parts deionized water; 55 to 79 parts of an inert, water-poor solvent; wherein the inert, water-poor solvent is selected from one or more of polyethylene glycol dimethyl ether or tetraethylene glycol; The selective separation material for carbon dioxide and hydrogen sulfide is prepared by the following steps: S1. Pre-solventization activation: The hindered hydrazine salt active component is mixed with the dielectric modulating dissociation agent, and lattice penetration is carried out under heating and stirring conditions to obtain a pre-activated slurry. S2, Dissolution aid: Add the deionized water to the pre-activated slurry and stir until the solid is completely dissolved to obtain a high-concentration salt solution; S3. Homogeneous compounding: The high-concentration salt solution is added to the inert, water-poor solvent and stirred until homogeneous to obtain the selective separation material for carbon dioxide and hydrogen sulfide.

2. The selective separation material for carbon dioxide and hydrogen sulfide according to claim 1, characterized in that, The hindered hydrazine salt active component was prepared by the following method: N,N'-di-tert-butylhydrazine was dissolved in a haloalkanes solvent, and phosphorus trichloride or chlorosulfonic acid was added dropwise at 0 to 5°C to obtain an intermediate. The intermediate was then dissolved in an alcohol solvent, and an alkali metal hydroxide or carbonate was added to adjust the pH to 9.0 to 10.

0. The product was then obtained by crystallization and drying.

3. The selective separation material for carbon dioxide and hydrogen sulfide according to claim 2, characterized in that, The halogenated hydrocarbon solvent is anhydrous dichloromethane; the alcohol solvent is selected from anhydrous ethanol or isopropanol.

4. The selective separation material for carbon dioxide and hydrogen sulfide according to claim 1, characterized in that, In step S1, the heating and stirring conditions are: temperature 40 to 50°C, stirring speed 500 to 800 rpm, and time 30 to 60 minutes.

5. The selective separation material for carbon dioxide and hydrogen sulfide according to claim 1, characterized in that, In step S3, the conditions for uniform mixing are: temperature 20 to 30°C, stirring speed 200 to 400 rpm, and time 1 to 2 hours.

6. The selective separation material for carbon dioxide and hydrogen sulfide according to claim 1, characterized in that, In step S2, the stirring time until the solid is completely dissolved is 10 to 50 minutes.