A polyamino absorbent for carbon dioxide capture and a method of capturing carbon dioxide from a gas mixture

Abstract

The application discloses a kind of polyamino absorbent for carbon dioxide capture and method for capturing carbon dioxide from gas mixture, belong to chemical material, gas separation and carbon capture utilization and storage technology field.The polyamino absorbent includes: first component: at least one organic amine with the following molecular formula: HO-C x H 2x ‑N(CH3)‑C y H 2y ‑O‑C z H 2z ‑N(CH3)2, x, y and z are each independently selected from one of 1, 2 and 3;Second component: at least one different basic compound from the first component;And solvent and selectively included additive;The content of the first component is 5~50%, the content of the second component is 10~50%, and the total content of the solvent and the selectively included additive is 30~80%.The polyamino absorbent of the application considers high cycle absorption amount, low absorption CO2 reaction heat, high diffusion coefficient and high absorption rate.

Description

Technical Field

[0001] This invention relates to a polyamine absorbent for carbon dioxide capture and a method for capturing carbon dioxide from a gas mixture, belonging to the fields of chemical materials, gas separation, and carbon capture, utilization, and storage. Background Technology

[0002] Emissions of greenhouse gases such as CO2 are a major contributor to climate change, making the capture or separation of CO2 from CO2-rich gas mixtures extremely important. These gas mixtures include mixtures containing carbon dioxide from flue gas, purge gas, and process gas generated during coal-fired power generation, steel metallurgy, cement and building materials, petrochemical, and coal chemical processes. These mixtures typically contain 5%–50% CO2, with other major gaseous components including N2, O2, CO, H2, CH4, C2H6, SO2, H2S, and organic sulfur compounds such as CH3SH and COS. The gases exhibit a wide pressure range (50–500 kPa), making chemical absorption or a combination of chemical and physical absorption methods suitable for capturing and separating CO2, SO2, H2S, and acidic gases such as CH3SH and COS.

[0003] Currently, the more mature industrial processes for CO2 separation from medium- and high-pressure gases mainly include the diethanolamine (DEA) method, the diisopropanolamine (DIPA) method, and the methyldiethanolamine (MDEA) method. To improve the absorption rate of CO2 by the absorption solution, faster-absorbing absorbents such as monoethanolamine (MEA) and piperazine (PZ) are added to absorbents with relatively slow absorption rates, such as DIPA and MDEA, resulting in some modified absorption and separation methods.

[0004] For the absorption and capture of low partial pressure CO2, a strongly alkaline absorbent is required. MEA (Metal-Based Acid) is the most traditional and widely used absorbent in industrial applications. A 30% (weight percentage, the same below) MEA solution (solvent: water) is typically used. At 40℃ and a CO2 partial pressure of 12 kPa, the CO2 equilibrium loading of a 30% MEA solution is 2.65 mol / kg. When the temperature is increased to 120℃ while the CO2 partial pressure remains constant, the CO2 equilibrium loading of the 30% MEA solution decreases to 1.5 mol / kg, the cyclic absorption loading is approximately 1.15 mol / kg, and the desorption rate is only 43%. Simultaneously, the heat of reaction for CO2 absorption by a 30% MEA solution at 40℃ is 90~100 kJ / mol.

[0005] Furthermore, sterically hindered amines have been applied due to their high solubility for CO2 in atmospheric pressure gases and their high cyclic loading for absorption and desorption. For example, US4112052 discloses organic amines having at least one secondary amino group linked to a secondary or tertiary carbon atom, or one primary amino group linked to a tertiary carbon atom, which increase CO2 solubility by 100% compared to MEAs. The most commonly used is 2-amino-2-methyl-1-propanol (AMP). A 30% AMP solution (water as solvent) at 40°C and a CO2 partial pressure of 12 kPa has a CO2 equilibrium loading of 2.2 mol / kg. When the temperature is increased to 120°C while the CO2 partial pressure remains constant, the CO2 equilibrium loading of the 30% AMP solution decreases to 0.3 mol / kg, the cyclic absorption loading is approximately 1.9 mol / kg, and the desorption rate is 86%, which is 100% higher than that of MEAs. Simultaneously, the heat of reaction for CO2 absorption by a 30% AMP solution at 40°C is 70–90 kJ / mol.

[0006] However, since sterically hindered amines (AMPs) are essentially primary amines, the reduction in reaction heat is not significant, and the energy consumption for capture remains high. Furthermore, AMPs undergo considerable degradation during use, resulting in high operating costs. Additionally, the complex molecular structure of sterically hindered amines makes their synthesis relatively difficult and increases manufacturing costs.

[0007] Some scholars have also proposed polyamine absorbents with good absorption capacity, such as hydroxyethyl ethylenediamine (AEEA, CN101091864A) and diethylenetriamine (DETA, CN101657247B). AEEA is a diamine with high solubility for CO2 absorption and contains one each of a highly polar primary amino group, a secondary amino group, and a hydroxyl group. A 30% AEEA solution (water as solvent) at 40℃ and a CO2 partial pressure of 12 kPa has a CO2 equilibrium loading of 2.6 mol / kg. When the temperature is increased to 120℃ while the CO2 partial pressure remains constant, the CO2 equilibrium loading of the 30% AEEA solution decreases to 1.0 mol / kg, the cyclic absorption loading is approximately 1.6 mol / kg, and the desorption rate is 62%, which is 44% higher than that of MEA. Meanwhile, the heat of reaction for CO2 absorption by a 30% AEEA solution at 40℃ is 75~80 kJ / mol. DETA has two primary amino groups and one secondary amino group, resulting in a more symmetrical molecular structure, better water solubility, and a higher CO2 absorption rate at the same concentration, with a higher absorption capacity compared to MEA. A 30% DETA solution (water as solvent) at 40℃ and a CO2 partial pressure of 12 kPa has a CO2 equilibrium loading of 3.8 mol / kg. When the temperature is increased to 120℃ while the CO2 partial pressure remains constant, the CO2 equilibrium loading of the 30% DETA solution decreases to 2.0 mol / kg, the cyclic absorption loading is approximately 1.8 mol / kg, and the desorption rate is 47%, which is 10% higher than that of MEA. Simultaneously, the heat of reaction for CO2 absorption by the 30% DETA solution at 40℃ is 80–85 kJ / mol.

[0008] CA2598388C proposed aminobutanols substituted with straight-chain alkyl or cycloalkyl groups, such as 4-diethylamino-2-butanol, 4-(isopropylamino)-2-butanol, 4-(piperidinyl)-2-butanol, 4-propylaminobutanol, and 4-((ethyl)(methyl)amino)-2-butanol. However, due to the large molecular weight of the substituents, the unit absorption capacity and solubility were not truly improved.

[0009] CN102596362A proposes ethylidene amines, propylidene amines, tris(2-aminoethyl)amines, 3,3-bis(2-aminoethyl)propylamines, N,N'-bis(2-aminoethyl)piperazines, and N,N'-bis(2-aminopropyl)piperazines with monoalkylated primary amino groups. The preferred substituent is isopropyl, which is sterically hindered and does not contain hydroxyl or primary amino functional groups, thus it is not easily oxidized and degraded. The sterically hindered secondary amino groups have high pKa and lower nucleophilicity, resulting in greater absorption capacity and easier desorption. However, they have poor compatibility with water and high molecular volatility.

[0010] CN108778467B proposes N-methyl or hydroxyethyl substituted hydroxy derivatives of 1,6-hexanediamine as absorbents (N,N,N'-trimethyl-N'-(2-hydroxyethyl)-1,6-hexanediamine, N,N'-dimethyl-N,N'-di(2-hydroxyethyl)-1,6-hexanediamine, N,N-dimethyl-N',N'-di(2-hydroxyethyl)-1,6-hexanediamine, N-methyl-N,N',N'-tri(2-hydroxyethyl)-1,6-hexanediamine), but because they are all tertiary amines and contain a hexyl C6 group, their unit absorption capacity is not high.

[0011] CN103201014A discloses 2-(3-aminopropoxy)ethylene-1-ol (EGPA) as an absorbent for removing acidic gases such as carbon dioxide from fluids. EGPA's molecular structure contains only one primary amino group and no tertiary amino groups. Because the primary amino group reacts with CO2 to form stable carbamates, the cyclic absorption capacity of EGPA is limited, and it also has a low desorption rate, high reaction heat, and high regeneration energy consumption.

[0012] CN108926963A discloses an anhydrous CO2 absorbent, the liquid phase of which contains 2-[2-(dimethylamino)ethoxy]ethanol. This compound contains only one amino group in its molecular structure, resulting in limited CO2 absorption capacity. Furthermore, the absorption rate of the single-component tertiary amine is slow, requiring combination with solid phase components such as amine-modified silica microspheres, making the system relatively complex.

[0013] CN110743326A discloses a class of alkoxy-functionalized aliphatic diamine non-aqueous absorbents, represented by N-(2-methoxyethyl)-N,N'-dimethylethylenediamine. These compounds contain an ether bond, a tertiary amino group, and a secondary amino group in their molecular structure, but lack a hydroxyl group. They exhibit high volatility and poor compatibility with water; furthermore, the carbamate formed by the reaction of the secondary amino group with CO2 is highly stable, leading to a low desorption rate and high heat of reaction. In addition, as a non-aqueous system, this absorbent has limited compatibility with existing industrial aqueous solution absorption processes.

[0014] From the perspective of the application value of absorbents, absorbents with energy-saving and consumption-reducing advantages are the most concerned in the industry. They generally need to simultaneously meet characteristics such as high circulating absorption capacity, low heat of reaction for CO2 absorption, and high absorption rate. During the absorption process, the energy consumption for capture mainly consists of the heat of absorption reaction, the heat of water volatilization in the solvent, and heat exchange losses from the heat exchanger, accounting for approximately 65%, 25%, and 10%, respectively. Therefore, reducing the heat of reaction for CO2 absorption is the key and guarantee for reducing capture energy consumption.

[0015] Furthermore, the diffusion coefficient of CO2 in the absorbent is one of the key physical properties affecting the gas-liquid mass transfer rate. A higher diffusion coefficient results in lower resistance to CO2 transfer from the gas phase to the liquid phase, which is more conducive to improving the mass transfer rate within the absorption tower and the processing capacity of the equipment. The viscosity of the absorbent is closely related to the diffusion coefficient; the lower the viscosity, the higher the diffusion coefficient. However, existing polyamine absorbents generally suffer from high viscosity, leading to a lower CO2 diffusion coefficient and higher gas-liquid mass transfer resistance, which to some extent limits the absorption rate and the mass transfer efficiency of the absorption tower.

[0016] Currently, polyamine absorbents are the main development direction, but existing absorbents are difficult to balance high circulating absorption capacity, low heat of reaction for CO2 absorption, high diffusion coefficient and high absorption rate. Therefore, the development of novel polyamine absorbents remains one of the urgent problems to be solved in this field. Summary of the Invention

[0017] To address the aforementioned technical problems, the present invention aims to provide a polyamine absorbent for carbon dioxide capture and a method for capturing carbon dioxide from a gas mixture. The polyamine absorbent of the present invention combines high circulating absorption capacity, low heat of reaction for CO2 absorption, high diffusion coefficient, and high absorption rate.

[0018] To achieve the above objectives, a first aspect of the present invention provides a polyamine absorbent for carbon dioxide capture, comprising: First component: at least one organic amine having the following molecular formula: HO-C x H 2x -N(CH3)-C y H 2y -OC z H 2z -N(CH3)2, where x, y, and z are each independently selected from one of 1, 2, and 3; Second component: at least one basic compound different from the first component; and Solvents and selective additives; Based on the total weight of the polyamine absorbent for carbon dioxide capture as 100%, the content of the first component is 5-50%, the content of the second component is 10-50%, and the total content of the solvent and selectively included additives is 30-80%.

[0019] A second aspect of the present invention provides a method for capturing carbon dioxide from a gas mixture, comprising the steps of: contacting the polyamine absorbent for carbon dioxide capture with a gas mixture containing carbon dioxide, thereby capturing carbon dioxide.

[0020] The present invention has at least the following beneficial effects: The polyamine absorbent of this invention uses an organic amine containing an ether bond, a hydroxyl group, and two tertiary amine groups (i.e., the first component) as its key component. It possesses advantages such as low gas-liquid mass transfer resistance (high diffusion coefficient), high cyclic absorption capacity, low heat of reaction, and high desorption rate in carbon dioxide absorption. This invention employs a compounding of this organic amine with other alkaline compounds (i.e., the second component), resulting in a synergistic absorption effect. This gives the polyamine absorbent advantages such as high solubility for carbon dioxide, large cyclic absorption capacity, high diffusion coefficient, high absorption rate, low heat of reaction for carbon dioxide absorption, high desorption rate, and low regeneration energy consumption. Using the polyamine absorbent of this invention enables low-energy and low-cost carbon capture. The polyamine absorbent of this invention is suitable for capturing acidic gases such as carbon dioxide from gas mixtures, especially for capturing low-partial-pressure carbon dioxide, and can be used in various absorption processes to capture or separate acidic gases such as carbon dioxide from various atmospheric-pressure gas mixtures. Detailed Implementation

[0021] To provide a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the present invention will now be described in detail below, but this should not be construed as limiting the scope of the invention.

[0022] It should be noted that, unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0023] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0024] It should be understood that the terms “comprising,” “including,” and / or “containing” as used herein specify the presence of the stated features, integers, steps, components, or combinations thereof, but do not exclude the presence or addition of one or more other features, integers, steps, components, or combinations thereof.

[0025] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0026] In the description of this invention, it should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0027] According to a specific embodiment of the first aspect of the present invention, the present invention provides a polyamine absorbent for carbon dioxide capture, comprising: First component: at least one organic amine having the following molecular formula: HO-C x H 2x -N(CH3)-C y H 2y -OC z H 2z -N(CH3)2, where x, y, and z are each independently selected from one of 1, 2, and 3; Second component: at least one basic compound different from the first component; and Solvents and selective additives; Based on the total weight of the polyamine absorbent for carbon dioxide capture as 100%, the content of the first component is 5-50%, for example, but not limited to 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%; the content of the second component is 10-50%, for example, but not limited to 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%; and the total content of the solvent and selectively included additives is 30-80%, for example, but not limited to 30%, 40%, 50%, 60%, 70%, or 80%.

[0028] In terms of the difficulty of developing absorbents, developing novel carbon skeletons is the most challenging, followed by developing substituted compounds, and finally developing novel mixtures. This invention proposes a novel carbon skeleton absorbent (i.e., the first component) with large absorption capacity and low desorption energy consumption, which can largely solve the problem of excessively high cost of carbon capture in current absorption methods.

[0029] To reduce the cost of carbon dioxide capture technology in gas-liquid mixtures using absorption methods, it is necessary to develop absorbents with excellent absorption performance. Previous research indicates that the absorption performance of an absorbent is primarily related to its molecular structure. An excellent absorbent should possess high CO2 recycling capacity, fast CO2 absorption rate, low heat of reaction (leading to low desorption energy consumption), and low oxidation and thermal degradation rates. Furthermore, physical properties such as viscosity, volatility, toxicity, acidity / alkalinity, and density must meet certain requirements to be suitable for use in absorption / desorption equipment.

[0030] Studies have found that molecular structure has a certain influence on the absorption performance of absorbents: the presence of hydrophilic groups such as hydroxyl and amino groups can reduce solvent volatility and increase solution alkalinity, making it easier to absorb CO2; excessively high molecular weight leads to increased solvent viscosity, reducing the diffusion coefficient and mass and heat transfer rates; the increase of amino groups can increase the circulating absorption capacity; increased steric hindrance can increase the desorption rate and reduce desorption energy consumption; different types of amino groups have different CO2 absorption mechanisms: primary and secondary amines absorb CO2 at high rates but with small absorption capacities, while tertiary amines absorb CO2 in large quantities but with low heat of reaction and slow rates; the distance between the hydroxyl and amino groups also has a certain impact, as a close distance will lead to a decrease in the electron cloud density of the amino group, making it difficult to absorb CO2.

[0031] This invention reveals that introducing ether bonds into the carbon chain of organic amines increases their water solubility and reduces their volatility due to the hydrogen bonding between the ether bonds and water. Simultaneously, it lowers the viscosity of the organic amine, increases the diffusion coefficient, and enhances gas-liquid mass transfer, thereby increasing the absorption rate to some extent. For example, 3-methoxypropylamine (containing ether) shows an apparent absorption rate increase of approximately 30% and a significant decrease in viscosity compared to 2-(isopropylamino)ethanol (without ether). The strong electronegativity of the oxygen atom in the ether bond reduces the electron cloud density of the nitrogen atom on adjacent carbons, thus decreasing absorption capacity. However, this reduction is primarily due to the intramolecular hydrogen bonding between the ether bond and the hydrogen atom on the amino group, causing some amino groups to be "shielded." This effect can be mitigated by increasing the number of carbon atoms between the oxygen atom and the amino group and by selecting tertiary amines whenever possible. The electron-withdrawing effect of the ether bond makes urethane esters easier to decompose, facilitating absorbent regeneration, reducing desorption difficulty, and lowering regeneration energy consumption.

[0032] Based on the above understanding, this invention simultaneously introduces ether bonds, hydroxyl groups, and two tertiary amine groups into the organic amine molecule, and designs an appropriate carbon chain length. These structural features produce a synergistic effect, thereby simultaneously achieving excellent comprehensive performance with high cycling absorption, low heat of reaction, high desorption rate, and high diffusion coefficient. Specifically, the ether bond can reduce viscosity, increase gas-liquid mass transfer, improve water solubility, and promote the decomposition of carbamates to reduce regeneration energy consumption; the hydroxyl group can reduce volatility, increase solution alkalinity, and improve water compatibility; the two tertiary amine groups have a higher stoichiometric ratio for the reaction with CO2 than primary and secondary amines, resulting in a larger absorption per mole. Furthermore, the tertiary amine does not form stable carbamates, has low heat of reaction, and high desorption rate. Simultaneously, the tertiary amine does not contain NH bonds and will not form intramolecular hydrogen bonds with the oxygen atoms of the ether bond, thus avoiding the problem of the amino group being "shielded." However, each of the above structural features has its limitations when present individually: absorbents containing only ether bonds and hydroxyl groups but only primary amines (such as 2-(3-aminopropoxy)ethanol-1-ol) have high heat of reaction and low desorption rate; absorbents containing only ether bonds, hydroxyl groups, and one tertiary amine (such as 2-[2-(dimethylamino)ethoxy]ethanol) have limited absorption capacity and slow absorption rate; absorbents containing ether bonds and two amino groups but no hydroxyl groups (such as N-(2-methoxyethyl)-N,N'-dimethylethylenediamine) have high volatility, poor water compatibility, high heat of reaction, and low diffusion coefficient. When ether bonds, hydroxyl groups, and two tertiary amine groups coexist in the same molecule and possess the structure of this invention, the advantages of each structural feature can be fully utilized and the disadvantages can be complemented, resulting in absorbents of this invention exhibiting better performance in terms of cyclic absorption capacity, heat of reaction, desorption rate, diffusion coefficient, absorption rate, and volatility.

[0033] The polyamine absorbent of this invention uses an organic amine (e.g., 2-[[2-[2-(dimethylamino)ethoxy]ethyl]methylamino]-ethanol) containing an ether bond, a hydroxyl group, and two tertiary amine groups as its key component. This invention employs a compounding of this organic amine with other basic compounds (such as other organic amines), resulting in a synergistic absorption effect. This gives the polyamine absorbent advantages such as high solubility for carbon dioxide, large circulating absorption capacity, high diffusion coefficient, high absorption rate, low heat of reaction for carbon dioxide absorption, low volatilization loss, high desorption rate, and low regeneration energy consumption. This facilitates low-energy, low-cost CO2 capture via absorption methods.

[0034] In some embodiments, preferably, the content of the first component is 10-45% based on 100% of the total weight of the polyamine absorbent for carbon dioxide capture.

[0035] In some embodiments, preferably, the content of the second component is 10-30% based on 100% of the total weight of the polyamine absorbent for carbon dioxide capture.

[0036] In some embodiments, the first component is 2-[[2-[2-(dimethylamino)ethoxy]ethyl]methylamino]-ethanol (DEME). Its molecular formula is: HO-C2H4-N(CH3)-C2H4-O-C2H4-N(CH3)2(C9H 22 N₂O₂), where x, y, and z are all 2, has the following structural formula: .

[0037] In some embodiments, the second component includes an organic basic compound and / or an inorganic basic compound.

[0038] In some embodiments, the organic basic compound includes one or more of chain monoamines, piperazines, sterically hindered amines, and chain polyamines, wherein the chain monoamines include primary amines and / or secondary amines.

[0039] In some embodiments, the primary amines include ethanolamine and / or n-propanolamine.

[0040] In some embodiments, the secondary amines include one or more of N-methylethanolamine, N-ethylethanolamine, and diethanolamine.

[0041] In some embodiments, the piperazine class includes one or more of piperazine, 1-methylpiperazine, N-(2-hydroxyethyl)piperazine, 2-methylpiperazine, N-aminoethylpiperazine, and 1,4-dimethylpiperazine.

[0042] In some embodiments, the sterically hindered amines include 2-amino-2-methyl-1-propanol, etc.

[0043] In some embodiments, the chain polyamines include one or more of hydroxyethyl ethylenediamine, diethylenetriamine, triethylenetetramine, N,N'-bis(2-hydroxyethyl)ethylenediamine, and N,N'-bis(2-hydroxypropyl)-1,3-propanediamine.

[0044] In some embodiments, preferably, the organic basic compound includes one or more of chain monoamines, piperazines, and chain polyamines, but excludes hindered amines. The organic basic compound used as the second component in this invention preferably excludes hindered amines, thereby enabling the absorbent of this invention to have lower heat of reaction, higher diffusion coefficient, and higher absorption rate.

[0045] In some embodiments, the inorganic alkaline compound includes potassium carbonate and / or sodium carbonate, etc.

[0046] In some embodiments, the solvent includes one or more of water, alcohols, ethers, esters, and sulfones. The present invention does not impose special limitations on the specific substance of the solvent, as long as it can fully dissolve the first and second components of the present invention; generally, water is used as the solvent.

[0047] In some embodiments, the additives include, but are not limited to, one or more of antioxidants, anti-degradation agents, corrosion inhibitors, and defoamers. This invention does not impose specific limitations on the specific substances included in these additives or their specific amounts; additives and their amounts disclosed in the prior art can be used.

[0048] According to a specific embodiment of a second aspect of the present invention, the present invention provides a method for capturing carbon dioxide from a gas mixture, comprising the steps of: contacting the polyamine absorbent for carbon dioxide capture with a gas mixture containing carbon dioxide, thereby capturing carbon dioxide.

[0049] In some embodiments, the partial pressure of carbon dioxide in the carbon dioxide-containing gas mixture is 3 to 200 kPa. The carbon dioxide-containing gas mixture is preferably at atmospheric pressure.

[0050] In some embodiments, the carbon dioxide-containing gas mixture includes one or more of the following: flue gas, purge gas, and process gas from one or more processes in coal-fired power generation, iron and steel metallurgy, cement building materials, petrochemicals, and coal chemicals.

[0051] In some embodiments, the polyamine absorbent for carbon dioxide capture, while capturing carbon dioxide in the gas mixture, also captures other acidic gases in the gas mixture, including one or more of sulfur dioxide, hydrogen sulfide, and organic sulfur compounds. The organic sulfur compounds may include carbonyl sulfide (COS) and / or methanethiol (CH3SH).

[0052] In some embodiments, the contact between the polyamine absorbent for carbon dioxide capture and the gas mixture containing carbon dioxide is carried out in an absorption tower, wherein the temperature at which the polyamine absorbent for carbon dioxide capture enters the absorption tower is 20-80°C, and the bottom pressure of the absorption tower is 50-500 kPa.

[0053] In some embodiments, the method for capturing carbon dioxide from a gas mixture further includes: desorbing the polyamine absorbent after capturing carbon dioxide, wherein the desorption is carried out in a regeneration tower, the temperature of the polyamine absorbent obtained after desorption is 80~150°C, and the bottom pressure of the regeneration tower is 50~500 kPa.

[0054] In some embodiments, the process flow used in the method for capturing carbon dioxide from the gas mixture can be a process flow in the prior art. For example, it can be a decarbonization process that includes absorption, flash evaporation, heat exchange and desorption, or it can be a combination process that includes interstage cooling of the absorption tower, rich liquid diversion, semi-lean liquid diversion, lean liquid flash evaporation and compression, lean liquid diversion, multi-stage absorption and multi-stage desorption.

[0055] The polyamine absorbent of the present invention has the advantages of high diffusion coefficient, low gas-liquid mass transfer resistance, high circulating absorption capacity, low absorption reaction heat, high absorption rate, high desorption rate and low volatility, and is suitable for capturing carbon dioxide at low partial pressure.

[0056] The technical solutions of the present invention are specifically illustrated by the following embodiments, but the present invention is not limited to these embodiments. Of course, various modifications can be made within the scope of the key points of the present invention.

[0057] Test method: The atmospheric pressure gas mixture used consisted of 12% CO2 and 88% N2, with a CO2 partial pressure of 12 kPa and the remainder being N2. During the experiment, the absorbent was brought into contact with this atmospheric pressure gas mixture at the experimental temperature. The gas-liquid contact chamber was brought to equilibrium when the total pressure dropped to a point where it essentially stopped changing (i.e., the pressure drop was less than 0.1 kPa over 8 hours). The initial temperature T1 and the temperature T2 of the absorbent after absorption equilibrium were measured during the experiment. The CO2 composition of the absorbed gas mixture was analyzed using acid-base titration to determine the number of moles of CO2 absorbed. The following formulas were used to calculate the CO2 equilibrium load, cyclic absorption load, absorption rate, heat of reaction for CO2 absorption, and desorption rate of the absorbent: CO2 equilibrium load (mol / kg) = number of moles of CO2 absorbed / mass of absorbent.

[0058] Cyclic absorption load (mol / kg) = CO2 equilibrium load at low temperature (40℃) – CO2 equilibrium load at high temperature (120℃).

[0059]

[0060] in, and These are the Henry's constants (Pa·m) for CO2 in the absorbent. 3 ( / mol) and diffusion coefficient (m) 2 / s), which are all physical constants of the absorbent; and These are the mass transfer flux of CO2 measured by kinetic experiments (mol / (m)). 2 The partial pressures of CO2 (Pa) and CO2. It is the total concentration of amines in the absorbent (mol / L).

[0061]

[0062] Where, m amine It is the mass of the absorbent, in kg; c p T1 is the specific heat capacity of the absorbent, kJ / (kg·K); T2 and T1 are the temperatures measured during the above experiment, in K. This is the mass of CO2 absorbed, expressed in tons (t). The specific heat capacity of the absorbent was determined using a differential scanning calorimeter (DSC), and the specific heat capacity value was directly provided by the instrument.

[0063] Desorption rate (%) = (1.0 – CO2 equilibrium load at high temperature (120℃) / CO2 equilibrium load at low temperature (40℃)) × 100.

[0064] The diffusion coefficient of CO2 in an absorbent is related to the viscosity of the absorbent; the lower the viscosity, the larger the diffusion coefficient, and the smaller the gas-liquid mass transfer resistance (ignoring chemical reactions), which is beneficial for improving the gas-liquid mass transfer rate within the absorption tower. The diffusion coefficient of CO2 in an amine solution is related to the ratio of the solution's viscosity to the viscosity of water. The following method is used to test the diffusion coefficient of CO2 in the absorbent. (i.e., the above text) ):

[0065] in, and These refer to the dynamic viscosity (cP) of water and absorbent, respectively. denoted as the diffusion coefficient of CO2 in water.

[0066] Example 1

[0067] This embodiment provides a polyamine absorbent, which, by weight of 100%, comprises: 20% 2-[[2-[2-(dimethylamino)ethoxy]ethyl]methylamino]-ethanol (DEME), 20% ethanolamine (MEA), and 60% water.

[0068] At 40°C, the polyamine absorbent of this embodiment was contacted with the aforementioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 2.58 mol / kg. Subsequently, the temperature was raised to 120°C, and the polyamine absorbent of this embodiment was contacted with the aforementioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 0.33 mol / kg, a cyclic absorption loading of approximately 2.25 mol / kg, and a desorption rate of 87%. The heat of reaction for CO2 absorption at 40°C was 1.56 GJ / tCO2, and the absorption rate was 7000 L / mol / s. The diffusion coefficient of CO2 in the absorbent at 40°C was 4.98 × 10⁻⁶. -9 m 2 ·s -1 .

[0069] For comparison, tests were conducted using 40% MEA aqueous solution and 40% DEME aqueous solution at 40℃ and 120℃ respectively, and the results are shown in Table 1.

[0070] At 40℃, a 40% MEA aqueous solution was contacted with the aforementioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 2.79 mol / kg. Subsequently, the temperature was raised to 120℃, and the same 40% MEA aqueous solution was used to absorb CO2 again, with a CO2 equilibrium loading of 1.5 mol / kg and a cyclic absorption loading of approximately 1.29 mol / kg. The desorption rate was 46%. The heat of reaction for CO2 absorption at 40℃ was 2.16 GJ / tCO2, and the absorption rate was 7700 L / mol / s. The diffusion coefficient of CO2 in a 40% MEA aqueous solution at 40℃ was 2.31 × 10⁻⁶. -9 m 2 ·s -1 It can be seen that when MEA is used alone as an absorbent, its CO2 diffusion coefficient is low, its circulating absorption capacity is small, its CO2 absorption reaction heat is high, and its desorption rate is low.

[0071] Table 1

[0072] As can be seen, this embodiment uses a combination of DEME and MEA as the effective components of the absorbent. The two have a synergistic effect and have the advantages of the highest CO2 cycling absorption capacity, low heat of absorption reaction, high desorption rate, high absorption rate, and high diffusion coefficient.

[0073] Example 2

[0074] This embodiment provides a polyamine absorbent, which, by weight of 100%, comprises: 20% 2-[[2-[2-(dimethylamino)ethoxy]ethyl]methylamino]-ethanol (DEME), 20% N,N'-bis(2-hydroxyethyl)ethylenediamine (BHED), and 60% water.

[0075] At 40°C, the polyamine absorbent of this embodiment was contacted with the aforementioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 2.42 mol / kg. Subsequently, the temperature was raised to 120°C, and the polyamine absorbent of this embodiment was contacted with the aforementioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 0.12 mol / kg, a cyclic absorption loading of approximately 2.30 mol / kg, and a desorption rate of 95%. The heat of reaction for CO2 absorption at 40°C was 1.48 GJ / tCO2, and the absorption rate was 7200 L / mol / s. The diffusion coefficient of CO2 in the absorbent at 40°C was 4.87 × 10⁻⁶. -9 m 2 ·s -1 .

[0076] For comparison, tests were conducted using 40% BHED aqueous solution and 40% DEME aqueous solution at 40℃ and 120℃ respectively, and the results are shown in Table 2.

[0077] At 40°C, a 40% BHED aqueous solution was contacted with the aforementioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 1.62 mol / kg. Subsequently, the temperature was raised to 120°C, and the same 40% BHED aqueous solution was used to absorb CO2 again, with a CO2 equilibrium loading of 0.18 mol / kg and a cyclic absorption loading of approximately 1.44 mol / kg. The desorption rate was 89%. The heat of reaction for CO2 absorption at 40°C was 1.56 GJ / tCO2, and the absorption rate was 7500 L / mol / s. The diffusion coefficient of CO2 in a 40% BHED aqueous solution at 40°C was 1.73 × 10⁻⁶. -9 m 2 ·s -1 It can be seen that when BHED is used alone as an absorbent, its CO2 recycling capacity is small, its CO2 diffusion coefficient is small, and its desorption rate is low.

[0078] Table 2

[0079] As can be seen, this embodiment uses a combination of DEME and BHED as the effective components of the absorbent. The two have a synergistic effect, which has the advantages of the highest CO2 cycling absorption capacity, low heat of absorption reaction, high desorption rate, high absorption rate and high diffusion coefficient.

[0080] Example 3

[0081] This embodiment provides a polyamino absorbent, which, by weight of 100%, comprises: 20% 2-[[2-[2-(dimethylamino)ethoxy]ethyl]methylamino]-ethanol (DEME), 20% piperazine (PZ), and 60% water.

[0082] At 40°C, the polyamine absorbent of this embodiment was contacted with the aforementioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 2.48 mol / kg. Subsequently, the temperature was raised to 120°C, and the polyamine absorbent of this embodiment was contacted with the aforementioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 0.42 mol / kg, a cyclic absorption loading of approximately 2.06 mol / kg, and a desorption rate of 83%. The heat of reaction for CO2 absorption at 40°C was 1.48 GJ / tCO2, and the absorption rate was 55000 L / mol / s. The diffusion coefficient of CO2 in the absorbent at 40°C was 3.98 × 10⁻⁶. -9 m 2 ·s -1 .

[0083] For comparison, 35% PZ aqueous solution (since 40% PZ aqueous solution exhibits crystallization, 35% PZ aqueous solution was used) and 40% DEME aqueous solution were tested at 40℃ and 120℃, respectively. The results are shown in Table 3.

[0084] At 40℃, a 35% PZ aqueous solution was contacted with the above-mentioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 2.44 mol / kg. Subsequently, the temperature was raised to 120℃, and the same 35% PZ aqueous solution was used to contact the above-mentioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 1.34 mol / kg, a cyclic absorption loading of approximately 1.1 mol / kg, and a desorption rate of 45%. The heat of reaction for CO2 absorption at 40℃ was 1.75 GJ / tCO2, and the absorption rate was 58000 L / mol / s. The diffusion coefficient of CO2 in the 35% PZ aqueous solution at 40℃ was 1.36 × 10⁻⁶. -9 m 2 ·s-1 It can be seen that when PZ is used alone as an absorbent, the CO2 recycling capacity is small, the heat of CO2 absorption reaction is high, the desorption rate is low, and the diffusion coefficient is low.

[0085] Table 3

[0086] It can be seen that this embodiment uses a combination of DEME and PZ as the effective components of the absorbent. The two have a synergistic effect and have the advantages of the highest CO2 cycling absorption capacity, low heat of absorption reaction, high desorption rate, high absorption rate and high diffusion coefficient.

[0087] Example 4

[0088] This embodiment provides a polyamine absorbent, which, by weight of 100%, comprises: 20% 2-[[2-[2-(dimethylamino)ethoxy]ethyl]methylamino]-ethanol (DEME), 20% diethylenetriamine (DETA), and 60% water.

[0089] At 40°C, the polyamine absorbent of this embodiment was contacted with the aforementioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 2.74 mol / kg. Subsequently, the temperature was raised to 120°C, and the polyamine absorbent of this embodiment was contacted with the aforementioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 0.19 mol / kg, a cyclic absorption loading of approximately 2.55 mol / kg, and a desorption rate of 93%. The heat of reaction for CO2 absorption at 40°C was 1.52 GJ / tCO2, and the absorption rate was 48000 L / mol / s. The diffusion coefficient of CO2 in the absorbent at 40°C was 4.32 × 10⁻⁶. -9 m 2 ·s -1 .

[0090] For comparison, tests were conducted using 40% DETA aqueous solution and 40% DEME aqueous solution at 40℃ and 120℃ respectively, and the results are shown in Table 4.

[0091] At 40°C, a 40% DETA aqueous solution was contacted with the aforementioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 4.2 mol / kg. Subsequently, the temperature was raised to 120°C, and the same 40% DETA aqueous solution was used to absorb CO2 again, with a CO2 equilibrium loading of 2.2 mol / kg and a cyclic absorption loading of approximately 2.0 mol / kg. The desorption rate was 48%. The heat of reaction for CO2 absorption at 40°C was 1.88 GJ / tCO2, and the absorption rate was 54500 L / mol / s. The diffusion coefficient of CO2 in the amine solution at 40°C was 0.85 × 10⁻⁶. -9 m 2 ·s -1 It can be seen that when DETA is used alone as an absorbent, its CO2 gas diffusion coefficient is small, the heat of CO2 absorption reaction is high, and the desorption rate is low.

[0092] Table 4

[0093] As can be seen, this embodiment uses a combination of DEME and DETA as the effective components of the absorbent. The two have a synergistic effect and have the advantages of the highest CO2 cycling absorption capacity, low heat of absorption reaction, high desorption rate, high absorption rate, and high diffusion coefficient.

[0094] Example 5

[0095] This embodiment provides a polyamino absorbent, which, by weight of 100%, comprises: 20% 2-[[2-[2-(dimethylamino)ethoxy]ethyl]methylamino]-ethanol (DEME), 20% N-(2-hydroxyethyl)piperazine (HEPZ), and 60% water.

[0096] At 40°C, the polyamine absorbent of this embodiment was contacted with the above-mentioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 2.55 mol / kg. Subsequently, the temperature was raised to 120°C, and a 40% HEPZ aqueous solution was used to contact the above-mentioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 0.13 mol / kg, a cyclic absorption loading of approximately 2.42 mol / kg, and a desorption rate of 95%. The heat of reaction for CO2 absorption at 40°C was 1.49 GJ / tCO2, and the absorption rate was 24300 L / mol / s. The diffusion coefficient of CO2 in a 40% HEPZ aqueous solution at 40°C was 4.77 × 10⁻⁶. -9 m 2 ·s-1 .

[0097] For comparison, tests were conducted using 40% HEPZ aqueous solution and 40% DEME aqueous solution at 40℃ and 120℃ respectively, and the results are shown in Table 5.

[0098] At 40℃, a 40% HEPZ aqueous solution was contacted with the above-mentioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 1.73 mol / kg. Subsequently, the temperature was raised to 120℃, and the same 40% HEPZ aqueous solution was used to absorb CO2 again, with a CO2 equilibrium loading of 0.21 mol / kg and a cyclic absorption loading of approximately 1.52 mol / kg. The desorption rate was 88%. The heat of reaction for CO2 absorption at 40℃ was 1.66 GJ / tCO2, and the absorption rate was 27800 L / mol / s. The diffusion coefficient of CO2 in the absorbent at 40℃ was 1.46 × 10⁻⁶. -9 m 2 ·s -1 It can be seen that when HEPZ is used alone as an absorbent, its CO2 recycling capacity is small, its CO2 absorption reaction heat is high, and its diffusion coefficient is low.

[0099] Table 5

[0100] It can be seen that this embodiment uses a combination of DEME and HEPZ as the effective components of the absorbent. The two have a synergistic effect and have the advantages of the highest CO2 cycling absorption capacity, low heat of absorption reaction, high desorption rate, high absorption rate and high diffusion coefficient.

[0101] Example 6

[0102] This embodiment provides a polyamine absorbent, which, by weight of 100%, comprises: 20% 2-[[2-[2-(dimethylamino)ethoxy]ethyl]methylamino]-ethanol (DEME), 20% hydroxyethyl ethylenediamine (AEEA), and 60% water.

[0103] At 40°C, the polyamine absorbent of this embodiment was contacted with the aforementioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 2.63 mol / kg. Subsequently, the temperature was raised to 120°C, and the polyamine absorbent of this embodiment was contacted with the aforementioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 0.24 mol / kg, a cyclic absorption loading of approximately 2.39 mol / kg, and a desorption rate of 91%. The heat of reaction for CO2 absorption at 40°C was 1.49 GJ / tCO2, and the absorption rate was 23800 L / mol / s. The diffusion coefficient of CO2 in the absorbent at 40°C was 4.18 × 10⁻⁶. -9 m 2 ·s -1 .

[0104] For comparison, 40% AEEA aqueous solution and 40% DEME aqueous solution were used to conduct tests at 40℃ and 120℃ respectively, and the results are shown in Table 6.

[0105] At 40℃, a 40% AEEA aqueous solution was contacted with the above-mentioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 2.58 mol / kg. Subsequently, the temperature was raised to 120℃, and the same 40% AEEA aqueous solution was used to absorb CO2 again, with a CO2 equilibrium loading of 0.98 mol / kg, a cyclic absorption loading of approximately 1.6 mol / kg, and a desorption rate of 62%. The heat of reaction for CO2 absorption at 40℃ was 1.76 GJ / tCO2, and the absorption rate was 22000 L / mol / s. The diffusion coefficient of CO2 in a 40% AEEA aqueous solution at 40℃ was 1.28 × 10⁻⁶. -9 m 2 ·s -1 It can be seen that when AEEA is used alone as an absorbent, its CO2 recycling capacity is small, the heat of CO2 absorption reaction is high, the desorption rate is low, and the diffusion coefficient is low.

[0106] Table 6

[0107] It can be seen that this embodiment uses a combination of DEME and AEEA as the effective components of the absorbent. The two have a synergistic effect and have the advantages of the highest CO2 cycle absorption capacity, low heat of absorption reaction, high desorption rate, high absorption rate and high diffusion coefficient.

[0108] Example 7

[0109] This embodiment provides a polyamino absorbent, which, by weight of 100%, comprises: 20% 2-[[2-[2-(dimethylamino)ethoxy]ethyl]methylamino]-ethanol (DEME), 10% 2-amino-2-methyl-1-propanol (AMP), and 70% water.

[0110] At 40°C, the polyamine absorbent of this embodiment was contacted with the aforementioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 2.61 mol / kg. Subsequently, the temperature was raised to 120°C, and the polyamine absorbent of this embodiment was contacted with the aforementioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 0.26 mol / kg, a cyclic absorption loading of approximately 2.35 mol / kg, and a desorption rate of 90%. The heat of reaction for CO2 absorption at 40°C was 1.68 GJ / tCO2, and the absorption rate was 2570 L / mol / s. The diffusion coefficient of CO2 in the absorbent at 40°C was 3.55 × 10⁻⁶. -9 m 2 ·s -1 .

[0111] It can be seen that using the combination of DEME and AMP as the effective components of the absorbent results in a very slow CO2 absorption rate. Compared with Examples 1-6, the absorption rate of this example is only 2570 L / mol / s, which is far lower than the 7000-55000 L / mol / s of Examples 1-6. Therefore, hindered amines are not preferred as the second component of this invention.

[0112] Comparative Example 1

[0113] This comparative example provides an absorbent, which is an aqueous solution of 30% by weight of 2-amino-2-methyl-1-propanol (AMP).

[0114] At 40°C, the absorbent of this comparative example was contacted with the aforementioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 2.2 mol / kg. Subsequently, the temperature was raised to 120°C, and the absorbent of this comparative example was contacted with the aforementioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 0.3 mol / kg, a cyclic absorption loading of approximately 1.9 mol / kg, and a desorption rate of 86%. The heat of reaction for CO2 absorption at 40°C was 1.82 GJ / tCO2, and the absorption rate was 1100 L / mol / s. The diffusion coefficient of CO2 in the absorbent at 40°C was 0.83 × 10⁻⁶. -9 m 2 ·s-1 .

[0115] It can be seen that using sterically hindered amine AMP as an absorbent results in a decent CO2 absorption cycle load, but its disadvantages include a low diffusion coefficient, a slow absorption rate, high heat of absorption reaction, complex molecular structure, high synthesis difficulty, and high price.

[0116] Comparative Example 2

[0117] This comparative example provides a polyamino absorbent comprising, by weight 100%, 25% 2-amino-2-methyl-1-propanol (AMP), 10% piperazine (PZ), and 65% water.

[0118] At 40°C, the polyamine absorbent of this comparative example was contacted with the above-mentioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 2.9 mol / kg. Subsequently, the temperature was raised to 120°C, and the polyamine absorbent of this comparative example was contacted with the above-mentioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 1.03 mol / kg, a cyclic absorption loading of approximately 1.87 mol / kg, and a desorption rate of 65%. The heat of reaction for CO2 absorption at 40°C was 1.75 GJ / tCO2, and the absorption rate was 15200 L / mol / s. The diffusion coefficient of CO2 in the absorbent at 40°C was 1.27 × 10⁻⁶. -9 m 2 ·s -1 .

[0119] It can be seen that although the CO2 recycling capacity of the combination of AMP and PZ as the effective components of the absorbent is acceptable, the heat of reaction is high, the diffusion coefficient is low, and the molecular structure of AMP is complex, making its synthesis difficult and expensive.

[0120] Comparative Example 3

[0121] This comparative example provides an absorbent, which is an aqueous solution of 40% by weight of 2-(3-aminopropoxy)ethanol-1-ol (EGPA, structural formula HO-CH2CH2-O-CH2CH2CH2-NH2).

[0122] At 40°C, the absorbent of this comparative example was contacted with the aforementioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 1.87 mol / kg. Subsequently, the temperature was raised to 120°C, and the absorbent of this comparative example was contacted with the aforementioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 1.12 mol / kg, a cyclic absorption loading of approximately 0.75 mol / kg, and a desorption rate of 40%. The heat of reaction for CO2 absorption at 40°C was 2.2 GJ / tCO2, and the absorption rate was 5300 L / mol / s. The diffusion coefficient of CO2 in the absorbent of this comparative example at 40°C was 1.99 × 10⁻⁶. -9 m 2 ·s -1 .

[0123] It can be seen that using EGPA as an absorbent results in low cyclic absorption capacity, low desorption rate, high heat of reaction, low diffusion coefficient, and slow absorption rate.

[0124] Comparative Example 4

[0125] This comparative example provides an absorbent, which is an aqueous solution of 40% by weight of 2-[2-(dimethylamino)ethoxy]ethanol (structural formula HO-CH2CH2-O-CH2CH2-N(CH3)2).

[0126] At 40°C, the absorbent of this comparative example was contacted with the aforementioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 1.38 mol / kg. Subsequently, the temperature was raised to 120°C, and the absorbent of this comparative example was contacted with the aforementioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 0.32 mol / kg, a cyclic absorption loading of approximately 1.06 mol / kg, and a desorption rate of 77%. The heat of reaction for CO2 absorption at 40°C was 1.95 GJ / tCO2, and the absorption rate was 950 L / mol / s. The diffusion coefficient of CO2 in the absorbent of this comparative example at 40°C was 1.33 × 10⁻⁶. -9 m 2 ·s -1 .

[0127] It can be seen that using 2-[2-(dimethylamino)ethoxy]ethanol as an absorbent results in limited CO2 absorption capacity, low diffusion coefficient, and slow absorption rate.

[0128] Comparative Example 5

[0129] This comparative example provides an absorbent, which is an aqueous solution of N-(2-methoxyethyl)-N,N'-dimethylethylenediamine (structural formula CH3-O-CH2CH2-N(CH3)-CH2CH2-NH(CH3)) at a weight percentage of 40%.

[0130] At 40°C, the absorbent of this comparative example was contacted with the aforementioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 2.02 mol / kg. Subsequently, the temperature was raised to 120°C, and the absorbent of this comparative example was contacted with the aforementioned atmospheric pressure gas mixture (CO2 partial pressure 12 kPa) to absorb CO2, with a CO2 equilibrium loading of 0.30 mol / kg, a cyclic absorption loading of approximately 1.72 mol / kg, and a desorption rate of 85%. The heat of reaction for CO2 absorption at 40°C was 1.87 GJ / tCO2, and the absorption rate was 990 L / mol / s. The diffusion coefficient of CO2 in the absorbent of this comparative example at 40°C was 1.47 × 10⁻⁶. -9 m 2 ·s -1 .

[0131] It can be seen that using N-(2-methoxyethyl)-N,N'-dimethylethylenediamine as an absorbent results in a high heat of reaction, a low diffusion coefficient, and a slow absorption rate.

[0132] As can be seen from the above embodiments and comparative examples, the first and second components of the present invention produce a synergistic effect. While maintaining the high circulating absorption capacity, high desorption rate, low heat of reaction, and high diffusion coefficient of the first component, the polyamine absorbent of the present invention exhibits an enhanced absorption rate, and the circulating absorption capacity is further increased. Furthermore, since the first component is an ether with low viscosity, the gas diffusion coefficient in the absorbent is high, greatly reducing the gas-liquid mass transfer resistance and facilitating gas-liquid mass transfer within the tower. Therefore, the polyamine absorbent of the present invention has multiple advantages, including high solubility for carbon dioxide, large circulating absorption capacity for carbon dioxide, high absorption rate for carbon dioxide, low viscosity and low gas-liquid mass transfer resistance, low heat of reaction for carbon dioxide absorption, high desorption rate, and low regeneration energy consumption.

[0133] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A polyamine absorbent for carbon dioxide capture, comprising: First component: at least one organic amine having the following molecular formula: HO-C x H 2x -N(CH3)-C y H 2y -OC z H 2z -N(CH3)2, where x, y, and z are each independently selected from one of 1, 2, and 3; Second component: at least one basic compound different from the first component; and Solvents and selective additives; Based on the total weight of the polyamine absorbent for carbon dioxide capture as 100%, the content of the first component is 5-50%, the content of the second component is 10-50%, and the total content of the solvent and selectively included additives is 30-80%.

2. The polyamine absorbent for carbon dioxide capture according to claim 1, wherein, Based on the total weight of the polyamine absorbent used for carbon dioxide capture being 100%, the content of the first component is 10-45%; And / or, based on 100% of the total weight of the polyamine absorbent for carbon dioxide capture, the content of the second component is 10-30%.

3. The polyamine absorbent for carbon dioxide capture according to claim 1, wherein, The first component is 2-[[2-[2-(dimethylamino)ethoxy]ethyl]methylamino]-ethanol.

4. The polyamine absorbent for carbon dioxide capture according to claim 1, wherein, The second component includes organic basic compounds and / or inorganic basic compounds.

5. The polyamine absorbent for carbon dioxide capture according to claim 4, wherein, The organic basic compound includes one or more of the following: chain monoamines, piperazines, hindered amines, and chain polyamines, wherein the chain monoamines include primary amines and / or secondary amines.

6. The polyamine absorbent for carbon dioxide capture according to claim 5, wherein, The primary amines include ethanolamine and / or n-propanolamine; And / or, the secondary amines include one or more of N-methylethanolamine, N-ethylethanolamine, and diethanolamine; And / or, the piperazines include one or more of piperazine, 1-methylpiperazine, N-(2-hydroxyethyl)piperazine, 2-methylpiperazine, N-aminoethylpiperazine and 1,4-dimethylpiperazine; And / or, the sterically hindered amines include 2-amino-2-methyl-1-propanol; And / or, the chain polyamines include one or more of hydroxyethyl ethylenediamine, diethylenetriamine, triethylenetetramine, N,N'-bis(2-hydroxyethyl)ethylenediamine and N,N'-bis(2-hydroxypropyl)-1,3-propanediamine.

7. The polyamine absorbent for carbon dioxide capture according to claim 5, wherein, The organic basic compounds include one or more of the following: chain monoamines, piperazines, and chain polyamines, but do not include sterically hindered amines.

8. The polyamine absorbent for carbon dioxide capture according to claim 4, wherein, The inorganic basic compounds include potassium carbonate and / or sodium carbonate.

9. The polyamine absorbent for carbon dioxide capture according to claim 1, wherein, The solvent includes one or more of water, alcohols, ethers, esters, and sulfones.

10. The polyamine absorbent for carbon dioxide capture according to claim 1, wherein, The additives include one or more of antioxidants, anti-degradation agents, corrosion inhibitors, and defoamers.

11. A method for capturing carbon dioxide from a gas mixture, comprising the following steps: The polyamine absorbent for carbon dioxide capture according to any one of claims 1-10 is brought into contact with a gas mixture containing carbon dioxide, thereby capturing carbon dioxide.

12. The method for capturing carbon dioxide from a gas mixture according to claim 11, wherein, The partial pressure of carbon dioxide in the gas mixture containing carbon dioxide is 3~200 kPa; And / or, the gas mixture containing carbon dioxide is at atmospheric pressure; And / or, the carbon dioxide-containing gas mixture includes one or more of the following: flue gas, purge gas, and process gas from one or more of the following processes: coal-fired power generation, iron and steel metallurgy, cement and building materials, petrochemicals, and coal chemicals.

13. The method for capturing carbon dioxide from a gas mixture according to claim 11, wherein, The polyamine absorbent used for carbon dioxide capture not only captures carbon dioxide in the gas mixture, but also captures other acidic gases in the gas mixture, including one or more of sulfur dioxide, hydrogen sulfide, and organic sulfur.

14. The method for capturing carbon dioxide from a gas mixture according to claim 11, wherein, The contact between the polyamine absorbent for carbon dioxide capture and the gas mixture containing carbon dioxide is carried out in an absorption tower. The temperature at which the polyamine absorbent for carbon dioxide capture enters the absorption tower is 20~80°C, and the pressure at the bottom of the absorption tower is 50~500 kPa. And / or, the method for capturing carbon dioxide from a gas mixture further includes: desorbing the polyamine absorbent after capturing carbon dioxide, the desorption being carried out in a regeneration tower, the temperature of the polyamine absorbent obtained after desorption being 80~150°C, and the bottom pressure of the regeneration tower being 50~500 kPa.

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