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

Abstract

The present invention discloses a polyamino absorbent for carbon dioxide capture and a method for capturing carbon dioxide from a gas mixture, belonging to the technical field of gas separation and carbon capture, utilization and storage. The polyamino absorbent comprises at least: a first component, which is at least one N-hydroxyalkyl-N'-hydroxyalkyl-alkanediamine; a second component, which is at least one organic amine different from the first component, the organic amine containing an amino group that is not a primary amino group and does not contain a sterically hindered amino group; and a solvent and an optional additive. The method for capturing carbon dioxide from a gas mixture comprises: contacting the polyamino absorbent with a gas mixture containing carbon dioxide, and then capturing carbon dioxide. The polyamino absorbent of the present invention has the advantages of low heat of reaction for absorbing carbon dioxide in atmospheric flue gas, high cyclic absorption capacity, high absorption rate, high desorption rate and low volatility.

Description

Technical Field

[0001] The present invention relates to the technical field of gas separation and carbon capture, utilization and storage (CCUS), and in particular to a polyamino absorbent for carbon dioxide capture and a method for capturing carbon dioxide from a gas mixture. Background Art

[0002] The emission of greenhouse gases such as CO2 is a major factor in climate change. Therefore, the capture or separation of CO2 from CO2-rich gas mixtures is extremely important. These gas mixtures include flue gases, purge gases, and process gases containing CO2 from coal-fired power generation, steel and metallurgy, cement and building materials, petrochemicals, and coal chemical industries. These gas mixtures typically contain 5% to 50% CO2, with other major gases including N2, O2, CO, H2, CH4, C2H6, SO2, H2S, and organic sulfur compounds such as CH3SH and COS. The gas pressure varies widely (50 to 500 kPa), making it suitable for capturing and separating the CO2 components, SO2, H2S, and other acidic gases such as organic sulfur compounds such as CH3SH and COS using chemical absorption or combined chemical and physical absorption methods.

[0003] Currently, the more mature industrial absorption processes for separating CO2 from medium- and high-pressure gases primarily include the diethanolamine (DEA) process, the diisopropanolamine (DIPA) process, and the methyldiethanolamine (MDEA) process. To increase the absorption rate of CO2 by the absorption solution, faster absorbents such as monoethanolamine (MEA) and piperazine (PZ) have been added to slower absorbents like DIPA and MDEA, resulting in several improved absorption separation methods.

[0004] For the absorption and capture of low-pressure CO₂, a highly alkaline absorbent is required. MEA is the most traditional and widely used absorbent in industrial applications. A 30% (weight percentage, the same below) MEA solution (solvent: water) is generally used. At 40°C and a CO₂ partial pressure of 12 kPa, the equilibrium CO₂ loading of a 30% MEA solution is 2.65 mol / kg. When the temperature rises to 120°C and the CO₂ partial pressure remains constant, the equilibrium CO₂ loading of the 30% MEA solution drops to 1.5 mol / kg, resulting in a circulating absorption loading of approximately 1.15 mol / kg and a desorption rate of only 43%. Furthermore, the heat of reaction for CO₂ absorption by a 30% MEA solution at 40°C is 90–100 kJ / mol.

[0005] Furthermore, sterically hindered amines have gained application due to their high solubility for CO₂ in atmospheric gases and their high cyclic absorption and desorption loads. For example, US Pat. No. 4,112,052 discloses organic amines with at least one secondary amino group linked to a secondary or tertiary carbon, or one primary amino group linked to a tertiary carbon. Their CO₂ solubility is 100% higher than that of MEA. The most commonly used amine is 2-amino-2-methyl-1-propanol (AMP). A 30% AMP solution (in water) at 40°C and a CO₂ partial pressure of 12 kPa exhibits an equilibrium CO₂ loading of 2.2 mol / kg. When the temperature is increased to 120°C and the CO₂ partial pressure remains constant, the equilibrium CO₂ loading of the 30% AMP solution drops to 0.3 mol / kg, resulting in a cyclic absorption loading of approximately 1.9 mol / kg and a desorption rate of 86%, a 100% increase over that of MEA. Furthermore, the heat of reaction for CO₂ absorption in a 30% AMP solution at 40°C is 70–90 kJ / mol.

[0006] However, because sterically hindered amines (AMPs) are still primary amines, the heat of reaction is not significantly reduced, and the capture energy consumption remains high. Furthermore, AMPs are subject to significant degradation during use, resulting in high costs. Furthermore, due to their complex molecular structure, the synthesis process is relatively difficult, resulting in high manufacturing costs.

[0007] Some researchers have also proposed polyamino absorbents with superior absorption capacity, such as hydroxyethylethylenediamine (AEEA, CN101091864A) and diethylenetriamine (DETA, CN101657247B). AEEA is a diamine with high CO2 solubility and contains highly polar primary and secondary amino groups, as well as a hydroxyl group. A 30% by weight AEEA solution (in water) at 40°C and a CO2 partial pressure of 12 kPa exhibits an equilibrium CO2 loading of 2.6 mol / kg. When the temperature rises to 120°C and the CO2 partial pressure remains constant, the equilibrium CO2 loading of the 30% AEEA solution drops to 1.0 mol / kg, resulting in a circulating absorption loading of approximately 1.6 mol / kg and a desorption rate of 62%, a 44% improvement over MEA. Furthermore, the heat of reaction for CO2 absorption in a 30% AEEA solution at 40°C is 75-80 kJ / mol. DETA has two primary and one secondary amino groups, a more symmetrical molecular structure, and good water solubility. It has a higher CO2 absorption rate at the same concentration and a higher absorption capacity than AEEA. A 30% by weight DETA solution (in water) at 40°C and a CO2 partial pressure of 12 kPa exhibits an equilibrium CO2 loading of 3.8 mol / kg. When the temperature rises to 120°C and the CO2 partial pressure remains constant, the equilibrium CO2 loading of the 30% DETA solution drops to 2.0 mol / kg, resulting in a cyclic absorption loading of approximately 1.8 mol / kg and a desorption efficiency of 47%, a 10% increase over that of MEA. Furthermore, the heat of reaction for CO2 absorption by a 30% DETA solution at 40°C is 80–85 kJ / mol.

[0008] From the perspective of absorbent application value, absorbents with energy-saving and consumption-reducing advantages are of greatest concern within the industry. These absorbents generally need to simultaneously meet the requirements of high cycle absorption capacity, low CO2 absorption reaction heat, and high absorption rate. During the absorption process, capture energy consumption is primarily composed of absorption reaction heat, volatilization heat of water in the solvent, and heat exchange losses in the heat exchanger, accounting for approximately 65%, 25%, and 10%, respectively. Therefore, reducing CO2 absorption reaction heat is the key to and guarantee of reducing capture energy consumption. Currently, polyamino absorbents are the primary development direction, and therefore, the development of new polyamino absorbents remains a pressing issue in this field. Summary of the Invention

[0009] To address at least one of the above-mentioned technical problems, the present invention provides a polyamino absorbent for carbon dioxide capture and a method for capturing carbon dioxide from a gas mixture. The polyamino absorbent of the present invention has the advantages of high carbon dioxide cyclic absorption capacity, low reaction heat of carbon dioxide absorption, high absorption rate, high desorption rate, and low volatility.

[0010] In order to achieve the above object, the first aspect of the present invention provides a polyamino absorbent for carbon dioxide capture, which comprises at least the following components:

[0011] The first component is at least one N-hydroxyalkyl-N'-hydroxyalkyl-alkanediamine having the following molecular formula: HO-C x H 2x -NH-C y H 2y -NH-C z H 2z -OH, wherein x, y and z are each independently selected from one of 2 and 3;

[0012] A second component: at least one organic amine different from the first component, the organic amine containing an amino group that is not a primary amino group and the organic amine containing no sterically hindered amino group; and

[0013] solvent and optionally additives;

[0014] Wherein, based on the total weight of the multi-amino absorbent for carbon dioxide capture being 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 the optionally included additives is 30-80%.

[0015] According to a specific embodiment of the present invention, preferably, the first component includes one or more of N,N'-bis(hydroxyethyl)ethylenediamine, N,N'-bis(hydroxypropyl)ethylenediamine, N,N'-bis(hydroxyethyl)propylenediamine, N,N'-bis(hydroxypropyl)propylenediamine, N-hydroxyethyl-N'-hydroxypropylethylenediamine, and N-hydroxyethyl-N'-hydroxypropylpropylenediamine. More preferably, the first component includes one or more of N,N'-bis(hydroxyethyl)ethylenediamine (BHED) and N,N'-bis(hydroxypropyl)propylenediamine (BHPD).

[0016] According to a specific embodiment of the present invention, preferably, the second component includes one or more of secondary and tertiary amino groups and one or more of secondary amines, tertiary amines and polyamines that do not contain sterically hindered amino groups. More preferably, the secondary amine includes one or more of N-methylethanolamine, N-ethylethanolamine, N-propylethanolamine, N-methylpropanolamine, N-ethylpropanolamine, N-propylpropanolamine, diethanolamine, dipropanolamine and ethanolpropanolamine; the tertiary amine includes one or more of N-methyldiethanolamine, N-methyldipropanolamine, N,N-dimethylethanolamine, N,N-diethylethanolamine, N,N-dimethylpropanolamine and N,N-diethylpropanolamine; the polyamine includes one or more of hydroxyethylethylenediamine, diethylenetriamine, triethylenetetramine, piperazine, N-methylpiperazine, N-ethylpiperazine, N-aminoethylpiperazine, N-hydroxyethylpiperazine and dimethylpiperazine.

[0017] According to a specific embodiment of the present invention, preferably, the solvent includes one or more of water, alcohols, ethers, esters and sulfones; the additive includes one or more of antioxidants, antidegradants, corrosion inhibitors and defoaming agents.

[0018] A second aspect of the present invention provides a method for capturing carbon dioxide from a gas mixture, comprising the following steps: contacting the polyamino absorbent for carbon dioxide capture with a gas mixture containing carbon dioxide, thereby capturing carbon dioxide.

[0019] According to a specific embodiment of the present invention, preferably, the carbon dioxide partial pressure in the gas mixture containing carbon dioxide is 3-200 kPa.

[0020] According to a specific embodiment of the present invention, preferably, the gas mixture containing carbon dioxide includes one or more of flue gas, purge gas and process gas in one or more processes of coal-fired power generation, steel metallurgy, cement building materials, petrochemical industry and coal chemical industry.

[0021] According to a specific embodiment of the present invention, preferably, the multi-amino absorbent for carbon dioxide capture captures carbon dioxide in the gas mixture while also capturing other acid gases in the gas mixture, wherein the other acid gases include one or more of sulfur dioxide, hydrogen sulfide and organic sulfur.

[0022] According to a specific embodiment of the present invention, preferably, contacting the multi-amino absorbent for carbon dioxide capture with a gas mixture containing carbon dioxide is carried out in an absorption tower, the temperature of the multi-amino absorbent for carbon dioxide capture entering the absorption tower is 20~80°C, and the bottom pressure of the absorption tower is 50~500 kPa.

[0023] According to a specific embodiment of the present invention, preferably, the method for capturing carbon dioxide from a gas mixture further comprises: desorbing the polyamino absorbent after capturing carbon dioxide, wherein the desorption is carried out in a regeneration tower, the temperature of the polyamino absorbent obtained after desorption is 80-150° C., and the bottom pressure of the regeneration tower is 50-500 kPa.

[0024] The present invention has at least the following beneficial effects:

[0025] The polyamino absorbent of the present invention uses N-hydroxyalkyl-N'-hydroxyalkyl-alkanediamine as a key component, and has the advantages of low reaction heat for absorbing carbon dioxide, high desorption rate, and low volatility. The present invention uses the N-hydroxyalkyl-N'-hydroxyalkyl-alkanediamine to compound with an organic amine containing an amino group that is not a primary amino group and does not contain a sterically hindered amino group. The two produce a synergistic absorption effect, so that the polyamino absorbent of the present invention has the advantages of high solubility for carbon dioxide, large cyclic absorption capacity of carbon dioxide, high absorption rate of carbon dioxide, low reaction heat for absorbing carbon dioxide, low volatility loss, high desorption rate, and low regeneration energy consumption. The present invention avoids the use of sterically hindered amines that are difficult to synthesize industrially, thereby avoiding the high cost and other problems of sterically hindered amines. The polyamino absorbent of the present invention can achieve low-energy and low-cost carbon capture. The polyamino absorbent of the present invention is suitable for capturing carbon dioxide from gas mixtures, and is particularly suitable for capturing low partial pressure carbon dioxide. DETAILED DESCRIPTION

[0026] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the present invention is now described in detail below, but it should not be understood as limiting the scope of implementation of the present invention.

[0027] It should be noted that, unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0028] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0029] It will be understood that the terms “comprises,” “comprising,” and / or “containing” when used herein specify the presence of stated features, integers, steps, components, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, components, or combinations thereof.

[0030] The endpoints of the ranges and any values ​​disclosed herein 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 endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to form one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed in the present invention.

[0031] According to a specific embodiment of the first aspect of the present invention, the present invention provides a multi-amino absorbent for carbon dioxide capture, which comprises at least the following components:

[0032] The first component is at least one N-hydroxyalkyl-N'-hydroxyalkyl-alkane diamine (also known as bishydroxyalkyl alkane diamine, abbreviated as BHAD) having the following molecular formula: HO-C x H 2x -NH-C y H 2y -NH-C z H 2z -OH, wherein x, y and z are each independently selected from one of 2 and 3;

[0033] A second component: at least one organic amine different from the first component, the organic amine containing an amino group that is not a primary amino group and the organic amine containing no sterically hindered amino group; and

[0034] solvent and optionally additives;

[0035] Wherein, based on the total weight of the multi-amino 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%, etc., preferably 10~45%; 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%, etc., preferably 10~30%; the total content of the solvent and the optionally included additives is 30~80%, for example, but not limited to 30%, 40%, 50%, 60%, 70% or 80%, etc.

[0036] It should be noted that the term "sterically hindered amino group" refers to a primary or secondary amino group attached to a tertiary carbon atom, a secondary amino group attached to a secondary carbon atom, or an amino group separated from a tertiary or quaternary carbon atom by one carbon atom. Organic amines containing a sterically hindered amino group are called sterically hindered amines, such as 2-amino-2-methyl-1-propanol (AMP).

[0037] Among commonly used polyamino absorbents, hydroxyethylethylenediamine (AEEA) has one primary amino group, while diethylenetriamine (DETA) has two. The presence of primary amino groups increases their CO2 solubility. At 40°C and a CO2 partial pressure of 12 kPa, the CO2 solubility of a 30% aqueous solution of DETA (3.6%), which has two primary and one secondary amino groups, is 1.0 higher than the CO2 solubility of a 30% aqueous solution of AEEA (2.6%), which has one primary and one secondary amino group. However, at 120°C and a CO2 partial pressure of 12 kPa, the CO2 cyclic absorption load (1.8 mol / kg) of the 30% aqueous solution of DETA (with one additional primary amino group) is only 0.2 mol / kg higher than that of the AEEA aqueous solution under the same conditions. Moreover, after CO2 absorption at 120°C and a CO2 partial pressure of 12 kPa, the desorption rate actually decreases from 62% for the AEEA aqueous solution to 47% for the DETA aqueous solution. Furthermore, at 40°C and a CO₂ partial pressure of 12 kPa, the heat of reaction for CO₂ absorption increases from 75-80 kJ / mol for AEEA aqueous solution to 80-85 kJ / mol for DETA aqueous solution. This indicates that the increase in primary amino groups in the polyamino absorbent reduces the desorption rate and increases the heat of reaction for CO₂ absorption.

[0038] After extensive research, the present invention selected N-hydroxyalkyl-N'-hydroxyalkyl-alkanediamine as the first component. This N-hydroxyalkyl-N'-hydroxyalkyl-alkanediamine contains two secondary amino groups and two hydroxyl groups, and contains neither primary nor sterically hindered amino groups. Experimental studies have revealed that the presence of hydroxyethyl and / or hydroxypropyl groups in the molecular structure of this N-hydroxyalkyl-N'-hydroxyalkyl-alkanediamine helps reduce volatilization losses during CO2 capture, while also increasing the absorbent's alkalinity, thereby improving CO2 absorption kinetics. Specifically, while this N-hydroxyalkyl-N'-hydroxyalkyl-alkanediamine has a high solubility in CO2, it significantly reduces the heat of reaction during CO2 absorption and significantly improves the desorption rate. This means that the energy consumption for regeneration of this absorbent is significantly reduced compared to other absorbents. Furthermore, this N-hydroxyalkyl-N'-hydroxyalkyl-alkanediamine also has low volatility, significantly reducing the solvent loss rate during the absorption and desorption process, thereby reducing solution replenishment costs.

[0039] The present invention utilizes N-hydroxyalkyl-N'-hydroxyalkyl-alkanediamine as the first component, overcoming the drawbacks of existing absorbents, which, while containing a high number of primary amino groups resulting in higher CO2 solubility, also result in lower desorption rates and increased CO2 absorption reaction heat. The first component of the present invention combines low CO2 absorption reaction heat, high desorption rates, and low volatility, a balance that existing absorbents struggle to achieve. The first component of the present invention can replace existing low-boiling primary amine absorbents and sterically hindered amine absorbents, such as MEA and AMP, which have higher reaction heats, thereby reducing capture energy consumption and volatilization losses.

[0040] Furthermore, the present invention selects N-hydroxyalkyl-N'-hydroxyalkyl-alkanediamine as the first component and compounded with an organic amine different from the first component as the second component. The second component contains an amino group that is not a primary amino group and does not contain sterically hindered amino groups. The first and second components of the present invention produce a synergistic effect, enabling the polyamino absorbent of the present invention to achieve enhanced cyclic absorption capacity and absorption rate while maintaining the high desorption rate, low reaction heat, and low volatility of the first component. Specifically, due to the difference in the CO2 absorbed products of the first and second components, the two amines in the absorption system compete for protons, helping the absorption product of the first component (a zwitterion) to break free of protons and bicarbonate, and then regenerate into the amine of the first component to continue CO2 capture. This synergistic absorption mechanism ensures the continuous conversion of CO2 into bicarbonate. When the synergistic absorption effect of the second component reaches its maximum level, the CO2 is converted into the amino carbonate of the first component. Therefore, the synergistic absorption effect between the first component and the second component of the present invention greatly increases the cyclic absorption amount and absorption rate of CO2 by the absorbent. Compared with using the first component alone or the second component alone, the multi-amino absorbent of the present invention has significantly improved CO2 cyclic absorption amount and absorption rate.

[0041] Therefore, the polyamino absorbent of the present invention has many advantages, such as high solubility for carbon dioxide, high circulating absorption capacity for carbon dioxide, high absorption rate for carbon dioxide, low reaction heat for absorbing carbon dioxide, low volatilization loss, high desorption rate, and low regeneration energy consumption.

[0042] In some embodiments, the first component includes one or more of N,N'-bis(hydroxyethyl)ethylenediamine, N,N'-bis(hydroxypropyl)ethylenediamine, N,N'-bis(hydroxyethyl)propylenediamine, N,N'-bis(hydroxypropyl)propylenediamine, N-hydroxyethyl-N'-hydroxypropylethylenediamine, and N-hydroxyethyl-N'-hydroxypropylpropylenediamine. Preferably, the first component includes one or more of N,N'-bis(hydroxyethyl)ethylenediamine (BHED) and N,N'-bis(hydroxypropyl)propylenediamine (BHPD). The hydroxyethyl group is 2-hydroxyethyl, the hydroxypropyl group is 2-hydroxypropyl or 3-hydroxypropyl, the ethylenediamine is 1,2-ethylenediamine, and the propylenediamine is 1,2-propylenediamine or 1,3-propylenediamine.

[0043] The N-hydroxyalkyl-N'-hydroxyalkyl-alkane diamine of the present invention can be obtained commercially or prepared by methods known in the art. Specifically, the method for preparing the N-hydroxyalkyl-N'-hydroxyalkyl-alkane diamine of the present invention may include the following steps: reacting an alkane diamine with ethylene oxide and / or propylene oxide to obtain the N-hydroxyalkyl-N'-hydroxyalkyl-alkane diamine.

[0044] In some embodiments, the second component comprises one or more of a secondary amino group and a tertiary amino group, and one or more of a secondary amine, a tertiary amine, and a polyamine that does not contain a sterically hindered amino group. The second component may contain one or more secondary amino groups, and / or one or more tertiary amino groups. Preferably, the secondary amine includes one or more of N-methylethanolamine, N-ethylethanolamine, N-propylethanolamine, N-methylpropanolamine, N-ethylpropanolamine, N-propylpropanolamine, diethanolamine, dipropanolamine and ethanolpropanolamine; the tertiary amine includes one or more of N-methyldiethanolamine, N-methyldipropanolamine, N,N-dimethylethanolamine, N,N-diethylethanolamine, N,N-dimethylpropanolamine and N,N-diethylpropanolamine; the polyamine includes one or more of hydroxyethylethylenediamine, diethylenetriamine, triethylenetetramine, piperazine, N-methylpiperazine, N-ethylpiperazine, N-aminoethylpiperazine, N-hydroxyethylpiperazine and dimethylpiperazine.

[0045] In some embodiments, the solvent includes one or more of water, alcohols, ethers, esters, and sulfones. The present invention does not impose any particular limitation on the specific substance of the solvent, as long as it can fully dissolve the first component and the second component of the present invention. Generally, water is used as the solvent.

[0046] In some embodiments, the additives include, but are not limited to, one or more of antioxidants, antidegradants, corrosion inhibitors, and defoamers. The present invention does not impose any particular restrictions on the specific substances and amounts of these additives, and the additives and amounts disclosed in the prior art can be used.

[0047] According to a specific embodiment of the second aspect of the present invention, the present invention provides a method for capturing carbon dioxide from a gas mixture, which comprises the following steps: contacting the multi-amino absorbent for carbon dioxide capture with a gas mixture containing carbon dioxide, thereby capturing carbon dioxide.

[0048] In some embodiments, the carbon dioxide partial pressure in the gas mixture containing carbon dioxide is 3-200 kPa. The gas mixture containing carbon dioxide is preferably at normal pressure.

[0049] In some embodiments, the gas mixture containing carbon dioxide includes one or more of flue gas, purge gas and process gas from one or more processes such as coal-fired power generation, steel metallurgy, cement building materials, petrochemical industry and coal chemical industry.

[0050] In some embodiments, the polyamino absorbent for carbon dioxide capture captures carbon dioxide from a gas mixture while also capturing other acid gases in the gas mixture. The other acid gases include one or more of sulfur dioxide, hydrogen sulfide, and organic sulfur. The organic sulfur may include carbonyl sulfide (COS) and / or methyl mercaptan (CH3SH).

[0051] In some embodiments, contacting the polyamino absorbent for carbon dioxide capture with a gas mixture containing carbon dioxide is carried out in an absorption tower, the temperature of the polyamino absorbent for carbon dioxide capture entering the absorption tower is 20-80° C., and the bottom pressure of the absorption tower is 50-500 kPa.

[0052] In some embodiments, the method for capturing carbon dioxide from a gas mixture further comprises: desorbing the polyamino absorbent after capturing carbon dioxide, wherein the desorption is performed in a regeneration tower, the temperature of the polyamino absorbent obtained after desorption is 80-150° C., and the bottom pressure of the regeneration tower is 50-500 kPa.

[0053] In some embodiments, the process flow adopted by the method for capturing carbon dioxide from a gas mixture can be a process flow in the prior art, for example, a decarbonization process including absorption, flash evaporation, heat exchange and desorption can be adopted, or a combined process including inter-stage cooling of the absorption tower, rich liquid diversion, semi-lean liquid diversion, lean liquid flash compression, lean liquid diversion, multi-stage absorption and multi-stage desorption can be adopted.

[0054] The polyamino absorbent of the present invention has the advantages of low absorption reaction heat for carbon dioxide in normal pressure flue gas, high cyclic absorption capacity, high absorption rate, high desorption rate and low volatility, and is suitable for capturing low partial pressure carbon dioxide.

[0055] The present invention will be specifically described below with reference to Examples. However, the present invention is not limited to these Examples and can be implemented with various modifications within the scope of the gist of the present invention.

[0056] Test method:

[0057] The composition of the atmospheric pressure gas mixture used is: 12% CO2 and 88% N2, of which the CO2 partial pressure is 12 kPa and the rest is N2. During the experiment, the absorbent is brought into contact with the atmospheric pressure gas mixture at the experimental temperature. When the total pressure of the gas-liquid contact chamber drops to a level that basically no longer changes (i.e., the pressure drop is less than 0.1 kPa within 8 hours), it indicates that the gas-liquid absorption has reached equilibrium. During the experiment, the initial temperature T1 of the absorbent and the temperature T2 of the absorbent after the absorption reaches equilibrium are measured. The acid-base titration method is used to analyze the CO2 composition of the gas mixture after absorption, and then determine the number of moles of CO2 absorbed. The following formulas are used to calculate the CO2 equilibrium load, cyclic absorption load, absorption rate, reaction heat of CO2 absorption, and desorption rate of the absorbent:

[0058] CO2 equilibrium loading (mol / kg) = number of moles of CO2 absorbed / mass of absorbent.

[0059] Circulating absorption load (mol / kg) = CO2 equilibrium load at low temperature (40°C) – CO2 equilibrium load at high temperature (120°C).

[0060] Absorption rate (L / mol / s) = ;

[0061] in, and They are the Henry constant of CO2 in the absorbent (Pa·m 3 / mol) and diffusion constant (m 2 / s), are physical constants of absorbent; and are the mass transfer flux of CO2 measured by kinetic experiments (mol / (m 2 ·s)) and CO2 partial pressure (Pa); is the total concentration of amines in the absorbent (mol / L).

[0062] CO2 mass transfer flux .

[0063] Reaction heat of CO2 absorption (GJ / tCO2) = ;

[0064] Among them, m amine is the mass of the absorbent, kg; c p is the specific heat capacity of the absorbent, kJ / (kg·K); T1 and T2 are the temperatures measured during the above experiments, K; is the mass of CO2 absorbed, t. The specific heat capacity of the absorbent is determined by differential scanning calorimetry (DSC), and the specific heat capacity value is directly given by the instrument.

[0065] Desorption rate (%) = (1.0 – CO2 equilibrium load at high temperature (120°C) / CO2 equilibrium load at low temperature (40°C)) × 100.

[0066] The following method was used to test the volatility of the absorbent: The experiment was conducted using a Rose kettle, which primarily consists of a kettle body, a heating device, a condensing device, and temperature and pressure measuring devices. The absorbent was added to the kettle body and maintained at a temperature of 40°C. The absorbent in the kettle volatilized and entered the condensing device. When the mass of the liquid collected from the condensing device ceased to change, the collected liquid was analyzed using a gas chromatograph to determine the mole fraction of the volatilized amine in the absorbent collected liquid. The volatilized amine partial pressure (Pa) was calculated as: the total absorbent pressure in the kettle body (at atmospheric pressure) × the mole fraction of the volatilized amine. Volatility was measured using the volatilized amine partial pressure.

[0067] Example 1

[0068] This embodiment provides a polyamino absorbent, which comprises, based on 100% of its total weight, 20% of N,N'-bis(2-hydroxyethyl)ethylenediamine (BHED), 10% of hydroxyethylethylenediamine (AEEA), and 70% of water.

[0069] At 40°C, the polyamino absorbent of this example was contacted with the atmospheric gas mixture (CO2 partial pressure of 12 kPa) to absorb CO2 at an equilibrium CO2 loading of 2.4 mol / kg. Subsequently, the temperature was raised to 120°C and the polyamino absorbent of this example was contacted with the atmospheric gas mixture (CO2 partial pressure of 12 kPa) to absorb CO2 at an equilibrium CO2 loading of 0.4 mol / kg, a circulating absorption loading of approximately 2.0 mol / kg, and a desorption efficiency of 83%. The heat of reaction for CO2 absorption at 40°C was 1.57 GJ / tCO2, and the absorption rate was 15,000 L / mol / s. The volatility of the absorbent at 40°C was 0.032 Pa.

[0070] In addition, this example also provides an aqueous solution of 45% BHED + 10% AEEA as a polyamino absorbent, and the corresponding data are listed in Table 1.

[0071] For comparison, 30% (weight percentage, the same below) AEEA aqueous solution and 30% BHED aqueous solution were tested at 40°C and 120°C, respectively. The results are shown in Table 1.

[0072] At 40°C, a 30% aqueous solution of BHED was contacted with the atmospheric gas mixture (CO₂ partial pressure of 12 kPa) to absorb CO₂ at an equilibrium CO₂ loading of 1.6 mol / kg. Subsequently, the temperature was raised to 120°C and a 30% aqueous solution of BHED was contacted with the atmospheric gas mixture (CO₂ partial pressure of 12 kPa) to absorb CO₂ at an equilibrium CO₂ loading of 0.18 mol / kg. The cyclic absorption loading was approximately 1.42 mol / kg, with a desorption efficiency of 89%. The heat of reaction for CO₂ absorption at 40°C was 1.53 GJ / tCO₂, and the absorption rate was 7290 L / mol / s. The volatility of the 30% aqueous solution of BHED at 40°C was 0.005 Pa. It can be seen that using BHED alone as an absorbent results in a low CO₂ absorption capacity and a slow absorption rate.

[0073] At 40°C, a 30% aqueous AEEA solution was contacted with the atmospheric gas mixture (CO₂ partial pressure of 12 kPa) to absorb CO₂ at an equilibrium CO₂ loading of 2.6 mol / kg. Subsequently, the temperature was raised to 120°C and a 30% aqueous AEEA solution was contacted with the atmospheric gas mixture (CO₂ partial pressure of 12 kPa) to absorb CO₂ at an equilibrium CO₂ loading of 1.0 mol / kg. The cyclic absorption loading was approximately 1.6 mol / kg, with a desorption efficiency of 62%. The heat of reaction for CO₂ absorption at 40°C was 1.76 GJ / tCO₂, and the absorption rate was 17,500 L / mol / s. The volatility of the 30% aqueous AEEA solution at 40°C was 0.1 Pa.

[0074] Table 1

[0075]

[0076] It can be seen that this embodiment uses a combination of BHED and AEEA as the effective components of the absorbent, and a synergistic effect is produced between the two, which has the advantages of the highest CO2 cycle absorption capacity, low absorption reaction heat, high desorption rate, high absorption rate, and low volatility.

[0077] Example 2

[0078] This embodiment provides a polyamino absorbent, which comprises, based on 100% of its total weight, 20% of N,N'-bis(2-hydroxyethyl)ethylenediamine (BHED), 10% of diethylenetriamine (DETA), and 70% of water.

[0079] At 40°C, the polyamino absorbent of this embodiment was contacted with the atmospheric gas mixture (CO2 partial pressure of 12 kPa) to absorb the CO2 therein, with a CO2 equilibrium load of 2.8 mol / kg. Subsequently, the temperature was raised to 120°C, and the polyamino absorbent of this embodiment was contacted with the atmospheric gas mixture (CO2 partial pressure of 12 kPa) to absorb the CO2 therein, with a CO2 equilibrium load of 0.5 mol / kg, a cyclic absorption load of approximately 2.3 mol / kg, and a desorption rate of 82%. The reaction heat of CO2 absorption at 40°C was 1.60 GJ / tCO2, and the absorption rate was 48,000 L / mol. 2 s. The volatility of the absorbent at 40°C is 0.070 Pa.

[0080] For comparison, 30% DETA aqueous solution and 30% BHED aqueous solution were tested at 40°C and 120°C, respectively. The results are shown in Table 2.

[0081] At 40°C, a 30% DETA aqueous solution was contacted with the atmospheric gas mixture (CO2 partial pressure of 12 kPa) to absorb CO2, resulting in an equilibrium CO2 loading of 3.8 mol / kg. Subsequently, the temperature was raised to 120°C and a 30% DETA aqueous solution was contacted with the atmospheric gas mixture (CO2 partial pressure of 12 kPa) to absorb CO2, resulting in an equilibrium CO2 loading of 2.0 mol / kg. The cycle absorption loading was approximately 1.8 mol / kg, with a desorption efficiency of 47%. The heat of reaction for CO2 absorption at 40°C was 1.88 GJ / tCO2, and the absorption rate was 50,400 L / mol / s. The volatility of the 30% DETA aqueous solution at 40°C was 0.200 Pa. It can be seen that using DETA alone as an absorbent results in a high CO2 absorption heat and a low desorption efficiency.

[0082] Table 2

[0083]

[0084] It can be seen that this embodiment uses a combination of BHED and DETA as the effective components of the absorbent, and a synergistic effect is produced between the two, which has the advantages of the highest CO2 cycle absorption capacity, low absorption reaction heat, high desorption rate, high absorption rate, and low volatility.

[0085] Example 3

[0086] This embodiment provides a polyamino absorbent, which comprises, based on 100% of its total weight, 25% of N,N'-bis(2-hydroxyethyl)ethylenediamine (BHED), 10% of piperazine (PZ), and 65% of water.

[0087] At 40°C, the polyamino absorbent of this example was contacted with the atmospheric gas mixture (CO2 partial pressure of 12 kPa) to absorb CO2 at an equilibrium CO2 loading of 1.95 mol / kg. Subsequently, the temperature was raised to 120°C and the polyamino absorbent of this example was contacted with the atmospheric gas mixture (CO2 partial pressure of 12 kPa) to absorb CO2 at an equilibrium CO2 loading of 0.45 mol / kg, a circulating absorption loading of approximately 1.50 mol / kg, and a desorption efficiency of 77%. The heat of reaction for CO2 absorption at 40°C was 1.59 GJ / tCO2, and the absorption rate was 41,000 L / mol / s. The volatility of the absorbent at 40°C was 3.07 Pa.

[0088] In addition, this example also provides an aqueous solution of 45% BHED + 10% PZ as a polyamino absorbent, and the corresponding data are listed in Table 3.

[0089] For comparison, 35% PZ aqueous solution and 35% BHED aqueous solution were tested at 40°C and 120°C, respectively. The results are shown in Table 3.

[0090] Table 3

[0091]

[0092] It can be seen that this embodiment uses a combination of BHED and PZ as the effective components of the absorbent, and a synergistic effect is produced between the two, which has the advantages of low CO2 absorption reaction heat, high desorption rate, high absorption rate, and low volatility. At the same time, the cyclic absorption capacity is also higher than that of using BHED alone or PZ alone.

[0093] Example 4

[0094] This embodiment provides a polyamino absorbent, which comprises, based on 100% of its total weight, 10% of N,N'-bis(2-hydroxypropyl)-1,3-propylenediamine (BHPD), 20% of N-ethylethanolamine (EMEA), and 70% of water.

[0095] At 40°C, the polyamino absorbent of this example was contacted with the atmospheric gas mixture (CO2 partial pressure of 12 kPa) to absorb CO2 at an equilibrium CO2 loading of 2.3 mol / kg. Subsequently, the temperature was raised to 120°C and the polyamino absorbent of this example was contacted with the atmospheric gas mixture (CO2 partial pressure of 12 kPa) to absorb CO2 at an equilibrium CO2 loading of 0.4 mol / kg, a circulating absorption loading of approximately 1.9 mol / kg, and a desorption efficiency of 83%. The heat of reaction for CO2 absorption at 40°C was 1.62 GJ / tCO2, and the absorption rate was 10,000 L / mol / s. The volatility of the absorbent at 40°C was 5.07 Pa.

[0096] For comparison, 30% EMEA aqueous solution and 30% BHPD aqueous solution were used to test at 40°C and 120°C, respectively. The results are shown in Table 4.

[0097] At 40°C, a 30% aqueous solution of BHPD was contacted with the atmospheric gas mixture (CO2 partial pressure of 12 kPa) to absorb CO2, resulting in an equilibrium CO2 loading of 1.64 mol / kg. Subsequently, the temperature was raised to 120°C and a 30% aqueous solution of BHPD was contacted with the atmospheric gas mixture (CO2 partial pressure of 12 kPa) to absorb CO2, resulting in an equilibrium CO2 loading of 0.19 mol / kg. The cyclic absorption loading was approximately 1.45 mol / kg, with a desorption efficiency of 88%. The heat of reaction for CO2 absorption at 40°C was 1.48 GJ / tCO2, and the absorption rate was 9800 L / mol / s. The volatility of the 30% aqueous solution of BHPD at 40°C was 0.007 Pa. It can be seen that using BHPD alone as an absorbent results in a low CO2 absorption capacity and a slow absorption rate.

[0098] Table 4

[0099]

[0100] It can be seen that this embodiment uses a combination of BHPD and EMEA as the effective components of the absorbent, and a synergistic effect is produced between the two, which has the advantages of the highest CO2 cycle absorption capacity, low absorption reaction heat, high desorption rate, low volatility, etc., while the absorption rate is moderate.

[0101] Example 5

[0102] This embodiment provides a polyamino absorbent, which comprises, based on 100% of its total weight, 10% of N,N'-bis(2-hydroxypropyl)-1,3-propylenediamine (BHPD), 20% of diethanolamine (DEA), and 70% of water.

[0103] At 40°C, the polyamino absorbent of this example was contacted with the atmospheric gas mixture (CO2 partial pressure of 12 kPa) to absorb CO2 at an equilibrium CO2 loading of 2.2 mol / kg. Subsequently, the temperature was raised to 120°C and the polyamino absorbent of this example was contacted with the atmospheric gas mixture (CO2 partial pressure of 12 kPa) to absorb CO2 at an equilibrium CO2 loading of 0.5 mol / kg, a circulating absorption loading of approximately 1.7 mol / kg, and a desorption efficiency of 77%. The heat of reaction for CO2 absorption at 40°C was 1.57 GJ / tCO2, and the absorption rate was 8200 L / mol / s. The volatility of the absorbent at 40°C was 0.016 Pa.

[0104] For comparison, 30% DEA aqueous solution and 30% BHPD aqueous solution were tested at 40°C and 120°C, respectively. The results are shown in Table 5.

[0105] Table 5

[0106]

[0107] It can be seen that this embodiment uses a combination of BHPD and DEA as the effective components of the absorbent, and a synergistic effect is produced between the two, which has the advantages of the highest CO2 cycle absorption capacity, low absorption reaction heat, high desorption rate, and low volatility.

[0108] Example 6

[0109] This embodiment provides a polyamino absorbent, which comprises, based on 100% of its total weight, 10% of N,N'-bis(2-hydroxypropyl)-1,3-propylenediamine (BHPD), 20% of diethanolamine (DEA), 2% of diethylenetriamine (DETA), and 68% of water.

[0110] At 40°C, the polyamino absorbent of this example was contacted with the atmospheric gas mixture (CO2 partial pressure of 12 kPa) to absorb CO2 at an equilibrium CO2 loading of 2.25 mol / kg. Subsequently, the temperature was raised to 120°C and the polyamino absorbent of this example was contacted with the atmospheric gas mixture (CO2 partial pressure of 12 kPa) to absorb CO2 at an equilibrium CO2 loading of 0.45 mol / kg, a circulating absorption loading of approximately 1.80 mol / kg, and a desorption efficiency of 80%. The heat of reaction for CO2 absorption at 40°C was 1.53 GJ / tCO2, and the absorption rate was 10,200 L / mol / s. The volatility of the absorbent at 40°C was 0.015 Pa.

[0111] In addition, this example also provides an aqueous solution of 10% BHPD+25% DEA+5% DETA as a polyamino absorbent, and the corresponding data are listed in Table 6.

[0112] For comparison, 30% DEA aqueous solution and 30% BHPD aqueous solution were tested at 40°C and 120°C, respectively. The results are shown in Table 6.

[0113] Table 6

[0114]

[0115] As can be seen, this example employs a combination of BHPD, DEA, and DETA as the active absorbent components, creating a synergistic effect. This combination results in the highest CO2 cycle absorption capacity, highest absorption rate, low absorption reaction heat, high desorption rate, and moderate volatility. To address the low absorption rate of the polyamino absorbent in Example 5, the absorption rate can be further increased by adding approximately 2-5% DETA and / or PZ.

[0116] Example 7

[0117] This embodiment provides a polyamino absorbent, which comprises, based on 100% of its total weight, 25% of N,N'-bis(2-hydroxypropyl)-1,3-propylenediamine (BHPD), 10% of diethylethanolamine (DEEA), and 65% of water.

[0118] At 40°C, the polyamino absorbent of this example was contacted with the atmospheric gas mixture (CO2 partial pressure of 12 kPa) to absorb CO2 at an equilibrium CO2 loading of 2.2 mol / kg. Subsequently, the temperature was raised to 120°C and the polyamino absorbent of this example was contacted with the atmospheric gas mixture (CO2 partial pressure of 12 kPa) to absorb CO2 at an equilibrium CO2 loading of 0.4 mol / kg, a circulating absorption loading of approximately 1.8 mol / kg, and a desorption efficiency of 82%. The heat of reaction for CO2 absorption at 40°C was 1.48 GJ / tCO2, and the absorption rate was 6000 L / mol / s. The volatility of the absorbent at 40°C was 0.074 Pa.

[0119] For comparison, 35% DEEA aqueous solution and 35% BHPD aqueous solution were tested at 40°C and 120°C, respectively. The results are shown in Table 7.

[0120] Table 7

[0121]

[0122] It can be seen that this embodiment uses a combination of BHPD and DEEA as the effective components of the absorbent, and a synergistic effect is produced between the two, which has the advantages of the highest CO2 cycle absorption capacity, low absorption reaction heat, and low volatility, while the desorption rate and absorption rate are moderate.

[0123] Example 8

[0124] This embodiment provides a polyamino absorbent, which comprises, based on 100% of its total weight, 25% of N,N'-bis(2-hydroxypropyl)-1,3-propylenediamine (BHPD), 10% of diethylethanolamine (DEEA), 2% of piperazine (PZ), and 63% of water.

[0125] At 40°C, the polyamino absorbent of this example was contacted with the atmospheric gas mixture (CO2 partial pressure of 12 kPa) to absorb CO2 at an equilibrium CO2 loading of 2.24 mol / kg. Subsequently, the temperature was raised to 120°C and the polyamino absorbent of this example was contacted with the atmospheric gas mixture (CO2 partial pressure of 12 kPa) to absorb CO2 at an equilibrium CO2 loading of 0.34 mol / kg, a cyclic absorption loading of approximately 1.9 mol / kg, and a desorption efficiency of 85%. The heat of reaction for CO2 absorption at 40°C was 1.50 GJ / tCO2, and the absorption rate was 12,500 L / mol / s. The volatility of the absorbent at 40°C was 0.80 Pa. The test results are shown in Table 8.

[0126] Table 8

[0127]

[0128] As can be seen, this example employs a combination of BHPD, DEEA, and PZ as the active components of the absorbent, creating a synergistic effect. This combination offers advantages such as maximum CO2 cyclic absorption and a high absorption rate, while also exhibiting low absorption reaction heat and moderate desorption rate and volatility. To address the low absorption rate of the polyamino absorbent in Example 7, the absorption rate can be further increased by adding approximately 2% of DETA and / or PZ.

[0129] Example 9

[0130] This embodiment provides a polyamino absorbent, which comprises, based on 100% of its total weight, 20% of N,N'-bis(2-hydroxypropyl)-1,3-propylenediamine (BHPD), 10% of diethylenetriamine (DETA), and 70% of water.

[0131] At 40°C, the polyamino absorbent of this example was contacted with the atmospheric gas mixture (CO2 partial pressure of 12 kPa) to absorb CO2 at an equilibrium CO2 loading of 2.3 mol / kg. Subsequently, the temperature was raised to 120°C and the polyamino absorbent of this example was contacted with the atmospheric gas mixture (CO2 partial pressure of 12 kPa) to absorb CO2 at an equilibrium CO2 loading of 0.4 mol / kg, a circulating absorption loading of approximately 1.9 mol / kg, and a desorption efficiency of 83%. The heat of reaction for CO2 absorption at 40°C was 1.57 GJ / tCO2, and the absorption rate was 45,000 L / mol / s. The volatility of the absorbent at 40°C was 0.072 Pa.

[0132] For comparison, 30% DETA aqueous solution and 30% BHPD aqueous solution were tested at 40°C and 120°C, respectively. The results are shown in Table 9.

[0133] Table 9

[0134]

[0135] It can be seen that this embodiment uses a combination of BHPD and DETA as the effective components of the absorbent, and a synergistic effect is produced between the two, which has the advantages of the highest CO2 cycle absorption capacity, low absorption reaction heat, high desorption rate, high absorption rate, and low volatility.

[0136] Example 10

[0137] This embodiment provides a polyamino absorbent, which comprises, based on 100% of its total weight, 25% of N,N'-bis(2-hydroxypropyl)-1,3-propylenediamine (BHPD), 10% of piperazine (PZ), and 65% of water.

[0138] At 40°C, the polyamino absorbent of this example was contacted with the atmospheric gas mixture (CO2 partial pressure of 12 kPa) to absorb CO2 at an equilibrium CO2 loading of 2.05 mol / kg. Subsequently, the temperature was raised to 120°C and the polyamino absorbent of this example was contacted with the atmospheric gas mixture (CO2 partial pressure of 12 kPa) to absorb CO2 at an equilibrium CO2 loading of 0.4 mol / kg, a circulating absorption loading of approximately 1.65 mol / kg, and a desorption efficiency of 80%. The heat of reaction for CO2 absorption at 40°C was 1.60 GJ / tCO2, and the absorption rate was 40,000 L / mol / s. The volatility of the absorbent at 40°C was 3.06 Pa.

[0139] For comparison, 35% PZ aqueous solution and 35% BHPD aqueous solution were tested at 40°C and 120°C, respectively. The results are shown in Table 10.

[0140] Table 10

[0141]

[0142] It can be seen that this embodiment uses a combination of BHPD and PZ as the effective components of the absorbent, and a synergistic effect is produced between the two, which has the advantages of the highest CO2 cycle absorption capacity, low absorption reaction heat, high desorption rate, high reaction rate and low volatility.

[0143] Comparative Example 1

[0144] This comparative example provides an absorbent, which is an aqueous solution of monoethanolamine (MEA) with a weight percentage of 30%.

[0145] At 40°C, the absorbent of this comparative example was contacted with the atmospheric gas mixture (CO₂ partial pressure of 12 kPa) to absorb CO₂ at an equilibrium CO₂ loading of 2.65 mol / kg. Subsequently, the temperature was raised to 120°C and the absorbent of this comparative example was contacted with the atmospheric gas mixture (CO₂ partial pressure of 12 kPa) to absorb CO₂ at an equilibrium CO₂ loading of 1.5 mol / kg. The cycle absorption loading was approximately 1.15 mol / kg, and the desorption efficiency was 43%. The heat of reaction for CO₂ absorption at 40°C was 2.16 GJ / tCO₂, and the absorption rate was 6500 L / mol / s. The volatility of the absorbent at 40°C was 10 Pa.

[0146] It can be seen that the disadvantages of using MEA as an absorbent are that the CO2 cycle absorption capacity is very low, the absorption rate is low, the desorption rate is low, and the CO2 absorption reaction heat is very high.

[0147] Comparative Example 2

[0148] This comparative example provides an absorbent which is a 30 weight % aqueous solution of 2-amino-2-methyl-1-propanol (AMP).

[0149] At 40°C, the absorbent of this comparative example was contacted with the atmospheric gas mixture (CO₂ partial pressure of 12 kPa) to absorb CO₂ at an equilibrium CO₂ 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 atmospheric gas mixture (CO₂ partial pressure of 12 kPa) to absorb CO₂ at an equilibrium CO₂ loading of 0.3 mol / kg, a cyclic absorption loading of approximately 1.9 mol / kg, and a desorption efficiency 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 volatility of the absorbent at 40°C was 0.1 Pa.

[0150] It can be seen that the use of sterically hindered amine AMP as an absorbent has a higher CO2 absorption cycle load, but its disadvantages are that the absorption rate is too slow, the absorption reaction heat is high, and the molecular structure is complex, the synthesis is difficult, and the price is high.

[0151] Comparative Example 3

[0152] This comparative example provides a polyamino absorbent, which comprises 25% of 2-amino-2-methyl-1-propanol (AMP), 10% of piperazine (PZ) and 65% of water, based on 100% of the total weight of the polyamino absorbent.

[0153] At 40°C, the polyamino absorbent of this comparative example was contacted with the atmospheric gas mixture (CO₂ partial pressure of 12 kPa) to absorb CO₂ at an equilibrium CO₂ loading of 2.9 mol / kg. Subsequently, the temperature was raised to 120°C and the polyamino absorbent of this comparative example was contacted with the atmospheric gas mixture (CO₂ partial pressure of 12 kPa) to absorb CO₂ at an equilibrium CO₂ loading of 1.13 mol / kg, a circulating absorption loading of approximately 1.87 mol / kg, and a desorption efficiency of 65%. The heat of reaction for CO₂ absorption at 40°C was 1.75 GJ / tCO₂, and the absorption rate was 15,200 L / mol / s. The volatility of the absorbent at 40°C was 3.1 Pa.

[0154] It can be seen that the combination of AMP and PZ as the effective component of the absorbent has a high CO2 cycle absorption capacity, but the reaction heat is high, and the molecular structure of AMP is complex, the synthesis is difficult, and the price is high.

[0155] Comparative Example 4

[0156] This comparative example provides a multi-amino absorbent, which comprises 20% of N,N'-bis(2-hydroxyethyl)ethylenediamine (BHED), 10% of monoethanolamine (MEA) and 70% of water, based on 100% of the total weight.

[0157] At 40°C, the polyamino absorbent of this comparative example was contacted with the atmospheric gas mixture (CO₂ partial pressure of 12 kPa) to absorb CO₂ at an equilibrium CO₂ loading of 1.85 mol / kg. Subsequently, the temperature was raised to 120°C and the polyamino absorbent of this comparative example was contacted with the atmospheric gas mixture (CO₂ partial pressure of 12 kPa) to absorb CO₂ at an equilibrium CO₂ loading of 0.50 mol / kg, a circulating absorption loading of approximately 1.35 mol / kg, and a desorption efficiency of 73%. The heat of reaction for CO₂ absorption at 40°C was 1.75 GJ / tCO₂, and the absorption rate was 7000 L / mol / s. The volatility of the absorbent at 40°C was 3.33 Pa.

[0158] It can be seen that the combination of BHED and primary amine MEA as the effective component of the absorbent has a low cycle absorption capacity, a low desorption rate, a high reaction heat and a slow CO2 absorption rate.

[0159] Comparative Example 5

[0160] This comparative example provides a polyamino absorbent, which comprises, based on 100% of its total weight, 20% of N,N'-bis(2-hydroxyethyl)ethylenediamine (BHED), 10% of 2-amino-2-methyl-1-propanol (AMP) and 70% of water.

[0161] At 40°C, the polyamino absorbent of this comparative example was contacted with the atmospheric gas mixture (CO₂ partial pressure of 12 kPa) to absorb CO₂ at an equilibrium CO₂ loading of 1.53 mol / kg. Subsequently, the temperature was raised to 120°C and the polyamino absorbent of this comparative example was contacted with the atmospheric gas mixture (CO₂ partial pressure of 12 kPa) to absorb CO₂ at an equilibrium CO₂ loading of 0.18 mol / kg, a circulating absorption loading of approximately 1.35 mol / kg, and a desorption efficiency of 88%. The heat of reaction for CO₂ absorption at 40°C was 1.72 GJ / tCO₂, and the absorption rate was 6200 L / mol / s. The volatility of the absorbent at 40°C was 0.036 Pa.

[0162] It can be seen that the combination of BHED and sterically hindered amine AMP as the effective component of the absorbent has a higher reaction heat and a slower CO2 absorption rate.

[0163] As can be seen from the above examples and comparative examples, the first and second components of the present invention produce a synergistic effect, which enables the polyamino absorbent of the present invention to have an increased cyclic absorption capacity and absorption rate while maintaining the high desorption rate, low reaction heat, and low volatility of the first component. Therefore, the polyamino absorbent of the present invention has multiple advantages, including high solubility for carbon dioxide, large cyclic absorption capacity for carbon dioxide, high carbon dioxide absorption rate, low reaction heat for carbon dioxide absorption, low volatilization loss, high desorption rate, and low regeneration energy consumption.

[0164] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is 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 in the scope of protection of the present invention.

Claims

1. A polyamino absorbent for carbon dioxide capture, comprising at least the following components: The first component is at least one N-hydroxyalkyl-N'-hydroxyalkyl-alkanediamine having the following molecular formula: HO-C x H 2x -NH-C y H 2y -NH-C z H 2z -OH, where x, y and z are each independently selected from one of 2 and 3; A second component: at least one organic amine different from the first component, the organic amine containing an amino group that is not a primary amino group and the organic amine containing no sterically hindered amino group; and solvent and optionally additives; Wherein, based on the total weight of the multi-amino absorbent for carbon dioxide capture being 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 the optionally included additives is 30-80%.

2. The multi-amino absorbent for carbon dioxide capture according to claim 1, wherein: The first component includes one or more of N,N'-bis(hydroxyethyl)ethylenediamine, N,N'-bis(hydroxypropyl)ethylenediamine, N,N'-bis(hydroxyethyl)propylenediamine, N,N'-bis(hydroxypropyl)propylenediamine, N-hydroxyethyl-N'-hydroxypropylethylenediamine and N-hydroxyethyl-N'-hydroxypropylpropylenediamine; And / or, the first component includes one or both of N,N'-bis(hydroxyethyl)ethylenediamine and N,N'-bis(hydroxypropyl)propylenediamine.

3. The multi-amino absorbent for carbon dioxide capture according to claim 1, wherein: The second component includes one or more of a secondary amine, a tertiary amine and a polyamine containing one or more of a secondary amino group and a tertiary amino group and not containing a sterically hindered amino group.

4. The multi-amino absorbent for carbon dioxide capture according to claim 3, wherein: The secondary amine includes one or more of N-methylethanolamine, N-ethylethanolamine, N-propylethanolamine, N-methylpropanolamine, N-ethylpropanolamine, N-propylpropanolamine, diethanolamine, dipropanolamine and ethanolpropanolamine; the tertiary amine includes one or more of N-methyldiethanolamine, N-methyldipropanolamine, N,N-dimethylethanolamine, N,N-diethylethanolamine, N,N-dimethylpropanolamine and N,N-diethylpropanolamine; the polyamine includes one or more of hydroxyethylethylenediamine, diethylenetriamine, triethylenetetramine, piperazine, N-methylpiperazine, N-ethylpiperazine, N-aminoethylpiperazine, N-hydroxyethylpiperazine and dimethylpiperazine.

5. The multi-amino absorbent for carbon dioxide capture according to claim 1, wherein: The solvent includes one or more of water, alcohols, ethers, esters and sulfones; the additive includes one or more of antioxidants, antidegradants, corrosion inhibitors and defoaming agents.

6. A method for capturing carbon dioxide from a gas mixture, comprising the steps of: The multi-amino absorbent for carbon dioxide capture according to any one of claims 1 to 5 is brought into contact with a gas mixture containing carbon dioxide to capture carbon dioxide.

7. The method for capturing carbon dioxide from a gas mixture according to claim 6, wherein: The carbon dioxide partial pressure in the gas mixture containing carbon dioxide is 3 to 200 kPa.

8. The method for capturing carbon dioxide from a gas mixture according to claim 6, wherein: The gas mixture containing carbon dioxide comes from one or more of flue gas, purge gas and process gas in one or more of the process of coal-fired power generation, steel metallurgy, cement building materials, petrochemical industry and coal chemical industry.

9. The method for capturing carbon dioxide from a gas mixture according to claim 6, wherein: The polyamino absorbent for carbon dioxide capture captures carbon dioxide in a gas mixture and also captures other acid gases in the gas mixture. The other acid gases include one or more of sulfur dioxide, hydrogen sulfide and organic sulfur.

10. The method for capturing carbon dioxide from a gas mixture according to claim 6, wherein: The contacting of the polyamino absorbent for carbon dioxide capture with the gas mixture containing carbon dioxide is carried out in an absorption tower. The temperature of the polyamino absorbent for carbon dioxide capture entering the absorption tower is 20-80° C., and the bottom pressure of the absorption tower is 50-500 kPa.

11. The method for capturing carbon dioxide from a gas mixture according to claim 6, wherein: The method further comprises: desorbing the polyamino absorbent after capturing carbon dioxide, wherein the desorption is performed in a regeneration tower, the temperature of the polyamino absorbent obtained after desorption is 80-150° C., and the bottom pressure of the regeneration tower is 50-500 kPa.

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