Mesh-shaped porous co 2-capturing solution and separation method for co 2 gas

Abstract

Provided in the present invention are a mesh-shaped porous CO2-capturing solution and a separation method for CO2 gas. The composition of the capturing solution comprises 1%-50% of a specific chemical agent and 50%-99% of water. The specific chemical agent is one or a combination of two or more of an imidazole substance, an imidazole ionic liquid, a piperazine substance, and an amino alcohol substance. The mesh-shaped porous CO2-capturing solution of the present invention remains stable and adsorbs CO2 at low temperatures, the porous structure disintegrates and releases CO2 at high temperatures, and the mesh-shaped porous CO2-capturing solution has advantages such as a fast absorption rate, a large absorption capacity, and a low regeneration temperature.

Description

A mesh porous CO2 capture liquid and CO2 gas separation method Technical Field

[0001] The invention relates to a mesh porous CO2 capture liquid and a CO2 gas separation method, belonging to the technical field of chemical separation. Background Art

[0002] CO2 capture, utilization, and storage (CCUS) is considered a key strategy for mitigating the greenhouse effect. Currently, a variety of carbon capture technologies are available, including physical absorption, chemical absorption, adsorption, membrane separation, and cryogenic separation. However, these technologies have inherent limitations. For example, chemical absorption suffers from solvent degradation, strong corrosion, and high energy consumption for solvent regeneration; membrane separation has low throughput and poor stability; and cryogenic separation is overly dependent on temperature and requires high energy.

[0003] The amine process is the most widely used CO2 capture method, but it suffers from issues such as high regeneration energy consumption and solvent degradation. Therefore, the search for a low-energy, high-efficiency CO2 capture method is crucial. Because a single absorbent rarely combines high absorption capacity, fast absorption rate, and low reaction heat, blending multiple absorbents to achieve novel absorbents with high absorption rates and capacities, while also requiring low regeneration energy, is a current research hotspot.

[0004] Summary of the Invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a mesh-like porous CO2 capture liquid.

[0006] Another object of the present invention is to provide a method for separating CO2 gas.

[0007] To achieve the above object, the present invention provides a reticulated porous CO2 capture liquid, wherein, based on the total mass of the capture liquid being 100%, the composition of the capture liquid comprises 1%-50% of a specific chemical agent and 50%-99% of water;

[0008] The specific chemical agent is one or a combination of two or more of imidazole substances, imidazole ionic liquids, piperazine substances, and alcoholamine substances.

[0009] The porous CO2 capture liquid provided by the present invention is formed by molecular self-assembly of a mixture of water and a specific chemical agent, which forms a porous reticulated structure. This reticulated porous CO2 capture liquid is stable and capable of adsorbing CO2 at relatively low temperatures (0°C-50°C). CO2 is stably adsorbed within the porous structure, but at higher temperatures (above 60°C), the porous structure gradually dissolves and releases the adsorbed CO2.

[0010] In the above-mentioned capture liquid, preferably, the specific chemical agent forms a network-like porous structure in water.

[0011] In the above-mentioned capture solution, preferably, the imidazole substance includes one or a combination of two or more of imidazole, 2-methylimidazole, 1-methylimidazole, 2-ethylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole and 2-phenylimidazole.

[0012] In the above-mentioned capture liquid, preferably, the imidazolium ionic liquid includes one or a combination of two or more of 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4], 1-hexyl-3-methylimidazolium tetrafluoroborate [HMIM][BF4], 1-hexyl-3-methylimidazolium hexafluorophosphate [HMIM][PF6], 1-ethyl-3-methylimidazolium chloride [EMIM][Cl], and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [EMIM][TF2N].

[0013] In the above-mentioned capture liquid, preferably, the piperazine substance includes one or a combination of two or more of piperazine (PZ), 1-(2-aminoethyl)piperazine (AEP), N-(2-hydroxyethyl)piperazine (HEPZ), 1-methylpiperazine (1-MPZ), and 2-methylpiperazine (2-MPZ).

[0014] In the above-mentioned capture liquid, preferably, the alcoholamine substance includes one or a combination of two or more of diethanolamine (DEA), N-methyldiethanolamine (MDEA), 2-amino-2-methyl-1-propanol (AMP), hydroxyethylethylenediamine (AEEA), diethylenetriamine (DETA), N-methylcyclohexylamine (MCA), and triethanolamine (TEA).

[0015] According to a specific embodiment of the present invention, the method for preparing the above-mentioned reticulated porous CO2 capture liquid includes the following steps: mixing a specific chemical agent and water, and stirring them evenly to form a dispersed and stable liquid.

[0016] The present invention also provides a method for separating CO2 gas, wherein the method utilizes the above-mentioned meshed porous CO2 capture liquid to capture CO2.

[0017] According to a specific embodiment of the present invention, preferably, the separation method is to achieve the separation of CO2 in a mixed gas of CO2 and N2.

[0018] In the above separation method, preferably, the absorption temperature during CO2 capture is 0°C-50°C.

[0019] In the above separation method, preferably, the absorption pressure during CO2 capture is 0.1 MPa-1 MPa.

[0020] In the above separation method, preferably, the method further comprises the step of desorbing the CO2-rich liquid obtained after capturing the CO2 under vacuum and heating conditions, and then regenerating the lean liquid for recycling. The heating temperature is preferably 60°C-100°C, and the absolute vacuum pressure is preferably below 80 kPa.

[0021] The reticulated porous CO2 capture liquid described in this invention maintains stability and adsorbs CO2 at relatively low temperatures (0°C-50°C). At higher temperatures (above 60°C), the porous structure gradually dissolves and releases the adsorbed CO2. This capture liquid also boasts a fast absorption rate, large absorption capacity, low desorption heat, low regeneration temperature, and resistance to degradation, offering broad application prospects in carbon capture and CO2 utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG1 is a graph showing the evaluation of CO2 solubility and absorption rate in Example 1.

[0023] FIG2 is a graph showing the CO2 solubility, absorption rate, and desorption heat evaluation in Example 2.

[0024] FIG3 shows the thermodynamic and kinetic experimental results of CO2 absorption by the regeneration solution in Example 3.

[0025] Figure 4 is a cryo-electron micrograph of the mesh-like porous CO2 capture liquid of the present invention, wherein: (a) absorbent I; (b) absorbent V; (c) absorbent VIII; (d) absorbent II.

[0026] Figure 5 is a schematic diagram of the pilot-scale CO2 / N2 continuous separation device in Example 5.

[0027] Description of Figure Numbers:

[0028] 501 CO2 cylinder

[0029] 502 air compressor

[0030] 503 Gas buffer tank

[0031] 504 Absorption tower inlet infrared CO2 monitor

[0032] 505 Absorption tower outlet infrared CO2 monitor

[0033] 506 Water Ring Vacuum Pump

[0034] 507 Absorption Tower

[0035] 508 Desorption Tower

[0036] 509 Centrifugal Pump

[0037] 510 Liquid Filling Tank

[0038] 511 Temperature Sensor

[0039] 512 Mass Flow Meter

[0040] 513 metering pump

[0041] 514 Pressure Transmitter

[0042] 515 Mixer

[0043] 516 Liquid Buffer Tank DETAILED DESCRIPTION

[0044] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of 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.

[0045] The experimental apparatus described in this invention is the same as that described in ZL201910327202.X, and is used for thermodynamic and kinetic experiments on pure gases and gas mixtures. For data processing procedures for related gas solubility and separation experiments, see paragraphs 0030-0048 of the specification of ZL201910327202.X (CN111821812A).

[0046] Example 1

[0047] This embodiment provides a set of reticulated CO2 capture liquids, namely: absorbent I, absorbent II, absorbent III, absorbent IV;

[0048] Wherein, based on the total mass of the solution as 100%, the composition of absorbent I is (30% 2-ethylimidazole + balance water); the composition of absorbent II is (30% imidazole + balance water); the composition of absorbent III is (30% MDEA + balance water); the composition of absorbent IV is (30% 2-methylimidazole + balance water);

[0049] Under the condition of an absorption temperature of 30°C, pure CO2 gas was used as the raw gas to test the absorption capacity (CO2 solubility) and absorption rate of each absorbent. The results are shown in Figure 1. In Figure 1, (a) is the absorption capacity test result, (b) is the absorption rate test result, the horizontal axis is the absorption pressure, and the vertical axis is the value of the absorption amount under the corresponding pressure.

[0050] Example 2

[0051] This embodiment provides a set of reticulated CO2 capture liquids, namely: absorbent V, absorbent VI;

[0052] Wherein, based on the total mass of the solution as 100%, the composition of absorbent V is (30% imidazole + 5% AEP + balance water); the composition of absorbent VI is (30% imidazole + 5% DEA + balance water);

[0053] Under the condition of an absorption temperature of 30°C, pure CO2 gas was used as the raw gas to test the absorption capacity (CO2 solubility), absorption rate and desorption heat of absorbent II, absorbent V and absorbent VI. The results are shown in Table 1 and Figure 2. In Figure 2, (a) is the absorption capacity test result, (b) is the absorption rate test result, and (c) is the desorption heat evaluation diagram of CO2 in absorbent V and absorbent VI.

[0054] Table 1 Average values ​​of absorption heat of different absorbents

[0055] From the experimental results in Table 1 and Figure 2, it can be seen that at the equilibrium pressure (P E ) was 1MPa, the absorption capacity of the composite absorbent system increased by 13.93% and 10.42%, respectively, compared to the aqueous solution of a single absorbent. Furthermore, the absorption kinetics of CO₂ by the composite solution were examined. At an inlet pressure of 200kPa, the absorption rate of the composite solution system (i.e., the amount absorbed per unit time) increased by 10 times and 4 times, respectively, compared to Absorbent II. This demonstrates that the hybrid absorbent significantly improves both CO₂ absorption capacity and absorption rate.

[0056] Example 3

[0057] In order to verify whether the absorbent in Example 2 can be reused for CO2 capture, pure CO2 gas is used as the raw gas, and the above-mentioned absorbent V is used to carry out multiple CO2 absorption-desorption operations to examine its reusability.

[0058] After the CO2 absorption experiment was completed, the rich liquid was desorbed at a temperature of 80°C and a desorption pressure of 80 kPa for 30 minutes, and the obtained lean liquid continued to be subjected to the CO2 capture experiment. The experimental results are shown in Figure 3. In Figure 3, (a) is the absorption capacity test result, and (b) is the absorption rate test result.

[0059] Under the desorption conditions, the separation performance of absorbent V decreased slightly compared with the fresh solution after multiple absorption-desorption cycle tests, but the absorption capacity and absorption rate tended to be stable after the second regeneration and there was no obvious decrease in multiple cycles, showing relatively excellent reuse performance.

[0060] Example 4

[0061] This embodiment provides a set of reticulated CO2 capture liquids, namely: absorbent VII, absorbent VIII, absorbent IX;

[0062] Wherein, based on the total mass of the solution as 100%, the composition of absorbent VII is (30% [BMIM][BF4] + balance water); the composition of absorbent VIII is (20% [BMIM][BF4] + 10% imidazole + balance water); the composition of absorbent IX is (20% [BMIM][BF4] + 10% AEP + balance water);

[0063] Under the condition of an absorption temperature of 40°C, pure CO2 gas was used as the raw gas to test the CO2 absorption capacity of absorbent VII, absorbent VIII, and absorbent IX. The results are shown in Table 2.

[0064] Table 2 Absorption test results of different absorbents

[0065] Figure 4 shows cryo-electron micrographs of the porous CO2 capture liquid of the present invention, including (a) Absorbent I, (b) Absorbent V, (c) Absorbent VIII, and (d) Absorbent II. These cryo-electron micrographs show that each absorbent forms a porous network structure.

[0066] Example 5

[0067] This embodiment provides a method for separating CO2 gas, which is to achieve continuous separation of CO2 / N2:

[0068] First, a 33% composite solution was prepared, which contained 30% imidazole and 3% 1-(2-aminoethyl)piperazine, with the balance being water;

[0069] Continuous separation tests were conducted using the absorbent as the separation medium. Figure 5 is a schematic diagram of the process of using the capture liquid for continuous carbon capture.

[0070] The device includes a CO2 gas cylinder 501, an air compressor 502, a gas buffer tank 503, an infrared CO2 monitor at the absorption tower inlet 504, an infrared CO2 monitor at the absorption tower outlet 505, a water ring vacuum pump 506, an absorption tower 507, a desorption tower 508, a centrifugal pump 509, a liquid adding tank 510, a temperature sensor 511, a mass flow meter 512, a metering pump 513, a pressure transmitter 514, a mixer 515, and a liquid buffer tank 516.

[0071] Among them, the CO2 cylinder 501 and the air compressor 502 are used to provide raw gas, and the two are merged into the same pipeline through the mixer 515 and then connected to the bottom inlet of the absorption tower 507. In addition, a one-way valve and a gas buffer tank 503 are provided between the CO2 cylinder 501 and the mixer 515, a pressure reducing valve and a liquid buffer tank 516 are provided between the air compressor 502 and the mixer 515, and an absorption tower inlet infrared CO2 monitor 504 and a mass flow meter 512 are provided between the mixer 515 and the bottom inlet of the absorption tower 507; wherein, the one-way valve is used to control the flow direction of the raw gas and avoid backflow; the pressure reducing valve is used to control the pressure of the raw gas; the absorption tower inlet infrared CO2 monitor 504 is used to monitor the concentration of CO2 in the mixed gas entering the absorption tower; the mass flow meter 512 is used to measure the amount of gas entering the absorption tower 507 and control parameters such as flow rate;

[0072] Absorption tower 507 has an inner diameter of 66 mm, a packing height of 2.5 m, and a maximum operating pressure of 1 MPa. The tower is filled with theta-ring random packing. Temperature sensors 511 are installed in the bottom, body, and top of absorption tower 507 to monitor the temperatures at the corresponding locations. An infrared CO2 monitor 505 is also installed at the top of absorption tower 507 to monitor the CO2 concentration in the mixed gas leaving the absorption tower.

[0073] The bottom outlet of the absorption tower 507 is connected to the top inlet of the desorption tower 508. The connecting pipes are provided with a pressure transmitter 514, a drain valve, and a centrifugal pump 509. The pressure transmitter is used to measure the pressure of the rich liquid leaving the bottom of the absorption tower 507, and the drain valve is used to discharge the slurry in the absorption tower 507.

[0074] The desorption tower 508 has an inner diameter of 66 mm, a packing height of 2.5 m, and a maximum operating pressure of 0.5 MPa. The tower is filled with θ-ring random packing. The upper and middle sections of the desorption tower 508 are electrically heated for insulation, with a heating power of 1 kW. Several temperature sensors 511 are located at appropriate locations within the desorption tower 508 to monitor the temperature at the corresponding locations.

[0075] The top inlet of the desorption tower 508 is connected to the inlet of the water ring vacuum pump 506, providing vacuum operating conditions for the desorption tower 508. A drain valve is provided at the outlet of the desorption tower 508, and this outlet is connected to the inlet of the metering pump 513. A liquid adding tank 510 is provided on the connecting pipeline between the two. The liquid adding tank 510 is used to pump the captured liquid into the absorption tower before the experiment begins and to replenish new captured liquid. The metering pump 513 is used to pump the captured liquid from the desorption tower into the absorption tower.

[0076] The outlet of the metering pump 513 is connected to the top inlet of the absorption tower 507. The connecting pipelines of the two are provided with a mass flow meter 512 and a metering pump 513 in sequence. The mass flow meter 512 is used to measure the flow rate of the captured liquid.

[0077] After desorption is completed in the desorption tower 508, the lean liquid is returned to the absorption tower 507 through the metering pump 513; after multiple cycles, the absorbent is separated from the CO2 / N2 mixed gas.

[0078] This example also examines the effect of desorption temperature on separation, and the specific results are shown in Table 3.

[0079] Table 3

[0080] In Table 3:

[0081] T de is the desorption temperature, is the gas-liquid ratio, P ab is the absorption pressure, P de is the desorption pressure, U in-gas is the mixed gas flow rate, C in-CO2 is the CO2 concentration at the absorption tower inlet, C out-CO2 is the CO2 concentration at the outlet of the absorption tower, ΔS V is the circulating absorption capacity, and η is the CO2 removal rate.

[0082] According to the data in Table 3, it can be seen that the technical solution of the present invention can well achieve the adsorption separation of CO2.

Claims

1. A mesh porous CO2 capture liquid, wherein: Based on the total mass of the capture liquid being 100%, the composition of the capture liquid comprises 1%-50% of a specific chemical agent and 50%-99% of water; Wherein, the specific chemical agent is one or a combination of two or more of imidazole substances, imidazole ionic liquids, piperazine substances, and alcohol amine substances.

2. The capture solution according to claim 1, wherein The specific chemical agent forms a network-like porous structure in water.

3. The capture solution according to claim 1 or 2, wherein: The imidazole substances include one or a combination of two or more of imidazole, 2-methylimidazole, 1-methylimidazole, 2-ethylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole and 2-phenylimidazole.

4. The capture solution according to claim 1 or 2, wherein: The imidazolium ionic liquid includes one or a combination of two or more of 1-butyl-3-methylimidazolium tetrafluoroborate, 1-hexyl-3-methylimidazolium tetrafluoroborate, 1-hexyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium chloride, and 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonyl imide.

5. The capture solution according to claim 1 or 2, wherein: The piperazine substances include one or a combination of two or more of piperazine, 1-(2-aminoethyl)piperazine, N-(2-hydroxyethyl)piperazine, 1-methylpiperazine, and 2-methylpiperazine.

6. The capture solution according to claim 1 or 2, wherein: The alcoholamine substances include one or a combination of two or more of diethanolamine, N-methyldiethanolamine, 2-amino-2-methyl-1-propanol, hydroxyethylethylenediamine, diethylenetriamine, N-methylcyclohexylamine, and triethanolamine.

7. A method for separating CO2 gas, wherein: The method is to capture CO2 using the mesh porous CO2 capture liquid described in any one of claims 1 to 6.

8. The separation method according to claim 7, wherein: The separation method is to achieve the separation of CO2 in a mixed gas of CO2 and N2.

9. The separation method according to claim 7, wherein: The absorption temperature during CO2 capture is 0°C-50°C.

10. The separation method according to claim 7, wherein: The absorption pressure during CO2 capture is 0.1MPa-1MPa.

11. The separation method according to claim 7, wherein: The method also includes the steps of desorbing the CO2 rich liquid obtained after capturing CO2 under vacuum and heating conditions, and then regenerating the lean liquid for recycling.

12. The separation method according to claim 11, wherein: The heating temperature is 60°C-100°C.

13. The separation method according to claim 11, wherein: The absolute pressure of the vacuum is 80 kPa or less.

Images