CN117717877A - Porous carbon dioxide absorbent and carbon dioxide separation method - Google Patents

Abstract

The invention provides a porous carbon dioxide absorbent and a carbon dioxide separation method. The composition of the absorbent comprises 1-10% of solid phase and 90-99% of liquid phase based on 100% of the total mass of the absorbent; wherein the solid phase is a particulate enhancer; the composition of the liquid phase comprises 5% -40% of a specific chemical agent and 60% -95% of water, based on 100% of the total mass of the liquid phase; the specific chemical agent comprises one or more than two of imidazole substances, imidazole ionic liquid, piperazine substances and alcohol amine substances. The porous absorbent provided by the invention is used for absorbing CO ₂ Has better absorption heat/dynamics performance and lower desorption heat, and can realize the effect of absorbing CO in the water-containing mixed gas ₂ And the components are trapped efficiently and with low consumption.

Description

A porous carbon dioxide absorbent and carbon dioxide separation method

Technical field

The invention belongs to the field of gas separation technology, and specifically relates to a porous carbon dioxide absorbent and a carbon dioxide separation method.

Background technique

CO ₂ capture, utilization and storage (CCUS) is currently the only emission reduction technology that can achieve large-scale low-carbon utilization. At present, the technical routes for CO ₂ capture mainly include post-combustion capture, pre-combustion capture and oxygen-rich fuel combustion capture. Post-combustion capture is a relatively widely used and mature technology in industry because it is simple to operate and does not require excessive modifications to existing power plants. Alcoholamine solution can quickly absorb _CO2 and has high selectivity for CO2 when the partial pressure of _CO2 is low. It is the most widely used _CO2 capture agent. _However , the biggest challenges in its utilization are its corrosiveness, easy degradation and regeneration. High energy consumption. Therefore, seeking a low-energy-consuming, high-efficiency _CO2 absorbent is crucial to reduce _CO2 emissions.

In recent years, metal organic frameworks (MOFs) materials have great development prospects in the field of gas separation due to their advantages of many active sites, large active surface area, controllable pore shape, and adjustable porosity, and zeolite imidazole frameworks (ZIFs) As a subcategory of MOFs, it has high thermal stability, chemical stability and excellent separation capabilities. Since ZIFs and other MOFs materials are powdery solids with fine particles and are easily blown away when in contact with gases, they cannot be directly used for the continuous capture of gases such as _CO2 . The slurry separation technology (absorption-adsorption coupling separation technology) currently proposed by Chen Guangjin's research group is to suspend ZIF-8 materials in a solvent containing specific chemical agents to form a porous slurry, which has higher separation selectivity and can achieve continuous operation and Hot integration. However, since it is difficult for a single absorbent to meet the requirements of high absorption capacity, fast absorption rate and low heat of reaction, it is still necessary to combine the compound characteristics of MOF materials and specific chemical agents to achieve low desorption heat at the same time. Combines the high capacity and selectivity of solid adsorbents.

Contents of the invention

In order to solve the above technical problems, the object of the present invention is to provide a porous carbon dioxide absorber.

Another object of the present invention is to provide a carbon dioxide separation method.

In order to achieve the above object, the present invention provides a porous carbon dioxide absorbent, wherein, based on the total mass of the absorbent being 100%, the composition of the absorbent includes 1%-10% solid phase, and 90%-99% % liquid phase; wherein the solid phase is a particle strengthening agent; based on the total mass of the liquid phase being 100%, the composition of the liquid phase includes 5%-40% of a specific chemical agent, and 60%- 95% water.

In the above absorbent, preferably, the specific chemical agent includes one or a combination of two or more of imidazole-based substances, imidazole-based ionic liquids, piperazine-based substances, and alcoholamine-based substances.

In the above absorbent, preferably, the particle strengthening agent includes one or a combination of two or more of zinc carbonate, basic zinc carbonate, zinc oxide, zinc chloride, and zinc hydroxide.

In the above absorbent, preferably, the added amount of the solid phase is 1.5%-5%.

In the above absorbent, preferably, the specific chemical agent forms a network porous structure in water.

The liquid phase in the porous CO ₂ absorbent provided by the present invention is composed of molecular self-assembly after mixing water and specific chemical agents. The specific chemical agents can form a network porous structure. The porous CO ₂ absorbent can remain stable at lower temperatures (0℃-50℃) and enable CO ₂ to be stably adsorbed in the porous structure. At higher temperatures (above 60℃), the porous structure gradually Dissolve and release the adsorbed CO ₂ .

In the above absorbent, preferably, the added amount of the specific chemical agent is 20%-40% based on the total mass of the liquid phase being 100%.

Among the above absorbents, preferably, the imidazoles include imidazole, 2-methylimidazole, 1-methylimidazole, 2-ethylimidazole, 1,2-dimethylimidazole, 2-ethyl-4 -One or a combination of two or more of methylimidazole and 2-phenylimidazole.

Among the above absorbents, preferably, the imidazole ionic liquid includes 1-butyl-3-methylimidazole tetrafluoroborate [BMIM] [BF ₄ ], 1-hexyl-3-methylimidazole tetrafluoro Borate [HMIM][BF ₄ ], 1-hexyl-3-methylimidazole hexafluorophosphate [HMIM][PF ₆ ], 1-ethyl-3-methylimidazole chloride [EMIM][Cl] , one or a combination of two or more of 1-ethyl-3-methylimidazole bistrifluoromethanesulfonimide salt [EMIM][TF ₂ N].

Among the above absorbents, preferably, the piperazine substances include piperazine (PZ), 1-(2-aminoethyl)piperazine (AEP), N-(2-hydroxyethyl)piperazine (HEPZ) ), one or a combination of two or more of 1-methylpiperazine (1-MPZ), 2-methylpiperazine (2-MPZ).

Among the above absorbents, preferably, the alcoholamine substances include diethanolamine (DEA), N-methyldiethanolamine (MDEA), 2-amino-2-methyl-1-propanol (AMP), hydroxylamine One or a combination of two or more of ethylethylenediamine (AEEA), diethylenetriamine (DETA), N-methylcyclohexylamine (MCA), and triethanolamine (TEA).

According to a specific embodiment of the present invention, the preparation method of the above-mentioned porous carbon dioxide absorber includes the following steps: mixing the particle strengthening agent, a specific chemical agent and water in a certain proportion, and stirring evenly to form a dispersed and stable slurry.

The present invention also provides a carbon dioxide separation method, wherein the method uses the above-mentioned porous carbon dioxide absorbent to capture _CO2 .

In the above separation method, preferably, the separation method is to achieve the separation of CO ₂ in the mixed gas of CO ₂ and N ₂ .

In the above separation method, preferably, the absorption temperature when performing _CO2 capture is 0-50°C.

In the above separation method, preferably, the absorption pressure when performing _CO2 capture is 0.1-1MPa.

In the above separation method, preferably, the method also includes the step of desorbing the CO ₂ rich liquid obtained after capturing CO ₂ under vacuum and heating conditions, and then regenerating the poor liquid for recycling.

In the above separation method, preferably, the heating temperature is 60-100°C.

In the above separation method, preferably, the absolute pressure of the vacuum is 80 kPa or less.

The porous absorbent of the present invention has excellent absorption heat/kinetic properties (large absorption capacity, fast absorption rate) for _CO2 , and at the same time has lower desorption heat; the prepared slurry absorbent is consistent with traditional MOF-based porous Compared with liquids, it has good dispersion and stability and low transportation energy consumption, and can achieve efficient and low-consumption capture of CO ₂ components in aqueous mixed gas.

Description of the drawings

Figure 1 is an evaluation diagram of CO ₂ solubility and absorption rate in Example 1 of the present invention.

Figure 2 shows the thermodynamic and kinetic experimental results of CO ₂ absorption by the regeneration solution in Example 2 of the present invention.

Figure 3 is an evaluation chart of CO ₂ desorption heat in Example 3 of the present invention.

Figure 4 is a schematic diagram of a pilot-scale CO ₂ /N ₂ continuous separation device in Embodiment 5 of the present invention.

Figure 5 is a cryo-electron microscope image of the absorbent V in Example 1.

Explanation of reference symbols:

401 CO ₂ cylinder

402 air compressor

403 gas buffer tank

404 Infrared CO ₂ monitor at the inlet of the absorption tower

405 Absorption tower outlet infrared CO ₂ monitor

406 water ring vacuum pump

407 Absorption tower

408 desorption tower

409 centrifugal pump

410 Liquid filling tank

411 temperature sensor

412 mass flow meter

413 metering pump

414 pressure transmitter

415 mixer

416 liquid buffer tank

Detailed ways

In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solutions of the present invention are described in detail below, but this should not be understood as limiting the implementable scope of the present invention.

The small test devices of the present invention are all devices recorded in ZL201910327202.X and are used for thermodynamic and kinetic experiments of pure gases and mixed gases. For the data processing process of related gas solubility experiments and separation experiments, please refer to paragraph 0030-0048 of the ZL201910327202.X (CN111821812A) instruction manual.

The preparation method of the porous CO ₂ absorbent in the embodiment of the present invention includes the following steps: Mix the particle strengthening agent, specific chemical agent and water in a certain proportion, and stir evenly to form a dispersed and stable slurry.

Example 1

This embodiment provides a set of porous CO ₂ absorbers, namely: absorber I, absorber II, absorber III, absorber IV, and absorber V;

The absorbent is prepared using the above-mentioned preparation method of porous CO ₂ absorbent, wherein, based on the total mass of the solution being 100%, the composition of absorbent I is (30% 1-methylimidazole + remaining water);

The composition of absorbent II is (30% 1-methylimidazole + 5% MDEA + balance water);

The composition of absorbent III is (30% 1-methylimidazole + 5% HEPZ + remaining water);

The composition of the absorbent IV is (2.5% basic zinc carbonate + 97.5% liquid phase); wherein, based on the total mass of the liquid phase being 100%, the liquid phase composition is (30% 1-methylimidazole + 5 % MDEA + balance water);

The composition of absorbent V is (2.5% basic zinc carbonate + 97.5% liquid phase); wherein, based on the total mass of the liquid phase being 100%, the liquid phase composition is (30% 1-methylimidazole + 5 % of HEPZ + balance water).

Among them, the cryo-electron micrograph of absorber V is shown in Figure 5. From Figure 5, it can be seen that a network porous structure is formed.

At an absorption temperature of 30°C, pure _CO2 gas was used as the raw material 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 abscissa is the absorption pressure, and the ordinate is the value of the absorption amount under the corresponding pressure. It can be seen from Figure 1 that adding particle strengtheners helps to improve the absorption capacity and absorption rate of the absorbent, and has better absorption heat/kinetic properties.

Next, the desorption heat of CO ₂ in the above-mentioned absorbent II, absorbent III, absorbent IV, and absorbent V was tested. The test results are shown in Table 1 and Figure 3.

Table 1. Average values of absorption heat of different absorbents

It can be seen from the experimental results in Table 1 and Figure 3 that compared with the absorbent II and absorbent III without particle reinforcement, the absorbent IV and absorbent V with particle reinforcement have lower desorption heat. .

Example 2

This embodiment provides a porous CO ₂ absorber VI;

The absorbent VI is prepared using the above preparation method of the porous CO ₂ absorbent. Based on the total mass of the solution being 100%, the composition of the absorbent VI is (1.5% basic zinc carbonate + 98.5% liquid phase); among them, the liquid phase The total mass of the phase is 100%, and the liquid phase composition is (30% 1-methylimidazole + 5% HEPZ + remaining water).

In order to verify whether the absorbent in this example can be reused for CO ₂ capture, pure CO ₂ gas was used as the raw material gas, and the above absorbent VI was used to perform multiple CO ₂ absorption-desorption operations to examine its reusability. After the CO ₂ absorption experiment is completed, the rich liquid is desorbed at a temperature of 80°C and a desorption pressure of 80 kPa for 20 minutes, and the resulting lean liquid is continued to undergo a CO ₂ capture experiment. The experimental results are shown in Figure 2. In Figure 2, (a) is the absorption capacity test result, and (b) is the absorption rate test result.

Under this desorption condition, after multiple absorption-desorption cycle tests, the separation performance of absorbent VI dropped slightly compared with the fresh solution, but the absorption capacity and absorption rate became stable after the second regeneration and it was recycled multiple times. There is no obvious decrease, showing relatively excellent reusability performance.

Example 3

This embodiment provides a set of porous CO ₂ absorbers, which are: absorber VII, absorber VIII, and absorber IX;

The absorbent is prepared using the above preparation method of porous CO ₂ absorbent, wherein, based on the total mass of the solution being 100%, the composition of absorbent VII is (20% [HMIM][BF ₄ ]+10% 1-methyl imidazole + balance water);

The composition of absorbent VIII is (20% [HMIM][BF ₄ ] + 10% HEPZ + balance water);

The composition of absorbent IX is (2.5% basic zinc carbonate + 97.5% liquid phase); among them, based on the total mass of the liquid phase being 100%, the liquid phase composition is (20% [HMIM] [BF ₄ ] + 10% HEPZ + balance water).

At an absorption temperature of 30°C, pure CO ₂ gas was used as the raw material gas to test the CO ₂ absorption of absorbent VII, absorbent VIII, and absorbent IX. The experimental results are shown in Table 2.

Table 2. Absorption capacity test results of different absorbents

Temperature(℃) Pressure(MPa) absorbent Absorption amount (mol/mol) 40 3 Absorbent VII 0.79 40 3 Absorbent VIII 0.82 40 3 Absorbent IX 0.85

It can be seen from the experimental results in Table 2 that the absorbent IX with the addition of particle enhancer has a greater CO ₂ absorption capacity.

Example 4

This embodiment provides a method for separating CO ₂ gas, which achieves continuous separation of CO ₂ /N ₂ :

First, a slurry is prepared. The raw materials of the slurry include 30% 1-methylimidazole, 5% 1-(2-aminoethyl)piperazine and 2.5% basic zinc carbonate, and the balance is water.

Continuous separation tests were conducted using the slurry absorbent as the separation medium. Figure 4 is a schematic flow diagram of the capture liquid used for continuous carbon capture.

The device includes a _CO2 gas cylinder 401, an air compressor 402, a gas buffer tank 403, an infrared _CO2 monitor 404 at the inlet of the absorption tower, an infrared _CO2 monitor 405 at the outlet of the absorption tower, a water ring vacuum pump 406, an absorption tower 407, and a desorption tower. 408. Centrifugal pump 409, liquid adding tank 410, temperature sensor 411, mass flow meter 412, metering pump 413, pressure transmitter 414, mixer 415, liquid buffer tank 416.

Among them, the CO ₂ gas cylinder 401 and the air compressor 402 are used to provide raw material gas. They are merged into the same pipeline through the mixer 415 and then connected to the tower still inlet of the absorption tower 407, and the CO ₂ gas cylinder 401 is connected to the mixer. There is a one-way valve and a gas buffer tank 403 between 415, a pressure reducing valve and a liquid buffer tank 416 between the air compressor 402 and the mixer 415, and a pressure reducing valve and a liquid buffer tank 416 between the mixer 415 and the reactor inlet of the absorption tower 407. Infrared CO ₂ monitor 404 and mass flow meter 412 at the entrance of the absorption tower; among them, 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 infrared CO ₂ monitor at the entrance of the absorption tower 404 is used to monitor the concentration of CO ₂ in the mixed gas entering the absorption tower; the mass flow meter 412 is used to measure the amount of gas entering the absorption tower 407 and control parameters such as flow rate;

The inner diameter of the absorption tower 407 is 66mm, the packing height is 2.5m, and the maximum working pressure is 1MPa. Theta ring random packing is placed in the tower; the tower kettle, tower body, and tower top of the absorption tower 407 are respectively equipped with several temperature sensors 411 for Monitor the temperature at the corresponding position; the top of the absorption tower 407 is also equipped with an absorption tower outlet infrared CO ₂ monitor 405 for monitoring the concentration of CO ₂ in the mixed gas leaving the absorption tower;

The tower kettle outlet of the absorption tower 407 is connected to the tower top inlet of the desorption tower 408, and the connecting pipelines between the two are successively provided with a pressure transmitter 414, a drain valve, and a centrifugal pump 409; among them, the pressure transmitter is used for measurement The pressure of the rich liquid leaving the bottom of the absorption tower 407, the drain valve is used to discharge the slurry in the absorption tower 407;

The inner diameter of the desorption tower 408 is 66mm, the packing height is 2.5m, and the maximum working pressure is 0.5MPa. Theta ring random packing is placed in the tower; the upper and middle sections of the desorption tower are equipped with electric heating insulation with a heating power of 1kW. The desorption tower 408 is equipped with Several temperature sensors 411 are used to monitor the temperature at corresponding locations;

The top inlet of the desorption tower 408 is connected to the inlet of the water ring vacuum pump 406 to provide vacuum operating conditions for the desorption tower 408; a drain valve is provided at the outlet of the desorption tower 408, and the outlet is connected to the inlet of the metering pump 413. The two A liquid adding tank 410 is provided on the connecting pipeline; among them, the liquid adding tank 410 is used to pump the capture liquid into the absorption tower before the experiment starts and to replenish new capture liquid, and the metering pump 413 is used to transfer the capture liquid from the desorption tower. The collected liquid is pumped into the absorption tower;

The outlet of the metering pump 413 is connected to the top inlet of the absorption tower 407, and the connecting pipelines between the two are successively provided with a mass flow meter 412 and a metering pump 413; among them, the mass flow meter 412 is used to measure the flow rate of the collection liquid;

After the desorption tower 408 completes the desorption, the lean liquid returns to the absorption tower 407 through the metering pump; after multiple cycles, the absorbent separates the CO ₂ /N ₂ mixed gas.

This embodiment also examined the effect of gas-liquid ratio on separation, and the specific results are shown in Table 3.

Table 3. Separation test results with different gas-liquid ratios

In Table 3:

V _{in-mix gas} is the flow rate of mixed gas, is the gas-liquid ratio, Cout _-CO2 is the _CO2 concentration at the outlet of the absorption tower, ΔS _V is the circulation absorption volume, and eta is the _CO2 removal rate.

According to the data in Table 3, it can be seen that the adsorption separation of CO ₂ can be well achieved by adopting the technical solution of the present invention.

Claims (10)

1. A porous carbon dioxide absorbent, wherein the composition of the absorbent comprises, based on 100% of the total mass of the absorbent, 1% -10% of a solid phase, and 90% -99% of a liquid phase;

wherein the solid phase is a particulate enhancer;

the composition of the liquid phase comprises 5% -40% of a specific chemical agent and 60% -95% of water, based on 100% of the total mass of the liquid phase;

the specific chemical agent comprises one or more than two of imidazole substances, imidazole ionic liquid, piperazine substances and alcohol amine substances.

2. The absorbent of claim 1, wherein the particulate reinforcement comprises one or a combination of two or more of zinc carbonate, basic zinc carbonate, zinc oxide, zinc chloride, zinc hydroxide;

preferably, the solid phase is added in an amount of 1.5% -5%.

3. The absorbent of claim 1, wherein the specific chemical forms a network-like porous structure in water;

preferably, the specific chemical agent is added in an amount of 20% to 40% based on 100% of the total mass of the liquid phase.

4. The absorbent according to claim 1 or 3, wherein the imidazole-based substance comprises 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.

5. An absorbent according to claim 1 or 3, wherein the imidazole-based ionic liquid comprises one or a combination of two or more of 1-butyl-3-methylimidazolium tetrafluoroborate, 1-hexyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonimide salt.

6. The absorbent according to claim 1 or 3, wherein the piperazine-based substance comprises one or a combination of two or more of piperazine, 1- (2-aminoethyl) piperazine, N- (2-hydroxyethyl) piperazine, 1-methylpiperazine, and 2-methylpiperazine.

7. The absorbent according to claim 1 or 3, wherein the alcohol amine substance comprises one or a combination of two or more of diethanolamine, N-methyldiethanolamine, 2-amino-2-methyl-1-propanol, hydroxyethyl ethylenediamine, diethylenetriamine, N-methylcyclohexylamine, triethanolamine.

8. A method for separating carbon dioxide, wherein the method comprises CO using the porous carbon dioxide absorbent according to any one of claims 1 to 7 ₂ Capturing;

preferably, the separation method is to realize CO ₂ And N ₂ CO in a mixed gas of (a) ₂ Is separated from the other components.

9. Root of Chinese characterThe separation method according to claim 8, wherein CO is carried out ₂ The absorption temperature during trapping is 0-50 ℃;

preferably, CO is performed ₂ The absorption pressure during trapping is 0.1-1MPa.

10. The separation method according to claim 8, wherein the method further comprises capturing the CO under vacuum heating ₂ CO obtained thereafter ₂ Desorbing the rich liquid, and then regenerating the lean liquid for recycling;

preferably, the temperature of the heating is 60-100 ℃;

preferably, the absolute pressure of the vacuum is 80kPa or less.