Composition for CO2 absorbent, CO2 absorbent, preparation method of CO2 absorbent and method for capturing CO2 in shift gas

Abstract

The invention relates to the field of gas separation in shift gas, and discloses a composition for a CO2 absorbent, the CO2 absorbent, a preparation method of the CO2 absorbent and a method for capturing CO2 in the shift gas. Based on the total weight of the composition, the composition contains 10 wt%-30 wt% of a powder material and 70 wt%-90 wt% of a liquid material, the powder material is zirconium 1, 4-carboxybenzene; the liquid material is selected from at least one of silicone oil, polyethylene glycol and polypropylene glycol. The CO2 absorbent prepared from the composition for the CO2 absorbent, provided by the invention, has a good application prospect in the field of changing gas in gas. The method for capturing the CO2 in the shift gas is simple, the CO2 absorbent can be desorbed and recycled without heating, and the CO2 absorbent can be recycled under the condition of low energy consumption.

Description

Technical Field

[0001] The present invention relates to the field of gas separation in shift gas, and specifically relates to a composition for a CO2 absorbent, a CO2 absorbent and a preparation method thereof, and a method for capturing CO2 in shift gas. Background Art

[0002] The water gas shift reaction (WGS) is a standard reaction widely used in industrial hydrogen production and carbon monoxide removal, and the produced shift gas contains CO2 and H2.

[0003] Currently, in industry, propylene carbonate (PC), alkanolamine solution, and fixed-bed pressure swing adsorption (Fixed-bed PSA) process are mainly used for decarbonization of shift gas.

[0004] PC has a large CO2 absorption capacity, which is 4 times that of water under the same conditions, but the selectivity of PC for the CO2 / H2 system is relatively low.

[0005] Alkanolamine solution has a high CO2 absorption rate, but there are problems such as medium regeneration loss and equipment corrosion.

[0006] The fixed-bed pressure swing adsorption process adsorbs CO2 under high pressure and desorbs CO2 at a lower pressure, and high-purity H2 can be obtained, but multiple adsorption towers and a complex valve control system are required to realize the switching between adsorption towers, and the operating system is relatively complex.

[0007] In recent years, metal-organic framework (MOF) materials have shown great potential in the field of gas adsorption and separation due to their unique pore structure and high specific surface area.

[0008] MOF slurry combines the high adsorption capacity of MOF with the fluidity of liquid, combines the advantages of physical adsorption and chemical absorption, and the slurry can realize continuous absorption-desorption cycle operation, and has high efficiency in thermal integration, which is a new and potential separation technology.

[0009] However, most of the slurries currently used for separating the CO2 / H2 system need to be heated and depressurized to realize the regeneration of the slurry, resulting in a large amount of energy consumption in the gas regeneration unit.

[0010] UiO-66 is a common MOF material, which is composed of zirconium metal centers and organic ligands, and has excellent chemical stability and relatively high original hydrothermal stability. Research shows that UiO-66 exhibits excellent performance in adsorbing CO2, and its adsorption capacity is as high as 5.63 mmol / g at 1 bar and 298K. After UiO-66 is made into a slurry, it can efficiently capture CO2. However, this porous material is prone to water absorption, resulting in a great reduction in its CO2 absorption capacity.

[0011] The recovery process of using an organic medium N-methyldiethanolamine (MDEA) to replace the absorbent to reduce energy consumption was introduced in US20100898188. Although MDEA is a good solution for absorbing CO2, its regeneration temperature is relatively high and it is corrosive to pipelines.

[0012] Therefore, the key to the current technology is how to configure a porous slurry that is stable, has good structural performance, can reduce energy consumption in industrial applications, and reduce the pipeline maintenance cost, as well as the recovery process based on this slurry. Summary of the Invention

[0013] The purpose of the present invention is to overcome the problem of high energy consumption during the regeneration process of the slurry used for separating CO2 / H2 mixed gas in the prior art.

[0014] To achieve the above purpose, on the one hand, the present invention provides a composition for a CO2 absorbent. Based on the total weight of the composition, the composition contains 10 wt%-30 wt% of powder materials and 70 wt%-90 wt% of liquid materials;

[0015] The powder material is zirconium 1,4-carboxybenzene;

[0016] The liquid material is selected from at least one of silicone oil, polyethylene glycol, and polypropylene glycol; and the viscosity of the silicone oil at 25°C is 10-30 cP, and the average molecular weights of the polyethylene glycol and the polypropylene glycol are each independently 400-600.

[0017] On the second aspect, the present invention provides a method for preparing a CO2 absorbent, which includes:

[0018] Stirring and mixing the components in the composition described in the first aspect above to obtain the CO2 absorbent.

[0019] On the third aspect, the present invention provides a CO2 absorbent prepared by the method described in the second aspect above.

[0020] On the fourth aspect, the present invention provides a method for capturing CO2 in shift gas. This method is carried out in a capture system, which includes: an absorption unit, a desorption unit, and a regeneration unit connected in sequence through pipelines. The absorption unit includes an absorption tower, and the desorption unit includes a desorption tower; the method includes:

[0021] (1) Adsorbing the CO2 absorbent and the shift gas in the absorption tower to obtain a CO2-rich slurry;

[0022] (2) Desorbing the CO2-rich slurry in the desorption tower to obtain a recycled CO2 absorbent;

[0023] (3) Use the regeneration unit to introduce the recycled CO2 absorbent into the absorption tower to achieve the recycling of the CO2 absorbent;

[0024] The CO2 absorbent is the CO2 absorbent described in the foregoing third aspect.

[0025] The CO2 absorbent provided by the present invention has excellent CO2 capture effect and is very suitable for application in the capture of CO2 in shift gas to achieve the separation of CO2 and H2.

[0026] Adopting the operation of capturing CO2 in the shift gas provided by the present invention is simple, enables high separation efficiency of CO2 and H2 in the shift gas, and can achieve the regeneration of the CO2 absorbent without heating, which can greatly reduce energy consumption. Description of the Drawings

[0027] Figure 1 is the flow chart of the capture system in the present invention;

[0028] Figure 2 is the solubility of CO2 and H2 in the CO2 absorbent prepared in Preparation Example 1 of the present invention at 30°C.

[0029] Description of the Reference Numerals

[0030] T101, absorption tower; T102, desorption tower; P101, first centrifugal pump; P102, second centrifugal pump; E101, heat exchanger; S101, shift gas; S102, CO2-rich slurry; S103, recycled CO2 absorbent; S104, condensed recycled CO2 absorbent; S105, top gas of the desorption tower; S106, unabsorbed shift gas. Detailed Embodiments

[0031] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0032] As described above, the first aspect of the present invention provides a composition for a CO2 absorbent. Based on the total weight of the composition, the composition contains 10 wt% - 30 wt% of powder and 70 wt% - 90 wt% of liquid material;

[0033] The powder is zirconium 1,4-carboxybenzene;

[0034] The liquid material is selected from at least one of silicone oil, polyethylene glycol, and polypropylene glycol; and the silicone oil has a viscosity of 10 - 30 cP at 25°C, and the average molecular weights of the polyethylene glycol and the polypropylene glycol are each independently 400 - 600.

[0035] Preferably, the specific surface area of the zirconium 1,4 - carboxybenzene is 600 - 750 m 2 / g. The inventors of the present invention have found that in this preferred case, the obtained CO2 absorbent has better absorption performance for CO2.

[0036] Preferably, the liquid material is dimethyl silicone oil.

[0037] Preferably, based on the total weight of the composition, the composition contains 25 wt% - 30 wt% of powder material and 75 wt% - 80 wt% of liquid material. The inventors of the present invention have found that in this preferred case, the obtained CO2 absorbent has better capture effect on CO2.

[0038] As described above, the second aspect of the present invention provides a method for preparing a CO2 absorbent, the method comprising:

[0039] Stirring and mixing the components in the composition described in the first aspect above to obtain the CO2 absorbent.

[0040] Preferably, the conditions for the stirring and mixing include: the temperature is 20 - 30°C.

[0041] As described above, the third aspect of the present invention provides a CO2 absorbent prepared by the method described in the second aspect above.

[0042] As described above, the fourth aspect of the present invention provides a method for capturing CO2 in shift gas, the method being carried out in a capture system, the system comprising: an absorption unit, a desorption unit, and a regeneration unit connected in sequence through pipelines, the absorption unit including an absorption tower, and the desorption unit including a desorption tower; the method comprising:

[0043] (1) Adsorbing the CO2 absorbent and the shift gas in the absorption tower to obtain a CO2 - rich slurry;

[0044] (2) Desorbing the CO2 - rich slurry in the desorption tower to obtain a recycled CO2 absorbent;

[0045] (3) Using the regeneration unit to introduce the recycled CO2 absorbent into the absorption tower to achieve the recycling use of the CO2 absorbent;

[0046] The CO2 absorbent is the CO2 absorbent described in the third aspect above.

[0047] It should be noted that in the present invention, the absorption tower adopts a gas-phase feeding method to introduce the shifted gas into the absorption tower.

[0048] Preferably, the feeding pressure of the absorption tower is 2 - 4 MPa, and the feeding temperature is 20 - 40 °C.

[0049] In the present invention, the rich CO₂ slurry obtained in step (1) is discharged from the bottom of the absorption tower to enter the desorption tower.

[0050] Preferably, the operating conditions for discharging the rich CO₂ slurry from the bottom of the absorption tower include: a pressure of 1 - 3 MPa and a temperature of 20 - 40 °C.

[0051] Preferably, the feeding pressure of the desorption tower is 1 - 3 MPa, and the temperature is 20 - 40 °C.

[0052] In the present invention, the recycled CO₂ absorbent obtained in step (2) is discharged from the bottom of the desorption tower to enter the regeneration unit.

[0053] Preferably, the pressure of the liquid withdrawn from the bottom of the desorption tower (i.e., the recycled CO₂ absorbent) is 10 - 20 kPa, and the temperature is 20 - 40 °C.

[0054] Preferably, in step (1), the molar ratio of CO₂ to H₂ in the shifted gas is 1:1 - 1.5.

[0055] Preferably, in step (1), at 20 °C, the volume ratio of the shifted gas to the CO₂ absorbent is 100 - 110:1.

[0056] Preferably, in step (1), the conditions for the adsorption treatment include: a pressure of 2 - 4 Mpa and a temperature of 20 - 40 °C.

[0057] Preferably, in step (2), the conditions for the desorption treatment include: a pressure of 1 - 3 Mpa and a temperature of 20 - 40 °C.

[0058] According to a preferred specific embodiment, the regeneration unit includes a first centrifugal pump connected to the bottom of the desorption tower;

[0059] The first centrifugal pump is used to transport the recycled CO₂ absorbent to the absorption tower to achieve the recycling of the CO₂ absorbent.

[0060] Preferably, the regeneration unit further includes a heat exchanger connected between the first centrifugal pump and the absorption tower;

[0061] The heat exchanger is used for condensing the circulated CO2 absorbent so as to enable the circulated CO2 absorbent to flow into the absorption tower for recycling.

[0062] Preferably, the conditions for the condensation treatment include: a temperature of 20 - 30 °C.

[0063] Preferably, the regeneration unit further includes a second centrifugal pump connected to the top of the desorption tower, and the second centrifugal pump is used to provide a vacuum state for the desorption tower.

[0064] Preferably, the pressure of the exhaust gas at the top of the desorption tower is 10 - 20 KPa, and the temperature is 20 - 40 °C.

[0065] Preferably, the capture system further includes a gas-liquid separation unit. The gas-liquid separation unit includes a gas-liquid separator connected to the top of the absorption tower. The gas-liquid separator is used to separate the residual liquid phase in the unconverted gas discharged from the top of the absorption tower that has not been absorbed, so as to obtain dry recycled unconverted gas.

[0066] It should be noted that in the present invention, the dry recycled unconverted gas can be selectively re-introduced into the absorption tower for absorption treatment to further improve the resource utilization efficiency, or can be directly discharged.

[0067] Preferably, the pressure of the exhaust gas at the top of the absorption tower is 1 - 3 MPa, and the temperature is 20 - 40 °C.

[0068] The following will describe in detail the method and the capture system for capturing CO2 in the unconverted gas provided by the present invention with reference to the accompanying drawings.

[0069] Figure 1 This is the flow chart of the capture system in the present invention:

[0070] From Figure 1 it can be seen that the capture system includes: an absorption unit, a desorption unit, and a regeneration unit that are sequentially connected through pipelines; the absorption unit includes an absorption tower T101; the desorption unit includes a desorption tower T102; the regeneration unit includes a first centrifugal pump P101 connected to the bottom of the desorption tower, a second centrifugal pump P102 connected to the top of the desorption tower, and a heat exchanger E101 connected between the centrifugal pump P101 and the absorption tower T101; the method for capturing CO2 in the unconverted gas is carried out in the above system, including:

[0071] The shifted gas S101 enters the absorption tower T101 and undergoes an adsorption process with the CO2 absorbent filled in the absorption tower T101 to obtain a CO2-rich slurry S102; the CO2-rich slurry S102 flows from the top of the absorption tower T101 into the desorption tower T102, and after undergoing a desorption process, a recycled CO2 absorbent S103 is obtained; the recycled CO2 absorbent S103 flows out from the bottom of the desorption tower T102 (the second centrifugal pump P102 is used to provide a vacuum degree for the desorption tower), and after being transported by the first centrifugal pump P101 to the heat exchanger E101 for condensation treatment, a condensed recycled CO2 absorbent S104 is obtained to enable the recycled CO2 absorbent to flow into the absorption tower for recycling; the desorbed top gas S105 flows out from the top of the desorption tower T102; the shifted gas S106 not absorbed by the absorption tower T101 flows out from the top of the absorption tower T101, and after passing through a gas-liquid separator (not shown in the figure) to absorb the residual liquid phase therein, a dry recycled shifted gas is obtained and directly discharged.

[0072] The present invention will be described in detail below through examples.

[0073] In the following examples, unless otherwise specified, all raw materials used are from commercial purchases and self-produced treatments.

[0074] Powder: zirconium 1,4-benzenedicarboxylate (UiO-66), specific surface area of 705 m 2 / g, prepared according to the reference DOI10.1002 / aic.15837.

[0075] Liquid materials:

[0076] Liquid material I-1: dimethyl silicone oil, viscosity at 25 °C is 20 cP, purchased from Shanghai Macklin Biochemical Technology Co., Ltd., product number S817597.

[0077] Liquid material I-2: polyethylene glycol 600, average molecular weight of 600, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., product number P615532.

[0078] Liquid material DI-1: dimethyl silicone oil, viscosity at 25 °C is 100 cP, purchased from Shanghai Macklin Biochemical Technology Co., Ltd., product number D817599.

[0079] In the following examples of the present invention, different raw material formulations are applied. Unless otherwise specified, the raw material dosages are in parts by weight, and each part by weight represents 10 g.

[0080] Preparation Example 1

[0081] This preparation example is used to illustrate the preparation of a CO2 absorbent according to the formulation in Table 1 and by the following method: The components in the composition of the CO2 absorbent were stirred and mixed (at a temperature of 25 °C) to obtain a CO2 absorbent, named Absorbent I-1.

[0082] Preparation Examples 2 - 3, Comparative Preparation Example 1, and Comparative Preparation Example 2 were all carried out in a similar manner to Preparation Example 1, except that: the formulations were different, as specifically shown in Table 1.

[0083] Table 1

[0084]

[0085] In the present invention, unless otherwise specified, the following examples all use the Figure 1 trapping system as shown, and the composition of the shifted gas is: 44.85 mol% CO2 + 55.15 mol% H2; the adsorption treatment was carried out at 20 °C for 10 min.

[0086] Example 1

[0087] This example is used to illustrate the method of trapping CO2 in the shifted gas according to the following steps:

[0088] (1) Absorbent I-1 (obtained in the aforementioned preparation example) and the shifted gas were subjected to an adsorption treatment in the absorption tower to obtain a CO2-rich slurry;

[0089] (2) The CO2-rich slurry was introduced into the desorption tower through the bottom of the absorption tower for desorption treatment to obtain a recycled CO2 absorbent;

[0090] (3) The recycled CO2 absorbent flowed out from the bottom of the desorption tower, was transported to a heat exchanger through a first centrifugal pump for condensation treatment to obtain a condensed recycled CO2 absorbent, so as to realize the circulation of the recycled CO2 absorbent to the absorption tower for recycling use;

[0091] The volume ratio of the shifted gas to Absorbent I-1 was 105:1 (the volume of Absorbent I-1 was 5.84 Nm 3 / h);

[0092] The pressure of the adsorption treatment was 2 Mpa and the temperature was 20 °C;

[0093] The pressure of the exhaust gas at the top of the absorption tower was 2 MPa and the temperature was 20 °C;

[0094] The pressure of the CO2-rich slurry discharged from the bottom of the absorption tower was 2 MPa and the temperature was 20 °C;

[0095] The feed pressure of the desorption tower was 2 MPa and the temperature was 25 °C;

[0096] The pressure for the desorption treatment is 2 Mpa and the temperature is 25 °C;

[0097] The pressure of the bottom product of the desorption column is 10 kPa and the temperature is 21 °C;

[0098] The pressure of the exhaust gas at the top of the desorption column is 10 kPa and the temperature is 21 °C;

[0099] Condensation treatment: The temperature is 20 °C.

[0100] Example 2

[0101] This example is carried out in a similar method to Example 1, the difference is that: the absorbent I-2 in the foregoing Preparation Example is used to replace the absorbent I-1 in Example 1.

[0102] Example 3

[0103] This example is carried out in a similar method to Example 1, the difference is that: the absorbent I-3 in the foregoing Preparation Example is used to replace the absorbent I-1 in Example 1.

[0104] Example 4

[0105] This example is carried out in a similar method to Example 1, the difference is that: on the premise of keeping the volume dosage of the absorbent I-1 unchanged, the volume ratio of the shift gas to the absorbent I-1 is adjusted to 41.38:1.

[0106] Comparative Example 1

[0107] This comparative example is carried out in a similar method to Example 1, the difference is that: the absorbent DI-1 in the foregoing Preparation Example is used to replace the absorbent I-1 in Example 1.

[0108] Comparative Example 2

[0109] This comparative example is carried out in a similar method to Example 1, the difference is that: the absorbent DI-2 in the foregoing Preparation Example is used to replace the absorbent I-1 in Example 1.

[0110] Test Example

[0111] 1. At 30 °C, measure the solubility of CO2 and H2 in the CO2 absorbent prepared in the foregoing Preparation Example 1. The specific operation is as follows:

[0112] Place the CO2 absorbent prepared in Preparation Example 1 in a gem cell. At 30 °C, introduce CO2 with a purity of 99.99% and H2 with a purity of 99.99% into the gem cell respectively. After the reaction reaches equilibrium, the calculation system connected to the pressure sensor automatically collects data, and the solubility of the CO2 absorbent in CO2 and H2 is measured through the pressure drop. The results are asFigure 2 As shown in Figure 2 the abscissa P e corresponds to the equilibrium pressure, and the ordinate S v corresponds to the absorption capacity):

[0113] Through Figure 2 it can be seen that the CO2 absorbent provided by the present invention has a good absorption capacity for CO2 at 30°C, while the absorption capacity for H2 is extremely low.

[0114] 2. The separation experiment results in each of the foregoing examples are processed by the following method:

[0115] The composition of the shift gas and the equilibrium gas (referring to the gas when the shift gas is absorbed to reach absorption equilibrium) is analyzed by a UP78900 type chromatograph;

[0116] The adsorption amounts of CO2 (n1) and H2 (n2) in the separation medium (CO2 absorbent) (unit: mol) are calculated by material balance.

[0117] The separation factor β measures the selectivity of CO2 in the adsorption process (that is, the separation ability of the CO2 absorbent for CO2 / H2), and its definition is:

[0118]

[0119] In formula (1), x1 and x2 are the molar compositions of CO2 and H2 in the separation medium phase after adsorption equilibrium; y1 and y2 are the molar compositions of CO2 and H2 in the equilibrium gas.

[0120] The separation factors in each of the above examples are solved, and the results are shown in Table 2.

[0121] Table 2

[0122] Separation factor Example 1 229.66 Example 2 223.36 Example 3 226.54 Example 4 135.58 Comparative Example 1 30.34 Comparative Example 2 44.75

[0123] From the above results, it can be seen that the CO2 absorbent obtained by using the CO2 absorbent composition of the present invention has excellent separation ability for the CO2 / H2 mixed gas, and the CO2 absorbent provided by the present invention can be recycled without heating, overcoming the problem of high energy consumption in the regeneration process of the traditional slurry for separating CO2 / H2 mixed gas.

[0124] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A composition for a CO2 absorbent, characterized in that, Based on the total weight of the composition, the composition contains 10 wt%-30 wt% of powder material and 70 wt%-90 wt% of liquid material; The powder material is zirconium 1,4-carboxybenzene; The liquid material is selected from at least one of silicone oil, polyethylene glycol and polypropylene glycol; and the viscosity of the silicone oil at 25 °C is 10-30 cP, and the average molecular weights of the polyethylene glycol and the polypropylene glycol are each independently 400-600.

2. The composition according to claim 1, wherein The specific surface area of the zirconium 1,4-carboxybenzene is 600-750 m2 / g; And / or, the liquid material is dimethyl silicone oil.

3. The composition according to claim 1 or 2, characterized in that, Based on the total weight of the composition, the composition contains 25 wt%-30 wt% of powder material and 75 wt%-80 wt% of liquid material.

4. A method for preparing a CO2 absorbent, characterized in that, The method includes: Stirring and mixing the components in the composition according to any one of claims 1-3 to obtain the CO2 absorbent.

5. A CO2 absorbent prepared by the method according to claim 4.

6. A method for capturing CO2 in shift gas, characterized in that, The method is carried out in a capture system, which includes: an absorption unit, a desorption unit and a regeneration unit connected in sequence through pipelines, the absorption unit includes an absorption tower, and the desorption unit includes a desorption tower; the method includes: (1) Adsorbing the CO2 absorbent and the shifted gas in the absorption tower to obtain a CO2-rich slurry; (2) Desorbing the CO2-rich slurry in the desorption tower to obtain a recycled CO2 absorbent; (3) Using the regeneration unit to introduce the recycled CO2 absorbent into the absorption tower to realize the recycling of the CO2 absorbent; The CO2 absorbent is the CO2 absorbent according to claim 5.

7. The method according to claim 6, wherein In step (1), the molar ratio of CO2 to H2 in the shifted gas is 1:1-1.5; And / or, in step (1), at 20 °C, the volume ratio of the shifted gas to the CO2 absorbent is 100-110:

1.

8. The method according to claim 6 or 7, characterized in that, In step (1), the conditions for the adsorption treatment include: a pressure of 2-4 Mpa and a temperature of 20-40 °C; And / or, in step (2), the conditions for the desorption treatment include: a pressure of 1-3 Mpa and a temperature of 20-40 °C.

9. The method according to any one of claims 6 - 8, characterized in that, The regeneration unit includes a first centrifugal pump connected to the bottom of the desorption tower; The first centrifugal pump is used to transport the recycled CO2 absorbent to the absorption tower to realize the recycling of the CO2 absorbent.

10. The method according to claim 9, wherein The regeneration unit further includes a heat exchanger connected between the first centrifugal pump and the absorption tower; The heat exchanger is used to condense the recycled CO2 absorbent to realize the circulation of the recycled CO2 absorbent to the absorption tower for recycling use.

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