Absorbent for carbon dioxide capture

Abstract

The invention discloses an absorbent for carbon dioxide capture. The absorbent is a binary anhydrous phase change absorbent composed of functionalized ionic liquid triethylene tetramine-3-bromophenolate and an alcohol solvent polyethylene glycol 200, the mass fraction ratio of the functionalized ionic liquid triethylene tetramine-3-bromophenolate to the alcohol solvent polyethylene glycol 200 is (1: 9)-(5: 5), and the corresponding absorption load is 0.97-2.37 mol CO2 / kg absorbent. According to the invention, the structural adjustability of the ionic liquid is fully utilized, and the multi-amino functionalized ionic liquid with high absorption load is designed and synthesized by adjusting the types of anion and cation donors.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon dioxide capture, and in particular relates to an absorbent for carbon dioxide capture. Background Art

[0002] Carbon dioxide capture, utilization and storage (CCUS) technology has been considered as one of the effective ways to achieve large-scale greenhouse gas emission reductions. Chemical absorption is currently the most widely used and mature carbon capture technology.

[0003] Absorbents represented by amine solutions have the advantage of high technical maturity, but they also have the defects of low absorption load and high regeneration energy consumption, which greatly increases the operating cost of carbon capture.

[0004] For example, a 30% by mass aqueous solution of monoethanolamine can capture 0.5 mol of carbon dioxide per mol. The regeneration energy consumption is as high as 3.6~4.5GJ / tCO2, accounting for more than 70% of the carbon capture cost and is also the main obstacle to its large-scale application.

[0005] Anhydrous phase change absorbents have great energy-saving potential due to their low energy consumption properties and are considered to be a new type of CO2 absorbent with promising application development prospects. This type of absorbent achieves anhydrous solvation, which can effectively reduce latent heat; at the same time, the characteristics of the phase change absorbent will gradually change from the homogeneous phase before absorption to liquid-liquid phase separation or liquid-solid phase separation as the reaction proceeds, and the absorbed CO2 is enriched in one phase (rich phase). During regeneration, only the rich phase needs to be desorbed, which reduces the desorption volume of the absorbent and thus reduces the desorption reaction heat.

[0006] Ionic liquids (ILs) are room-temperature molten salts composed of anions and cations. They have good chemical and thermal stability, as well as structural designability, and are considered to be new green chemical absorbents that can be used for CO2 capture.

[0007] On the basis of conventional ionic liquids, functionalized ionic liquids with corresponding functions are obtained by adjusting the combination of anions and cations or introducing specific functional groups; however, the viscosity of ionic liquids is relatively high at room temperature, which is very unfavorable for mass transfer with CO2, thus affecting the absorption and desorption of CO2, as well as large-scale industrial applications. Summary of the invention

[0008] The present invention aims at solving the deficiencies in the prior art and provides an absorbent for capturing carbon dioxide.

[0009] The technical solution of the present invention is: an absorbent for carbon dioxide capture, the absorbent is a binary anhydrous phase change absorbent composed of functionalized ionic liquid triethylenetetramine-3-bromophenolate and alcohol solvent polyethylene glycol 200, the mass fraction ratio of the functionalized ionic liquid triethylenetetramine-3-bromophenolate and the alcohol solvent polyethylene glycol 200 is 1:9~5:5, and the corresponding absorption load is 0.97~2.37molCO2 / kg 吸收剂 .

[0010] Furthermore, the binary anhydrous phase change absorbent is used to absorb pure CO2 gas. It is homogeneous before absorbing CO2, and gradually becomes a liquid-solid two-phase phase in the process of absorbing CO2 until saturation, and CO2 is enriched in the lower rich phase solid; the pure CO2 gas introduction flow rate is 100~140mL / min; CO2 gas is introduced into the binary anhydrous phase change absorbent for absorption, and regeneration is achieved by heating in an oil bath after absorption saturation.

[0011] Furthermore, CO2 gas is introduced into the binary anhydrous phase change absorbent, the absorption temperature is 25-45°C, and the corresponding absorption load is 1.91-2.37 molCO2 / kg 吸收剂 .

[0012] Furthermore, after the binary anhydrous phase-change absorbent reaches saturation, the volume of the lower rich phase solid accounts for 53.2% of the total volume.

[0013] Furthermore, the binary anhydrous phase change absorbent is regenerated by heating in an oil bath after absorption saturation, the regeneration temperature is 120° C., the regeneration time is 90 min, and the regeneration efficiency is 82%.

[0014] Furthermore, the binary anhydrous phase change absorbent is regenerated by heating in an oil bath after absorption saturation, the regeneration temperature is 120° C., the regeneration time is 90 min, and the regeneration efficiency after 5 cycles is 72-82%.

[0015] The functionalized ionic liquid triethylenetetramine-3-bromophenolate is used as the main absorbent, and the alcohol solvent polyethylene glycol 200 is used as an anhydrous auxiliary solvent. The liquid-solid phase change of the absorbent is achieved by regulating the mass fraction ratio of the functionalized ionic liquid triethylenetetramine-3-bromophenolate and the alcohol solvent polyethylene glycol 200 and the CO2 load.

[0016] The absorbent has the advantages of both the high CO2 absorption load of functionalized ionic liquids and the energy-saving advantages of anhydrous phase change solvents. After absorbing CO2, liquid-solid phase separation occurs and the product is easily separated and regenerated, thereby achieving the development goal of an absorbent with low viscosity, high absorption load and low regeneration energy consumption, providing new ideas for the research of efficient and low-consumption carbon capture technology.

[0017] The beneficial technical effect of the present invention is that the structurally adjustable properties of ionic liquids are fully utilized, and by adjusting the types of anion and cation donors, a multi-amino functionalized ionic liquid [TETAH][3-Br-PhO] with a high absorption load (absorption capacity of 1.72 molCO2 / kg 离子液体 ).

[0018] The present invention overcomes the defect of high viscosity of polyamino functionalized ionic liquids, uses alcohol solvent PEG200 as an anhydrous cosolvent, and constructs a composite having low viscosity (viscosity of 33.43-444.6 mPa∙s) and high absorption load (absorption load of 0.97-2.37 molCO2 / kg 吸收剂 ) as the dominant multi-amino functionalized ionic liquid binary anhydrous phase change absorbent [TETAH][3-Br-PhO]-PEG200.

[0019] The present invention possesses the excellent energy-saving characteristics of liquid-solid phase change absorbent, effectively reducing the volume of the regeneration phase (the volume of the lower rich phase solid accounts for 53.2-90.3% of the total volume), thereby reducing the regeneration energy consumption of the absorbent; at the same time, since the lower rich phase solid is in powder form, it is beneficial to the efficient separation of the product and the solvent, and has good regeneration performance (the regeneration efficiency of 5 cycles is 72-82%).

[0020] The present invention breaks through the defects of traditional organic amines and ionic liquids. Since [TETAH][3-Br-PhO] has multiple primary amine and secondary amine groups, it ensures that the absorbent has a higher absorption load. The addition of PEG200 with lower viscosity ensures the low viscosity characteristics of the absorbent and strengthens the mass transfer effect between the absorbent and CO2. The constructed [TETAH][3-Br-PhO]-PEG200 increases the diversity of CO2 capture by ionic liquids and provides a new approach and method for green carbon capture technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the CO2 absorption performance of the multi-amino functionalized ionic liquid binary anhydrous phase change absorbent of the present invention with different mass fraction ratios.

[0022] Figure 2 These are actual photos of samples in which the mass fraction ratio of the functionalized ionic liquid to polyethylene glycol 200 of the present invention is 3:7, wherein a-before absorption, b-after saturation, and c-after standing.

[0023] Figure 3 It is a regeneration performance effect diagram of the multi-amino functionalized ionic liquid binary anhydrous phase change absorbent of the present invention at different regeneration temperatures and times.

[0024] Figure 4This is a diagram showing the recycling performance of the multi-amino functionalized ionic liquid binary anhydrous phase change absorbent of the present invention. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0026] A multi-amino functionalized ionic liquid binary anhydrous phase-change absorbent for carbon dioxide capture is composed of functionalized ionic liquid triethylenetetramine-3-bromophenolate ([TETAH][3-Br-PhO]) and alcohol solvent polyethylene glycol 200 (PEG200), wherein the mass fraction ratio of triethylenetetramine-3-bromophenolate ([TETAH][3-Br-PhO]) and polyethylene glycol 200 (PEG200) is 1:9-5:5 (most preferably 3:7).

[0027] Formula I is the chemical formula of the functionalized ionic liquid triethylenetetramine-3-bromophenolate ([TETAH][3-Br-PhO]):

[0028] Example 1 provides a multi-amino functionalized ionic liquid binary anhydrous phase change absorbent for carbon dioxide capture, which is composed of functionalized ionic liquid triethylenetetramine-3-bromophenolate ([TETAH][3-Br-PhO]) and alcohol solvent polyethylene glycol 200 (PEG200), wherein the mass fraction of triethylenetetramine-3-bromophenolate is 20%.

[0029] Example 2 provides a multi-amino functionalized ionic liquid binary anhydrous phase change absorbent for carbon dioxide capture, which is composed of functionalized ionic liquid triethylenetetramine-3-bromophenolate ([TETAH][3-Br-PhO]) and alcohol solvent polyethylene glycol 200 (PEG200), wherein the mass fraction of triethylenetetramine-3-bromophenolate is 30%.

[0030] Comparative Example 1 provides a functionalized ionic liquid triethylenetetramine-3-bromophenolate ([TETAH][3-Br-PhO]) absorbent for carbon dioxide capture, wherein the mass fraction of triethylenetetramine-3-bromophenolate is 100%.

[0031] Comparative Example 2 provides a conventional organic amine monoethanolamine (MEA) absorbent for carbon dioxide capture, wherein the mass fraction of monoethanolamine is 30%.

[0032] Experimental Example 1: Multi-amino functionalized ionic liquid binary anhydrous phase change absorbent [TETAH][3-Br-PhO]-PEG200 was used for CO2 capture.

[0033] In this experimental example, the CO2 absorption performance and phase separation effect of the multi-amino functionalized ionic liquid binary anhydrous phase change absorbent of Example 1 and Example 2 were tested at 25°C.

[0034] The specific steps are as follows: according to the corresponding mass fraction ratio, take 20g of [TETAH][3-Br-PhO]-PEG200 absorbent with a total mass, pour them into the bubbling absorption tube respectively, place them in a constant temperature water bath at 25℃ for insulation and experimental temperature stabilization, then introduce CO2 gas to start the absorption experiment (CO2 inlet flow rate is 120mL / min), and when the CO2 gas flow rate introduced is consistent with the CO2 gas flow rate at the outlet, the absorption is considered saturated. After saturation, remove the bubbling absorption bottle and let it stand for 24h to observe the phase separation.

[0035] Take 20 g of each of the multi-amino functionalized ionic liquid binary anhydrous phase change absorbent ([TETAH][3-Br-PhO]-PEG200) in Example 1 and Example 2 and the functionalized ionic liquid triethylenetetramine-3-bromophenolate ([TETAH][3-Br-PhO]) absorbent in Comparative Example 1, place them in bubbling absorption tubes, keep them in a water bath at 25°C to a constant temperature, and then pass 120 mL / min of CO2 gas to carry out an absorption experiment until the absorption is saturated.

[0036] like Figure 1 The figure shows the CO2 absorption performance of the multi-amino functionalized ionic liquid binary anhydrous phase change absorbent ([TETAH][3-Br-PhO]-PEG200) with different mass fractions. Figure 1 It can be seen that [TETAH][3-Br-PhO]-PEG200 with different mass fraction ratios have obvious differences in CO2 absorption performance. With the increase of the content of multi-amino functionalized ionic liquid, the CO2 absorption load shows a trend of first increasing and then decreasing. In the [TETAH][3-Br-PhO]-PEG200 absorbent, when the mass fraction ratio of [TETAH][3-Br-PhO] to PEG200 is 3:7, the CO2 absorption load is the largest, which is 2.37 molCO2 / kg 吸收剂 .

[0037] like Figure 2 The following are the phase separation and physical photos of the multi-amino functionalized ionic liquid binary anhydrous phase change absorbent ([TETAH][3-Br-PhO]-PEG200) of Example 2 before and after CO2 absorption and after saturated standing. Figure 2 (a) is the phase separation of the multi-amino functionalized ionic liquid binary anhydrous phase change absorbent before absorbing CO2. Figure 2(b) is the phase separation of the multi-amino functionalized ionic liquid binary anhydrous phase change absorbent after saturation with CO2. Figure 2 (c) is the phase separation of the polyamino functionalized ionic liquid binary anhydrous phase change absorbent after absorbing CO2 saturated and standing. Figure 2 It can be seen that the fresh absorbent is in liquid phase before absorption, and solid phase gradually precipitates as the CO2 absorption reaction proceeds. After saturated CO2 absorption and standing, the liquid-solid phase separation becomes more obvious.

[0038] Experimental Example 2: Regeneration performance of multi-amino functionalized ionic liquid binary anhydrous phase change absorbent [TETAH][3-Br-PhO]-PEG200.

[0039] Take the [TETAH][3-Br-PhO]-PEG200 absorbent in Example 2, and carry out the CO2 absorption experiment again according to the method in Experimental Example 1. The lower solid phase of the absorbent after absorbing CO2 is saturated and allowed to stand is separated and regenerated by thermal desorption method (oil bath heating). The experimental conditions are different regeneration temperatures (80~120℃) and times (30~90min) to obtain the optimal regeneration conditions of the absorbent.

[0040] like Figure 3 The figure shows the regeneration performance effect of the multi-amino functionalized ionic liquid binary anhydrous phase change absorbent of Example 2 at different regeneration temperatures and times. Figure 3 It can be seen that higher regeneration temperature and longer regeneration time are more conducive to the regeneration of the absorbent.

[0041] After heating at 80°C for 30 minutes, the regeneration efficiency of the absorbent was only 18%. After the heating time was extended to 90 minutes, the regeneration efficiency of the absorbent was 52%. When the temperature was raised to 120°C and the heating time was extended to 90 minutes, the regeneration efficiency of the absorbent was increased to 82%. This shows that the multi-amino functionalized ionic liquid binary anhydrous phase change absorbent in the present invention has good regeneration performance and has a prospect for recycling.

[0042] Experimental Example 3: Recycling performance of multi-amino functionalized ionic liquid binary anhydrous phase change absorbent [TETAH][3-Br-PhO]-PEG200.

[0043] Due to the large amount of industrial flue gas generated, the recycling of the absorbent is an important factor in evaluating whether it is excellent and cost-saving. Take the [TETAH][3-Br-PhO]-PEG200 absorbent in Example 2, and perform the CO2 absorption experiment again according to the method in Experimental Example 1. The lower solid phase of the absorbent after absorbing CO2 is saturated and allowed to stand is separated and regenerated by thermal desorption, and the regeneration temperature is 120°C and the regeneration time is 90 minutes. Then the regenerated absorbent is cooled and moved to a constant temperature water bath at 25°C; and the CO2 absorption experiment is performed again according to the method in Experimental Example 1. The absorption-regeneration cycle is repeated 5 times to obtain the recycling performance of the absorbent.

[0044] like Figure 4 The figure shows the recycling performance effect of the multi-amino functionalized ionic liquid binary anhydrous phase change absorbent of Example 2 under the conditions of a regeneration temperature of 120°C and a regeneration time of 90 minutes. Figure 4 It can be seen that the recycling efficiency of the absorbent decreases with the increase of the frequency of use. After the [TETAH][3-Br-PhO]-PEG200 absorbent was recycled for 5 times, the regeneration efficiency decreased from the initial 82% to 72%. That is, the absorbent has good recycling performance and has certain potential for industrial application.

[0045] The polyamino-energized ionic liquid [TETAH][3-Br-PhO] was synthesized by the inventors themselves. The above description is only a preferred embodiment of the present invention, not all embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but only represents selected embodiments of the present invention. That is, equivalent changes and modifications made according to the scope of the present invention and the contents of the specification should still be within the scope of the present invention.

Claims

1. An absorbent for carbon dioxide capture, characterized in that The absorbent is a binary anhydrous phase-change absorbent composed of functionalized ionic liquid triethylenetetramine-3-bromophenolate and alcohol solvent polyethylene glycol 200, wherein the mass fraction ratio of the functionalized ionic liquid triethylenetetramine-3-bromophenolate and the alcohol solvent polyethylene glycol 200 is 1:9-5:5, and the corresponding absorption load is 0.97-2.37 molCO2 / kg 吸收剂 .

2. The absorbent for carbon dioxide capture according to claim 1, characterized in that The binary anhydrous phase change absorbent is used to absorb pure CO2 gas. It is a homogeneous phase before absorbing CO2. In the process of absorbing CO2 until saturation, it gradually becomes a liquid-solid two-phase phase, and CO2 is enriched in the lower rich phase solid; the pure CO2 gas introduction flow rate is 100~140mL / min; CO2 gas is introduced into the binary anhydrous phase change absorbent for absorption, and after absorption saturation, it is regenerated by heating in an oil bath.

3. The absorbent for carbon dioxide capture according to claim 2, characterized in that The CO2 gas is introduced into the binary anhydrous phase change absorbent, the absorption temperature is 25-45°C, and the corresponding absorption load is 1.91-2.37 molCO2 / kg 吸收剂 .

4. The absorbent for carbon dioxide capture according to claim 2, characterized in that After the binary anhydrous phase-change absorbent is saturated with absorption, the volume of the lower rich phase solid accounts for 53.2% of the total volume.

5. The absorbent for carbon dioxide capture according to claim 4, characterized in that After the binary anhydrous phase-change absorbent reaches saturation, it is regenerated by heating in an oil bath. The regeneration temperature is 120° C., the regeneration time is 90 min, and the regeneration efficiency is 82%.

6. The absorbent for carbon dioxide capture according to claim 5, characterized in that The binary anhydrous phase change absorbent is regenerated by heating in an oil bath after absorption saturation, the regeneration temperature is 120° C., the regeneration time is 90 min, and the regeneration efficiency after 5 cycles is 72-82%.

Images