Novel CO2 trapping phase change absorbent

Abstract

The invention provides a novel CO2 capture phase change absorbent, and belongs to the technical field of absorbents, an amino-azolyl bifunctional ionic liquid-organic alcohol-water ternary phase change system is adopted, an ionic liquid containing an active group is adopted as a main absorbent, propyl alcohol is adopted as a phase splitting agent, and finally water is added as a solvent to reduce the viscosity of a rich-phase solution. The absorption load and the absorption capacity can be ensured, the hydrolysis conversion of carbamate can be promoted, and the defect of low regeneration efficiency is overcome; the phase change absorbent prepared by the method can still be used after multiple thermal desorption, the absorbent has good thermal stability and has good economic advantages in reusability, and the system can effectively make up for the defects of the current phase change absorbent in industrial popularization.

Description

Technical Field

[0001] The invention belongs to the technical field of absorbents and relates to a novel CO2 capture phase-change absorbent. Background Art

[0002] The existing amino-functionalized ionic liquid (FILs) phase change system is a ternary phase change system consisting of FILs / ethanol / water. The system uses ethanol with a higher vapor pressure as a phase separation agent. Although it promotes phase separation, the boiling point of this organic solvent is low, which can easily cause a large solvent loss during pyrolysis and increase regeneration energy consumption. Existing phase change absorbents have defects such as low CO2 absorption load, high rich liquid viscosity, poor regeneration, and high regeneration energy consumption, which limit their industrial applications. In order to further improve the performance and regeneration energy consumption of phase change solutions, it is necessary to develop a new type of phase change absorbent that is more energy-saving and efficient. Summary of the invention

[0003] In order to solve the technical problems existing in the above-mentioned background technology, the present invention proposes an amino-azole bifunctional ionic liquid-organic alcohol-water ternary phase change system. The main absorbent in the novel phase change absorbent is an ionic liquid [TEPAH][Im] containing an active group, which can not only ensure the absorption load and absorption capacity, but also promote the hydrolysis conversion of carbamate, breaking through the defect of low regeneration efficiency. In addition, n-propanol with low vapor pressure is selected as a phase separation agent, which can not only improve the regeneration performance, but also improve the problem of large solvent loss during pyrolysis. Water is finally added as a solvent in this design to reduce the viscosity of the rich phase solution. This system can effectively make up for the shortcomings of the current phase change absorbent in industrial promotion.

[0004] In order to realize the above technical scheme, the present invention provides a new CO2 capture phase change absorbent, which adopts an amino-azole bifunctional ionic liquid-organic alcohol-water ternary phase change system, the main absorbent adopts an ionic liquid containing active groups, propanol is used as a phase separation agent, and finally water is added as a solvent to reduce the viscosity of the rich phase solution.

[0005] Furthermore, the configuration process of the ionic liquid containing active groups includes: preparing an ethanol-water solution, weighing equimolar amounts of TEPAH and Im respectively, dissolving them in an ethanol-water mixture, and placing them in a single-necked flask, magnetically stirring for a set time under a first temperature condition to allow the acid and base to fully undergo a neutralization reaction, transferring the mixture to a round-bottom flask, and placing it in a rotary evaporator under a second temperature condition for complete rotary evaporation, thereby obtaining an ionic liquid.

[0006] Furthermore, finally, the ionic liquid was transferred to a volumetric flask and fixed to volume in a 25 ML volumetric flask with n-propanol-water solution of different volume fractions, and finally an ionic liquid with a concentration of 0.5 mol / L was obtained.

[0007] Furthermore, the preparation volume ratio is 4:1 ethanol-water solution 150mL.

[0008] Furthermore, the first temperature is 25 degrees Celsius.

[0009] Furthermore, the set time is 24 hours.

[0010] Furthermore, the second temperature is 70 degrees Celsius.

[0011] The beneficial effects of the present invention are: 1. The present invention designs an amino-azole bifunctional ionic liquid-organic alcohol-water ternary phase change system. The main absorbent in the phase change absorbent is an ionic liquid [TEPAH][Im] containing an active group, which can not only ensure the absorption load and absorption capacity, but also promote the hydrolysis and conversion of carbamate, breaking through the defect of low regeneration efficiency; the results show that the [TEPAH][Im]-n-propanol-H2O absorption system can still be used after multiple thermal desorptions, and the absorbent has good thermal stability and good economic advantages in terms of reusability.

[0012] 2. The present invention uses n-propanol with low vapor pressure as a phase separation agent, which can not only improve the regeneration performance, but also improve the problem of large solvent loss during pyrolysis. Finally, water is added as a solvent to reduce the viscosity of the rich phase solution. This system can effectively make up for the shortcomings of the current phase change absorbent in industrial promotion.

[0013] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0015] Figure 1 Absorption flow chart of the present invention; Figure 2 It is a phase separation effect diagram of the present invention; Figure 3 is a bar graph of absorption loads for different propanol-water ratios of the present invention; Figure 4 It is a bar graph of the volume ratio of the rich and poor phases at different propanol-water ratios of the present invention; Figure 5 The effect of temperature on the CO2 absorption characteristics of the ionic solution [TEPAH][Im]-n-propanol-water; Among them: 1. CO2 cylinder; 2. N2 cylinder; 3. Mass flow controller; 4. Iron stand; 5. Absorption tube; 6. Constant temperature water bath; 7. Gas analyzer. DETAILED DESCRIPTION

[0016] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0017] It should be noted that the following detailed descriptions are all illustrative and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in this embodiment have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0018] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0019] In the present invention, terms such as "upper", "lower", "left", "right", "front", "back", "vertical", "horizontal", "side", "bottom", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are relational words determined only for the convenience of describing the structural relationships of the various parts or elements of the present invention, and do not specifically refer to any part or element in the present invention and should not be understood as limitations on the present invention.

[0020] In the present invention, terms such as "fixed connection", "connected", "connection", etc. should be understood in a broad sense, indicating that it can be fixedly connected, integrally connected or detachably connected; it can be directly connected or indirectly connected through an intermediate medium. Relevant scientific research or technical personnel in this field can determine the specific meanings of the above terms in the present invention according to specific circumstances, and they should not be understood as limiting the present invention.

[0021] Embodiment 1, as Figure 1-Figure 5 As shown, this embodiment provides a novel CO2 capture phase change absorbent, which adopts an amino-azole bifunctional ionic liquid-organic alcohol-water ternary phase change system, the main absorbent adopts an ionic liquid containing active groups, propanol is used as a phase separation agent, and finally water is added as a solvent to reduce the viscosity of the rich phase solution.

[0022] The preparation process of the ionic liquid containing active groups includes: taking the synthetic ionic liquid [TEPAH][Im] ([tetraethylenepentamine][imidazole]) as an example, preparing 150 mL of an ethanol-water solution with a volume ratio of 4:1, weighing equimolar (0.0125 mol) TEPAH and Im respectively and dissolving them in an ethanol-water mixture (4:1, V / V), placing them in a single-necked flask, and magnetically stirring them at 25 degrees Celsius for 24 hours to allow the acid and base to fully neutralize, transferring the mixture to a round-bottom flask, and placing it in a rotary evaporator at 70 degrees Celsius for complete rotary evaporation, thereby obtaining the ionic liquid [TEPAH][Im].

[0023] The preparation process of amino-azole bifunctional ionic liquid-organic alcohol-water ternary phase change system: the ionic liquid [TEPAH][Im] was transferred to a volumetric flask and fixed to volume in a 25ML volumetric flask with n-propanol / water solution of different volume fractions, and finally the amino-azole bifunctional ionic liquid-organic alcohol-water ternary phase change system with a concentration of 0.5 mol / L was obtained.

[0024] The amino-azole difunctionalized ionic liquid-organic alcohol-water ternary phase change system includes an amino-azole difunctionalized ionic liquid, an organic alcohol (n-propanol), and water. Since increasing the number of amino groups on anions and cations is an effective way to increase the CO2 absorption load of ionic liquids, the number of amino groups on ionic liquids cannot be increased indefinitely due to the steric hindrance effect and the relatively stable structure of the carbamate product generated after the reaction of amino groups and CO2, which leads to the defect of difficult regeneration. Unlike amino-functionalized ionic liquids, nitrogen-containing azole-type functionalized ionic liquids have a higher active group utilization rate when capturing carbon dioxide and are easier to regenerate. Therefore, the present invention uses tetraethylenepentamine and imidazole to synthesize a new amino-azole difunctionalized ionic liquid to achieve the purpose of efficient and reversible capture of CO2. The main absorbent in the phase change absorbent selects an amino-azole difunctionalized ionic liquid [TEPAH][Im] containing an active group, which can not only ensure the absorption load and absorption capacity, but also promote the hydrolysis conversion of carbamate, breaking through the defect of low regeneration efficiency. In addition, the selection of n-propanol with low vapor pressure as a phase separation agent can not only improve the regeneration performance, but also improve the problem of large solvent loss during pyrolysis. In this design, water is added as a solvent at the end to reduce the viscosity of the rich phase solution. This system can effectively make up for the shortcomings of the current phase change absorbent in industrial promotion.

[0025] Absorption steps: The absorption flow chart of this design is as follows Figure 1The absorption process includes CO2 cylinder 1, N2 cylinder 2, mass flow controller 3, iron stand 4, absorption tube 5, constant temperature water bath 6, and gas analyzer 7. First, the constant temperature water bath is set to the operating temperature; second, the absorption tube is fixed with the help of the iron stand and placed in the constant temperature water bath; then, the CO2 gas line is opened and the flow rate is controlled with the help of the mass flow controller. The CO2 flow rate setting value is 100 mL min -1 ; When the gas path is stable, proceed to the next step. Pour 25 mL of the preheated absorbent to be tested into the absorption tube for absorption performance test. Use a stopwatch and a gas analyzer to record the CO2 gas concentration at the outlet of the absorption tube at different times.

[0026] Regeneration step: The desorption process is carried out under normal pressure. A certain amount of CO2 saturated solution is introduced into the bubbling absorption tube and maintained at a certain desorption temperature through a constant temperature water bath. -1 ) Introduce pure N2 as purge gas. Analyze and record the CO2 concentration in the gas leaving the flask using a CO2 analyzer. When the CO2 concentration of the solution drops to 0, desorption is considered complete. The desorbent is subjected to the absorption experiment again.

[0027] The phase change characteristics of the [TEPAH][Im]-propanol-water absorption system are mainly determined by the propanol-water ratio. Therefore, the concentration of [TEPAH][Im] was kept at 0.5 mol / L, the propanol-water ratio was changed, and the phase separation effect and various physical parameters of the absorbent were investigated. The experimental results are shown in Figure 2 .

[0028] The absorption load of the absorbents with different propanol-water ratios increases with the increase of reaction time and eventually reaches absorption saturation. When the volume ratio of propanol-water is 5:5, it is the best ratio of absorbent solvent.

[0029] When the volume ratio of propanol to water reaches 5:5, the absorbent can be separated into liquid-liquid phases after absorption saturation. As the volume ratio of propanol to water gradually increases, the volume of the lower solution gradually decreases after absorption saturation, and the volume of the upper solution gradually increases. The absorption experiment under the condition of the optimal solvent ratio has the following phase separation effect: Figure 2 Under the optimal conditions, the volume of the rich liquid after absorption saturation accounts for only one third of the total volume, and the absorption load can reach 1.34 mol·mol -1, and the viscosity is only 3.58mPa·s. Under this solvent ratio, the absorbent can maintain a high absorption load and a faster absorption rate, so that it maintains very good absorption performance. Since the water content in the absorbent is relatively high, after absorption saturation, the solution can have a phase separation phenomenon and a lower rich liquid viscosity. Since the CO2 load is mainly concentrated in the lower solution, it is conducive to the regeneration of the absorbent in the later stage. The lower viscosity makes the absorbent easier to transport in practical industrial applications, and the low viscosity is also more conducive to the mass transfer of CO2 in the absorbent.

[0030] In the actual application of absorbents, CO2 capture is usually carried out after flue gas desulfurization, and the temperature of the flue gas at its outlet usually fluctuates in the range of 303-333K. According to previous reports, the phase change characteristics of the absorbent will be affected by temperature. Therefore, this experiment explored the effect of temperature on CO2 capture by [TEPAH][Im]-n-propanol-H2O in the range of 303-333K, and the results are shown in the figure.

[0031] The regeneration efficiency of the absorbent saturated solution increases with the increase of regeneration time and regeneration temperature. Therefore, the optimal regeneration temperature of [TEPAH][Im]-n-propanol-H2O is 363K. The regeneration efficiency of the absorbent only slightly decreases with the increase of the number of cycles, and after 5 absorption-desorption cycles, the regeneration efficiency of the absorbent can still reach 73.89%. This result shows that the [TEPAH][Im]-n-propanol-H2O absorption system can still be used after multiple thermal desorptions. The absorbent has good thermal stability and has good economic advantages in terms of reusability.

[0032] like Figure 3-Figure 4 It is the absorption load diagram of different ratios (C[TEPAH][Im]:0.5mol / L; T:303K; QCO2:100mL / min; V[TEPAH][Im]:25mL); like Figure 5 The effect of temperature on the CO2 absorption characteristics of [TEPAH][Im]-n-propanol-water (C[TEPAH][Im]:0.5mol / L; Vwater:Vethanol=5:5; QCO2:100mL / min;VL:25mL); Table 1 is the physical property parameter table of ionic solution [TEPAH][Im] / n-propanol / water for capturing CO2 at different temperatures:

[0033] As the reaction temperature continues to rise, the reaction between the absorbent and CO2 becomes more intense, which accelerates the absorption rate. High temperature will also reduce the solubility of CO2 in the solution, causing the absorption load to continue to decrease. The results are shown in Table 2. Table 2 is as follows:

[0034] Subsequently, the regeneration efficiency of the absorbent saturated solution at different alcohol-water ratios at 333K and the cyclic regeneration efficiency at different temperatures (333-363K) were measured. The results are shown in Tables 3 and 4. Table 3 is as follows:

[0035] Table 4 is as follows:

[0036] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A novel phase-change absorbent for CO2 capture, characterized in that: An amino-azole bifunctional ionic liquid-organic alcohol-water ternary phase change system is adopted, an ionic liquid containing active groups is used as the main absorbent, propanol is used as a phase separation agent, and finally water is added as a solvent to reduce the viscosity of the rich phase solution.

2. The novel CO2 capture phase change absorbent according to claim 1, characterized in that: The preparation process of the ionic liquid containing active groups includes: preparing an ethanol-water solution, weighing equimolar TEPAH and Im respectively, dissolving them in the ethanol-water mixture, and placing them in a single-necked flask, magnetically stirring for a set time under a first temperature condition to allow the acid and base to fully undergo a neutralization reaction, transferring the mixture to a round-bottom flask, placing it in a rotary evaporator under a second temperature condition for complete rotary evaporation, and thus obtaining an ionic liquid.

3. The novel CO2 capture phase change absorbent according to claim 2, characterized in that: Finally, the ionic liquid was transferred to a volumetric flask and fixed to volume in a 25 ML volumetric flask with n-propanol-water solution of different volume fractions, and finally an ionic liquid with a concentration of 0.5 mol / L was obtained.

4. The novel CO2 capture phase change absorbent according to claim 2, characterized in that: The preparation volume ratio is 4:1 ethanol-water solution 150mL.

5. The novel CO2 capture phase change absorbent according to claim 2, characterized in that: The first temperature is 25 degrees Celsius.

6. The novel CO2 capture phase change absorbent according to claim 2, characterized in that: The set time is 24h.

7. The novel CO2 capture phase change absorbent according to claim 2, characterized in that: The second temperature is 70 degrees Celsius.

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