Ionic phase change absorbent as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of gas separation, and particularly relates to an ionic phase change absorbent as well as a preparation method and application thereof. The ionic phase change absorbent comprises functionalized ionic liquid, organic amine, a stabilizer, an absorption enhancer and water, wherein anions of the functionalized ionic liquid are lysine radicals, and cations of the functionalized ionic liquid are hydrophobic quaternary phosphonium cations or quaternary ammonium cations. The ionic phase change absorbent has the advantages of the functionalized ionic liquid and the phase change absorbent, makes up the respective defects, and is free of volatilization, low in regeneration energy consumption, safe and environment-friendly.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas separation, and in particular relates to an ionic phase-change absorbent and a preparation method and application thereof. Background Art

[0002] Chemical absorbents used in CO2 capture technology have undergone three generations of development: from first-generation absorbents such as MEA, DEA, and MDEA, to second-generation composite amine absorbents such as AEEA, DEEA, and PZ, and finally to third-generation absorbents such as phase-change absorbents, anhydrous absorbents, and ionic liquids. Phase-change absorbents, among others, have attracted extensive attention from researchers both domestically and internationally due to their potential to significantly reduce regeneration energy consumption. Phase-change absorbents consist of an active amine (a fast-reacting primary amine) and a phase separator (a slower-reacting tertiary amine or a non-reactive physical solvent). After absorbing CO2, the phase-change absorbent forms an aqueous phase and an organic phase. The aqueous phase primarily consists of CO2 reaction products and water, while the organic phase primarily consists of the phase separator and a small amount of unreacted active amine. Because the organic phase is generally less dense than the aqueous phase, it is typically located in the upper layer. In the initial stages of CO2 absorption, the active amine predominates in the reaction with CO2, forming ionic carbamates. When the CO2 absorption load is high, some of the tertiary amine phase separator participates in the CO2 reaction, forming bicarbonate. When phase separation occurs, the carbamate ions, bicarbonate ions and protonated amines are easily soluble in the aqueous phase because they are charged and have strong ion-dipole bonds with water. The unreacted tertiary amines and a small amount of active amine molecules have weaker polarity and are enriched in the organic phase.

[0003] After absorbing carbon dioxide, the phase-change absorbent forms two mutually incompatible phases: a lean liquid phase (low in carbon dioxide content) and a rich liquid phase (high in carbon dioxide content). This phase separation allows carbon dioxide to primarily concentrate in the rich liquid phase, thus reducing the amount of rich liquid required for regeneration. The separated lean liquid is then recycled to the absorber to capture carbon dioxide, while the rich liquid is recycled to the desorption tower for desorption. This process improves the efficiency of both the absorption and desorption processes while also effectively reducing the consumption of sensible heat and latent heat of vaporization during the regeneration process, thereby lowering energy costs.

[0004] The phase-change absorbents currently used in phase-change absorbers are volatile and corrosive, causing secondary pollution to the environment and increasing absorbent replenishment costs. Furthermore, the corrosive nature of phase-change absorbers can also affect the service life of equipment such as towers, packing, and piping. Summary of the Invention

[0005] The purpose of the present invention is to provide an ionic phase change absorbent and its preparation method and application. The ionic phase change absorbent has the advantages of both functionalized ionic liquids and phase change absorbents, makes up for their respective defects, does not volatilize, has low regeneration energy consumption, and is safe and environmentally friendly.

[0006] Specifically, the present invention provides the following technical solutions:

[0007] An ionic phase-change absorbent comprising a functionalized ionic liquid, an organic amine, a stabilizer, an absorption promoter, and water;

[0008] Wherein, the anion of the functionalized ionic liquid is lysine ([Lys] - ), the cation is a hydrophobic quaternary phosphine cation or a quaternary ammonium cation.

[0009] In the ionic phase change absorbent of the present invention, the organic amine acts as an active amine, and the functionalized ionic liquid acts as both a phase separator and an active amine, that is, it has both the ability to absorb carbon dioxide and the ability to change phase. - It contains both amino groups -NH2 and carboxyl groups -COOH, which can synergistically capture carbon dioxide, thereby acting as an active amine; the cations of the functionalized ionic liquid are hydrophobic quaternary phosphine cations or quaternary ammonium cations. After the functionalized ionic liquid absorbs carbon dioxide, it becomes a hydrophobic organic matter, which can act as a phase separation agent, thus eliminating the need to add additional organic solvents as phase separation agents.

[0010] Preferably, the cation of the functionalized ionic liquid is tetrahexyltetradecylphosphine ([P 66614 ] + ) and / or trioctylmethylammonium ([N 8881 ] + ). Studies have found that in the system of the present invention, tetrahexyltetradecylphosphine and trioctylmethylammonium cations are used as cations of the functionalized ionic liquid, which contain long-chain alkyl groups (chain length between C6-C16) and are insoluble in water, and can further promote phase separation.

[0011] Preferably, the organic amine is selected from at least one of monoethanolamine, N-methyldiethanolamine, and dimethylaminocyclohexylamine. The above organic amines can achieve the efficacy of the present invention while being cheap, readily available, and more economical.

[0012] Preferably, the stabilizer is selected from at least one of glycine, aminopiperazine, hydroxypiperazine, butylated hydroxytoluene, tert-butylhydroquinone, 2-amino-2-methyl-1,3-propanediol, 2-amino-2-ethyl-1,3-propanediol, 2-amino-2-hydroxymethyl-1,3-propanediol, tert-butylaminoethoxyethanol, and 3-amino-1-propanol. Studies have found that adding an appropriate amount of the above stabilizers to the system of the present invention can significantly reduce the decomposition of organic amines and extend the service life of the two-phase absorbent.

[0013] Preferably, the absorption enhancer is selected from at least one of tetrasodium ethylenediaminetetraacetic acid, o-phenanthroline, potassium sodium tartrate, ammonium citrate, diethylenetriaminepentaacetic acid, 2,2'-bipyridine, aminotriacetic acid (NTA), and 8-hydroxyquinoline. Studies have found that adding an appropriate amount of the aforementioned absorption enhancers to the system of the present invention significantly improves the absorption efficiency of carbon dioxide, resulting in a higher absorption rate of carbon dioxide by the two-phase absorbent of the present invention.

[0014] Preferably, the composition comprises, by mass percentage, 10-50% of functionalized ionic liquid, 10-60% of organic amine, 0.1%-10% of stabilizer, 0.01-10% of absorption promoter and 10-50% of water.

[0015] More preferably, the composition comprises, by mass percentage, 20-30% of functionalized ionic liquid, 25-35% of organic amine, 0.5-1.5% of stabilizer, 0.5-1.5% of absorption enhancer, and the remainder is water.

[0016] The present invention also provides a method for preparing the above-mentioned ionic phase-change absorbent, comprising the following steps:

[0017] The functionalized ionic liquid is added into water to dissolve, then mixed with organic amine, and then a stabilizer and an absorption promoter are added to obtain the product.

[0018] The present invention also provides use of the ionic phase-change absorbent in adsorbing carbon dioxide.

[0019] Preferably, in the above application, the operating temperature range of the ionic phase change absorbent is 20-45° C., and the absorption effect is better within this range.

[0020] The beneficial effects of the present invention are at least:

[0021] 1) The present invention provides an ionic phase change absorbent, which is a functionalized ionic liquid containing lysine anions, wherein the anion lysine radical [Lys] - Containing both amino groups (NH2) and carboxyl groups (COOH), they can synergistically capture carbon dioxide. The cations are hydrophobic quaternary phosphine or ammonium cations, which can promote phase separation after absorption. It combines the advantages of functionalized ionic liquids and phase change absorbents while compensating for their respective shortcomings. It is non-volatile, has low regeneration energy consumption, and is safe and environmentally friendly. It is an innovation in carbon dioxide absorbents.

[0022] 2) The present invention provides an ionic phase-change absorbent, wherein the cation of the functionalized ionic liquid is preferably tetrahexyltetradecylphosphine and / or trioctylmethylammonium cation, which contains a long-chain alkyl group (chain length between C6-C16), is insoluble in water, and can further promote phase separation;

[0023] 3) The ionic phase-change absorbent provided by the present invention can significantly reduce the decomposition of organic amines and improve the absorption efficiency of carbon dioxide by adding appropriate amounts of specific stabilizers and specific absorption promoters;

[0024] 4) The ionic phase-change absorbent provided by the present invention has a simple preparation process and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The flowchart of the embodiment of the invention is to use an ionic phase change absorbent to adsorb carbon dioxide.

[0026] Among them: 1-air compressor, 2-first mass flow meter, 3-CO2 gas storage tank, 4-second mass flow meter, 5-mixing tank, 6-first CO2 analyzer, 7-absorption tower, 8-circulation pump, 9-transfer pump, 10-phase separator, 11-second CO2 analyzer.

[0027] Figure 2 This is a graph showing the change in carbon dioxide adsorption capacity of the ionic phase-change absorbent IPTA-1 of Example 1 over time. DETAILED DESCRIPTION

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described below. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention. If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions shall be followed.

[0029] Figure 1 This is a flow chart of the adsorption of carbon dioxide using an ionic phase change absorbent in the following examples. The specific process is as follows:

[0030] 1. Mix the air in the air compressor 1 and the CO2 in the CO2 storage tank 3 in the mixing tank 5, and adjust the flow rates of the first mass flow meter 2 and the second mass flow meter 4 to prepare a mixed gas with the required carbon dioxide concentration. Use the first CO2 analyzer 6 to monitor the carbon dioxide concentration of the mixed gas;

[0031] 2. The mixed gas is fed into the absorption tower 7 from the top of the tower and contacts the absorbent fed into the tower. The absorbed mixed gas is discharged from the bottom of the tower and the carbon dioxide concentration of the mixed gas after absorption is monitored by a second CO2 analyzer 11. The unsaturated absorbent is transported to the top of the absorption tower 7 by the circulation pump 8 to continue absorbing carbon dioxide.

[0032] 3. After the absorbent is saturated, it is transported by the delivery pump 9 to the splitter 10 for liquid-liquid phase separation.

[0033] Example 1

[0034] Tetrahexyltetradecylphosphine lysine salt ([P 66614 ] + [Lys] - ), monoethanolamine, aminopiperazine, ethylenediaminetetraacetic acid tetrasodium salt and water were mixed to prepare 500g of absorbent, wherein tetrahexyltetradecylphosphine lysine salt ([P 66614 ] + [Lys] - ) with a mass fraction of 30%, monoethanolamine with a mass fraction of 30%, aminopiperazine with a mass fraction of 1%, ethylenediaminetetraacetic acid tetrasodium salt with a mass fraction of 0.5%, and water with a mass fraction of 38.5%, constituting the ionic phase change absorbent IPTA-1.

[0035] use Figure 1 The process achieved a decarbonization rate of 92.1% at a temperature of 30°C and a carbon dioxide inlet concentration of 1%. The absorbent was used to absorb the carbon dioxide until saturation, and then transferred to a phase separator. After absorbing the carbon dioxide, the absorbent formed a liquid-liquid two-phase structure. The carbon dioxide absorption capacity, measured by acid desorption, was 1.26 mol / mol (per mole of absorbent).

[0036] Figure 2 This is a graph showing the change in carbon dioxide adsorption capacity of the ionic phase-change absorbent IPTA-1 of Example 1 over time.

[0037] Example 2

[0038] Trioctylmethylammonium lysine salt ([N 8881 ] + [Lys] - ), N-methyldiethanolamine, glycine, diethylenetriamine pentaacetic acid and water were mixed to prepare 500g of absorbent, wherein trioctylmethylammonium lysine salt ([N 8881 ] + [Lys] - ) with a mass fraction of 20%, N-methyldiethanolamine with a mass fraction of 30%, glycine with a mass fraction of 1%, diethylenetriaminepentaacetic acid with a mass fraction of 1%, and water with a mass fraction of 48%, constituting the ionic phase change absorbent IPTA-2.

[0039] use Figure 1 The process achieved a decarbonization rate of 90.2% at a temperature of 30°C and a carbon dioxide inlet concentration of 1%. The absorbent was used to absorb the carbon dioxide until saturation, and then transferred to a phase separator. After absorbing the carbon dioxide, the absorbent formed a liquid-liquid two-phase structure. The carbon dioxide absorption capacity, measured by acid desorption, was 1.02 mol / mol.

[0040] In the present invention, the functional ionic liquid has both a phase separation effect and a certain active amine effect. The cation in the functional ionic liquid should be a hydrophobic quaternary phosphine cation or a quaternary ammonium cation containing a long-chain alkyl group, and at the same time, it is matched with an anion containing an amino group and having a certain hydrophilicity to achieve phase separation behavior. If a short-chain ammonium cation is used, the phase separation effect cannot be achieved. For example, the tetramethylammonium cation [N 1111 ] + .

[0041] Comparative Example 1

[0042] Tetramethylammonium lysine salt ([N 1111 ] + [Lys] - ), N-methyldiethanolamine, glycine, diethylenetriamine pentaacetic acid and water were mixed to prepare 500g of absorbent, wherein tetramethylammonium lysine salt ([N 1111 ] + [Lys] - The mass fraction of ethanol ( ) was 20%, the mass fraction of N-methyldiethanolamine was 30%, the mass fraction of glycine was 1%, the mass fraction of diethylenetriaminepentaacetic acid was 1%, and the mass fraction of water was 48%. The resulting absorbent did not show any obvious separation after absorbing carbon dioxide.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. An ionic phase change absorbent, characterized in that: including functionalized ionic liquid, organic amine, stabilizer, absorption enhancer and water; The anion of the functionalized ionic liquid is a lysine radical, and the cation is a hydrophobic quaternary phosphine cation or a quaternary ammonium cation.

2. The ionic phase change absorbent according to claim 1, characterized in that: The cation of the functionalized ionic liquid is tetrahexyltetradecylphosphine and / or trioctylmethylammonium.

3. The ionic phase change absorbent according to claim 1 or 2, characterized in that: The organic amine is selected from at least one of monoethanolamine, N-methyldiethanolamine and dimethylaminocyclohexylamine.

4. The ionic phase change absorbent according to claim 1 or 2, characterized in that: The stabilizer is selected from at least one of glycine, aminopiperazine, hydroxypiperazine, butylated hydroxytoluene, tert-butylhydroquinone, 2-amino-2-methyl-1,3-propanediol, 2-amino-2-ethyl-1,3-propanediol, 2-amino-2-hydroxymethyl-1,3-propanediol, tert-butylaminoethoxyethanol, and 3-amino-1-propanol.

5. The ionic phase change absorbent according to claim 1 or 2, characterized in that: The absorption enhancer is selected from at least one of tetrasodium ethylenediaminetetraacetic acid, o-phenanthroline, potassium sodium tartrate, ammonium citrate, diethylenetriaminepentaacetic acid, 2,2'-pyridine, aminotriacetic acid, and 8-hydroxyquinoline.

6. The ionic phase change absorbent according to claim 1 or 2, characterized in that: Calculated by mass percentage, the invention comprises 10-50% of functionalized ionic liquid, 10-60% of organic amine, 0.1%-10% of stabilizer, 0.01-10% of absorption promoter and 10-50% of water.

7. The ionic phase change absorbent according to claim 6, characterized in that: Calculated by mass percentage, the invention comprises 20-30% of functionalized ionic liquid, 25-35% of organic amine, 0.5-1.5% of stabilizer, 0.5-1.5% of absorption promoter, and the rest is water.

8. The method for preparing the ionic phase-change absorbent according to any one of claims 1 to 7, characterized in that: The following steps are involved: The functionalized ionic liquid is added into water to dissolve, then mixed with organic amine, and then a stabilizer and an absorption promoter are added to obtain the product.

9. Use of the ionic phase-change absorbent according to any one of claims 1 to 7 in adsorbing carbon dioxide.

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