Preparation method of a double-imidazolium-based deep eutectic solvent and its application in SO2 absorption and removal

Abstract

The present invention discloses a bis-imidazolium-based deep eutectic solvent (DESs) and uses it for absorbing SO2 gas. It uses 1-ethyl-3-methylimidazolium chloride (EmimCl) as a hydrogen bond acceptor (HBAs) and bis(hydroxymethyl) imidazolidinyl urea (DDU) or imidazolidinyl urea (IDU) as a hydrogen bond donor (HBDs), and is prepared by a simple heating and stirring method. The bis-imidazolium-based deep eutectic solvent in the present invention has a simple preparation method, high raw material utilization rate, and is green and environmentally friendly. Under the conditions of 25 °C and 1.0 bar, when the molar ratio of EmimCl:DDU is 32:1, the absorption capacity for SO2 is as high as 1.100 g / g; it has a high SO2 / CO2 selectivity, and the ideal gas selectivity index is 458.3; it has good cycling performance, and the activity shows no obvious decline after 30 absorption-desorption cycles; it has high stability, and there is no phase change and the absorption capacity remains basically unchanged after being sealed and stored for 30 days. In addition, the rapid absorption experiment shows that the synthesized DESs can basically achieve absorption equilibrium within 40 s.

Description

Technical Field

[0001] The present invention relates to a deep eutectic solvent, and particularly to a preparation method of a bis-imidazolium-based deep eutectic solvent and its use in the selective absorption reaction of SO2. Background Art

[0002] As one of the typical acidic toxic gases, the large emission of SO2 will cause environmental pollution problems such as acid rain and haze, threatening human health and the ecological environment. In recent years, for environmental protection and sustainable development, countries around the world have successively introduced a large number of laws and regulations to limit the sulfur content in fossil fuels. However, sulfur-free fossil fuels still cannot be obtained. These sulfides are burned to form SO2 gas, which is directly discharged into the atmosphere along with the flue gas. Therefore, realizing deep desulfurization of flue gas is crucial for environmental protection. One of the key issues in the flue gas desulfurization process is the selection of absorbents. Therefore, there is an urgent need to design and prepare a class of high-performance absorbents for the flue gas desulfurization process.

[0003] Since deep eutectic solvents (DESs) were first reported in 2003, they have received extensive attention from scientific researchers and have been used in fields such as organic synthesis, catalyst preparation, and gas absorption and separation. Especially in the field of flue gas desulfurization, DESs are considered to be absorbents with great potential for industrial application in flue gas desulfurization due to their advantages such as easy preparation, greenness, high absorption capacity, and excellent recycling performance. The synthesis of DESs is very simple. A certain stoichiometric ratio of HBDs and HBAs is mixed, and they mainly form a liquid with a melting point lower than each component through hydrogen bond interaction, π-π interaction, and halogen bond. The properties of DESs formed by different stoichiometric ratios, different types of hydrogen bond donors (HBDs), and hydrogen bond acceptors (HBAs) usually vary. Therefore, in order to achieve high-performance absorption of SO2 gas in flue gas, a reasonable selection of HBDs and HBAs is the key to preparing DESs absorbents.

[0004] 1-Ethyl-3-methylimidazolium chloride (EmimCl) is a common HBA and has been used to synthesize different types of DESs. In addition, according to literature reports, HBDs with nitrogen heterocycles (such as imidazole ring, pyrrole ring, and pyridine ring, etc.) in their molecular structures form DESs with high absorption performance for SO2 gas. In addition, when the structure of HBDs contains functional groups such as -OH and -NH2, it is beneficial to synthesize DESs with high SO2 gas absorption performance. Bis(hydroxymethyl) imidazolidinyl urea (DDU) and imidazolidinyl urea (IDU) are two nitrogen-containing heterocyclic compounds with multiple functional groups, and both have multiple HBA sites and HBDs sites. If they are combined with EmimCl, it is expected to prepare a class of DESs absorbents with high SO2 gas absorption performance. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a bis-imidazolium-based DESs absorbent, a preparation method thereof, and an application for absorbing and removing SO2.

[0006] To solve the above technical problem, the technical solution adopted by the present invention is as follows:

[0007] A bis-imidazolium-based deep eutectic solvent absorbent is a bis-imidazolium-based deep eutectic solvent DESs prepared by a heating and stirring method from hydrogen bond acceptors HBAs and hydrogen bond donors HBDs; the molar ratio of the HBAs to the HBDs is 8:1 to 36:1.

[0008] Among them, the HBAs is 1-ethyl-3-methylimidazolium chloride EmimCl, and the HBDs is bis(hydroxymethyl) imidazolidinyl urea DDU or imidazolidinyl urea IDU.

[0009] The DESs is a liquid at room temperature. Due to the hydrogen bond interaction, π-π interaction and halogen bond formation between the hydrogen bond acceptor HBAs and the hydrogen bond donor HBDs, the melting point of the DESs is much lower than that of the single-component HBAs and HBDs.

[0010] A preparation method of a bis-imidazolium-based deep eutectic solvent absorbent comprises the steps of:

[0011] Put HBAs and HBDs with a certain molar ratio into a container, seal it and place it in an oil bath and heat it to 70 - 110 °C, and at the same time stir strongly at a rotation speed of 500 - 1500 rpm. After heating and stirring for 1 - 5 h, take the container out of the oil bath and cool it to room temperature to obtain the required bis-imidazolium-based deep eutectic solvent absorbent DESs.

[0012] Further, the oil bath heating temperature is 100 °C, the stirring rate is 800 rmp, and the stirring time is 3 h.

[0013] Further, the molar ratio of the HBAs to the HBDs is 8:1 to 36:1.

[0014] The DESs prepared from HBAs and HBDs with different molar ratios is named EmimCl + DDU-n or EmimCl + IDU-n, where n = 8 - 36.

[0015] The application of the above bis-imidazolium-based deep eutectic solvent absorbent in SO2 absorption.

[0016] The specific application method is as follows: Use a "dual-tank" gas absorption device to conduct absorption experiments on SO2 or CO2. Weigh 0.0100 - 1.0000 g of the sample (w) with an analytical balance (accuracy of ±0.0001 g) and place it in the absorption tank. After sealing the device, put it into a constant temperature water bath, set the required temperature (25 - 80 °C), and conduct gas absorption experiments at different temperatures.

[0017] The present invention has the following advantages:

[0018] (1) The prepared bis-imidazolium-based DESs absorbent can efficiently absorb SO2 gas in a short time, up to 1.100 g / g (25 °C, 1.0 bar); the DESs has a fast absorption rate and basically reaches the absorption equilibrium within 40 s.

[0019] (2) The prepared bis-imidazolium-based DESs absorbent has excellent SO2 / CO2 selectivity, and the ideal gas selectivity index of EmimCl + DDU-32 is 458.3 (25 °C, 1.0 bar).

[0020] (3) The prepared bis-imidazolium-based DESs absorbent has excellent recycling performance and stability. The activity of EmimCl + DDU-32 still does not decrease significantly after 30 absorption-desorption cycles; there is no phase change and the absorption capacity remains basically unchanged after being sealed and stored for 30 days. Description of the Drawings

[0021] Figure 1 It is a schematic diagram of the gas absorption device. In the figure, GT: gas storage tank; AT: absorption tank; CT: constant temperature water bath; MS: magnetic stirrer; F1 - F4: gas valves; PV, SV: pressure sensors; CP: computer; VP: vacuum pump.

[0022] Figure 2 It is the SO2 absorption capacity of DESs prepared with different molar ratios of two raw materials.

[0023] Figure 3 It is the effect of temperature on the SO2 absorption capacity of EmimCl + DDU-32.

[0024] Figure 4 It is the effect of temperature on the SO2 absorption capacity of EmimCl + IDU-32.

[0025] Figure 5 It is the SO2 absorption rate of EmimCl + DDU-n.

[0026] Figure 6 It is the absorption capacity of DESs with different HBDs for SO2 and CO2.

[0027] Figure 7(a) Recycling performance of EmimCl + DDU-32; (b) Stability of EmimCl + DDU-32. Detailed implementation manners

[0028] The present invention can be better understood according to the following embodiments. However, those skilled in the art can easily understand that the content described in the embodiments is only used to illustrate the present invention and should not and will not limit the present invention described in detail in the claims.

[0029] The gas absorption device used in the following embodiments:

[0030] As Figure 1 shown, the volume of the gas storage tank (GT) is 122.300 cm 3 , denoted as V GT ; the volume of the absorption tank (AT) is 46.187 cm 3 , and it is equipped with a magnetic stirrer with a certain volume, denoted as V AT . A magnetic stirrer (MS) is equipped directly below the absorption tank. To reduce errors, its rotation speed is maintained at 350 rpm. The accuracy of the pressure sensors PV and SV is ±0.2%, and they measure the pressures of the gas storage tank and the absorption tank and transmit them to the computer (CP), denoted as and The measurement accuracy of the temperature control device in the constant temperature water bath (CT) is ±0.1 °C, which is used to adjust the temperatures of the absorption tank and the gas storage tank, so as to explore the gas absorption performance at different temperatures. The vacuum pump (VP) is used to pump out the air or N2 in the tank before gas absorption and remove the remaining acidic gas in the tank after absorption. To protect the safety of personnel and prevent harmful gases from being directly discharged into the atmosphere, the remaining acidic gas should be slowly introduced into a high-concentration sodium hydroxide (NaOH) solution for tail gas treatment.

[0031] The SO2 absorption performance of the prepared DESs was explored under different temperature and different pressure conditions. Weigh a certain mass of the sample (w) (with an accuracy of ±0.0001 g) using an analytical balance and put it into the absorption tank. After closing the device, place it in the constant temperature water bath and set the required temperatures (25 - 80 °C in sequence). After the temperatures of all parts are stable, close F1 and F2, open F3 and F4, evacuate the gas storage tank and the absorption tank and then close the gas valve and the vacuum pump. At this time, the reading of PV is The reading of SV is After stabilizing for about 10 minutes, open F1 to introduce a certain amount of SO2 into the gas storage tank and then close the gas valve. After the reading of PV is stable, record it as The reading of SV is At this time, the pressure of SO2 in the gas storage tank is Turn on the magnetic stirrer, open F3 and slowly introduce a certain amount of SO2 into the suction tank, then close the gas valve. After the reading of SV stabilizes, record it as The pressure of SO2 in the absorption tank is At this time, record the reading of PV as The pressure of SO2 in the gas storage tank is Subsequently, calculate the absorption capacity (m gas ) of SO2 gas according to formula (1):

[0032]

[0033] Among them, respectively represent the density (g / cm GT1 ), P GTi ), P ATi ) of the gas at time, and the values are obtained from the NIST Chemistry WebBook database; V 3 ), V GT ), V AT respectively represent the volumes (cm 3 ) of the gas storage tank and the absorption tank; w and ρ respectively represent the mass (g) and density (g / cm 3 ) of DESs.

[0034] The test method for the CO2 gas absorption performance of DESs is similar to that for the SO2 gas absorption performance.

[0035] Example 1:

[0036] Weigh 11.7296 g (80 mmol) of EmimCl and 1.3015 g (10 mmol) of DDU into a flask, stir and mix them at 100 °C for 3 hours until a homogeneous liquid phase is formed, then the bis-imidazolium-based DESs (EmimCl + DDU-8) can be obtained.

[0037] Weigh 0.1000 g of the prepared bis-imidazolium-based DESs (EmimCl + DDU-8) and place it in the absorption tank and stir it with a magnetic stir bar (350 rpm). After sealing the absorption tank and the gas storage tank, place them in a constant temperature water bath with precise temperature control at 25 °C. First, fill the gas storage tank with enough SO2 (~2.0 bar). After the pressure stabilizes, fill the absorption tank with SO2. The absorption time for every 0.1 bar is 10 min. After 100 min of absorption (1.0 bar), the maximum absorption capacity is 0.917 g / g.

[0038] Example 2:

[0039] Weigh 17.5944 g (120 mmol) of EmimCl and 1.3015 g (10 mmol) of DDU into a flask, stir and mix them at 100 °C for 3 hours until a homogeneous liquid phase is formed, then the bis-imidazolium-based DESs (EmimCl + DDU-12) can be obtained.

[0040] Weigh 0.1000 g of the prepared bis-imidazolium-based DESs (EmimCl + DDU-12) and place it in an absorption tank and stir it with a magnetic stirrer (350 rpm). After sealing the absorption tank and the gas storage tank, place them in a constant temperature water bath with precise temperature control at 25 °C. First, fill the gas storage tank with enough SO2 (∼2.0 bar). After the pressure stabilizes, fill SO2 into the absorption tank. The absorption time for every 0.1 bar is 10 min. After 100 min of absorption (1.0 bar), the maximum absorption capacity is 0.961 g / g.

[0041] Example 3:

[0042] Weigh 23.4592 g (160 mmol) of EmimCl and 1.3015 g (10 mmol) of DDU into a flask, stir and mix them at 100 °C for 3 hours until a homogeneous liquid phase is formed, then the bis-imidazolium-based DESs (EmimCl + DDU-16) can be obtained.

[0043] Weigh 0.1000 g of the prepared bis-imidazolium-based DESs (EmimCl + DDU-16) and place it in an absorption tank and stir it with a magnetic stirrer (350 rpm). After sealing the absorption tank and the gas storage tank, place them in a constant temperature water bath with precise temperature control at 25 °C. First, fill the gas storage tank with enough SO2 (∼2.0 bar). After the pressure stabilizes, fill SO2 into the absorption tank. The absorption time for every 0.1 bar is 10 min. After 100 min of absorption (1.0 bar), the maximum absorption capacity is 1.026 g / g.

[0044] Example 4:

[0045] Weigh 29.3240 g (200 mmol) of EmimCl and 1.3015 g (10 mmol) of DDU into a flask, stir and mix them at 100 °C for 3 hours until a homogeneous liquid phase is formed, then the bis-imidazolium-based DESs (EmimCl + DDU-20) can be obtained.

[0046] Weigh 0.1000 g of the prepared bis-imidazolium-based DESs (EmimCl + DDU-20) and place it in the absorption tank, then stir it with a magnetic stirrer (350 rpm). After sealing the absorption tank and the gas storage tank, place them in a constant temperature water bath with precise temperature control at 25 °C. First, fill the gas storage tank with enough SO2 (∼2.0 bar). After the pressure stabilizes, fill the absorption tank with SO2. The absorption time for every 0.1 bar is 10 min. After 100 min of absorption (1.0 bar), the maximum absorption capacity is 1.056 g / g.

[0047] Example 5:

[0048] Weigh 35.1888 g (240 mmol) of EmimCl and 1.3015 g (10 mmol) of DDU into a flask, and stir and mix them at 100 °C for 3 hours until a homogeneous liquid phase is formed, then the bis-imidazolium-based DESs (EmimCl + DDU-24) can be obtained.

[0049] Weigh 0.1000 g of the prepared bis-imidazolium-based DESs (EmimCl + DDU-24) and place it in the absorption tank, then stir it with a magnetic stirrer (350 rpm). After sealing the absorption tank and the gas storage tank, place them in a constant temperature water bath with precise temperature control at 25 °C. First, fill the gas storage tank with enough SO2 (∼2.0 bar). After the pressure stabilizes, fill the absorption tank with SO2. The absorption time for every 0.1 bar is 10 min. After 100 min of absorption (1.0 bar), the maximum absorption capacity is 1.078 g / g.

[0050] Example 6:

[0051] Weigh 41.0536 g (280 mmol) of EmimCl and 1.3015 g (10 mmol) of DDU into a flask, and stir and mix them at 100 °C for 3 hours until a homogeneous liquid phase is formed, then the bis-imidazolium-based DESs (EmimCl + DDU-28) can be obtained.

[0052] Weigh 0.1000 g of the prepared bis-imidazolium-based DESs (EmimCl + DDU-28) and place it in the absorption tank, then stir it with a magnetic stirrer (350 rpm). After sealing the absorption tank and the gas storage tank, place them in a constant temperature water bath with precise temperature control at 25 °C. First, fill the gas storage tank with enough SO2 (∼2.0 bar). After the pressure stabilizes, fill the absorption tank with SO2. The absorption time for every 0.1 bar is 10 min. After 100 min of absorption (1.0 bar), the maximum absorption capacity is 1.080 g / g.

[0053] Example 7:

[0054] Weigh 46.9184 g (320 mmol) of EmimCl and 1.3015 g (10 mmol) of DDU into a flask, stir and mix them at 100 °C for 3 hours until a homogeneous liquid phase is formed, then the bis-imidazolium-based DESs (EmimCl + DDU-32) can be obtained.

[0055] Weigh 0.1000 g of the prepared bis-imidazolium-based DESs (EmimCl + DDU-32) and place it in an absorption tank and stir it with a magnetic stirrer (350 rpm). After sealing the absorption tank and the gas storage tank, place them in a constant temperature water bath with precise temperature control at 25 °C. First, fill the gas storage tank with enough SO2 (~2.0 bar). After the pressure is stable, fill SO2 into the absorption tank. The absorption time for every 0.1 bar is 10 min. After absorbing for 100 min (1.0 bar), the maximum absorption capacity is 1.100 g / g.

[0056] Example 8

[0057] Weigh 52.7832 g (360 mmol) of EmimCl and 1.3015 g (10 mmol) of DDU into a flask, stir and mix them at 100 °C for 3 hours until a homogeneous liquid phase is formed, then the bis-imidazolium-based DESs (EmimCl + DDU-36) can be obtained.

[0058] Weigh 0.1000 g of the prepared bis-imidazolium-based DESs (EmimCl + DDU-36) and place it in an absorption tank and stir it with a magnetic stirrer (350 rpm). After sealing the absorption tank and the gas storage tank, place them in a constant temperature water bath with precise temperature control at 25 °C. First, fill the gas storage tank with enough SO2 (~2.0 bar). After the pressure is stable, fill SO2 into the absorption tank. The absorption time for every 0.1 bar is 10 min. After absorbing for 100 min (1.0 bar), the maximum absorption capacity is 1.092 g / g.

[0059] Example 9:

[0060] Weigh 11.7296 g (80 mmol) of EmimCl and 3.8829 g (10 mmol) of IDU into a flask, stir and mix them at 100 °C for 3 hours until a homogeneous liquid phase is formed, then the bis-imidazolium-based DESs (EmimCl + IDU-8) can be obtained.

[0061] Weigh 0.1000 g of the prepared bis-imidazolium-based DESs (EmimCl + IDU-8) and place it in the absorption tank, then stir it with a magnetic stirrer (350 rpm). After sealing the absorption tank and the gas storage tank, place them in a constant temperature water bath with precise temperature control at 25 °C. First, fill the gas storage tank with enough SO2 (~2.0 bar). After the pressure stabilizes, fill the absorption tank with SO2. The absorption time for every 0.1 bar is 10 min. After 100 min of absorption (1.0 bar), the maximum absorption capacity is 0.875 g / g.

[0062] Example 10:

[0063] Weigh 17.5944 g (120 mmol) of EmimCl and 3.8829 g (10 mmol) of IDU into a flask, and stir and mix them at 100 °C for 3 hours until a homogeneous liquid phase is formed, then the bis-imidazolium-based DESs (EmimCl + IDU-12) can be obtained.

[0064] Weigh 0.1000 g of the prepared bis-imidazolium-based DESs (EmimCl + IDU-12) and place it in the absorption tank, then stir it with a magnetic stirrer (350 rpm). After sealing the absorption tank and the gas storage tank, place them in a constant temperature water bath with precise temperature control at 25 °C. First, fill the gas storage tank with enough SO2 (~2.0 bar). After the pressure stabilizes, fill the absorption tank with SO2. The absorption time for every 0.1 bar is 10 min. After 100 min of absorption (1.0 bar), the maximum absorption capacity is 0.942 g / g.

[0065] Example 11:

[0066] Weigh 23.4592 g (160 mmol) of EmimCl and 3.8829 g (10 mmol) of IDU into a flask, and stir and mix them at 100 °C for 3 hours until a homogeneous liquid phase is formed, then the bis-imidazolium-based DESs (EmimCl + IDU-16) can be obtained.

[0067] Weigh 0.1000 g of the prepared bis-imidazolium-based DESs (EmimCl + IDU-16) and place it in the absorption tank, then stir it with a magnetic stirrer (350 rpm). After sealing the absorption tank and the gas storage tank, place them in a constant temperature water bath with precise temperature control at 25 °C. First, fill the gas storage tank with enough SO2 (~2.0 bar). After the pressure stabilizes, fill the absorption tank with SO2. The absorption time for every 0.1 bar is 10 min. After 100 min of absorption (1.0 bar), the maximum absorption capacity is 0.973 g / g.

[0068] Example 12:

[0069] Weigh 29.3240 g (200 mmol) of EmimCl and 3.8829 g (10 mmol) of IDU into a flask, stir and mix them at 100 °C for 3 hours until a homogeneous liquid phase is formed, then the bis-imidazolium-based DESs (EmimCl + IDU-20) can be obtained.

[0070] Weigh 0.1000 g of the prepared bis-imidazolium-based DESs (EmimCl + IDU-20) and place it in an absorption tank and stir it with a magnetic stirrer (350 rpm). After sealing the absorption tank and the gas storage tank, place them in a constant temperature water bath with precise temperature control at 25 °C. First, fill the gas storage tank with enough SO2 (~2.0 bar). After the pressure is stable, fill SO2 into the absorption tank. The absorption time for every 0.1 bar is 10 min. After absorbing for 100 min (1.0 bar), the maximum absorption capacity is 1.003 g / g.

[0071] Example 13:

[0072] Weigh 35.1888 g (240 mmol) of EmimCl and 3.8829 g (10 mmol) of IDU into a flask, stir and mix them at 100 °C for 3 hours until a homogeneous liquid phase is formed, then the bis-imidazolium-based DESs (EmimCl + IDU-24) can be obtained.

[0073] Weigh 0.1000 g of the prepared bis-imidazolium-based DESs (EmimCl + IDU-24) and place it in an absorption tank and stir it with a magnetic stirrer (350 rpm). After sealing the absorption tank and the gas storage tank, place them in a constant temperature water bath with precise temperature control at 25 °C. First, fill the gas storage tank with enough SO2 (~2.0 bar). After the pressure is stable, fill SO2 into the absorption tank. The absorption time for every 0.1 bar is 10 min. After absorbing for 100 min (1.0 bar), the maximum absorption capacity is 1.025 g / g.

[0074] Example 14:

[0075] Weigh 41.0536 g (280 mmol) of EmimCl and 3.8829 g (10 mmol) of IDU into a flask, stir and mix them at 100 °C for 3 hours until a homogeneous liquid phase is formed, then the bis-imidazolium-based DESs (EmimCl + IDU-28) can be obtained.

[0076] Weigh 0.1000 g of the prepared bis-imidazolium-based DESs (EmimCl + IDU-28) and place it in the absorption tank, then stir it with a magnetic stirrer (350 rpm). After sealing the absorption tank and the gas storage tank, place them in a constant temperature water bath with precise temperature control at 25 °C. First, fill the gas storage tank with enough SO2 (∼2.0 bar). After the pressure stabilizes, fill the absorption tank with SO2. The absorption time for every 0.1 bar is 10 min. After 100 min of absorption (1.0 bar), the maximum absorption capacity is 1.058 g / g.

[0077] Example 15:

[0078] Weigh 46.9184 g (320 mmol) of EmimCl and 3.8829 g (10 mmol) of IDU into a flask, and stir and mix them at 100 °C for 3 hours until a homogeneous liquid phase is formed, then the bis-imidazolium-based DESs (EmimCl + IDU-32) can be obtained.

[0079] Weigh 0.1000 g of the prepared bis-imidazolium-based DESs (EmimCl + IDU-32) and place it in the absorption tank, then stir it with a magnetic stirrer (350 rpm). After sealing the absorption tank and the gas storage tank, place them in a constant temperature water bath with precise temperature control at 25 °C. First, fill the gas storage tank with enough SO2 (∼2.0 bar). After the pressure stabilizes, fill the absorption tank with SO2. The absorption time for every 0.1 bar is 10 min. After 100 min of absorption (1.0 bar), the maximum absorption capacity is 1.088 g / g.

[0080] Example 16:

[0081] Weigh 52.7832 g (360 mmol) of EmimCl and 3.8829 g (10 mmol) of IDU into a flask, and stir and mix them at 100 °C for 3 hours until a homogeneous liquid phase is formed, then the bis-imidazolium-based DESs (EmimCl + IDU-36) can be obtained.

[0082] Weigh 0.1000 g of the prepared bis-imidazolium-based DESs (EmimCl + IDU-36) and place it in the absorption tank, then stir it with a magnetic stirrer (350 rpm). After sealing the absorption tank and the gas storage tank, place them in a constant temperature water bath with precise temperature control at 25 °C. First, fill the gas storage tank with enough SO2 (∼2.0 bar). After the pressure stabilizes, fill the absorption tank with SO2. The absorption time for every 0.1 bar is 10 min. After 100 min of absorption (1.0 bar), the maximum absorption capacity is 1.085 g / g.

[0083] Figure 2Comparison chart of SO₂ absorption capacities of DESs prepared with different molar ratios of EmimCl+DDU-n obtained in Examples 1-8 and EmimCl+IDU-n obtained in Examples 9-16. As can be seen from the figure, the absorption capacity of EmimCl+DDU-n is in the range of 0.917-1.100 g / g, and the absorption capacity of EmimCl+IDU-n is in the range of 0.875-1.088 g / g.

[0084] Example 17:

[0085] Weigh 0.1000 g of the bis-imidazolium-based DESs (EmimCl+DDU-32) prepared in Example 7 and place it in the absorption tank and stir with a magnetic stirrer (350 rpm). After sealing the absorption tank and the gas storage tank, place them in a constant temperature water bath with precise temperature control at 40 °C. First, fill the gas storage tank with enough SO₂ (~2.0 bar). After the pressure stabilizes, fill the absorption tank with SO₂. The absorption time for every 0.1 bar is 10 min. After 100 min of absorption (1.0 bar), the maximum absorption capacity is 0.867 g / g.

[0086] Example 18:

[0087] Weigh 0.1000 g of the bis-imidazolium-based DESs (EmimCl+DDU-32) prepared in Example 7 and place it in the absorption tank and stir with a magnetic stirrer (350 rpm). After sealing the absorption tank and the gas storage tank, place them in a constant temperature water bath with precise temperature control at 60 °C. First, fill the gas storage tank with enough SO₂ (~2.0 bar). After the pressure stabilizes, fill the absorption tank with SO₂. The absorption time for every 0.1 bar is 10 min. After 100 min of absorption (1.0 bar), the maximum absorption capacity is 0.736 g / g.

[0088] Example 19:

[0089] Weigh 0.1000 g of the bis-imidazolium-based DESs (EmimCl+DDU-32) prepared in Example 7 and place it in the absorption tank and stir with a magnetic stirrer (350 rpm). After sealing the absorption tank and the gas storage tank, place them in a constant temperature water bath with precise temperature control at 80 °C. First, fill the gas storage tank with enough SO₂ (~2.0 bar). After the pressure stabilizes, fill the absorption tank with SO₂. The absorption time for every 0.1 bar is 10 min. After 100 min of absorption (1.0 bar), the maximum absorption capacity is 0.648 g / g.

[0090] Figure 3 For the influence of EmimCl+DDU-32 obtained at different temperatures on the SO₂ absorption capacity in Example 7, Example 17, Example 18 and Example 19, as can be seen from the figure, the higher the temperature, the lower the SO₂ absorption capacity of the obtained product.

[0091] Example 20:

[0092] Weigh 0.1000 g of the bis-imidazolium-based DESs (EmimCl + IDU-32) prepared in Example 15 and place it in the absorption tank and stir it with a magnetic stirrer (350 rpm). After sealing the absorption tank and the gas storage tank, place them in a constant temperature water bath with precise temperature control at 40 °C. First, fill the gas storage tank with enough SO2 (~2.0 bar). After the pressure stabilizes, fill the absorption tank with SO2. The absorption time for every 0.1 bar is 10 min. After 100 min of absorption (1.0 bar), the maximum absorption capacity is 0.857 g / g.

[0093] Example 21:

[0094] Weigh 0.1000 g of the bis-imidazolium-based DESs (EmimCl + IDU-32) prepared in Example 15 and place it in the absorption tank and stir it with a magnetic stirrer (350 rpm). After sealing the absorption tank and the gas storage tank, place them in a constant temperature water bath with precise temperature control at 60 °C. First, fill the gas storage tank with enough SO2 (~2.0 bar). After the pressure stabilizes, fill the absorption tank with SO2. The absorption time for every 0.1 bar is 10 min. After 100 min of absorption (1.0 bar), the maximum absorption capacity is 0.711 g / g.

[0095] Example 22:

[0096] Weigh 0.1000 g of the bis-imidazolium-based DESs (EmimCl + IDU-32) prepared in Example 15 and place it in the absorption tank and stir it with a magnetic stirrer (350 rpm). After sealing the absorption tank and the gas storage tank, place them in a constant temperature water bath with precise temperature control at 80 °C. First, fill the gas storage tank with enough SO2 (~2.0 bar). After the pressure stabilizes, fill the absorption tank with SO2. The absorption time for every 0.1 bar is 10 min. After 100 min of absorption (1.0 bar), the maximum absorption capacity is 0.614 g / g.

[0097] Figure 4 For the influence of EmimCl + IDU-32 obtained at different temperatures on the SO2 absorption capacity in Example 15, Example 20, Example 21 and Example 22, it can be seen from the figure that the higher the temperature, the lower the SO2 absorption capacity of the obtained product.

[0098] Example 23:

[0099] Weigh 0.1000 g of the bis-imidazolium-based DESs (EmimCl + DDU-n, n = 8, 12, 16, 20, 24, 28, 32, and 36) prepared in Examples 1-8 and place them in the absorption tank and stir with a magnetic stirrer (350 rpm). After sealing the absorption tank and the gas storage tank, place them in a constant temperature water bath with precise temperature control at 25 °C. First, fill the gas storage tank with enough SO2 (∼2.0 bar). After the pressure stabilizes, fill the absorption tank with ∼1.0 bar of SO2, record the pressure change per second. After 40 s of absorption (1.0 bar), the absorption equilibrium is basically reached.

[0100] Figure 5 The SO2 absorption rate of EmimCl + DDU-n. The products obtained from raw materials with various ratios all reach the absorption equilibrium in about 40 s.

[0101] Example 24:

[0102] Weigh 0.2000 g of the bis-imidazolium-based DESs (EmimCl + DDU-32) prepared in Example 7 and place them in the absorption tank and stir with a magnetic stirrer (350 rpm). After sealing the absorption tank and the gas storage tank, place them in a constant temperature water bath with precise temperature control at 25 °C. First, fill the gas storage tank with enough CO2 (∼2.0 bar). After the pressure stabilizes, fill the absorption tank with 1.0 bar of CO2. When the pressure drops, replenish CO2 in time to maintain the pressure at 1.0 bar. After absorption saturation, the maximum absorption capacity is 0.0024 g / g. Under the same conditions, the SO2 absorption capacity is 1.0999 g / g. The data is as Figure 6 shown. The ideal selectivity index of this absorbent for SO2 / CO2 is 458.3.

[0103] Example 25:

[0104] Weigh 0.2000 g of the bis-imidazolium-based DESs (EmimCl + IDU-32) prepared in Example 15 and place them in the absorption tank and stir with a magnetic stirrer (350 rpm). After sealing the absorption tank and the gas storage tank, place them in a constant temperature water bath with precise temperature control at 25 °C. First, fill the gas storage tank with enough CO2 (∼2.0 bar). After the pressure stabilizes, fill the absorption tank with 1.0 bar of CO2. When the pressure drops, replenish CO2 in time to maintain the pressure at 1.0 bar. After absorption saturation, the maximum absorption capacity is 0.0022 g / g. Under the same conditions, the SO2 absorption capacity is 1.0883 g / g. The data is as Figure 6 shown. It can be seen that the ideal selectivity index of this absorbent for SO2 / CO2 is 494.7.

[0105] Example 26:

[0106] Weigh 0.1000 g of the bis-imidazolium-based DESs (EmimCl + DDU-32) prepared in Example 7 and place it in the absorption tank, then stir it with a magnetic stirrer (350 rpm). After sealing the absorption tank and the gas storage tank, place them in a constant temperature water bath with precise temperature control at 25 °C. First, fill the gas storage tank with enough SO2 (~2.0 bar). After the pressure stabilizes, fill the absorption tank with SO2 until the pressure reaches 1.0 bar. When the pressure drops, replenish SO2 in a timely manner to maintain the pressure at 1.0 bar. After absorption saturation, evacuate the residual gas in the stainless steel tank, and raise the temperature of the constant temperature water bath to 80 °C. After continuously evacuating for 60 min, introduce N2 to exhaust all the SO2 gas in the stainless steel tank. Lower the temperature to 25 °C, and continue the above absorption experiment after the temperatures of all parts are stable. Repeat this process 30 times to complete the investigation of the recycling performance. After the absorbent is reused 30 times, the absorption capacity can still reach 1.1153 g / g, as shown in Figure 7 (a).

[0107] Example 27:

[0108] Weigh 0.1000 g of the bis-imidazolium-based DESs (EmimCl + DDU-32) prepared in Example 7 and place it in the absorption tank, then stir it with a magnetic stirrer (350 rpm). After sealing the absorption tank and the gas storage tank, place them in a constant temperature water bath with precise temperature control at 25 °C. First, fill the gas storage tank with enough SO2 (~2.0 bar). After the pressure stabilizes, fill the absorption tank with SO2 and measure the absorption capacity (1.100 g / g) at a pressure of 1.0 bar. Seal and store the remaining sample. Weigh 0.1000 g of the sample every 10 days and measure its absorption capacity at a pressure of 1.0 bar. The absorption capacities on the 10th, 20th, and 30th days are 1.086, 1.088, and 1.101 g / g, respectively, as shown in Figure 7 (b).

Claims

1. A bisimidazole-based deep eutectic solvent absorbent, characterized in that, The bistriazolium-based deep eutectic solvents (DESs) are prepared by heating and stirring hydrogen bond acceptors (HBAs) and hydrogen bond donors (HBDs). Among them, the HBA is 1-ethyl-3-methylimidazolium chloride (EmimCl). The HBD is 1,3-bis(hydroxymethyl)-5,5-dimethylhydantoin (DDU) or imidazolidinyl urea (IDU). The molar ratio of the HBAs to the HBDs is 8:1 to 36:

1.

2. The bis-imidazolium-based deep eutectic solvent absorbent according to claim 1, wherein The DESs are liquid at room temperature, and their melting points are much lower than those of the single-component HBAs and HBDs.

3. The preparation method of the bis-imidazolium-based deep eutectic solvent absorbent according to claim 1, characterized in that, The steps are as follows: Put HBAs and HBDs with a certain molar ratio into a container, seal it and place it in an oil bath and heat it to 70 - 110 °C, and at the same time stir strongly at a rotation speed of 500 - 1500 rpm. After heating and stirring for 1 - 5 h, take the container out of the oil bath and cool it to room temperature to obtain the required bistriazolium-based deep eutectic solvent absorbent (DESs).

4. The preparation method of the bis-imidazolium-based deep eutectic solvent absorbent according to claim 3, characterized in that, The oil bath heating temperature is 100 °C, the stirring rate is 800 rmp, and the stirring time is 3 h.

5. Application of the bistriazolium-based deep eutectic solvent absorbent according to claim 1 in SO2 absorption.

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