A method for absorbing carbon monoxide by a composite system of ionic liquid and dihydric phenol

Abstract

The invention discloses a method for absorbing carbon monoxide by a composite system of ionic liquid and dihydric phenol. The method adopts an ionic liquid composite system composed of an ionic liquid containing cuprous functional anions and a dihydric phenol solvent as an absorbent, the absorption gas pressure is 10kPa-800kPa, the absorption temperature is 10℃-100℃, and the absorption time is 0.5-10h; the desorption process of the composite system absorbing carbon monoxide is as follows: directly connect the composite system absorption tank containing saturated carbon monoxide to a vacuum pump, evacuate the absorbent system for 0.5-2h, and keep the desorption temperature at 50℃-120℃ during the desorption process. The invention improves the carbon monoxide absorption and separation capacity by utilizing phenolic hydroxyl groups to assist cuprous anions and regulate the interaction between cuprous and carbon monoxide, and the absorption amount can reach 0.64mol / mol at normal temperature and pressure.

Description

Technical Field

[0001] The invention belongs to the technical field of carbon monoxide absorption and separation, and relates to a method for absorbing carbon monoxide by a composite system of ionic liquid and dihydric phenol, and specifically relates to an ionic liquid composite system composed of an ionic liquid with cuprous functional anions and a dihydric phenol solvent as an adsorbent for carbon monoxide absorption, wherein the ionic liquid composite system utilizes phenolic hydroxyl groups to assist cuprous anions and improve the carbon monoxide absorption and separation capacity. Background Art

[0002] Carbon monoxide is a colorless, odorless, toxic and harmful gas that mainly comes from water gas hydrogen production, carbon steel refining process, automobile exhaust and other processes of incomplete carbon combustion. When hydrogen is used in fuel cells, if there is residual carbon monoxide in the system, it will poison the catalyst of the fuel cell and cause the battery to fail. If humans or animals inhale a large amount of incompletely burned carbon monoxide, it will cause human poisoning. On the other hand, carbon monoxide is also a resource. Carbon monoxide can be recovered and used as a carbonylation reagent to react with different substrates to obtain the corresponding carbonylation products. Therefore, the absorption, separation and purification of carbon monoxide is of great value in the upgrading of life health and chemical products industry.

[0003] The traditional industrial method for absorbing carbon monoxide is to use CuAlCl4 dissolved in aromatic solvents such as benzene as the absorption liquid. However, the benzene and other benzene series used in this method are highly toxic to the human body, and the utilization rate of cuprous salts is low, resulting in a low carbon monoxide absorption capacity of the absorbent, which does not conform to the principle of sustainable development.

[0004] In recent years, ionic liquids have attracted extensive attention as a green solvent system with good solubility, extremely low volatility, high thermal stability and chemical stability, and designability, and have been used in dissolution and catalytic conversion reactions. The strong solubility of ionic liquids for inorganic systems provides a good opportunity for carbon monoxide absorption and separation. For example, Ortiz et al. reported that 1-hexyl-3-methylimidazolium cuprous chloride ionic liquid ([Hmim][CuCl2]) can absorb carbon monoxide through chemical reaction, and the absorption capacity at 35°C and 100 kPa is 0.02 mol / mol (Separation and Purification Technology, 2012, 97, 65-72); Hu et al. reported that triethylammonium cuprous chloride ionic liquid ([TEA][CuCl2]) can absorb 0.078 mol / mol of carbon monoxide at 30°C and 100 kPa through the chemical reaction between carbon negative and carbon monoxide (Chemical Communications. 2019, 55, 3390-3393).

[0005] In recent years, composite absorbent systems based on ionic liquids have attracted people's attention because they not only have the advantages of ionic liquids, but also overcome the shortcomings of pure ionic liquids, such as high viscosity and low gas mass transfer. Therefore, by adjusting the structure and developing a new composite absorbent system based on ionic liquids, the utilization efficiency of cuprous salts can be improved, thereby increasing the capacity of carbon monoxide absorption and separation. Summary of the invention

[0006] In view of the above problems existing in the prior art, the purpose of the present invention is to provide a method for absorbing carbon monoxide by a composite system of ionic liquid and diphenol, that is, to design and synthesize an ionic liquid composite system consisting of an ionic liquid with cuprous functional anions and a diphenol solvent, and to utilize phenolic hydroxyl groups to assist cuprous anions to improve the carbon monoxide absorption and separation capacity, thereby achieving efficient, high-capacity and reversible absorption of carbon monoxide gas.

[0007] The invention provides a method for absorbing carbon monoxide by a composite system of ionic liquid and dihydric phenol, which specifically comprises: using an ionic liquid composite system composed of an ionic liquid containing cuprous functional anions and a dihydric phenol solvent as an absorbent, utilizing phenolic hydroxyl groups to assist cuprous anions, and improving the carbon monoxide absorption and separation capacity; during the absorption process, the absorption gas pressure is 10 kPa to 800 kPa, the absorption temperature is 10° C. to 100° C., and the absorption time is 0.5 to 10 hours; the desorption process of the composite system for absorbing carbon monoxide is as follows: directly connecting an absorption tank of the composite system for absorbing saturated carbon monoxide to a vacuum pump, evacuating the absorbent system for 0.5 to 2 hours, and maintaining the desorption temperature at 50° C. to 120° C. during the desorption process.

[0008] The preparation process of the ionic liquid and dihydric phenol composite system defined in the present invention is: under nitrogen protection, the ionic liquid of cuprous anion function and dihydric phenol compound are mixed, heated to 60-100° C. in an oil bath, and stirred at normal pressure for 2-3 hours to obtain the composite system.

[0009] Furthermore, the present invention also defines the molar ratio of the ionic liquid of cuprous functional anions to the diphenol compound as 1:0.5 to 1:7, preferably 1:1.3-1.7.

[0010] Furthermore, the present invention also defines the cuprous functional anion as cuprous chloride anion; the cation of the ionic liquid is: N-hydrogen-2-methylpyridinium, N-hydrogen-N'-methylimidazolium, N-hydrogen-N,N-dimethylpropylammonium, P-hydrogen-tributylphosphonium, P-hydrogen-triphenylphosphonium; the dihydric phenol solvent is catechol, resorcinol, hydroquinone, 4-fluorocatechol, 4-chlororesorcinol or 4-bromohydroquinone, etc.

[0011] Furthermore, the present invention also defines the ionic liquid composite system as a composite system of N-hydrogen-2-methylpyridinium cation, cuprous chloride anion and catechol, and the molar ratio thereof is 1:3.

[0012] By adopting the above technology, compared with the prior art, the present invention adopts an ionic liquid composite system composed of an ionic liquid containing cuprous functional anions and a diphenol solvent as an absorbent, and utilizes phenolic hydroxyl groups to assist cuprous anions to improve the carbon monoxide absorption and separation capacity, and has the following advantages: (1) high absorption capacity, the absorption amount can reach 0.64 mol / mol at normal temperature and pressure; (2) good stability and easy circulation, so the loss of absorbent in the absorption and desorption process can be greatly reduced. DETAILED DESCRIPTION

[0013] The above contents of the present invention are further described in detail below through examples, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples, and all technologies implemented based on the above contents of the present invention belong to the scope of the present invention.

[0014] Example 1

[0015] The absorption device adopts a double tank method (two 316L stainless steel chambers), in which the larger tank is a gas storage tank, and the other tank is an absorption tank. The absorption tank is filled with an ionic liquid composite system (as shown in Table 1). The gas storage tank and the absorption tank are connected through a conduit, and a control valve is provided on the conduit. The tank is provided with a pressure gauge and connected to a computer. The double tanks are placed in a water bath at the same temperature for gas absorption. The pressure changes of the gas storage tank and the absorption tank during the absorption process are automatically recorded by a computer to obtain the equilibrium absorption amount of carbon monoxide by the system under the corresponding equilibrium pressure and temperature conditions. The dihydric phenol compound in the control system is catechol (the molar ratio of ionic liquid to catechol is 1:3), the control temperature is 20°C, the gas pressure is 100kPa when the absorption is balanced, and the absorption capacity is measured. The absorption results of carbon monoxide gas are shown in Table 1.

[0016] Table 1 Effect of cations with different structures on the capture behavior of carbon monoxide by ionic liquid composite system

[0017]

[0018] It can be seen from Table 1 that under the same absorption conditions, the ionic liquid composite system using pyridine as the cation has a higher absorption of carbon monoxide. However, the different cation structures of the ionic liquid still have little effect on the absorption of carbon monoxide by the system.

[0019] Example 2

[0020] Similar to Example 1, N-hydrogen-2-methylpyridinium is used as a cation, cuprous chloride is used as an anion to form an ionic liquid, different phenolic organic substances are used as additives, and the molar ratio of the ionic liquid to the dihydric phenol is 1:1 to 1:5. The temperature is controlled to be 20°C, the gas pressure is 100 kPa at absorption equilibrium, and the absorption capacity is measured. The absorption results of carbon monoxide gas are shown in Table 2.

[0021] Table 2 Effects of different diphenols and mixed molar ratios on the capture of carbon monoxide by ionic liquid composite systems

[0022]

[0023]

[0024] As can be seen from Table 2, under the same absorption conditions, the addition of substituents and the different structures of different isomers of diphenols have a relatively small effect on the absorption capacity of carbon monoxide by the ionic liquid composite absorbent system. However, the ratio of ionic liquid to diphenol has a significant effect on the absorption capacity of carbon monoxide by the composite system. When the diphenol content is low, the absorption capacity is relatively low. The absorption capacity of the system for carbon monoxide increases with the increase of the diphenol content in the system. When the diphenol content is high, the absorption capacity is maintained at a certain level, and the carbon monoxide absorption capacity of the system does not change significantly when the diphenol content is increased.

[0025] Example 3

[0026] Similar to Example 1, N-hydrogen-2-methylpyridinium is used as a cation, cuprous chloride is used as an anion to form an ionic liquid, catechol is used as an additive to form an ionic liquid composite system, and the molar ratio of the ionic liquid to the dihydric phenol is 1:3. The temperature is controlled to be 10-100°C, the gas pressure is 10-800 kPa at absorption equilibrium, and the absorption time is 0.5-10h; the absorption capacity is measured. The absorption results of carbon monoxide gas are shown in Table 3.

[0027] Table 3 Effects of different temperatures and carbon monoxide partial pressures on the carbon monoxide capture behavior of the ionic liquid composite system

[0028]

[0029]

[0030] As can be seen from Table 3, the absorption amount of carbon monoxide gas will change significantly with different absorption temperatures. When the gas pressure is 100kPa at the absorption equilibrium, the lower the absorption temperature, the higher the capture capacity of carbon monoxide gas absorbed by the ionic liquid composite system, but the longer the absorption time required to reach equilibrium; the higher the absorption temperature, the lower the capture capacity of carbon monoxide gas absorbed by the ionic liquid composite system, but the equilibrium absorption time is shortened. The absorption amount of carbon monoxide gas will change significantly with different absorption equilibrium pressures. When the absorption temperature remains unchanged at 20°C, the lower the absorption gas equilibrium pressure, the lower the capture capacity of carbon monoxide gas absorbed by the ionic liquid composite system, and the longer the absorption time required to reach equilibrium; the higher the absorption gas equilibrium pressure, the higher the capture capacity of carbon monoxide gas absorbed by the ionic liquid composite system, and the shorter the absorption time required to reach equilibrium. At a certain temperature, at low pressure, the system's absorption capacity for carbon monoxide is very low; at high pressure, the system's absorption capacity for carbon monoxide approaches 1 mol / mol IL; in the medium pressure range, the system's absorption capacity for carbon monoxide increases rapidly with increasing pressure.

[0031] Example 4

[0032] Similar to Example 1, N-hydrogen-2-methylpyridinium is used as a cation, cuprous chloride is used as an anion to form an ionic liquid, catechol is used as an additive to form an ionic liquid composite system, and the molar ratio of the ionic liquid to the dihydric phenol is 1:3. The control temperature is 20°C, and the gas pressure is 100kPa when the absorption equilibrium is reached. After the absorption is completed, the desorption temperature is 50-120°C, and the desorption time is 0.5-2h. The mass change of the system after vacuuming is used to determine whether the desorption of carbon monoxide is completed and the desorption residue. The results are shown in Table 4.

[0033] Table 4 Effect of desorption temperature on desorption of carbon monoxide by ionic liquid composite system

[0034] Serial number Desorption temperature(℃) Desorption time (h) Residual carbon monoxide (mol / molIL) 1 50 2 0 2 50 1.5 0.05 3 50 1 0.1 4 50 0.5 0.2 5 80 1 0 6 80 0.5 0.15 7 90 0.5 0.1 8 100 0.5 0.05 9 120 0.5 0

[0035] As can be seen from Table 4, the composite system of ionic liquid and dihydric phenol requires a long desorption time when desorbed at low temperature; the desorption rate is relatively fast when desorbed at high temperature. When desorbed at high temperature, there is no residual carbon monoxide in the system, and the desorption is complete. In summary, the system can also be completely desorbed at higher temperature and longer time.

[0036] Example 5

[0037] Similar to Example 1, N-hydrogen-2-methylpyridinium is used as a cation, cuprous chloride is used as an anion to form an ionic liquid, catechol is used as an additive to form an ionic liquid composite system, and the molar ratio of the ionic liquid to the dihydric phenol is 1:3. The temperature is controlled to be 20°C, and the gas pressure is 100kPa when the absorption is balanced. The absorption capacity is measured. The ionic liquid composite system after the absorption is desorbed similarly to Example 6, with a desorption temperature of 80°C and a desorption time of 1h. After the desorption is completed, the next absorption is continued. The cyclic absorption results of carbon monoxide gas are shown in Table 5.

[0038] Table 5 Cyclic absorption capacity of ionic liquid composite system

[0039]

[0040] It can be seen from Table 5 that the carbon monoxide absorption capacity of the composite system of ionic liquid and dihydric phenol does not decrease significantly after five absorption and desorption cycles.

[0041] The basic principles, main features and advantages of the present invention are shown and described above. Without departing from the spirit and scope of the present invention, the present invention may also be subject to various changes and improvements, which all fall within the scope of the present invention to be protected.

Claims

1. A method for absorbing carbon monoxide by a composite system of ionic liquid and dihydric phenol, characterized in that The ionic liquid composite system composed of an ionic liquid containing cuprous functional anions and a dihydric phenol solvent is used as an absorbent, and the phenolic hydroxyl group is used to assist the cuprous anions to improve the carbon monoxide absorption and separation capacity. During the absorption process, the absorption gas pressure is 10kPa~800kPa, the absorption temperature is 10℃~100℃, and the absorption time is 0.5~10h; the desorption process of the composite system for absorbing carbon monoxide is as follows: directly connect the composite system absorption tank containing saturated carbon monoxide to a vacuum pump, and The absorbent system is evacuated for 0.5-2h, and the desorption temperature is maintained at 50-120°C during the desorption process; the molar ratio of the ionic liquid with cuprous functional anions to the diphenol compound is 1:1.3-1.7; the cuprous functional anions are cuprous chloride anions; the cation of the ionic liquid is one of N-hydrogen-2-methylpyridinium, N-hydrogen-N'-methylimidazolium, N-hydrogen-N,N-dimethylpropylammonium, P-hydrogen-tributylphosphonium, and P-hydrogen-triphenylphosphonium.

2. The method for absorbing carbon monoxide by a composite system of an ionic liquid and a dihydric phenol according to claim 1, characterized in that The preparation process of the composite system of ionic liquid containing cuprous functional anions and dihydric phenol is as follows: under nitrogen protection, the ionic liquid containing cuprous functional anions and dihydric phenol compounds are mixed, heated to 60°C-100°C in an oil bath, and stirred at normal pressure for 2-3 hours to obtain the composite system.

3. The method for absorbing carbon monoxide by a composite system of ionic liquid and dihydric phenol according to claim 1, characterized in that The diphenol solvent is catechol, resorcinol, hydroquinone, 4-fluorocatechol, 4-chlororesorcinol or 4-bromohydroquinone.

4. The method for absorbing carbon monoxide by a composite system of ionic liquid and dihydric phenol according to claim 1, characterized in that The ionic liquid composite system is a composite system of N-hydrogen-2-methylpyridinium cation, cuprous chloride anion and catechol, and the molar ratio thereof is 1:

3.

5. The method for absorbing carbon monoxide by a composite system of ionic liquid and dihydric phenol according to claim 1, characterized in that The absorption gas pressure is 200kPa~800kPa, the absorption temperature is 10℃~50℃, and the absorption time is 0.5~6h.

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