An iron-based ionic liquid deoxidizer and its application

Abstract

The present invention discloses an iron-based ionic liquid deoxidizer, relates to the technical field of deoxidizers, and the iron-based ionic liquid deoxidizer includes an iron-based ionic liquid, and the iron-based ionic liquid is an imidazole iron-based ionic liquid. The present invention also provides the application of the above-mentioned deoxidizer. The beneficial effects of the present invention are: relative to traditional deoxidation processes, the iron-based ionic liquid deoxidation process has the advantages of mild operating conditions (room temperature, normal pressure), low energy consumption, easy desorption (room temperature, pressure control at -0.05MPa to -0.1MPa), no secondary pollution, etc., can be applied to the enrichment of methane in coalbed methane and the separation of oxygen in the purification process of rare gases, and has a large application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of deoxidizers, and in particular to an iron-based ionic liquid deoxidizer and application thereof. Background Art

[0002] Oxygen has important applications in many fields (metallurgy, medical industry, fuel cells), but in some cases, the removal of oxygen also has important industrial significance. For example, the presence of oxygen will cause certain safety hazards in the exploitation of coalbed methane, and is not conducive to the enrichment of coalbed methane (CH4 volume fraction 3% to 60%, O2 volume fraction 8% to 20%) [Environmental Science and Pollution Research International, 2017, 24 (18): 15240-15253]; in the production and purification of rare gas helium, the removal of oxygen is also particularly important [Guangdong Chemical Industry, 2021, 48 (08): 57-59]; the presence of a small amount of oxygen in the natural gas pipeline will cause pipeline corrosion and oxidation of other components; in the downstream synthesis process of biogas, the presence of a small amount of oxygen will cause the catalyst to deactivate immediately [Chemie Ingenieur Technik, 2018, 90 (10): 1446-1452]. In 2017, my country's coalbed methane extraction volume was 17.8 billion cubic meters, and the underground extraction volume was 12.8 billion cubic meters. However, due to its high oxygen concentration, its utilization rate was low, only 52.8%.

[0003] The current deoxygenation technologies mainly include catalytic combustion, pressure swing adsorption, cryogenic separation, non-metallic reduction and membrane separation. Catalytic combustion is to directly react hydrocarbons with oxygen in the presence of a catalyst to achieve deoxygenation. The precious metal catalysts used are relatively expensive and will consume a large amount of alkanes in the raw gas. Pressure swing adsorption is mostly based on the principle of physical adsorption, using the difference in the equilibrium adsorption amount of each component gas in the gas mixture by the adsorbent, the kinetic diffusion rate inside and outside the particles, or the steric effect of the micropores on the molecules of each component to achieve separation [China: CN85103557, 1986]. However, the pressure swing process expands the explosion range of conventional methane. In order to ensure safe operation, a large amount of inert gas needs to be added [CIESC Journal, 2017, 68(2): 724-728]; cryogenic liquefaction separation is a separation technology that utilizes different boiling points of gases, but the investment is too large and the energy consumption is too high; the non-metallic reduction method is to react metal sulfides with oxygen to form sulfates, and then reduce them to sulfides through CO / H2 [Energy & Fuels, 2017, 31(12): 13842-13851] to achieve circulation, but there are problems such as complex technology and high energy consumption; the membrane separation method has too high requirements on materials [US: US6425267, 2002], and there are still safety hazards for systems with high oxygen content, and the kinetic molecular sizes of O2 and CH4 are close, making it difficult to separate them through membranes. A comparison of conventional deoxygenation technologies is shown in Table 1.

[0004] As an environmentally friendly green solvent, ionic liquids have a wide liquid range, high thermal and chemical stability, low vapor pressure, non-volatility, strong solubility, adjustable structure, and easy recycling compared to traditional organic solvents. They are widely used in organic synthesis, catalysis, separation, and electrochemistry. In addition, the pore structure composed of the interwoven hydrogen bond network in ionic liquids [Journal of Physical Chemistry A, 2006, 110 (31): 9775-9782] is very beneficial to its absorption of gas. Metal-based ionic liquids combine the catalytic function of metal ions and the characteristics of ionic liquids, and have both catalytic centers and gas absorption centers. For example, the patent application with publication number CN112337285A discloses an iron-based ion desulfurization liquid that absorbs H2S. Relevant data show that appropriately adding organic solvents to ionic liquids can significantly reduce the viscosity of the desulfurization liquid and improve the mass transfer capacity between gas and liquid [Journal of Chemistry in Higher Education, 2020, 41 (02): 317-323].

[0005] In recent years, research on oxygen absorption by Co(Ⅱ) chelated ionic liquids has been reported repeatedly [Journal of Molecular Liquids, 2020, 318: 114365; Journal of Membrane Science, 2017, 541: 393-402; Separation and Purification Technology, 2020, 248: 117018]. This ionic liquid uses the coordination of Co(Ⅱ) and O2 to chemically absorb O2, and its absorption capacity is much higher than that of conventional ILs [Science China: Chemistry, 2020, 50(04): 476-488]. After 5 absorption and desorption cycles, the oxygen absorption performance of this oxygen-absorbing material did not decrease significantly, and it has great prospects for oxygen absorption. However, the viscosity of this ionic liquid is extremely high, which is not conducive to the mass transfer and liquid phase transfer of the system, and its industrial application is severely limited.

[0006] Table 1. Comparison of conventional deoxidation technologies

[0007] Summary of the invention

[0008] The technical problem to be solved by the present invention is that conventional deoxygenation technology has poor deoxygenation effect, high cost and certain risks. Co(II) chelated ionic liquid has a large viscosity as an oxygen absorber. An iron-based ionic liquid deoxidizer with a different deoxygenation mechanism and low viscosity and its application are provided.

[0009] The present invention solves the above technical problems through the following technical means:

[0010] An iron-based ionic liquid deoxidizer comprises an iron-based ionic liquid, wherein the iron-based ionic liquid is an imidazole iron-based ionic liquid.

[0011] Beneficial effects: Hydrogen bonds occur between the hydrogen on the imidazolium cation of the iron-based ionic liquid and the oxygen molecules. The π-π stacking effect between the anions and cations of the ionic liquid and the oxygen molecules promotes the formation of a hydrogen bond network within the system and exhibits a porous structure, which is beneficial to the absorption of oxygen.

[0012] The iron-based ionic liquid deoxidizer in the present invention has a very strong oxygen absorption capacity, but its viscosity is reduced by one to two orders of magnitude, which is more conducive to gas-liquid mass transfer and liquid phase transfer. Different from the coordination reaction between Co(II) chelated ionic liquid and oxygen, the absorption of oxygen by the iron-based ionic liquid mainly depends on the intermolecular interaction therein, so it is easier to achieve desorption and separation after oxygen absorption, and its recyclability is better.

[0013] The iron-based ionic liquid deoxidizer in the present invention is different from the molecular sieve pressure swing adsorption method which is widely used in the current industry. The system uses a liquid absorbent. For solid adsorbents such as molecular sieves, their absorption performance can only be improved by pressurization, cooling, etc., which consumes a lot of energy. For iron-based ionic liquid deoxidizers, their absorption capacity can be enhanced by using an external field to strengthen the mass transfer process, adding a stirring device, or using the characteristics of iron-based ionic liquid magnetic fluids to strengthen mass transfer by applying an external magnetic field, which can significantly improve the oxygen absorption capacity.

[0014] Traditional oxygen separation technologies require high-pressure and low-temperature operating conditions. However, iron-based ionic liquids have better absorption performance at normal pressure and room temperature. When the temperature is raised to no more than 45°C, increasing the oxygen partial pressure can significantly improve the oxygen absorption capacity.

[0015] The iron-based ionic liquid deoxygenation process has the advantages of mild operating conditions, low energy consumption, easy desorption, and no secondary pollution. It can be used for the enrichment of methane in coalbed methane and the separation of oxygen in the process of rare gas purification, and has great application prospects.

[0016] Preferably, the iron-based ionic liquid deoxidizer further comprises an organic solvent, and the organic solvent is an aprotic polar organic solvent.

[0017] Beneficial effects: Adding a certain amount of organic solvent can obtain an efficient deoxygenation co-solvent system with low viscosity, low saturated vapor pressure and strong thermal stability, and the oxygen absorption capacity reaches 6.92.g O2 / L. The compounded organic solvent reduces the viscosity of the system and optimizes the binding mechanism of oxygen molecules in the compounded ionic liquid, transforming the binding mechanism of O2 molecules-cations and O2 molecules-anions into the synergistic binding mechanism of O2 molecules-solvent molecules and O2 molecules-cations / anions. The solvent molecules interact with the anions and cations of the iron-based ionic liquid, which increases the distance between anions and cations, changes the original hydrogen bond network, and makes it easier for oxygen molecules to enter; at the same time, the solvent molecules will also form hydrogen bonds and π-π stacking interactions with oxygen molecules to enhance oxygen absorption.

[0018] Preferably, the aprotic polar organic solvent includes polyethylene glycol dimethyl ether (NHD), 1,3-dimethyl-2-imidazolidinone (DMI), N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMAC).

[0019] Preferably, the volume ratio of the iron-based ionic liquid to the organic solvent is 1-2:1-2.

[0020] Beneficial effects: By adjusting the compounding ratio of the organic solvent, the hydrogen bond network of the oxygen absorption system can be further optimized, thereby regulating the absorption capacity of the deoxygenation system.

[0021] Preferably, the volume ratio of the iron-based ionic liquid to the organic solvent is 2:1.

[0022] Beneficial effect: When the volume ratio is 2:1, the deoxidation rate is the highest.

[0023] Preferably, the preparation method of the iron-based ionic liquid comprises the following steps: mixing 1-butyl-3-methylimidazolium chloride and ferric chloride hexahydrate in a molar ratio of 1:2 and stirring for 24 hours, allowing the mixed product to stand for stratification, taking the upper layer of liquid, and vacuum drying it at 80°C for 24 hours to obtain the iron-based ionic liquid BmimFeCl4.

[0024] Beneficial effect: Oxygen enters the ionic liquid and, according to the dual-mode theory, first enters the liquid phase through the liquid membrane and then diffuses inside the liquid phase. Oxygen molecules easily react with the iron-based ionic liquid [Bmim] + The cations combine under the action of π-π and hydrogen bonding, and there is also a strong π-anion interaction between the oxygen molecules and the ferric chloride anions, which promotes the absorption of oxygen.

[0025] The method for preparing the iron-based ionic liquid deoxidizer comprises the following steps: removing oxygen from the iron-based ionic liquid by rotary evaporation to obtain the iron-based ionic liquid deoxidizer.

[0026] Beneficial effects: The deoxidizer of the present invention is simple to prepare, and the obtained deoxidizer has extremely strong oxygen absorption capacity and low viscosity.

[0027] Preferably, the iron-based ionic liquid deoxidizer also includes an organic solvent. After the iron-based ionic liquid and the organic solvent are mixed, they are sealed and stirred, and then rotary evaporated to remove oxygen.

[0028] The deoxidation method using the iron-based ionic liquid deoxidizer comprises the following steps: the iron-based ionic liquid deoxidizer is placed in an oxygen-containing environment and stirred.

[0029] Beneficial effects: Increasing the stirring rate can enhance the mass transfer process and increase its oxygen absorption rate.

[0030] Preferably, the temperature of the oxygen-containing environment is 25-45°C.

[0031] Beneficial effects: When the temperature is below 45℃, increasing the temperature and the oxygen partial pressure can significantly improve the oxygen absorption capacity.

[0032] Preferably, the stirring rate is 200-400 r / min.

[0033] Preferably, the oxygen-containing environment is a deoxygenation tower.

[0034] The raw gas is passed into the deoxidizer, and the temperature and pressure are adjusted to separate the O2 in the raw gas. The main component of the gas discharged from the top of the deoxidation tower is methane, and it also contains a small amount of CO2. The ionic liquid deoxidation system that absorbs oxygen can realize the desorption of oxygen and the regeneration of ionic liquid under the conditions of reduced pressure and increased temperature, thereby realizing the circulation of the entire system.

[0035] The desorption method after deoxidation using the above iron-based ionic liquid deoxidizer comprises the following steps: after heating (45° C.-90° C.), a vacuum pump is used to desorb oxygen from the oxygen-saturated deoxidizer.

[0036] Beneficial effects: Since the deoxygenation system relies on the intermolecular hydrogen bond network to achieve efficient absorption of oxygen, when the temperature is increased, the internal structure of the deoxygenated solution changes, the intermolecular force forming the hydrogen bond network weakens, the binding capacity for oxygen is reduced, and oxygen is easily separated.

[0037] The saturated ionic liquid deoxygenation system is continuously pumped for 1 hour at room temperature using a vacuum pump, with the pumping pressure maintained at -0.05MPa to -0.1MPa. The oxygen desorption rate can reach 95.8%. After 2 hours of pumping, the desorption rate can reach 100%, thereby achieving separation of oxygen and absorbent, and the ionic liquid can be recycled.

[0038] The advantages of the present invention are that hydrogen bonds occur between hydrogen on the imidazolium cations of the iron-based ionic liquid and oxygen molecules, and the π-π stacking effect between the anions and cations of the ionic liquid and the oxygen molecules promotes the formation of a hydrogen bond network in the system, and exhibits a porous structure characteristic, which is beneficial to the absorption of oxygen.

[0039] The iron-based ionic liquid deoxidizer in the present invention has a very strong oxygen absorption capacity, but its viscosity is reduced by one to two orders of magnitude, which is more conducive to gas-liquid mass transfer and liquid phase transfer. Different from the coordination reaction between Co(II) chelated ionic liquid and oxygen, the absorption of oxygen by the iron-based ionic liquid mainly depends on the intermolecular interaction therein, so it is easier to separate oxygen and has better recyclability.

[0040] The iron-based ionic liquid deoxidizer in the present invention is different from the molecular sieve pressure swing adsorption method which is widely used in the current industry. The system uses a liquid absorbent. For solid adsorbents such as molecular sieves, their absorption performance can only be improved by pressurization, cooling, etc., which consumes a lot of energy. For iron-based ionic liquid deoxidizers, their absorption capacity can be enhanced by using an external field to strengthen the mass transfer process, adding a stirring device, or using the characteristics of iron-based ionic liquid magnetic fluids to strengthen mass transfer by applying an external magnetic field, which can significantly improve the oxygen absorption capacity.

[0041] Traditional oxygen separation technologies require high-pressure and low-temperature operating conditions. However, iron-based ionic liquids have better absorption performance at normal pressure and room temperature. Appropriately increasing the temperature and increasing the oxygen partial pressure can significantly improve the oxygen absorption capacity.

[0042] The iron-based ionic liquid deoxygenation process has the advantages of mild operating conditions, low energy consumption, easy desorption, and no secondary pollution. It can be used for the enrichment of methane in coalbed methane and the separation of oxygen in the process of rare gas purification, and has great application prospects.

[0043] The deoxidizer of the invention is simple to prepare, and the obtained deoxidizer has extremely strong oxygen absorption capacity and low viscosity.

[0044] When the temperature is below 45℃, increasing the temperature and the oxygen partial pressure can significantly improve the oxygen absorption capacity.

[0045] Since the deoxygenation system relies on the intermolecular hydrogen bond network to achieve efficient absorption of oxygen, when the temperature is increased (room temperature to 90°C), the internal structure of the deoxygenated solution changes, the intermolecular forces forming the hydrogen bond network weaken, the binding capacity for oxygen is reduced, and oxygen is easily separated.

[0046] The saturated ionic liquid deoxygenation system is continuously pumped for 1 hour at room temperature using a vacuum pump, with the pumping pressure maintained at -0.05MPa to -0.1MPa. The oxygen desorption rate can reach 95.8%. After 2 hours of pumping, the desorption rate can reach 100%, thereby achieving separation of oxygen and absorbent, and the ionic liquid can be recycled. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 The cyclic voltammetric characteristic curve of the iron-based ionic liquid before and after oxygen absorption in Example 11 of the present invention;

[0048] Figure 2 This is an infrared spectrum of the iron-based ionic liquid before and after oxygen absorption in Example 11 of the present invention;

[0049] Figure 3 This is the ultraviolet spectrum of the iron-based ionic liquid before and after oxygen absorption in Example 11 of the present invention;

[0050] Figure 4 is the conductivity of different oxygen absorbers before and after oxygen absorption in Example 12 of the present invention;

[0051] Figure 5 This is a diagram of the hydrogen bond network structure of the iron-based ionic liquid after oxygen absorption in Example 14 of the present invention;

[0052] Figure 6 This is a graph showing oxygen desorption performance of the iron-based ionic liquid in Example 14 of the present invention;

[0053] Figure 7 This is a process flow chart of the iron-based ionic liquid / organic solvent oxygen absorption separation cycle in Example 15 of the present invention. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0055] Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0056] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the art or according to the product instructions.

[0057] Example 1

[0058] Preparation of deoxidizer

[0059] 1. Preparation of iron-based ionic liquids

[0060] Add 500g (1.85mol) of solid ferric chloride hexahydrate (FeCl3·6H2O) into a 1000mL beaker and place it in a water bath at 70°C. After the solid ferric chloride hexahydrate melts, slowly add 161.55g of 1-butyl-3-methylimidazolium chloride (BmimCl) while stirring. After stirring and reacting at room temperature for 24h, the solution is separated into two phases. The upper dark green liquid is centrifuged and dried in vacuo at 80°C for 24h to obtain the imidazole iron-based ionic liquid BmimFeCl4.

[0061] 2. Preparation of deoxidizer 1#

[0062] Take 50 mL of the synthesized BmimFeCl4, and perform rotary evaporation for 30 min at 70°C under vacuum conditions. After removing oxygen, store it in a vacuum desiccator to obtain the 1# deoxidizer.

[0063] Example 2

[0064] Preparation of compound deoxidizer

[0065] Take 20 mL of the imidazole iron-based ionic liquid BmimFeCl4 in Example 1, add 10 mL of weakly polar organic solvent polyethylene glycol dimethyl ether (NHD), seal and stir at room temperature for 2 hours, then rotary evaporate at 70°C for 30 minutes to remove oxygen to obtain BmimFeCl4-NHD, recorded as 2# deoxidizer.

[0066] Example 3

[0067] Preparation of compound deoxidizer

[0068] Take 20 mL of the imidazole iron-based ionic liquid BmimFeCl4 in Example 1, add 10 mL of moderately polar organic solvent N-methylpyrrolidone (NMP), seal and stir at room temperature for 2 hours, then rotary evaporate at 70°C for 30 minutes to remove oxygen to obtain BmimFeCl4-NMP, recorded as deoxidizer #3.

[0069] Example 4

[0070] Preparation of compound deoxidizer

[0071] Take 20 mL of the imidazolyl iron-based ionic liquid BmimFeCl4 in Example 1, add 10 mL of a moderately polar organic solvent 1,3-dimethyl-2-imidazolidinone (DMI), seal and stir at room temperature for 2 h, then rotary evaporate at 70 ° C for 30 min to remove oxygen to obtain BmimFeCl4-DMI, recorded as 4# deoxidizer.

[0072] Example 5

[0073] Preparation of compound deoxidizer

[0074] Take 20 mL of the imidazole iron-based ionic liquid BmimFeCl4 in Example 1, add 10 mL of a suitably polar organic solvent N,N-dimethylformamide (DMF), seal and stir at room temperature for 2 h, then rotary evaporate at 70 ° C for 30 min to remove oxygen to obtain BmimFeCl4-DMF, recorded as 5# deoxidizer.

[0075] Example 6

[0076] Preparation of compound deoxidizer

[0077] Take 20 mL of the imidazolyl iron-based ionic liquid BmimFeCl4 in Example 1, add 10 mL of a suitably polar organic solvent N,N-dimethylacetamide (DMAC), seal and stir at room temperature for 2 h, then rotary evaporate at 70°C for 30 min to remove oxygen to obtain BmimFeCl4-DMAC, recorded as deoxidizer #6.

[0078] Example 7

[0079] The difference between this embodiment and embodiment 2 is that the volume ratio of imidazole iron-based ionic liquid BmimFeCl4 to N-methylpyrrolidone is 1:1.

[0080] Example 8

[0081] The difference between this embodiment and embodiment 2 is that the volume ratio of imidazole iron-based ionic liquid BmimFeCl4 to N-methylpyrrolidone is 1:2.

[0082] Example 9

[0083] Deoxidation performance test

[0084] Take 10mL of the deoxidizer in Examples 1 to 8 respectively, place it in a 250mL three-necked flask, and absorb oxygen at an absorption temperature of 25°C under an environment where the oxygen concentration is greater than 99%. And record its absorption rate and equilibrium adsorption amount in the first 5 hours, as shown in Table 2. The oxygen absorption capacity of pure iron-based ionic liquid is as high as 7.82g O2 / L, but due to its high viscosity, its oxygen absorption rate is relatively low, which is 1.65mg O2 / h. The oxygen absorption rate of the deoxidizer in Example 2, Example 7, and Example 8 is significantly reduced in the first five hours, which is 2.24mg O2 / h, 1.94mg O2 / h, and 1.89mg O2 / h, respectively, indicating that the increase in the ratio of organic solvent will reduce its oxygen absorption rate and oxygen absorption, and the deoxidation capacity of the deoxidizer can be controlled by adjusting the solvent ratio. Judging from the absorption rate in the first 5 hours, the addition of solvent increased the mass transfer capacity of the system and significantly improved the oxygen absorption rate of the deoxygenation system, but its saturated adsorption capacity decreased to varying degrees, which indicates that the addition of solvent will cause changes in the hydrogen bond network inside the ionic liquid.

[0085] Table 2. Deoxidation capacity of different deoxidizers

[0086]

[0087] Example 10

[0088] Deoxygenation performance control

[0089] 1. Temperature control

[0090] 10 mL of the deoxidizer #1 in Example 1 was placed in a 250 mL three-necked flask, and oxygen absorption was performed at absorption temperatures of 25°C, 35°C, and 45°C in an environment where the oxygen concentration was greater than 99%. The absorption rates in the first 5 hours were 1.95 mg O2 / h, 2.23 mg O2 / h, and 2.46 mg O2 / h, respectively.

[0091] Take 10mL of the composite ionic liquid oxygen absorption system of Example 2 to Example 6 and place it in a 250mL three-necked flask. The oxygen concentration in the flask is greater than 99%, the temperature is 25-45°C, the initial pressure is 1atm, and the change in the oxygen volume inside the flask is detected by an external vacuum gauge. After oxygen absorption is saturated, the oxygen absorption capacity of each composite system exceeds 2.5g O2 / L.

[0092] 2. Mass transfer regulation

[0093] 10 mL of the 1# deoxidizer in Example 1 was placed in a 250 mL three-necked flask, and oxygen absorption was performed at an absorption temperature of 25°C, stirring rates of 200 r / min, 300 r / min and 400 r / min, respectively, under an oxygen concentration greater than 99%. The absorption rates in the first 5 hours were 1.89 mg O2 / h, 2.35 mg O2 / h and 2.90 mg O2 / h, respectively. This indicates that the mass transfer process can be enhanced and its oxygen absorption rate can be increased by appropriately raising the temperature (25°C-45°C) and increasing the stirring rate.

[0094] Embodiment 11

[0095] Characterization of oxygen absorption mechanism of iron-based ionic liquids

[0096] 1. Cyclic voltammetry curve determination

[0097] Experimental instrument: electrochemical workstation (RST3100), Zhengzhou Shi Ruisi Instrument Co., Ltd. A three-electrode system was used, the working electrode was a glassy carbon electrode with a diameter of 2 mm, the auxiliary electrode was an Ag / AgCl electrode, the reference electrode was a platinum wire electrode, the temperature was 298.15 K, the scanning rate was 50 mV / s, and the scanning range was -2 to 2 V.

[0098] Characterization analysis: The cyclic voltammetric characteristic curve of oxygen absorber 1# before and after oxygen absorption was measured. The results are as follows: Figure 1 As shown. Figure 1 It can be seen that after the iron-based ionic liquid absorbs oxygen, the redox peak moves to both ends and the current density increases significantly, which indicates that oxygen interacts with the iron-based ionic liquid to weaken Bmim + With FeCl4 - The interaction between them increases, which makes the binding force of chlorine on iron stronger, and the distance between anions and cations becomes larger, making ion migration easier.

[0099] 2. Infrared spectroscopy

[0100] Experimental instrument: Fourier transform infrared spectrometer (TENSOR27), BRUKER, Germany. Resolution 1cm -1 , infrared scanning range is 400~4000cm -1, scan number 64. Potassium bromide windows.

[0101] Characterization analysis: The infrared spectrum of deoxidizer 1# before and after oxygen absorption was characterized, such as Figure 2 The results show that after absorbing oxygen, the carbon-hydrogen bond stretching vibration peak on the imidazole ring increases from 3149 cm -1 Red shifted to 3148 cm -1 The stretching vibration peak of the carbon-hydrogen bond on the alkyl chain is 2936cm -1 Red shifted to 2935 cm -1 , which suggests that the oxygen molecule may interact with the hydrogen on the imidazole ring and the hydrogen on the alkyl chain.

[0102] 3. UV-visible spectroscopy

[0103] Experimental instrument: Double-beam UV-visible spectrophotometer (TU-1901), Beijing Puxi General Instrument Co., Ltd. Scanning range 200nm-900nm.

[0104] Characterization analysis: UV spectroscopy was performed on deoxidizer 1# before and after oxygen absorption. The results are as follows: Figure 3 As shown, the characteristic peak at 421 nm shifts and the characteristic peak at 435 nm disappears, which indicates that after oxygen absorption, there is an interaction force between oxygen molecules and ferric chloride anions.

[0105] Example 12

[0106] Effect of solvent on oxygen absorption properties of iron-based ionic liquids

[0107] 1. Conductivity measurement

[0108] Experimental instrument: Leici DDS-307A conductivity meter, temperature is 298.15K.

[0109] Characterization analysis: The conductivity of deoxidizers 1#, 2#, 3#, 4#, 5#, and 6# before and after oxygen absorption was measured. Figure 4 The test results show that after the deoxidizer absorbs oxygen, the conductivity increases, and the deoxidizers 5# and 6# with high conductivity have poor deoxidation performance, while the deoxidizers 2#, 3#, and 4# with low conductivity have better deoxidation performance.

[0110] 2. Determination of cyclic voltammetric characteristic curve

[0111] Experimental instrument: electrochemical workstation (RST3100), Zhengzhou Shi Ruisi Instrument Co., Ltd. A three-electrode system was used, the working electrode was a glassy carbon electrode with a diameter of 2 mm, the auxiliary electrode was an Ag / AgCl electrode, the reference electrode was a platinum wire electrode, the temperature was 298.15 K, the scanning rate was 50 mV / s, and the scanning range was -2 to 2 V.

[0112] Characterization analysis: Cyclic voltammetry characteristic curves of deoxidizers 1#, 2#, 3#, 4#, 5#, and 6# before and after oxygen absorption were measured. The results are shown in Table 3, which shows that the redox potential difference of the deoxidizer increases after oxygen absorption, and the system with a larger redox potential difference has better deoxidation performance.

[0113] Table 3. Peak potential of cyclic voltammetric characteristic curves of different deoxidizers before and after oxygen absorption

[0114]

[0115]

[0116] 3. Infrared spectroscopy

[0117] Experimental instrument: Fourier transform infrared spectrometer (TENSOR27), BRUKER, Germany. Resolution 1cm -1 , infrared scanning range is 400~4000cm -1 , scan number 64. Potassium bromide windows.

[0118] Characterization analysis: Infrared spectra of deoxidizers 1#, 2#, 3#, 4#, 5#, and 6# before and after oxygen absorption were measured, as shown in Table 4. The results show that after the deoxidizer absorbs oxygen, the stretching vibration peaks of the carbon-hydrogen bond on the imidazole cation ring and the stretching vibration peaks of the alkyl chain are shifted, which indicates that oxygen molecules are easy to interact with them.

[0119] Table 4. Infrared spectra characteristic peak positions of different deoxidizers before and after oxygen absorption

[0120]

[0121] Example 13

[0122] Absorption performance of iron-based ionic liquids for carbon dioxide and methane

[0123] 1. Iron-based ionic liquid absorbs CO2

[0124] Take 30mL of deoxidizer 1# and inject it into the high-pressure reactor. Set the temperature to 298.15K, introduce pure CO2 into the reactor, change the pressure in the reactor, and measure the absorption performance. When the pressure does not change for 30 minutes, record the equilibrium pressure and obtain the solubility of carbon dioxide. As shown in Table 5, the absorption of carbon dioxide by iron-based ionic liquids conforms to Henry's law, and pressurization can significantly increase the solubility of carbon dioxide. However, under normal pressure, iron-based ionic liquids basically have no ability to absorb carbon dioxide.

[0125] Table 5.298.15K conditions, CO2 solubility data in iron-based ionic liquids at different pressures

[0126]

[0127] 2. Iron-based ionic liquid absorbs CH4

[0128] Take 30mL of deoxidizer 1#, inject it into the high-pressure reactor, set the temperature to 298.15K, introduce pure CH4 into the reactor, change the pressure inside the reactor, and measure the absorption performance. For BmimFeCl4, when the initial pressure increases from 0.80Mpa to 2.40Mpa, the pressure inside the reactor does not change significantly during the absorption process, so BmimFeCl4 basically has no absorption capacity for methane.

[0129] Embodiment 14

[0130] Oxygen desorption by iron-based ionic liquids

[0131] Take 5 mL of oxygen-saturated oxygen absorber 1# and place it in a 250 mL three-necked flask. Use a vacuum pump to desorb oxygen at 298.15 K. Since the above deoxygenation system relies on the intermolecular hydrogen bond network to achieve efficient oxygen absorption, see Figure 5 Therefore, after the temperature is increased, the internal structure of the deoxygenated solution changes, the intermolecular force forming the hydrogen bond network is weakened, the binding ability to oxygen is reduced, and oxygen is easily separated.

[0132] The desorption results are shown in Figure 6 At room temperature, when the suction pressure is -0.05MPa, the desorption efficiency can reach 95.8% after desorption for 1h, and the desorption rate can reach 100% after desorption for 2h. The desorption conditions are relatively mild, and high temperature and vacuum degree are not required. After the iron-based ionic liquid is absorbed and desorbed for 3 cycles, its absorption capacity does not change significantly, and is 7.62g / L, 7.82g / L, and 7.84g / L respectively. This shows that the separation of oxygen and deoxidizer can be achieved, and the ionic liquid can be recycled.

[0133] Embodiment 15

[0134] Iron-based ionic liquid oxygen separation circulation process

[0135] like Figure 7 As shown, the raw gas is passed into the deoxidizer, and the temperature and pressure are adjusted to separate the O2 in the raw gas. The main component of the gas out of the top of the deoxidation tower is methane, and it also contains a small amount of CO2. The ionic liquid deoxidation system that absorbs oxygen is passed into the desorption tower. Through the vacuum pump, the desorption of oxygen and the regeneration of the ionic liquid can be achieved under the conditions of reduced pressure and increased temperature, and then passed into the liquid storage tank to realize the circulation of the entire system.

[0136] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. 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 embodiments of the present invention.

Claims

1. Application of an iron-based ionic liquid deoxidizer in coalbed methane and rare gas, characterized in that: The iron-based ionic liquid deoxidizer is used to absorb oxygen in coal-bed methane and rare gases, and the oxygen absorption conditions are to absorb oxygen at room temperature to 45°C and above normal pressure; The iron-based ionic liquid deoxidizer is an imidazole iron-based ionic liquid and an organic solvent, and the volume ratio of the imidazole iron-based ionic liquid to the organic solvent is 2:1; The desorption method of the iron-based ionic liquid deoxidizer comprises the following steps: heating the iron-based ionic liquid deoxidizer, desorbing oxygen from the oxygen-absorbed iron-based ionic liquid deoxidizer using a vacuum pump, the desorption pressure being between -0.05 MPa and -0.1 MPa, and removing oxygen from the iron-based ionic liquid deoxidizer by rotary evaporation to obtain a recovered iron-based ionic liquid deoxidizer; The organic solvent includes polyethylene glycol dimethyl ether, 1,3-dimethyl-2-imidazolidinone, N-methylpyrrolidone, N,N-dimethylformamide or N,N-dimethylacetamide; The preparation method of the imidazole iron-based ionic liquid is as follows: 1-butyl-3-methylimidazolium chloride and ferric chloride hexahydrate are mixed and stirred in a molar ratio of 1:2 for 24 hours, the mixed product is allowed to stand for stratification, the upper layer of liquid is taken, and vacuum dried at 80° C. for 24 hours to obtain the iron-based ionic liquid BmimFeCl4.

2. The use of the iron-based ionic liquid deoxidizer in coalbed methane and rare gas according to claim 1, characterized in that: The iron-based ionic liquid deoxidizer is placed in coal-bed methane or rare gas, and oxygen in the coal-bed methane or rare gas is absorbed by the iron-based ionic liquid deoxidizer through gas-liquid mixing.

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