A method for efficient oxygen capture

Abstract

The application discloses a method for efficiently capturing oxygen, in which anion functionalized ionic liquid containing Mo, W, B and V is used as an absorbent to absorb O2; during the absorption process, the absorption pressure is 0.02-0.1 MPa, the absorption temperature is 20-100 DEG C, and the absorption time is 2-8 h; the desorption process is carried out under 0.02-0.1 MPa, the desorption temperature is 70-120 DEG C, and the desorption time is 0.5-4 h; the functionalized ionic liquid is composed of alkyl quaternary phosphonium cation and molybdate, tungstate, metaborate and orthovanadate. The application realizes efficient and recyclable capture of O2 by using the coordination of O2 and anions, has the advantages of high absorption efficiency, large absorption capacity, wide use environment for absorption of O2, wide absorption temperature control range, and the like, and can reduce the viscosity of the system after absorption of O2, which is beneficial to desorption and recycling of O2.

Description

Technical Field

[0001] This invention relates to the field of gas separation technology, and in particular to a method for efficiently capturing oxygen. Background Technology

[0002] Ionic liquids (ILs) are organic salts composed of organic cations and inorganic or organic anions through electrostatic interactions and are liquid below 100°C. They have advantages such as low vapor pressure, good thermal and chemical stability, wide electrochemical window, and tunable structure and properties, and are widely used for the efficient capture and separation of acidic gases such as CO2, SO2, and H2S, and alkaline gases such as NH3.

[0003] The high efficiency of solvents (ILs) in absorbing acidic and basic gases mainly utilizes the tunability of their structure and properties. Through the reactivity of their anions and cations with these gases, they achieve high-capacity absorption and low-energy desorption of acidic or basic gases. Compared to acidic gases such as CO2, SO2, and H2S, and basic gases such as NH3, O2 is a neutral gas, and its interaction with ILs is weaker, with physical interactions dominating. Existing research results indicate that the O2 absorption performance of ILs and the solubility of O2 in ILs are relatively low. For example, Zhou et al. compared the absorption capacities of CO2, H2, N2 and O2 in ionic liquid 1-n-butyl-3-methylimidazolium heptafluorobutyrate ([C4mim][CF3CF2CF2COO]). The results showed that the absorption capacity of O2 at 303.15 K and 22.4 bar was 0.1008 mol O2 / mol IL, which was slightly higher than that of H2, close to that of N2, but much lower than that of CO2 (Zhou L, Fan J, Shang X, et al. Solubilities of CO2, H2, N2 and O2 in ionic liquid 1-n-butyl-3-methylimidazolium heptafluorobutyrate[J].The Journal of Chemical Thermodynamics,2013,59:28-34.). Furthermore, at 298.5 K and 13 bar, the solubility of O2 in 1-butyl-3-methylimidazolium hexafluorophosphate ILs ([Bmim][PF6]) and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ILs ([Bmim][Tf2N]) was only 1.7 × 10⁻⁶. –3 and 2.98×10 –3The ratio of mol O2 / mol IL (Anthony JL, Anderson JL, Maginn EJ, et al. Anion effects on gas solubility in ionic liquids[J].The Journal of Physical Chemistry B,2005,109(13):6366-6374.) indicates that the absorption of O2 by the aforementioned ILs is a physical absorption. Due to the differences in structure and properties between O2 and CO2, SO2, NH3, etc., it is not feasible to directly apply existing strategies for improving the absorption of acidic or alkaline gases by ILs to improve the absorption performance of O2. Therefore, based on the molecular structure characteristics of O2 and combined with the designability advantages of the structure and properties of ILs, developing a method for the efficient absorption of O2 by ILs has significant application value. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for efficiently capturing O2. It utilizes a functionalized ILs with alkyl quaternary phosphine as the cation and empty orbital elements as the anion to achieve efficient and recyclable O2 capture by leveraging the coordination between O2 and the anion. It has the advantages of high absorption efficiency, large absorption capacity, wide application environment for O2 absorption, and wide range of absorption temperature control. At the same time, it can also reduce the viscosity of the system after absorbing O2, which is beneficial to the desorption and recycling of O2.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A highly efficient method for capturing oxygen involves using a functionalized ionic liquid composed of an alkyl quaternary phosphine cation and anions containing Mo, W, B, or V as the absorbent to absorb O2. During absorption, the absorption pressure is 0.02–0.1 MPa, the absorption temperature is 20–100 °C, and the absorption time is 2–8 h. The desorption process is carried out at 0.02–0.1 MPa, the desorption temperature is 70–120 °C, and the desorption time is 0.5–4 h. In fact, functionalized ILs containing Mo, W, B, and V anions can also be used in various oxidation reactions involving oxygen.

[0007] The anion is molybdate ([MoO4]). 2- ), tungstate ([WO4]) 2- ), metaborate ([BO2]) - ), orthovanadate ([VO4) 3- One of them.

[0008] The functionalized ILs are any one of the following: tributylethyl quaternary phosphine tungstate (structural formula as shown in Formula A), tributylethyl quaternary phosphine molybdate (structural formula as shown in Formula B), tributylethyl quaternary phosphine metaborate (structural formula as shown in Formula C), tributylethyl quaternary phosphine vanadate (structural formula as shown in Formula D), trihexyltetradecyl quaternary phosphine tungstate (structural formula as shown in Formula E), trihexyltetradecyl quaternary phosphine molybdate (structural formula as shown in Formula F), trihexyltetradecyl quaternary phosphine metaborate (structural formula as shown in Formula G), and trihexyltetradecyl quaternary phosphine vanadate (structural formula as shown in Formula H).

[0009]

[0010]

[0011] O2 was absorbed using tributylethyl quaternary phosphine tungstate as the absorbent. The absorption pressure was 0.1 MPa, the absorption temperature was 30 °C, and the absorption time was 6 h. The O2 absorption capacity was 1.8 mol / mol IL. Preferably, under the same treatment conditions, tributylethyl quaternary phosphine tungstate ILs achieved the maximum oxygen saturation absorption capacity.

[0012] The Mo-containing anion-functionalized ionic liquid was synthesized by neutralization reaction of alkyl quaternary phosphine hydroxide and molybdate in a molar ratio of 2:1; the W-containing anion-functionalized ionic liquid was synthesized by neutralization reaction of alkyl quaternary phosphine hydroxide and tungstate in a molar ratio of 2:1; the B-containing anion-functionalized ionic liquid was synthesized by neutralization reaction of alkyl quaternary phosphine hydroxide and metaboric acid in a molar ratio of 1:1; and the V-containing anion-functionalized ionic liquid was synthesized by metathesis reaction of alkyl quaternary phosphine hydroxide and vanadium pentoxide in a molar ratio of 6:1.

[0013] The method for preparing the functionalized ionic liquid includes the following steps:

[0014] (1) Preparation of alkyl quaternary phosphine hydroxide ethanol solution: In a N2 atmosphere, brominated alkanes and trialkylphosphines are used as raw materials and stirred at 60-90℃ in a molar ratio of 1:1 to synthesize brominated alkyl quaternary phosphine salts. Then, the brominated alkyl quaternary phosphine salts are passed through a strong base anion exchange resin to obtain alkyl quaternary phosphine hydroxide ethanol solution.

[0015] (2) Preparation of functionalized ionic liquid: Mix alkyl quaternary phosphine ethanol solution with tungstic acid at a molar ratio of 2:1, or mix alkyl quaternary phosphine ethanol solution with molybdic acid at a molar ratio of 2:1, or mix alkyl quaternary phosphine ethanol solution with metaboric acid at a molar ratio of 1:1, or mix alkyl quaternary phosphine ethanol solution with vanadium pentoxide at a molar ratio of 6:1; stir the reaction at 50°C, remove ethanol after the reaction is completed, dry the product, and obtain the functionalized ionic liquid.

[0016] The bromoalkanes are bromoethane or 1-bromotetradecane, and the trialkylphosphines are tributylphosphine or trihexylphosphine.

[0017] The beneficial effects of this invention are:

[0018] (1) In the designed functionalized ILs containing Mo, W, B, or V anions, the anions have Structural fragments; by utilizing the empty d orbitals of Mo, V, or W in anions and the empty p orbitals of B to coordinate with O2, high-efficiency O2 capture is achieved, which greatly improves the O2 capture capacity. The highest O2 absorption capacity can reach 1.8 mol / mol IL at room temperature and pressure.

[0019] (2) The functionalized ILs have good thermal stability, which makes the temperature range for O2 absorption control wide and effectively broadens the O2 capture environment (high efficiency O2 capture can be achieved at absorption temperatures of 20 to 100℃). Attached Figure Description

[0020] Figure 1 Absorption capacity diagram of O2 for the functionalized ILs prepared in Examples 1-4 (30°C, ambient pressure);

[0021] Figure 2 The attached diagram shows the cyclic adsorption / desorption of the functionalized ILs prepared in Example 1;

[0022] Figure 3 The attached diagram shows the cyclic adsorption / desorption of the functionalized ILs prepared in Example 2;

[0023] Figure 4 The attached diagram shows the cyclic adsorption / desorption of the functionalized ILs prepared in Example 3;

[0024] Figure 5 The attached diagram shows the cyclic adsorption / desorption of the functionalized ILs prepared in Example 4;

[0025] Figure 6 FT-IR images of the functionalized ILs prepared in Example 1 before and after adsorption / desorption;

[0026] Figure 7 FT-IR images of the functionalized ILs prepared in Example 2 before and after adsorption / desorption;

[0027] Figure 8 FT-IR images of the functionalized ILs prepared in Example 3 before and after adsorption / desorption;

[0028] Figure 9 FT-IR images of the functionalized ILs prepared in Example 4 before and after adsorption / desorption. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0030] Different types of functionalized ILs were prepared according to the raw materials and reaction conditions shown in Table 1. The preparation method of functionalized ILs includes the following steps:

[0031] (1) Preparation of ethanol solution of alkyl quaternary phosphine hydroxide: In N2 atmosphere, brominated alkanes and trialkylphosphine were used as raw materials and stirred at 60-90℃ for 24h in a molar ratio of 1:1 to synthesize brominated alkyl quaternary phosphine salt. The brominated alkyl quaternary phosphine salt was then passed through a strong base anion exchange resin to obtain an ethanol solution of alkyl quaternary phosphine hydroxide.

[0032] (2) Preparation of functionalized ILs: The alkyl quaternary phosphine ethanol solution was mixed with tungstic acid at a molar ratio of 2:1, or the alkyl quaternary phosphine ethanol solution was mixed with molybdic acid at a molar ratio of 2:1, or the alkyl quaternary phosphine ethanol solution was mixed with metaboric acid at a molar ratio of 1:1, or the alkyl quaternary phosphine ethanol solution was mixed with vanadium pentoxide at a molar ratio of 6:1. The mixture was stirred at 50°C for 12 h. After the reaction was completed, the ethanol was removed by rotary evaporation. The product after rotary evaporation was dried under vacuum at 70°C for 24 h to obtain functionalized ILs.

[0033] Table 1. Raw materials and reaction conditions used to prepare different types of functionalized ILs

[0034]

[0035] Examples 1-8

[0036] Add 1g of the functionalized ILs prepared by the above method to a glass container with a diameter of 1cm and a volume of 5mL. Control the experimental temperature at 30℃, slowly introduce O2 under magnetic stirring, control the flow rate at 60-80mL / min and the absorption pressure at 0.1MPa, and absorb until saturation (i.e. the weight remains unchanged). Calculate the saturation absorption amount.

[0037] The results of O2 capture by different types of functionalized ILs are shown in Table 2.

[0038] Table 2 O2 capture performance of functionalized ILs

[0039]

[0040]

[0041] A graph was plotted on the O2 absorption capacity of the functionalized ILs in Examples 1-4, and the results are as follows: Figure 1 As shown in the figure. It can be seen from the figure that [P] 4442 2WO4 has a higher absorption capacity than the other three functionalized ILs.

[0042] Examples 9-17

[0043] Following the method in Example 1, 1g of tributylethyl quaternary phosphine tungstate ILs([P 4442 Oxygen absorption tests were conducted at different absorption temperatures, and the amount of O2 absorbed was calculated. The results of O2 absorption by tributylethyl quaternary phosphine tungstate (ILs) under different conditions are shown in Table 3.

[0044] Table 3 O2 absorption performance of tributylethyl quaternary phosphotungstate (ILs)

[0045]

[0046] Examples 18-25

[0047] 1 g of the prepared functionalized ILs were added to glass containers with a diameter of 1 cm and a volume of 5 mL. The experimental temperature was controlled at 30 °C, and O2 was slowly introduced under magnetic stirring at a flow rate of 60-80 mL / min and an absorption pressure of 0.02 MPa. The O2 absorption was calculated. The results of O2 capture by different types of functionalized ILs are shown in Table 4.

[0048] Table 4 O2 capture performance of functionalized ILs

[0049]

[0050] Examples 26-33

[0051] 1 g of the prepared functionalized ILs were added to glass containers with a diameter of 1 cm and a volume of 5 mL. The experimental temperature was controlled at 20 °C, and O2 was slowly introduced under magnetic stirring at a flow rate of 60-80 mL / min and an absorption pressure of 0.1 MPa until saturation (i.e., constant weight). The saturation absorption was then calculated. The results of O2 capture by different types of functionalized ILs are shown in Table 5.

[0052] Table 5 O2 capture performance of functionalized ILs

[0053]

[0054] Examples 34-41

[0055] 1 g of the prepared functionalized ILs were added to glass containers with a diameter of 1 cm and a volume of 5 mL. The experimental temperature was controlled at 100 °C, and O2 was slowly introduced under magnetic stirring at a flow rate of 60-80 mL / min and an absorption pressure of 0.1 MPa. The absorption was continued until saturation (i.e., the weight remained constant), and the saturation absorption was calculated. The results of O2 capture by different types of functionalized ILs are shown in Table 6.

[0056] Table 6 O2 capture performance of functionalized ILs

[0057]

[0058] Examples 42-45:

[0059] The anion-functionalized ILs that had reached O2 absorption saturation in Examples 1-4 were added to glass containers with a diameter of 1 cm and a volume of 5 mL. High-purity N2 was slowly introduced at a flow rate of 60 mL / min, and the desorption temperature was controlled at 80 °C under 0.1 MPa. Oxygen was completely desorbed (weighed until the mass remained constant), and the desorption time was measured to be 1.5 h. The desorbed anion-functionalized ILs were then subjected to O2 absorption experiments according to Examples 1-4, and their saturation absorption capacity was calculated again. The adsorption capacity of the anion-functionalized ILs for oxygen remained essentially unchanged before and after desorption.

[0060] Table 7. O2 desorption performance of ILs

[0061]

[0062] Figures 2-5 For [P] 4442 ]2WO4、[P 4442 ]2MoO4、[P 4442 ]BO2、[P 4442 The adsorption / desorption curves of 3VO4 over multiple cycles (absorption pressure 0.1 MPa, absorption temperature 30℃, absorption time 6 h; desorption process at 0.1 MPa, desorption temperature 80℃, desorption time 1.5 h) show that the four functionalized ILs maintain high absorption and desorption capacities throughout the four cycles, indicating that O2 absorption by these four functionalized ILs is highly efficient and reversible. Figure 6-9 The infrared spectra of ILs before and after O2 absorption show that the structure of the ILs obtained after analysis remains unchanged and is consistent with the infrared spectrum of the ILs before absorption, indicating that the ILs have good recyclability.

[0063] Examples 46-53:

[0064] The anion-functionalized ILs that had reached O2 absorption saturation in Examples 1-8 were added to glass containers with a diameter of 1 cm and a volume of 5 mL. High-purity N2 was slowly introduced at a flow rate of 60 mL / min, and the desorption temperature was controlled at 70 °C under 0.1 MPa until oxygen was completely desorbed (weighed until the mass remained unchanged). The desorbed anion-functionalized ILs were then subjected to O2 absorption experiments according to Examples 1-8, and the saturation absorption capacity was calculated again. The adsorption capacity of the anion-functionalized ILs for oxygen remained essentially unchanged before and after desorption.

[0065] Table 8. O2 desorption performance of ILs

[0066]

[0067] Examples 54-61:

[0068] The anion-functionalized ILs that had reached O2 saturation in Examples 1-8 were added to glass containers with a diameter of 1 cm and a volume of 5 mL. High-purity N2 was slowly introduced at a flow rate of 60 mL / min, and the desorption temperature was controlled at 120 °C under 0.1 MPa until oxygen was completely desorbed (weighed until the mass remained unchanged). The desorbed anion-functionalized ILs were then subjected to O2 absorption experiments according to Examples 1-8, and the saturation absorption capacity was calculated again. The adsorption capacity of the anion-functionalized ILs for oxygen remained essentially unchanged before and after desorption.

[0069] Table 9. O2 desorption performance of ILs

[0070]

[0071]

[0072] Examples 59-69:

[0073] The anion-functionalized ILs that had reached O2 absorption saturation in Examples 15-22 were added to glass containers with a diameter of 1 cm and a volume of 5 mL. High-purity N2 was slowly introduced at a flow rate of 60 mL / min, and the desorption temperature was controlled at 120 °C under 0.02 MPa until oxygen was completely desorbed (weighed until the mass remained unchanged). The desorbed anion-functionalized ILs were then subjected to O2 absorption experiments according to Examples 15-22, and the saturation absorption capacity was calculated again. The adsorption capacity of the anion-functionalized ILs for oxygen remained essentially unchanged before and after desorption.

[0074] Table 10. O2 desorption performance of ILs

[0075]

[0076] Comparative Example

[0077] Taking a cyclic acylurea anion-functionalized ionic liquid with tributylethylphosphine as the cation and 1-butylhydantoin or hydantoin as the anion, at an absorption pressure of 0.1 MPa, its absorption temperature, absorption time to reach saturation absorption, and O2 absorption are shown in Table 11. In addition, the traditional ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4) was also selected as a comparison, and its absorption temperature, absorption time, and O2 absorption are shown in Table 11. At the same absorption temperature and absorption pressure, the O2 absorption of the above two types of ionic liquids is less than that of the ionic liquid in this invention. This is because the above two ionic liquids lack empty orbital atoms that coordinate with O2.

[0078] Table 11

[0079]

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for efficiently capturing oxygen, characterized in that: A functionalized ionic liquid composed of alkyl quaternary phosphine cations and anions containing Mo, W, B, or V was used as the absorbent to absorb O2. During the absorption process, the absorption pressure was 0.02–0.1 MPa, the absorption temperature was 20–100°C, and the absorption time was 2–8 h. The desorption process was carried out at 0.02–0.1 MPa, the desorption temperature was 70–120°C, and the desorption time was 0.5–4 h. The anion is one of molybdate, tungstate, metaborate, and vanadate; the functionalized ionic liquid is any one of tributylethyl quaternary phosphine molybdate, tributylethyl quaternary phosphine tungstate, tributylethyl quaternary metaborate, tributylethyl quaternary phosphine vanadate, trihexyltetradecyl quaternary phosphine molybdate, trihexyltetradecyl quaternary phosphine tungstate, trihexyltetradecyl quaternary phosphine metaborate, and trihexyltetradecyl quaternary phosphine vanadate.

2. The method for efficiently capturing oxygen as described in claim 1, characterized in that: O2 was absorbed using tributylethyl quaternary phosphine tungstate as the absorbent. The absorption pressure was 0.1 MPa, the absorption temperature was 30°C, the absorption time was 6 h, and the O2 absorption capacity was 1.8 mol / mol IL.

3. The method for efficiently capturing oxygen as described in claim 1, characterized in that: The Mo-containing anion-functionalized ionic liquid was synthesized by neutralization reaction of alkyl quaternary phosphine hydroxide and molybdate in a molar ratio of 2:1; the W-containing anion-functionalized ionic liquid was synthesized by neutralization reaction of alkyl quaternary phosphine hydroxide and tungstate in a molar ratio of 2:1; the B-containing anion-functionalized ionic liquid was synthesized by neutralization reaction of alkyl quaternary phosphine hydroxide and metaboric acid in a molar ratio of 1:1; and the V-containing anion-functionalized ionic liquid was synthesized by metathesis reaction of alkyl quaternary phosphine hydroxide and vanadium pentoxide in a molar ratio of 6:

1.

4. The method for efficiently capturing oxygen as described in claim 1, characterized in that: The method for preparing the functionalized ionic liquid includes the following steps: (1) Preparation of alkyl quaternary phosphine hydroxide ethanol solution: In a N2 atmosphere, brominated alkanes and trialkylphosphines are reacted at a molar ratio of 1:1 at 60-90°C to synthesize brominated alkyl quaternary phosphine salts, which are then passed through a strong base anion exchange resin to obtain alkyl quaternary phosphine hydroxide ethanol solution. (2) Preparation of functionalized ionic liquid: Mix alkyl quaternary phosphine ethanol solution with tungstic acid at a molar ratio of 2:1, or mix alkyl quaternary phosphine ethanol solution with molybdic acid at a molar ratio of 2:1, or mix alkyl quaternary phosphine ethanol solution with metaboric acid at a molar ratio of 1:1, or mix alkyl quaternary phosphine ethanol solution with vanadium pentoxide at a molar ratio of 6:1; stir the reaction at 50°C, remove ethanol after the reaction is completed, dry the product, and obtain the functionalized ionic liquid.

5. The method for efficiently capturing oxygen as described in claim 4, characterized in that: The bromoalkanes are bromoethane or 1-bromotetradecane, and the trialkylphosphines are tributylphosphine or trihexylphosphine.

Images