Method for improving stability of silver-containing ionic liquid

Abstract

The invention relates to a method for improving the stability of a silver-containing ionic liquid, which is characterized in that the stability of the silver-containing ionic liquid is improved by adding a functional group-containing stabilizer into the silver-containing ionic liquid according to a certain proportion. The silver-containing ionic liquid comprises the following components: silver salt, ionic liquid and a stabilizer. According to the method, the stability of the silver ions in the silver ion-containing liquid can be improved, and the inactivation rate of the silver ions is slowed down. In addition, the silver-ion-containing liquid added with the stabilizer can rapidly desorb olefin by adopting a heating or decompression mode, and the desorption amount can be increased. The method has a wide application prospect in the field of low-carbon olefin / alkane gas separation and purification.

Description

Technical Field

[0001] The invention belongs to the field of gas separation and purification, and particularly relates to a method for improving the stability of a silver-containing ion liquid. The method can improve the stability of silver ions in the silver-containing ion liquid and is used for the efficient separation of light olefins / alkanes. Background Art

[0003] Light olefins and alkanes in industrial off-gases are difficult to separate due to their similar structures and properties. Currently, the industry primarily uses cryogenic separation processes to separate these hydrocarbons. This process requires maintaining temperatures below -40°C and a high pressure of 7 bar in a distillation column with approximately 180 trays, resulting in high energy consumption. Therefore, developing novel separation methods has become a research hotspot for separating light olefins and alkanes.

[0004] In order to reduce separation energy consumption, the separation of light olefins / alkanes using absorption separation processes has become a research hotspot in academia. A variety of absorbents for light olefin / alkanes separation have been reported in the literature, mainly including organic solvents, ionic liquids, and ionic liquid-transition metal salt systems. Organic solvents generally have low boiling points and are volatile; ionic liquids have almost no saturated vapor pressure and good thermal stability. Their absorption performance can be optimized by adjusting the anion and cation structures, but their specific absorption capacity for light olefins is limited, and the separation selectivity is not high. Ionic liquid-transition metal salt systems have high separation selectivity due to the specific effect of transition metal salts on double bonds. They have unique advantages in the field of gas separation and provide new opportunities for the efficient separation and recovery of olefins.

[0005] Lee et al. (J. Membr. Sci. 2012, 423-424: 159-164) found that the separation selectivities of three absorbents with similar viscosities, polyethylene glycol, [MOIM][NO3] and [BMIM][BF4], for propylene / propane mixtures were 1.1, 2.8 and 3.2, respectively, indicating that ionic liquids have better selectivity than organic solvents in gas absorption. Liu et al. (AIChE J. 2014, 60: 2607-2612) designed functionalized ionic liquids [P (14)TMPP has a high absorption capacity for propane due to its long alkyl chain, while its absorption capacity for propylene is very low, enabling its separation. However, due to its long alkyl chain, it has a high viscosity. Patents US2011092758A1 (B2) report a method for purifying olefins using pyrrolidinyl or piperidinyl ionic liquids containing copper (I) halide, which improves propylene absorption. However, copper-containing ionic liquids are sensitive to water and air and easily deactivate. Patent CN117753171 A reports a method for preparing silver-containing ionic liquids, which achieve high absorption and selectivity for olefins. Patent CN117756596 A increases the silver ion concentration in the ionic liquid by using a cosolvent and utilizes the synergistic effect of double silver salts to significantly improve silver ion utilization. However, the photosensitivity of silver-containing ionic liquids still leads to a decrease in their absorption performance for olefins, and research in this area remains unexplored. Therefore, the design and development of ionic liquid-transition metal salt systems with excellent stability and high absorption capacity for the separation of light olefins is of great significance. Summary of the Invention

[0006] To address the technical challenge of silver ions being easily deactivated in silver ion liquids, the present invention provides a method for improving the stability of silver ion liquids. This method improves the stability of silver ions in the silver ion liquid and enables stable and efficient separation of olefins.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a method for improving the stability of a silver-containing ionic liquid. The silver-containing ionic liquid prepared by the method is composed of a silver salt, an ionic liquid, and a stabilizer. The ionic liquid and the stabilizer are compounded in a certain molar ratio, a certain amount of silver salt is added, and after reacting for a certain time at a certain temperature and stirring speed, a highly stable silver-containing ionic liquid is prepared by drying. In the silver-containing ionic liquid prepared by the method, the dissolution effect of the ionic liquid on the silver salt enables it to efficiently absorb olefins, and the weak coordination effect formed between the stabilizer and the silver ions enables it to obtain better thermal stability and light stability, thereby achieving green and efficient separation of light olefins / alkanes.

[0008] The ionic liquids in the silver-containing ionic liquids prepared by the method include imidazole ionic liquids, pyridine ionic liquids, pyrrole ionic liquids, and piperidine ionic liquids.

[0009] The stabilizer in the silver-containing ionic liquid prepared by the method comprises a pyridyl ionic liquid or an imidazole ionic liquid having a functional group on the side chain, and the general structural formula thereof is: or ; Wherein, R1 in the stabilizer is a short alkyl chain containing alkenyl, hydroxyl or amino functional groups, and R2 is a carbon number C1-C 10 The alkyl chain of X- For BF4 - 、NO3 - NT f2 - ,OTf - or PF6 - Any one of .

[0010] The silver salt in the silver-containing ionic liquid prepared by the method includes any one of AgNO3, AgBF4, AgNTf2, AgOTf or AgPF6.

[0011] The molar ratio of the ionic liquid to the stabilizer in the silver-containing ionic liquid prepared by the method is (0.1-100):1.

[0012] The molar content of silver salt in the silver-containing ionic liquid prepared by the method is 0.1-99.9%.

[0013] The preparation temperature of the silver ion liquid prepared by the method is 25-90°C.

[0014] The silver ion liquid prepared by the method has a stirring speed of 100 to 2000 rpm and a stirring time of 1 to 24 hours.

[0015] The drying temperature of the silver ion liquid prepared by the method is 40-80°C, and the drying time is 24-72 hours.

[0016] The silver-containing ionic liquid prepared by the method can be applied to the gas separation process of light olefins / alkanes, including one or more of ethylene, ethane, propylene, propane, butylene and butane.

[0017] The olefin forms a strong hydrogen bond and π complexation with the silver-containing ionic liquid prepared by the method and is absorbed, and the olefin can be desorbed by heating or reducing pressure.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The silver-containing ionic liquid prepared by the method provided by the present invention has a higher absorption capacity for olefins than organic solvents and existing ionic liquids. It also exhibits improved thermal and light stability compared to existing ionic liquid-transition metal salt systems. The silver-containing ionic liquid with the addition of a stabilizer can rapidly desorb olefins by heating or reducing pressure, increasing the desorption capacity and facilitating regeneration and recycling.

[0019] The following describes the details in conjunction with specific embodiments. DETAILED DESCRIPTION

[0020] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0021] Example 1 This embodiment provides a method for improving the stability of a silver-containing ionic liquid. The silver-containing ionic liquid prepared by the method comprises the following components: 32.8% AgBF4, 31.0% 1-ethyl-3-methylimidazolium tetrafluoroborate (EmimBF4), and 36.1% 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate (HOEmimBF4); The preparation method comprises the following steps: (1) [Emim][BF4] and [HOEmim][BF4] were mixed and reacted at 30 °C for 10 h to obtain an ionic liquid composite product; (2) AgBF4 was mixed with the composite product of step (1), reacted at 60°C for 6 h, and then vacuum dried at 60°C for 48 h to obtain a silver ion liquid.

[0022] Example 2 This embodiment provides a method for improving the stability of a silver-containing ionic liquid. The silver-containing ionic liquid prepared by the method comprises the following components: 32.7% AgNTf2, 33.0% 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt (EmimNTf2), and 34.3% 1-hydroxyethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt (HOEmimNTf2); The preparation method comprises the following steps: (1) [Emim][NTf2] and [HOEmim][NTf2] were mixed and reacted at 50 °C for 6 h to obtain an ionic liquid composite product; (2) AgNTf2 was mixed with the composite product of step (1), reacted at 50 °C for 8 h, and then vacuum dried at 55 °C for 24 h to obtain a silver ion liquid.

[0023] Example 3 This embodiment provides a method for improving the stability of a silver-containing ionic liquid. The silver-containing ionic liquid prepared by the method comprises the following components: 30.1% AgBF4, 36.7% 3-methyl-N-butylpyridinium tetrafluoroborate (BMPyBF4), and 33.1% 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate (HOEmimBF4); The preparation method comprises the following steps: (1) [BMPy][BF4] and [HOEmim][BF4] were mixed and reacted at 40 °C for 6 h to obtain an ionic liquid composite product; (2) AgBF4 was mixed with the composite product of step (1), reacted at 60°C for 8 h, and then vacuum dried at 45°C for 24 h to obtain a silver ion liquid.

[0024] Example 4 This embodiment provides a method for improving the stability of a silver-containing ionic liquid. The silver-containing ionic liquid prepared by the method comprises the following components: 33.1% AgBF4, 31.3% 1-butyl-3-methylimidazolium tetrafluoroborate (BmimBF4), and 35.7% 1-allyl-3-methylimidazolium tetrafluoroborate (AMImBF4); The preparation method comprises the following steps: (1) [Bmim][BF4] and [AMIm][BF4] were mixed and reacted at 60 °C for 6 h to obtain a silver ion liquid; (2) AgBF4 was mixed with the composite product of step (1), reacted at 40°C for 8 h, and then vacuum dried at 60°C for 24 h to obtain a silver ion liquid.

[0025] Example 5 This embodiment provides a method for improving the stability of a silver-containing ionic liquid. The silver-containing ionic liquid prepared by the method comprises the following components: 31.4% AgBF4, 2.97% 1-octyl-3-methylimidazolium tetrafluoroborate (OmimBF4), and 65.6% 1-aminoethyl-3-methylimidazolium tetrafluoroborate (AEmimBF4); The preparation method is the same as that in Example 1.

[0026] Example 6 This embodiment provides a method for improving the stability of a silver-containing ionic liquid. The silver-containing ionic liquid prepared by the method comprises the following components: 34.4% AgBF4, 61.8% 1-octyl-3-methylimidazolium tetrafluoroborate (OmimBF4), and 3.78% 1-aminoethyl-3-methylimidazolium tetrafluoroborate (AEmimBF4); The preparation method is the same as that in Example 1.

[0027] Example 7 This embodiment provides a silver ion liquid and a preparation method thereof, which is the same as that of Example 1 except that the first reaction temperature in step (1) is 25°C.

[0028] Example 8 This embodiment provides a silver ion liquid and a preparation method thereof, which is the same as that of Example 1 except that the first reaction temperature in step (2) is 90°C.

[0029] Comparative Example 1 This comparative example provides a silver ion liquid, comprising the following components: 34.6% AgBF4 and 65.4% 1,3-dimethylimidazolium tetrafluoroborate (DmimBF4).

[0030] The preparation method comprises: mixing [Dmim][BF4] and AgBF4, reacting at 60°C for 12 hours, and then vacuum drying at 60°C for 48 hours to obtain a silver salt-containing ionic liquid.

[0031] Comparative Example 2 This comparative example provides a silver ion liquid comprising the following components: 31.3% AgBF4 and 68.7% 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate (HOEmimBF4).

[0032] The preparation method comprises: mixing [HOEmim][BF4] and AgBF4, reacting at 60°C for 12 hours, and then vacuum drying at 60°C for 48 hours to obtain a silver salt-containing ionic liquid.

[0033] Comparative Example 3 This comparative example provides a silver ion liquid comprising the following components: 29.1% AgBF4 and 70.9% 3-methyl-N-butylpyridinium tetrafluoroborate (BMPyBF4).

[0034] The preparation method comprises: mixing AgBF4 and [BMPy][BF4], reacting at 45°C for 14 hours, and then vacuum drying at 60°C for 24 hours to obtain a silver salt-containing ionic liquid.

[0035] Comparative Example 4 This comparative example provides a silver ion liquid, comprising the following components: 33.1% AgNTf2 and 66.9% 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EmimNTf2).

[0036] The preparation method comprises: mixing [Emim][NTf2] and AgNTf2, reacting at 50°C for 14 hours, and then vacuum drying at 60°C for 24 hours to obtain a silver salt-containing ionic liquid.

[0037] The silver-containing ionic liquids prepared in the above examples and comparative examples were used to separate olefins. The application involved adding 5 g of the ionic liquid absorbent to a custom absorption bottle, connecting the bottle to a mixed gas absorption device, and then introducing a 1:1 volume ratio of different light olefins / alkanes at a controlled gas flow rate of 20 mL / min. The reaction was carried out at 25°C and 0.1 MPa, and the exhaust gas composition was analyzed online by gas chromatography. The absorption capacity and selectivity of the gases in the ionic liquid absorbent were calculated, and the results are shown in Table 1.

[0038] Table 1

[0039] The following points can be drawn from Table 1: (1) The silver salt-containing ionic liquid prepared by the preparation method provided in Examples 1-4 of the present invention can achieve high absorption and high selectivity for olefins while also having a desorption rate greater than 80%, exhibiting good cycle performance; (2) From the comparison between Example 1 and Examples 5-6, it can be seen that when the weight ratio of the ionic liquid or the stabilizer is too low or too high, the synergistic effect of the two ionic liquids is small, resulting in a decrease in the absorption amount of the prepared silver-containing ionic liquid for olefins or a decrease in selectivity; (3) From the comparison between Example 1 and Examples 7-8, it can be seen that within the preparation temperature range, the absorption amount and selectivity of the silver ion liquid are relatively stable; (4) From the comparison between Example 1 and Comparative Examples 1-4, it can be seen that when only a single silver salt is mixed with the ionic liquid, the desorption performance of olefins is poor.

[0040] The silver-containing ionic liquids prepared in the above examples and comparative examples were used in a photostability experiment. The photostability experiment involved illuminating the silver-containing ionic liquid with a cold light source and sampling for absorption experiments at different illumination times. 5g of ionic liquid absorbent was added to a custom absorption bottle connected to a mixed gas absorption device. A 1:1 volume ratio of C3H6 and C3H8 gas mixture was then introduced. The gas flow rate was controlled at 20 mL / min, and the reaction was carried out at 25°C and 0.1 MPa. The tail gas components were analyzed online by gas chromatography. The absorption capacity and deactivation rate of C3H6 and C3H8 in the silver-containing ionic liquid (the percentage of the absorbed amount of olefin lost before and after illumination to the absorbed amount before illumination) were calculated using 1. The results are shown in Table 2.

[0041] Table 2

[0042] The following points can be drawn from Table 2: (1) The silver salt-containing ionic liquid prepared by the preparation method provided in Examples 1-4 of the present invention can achieve high absorption and high selectivity for propylene while having a photoinactivation rate of less than 18%, showing good photostability; (2) From the comparison between Example 1 and Example 5, it can be seen that when the weight proportion of the ionic liquid is low, the photostability of the silver-containing ionic liquid to propylene is better; from the comparison between Example 1 and Example 6, it can be seen that when the weight proportion of the stabilizer is too low, the photostability of the silver-containing ionic liquid to propylene is poor; (3) From the comparison between Example 1 and Examples 7-8, it can be seen that when the preparation is within the range, the photostability of the silver ion liquid is relatively stable; (5) From the comparison between Example 1 and Comparative Examples 1-4, it can be seen that when only a single silver salt is mixed with the ionic liquid, the photostability of the silver ions contained therein is poor.

[0043] The silver-containing ionic liquids prepared in Example 1 and Comparative Example 1 were used in an olefin recycling experiment. The experiment involved adding 3.0 g of the silver-containing ionic liquid absorbent to each of two absorption bottles, then introducing pure C₂H₄ gas at a controlled gas flow rate of 50 mL / min. The reaction was conducted at 25°C and 0.1 MPa, and the absorption bottles were weighed every 120 minutes. After 120 minutes of absorption, ethylene was separated by desorption. The desorption conditions were: introducing N₂ at a flow rate of 50 mL / min and desorption at 70°C for 120 minutes. This absorption-desorption cycle was repeated five times. The absorption performance of the silver-containing ionic liquid for ethylene is shown in Table 3.

[0044] Table 3

[0045] As shown in Table 3, the silver ion liquid prepared by the method is easier to desorb and has good regeneration stability. After multiple cycles, it can still maintain a high ethylene absorption capacity.

[0046] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for improving the stability of a silver-containing ionic liquid, characterized in that: The method comprises the following steps: The ionic liquid and the stabilizer are compounded in a molar ratio of (0.1-100):1, and then a silver salt is added to obtain a mixture, wherein the molar content of the silver salt in the mixture is 0.1-99.9%; The mixture is reacted under stirring at a temperature of 25-90° C., a stirring speed of 100-2000 rpm, and a reaction time of 1-24 h, and then dried.

2. The method according to claim 1, characterized in that The ionic liquid includes at least one of imidazole ionic liquid, pyridine ionic liquid, pyrrole ionic liquid and piperidine ionic liquid.

3. The method according to claim 1, characterized in that The stabilizer comprises a pyridyl ionic liquid or an imidazole ionic liquid having a functional group on the side chain, and the general structural formula thereof is: or ; Wherein, R1 in the stabilizer is a short alkyl chain containing alkenyl, hydroxyl or amino functional groups, and R2 is a carbon number C1-C 10 The alkyl chain of X - For BF4 - 、NO3 - NTf2 - ,OTf - or PF6 - Any one of .

4. The method according to claim 1, wherein The silver salt includes any one of AgNO3, AgBF4, AgNTf2, AgOTf or AgPF6.

5. The method according to claim 1, wherein The drying temperature is 40-80°C and the drying time is 24-72 hours.

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