A double silver salt ionic liquid and a preparation method and application thereof

Abstract

The present application relates to a kind of double silver salt ionic liquid and its preparation method and application, the double silver salt ionic liquid includes the following components: ionic liquid, first silver salt and second silver salt;The first silver salt and second silver salt contain different anions.The preparation method includes the following steps: (1) ionic liquid and first silver salt are mixed, first reaction is carried out, and the ionic liquid containing double cation is obtained;(2) second silver salt is mixed with the ionic liquid containing double cation in step (1), second reaction is carried out, and the double silver salt ionic liquid is obtained.The present application adopts the double silver salt of different anions, can form anion cluster around silver ion, strengthen its stability, and the synergistic effect between two kinds of silver salt, improve the utilization rate of silver salt in ionic liquid, and have the advantages such as easy to desorb, can be recycled multiple times.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of petroleum, coal combustion and chemical gas separation and purification, and particularly relates to a double-silver salt ionic liquid and a preparation method and application thereof. BACKGROUND

[0002] Olefins are important chemical raw materials and one of the largest chemical products in the world. In the refinery dry gas process, catalytic cracking dry gas contains a large amount of low-carbon olefin resources, but the utilization degree of olefins is insufficient at present, and they are usually used as fuel, causing serious waste and environmental pollution. Ethylene products are the core of the petrochemical industry, accounting for more than 75% of petrochemical products. If ethylene in dry gas can be reasonably utilized, great economic benefits will be generated, and air pollution will also be reduced. The catalytic cracking, thermal cracking and delayed coking of refineries produce a large amount of dry gas, and the content of ethylene is about 20%. Except for a small amount of fuel reuse, most of them are directly burned, causing large CO2 emissions in the air, great waste of ethylene resources and serious environmental pollution.

[0003] At present, the main methods for separating olefins and alkanes are low-temperature rectification, membrane separation, adsorption separation and absorption separation. Low-temperature rectification has high energy consumption and equipment cost; membrane separation has small gas treatment capacity and high cost; and adsorption separation has low selectivity. In summary, absorption separation is the most practical, mature and widely used technology. Researchers have conducted some research on the absorption separation of olefins / alkanes by ionic liquids. CN104277880B discloses a method for absorbing and separating light hydrocarbons from dry gas or industrial tail gas by using ionic liquids. The steps for absorbing and separating light hydrocarbons are as follows: using ionic liquids as absorbents, contacting with dry gas or industrial tail gas, absorbing to obtain an absorption liquid containing light hydrocarbons, and then separating light hydrocarbons by desorption. The light hydrocarbons are mainly C2-C4 alkanes or olefins. The ionic liquid is tetrabutylphosphonium n-octanoate. However, the selectivity of the method for separating olefins is not high.

[0004] In order to improve the selectivity of olefin / alkane separation, metal complex absorption is used for olefin / alkane separation. Among transition metals, Ag + has the ability to complex with double bonds in olefins, and the generated coordination compounds are easy to desorb and can be recycled for absorption and desorption separation of low-carbon olefins and alkanes.

[0005] CN107398146A discloses a protonated ionic liquid absorbent containing a metal salt and its application. The absorbent comprises a protonated ionic liquid as a solvent and a silver salt as an olefin complexing support. The preparation method of the protonated ionic liquid is as follows: An organic compound and nitric acid are mixed in a 1:1 molar ratio. The nitric acid is added dropwise to an aqueous or alcoholic solution of the organic compound, and the mixture is stirred in an ice-water bath for 0.5–2 h. Then, the mixture is stirred at 25–60 °C for 4–8 h to obtain a protonated ionic liquid aqueous or alcoholic solution. The solvent is removed by rotary evaporation under vacuum at 65–80 °C for 6–8 h, yielding the protonated ionic liquid. However, Ag… + It is unstable in ionic liquids and is easily deactivated and reduced to nano-silver.

[0006] Therefore, to address the above problems, it is necessary to develop a new type of ionic liquid that can achieve high absorption capacity and high selectivity for olefins. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a double silver salt ionic liquid, its preparation method, and its application. The double silver salt ionic liquid increases the concentration of silver ions in the ionic liquid through a co-solvent. By utilizing the synergistic effect between the two silver salts, the utilization rate of silver ions is greatly improved. While increasing the stability of silver ions in the ionic liquid, it also improves the absorption and selectivity of olefins.

[0008] To achieve the above-mentioned technical effects, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a double silver salt ionic liquid, the double silver salt ionic liquid comprising the following components: an ionic liquid, a first silver salt and a second silver salt;

[0010] The first silver salt and the second silver salt contain different anions.

[0011] This invention uses two silver salts with different anions, which can form anion clusters near silver ions, enhancing their stability. Furthermore, the two silver salts have a synergistic promoting effect, improving the utilization rate of silver salts in ionic liquids. It also has the advantages of easy desorption and multiple recycling.

[0012] As a preferred embodiment of the present invention, the bissilver salt ionic liquid further includes a co-solvent.

[0013] In this invention, when the amount of silver salt added is small, a co-solvent may not be added.

[0014] Preferably, the dual silver salt ionic liquid comprises the following components by mass percentage: 5%-80% ionic liquid, 5%-50% first silver salt, 5%-50% second silver salt, and 0-30% co-solvent.

[0015] In this invention, the double silver salt ionic liquid comprises the following components by mass percentage: 50%-70% ionic liquid, 10%-20% first silver salt, 10%-20% second silver salt, and 5%-15% co-solvent.

[0016] In this invention, the bis-silver salt ionic liquid promotes the efficient absorption of low-carbon olefins through the synergistic effects of the strong negative charge of the anions in the ionic liquid, the weak acid-base relationship between the cations and the silver ions, the soft acid relationship between the silver ions and the soft base relationship between the olefins, hydrogen bonding, and π-complexation. The co-solvent can reduce the viscosity of the bis-silver salt ionic liquid and increase the solubility of the silver salt, thereby improving the absorption rate and total amount of low-carbon olefins absorbed. Simultaneously, the anions in the bis-silver salt ionic liquid in Ag... + Stable anion aggregation forms nearby, effectively protecting Ag. + This prevents it from being reduced, thus improving the stability of the bissilver salt ionic liquid.

[0017] In this invention, the mass percentage of the ionic liquid is 5%-80%, for example, it can be 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70% or 80%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] In this invention, the mass percentage of the first silver salt is 5%-50%, for example, it can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] In this invention, the mass percentage of the second silver salt is 5%-50%, for example, it can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] In this invention, the mass percentage of the co-solvent is 0-30%, for example, it can be 0%, 5%, 10%, 15%, 20%, 25% or 30%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] As a preferred embodiment of the present invention, the ionic liquid includes ionic liquids containing imidazole, pyrazole or triazole.

[0022] Preferably, the anion of the ionic liquid includes BF4. - NO3 - NTf2 - OTf - PF6 - or CH3COO - Any one of them.

[0023] In this invention, the structural formula of the ionic liquid includes any one of Formula I, Formula II, or Formula III.

[0024]

[0025] Among them, R1, R4, and R7 are each independently C m H 2m+1 (m is an integer, 1≤m≤8); R2, R6, and R9 are independently H, CH3, or C2H5, respectively; R3, R6, and R8 are independently C k H 2k+1 (k is an integer, 1≤k≤4); the X - BF4 - NO3 - NTf2 - OTf - PF6 - or CH3COO - Any one of them.

[0026] As a preferred embodiment of the present invention, the first silver salt includes any one of AgNO3, AgBF4, AgNTf2, AgOTf, AgPF6, or AgC2H3O2.

[0027] Preferably, the second silver salt includes any one of AgNO3, AgBF4, AgNTf2, AgOTf, AgPF6, or AgC2H3O2.

[0028] As a preferred embodiment of the present invention, the co-solvent includes water and / or polyols.

[0029] Preferably, the polyol includes any one or a combination of at least two of ethylene glycol, glycerol, or polyethylene glycol. Typical but non-limiting examples of such combinations include combinations of ethylene glycol and glycerol, combinations of glycerol and polyethylene glycol, or combinations of ethylene glycol, glycerol, and polyethylene glycol.

[0030] In a second aspect, the present invention provides a method for preparing the double silver salt ionic liquid described in the first aspect, the method comprising the following steps:

[0031] (1) Mix the ionic liquid and the first silver salt to carry out the first reaction and obtain the ionic liquid containing two cations;

[0032] (2) The second silver salt is mixed with the ionic liquid containing two cations described in step (1) to carry out a second reaction, thereby obtaining a double silver salt ionic liquid.

[0033] As a preferred technical solution of the present invention, the temperature of the first reaction in step (1) is 20-120℃, for example, it can be 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃ or 120℃, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] Preferably, the reaction time in step (1) is 4-20h, for example, it can be 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h or 20h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] Preferably, the temperature of the second reaction in step (2) is 20-120℃, for example, it can be 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃ or 120℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] Preferably, the reaction time in step (2) is 4-20h, for example, it can be 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h or 20h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] As a preferred technical solution of the present invention, step (2) after the second reaction further includes: adding a co-solvent and stirring to mix.

[0038] Preferably, the mixing time is 1-3 hours, for example, it can be 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours or 3 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] Thirdly, the present invention provides an application of the double silver salt ionic liquid described in the first aspect in the separation of olefins / alkanes, the application comprising: using the double silver salt ionic liquid as an absorbent, mixing and reacting it with a feed gas containing olefins and alkanes to obtain an absorbent rich in olefins, and then separating the olefins by desorption.

[0040] As a preferred technical solution of the present invention, the flow rate of the raw material gas is 0.1-1000 mL / min, for example, it can be 0.01 mL / min, 1 mL / min, 20 mL / min, 50 mL / min, 100 mL / min, 300 mL / min, 500 mL / min, 700 mL / min, 900 mL / min or 150 mL / min, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 10-150 mL / min.

[0041] Preferably, the reaction temperature is 10-60℃, for example, it can be 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃ or 60℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0042] Preferably, the reaction pressure is 0.1-6 MPa, for example, it can be 0.1 MPa, 0.5 MPa, 1 MPa, 2 MPa, 3 MPa, 4 MPa, 5 MPa or 6 MPa, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0043] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] (1) This invention mixes two silver salts with different anions with an ionic liquid to enhance the stability of silver ions. The two silver salts also have a synergistic effect, improving the utilization rate of silver salts in the ionic liquid. Furthermore, it has advantages such as easy desorption and multiple recycling, effectively solving the problems of Ag in the prior art. + The problem of poor stability of silver ions in the -IL system; by using a co-solvent, the viscosity of the bissilver salt ionic liquid can be reduced, the solubility of silver salt can be increased, and the absorption rate and total amount of low-carbon olefins can be improved.

[0046] (2) The preparation method described in this invention has low production cost, simple process flow, and is easy to industrialize. Detailed Implementation

[0047] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0048] Example 1

[0049] This embodiment provides a bis-silver salt ionic liquid and its preparation method. The bis-silver salt ionic liquid comprises the following components: 66.3% 1-butyl-3-methylimidazolium nitrate (BmimNO3), 14% AgNO3, 10.6% AgOTf and 9.1% ethylene glycol;

[0050] The preparation method includes the following steps:

[0051] (1) Mix BmimNO3 and AgNO3 and react at 80℃ for 5 hours to obtain an ionic liquid containing two cations;

[0052] (2) Mix AgOTf with the ionic liquid containing two cations described in step (1), react at 80°C for 5 hours, then add ethylene glycol and stir for 2 hours, and dry under vacuum at 60°C for 48 hours to obtain the bis-silver salt ionic liquid.

[0053] Example 2

[0054] This embodiment provides a bis-silver salt ionic liquid and its preparation method. The bis-silver salt ionic liquid comprises the following components: 59.1% 1-butyl-3-methylimidazolium tetrafluoroborate (BmimBF4), 19.1% AgBF4, 12.7% AgNTf2 and 9.1% ethylene glycol;

[0055] The preparation method includes the following steps:

[0056] (1) Mix BmimBF4 and AgBF4 and react at 30℃ for 15 h to obtain an ionic liquid containing two cations;

[0057] (2) Mix AgNTf2 with the ionic liquid containing two cations described in step (1), react at 100°C for 4 hours, then add ethylene glycol and stir for 2 hours, and dry under vacuum at 60°C for 48 hours to obtain the bis-silver salt ionic liquid.

[0058] Example 3

[0059] This embodiment provides a bis-silver salt ionic liquid and its preparation method. The bis-silver salt ionic liquid comprises the following components: 67.1% 1-ethyl-3-methylimidazolium tetrafluoroborate (EmimBF4), 16.5% AgBF4, 7.3% AgOTf and 9.1% water;

[0060] The preparation method includes the following steps:

[0061] (1) Mix EmimBF4 and AgBF4 and react at 100℃ for 4 hours to obtain an ionic liquid containing two cations;

[0062] (2) Mix AgOTf with the ionic liquid containing two cations described in step (1), and react at 60°C for 6 hours. Then add water and stir for 2 hours to obtain the bis-silver salt ionic liquid.

[0063] Example 4

[0064] This embodiment provides a double silver salt ionic liquid and its preparation method. The double silver salt ionic liquid comprises the following components: 50% BmimNO3, 20% AgNO3, 20% AgOTf, and 10% ethylene glycol.

[0065] The preparation method includes the following steps:

[0066] (1) Mix BmimNO3 and AgNO3 and react at 80℃ for 5 hours to obtain an ionic liquid containing two cations;

[0067] (2) Mix AgOTf with the ionic liquid containing two cations described in step (1), and react at 80°C for 5 hours. Then add ethylene glycol and stir for 2 hours. Dry under vacuum at 60°C for 48 hours to obtain the bis-silver salt ionic liquid.

[0068] Example 5

[0069] This embodiment provides a bis-silver salt ionic liquid and its preparation method. The bis-silver salt ionic liquid comprises the following components: 65% 1-butyl-4-methylpyrazole tetrafluoroborate (BmpyBF4), 20% AgBF4, 10% AgOTf and 5% ethylene glycol.

[0070] The preparation method is the same as in Example 1.

[0071] Example 6

[0072] This embodiment provides a double silver salt ionic liquid and its preparation method. The double silver salt ionic liquid comprises the following components: 40% BmimNO3, 3% AgNO3, 52% AgOTf and 5% ethylene glycol.

[0073] The preparation method is the same as in Example 1.

[0074] Example 7

[0075] This embodiment provides a double silver salt ionic liquid and its preparation method. The double silver salt ionic liquid comprises the following components: 60% BmimNO3, 26% AgNO3, 4% AgOTf and 10% ethylene glycol.

[0076] The preparation method is the same as in Example 1.

[0077] Example 8

[0078] This embodiment provides a double silver salt ionic liquid and its preparation method. Except for the first reaction temperature of 140°C in step (1), all other steps are the same as in Example 1.

[0079] Example 9

[0080] This embodiment provides a double silver salt ionic liquid and its preparation method. Except for the second reaction temperature of 140°C in step (2), all other steps are the same as in Example 1.

[0081] Example 10

[0082] This embodiment provides a double silver salt ionic liquid and its preparation method. Except for step (2), which does not involve adding ethylene glycol and stirring for 2 hours, the other steps are the same as in Example 1.

[0083] Comparative Example 1

[0084] This comparative example provides a silver salt ionic liquid and its preparation method, wherein the silver salt ionic liquid comprises the following components: 76% BmimNO3 and 24% AgNO3;

[0085] The preparation method includes: mixing BmimNO3 and AgNO3, reacting at 80°C for 6 hours, and then drying under vacuum at 60°C for 48 hours to obtain a silver salt ionic liquid.

[0086] Comparative Example 2

[0087] This comparative example provides a silver salt ionic liquid and its preparation method, wherein the silver salt ionic liquid comprises the following components: 67.7% BmimNO3 and 32.3% AgNO3;

[0088] The preparation method includes: mixing BmimNO3 and AgNO3, reacting at 80°C for 5 hours, and then drying under vacuum at 60°C for 48 hours to obtain a silver salt ionic liquid.

[0089] Comparative Example 3

[0090] This comparative example provides a silver salt ionic liquid and its preparation method. The silver salt ionic liquid comprises the following components: 61% BmimNO3, 30% AgBF4 and 9% ethylene glycol.

[0091] The preparation method includes: mixing BmimNO3 and AgBF4, reacting at 80°C for 6 hours, then adding ethylene glycol and stirring for 2 hours, and drying under vacuum at 60°C for 48 hours to obtain a silver salt ionic liquid.

[0092] Comparative Example 4

[0093] This comparative example provides a double silver salt ionic liquid and its preparation method, wherein the composition of the double silver salt ionic liquid is the same as that in Example 1;

[0094] The preparation method includes: reacting BmimNO3, AgNO3, AgOTf and ethylene glycol at 80°C for 5 h, and then drying under vacuum at 60°C for 48 h to obtain a double silver salt ionic liquid.

[0095] The ionic liquid absorbents prepared in the above examples and comparative examples were used to separate olefins / alkanes. The application included: adding 5g of the ionic liquid absorbent to a self-made absorption bottle, connecting the bottle to a mixed gas absorption device, and then introducing a 1:1 volume ratio of C2H4 and C2H6 gas at a flow rate of 50mL / min. The reaction was carried out at 25℃ and 0.1MPa, and the tail gas components were analyzed online by gas chromatography. The absorption capacity and selectivity of C2H4 and C2H6 in the ionic liquid absorbent were calculated after 10min and 120min, and the results are shown in Table 1.

[0096] Table 1

[0097]

[0098]

[0099] The following points can be drawn from Table 1:

[0100] (1) The double silver salt ionic liquid prepared by the preparation method provided in Examples 1-5 of the present invention can achieve high absorption capacity and high selectivity for ethylene;

[0101] (2) As can be seen from the comparison between Example 1 and Example 6-7, when the content of the first silver salt or the second silver salt is too low or too high, the synergistic effect of the two silver salts is small, resulting in a decrease in the absorption of ethylene by the prepared double silver salt ionic liquid and a decrease in selectivity.

[0102] (3) As can be seen from the comparison between Example 1 and Example 8-9, when the first reaction temperature or the second reaction temperature is too high, the high temperature accelerates the reduction of silver ions, resulting in a decrease in the absorption capacity and selectivity of the prepared double silver salt ionic liquid for ethylene; As can be seen from the comparison between Example 1 and Example 10, when no co-solvent is added, the viscosity of the ionic liquid absorbent is high, which further leads to a decrease in the absorption capacity and selectivity of the prepared double silver salt ionic liquid for ethylene.

[0103] (5) As can be seen from the comparison between Example 1 and Comparative Examples 1-3, when only a single silver salt is used to mix with the ionic liquid, the selectivity for ethylene is low and the stability is poor. As can be seen from the comparison between Example 1 and Comparative Example 4, when silver ionic liquid is prepared by one-step mixing, due to the different solubilities of different silver salts in the ionic liquid, there is competitive dissolution, which leads to a reduction in the absorption of ethylene and a decrease in selectivity of the prepared ionic liquid.

[0104] The ionic liquid absorbents prepared in Example 1 and Comparative Example 3 were used to separate olefins / alkanes. The application included: adding 3.0 g of the ionic liquid absorbent to each of two absorption bottles, then introducing pure C2H4 gas at a flow rate of 50 mL / min, reacting at 25 °C and 0.1 MPa, and weighing the absorption bottles at 120-min intervals. After 120 min of absorption, ethylene was obtained by desorption. The desorption conditions were: introducing N2 at a flow rate of 40 mL / min, desorbing at 80 °C for 120 min, and repeating the absorption-desorption cycle five times. The absorption performance of the ionic liquid absorbent for ethylene is shown in Table 2.

[0105] Table 2

[0106]

[0107]

[0108] As shown in Table 2, the ionic liquid absorbent prepared using double silver salts is easier to desorb, effectively reducing desorption energy consumption. Furthermore, the absorbent has good regeneration stability and can maintain a high ethylene absorption capacity even after multiple cycles.

[0109] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a double silver salt ionic liquid, characterized in that, The preparation method includes the following steps: (1) Mix the ionic liquid and the first silver salt and carry out the first reaction at a temperature of 20-120℃ to obtain an ionic liquid containing two cations; (2) Mix the second silver salt with the ionic liquid containing two cations described in step (1), carry out the second reaction at a temperature of 20-120℃, add a co-solvent and stir to mix, and obtain the double silver salt ionic liquid; The bissilver salt ionic liquid comprises the following components by mass percentage: 5%-80% ionic liquid, 5%-50% first silver salt, 5%-50% second silver salt, and 5%-30% cosolvent; The first silver salt and the second silver salt contain different anions; the co-solvent is selected from any one or a combination of at least two of ethylene glycol, glycerol or polyethylene glycol.

2. The preparation method according to claim 1, characterized in that, The ionic liquid includes ionic liquids containing imidazole, pyrazole, or triazole.

3. The preparation method according to claim 1, characterized in that, The anions of the ionic liquid include BF4. - NO3 - NTf2 - OTf - PF6 - or CH3COO - Any one of them.

4. The preparation method according to claim 1, characterized in that, The first silver salt includes any one of AgNO3, AgBF4, AgNTf2, AgOTf, AgPF6, or AgC2H3O2.

5. The preparation method according to claim 1, characterized in that, The second silver salt includes any one of AgNO3, AgBF4, AgNTf2, AgOTf, AgPF6, or AgC2H3O2.

6. The preparation method according to claim 1, characterized in that, Step (1) The first reaction time is 4-20 hours.

7. The preparation method according to claim 1, characterized in that, The reaction time in step (2) is 4-20 hours.

8. The preparation method according to claim 1, characterized in that, The mixing time is 1-3 hours.

9. An application of a double silver salt ionic liquid in the separation of olefins / alkanes, characterized in that, The application includes: using a double silver salt ionic liquid as an absorbent, mixing and reacting it with a raw gas containing olefins and alkanes to obtain an absorbent rich in olefins, and then separating the olefins by desorption; The preparation method of the bissilver salt ionic liquid includes the following steps: (1) Mix the ionic liquid and the first silver salt and carry out the first reaction at a temperature of 20-120℃ to obtain an ionic liquid containing two cations; (2) Mix the second silver salt with the ionic liquid containing two cations described in step (1), carry out the second reaction at a temperature of 20-120℃, add a co-solvent and stir to mix, and obtain the double silver salt ionic liquid; The bissilver salt ionic liquid comprises the following components by mass percentage: 5%-80% ionic liquid, 5%-50% first silver salt, 5%-50% second silver salt, and 5%-30% cosolvent; The first silver salt and the second silver salt contain different anions; the co-solvent is selected from any one or a combination of at least two of ethylene glycol, glycerol or polyethylene glycol.

10. The application according to claim 9, characterized in that, The flow rate of the raw material gas is 0.1-1000 mL / min.

11. The application according to claim 10, characterized in that, The flow rate of the raw gas is 10-150 mL / min.

12. The application according to claim 9, characterized in that, The reaction temperature is 10-60℃.

13. The application according to claim 9, characterized in that, The reaction is carried out at a pressure of 0.1-6 MPa.

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