Ionic liquid type aromatic hydrocarbon extraction agent

Abstract

The invention belongs to the technical field of chemical products, and discloses an ionic liquid type aromatic hydrocarbon extraction extractant, which is 1, 3-dimethylimidazole tetrafluoroborate or 1, 3-dimethylimidazole bis (fluorosulfonyl) imine salt or 1-ethyl-3-methylimidazole bis (fluorosulfonyl) imine salt, and the ionic liquid type aromatic hydrocarbon extraction extractant is a mixture of 1, 3-dimethylimidazole tetrafluoroborate, 1, 3-dimethylimidazole bis (fluorosulfonyl) imine salt and 1, 3-dimethylimidazole bis (fluorosulfonyl) imine salt. The method comprises the following steps: putting a mixture of an extracting agent, methylbenzene and methyl cyclohexane into an extraction bottle of a liquid-liquid equilibrium kettle, uniformly mixing, stirring at constant temperature, and standing for 10-16 hours, so as to obtain an extracting solution rich in methyl cyclohexane on the upper layer, and obtain a raffinate rich in methylbenzene and imidazole ionic liquid on the lower layer. The separation effect of the ionic liquid type aromatic hydrocarbon extraction extractant reaches up to 85% or above, the recovery rate of imidazolium ionic liquid reaches up to 95% or above, and the ionic liquid type aromatic hydrocarbon extraction extractant can be used for efficient separation of aromatic hydrocarbon-non-aromatic hydrocarbon occurring in the process of preparing aromatic hydrocarbon through carbon dioxide hydrogenation.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical products, and in particular relates to an ionic liquid type aromatic hydrocarbon extraction agent. Background Art

[0002] Aromatics mainly come from catalytic reforming units in refineries, ethylene cracking gasoline in petrochemical plants, aromatics production complexes, and coal coking units. However, the production of traditional aromatics mainly relies on the petroleum route. With the increasing depletion of petroleum resources and the growing demand for aromatics, traditional production methods face huge challenges. The technology of hydrogenating carbon dioxide to aromatics has opened up a new source for the production of aromatics. This technology uses carbon dioxide and hydrogen as raw materials, and converts carbon dioxide into high-value-added aromatic products through specific catalysts and process conditions. However, in this process, many aromatics and non-aromatics have azeotropic properties and cannot be separated by ordinary methods.

[0003] Aromatic hydrocarbons, as important basic organic raw materials, are widely used in synthetic resins, medicine and other fields. Alkanes are used as solvents in the coating and ink industries; in the energy field, some non-aromatic hydrocarbons can be used as fuel additives to increase the octane number; in the field of materials science, they can be used as raw materials for synthesizing new materials. Therefore, the separation of aromatic hydrocarbons and non-aromatic hydrocarbons is of great significance for promoting the sustainable development of the chemical industry, improving product quality and reducing production costs.

[0004] Solvents play a vital role in aromatic extraction. Different solvents have different mechanisms of action, and their characteristics directly affect the efficiency of aromatic extraction and product quality. The traditional extractant for aromatic extraction is sulfolane, but the whole process requires a large amount of extractant and sulfolane is easy to decompose at high temperature to produce acidic substances. The polymerization of acidic substances not only corrodes equipment but also reduces the performance of solvents.

[0005] Researchers have discovered many advantages of ionic liquids as green solvents. Ionic liquids have high boiling points, low vapor pressures, good thermal stability and chemical stability. Ionic liquids can dissolve a variety of organic matter, making them effective solvents for the extraction and separation of aromatic hydrocarbons with similar boiling points. Using ionic liquids as extraction solvents can improve the separation efficiency of aromatic hydrocarbons, and ionic liquids can be recycled, reducing production costs and reducing pollution to the environment. However, the existing ionic liquids are not all efficient in separating aromatic and non-aromatic hydrocarbons, and the recovery rates of ionic liquids vary greatly.

[0006] Therefore, providing an ionic liquid aromatic extraction agent with high efficiency and high recovery efficiency for efficient separation of aromatics and non-aromatics has become a technical problem that urgently needs to be solved in the field. Summary of the invention

[0007] In order to overcome the shortcomings of the prior art, the present invention provides an ionic liquid type aromatic hydrocarbon extraction extractant, wherein the extractant is 1,3-dimethylimidazolium tetrafluoroborate or 1,3-dimethylimidazolium bis(fluorosulfonyl)imide salt or 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide salt, which is used to extract toluene from a mixture of toluene and methylcyclohexane, with a separation effect of more than 85%, an ionic liquid recovery rate of more than 95%, and can be used for the efficient separation of aromatic hydrocarbons and non-aromatic hydrocarbons occurring in the process of hydrogenating carbon dioxide to produce aromatic hydrocarbons.

[0008] The present invention is achieved through the following technical solutions:

[0009] The invention provides an ionic liquid type aromatic hydrocarbon extraction extractant, wherein the extractant is 1,3-dimethylimidazolium tetrafluoroborate ([MMIm][BF4]) or 1,3-dimethylimidazolium bis(fluorosulfonyl)imide ([MMIm][FSI]) or 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide ([EMIm][FSI]), and is used for extracting toluene from a mixture of toluene and methylcyclohexane.

[0010] Furthermore, the method of use is: placing the extractant, toluene and methylcyclohexane mixture in an extraction bottle of a liquid-liquid equilibrium kettle, mixing them evenly, stirring them at a constant temperature and then standing them for 10 to 16 hours, obtaining an extract rich in methylcyclohexane on the upper layer and a raffinate rich in toluene and imidazole ionic liquid on the lower layer.

[0011] Furthermore, the mass ratio of the extractant to the mixture of toluene and methylcyclohexane is 13:1 to 1:5.

[0012] Furthermore, the temperature of the liquid-liquid equilibrium kettle is 25-45°C.

[0013] The extractants of the present invention, 1,3-dimethylimidazolium tetrafluoroborate ([MMIm][BF4]), 1,3-dimethylimidazolium bis(fluorosulfonyl)imide salt ([MMIm][FSI]), and 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide salt ([EMIm][FSI]), are imidazole ionic liquids having the characteristics of low vapor pressure, which can effectively reduce the volatilization loss of the solvent. This not only reduces the production cost, but also reduces the pollution to the environment. In addition, the low vapor pressure also makes the ionic liquid more stable during the extraction process and is not prone to phase change, thereby ensuring the continuity and stability of the extraction process.

[0014] The thermal stability of ionic liquids shows obvious advantages in the high-temperature extraction process. They can maintain stable physical and chemical properties over a wide temperature range, so that ionic liquids can play a better role in the high-temperature extraction process and improve the extraction efficiency and purity of aromatics.

[0015] Ionic liquids can have a certain similarity or interaction with the molecular structure of aromatic hydrocarbons, making the solubility of aromatic hydrocarbons in ionic liquids relatively high. In contrast, the molecular structure of non-aromatic hydrocarbons has a weaker interaction with ionic liquids and has a lower solubility in ionic liquids, thereby achieving the initial separation of aromatic hydrocarbons and non-aromatic hydrocarbons.

[0016] The advantages and positive effects of the present invention are:

[0017] (1) The present invention adopts ionic liquid type aromatics extraction agent to extract aromatics, and the separation effect is as high as more than 85%.

[0018] (2) The present invention uses a simple recovery method to achieve a recovery rate of more than 95% of the extracted imidazole ionic liquid.

[0019] (3) The present invention uses an ionic liquid type aromatic hydrocarbon extraction agent, which has the advantages of low energy consumption and simple process. Imidazole ionic liquid type extraction agents are used in aromatic hydrocarbon extraction and have the advantages of high extraction efficiency, green environmental protection, and low price. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention is a schematic diagram of the structure of a device for separating a mixture of toluene and methylcyclohexane using an ionic liquid aromatic hydrocarbon extraction agent.

[0021] The reference numerals are as follows:

[0022] 1- agitator; 2- extraction bottle; 3- liquid-liquid balance kettle; 4- stirrer; 5- condenser; 6- constant temperature reaction kettle. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below through specific examples. The following examples are only illustrative and not restrictive, and the protection scope of the present invention cannot be limited thereto.

[0024] like Figure 1 The schematic diagram of the structure of the device for separating a mixture of toluene and methylcyclohexane using an ionic liquid aromatic hydrocarbon extraction agent of the present invention is shown, the device comprises a constant temperature reactor 6, a stirrer 4, a stirrer 1, a liquid-liquid balance reactor 3 and an extraction bottle 2, the constant temperature reactor 6 is connected to the liquid-liquid balance reactor 3 through two condensers 5, and the temperature of the liquid-liquid balance reactor 3 is controlled by liquid circulation; the constant temperature reactor 6 is connected to the stirrer 4 through a line, the stirrer 1 is installed on the stirrer, and the stirrer 1 is placed in the extraction bottle 2, and the liquid in the extraction bottle 2 can be stirred. The device is used to carry out the following examples.

[0025] Example 1

[0026] The invention discloses an ionic liquid type aromatic hydrocarbon extraction extractant, wherein the extractant is 1,3-dimethyl imidazolium tetrafluoroborate ([MMIm][BF4]). The method for using the extractant is as follows: placing a mixture of 21.7 g toluene and methyl cyclohexane in an extraction bottle 2 of a liquid-liquid equilibrium kettle 3, adding 28.5 g of 1,3-dimethyl imidazolium tetrafluoroborate, and mixing them uniformly; a constant temperature reaction kettle 6 controls the reaction temperature of the liquid-liquid equilibrium kettle 3 to be 25°C; a stirrer 4 drives a stirrer 1 to stir the mixed liquid for 2 hours and then allows the mixed liquid to stand for 12 hours; an extract rich in methyl cyclohexane is obtained in the upper layer, and a raffinate rich in toluene and ionic liquid is obtained in the lower layer; then the upper extract and the lower raffinate are taken for gas chromatography analysis respectively; and the parameters for the gas chromatography analysis are as follows: the samples obtained in the experiment are analyzed by a Thermo Fisher Trace 1300 gas chromatograph, and the chromatographic column is HP-5. The temperature settings of the gas chromatograph were: column temperature 200°C; injection port temperature 260°C; detector temperature 290°C. The analysis results showed that the extraction rate of [MMIm][BF4] was 87%.

[0027] After the extraction is completed, [MMIm][BF4] is recovered, and the remaining solution is placed in a flask for rotary evaporation. Toluene and methylcyclohexane are removed by controlling the temperature and pressure within a suitable range. The recovered ionic liquid [MMIm][BF4] is analyzed, and the main component is still [MMIm][BF4], and the purity is high, with a recovery rate of 97%. Then different batches of aromatics-non-aromatics are treated to observe the recovery effect of [MMIm][BF4]. The results show that after multiple cycles, the performance of [MMIm][BF4] remains basically unchanged, and it can still effectively separate aromatics and non-aromatics, with an extraction rate of 89%.

[0028] Example 2

[0029] An ionic liquid type aromatic hydrocarbon extraction extractant, the extractant is 1,3-dimethyl imidazole bis (fluorosulfonyl) imide salt ([MMIm][FSI]), the use method is: 18.3g of toluene and methyl cyclohexane mixture is placed in the extraction bottle 2 of the liquid-liquid equilibrium kettle 3, 33g of 1,3-dimethyl imidazole bis (fluorosulfonyl) imide salt is added, and the mixture is mixed evenly, the reaction temperature of the liquid-liquid equilibrium kettle 3 is controlled to be 25°C by the constant temperature reaction kettle 6, the stirrer 4 drives the stirrer 1 to stir the mixed liquid for 2 hours and then stands for 12 hours, the upper layer obtains an extract rich in methyl cyclohexane, and the lower layer obtains a raffinate rich in toluene and ionic liquid. Then the upper extract and the raffinate are taken for gas chromatography analysis respectively, and the parameters of the gas chromatography analysis are: the sample obtained in the experiment is analyzed by using a ThermoFisher Trace1300 gas chromatograph, and the chromatographic column is HP-5. The temperature settings of the gas chromatograph were: column temperature 200°C; injection port temperature 260°C; detector temperature 290°C. The analysis results showed that the extraction rate of [MMIm][FSI] was 89%.

[0030] After the extraction is completed, [MMIm][FSI] is recovered, and the remaining solution is placed in a flask for rotary evaporation, and toluene and methylcyclohexane are removed by controlling the temperature and pressure within a suitable range. The recovered ionic liquid [MMIm][FSI] is analyzed, and the main component is still [MMIm][FSI], and the purity is high, with a recovery rate of 95%. Then different batches of aromatics-non-aromatics are treated to observe the recovery effect of [MMIm][FSI]. The results show that after multiple cycles, the performance of [MMIm][FSI] remains basically unchanged, and it can still effectively separate aromatics and non-aromatics, with an extraction rate of 92%.

[0031] Example 3

[0032] An ionic liquid type aromatic hydrocarbon extraction extractant, the extractant is 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide salt ([EMIm][FSI]), the use method is: 16.7g of toluene and methylcyclohexane mixture is placed in an extraction bottle 2 of a liquid-liquid equilibrium kettle 3, 33.8g of 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide salt is added and mixed evenly, the constant temperature reaction kettle 6 controls the reaction temperature of the liquid-liquid equilibrium kettle 3 to be 25°C, the stirrer 4 drives the stirrer 1 to stir the mixed liquid for 2 hours and then leaves it to stand for 12 hours, the upper layer obtains an extract rich in methylcyclohexane, and the lower layer obtains a raffinate rich in toluene and ionic liquid. Then the extract and the lower raffinate are taken for gas chromatography analysis respectively, and the parameters of the gas chromatography analysis are: the sample obtained in the experiment is analyzed by using a Thermo Fisher Trace1300 gas chromatograph, and the chromatographic column is HP-5. The temperature settings of the gas chromatograph were: column temperature 200°C; injection port temperature 260°C; detector temperature 290°C. The analysis results showed that the extraction rate of [EMIm][FSI] was 85%.

[0033] After the extraction is completed, [EMIm][FSI] is recovered, and the remaining solution is placed in a flask for rotary evaporation, and toluene and methylcyclohexane are removed by controlling the temperature and pressure within a suitable range. The recovered ionic liquid [EMIm][FSI] was analyzed and it was found that its main component was still [EMIm][FSI], and the purity was high, with a recovery rate of 98%. Then different batches of aromatic-non-aromatic hydrocarbons were treated to observe the recovery effect of [EMIm][FSI]. The results showed that after multiple cycles, the performance of [EMIm][FSI] remained basically unchanged, and it was still able to effectively separate aromatics and non-aromatic hydrocarbons, with an extraction rate of 87%.

[0034] Comparative Example 1

[0035] The only difference from Example 1 is that the extractant is the pyridine ionic liquid 3-methyl-N-butylpyridine bis(trifluoromethanesulfonyl)imide salt, the extraction rate is 77%, and the recovery rate of 3-methyl-N-butylpyridine bis(trifluoromethanesulfonyl)imide salt is 89%.

[0036] Comparative Example 2

[0037] The only difference from Example 1 is that the extractant is a quaternary ammonium ionic liquid triethylammonium tetrafluoroborate. The extraction rate is 79%, and the recovery rate of triethylammonium tetrafluoroborate is 95%.

[0038] Comparative Example 3

[0039] The only difference from Example 1 is that the extractant is quaternary phosphorus ionic liquid tetrabutylphosphonium trifluoromethanesulfonate. The extraction rate is 65%, and the recovery rate of tetrabutylphosphonium trifluoromethanesulfonate is 88%.

[0040] Comparative Example 4

[0041] The only difference from Example 1 is that the extractant is pyrrolidine ionic liquid N-ethyl-N-methylpyrrolidine dinitrile amide salt. The extraction rate is 73%, and the recovery rate of N-ethyl-N-methylpyrrolidine dinitrile amide salt is 92%.

[0042] The above description is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the inventive concept, which all belong to the protection scope of the present invention.

Claims

1. An ionic liquid aromatics extraction agent, characterized in that: The extractant is 1,3-dimethyl imidazolium tetrafluoroborate or 1,3-dimethyl imidazolium bis(fluorosulfonyl) imide salt or 1-ethyl-3-methyl imidazolium bis(fluorosulfonyl) imide salt, and is used for extracting toluene from a mixture of toluene and methylcyclohexane.

2. The ionic liquid aromatics extraction agent according to claim 1, characterized in that: The method of use is: place the extractant, toluene and methylcyclohexane mixture in the extraction bottle of the liquid-liquid equilibrium kettle, mix them evenly, stir them at a constant temperature, and then let them stand for 10 to 16 hours, and the upper layer will obtain an extract rich in methylcyclohexane, and the lower layer will obtain a raffinate rich in toluene and imidazole ionic liquid.

3. The ionic liquid aromatics extraction agent according to claim 2, characterized in that: The mass ratio of the extractant to the mixture of toluene and methylcyclohexane is 13:1 to 1:

5.

4. The ionic liquid aromatics extraction agent according to claim 2, characterized in that: The temperature of the liquid-liquid equilibrium kettle is 25-45°C.

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