CN113713427A - Method for extracting and separating aromatic hydrocarbon from alkane - Google Patents
Method for extracting and separating aromatic hydrocarbon from alkane Download PDFInfo
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Abstract
The invention belongs to the field of petrochemical aromatic hydrocarbon separation, and relates to a method for extracting and separating aromatic hydrocarbon from alkane, which comprises the following steps: extracting and extracting the mixture of the aromatic hydrocarbon and the alkane in sequence under the action of an extracting agent to separate the aromatic hydrocarbon, rectifying the residual material of the separated aromatic hydrocarbon to separate the target product aromatic hydrocarbon, and purifying the residual material of the separated target product aromatic hydrocarbon by a flash tank to separate the extracting agent for reuse; the extracting agent is prepared from the following components in a molar ratio of 10: 1-7: 3 to 9 alkyl imidazole cation, sulfate anion and (R)3)2A mixed ionic liquid extracting agent consisting of sulfonimide anions. The aromatic hydrocarbon content in the alkane material flow obtained by the operation method is less than 0.5 wt%, and the purity of the aromatic hydrocarbon product reaches 99.95 wt% or more. Compared with the traditional sulfolane aromatic hydrocarbon extraction process, the process does not need an extractant recovery tower in raffinate phase, simplifies the process flow, saves the equipment investment, and can reduce the aromatic hydrocarbon loss in production.
Description
Technical Field
The invention belongs to the field of petrochemical aromatic hydrocarbon separation, and relates to a method for extracting and separating aromatic hydrocarbon from alkane.
Background
Alkanes are important chemical raw materials and energy materials, and are commonly used in the production processes of rubber, pharmacy, perfume, shoemaking, leather, textile, furniture, paint and the like. In recent years, some alkanes, such as n-hexane, have also been used as diluents for adhesive production or as organic cleaning agents. Aromatic hydrocarbon generally refers to hydrocarbon with aromatic odor and benzene ring structure in the molecule, and is one of the most important organic chemical raw materials. The arene is widely applied to the fields of producing synthetic resin, plastics, synthetic fiber, rubber, detergent, dye, medicine, pesticide, explosive and the like. Aromatic hydrocarbons are the basic raw materials of the chemical industry with important position, and the yield and the production technical level are one of the marks of the national petrochemical industry development level.
CN01141471.5, "method for recovering aromatic hydrocarbons by extraction and extractive distillation", reports a method for recovering aromatic hydrocarbons from hydrocarbon mixtures, which realizes the recovery of benzene, toluene and xylene from hydrocarbon mixtures with high aromatic hydrocarbon content by operations such as prefractionation, liquid-liquid extraction and extractive distillation. Compared with the sulfolane process, the method avoids the blending operation of raffinate oil, reduces energy consumption, but has more complex process flow and large equipment investment.
The common industrial aromatic hydrocarbon extraction and separation method uses sulfolane as solvent to extract and separate aromatic hydrocarbon in hydrocarbon mixture. However, in the process of aromatic hydrocarbon extraction, sulfolane is decomposed and degraded when meeting oxygen or high temperature to generate sulfonic acid acidic substances. The equipment of the aromatic extraction device is mainly made of carbon steel, is in an acid corrosion environment, is easy to age, causes leakage and the like, and seriously threatens normal safe production. Meanwhile, because impurities such as sulfonate exist in the product, the product quality is influenced, and the market competitiveness of the product is reduced, the extraction agent which has the advantages of high aromatic hydrocarbon yield, low energy consumption and easy recovery is still needed to realize the purification of the aromatic hydrocarbon.
Disclosure of Invention
In order to overcome the problems in the prior art, the invention provides a method for extracting and separating aromatic hydrocarbon from alkane, which replaces sulfolane with a mixed ionic liquid extractant consisting of anions and cations with high partition coefficient and high selectivity, and realizes the separation of the aromatic hydrocarbon in a hydrocarbon mixture by using a method combining extraction and extractive rectification. Compared with the sulfolane process, the method saves the cost input of a raffinate phase solvent recovery tower, improves the yield of aromatic hydrocarbon products, and reduces the process energy consumption.
The mixed ionic liquid extractant in the invention is salt which is liquid at room temperature or close to room temperature and completely consists of anions and cations. It is composed of alkyl imidazole cation, sulfate anion and (R)3)2Sulfonimide anions. The solvent has good thermal stability and chemical stability, is not easy to volatilize, is not easy to burn and is non-toxic, is a green solvent, has wide operable temperature range and has good dissolving performance on organic matters and inorganic matters.
In order to realize the purpose of the invention, the adopted technical scheme is as follows:
a method for extracting and separating aromatic hydrocarbon from alkane comprises the following steps:
the method comprises the following steps of extracting and extracting a mixture of aromatic hydrocarbon and alkane in sequence under the action of an extracting agent to separate the aromatic hydrocarbon, rectifying the residual material from which the aromatic hydrocarbon is separated to separate the target product aromatic hydrocarbon, purifying one part of the residual material from which the target product aromatic hydrocarbon is separated by a flash tank to separate the extracting agent for reuse, and returning the other part of the residual material to the extracting tower together with the mixture of the aromatic hydrocarbon and the alkane;
the mass content of aromatic hydrocarbon in the mixture of the aromatic hydrocarbon and alkane is less than 60 percent, and the extracting agent is prepared from the following components in a molar ratio of 10: 1-7: 3 to 9 alkyl imidazole cation, sulfate anion and (R)3)2A mixed ionic liquid extractant consisting of sulfonimide anions;
specifically, the structural general formula of the alkyl imidazole cation is
The structural general formula of the sulfate anions is
(R3)2Structure of sulfonimide anionHas the general formula
Wherein R is1And R2Each independently is any one of alkyl with 1-4 carbon atoms, R3Is one of trifluoromethyl, halogeno, alkyl with carbon number of 1-3, hydroxyl, thiol and cyano.
Further, in the extraction process, the operating pressure of the extraction tower is 1.2-1.8 MPa, the temperature is controlled to be 30-60 ℃ (30-40 ℃ is further preferred), and the operating pressure is controlled to be 1.2-1.8 MPa; the temperature in the extraction process is controlled to be 50-150 ℃, and the operating pressure is 0.2-0.4 MPa; the temperature is controlled to be 110-180 ℃ in the rectification process, and the operating pressure is 0.005-0.02 MPa; the operating temperature of the flash tank is 150-240 ℃, and the operating pressure is 0.001-0.003 MPa.
According to the extraction and rectification process design, the high-purity aromatic hydrocarbon is obtained by coordinating the coupling flow of extraction and rectification according to the separation performance of the selected extracting agent, and the solvent is purified by using a flash tank to be recycled. Preferably, the extraction process is carried out based on an extraction tower, the theoretical plate number of the extraction tower is 10-20, and the extraction agent recycling means that the extraction agent material separated from the bottom of the flash tank is introduced to the extraction agent feeding position of the extraction tower.
Preferably, the mixture of the aromatic hydrocarbon and the alkane is introduced into the extraction tower from the lower part of the extraction tower, and particularly enters the extraction tower from the lowest theoretical plate of the extraction tower.
Preferably, the extractant returned from the flash tank is mixed with fresh supplementary extractant and is introduced into the extraction tower from the first theoretical plate of the extraction tower;
further, the material separated from the top of the flash tank flows back to the extraction tower, the feeding position is 2 nd to 5 th theoretical plates counted upwards from the bottom of the extraction tower, the rectification process is carried out in the aromatic hydrocarbon product tower, the target product aromatic hydrocarbon is discharged from the top of the aromatic hydrocarbon product tower, the residual material for separating the target product aromatic hydrocarbon is divided into two strands at the bottom of the aromatic hydrocarbon product tower, one strand enters the flash tank, the other strand is mixed with the material separated from the top of the flash tank and flows into the extraction tower together, and the other strand is 50-70% of the mass of the residual material for separating the target product aromatic hydrocarbon;
in the method, the mass concentration of the high-purity aromatic hydrocarbon product obtained from the top of the aromatic hydrocarbon product tower is not less than 99.95%.
The comprehensive mass loss rate of the extractant is less than 0.01 percent.
In the present invention, the pressure is absolute pressure, and the unspecified composition or content is mass composition or content.
Compared with the prior art, the invention has the following advantages:
(1) the compound is prepared from alkyl imidazole cation, sulfate anion and (R)3)2The extractant composed of the sulfonimide anions has strong chemical stability, high thermal stability, safety and good effect, and the three are not indispensable;
(2) according to the invention, through extraction, rectification and flash evaporation processes, and by combining operation conditions and structural parameters such as feeding position, theoretical plate number and the like, not only can the heat load and cooling load be reduced, but also the separation efficiency can be improved, and high-purity alkane and aromatic hydrocarbon can be obtained, wherein the mass fraction of the obtained alkane is more than 99.50%, and the mass fraction of the aromatic hydrocarbon is not less than 99.95%;
(3) due to the characteristic that the extractant is insoluble in the raffinate phase, compared with the traditional sulfolane aromatic extraction separation, the method has high separation efficiency, saves the investment of a raffinate phase extractant recovery tower, reduces the aromatic hydrocarbon loss in the production flow, and reduces the loss of the extractant and the process energy consumption.
(4) The compound is prepared from alkyl imidazole cation, sulfate anion and (R)3)2The extractant composed of the sulfonimide anions has better separation effect than the common ionic liquid composed of one kind of anions and one kind of cations, and the aromatic hydrocarbon and the alkane obtained by separation under the same feeding condition have higher purity, better yield and lower process energy consumption.
(5) The solvent compounded by binary anions and cations and the organic solvent in CN104945328A improves the content of diesel oilThe efficiency and recovery rate of the extraction and separation of the aromatic hydrocarbon are greatly improved compared with those of organic solvent DFM. The patent combines an ionic liquid and an organic solvent such as sulfolane and the like to enhance the extraction effect, and has the greatest innovation point in the invention, namely that the ionic liquid is prepared from one kind of cation (alkyl imidazole cation), two kinds of anions (sulfate anions and (R)3)2Sulfonimide anions) are composed according to different proportions-differing significantly in composition. The invention provides more selectivity in the selection of the anionic and cationic groups, is not limited to trifluoromethyl groups, and also comprises halogen (fluorine, chlorine, bromine) groups, C1-3 alkyl groups, hydroxyl groups, thiol groups, cyano groups and the like. The method combining the ionic liquid and the organic solvent improves the recovery rate, but the recovery process of the compound solvent is complex and the cost is higher, the method greatly improves the recovery efficiency of the aromatic hydrocarbon and the alkane (the mass fraction of the obtained alkane is more than 99.50 percent, and the mass fraction of the aromatic hydrocarbon is not less than 99.95 percent), simultaneously avoids the investment of a raffinate phase solvent recovery tower, and reduces the loss of an extracting agent and the energy consumption of the process.
(6) CN110819445A adopts an ionic liquid of the combination of alkyl benzene sulfonic acid anion and 1-butyl-3-methyl benzimidazole onium cation to remove polycyclic aromatic hydrocarbon in grease. The grease is vegetable oil, represented by peanut oil, rapeseed oil and the like, and the polycyclic aromatic hydrocarbon is high-carbon aromatic hydrocarbon such as naphthalene, anthracene, phenanthrene and the like. The ionic liquid used in this patent is a combination of a cation and an anion, and in the present invention consists of a cation (alkyl imidazolium cation), two anions (sulfate anions and (R)3)2Sulfonimide anions) are greatly different in composition according to ion extractants with different proportions, the recovery efficiency of aromatic hydrocarbon is greatly improved, the aromatic hydrocarbon content in alkane material flow obtained by the operation method is less than 0.5 wt%, and the purity of aromatic hydrocarbon products reaches 99.95 wt% or more, and the difference is thatThe greatest innovation of the invention is.
(7) In CN103666550A, the aromatic hydrocarbon content in the saturated hydrocarbon material flow entering the cracking process is reduced to below 2 wt% through the pretreatment of ionic liquid, the cracking raw material source is enlarged, and the yield of low-carbon olefin is improved. The ionic liquid described in the patent is a combination of a cation and an anion, and the ionic liquid used in the invention is prepared from a cation (alkyl imidazole cation), two anions (sulfate anions and (R)3)2Sulfonimide anions) differ in composition according to the composition of the ionic extractant in different proportions. In the invention, by adjusting the proportion of anions and cations, the operation conditions and the structural parameters, the mass fraction of the obtained alkane is more than 99.50 percent, the mass fraction of the aromatic hydrocarbon is not less than 99.95 percent, and the separation efficiency is greatly improved.
Drawings
FIG. 1 shows a process flow diagram in an embodiment of the invention.
FIG. 2 is a flow chart showing the process of comparative example 1 of the present invention using sulfolane as the extractant.
Detailed Description
The invention provides an ionic liquid extracting agent for promoting extraction and separation of aromatic hydrocarbon and a process method by combining experimental data and simulation, and the purpose of separating aromatic hydrocarbon and alkane is achieved by the ionic liquid extracting agent, and meanwhile, a high-purity aromatic hydrocarbon product is obtained.
FIG. 1 is a flow chart of the present invention, which is characterized in that an ionic liquid extracting agent recycled from the flow chart is mixed with a fresh ionic liquid extracting agent and is introduced into the upper part of an extraction tower, and an alkane and aromatic hydrocarbon mixture and a raw material which are cooled and recovered from the top of the extraction tower are mixed and are introduced into the bottom of the extraction tower. And recovering the alkane product from the top of the extraction tower after liquid-liquid extraction, and allowing raffinate phase at the bottom of the extraction tower to enter an extraction tower. And cooling the mixture of the alkane and the aromatic hydrocarbon at the top of the extraction tower, returning the cooled mixture to be mixed with the raw material, introducing the mixture into the bottom of the extraction tower, and introducing the mixture of the aromatic hydrocarbon and the extracting agent led out from the bottom of the extraction tower into an aromatic hydrocarbon product tower. And (3) obtaining an aromatic hydrocarbon product at the top of the rectified aromatic hydrocarbon product tower, purifying 30-50% of the extracting agent led out from the bottom of the tower by a flash tank, leading the extracting agent from the bottom of the flash tank to the top of the extraction tower to be recycled as the extracting agent, and mixing the other 50-70% of the extracting agent with the discharged material at the top of the flash tank and returning the mixture to the bottom of the extraction tower for feeding.
FIG. 2 is a flow diagram of a sulfolane process, in which a mixture of a sulfolane solvent recycled from the process and a fresh sulfolane solvent is introduced into the upper part of an extraction tower, and a mixture of alkane and aromatic hydrocarbon and a raw material which are cooled and recovered from the top of the extraction tower are introduced into the bottom of the extraction tower. And (3) after liquid-liquid extraction, enabling the raffinate phase obtained from the tower top to enter a raffinate phase solvent recovery tower, and enabling the extract phase at the tower bottom to enter an extraction tower. And rectifying the raffinate phase by a raffinate phase solvent recovery tower to obtain an alkane product from the tower top, and returning sulfolane obtained at the tower bottom to the upper part of the extraction tower for feeding. The extract phase enters an extraction tower to remove residual alkane, the mixture of alkane and aromatic hydrocarbon obtained from the top of the tower is cooled and then returns to the bottom of the extraction tower to be mixed with the raw material, and the mixture of aromatic hydrocarbon and sulfolane obtained from the bottom of the tower enters an aromatic hydrocarbon product tower. Finally, the aromatic hydrocarbon product can be obtained at the top of the aromatic hydrocarbon product, and the sulfolane at the bottom of the tower returns to the upper part of the extraction tower for recycling.
Both fig. 1 and fig. 2 show only the most basic flow schemes of extractive distillation and flash, and do not involve valves, pumps, reboilers, condensers, etc., but are well known to those skilled in the art.
Example 1
The molar ratio of 1-n-butyl-methylimidazole cation, bishydroxy sulfonimide anion and ethyl sulfate is 10:3:7, the solvent-oil ratio of extractive distillation is 9.3:1 (the solvent-oil ratio refers to a control parameter in the petroleum catalytic cracking process and represents the ratio of the catalyst circulation amount to the total feeding amount) (quality), and the extractive distillation separation is carried out on the mixture of the benzene and the normal hexane according to the flow chart of figure 1, and the implementation steps are as follows:
a) introducing a mixture of benzene and n-hexane with the mass content of 55% into the bottom of the extraction tower;
b) introducing the mixture of the extractant returned from the flash tank and the fresh extractant into the top of the extraction tower; the ratio of the total mass of the circulating solvent and the fresh solvent to the total mass of the crude mixture is 20: 9;
c) mixing the top discharge of the flash tank and 60 percent of extractant shunted at the bottom of the aromatic product tower, and returning the mixture to the lower part of the extraction tower;
d) separated n-hexane can be obtained from the top of the extraction tower after liquid-liquid extraction;
e) extracting the extract phase from the bottom of the extraction tower and sending the extract phase into an extraction tower;
f) the mixture of normal hexane and benzene obtained from the top of the extraction tower is circulated to the bottom of the extraction tower to be mixed with the raw materials;
g) the mixture of the benzene and the extractant which is led out from the bottom of the extraction tower enters an aromatic product tower;
h) obtaining a benzene product from the top of the aromatic product tower after rectification;
i) leading 40% of the extractant out of the bottom of the aromatic product tower and entering a flash tank for purification;
j) the purified extractant obtained from the bottom of the tank after flash evaporation is circulated to the top of the extraction tower for reuse;
k) the discharge from the top of the tank is mixed with the other 60 percent of the extractant shunted from the bottom of the aromatic product tower and returns to the lower part of the extraction tower.
The operating conditions, raw material compositions, agent-oil ratios, feed positions and the like are shown in table 1, and product indexes are shown in table 2.
Example 2
The extraction and rectification separation of a mixture of toluene and n-heptane is carried out according to the flow chart of fig. 1 by using an extracting agent with a molar ratio of 1-ethyl-3-methylimidazole cation, bistrifluoromethanesulfonylimide anion and ethyl sulfate anion of 10:9:1, keeping the theoretical plate number of the extraction and rectification tower and the raw material feeding position consistent with example 1, and the implementation steps are basically consistent with example 1. The benzene product is ensured to be qualified by changing the oil ratio of the extractive distillation agent to be 5.5: 1. The operating conditions for this example are set forth in Table 1 and the product specifications are set forth in Table 2.
Example 3
The method is characterized in that an extractant with the molar ratio of 1-ethyl-3-methylimidazole cations to bis (trifluoromethanesulfonimide) anions to ethyl sulfate being 10:5:5 is used, the theoretical plate number and the raw material feeding position of an extractive distillation tower are kept consistent with those of example 1, and the mixture of ethylbenzene and n-octane is subjected to extractive distillation separation according to the flow chart of figure 1, and the implementation steps are basically consistent with those of example 1. The benzene product is ensured to be qualified by changing the solvent-oil ratio of the extraction and rectification to be 7.2: 1. The operating conditions for this example are set forth in Table 1 and the product specifications are set forth in Table 2.
Example 4
The process is carried out in the same manner as in example 1 by using an extractant having a molar ratio of 1-ethyl-3-methylimidazole cation to bistrifluoromethylsulfonyl imide anion to ethyl sulfate anion of 10:3:7 and keeping the number of theoretical plates of an extractive distillation column and the feed position of the raw material in accordance with example 1 and subjecting a mixture of propylbenzene and n-decane to extractive distillation separation according to the flow chart of FIG. 1. The qualification of aromatic hydrocarbon products is ensured by changing the solvent-oil ratio of the extraction and rectification to be 8.1: 1. The operating conditions for this example are set forth in Table 1 and the product specifications are set forth in Table 2.
Example 5
The extraction and rectification separation of the mixture of benzene and n-hexane is carried out according to the flow chart of figure 1 by using an extracting agent with the molar ratio of 1-n-butyl-3-methylimidazole cation, bischlorosulfonimide anion and methyl sulfate anion being 10:3:7, keeping the theoretical plate number and the raw material feeding position of an extraction and rectification tower consistent with those of example 1, and the implementation steps are basically consistent with those of example 1. The qualification of aromatic hydrocarbon products is ensured by changing the solvent-oil ratio of the extraction and rectification to be 8.7: 1. The operating conditions for this example are set forth in Table 1 and the product specifications are set forth in Table 2.
Example 6
The extraction and rectification separation of the mixture of benzene and n-hexane is carried out according to the flow chart of figure 1 by using an extracting agent with the molar ratio of 1-n-butyl-3-methylimidazole cation, dicyanosulfonimide anion and ethyl sulfate anion being 10:3:7, keeping the theoretical plate number and the raw material feeding position of an extraction and rectification tower consistent with those of example 1, and the implementation steps are basically consistent with those of example 1. The qualification of aromatic hydrocarbon products is ensured by changing the solvent-oil ratio of the extraction and rectification to be 5.9: 1. The operating conditions for this example are set forth in Table 1 and the product specifications are set forth in Table 2.
Example 7
The extraction and rectification separation of the mixture of benzene and n-hexane is carried out according to the flow chart of figure 1 by using an extracting agent with the molar ratio of 1-n-butyl-3-methylimidazole cation, dithiohydroxy sulfimide anion and propyl sulfate anion being 10:3:7, keeping the theoretical plate number of the extraction and rectification tower and the raw material feeding position consistent with that of example 1, and the implementation steps are basically consistent with that of example 1. The qualification of aromatic hydrocarbon products is ensured by changing the solvent-oil ratio of the extraction and rectification to be 8.3: 1. The operating conditions for this example are set forth in Table 1 and the product specifications are set forth in Table 2.
Comparative example 1
The sulfolane is used as an extracting agent, and the extractive distillation separation is carried out on the mixture of benzene and normal hexane according to the flow chart of figure 2, and the implementation steps are as follows:
a) cooling the mixture of benzene and normal hexane at the top of the extraction tower, returning the cooled mixture to be mixed with the benzene and normal hexane raw materials with the mass content of 55 percent, and introducing the mixture into the bottom of the extraction tower;
b) mixing the solvent returned from the bottoms of the raffinate phase solvent recovery tower and the aromatic hydrocarbon product tower with the fresh solvent, and introducing the mixture into the top of the extraction tower; the ratio of the total mass of the circulating solvent and the fresh solvent to the total mass of the crude mixture is 20: 9;
c) after liquid-liquid extraction, introducing the raffinate phase into a raffinate phase solvent recovery tower from the top of the extraction tower, and introducing the extract phase into an extraction tower from the bottom of the extraction tower;
d) the raffinate phase solvent recovery tower obtains a rectified normal hexane product at the top of the tower, and the solvent recovered at the bottom of the tower returns to be mixed with a fresh solvent and then is introduced into the top of the extraction tower for recycling;
e) cooling the mixture of benzene and normal hexane obtained at the top of the extraction tower, mixing the cooled mixture with the raw materials, introducing the mixture into the top of the extraction tower, and introducing the mixture of benzene and solvent at the bottom of the extraction tower into an aromatic product tower;
f) after the aromatic product is rectified by the aromatic product tower, a benzene product is obtained from the tower top, and the solvent at the tower bottom is cooled and then returns to be mixed with a fresh solvent to be introduced into the top of the extraction tower for recycling.
The above-mentioned operating conditions, raw material compositions, feed positions, etc. are shown in Table 1, and various product indexes are shown in Table 2.
Comparative example 2
The extraction agent with the molar ratio of 1-n-butyl-3-methylimidazole cation to ethyl sulfate anion of 1:1 is used, the theoretical plate number of the extractive distillation tower and the feeding position of the raw material are kept consistent with those of example 1, the mixture of benzene and normal hexane is subjected to extractive distillation separation according to the flow chart of figure 1, and the implementation steps are basically consistent with those of example 1. The benzene product is ensured to be qualified by changing the oil ratio of the extractive distillation agent to be 9.3: 1. The operating conditions for this example are set forth in Table 1 and the product specifications are set forth in Table 2.
Comparative example 3
The extraction agent with the molar ratio of 1-n-butyl-3-methylimidazole cation to bis (trifluoromethyl) sulfimide anion of 1:1 is used, the theoretical plate number of the extractive distillation tower and the feeding position of the raw material are kept consistent with those of example 1, the mixture of benzene and n-hexane is subjected to extractive distillation separation according to the flow chart of figure 1, and the implementation steps are basically consistent with those of example 1. The qualification of aromatic hydrocarbon products is ensured by changing the solvent-oil ratio of the extraction and rectification to be 9.3: 1. The operating conditions for this example are set forth in Table 1 and the product specifications are set forth in Table 2.
TABLE 1
TABLE 2
In the above-mentioned examples 1-9, for the mixture of alkane and arene with different compositions, the purity of the recovered alkane is above 99.50%, the yield is not lower than 99.90%, the purity of the arene is greater than 99.95%, and the yield is not lower than 99.50% by using the process and the ionic liquid extractant of the present invention; compared with the traditional sulfolane extraction process, the ionic liquid adopted by the method is more green, safe and efficient, and the method has the advantages of lower energy consumption and lower cost in consideration of the investment of a raffinate phase solvent recovery tower and the recoverability of the ionic liquid; compared with binary ionic liquid with the same feeding and the same conditions, the ionic liquid extracting agent provided by the invention has the advantages that the separation effect is better, the purity of the obtained product is higher, the yield is better, and the energy consumption is lower.
In light of the foregoing description of the preferred embodiment of the present invention, many modifications and variations will be apparent to those skilled in the art without departing from the spirit and scope of the invention. The technical scope of the present invention is not limited to the content of the specification, and must be determined according to the scope of the claims.
Claims (9)
1. A method for extracting and separating aromatic hydrocarbon from alkane is characterized in that: the method comprises the following steps:
the method comprises the following steps of extracting and extracting a mixture of aromatic hydrocarbon and alkane in sequence under the action of an extracting agent to separate the aromatic hydrocarbon, rectifying the residual material from which the aromatic hydrocarbon is separated to separate the target product aromatic hydrocarbon, purifying one part of the residual material from which the target product aromatic hydrocarbon is separated by a flash tank to separate the extracting agent for reuse, and returning the other part of the residual material to the extracting tower together with the mixture of the aromatic hydrocarbon and the alkane;
the mass content of aromatic hydrocarbon in the mixture of the aromatic hydrocarbon and alkane is less than 60 percent, and the extracting agent is prepared from the following components in a molar ratio of 10: 1-7: 3 to 9 alkyl imidazole cation, sulfate anion and (R)3)2A mixed ionic liquid extracting agent consisting of sulfonimide anions.
2. The method for extracting and separating aromatic hydrocarbon from alkane according to claim 1, wherein: the structural general formula of the alkyl imidazole cation is
The structural general formula of the sulfate anions is
(R3)2The structural general formula of the sulfonimide anion is
Wherein R is1And R2Each independently is any one of alkyl with 1-4 carbon atoms, R3Is one of trifluoromethyl, halogeno, alkyl with carbon number of 1-3, hydroxyl, thiol and cyano.
3. The method for extracting and separating aromatic hydrocarbon from alkane according to claim 1, wherein: in the extraction process, the operating pressure of the extraction tower is 1.2-1.8 Mpa, the temperature is controlled to be 30-60 ℃, and the operating pressure is controlled to be 1.2-1.8 Mpa; the temperature in the extraction process is controlled to be 50-150 ℃, and the operating pressure is 0.2-0.4 MPa; the temperature is controlled to be 110-180 ℃ in the rectification process, and the operating pressure is 0.005-0.02 MPa; the operating temperature of the flash tank is 150-240 ℃, and the operating pressure is 0.001-0.003 MPa.
4. The method for extracting and separating aromatic hydrocarbon from alkane according to claim 3, wherein: the temperature in the extraction process is controlled to be 30-40 ℃.
5. The method for extracting and separating aromatic hydrocarbon from alkane according to claim 1, wherein: the extraction process is carried out based on an extraction tower, the theoretical plate number of the extraction tower is 10-20, and the extraction agent recycling means that the extraction agent material separated from the bottom of a flash tank is introduced to an extraction agent feeding position of the extraction tower.
6. The method for extracting and separating aromatic hydrocarbon from alkane according to claim 1, wherein: the mixture of the aromatic hydrocarbon and the alkane enters the extraction tower from the lowest theoretical plate of the extraction tower.
7. The method for extracting and separating aromatic hydrocarbon from alkane according to claim 1, wherein: the extractant returned from the flash tank is mixed with fresh make-up extractant and passed to the extraction column at the first theoretical plate of the extraction column.
8. The method for extracting and separating aromatic hydrocarbon from alkane according to claim 1, wherein: and refluxing the material separated from the top of the flash tank to the extraction tower, wherein the feeding position is 2 to 5 theoretical plates counted upwards from the bottom of the extraction tower, the rectification process is carried out in the aromatic hydrocarbon product tower, the target product aromatic hydrocarbon is discharged from the top of the aromatic hydrocarbon product tower, the residual material for separating the target product aromatic hydrocarbon is divided into two strands at the bottom of the aromatic hydrocarbon product tower, one strand enters the flash tank, the other strand is mixed with the material separated from the top of the flash tank and flows into the extraction tower together, and the other strand is 50 to 70 percent of the mass of the residual material for separating the target product aromatic hydrocarbon.
9. The method for extracting and separating aromatic hydrocarbon from alkane according to claim 1, wherein: 30-50 wt% of the residual material of the target product aromatic hydrocarbon is separated and enters a flash tank.
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| Publication number | Priority date | Publication date | Assignee | Title |
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