CN110479037B - Composite absorbent and method for separating and purifying ethylene oxide by using same - Google Patents
Composite absorbent and method for separating and purifying ethylene oxide by using same Download PDFInfo
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- CN110479037B CN110479037B CN201910786256.2A CN201910786256A CN110479037B CN 110479037 B CN110479037 B CN 110479037B CN 201910786256 A CN201910786256 A CN 201910786256A CN 110479037 B CN110479037 B CN 110479037B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1487—Removing organic compounds
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1493—Selection of liquid materials for use as absorbents
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D301/00—Preparation of oxiranes
- C07D301/32—Separation; Purification
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D303/00—Compounds containing three-membered rings having one oxygen atom as the only ring hetero atom
- C07D303/02—Compounds containing oxirane rings
- C07D303/04—Compounds containing oxirane rings containing only hydrogen and carbon atoms in addition to the ring oxygen atoms
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2252/00—Absorbents, i.e. solvents and liquid materials for gas absorption
- B01D2252/20—Organic absorbents
Abstract
The invention provides a composite absorbent and a method for separating and purifying ethylene oxide by using the same. The composite absorbent contains the ionic liquid with a specific structure, so that when the absorbent is used for separation and purification of ethylene oxide, the absorbent has high absorption capacity on the ethylene oxide, can remarkably increase the selectivity of the ethylene oxide for absorption and separation, can effectively reduce the vapor pressure of the absorbent and reduce the loss of a solvent in a desorption process, and has the characteristics of simple process flow, high operation flexibility, low energy consumption, remarkable absorption effect and the like, and the industrial application prospect is good.
Description
Technical Field
The invention relates to the technical field of separation, in particular to a composite absorbent and a method for separating and purifying ethylene oxide by using the same.
Background
Ethylene Oxide (EO) is an important petrochemical product, has excellent sterilization and disinfection effects, and is mainly used in washing, pharmaceutical and printing and dyeing industries. At present, the main production method of ethylene oxide is ethylene oxidation method, ethylene and oxygen generate ethylene oxide under the condition of silver catalyst, but because the conversion rate and selectivity are low, the ethylene oxide is generated, and at the same time, partial gases of methane, ethane, carbon dioxide and the like are generated and unreacted ethylene exists.
The existing process using water as an absorbent has the problems of complex flow, poor operation elasticity, high energy consumption and the like, and a plurality of patents at home and abroad make improved measures against the problem. US3948621a1 discloses the use of methanol as an absorbent for the separation and purification of ethylene oxide, which has good absorption effect and low energy consumption during desorption, but methanol is liable to react with ethylene oxide, the absorption temperature needs to be strictly controlled, and methanol is liable to be lost along with the volatilization of the desorbed gas during desorption. US4221727a1 discloses a method for separating ethylene oxide by absorbing ethylene carbonate as an absorbent, wherein the ethylene carbonate is used as the absorbent, the absorption effect is good, and side reactions can be avoided in the absorption process, but in the desorption process, the desorption temperature is 150 ℃, the pressure is 5KPa, and part of ethylene carbonate volatilizes along with desorption gas, so that the solvent loss is caused. Similarly, US5559255A discloses the use of propylene carbonate as an absorbent and CN102911137A discloses the use of a mixture of ethylene carbonate and water as an ethylene oxide absorbent, but none addresses the problem of solvent loss by volatilization during stripping.
Therefore, in order to better realize the separation of ethylene oxide from the mixed gas after the oxidation of ethylene, a new absorbent needs to be researched, so that the loss of the absorbent is not influenced, and the absorption energy consumption can be reduced.
Disclosure of Invention
In view of the problems in the prior art, the invention provides a composite absorbent and a method for separating and purifying ethylene oxide, wherein the absorbent comprises ionic liquid and ethylene carbonate, and the structure of the ionic liquid is shown as formula I. The composite absorbent contains the ionic liquid with a specific structure, and when the composite absorbent is used for separating and purifying ethylene oxide, the absorption rate of the ethylene oxide and the recycling rate of the composite absorbent can be effectively improved, the cost is reduced, and the energy consumption is reduced.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a composite absorbent, which includes an ionic liquid and ethylene carbonate, wherein the ionic liquid has a structure represented by formula I:
wherein R is1And R2Each independently selected from any one of substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C2-C6 alkenyl, substituted or unsubstituted C2-C6 alkynyl, substituted or unsubstituted C6-C30 aryl, substituted or unsubstituted C3-C30 heteroaryl or substituted or unsubstituted C1-C6 alkoxy;
anion X-Selected from BF4 -、PF6 -、Tf2N-、RCOO-、Cl-Or Br-Any one of the above; r is selected from any one of alkyl, alkenyl or alkynyl.
As used herein, the term "C1-C6 alkyl" refers to a straight or branched chain alkyl group having 1, 2, 3, 4, 5, or 6 carbon atoms and includes, without limitation, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, n-hexyl, and the like. The term "C2-C6 alkenyl" refers to a straight or branched chain alkenyl group having 2, 3, 4, 5, or 6 carbon atoms, which includes at least one double bond in the molecular chain, including, without limitation, -CH ═ CH (CH)3)、-CH＝C(CH3)2、-C(CH3)＝CH2、-C(CH3)＝CH(CH3)、-C(CH2CH3)＝CH2Butadienyl, pentadienyl or hexadienyl groups, and the like. The term "C2-C6 alkynyl" refers to straight or branched chain alkynyl groups having 2, 3, 4, 5 or 6 carbon atoms, including, without limitation, -C.ident.CH, -C.ident.C (CH)3)、-C≡C(CH2CH3)、-CH2C≡CH、-CH2C≡C(CH3) or-CH2C≡C(CH2CH3) And the like. The term "C6-C30 aryl" is an aryl group having 6-30 carbon atoms, e.g., may contain 6, 12 or 18 carbon atomsAnd the like, including without limitation phenyl, naphthyl, biphenyl, and the like. The term "C3-C30 heteroaryl" refers to a monocyclic, bicyclic, or tricyclic, etc. aromatic ring system having 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30, etc. ring atoms and which contains at least one heteroatom which may be the same or different, such as oxygen, nitrogen, or sulfur, and further may be benzo-fused in each instance, including, without limitation, thienyl, furyl, pyrrolyl, oxazolyl, thiazolyl, imidazolyl, pyrazolyl, isoxazolyl, isothiazolyl, oxadiazolyl, triazolyl, benzofuranyl, benzothienyl, benzoxazolyl, benzisoxazolyl, benzimidazolyl, benzotriazolyl, indazolyl, indolyl, isoindolyl, pyridyl, pyridazinyl, etc, Pyrimidinyl, pyrazinyl, triazinyl, quinolinyl, quinazolinyl, isoquinolinyl, and the like. The term "C1-C6 alkoxy" refers to a straight or branched chain alkoxy group having 1, 2, 3, 4, 5, or 6 carbon atoms, including without limitation methoxy, ethoxy, n-propoxy, isopropoxy, or tert-butoxy groups, and the like.
The composite absorbent containing the ionic liquid has high absorption capacity on ethylene oxide, can obviously increase the selectivity of ethylene oxide absorption and separation, can effectively reduce the vapor pressure of the absorbent, reduces the loss of a solvent in a desorption process, has the characteristics of simple process flow, high operation flexibility, low energy consumption, obvious absorption effect and the like, and has good industrial application prospect.
Preferably, R1And R2Wherein the substituted groups are respectively and independently selected from any one of hydroxyl, amino, nitro, aldehyde group, ester group, carboxyl or sulfhydryl.
Preferably, R1And R2Wherein said substituted group is a hydroxyl group or an amino group.
Preferably, the anion X-Is BF4 -Or PF6 -。
In a preferred embodiment of the present invention, the ionic liquid is selected from any one of 1-hydroxyethyl-3-methylimidazolium hexafluorophosphate, 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate, 1-aminoethyl-3-methylimidazolium hexafluorophosphate, 1-hydroxyethyl-3-ethylimidazolium hexafluorophosphate, and 1-hydroxyethyl-3-ethylimidazolium tetrafluoroborate, or a combination of at least two thereof.
Preferably, the mass ratio of the ionic liquid in the composite absorbent is 10 to 60%, for example, 10%, 12%, 15%, 17%, 19%, 20%, 23%, 25%, 27%, 30%, 33%, 35%, 37%, 38%, 40%, 42%, 45%, 49%, 50%, 53%, 55%, 59%, 60%, etc., preferably 30 to 50%.
The reason why the mass ratio of the ionic liquid to the ethylene carbonate is preferably controlled within the above range in the present invention is that when the content of the ionic liquid is too high, the viscosity of the composite absorbent increases and the composite absorbent cannot be brought into sufficient contact with ethylene oxide, which may decrease the absorption efficiency of ethylene oxide, and if the content of the ionic liquid is too low, the selective absorption of the composite absorbent is reduced, which may also affect the absorption effect of ethylene oxide.
In a second aspect, the present invention also provides a method for separation and purification of ethylene oxide, which uses the composite absorbent according to the first aspect.
The method for separating and purifying the ethylene oxide uses the composite absorbent of the ionic liquid and the ethylene carbonate, can effectively improve the absorption capacity of the ethylene oxide in the raw material gas, simplifies the process flow, increases the operation flexibility of the device, reduces the energy consumption, and provides technical support for continuously producing and purifying the ethylene oxide.
Preferably, the method comprises the steps of: and (3) contacting the composite absorbent with feed gas containing ethylene oxide, returning the lean mixed gas after removing the ethylene oxide to an ethylene oxidation stage, and desorbing the ethylene oxide-rich absorption liquid to obtain the ethylene oxide.
The feed gas comprises the following components in percentage by mol: ethylene oxide 2.6%, methane 52.77%, ethylene 32.53%, oxygen 4.9%, carbon dioxide 1.5%, argon 4.18%, nitrogen 1% and ethane 0.52%. The raw material gas used by the invention has low content of ethylene oxide, and the ethylene oxide with higher purity can be obtained by separating and purifying the raw material gas by the composite absorbent of the ionic liquid and the ethylene carbonate, so that the absorption efficiency is obviously improved.
Further preferably, the method comprises the steps of: the composite absorbent and feed gas containing ethylene oxide are in countercurrent full contact in an absorption tower, lean mixed gas after ethylene oxide removal at the tower top is treated and then returns to an ethylene oxidation stage, ethylene oxide-rich absorption liquid at the tower bottom enters a desorption tower after heat exchange, gas phase is extracted from the tower top after desorption to obtain ethylene oxide, and desorption lean liquid of a liquid phase after desorption returns to the absorption tower after heat exchange from the tower bottom.
Preferably, the molar concentration of ethylene oxide in the feed gas is 0.1-5%, for example, it may be 0.1%, 0.3%, 0.5%, 0.8%, 0.9%, 1.0%, 1.2%, 1.5%, 2%, 2.5%, 2.6%, 2.8%, 3.0%, 3.5%, 4.0%, 4.5%, or 5%, etc., preferably 2-3%.
Preferably, the feed gas has an inlet temperature of 40 to 100 ℃, for example, 40 ℃, 42 ℃, 43 ℃, 45 ℃, 48 ℃, 50 ℃, 51 ℃, 56 ℃, 59 ℃, 60 ℃, 65 ℃, 68 ℃, 70 ℃, 72 ℃, 73 ℃, 75 ℃, 78 ℃, 79 ℃, 80 ℃, 83 ℃, 85 ℃, 87 ℃, 90 ℃, 92 ℃, 95 ℃, 97 ℃, 99 ℃ or 100 ℃, preferably 50 to 80 ℃.
Preferably, the operating pressure of the absorption column is 0.1 to 5MPa, and may be, for example, 0.1MPa, 0.2MPa, 0.3MPa, 0.5MPa, 0.8MPa, 1.0MPa, 1.2MPa, 1.5MPa, 1.9MPa, 2.0MPa, 2.3MPa, 2.5MPa, 2.6MPa, 2.9MPa, 3.0MPa, 3.5MPa, 3.8MPa, 4.0MPa, 4.2MPa, 4.5MPa or 5.0MPa, and the like, and preferably 1 to 3 MPa.
Preferably, the absorption tower operating temperature is 40-100 ℃, for example can be 40 degrees, 42 degrees, 43 degrees, 45 degrees, 48 degrees, 50 degrees, 51 degrees, 56 degrees, 59 degrees, 60 degrees, 65 degrees, 68 degrees, 70 degrees, 72 degrees, 73 degrees, 75 degrees, 78 degrees, 79 degrees, 80 degrees, 83 degrees, 85 degrees, 87 degrees, 90 degrees, 92 degrees, 95 degrees, 97 degrees, 99 degrees or 100 degrees, preferably 50-80 ℃.
Preferably, the molar ratio of the composite absorbent to the raw material gas is (1-4):1, and may be, for example, 1:1, 1.5:1, 1.7:1, 2:1, 2.1:1, 2.3:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3:1, 3.2:1, 3.5:1, 3.6:1, 3.9:1 or 4:1, and the like, and preferably (2-3): 1.
Preferably, the operating pressure of the desorber is in the range of 10 to 150KPa, for example 10KPa, 12KPa, 15KPa, 18KPa, 20KPa, 25KPa, 30KPa, 36KPa, 38KPa, 40KPa, 45KPa, 48KPa, 50KPa, 52KPa, 55KPa, 60KPa, 62KPa, 65KPa, 70KPa, 75KPa, 80KPa, 85KPa, 90KPa, 94KPa, 100KPa, 110KPa, 120KPa, 130KPa, 135KPa, 140KPa, 145KPa or 150KPa and the like, preferably 50 to 150 KPa.
Preferably, the desorption column operating temperature is 80-150 degrees C, for example can be 80 degrees C, 84 degrees C, 85 degrees C, 87 degrees C, 89 degrees C, 90 degrees C, 95 degrees C, 98 degrees C, 100 degrees C, 105 degrees C, 108 degrees C, 110 degrees C, 115 degrees C, 120 degrees C, 125 degrees C, 130 degrees C, 134 degrees C, 140 degrees C, 145 degrees C, 148 degrees C or 150 degrees C, preferably 90-130 degrees C.
Preferably, the lean desorption solution in the bottom of the desorption tower is circulated to the absorption tower after heat exchange to 50 to 80 ℃, and may be, for example, 50 ℃, 53 ℃, 54 ℃, 55 ℃, 57 ℃, 60 ℃, 63 ℃, 65 ℃, 68 ℃, 70 ℃, 72 ℃, 73 ℃, 75 ℃, 78 ℃, 79 ℃ or 80 ℃.
Preferably, the ethylene oxide-rich absorbent in the bottom of the absorption column is heat-exchanged to 90 to 130 ℃ and then introduced into the desorption column, and may be, for example, 90 ℃, 92 ℃, 93 ℃, 95 ℃, 98 ℃, 99 ℃, 100 ℃, 102 ℃, 105 ℃, 108 ℃, 110 ℃, 115 ℃, 118 ℃, 120 ℃, 124 ℃, 125 ℃, 126 ℃, 128 ℃, 129 ℃ or 130 ℃.
Compared with the prior art, the invention has the following beneficial effects:
(1) the invention provides a composite absorbent containing ionic liquid and ethylene carbonate, which can increase the selectivity of absorbing and separating ethylene oxide, effectively reduce the vapor pressure of the composite absorbent, reduce the solvent loss in the desorption process, and has the characteristics of simple process flow, high operation flexibility, low energy consumption, remarkable absorption effect and the like, and has better industrial application prospect;
(2) the composite absorbent is used for separating and purifying the ethylene oxide, the removal rate of the ethylene oxide can reach 93.1-99.8%, the absorption capacity of the ethylene oxide in the raw material gas is effectively improved, simultaneously, the purity of the ethylene oxide obtained from the top of the desorption tower is over 80%, and the selective absorption capacity of the composite absorbent on the ethylene oxide is effectively improved.
Drawings
FIG. 1 is a schematic flow diagram of the separation and purification of ethylene oxide according to the present invention.
Wherein, T1 is an ethylene oxide absorption tower, T2 is an ethylene oxide desorption tower, E1 is an ethylene oxide rich liquid lean liquid heat exchanger, E2 is an ethylene oxide lean liquid cooler, E3 is an ethylene oxide rich liquid heater, 1 is a feed gas containing ethylene oxide, 2 is a composite absorbent, 3 is an ethylene oxide rich absorption liquid, 4 is a heat-exchanged ethylene oxide rich absorption liquid, 5 is a desorption lean liquid, 6 is a heat-exchanged desorption lean liquid, 7 is a desorbed ethylene oxide gas, and 8 is a lean mixed gas after ethylene oxide removal.
Detailed Description
The present invention is described in further detail below. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.
The process flow of the separation and purification of the ethylene oxide is shown in figure 1, and specifically comprises the following steps: the mixed gas 1 of ethylene oxide enters an absorption tower T1 from the bottom of the tower, the composite absorbent 2 enters from the top of the absorption tower T1, and the content of ethylene oxide 8 at the top of the absorption tower is measured after absorption. The ethylene oxide-containing composite absorbent 3 is heated to a certain temperature through heat exchange to obtain a high-temperature ethylene oxide-containing absorbent 4, the high-temperature ethylene oxide-containing absorbent 4 enters a desorption tower T2, the ethylene oxide 7 at the top of the tower is obtained through desorption, and the degassed composite absorbent 5 is subjected to heat exchange to obtain a certain-temperature composite absorbent 6, the certain-temperature composite absorbent 6 enters an absorption tower T1 and is continuously used as an absorbent for recycling.
Example 1:
the group of embodiments provides a composite absorbent and a method for separating and purifying ethylene oxide by using the composite absorbent. The composite absorbent is prepared from ionic liquid 1-hydroxyethyl-3-methylimidazolium hexafluorophosphate ([ Hemim)][PF6]) And ethylene carbonate, and the composite absorbent is used for absorbing and desorbing the feed gas containing the ethylene oxide, and the specific operation is as follows:
introducing mixed gas containing 2.26% of ethylene oxide at 50 ℃ into an absorption tower T1 from the bottom of the tower, and introducing ionic liquid [ Hemim][PF6]The ethylene carbonate and ethylene carbonate are uniformly mixed and then enter from the top of an absorption tower T1, and the content of ethylene oxide at the top of the tower is measured after absorption. The absorbent containing ethylene oxide is heated to a certain temperature through heat exchange and enters a desorption tower T2 with 50KPa, the content of ethylene oxide on the top of the tower is obtained through desorption, and the degassed ionic liquid and ethylene carbonate enter an absorption tower T1 after heat exchange to 50 ℃ and continue to serve as the absorbent for recycling. The specific parameters and corresponding results are shown in table 1 below:
TABLE 1
The data in table 1 show that the removal rate of ethylene oxide in the process of separating and purifying ethylene oxide by using the composite absorbent obtained by compounding 1-hydroxyethyl-3-methylimidazole hexafluorophosphate and ethylene carbonate can reach 94.9% -99.3%, which indicates that the absorption and separation capacity of ethylene oxide can be improved by adding the ionic liquid, and the absorption effect is obvious; in addition, the purity of the ethylene oxide at the top of the desorption tower obtained by separating and purifying the ethylene oxide by using the composite absorbent is higher than 95.3 percent, namely the selective absorption of the ethylene oxide in the raw material gas is obviously improved.
As can be seen by comparing examples 1-1, 1-2, 1-3, 1-4 and 1-5, the EO purity obtained at the top of the desorber showed a marked tendency to increase with the ionic liquid content. This indicates that the higher the ionic liquid content, the higher the selective absorption of ethylene oxide in the feed gas.
As can be seen by comparing examples 1-1, 1-2, 1-3 and 1-4, EO removal rates exhibited a decreasing trend as the ionic liquid content increased. This is because the ionic liquid has a higher viscosity and, when its content is higher, affects the absorption effect on ethylene oxide. However, it can be seen from the data of examples 1-5 that too low an ionic liquid content results in a significant reduction in the EO concentration obtained at the top of the desorber, i.e. a reduction in the selectivity of the composite absorbent for ethylene oxide absorption.
Example 2:
the group of embodiments provides a composite absorbent and a method for separating and purifying ethylene oxide by using the composite absorbent. The composite absorbent is prepared from ionic liquid 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate ([ Hemim)][BF4]) And ethylene carbonate, and absorbing and desorbing the feed gas containing the ethylene oxide by using the composite absorbent, wherein the operation is as follows:
introducing mixed gas containing 2.26% of ethylene oxide at 60 ℃ into an absorption tower T1 from the bottom of the tower, and introducing ionic liquid [ Hemim][BF4]The ethylene carbonate and ethylene carbonate are uniformly mixed and then enter from the top of an absorption tower T1, and the content of ethylene oxide at the top of the tower is measured after absorption. The absorbent containing ethylene oxide is heated to a certain temperature through heat exchange and enters a desorption tower T2 with 60KPa, the content of the ethylene oxide on the top of the tower is obtained through desorption, and the degassed ionic liquid and ethylene carbonate enter an absorption tower T1 after the heat exchange is carried out to 60 ℃ and continue to serve as the absorbent for recycling. The specific parameters and corresponding results are shown in table 2 below:
TABLE 2
The data in table 2 show that the removal rate of ethylene oxide in the process of separating and purifying ethylene oxide by using the composite absorbent obtained by compounding 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate and ethylene carbonate can reach 93.1% -99.6%, which indicates that the addition of the ionic liquid can improve the absorption and separation capacity of ethylene oxide and has obvious absorption effect; meanwhile, the purity of the ethylene oxide at the top of the desorption tower obtained by separating and purifying the ethylene oxide by using the composite absorbent is higher than 82.4 percent, namely the selective absorption of the ethylene oxide in the feed gas is obviously improved.
By comparing example 2-1, example 2-2, example 2-3 and example 2-4, it can be seen that the EO removal rate shows a downward trend and the EO concentration at the top of the desorber tower shows an upward trend as the ionic liquid content increases. This is consistent with the data conclusions in table 1.
Example 3:
the group of embodiments provides a composite absorbent and a method for separating and purifying ethylene oxide by using the composite absorbent. The composite absorbent is prepared from ionic liquid 1-aminoethyl-3-methylimidazolium tetrafluoroborate ([ C ]2NH2mim][BF4]) And ethylene carbonate, and the composite absorbent is used for absorbing and desorbing the feed gas containing the ethylene oxide, and the specific operation is as follows:
introducing mixed gas containing 2.26% of ethylene oxide at 70 deg.C into absorption tower T1 from the bottom of the tower, and introducing ionic liquid [ C2NH2mim][BF4]) The ethylene carbonate and ethylene carbonate are uniformly mixed and then enter from the top of an absorption tower T1, and the content of ethylene oxide at the top of the tower is measured after absorption. The absorbent containing ethylene oxide is heated to a certain temperature through heat exchange and enters a desorption tower T2 with 70KPa, the content of ethylene oxide on the top of the tower is obtained through desorption, and the degassed ionic liquid and ethylene carbonate enter an absorption tower T1 after the heat exchange to 70 ℃ and continue to serve as the absorbent for recycling. The specific parameters and corresponding results are shown in table 3 below:
TABLE 3
The data in table 3 show that the removal rate of ethylene oxide in the separation and purification of ethylene oxide by using the composite absorbent obtained by compounding 1-aminoethyl-3-methylimidazole tetrafluoroborate and ethylene carbonate can reach 94.7% -99.8%, which indicates that the addition of the ionic liquid can improve the absorption and separation capacity of ethylene oxide and the absorption effect is significant.
As can be seen by comparing example 3-1, example 3-2, example 3-3 and example 3-4, the EO removal rate tends to decrease with increasing ionic liquid content, while the EO concentration at the top of the desorber column tends to increase, i.e., the EO selectivity tends to increase. This is consistent with the data conclusions in tables 1 and 2.
Example 2 used an ionic liquid of 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate, example 3 used an ionic liquid of 1-aminoethyl-3-methylimidazolium tetrafluoroborate, the two ionic liquids differ only in the cationic substituent, example 2 the ionic liquid of cationic substituent is hydroxyl, example 3 the ionic liquid of cationic substituent is amino; comparing the data in tables 2 and 3, it can be seen that when the cation substituent is hydroxyl, the purity of the ethylene oxide obtained at the top of the desorption tower is higher, and the removal rate is lower, i.e. the selectivity of absorbing and separating ethylene oxide is higher than that of amino, but the absorption capacity is lower than that of amino.
Comparative example 1
The present pair of proportions provides an absorbent and a process for the separation and purification of ethylene oxide which differs from example 1 only in that the absorbent consists only of ethylene carbonate.
The specific parameters and corresponding results are shown in table 4 below:
TABLE 4
Comparing the data in table 4 and tables 1-3, it can be seen that, when ethylene oxide is separated and purified by using the absorbent containing only ethylene carbonate, the purity of ethylene oxide obtained at the top of the desorption tower is obviously lower than that of the composite absorbent containing ionic liquid, which indicates that the selectivity of ethylene oxide by using single ethylene carbonate is obviously lower than that of the composite absorbent using ionic liquid and ethylene carbonate, that is, the addition of ionic liquid can improve the selectivity of ethylene oxide absorption and separation, and the absorption effect is obvious.
Comparative example 2
The comparative example provides a composite absorbent and a method for separating and purifying ethylene oxide. The only difference from example 1 is that 1-hydroxyethyl-3-methylimidazolium hexaFluorophosphate ([ Hemim)][PF6]) Replacing with water, and specifically operating as follows:
the mixed gas containing 2.26 percent of ethylene oxide at 50 ℃ enters an absorption tower T1 from the bottom of the tower, water and ethylene carbonate are uniformly mixed and then enter from the top of the absorption tower T1, and the content of the ethylene oxide at the top of the tower is measured after absorption. The absorbent containing ethylene oxide is heated to a certain temperature through heat exchange and enters a desorption tower T2 with 50KPa, the content of ethylene oxide on the top of the tower is obtained through desorption, and the degassed water and ethylene carbonate enter an absorption tower T1 after the heat exchange is carried out to 50 ℃ and continue to serve as the absorbent for recycling. The specific parameters and corresponding results are shown in table 5 below:
the specific parameters and corresponding results are shown in table 5 below:
TABLE 5
Comparing the data in table 5 and tables 1-3, it can be seen that, in the present invention, the composite absorbent containing ionic liquid is used to separate and purify ethylene oxide, and the concentration of ethylene oxide obtained at the top of the desorption tower is significantly higher than that obtained by using the composite absorbent containing water and ethylene carbonate, which indicates that the selective absorption of the composite absorbent containing ionic liquid is significantly higher than that of the composite absorbent containing water and ethylene carbonate, which indicates that the composite absorbent containing ionic liquid has strong absorption capacity and significant absorption effect, and provides a new option for efficiently separating and purifying ethylene oxide.
The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must be implemented depending on the above detailed structural features. It should be understood by those skilled in the art that any modifications of the present invention, equivalent substitutions of selected components of the present invention, additions of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (14)
1. A method for separating and purifying ethylene oxide is characterized by comprising the following steps: the composite absorbent and feed gas containing ethylene oxide are in countercurrent full contact in an absorption tower, lean mixed gas after ethylene oxide removal at the tower top is treated and then returns to an ethylene oxidation stage, ethylene oxide-rich absorption liquid at the tower bottom enters a desorption tower after heat exchange, gas phase is extracted at the tower top after desorption to obtain ethylene oxide, and desorption lean liquid of a liquid phase after desorption returns to the absorption tower after heat exchange from the tower bottom;
the operating pressure of the desorption tower is 10-150KPa, and the operating temperature of the desorption tower is 80-150 ℃;
the composite absorbent comprises ionic liquid and ethylene carbonate, wherein the structure of the ionic liquid is shown as a formula I:
wherein R is1And R2Each independently selected from substituted C1-C6 alkyl; anion X-Selected from BF4 -；R1And R2Wherein said substituted group is hydroxy or amino;
the mass percentage of the ionic liquid in the composite absorbent is 20-50%.
2. The method for separating and purifying ethylene oxide according to claim 1, wherein the ionic liquid is selected from any one of or a combination of at least two of 1-hydroxyethyl-3-methylimidazole tetrafluoroborate, 1-aminoethyl-3-methylimidazole tetrafluoroborate and 1-hydroxyethyl-3-ethylimidazole tetrafluoroborate.
3. The method for separating and purifying ethylene oxide according to claim 1, wherein the mass ratio of the ionic liquid in the composite absorbent is 30-50%.
4. The method for separating and purifying ethylene oxide as claimed in claim 1, wherein the molar percentage of ethylene oxide in the raw material gas is 0.1-5%.
5. The method for separating and purifying ethylene oxide as claimed in claim 4, wherein the molar percentage of ethylene oxide in the raw material gas is 2-3%.
6. The method for separation and purification of ethylene oxide according to claim 1, wherein the operating pressure of the absorption column is 0.1 to 5 MPa.
7. The method for separating and purifying ethylene oxide according to claim 6, wherein the operating pressure of the absorption column is 1 to 3 MPa.
8. The method for separation and purification of ethylene oxide according to claim 1, wherein the operating temperature of the absorption column is 40 to 100 ℃.
9. The method for separation and purification of ethylene oxide according to claim 8, wherein the operating temperature of the absorption column is 50 to 80 ℃.
10. The method for separating and purifying ethylene oxide according to claim 1, wherein the molar ratio of the composite absorbent to the raw material gas is (1-4): 1.
11. The method for separating and purifying ethylene oxide according to claim 10, wherein the molar ratio of the composite absorbent to the raw material gas is (2-3): 1.
12. The method for separating and purifying ethylene oxide according to claim 1, wherein the operating pressure of the desorption column is 50 to 150 KPa.
13. The method for separating and purifying ethylene oxide according to claim 1, wherein the desorption lean solution is recycled to the absorption tower after heat exchange to 50-80 ℃.
14. The method for separating and purifying the ethylene oxide as claimed in claim 1, wherein the ethylene oxide-rich absorption liquid enters the desorption tower after heat exchange to 80-150 ℃.
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| US20220274944A1 (en) * | 2019-08-23 | 2022-09-01 | Institute Of Process Engineering, Chinese Academy Of Sciences | Composite absorbent and use thereof |
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| CN101284211A (en) * | 2008-06-02 | 2008-10-15 | 中国科学院过程工程研究所 | Glyoxaline ion liquid reclaiming agent regeneration and cyclic utilization method |
| CN102481513A (en) * | 2009-06-25 | 2012-05-30 | Vtu控股有限责任公司 | Method of use of an ionic liquid and device for sorption of a gas |
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| US4221727A (en) * | 1979-08-17 | 1980-09-09 | The Dow Chemical Company | Ethylene oxide recovery |
| DE102004053167A1 (en) * | 2004-11-01 | 2006-05-04 | Degussa Ag | Polymeric absorbent for gas absorption and absorption process |
| CN102911137A (en) * | 2012-11-20 | 2013-02-06 | 中国石油化工股份有限公司 | Method for separating and recovering EO (ethylene oxide) from direct oxidation products of ethylene |
| CN109422708B (en) * | 2017-08-28 | 2021-03-30 | 中国石油化工股份有限公司 | Ethylene oxide purification process |
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| CN101284211A (en) * | 2008-06-02 | 2008-10-15 | 中国科学院过程工程研究所 | Glyoxaline ion liquid reclaiming agent regeneration and cyclic utilization method |
| CN102481513A (en) * | 2009-06-25 | 2012-05-30 | Vtu控股有限责任公司 | Method of use of an ionic liquid and device for sorption of a gas |
| GB2524570A (en) * | 2014-03-27 | 2015-09-30 | Univ Belfast | Process for preparing alkanolamines useful in removal of acid-gas from a gaseous stream |
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