WO2021036238A1 - 一种复合吸收剂及其用途 - Google Patents

一种复合吸收剂及其用途 Download PDF

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WO2021036238A1
WO2021036238A1 PCT/CN2020/080560 CN2020080560W WO2021036238A1 WO 2021036238 A1 WO2021036238 A1 WO 2021036238A1 CN 2020080560 W CN2020080560 W CN 2020080560W WO 2021036238 A1 WO2021036238 A1 WO 2021036238A1
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ethylene oxide
absorption
optionally
tower
substituted
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English (en)
French (fr)
Inventor
成卫国
董丽
褚俊杰
张增亮
苏倩
陈嵩嵩
刘一凡
张香平
张锁江
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Institute of Process Engineering of CAS
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Institute of Process Engineering of CAS
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Priority claimed from CN201910785196.2A external-priority patent/CN110437201B/zh
Priority claimed from CN201910786256.2A external-priority patent/CN110479037B/zh
Application filed by Institute of Process Engineering of CAS filed Critical Institute of Process Engineering of CAS
Priority to US17/637,241 priority Critical patent/US20220274944A1/en
Publication of WO2021036238A1 publication Critical patent/WO2021036238A1/zh
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D301/00—Preparation of oxiranes
    • C07D301/32—Separation; Purification
    • 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
    • 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
    • B01D53/1418—Recovery of products
    • 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
    • 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
    • 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
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D317/00—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms
    • C07D317/08—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms having the hetero atoms in positions 1 and 3
    • C07D317/10—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms having the hetero atoms in positions 1 and 3 not condensed with other rings
    • C07D317/32—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms having the hetero atoms in positions 1 and 3 not condensed with other rings with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
    • C07D317/34—Oxygen atoms
    • C07D317/36—Alkylene carbonates; Substituted alkylene carbonates
    • C07D317/38—Ethylene carbonate
    • 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
    • B01D2252/205—Other organic compounds not covered by B01D2252/00 - B01D2252/20494
    • 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
    • B01D2252/30—Ionic liquids and zwitter-ions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/70—Organic compounds not provided for in groups B01D2257/00 - B01D2257/602

Definitions

  • This application belongs to the technical field of chemical industry, for example, it relates to a composite absorbent and its use in the ethylene oxide absorption conversion coupling co-production method of ethylene carbonate, and a composite absorbent and its use in the separation and purification of ethylene oxide method.
  • Ethylene carbonate known as the 21st century green chemical raw material, is a chemical intermediate and excellent solvent with a wide range of applications.
  • Ethylene oxide one of the raw materials for the synthesis of ethylene carbonate, mainly uses ethylene to be oxidized under the action of a silver-containing catalyst to generate ethylene oxide.
  • impurity gases such as methane and ethane.
  • the industry often uses the absorption method to absorb ethylene oxide from the mixed gas, and then refines it through the process of steam stripping and concentration to obtain high-purity ethylene oxide; refined ethylene oxide Alkane and carbon dioxide catalyze the synthesis of ethylene carbonate in the reactor.
  • ethylene oxide is also an important petrochemical product with excellent sterilization and disinfection effects, and is mainly used in the washing, pharmaceutical and printing and dyeing industries.
  • the main production method of ethylene oxide is ethylene oxidation. Ethylene and oxygen are used to generate ethylene oxide under the condition of silver catalyst. However, due to the low conversion rate and selectivity, there will be part of the ethylene oxide produced at the same time.
  • water is usually used as an absorbent, and then desorption, concentration, and purification are performed to obtain a relatively pure ring. Oxyethane.
  • US3948621A1 discloses the use of methanol as an absorbent for the separation and purification of ethylene oxide. This absorbent has good absorption effect and low energy consumption in the desorption process. However, methanol is easy to react with ethylene oxide, and the absorption temperature needs to be strictly controlled. In addition, methanol is easily lost with the volatilization of the desorption gas during desorption.
  • US4221727A1 discloses a method of using ethylene carbonate as an absorbent to absorb and separate ethylene oxide.
  • ethylene carbonate as an absorbent not only has a good absorption effect, but also can avoid side reactions during the absorption process, but in the desorption process, the desorption temperature The temperature is 150°C and the pressure is 5kPa. At this time, part of the ethylene carbonate will volatilize with the desorption gas, causing solvent loss.
  • US5559255A discloses the use of propylene carbonate as an absorbent
  • CN102911137A discloses a mixture of ethylene carbonate and water as an ethylene oxide absorbent, but neither solves the problem of solvent volatilization loss during the stripping process.
  • CN109422708A discloses a method using triethylene glycol dimethyl ether and ionic liquid as absorbents. These absorbents improve the absorption capacity and selectivity of ethylene oxide, but in the entire process, the process of stripping ethylene oxide still consumes a lot of energy, and the process is complicated, the equipment cost is high, and the one-time investment is large. .
  • the purpose of the present application includes providing a composite absorbent and a method for ethylene oxide absorption conversion coupled and co-production of ethylene carbonate.
  • This application uses a composite absorbent of ionic liquid and ethylene carbonate to absorb ethylene oxide and carbon dioxide.
  • the ionic liquid can also be used as a catalyst to react the absorbed ethylene oxide and carbon dioxide to produce ethylene carbonate. This not only improves the absorption effect of ethylene oxide, but also reduces the process of ethylene oxide desorption and refining, realizes pre-conversion while absorbing, reduces energy consumption, and has good industrial application value.
  • the purpose of this application also includes providing a composite absorbent and a method for separating and purifying ethylene oxide.
  • the absorbent includes an ionic liquid and ethylene carbonate.
  • the structure of the ionic liquid is shown in Formula I.
  • the composite absorbent of this application contains an ionic liquid with a specific structure.
  • the present application provides a composite absorbent, the composite absorbent includes an ionic liquid and ethylene carbonate, and the structure of the ionic liquid is shown in Formula I:
  • R 1 and R 2 in formula I are each independently selected from substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C2-C6 alkenyl, substituted or unsubstituted C2-C6 alkynyl, substituted Or any one of unsubstituted C6-C30 aryl, substituted or unsubstituted C3-C30 heteroaryl, or substituted or unsubstituted C1-C6 alkoxy;
  • Formula I is the anion X - is selected from BF 4 -, PF 6 -, Tf 2 N -, RCOO -, Cl - or Br - any one of; R & lt selected from alkyl, any alkenyl or alkynyl group One kind.
  • C1-C6 alkyl refers to a straight or branched chain alkyl group having 1, 2, 3, 4, 5 or 6 carbon atoms, including, without limitation, methyl, ethyl, n-propyl Base, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, n-pentyl, isopentyl, n-hexyl, etc.
  • C2-C6 alkynyl refers to a straight or branched chain alkynyl group having 2, 3, 4, 5, or 6 carbon atoms, including without limitation -C ⁇ CH, -C ⁇ C(CH 3 ) , -C ⁇ C(CH 2 CH 3 ), -CH 2 C ⁇ CH, -CH 2 C ⁇ C(CH 3 ) or -CH 2 C ⁇ C(CH 2 CH 3 ), etc.
  • C6-C30 aryl refers to an aryl group having 6-30 carbon atoms, for example, it may contain 6, 12, or 18 carbon atoms, etc., and includes, without limitation, phenyl, naphthyl, or biphenyl, etc. .
  • C3-C30 heteroaryl refers to monocyclic, bicyclic or tricyclic rings 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, and other aromatic ring systems, and it contains at least one heteroatom that may be the same or different, so
  • the heteroatoms are such as oxygen, nitrogen or sulfur, and in addition may be benzo-fused in each case, including but not limited to thienyl, furyl, pyrrolyl, oxazolyl, thiazolyl, imidazolyl, pyridine Azolyl, isoxazolyl, isothiazolyl, oxadiazolyl, triazolyl, benzofuranyl, benzothienyl, benzoxazolyl, benzisoxazolyl, benzimidazolyl, benzene O-triazolyl, indazolyl, indolyl, isoindolyl, pyri
  • C1-C6 alkoxy refers to a straight or branched chain alkoxy group having 1, 2, 3, 4, 5 or 6 carbon atoms, including non-limiting methoxy, ethoxy, n- Propoxy, isopropoxy or terbutoxy, etc.
  • the composite absorbent containing the ionic liquid of the present invention not only has a higher absorption capacity for ethylene oxide, but also can significantly increase the selectivity of ethylene oxide absorption and separation, and at the same time can effectively reduce the vapor pressure of the absorbent and reduce desorption
  • the loss of solvent in the process has the characteristics of simple process flow, high operating flexibility, low energy consumption, and significant absorption effect, and has a good industrial application prospect.
  • the anion X - is selected from BF 4 -, PF 6 -, Tf 2 N - or RCOO - in any one, optionally the anion X - is BF 4 - or PF 6 -.
  • the substituted groups in R 1 and R 2 are each independently selected from any one of a hydroxyl group, an amino group, a nitro group, an aldehyde group, an ester group, a carboxyl group, or a mercapto group.
  • substituted groups in R 1 and R 2 are hydroxyl or amino.
  • the ionic liquid is selected from the group consisting of 1-hydroxyethyl-3-methylimidazole hexafluorophosphate, 1-hydroxyethyl-3-methylimidazole tetrafluoroborate, 1- Aminoethyl-3-methylimidazole tetrafluoroborate, 1-aminoethyl-3-methylimidazole hexafluorophosphate, 1-hydroxyethyl-3-ethylimidazole hexafluorophosphate or 1-hydroxy Any one or a combination of at least two of ethyl-3-ethylimidazole tetrafluoroborate;
  • the mass ratio of the ionic liquid in the composite absorbent is 10-60%, for example, it can be 10%, 12%, 15%, 17%, 19%, 20%, 23%, 25%. %, 27%, 30%, 33%, 35%, 37%, 38%, 40%, 42%, 45%, 49%, 50%, 53%, 55%, 59% or 60%, etc., optional Is 30-50%.
  • the mass ratio of ionic liquid and ethylene carbonate is preferably controlled within the above range, because when the content of ionic liquid is too high, the viscosity of the composite absorbent increases and cannot fully contact with ethylene oxide, which may reduce ethylene oxide. If the ionic liquid content is too low, the selective absorption of the composite absorbent will be weakened, which will also affect the absorption effect of ethylene oxide.
  • the present invention also provides a method for separation and purification of ethylene oxide, which uses the composite absorbent as described in the first aspect.
  • the method for separating and purifying ethylene oxide of the present invention uses the composite absorbent of the ionic liquid and ethylene carbonate, which can effectively improve the absorption capacity of ethylene oxide in the raw material gas, simplify the process flow, and increase the operating flexibility of the device , Reduce energy consumption, and provide technical support for continuous production and purification of ethylene oxide.
  • the method includes the following steps: contacting the composite absorbent with a feed gas containing ethylene oxide, returning the lean mixed gas after removing ethylene oxide to the ethylene oxidation stage, and enriching the ethylene oxide absorption liquid Desorption is performed to obtain ethylene oxide.
  • the components and mole percentages of the feed gas of the present invention are: ethylene oxide 2.6%, methane 52.77%, ethylene 32.53%, oxygen 4.9%, carbon dioxide 1.5%, argon 4.18%, nitrogen 1% and Composition of ethane 0.52%.
  • the raw material gas used in the present invention has a low content of ethylene oxide, and separation and purification by a composite absorbent of ionic liquid and ethylene carbonate can obtain ethylene oxide with higher purity, and the absorption efficiency is significantly improved.
  • the method includes the following steps: the composite absorbent and the feed gas containing ethylene oxide are fully contacted in countercurrent in the absorption tower, and the lean mixed gas after removing ethylene oxide at the top of the tower is processed and then returned In the ethylene oxidation stage, the ethylene oxide-rich absorption liquid in the tower bottom enters the desorption tower after heat exchange. After desorption, the gas phase is extracted from the top of the tower to obtain ethylene oxide. After desorption, the desorbed lean liquid in the liquid phase passes through the heat exchange from the tower bottom Return to the absorption tower.
  • the molar concentration of ethylene oxide in the feed gas is 0.1-5%, for example, it can be 0.1%, 0.3%, 0.5%, 0.8%, 0.9%, 1.0%, 1.2%, 1.5%, 2% , 2.5%, 2.6%, 2.8%, 2.8%, 3.0%, 3.5%, 4.0%, 4.5% or 5%, etc., optional 2-3%.
  • the inlet temperature of the raw material gas is 40-100°C, for example, 40°C, 42°C, 43°C, 45°C, 48°C, 50°C, 51°C, 56°C, 59°C, 60°C , 65°C, 68°C, 70°C, 72°C, 73°C, 75°C, 78°C, 79°C, 80°C, 83°C, 85°C, 87°C, 90°C, 92°C, 95°C, 97°C, 99 °C or 100°C, etc., 50-80°C can be selected.
  • the operating pressure of the absorption tower is 0.1-5 MPa, for example, it can be 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.5 MPa, 0.8 MPa, 1.0 MPa, 1.2 MPa, 1.5 MPa, 1.9 MPa, 2.0 MPa, 2.3 MPa, 2.5MPa, 2.6MPa, 2.9MPa, 3.0MPa, 3.5MPa, 3.8MPa, 4.0MPa, 4.2MPa, 4.5MPa or 5.0MPa, etc., optional 1-3MPa.
  • the operating temperature of the absorption tower is 40-100°C, for example, 40°C, 42°C, 43°C, 45°C, 48°C, 50°C, 51°C, 56°C, 59°C, 60°C, 65°C ⁇ 68°C ⁇ 70°C ⁇ 72°C ⁇ 73°C ⁇ 75°C ⁇ 78°C ⁇ 79°C ⁇ 80°C ⁇ 83°C ⁇ 85°C ⁇ 87°C ⁇ 90°C ⁇ 92°C ⁇ 95°C ⁇ 97°C ⁇ 99°C Or 100°C, etc., 50-80°C can be selected.
  • the molar ratio of the composite absorbent to the raw gas is (1-4):1, for example, it can be 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, etc., optional It is (2-3):1.
  • the operating pressure of the desorption tower is 10-150kPa, for example, it can be 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, etc., 50-150kPa can be selected.
  • the operating temperature of the desorption tower is 80-150°C, such as 80°C, 84°C, 85°C, 87°C, 89°C, 90°C, 95°C, 98°C, 100°C, 105°C, 108°C, 110°C, 115°C, 120°C, 125°C, 130°C, 134°C, 140°C, 145°C, 148°C or 150°C, etc., 90-130°C can be selected.
  • the desorption lean liquid in the bottom of the desorption tower is heat-exchanged to 50-80°C and then circulated back to the absorption tower, for example, it may be 50°C, 53°C, 54°C, 55°C, 57°C, 60°C , 63°C, 65°C, 68°C, 70°C, 72°C, 73°C, 75°C, 78°C, 79°C or 80°C etc.
  • the ethylene oxide-rich absorption liquid in the bottom of the absorption tower enters the desorption tower after heat exchange to 90-130°C, for example, it may be 90°C, 92°C, 93°C, 95°C, 98°C , 99°C, 100°C, 102°C, 105°C, 108°C, 110°C, 115°C, 118°C, 120°C, 124°C, 125°C, 126°C, 128°C, 129°C or 130°C etc.
  • the present invention provides a composite absorbent, which includes an ionic liquid and ethylene carbonate, and the structure of the ionic liquid is as shown in formula II or formula III:
  • R 3 , R 4 , R 5 and R 6 in formula II are each independently selected from substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C2-C6 alkenyl, substituted or unsubstituted C2-C6 Any one of alkynyl, substituted or unsubstituted C6-C30 aryl, substituted or unsubstituted C3-C30 heteroaryl, or substituted or unsubstituted C1-C6 alkoxy;
  • R 7 , R 8 , R 9 and R 10 in formula III are each independently selected from substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C2-C6 alkenyl, substituted or unsubstituted C2-C6 Any one of alkynyl, substituted or unsubstituted C6-C30 aryl, substituted or unsubstituted C3-C30 heteroaryl, or substituted or unsubstituted C1-C6 alkoxy;
  • Formula and Formula II III anion X - is independently selected from Cl -, Br - or I - in any one.
  • This application uses a composite absorbent of ionic liquid and ethylene carbonate to absorb ethylene oxide and carbon dioxide.
  • the ionic liquid can also be used as a catalyst to react the absorbed ethylene oxide and carbon dioxide to produce ethylene carbonate. This not only improves the absorption effect of ethylene oxide, but also reduces the process of ethylene oxide desorption and refining, realizes pre-conversion while absorbing, reduces energy consumption, and has good industrial application value.
  • the absorbent composite of the present application the anion of the ionic liquid is selected from the specific Cl -, Br - or I - any one of which is due to the cation of the ionic liquid can cause the polarization of ethylene oxide CO bond, and At the same time, halide ions attack the ⁇ -carbon atom with less steric hindrance in the epoxy ring, and the two effects are carried out at the same time, resulting in easy ring opening of ethylene oxide and carbon dioxide reaction to produce ethylene carbonate.
  • the substituted groups are each independently selected from among hydroxyl, amino, nitro, aldehyde, ester, carboxy, nitroso, amide or carbonyl groups. Any kind.
  • the mass ratio of the ionic liquid to the ethylene carbonate is 1:(1-10), for example, it may be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10 etc.
  • This application can choose to control the mass ratio of ionic liquid and ethylene carbonate within the above range, because when the content of ionic liquid is too high, the viscosity of the composite absorbent will increase, and it will not be in full contact with ethylene oxide, which may reduce ethylene oxide. If the content of ionic liquid is too low, the selective absorption of the composite absorbent will be weakened, which will affect the absorption effect of ethylene oxide. At the same time, if the content of ionic liquid is too low, it will absorb the pre-reaction stage of ethylene oxide and The catalytic efficiency of the carbon dioxide cycloaddition reaction will be significantly reduced.
  • the present application also provides a method for ethylene oxide absorption conversion coupling and co-production of ethylene carbonate, which uses the composite absorbent as described in the first or third aspect.
  • This application creatively uses the composite of ionic liquid and ethylene carbonate as the absorbent to couple the absorption and conversion of ethylene oxide to realize the one-step absorption and conversion of ethylene oxide, which effectively reduces the energy consumption and cost of the device.
  • the method includes the following steps: contacting the composite absorbent with a raw material gas containing ethylene oxide, and the obtained ethylene oxide-rich absorbing liquid enters the main reactor to obtain ethylene carbonate.
  • the components of the feed gas described in this application and their molar percentages are: ethylene oxide 2.6%, methane 52.77%, ethylene 32.53%, oxygen 4.9%, carbon dioxide 1.5%, argon 4.18%, nitrogen 1% and Composition of ethane 0.52%.
  • the raw material gas mentioned in this application is the mixed gas after ethylene oxidation. Ethylene oxide and carbon dioxide are present in the raw material gas. During the absorption process, the ionic liquid can not only effectively absorb ethylene oxide and carbon dioxide, but also catalyze the reaction between the two.
  • ethylene carbonate realizes the pre-reaction for preparing ethylene carbonate while absorbing, reduces energy consumption, and also reduces the ethylene oxide tail gas content of the main reaction unit of the subsequent carbonylation, ensuring safety, and has good industrial application value .
  • the ethylene oxide conversion rate of the pre-reaction described in this application is 2-35%, for example, 2%, 5%, 8%, 10%, 12%, 15%, 20%, 23%, 27%, 30% or 35% etc.
  • the conversion rate of ethylene oxide in the pre-reaction stage described in this application is only 2-35%. This is because the pre-reaction stage cannot provide excessive carbon dioxide and the catalyst cannot reach the optimal conversion rate at the pre-reaction temperature, resulting in pre-reaction temperature. The conversion rate of ethylene oxide in the reaction stage is low.
  • the method includes the following steps: the composite absorbent is fully contacted with the feed gas containing ethylene oxide in countercurrent in the absorption tower, and the lean mixed gas after removing ethylene oxide at the top of the tower is processed and then returned to ethylene
  • the ethylene oxide-rich absorption liquid in the tower tank enters the main reactor after heat exchange to obtain a reaction liquid.
  • a part of the obtained reaction liquid containing ionic liquid is recycled as the absorption liquid, and the other part is processed to obtain high-purity carbonic acid.
  • Vinyl ester is used to obtain high-purity carbonic acid.
  • carbon dioxide will be added to the main reactor so that the amount of carbon dioxide is sufficient relative to ethylene oxide, that is, sufficient carbon dioxide can react with the absorbed ethylene oxide. This produces ethylene carbonate.
  • the ethylene oxide obtained by the catalytic absorption of the ionic liquid reacts with carbon dioxide to produce ethylene carbonate.
  • an absorption tower is currently used to absorb ethylene oxide, and after steam stripping and refining, it enters the reactor to generate ethylene carbonate.
  • this application is the first to creatively use a composite absorbent of ethylene carbonate and ionic liquid to absorb, convert, and co-produce ethylene carbonate, which not only has high absorption performance for ethylene oxide, but also ionic liquid has the advantages of low vapor pressure and small specific heat capacity. Performance.
  • the product can be used as an absorbent to be recycled to the absorption tower for recycling, which simplifies the separation and recycling process.
  • the method described in this application directly couples absorption and conversion to realize one-step production of ethylene carbonate, which not only has a small workload and low equipment cost, but also reduces the stripping process, reduces energy consumption, and achieves a cost-effective, energy-saving and environmentally friendly Claim.
  • the mass ratio (liquid-gas mass ratio) of the composite absorbent and the raw material gas containing ethylene oxide is (1-5):1, for example, it can be 1:1, 1.5:1, 2: 1. 2.3:1, 3:1, 3.5:1, 4:1 or 5:1, etc., (2-3):1 can be selected.
  • the operating pressure of the absorption tower is 1-5 MPa, for example, it can be 1 MPa, 1.5 MPa, 2 MPa, 2.3 MPa, 3 MPa, 3.5 MPa, 4 MPa, 4.6 MPa or 5 MPa, etc., optionally 1.5-2.5 MPa.
  • the operating temperature of the absorption tower is 50-100°C, for example, 50°C, 60°C, 70°C, 80°C, 90°C, or 100°C, etc., optionally 60-80°C.
  • the reaction pressure of the main reactor is 1-5 MPa, for example, 1 MPa, 1.2 MPa, 2 MPa, 2.5 MPa, 3 MPa, 3.4 MPa, 4 MPa, 4.5 MPa, or 5 MPa, etc., optionally 2-3 MPa.
  • the reaction temperature of the main reactor is 80-300°C, for example, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C , 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C or 300°C, etc., 100-200°C can be selected.
  • reaction time is 0.5-5h, for example, it can be 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, etc., and can be 1-3h.
  • the ethylene oxide-rich absorption liquid enters the main reactor after heat exchange to 100-200°C, for example, it may be 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C or 200°C etc.
  • a part of the reaction liquid is cooled to 60-80°C before entering the absorption tower, for example, it may be 60°C, 62°C, 65°C, 68°C, 70°C, 73°C, 76°C, or 80°C.
  • This application uses a composite absorbent of ionic liquid and ethylene carbonate to absorb ethylene oxide and carbon dioxide.
  • the ionic liquid can also be used as a catalyst to react the absorbed ethylene oxide and carbon dioxide to produce Ethylene carbonate, which not only improves the absorption effect of ethylene oxide, but also reduces the process of ethylene oxide desorption and refining, realizes pre-conversion at the same time of absorption, reduces energy consumption, and has good industrial application value;
  • This application is the first to creatively use a composite absorbent of ethylene carbonate and ionic liquid to absorb, transform and co-produce ethylene carbonate, which not only has high absorption performance for ethylene oxide, but also has low vapor pressure and small specific heat capacity. After the complete reaction, the product can be recycled to the absorption tower for recycling after the complete reaction, which simplifies the separation and recycling process.
  • the method described in this application directly couples absorption and conversion to realize one-step production of ethylene carbonate, which not only has a small workload and low equipment cost, but also reduces the stripping process, reduces energy consumption, and achieves a cost-effective, energy-saving and environmentally friendly Claim;
  • the absorption rate of ethylene oxide can reach 98.5% or more.
  • the conversion rate of ethylene oxide is up to 99.2%, and the selectivity is also above 92%.
  • This application provides a composite absorbent containing ionic liquid and ethylene carbonate, which can increase the selectivity of ethylene oxide absorption and separation, and can also effectively reduce the vapor pressure of the composite absorbent and reduce the desorption process.
  • the loss of the solvent is characterized by simple process flow, high operating flexibility, low energy consumption, and significant absorption effect, and has a good industrial application prospect;
  • This application uses the above composite absorbent to separate and purify ethylene oxide, and the removal rate of ethylene oxide can reach 88.8%-99.8%, which effectively improves the absorption capacity of ethylene oxide in the raw material gas.
  • the purity of the ethylene oxide obtained at the top of the desorption tower is above 80%, which effectively improves the ability of the composite absorbent to selectively absorb ethylene oxide.
  • the composite absorbent described in this application is used to separate and purify ethylene oxide. The process flow is simplified, the operation flexibility of the device is increased, the energy consumption is reduced, and technical support is provided for the continuous production and purification of ethylene oxide.
  • Figure 1 is a schematic diagram of the separation and purification process of ethylene oxide described in the present application.
  • T1 is the ethylene oxide absorption tower
  • T2 is the ethylene oxide desorption tower
  • E1 is the ethylene oxide rich liquid and lean liquid heat exchanger
  • E2 is the ethylene oxide lean liquid cooler
  • E3 is the ethylene oxide
  • 1 is the feed gas containing ethylene oxide
  • 2 is the composite absorbent
  • 3 is the ethylene oxide-rich absorbing liquid
  • 4 is the ethylene oxide-rich absorbing liquid after heat exchange
  • 5 is the desorption Lean liquid
  • 6 is the desorption lean liquid after heat exchange
  • 7 is the ethylene oxide gas after desorption
  • 8 is the lean mixed gas after ethylene oxide removal.
  • Fig. 2 is a schematic diagram of the process of ethylene oxide absorption conversion coupled with co-production of ethylene carbonate according to the present application.
  • T3 is an ethylene oxide absorption tower
  • R1 is an ethylene oxide reactor
  • a is a mixed gas for removing ethylene oxide
  • b is a composite absorbent
  • c is a raw material gas containing ethylene oxide
  • d is a circulation CO 2 gas
  • e is the absorption liquid rich in ethylene oxide
  • f is fresh CO 2 gas
  • g is ethylene carbonate product.
  • This embodiment provides a composite absorbent and a method for ethylene oxide absorption conversion coupling and co-production of ethylene carbonate.
  • the specific operation steps are as follows:
  • the raw material gas containing 2.26 mol% ethylene oxide at 80°C enters the absorption tower from the bottom of the tower, the composite absorbent ionic liquid 1-(2-hydroxyethyl)-3-methylimidazolium bromide ([Hemim]Br) and carbonic acid Vinyl ester is evenly mixed at a mass ratio of 1:10 and then enters from the top of the absorption tower (T1).
  • the feed gas is in countercurrent contact with the absorbent.
  • the absorption temperature is 80°C
  • the operating pressure is 2MPa
  • the mass ratio of liquid to gas is 3.
  • the conversion rate of ethylene oxide in the conversion section is 28.8%
  • the concentration of ethylene oxide at the top of the absorption tower is 69 ppm, and the absorption rate at this time is 99.9%.
  • the above-mentioned absorption liquid is added to the reactor, and the reaction temperature is increased to 125° C., and the reaction is carried out at a pressure of 2 MPa for 1 h. After detection, the conversion rate of the remaining ethylene oxide is 95.2%, and the selectivity is 99.8%.
  • This embodiment provides a composite absorbent and a method for ethylene oxide absorption conversion coupling and co-production of ethylene carbonate.
  • the specific operation steps are as follows:
  • the raw material gas containing 2.26 mol% ethylene oxide at 80°C enters the absorption tower from the bottom of the tower, and the composite absorbent ionic liquid 1-hexyl-3-methylimidazolium bromide ([Hmim]Br) and ethylene carbonate are 1:10 After mixing uniformly, it enters from the top of the absorption tower (T1), the feed gas is in countercurrent contact with the absorbent, the absorption temperature is 80°C, the operating pressure is 2MPa, the liquid-gas mass ratio is 3, and the ethylene oxide in the pre-conversion stage is absorbed The conversion rate is 15.8%, the concentration of ethylene oxide at the top of the absorption tower is 227 ppm, and the absorption rate is 99.5%.
  • the above-mentioned absorption liquid is added to the reactor, and the reaction temperature is increased to 120° C. and the pressure is 2 MPa to react for 3 hours. After detection, the conversion rate of the remaining ethylene oxide is 52.5% and the selectivity is 99.8%.
  • This embodiment provides a composite absorbent and a method for ethylene oxide absorption conversion coupling and co-production of ethylene carbonate.
  • the specific operation steps are as follows:
  • the raw material gas containing 2.26 mol% ethylene oxide at 80°C enters the absorption tower from the bottom of the tower, the composite absorbent ionic liquid 1-(2-hydroxyethyl)-3-methylimidazolium bromide ([Hemim]Br) and carbonic acid Vinyl ester enters from the top of the absorption tower (T1) after being evenly mixed in a mass ratio of 1:9.
  • the feed gas is in countercurrent contact with the absorbent.
  • the absorption temperature is 80°C
  • the operating pressure is 2MPa
  • the mass ratio of liquid to gas is 3.
  • the conversion rate of ethylene oxide in the conversion section is 32.2%
  • the concentration of ethylene oxide at the top of the absorption tower is 44 ppm, and the absorption rate at this time is 99.9%.
  • the above-mentioned absorption liquid is added to the reactor, and the reaction temperature is increased to 120° C., and the reaction is carried out at a pressure of 2 MPa for 1 h. After detection, the conversion rate of the remaining ethylene oxide is 99.2%, and the selectivity is 99.8%.
  • This embodiment provides a composite absorbent and a method for ethylene oxide absorption conversion coupling and co-production of ethylene carbonate.
  • the specific operation steps are as follows:
  • the raw material gas containing 2.26 mol% ethylene oxide at 80°C enters the absorption tower from the bottom of the tower, and the composite absorbent ionic liquid 2-hydroxyethyltributylammonium bromide (HETBAB) and ethylene carbonate have a mass of 1:10 After uniform mixing ratio, it enters from the top of the absorption tower (T1), the feed gas is in countercurrent contact with the absorbent, the absorption temperature is 80°C, the operating pressure is 2MPa, the liquid-gas mass ratio is 3, and the conversion of ethylene oxide in the absorption pre-conversion section The rate is 29.2%, the concentration of ethylene oxide at the top of the absorption tower is 55 ppm, and the absorption rate is 99.9%.
  • HETBAB 2-hydroxyethyltributylammonium bromide
  • the above-mentioned absorption liquid is added to the reactor, and the reaction temperature is increased to 125° C., and the reaction is carried out at a pressure of 2 MPa for 1 h. After detection, the conversion rate of the remaining ethylene oxide is 95.8%, and the selectivity is 99.8%.
  • This embodiment provides a composite absorbent and a method for ethylene oxide absorption conversion coupling and co-production of ethylene carbonate.
  • the specific operation steps are as follows:
  • the raw material gas containing 2.26 mol% ethylene oxide at 80°C enters the absorption tower from the bottom of the tower, and the composite absorbent ionic liquid ethylene bis(triphenylphosphonium bromide) (E[TPB]) is combined with ethylene carbonate.
  • the mass ratio of 1:10 is evenly mixed and enters from the top of the absorption tower (T1).
  • the feed gas is in countercurrent contact with the absorbent.
  • the absorption temperature is 80°C
  • the operating pressure is 3MPa
  • the liquid-to-gas mass ratio is 3
  • the absorption pre-conversion section ring The conversion rate of ethylene oxide is 25.6%
  • the concentration of ethylene oxide at the top of the absorption tower is 95 ppm
  • the absorption rate at this time is 99.8%.
  • the above-mentioned absorption liquid is added to the reactor, and the reaction temperature is increased to 160° C., and the reaction is carried out at a pressure of 3 MPa for 3 hours. After detection, the conversion rate of the remaining ethylene oxide is 92.9%, and the selectivity is 99%.
  • This embodiment provides a composite absorbent and a method for ethylene oxide absorption conversion coupling and co-production of ethylene carbonate.
  • the specific operation steps are as follows:
  • the raw material gas containing 2.26 mol% ethylene oxide at 60°C enters the absorption tower from the bottom of the tower, the composite absorbent ionic liquid 1-(2-hydroxyethyl)-3-methylimidazolium bromide ([Hemim]Br) and carbonic acid Vinyl ester is uniformly mixed at a mass ratio of 1:1 and then enters from the top of the absorption tower (T1).
  • the feed gas is in countercurrent contact with the absorbent.
  • the absorption temperature is 60°C
  • the operating pressure is 2MPa
  • the liquid-to-gas mass ratio is 2.
  • the conversion rate of ethylene oxide in the absorption pre-conversion section is 18.2%
  • the concentration of ethylene oxide at the top of the absorption tower 2 is 152 ppm, and the absorption rate at this time is 99.4%.
  • the above-mentioned absorption liquid is added to the reactor, and the reaction temperature is increased to 80° C. and the pressure is 5 MPa to react for 0.5 h. After detection, the conversion rate of the remaining ethylene oxide is 65.5% and the selectivity is 98.2%.
  • This embodiment provides a composite absorbent and a method for ethylene oxide absorption conversion coupling and co-production of ethylene carbonate.
  • the specific operation steps are as follows:
  • the raw material gas containing 2.26 mol% ethylene oxide at 100°C enters the absorption tower from the bottom of the tower, the composite absorbent ionic liquid 1-(2-hydroxyethyl)-3-methylimidazolium bromide ([Hemim]Br) and carbonic acid Vinyl ester is evenly mixed at a mass ratio of 1:5 and then enters from the top of the absorption tower (T1).
  • the feed gas is in countercurrent contact with the absorbent.
  • the absorption temperature is 100°C
  • the operating pressure is 2MPa
  • the liquid-to-gas mass ratio is 3.
  • the conversion rate of ethylene oxide in the conversion section is 30.1%, and the concentration of ethylene oxide at the top of the absorption tower is 395 ppm, and the absorption rate at this time is 98.5%.
  • the above-mentioned absorption liquid is added to the reactor, and the reaction temperature is increased to 300° C. and the pressure is 2 MPa to react for 5 hours. After testing, the conversion rate of the remaining ethylene oxide is 95.2%, and the selectivity is 98.2%.
  • This embodiment provides a composite absorbent and a method for ethylene oxide absorption conversion coupling and co-production of ethylene carbonate.
  • the specific operation steps are as follows:
  • the raw material gas containing 2.26mol% ethylene oxide at 60°C enters the absorption tower from the bottom of the tower, and the composite absorbent ionic liquid 2-hydroxyethyltributylammonium bromide (HETBAB) and ethylene carbonate are in a mass ratio of 1:7 After mixing uniformly, it enters from the top of the absorption tower (T1), the feed gas is in countercurrent contact with the absorbent, the absorption temperature is 60°C, the operating pressure is 2MPa, and the liquid-to-gas mass ratio is 2. Among them, the absorption pre-conversion stage ethylene oxide The conversion rate is 17.2%, the concentration of ethylene oxide at the top of the absorption tower is 108 ppm, and the absorption rate is 99.5%.
  • HETBAB 2-hydroxyethyltributylammonium bromide
  • the above-mentioned absorption liquid is added to the reactor, and the reaction temperature is increased to 200° C. and the pressure is 1.5 MPa to react for 2 hours. After testing, the conversion rate of the remaining ethylene oxide is 85.1%, and the selectivity is 92%.
  • This embodiment provides a composite absorbent and a method for ethylene oxide absorption conversion coupling and co-production of ethylene carbonate.
  • the difference from embodiment a1 is only: 1-(2-hydroxyethyl)-3-
  • the mass ratio of methylimidazole bromide ([Hemim]Br) to ethylene carbonate is 1:12.
  • the conversion rate of ethylene oxide in the absorption pre-conversion section is 17%, and the concentration of ethylene oxide at the top of the absorption tower is 158 ppm, and the absorption rate is 99.4% at this time; the above-mentioned absorption liquid is added to the reactor, and the result is measured after the reaction.
  • the conversion rate of the remaining ethylene oxide was 95.2%, and the selectivity was 99.8%.
  • This embodiment provides a composite absorbent and a method for ethylene oxide absorption conversion coupling and co-production of ethylene carbonate.
  • the specific operation steps are as follows:
  • the feed gas containing 2.26 mol% ethylene oxide at 80°C enters the absorption tower from the bottom of the tower, the absorbent ethylene carbonate enters from the top of the absorption tower (T1), the feed gas and the absorbent are in countercurrent contact, and the absorption temperature is 80°C.
  • the operating pressure is 2 MPa, the liquid-gas mass ratio is 3, and the concentration of ethylene oxide at the top of the absorption tower is 450 ppm, and the absorption rate is 98.2%.
  • the composite absorbent described in this application is used in the process of ethylene oxide absorption and conversion coupled with co-production of ethylene carbonate.
  • the absorption rate of ethylene oxide can reach Above 98.5%, this indicates that the composite absorbent of ionic liquid and ethylene carbonate has a high absorption capacity for ethylene oxide, and because ionic liquid has excellent properties such as low vapor pressure and small specific heat capacity, the product will be produced after complete reaction. It can be recycled to the absorption tower as an absorbent, which simplifies the separation and recycling process.
  • the conversion rate of ethylene oxide is 15.8-32.2%.
  • the conversion rate of ethylene oxide is up to 99.2%, and the selectivity is also above 99%.
  • this application directly couples the absorption and conversion of ethylene oxide to realize the production of ethylene carbonate in one step, which not only reduces the workload and equipment cost, but also reduces the stripping process, reduces energy consumption, and realizes It meets the requirements of economic efficiency, energy saving and environmental protection.
  • Comparative Example a1 Compared with Example a1, Comparative Example a1 only uses ethylene carbonate in the absorption stage of ethylene oxide, and then the esterification reaction of ethylene oxide and carbon dioxide is realized by adding a catalyst in the main reaction stage. It can be seen from the data. In the absorption stage, the absorption rate of ethylene oxide in Comparative Example a1 is lower than that of the composite absorbent containing ionic liquid for ethylene oxide. In the main reaction stage, the conversion rate of ethylene oxide is also low. The conversion rate of the main reaction catalyzed by the ionic liquid in Example a1. This shows that the addition of ionic liquid during the absorption and conversion process of ethylene oxide can not only enhance the selective absorption of ethylene oxide, but also has a higher catalytic efficiency for the esterification reaction of ethylene oxide and carbon dioxide.
  • the process flow of the separation and purification of ethylene oxide described in this application is shown in Figure 1, and specifically includes the following steps: the mixed gas 1 of ethylene oxide enters the absorption tower T1 from the bottom of the tower, and the composite absorbent 2 passes from the absorption tower T1. The top enters, 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 by heat exchange to obtain a higher temperature ethylene oxide-containing absorbent 4 and enters the desorption tower T2. After desorption, the top ethylene oxide 7 is obtained, and the gas is degassed.
  • the latter composite absorbent 5 obtains a certain temperature through heat exchange and enters the absorption tower T1 to continue to serve as the absorbent for recycling.
  • This group of embodiments provides a composite absorbent and a method for separating and purifying ethylene oxide.
  • the composite absorbent is composed of ionic liquid 1-hydroxyethyl-3-methylimidazole hexafluorophosphate ([Hemim][PF 6 ]) and ethylene carbonate.
  • the composite absorbent is used for raw materials containing ethylene oxide. The specific operations are as follows:
  • the 50°C mixed gas containing 2.26% ethylene oxide enters the absorption tower T1 from the bottom of the tower, the ionic liquid [Hemim][PF 6 ] and ethylene carbonate are uniformly mixed and enters from the top of the absorption tower T1. After absorption, the measuring tower Top ethylene oxide content.
  • the absorbent containing ethylene oxide is heated to a certain temperature by heat exchange and enters the 50kPa desorption tower T2. After desorption, the content of ethylene oxide at the top of the tower is obtained.
  • the ionic liquid and ethylene carbonate exchange heat to After 50°C, it enters the absorption tower T1 and continues to serve as an absorbent for recycling.
  • Table 1 The specific parameters and corresponding results are shown in Table 1 below:
  • Example b1-1 Comparing Example b1-1, Example b1-2, Example b1-3, Example b1-4 and Example b1-5, it can be seen that with the increase of the ionic liquid content, the EO obtained from the top of the desorption tower is The purity showed a clear upward trend. This shows that the higher the ionic liquid content, the higher the selective absorption of ethylene oxide in the feed gas.
  • Example b1-1 Comparing Example b1-1, Example b1-2, Example b1-3 and Example b1-4, it can be seen that as the content of the ionic liquid increases, the EO removal rate shows a downward trend. This is because the viscosity of the ionic liquid is relatively high, and when its content is relatively high, it affects the absorption effect of ethylene oxide. However, it can be seen from the data of Examples b1-5 that too low ionic liquid content will significantly reduce the EO concentration obtained at the top of the desorption tower, that is, reduce the absorption selectivity of the composite absorbent for ethylene oxide.
  • This group of embodiments provides a composite absorbent and a method for separating and purifying ethylene oxide.
  • the composite absorbent is composed of ionic liquid 1-hydroxyethyl-3-methylimidazole tetrafluoroborate ([Hemim][BF 4 ]) and ethylene carbonate, and the composite absorbent is combined with the ethylene oxide
  • the alkane feed gas is absorbed and desorbed, and the specific operations are as follows:
  • the mixed gas containing 2.26% ethylene oxide at 60°C enters the absorption tower T1 from the bottom of the tower, the ionic liquid [Hemim][BF 4 ] and ethylene carbonate are uniformly mixed and enters from the top of the absorption tower T1. After absorption, the measuring tower Top ethylene oxide content.
  • the absorbent containing ethylene oxide is heated to a certain temperature by heat exchange and enters the 60kPa desorption tower T2. After desorption, the content of ethylene oxide at the top of the tower is obtained.
  • the ionic liquid and ethylene carbonate exchange heat to 60 After °C, it enters the absorption tower T1 and continues to be used as an absorbent for recycling.
  • Table 2 The specific parameters and corresponding results are shown in Table 2 below:
  • the composite absorbent obtained by compounding 1-hydroxyethyl-3-methylimidazole tetrafluoroborate and ethylene carbonate is used to separate and purify ethylene oxide in the removal of ethylene oxide.
  • the removal rate can reach 93.1%-99.6%, which shows that the addition of ionic liquid can improve the absorption and separation capacity of ethylene oxide, and the absorption effect is significant; at the same time, the top of the desorption tower obtained by separating and purifying ethylene oxide using the above-mentioned composite absorbent
  • the purity of ethylene oxide is higher than 82.4%, that is, the selective absorption of ethylene oxide in the feed gas is obviously improved.
  • Example b2-1 Comparing Example b2-1, Example b2-2, Example b2-3 and Example b2-4, it can be seen that as the content of ionic liquid increases, the EO removal rate shows a downward trend, while the top of the desorption tower The concentration of EO is on the rise. This is consistent with the data conclusions in Table 1.
  • This group of embodiments provides a composite absorbent and a method for separating and purifying ethylene oxide.
  • the composite absorbent is composed of ionic liquid 1-aminoethyl-3-methylimidazole tetrafluoroborate ([C 2 NH 2 mim][BF 4 ]) and ethylene carbonate.
  • the specific operations for the absorption and desorption of ethylene oxide feed gas are as follows:
  • the ethylene oxide mixed gas containing 2.26% at 70°C enters the absorption tower T1 from the bottom of the tower, and the ionic liquid [C 2 NH 2 mim][BF 4 ]) is uniformly mixed with ethylene carbonate and then enters from the top of the absorption tower T1. After absorption, the content of ethylene oxide at the top of the tower is determined.
  • the absorbent containing ethylene oxide is heated to a certain temperature by heat exchange and enters the 70kPa desorption tower T2. After desorption, the content of ethylene oxide at the top of the tower is obtained.
  • Table 3 The specific parameters and corresponding results are shown in Table 3 below:
  • Example b3-1 Comparing Example b3-1, Example b3-2, Example b3-3 and Example b3-4, it can be seen that with the increase of the ionic liquid content, the EO removal rate shows a downward trend, while the EO at the top of the desorption tower The concentration is on the rise, that is, the selectivity of EO is on the rise. This is consistent with the data conclusions in Table 1 and Table 2.
  • the ionic liquid used in Example b2 is 1-hydroxyethyl-3-methylimidazole tetrafluoroborate
  • the ionic liquid used in Example b3 is 1-aminoethyl-3-methylimidazole tetrafluoroborate
  • the cationic substituent of the ionic liquid of Example b2 is a hydroxyl group
  • the cationic substituent of the ionic liquid of Example b3 is an amino group; comparing the data in Table 2 and Table 3, it can be seen that When the cationic substituent is a hydroxyl group, the purity of the ethylene oxide obtained from the top of the desorption tower is higher, and the removal rate is lower, that is, the selectivity of absorbing and separating ethylene oxide is greater than that of amino groups, but the absorption capacity is less than that of amino groups. .
  • This set of comparative examples provides an absorbent and a method for separating and purifying ethylene oxide.
  • the difference from Example b1 is only that the absorbent consists only of ethylene carbonate.
  • This comparative example provides a composite absorbent and a method for separating and purifying ethylene oxide.
  • the only difference from Example b1 is that the 1-hydroxyethyl-3-methylimidazole hexafluorophosphate ([Hemim][PF 6 ]) is replaced with water, and the specific operation is as follows:
  • the 50°C mixed gas containing 2.26% ethylene oxide enters the absorption tower T1 from the bottom of the tower, and the water and ethylene carbonate are evenly mixed and enters from the top of the absorption tower T1. After absorption, the ethylene oxide content at the top of the tower is measured.
  • the absorbent containing ethylene oxide is heated to a certain temperature by heat exchange and enters the 50kPa desorption tower T2. After desorption, the content of ethylene oxide at the top of the tower is obtained.
  • Table 5 The specific parameters and corresponding results are shown in Table 5 below:

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Abstract

一种复合吸收剂及其用于环氧乙烷吸收转化耦合联产碳酸乙烯酯的方法。复合吸收剂包括离子液体和碳酸乙烯酯，离子液体为咪唑类、季铵类和季磷类离子液体。将上述复合吸收剂用来吸收环氧乙烷和二氧化碳，还用于环氧乙烷吸收转化耦合联产碳酸乙烯酯。

Description

一种复合吸收剂及其用途 技术领域
本申请属于化工技术领域，例如涉及一种复合吸收剂及其用于环氧乙烷吸收转化耦合联产碳酸乙烯酯的方法，以及一种复合吸收剂及其用于环氧乙烷分离纯化的方法。
背景技术
被称为21世纪绿色化工原料的碳酸乙烯酯是一种应用十分广泛的化工中间体和优良溶剂。合成碳酸乙烯酯的原料之一环氧乙烷主要利用乙烯在含银催化剂作用下氧化生成环氧乙烷，在制备环氧乙烷的过程中同时会存在甲烷、乙烷等杂质气体。为了得到精制的环氧乙烷，工业上常常利用吸收法将环氧乙烷从混合气中吸收下来，然后经过汽提、浓缩等过程精制得到高纯度的环氧乙烷；精制的环氧乙烷与二氧化碳在反应釜中催化合成碳酸乙烯酯。
同时，环氧乙烷(EO)也是一种重要的石化产品，具有优良的杀菌消毒效果，主要用于洗涤、制药和印染行业。目前，环氧乙烷的主要生产方法为乙烯氧化法，乙烯和氧气在银催化剂条件下生成环氧乙烷，但是由于转化率和选择性较低，生成环氧乙烷的同时还会有部分甲烷、乙烷、二氧化碳等气体的生成以及未参与反应的乙烯存在，工业上为了制得较纯的环氧乙烷，通常使用水为吸收剂，然后经过解吸、浓缩、精制获得较纯的环氧乙烷。
水为吸收剂的工艺目前存在流程复杂、操作弹性差、能耗高等问题，国内外许多专利针对这一点做出了改进的措施。US3948621A1公开了以甲醇作为吸收剂，用于分离提纯环氧乙烷，此吸收剂吸收效果好，而且在解吸过程中能耗低，但是甲醇易与环氧乙烷反应，吸收温度需严格控制，而且解吸时甲醇易随 解吸气挥发而流失。US4221727A1公开了一种以碳酸乙烯酯为吸收剂吸收分离环氧乙烷，以碳酸乙烯酯为吸收剂不仅吸收效果好，而且在吸收过程中能够避免副反应发生，但是在解吸过程中，解吸温度为150℃，压力为5kPa，此时部分碳酸乙烯酯会随解吸气挥发，造成溶剂损失。类似地，US5559255A公开了采用碳酸丙烯酯作为吸收剂，CN102911137A公开了以碳酸乙烯酯与水的混合液作为环氧乙烷吸收剂，但都未解决气提过程中溶剂挥发损失问题。CN109422708A公开了一种以三乙二醇二甲醚和离子液体为吸收剂的方法等。这些吸收剂提高了对环氧乙烷的吸收能力和选择性，但是在整个工艺流程中，汽提环氧乙烷的过程仍然消耗大量能量，而且工艺流程复杂、设备造价高、一次性投资大。
因此，为了更好地实现乙烯氧化后的混合气中环氧乙烷的吸收和碳酸乙烯酯的生产，仍需要新型吸收剂和工艺，使之既能够高效吸收环氧乙烷，又能够解决汽提过程中能耗大的问题。
发明内容
本申请的目的包括提供一种复合吸收剂及其用于环氧乙烷吸收转化耦合联产碳酸乙烯酯的方法。本申请利用离子液体和碳酸乙烯酯的复合吸收剂进行环氧乙烷和二氧化碳的吸收，在吸收的过程中离子液体还可以作为催化剂，将吸收得到的环氧乙烷和二氧化碳反应生产碳酸乙烯酯，这样既提高了环氧乙烷的吸收效果，也减少了环氧乙烷解吸精制的过程，吸收的同时实现预转化，降低了能耗，具有较好的工业应用价值。
本申请的目的还包括提供一种复合吸收剂及其用于环氧乙烷分离纯化的方法，所述吸收剂包括离子液体和碳酸乙烯酯，所述离子液体的结构如式I所 示。本申请复合吸收剂中含有特定结构的离子液体，将该复合吸收剂用于分离纯化环氧乙烷时能够有效提高环氧乙烷的吸收率和该复合吸收剂的循环利用率，降低成本，减少能耗。
为达此目的，本申请采用以下技术方案：
第一方面，本申请提供一种复合吸收剂，所述复合吸收剂包括离子液体和碳酸乙烯酯，所述离子液体的结构如式I所示：
Figure PCTCN2020080560-appb-000001
其中，式I中的R 1和R 2各自独立地选自取代或未取代的C1-C6烷基、取代或未取代的C2-C6烯基、取代或未取代的C2-C6炔基、取代或未取代的C6-C30芳基、取代或未取代的C3-C30杂芳基或取代或未取代的C1-C6烷氧基中的任意一种；
式I中的阴离子X -选自BF 4 -、PF 6 -、Tf 2N -、RCOO -、Cl -或Br -中的任意一种；R选自烷基、烯基或炔基中的任意一种。
本申请所用术语“C1-C6烷基”是指具有1、2、3、4、5或6个碳原子的直链或支链烷基，非限制性地包括甲基、乙基、正丙基、异丙基、正丁基、异丁基、仲丁基、特丁基、正戊基、异戊基、正己基等。术语“C2-C6烯基”是指具有2、3、4、5或6个碳原子的直链或支链烯基，其分子链中至少包括一个双键，非限制性地包括-CH＝CH(CH 3)、-CH＝C(CH 3) 2、-C(CH 3)＝CH 2、-C(CH 3)＝CH(CH 3)、-C(CH 2CH 3)＝CH 2、丁二烯基、戊二烯基或己二烯基等。术语“C2-C6炔基”是指具有2、3、4、5或6个碳原子的直链或支链炔基，非限制性地包括 -C≡CH、-C≡C(CH 3)、-C≡C(CH 2CH 3)、-CH 2C≡CH、-CH 2C≡C(CH 3)或-CH 2C≡C(CH 2CH 3)等。术语“C6-C30芳基”是具有6-30个碳原子的芳基，例如可以包含6个、12个或18个碳原子等，非限制性地包括苯基、萘基或联苯基等。术语“C3-C30杂芳基”是指单环、双环或三环等的具有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或30等个环原子的芳族环体系，并且其含有至少一个可以相同或不同的杂原子，所述杂原子是诸如氧、氮或硫，并且此外在各个情况中可以是苯并稠合的，非限制性地包括噻吩基、呋喃基、吡咯基、噁唑基、噻唑基、咪唑基、吡唑基、异噁唑基、异噻唑基、噁二唑基、三唑基、苯并呋喃基、苯并噻吩基、苯并噁唑基、苯并异噁唑基、苯并咪唑基、苯并三唑基、吲唑基、吲哚基、异吲哚基、吡啶基、哒嗪基、嘧啶基、吡嗪基、三嗪基、喹啉基、喹唑啉基、异喹啉基等。术语“C1-C6烷氧基”是指具有1、2、3、4、5或6个碳原子的直链或支链烷氧基，非限制性地包括甲氧基、乙氧基、正丙氧基、异丙氧基或特丁氧基等。
本发明含有所述离子液体的复合吸收剂不仅对环氧乙烷具有较高的吸收能力而且可以显著增加环氧乙烷吸收分离的选择性，同时还能有效降低吸收剂的蒸汽压，减少解吸过程中溶剂的损失，具有工艺流程简单、操作弹性高、能耗低、吸收效果显著等特点，工业应用前景较好。
可选地，阴离子X -选自BF 4 -、PF 6 -、Tf 2N -或RCOO -中的任意一种，可选为所述阴离子X -为BF 4 -或PF 6 -。
可选地，R 1和R 2中所述取代的基团各自独立地选自羟基、氨基、硝基、醛基、酯基、羧基或巯基中的任意一种。
可选地，R 1和R 2中所述取代的基团为羟基或氨基。
作为本发明的可选技术方案，所述离子液体选自1-羟乙基-3-甲基咪唑六氟磷酸盐、1-羟乙基-3-甲基咪唑四氟硼酸盐、1-胺乙基-3-甲基咪唑四氟硼酸盐、1-胺乙基-3-甲基咪唑六氟磷酸盐、1-羟乙基-3-乙基咪唑六氟磷酸盐或1-羟乙基-3-乙基咪唑四氟硼酸盐中的任意一种或至少两种的组合；
可选地，所述离子液体在所述复合吸收剂中的质量占比为10-60％，例如可以是10％、12％、15％、17％、19％、20％、23％、25％、27％、30％、33％、35％、37％、38％、40％、42％、45％、49％、50％、53％、55％、59％或60％等，可选为30-50％。
本发明优选将离子液体和碳酸乙烯酯的质量比控制在上述范围，是由于当离子液体含量过高，复合吸收剂的粘度增加，无法和环氧乙烷充分接触，可能会降低环氧乙烷的吸收效率，而如果离子液体含量过低，那么复合吸收剂的选择吸收性减弱，也会影响环氧乙烷的吸收效果。
第二方面，本发明还提供了一种环氧乙烷分离纯化的方法，所述方法使用如第一方面所述的复合吸收剂。
本发明所述环氧乙烷分离纯化的方法使用所述离子液体和碳酸乙烯酯的复合吸收剂，能有效提高对原料气中环氧乙烷的吸收能力，简化工艺流程，增加装置的操作弹性，减少能耗，为连续化生产纯化环氧乙烷提供了技术支撑。
可选地，所述方法包括如下步骤：将所述复合吸收剂与含有环氧乙烷的原料气接触，脱环氧乙烷后的贫混合气返回乙烯氧化阶段，富环氧乙烷吸收液进行解吸得到环氧乙烷。
本发明所述原料气的组分及其摩尔百分含量分别为：环氧乙烷2.6％、甲烷52.77％、乙烯32.53％、氧气4.9％、二氧化碳1.5％、氩气4.18％、氮气1％和乙烷0.52％组成。本发明使用的所述原料气中环氧乙烷的含量低，而通过离子液 体和碳酸乙烯酯的复合吸收剂进行分离纯化，能得到纯度较高的环氧乙烷，吸收效率得到显著提高。
可选地，所述方法包括如下步骤：将所述复合吸收剂与含有环氧乙烷的原料气在吸收塔内逆流充分接触，塔顶脱环氧乙烷后的贫混合气经过处理后返回乙烯氧化阶段，塔釜富环氧乙烷吸收液经换热后进入解吸塔，解吸后气相塔顶采出，得到环氧乙烷，解吸后液相的解吸贫液从塔釜经过换热后返回吸收塔。
可选地，所述原料气中环氧乙烷摩尔浓度为0.1-5％，例如可以是0.1％、0.3％、0.5％、0.8％、0.9％、1.0％、1.2％、1.5％、2％、2.5％、2.6％、2.8％、2.8％、3.0％、3.5％、4.0％、4.5％或5％等，可选为2-3％。
可选地，所述原料气的进气温度为40-100℃，例如可以是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℃或100℃等，可选为50-80℃。
可选地，所述吸收塔的操作压力为0.1-5MPa，例如可以是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或5.0MPa等，可选为1-3MPa。
可选地，所述吸收塔的操作温度为40-100℃，例如可以是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℃或100℃等，可选为50-80℃。
可选地，所述复合吸收剂与所述原料气的摩尔比为(1-4):1，例如可以是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或4:1等，可选为(2-3):1。
可选地，所述解吸塔的操作压力为10-150kPa，例如可以是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或150kPa等，可选为50-150kPa。
可选地，所述解吸塔的操作温度为80-150℃，例如可以是80℃、84℃、85℃、87℃、89℃、90℃、95℃、98℃、100℃、105℃、108℃、110℃、115℃、120℃、125℃、130℃、134℃、140℃、145℃、148℃或150℃等，可选为90-130℃。
可选地，所述解吸塔的塔釜的解吸贫液换热至50-80℃后循环回所述吸收塔，例如可以是50℃、53℃、54℃、55℃、57℃、60℃、63℃、65℃、68℃、70℃、72℃、73℃、75℃、78℃、79℃或80℃等。
可选地，所述吸收塔的塔釜的富环氧乙烷吸收液换热至90-130℃后进入所述解吸塔，例如可以是90℃、92℃、93℃、95℃、98℃、99℃、100℃、102℃、105℃、108℃、110℃、115℃、118℃、120℃、124℃、125℃、126℃、128℃、129℃或130℃等。
第三方面，本发明提供一种复合吸收剂，所述复合吸收剂包括离子液体和碳酸乙烯酯，所述离子液体的结构如式Ⅱ或式Ⅲ所示：
Figure PCTCN2020080560-appb-000002
式Ⅱ中的R 3、R 4、R 5和R 6各自独立地选自取代或未取代的C1-C6烷基、 取代或未取代的C2-C6烯基、取代或未取代的C2-C6炔基、取代或未取代的C6-C30芳基、取代或未取代的C3-C30杂芳基或取代或未取代的C1-C6烷氧基中的任意一种；
式Ⅲ中的R 7、R 8、R 9和R 10各自独立地选自取代或未取代的C1-C6烷基、取代或未取代的C2-C6烯基、取代或未取代的C2-C6炔基、取代或未取代的C6-C30芳基、取代或未取代的C3-C30杂芳基或取代或未取代的C1-C6烷氧基中的任意一种；
式Ⅱ和式Ⅲ中的阴离子X -各自独立地选自Cl -、Br -或I -中的任意一种。
本申请利用离子液体和碳酸乙烯酯的复合吸收剂进行环氧乙烷和二氧化碳的吸收，在吸收的过程中离子液体还可以作为催化剂，将吸收得到的环氧乙烷和二氧化碳反应生产碳酸乙烯酯，这样既提高了环氧乙烷的吸收效果，也减少了环氧乙烷解吸精制的过程，吸收的同时实现预转化，降低了能耗，具有较好的工业应用价值。
本申请所述复合吸收剂中离子液体的阴离子选自特定的Cl -、Br -或I -中的任意一种，这是由于离子液体的阳离子能够造成环氧乙烷C-O键的极化，与此同时卤素离子进攻环氧环中空间位阻较小的β-碳原子，两种作用同时进行造成了环氧乙烷容易开环和二氧化碳反应生成碳酸乙烯酯。
可选地，式I、式Ⅱ和式Ⅲ中，所述取代的基团各自独立地选自羟基、氨基、硝基、醛基、酯基、羧基、亚硝基、酰胺基或羰基中的任意一种。
可选地，所述离子液体与碳酸乙烯酯质量比为1:(1-10)，例如可以是1:1、1:2、1:3、1:4、1:5、1:6、1:7、1:8、1:9或1:10等。
本申请可选将离子液体和碳酸乙烯酯的质量比控制在上述范围，是由于当离子液体含量过高，复合吸收剂的粘度增加，无法和环氧乙烷充分接触，可能 会降低环氧乙烷的吸收效率，而如果离子液体含量过低，那么复合吸收剂的选择吸收性减弱，会影响环氧乙烷的吸收效果，同时离子液体含量过低，吸收预反应阶段，环氧乙烷和二氧化碳环加成反应的催化效率会明显降低。
第四方面，本申请还提供了一种环氧乙烷吸收转化耦合联产碳酸乙烯酯的方法，所述方法使用如第一方面或第三方面所述的复合吸收剂。
本申请创造性地采用离子液体和碳酸乙烯酯复合作为吸收剂将环氧乙烷进行吸收转化耦合，实现一步吸收转化环氧乙烷，有效减少了装置的能耗和费用。
可选地，所述方法包括如下步骤：将所述复合吸收剂与含有环氧乙烷的原料气接触，得到的富环氧乙烷吸收液进入主反应器中，得到碳酸乙烯酯。
本申请所述原料气的组分及其摩尔百分含量分别为：环氧乙烷2.6％、甲烷52.77％、乙烯32.53％、氧气4.9％、二氧化碳1.5％、氩气4.18％、氮气1％和乙烷0.52％组成。本申请所述原料气为乙烯氧化后的混合气，原料气中同时存在环氧乙烷和二氧化碳，在吸收过程中，离子液体不仅能够有效吸收环氧乙烷和二氧化碳，还能够催化两者反应生成碳酸乙烯酯，在吸收的同时实现了制备碳酸乙烯酯的预反应，降低了能耗，还降低后段羰基化主反应单元环氧乙烷尾气含量，保证安全，具有较好的工业应用价值。
本申请中所述预反应的环氧乙烷转化率为2-35％，例如可以是2％、5％、8％、10％、12％、15％、20％、23％、27％、30％或35％等。
本申请所述预反应阶段环氧乙烷的转化率仅为2-35％，是由于预反应阶段无法提供过量的二氧化碳，而且催化剂在预反应的温度下无法达到最佳转化率，造成了预反应阶段环氧乙烷的转化率较低。
可选地，所述方法包括如下步骤：将所述复合吸收剂与含有环氧乙烷原料气在吸收塔内逆流充分接触，塔顶脱环氧乙烷后的贫混合气经过处理后返回乙烯氧化阶段，塔釜富环氧乙烷吸收液经换热后进入主反应器反应得到反应液，将得到的包含离子液体的反应液一部分作为吸收液循环，另一部分经过处理后得到高纯度的碳酸乙烯酯。
需要说明的是，在所述反应阶段会向主反应器中添加二氧化碳，使二氧化碳的量相对于环氧乙烷是充足的，即能满足有足够多的二氧化碳和吸收得到的环氧乙烷反应生成碳酸乙烯酯。
本申请所述主反应器中，离子液体催化吸收得到的环氧乙烷和二氧化碳反应生产碳酸乙烯酯。对于乙烯氧化后的尾气处理工艺，目前采用吸收塔将环氧乙烷吸收下来，经过汽提、精制后进入反应器生成碳酸乙烯酯。而本申请首次创造性使用碳酸乙烯酯和离子液体的复合吸收剂来吸收转化耦合联产碳酸乙烯酯，不仅对环氧乙烷具有较高吸收性能，而且离子液体还具有蒸汽压低和比热容小等优良性能，在完全反应后，产物可作为吸收剂再次循环至吸收塔内循环使用，简化了分离循环过程。对于工艺流程，本申请所述方法将吸收和转化直接耦合，实现一步生产碳酸乙烯酯，不仅工作量小，设备造价低，而且减少汽提过程，降低能耗，实现了经济高效和节能环保的要求。
可选地，所述复合吸收剂与所述含有环氧乙烷原料气的质量比(液气质量比)为(1-5):1，例如可以是1:1、1.5:1、2:1、2.3:1、3:1、3.5:1、4:1或5:1等，可选为(2-3):1。
可选地，所述吸收塔的操作压力为1-5MPa，例如可以是1MPa、1.5MPa、2MPa、2.3MPa、3MPa、3.5MPa、4MPa、4.6MPa或5Mpa等，可选1.5-2.5MPa。
可选地，所述吸收塔的操作温度为50-100℃，例如可以是50℃、60℃、70℃、80℃、90℃或100℃等，可选为60-80℃。
可选地，所述主反应器的反应压力为1-5MPa，例如可以是1MPa、1.2MPa、2MPa、2.5MPa、3MPa、3.4MPa、4MPa、4.5MPa或5MPa等，可选2-3MPa。
可选地，所述主反应器的反应温度为80-300℃，例如可以是80℃、90℃、100℃、110℃、120℃、130℃、140℃、150℃、160℃、170℃、180℃、190℃、200℃、210℃、220℃、230℃、240℃、250℃、260℃、270℃、280℃、290℃或300℃等，可选为100-200℃。
可选地，所述反应的时间为0.5-5h，例如可以是0.5h、1h、1.5h、2h、2.5h、3h、3.5h、4h、4.5h或5h等，可选为1-3h。
可选地，所述富环氧乙烷吸收液换热至100-200℃后进入主反应器，例如可以是100℃、110℃、120℃、130℃、140℃、150℃、160℃、170℃、180℃、190℃或200℃等。
可选地，所述反应液的一部分进入吸收塔前降温至60-80℃，例如可以是60℃、62℃、65℃、68℃、70℃、73℃、76℃或80℃等。
相对于现有技术，本申请具有以下有益效果：
(1)本申请利用离子液体和碳酸乙烯酯的复合吸收剂进行环氧乙烷和二氧化碳的吸收，在吸收的过程中离子液体还可以作为催化剂，将吸收得到的环氧乙烷和二氧化碳反应生产碳酸乙烯酯，这样既提高了环氧乙烷的吸收效果，也减少了环氧乙烷解吸精制的过程，吸收的同时实现预转化，降低了能耗，具有较好的工业应用价值；
(2)本申请首次创造性使用碳酸乙烯酯和离子液体的复合吸收剂来吸收转 化耦合联产碳酸乙烯酯，不仅对环氧乙烷具有较高吸收性能，而且离子液体还具有蒸汽压低和比热容小等优良性能，在完全反应后，产物可作为吸收剂再次循环至吸收塔内循环使用，简化了分离循环过程。对于工艺流程，本申请所述方法将吸收和转化直接耦合，实现一步生产碳酸乙烯酯，不仅工作量小，设备造价低，而且减少汽提过程，降低能耗，实现了经济高效和节能环保的要求；
(3)本申请所述复合吸收剂在用于环氧乙烷吸收转化耦合联产碳酸乙烯酯的过程中，在吸收阶段，环氧乙烷的吸收率均能达到98.5％以上，在主反应阶段，环氧乙烷的转化率最高可达99.2％，选择性也均在92％以上。
(4)本申请提供了一种含有离子液体和碳酸乙烯酯的复合吸收剂，能够增加对环氧乙烷吸收分离的选择性，同时也能有效降低复合吸收剂的蒸气压，减少解吸过程中的溶剂损失，具有工艺流程简单、操作弹性高、能耗低、吸收效果显著等特点，工业应用前景较好；
(5)本申请将上述复合吸收剂用来分离纯化环氧乙烷，环氧乙烷的脱除率可达88.8％-99.8％，有效提高了对原料气中环氧乙烷的吸收能力，同时，解吸塔塔顶得到的环氧乙烷的纯度均在80％以上，有效提高了复合吸收剂对环氧乙烷选择吸收的能力，利用本申请所述复合吸收剂分离纯化环氧乙烷简化了工艺流程，增加装置的操作弹性，减少能耗，为连续化生产纯化环氧乙烷提供技术支撑。
附图说明
图1是本申请所述环氧乙烷分离纯化的流程示意图。
其中，T1为环氧乙烷吸收塔，T2为环氧乙烷解吸塔，E1为环氧乙烷富液贫液换热器，E2为环氧乙烷贫液冷却器，E3为环氧乙烷富液加热器，1为含有 环氧乙烷的原料气，2为复合吸收剂，3为富环氧乙烷吸收液，4为换热后的富环氧乙烷吸收液，5为解吸贫液，6为换热后的解吸贫液，7为解吸后的环氧乙烷气体，8为脱环氧乙烷后的贫混合气。
图2是本申请所述环氧乙烷吸收转化耦合联产碳酸乙烯酯的流程示意图。
其中，T3为环氧乙烷吸收塔，R1为环氧乙烷反应器，a为脱环氧乙烷混合气，b为复合吸收剂，c为含环氧乙烷的原料气，d为循环CO 2气体，e为富含环氧乙烷的吸收液，f为新鲜CO 2气体，g为碳酸乙烯酯产品。
具体实施方式
下面通过具体实施方式来进一步说明本申请的技术方案。本领域技术人员应该明了，所述实施例仅仅是帮助理解本申请，不应视为对本申请的具体限制。
实施例a1
本实施例提供了一种复合吸收剂及其用于环氧乙烷吸收转化耦合联产碳酸乙烯酯的方法，具体操作步骤如下：
将80℃含2.26mol％环氧乙烷的原料气由塔底进入吸收塔，复合吸收剂离子液体1-(2-羟乙基)-3-甲基咪唑溴([Hemim]Br)与碳酸乙烯酯以1:10的质量比混合均匀后从吸收塔(T1)塔顶进入，原料气与吸收剂逆流接触，吸收温度为80℃，操作压力为2MPa，液气质量比为3，吸收预转化段环氧乙烷的转化率为28.8％，吸收塔塔顶环氧乙烷的浓度69ppm，此时吸收率为99.9％。
将上述吸收液加入到反应器中，升高反应温度为125℃，压力为2MPa下反应1h，经过检测所得，剩余环氧乙烷的转化率为95.2％，选择性为99.8％。
实施例a2
本实施例提供了一种复合吸收剂及其用于环氧乙烷吸收转化耦合联产碳酸 乙烯酯的方法，具体操作步骤如下：
将80℃含2.26mol％环氧乙烷的原料气由塔底进入吸收塔，复合吸收剂离子液体1-己基-3-甲基咪唑溴([Hmim]Br)与碳酸乙烯酯以1:10的质量比混合均匀后从吸收塔(T1)塔顶进入，原料气与吸收剂逆流接触，吸收温度为80℃，操作压力为2MPa，液气质量比为3，吸收预转化段环氧乙烷的转化率为15.8％，吸收塔塔顶环氧乙烷的浓度227ppm，此时吸收率为99.5％。
将上述吸收液加入到反应器中，升高反应温度为120℃，压力为2MPa下反应3h，经过检测所得，剩余环氧乙烷的转化率为52.5％，选择性为99.8％。
实施例a3
本实施例提供了一种复合吸收剂及其用于环氧乙烷吸收转化耦合联产碳酸乙烯酯的方法，具体操作步骤如下：
将80℃含2.26mol％环氧乙烷的原料气由塔底进入吸收塔，复合吸收剂离子液体1-(2-羟乙基)-3-甲基咪唑溴([Hemim]Br)与碳酸乙烯酯以1:9的质量比混合均匀后从吸收塔(T1)塔顶进入，原料气与吸收剂逆流接触，吸收温度为80℃，操作压力为2MPa，液气质量比为3，吸收预转化段环氧乙烷的转化率为32.2％，吸收塔塔顶环氧乙烷的浓度44ppm，此时吸收率为99.9％。
将上述吸收液加入到反应器中，升高反应温度为120℃，压力为2MPa下反应1h，经过检测所得，剩余环氧乙烷的转化率为99.2％，选择性为99.8％。
实施例a4
本实施例提供了一种复合吸收剂及其用于环氧乙烷吸收转化耦合联产碳酸乙烯酯的方法，具体操作步骤如下：
将80℃含2.26mol％环氧乙烷的原料气由塔底进入吸收塔，复合吸收剂离子液体2-羟乙基三丁基溴化铵(HETBAB)与碳酸乙烯酯以1:10的质量比混合均 匀后从吸收塔(T1)塔顶进入，原料气与吸收剂逆流接触，吸收温度为80℃，操作压力为2MPa，液气质量比为3，吸收预转化段环氧乙烷的转化率为29.2％，吸收塔塔顶环氧乙烷的浓度55ppm，此时吸收率为99.9％。
将上述吸收液加入到反应器中，升高反应温度为125℃，压力为2MPa下反应1h，经过检测所得，剩余环氧乙烷的转化率为95.8％，选择性为99.8％。
实施例a5
本实施例提供了一种复合吸收剂及其用于环氧乙烷吸收转化耦合联产碳酸乙烯酯的方法，具体操作步骤如下：
将80℃含2.26mol％环氧乙烷的原料气由塔底进入吸收塔，复合吸收剂离子液体亚乙基双(三苯基溴化磷鎓)(E[TPB])与碳酸乙烯酯以1:10的质量比混合均匀后从吸收塔(T1)塔顶进入，原料气与吸收剂逆流接触，吸收温度为80℃，操作压力为3MPa，液气质量比为3，吸收预转化段环氧乙烷的转化率为25.6％，吸收塔塔顶环氧乙烷的浓度95ppm，此时吸收率为99.8％。
将上述吸收液加入到反应器中，升高反应温度为160℃，压力为3MPa下反应3h，经过检测所得，剩余环氧乙烷的转化率为92.9％，选择性为99％。
实施例a6
本实施例提供了一种复合吸收剂及其用于环氧乙烷吸收转化耦合联产碳酸乙烯酯的方法，具体操作步骤如下：
将60℃含2.26mol％环氧乙烷的原料气由塔底进入吸收塔，复合吸收剂离子液体1-(2-羟乙基)-3-甲基咪唑溴([Hemim]Br)与碳酸乙烯酯以1:1的质量比混合均匀后从吸收塔(T1)塔顶进入，原料气与吸收剂逆流接触，吸收温度为60℃，操作压力为2MPa，液气质量比为2，其中，吸收预转化段环氧乙烷的转化率为18.2％，吸收塔2塔顶环氧乙烷的浓度152ppm，此时吸收率为99.4％。
将上述吸收液加入到反应器中，升高反应温度为80℃，压力为5MPa下反应0.5h，经过检测所得，剩余环氧乙烷的转化率为65.5％，选择性为98.2％。
实施例a7
本实施例提供了一种复合吸收剂及其用于环氧乙烷吸收转化耦合联产碳酸乙烯酯的方法，具体操作步骤如下：
将100℃含2.26mol％环氧乙烷的原料气由塔底进入吸收塔，复合吸收剂离子液体1-(2-羟乙基)-3-甲基咪唑溴([Hemim]Br)与碳酸乙烯酯以1:5的质量比混合均匀后从吸收塔(T1)塔顶进入，原料气与吸收剂逆流接触，吸收温度为100℃，操作压力为2MPa，液气质量比为3，吸收预转化段环氧乙烷的转化率为30.1％，吸收塔塔顶环氧乙烷的浓度395ppm，此时吸收率为98.5％。
将上述吸收液加入到反应器中，升高反应温度为300℃，压力为2MPa下反应5h，经过检测所得，剩余环氧乙烷的转化率为95.2％，选择性为98.2％。
实施例a8
本实施例提供了一种复合吸收剂及其用于环氧乙烷吸收转化耦合联产碳酸乙烯酯的方法，具体操作步骤如下：
将60℃含2.26mol％环氧乙烷的原料气由塔底进入吸收塔，复合吸收剂离子液体2-羟乙基三丁基溴化铵(HETBAB)与碳酸乙烯酯以1:7的质量比混合均匀后从吸收塔(T1)塔顶进入，原料气与吸收剂逆流接触，吸收温度为60℃，操作压力为2MPa，液气质量比为2，其中，吸收预转化段环氧乙烷的转化率为17.2％，吸收塔塔顶环氧乙烷的浓度108ppm，此时吸收率为99.5％。
将上述吸收液加入到反应器中，升高反应温度为200℃，压力为1.5MPa下反应2h，经过检测所得，剩余环氧乙烷的转化率为85.1％，选择性为92％。
实施例a9
本实施例提供了一种复合吸收剂及其用于环氧乙烷吸收转化耦合联产碳酸乙烯酯的方法，与实施例a1的区别仅在于：1-(2-羟乙基)-3-甲基咪唑溴([Hemim]Br)与碳酸乙烯酯的质量比为1:12。
吸收预转化段环氧乙烷的转化率为17％，吸收塔塔顶环氧乙烷的浓度158ppm，此时吸收率99.4％；将上述吸收液加入到反应器中，反应后经过检测所得，剩余环氧乙烷的转化率为95.2％，选择性为99.8％。
对比例a1
本实施例提供了一种复合吸收剂及其用于环氧乙烷吸收转化耦合联产碳酸乙烯酯的方法，具体操作步骤如下：
将80℃含2.26mol％环氧乙烷的原料气由塔底进入吸收塔，吸收剂碳酸乙烯酯从吸收塔(T1)塔顶进入，原料气与吸收剂逆流接触，吸收温度为80℃，操作压力为2MPa，液气质量比为3，吸收塔塔顶环氧乙烷的浓度450ppm，此时吸收率为98.2％。
将上述吸收液加入到主反应器中，加入催化剂1-丁基-3-甲基咪唑溴([bmim]Br)，升高反应温度为120℃，压力为2MPa下反应3h，经过检测所得，剩余环氧乙烷的转化率为51.6％，选择性为99.9％。
由实施例和检测结果可以看出，本申请所述复合吸收剂在用于环氧乙烷吸收转化耦合联产碳酸乙烯酯的过程中，在吸收阶段，环氧乙烷的吸收率均能达到98.5％以上，这说明采用离子液体和碳酸乙烯酯的复合吸收剂，对环氧乙烷具有较高的吸收能力，并且，由于离子液体具有蒸汽压低和比热容小等优良性能，在完全反应后产物可作为吸收剂再次循环至吸收塔内循环使用，简化了分离循环过程。在吸收阶段，环氧乙烷的转化率在15.8-32.2％，在主反应阶段， 环氧乙烷的转化率最高可达99.2％，选择性也均在99％以上。对于整个工艺流程，本申请将吸收和转化环氧乙烷直接耦合，实现一步生产碳酸乙烯酯，不仅减少了工作量，降低了设备造价，而且还减少了汽提过程，降低了能耗，实现了经济高效和节能环保的要求。
相比实施例a1，对比例a1在环氧乙烷的吸收阶段只采用了碳酸乙烯酯，然后通过在主反应阶段添加催化剂来实现环氧乙烷和二氧化碳的酯化反应，从数据上可以看出，在吸收阶段，对比例a1中环氧乙烷的吸收率低于使用含离子液体的复合吸收剂对环氧乙烷的吸收效率，在主反应阶段，环氧乙烷的转化率也低于实施例a1中离子液体催化主反应的转化率。这说明在环氧乙烷吸收转化过程中添加离子液体，不仅能增强对环氧乙烷的选择吸收性，还对环氧乙烷和二氧化碳的酯化反应有较高的催化效率。
本申请所述环氧乙烷分离纯化的工艺流程如图1所示，具体包括以下步骤：将环氧乙烷的混合气1由塔底进入吸收塔T1，复合吸收剂2从吸收塔T1塔顶进入，经吸收后测定吸收塔塔顶环氧乙烷8的含量。含环氧乙烷的复合吸收剂3经换热加热至一定温度得到温度较高的含环氧乙烷吸收剂4进入解吸塔T2中，通过解吸后得到塔顶环氧乙烷7，脱气后的复合吸收剂5经过换热得到一定温度的复合吸收剂6进入吸收塔T1继续充当吸收剂循环使用。
实施例b1：
本组实施例提供了一种复合吸收剂及其分离纯化环氧乙烷的方法。所述复合吸收剂由离子液体1-羟乙基-3-甲基咪唑六氟磷酸盐([Hemim][PF 6])与碳酸乙烯酯组成，将该复合吸收剂对含环氧乙烷原料气进行吸收与解吸，具体操作如下：
将50℃含2.26％环氧乙烷的混合气由塔底进入吸收塔T1，离子液体[Hemim][PF 6]与碳酸乙烯酯混合均匀后从吸收塔T1塔顶进入，经吸收后测定塔顶环氧乙烷的含量。含环氧乙烷的吸收剂经换热加热至一定温度进入50kPa的解吸塔T2中，通过解吸后得到塔顶环氧乙烷的含量，脱气后的离子液体与碳酸乙烯酯经过换热到50℃后进入吸收塔T1继续充当吸收剂循环使用。具体参数和相应的结果如下表1所示：
表1
Figure PCTCN2020080560-appb-000003
从表1中数据可以看出使用1-羟乙基-3-甲基咪唑六氟磷酸盐和碳酸乙烯酯复配得到的复合吸收剂分离纯化环氧乙烷的中环氧乙烷的脱除率可达94.9％-99.3％，这表明离子液体的加入可以提高对环氧乙烷吸收分离能力，吸收效果显著；另外还能看出，使用上述复合吸收剂分离纯化环氧乙烷得到的解吸塔塔顶环氧乙烷的纯度均高于95.3％，即对原料气中环氧乙烷的选择吸收性明显提高。
对比实施例b1-1、实施例b1-2、实施例b1-3、实施例b1-4和实施例b1-5可以看出，随着离子液体含量的增加，解吸塔塔顶得到的EO的纯度呈现明显上升趋势。这说明离子液体含量越高，对原料气中环氧乙烷的选择吸收性越高。
对比实施例b1-1、实施例b1-2、实施例b1-3和实施例b1-4可以看出，随着离子液体含量的增加，EO脱除率呈现下降趋势。这是由于离子液体粘度较大，当其含量较高时，影响对环氧乙烷的吸收效果。但是从实施例b1-5的数据中可以看出，离子液体含量太低会使得解吸塔塔顶得到的EO浓度明显降低，即降低了复合吸收剂对环氧乙烷的吸收选择性。
实施例b2：
本组实施例提供了一种复合吸收剂及其分离纯化环氧乙烷的方法。所述复合吸收剂由离子液体1-羟乙基-3-甲基咪唑四氟硼酸盐([Hemim][BF 4])与碳酸乙烯酯组成，并将该复合吸收剂对含环氧乙烷原料气进行吸收与解吸，具体操作如下：
将60℃含2.26％环氧乙烷的混合气由塔底进入吸收塔T1，离子液体[Hemim][BF 4]与碳酸乙烯酯混合均匀后从吸收塔T1塔顶进入，经吸收后测定塔顶环氧乙烷的含量。含环氧乙烷的吸收剂经换热加热至一定温度进入60kPa的解吸塔T2中，通过解吸后得到塔顶环氧乙烷的含量，脱气后的离子液体与碳酸乙烯经过换热到60℃后进入吸收塔T1继续充当吸收剂循环使用。具体参数和相应的结果如下表2所示：
表2
Figure PCTCN2020080560-appb-000004
Figure PCTCN2020080560-appb-000005
从表2中数据可以看出使用1-羟乙基-3-甲基咪唑四氟硼酸盐和碳酸乙烯酯复配得到的复合吸收剂分离纯化环氧乙烷的中环氧乙烷的脱除率可达93.1％-99.6％，这表明离子液体的加入可以提高对环氧乙烷吸收分离能力，吸收效果显著；同时，使用上述复合吸收剂分离纯化环氧乙烷得到的解吸塔塔顶环氧乙烷的纯度均高于82.4％，即对原料气中环氧乙烷的选择吸收性明显提高。
对比实施例b2-1、实施例b2-2、实施例b2-3和实施例b2-4，可以看出，随着离子液体含量的增加，EO脱除率呈现下降趋势，而解吸塔塔顶EO浓度呈上升趋势。这与表1中的数据结论一致。
实施例b3：
本组实施例提供了一种复合吸收剂及其分离纯化环氧乙烷的方法。所述复合吸收剂由离子液体1-胺乙基-3-甲基咪唑四氟硼酸盐([C 2NH 2mim][BF 4])与碳酸乙烯酯组成，将该复合吸收剂对含环氧乙烷原料气的吸收与解吸，具体操作如下：
将70℃含2.26％的环氧乙烷混合气由塔底进入吸收塔T1，离子液体[C 2NH 2mim][BF 4])与碳酸乙烯酯混合均匀后从吸收塔T1塔顶进入，经吸收后测定塔顶环氧乙烷的含量。含环氧乙烷的吸收剂经换热加热至一定温度进入70kPa的解吸塔T2中，通过解吸后得到塔顶环氧乙烷的含量，脱气后的离子液体与碳酸乙烯经过换热到70℃后进入吸收塔T1继续充当吸收剂循环使用。具体参数和相应的结果如下表3所示：
表3
Figure PCTCN2020080560-appb-000006
Figure PCTCN2020080560-appb-000007
从表3中数据可以看出使用1-胺乙基-3-甲基咪唑四氟硼酸盐和碳酸乙烯酯复配得到的复合吸收剂分离纯化环氧乙烷的中环氧乙烷的脱除率可达94.7％-99.8％，这表明离子液体的加入可以提高对环氧乙烷吸收分离能力，吸收效果显著。
对比实施例b3-1、实施例b3-2、实施例b3-3和实施例b3-4可以看出，随着离子液体含量的增加，EO脱除率呈现下降趋势，而解吸塔塔顶EO浓度呈上升趋势，即EO的选择性呈上升趋势。这与表1和表2中的数据结论一致。
实施例b2使用的离子液体为1-羟乙基-3-甲基咪唑四氟硼酸盐，实施例b3使用的离子液体为1-胺乙基-3-甲基咪唑四氟硼酸盐，两种离子液体的区别仅在于阳离子的取代基不同，实施例b2离子液体的阳离子取代基为羟基，实施例b3离子液体的阳离子取代基为氨基；将表2和表3中数据对比可以看出，当阳离子取代基为羟基时，解吸塔塔顶得到的环氧乙烷的纯度更高，而脱除率更低，即其吸收分离环氧乙烷的选择性大于氨基，但是吸收能力小于氨基。
对比例b1
本组对比例提供了一种吸收剂及其分离纯化环氧乙烷的方法，与实施例b1的区别仅在于，所述吸收剂仅由碳酸乙烯酯组成。
具体参数和相应的结果如下表4所示：
表4
Figure PCTCN2020080560-appb-000008
对比表4和表1-3中的数据可以看出，将仅含碳酸乙烯酯的吸收剂对环氧乙烷进行分离纯化，解吸塔塔顶得到的环氧乙烷的纯度明显低于含离子液体的复合吸收剂，这说明单一碳酸乙烯酯对环氧乙烷的选择性明显低于使用离子液体和碳酸乙烯酯的复合吸收剂，即离子液体的加入可以提高对环氧乙烷吸收分离的选择性，吸收效果显著。
对比例b2
本对比例提供了一种复合吸收剂及其分离纯化环氧乙烷的方法。与实施例b1的区别仅在于，将1-羟乙基-3-甲基咪唑六氟磷酸盐([Hemim][PF 6])替换为水，具体操作如下：
将50℃含2.26％环氧乙烷的混合气由塔底进入吸收塔T1，水与碳酸乙烯酯混合均匀后从吸收塔T1塔顶进入，经吸收后测定塔顶环氧乙烷的含量。含环氧乙烷的吸收剂经换热加热至一定温度进入50kPa的解吸塔T2中，通过解吸后得到塔顶环氧乙烷的含量，脱气后的水与碳酸乙烯酯经过换热到50℃后进入吸收塔T1继续充当吸收剂循环使用。具体参数和相应的结果如下表5所示：
具体参数和相应的结果如下表5所示：
表5
Figure PCTCN2020080560-appb-000009
对比表5和表1-3中的数据可见，本申请使用含离子液体的复合吸收剂对环氧乙烷进行分离纯化，解吸塔塔顶得到的环氧乙烷的浓度明显高于使用水和碳酸乙烯酯的复合吸收剂得到的环氧乙烷的浓度，这说明含有离子液体的复合吸收剂的选择吸收性明显高于使用水和碳酸乙烯酯的复合吸收剂的选择吸收性，这说明本申请所述含离子液体的复合吸收剂吸收能力强，吸收效果显著，为高效分离纯化环氧乙烷提供了新的选择。
申请人声明，以上所述仅为本申请的具体实施方式，但本申请的保护范围并不局限于此。

Claims (21)

  1. 一种复合吸收剂，其中，所述复合吸收剂包括离子液体和碳酸乙烯酯，所述离子液体的结构如式I所示：
    Figure PCTCN2020080560-appb-100001
    其中，式I中的R 1和R 2各自独立地选自取代或未取代的C1-C6烷基、取代或未取代的C2-C6烯基、取代或未取代的C2-C6炔基、取代或未取代的C6-C30芳基、取代或未取代的C3-C30杂芳基或取代或未取代的C1-C6烷氧基中的任意一种；
    式I中的阴离子X -选自BF 4 -、PF 6 -、Tf 2N -、RCOO -、Cl -或Br -中的任意一种；R选自烷基、烯基或炔基中的任意一种。
  2. 如权利要求1所述的复合吸收剂，其中，阴离子X -选自BF 4 -、PF 6 -、Tf 2N -或RCOO -中的任意一种，可选为BF 4 -或PF 6 -。
  3. 如权利要求1或2所述的复合吸收剂，其中，R 1和R 2中所述取代的基团各自独立地选自羟基、氨基、硝基、醛基、酯基、羧基或巯基中的任意一种；
    可选地，R 1和R 2中所述取代的基团为羟基或氨基。
  4. 如权利要求1-3中任一项所述的复合吸收剂，其中，所述离子液体选自1-羟乙基-3-甲基咪唑六氟磷酸盐、1-羟乙基-3-甲基咪唑四氟硼酸盐、1-胺乙基-3-甲基咪唑四氟硼酸盐、1-胺乙基-3-甲基咪唑六氟磷酸盐、1-羟乙基-3-乙基咪唑六氟磷酸盐或1-羟乙基-3-乙基咪唑四氟硼酸盐中的任意一种或至少两种的组合；
    可选地，所述离子液体在所述复合吸收剂中的质量占比为10-60％，可选为 30-50％。
  5. 一种环氧乙烷分离纯化的方法，其中，所述方法使用如权利要求2-4任一项所述的复合吸收剂。
  6. 根据权利要求5所述的方法，其中，所述方法包括如下步骤：将所述复合吸收剂与含有环氧乙烷的原料气接触，脱环氧乙烷后的贫混合气返回乙烯氧化阶段，富环氧乙烷吸收液进行解吸得到环氧乙烷。
  7. 根据权利要求5或6所述的方法，其中，所述方法包括如下步骤：将所述复合吸收剂与含有环氧乙烷的原料气在吸收塔内逆流充分接触，塔顶脱环氧乙烷后的贫混合气经过处理后返回乙烯氧化阶段，塔釜富环氧乙烷吸收液经换热后进入解吸塔，解吸后气相塔顶采出，得到环氧乙烷，解吸后液相的解吸贫液从塔釜经过换热后返回吸收塔。
  8. 根据权利要求7所述的方法，其中，所述原料气中环氧乙烷的摩尔浓度为0.1-5％，可选为2-3％。
  9. 根据权利要求7或8所述的方法，其中，所述吸收塔的操作压力为0.1-5MPa，可选为1-3MPa；
    可选地，所述吸收塔的操作温度为40-100℃，可选为50-80℃；
    可选地，所述复合吸收剂与所述原料气的摩尔比为(1-4):1，可选为(2-3):1；
    可选地，所述解吸塔的操作压力为10-150kPa，可选为50-150kPa；
    可选地，所述解吸塔的操作温度为80-150℃，可选为90-130℃。
  10. 根据权利要求7-9任一项所述的方法，其中，所述解吸贫液换热至50-80℃后循环回所述吸收塔。
  11. 根据权利要求7-10任一项所述的方法，其中，所述富环氧乙烷吸收液换热至90-130℃后进入所述解吸塔。
  12. 一种复合吸收剂，其中，所述复合吸收剂包括离子液体和碳酸乙烯酯，所述离子液体的结构如式Ⅱ或式Ⅲ所示：
    Figure PCTCN2020080560-appb-100002
    式Ⅱ中的R 3、R 4、R 5和R 6各自独立地选自取代或未取代的C1-C6烷基、取代或未取代的C2-C6烯基、取代或未取代的C2-C6炔基、取代或未取代的C6-C30芳基、取代或未取代的C3-C30杂芳基或取代或未取代的C1-C6烷氧基中的任意一种；
    式Ⅲ中的R 7、R 8、R 9和R 10各自独立地选自取代或未取代的C1-C6烷基、取代或未取代的C2-C6烯基、取代或未取代的C2-C6炔基、取代或未取代的C6-C30芳基、取代或未取代的C3-C30杂芳基或取代或未取代的C1-C6烷氧基中的任意一种；
    式Ⅱ和式Ⅲ中的阴离子X -各自独立地选自Cl -、Br -或I -中的任意一种。
  13. 根据权利要求1或12所述的复合吸收剂，其中，式I、式Ⅱ和式Ⅲ中，所述取代的基团各自独立地选自羟基、氨基、硝基、醛基、酯基、羧基、亚硝基、酰胺基或羰基中的任意一种。
  14. 根据权利要求1、12或13任一项所述的复合吸收剂，其中，所述离子液体与碳酸乙烯酯质量比为1:(1-10)。
  15. 一种环氧乙烷吸收转化耦合联产碳酸乙烯酯的方法，其中，所述方法使用如权利要求1、12-14中任一项所述的复合吸收剂。
  16. 根据权利要求15所述的方法，其中，所述方法包括如下步骤：将所述 复合吸收剂与含有环氧乙烷的原料气接触，得到的富环氧乙烷吸收液进入主反应器中，得到碳酸乙烯酯。
  17. 根据权利要求15或16所述的方法，其中，所述方法包括如下步骤：将所述复合吸收剂与含有环氧乙烷原料气在吸收塔内逆流充分接触，塔顶脱环氧乙烷后的贫混合气经过处理后返回乙烯氧化阶段，塔釜富环氧乙烷吸收液经换热后进入主反应器，反应，得到反应液，将得到的包含离子液体的反应液一部分作为吸收液循环，另一部分经过处理后得到高纯度的碳酸乙烯酯。
  18. 根据权利要求17所述的方法，其中，所述复合吸收剂与所述含有环氧乙烷原料气的质量比为(1-5):1，可选为(2-3):1。
  19. 根据权利要求17或18所述的方法，其中，所述吸收塔的操作压力为1-5MPa，可选1.5-2.5MPa；
    可选地，所述吸收塔的操作温度为50-100℃，可选为60-80℃；
    可选地，所述主反应器的反应压力为1-5MPa，可选2-3MPa；
    可选地，所述主反应器的反应温度为80-300℃，可选为100-200℃；
    可选地，所述反应的时间为0.5-5h，可选为1-3h。
  20. 根据权利要求17-19任一项所述的方法，其中，所述富环氧乙烷吸收液换热至100-200℃后进入主反应器。
  21. 根据权利要求17-20任一项所述的方法，其中，所述反应液的一部分进入吸收塔前降温至60-80℃。
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CHENG MUXI, WANG KAI; HE LIN; TAN YANAN; WANG HUA; ZHENG MIN; WANG KE: "Catalyst study of the ethylene oxide and carbon dioxide esterification reaction to produce ethylene carbonate ", CHEMICAL INDUSTRY AND ENGINEERING PROGRESS, vol. 36, no. S1, 15 November 2017 (2017-11-15), pages 274 - 277, XP055785747, ISSN: 1000-6613 *

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