A complex absorbent, its application and a method for recovering an epoxy butane tail gas

Abstract

The present application relates to a kind of complex absorbent and its application and the method for recovering epoxy butane in epoxy butane tail gas mixture using complex absorbent, comprising the following steps: the epoxy butane tail gas mixture containing in the feed to absorption tower is absorbed under the action of complex absorbent, and the absorbed tail gas is discharged at tower top after absorption, after the absorption liquid mixture at tower bottom after separation is flashed by flash tank, desorption is obtained complex absorbent and target product epoxy butane, and the complex absorbent obtained after separation is mixed with supplementary fresh absorbent and reused.The epoxy butane content in the absorbed tail gas obtained by the present application is close to 0.Compared with prior art, the present application simplifies the process flow of epoxy butane recovery in tail gas, saves production cost, and has high absorption separation efficiency.

Description

Technical Field

[0001] This invention relates to a compound absorbent, its application, and a method for recovering epoxide tail gas. Background Technology

[0002] Butylene oxide, also known as 1,2-epoxybutane, is a chemical substance with a three-membered ring structure. Industrially, butylene oxide is derived from the recovery of byproducts in the production of propylene oxide. Similar in chemical properties to propylene oxide, butylene oxide can be used as a raw material monomer for polyether polyols and also as a thinner for nitrocellulose lacquer, replacing acetone. Butylene oxide has wide applications in surfactants, synthetic rubber, synthetic plastics, and agrochemicals.

[0003] Currently, the main methods for purifying industrial exhaust gas mixtures containing propylene oxide or ethylene oxide are high-temperature catalytic combustion, chemical absorption, and solid acid catalysis.

[0004] CN01274679.7 discloses a treatment method that introduces waste gas into an incineration system for catalytic combustion, but flammable substances such as propylene oxide are prone to reaching their explosion limits at high temperatures, posing a serious safety hazard.

[0005] CN200910188103.4 discloses a method for converting propylene oxide into propylene glycol through a ring-opening reaction with water under acid catalysis. However, this process is complex, produces many byproducts, and pollutes the environment.

[0006] CN102357309A discloses a method for recovering epoxides by water spraying under acid catalysis, but this process has the disadvantage of slow reaction rate.

[0007] CN111116517A discloses a method for physically absorbing butane oxide using n-octane or isooctane, but the process is complex and cumbersome, with high input costs, and low returns without introducing a butane oxide production process.

[0008] CN111116519A relates to a method for utilizing epoxides. This invention involves feeding tail gas containing epoxides, nitrogen, water, aldehydes, and methanol (or acetone or isopropanol) into a compressor, pressurizing it, and then cooling it in a cooler. The coolant then enters a gas-liquid separator for separation. The gas phase enters from the bottom of the absorption tower, while the cold methanol solution enters from the top. The gas phase at the top of the absorption tower is sent to a flare for further processing. The liquid phase at the bottom of the tower and the liquid phase at the bottom of the gas-liquid separator are mixed and then sent to an extractive distillation column in the epoxide refining unit. This method effectively recovers epoxides from the tail gas, reduces the propylene oxide content in the exhaust gas, and can be used in the industrial production of epoxide plants.

[0009] CN111116515A relates to a method for recovering epoxide alkane. This invention involves feeding tail gas containing epoxide alkane, nitrogen, water, acetaldehyde, etc., into a compressor. After compression, the gas enters a condenser where it is cooled with water. A solution of cumene or ethylbenzene is added to the condensate, and the mixture is thoroughly mixed in a mixer. Gas-liquid separation occurs in a gas-liquid separator. The liquid phase is then separated in a high-efficiency liquid-liquid separator, and the organic phase is fed into a crude epoxide alkane separation tower in an epoxidation unit. This method effectively recovers epoxide alkane from the tail gas, reduces the water content in the recovered epoxide alkane, and can be used in the industrial production of epoxide alkane plants.

[0010] CN111116516A relates to a method for recovering epoxides. This invention involves feeding tail gas containing epoxides, nitrogen, water, and acetaldehyde into a pressurization unit (e.g., a compressor). After pressurization, the gas enters a cooler for cooling. The coolant is then separated into gas and liquid phases by a gas-liquid separator. The gas phase enters from the bottom of the absorption tower, while the cold extractant enters from the upper part of the tower. The gas phase at the top of the absorption tower is sent to a flare for further processing. The liquid phase at the bottom of the tower is mixed with the liquid phase at the bottom of the gas-liquid separator and then sent to an epoxide refining unit for extractive distillation to recover the epoxides. This method effectively recovers epoxides from the tail gas, reduces the epoxide content in the exhaust gas, and effectively solves the VOCs emission problem. It can be used in the industrial production of epoxide plants.

[0011] CN111116518A relates to a method for recovering and utilizing epoxides. This invention involves pressurizing tail gas containing epoxides, nitrogen, water, aldehydes, and methanol, and then introducing it from the bottom of an absorption tower. The absorbent enters from the top of the tower. The gas phase at the top of the absorption tower undergoes post-treatment such as a flare, while the liquid phase at the bottom of the tower is sent to an extractive distillation column in an epoxide refining unit. This method effectively recovers epoxides from the tail gas, reduces the propylene oxide content in the emitted tail gas, and can be used in the industrial production of epoxide plants. Summary of the Invention

[0012] To overcome the difficulties in the prior art, the present invention aims to provide a method for recovering epoxide tail gas, using a compound solvent composed of anions and cations with high partition coefficient and high selectivity as the absorbent. Preferably, the method combines absorption in an absorption tower and desorption in a gas-liquid separator to recover epoxide from the epoxide-containing tail gas without the need for a desorption tower. The ionic liquid absorbent has high absorption efficiency, and the content of ionic liquid in the tail gas after absorption is close to 0.

[0013] This invention innovatively combines a compound absorbent and a dual-tower process, simplifying the process of recovering epoxide from tail gas, increasing the yield of epoxide tail gas, and reducing process energy consumption.

[0014] The compound absorbent of this invention is a salt composed entirely of cations and anions, which is liquid at or near room temperature. It mainly contains alkylpyrrole cations, thiocyanate anions, and amino acid anions. This compound absorbent exhibits good thermal and chemical stability, is non-volatile, non-flammable, and non-toxic, making it a green solvent with a wide operating temperature range and good solubility for both organic and inorganic substances.

[0015] The interaction mechanism between the composite absorbent and epoxide described in this invention is explained from a molecular perspective. The Dmol3 module in Materials Studio software was used to optimize and analyze the molecular / ionic and molecular cluster structures, ultimately obtaining the intermolecular interaction energies. GGA / VWN-BP density functional theory and DNP were employed in the calculations. + The basis set, the interaction energies between different molecules / ions are calculated using the following formula:

[0016] ΔE binding =E AB -E A -E B

[0017] In the formula, E AB E is the intermolecular interaction energy. A and E B The energies of molecules A and B are calculated as follows:

[0018]

[0019] As described above, the cations and anions in the composite absorbent of this invention exhibit strong mutual attraction with the butylene oxide in the tail gas to be absorbed. This further verifies the feasibility of the composite solvent of this invention as an butylene oxide absorbent.

[0020] According to a first aspect of the present invention, the present invention provides a compound absorbent containing: alkylpyrrole cation, thiocyanate anion and amino acid anion; preferably, the molar ratio of alkylpyrrole cation, thiocyanate anion and amino acid anion is 10:1 to 7:3 to 9.

[0021] According to a second aspect of the present invention, the present invention provides a method for recovering epoxide tail gas, the method comprising: (1) contacting a mixture of epoxide tail gas with a compound absorbent for absorption, and discharging the absorbed tail gas; (2) desorbing the absorbent mixture of step (1) to obtain a compound absorbent and the target product epoxide; optionally, returning the desorbed compound absorbent to step (1) for recycling; wherein the compound absorbent is the compound absorbent described in the present invention.

[0022] According to a third aspect of the invention, the invention provides the application of a compound absorbent in the treatment of alkylene oxide-containing gases.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (1) The composite absorbent containing alkyl pyrrole cations, thiocyanate anions and amino acid anions used in this invention has strong chemical stability, high thermal stability, safety, low dosage and good effect, and all three are indispensable.

[0025] (2) In a preferred embodiment of the present invention, by using a dual-tower process and designing different operating conditions and structural parameters, the heat load can be reduced and the economic efficiency of the device can be improved.

[0026] (3) In the preferred embodiment of the present invention, the combination of compound absorbent and dual tower process not only simplifies the process and increases the absorption and separation efficiency, but also reduces the amount of absorbent used, minimizes losses, saves production costs, and is environmentally friendly.

[0027] (4) There are few reports on the recovery of epoxide tail gas. CN111116517A discloses a method for physically absorbing epoxide using n-octane or isooctane, but the process is complicated and cumbersome, with high input costs and low returns without introducing epoxide production process.

[0028] (5) The content of epoxide in the exhaust gas after absorption obtained by the method of the present invention is less than 5 ppm, close to 0, and the overall mass loss rate of the compound absorbent is less than 0.01%. Attached Figure Description

[0029] Figure 1 The diagram shown is a flow chart of the absorption-desorption process in an embodiment of the present invention. Detailed Implementation

[0030] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0031] In this invention, the composite absorbent only needs to contain the aforementioned ions to achieve the purpose of this invention, for example, it can be one or more ionic liquids containing the aforementioned ions. Ionic liquids refer to salts that are liquid at room temperature or near room temperature and are composed entirely of cations and anions. Common cations include quaternary ammonium salts and imidazole salts, while anions include halide ions and tetrafluoroborate ions. In this invention, ionic liquids can be designed and synthesized according to different combinations of cations and anions; this invention does not have special requirements in this regard and will not be described in detail here.

[0032] The present invention provides a compound absorbent containing: alkylpyrrole cations, thiocyanate anions, and amino acid anions.

[0033] In this invention, the ratio of alkylpyrrole cations, thiocyanate anions, and amino acid anions can be selected within a wide range. Preferably, for this invention, the molar ratio of alkylpyrrole cations, thiocyanate anions, and amino acid anions is 10:1 to 7:3 to 9. The composite absorbent containing alkylpyrrole cations, thiocyanate anions, and amino acid anions of this invention exhibits strong chemical stability, high thermal stability, safety, low dosage, and excellent effect; all three components are indispensable.

[0034] In this invention, any alkylpyrrole cation can be used. According to a preferred embodiment of this invention, the general structural formula of the alkylpyrrole cation is: R1 is any one of a normal or isoalkyl group containing 1 to 3 carbon atoms, preferably a normal alkyl group, such as methyl, ethyl, n-propyl or isopropyl.

[0035] According to a preferred embodiment of the present invention, the general structural formula of the thiocyanate anion is:

[0036] In this invention, amino acid anions can all be used. According to a preferred embodiment of this invention, the general structural formula of amino acid anions is: R2 is any one of the alkane groups containing 1 to 3 carbon atoms, such as methyl, ethyl, propyl or isopropyl.

[0037] The compound absorbent of this invention can be used in various absorption fields, and is particularly suitable for application in the absorption of tail gases containing alkyl oxides. This invention provides the application of the compound absorbent of this invention in the treatment of gases containing alkyl oxides, preferably wherein the alkyl oxide is propylene oxide and / or butane oxide, more preferably butane oxide.

[0038] In this invention, the preferred composite absorbent is an ionic liquid containing alkylpyrrole cations, thiocyanate anions, and amino acid anions.

[0039] In this invention, there are no special requirements for the preparation method of the compound absorbent; as long as the compound absorbent as required by the present invention can be obtained, the purpose of the present invention can be achieved.

[0040] According to a preferred embodiment of the present invention, the present invention provides a method for recovering epoxide tail gas, the method comprising:

[0041] (1) The mixture of tail gas containing epoxide is contacted with a compound absorbent for absorption, and the absorbed tail gas is discharged.

[0042] (2) The absorbent mixture from step (1) is desorbed to obtain a compound absorbent and the target product, butane oxide; optionally, the desorbed compound absorbent is returned to step (1) for recycling; the compound absorbent is the compound absorbent described in this invention. Currently, there are few reports on butane oxide tail gas recovery. CN111116517A discloses a method for physically absorbing butane oxide using n-octane or isooctane, but this process is complex and cumbersome, with high input costs, and low returns without introducing a butane oxide production process. The butane oxide content in the absorbed tail gas obtained by the method of this invention is less than 5 ppm, close to 0, and the overall mass loss rate of the compound absorbent is less than 0.01%.

[0043] According to a preferred embodiment of the present invention, the method includes:

[0044] (1) The mixture of epoxide-containing tail gas fed into the absorption tower is absorbed by the compound absorbent and then discharged at the top of the tower.

[0045] (2) The bottom absorbent mixture separated in step (1) is desorbed by flash evaporation in a flash tank to obtain the compound absorbent and the target product epoxide butane. The compound absorbent obtained by separation is mixed with fresh compound absorbent and returned to step (1) for recycling.

[0046] The purpose of this invention can be achieved by using any method of this invention. There are no special requirements for the feeding process and the operating conditions for absorption and desorption. The specific requirements can be adjusted according to the actual process.

[0047] According to a preferred embodiment of the present invention, during the feeding process, the feeding temperature of the compound absorbent is 10-45°C and the feeding pressure is 0.15-0.50 MPaG.

[0048] According to a preferred embodiment of the present invention, during the feeding process, the feed temperature of the mixture containing epoxide tail gas is 25-50°C and the feed pressure is 0.15-0.50 MPaG.

[0049] According to a preferred embodiment of the present invention, during the absorption process, the operating temperature is 30-55°C and the operating pressure is 0.15-0.50 MPaG.

[0050] According to a preferred embodiment of the present invention, during the desorption process, the operating temperature is 30-55°C and the operating pressure is 0.005-0.050 MPaG.

[0051] In this invention, temperature and pressure can be conventionally selected, and those skilled in the art can make reasonable selections based on the method of this invention. This is not the focus of this invention and will not be described in detail.

[0052] According to a preferred embodiment of the present invention, the absorption process is carried out based on an absorption tower, wherein the theoretical plate number of the absorption tower is 10 to 30.

[0053] The aforementioned preferred process parameters can all play a positive role in the absorption method of the present invention, which can reasonably promote the absorption of exhaust gas and reduce the operational risks of the device.

[0054] According to a preferred embodiment of the present invention, the tail gas mixture containing butylene oxide may include various gases such as butylene oxide and nitrogen. This paper focuses on demonstrating the assistance of the novel absorbent in the recovery of butylene oxide, and the possibility of the absorbent recovering butylene oxide has been analyzed from the perspective of intermolecular forces. The specific composition of the tail gas mixture, such as nitrogen, does not affect the absorption of butylene oxide and can be disregarded. In this invention, the ionic liquid is composed of cations and anions; for example, the solvent composed of cations and anions in this paper is a low-temperature molten salt at room temperature or near room temperature.

[0055] The source of the butane oxide-containing tail gas mixture of the present invention is not particularly required. Preferably, the butane oxide-containing tail gas mixture is derived from the recovery of by-products from the industrial production of propylene oxide.

[0056] According to a preferred embodiment of the present invention, the volume ratio of the butane oxide-containing tail gas mixture to the compound absorbent is 1:1-5. This ratio refers to the absorption process ratio; in reality, the absorbent can be almost completely recycled and reused, therefore the volume ratio has no specific impact on industrial implementation.

[0057] According to a preferred embodiment of the present invention, a mixture of butane-containing tail gas is absorbed by countercurrent contact with a compound absorbent.

[0058] There are no special requirements on the entry location and manner of the butane oxide-containing tail gas mixture into the absorption tower. According to a preferred embodiment of the present invention, the butane oxide-containing tail gas mixture enters the absorption tower from the middle or lower part of the absorption tower, for example, from the lowest theoretical plate.

[0059] According to a preferred embodiment of the present invention, the recycling refers to selectively mixing the desorbed compound absorbent with fresh compound absorbent and introducing it into the compound absorbent feed position of the absorption tower.

[0060] According to a preferred embodiment of the present invention, the compound absorbent returned from the flash tank is mixed with fresh compound absorbent and then introduced into the absorption tower from the first theoretical plate of the absorption tower.

[0061] According to a preferred embodiment of the present invention, a method for recovering epoxide tail gas using a compound absorbent is provided, comprising the following steps:

[0062] The mixture of epoxide-containing tail gas fed into the absorption tower is absorbed by the compound absorbent and discharged at the top of the tower. The bottom absorbent mixture after separation is desorbed by flash evaporation in a flash tank to obtain the compound absorbent and the target product epoxide. The separated compound absorbent is mixed with fresh absorbent and recycled.

[0063] The compound absorbent is composed of alkyl pyrrole cations, thiocyanate anions, and amino acid anions in a molar ratio of 10:1 to 7:3 to 9.

[0064] Specifically, the general structural formula of alkylpyrrole cations is: The general structural formula of the thiocyanate anion is: The general structural formula of amino acid anions is: Wherein R1 is any one of the normal or isomeric alkyl groups containing 1 to 3 carbon atoms, and R2 is any one of the alkane groups containing 1 to 3 carbon atoms.

[0065] According to a preferred embodiment of the present invention, during the feeding process, the feed temperature of the compound absorbent is 10–45°C, and the feed pressure is 0.15–0.50 MPaG; the feed temperature of the mixture containing epoxide tail gas is 25–50°C, and the feed pressure is 0.15–0.50 MPaG. During the absorption process, the operating temperature of the absorption tower is 30–55°C, and the operating pressure is 0.15–0.50 MPaG. During the desorption process, the operating temperature of the flash tank is 30–55°C, and the operating pressure is 0.005–0.050 MPaG.

[0066] According to a preferred embodiment of the present invention, the design of the absorption tower absorption-gas-liquid separator desorption process of this application obtains high-purity epoxide butane tail gas based on the separation performance of the selected compound absorbent, while simultaneously utilizing a flash tank to recover the compound absorbent for recycling. Preferably, the absorption process is carried out based on an absorption tower, wherein the theoretical plate number of the absorption tower is 10 to 30, and the recycling of the compound absorbent refers to introducing the absorbent separated from the bottom of the flash tank into the compound absorbent feed inlet of the absorption tower.

[0067] According to a preferred embodiment of the present invention, the epoxide-containing tail gas mixture is introduced into the absorption tower from the bottom, specifically from the middle or lower middle part of the absorption tower, for example, from the bottommost theoretical plate.

[0068] According to a preferred embodiment of the present invention, the compound absorbent returned from the flash tank is mixed with freshly replenished compound absorbent and then introduced into the absorption tower from the first theoretical plate of the absorption tower.

[0069] All unspecified components or contents described in this invention refer to mass composition or content.

[0070] This invention provides a method for recovering epoxide tail gas, which achieves low-energy consumption and high-efficiency recovery of high-purity epoxide products by combining the absorption performance of a compound absorbent with a dual-tower process.

[0071] Figure 1 This is a flow chart of the absorption-desorption separation process of the present invention. A mixture of butane-containing tail gas is introduced into the absorption tower from the bottom and comes into countercurrent contact with the compound absorbent entering from the top of the tower to achieve absorption. The absorbed tail gas is discharged from the top of the absorption tower to the next processing stage or directly vented. The bottom stream of the absorption tower is a mixture of the compound absorbent and butane-containing tail gas, which is pumped to a flash tank. After flash evaporation, the target product, butane-containing tail gas, is obtained from the top of the flash tank. The compound absorbent at the bottom of the flash tank is mixed with fresh replenished compound absorbent and then fed to the top of the absorption tower for recycling.

[0072] Figure 1 Only the most basic absorption-desorption process is given, without mentioning valves, pumps, heaters, condensers, etc., but this is well known to those skilled in the art.

[0073] Example 1

[0074] A compound absorbent with a molar ratio of 1-ethyl-1-methylpyrrole cation, thiocyanate anion, and amino acid anion (R2 being methyl) of 10:5:5 was used to achieve a solvent ratio of 1:1 (molar ratio of absorbent to the epoxide-containing tail gas mixture) for the absorption-desorption operation. Figure 1 The process involves absorption and separation of tail gas containing epoxide, and the implementation steps are as follows:

[0075] a) A tail gas mixture with an epoxide content of 25 vol% (the rest being nitrogen) is introduced into the bottom of the absorption tower;

[0076] b) At the same time, the compound absorbent returned from the flash tank is mixed with the replenished fresh compound absorbent and pumped to the top of the absorption tower. The ratio of the total amount of circulating compound absorbent and replenished fresh compound absorbent to the total amount of exhaust gas is 1:1 (molar ratio).

[0077] c) The absorbed exhaust gas is drawn out from the top of the absorption tower after absorption;

[0078] d) The mixture of compound absorbent and epoxide is drawn from the bottom of the absorption tower and sent to the flash tank;

[0079] e) Obtain high-purity epoxide butane product from the top of the flash tank;

[0080] f) The compound absorbent drawn from the bottom of the flash tank is circulated to the absorption tower.

[0081] The above operating conditions, raw material composition, solvent ratio, solubility of the circulating compound absorbent, content of epoxide in the tail gas after absorption, and epoxide product indicators are listed in Table 1.

[0082] Example 2

[0083] This embodiment is basically the same as Embodiment 1, except that:

[0084] The butane oxide content in the tail gas feed is 40 vol% (the remainder is nitrogen). Due to the increased butane oxide content in the raw material to be treated, while the molar ratio of the compound absorbent to the raw material remains at 1:1, the butane oxide content in the tail gas after absorption increases slightly, but still meets the absorption requirements. The operating conditions and various product indicators of this example are listed in Table 1.

[0085] Example 3

[0086] This embodiment is basically the same as Embodiment 1, except that:

[0087] The butane oxide content in the tail gas feed is 45 vol% (the remainder is nitrogen). Due to the increased butane oxide content in the raw material to be treated, while the molar ratio of the compound absorbent to the raw material remains at 1:1, the butane oxide content in the tail gas after absorption increases slightly, but still meets the absorption requirements. The operating conditions and various product indicators of this example are listed in Table 1.

[0088] Example 4

[0089] The exhaust gas feed contains 55 vol% epoxide butane (the remainder is nitrogen), the difference being:

[0090] The solvent ratio for the absorption process was 1.5:1. The results show that as the solvent ratio increases, the epoxide in the tail gas is absorbed more completely. The operating conditions and product specifications for this example are listed in Table 1.

[0091] Example 5

[0092] The exhaust gas feed contains 60 vol% epoxide butane (the remainder is nitrogen), the difference being:

[0093] The solvent ratio in the absorption process was 2:1. It is evident that as the solvent ratio increases, the epoxide in the tail gas is absorbed more completely. The operating conditions and product specifications for this embodiment are listed in Table 1.

[0094] Example 6

[0095] The exhaust gas feed contains 35 vol% epoxide butane (the remainder is nitrogen), the difference being:

[0096] A composite absorbent was used, consisting of 1-isopropyl-1-methylpyrrole cations, thiocyanate anions, and amino acid ions (R2 being methyl) in a molar ratio of 10:5:5. The change in the composite absorbent affected the composition distribution within the column, thus impacting the absorption efficiency. The fundamental reason for this was the steric hindrance created by the branched absorbent, which slightly weakened the absorption effect. The operating conditions and product specifications for this embodiment are listed in Table 1.

[0097] Example 7

[0098] The content of epoxide butane in the exhaust gas feed is 32 vol%, the difference is:

[0099] A compound absorbent was used, consisting of 1-n-propyl-1-methylpyrrole cation, thiocyanate anion, and amino acid anion (R2 being methyl) in a molar ratio of 10:3:7. The operating conditions and product specifications for this example are listed in Table 1.

[0100] Example 8

[0101] The difference is that the epoxide butane content in the exhaust gas feed is 30 vol%.

[0102] A compound absorbent was used, consisting of 1-ethyl-1-methylpyrrole cation, thiocyanate anion, and amino acid anion (R2 being methyl) in a molar ratio of 10:6:4. The operating conditions and product specifications for this example are listed in Table 1.

[0103] Example 9

[0104] This embodiment is basically the same as Embodiment 1, except that:

[0105] A compound absorbent was used, consisting of 1-ethyl-1-methylpyrrole cation, thiocyanate anion, and amino acid anion (R2 being ethyl) in a molar ratio of 10:5:5. The operating conditions and product specifications for this example are listed in Table 1.

[0106] Example 10

[0107] This embodiment is basically the same as Embodiment 1, except that:

[0108] A compound absorbent was used, consisting of 1-ethyl-1-methylpyrrole cation, thiocyanate anion, and amino acid anion (R2 being n-propyl) in a molar ratio of 10:5:5. The operating conditions and product specifications for this example are listed in Table 1.

[0109] Example 11

[0110] This embodiment is basically the same as Embodiment 1, except that:

[0111] A composite absorbent was used, consisting of a 10:5:5 molar ratio of 1-(2,2-dimethylbutane)-1-methylpyrrole cation, thiocyanate anion, and amino acid anion (R2 being isopropyl). Under the same operating conditions, the yield of the target product, epoxide, decreased slightly. The operating conditions and product specifications for this example are listed in Table 1.

[0112] Example 12

[0113] This embodiment is basically the same as Embodiment 1, except that:

[0114] A composite absorbent was used, consisting of 1-ethyl-1-methylpyrrole cation, thiocyanate anion, and amino acid anion (R2 being isobutyl) in a molar ratio of 10:5:5. Under the same operating conditions, the yield of the target product, epoxide, decreased slightly. The operating conditions and product specifications for this example are listed in Table 1.

[0115] Comparative Example 1

[0116] This embodiment is basically the same as Embodiment 1, except that:

[0117] A compound absorbent with a 1:1 molar ratio of 1-ethyl-1-methylpyrrole cation and amino acid anion (R2 being methyl) was used. The yield of the target product, epoxide, decreased significantly. The operating conditions and product parameters for this example are listed in Table 1.

[0118] Comparative Example 2

[0119] This embodiment is basically the same as Embodiment 1, except that:

[0120] A compound absorbent with a 1:1 molar ratio of 1-ethyl-1-methylpyrrole cations to thiocyanate anions was used. The yield of the target product, epoxide, decreased significantly. The operating conditions and product parameters for this example are listed in Table 1.

[0121] Comparative Example 3

[0122] This embodiment is basically the same as Embodiment 1, except that:

[0123] A compound absorbent was used, consisting of 1-ethyl-1-methylimidazolium cation, thiocyanate anion, and amino acid anion (R2 being methyl) in a molar ratio of 10:5:5. The yield of the target product, epoxide, decreased significantly. The operating conditions and product specifications for this example are listed in Table 1.

[0124] As can be seen from the table data, using the method of the present invention and the preferred embodiment of the present invention, the separated compound absorbent and epoxide can both achieve a purity of 99.99%, which is completely impossible to achieve in the comparative ratio.

[0125] Based on the content of the cyclic compound absorbent described in the present invention, it can be seen that the content of the absorbent described in the present invention can be understood as meaning that the absorbent is almost not lost during the absorption process, and can be completely recovered and re-entered into the cycle.

[0126] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

[0127] Table 1

[0128]

[0129] The solvent ratio refers to the molar ratio of the compound absorbent to the mixture of butane-containing tail gas.

[0130] If the data in the table is inconsistent with the data described in the previous embodiments, the data in the table shall prevail.

[0131] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A compound absorbent, characterized in that, The absorbent contains: alkylpyrrole cations, thiocyanate anions, and amino acid anions; the molar ratio of alkylpyrrole cations, thiocyanate anions, and amino acid anions is 10:1~7:3~9; The general structural formula of the alkylpyrrole cation is as follows: R1 is methyl, ethyl, n-propyl or isopropyl; The general structural formula of the thiocyanate anion is: ; The general structural formula of amino acid anions is: R2 is methyl, ethyl, n-propyl or isopropyl; The compound absorbent is an ionic liquid containing alkylpyrrole cations, thiocyanate anions, and amino acid anions.

2. The application of the compound absorbent according to claim 1 in the treatment of gases containing epoxides, wherein the epoxide is epoxide butane.

3. A method for recovering epoxide tail gas, characterized in that, The method includes: (1) The mixture of epoxide-containing tail gas is contacted with a compound absorbent for absorption, and the absorbed tail gas is discharged. (2) Desorb the absorbent mixture from step (1) to obtain the compound absorbent and the target product epoxide; optionally, the desorbed compound absorbent is returned to step (1) for recycling; The compound absorbent is the compound absorbent as described in claim 1.

4. The method according to claim 3, wherein, The method includes: (1) The mixture of butane-containing tail gas fed into the absorption tower is absorbed by the compound absorbent and then discharged at the top of the tower. (2) The mixture of bottom absorbent liquid separated in step (1) is desorbed by flash evaporation in a flash tank to obtain compound absorbent and target product epoxide butane. The compound absorbent obtained by separation is mixed with fresh compound absorbent and returned to step (1) for recycling.

5. The method according to claim 3 or 4, wherein, During the feeding process, The feed pressure of the butane oxide tail gas mixture is 0.15~0.50 MPaG.

6. The method according to claim 3 or 4, wherein, During the absorption process, the operating pressure is 0.15~0.50 MPaG; and / or During desorption, the operating pressure is 0.005~0.050 MPaG; and / or The absorption process is carried out using an absorption tower, wherein the theoretical plate number of the absorption tower is 10 to 30.

7. The method according to claim 3 or 4, wherein, The butane content in the butane-containing tail gas mixture is 10-80 vol%; and / or The butane oxide tail gas mixture originates from the recovery of byproducts from industrial propylene oxide production; and / or The molar ratio of the epoxide-containing tail gas mixture to the compound absorbent is 1:1-5.

8. The method according to claim 7, wherein, The content of epoxide in the tail gas mixture containing epoxide is 20-60 vol.

9. The method according to claim 3 or 4, wherein, Butane oxide-containing tail gas mixture is absorbed by countercurrent contact with a compound absorbent; and / or The recycling refers to the selective mixing of the desorbed compound absorbent with fresh compound absorbent and introducing it into the compound absorbent feed position of the absorption tower.

10. The method according to claim 3 or 4, wherein, The compound absorbent returned from the flash tank is mixed with fresh compound absorbent and then introduced into the absorption tower through the first theoretical plate.

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