CN113200820B - Method for separating dimethyl carbonate and methanol by using imidazole ionic liquid - Google Patents
Method for separating dimethyl carbonate and methanol by using imidazole ionic liquid Download PDFInfo
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- CN113200820B CN113200820B CN202110498468.8A CN202110498468A CN113200820B CN 113200820 B CN113200820 B CN 113200820B CN 202110498468 A CN202110498468 A CN 202110498468A CN 113200820 B CN113200820 B CN 113200820B
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- C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
- C07C29/76—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment
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- C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
- C07C29/76—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment
- C07C29/80—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment by distillation
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- C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
- C07C29/76—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment
- C07C29/86—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment by liquid-liquid treatment
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Abstract
The invention relates to a method for separating dimethyl carbonate and methanol by using imidazole ionic liquid and a device suitable for the method. The method uses imidazole ionic liquid as an extracting agent, dimethyl carbonate and methanol firstly enter a liquid-liquid extraction tower for extraction and separation, materials at the bottom of the liquid-liquid extraction tower enter a flash tank for separation, high-purity dimethyl carbonate is obtained at the top of the extraction tower, and the extracting agent is recycled after being extracted from the bottom of the flash tank. The method has the advantages of low energy consumption, simple process, high purity of the separated dimethyl carbonate and methanol and the like, the adopted extractant imidazole ionic liquid is almost non-volatile, the loss of the extractant is reduced, and the method is easy to recover, good in chemical thermal stability, green and pollution-free.
Description
[ technical field ] A method for producing a semiconductor device
The invention belongs to the field of chemical separation and purification, and particularly relates to a method for separating methanol and dimethyl carbonate by using imidazole ionic liquid, namely a method for separating methanol and dimethyl carbonate by using imidazole ionic liquid through a liquid-liquid extraction method, and then recovering and utilizing ionic liquid through flash evaporation.
[ background of the invention ]
Dimethyl carbonate (DMC), a low toxicity, environmental protection, excellent, use extensive chemical raw materials, it is an important organic synthesis intermediate, because its molecular structure contains carbonyl, methyl, methoxy and carbonyl methoxy, so can be used in carbonylation, methylation, methoxy and carbonyl methylation organic synthesis reaction, it is a "green" chemical product with development prospect. In the DMC synthesis process, the transesterification and oxidative carbonylation processes are the most promising industrial processes, but since complete conversion of methanol (MeOH) is always difficult to achieve, the end result is a mixture of dimethyl carbonate and methanol, which is a difficult azeotrope to separate from each other, and must be separated from methanol to obtain pure dimethyl carbonate.
The azeotropic temperature of DMC-MeOH under normal pressure was 63.7 ℃ and the azeotropic composition was 70% by mass of methanol (hereinafter, the same applies) and 30% by mass of dimethyl carbonate. The common rectification separation process is difficult to achieve the required high-purity product, and the purity of the dimethyl carbonate product directly influences the production benefit, so the research of the methanol-dimethyl carbonate azeotrope separation process is particularly important.
Imidazole ionic liquids such as [ MIM ] [ HSO4], [ HMIM ] [ PF6], [ OMIM ] [ OTF ] and the like, and the patent takes [ MIM ] [ PF6] as an example to illustrate a method for separating dimethyl carbonate-methanol by liquid-liquid extraction of imidazole plasma.
Chinese patent CN104370699B discloses a method for separating methanol-dimethyl carbonate azeotropic liquid, which utilizes different selective permeability of pervaporation membranes for component adsorption, effectively breaks the bottleneck of methanol-dimethyl carbonate azeotropy, the feed liquid at the low concentration side of dimethyl carbonate returns to a reaction rectifying tower for circular separation, the feed liquid at the high concentration side of dimethyl carbonate is conveyed to a normal pressure rectifying tower, and the dimethyl carbonate product with the mass purity of more than 99.6 percent is obtained at the tower bottom after the separation of the normal pressure rectifying tower.
Chinese patent CN101143803 discloses a method for separation of dimethyl carbonate and methanol azeotrope by pervaporation-rectification integration. The method comprises the steps of conveying azeotrope saturated steam to a membrane separator to contact with a separation membrane, allowing dimethyl carbonate to permeate the membrane and concentrate on the permeation side of the membrane, condensing the dimethyl carbonate into liquid under vacuum and low pressure, directly feeding the liquid into a normal pressure rectifying tower, obtaining over 99.5% of dimethyl carbonate at the bottom of the tower, and obtaining high-concentration methanol at the interception side of the membrane. The patent preferentially permeates the dimethyl carbonate component with low content in the membrane, which is beneficial to reducing the area of the membrane and reducing the investment.
Chinese patent CN103084076 describes a method for preparing a hollow fiber membrane for separating a mixture of methanol and dimethyl carbonate and an application thereof, the mixture of methanol and dimethyl carbonate to be separated is filled into a feed liquid tank, the feed liquid permeates from the feed liquid side to a permeation side through a permeation component, a vacuum pump is used for providing negative pressure at the permeation side, and a permeation liquid is collected in a cold trap. However, the above patents only show that the pervaporation separation experiments show higher selectivity and greater permeation flux, and do not relate to industrial applications, and it can be expected that the collected permeate needs to be further separated.
The imidazole ionic liquid-liquid extraction-flash evaporation device is used for realizing high-purity recovery of dimethyl carbonate in a dimethyl carbonate-methanol mixture, and the purity of the separated dimethyl carbonate is up to more than 99.96 percent by using [ MIM ] [ PF6] ionic liquid as an extractant and utilizing the characteristic of high solubility of methanol in the extractant; the extraction agent has the characteristics of high thermal stability and chemical stability, very small vapor pressure, non-volatility and the like, so that the extraction agent can be recycled, the separation cost is reduced, and the method has low energy consumption and simple process.
[ summary of the invention ]
[ problem to be solved ]
The invention aims to provide a method for separating a mixture by liquid-liquid extraction of imidazole ionic liquid and efficiently recovering the ionic liquid.
Another object of the present invention is to provide a method for separating methanol-dimethyl carbonate and recovering ionic liquid by using the device, namely imidazole ionic liquid-liquid extraction.
The invention also aims to provide the application of the imidazole salt ionic liquid as an extracting agent in liquid-liquid extraction-flash separation of methanol and methyl carbonate.
[ solution ]
The invention is realized by the following technical scheme.
A method for separating dimethyl carbonate and methanol by using imidazole ionic liquid is characterized in that a device for realizing the method mainly comprises the following parts: liquid-liquid extraction column (LET), flash tank (FLA), condenser (COL), mixer (MIX); wherein the bottom of the liquid-Liquid Extraction Tower (LET) is connected with an inlet of the flash tank (FLA) and is connected into the flash tank (FLA), the bottom of the flash tank (FLA) enters the Mixer (MIX) through the Condenser (COL), and the recovered ionic liquid and the supplemented fresh ionic liquid enter the extraction tower (LET) through the Mixer (MIX) and the top of the extraction tower (LET). The components to be separated enter via the bottom of an extraction column (LET).
The method for separating dimethyl carbonate and methanol by using the imidazole ionic liquid comprises the following steps:
(1) The method comprises the following steps that a mixture of dimethyl carbonate and methanol enters from the bottom of a liquid-Liquid Extraction Tower (LET), an extracting agent enters from the top of the liquid-Liquid Extraction Tower (LET), after effective contact extraction and separation, the dimethyl carbonate flows out from the top of the extraction tower (LET), and the methanol and ionic liquid flow out from the bottom of the extraction tower (LET) and enter a flash tank (FLA);
(2) After flash evaporation through a flash tank (FLA), methanol flows out from the top material flow, the material flow at the bottom of the flash tank (FLA) is almost pure ionic liquid, the ionic liquid enters a Cooler (COL) for cooling, and then enters a Mixer (MIX) and enters a liquid-Liquid Extraction Tower (LET) together with supplemented fresh ionic liquid for recycling;
the extracting agent is imidazole ionic liquid.
According to another preferred embodiment of the invention, it is characterized in that: the imidazole ionic liquid has the characteristics of high thermal stability and chemical stability, very small vapor pressure, non-volatility and the like, and common imidazole ionic liquids comprise [ MIM ] [ PF6], [ HMIM ] [ PF6], [ OMIM ] [ OTF ] and the like, which shows that the method for separating dimethyl carbonate-methanol by liquid-liquid extraction of imidazole plasmas.
According to another preferred embodiment of the invention, it is characterized in that: the liquid-Liquid Extraction Tower (LET) has the operating pressure of normal pressure, 5-10 tower plates, the ionic liquid feeding temperature of 25 ℃, the flash tank (FLA) operating pressure of 0.5bar and the flash temperature of 150 ℃.
According to another preferred embodiment of the invention, it is characterized in that: the mass ratio of the feed flow of the extracting agent to the mixture of methanol and dimethyl carbonate is 0.3-0.5.
According to another preferred embodiment of the invention, it is characterized in that: in the binary mixed solution of methanol and dimethyl carbonate, the mass fraction of methanol is 20-30% and the mass fraction of dimethyl carbonate is 80-70%.
According to another preferred embodiment of the invention, it is characterized in that: the purity of the ionic liquid recovered from the bottom of the flash tank (FLA) is higher than 99.91%, and the recycling rate is higher than 99.91%.
[ advantageous effects ]
Compared with the prior art, the invention has the following beneficial effects:
(1) The method is adopted to separate the dimethyl carbonate and the methanol to obtain the high-purity dimethyl carbonate, so that the high-purity component can be obtained from the binary azeotropic mixture, and the problem that the dimethyl carbonate and the methanol are difficult to separate is solved.
(2) The method has the advantages of simple process, less investment equipment, high purity of the separated dimethyl carbonate, high recovery rate and the like, and the adopted extractant imidazole ionic liquid is easy to recover, good in chemical thermal stability, green and pollution-free.
(3) The adopted extractant imidazole ionic liquid is almost non-volatile, the loss of the extractant is reduced, the secondary pollution of dimethyl carbonate and methanol is avoided, in addition, the extractant is easy to recycle, and the separation cost is reduced.
[ description of the drawings ]
FIG. 1 is a process flow diagram for the liquid-liquid extraction-flash separation of phenol and water according to the present invention.
In the figure, LET-liquid extraction column; FLA-flash tank; a COL-cooler; a MIX-mixer; the numbers represent the respective lines.
[ detailed description ] A
Example 1:
the feed flow is 1000kg/h, the feed contains 20% of methanol and 80% of dimethyl carbonate (mass fraction), the number of theoretical plates of a liquid-Liquid Extraction Tower (LET) is 9, a mixture of phenol and water enters from the bottom of the liquid-Liquid Extraction Tower (LET), an extracting agent enters from the top of the liquid-Liquid Extraction Tower (LET), the extracting agent is [ OMIM ] [ OTF ] ionic liquid, the flow is 500kg/h (the feed flow mass ratio of the extracting agent to the dimethyl carbonate-methanol mixture is 0.5), and the temperature of the liquid-Liquid Extraction Tower (LET) is 16 ℃. The operating pressure of the flash tank (FLA) was 0.4bar, the purity of the separated dimethyl carbonate was 99.90% and the purity of the ionic liquid was 99.91%.
Example 2:
the feed flow was 1000kg/h, the feed contained 20% methanol and 80% dimethyl carbonate (mass fraction), the number of theoretical plates of the liquid-liquid extraction column (LET) was 9, the phenol and water mixture was fed from the bottom of the liquid-liquid extraction column (LET), the extractant was fed from the top of the liquid-liquid extraction column (LET), the extractant was [ MIM ] [ PF6] ionic liquid, the flow was 500kg/h (feed flow mass ratio of extractant to dimethyl carbonate-methanol mixture was 0.5), and the temperature of the liquid-liquid extraction column (LET) was 16 ℃. The operating pressure of the flash tank (FLA) was 0.4bar, the purity of the separated dimethyl carbonate was 99.95% and the purity of the ionic liquid was 99.91%.
Example 3:
the feed flow is 1000kg/h, the feed contains 20% of methanol and 80% of dimethyl carbonate (mass fraction), the number of theoretical plates of a liquid-Liquid Extraction Tower (LET) is 9, a mixture of phenol and water enters from the bottom of the liquid-Liquid Extraction Tower (LET), an extracting agent enters from the top of the liquid-Liquid Extraction Tower (LET), the extracting agent is [ HMIM ] [ PF6] ionic liquid, the flow is 500kg/h (the feed flow mass ratio of the extracting agent to the dimethyl carbonate-methanol mixture is 0.5), and the temperature of the liquid-Liquid Extraction Tower (LET) is 16 ℃. The operating pressure of the flash tank (FLA) was 0.4bar, the purity of the separated dimethyl carbonate was 99.97%, and the purity of the ionic liquid was 99.91%.
Claims (5)
1. A method for separating dimethyl carbonate and methanol by using imidazole ionic liquid is characterized in that a device for realizing the method mainly comprises the following parts: liquid-liquid extraction column (LET), flash tank (FLA), condenser (COL), mixer (MIX); wherein the bottom of the liquid-Liquid Extraction Tower (LET) is connected with an inlet of the flash tank (FLA) and is connected into the flash tank (FLA), the bottom of the flash tank (FLA) enters a Mixer (MIX) through a Condenser (COL), the recovered ionic liquid and supplemented fresh ionic liquid enter the extraction tower (LET) through the Mixer (MIX) and the top of the extraction tower (LET), and components to be separated enter the extraction tower (LET) through the bottom of the extraction tower (LET);
the method for separating dimethyl carbonate from methanol by using the imidazole ionic liquid comprises the following steps:
(1) The method comprises the following steps that a mixture of dimethyl carbonate and methanol enters from the bottom of a liquid-Liquid Extraction Tower (LET), an extracting agent enters from the top of the liquid-Liquid Extraction Tower (LET), after effective contact extraction and separation, the dimethyl carbonate flows out from the top of the extraction tower (LET), and the methanol and ionic liquid flow out from the bottom of the extraction tower (LET) and enter a flash tank (FLA);
(2) After flash evaporation through a flash tank (FLA), methanol flows out from the top material flow, the material flow at the bottom of the flash tank (FLA) is almost pure ionic liquid, the ionic liquid enters a Cooler (COL) for cooling, and then enters a Mixer (MIX) and enters a liquid-Liquid Extraction Tower (LET) together with supplemented fresh ionic liquid for recycling;
the extraction agent is imidazole ionic liquid, the imidazole ionic liquid has the characteristics of high thermal stability and chemical stability, very small vapor pressure and non-volatility, and the ionic liquid is [ MIM ] [ PF6], [ HMIM ] [ PF6], [ OMIM ] [ OTF ].
2. The method for separating dimethyl carbonate from methanol by using the imidazole ionic liquid according to claim 1, which is characterized by comprising the following steps: the liquid-Liquid Extraction Tower (LET) has the operating pressure of normal pressure, 5-10 tower plates, the ionic liquid feeding temperature of 25 ℃, the flash tank (FLA) operating pressure of 0.5bar and the flash temperature of 150 ℃.
3. The method for separating dimethyl carbonate from methanol by using the imidazole ionic liquid as claimed in claim 1, which is characterized in that: the mass ratio of the feed flow of the extracting agent to the mixture of methanol and dimethyl carbonate is 0.3-0.5.
4. The method for separating dimethyl carbonate from methanol by using the imidazole ionic liquid as claimed in claim 1, which is characterized in that: in the binary mixed solution of methanol and dimethyl carbonate, the mass fraction of methanol is 20-30% and the mass fraction of dimethyl carbonate is 80-70%.
5. The method for separating dimethyl carbonate from methanol by using the imidazole ionic liquid according to claim 1, which is characterized by comprising the following steps: the purity of the ionic liquid recovered from the bottom of the flash tank (FLA) is higher than 99.91%, and the recycling rate is higher than 99.91%.
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Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| JPH0625104A (en) * | 1991-07-19 | 1994-02-01 | Ube Ind Ltd | Continuous production of dimethyl carbonate |
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| JP3214576B2 (en) * | 1992-07-01 | 2001-10-02 | 旭化成株式会社 | Separation method of methanol and dimethyl carbonate |
| CN107915642A (en) * | 2016-10-10 | 2018-04-17 | 中国石油化工股份有限公司 | The separation method of dimethyl carbonate and methanol |
| CN111004092B (en) * | 2019-12-26 | 2022-04-29 | 昌德新材科技股份有限公司 | Method for separating dimethyl carbonate and methanol |
| CN112225634A (en) * | 2020-10-02 | 2021-01-15 | 洪泽县恒泰科工贸有限公司 | Method for separating cyclohexane and tert-butyl alcohol by liquid-liquid extraction-flash evaporation |
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| JPH0625104A (en) * | 1991-07-19 | 1994-02-01 | Ube Ind Ltd | Continuous production of dimethyl carbonate |
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