Method for separating methyl tert-amyl ether-methanol-water azeotropic mixture through low-pressure heat pump extractive distillation

Abstract

The invention discloses a method for separating a tert-amyl methyl ether-methanol-water azeotropic system by pressure swing extractive distillation through two different mixed entrainers on the basis of a heat pump technical process strengthening scheme. Through three-tower operation of an extraction vacuum distillation tower T1, an extraction vacuum distillation tower T2 and a solvent recovery tower T3, a methyl tert-amyl ether-methanol-water azeotropic mixed solution is separated, the purity of separated methyl tert-amyl ether is greater than 99.9%, the purity of methanol is greater than 99.9%, the yield is greater than 99.9%, the purity of water is greater than 99.9%, and the yield is greater than 99.9%. A heat pump technology is used as an effective process strengthening means, steam at the top of an extraction decompression rectifying tower T1 circularly enters a compressor to be compressed and heated through the compressor, the compressed steam serves as heat flow to heat cold flow at the bottom of the tower, and the top flow is finally condensed after heat transfer. And the reboiling flow at the bottom of the tower can reach the required reboiling ratio, so that the heat load consumption of the T1 tower is obviously reduced. By applying the method, the process cost and the environmental pollution can be further reduced, and the annual total cost and the gas emission are respectively reduced by 9.19% and 23.55%. According to the process, heat energy is fully utilized, energy consumption is reduced, the purity and the yield of the tert-amyl methyl ether are improved, and the equipment cost is reduced. The adopted mixed entrainer is small in dosage, relatively weak in volatility, small in extraction agent loss, easy to recover and environment-friendly.

Description

[Technical field]

[0001] The invention belongs to the field of chemical separation and purification, and in particular relates to a method for separating tert-amyl methyl ether-methanol-water azeotropic mixture by using pressure swing distillation. [Background technology]

[0002] Tert-amyl methyl ether (TAME) is a very important chemical raw material. As a new type of gasoline additive, it can increase the oxygen content in gasoline, reduce the lead content, and improve the anti-knock performance and quality of gasoline. At the same time, due to its good solubility and volatility, it can be used as a solvent in the production of coatings, glues, detergents, etc., which can effectively dissolve a variety of organic substances and improve the stability of the solution. Tert-amyl methyl ether is also used as an extractant to separate and purify substances, such as separating naphtha and solvent oil in the petroleum industry. In medicine, it can also be used as a drug solvent and protective agent to ensure the stability and activity of drugs. In addition, tert-amyl methyl ether can be obtained from renewable resources such as bioethanol, cellulose and agricultural products, and has sustainable development potential.

[0003] The synthesis of tert-amyl methyl ether from tert-amyl alcohol and methanol is gradually being regarded by the public as a relatively new synthesis route. In the reaction route of synthesizing tert-amyl methyl ether from tert-amyl alcohol and methanol, a large amount of water is produced. At the same time, in order to improve the selectivity of the primary reaction and the conversion rate of the reactants, excessive methanol is usually injected. However, methanol, tert-amyl methyl ether and water will form two binary azeotropic systems, which leads to a sharp increase in the difficulty of separating tert-amyl methyl ether. In order to obtain high-purity tert-amyl methyl ether, ordinary distillation methods cannot achieve effective separation, so special distillation methods are required.

[0004] Chinese patent CN107628930A discloses an energy-saving process for separating methanol, isopropanol and water by heat pump extraction distillation. The invention appropriately increases the temperature and pressure of the steam at the top of the dehydration tower by a heat pump compressor, and uses it as a heat source to heat the kettle liquid, thereby achieving a reasonable and effective energy cycle; the cost generated by the heat pump compressor of the present invention is lower than the cost of traditional external heating and cooling water, resulting in good economic benefits.

[0005] Chinese patent CN116768713A discloses a method for separating diethoxymethane, ethanol and toluene by extractive distillation using a mixed extractant, utilizing the property that the relative volatility between molecules of diethoxymethane-ethanol and toluene-ethanol azeotropic system changes with the addition of a mixed extractant, and realizing efficient separation of a ternary mixture by operating a distillation tower (T1), a distillation tower (T2) and a distillation tower (T3). The present invention solves the problem that the azeotropic system is difficult to separate using ordinary distillation, is flexible in operation, economical and environmentally friendly, and can realize effective separation of a ternary azeotropic mixture through three towers.

[0006] In the present invention, the separation of azeotropic components of tert-amyl methyl ether-methanol-water mixture is complex and energy-intensive during production. A mixed entrainer pressure swing distillation process with good separation effect is designed, and heat pump recompression technology is used as a means of process intensification to save energy and reduce emissions. [Summary of the invention]

[0007] [Technical issues to be solved]

[0008] The purpose of the present invention is to provide a method for separating tert-amyl methyl ether-methanol-water mixture by pressure swing extraction and rectification.

[0009] Another object of the present invention is to provide a method for achieving a superior separation of tert-amyl methyl ether-methanol-water mixture using an entraining agent.

[0010] Another object of the present invention is to provide a method for separating tert-amyl methyl ether-methanol-water mixture by low-pressure heat pump extractive distillation using the device.

[0011] [Technical solution]

[0012] The present invention is achieved through the following technical solutions.

[0013] A method for separating tert-amyl methyl ether-methanol-water mixture by pressure swing distillation, characterized in that the device for separating tert-amyl methyl ether-methanol-water azeotropic system mainly comprises the following parts:

[0014] Vacuum extractive distillation tower (T1), low-pressure extractive distillation tower (T2), extractant recovery tower (T3), condenser (CL1), condenser (CL2), reboiler (H1), reboiler (H2), reboiler (H3), storage tank (C1), top storage tank (C2), centrifugal pump (P1), centrifugal pump (P2), centrifugal pump (P3), cooler (COL), pressure reducing valve (V1), compressor (Comp); raw materials enter the low-pressure extractive distillation tower (T1); the steam cycle at the top of the low-pressure extractive distillation tower (T1) enters the compressor for compression and heating, and the compressed steam is used as a heat flow to heat the cold flow at the bottom of the tower. The reboiled flow at the bottom of the tower can also achieve the required reboil ratio, thereby significantly reducing the heat load consumption of the T1 tower. The low-pressure extractive distillation tower (T1) is connected to the low-pressure extractive distillation tower (T2) through a centrifugal pump (P1); the low-pressure extractive distillation tower (T2) is connected to the extractant recovery tower (T3) through the centrifugal pump (P2), and the extractant returns to the reduced-pressure extraction tower (T1) through a cooler (COL).

[0015] A method for separating tert-amyl methyl ether-methanol-water mixture by low-pressure heat pump extraction and distillation using the above device comprises the following steps:

[0016] (1) The raw material mixture of tert-amyl methyl ether, methanol and water is placed in a low-pressure extractive distillation tower (T1). In the low-pressure extractive distillation tower (T1), the separation of tert-amyl methyl ether is achieved. The steam at the top of the low-pressure extractive distillation tower (T1) is circulated into the compressor (Comp) for compression and heating. The compressed steam is used as a hot flow to heat the cold flow at the bottom of the tower. When designing the compressor, the compressor exhaust pressure is adjusted to 0.4atm, which will cause the top flow to eventually condense after heat transfer. The reboiled flow at the bottom of the tower can also achieve the required reboil ratio, thereby significantly reducing the heat load consumption of the T1 tower. A part of the bottom flow of the low-pressure extractive distillation tower (T1) is returned to the vacuum tower (T1) after heat exchange in the reboiler (H1), and the other part is passed from the bottom of the vacuum tower (T1) to the vacuum tower (T2) through a centrifugal pump (P1).

[0017] (2) In the vacuum tower (T2), methanol is separated. The material distilled from the top of the vacuum tower (T2) is condensed by the condenser (CL1) and enters the top storage tank (C1). A part of the bottom flow of the vacuum tower (T2) is returned to the vacuum tower (T2) after heat exchange in the reboiler (H2), and the other part is sent from the bottom of the vacuum tower (T2) to the extractant recovery tower (T3) through the centrifugal pump P2.

[0018] (3) In the extractant recovery tower (T3), the extractant mixed with the extractant dimethyl sulfoxide-1,3-propylene glycol is recovered, and the top stream is collected by the condenser (C3) and the condensation reflux tank (D3), and a part of it is returned to the distillation tower, and more than 99.9% of dimethyl sulfoxide is extracted; a part of the bottom stream is reboiled by the reboiler (H3) and returned to the solvent recovery tower (T3), and a part of it enters the cooler (COL), is mixed with the supplementary extractant, and then returned to the vacuum extraction distillation tower (T1) for recycling.

[0019] The operating pressure of the vacuum tower (T1) is 0.4atm, the number of theoretical plates is 48-56, the feeding position of tert-amyl methyl ether-methanol-water mixture is the 25th tower plate, the feeding position of the extractant is the 5th tower plate, and the reflux ratio is 3.27; the operating pressure of the vacuum tower (T2) is 0.1158atm, the number of theoretical plates is 44-52, the feeding position is the 33rd tower plate, and the reflux ratio is 0.538; the operating pressure of the extractant recovery tower (T3) is 0.0987, and the number of theoretical plates is 15-20.

[0020] According to another preferred embodiment of the present invention, it is characterized in that the application of heat pump technology reduces the consumption of T1 reboiler and condenser. Compared with the dimethyl sulfoxide-1,3-propylene glycol pressure swing extraction distillation process without adding a heat pump, the load of the reboiler and condenser are significantly reduced by 23.55% and 21.98%, respectively.

[0021] According to another preferred embodiment of the present invention, it is characterized in that: compared with the dimethyl sulfoxide single entrainer process, the dimethyl sulfoxide-1,3-propylene glycol mixed entrainer reduces TAC by 7.03%.

[0022] [Beneficial Effects]

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

[0024] (1) The problem of difficult separation of tert-amyl methyl ether-methanol-water mixture is solved.

[0025] (2) This method adopts a low-pressure-heat pump extraction distillation coupling process to effectively utilize the heat load of the extractant recovery tower reboiler, thereby reducing energy consumption and production costs in the production process.

Brief Description of the Drawings

[0026] Figure 1 The present invention is a process flow chart for separating tert-amyl methyl ether-methanol-water mixture by low-pressure heat pump extraction and distillation.

[0027] In the figure, T1-low-pressure extractive distillation tower; T2-low-pressure extractive distillation tower; T3-extractant recovery tower; CL1-condenser, CL2-condenser, H1-heat exchanger, H2-reboiler, H3-reboiler, C1-tower top storage tank, C2-tower top storage tank, P1-centrifugal pump, P2-centrifugal pump, P3-centrifugal pump; COL-cooler, Comp-compressor. [Specific implementation method]

[0028] Embodiment 1:

[0029] The feed flow rate is 100 kmol / h, the feed contains 0.125 tert-amyl methyl ether, 0.75 methanol, and 0.125 water (molar fraction). The vacuum extractive distillation tower (T1) has 86 theoretical plates, the tower pressure is 0.2685 atm, the tert-amyl methyl ether-methanol-water mixture enters from the 52nd plate, the extractant is 89.74 kmol / h of dimethyl sulfoxide, which is added from the 5th plate, the top discharge of the vacuum extractive distillation tower (T1) is 12.50 kmol / h of 99.99% tert-amyl methyl ether, and the bottom discharge enters the vacuum extractive distillation tower (T2) for separation; the number of plates of the vacuum extractive distillation tower (T2) is 52, the tower pressure is 0.1039 atm, and the feed position is the 39th plate; the extractant recovery tower (T3) has 48 plates, and the feed position is the 15th plate. After separation, the purity of tert-amyl methyl ether is 99.99%, the purity of methanol is 99.99%, the purity of water is 99.90%, and the extractant is recycled.

[0030] Example 2:

[0031] The feed flow rate is 100 kmol / h, and the feed contains 0.125 water, 0.125 methyl tert-amyl ether, and 0.75 methanol (molar fraction). The vacuum tower (T1) has 52 theoretical plates, and the mixture of methyl tert-amyl ether, methanol, and water enters T1 from the 25th plate; the operating pressure of the vacuum tower (T1) is 0.1478 atm, and after separation, 12.50 kmol / h of 99.99% methyl tert-amyl ether is obtained at the top of the vacuum tower (T1). The mixture enters from the 33rd plate of the vacuum tower (T2) with a flow rate of 161.36 kmol / h. The vacuum tower (T2) has 38 theoretical plates, and the operating pressure of the vacuum tower (T2) is 0.1158 atm. After separation, 103.87 kmol / h of 0.7303 dimethyl sulfoxide and 0.1249 1,3-propylene glycol are obtained at the bottom of the tower. The yield of methanol is 99.99%. The theoretical number of plates of the extractant recovery tower (T3) is 19. A mixture of dimethyl sulfoxide, 1,3-propylene glycol and water enters T3 from the 7th plate. After separation, 99.97% of water is obtained at the top of the tower, and the extractant is recycled.

[0032] Example 3:

[0033] The feed flow rate is 100 kmol / h, and the feed contains 0.125 water, 0.125 tert-amyl methyl ether, and 0.75 methanol (molar fraction). The vacuum tower (T1) has 52 theoretical plates, and the mixture of tert-amyl methyl ether, methanol and water enters T1 from the 25th plate; after separation, 12.50 kmol / h of 99.99% tert-amyl methyl ether is obtained from the top of the vacuum tower (T1). The steam cycle at the top of the vacuum tower (T1) enters the compressor for compression and heating, and the compressed steam is used as a heat flow to heat the cold flow at the bottom of the tower. The mixture enters the 33rd plate of the vacuum tower (T2) with a flow rate of 161.36 kmol / h. The vacuum tower (T2) has 38 theoretical plates, the operating pressure of the vacuum tower (T2) is 0.1158 atm, and the yield of methanol is 99.99%. The extractant recovery tower (T3) has 19 theoretical plates, and a mixture of dimethyl sulfoxide, 1,3-propylene glycol and water enters T3 from the 7th plate. After separation, 99.97% of water is obtained at the top of the tower, and the extractant is recycled.

Claims

1. A method for separating tert-amyl methyl ether-methanol-water azeotropic mixture by pressure swing distillation, characterized in that The device for separating methyl tert-amyl ether-methanol-water azeotropic system mainly comprises the following parts: vacuum extractive distillation tower (T1), low-pressure extractive distillation tower (T2), extractant recovery tower (T3), condenser (CL1), condenser (CL2), reboiler (H1), reboiler (H2), reboiler (H3), tower top storage tank (C1), pressure reducing valve (V1), tower top storage tank (C2), centrifugal pump (P1), centrifugal pump (P2), centrifugal pump (P3), cooler (COL), compressor (Comp); raw materials enter the low-pressure extractive distillation tower (T1); the steam at the top of the low-pressure extractive distillation tower (T1) circulates into the compressor for compression and heating, and the compressed steam is used as a heat flow to heat the cold flow at the bottom of the tower. The reboiled flow at the bottom of the tower can also achieve the required reboil ratio, thereby significantly reducing the heat load consumption of the T1 tower. The low-pressure extractive distillation tower (T1) is connected to the low-pressure extractive distillation tower (T2) through a centrifugal pump (P1); the low-pressure extractive distillation tower (T2) is connected to the extractant recovery tower (T3) through the centrifugal pump (P2), and the extractant returns to the reduced-pressure extraction tower (T1) through a cooler (COL).

2. According to claim 1, it is characterized in that A method for separating tert-amyl methyl ether-methanol-water azeotropic mixture by pressure swing distillation is as follows: The raw material mixture of tert-amyl methyl ether, methanol and water is placed in a low-pressure extractive distillation tower (T1). In the low-pressure extractive distillation tower (T1), the separation of tert-amyl methyl ether is achieved. The steam at the top of the low-pressure extractive distillation tower (T1) is circulated into the compressor (Comp) for compression and heating. The compressed steam is used as a hot flow to heat the cold flow at the bottom of the tower. When designing the compressor, the compressor exhaust pressure is adjusted to 0.4atm, which will eventually condense the top flow after heat transfer. The reboiled flow at the bottom of the tower can also achieve the required reboil ratio, thereby significantly reducing the heat load consumption of the T1 tower. A part of the bottom flow of the low-pressure extractive distillation tower (T1) returns to the vacuum tower (T1) after heat exchange in the reboiler (H1), and the other part is passed from the bottom of the vacuum tower (T1) to the vacuum tower (T2) through a centrifugal pump (P1). In the vacuum tower (T2), methanol is separated. The material distilled from the top of the vacuum tower (T2) is condensed by the condenser (CL1) and enters the top storage tank (C1). A part of the bottom stream of the vacuum tower (T2) is returned to the vacuum tower (T2) after heat exchange in the reboiler (H2), and the other part enters the extractant recovery tower (T3) from the bottom of the vacuum tower (T2) through the centrifugal pump P2. In the extractant recovery tower (T3), the extractant mixed with the extractant dimethyl sulfoxide-1,3-propylene glycol is recovered. After the top stream is collected by the condenser (C3) condensation reflux tank (D3), a part of it is returned to the distillation tower, and more than 99.9% of dimethyl sulfoxide is extracted; a part of the bottom stream is reboiled in the reboiler (H3) and returned to the solvent recovery tower (T3), and a part enters the cooler (COL), mixed with the supplementary extractant, and returned to the vacuum extraction distillation tower (T1) for recycling. The operating pressure of the vacuum tower (T1) is 0.4atm, the number of theoretical plates is 48-56, the feeding position of tert-amyl methyl ether-methanol-water mixture is the 25th tower plate, the feeding position of the extractant is the 5th tower plate, and the reflux ratio is 3.27; the operating pressure of the vacuum tower (T2) is 0.1158atm, the number of theoretical plates is 34-52, the feeding position is the 33rd tower plate, and the reflux ratio is 0.538; the operating pressure of the extractant recovery tower (T3) is 0.0987, and the number of theoretical plates is 15-20.

3. According to claim 1, it is characterized in that: The application of heat pump technology reduces the consumption of T1 reboiler and condenser. Compared with the DMSO-1,3-propylene glycol pressure swing extraction distillation process without adding heat pump, the load of reboiler and condenser are significantly reduced by 23.55% and 21.98%, respectively.

4. According to claim 1, it is characterized in that: Compared with the DMSO single entrainer process, the DMSO-1,3-propylene glycol mixed entrainer reduced TAC by 7.03%.

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