Method for separating n-propyl formate-n-propyl alcohol-water mixture through liquid-liquid split-phase coupling variable-pressure assisted extractive distillation

Abstract

The invention relates to a method for separating an n-propyl formate-n-propyl alcohol-water mixture by liquid-liquid phase separation coupling extractive distillation, which comprises the following steps of: dividing a raw material into a water phase and an organic phase by using a phase splitter based on the heterogeneous characteristic of an azeotropic system, and carrying out four-tower operation on a rectifying tower (C1), a rectifying tower (C2), a rectifying tower (C3) and a rectifying tower (C4) to obtain an n-propyl formate-n-propyl alcohol-water mixture. The efficient separation of the n-propyl formate-n-propyl alcohol-water mixture is realized. After separation, the molar fraction of n-propyl formate is greater than 99.99%, the molar fraction of n-propyl alcohol is greater than 99.99%, and the molar fraction of water is greater than 99.99%. The method provided by the invention realizes high-efficiency and low-energy-consumption separation of the n-propyl formate-n-propanol-water azeotropic mixture, and has economic benefits and environmental friendliness.

Description

Technical Field

[0001] This invention belongs to the field of chemical separation and purification, specifically relating to a method for separating a mixture of n-propyl formate, n-propanol, and water by liquid-liquid phase-coupling pressure-swing assisted extraction distillation. More specifically, it relates to a method for separating a mixture of n-propyl formate, n-propanol, and water by extraction distillation using a phase separator as a pre-separation device and glycerol and 1,3-propanediol as mixed extractants. Background Technology

[0002] n-Propyl formate and n-propanol are important industrial raw materials. n-Propyl formate can be used as a solvent, fragrance, and bactericide, while n-propanol, as an important low-carbon alcohol, can be used as a solvent, fuel additive, and pharmaceutical synthesis intermediate. n-Propyl formate is prepared by esterification of formic acid and n-propanol, a process that produces a large amount of water as a byproduct. Because this esterification reaction is reversible, the resulting mixture contains a large amount of n-propyl formate-n-propanol-water. Under normal pressure, this mixture contains three binary azeotropes (n-propyl formate-n-propanol, n-propyl formate-water, and n-propanol-water) and one ternary azeotrope (n-propyl formate-n-propanol-water), making it difficult to effectively separate using conventional methods.

[0003] This invention uses glycerol and 1,3-propanediol as a mixed extractant to alter the relative volatility between molecules in an azeotropic mixture. A phase separator and extractive distillation apparatus are employed to achieve the separation and purification of a mixture of n-propyl formate, n-propanol, and water. After separation, the purity of n-propyl formate, n-propanol, and water all reaches over 99.9%, and the extractant can be recovered and reused, significantly reducing separation costs. Furthermore, most of the water in the system is separated at the bottom of the first distillation column (C1), resulting in lower energy consumption and costs. Summary of the Invention

[0004] [Technical problem to be solved] The purpose of this invention is to provide a method for separating and purifying a mixture of n-propyl formate, n-propanol, and water using the aforementioned apparatus.

[0005] Another object of the present invention is to provide an apparatus for separating a mixture of n-propyl formate, n-propanol, and water by liquid-liquid phase-splitting coupled pressure-switching assisted extraction distillation.

[0006] Another object of the present invention is to provide the use of glycerol / 1,3-propanediol as an extractant in the separation of n-propyl formate-n-propanol-water mixtures.

[0007] [Technical Solution]

[0008] This invention is achieved through the following technical solution: A method for separating a mixture of n-propyl formate, n-propanol, and water using liquid-liquid phase-separation coupled extractive distillation is characterized by an apparatus comprising the following components: distillation column 1 (C1), distillation column 2 (C2), distillation column 3 (C3), distillation column 4 (C4), condenser 1 (CO1), condenser 2 (CO2), condenser 3 (CO3), condenser 4 (CO4), reboiler 1 (R1), reboiler 2 (R2), reboiler 3 (R3), reboiler 4 (R4), phase separator (DE), mixer (MIX), cooler (COO1), centrifugal pump 1 (P1), centrifugal pump 2 (P2), and centrifugal pump 3 (P3); wherein the feed is separated into layers in the phase separator, with the upper layer being the organic phase. The lower layer is the aqueous phase; the aqueous phase enters distillation column 1 (C1), and high-purity water is collected at the bottom of distillation column 1 (C1); the organic phase and the top product of distillation column 1 (C1) enter the mixer (MIX) together, and after mixing, enter distillation column 2 (C2); high-purity n-propyl formate is collected at the top of distillation column 2 (C2), and the bottom mixture enters distillation column 3 (C3); high-purity n-propanol is collected at the top of distillation column 3 (C3), and the bottom mixture enters distillation column 4 (C4); high-purity water is collected at the top of distillation column 4 (C4), and high-purity extractant is obtained from the bottom stream, which passes through P3 and enters the cooler (COO1). After cooling, extractant is added and then refluxed to distillation column 2 (C2) and distillation column 3 (C3).

[0009] A method for separating a mixture of n-propyl formate, n-propanol, and water using the above-described apparatus includes the following steps: (1) The formate-propanol-water mixture enters the phase separator (DE) for stratification. The upper layer is the organic phase and the lower layer is the aqueous phase. The aqueous phase enters from the middle and lower part of distillation column 1 (C1). After efficient heat and mass transfer separation of the vapor and liquid phases in the column, high-purity product water is collected at the bottom of distillation column 1 (C1). The formate-propanol-water mixture collected from the top of the column is mixed with the organic phase separated in the phase separator in the mixer (MIX) and then enters distillation column 2 (C2). (2) The formate-propanol-water mixture enters from the middle and lower part of the distillation column 2 (C2), and the extractant enters from the upper part of the distillation column 2 (C2). High-purity formate is collected at the top of the distillation column 2 (C2), and the bottom stream is a mixture of propanol-water-extractant, which is transported to the distillation column 3 (C3) by centrifugal pump 1 (P1). (3) The n-propanol-water-extractant mixture enters from the lower part of the distillation column 3 (C3), and the extractant enters from the upper part of the distillation column 3 (C3). High-purity n-propanol is collected at the top of the distillation column 3 (C3). The water-extractant mixture is transported to the distillation column 4 (C4) by centrifugal pump 2 (P2). High-purity water is collected at the top of the distillation column 4 (C4). (4) The high-purity extractant is collected from the bottom stream of distillation column 4 (C4), and enters the cooler (COO1) via centrifugal pump 3 (P3). After cooling and replenishing the extractant, it is transported to distillation column 2 (C2) and distillation column 3 (C3). According to claim 1, the method is characterized in that: the operating pressure of distillation column 1 (C1) is 0.16 atm, the operating pressure of distillation column 2 (C2), distillation column 3 (C3) and distillation column 4 (C4) is 0.1 atm, the number of trays of distillation column 1 (T1) is 25-35, and the feed position is 15-20; the number of trays of distillation column 2 (T2) is 30-40, the feed position is 15-25, and the feed position of the extractant is 3-10; the number of trays of distillation column 3 (T3) is 50-60, the feed position is 30-45, and the feed position of the extractant is 3-10; the number of trays of distillation column 4 (T4) is 15-25, and the feed position is 5-13.

[0010] According to another preferred embodiment of the present invention, the temperature range of distillation column 1 (T1) is 25~75℃; the temperature range of distillation column 2 (T2) is 20~100℃; the temperature range of distillation column 3 (T3) is 40~170℃; and the temperature range of distillation column 4 (T4) is 40~190℃.

[0011] According to another preferred embodiment of the present invention, the extractant is a mixture of glycerol and 1,3-propanediol.

[0012] According to another preferred embodiment of the present invention, the molar fraction of glycerol in the extractant is 50% to 70%.

[0013] According to another preferred embodiment of the present invention, the feed flow rate molar ratio of the extractant to the n-propyl formate-n-propanol-water mixture is 0.2~0.5.

[0014] According to another preferred embodiment of the present invention, the formate-propanol-water mixture contains 62.92% formate, 4.31% propanol, and 32.77% water.

[0015] According to another preferred embodiment of the present invention, the water recovered from the bottom of distillation column 1 (C1) and the top of distillation column 4 (C4) has a purity higher than 99.9% and a yield higher than 99.9%; the n-propyl formate recovered from the top of distillation column 2 (C2) has a purity higher than 99.9% and a yield higher than 99.9%; and the n-propanol recovered from the top of distillation column 3 (C3) has a purity higher than 99.9% and a yield higher than 99.9%.

[0016] [Beneficial Effects]

[0017] Compared with the prior art, the present invention has the following main advantages: (1) The method was used to separate and purify the mixture of n-propyl formate-n-propanol-water to obtain high-purity n-propyl formate, n-propanol and water, which solved the problem that the mixture was difficult to separate by conventional means.

[0018] (2) Compared with conventional extraction distillation process, this method has low energy consumption and cost, and the formate, n-propanol and water obtained after separation have high purity. The extractant used has low toxicity, good thermal stability and is green and pollution-free.

[0019] (3) The extractant used in this method is not volatile and is easy to recover, resulting in less loss of extractant. Attached Figure Description

[0020] Figure 1 This is a process flow diagram of the liquid-liquid phase-coupling extraction distillation separation of a mixture of n-propyl formate, n-propanol, and water according to the present invention.

[0021] In the diagram, C1 is a distillation column, C2 is a distillation column, C3 is a distillation column, C4 is a distillation column, CO1 is a condenser, CO2 is a condenser, CO3 is a condenser, CO4 is a condenser, R1 is a reboiler, R2 is a reboiler, R3 is a reboiler, R4 is a reboiler, DE is a phase separator, MIX is a mixer, COO1 is a cooler, P1 is a centrifugal pump, P2 is a centrifugal pump, and P3 is a centrifugal pump. Detailed Implementation

[0022] Example:

[0023] The feed flow rate is 100 kmol / h, and the molar fractions of the components in the feed are: propyl formate 62.92%, n-propanol 4.31%, and water 32.77%. The propyl formate-propanol-water mixture enters the phase separator (DE), with the upper layer being the organic phase and the lower layer being the aqueous phase. Distillation column 1 (C1) has 29 theoretical plates and operates at a pressure of 0.16 atm. The aqueous phase from the phase separator (DE) enters from the lower middle section of distillation column 1 (C1); 26.99 kmol / h of 99.9% water is collected from the bottom of distillation column 1 (C1). The organic phase from the phase separator (DE) mixes with the propyl formate-propanol-water mixture collected from the top of distillation column 1 (C1) and enters distillation column 2 (C2) from the lower middle section of the column, with a feed flow rate of 73.01 kmol / h. Distillation column 2 (C2) has 30 theoretical plates. A mixed extractant of glycerol / 1,3-propanediol with a flow rate of 28 kmol / h enters from the top of column 2 (C2), yielding n-propyl formate with a flow rate of 62.92 kmol / h and a purity of 99.9% at the top. Distillation column 3 (C3) has 53 theoretical plates. The bottom stream from distillation column 2 (C2) enters from the lower middle part of column 3 (C3), while the extractant enters from the top, yielding n-propanol with a flow rate of 4.31 kmol / h and a purity of 99.9% at the top. Distillation column 4 (C4) has 19 plates. The water-extractant mixture from the bottom of distillation column 3 (C3) enters from the middle of column 4 (C4), completing the separation of water and extractant. The operating pressure of distillation column 1 (C1) was 0.16 atm, the operating pressure of distillation column 2 (C2) was 0.1 atm, the operating pressure of distillation column 3 (C3) was 0.1 atm, and the operating pressure of distillation column 4 (C4) was 0.1 atm. After separation, the purity of n-propyl formate was 99.9%, and the yield was 99.9%; the purity of n-propanol was 99.9%, and the yield was 99.9%; and the purity of water was 99.9%, and the yield was 99.9%.

Claims

1. A process for separating a mixture of n-propyl formate - n-propanol - water by liquid-liquid phase coupling pressure swing assisted extractive distillation, characterized in that The device of the separation process mainly comprises the following parts: rectifying column 1 (C1), rectifying column 2 (C2), rectifying column 3 (C3), rectifying column 4 (C4), condenser 1 (CO1), condenser 2 (CO2), condenser 3 (CO 3), condenser 4 (CO4), reboiler 1 (R1), reboiler 2 (R2), reboiler 3 (R3), reboiler 4 (R4), phase separator (DE), mixer (MIX), cooler (COO1), centrifugal pump 1 (P1), centrifugal pump 2 (P2), centrifugal pump 3 (P3); wherein the feed is layered in the phase separator, the upper layer is the organic phase, and the lower layer is the aqueous phase; the aqueous phase enters the rectifying column 1 (C1), and high-purity water is collected at the bottom of the rectifying column 1 (C1); the organic phase and the overhead stream of the rectifying column 1 (C1) enter the mixer (MIX) together, and after mixing, they are used as the feed of the rectifying column 2 (C2); high-purity n-propyl formate is collected at the top of the rectifying column 2 (C2), and the mixture at the bottom enters the rectifying column 3 (C3); high-purity n-propanol is collected at the top of the rectifying column 3 (C3), and the stream at the bottom enters the rectifying column 4 (C4); high-purity product water is collected at the top of the rectifying column 4 (C4), and high-purity extractant is obtained at the bottom, which is transported to the cooler (COO1) by P3, and after cooling, the extractant is supplemented and then refluxed to the rectifying column 2 (C2) and the rectifying column 3 (C3); The method for separating n-propyl formate-n-propanol-water mixture by liquid-liquid phase separation coupled with pressure swing auxiliary extractive distillation comprises the following steps: (1) The n-propyl formate-n-propanol-water mixture enters the phase separator (DE) to be layered, the upper layer is the organic phase, and the lower layer is the aqueous phase, the aqueous phase enters the middle part of the rectifying column 1 (C1), the operating pressure is 0.16 atm, the number of trays is 25-35, the feeding position is 15-20, after high-efficiency heat and mass transfer separation of the vapor-liquid two-phase in the column, high-purity product water is collected at the bottom of the rectifying column 1 (C1), and the n-propyl formate-n-propanol-water mixture collected at the top is mixed with the organic phase separated in the phase separator in the mixer (MIX) and then enters the rectifying column 2 (C2); (2) The n-propyl formate-n-propanol-water mixture enters the middle and lower part of the rectifying column 2 (C2), the operating pressure is 0.1 atm, the number of trays is 30-40, the feeding position is 15-25, the extractant enters the upper part of the rectifying column 2 (C2), the feeding position is 3-10, high-purity n-propyl formate is collected at the top of the rectifying column 2 (C2), and the stream at the bottom is the n-propanol-water-extractant mixture which is transported to the rectifying column 3 (C3) by the centrifugal pump 1 (P1); (3) The mixture of n-propanol-water-extractant is fed from the lower part of rectification column 3 (C3), the operating pressure of which is 0.1 atm, the number of plates is 50-60, the feeding position is 30-45, the extractant is fed from the upper part of rectification column 3 (C3), the feeding position of which is 3-10, high purity n-propanol is obtained from the top of rectification column 3 (C3), and the water-extractant mixture from the bottom of rectification column 3 (C3) is sent to rectification column 4 (C4) through centrifugal pump 2 (P2), the operating pressure of which is 0.1 atm, the number of plates is 15-25, the feeding position is 5-13, and high purity water is obtained from the top of rectification column 4 (C4) ; (4) The extractant with high purity from the bottom of rectification column 4 (C4) is fed into cooler (COO1) through centrifugal pump 3 (P3), and then is fed into rectification column 2 (C2) and rectification column 3 (C3) after being cooled and supplemented with extractant.

2. According to claim 1, the method is further characterized in that the temperature range of rectification column 1 (T1) is 25-75℃; the temperature range of rectification column 2 (T2) is 20-100℃; the temperature range of rectification column 3 (T3) is 40-170℃; and the temperature range of rectification column 4 (T4) is 40-190℃.

3. According to claim 1, the method is further characterized in that the extractant is a mixture of glycerol and 1,3-propanediol.

4. According to claim 1, the method is further characterized in that the molar fraction of glycerol in the extractant is 50%-70%.

5. According to claim 1, the method is further characterized in that the molar ratio of the feeding flow rate of the extractant to the mixture of n-propyl formate-n-propanol-water is 0.2-0.

5.

6. According to claim 1, the method is further characterized in that the molar fraction of n-propyl formate in the mixture of n-propyl formate-n-propanol-water is 62.92%, the molar fraction of n-propanol is 4.31%, and the molar fraction of water is 32.77%.

7. According to claim 1, the method is further characterized in that the purity of water recovered from the bottom of rectification column 1 (C1) and the top of rectification column 4 (C4) is higher than 99.9%, the yield is higher than 99.9%; the purity of n-propyl formate recovered from the top of rectification column 2 (C2) is higher than 99.9%, the yield is higher than 99.9%; and the purity of n-propanol recovered from the top of rectification column 3 (C3) is higher than 99.9%, the yield is higher than 99.9%.

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