阅读说明：本技术 共沸精馏分离二异丙胺和乙醇混合物的方法 (Method for separating mixture of diisopropylamine and ethanol by azeotropic distillation ) 是由 钱超 洪增 阮建成 周少东 陈新志 于 2020-11-23 设计创作，主要内容包括：本发明公开了一种共沸精馏分离二异丙胺和乙醇混合物的方法,作为原料的二异丙胺和乙醇混合物为主要由二异丙胺和乙醇组成、且包含少量水的混合溶液,先将混合溶液进行除水处理,直至得含水率＜1％的除水后混合溶液；共沸剂与除水后混合溶液在共沸精馏塔内,采用间歇精馏方法或者三塔连续精馏方法进行精馏,共沸剂将除水后混合溶液中的乙醇夹带出来,从而实现分离二异丙胺和乙醇的目的；所述共沸剂为甲苯。本发明以水作为萃取剂回收甲苯,避免了增加额外第三组分分离回收甲苯,降低了能耗。(The invention discloses a method for separating a mixture of diisopropylamine and ethanol by azeotropic distillation, wherein the mixture of diisopropylamine and ethanol as raw materials is a mixed solution which mainly comprises diisopropylamine and ethanol and contains a small amount of water, and the mixed solution is subjected to dehydration treatment until a dehydrated mixed solution with the water content of less than 1 percent is obtained; rectifying the entrainer and the dehydrated mixed solution in an azeotropic rectifying tower by adopting an intermittent rectifying method or a three-tower continuous rectifying method, and carrying out ethanol in the dehydrated mixed solution by the entrainer so as to realize the purpose of separating diisopropylamine and ethanol; the entrainer is toluene. According to the invention, water is used as an extracting agent to recover the toluene, so that an additional third component is avoided to separate and recover the toluene, and the energy consumption is reduced.)

1. A process for separating a mixture of diisopropylamine and ethanol by azeotropic distillation, wherein the mixture of diisopropylamine and ethanol as a raw material is a mixed solution mainly composed of diisopropylamine and ethanol and containing a small amount of water, characterized in that:

firstly, carrying out dehydration treatment on the mixed solution until a dehydrated mixed solution with the water content of less than 1% is obtained;

rectifying the entrainer and the dehydrated mixed solution in an azeotropic rectifying tower by adopting an intermittent rectifying method or a three-tower continuous rectifying method, and carrying out ethanol in the dehydrated mixed solution by the entrainer so as to realize the purpose of separating diisopropylamine and ethanol;

the entrainer is toluene.

2. The method for separating diisopropylamine from ethanol by azeotropic distillation according to claim 1, wherein:

when batch rectification is employed, the entrainer: and (3) removing water, wherein the mixed solution is 0.1-0.8: 1 in mass ratio;

when three-tower continuous rectification is adopted, the entrainer: and (3) removing water, wherein the mixed solution is 0.1-0.6: 1, mass ratio.

3. The method for separating diisopropylamine from ethanol by azeotropic distillation according to claim 2, wherein: the batch distillation is adopted, and the following two conditions are adopted:

case one, include the following steps:

1.1) mixing toluene as an entrainer with the dehydrated mixed solution, adding the mixture into the bottom of an intermittent rectifying kettle, and starting to extract fractions when the temperature of the top of the intermittent rectifying kettle is stable after total reflux;

1.2) condensing the distillate at the top of the batch rectifying still by a condenser, then feeding the distillate into an azeotrope collecting tank, and extracting a reflux ratio (5 +/-0.5): 1; when the concentration of ethanol in the overhead fraction of the batch distillation kettle is reduced to be less than or equal to 15%, a transition fraction collecting tank is used for receiving the ethanol, and the reflux ratio of the extracted ethanol is 2.8-3.2: 1; when the ethanol concentration in the overhead fraction of the batch distillation kettle is reduced to be less than or equal to 1%, replacing a product collecting tank, and extracting the reflux ratio of 1.8-2.2: 1; when the temperature at the top of the tower is more than or equal to 85 ℃, ending the rectification;

case two, include the following steps:

2.1) adding the mixed solution into the batch rectifying still after water removal, and adding toluene into the batch rectifying still from the upper half part of the side wall of the batch rectifying still or the top of the batch rectifying still after reflux is formed; the toluene and the rising ethanol steam form azeotropy, and when the temperature at the top of the tower is stable, the distillate is extracted;

2.2), same as 1.2);

2.3) and feeding the azeotropic mixed liquid in the azeotrope collecting tank into an extraction tower, and adding water into the extraction tower, thereby realizing extraction and recovering toluene from the top of the extraction tower.

4. The method for separating diisopropylamine from ethanol by azeotropic distillation according to claim 3, wherein:

in the step 2.3), the amount of water is 0.3-0.4 times of the mass of the dehydrated mixed solution.

5. The method for separating diisopropylamine from ethanol by azeotropic distillation according to claim 2, wherein: three-tower continuous rectification is adopted, and the method comprises the following steps:

after dewatering, the mixed solution and toluene enter an azeotropic distillation tower respectively according to the flow ratio of 1.8-2.2;

taking out a formed toluene and ethanol azeotrope from the top of an azeotropic distillation tower, condensing the azeotrope by a condenser, controlling the reflux ratio of the azeotropic distillation tower to be 2.8-3.2: 1, feeding the azeotrope into the bottom of an extraction tower under the action of a centrifugal pump, and carrying out countercurrent contact with water injected from a water inlet at the top of the extraction tower in the extraction tower to recover toluene; mixed solution of ethanol and water is obtained at the bottom of the extraction tower, and toluene is discharged from the top of the extraction tower;

the mixture of toluene and diisopropylamine extracted from the bottom of the azeotropic distillation kettle enters a product distillation tower for separation after passing through a reboiler, and returns to the azeotropic distillation kettle after entering the reboiler: and (3) enabling a mixture leaving the reboiler to enter a product rectifying tower at a volume ratio of 2.8-3.2: 1, obtaining diisopropylamine at the top of the product rectifying tower, fully condensing the diisopropylamine through a condenser, and controlling the reflux ratio of the product rectifying tower to be 2.5: 1;

toluene obtained at the bottom of the product rectifying tower passes through a reboiler, enters the reboiler and then returns to the product rectifying tower: and the toluene leaving the reboiler is 1.8-2.2 volume ratio, and the toluene leaving the reboiler and the toluene discharged from the top of the extraction tower are converged and then enter the azeotropic distillation tower together, so that the cyclic utilization is realized.

6. The method of azeotropic distillation separation of diisopropylamine and ethanol according to claim 5, wherein:

and (3) the flow ratio of the mixed solution after water removal to water entering the extraction tower is 8: 2.5-3.5.

7. The method for separating diisopropylamine from ethanol by azeotropic distillation according to claim 5 or 6, wherein:

the top temperature of the azeotropic distillation tower is 76.8 +/-1 ℃, and the kettle temperature is 92.8 +/-1 ℃;

the top temperature of the product rectifying tower is 83.2 +/-1 ℃, and the kettle temperature is 110.5 +/-1 ℃.

8. The method for separating diisopropylamine from ethanol by azeotropic distillation according to any one of claims 1 to 7, wherein:

in the mixture of diisopropylamine and ethanol, the mass ratio of ethanol to diisopropylamine is 0.1-1: 1.

Technical Field

The invention belongs to the field of fine chemical engineering, and particularly relates to a method for separating diisopropylamine and ethanol by azeotropic distillation.

Background

Diisopropylamine is colorless liquid at normal temperature, has a boiling point of 84 ℃, has an irritant ammonia smell, is miscible with water and can be dissolved in most organic solvents; is an important raw material for producing fine chemicals such as pesticides, medicines, dyes, emulsifiers and the like, in particular to one of important raw materials for producing non-nucleophilic amine base N, N-diisopropylethylamine. Ethanol, a colorless and transparent liquid at normal temperature, has a boiling point of 78.5 ℃, is the most widely used alcohol, and is an important organic synthetic raw material and an organic solvent.

In the process of industrial production of DIPEA (N, N-diisopropylethylamine, diisopropylethylamine for short), a mixed solution containing a large amount of diisopropylamine and ethanol is often generated. In the mixed solution, the mass ratio of ethanol to diisopropylamine is 0.1-1: 1; the mixed solution contains water with the content of about 4.5 percent and trace impurities besides ethanol and diisopropylamine, wherein the impurities mainly comprise N-isopropyl ethylamine and N, N-diisopropylethylamine which are ignored.

Diisopropylamine (boiling point 84 ℃) and ethanol (boiling point 78.5 ℃) do not have azeotropy under normal pressure, but because the boiling points of the diisopropylamine and the ethanol are close and form hydrogen bonds, the relative volatility is low, and the diisopropylamine and the ethanol cannot be separated by adopting a common normal pressure rectification method. Resulting in a portion of the diisopropylamine raw material being difficult to recover, which undoubtedly increases the operating cost of the enterprise. At present, there is no report of separating diisopropylamine from ethanol.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a method for separating a mixture of diisopropylamine and ethanol by azeotropic distillation, which can be used for intermittent operation or continuous operation of separating diisopropylamine and ethanol.

In order to solve the technical problems, the invention provides a method for separating a mixture of diisopropylamine and ethanol by azeotropic distillation, wherein the mixture of diisopropylamine and ethanol as raw materials is a mixed solution which mainly consists of diisopropylamine and ethanol and contains a small amount of water;

i.e. the sum of the contents of diisopropylamine and ethanol is more than 95%; the content of water is less than 5 percent; % by mass;

firstly, carrying out dehydration treatment on the mixed solution until a dehydrated mixed solution with the water content of less than 1 percent (mass percent) is obtained;

rectifying the entrainer and the dehydrated mixed solution in an azeotropic rectifying tower by adopting an intermittent rectifying method or a three-tower continuous rectifying method, and carrying out ethanol in the dehydrated mixed solution by the entrainer so as to realize the purpose of separating diisopropylamine and ethanol;

the entrainer is toluene.

The improvement of the method for separating diisopropylamine and ethanol by azeotropic distillation of the invention comprises the following steps:

when batch rectification is employed, the entrainer: and (3) removing water, wherein the mixed solution is 0.1-0.8: 1 in mass ratio;

when three-tower continuous rectification is adopted, the entrainer: and (3) removing water, wherein the mixed solution is 0.1-0.6: the mass ratio of 1 is, for example, 0.5: 1.

As a further improvement of the method for separating diisopropylamine and ethanol by azeotropic distillation of the invention:

the batch distillation is adopted, and the following two conditions are adopted:

case one, include the following steps:

1.1) mixing toluene serving as an entrainer with the dehydrated mixed solution, adding the mixed solution to the bottom of the batch distillation kettle, and completely refluxing until the temperature of the top of the batch distillation kettle is stable (namely, the display temperature of a temperature measuring point at the top of the tower is 66-67 ℃), and starting to extract a fraction;

1.2) condensing the distillate at the top of the batch rectifying still by a condenser, then feeding the distillate into an azeotrope collecting tank, and extracting a reflux ratio (5 +/-0.5): 1 (namely the volume ratio of feed liquid returned to the batch still to the feed liquid entering an azeotrope collecting tank is 5 +/-0.5: 1); when the concentration of ethanol in the overhead fraction of the batch distillation kettle is reduced to be less than or equal to 15%, a transition fraction collecting tank is used for receiving the ethanol, and the reflux ratio of the extracted ethanol is 2.8-3.2: 1 (preferably 3: 1); when the ethanol concentration in the overhead fraction of the batch distillation kettle is reduced to be less than or equal to 1%, replacing a product collecting tank, and extracting a reflux ratio of 1.8-2.2: 1 (preferably 2: 1); when the temperature at the top of the tower is more than or equal to 85 ℃, ending the rectification;

case two, include the following steps:

2.1) adding the mixed solution into the batch rectifying still after water removal, and adding toluene into the batch rectifying still from the upper half part of the side wall of the batch rectifying still or the top of the batch rectifying still after reflux (total reflux) is formed; the toluene and the rising ethanol steam form azeotropy, and when the temperature at the top of the tower is stable (namely, the display temperature of a temperature measuring point at the top of the tower is 74-76 ℃), the distillate is extracted;

2.2), same as 1.2);

2.3) and feeding the azeotropic mixed liquid in the azeotrope collecting tank into an extraction tower, and adding water into the extraction tower, thereby realizing extraction and recovering toluene from the top of the extraction tower.

As a further improvement of the method for separating diisopropylamine and ethanol by azeotropic distillation of the invention:

in the step 2.3), the amount of water is 0.3-0.4 times of the mass of the dehydrated mixed solution.

As a further improvement of the method for separating diisopropylamine and ethanol by azeotropic distillation of the invention:

three-tower continuous rectification is adopted, and the method comprises the following steps:

after dewatering, respectively feeding the mixed solution and toluene into an azeotropic distillation tower according to a flow ratio (mass flow ratio) of 1.8-2.2 (preferably 2: 1);

taking out a formed toluene and ethanol azeotrope from the top of an azeotropic distillation tower, condensing the azeotrope by a condenser, controlling the reflux ratio of the azeotropic distillation tower to be 2.8-3.2: 1 (preferably 3: 1), feeding the azeotrope into the bottom of an extraction tower under the action of a centrifugal pump, and carrying out countercurrent contact with water injected from a water inlet at the top of the extraction tower in the extraction tower to recover toluene; the bottom of the extraction tower obtains mixed solution of ethanol and water, and toluene (liquid state) is discharged from the top of the extraction tower;

the mixture of toluene and diisopropylamine extracted from the bottom of the azeotropic distillation kettle enters a product distillation tower for separation after passing through a reboiler, and returns to the azeotropic distillation kettle after entering the reboiler: and (3) enabling a mixture leaving the reboiler to enter a product rectifying tower to have a volume ratio of 2.8-3.2: 1 (preferably 3: 1), obtaining diisopropylamine at the top of the product rectifying tower, fully condensing the diisopropylamine by using a condenser, and controlling the reflux ratio of the product rectifying tower to be 2.5: 1;

toluene obtained at the bottom of the product rectifying tower passes through a reboiler, enters the reboiler and then returns to the product rectifying tower: and the volume ratio of the toluene leaving the reboiler is 1.8-2.2 (preferably 2:1), and the toluene leaving the reboiler and the toluene discharged from the top of the extraction tower are converged and then enter the azeotropic distillation tower together, so that the cyclic utilization is realized.

As a further improvement of the method for separating diisopropylamine and ethanol by azeotropic distillation of the invention:

the flow ratio (mass flow ratio) of the mixed solution after water removal to water entering the extraction column is 8:2.5 to 3.5 (preferably 8: 3).

As a further improvement of the method for separating diisopropylamine and ethanol by azeotropic distillation of the invention:

the top temperature of the azeotropic distillation tower is 76.8 +/-1 ℃, and the kettle temperature is 92.8 +/-1 ℃;

the top temperature of the product rectifying tower is 83.2 +/-1 ℃, and the kettle temperature is 110.5 +/-1 ℃.

As a further improvement of the method for separating diisopropylamine and ethanol by azeotropic distillation of the invention:

in the mixture of diisopropylamine and ethanol, the mass ratio of ethanol to diisopropylamine is 0.1-1: 1.

the invention adopts intermittent rectification or three-tower continuous rectification to the mixture of diisopropylamine and ethanol and the entrainer, and the entrainer carries out ethanol separation to realize the separation of diisopropylamine and ethanol.

One key factor in the success of the present invention is that the moisture content of the feedstock is as low as possible because water can be carried over with diisopropylamine at a lower temperature (74 ℃) to form an azeotrope, and water can form an azeotrope with toluene at 66.7 ℃ to consume the entrainer, so the feedstock must be dried to a moisture content of 1.5% or less before operation.

The main technical advantages of the invention are as follows:

1. the invention solves the problem that the diisopropylamine and the ethanol system are difficult to separate, and can flexibly implement intermittent or continuous process flow according to the composition and conditions of materials.

2. The invention adopts toluene as the entrainer, the entrainer is easily available in source and convenient to recycle, and the secondary investment of the entrainer is reduced.

3. Water is used as an extracting agent to recover the toluene, so that the additional third component is avoided to separate and recover the toluene, and the energy consumption is reduced.

Drawings

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.

FIG. 1 is a schematic view of the structure of a batch rectification apparatus;

FIG. 2 is a schematic diagram of a three-column continuous rectification apparatus.

Detailed Description

The invention will be further described with reference to specific examples, but the scope of the invention is not limited thereto:

case 1, industrial production of DIPEA: halogenated ethane and diisopropylamine react in the presence of a catalyst, since at the end of the reaction, both diisopropylamine and halogenated ethane do not react completely, hydrolysis occurs in the neutralization step, so that a lot of ethanol byproducts are produced, and after rectification, an original mixed solution i containing a large amount of diisopropylamine and ethanol is obtained, wherein the original mixed solution i has a water content of 4.5%, an ethanol content of about 38.2%, and a diisopropylamine content of about 57.3%, namely, ethanol: diisopropylamine 1: 1.5; impurities are ignored.

Carrying out dewatering treatment on the original mixed solution I by using sodium hydroxide: adding 3g of sodium hydroxide into 100g of the original mixed solution, stirring to dissolve the sodium hydroxide, separating a water layer, repeating for many times until no new water layer is separated out, and measuring the water content to show that the water content is 0.75 percent, so the water content can be ignored; and (5) obtaining the dehydrated mixed solution I.

Case 2, industrial production of DIPEA: halogenated ethane and diisopropylamine react in the presence of a catalyst, because at the end of the reaction, both diisopropylamine and halogenated ethane do not react completely, hydrolysis is caused in the neutralization step, so that a plurality of ethanol byproducts are generated, and after rectification, an original mixed solution II containing a large amount of diisopropylamine and ethanol is obtained, wherein in the original mixed solution II, the water content is 3.5%, the ethanol content is about 19.3%, the diisopropylamine content is about 77.2%, namely, the mass ratio of ethanol to diisopropylamine is 0.25: 1, neglecting to take impurities.

Carrying out water removal treatment on the original mixed solution II by using sodium hydroxide until the water content is 0.5 percent, so that the water content can be ignored; and obtaining the dehydrated mixed solution II.

The device I is an intermittent rectification device, as shown in figure 1, and comprises an intermittent rectification kettle 1, a toluene tank 4 and an extraction tower 10; the batch distillation kettle 1 is provided with a tower kettle temperature measuring point 2, a tower kettle sampling point 12 and a tower top temperature measuring point 3.

An outlet of the toluene tank 4 is connected with the top of the batch rectifying still 1 after passing through a stop valve 21; the inlet of the toluene tank 4 is connected with the top of the extraction tower 10;

the discharge port at the top of the batch still 1 is divided into the following two paths after passing through a condenser 5: one path passes through the stop valve 22 and then is connected with the following 3 parts in parallel: the product is communicated with the azeotrope collecting tank 6 after passing through the stop valve 25, communicated with the excessive fraction collecting tank 7 after passing through the stop valve 26, and communicated with the product collecting tank 8 after passing through the stop valve 27; the other path is communicated with a top reflux port of the batch rectifying still 1.

At the outlet of the condenser 5, an overhead sampling point 11 is provided.

The bottom of the azeotrope collecting tank 6 is connected with the lower part of the side wall of the extraction tower 10 through a stop valve 28 and a centrifugal pump 9 in sequence, and the water inlet pipe 13 is connected with the upper part of the side wall of the extraction tower 10. An ethanol aqueous solution discharge port 14 is provided at the bottom of the extraction column 10.

The condenser 5 is used for cooling the fraction (gas) extracted from the top of the batch distillation kettle 1 to liquid, and the liquid enters one of an azeotrope collecting tank 6, an excessive fraction collecting tank 7 and a product collecting tank 8 according to a set requirement; when the azeotrope is selected to enter the azeotrope collecting tank 6, the stop valve 25 is opened, and the stop valves 26 and 27 are closed; similarly, when the excessive fraction collecting tank 7 is selected to enter, the stop valve 26 is opened, and the stop valves 25 and 27 are closed; when access to the product collection tank 8 is selected, the shut-off valve 27 is open, and both the shut-off valves 25, 26 are closed.

The stop valve 25 is used for adjusting the reflux ratio of the distillate when entering the azeotrope collecting tank 6; similarly, the stop valve 26 is used for adjusting the reflux ratio of the fraction entering the transition fraction collecting tank 7, and the stop valve 27 is used for adjusting the reflux ratio of the fraction entering the product collecting tank 8.

When the reaction is started, the stop valve 22 is fully closed, namely, the feed liquid at the outlet of the condenser 5 fully flows back to the batch distillation kettle 1; when the fraction starts to be produced, the shut-off valve 22 is fully opened.

Example 1-1, a method for separating diisopropylamine and ethanol by azeotropic distillation, aiming at the situation that the batch distillation process is adopted for the mixed solution I after water removal,

in the first embodiment, both the cut-off valves 21 and 28 are closed, i.e., neither the toluene tank 4 nor the extraction column 10 is used in the first embodiment 1-1.

The method comprises the following specific steps:

after mixing 360g of the dehydrated mixed solution I and 100g of toluene serving as an entrainer, adding the mixture into the bottom of an intermittent distillation kettle 1 together, carrying out total reflux until the temperature at the top of the tower is stable (namely, the display temperature of a temperature measuring point 3 at the top of the tower is 66-67 ℃), then starting to extract a fraction, condensing the fraction by a condenser 5 to an azeotrope collecting tank 6, and controlling the reflux ratio by 5:1 (i.e. the volume ratio of feed liquid returned to batch still 1 to feed liquid entering azeotrope collection tank 6 is 5: 1); when the ethanol concentration in the overhead distillate (i.e., as detected at overhead sampling point 11) drops below 15%, it is received instead by transition fraction receiver tank 7 at a reflux ratio of 3: 1, extracting; when the concentration of ethanol in the fraction extracted from the top of the batch distillation kettle 1 is reduced to be less than or equal to 1 percent, the product collecting tank 8 is used instead, and the reflux ratio is 2:1, extracting the product. And when the temperature of the top of the batch rectifying still 1 is more than or equal to 85 ℃, ending the steps.

After the rectification is finished, the composition of substances in each part of the batch rectification device is as follows (mass fraction):

TABLE 1

In this case, since the entrainer is refluxed only in the batch distillation still 1 and is not extracted, the toluene is not recovered by the extraction tower 10, and the still liquid is reused, that is, after the fraction collected by the excessive fraction tank 7 is mixed with the dehydrated mixed solution I of the next batch, the azeotropic distillation is carried out again to separate diisopropylamine and ethanol; and the bottom liquid of the batch rectifying still 1 can be recycled. The distillate collected by the azeotrope collection tank 6 may be subjected to subsequent treatment according to conventional biochemical treatment.

The once recovery rate of the diisopropylamine is equal to the mass of the diisopropylamine in the product collecting tank 8/the mass of the diisopropylamine in the raw material;

the secondary recovery rate of the diisopropylamine is the sum of the mass of the diisopropylamine in the transition fraction collecting tank 7 and the mass of the diisopropylamine in the product collecting tank 8/the mass of the diisopropylamine in the raw material;

therefore, after the rectification is finished, 99g of 99% diisopropylamine is obtained, the primary recovery rate of the diisopropylamine is about 45.3%, and the secondary recovery rate is 86%.

Example 1-2, the fraction collected in the excess fraction tank 7 was combined with the next batch of the water-removed mixed solution i and rectified as follows:

mixing 103g of fraction collected by the transition fraction collecting tank 7 obtained in example 1-1 and 248g of mixed solution I after water removal, and then adding 109g of bottom liquid of the batch rectifying still 1 obtained in example 1-1 for mixing; the procedure of example 1-1 was followed to obtain the following results in Table 2:

TABLE 2

Example 2, the amount of toluene used was changed from 100g to 144g, i.e., entrainer: after water removal, the mixed solution i is 0.4: 1 in mass ratio; the rest was equivalent to example 1-1. The final results were: about 120g of 99% diisopropylamine is obtained, and the secondary recovery rate reaches 88.1%.

Example 3, the amount of toluene used was changed from 100g to 288g, i.e., entrainer: after water removal, the mixed solution i is 0.8: 1 in mass ratio; the rest was equivalent to example 1-1. The final result was about 135g of 99% diisopropylamine, and the secondary recovery rate reached 89.1%.

Embodiment 4, a method for separating diisopropylamine and ethanol by azeotropic distillation, which is directed at the case two of using batch distillation process for the mixed solution i after water removal, i.e. the entrainer can be directly added into the batch distillation still 1 from the tower section; such as from the top of the column, which is less than the case of a corresponding direct bottom addition, but requires extraction to recover the toluene.

With the first device, in the initial condition, the stop valve 21 is opened; the shut-off valve 28 is closed.

The difference from example 1-1 is that: adding 360g of the dewatered mixed solution I into the batch distillation kettle 1, carrying out total reflux, and adding 80g of toluene in the toluene tank 4 into the top of the batch distillation kettle 1 at a flow rate of 2ml/min after the reflux is formed; the toluene and the rising ethanol steam form azeotropy, and when the temperature at the top of the tower is stable (namely, the display temperature of a temperature measuring point 3 at the top of the tower is 74-76 ℃), a fraction is extracted; the rest is equal to the example 1, namely, when the temperature of the top of the batch rectifying still 1 is more than or equal to 85 ℃, the rectifying separation is finished.

After the rectification, the composition (mass fraction) of each component of the batch rectification device is as follows in table 3:

TABLE 3

The final results were: about 122.5g of 98.8 percent diisopropylamine is obtained, the primary recovery rate of the diisopropylamine is 56.0 percent, and the secondary recovery rate is 82.0 percent.

After the rectification is finished, the stop valve 28 is opened, and the azeotropic mixed liquid in the azeotrope collecting tank 6 is pumped into the extraction tower 10 by the centrifugal pump 9; adding 120g of water into an extraction tower 10 from a water inlet pipe 13, wherein the extraction tower 10 is a packed tower, multi-stage countercurrent extraction is carried out, the theoretical stage number is 10, the flow of the water is 30ml/min, and the flow of an azeotropic mixed solution is 50 ml/min; finally, recovered toluene (consisting of 1% of diisopropylamine and 99% of toluene) is obtained from the top of the extraction column 10; the aqueous phase produced in the extraction column 10, which consists essentially of about 40.4% water and 54.6% ethanol, the remainder being diisopropylamine, is discharged from an aqueous ethanol discharge 14.

The energy consumed is mainly the electric power consumed by the centrifugal pump 9, and is about 0.04kw · h.

Comparative example 1, the azeotropic mixture in the azeotrope collecting tank 6 obtained in example 4 was extracted and rectified with n-butylbenzene; the method specifically comprises the following steps:

the azeotropic mixture in the azeotrope collecting tank 6 obtained in example 4 was mixed with 120g of n-butylbenzene, and then added to the bottom of the batch still (for example, the batch still 1 shown in fig. 1 may be used, and the stop valve 21 and the stop valve 28 are both closed, that is, the toluene tank 4 and the extraction column 10 are not used in this comparative example 1), and the mixture was refluxed for a certain period of time, and then the top of the column was refluxed at a reflux ratio of 5:1, ethanol is extracted, followed by extraction of 2:1 ratio of toluene. 56g of toluene was finally recovered from the column top in a yield of 92.2%. The energy consumed was 3.6kw · h.

Therefore, if the ethanol and the toluene are separated by extractive distillation using n-butylbenzene as an extractant according to the conventional technique, more energy is consumed.

Comparative example 2-1, 3 reflux ratios in example 1-1 were all set to 2: 1; the rest was equivalent to example 1-1.

The results obtained were: about 45g of 99% diisopropylamine is obtained, and the secondary recovery rate reaches 65.1%.

Comparative example 2-2, water removal treatment of the mixed solution was cancelled; that is, the same procedure as in example 1-1 was repeated except that the mixed solution I (water content: 0.75%) obtained in example 1-1 after water removal was changed to the original mixed solution I (water content: 4.5%).

The results obtained were: about 30g of 99% diisopropylamine is obtained, and the secondary recovery rate reaches 40%.

Comparative examples 2-3, the entrainer was changed from toluene to cyclohexane with the amount remaining unchanged; the rest was equivalent to example 1-1.

The results obtained were: about 45g of 99% diisopropylamine is obtained, and the secondary recovery rate reaches 55.1%.

The device II and the device III carry out continuous rectification and comprise an azeotropic rectification tower 30, a product rectification tower 40 and an extraction tower 50;

a raw material feed port 31 is arranged in the middle of the side wall of the azeotropic distillation tower 30, an entrainer feed port 32 is arranged at the upper part of the side wall of the azeotropic distillation tower 30, and toluene enters the azeotropic distillation tower 30 through the entrainer feed port 32.

The azeotrope (toluene and ethanol azeotrope) extracted from the top outlet of the azeotropic distillation tower 30 is condensed by the condenser 33 and then divided into two paths, one path enters the bottom of the extraction tower 50 after passing through the centrifugal pump 60, and the other path reflows to the top of the azeotropic distillation tower 30.

The bottom of the extraction tower 50 is provided with an ethanol water outlet 51, and the top is provided with a water inlet 52.

The bottom of the azeotropic distillation tower 30 is provided with a reboiler 34, and after the kettle liquid (the mixture of toluene and diisopropylamine) extracted from the bottom of the azeotropic distillation tower 30 passes through the reboiler 34, a part of the kettle liquid returns to the bottom of the azeotropic distillation tower 30 again, and the other part of the kettle liquid enters the product distillation tower 40.

Diisopropylamine extracted from the top outlet of the product rectification tower 40 is condensed by a condenser 41 and then divided into two paths, one path is discharged from a diisopropylamine discharge port 43, and the other path reflows to the top of the product rectification tower 40.

A reboiler 42 is arranged at the bottom of the product rectifying tower 40, and after the kettle liquid (toluene) extracted from the bottom of the product rectifying tower 40 passes through the reboiler 42, a part of the kettle liquid returns to the bottom of the product rectifying tower 40 again; the other part of the toluene is combined with the toluene extracted from the top outlet of the extraction tower 50 and then enters the azeotropic distillation tower 30 through the entrainer feed inlet 32. Valve 35 was used for initial toluene feed until toluene recycle flow in the three columns stabilized.

Example 5, a method for separating diisopropylamine and ethanol by azeotropic distillation, aiming at a mixed solution II consisting of diisopropylamine and ethanol, three-tower continuous distillation (device II) is adopted,

the dehydrated mixed solution II enters the azeotropic distillation tower 30 through the raw material feed inlet 31 according to the feed flow of about 8kg/h (namely, the mixed solution II is fed from the middle part of the distillation kettle), the toluene serving as the entrainer enters the azeotropic distillation tower 30 through the entrainer feed inlet 32 according to the feed flow of about 4kg/h, and the temperature of the azeotropic distillation tower 30 is set as described in the following table 4; the formed toluene and ethanol azeotrope is taken out from the top of the azeotropic distillation tower 30, and after being condensed by a condenser 33, the reflux ratio of the azeotropic distillation tower 30 is controlled to be 3: 1, entering the bottom of an extraction tower 50 under the action of a centrifugal pump 60, and carrying out countercurrent contact with water (the flow rate of the water is 3kg/h) injected from a water inlet 52 at the top of the extraction tower 50 in the extraction tower 50 to recover toluene, wherein the extraction tower 50 is a packed tower and the theoretical stage number is 10. The mixed solution of ethanol and water is obtained at the bottom of the extraction column 50 and is discharged from an ethanol water solution outlet 51. Toluene (liquid) was withdrawn from the top of the extraction column 50.

The mixture of toluene and diisopropylamine extracted from the bottom of the azeotropic distillation still 30 enters a product distillation tower 40 for separation after reboiling treatment by a reboiler 34, and the volume ratio of the mixture entering the reboiler to the mixture leaving the reboiler and entering the product distillation tower is 3: 1, setting the temperature of the product rectification column 40 as described in table 5 below;

and (3) obtaining a product diisopropylamine at the top of the product rectifying tower 40, fully condensing the diisopropylamine by using a condenser 41, and controlling the reflux ratio of the product rectifying tower 40 to be 2.5: 1, the diisopropylamine discharged from the diisopropylamine discharge port 43 is collected as a product.

The toluene obtained at the bottom of the product rectifying tower 40 is reboiled by a reboiler 42, and the volume ratio of the toluene returning to the product rectifying tower after entering the reboiler to the toluene leaving the reboiler is 2:1, the toluene leaving the reboiler and the toluene discharged from the top of the extraction tower 50 are merged and then enter the azeotropic distillation tower 30 through the entrainer feed port 32, so that the cyclic utilization is realized.

When the starting material was used up, the reaction was terminated.

TABLE 4 Steady-State operating parameters and component contents (% by mass) of azeotropic distillation column 30

TABLE 5 product rectification column 40 operating parameters

Note: the top temperature refers to the temperature of the reflux condensate at the top of the column, and the kettle temperature refers to the temperature of the kettle.

The final stable product flow is about 6kg/h, the purity of the obtained diisopropylamine product is more than or equal to 99 percent, and the primary recovery rate is more than or equal to 94 percent.

The first recovery rate is the flow rate of diisopropylamine in the product/the flow rate of diisopropylamine in the raw material.

In comparative example 3-1, the parameters of the continuous rectification process in example 5 were changed as follows: the flow rate of toluene was changed to 1 kg/h. The rest is equivalent to example 5.

The results obtained were: the final stable product flow is about 1.5kg/h, the purity of the obtained diisopropylamine product is more than or equal to 99 percent, and the primary recovery rate is more than or equal to 23 percent.

Comparative example 3-2, the water removal treatment of the mixed solution was cancelled. That is, the same procedure as in example 5 was repeated except that the mixed solution II (water content: 0.5%) obtained in example 5 after the water removal was changed to the original mixed solution II (water content: 3.5%).

The results obtained were: the final stable product flow is about 1.2kg/h, the purity of the obtained diisopropylamine product is more than or equal to 99 percent, and the primary recovery rate is more than or equal to 18 percent.

Comparative example 3-3, the entrainer was changed from toluene to cyclohexane with the amount remaining unchanged; the rest is equivalent to example 5.

The results obtained were: the final stable product flow is about 2.1kg/h, the purity of the obtained diisopropylamine product is more than or equal to 99 percent, and the primary recovery rate is more than or equal to 32 percent.

Finally, it is also noted that the above-mentioned lists merely illustrate a few specific embodiments of the invention. It is obvious that the invention is not limited to the above embodiments, but that many variations are possible. All modifications which can be derived or suggested by a person skilled in the art from the disclosure of the present invention are to be considered within the scope of the invention.