CN104961641A - Method for preparing monoisopropanolamine by virtue of reactive rectification - Google Patents

Abstract

The present invention relates to a production method for reactive distillation to prepare isopropanolamine. The method comprises the following steps: input liquid ammonia from the lower part of the reactive distillation tower through a pressure reducing valve, and at the same time, feed propylene oxide from The second tray in the upper part of the tower is input, and the catalyst water is input from the top of the tower at 15 ° C ~ 40 ° C, wherein the feed ammonia: propylene oxide feed molar ratio = 0.8-2.0: 1, the feed amount of water is the total 10-50% of the mass fraction of the feed amount, the total feed amount is the sum of water, liquid ammonia and propylene oxide quality; At 31~50°C, the temperature of the tower bottom is 165~310°C, and the temperature of the tower is 0.8MPa~1.5MPa; the feeding position of liquid ammonia is the bottom of the rectification tower or the first or second tray above the bottom of the tower . Compared with the traditional technique, the content of the monoisopropanolamine in the present invention is increased by nearly 100%, while the content of the triisopropanolamine is reduced by about 95% compared with the traditional technique.

Description

A kind of reactive distillation prepares the method for monoisopropanolamine

technical field

The invention belongs to the field of chemical reaction and separation, and specifically relates to a method for preparing monoisopropanolamine through reactive distillation.

Background technique

Monoisopropanolamine is a common name for 1-amino-2-propanol (chemical formula: CH ₃ CH(OH)CH ₂ NH ₂ ), also known as monoisopropanolamine. Monoisopropanolamine has a wide range of uses: it can be used in daily chemicals such as detergents, liquid detergents, and shampoos; it can be used in fabrics, wool spinning, and leather auxiliaries; it can be used in detergents for metal electronic liquid crystals and semiconductors; it can be used Used in the synthesis of pharmaceuticals, pesticides and flavors and fragrances intermediates.

The reaction of propylene oxide and ammonia is strongly exothermic. When there is absolutely no water, it is difficult for propylene oxide to react with ammonia, and the addition of water can initiate a catalytic reaction. The ammonolysis reaction of propylene oxide is a series of sequential reactions for ammonia, and a series of parallel competing reactions for propylene oxide, and the products are monoisopropanolamine, diisopropanolamine and triisopropanolamine in sequence Alcoholamine. It can be expected that as long as they react together, a mixture of three kinds of isopropanolamines will be formed, and it is impossible to generate a certain kind of isopropanolamines alone.

The activation energies of the above three reaction steps are almost the same, and the reaction rate has an approximate quadratic dependence on the water content in the ammonia-water mixture. Therefore, the adjustment of the product composition mainly depends on the molar excess of ammonia. A high ammonia ring ratio is obviously conducive to the formation of One isopropanolamine, so a large excess of ammonia is necessary, and the amount of catalyst water also needs to be controlled within an appropriate range. Too little water will cause slow reaction, and too much water will cause more side reactions and increase the energy consumption of subsequent dehydration treatment of products. .

The method of producing monoisopropanolamine in the traditional industry is mostly to put reaction material ammonia, propylene oxide and catalyst water in the high-pressure reactor first, then through deammonization and dehydration treatment, and then gradually separate monoisopropanolamine, Diisopropanolamine, triisopropanolamine three products. In order to improve the selectivity of the product to one isopropanolamine and create a high molar ratio of ammonia to propylene oxide, it needs to be controlled in a very high range (15-50:1), resulting in a large excess of ammonia, which will be removed after the reaction. The energy consumption of ammonia and dehydration is large, and the average steam consumption per ton of product is more than 30 tons. In addition, there are 20-30% triisopropanolamine in the reaction product, which is difficult to utilize because of the small market demand. The traditional production process of monoisopropanolamine is high in energy consumption, difficult to separate, complex in process, harsh in process conditions, and huge in operating costs.

Contents of the invention

The purpose of the present invention is to aim at the high ratio of molar ratio of ammonia ring to feed that exists in the traditional monoisopropanolamine production process, the huge energy consumption produced in the deamination and dehydration process, various equipment and high proportion of triisopropanolamine in the product Insufficient, provide a kind of reactive distillation to prepare the production technique of monoisopropanolamine, this technique will react and separate and synthesize one step, while reducing the energy consumption in the traditional technique, dwindled the ammonia ring molar ratio (0.8-2.0), Improve product selectivity, the reaction product is monoisopropanolamine, a small amount of diisopropanolamine does not generate triisopropanolamine.

Technical scheme of the present invention is:

A kind of reactive distillation is produced the production method of isopropanolamine, comprises the following steps:

The liquid ammonia is input from the lower part of the reactive distillation column through the pressure reducing valve, at the same time, the propylene oxide is input from the second tray in the upper part of the column at 25 ° C, and the catalyst water is input from the top of the column at 15 ° C ~ 40 ° C, wherein, Feed ammonia: propylene oxide feed molar ratio = 0.8-2.0: 1, the feed amount of water is 10-50% of the mass fraction of the total feed amount, and the total feed amount is water, liquid ammonia and ring The sum of the mass of oxypropane;

The number of trays in the reactive distillation tower is 25-45, the temperature at the top of the tower is controlled at 31-50°C, the temperature at the bottom of the tower is 165-310°C, and the pressure of the tower is controlled to ensure that the ammonia is in a liquid state, ranging from 0.8MPa to 1.5 MPa; the liquid ammonia feed position is the first or second tray above the bottom of the rectification column.

The steam at the top of the tower is condensed by the first condenser, all of which flow back to the top of the tower and flow back into the tower; the bottom products of the reactive distillation tower are all extracted from the bottom of the tower.

Described reactive distillation produces the production method of isopropanolamine, also comprises the refining process of product, comprises the steps:

After the bottom product is heated to 80 degrees by the heat exchanger, it enters the dehydration tower. The number of plates in the dehydration tower is 20-25, and the feeding position is the 7th-13th plate. The operating pressure of the tower is normal pressure. The temperature at the top is 99-101°C, the temperature at the bottom of the tower is 150-200°C, and the operating reflux ratio is 0.34-2. The extract is water, or a mixture of water and a small amount of ammonia (the content of ammonia is 0-10%); the bottom product of the dehydration tower is monoisopropanolamine and diisopropanolamine, which are passed through the second reboiler Raise the temperature to 80°C, and then enter the 6th-10th plate of the vacuum distillation tower, the number of plates in the tower is 15-20, the operating pressure of the tower is 0.01MPa, the temperature at the top of the tower is 90-120°C, and the temperature at the bottom of the tower is The temperature is 200-250°C, the operating reflux ratio is 0.04-2, and the final tower top is condensed by the third condenser, the distillate is pure monoisopropanolamine, and the bottom product is pure diisopropanolamine.

The reactive distillation tower is specifically a valve tower, a bubble cap tower, a sieve tray tower, a packed tower or a CTST tray.

Substantive features of the present invention are:

Reactive distillation technology combines the technological characteristics of the reaction process with the engineering characteristics of the rectification separation equipment. It can not only use the separation effect of rectification to improve the equilibrium conversion rate of the reaction, suppress the occurrence of side reactions, and effectively improve the separation efficiency of the tower. To achieve the purpose of increasing productivity and saving investment. The use of reactive distillation technology to replace the traditional production process not only simplifies the production process, reduces material consumption and energy consumption, improves production capacity, and reduces production costs, it is of great significance to improve the market competitiveness of enterprises.

Studies have shown that the reaction rate between ammonia and propylene oxide is a very rapid liquid phase reaction with a large difference in boiling point between the reactants and products. The inventor, through a lot of research, utilizes the special physical property relationship between this unique reactant and the product to carry out the process of reactive distillation, and purifies the product isopropanolamine while ammonia and propylene oxide react, and adjusts the isopropanolamine product ratio.

After adopting the present invention to remove water from the product flowing out from the bottom of the tower in the reactive distillation tower, the content of monoisopropanolamine can reach 85-93% (wt), and that of diisopropanolamine can reach 7-15% (wt). ), less than 0.5% (wt) of triisopropanolamine, and the mol ratio of monoisopropanolamine to diisopropanolamine can reach 12.6. The content of triisopropanolamine in the product is very low (it can be considered that there is no generation), and the content of monoisopropanolamine product meets the ideal standard. In the traditional process, the range of monoisopropanolamine is 30-60% (wt), and the content of triisopropanolamine is 20-30% (wt). Compared with traditional technology, the ratio of monoisopropanolamine is greatly improved , and basically eliminated the formation of triisopropanolamine.

The reactive distillation device involved in the present invention is not limited by the type of specific tower, as long as it can provide an internal contact area, traditional packed towers and plate towers can be used.

The beneficial effects of the present invention are:

1) Simplify multiple reactions into one step, saving equipment and operating costs. In the traditional process, the reaction materials ammonia, propylene oxide and catalyst water are first put into the high-pressure reactor, and the reaction products obtained in the reactor need to be deammonized in turn, and after dehydration, they are passed through an isopropanolamine tower in turn. , Diisopropanolamine tower The present invention combines reaction and separation into one step, reduces the energy consumption in the high-pressure reactor in the traditional process, and also greatly reduces the huge energy consumption produced in the deamination and dehydration process. The energy consumption of the present invention in the reactive distillation tower is compared with the energy consumption of the high-pressure reactor in the traditional process (taking the ammonia ring feeding molar ratio as 15:1 as an example), and it can save energy by at least 60%. ;

2) Utilize the heat released by the exothermic reaction of ammonia and propylene oxide, saving the heating energy consumption at the bottom of the tower;

3) By balancing the heat of reaction of the exothermic reaction and exchanging the relationship between the heat of vaporization of the reactant stream, the unreacted ammonia is circulated to reduce the generation of side reactions. In a traditional high-pressure reactor, the feeding ratio of ammonia is 15:1 to 50: 1; In the present invention, the feed ratio of the ammonia ring is close to about 1:1, while the ammonia ring ratio at the top of the tower can reach 100:1 or even higher, which is much higher than the traditional ammonia ring feed ratio, so it can more effectively reduce the side effects reaction generation;

4) According to the research results obtained by the predecessors, ammonia contacts with propylene oxide, the higher the ratio of ammonia to propylene oxide, the higher the ratio of monoisopropanolamine in the product, in order to improve the ratio of monoisopropanolamine in the reaction product The content of propanolamine, ammonia must be greatly excessive, and the large ammonia ring ratio undoubtedly brings higher energy consumption for the subsequent deamination and dehydration treatment. The present invention reduces the feed molar ratio of ammonia and propylene oxide without increasing At the same time of energy demand, the proportion of monoisopropanolamine in the product is greatly increased, and the production of triisopropanolamine is basically eliminated. The ratio of three isopropanolamine products in traditional production is 40%: 40%: 20 %, the ratio of three kinds of isopropanolamines in the product in the present invention is 85%～92%: 8%～13%: 0.1%～2%. Compared with traditional technology, the content of one isopropanolamines has improved Nearly 100%, and the triisopropanolamine content is reduced by about 95% compared with the traditional process.

Description of drawings:

Fig. 1 is the process flow sheet that reactive distillation of the present invention produces one isopropanolamine

Specific examples:

The present invention is described in detail below with reference to FIG. 1 , but it is for illustration only and does not limit the present invention.

Reactive distillation provided by the present invention produces the method for monoisopropanolamine in detail as follows:

Example 1

Reactive distillation tower 1 is a sieve tray tower with 25 actual plates, and its operating pressure is 1.2MPa, which is used to ensure that the press is in a liquid phase state and an effective reaction phase state. mining. The temperature at the top of the tower is controlled at about 35°C, and the temperature at the bottom of the tower is 204-205°C. Water at 25°C enters from the first block of the reactive distillation column 1, and the feed flow rate is 400kg/h. Propylene oxide at 25°C enters from the second plate with a feed flow rate of 1160kg/h. Liquid ammonia enters from the 24th plate of the reactive distillation column 1; the feed flow rate is 340kg/h. The molar ratio of liquid ammonia to propylene oxide is 1:1; the condenser 2 in the tower is a total condenser, and the reboiler 3 in the tower is a kettle-type reboiler, and its heat load is 7863kw. The tower top consists of unreacted ammonia and a small amount of water and propylene oxide, and the bottom stream W2 product includes water, monoisopropanolamine, diisopropanolamine and trace triisopropanolamine, and there is no propylene oxide residue in the product , the output is 1899.9kg/h, and its water accounts for the mass fraction of total product as 53.3%, monoisopropanolamine is 43.3%, diisopropanolamine is 3.3%, and triisopropanolamine mole is 0.2%. The bottom stream W1 is preheated to 80°C by the heat exchanger and enters the dehydration tower 4. There are 20 plates in the dehydration tower 4, and the feeding position is the 8th plate. The operating pressure is normal pressure and the reflux ratio is 0.42. The condenser 5 is a total condenser, and the reboiler 6 is a kettle-type reboiler. The heat load of the reboiler is 428kw, the temperature at the top of the tower is 99.7°C, and the temperature at the bottom of the tower is 172°C. The output is 399.9kg/h, which is composed of water; the output of tower bottom stream W2 is 1499.9kg/h, and in the product after dehydration, the mass fraction of monoisopropanolamine accounts for 87.6% of the total product, and diisopropanolamine accounts for 87.6%. The mass fraction of the total product is 12.3%, and the mass fraction of triisopropanolamine in the total product is only 0.12%. The bottom stream W2 of the dehydration tower 4 continues to enter the vacuum rectification tower 7 through the kettle type reboiler 6. The vacuum rectification tower 7 has 15 plates in total, and the 7th plate is at the feeding position, and the operating pressure of the tower is 0.01 MPa, the reflux ratio is 2, the condenser 8 is a total condenser, the reboiler is a tank reboiler, the temperature at the top of the tower is 99°C, the temperature at the bottom of the tower is 220°C, and the heat load of the reboiler 6 is 844.7kw. IM D3, the output is 1315.8kg/h, and it is composed of monoisopropanolamine, and the bottom product W3, the output is 183.7kg/h, and its composition is 99% of the massfraction of diisopropanolamine, Triisopropanolamine 1%.

The result shows that the feed molar ratio of ammonia and propylene oxide is only 1:1, and its initial feed molar ratio is very low, but the mol ratio of ammonia and propylene oxide in the column in the reactive distillation process reaches its feed ratio. The molar ratio is much higher, reaching 2711.1, which is an ideal ammonia ring ratio for the production of monoisopropanolamine. In the whole process, there is no propylene oxide at the bottom of the tower, and it can be considered that all propylene oxide has been converted. The energy consumption of the present invention in the reactive distillation tower alone is compared with the energy consumption in the high-pressure reactor item in the traditional technology (being 15:1 as an example with the ammonia ring feeding molar ratio) (reactive distillation tower The heat load of the reboiler is 7863kw), which saves energy by at least 60%;

This example shows that through reactive distillation technology, propylene oxide has a very high conversion rate to isopropanolamine, and reactive distillation technology can be used to produce the required monoisopropanolamine to the maximum extent, and eliminate triisopropanol as much as possible Amine formation.

Example 2:

Reactive distillation tower 1 is a stainless steel θ-ring packed tower with an equal plate height of 40 blocks. The operating pressure is 1.1 MPa, which is used to ensure that the press is in a liquid phase state and an effective reaction phase state. The top of the tower is fully refluxed and the temperature of the tower is controlled. At about 31°C, the temperature of the tower kettle is about 165°C. Water at 25° C. enters from the top of the reactive distillation column 1, and the feed flow rate is 400 kg/h. Propylene oxide at 25°C enters from a position slightly lower than the water feed, and the feed flow rate is 1160kg/h. Liquid ammonia enters from the bottom of the reactive distillation column 1, and the feed flow rate is 510kg/h. The feed molar ratio of ammonia to propylene oxide was 1.5:1. The condenser 2 in the tower is a total condenser, and the reboiler 3 in the tower is a kettle-type reboiler, and its heat load is 7391kw. The top composition includes unreacted ammonia, propylene oxide and a small amount of water, and the bottom stream W1 product includes water, a small amount of unreacted ammonia, monoisopropanolamine, diisopropanolamine and trace triisopropanolamine, and the product There is no propylene oxide remaining in the whole process, and there is no propylene oxide at the bottom of the tower, so it can be considered that all propylene oxide has been converted. The output W1 flow rate of the tower kettle is 2135.29kg/h, of which the water content is 399.93kg/h, the ammonia content is 65.2kg/h, the monoisopropanolamine is 1281.475kg/h, the diisopropanolamine is 191.764kg/h, three Isopropanolamine 2.03kg/h. Subsequent material W1 is preheated to 80°C through a heat exchanger, and enters the 12th plate of rectification tower 4. The number of plates of rectification tower 4 is 30, the operating pressure is normal pressure, the operating reflux ratio is 0.4, and the tower top temperature is The temperature at the bottom of the tower is 99°C, the temperature at the bottom of the tower is 161°C, and the heat load of the reboiler is 460kw. The top product D2 is obtained, and its output is 465.1kg/h, wherein the mass fraction of water is 85.9%, and ammonia is 14.1%. The flow rate of the tower bottom stream W2 in the rectification tower 4 is 1670.19kg/h, and the tower bottom stream W2 is preheated to 80°C through a heat exchanger and enters the seventh plate of the vacuum tower 7, and the rectification tower 7 has 15 plates in total , the reflux ratio is 1.8, the operating pressure is 0.1bar, the tower top temperature is 95°C, the tower bottom temperature is 218°C, the heat load of the reboiler is 820kw, and finally the overhead stream D3 is obtained, and its discharge flow rate is 1281.475kg/ h, its composition I-isopropanolamine, the bottom stream is W3, the content of its composition diisopropanolamine is 98.9%, and triisopropanolamine is 1.1%.

Matters not covered in the present invention are known technologies.

Claims (3)

1. reactive distillation produces a production method for monoisopropanolamine, it is characterized by the method and comprises the following steps:

Liquefied ammonia is inputted from reactive distillation column bottom by reducing valve, simultaneously, propylene oxide is the 2nd piece of column plate input from tower top at 25 DEG C, catalyzer water inputs from tower top at 15 DEG C ~ 40 DEG C, wherein, feed ammonia: propylene oxide feed mol ratio=0.8-2.0:1, the inlet amount of water is the 10-50% of total feed massfraction, and described total feed is water, liquefied ammonia and propylene oxide quality sum;

The stage number of reactive distillation column is 25 ~ 45 pieces, and tower top temperature is for controlling at 31 ~ 50 DEG C, and bottom temperature is 165 ~ 310 DEG C, and the pressure-controlling of tower is liquid at guarantee ammonia, and scope is at 0.8MPa ~ 1.5MPa; Described liquefied ammonia feed entrance point is first or second block of column plate above tower bottom of rectifying tower;

Overhead vapours, through the first condenser condenses, is all back to tower top and flows back in tower; Reactive distillation column bottom product is all from extraction at the bottom of tower.

2. reactive distillation as claimed in claim 1 produces the production method of monoisopropanolamine, it is characterized by described reactive distillation column and is specially valve tray column, bubble-plate column, sieve-tray tower, packing tower or CTST column plate.

3. reactive distillation as claimed in claim 1 produces the production method of monoisopropanolamine, it is characterized by the treating process also comprising product, comprises the steps:

After bottom product after interchanger is warming up to 80 degree, enter in dehydration tower, the plate number 20-25 block in dehydration tower, feed entrance point is 7-13 block plate, the working pressure of tower is normal pressure, and tower top temperature is 99-101 DEG C, and column bottom temperature is 150-200 DEG C, operating reflux ratio is 0.34-2,, enter dehydration column overhead overhead product through the second condenser condenses, phegma is by trim the top of column, overhead extraction thing is water, or the mixture of water and a small amount of ammonia; The bottom product of dehydration tower is monoisopropanolamine and diisopropanolamine (DIPA), 80 DEG C are warming up to through the second reboiler, then enter the 6-10 block plate of vacuum rectification tower, the plate number 15-20 block in tower, the working pressure of tower is 0.01MPa, tower top temperature is 90-120 DEG C, column bottom temperature is 200-250 DEG C, and operating reflux ratio is 0.04-2, and final tower top is through the 3rd condenser condenses, overhead product is single α-amino isopropyl alcohol, and bottom product is pure diisopropanolamine (DIPA).