JP2000355576A - Start up of alkanolamine production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a safe and efficient method for starting up a production of an alkanolamine in producing the alkanolamine by using ammonia, an alkylene oxide and a solid catalyst under an adiabatic condition. SOLUTION: This method for starting up a production of an alkanolamine is characterized by starting the reaction at a higher temperature then a prescribed temperature at the inlet port of a reactor and at an alkylene oxide concentration lower than a prescribed concentration, then gradually proceeding to the prescribed temperature at the inlet port and the prescribed alkylene oxide concentration. Even under an adiabatic condition using a nonhomogeneous catalyst system excellent in heat resistance, it is possible to prevent the reaction heat from a rapid elevation, not to mingle the unreacted raw material with the product and attain a stable starting up.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a start-up method for producing an alkanolamine, and more particularly, to a raw material component for contacting a raw material component with a catalyst component using an adiabatic reactor in the presence of a solid catalyst. And a start-up method for adjusting the temperature and concentration of alkanolamine to safely and efficiently start the production of alkanolamine.

[0002]

2. Description of the Related Art As one of methods for producing alkanolamines, there is known a method in which ethylene oxide is reacted with ammonia in the presence of water to produce ethanolamines. There is also a method of reacting an alkylene oxide with ammonia using an organic acid, an inorganic acid, an ammonium salt, or the like as a catalyst other than water. However, when water is used as a catalyst, a water recovery operation is required, which makes it difficult to produce ethanolamines at low cost. Similarly, in the reaction between ethylene oxide and ammonia, even when a homogeneous catalyst such as an organic acid or an inorganic acid is used, an operation of separating the product, alkanolamine, from the catalyst is required. Therefore, it is difficult to produce inexpensive and simple alkanolamines in a homogeneous system in which the phases of the catalyst and the product are the same.

[0003] From such circumstances, as one of the methods for simplifying the operation of separating the product from the catalyst and improving the catalytic activity to improve the yield of alkanolamine, a method in which a homogeneous acid catalyst is immobilized is used. Methods have been developed for use.
For example, Japanese Patent Publication No. 49-47728 discloses a method using an ion-exchange resin in which a sulfonic acid group is bonded to a synthetic resin, wherein the reaction solution can maintain a liquid phase at the highest temperature at which a reaction mixture is formed. A method of reacting ammonia with an alkylene oxide under pressure is disclosed. The feature of this method is that the alkylene oxide and ammonia react at a reaction temperature equal to or lower than the boiling point of the raw material mixture at the working pressure, and at least the vapor pressure of ammonia at the maximum temperature at which the reaction mixture reaches the reaction process. And maintains the reaction product in the liquid phase throughout the reaction.

However, among solid catalysts, the ion exchange resin is prepared from a polymer compound, and thus has a low heat-resistant temperature. On the other hand, since the reaction between ammonia and the alkylene oxide is an exothermic reaction, if the heat of reaction exceeds the heat resistant temperature of the ion exchange resin, the ion exchange resin may be deteriorated. For this reason, in the above-mentioned publication, the reaction is carried out at a temperature of 150 ° C. or lower by an isothermal reaction at 75 to 150 ° C. using a cooling jacket or the like or by an adiabatic reaction due to a large excess of ammonia. However, the use of a cooling jacket requires a separate cooling device, which complicates the device. For this reason, the adiabatic reaction is adopted also in the embodiments of the above publication, and the ratio of ethylene oxide to ammonia is kept low to prevent the temperature rise of the catalyst layer due to the heat of reaction.

[0005] In recent years, in order to overcome the problem of heat resistance due to the use of such an ion exchange resin, the use of an inorganic catalyst having excellent thermal stability under adiabatic reaction has been studied. For example, JP-A-7-173114 discloses a catalyst for producing alkanolamine, wherein a rare earth element is supported on an inorganic refractory carrier. Unlike the ion exchange resin, the catalyst itself has heat resistance, so the temperature is 50 to 300 ° C, more preferably 80 to 200 ° C.
The reaction can be carried out at ℃. If such a heterogeneous catalyst having excellent heat resistance is used, the ratio of alkylene oxide can be increased to improve the productivity, and the ratio of ammonia can be kept low, so that the reactor can be downsized. . Further, since the reaction temperature itself can be kept high, the reaction efficiency can be improved. Further, the adiabatic reaction has an advantage that the reaction is continued by the reaction heat generated once the reaction starts, and a sufficient temperature rise for performing a quick reaction is ensured.

[0006] However, when ammonia and alkylene oxide are reacted using such a heterogeneous catalyst having excellent heat resistance under heat insulation conditions in which heat insulation treatment is performed between the outside and the reactor, a start-up is required. After a while, the inside of the reactor becomes unstable. When using a heterogeneous catalyst having excellent heat resistance, the ratio of ethylene oxide to ammonia can be increased,
Efficient alkanolamine production can be achieved while maintaining a high ethylene oxide concentration. In such a state where the conditions are stable, the reaction temperature in the preheater or the reactor, and also the molar ratio of ethylene oxide to ammonia are stable, and alkanolamine of constant quality can be produced.

On the other hand, in the early stage of the reaction before reaching such a stable state, it is difficult to rapidly produce alkanolamine. Since the reaction starts from the time of contact between the raw material components and the catalyst, even if a mixed liquid of ammonia and alkylene oxide, which is a raw material, is introduced into the reactor filled with the catalyst, the temperature in the reactor is immediately uniform. It does not rise. The temperature in the reactor does not reach the highest reaction temperature until the mixed gas reaches the end of the catalyst bed, and the temperature in the reactor has a difference in temperature distribution from the inlet to the outlet. In particular, when a heterogeneous catalyst having excellent heat resistance is used, the temperature rise is large, so that the temperature difference between the inlet and the outlet of the reactor also increases. Therefore, when using the reactor inlet temperature that is set in the steady state from the beginning at startup,
In the initial stage, alkylene oxide does not react and unreacted alkylene oxide flows out of the reactor in large quantities, resulting in loss of raw materials, and also reactive alkylene oxide flows out to the ammonia recovery system, which poses a safety problem. There are cases.
Further, if unreacted raw materials are mixed in the product, it is difficult to ensure uniform production of the product. In addition, it is difficult to control the temperature due to instability of the catalyst temperature, and a sudden rise in temperature at startup may cause dangers such as polymerization and blockage of the catalyst layer.On the other hand, simply increasing the ratio of ammonia to ethylene oxide In this case, the reaction efficiency is reduced, and the reactor needs to be expanded with an increase in the amount of ammonia, which is disadvantageous.

[0008]

As described above, when a catalyst having poor heat resistance, such as a conventional ion exchange resin, is used, the reaction temperature is low. Such a low reaction temperature results in a molar ratio of ammonia to ethylene oxide of 2
It was obtained by setting it to about 5 or more. Under such circumstances, even in the case of adiabatic reaction, the temperature rise in the reactor was small. Therefore, even if the temperature inside the catalyst was not uniform, there was no particular inconvenience and no major obstacle existed without any special operation at startup. However, with the development of heterogeneous catalysts that are heat resistant and have excellent reaction activity,
The problems described above have arisen during startup before reaching a stable state.

[0009]

The above object is achieved by the following (1) to (5).

(1) A start-up method for producing an alkanolamine by reacting ammonia with an alkylene oxide using an adiabatic reactor in the presence of a solid catalyst, wherein a reactor inlet temperature higher than a predetermined temperature and a predetermined temperature A start-up method in alkanolamine production, wherein the reaction is started at an alkylene oxide concentration lower than the concentration, and thereafter gradually shifted to a predetermined reactor inlet temperature and a predetermined alkylene oxide concentration.

(2) The start-up method according to the above (1), wherein the reactor inlet temperature is higher by 20 to 100 ° C. than a predetermined temperature.

(3) The start-up method according to the above (1) or (2), wherein the alkylene oxide concentration at the start of the reaction is 10 to 90% of a predetermined concentration.

(4) Any one of the above (1) to (3), wherein the predetermined temperature is 20 to 100 ° C.
Startup method described in section.

(5) The predetermined alkylene oxide concentration is 2 to 2 moles of ammonia per mole of alkylene oxide.
The startup method according to any one of the above (1) to (4), wherein the amount is 30 mol.

[0015]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a start-up method for producing an alkanolamine by reacting ammonia and an alkylene oxide using an adiabatic reactor in the presence of a solid catalyst. This is a start-up method in alkanolamine production, characterized by starting a reaction at an inlet temperature and an alkylene oxide concentration lower than a predetermined concentration, and then gradually shifting to a predetermined reactor inlet temperature and a predetermined alkylene oxide concentration.

When a heterogeneous catalyst is used, the molar ratio of alkylene oxide to ammonia can be increased to efficiently produce alkylene oxide. However, since the reaction is active, the inside of the reactor becomes unstable at start-up,
It becomes difficult to control the temperature, which may cause unreacted raw materials to be mixed in the product. However, according to the start-up method of the present invention, by adjusting the concentration of the alkylene oxide and the temperature of the raw material introduced into the reactor, there is no danger of a sharp rise in temperature, and the safety is excellent. Can be prevented from flowing out to the ammonia recovery system. Hereinafter, the present invention will be described in detail.

The alkylene oxide used in the present invention is not particularly restricted but includes, for example, ethylene oxide, propylene oxide, butylene oxide and the like. In the present invention, one type may be used alone as the alkylene oxide, or two types may be used in combination. In the present invention, among these alkylene oxides, ethylene oxide is preferable because ethanolamines which are particularly useful industrially can be obtained.

The alkanolamine produced by the reaction is a compound corresponding to the above alkylene oxide. By changing the molar ratio between ammonia and alkylene oxide, three kinds of products (monoalkanolamine, dialkanolamine, trialkanolamine) in which the number of addition of alkylene oxide molecule to one molecule of ammonia is 1, 2, 3 are obtained. Can be manufactured. Therefore, the alkanolamines produced include ethanolamine (mono, di, tri), propanolamine (mono, di, tri), butanolamine (mono, di, tri)
And the like.

The catalyst that can be used in the present invention is not particularly limited as long as it is a heterogeneous catalyst. Examples of such a heterogeneous catalyst include cation exchange resins, acid-activated clays, silica alumina, and molecular sieves. Various kinds of conventionally known heterogeneous catalysts such as (trade name; synthetic zeolite), solid acid catalysts such as zeolite, etc .; rare earth element-supported catalysts; and crosslinked layered compound catalysts can be used.

In the present invention, among these heterogeneous catalysts,
Inorganic catalysts are preferred because of their excellent heat resistance, and catalysts in which a rare earth element is supported on a heat-resistant carrier are particularly preferred.
The present invention aims at safety during startup when the temperature rise in the adiabatic reaction is large, and the inorganic catalyst is excellent in heat resistance and is particularly suitable for the practice of the present invention because the temperature rise in the adiabatic reaction is large. ing. This allows
The reaction temperature can be adjusted by the molar ratio of ammonia to alkylene oxide, and if the catalyst has excellent heat resistance, an efficient alkanolamine can be produced by increasing the alkylene oxide ratio.

Further, according to the present invention, a rise in the temperature inside the reactor (continuous flow reactor) can be suppressed, and therefore, when the molar ratio of ammonia to alkylene oxide is low due to poor heat resistance, An ion exchange resin which cannot be used when the concentration of the alkylene oxide in the reaction solution is high) can also be used as the heterogeneous catalyst according to the present invention.

"Adiabatic reactor" used in the present invention
Is not particularly limited as long as the reaction can be continued in an adiabatic state and the reactor is of a continuous flow type. Here, the adiabatic state means a state in which heat transfer between the reactor and the outside is cut off.
For example, a reactor in which a heat insulator is coated on the outer periphery of the reactor corresponds to the reactor. The present invention effectively utilizes the reaction heat generated by the contact between the catalyst and the raw material components, and controls the reaction temperature by adjusting the concentration of the raw material components, thereby starting up efficient alkanolamine production. It provides a way. Therefore, an adiabatic reactor in which a cooling device is provided outside the reactor and the reaction temperature is adjusted to be constant, or an adiabatic reactor having an external heating device to keep the temperature in the reactor constant is originally used in the present invention. It is not the intended adiabatic reactor of the invention. However, it is also possible to carry out the process according to the invention using an adiabatic reactor equipped with these temperature regulating devices,
When the process is performed without using the temperature control function, this corresponds to the adiabatic reactor of the present invention.

As such adiabatic reactor, conventionally known various reactors for filling a heterogeneous catalyst and producing alkanolamine from ammonia and alkylene oxide can be used. It is sufficient that the heterogeneous catalyst is filled in the reactor by a known method, and there is no particular limitation on a method of supplying a raw material to the reactor or a method of charging the catalyst. As an example of an embodiment of the present invention, a reactor is shown in FIG. 1, and a method for producing alkanolamine by reacting ammonia and alkylene oxide using an adiabatic reactor in the presence of a solid catalyst will be outlined.

First, ammonia is supplied from the ammonia cylinder 10 via the ammonia pump 4 and alkylene oxide is supplied from the alkylene oxide cylinder 11 via the alkylene oxide pump 5 to the preheater 2. The feedstock is
The mixture is heated by the preheater 2 and introduced into the reactor 1. The temperature in the preheater at which the reaction has become stable is maintained at 20 to 100 ° C, more preferably 30 to 80 ° C, and particularly preferably 30 to 70 ° C. If the temperature is lower than 20 ° C., it is not possible to maintain the catalyst temperature with good reaction efficiency. On the other hand, if it exceeds 100 ° C., it is difficult to adjust the temperature in the reactor due to the reaction heat generated in the reactor, which is not preferable.

[0025] The raw material mixture introduced into the preheater is introduced into the reactor inlet while maintaining its temperature. The alkylene oxide reacts with ammonia in the reactor 1 to form an alkanolamine. The temperature in the reactor in the steady state is not particularly limited, but is preferably in the range of 20 ° C to 300 ° C, more preferably in the range of 30 ° C to 250 ° C, and preferably in the range of 30 ° C to 200 ° C. Most preferred. The temperature inside the reactor varies greatly from the reactor inlet to the reactor outlet due to the adiabatic reaction. Therefore, the above temperature does not mean that this temperature is uniform from the inlet to the outlet of the reactor.

The temperature of the reactor 1 is provided by the temperature of the raw material components heated by the preheater and the generated reaction heat. In an adiabatic reactor, if the reaction temperature is lower than 20 ° C., the reaction rate will be low, and the amount of catalyst required to completely convert the alkylene oxide to the desired alkanolamine will be too large. For this reason, increasing the size of the reactor is not preferable because the equipment cost increases. On the other hand, if the reaction temperature is higher than 300 ° C., the temperature inside the reactor becomes too high, and the product may be undesirably colored. Incidentally, such temperature adjustment in the reactor can be achieved by adjusting the preheater temperature and the molar ratio of alkylene oxide to ammonia under adiabatic conditions.

The amount of ammonia added to the alkylene oxide is not particularly limited, but is preferably in the range of 2 to 30 moles of ammonia, more preferably in the range of 4 to 20 moles per mole of the alkylene oxide. preferable. As described above, the reaction temperature can be adjusted by the molar ratio. Therefore, if the amount is less than 2 mol, the molar ratio of the alkylene oxide to ammonia is too large, and the generated heat of reaction is too large to cause coloring of the product, which is not preferable. On the other hand, if it exceeds 30 mol, the molar ratio of alkylene oxide to ammonia is too small, and the amount of ammonia to be recovered becomes too large.

The reaction pressure in a stable state of the reaction is 2M
The range of Pa to 30 MPa is preferable, and 4 MPa to 20 M
More preferably, the range of Pa is 5 MPa to 15 Mpa.
Is most preferable. If the reaction pressure is lower than 2 MPa, the liquid phase cannot be completely maintained during the reaction, and the amount of ammonia vaporized is too large, and the liquid phase portion is reduced. Therefore, the reaction between the ammonia and the alkylene oxide does not proceed smoothly, which is not preferable. On the other hand, if the reaction pressure is higher than 30 MPa, the pressure resistance of the device is unnecessarily required and the price of the device is undesirably increased.

The reaction is carried out in the liquid phase as described above, but the temperature and pressure may be such that a portion of the ammonia evaporates during the reaction. In this case, the temperature rise in the reactor is suppressed by the heat of vaporization of ammonia, and a reaction with a high alkylene oxide concentration can be performed.

Under the above conditions, the LHSV (liquid hourly space velocity) depends on the reaction temperature, the type of the catalyst and the amount used, but
It is preferably in the range of 0.5 hr ^{-1 to} 100 hr ^-1 and 1 h
More preferably, it is in the range of r ^{-1 to} 50 hr ^-1 . LHSV
Is less than 0.5 hr ^-1 , the contact time of ammonia and alkylene oxide with the catalyst is sufficiently long, so that the alkylene oxide can be efficiently converted to the desired alkanolamine, but the alkylene oxide is completely converted. The amount of catalyst required to convert to the desired alkanolamine is too high. Further, the amount of alkanolamines produced per unit time is reduced. On the other hand, enlarging the reactor is disadvantageous because equipment costs are required. On the other hand, LHSV is 100 hr.
If it is larger than ^-1 , the contact time between ammonia and the alkylene oxide with the catalyst is too short, and it is not preferable because the alkylene oxide cannot be sufficiently converted into the desired alkanolamine. Note that the LHSV at startup may be different from the LHSV in the steady state.

From the top of the reactor, ammonia and alkanolamine as a product are distilled off, and the ammonia recovery column 7
And separated into ammonia and alkanolamine. The product alkanolamine is obtained from the bottom of the ammonia recovery column 7. On the other hand, the ammonia distilled from the top of the ammonia recovery tower 7 is cooled and separated by the heat exchanger 9 and recovered in the ammonia recovery tank 8. The recovered ammonia is supplied to a recycled ammonia pump 6
To the preheater 2.

Next, the start-up method of the present invention when starting such a process for producing an alkanolamine will be described.

First, the raw material containing no alkylene oxide is preheated in the preheater 2. The preheating temperature is 2
The temperature is raised from 0 to 100 ° C, preferably from 30 to 90 ° C, particularly preferably from 40 to 80 ° C. In this way, by heating only ammonia and sending it to the reactor, the temperature in the catalyst layer can be made the same as that of the raw material fluid. This is because the reaction rate of the subsequently supplied alkylene oxide can be increased.

The term "predetermined" in the present invention means a steady state in which the reaction is stable with the molar ratio of catalyst and ammonia to alkylene oxide substantially constant, and the predetermined temperature is defined as the predetermined temperature. Refers to the reactor inlet temperature in normal operation. When the raw material compound is immediately introduced into the reactor from the preheater, the preheater temperature and the reactor inlet temperature become the same. The predetermined reactor inlet temperature varies depending on the catalyst to be used, the molar ratio of the starting material, ammonia and alkylene oxide, the scale of the reaction apparatus, and the like. The reactor inlet temperature is 20 to 100 ° C., preferably 30 to 90 ° C.
C. More preferably, it is 30 to 80.degree. This is because if the predetermined temperature is set in consideration of the fact that the product causes coloring or the like under high temperature conditions, it is possible to prevent a sharp rise in temperature in the above range and also to prevent the unreacted product from distilling out.

Next, the alkylene oxide is added at a predetermined concentration of 10 to 90 v / v%, preferably 20 to 80 v / v%,
Particularly preferably, the supply to the reactor is started at a concentration of 20 to 70 v / v%. If it exceeds 90 v / v%, it is difficult to avoid a rapid rise in reaction temperature due to the heat of reaction of the alkylene oxide, while if it is less than 10 v / v%, sufficient reaction heat cannot be obtained. Here, the predetermined concentration refers to the concentration of the alkylene oxide in a steady state, as described above, and varies depending on the type of catalyst used, the molar ratio to ammonia, and the like.

Next, when the reaction proceeds and the catalyst layer temperature rises due to the reaction heat, the temperature of the preheater 2 is gradually lowered, and the alkylene oxide concentration is gradually increased to shift to a predetermined temperature and a predetermined alkylene oxide concentration. Let it. Therefore, the adjustment of the preheating temperature and the like can be determined by checking the rise in the catalyst temperature.

The present invention is a start-up method for producing safe and excellent quality products under conditions that more efficiently utilize the heat of reaction generated by using an adiabatic reactor. According to the present invention, by starting the reaction at a reaction temperature higher than the predetermined temperature, it is possible to prevent unreacted alkylene oxide from flowing out of the system. Moreover, by starting the reaction at an alkylene oxide concentration lower than the predetermined concentration, even when the reactor inlet temperature is higher than the predetermined temperature, the temperature in the catalyst layer does not become too high, and the quality does not deteriorate. Once the temperature inside the catalyst layer is raised above the predetermined temperature, even if the temperature gradually shifts to the predetermined inlet temperature / alkylene oxide concentration thereafter, there is no rapid change in the catalyst layer temperature, and the inside of the reactor is stabilized, There is no danger of polymerization or blockage of the catalyst layer, and the outflow of unreacted alkylene oxide can be prevented.

[0038]

The present invention will be described in detail with reference to the following examples, but the present invention is not limited to these examples.

Reference Example 1: Preparation of Catalyst Aqueous solution of 0.05 mol / L yttrium nitrate 5
10 kg of montmorillonite was added to 00 liter with stirring. The mixture was stirred at room temperature for 1 day and then filtered. Then, the solid obtained by filtration was
After washing with 0 L of pure water, adding 5 kg of crystalline cellulose powder and kneading with a kneader, the extruder was used to extrude the powder with a diameter of 0.1 kg.
It was molded to a length of 4 mm and a length of 1 mm to 3 mm. Further, the solid was dried at 100 ° C. for 1 day, and then subjected to a high temperature treatment at 500 ° C. for 5 hours under flowing air to obtain a catalyst. This catalyst is called catalyst A.

Example 1 Using the catalyst A, a reaction was carried out using the reactor shown in FIG. First, 6 liters of the catalyst A was charged into a reactor 1 (made of steel: 67 mm in inner diameter) having an internal volume of 7 liters. On the other hand, in front of the reactor (upstream side), a tubular preheater 2 (inner diameter of the preheating section 20 mm, length 1 m, diameter 5 mm) provided with an electric heater (not shown) is provided outside, and the preheating section is heated by an electric heater. did. Next, high pressure pumps 4 and 5 were used to continuously feed ammonia and ethylene oxide into the preheater 2 at a constant rate. Thereby, the ammonia raw material cylinder 1
Ammonia and ethylene oxide raw material tank 11
The mixture was heated with ethylene oxide in the reactor and supplied to the reactor 1. The reactor 1 was slightly heated by a heater (electric heater) (not shown) for keeping the temperature, and supplied with the amount of heat lost by heat radiation to make it substantially insulated. Reaction pressure 1
It was controlled at 2 MPa. Then, ethylene oxide and ammonia were continuously reacted. The reaction conditions in the steady state were as follows: the reactor inlet temperature was 55 ° C., and the LHSV was 3.5 hours.
r ^-1 and the ammonia / ethylene oxide molar ratio were set to 14.

The start-up for starting this reaction was performed in the following procedure. (1) Only ammonia was supplied to the reactor at a reactor inlet temperature of 100 ° C., and the reactor was heated to almost 100 ° C. up to the outlet layer. (2) The supply was started such that the molar ratio of ammonia to ethylene oxide was 25, and the LHSV was 5.25 hr ^-1 . The reaction was continued under these conditions for 17 minutes. (3) Ethylene oxide was increased so that the molar ratio of ammonia to ethylene oxide became 20, and at the same time, the preheater temperature was gradually lowered, and after 34 minutes, the inlet temperature was 70 ° C. (4) The LHSV was set to 3.5 hr ^-1 , the ethylene oxide was increased so that the molar ratio of ammonia to ethylene oxide became 16, and the preheater temperature was gradually lowered at the same time. After 50 minutes, the inlet temperature was set to 55 ° C. . (5) Then, the molar ratio of ammonia to ethylene oxide was set to a predetermined value of 14, and the reactor inlet temperature was set to a predetermined value of 55 ° C., and a steady operation was started.

FIG. 2 shows the temperature distribution of the catalyst layer at each time in Example 1. It can be seen that the catalyst layer temperature is kept at a sufficiently high level as a whole and does not rise abnormally.
Ethylene oxide was not detected in the reaction solution at the outlet from the early stage of the startup, and it was found that there was almost no unreacted ethylene oxide.

Comparative Example 1 The start-up procedure was carried out under the predetermined reaction conditions (inlet temperature 55 ° C., molar ratio of ammonia to ethylene oxide 14, LHSV
The same operation as in Example 1 was performed except that the reaction pressure was 3.5 hr ^-1 and the reaction pressure was 12 MPa.

FIG. 3 shows the temperature distribution of the catalyst layer at each time. It can be seen that the temperature of the catalyst layer does not sufficiently rise at the beginning, and the temperature of the reactor only rises after 30 minutes or more. Also, the initial ethylene oxide conversion was only about 40%, and a large amount of unreacted ethylene oxide was flowing out of the reactor.

Example 2 A predetermined inlet temperature of 45 ° C., a molar ratio of ammonia to ethylene oxide of 8, a reaction pressure of 10 MPa, and an LHSV of 3.5 h
A steady-state reaction was carried out in the same manner as in Example 1 except that the condition was r ^-1 . Start-up at the start of this reaction was performed according to the following procedure. (1) Only ammonia was supplied to the reactor at a reactor inlet temperature of 90 ° C., and the reactor was heated so that the temperature reached approximately 90 ° C. to the outlet layer. (2) A molar ratio of ammonia to ethylene oxide 2
0, the supply was started so as to satisfy the condition of LHSV 7 hr ^-1 . The reaction was continued under these conditions for 17 minutes. (3) Molar ratio of ammonia to ethylene oxide: 1
Ethylene oxide was increased to 8 and the preheater temperature was gradually lowered at the same time.
0 ° C. (4) LHSV was 3.5 hr ^-1 , ethylene oxide was increased so that the molar ratio of ammonia to ethylene oxide was 13, and simultaneously the preheater temperature was gradually lowered, and after 50 minutes, the reactor inlet temperature was raised to 45 ° C. did. (5) Ethylene oxide was increased so that the molar ratio of ammonia to ethylene oxide was 10, and the reaction was continued for up to 68 minutes. (6) Subsequently, the molar ratio of ammonia to ethylene oxide was set to a predetermined value of 8, and the reactor inlet temperature was set to a predetermined value of 45 ° C., and a steady operation was started.

FIG. 4 shows the temperature distribution of the catalyst layer at each time. The catalyst layer temperature is maintained at a sufficiently high level throughout,
Further, it can be seen that it does not become abnormally high. Ethylene oxide was not detected in the reaction solution at the outlet from the early stage of the startup, and it was found that there was almost no unreacted ethylene oxide. Also, it can be seen that a stable start-up can be performed even under the condition that the molar ratio is as small as 8 and the ethylene oxide concentration is high.

Comparative Example 2 The start-up procedure was carried out under the predetermined reaction conditions (inlet temperature 45 ° C., ammonia / ethylene oxide molar ratio 8, LHSV 3.5 hr) without following the procedure as in Example 2.
^-1 , the same operation as in Example 2 was performed except that the reaction pressure was 10 MPa). The catalyst layer temperature did not rise sufficiently in the initial
Only after about 0 minutes did the reactor temperature rise. The initial ethylene oxide conversion was only about 20%, and a large amount of unreacted ethylene oxide was flowing out of the reactor.

[0048]

According to the start-up method of the present invention, the temperature of the catalyst layer can be kept high from the beginning of the start-up by supplying ammonia having a temperature higher than a predetermined temperature to the reaction tank (17 in FIG. 2). Minutes). Heating the reactor from the outside requires a separate device, but the present invention uses an adiabatic reactor, and can easily increase the reactor inlet temperature by using a normally arranged preheater. (FIG. 2). In this regard, in FIG. 3, the temperature of the catalyst layer did not sufficiently rise at the beginning, and the temperature of the reactor only rose after 30 minutes or more. Therefore, the conversion of ethylene oxide was low, and unreacted ethylene oxide flowed out of the reactor.

After the reactor temperature has risen, a lower alkylene oxide is supplied and its concentration is gradually increased, so that the supplied alkylene oxide can obtain a reaction activity under a sufficient catalyst temperature, There is no unreacted material at the outlet of the catalyst layer. Therefore, there is no need to remove unreacted raw materials mixed in the product, and a high-quality product can be obtained extremely efficiently. This is because the start-up can be stably performed even under the condition that the molar ratio of alkanolamine to ammonia is as small as 8 as shown in FIG.

According to such a start-up method, the temperature of the catalyst layer gradually rises due to the heat of reaction, so that the temperature rise does not suddenly occur. Therefore, even when the heterogeneous catalyst having excellent heat resistance is used and the alkylene oxide concentration is increased to perform a steady operation, there is no danger of polymerization or clogging of the catalyst due to a rapid temperature change at the time of startup.

[Brief description of the drawings]

FIG. 1 is a diagram showing an apparatus for producing an alkanolamine.

FIG. 2 is a diagram showing a temperature distribution of a catalyst layer in a reactor in Example 1.

FIG. 3 is a diagram showing a temperature distribution of a catalyst layer in a reactor in Comparative Example 1.

FIG. 4 is a diagram showing a temperature distribution of a catalyst layer in a reactor in Example 2.

[Explanation of symbols]

 1: reactor, 2: preheater, 3: catalyst layer, 4: ammonia pump, 5: alkylene oxide, 6: recycled ammonium pump, 7: ammonia recovery tower, 8: ammonia tank, 9: heat exchanger, 10: Ammonia cylinder, 11: alkylene oxide cylinder.

Claims (3)

[Claims] 1. A start-up method for producing alkanolamine by reacting ammonia and alkylene oxide using an adiabatic reactor in the presence of a solid catalyst, comprising a reactor inlet temperature higher than a predetermined temperature and a predetermined concentration. A start-up method in alkanolamine production, characterized in that the reaction is started at a lower alkylene oxide concentration and then gradually shifted to a predetermined reactor inlet temperature and a predetermined alkylene oxide concentration. 2. The predetermined reactor inlet temperature is 20 to 100 ° C.
The start-up method according to claim 1, wherein the reactor inlet temperature at the start of the reaction is 20 to 100C higher than the predetermined temperature. 3. The predetermined alkylene oxide concentration is in the range of 2 to 30 mol of ammonia per 1 mol of the alkylene oxide, and the alkylene oxide concentration at the start of the reaction is 10 to 90 v / v% of the predetermined concentration. 3. The start-up method according to claim 1, wherein: