JPS6318933B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for the preparation of alkanolamines, and more particularly, to the production of alkanolamines in high yields by reacting an alkylene oxide with a large excess of ammonia while maintaining the reaction mixture as a supercritical fluid in a single phase. The present invention relates to a method for continuously producing alkanolamines containing monoalkanolamines.

Alkanolamines are used in a variety of commercial applications, as emulsifiers for soaps and cosmetics, and as starting materials for the production of raw materials such as detergents, wetting agents, emulsifiers, textile aids, and alkylene oxides. is known to be produced by reacting with ammonia or amines. Thus, the alkanolamine product in this case is a mixture of mono-, di-, and tri-alkanolamines, and in most cases the relative proportions of these three alkanolamines are generally equal. However, the relative proportions of these three alkanolamines in the product mixture are
It is known that it depends on the relative amounts of alkylene oxide and ammonia reacted;
Various methods have been employed and proposed in the past to obtain higher yields of one or more alkanolamines in the mixture. Methods include changing the mixing ratio of reactants such as increasing the amount of ammonia to alkylene oxide to obtain more monoalkyl amine, as well as other process modifications.

For example, U.S. Pat. No. 2,196,554 to HM Guinot teaches mono-hydroxyalkylamines in 90-95% yield by reacting at least 30 parts by weight of ammonia with 1 part by weight of alkylene oxide in a liquid phase reaction. A method of manufacturing is described. In this method, a relatively dilute aqueous ammonia solution is used, and the steam generated during concentration of the reaction product mixture is used to subsequently heat the reaction product mixture and separate the ammonia gas therefrom. , which is disclosed to reduce the thermal energy requirements for the method. Also, another method is
Weibull et al., U.S. Pat. No. 3,697,598, teaches that a very large amount of monoalkanolamine and a very small amount of di-
and a method for producing alkanolamines containing tri-alkanolamines.
The molar ratio of ammonia to alkylene oxide used in this process ranges from 10:1 to
The ratio is in the 80:1 range and the reaction is carried out in the presence of a cationic exchange resin catalyst. The process is continuous and isothermally or preferably adiabatically heated to 20°C if a sufficiently high pressure is employed to keep the reactants and reaction products in the liquid phase during the reaction. It is disclosed that it can be carried out at temperatures ranging from 250°C to 250°C. However, this patent does not disclose what types of alkanolamines can be obtained in high yields when the process is carried out either adiabatically or isothermally without the use of cationic exchange resin catalysts. It is stated that it is impossible to perform an adiabatic reaction without using a cationic exchange resin catalyst because the reaction is too slow. Furthermore,
Goetze et al., U.S. Pat.
A method is disclosed for preparing mixtures of alkanolamines by reaction in the liquid phase in a ratio of 14 to 40 to 1. According to this patent, if the reaction is carried out in the presence of up to 1 mole of diethanolamine to 1 mole of ethylene oxide, the resulting products are monoethanolamine and triethanolamine with little or no diethanolamine present. It is taught that it is a mixture only with ethanolamine. The process of this patent is described as being continuous and can be carried out either isothermally or adiabatically. When carried out continuously, the reaction is carried out at temperatures ranging from 60° to 150°C and at 20°C.
carried out in the liquid phase under pressures from atm to 120 atm,
Generally the monoethanolamine content of the product mixture does not exceed 70% by weight. In a preferred continuous embodiment, ethylene oxide is first reacted in the liquid phase with excess ammonia to form a mixture of alkanolamines from which diethanolamine is separated and recycled. The recycled diethanolamine, when added in proportions to the fresh ammonia and ethylene oxide feed reactants, results in reduced diethanolamine production in net production. However, this process requires continuous separation of diethanolamine from the product mixture and is carried out in the liquid phase.

In Japanese Unexamined Patent Publication No. 59-33247 of the same applicant, alkanolamines containing monoalkanolamines are produced in high yields by reacting alkylene oxide with a large excess of ammonia in a single supercritical fluid phase. A method of manufacturing is disclosed. It is stated that the process can be carried out batchwise or continuously under isothermal or adiabatic conditions. If the method is carried out continuously, it can be carried out as efficiently as possible with a “plug flow”.
A reactor such as a “flow)” reactor is employed to carry out the reaction.
It relates to a preferred embodiment of the continuous production method described in Publication No. 33247.

Now, in accordance with the present invention, a fluid comprising a homogeneous mixture of an alkylene oxide and ammonia having from 2 to 4 carbon atoms has a molar ratio of ammonia to alkylene oxide in the range of about 15:1 to about 50:1. The reaction mixture is heated at a temperature of at least about 240 Kg/m ³ (15
under sufficient pressure to maintain the alkanolamine product mixture in a single supercritical fluid phase having a density of (pounds per cubic foot) for a period of time necessary to form an alkanolamine product mixture containing primarily monoalkanolamines. A continuous process for producing alkanolamines containing high yields of monoalkanolamines is provided, comprising continuous reaction in a plug-flow reactor. Unreacted ammonia is separated from the product mixture and recycled while recovering the alkanolamine product mixture. Or, if desired,
The product mixture may be used to make further amine products.

The temperature employed to carry out the reaction is preferably as high as possible to allow the reaction to proceed at a suitable rate. It is also advantageous to employ a temperature above the critical temperature of the reaction mixture. The pressure should be high enough to maintain the reaction mixture as a supercritical fluid in a single homogeneous phase at all points of the reaction. The density of the supercritical fluid reaction mixture is an important consideration for the rate at which the reaction proceeds and should be as high as possible during the reaction.
Normally it should be kept at least about 240 kg/m ³ (15 lb/ft3). The reaction may be carried out under isothermal or preferably adiabatic conditions. Although no catalyst is required, the presence of a small amount of water in the reaction mixture is advantageous for its catalytic effect. As used herein, the term "supercritical liquid" is defined as the physical state of a reaction mixture in which either only the pressure or both the temperature and pressure are above their critical values. As used herein, a "plug-flow reactor" refers to a reactor in which no mixing of the fluid streams occurs in the direction of flow of the fluid streams through the reactor. Such plug flow reactors include non-insulated tubes and insulated pipes.

Describing the invention in detail, the process of the invention comprises a molar ratio of ammonia to alkylene oxide ranging from about 15:1 to about 50:1.
The temperature at which the reaction proceeds above about 100°C while maintaining a homogeneous fluid stream of a mixture of alkylene oxide with 5 carbon atoms and ammonia as a supercritical fluid in a single homogeneous phase. under at least 240Kg/ ^m3 (15lb/m3)
consisting primarily of monoalkanolamines (usually about 75%) and small amounts of di- and tri-alkanolamines under pressure high enough to maintain the reaction mixture in a supercritical fluid phase with a density of It consists of reacting continuously for the time necessary to form the product mixture. Depending on your wishes,
Unreacted ammonia is separated from the product mixture at the end of the reaction with the alkylene oxide and recycled, while the alkanolamine product mixture is recovered. Mono-, di- and tri-alkanolamines can be separated as desired. The product mixture containing unreacted ammonia is also used to make other amine products.

The alkylene oxide that can be used in the process of the invention can be any alkylene oxide having 2 to 4 carbon atoms, such as ethylene oxide, propylene oxide, 1,2-butylene oxide, 2,3-butylene oxide, Contains isobutylene oxide.

According to the invention, it is essential that a large excess of ammonia with respect to the alkylene oxide is used during the reaction in order to obtain the monoalkanolamine with a yield of at least 65% by weight. For each mole of alkylene oxide, from about 15 to about 50 moles of ammonia, and preferably from about 20 to about 35 moles, are used to obtain monoalkanolamines, often in yields of about 70 to 85% by weight. It is advantageous to use up to

In order for the reaction of alkylene oxide and ammonia to proceed at a suitable rate, it is essential that it be carried out in a homogeneous, single supercritical fluid phase. This reaction can be carried out under isothermal or preferably adiabatic conditions. The temperature at which this reaction is conducted ranges from about 100°C to about 200°C, although the upper limit is not critical. Preferably, the reaction temperature is at the critical temperature of the reaction mixture (usually about 130°C).
to about 180℃. Since the reaction is strongly exothermic, under isothermal conditions it is necessary to remove heat from the reaction mixture in order to keep the temperature nearly constant.

If the reaction is conducted under adiabatic or near adiabatic conditions, the raw materials (reactants) are preferably brought to a temperature in the range of about 100°C to about 160°C prior to introduction into the reactor. Preheat. The initial reaction temperature, however chosen, increases rapidly due to the generation of reaction heat. Therefore, the initial reaction temperature is
It should be selected such that the desired maximum temperature is obtained while the reaction mixture remains in the reactor. A preferred maximum temperature is between about 170°C and 180°C. However, the higher the reaction temperature, the higher the pressure required to maintain the density of the reaction mixture as high as possible.

At such reaction temperatures, it is essential that the pressure applied to the reaction system be high enough to maintain the reaction mixture in a single supercritical fluid phase. In all cases, the reaction pressure should be at least as high as the critical pressure of the reaction mixture at any point in the reaction. Preferably,
The pressure imposed on the reaction system ranges from about 170 atmospheres to about 240 atmospheres. Approximately 240 atm is a realistic upper limit, but not critical.

As mentioned above, it is important to maintain the reaction mixture as a supercritical fluid in a single homogeneous phase and to keep its density as high as possible so that the reaction proceeds at a suitable rate. The density of the reaction mixture is above its critical density, usually at least 240 Kg/m ³
(15 pounds per cubic foot). Preferably, the density of the reaction mixture should be maintained between about 336 and about 448 atm/m ³ or slightly higher if practical. The molar ratio of ammonia to alkylene oxide raw materials (reactants) and the reaction temperature have a significant effect on the density of the reaction mixture. It is therefore important not only to maintain the reaction mixture in a single supercritical fluid phase, but also to keep the reaction pressure as high as possible in order to make the mixture as dense as possible.

Although it is not essential that the process of the invention be carried out in the presence of a catalyst, in an advantageous embodiment of the invention a small amount of water is present in the reaction system together with the alkylene oxide and ammonia feedstocks (reactors). Implemented in coexistence with Although the presence of small amounts of water in the reaction mixture does not appear to affect the yield of monoalkanolamine in the product mixture, we have found that the presence of small amounts of water in the reaction mixture has a catalytic effect that favors the reaction rate to produce alkanolamines. I found out that it gives The amount of water present is not critical; even very small amounts of water will have the desired catalytic effect. Generally, from about 0.5 to about 5 weight percent water, based on the weight of the reaction mixture, will be present. However, excess amounts of water above what is catalytically useful should be avoided in order to limit the energy usage required to separate the water from the product mixture.

According to the invention, the process is carried out continuously under isothermal or preferably adiabatic conditions in a plug-flow reactor or a series of reactors with a small cross section compared to the length. A tubular plug flow reactor provides a unidirectional flow of the reactant process stream that minimizes back mixing within the reactor. In the reactor,
Heat exchange means are provided to maintain the temperature of the flowing reaction mixture at a predetermined level, but such temperature control means are not required if the reaction is carried out under adiabatic conditions.

In the continuous reaction process of the present invention, a liquid mixture of ammonia and alkylene oxide feedstock having the above-mentioned molar ratios, preferably mixed with a small amount of water, is preheated and then a swirling motion is imposed on the feed stream at the inlet. is sent to the reactor through a portion. If a tubular reactor (non-adiabatic) is employed, the temperature of the feed mixture may vary over a wide temperature range, e.g. from about 20°C to about 100°C; It is regulated to operate within a relatively narrow temperature range. Under adiabatic conditions, a predetermined maximum reaction temperature (usually about 170° to
200℃), the raw material mixture is heated to about 100℃
It should be preheated to a temperature of ~160°C.
The pressure within the reactor should be high enough to maintain the reaction mixture in a single homogeneous phase as a supercritical fluid with as high a density as possible everywhere within the reactor.

The rate of feed of the reaction mixture is such that the residence time (usually within about 1/2 hour) is sufficient to drive the reaction to completion in the reactor or reactors.
should be selected so as to give In an adiabatic reactor with the inlet feed structure described above, the flow rate of the flowing stream is about 0.15 to 0.5 ft/sec or higher to provide plug flow operation. It is advantageous to employ speed. At the end of the reaction, usually when all the alkylene oxide has reacted, unreacted ammonia can be removed by reducing the pressure of the product mixture below the pressure at which ammonia is in the gas phase, or by distilling it under pressure. The alkanolamine product mixture can be separated from the product mixture using known means such as, from which the alkanolamine product mixture is recovered. The unreacted separated ammonia can then be recycled, if desired, either repressurized or condensed to a liquid state prior to mixing with fresh alkylene oxide. Alkanolamine analogs in the product mixture are also separated by known distillation methods. The product mixture obtained during the continuous reaction process is also used without further treatment as starting material for the production of other organic amines.

Next, the attached drawings will be explained.

According to FIG. 1, liquid ammonia and alkylene oxide are blended in a predetermined proportion in a supply pipe 1. If desired, a small amount of water is also added. The mixture of raw materials is pumped through line 2 to a preheater 3, where the mixture is heated to a temperature in the range of about 100°C to about 160°C, and then pumped through an axial inlet pipe 4. and then fed into the adiabatic reactor. Adiabatic reactors have a single plug
Either a flow reactor or a reactor with a series of plug flow stages 5a, 5b, 5c as shown, with each plug
The flow stage has an axial inlet pipe. In order to minimize thermal stratification without increasing axial mixing, means are provided to impart overwinding motion to the reaction mixture feed stream entering each reactor stage. The pressure within each reactor stage is such that the reaction mixture stream is maintained in a single supercritical fluid phase everywhere within the reactor and has a density of at least 240 kg/m ³ (15 lb/ft3). As such, the pressure is generally maintained within a range of approximately 170 to 240 atmospheres by means of a pressure regulating valve 6.

The number of reactors used will vary depending on the amount of product being produced, the overall length of reactor required to achieve the desired production rate, the practical length of each reactor stage, etc. A typical reaction system is approximately 30.5 m (100 feet)
It is advantageous to use 1 to 6 reactor stages with a length of up to or longer, usually 3 to 5 reactor stages.

The product mixture, in which all or substantially all the alkylene oxide has been converted to alkanolamine, is fed from the last adiabatic reactor 5c through pressure regulating valve 6 and line 10, where the product mixture stream is approximately It is depressurized to a range of from atmospheric pressure to 40 atmospheres and then immediately fed to the flash separator 11. In the flash separator 11, substantially all of the unreacted ammonia is
It is immediately separated as a gas from the product mixture, removed from the top of separator 11 and recycled via line 12 through compressor or condenser 13. The alkanolamine product mixture is removed from the bottom of separator 11 through line 14 for purification, if desired.

FIG. 2 shows the reactor stages 5a, 5 of FIG.
Fig. 5 shows an adiabatic reactor 5 representative of Figs.b and 5c. The reactor 5 consists of an axial inlet pump 4 and a generally cylindrical hollow body 7 having a small cross-section compared to its length and providing an internal passage extending in the longitudinal direction. Inside the inlet end 20, 1
A pair of intersecting semi-elliptical control plates 21 are fitted, which impart an overwound motion to the fed reaction mixture, functioning as an overwrap plug-flow type reactor. Intermediate between the inlet pipe 4 and the intersecting regulating plate 21 in the inlet end 20 of the reactor 5 serves to distribute and direct the flow of fluid entering the cylinder body 7 of the reactor 5. A perforated plate 8 is fitted therein. The semi-elliptical baffle plate 21 imparting overwound motion to the flowing stream of fluid within the reactor has a major axis to minor axis ratio of about 1.25:1 to about
It is made from semicircular elliptical plates with a ratio of 2.0:1. Other means for imparting overcoiling motion to the fluid flow within the reactor include, for example, adjustment plates of varying structure, spacing, number, and size.
In addition, the method of fitting into the inlet end of the reactor, the cross section and length of the reactor, the velocity of the fluid flowing inside the reactor, etc.
These are factors that must be taken into consideration when selecting a specific target structure.

In a typical embodiment of the process of the invention, liquid ethylene oxide and ammonia, with a molar ratio of ammonia to ethylene oxide of 30:1, are mixed together with 3% by weight of water in the feed pipe 1. The mixture of raw materials passes through line 2, and the mixture is about 130
The reactor is pumped to a preheater 3 where it is heated to a temperature of about 9.2 °C and then into an adiabatic plug flow reactor 5a having an outside diameter of about 76.2 cm (30 inches) and a length of about 30.5 m (100 feet). It is delivered at a speed of cm/sec (0.3 ft/sec). The reaction mixture is subsequently fed at the same rate through three adiabatic plug flow reactors in series with similar dimensions and inlet configuration. The pressure in the reactor is sufficient to maintain the reaction mixture in a single homogeneous phase anywhere within the reactor as a supercritical fluid with a density of approximately 384 Kg/m ³ (24 pounds cubic feet). The pressure is regulated by the pressure control valve 6 so that the pressure is as high as 200 to 210 atmospheres. Approximately 25 ~ in the reactor
After a total residence time of 30 minutes, the product mixture leaves the last reactor at a temperature of approximately 175°C and passes through pressure regulating valve 6 and line 10 to flash separator 11.
sent to. The product mixture sent through line 10 is vacuumed to approximately 20 atmospheres. Once the product mixture enters flash separator 11, unreacted ammonia is rapidly separated and leaves the top of the separator through line 12. Unreacted ammonia is then condensed to a liquid in condenser 12 and recycled.

The alkanolamine product mixture is in line 14
It exits the bottom of the separator 11 through the filtrate and is purified and recovered by known distillation means.

The present invention is provided only to illustrate the invention and in no way limit it, which will become clearer if the following examples are considered. All parts and percentages are by weight unless otherwise indicated.

EXAMPLE 1 The drawings (Figures 1 and 1) are similar to those shown in Figure 1, except that the adiabatic plug flow reactor consists of four reactor stages having a diameter of about 30 inches and a length of about 100 feet. A reactor and apparatus similar to that shown in Figure 2) was used in a series of experiments to react ethylene oxide with ammonia. In this experiment, 227 kg/hr (500 lb/hr) of liquid ethylene oxide was mixed with approximately 40,824 kg/hr so that the ammonia to ethylene oxide molar ratio was 45:1.
(90,000 lb/hr) of liquid ammonia/water mixture feed (96% NH ₃ , 4% water). The mixed ammonia and ethylene oxide feed was preheated to a temperature of about 150°C and then pumped to the first reactor stage at a rate of about 8.2 cm/sec (0.27 ft/sec). The reactor stage pressure was adjusted to maintain a fluidized stream in a single supercritical fluid phase with an average reaction mixture density of approximately 344 Kg/m ³ (21.5 pounds/cubic foot). The pressure at the exit of the last reactor stage is approximately 184 atmospheres (approximately 2700 psig)
and the temperature of the product mixture at the exit of the fourth reactor stage was approximately 170° C. after a residence time in the reactor stage of 28 minutes.
The product mixture emerging from the last reactor stage is reduced to approximately 27 atmospheres (approximately 400 psig) in a line leading to the flash tank separator, and substantially all unreacted ammonia is removed from the flash tank separator. was separated from the product mixture in the vessel. The separated ammonia [(-COMMAND-)100] was removed from the top of the separator, pumped to a condenser where it was condensed to a liquid, and then recycled.

The product mixture was removed from the bottom of the flash tank separator, purified to remove any small amounts of unreacted ammonia present therein, and then collected. As a result of gas chromatographic analysis, the composition of the product mixture was found to be as follows.

Monoethanolamine 80% by weight Diethanolamine 17.5% by weight Triethanolamine 2.5% by weight No measurable amounts of unreacted ethylene oxide were found.

Example 2 Using the reaction system and apparatus described in Example 1, the molar ratio of ammonia to ethylene oxide was 44:1.
Approximately 2359Kg/hour (5200 lbs/hour)
of liquid ethylene oxide was mixed with about 40,824 Kg/hr (90,000 lb/hr) of a liquid ammonia/water mixture feed (97% _NH3 , 3% water) in a continuous experiment. The mixed ammonia and ethylene oxide feed is preheated to a temperature of about 154°C and is heated at about 7.9 cm/sec (about 0.26 ft/sec).
was pumped to the first reactor stage at a rate of . The pressure in the reactor stage is approximately 360Kg/m ³
(The pressure at the exit of the last reactor stage was approximately 204 atm ( 3000 psig) and the temperature of the product mixture at the exit of the last reactor was approximately 174.5°C after a residence time of 29 minutes.The temperature of the reaction mixture at the exit of each reactor stage was: I found out something.

Outlet of first reactor stage 166°C Outlet of second reactor stage 169.6°C Outlet of third reactor stage 174.8°C The product mixture leaving the last reactor stage is
The pressure was reduced to approximately 27.2 atmospheres (approximately 400 psig) and sent to a flash tank separator. There, virtually all unreacted ammonia was immediately separated from the product mixture, removed from the top of the separator, condensed to a liquid, and finally recycled.

The product mixture removed from the bottom of the separator was collected and found to consist of the following composition:

Monoethanolamine 83% by weight Diethanolamine 15% by weight Triethanolamine 2% by weight No measurable amounts of unreacted ethylene oxide were found in the product mixture.

Example 3 Using the reaction system and equipment described in Example 1, approximately 10,000 pounds/hour of ammonia to ethylene oxide molar ratio of 29:1 was produced.
of liquid ethylene oxide supply and approximately 51710
Kg/hr (114000 lbs/hr) of liquid ammonia/
A water mixture feed (97.5% NH ₃ , 2.5% water) was mixed and continuous experiments were performed. The raw material mixture is approx.
It is preheated to a temperature of 150℃, approximately 10cm/sec (0.33
ft/sec) to the first reactor stage. The pressure in the reactor stage is
The reaction mixture was adjusted to maintain the reaction mixture in a single supercritical fluid phase with an average reaction mixture density of approximately 23 pounds per cubic ^foot .

The pressure at the exit of the last reactor stage was about 204 atmospheres (3000 psig) and the temperature of the product mixture at the exit of the last reactor stage was about 180° C. after a residence time of 23 minutes.

After separating the unreacted ammonia, the resulting mixture was analyzed and found to be as follows.

Monoethanolamine 76.2% by weight Diethanolamine 20.8% by weight Triethanolamine 3.0% by weight It was also found that 0.1% of unreacted ethylene oxide was present in the product mixture.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a typical adiabatic reaction system used in the present invention. FIG. 2 is a schematic diagram illustrating an adiabatic overplug flow reactor suitable for use in the present invention.

Claims (1)

[Claims] 1 maintained in a single supercritical fluid phase having a molar ratio of ammonia to alkylene oxide in the range of 15:1 to 50:1 and having a density of at least 240 Kg/m ³ (15 lb/ft3); A swirling stream of a homogeneous mixture of an alkylene oxide having 2 to 4 carbon atoms, ammonia and a catalytic amount of water is processed under pressures ranging from 170 to 240 atm at temperatures up to 200°C. are reacted continuously to form an alkanolamine product mixture containing primarily monoalkanolamine; unreacted ammonia is separated from the alkanolamine product mixture after the alkylene oxide reaction is completed; and then the separated unreacted ammonia is characterized in that it is liquefied and recycled with a new amount of alkylene oxide for the reaction,
A method for continuously producing alkanolamines that obtains monoalkanolamines in high yields.