JPH1045833A - Production of oligomer of alpha-olefin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an industrially advantageous method for producing an oligomer of an α-olefin by which a maintaining temperature high in reactivity can be adopted without causing an isomerization reaction of the product, and thereby capable of readily corresponding to a method by which a byproduct polymer and a catalyst component are simultaneously concentrated and separated while suppressing the precipitation of the byproduct polymer. SOLUTION: This method for producing an oligomer of an α-olefin is performed by oligomerizing the α-olefin in the presence of a chrome-based catalyst and a reaction solvent in an oligomerization reactor, supplying a part or whole of the obtained reaction liquid to a degassing tower to recover the unreacted α-olefin, further supplying the reaction liquid discharged from the degassing tower to a product distillation tower to recover the produced oligomer of the α-olefin as a distillate. The temperature of the reaction liquid in a process line from the exit of the reactor to the entrance of the product distillation tower is maintained within the range of 100-150 deg.C, and the retention time of the reaction liquid from the supply to the degassing tower to the supply to the product distillation tower is within 1hr in the method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an α-olefin low polymer, and more particularly, to a method for producing an α-olefin low polymer mainly composed of 1-hexene from ethylene in a high yield. The present invention relates to an industrially advantageous method for producing an α-olefin low polymer which can be produced at a high selectivity.

[0002]

2. Description of the Related Art In recent years, many proposals have been made as industrially advantageous methods for producing low α-olefin polymers.
For example, JP-A-7-118174 and JP-A-7-11817
No. 5, 7-118326, 7-118327,
7-149671, 7-149673, 7-
Nos. 149,674, 7-149,675 and 7-149
Nos. 676 and 7-165815 use at least a chromium-based catalyst comprising a combination of a chromium compound (a), an amine or metal amide (nitrogen-containing compound) (b), and an alkylaluminum compound (c). Various improved inventions have been proposed.

Further, Japanese Patent Application Laid-Open Nos.
JP-A-134131 discloses at least a chromium compound (a), an amine or a metal amide (nitrogen-containing compound).
An invention using a chromium-based catalyst comprising a combination of (b), an alkylaluminum compound (c), and a halogen-containing compound (d) has been proposed.

In each of the above proposals, α-olefin and a chromium-based catalyst are brought into contact with each other in such a manner that the chromium compound (a) and the alkylaluminum compound (c) do not come into contact in advance to reduce the low polymerization of α-olefin. It is disclosed that by performing the process, a target α-olefin low polymer (for example, 1-hexene) can be obtained with higher selectivity.

[0005] By any of the above methods,
By-products of the polymer are inevitable, and in particular, in an industrial production method of an α-olefin low polymer, how to separate the by-product polymer is an important issue. The present inventors previously disclosed in Japanese Patent Application No. 7-349702 a method in which a low-polymer of α-olefin was separated from a reaction solution by distillation, and a by-product polymer in the reaction solution was concentrated together with a catalyst component to be separated. Suggested.

Further, the present inventors have disclosed in Japanese Patent Application No. 7-3497.
No. 02 proposed a method for maintaining the by-product polymer and the catalyst component in the reaction liquid in a dispersed state in the process line from the outlet of the reactor to the inlet of the product distillation column as the above-mentioned improved method. As a method of maintaining the by-product polymer in a dispersed state in the reaction solution, a method of maintaining the temperature of the reaction solution at a temperature at which the by-product polymer does not precipitate, a method of causing hydrogen to be present in the gas phase of the reactor to remove the by-product polymer A method for reforming into a granular form is disclosed, and as a method for maintaining a catalyst component in a dispersed state in a reaction solution, a method for solubilizing the catalyst component by adding a specific additive to the reaction solution is disclosed. I have.

In the method of maintaining the temperature of the reaction solution at a temperature at which the by-product polymer does not precipitate, the higher the temperature, the better. However, as the temperature increases, the isomerization reaction of the target product occurs, and the product distillation column There is a problem that the yield of the objective α-olefin low polymer to be recovered is reduced.
The isomerization reaction is different from the α-olefin trimerization reaction. For example, when the target product is 1-hexene,
This is a reaction in which 1-hexene is isomerized into another hexene and the content of 1-hexene in hexene decreases. And
According to the findings of the present inventors, the above-mentioned isomerization reaction is caused by a reaction activity other than the trimerization reaction expressed in the chromium-based catalyst as α-olefin is separated from the reaction solution, and the α-olefin of the raw material is produced. There is little problem in reactors where olefins are present.

The above-mentioned isomerization reaction is apt to be specifically caused in the following cases. That is, in the industrial production of 1-hexene, a batch system, a semi-batch system or a continuous system is appropriately employed according to the scale. In the case of the batch system, the reaction solution is temporarily stored, and the product distillation column is used. It may be efficient to collectively perform the processing in. It is also conceivable that the product is extracted from the gas phase of the reactor and a small amount of the reaction solution is continuously or discontinuously extracted from the reactor in order to prevent accumulation of the by-product polymer in the reactor. Also in this case, it may be efficient to temporarily store the reaction solution and collectively perform the treatment in the product distillation column. In such a case, the reaction solution needs to be maintained at a high temperature for a long period of time, and as a result, an isomerization reaction is easily caused.

Further, separately from the above, when the reaction solution is supplied to a degassing tower to recover unreacted α-olefin after the completion of the reaction, the recovered unreacted α-olefin is supplied to a pressurized reaction system. In order to perform the circulation economically, the pressure may be gradually reduced by a plurality of degassing towers arranged in parallel to perform the degassing treatment. Even in such a case, the reaction solution is maintained at a high temperature for a long time, and as a result, an isomerization reaction is easily caused.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to employ a high maintenance temperature of a reaction solution without causing an isomerization reaction of a product. Accordingly, there is provided an industrially advantageous method for producing an α-olefin low polymer, which can prevent a by-product polymer from being precipitated and can easily cope with a method of concentrating and separating both a by-product polymer and a catalyst component. Is to do.

[0011]

That is, the gist of the present invention is that low polymerization of α-olefin is carried out in a low polymerization reactor in the presence of a chromium-based catalyst and a reaction solvent. Unreacted α-olefin is recovered by supplying part or all to the degassing column, and then the reaction solution from the degassing column is supplied to the product distillation column, and the generated α-olefin low polymer is distilled off. In the method for producing an α-olefin low polymer recovered as a process, the temperature of the reaction solution is set to 1 in the process line from the outlet of the reactor to the inlet of the product distillation column.
Characterized in that the retention time of the reaction solution from the supply to the degassing column to the supply to the product distillation column is within 1 hour. The present invention relates to a method for producing a polymer.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
In the present invention, as the chromium-based catalyst, a catalyst system comprising at least a combination of at least a chromium compound (a), a nitrogen-containing compound (b) and an alkylaluminum compound (c) is used. In a preferred embodiment, the chromium compound (a), the nitrogen-containing compound (b), the alkylaluminum compound (c), and the halogen-containing compound (d)
Is used. The above three-component or four-component chromium-based catalyst is known as described above. In the present invention, these known chromium-based catalysts can be used without any restriction.

Specifically, as the above-mentioned three-component chromium-based catalyst, for example, a chromium-based catalyst composed of each component described in detail in [0014] to [0025] of JP-A-7-118174 is used. Examples of the four-component chromium-based catalyst that can be used include those described in JP-A-8-3216, [0015] to [0028], or JP-A-8-1.
A chromium-based catalyst composed of the components described in detail in JP-A-34131 [0016] to [0041] can be used.

The chromium compound (a) is typically a carboxyl salt of chromium, and specific examples thereof include chromium (II) acetate, chromium (III) acetate, and chromium (III) -2. -Ethylhexanoate, chromium (III) benzoate, chromium (III) naphthenate and the like. Of these, chromium (III) -2-ethylhexanoate is most preferred.

The nitrogen-containing compound (b) is typically a secondary amine, and specific examples thereof include pyrrole, 2,5-dimethylpyrrole, 3,4-dimethylpyrrole, 4-dichloropyrrole, 2,3
4,5-tetrachloropyrrole and 2-acetylpyrrole are exemplified. Of these, 2,5-dimethylpyrrole is most preferred.

The above alkylaluminum compound (c)
Typical examples include trialkylaluminum compounds, and specific examples thereof include trimethylaluminum, triethylaluminum, and triisobutylaluminum. Of these, triethylaluminum is most preferred.

As the above-mentioned halogen-containing compound (d), in particular, those described in JP-A-8-134131
Preferred are straight-chain hydrocarbons having 2 or more carbon atoms substituted with 3 or more halogen atoms. And as specific examples, 1,1,1-trichloroethane, 1,1,2,2
Examples thereof include 2, -tetrachloroethane, pentachloroethane, and hexachloroethane.

In the present invention, a substituted or unsubstituted α-olefin having 2 to 30 carbon atoms is used as a raw material α-olefin. Specific examples include ethylene, propylene, 1-butene, 1-hexene, 1-octene, 3-methyl-1-butene, 4-methyl-1-pentene, and the like. In particular, ethylene is preferable as the raw material α-olefin, and 1-hexene, a trimer thereof, can be obtained from ethylene with high yield and high selectivity.

In the present invention, as a reaction solvent, butane, pentane, 3-methylpentane, hexane, heptane, 2-methylhexane, octane, cyclohexane,
A chain or alicyclic saturated hydrocarbon having 1 to 20 carbon atoms, such as methylcyclohexane, 2,2,4-trimethylpentane, decalin, and an aromatic hydrocarbon such as benzene, toluene, xylene, ethylbenzene, mesitylene, and tetralin. Is used. These can be used alone or as a mixed solvent.

As the reaction solvent, α-olefin itself as a reaction raw material or α-olefin other than the main raw material can be used. As the reaction solvent, α-olefin having 4 to 30 carbon atoms is used, and α-olefin which is liquid at normal temperature is particularly preferable.

In particular, the reaction solvent may have 4 to 1 carbon atoms.
A chain saturated hydrocarbon or an alicyclic saturated hydrocarbon of 0 is preferred. By using these solvents, by-products of the polymer can be suppressed, and when an alicyclic hydrocarbon is used, there is an advantage that a high catalytic activity can be obtained.

First, in the present invention, low polymerization of α-olefin is carried out in a reactor in the presence of the chromium-based catalyst and the reaction solvent. As the reactor, a pipe reactor or a single-stage or multi-stage mixing tank is usually used. The pipe reactor is basically a type of reactor in which a reaction component is introduced from one end of a straight pipe or a coiled or U-shaped curved pipe, and a reaction product is discharged from the other end. The multi-stage mixing tank is basically a type in which the reaction components are introduced into a first tank of a plurality of mixing tanks arranged in series, sequentially moved to a subsequent tank, and a reaction product is discharged from a final tank. Of the reactor.

In the present invention, it is preferable to contact α-olefin with a chromium-based catalyst in such a manner that the chromium compound (a) and the alkylaluminum compound (c) do not come into contact in advance. According to such a specific contact mode, 1-hexene can be obtained in high yield from the raw material ethylene by selectively performing a trimerization reaction. The above specific contact mode is described in, for example, Japanese Patent Application Laid-Open No. Hei 7-118174 [0027]-
[0031] and [002] of JP-A-8-3216.
8] to [0032], and [0029] to [0050] of JP-A-8-134131, some examples of which are as follows.

(1) A method of introducing α-olefin and a chromium-containing compound into a reaction solvent containing a nitrogen-containing compound and an alkylaluminum compound. (2) a nitrogen-containing compound, an alkylaluminum compound,
A method of introducing α-olefin into a reaction solvent containing a halogen-containing compound. (3) A method of introducing α-olefin, a chromium-containing compound and a halogen-containing compound into a reaction solvent containing a nitrogen-containing compound and an alkylaluminum compound.

However, in the present invention, in addition to preparing the catalyst in the reactor according to the above-described contact mode, a low-polymerization reaction may be performed by supplying a separately prepared chromium-based catalyst to the reactor. For example, first, a nitrogen-containing compound (b) (particularly a pyrrole-containing compound), an alkylaluminum compound (c) and a halogen-containing compound (d) in a hydrocarbon and / or halogenated hydrocarbon solvent in the absence of α-olefin. ) And then reacting the obtained reaction solution for catalyst preparation with the chromium compound (a), whereby a chromium catalyst having excellent performance can be prepared.

In the present invention, the amount of the chromium compound to be used is usually 1.0 × 10 ^{−7 to} 0.1 × / l of the solvent.
5 mol, preferably 1.0 × 10 ^{−6 to} 0.2 mol,
More preferably, it is in the range of 1.0 × 10 ^{−5 to} 0.05 mol. On the other hand, the amount of the alkylaluminum compound to be used is usually 50 mmol or more per 1 mol of the chromium compound, but is preferably 0.1 mol or more from the viewpoint of catalytic activity and trimer selectivity. And the upper limit is usually 1.0 × 10 ⁴ mol. The amount of the nitrogen-containing compound to be used is usually 0.001 mol or more, preferably 0.005 to 5 mol, per 1 mol of the chromium compound.
1000mol, more preferably 0.01-100mo
1 range. The amount of the halogen-containing compound used is in the same range as the amount of the nitrogen-containing compound used.

In the present invention, the chromium compound (a),
Molar ratio (a) of nitrogen-containing compound (b), alkylaluminum compound (c) and halogen-containing compound (d):
(B): (c): (d) is 1: 1 to 50: 1 to 200:
1 to 50 are preferred, and 1 to 1 to 30 to 10 to 150: 1.
To 30 are particularly preferred. By combining such specific conditions,
As an α-olefin low polymer, for example, hexene is 9
It can be produced in a yield of 0% or more (ratio to the total amount of production), and the purity of 1-hexene in hexene can be increased to 99% or more.

Usually, the reaction temperature can be selected from 0 to 250 ° C., the reaction pressure can be selected from normal pressure to 250 kg / cm ² , and the reaction time can be selected from 1 minute to 20 hours, preferably 0.5 to 6 hours. However, regarding the reaction time,
The temperature is preferably set to 100 ° C. or higher, particularly preferably 120 ° C. or higher, from the viewpoint that it is desirable that the by-product polymer is not precipitated even in the reactor. The reaction pressure is preferably selected in relation to the employed reaction temperature.

The reaction conditions satisfying the following formulas (1) and (2) are such that the by-product polymer does not dissolve and precipitate in the reactor and the performance of the chromium-based catalyst at a high temperature can be prevented from deteriorating. Preferred. In the formula, T represents a reaction temperature (° C.), and P represents a reaction pressure (kg / cm ² G).

[0030]

T ≧ 100 ° C. (1) P> 0.5T−15 (2)

Next, in the present invention, part or all of the obtained reaction solution is supplied to a degassing column to recover unreacted α-olefin. That is, in the present invention, the degassing operation is performed prior to the other unit operations. Conventionally, in the industrialized α-olefin low polymerization process, the separation of the by-product polymer is performed using a solid-liquid separation device separately from the catalyst component, unlike the case of the present invention. In that case, the by-product polymer is separated without lowering the pressure and almost maintaining the pressure in the reaction. The reason is that, especially in the production of 1-hexene by the above-mentioned conventional method, the yield of 1-hexene is not sufficient, and a large amount of low-boiling component (1-butene) of about 15% by weight or more is produced as a by-product. Therefore, if the pressure drops to around normal pressure after the reaction,
1-butene from unreacted ethylene (boiling point: -6.47
This is because the cooling load required for the distillation separation of (° C.) increases.

Accordingly, in the case of the above conventional method, after the reaction, the by-product polymer is separated without lowering the pressure, the 1-butene is separated by distillation, and the pressure must be gradually reduced in the subsequent unit operation. Absent. However, the method of separating the by-product polymer in a pressurized state not only requires a special solid-liquid separation device, but also has poor operability, and sometimes the solid-liquid separation device is blocked by the by-product polymer. There are significant disadvantages.

On the other hand, in the low polymerization of α-olefin by the chromium catalyst system employed in the method of the present invention, 1
Α-olefin low polymers other than -hexene, especially 1-
Since 1-hexene is obtained in a high yield because of little by-product of butene, 1-butene is not required to be recovered, and even when recovered by atmospheric distillation, the cooling load required for distillation separation is significantly reduced. Can be reduced. As a result, in the present invention, the degassing operation can be performed prior to other unit operations, but this not only can avoid the complicated steps and disadvantages of the conventional method, but also This has the advantage that the subsequent unit operation can be operated at a temperature near normal pressure, which is excellent in operability.

In the present invention, the degassing treatment is usually carried out by
The pressure is reduced to 15 kg / cm ² G or less, but it is preferable to reduce the pressure to 1.9 kg / cm ² G or less, which is regarded as a second-class high-pressure container, from the viewpoint of the rules for handling the high-pressure vessel. If the pressure is reduced to 0.2 kg / cm ² G or less, almost the same operation as normal pressure can be performed, so that it is more preferable.

Next, in the present invention, the reaction solution from the degassing column is supplied to the product distillation column, and the generated α-olefin low polymer is recovered as a distillate.

The most important feature of the present invention is that in the process line from the outlet of the reactor to the inlet of the product distillation column, the temperature of the reaction solution is maintained in the range of 100 to 150 ° C. The point is that the residence time of the reaction solution from the completion of the reaction to the supply to the product distillation column is within 1 hour. In the present invention, the above-mentioned process line also includes a storage tank for a reaction solution used in a batch reaction or the like, and is not necessarily connected to these between the degassing column and the product distillation column. Absent.

If the maintenance temperature of the reaction solution is lower than 100 ° C., various troubles occur due to adhesion and deposition of by-product polymers in the process line (for example, auxiliary equipment such as piping). Isomerization reaction of the target product is induced, and the target α recovered from the product distillation column
The yield of olefinic low polymers is reduced. If the residence time of the reaction solution from supply to the degassing column to supply to the product distillation column exceeds 1 hour, the isomerization reaction Cannot be sufficiently suppressed.

The above conditions specified in the present invention include, for example,
This is important when, for example, a batch reaction method is used to temporarily store a reaction solution and collectively perform treatments in a product distillation column.
The above residence time is preferably shortened as the maintenance temperature of the reaction solution increases, but in any case, it is particularly preferably 30 minutes or less.

In the present invention, it is not impossible that the by-product polymer in the reaction solution is separated, for example, by a solid-liquid separator immediately after the reaction. However, in the above case, not only the solid-liquid separation device for the by-product polymer is required separately from the separation of the metal component, but also the metallization due to the heat history received during the distillation separation of each component in the reaction solution. It becomes extremely difficult to separate the separated metal components. That is, for example, when an attempt is made to separate a high boiling point component and a metal component by using a heating evaporator, the metal component adheres to the heat transfer surface of the heating evaporator and becomes substantially inseparable. Then, the metal component attached to the heat transfer surface hinders the operation of the heating evaporator.

Therefore, in the present invention, it is preferable to separate the by-produced polymer by concentrating it together with the catalyst component, as described later. According to such a separation mode, the catalyst component is very easily separated by the plasticity of the by-product polymer. In addition, a solid-liquid separator for a by-product polymer can be omitted, and the process can be made compact.

In the present invention, in the process line from the outlet of the reactor to the inlet of the product distillation column,
Preferably, the catalyst components are maintained in a dispersed state in the reaction solution. Generally speaking, it is considered that the catalyst component is less likely to adhere and precipitate in the process line as much as the by-product polymer.

However, in the present invention, a compound soluble in a reaction solvent and capable of forming a ligand for chromium is contained in a reaction solution in a process line from an outlet of a reactor to an inlet of a product distillation column. It is preferable to positively maintain the state of dispersion of the catalyst component in the reaction solution by adding. In addition, the above-mentioned compounds have the effect of deactivating the reaction activities other than the trimerization reaction expressed in the chromium-based catalyst as the concentration of α-olefin in the reaction solution decreases. It is also useful for suppressing the chemical reaction.

A compound soluble in a reaction solvent and capable of forming a ligand for chromium (hereinafter referred to as a metal solubilizer)
In general, a low molecular compound having a -XH functional group (where X represents a hetero atom and H represents a hydrogen atom) or a low molecular compound having an active methylene group is used. Examples of the former include alcohols, phenols, carboxylic acids, primary or secondary amines, and ammonia, and examples of the latter include acetylacetone.

Specific examples of the above alcohols include methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, benzyl alcohol, ethylene glycol, trimethylene glycol and propanediol. Examples of phenols include phenol, cresol, and hydroquinone. Specific examples of carboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, and decane. Acid, benzoic acid, phenylacetic acid, phthalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, acrylic acid, maleic acid, fumaric acid, salicylic acid, etc. Specific examples of primary or secondary amines include , As a component of the catalyst Each amines described above can be mentioned.

The use ratio of the metal solubilizing agent can be selected from a wide range ranging from a trace amount to the amount of the solvent, and the concentration in the solvent is usually 0.001 to 50% by weight, preferably 0.1% by weight. It is in the range of 01 to 10% by weight. The timing of adding the metal solubilizing agent may be selected at any stage before the components are separated by distillation in the reaction solution. When there are a plurality of distillation separation steps, they may be added immediately before the final distillation step in which metallization of the metal component is most likely to occur, but it is preferable to add them immediately after the reaction step. In addition, a method in which an antistatic agent already proposed in the field of polymerization of α-olefin is added to the reaction solution instead of the metal solubilizing agent can also be suitably used.

According to the above preferred embodiment of the present invention,
The loss of both the by-product polymer and the catalyst component up to the simultaneous recovery process can be minimized.

In the present invention, the concentration and separation of the by-product polymer and the catalyst component from the reaction solution can be carried out simultaneously with the simple removal of all the components having a low boiling point from the degassed reaction solution. It can be carried out simultaneously with the last distillation separation when each component is successively separated from the reaction solution by distillation.

For example, when α-olefin is ethylene, 1-hexene is obtained as an α-olefin low polymer. In this case, after the reaction, ethylene is removed, and then 1-hexene and a solvent are removed from the reaction solution. And the catalyst component is concentrated and separated together with the by-product polyethylene. Then, the obtained concentrated liquid containing the by-product polymer and the catalyst component can be directly discarded.

As described above, in the catalyst system used in the method of the present invention, 1-butene is less produced as by-product and 1-hexene can be obtained in high yield. By treating in a product distillation column, 1-hexene and the reaction solvent can be separated into a high boiling component including a by-product polymer and a catalyst component. As a result, the most compact and economical process can be realized. Can be realized.

In the preferred embodiment of the present invention, at least a part of each of the by-product polymer and the catalyst component is simultaneously separated. Preferably, all of the catalyst components, more preferably, the by-product polymer and the catalyst component are separated. Simultaneous separation is performed for all components. And in any case,
The bottoms containing the by-product polymer and the catalyst component recovered from the product distillation column are supplied to a heating evaporator to recover the high boiling components and to further concentrate and recover the by-product polymer and the catalyst component. preferable.

As the above-mentioned heating evaporator, conventionally known various types can be used. For example, a thin film evaporator equipped with a scraping blade that rotates with respect to a heat transfer surface of a cylindrical type,
An evaporator having a built-in plate fin heater can be used. An evaporator with a built-in plate-fin heater
The high-viscosity fluid can be heated instantaneously by the fins arranged at high density, and the volatile substances contained therein can be efficiently removed.

As the heating evaporator having the above-mentioned structure, for example, "Hibiscus Evaporator" (trade name) manufactured by Mitsui Engineering & Shipbuilding Co., Ltd. is exemplified. When such a heating evaporator is used, the by-product polymer and the catalyst component concentrated by the built-in plate-fin type heater flow down from the lower portion of the heating evaporator due to the plasticity of the by-product polymer. Therefore, it can be cut and recovered easily after being cooled appropriately.

In the present invention, a particularly recommended heating evaporator is a monotube evaporator provided with a heating tube having a sufficient length and a collecting can capable of holding under reduced pressure. As the heating evaporator having such a structure, for example, "CRUX SYSTEM" (trade name) manufactured by Hosokawa Mikaron Co., Ltd. and the like can be mentioned. In such a monotube evaporator, the concentrated solution heated and evaporated by the heating tube is spouted at a high speed of about the speed of sound to a collecting can to efficiently remove volatile substances contained therein. The by-product polymer and the catalyst component concentrated in the collection can flow down from the lower part of the collection chamber due to the plasticity of the by-product polymer. Therefore, it can be cut and recovered easily after being cooled appropriately.

On the other hand, the recovered α-olefin low polymer is purified if necessary. For purification, distillation purification is usually employed, and a target component can be recovered with high purity. In the present invention, in particular, 1-hexene of high purity can be industrially advantageously produced from ethylene. Further, L-LDPE, which is a useful resin, can be produced from 1-hexene obtained by the production method of the present invention by a polymerization reaction using a known polymerization catalyst.

[0055]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist of the invention.

Example 1 A complete mixing tank type reactor, a degassing column, a product distillation column equipped with two side stream withdrawing sections and a total of 30 stages of product distillation columns, and an evaporator were provided. A continuous low-polymerization reaction of ethylene was performed between the gas column and a gas column according to a process provided with a compressor for circulating degassed ethylene to the reactor. In addition, a 20-liter autoclave provided with two supply pipes was used as a complete mixing tank type reactor, and a heating tube having a length of 8 m and a collecting can capable of holding under reduced pressure were used as an evaporator. Mono tube type evaporator “CRUX SYST”
EM "(trade name, manufactured by Hosokawa Mikaron Co., Ltd.).

A solution of chromium (III) -2-ethylhexanoate (a) in n-heptane and hexachloroethane (d) together with ethylene from one supply pipe of the complete mixing tank reactor.
N-heptane solution was continuously supplied, and the n-heptane solution of 2,5-dimethylpyrrole (b) and the n-heptane solution of triethylaluminum (c) were continuously supplied from the other supply pipe. . (A): (b): (c):
The molar ratio of (d) is 1: 6: 40: 4. The reaction conditions were 120 ° C. × 50 kg / cm ² G.

The reaction liquid continuously withdrawn from the reactor was supplied to the degassing tower while maintaining the temperature at 120 ° C. The degassed reaction liquid was supplied to the product distillation column while substantially maintaining the above temperature, and the bottom liquid was supplied to the evaporator and concentrated. Eighth from the bottom of the product distillation column
The solvent n-heptane was discharged from the side draining part at the 26th stage.
The product hexene was extracted and collected as side cuts from the side draining part of the stage, and components having a boiling point lower than that of hexene were distilled off from the top of the column and collected. The residence time of the reaction solution from the supply to the degassing column to the supply to the product distillation column was 15 minutes.

In the evaporator, the evaporated high-boiling components were condensed and recovered, and the catalyst component concentrated together with the by-product polyethylene was recovered from the lower part of the collection chamber. On the other hand, ethylene degassed in the degassing tower is pressurized by the compressor and circulated to the reactor, and n-heptane recovered from the product distillation column is circulated to the reactor via a circulating pipe. Was done. Table 1 shows the operating conditions of each unit after the product distillation column. Table 2 shows the mass balance in the above process. In Table 2, Cr (2EHA) ₃ is chromium (III) −
Represents 2-ethylhexanoate.

[0060]

[Table 1] Product distillation column: Top pressure 3 kg / cm ² G Reflux ratio (R / D) 18 Bottom temperature 162 ° C Heating tube temperature: 200 ° C Collector temperature: 150 ° C Collector pressure: 200 torr

[0061]

[Table 2] ──────────────────────────────────── Reaction liquid Degassing liquid Distillation column Evaporator Evaporation vesselBottom liquid Evaporation component Concentration component Unit: / hr 36.1kg 30.8kg 0.20kg 0.18kg 22.0g Cr (2EHA)_Three(ppm) 3.0 3.5 160 0.0 0.148wt% 2,5-dimethylmethyl (ppm) 3.6 4.2 190 213.2 0.0 Triethylaluminum (ppm) 28.4 33.0 1521 0.0 1.40wt% Hexachloroethane (ppm) 7.4 8.6 394 442.0 0.0 Heptane (wt% 66.8 78.3 0.0 0.0 0.0 Ethylene (wt%) 14.6 0.0 0.0 0.0 0.0 1-Hexene (wt%) 18.0 21.1 0.0 0.0 0.0 High-boiling component (wt%) 0.50 0.59 89.1 99.9 0.0 Polyethylene (ppm) 600 703 10.69wt% 0.0 98.5wt% Total (wt%) 100.0 100.0 100.0 100.0 100.0 Catalyst efficiency: 555,556 g-1-hexene / g-chromium

The operation of the evaporator in the above process is as follows:
Since the catalyst component containing the metal was recovered as a concentrated mixture together with the by-produced polyethylene, it dropped and separated from the lower part of the collection chamber by its own weight due to the plasticity of the polyethylene, and was performed well.

On the other hand, the results of the composition analysis of the reaction solution (reactor and degassing tower outlet) in the above Examples are shown in Table 3 together with the result of the composition analysis after the thermal stability test of the reaction solution separately performed. The heat stability test was conducted at 120 ° C collected from the degassing tower.
The reaction was carried out by allowing a part of the reaction solution to stay for a predetermined time.

[0064]

[Table 3]

Example 2 A continuous low-polymerization reaction of ethylene was carried out in the same manner as in Example 1 except that tetrachloroethane was used as the halogen-containing compound. Table 4 shows the mass balance of this example. The operation of the evaporator was as good as in Example 1. Table 5 shows the results of the composition analysis after the thermal stability test of the reaction solution performed in the same manner as in Example 1.

[0066]

[Table 4] Reaction liquid Degassing liquid Distillation column Evaporator Evaporation vesselBottom liquid Evaporation component Concentration component Unit: / hr 36.1kg 30.8kg 0.18kg 0.16kg 19.8g Cr (2EHA)_Three(ppm) 3.0 3.5 178 0.0 0.164wt% 2,5-dimethylmethyl (ppm) 3.6 4.2 211 236.9 0.0 Triethylaluminum (ppm) 28.4 33.0 1689 0.0 1.55wt% Tetrachloroethane (ppm) 5.2 6.1 310 348.3 0.0 Heptane (wt% 68.9 80.7 0.0 0.0 0.0 Ethylene (wt%) 14.6 0.0 0.0 0.0 0.0 1-Hexene (wt%) 16.0 18.7 0.0 0.0 0.0 High boiling component (wt%) 0.45 0.53 89.1 99.9 0.0 Polyethylene (ppm) 540 632 10.69wt% 0.0 98.3wt% Total (wt%) 100.0 100.0 100.0 100.0 100.0 Catalyst efficiency: 493,827 g-1-hexene / g-chromium

[0067]

[Table 5]

Example 3 Continuous low-polymerization of ethylene was carried out in the same manner as in Example 1 except that octanoic acid (2-ethylhexanoic acid) was continuously added as a metal solubilizer to the degassing tank. The reaction was performed. The amount of the metal solubilizing agent added was such that the concentration in the reaction solvent in the degassing tank was 0.022% by weight.

The bottom liquid of the product distillation column is sampled,
Analysis of the deposited metal component was carried out, but the deposited metal component was not substantially present. In addition, the analysis of the deposited metal component
A method of filtering a sample with a filter paper (5A), washing the filter paper surface with an n-heptane solution, washing with a 10% by weight aqueous nitric acid solution, and measuring the concentration of a metal component in the aqueous nitric acid solution by high-frequency plasma emission spectroscopy Made by. Table 6 shows the mass balance of this example. The operation of the evaporator was as good as in Example 1. Table 5 shows the results of the composition analysis after the thermal stability test of the reaction solution performed in the same manner as in Example 1.

[0070]

[Table 6] Reaction liquid Degassing liquid Distillation tower Evaporator Evaporation vesselBottom liquid Evaporation component Concentration component Unit: / hr 36.1kg 30.8kg 0.23kg 0.21kg 24.5g Cr (2EHA)_Three(ppm) 3.0 3.5 462 0.0 0.442wt% 2,5-dimethylmethyl (ppm) 3.6 4.2 548 611.9 0.0 Triethylaluminum (ppm) 28.4 33.0 4383 0.0 4.19wt% Hexachloroethane (ppm) 7.4 8.6 1136 1268.5 0.0 Heptane (wt% ) 65.5 76.7 0.0 0.0 0.0 Ethylene (wt%) 14.6 0.0 0.0 0.0 0.0 1-Hexene (wt%) 19.2 22.5 0.0 0.0 0.0 High boiling component (wt%) 0.58 0.68 89.4 99.8 0.0 Polyethylene (ppm) 720 844 9.98wt% − 95.4wt% Total (wt%) 100.0 100.0 100.0 100.0 100.0 Catalyst efficiency: 592,593 g-1-hexene / g-chromium

[0071]

[Table 7]

Example 4 A continuous low-polymerization reaction of ethylene was carried out in the same manner as in Example 1 except that the reaction temperature and pressure were changed to 120 ° C. and 70 kg / cm ² G. Table 8 shows the mass balance of this example. The operation of the evaporator is described in Example 1.
As good as. Table 9 shows the results of the composition analysis after the thermal stability test of the reaction solution performed in the same manner as in Example 1.

[0073]

[Table 8] ──────────────────────────────────── Reaction liquid Degassing liquid Distillation column Evaporator Evaporation vesselBottom liquid Evaporation component Concentration component Unit: / hr 36.1kg 27.9kg 0.66kg 0.61kg 49.1g Cr (2EHA)_Three(ppm) 3.0 3.9 49 0.0 0.066wt% 2,5-dimethylmethyl (ppm) 3.6 4.6 58 62.7 0.0 Triethylaluminum (ppm) 28.4 37.0 465 0.0 0.63wt% Hexachloroethane (ppm) 5.2 6.8 85 92.2 0.0 Heptane (wt% ) 41.5 53.7 0.0 0.0 0.0 Ethylene (wt%) 22.7 0.0 0.0 0.0 0.0 1-Hexene (wt%) 34.0 44.0 0.0 0.0 0.0 High boiling component (wt%) 1.70 2.20 92.6 100.0 0.0 Polyethylene (ppm) 1350 1746 7.35wt% 0.0 99.3wt% Total (wt%) 100.0 100.0 100.0 100.0 100.0 Catalytic efficiency: 1,049,383 g-1-hexene / g-chromium

[0074]

[Table 9]

Examples 5 to 8 In Example 3, 1-hexanol (Example 5), hexylamine (Example 6), ammonia (Example 7), acetylacetone were used as metal solubilizers to be added to the degassing tank. A continuous low-polymerization reaction of ethylene was carried out in the same manner as in Example 3 except that (Example 8) was used. As a result, the operation of the evaporator was as good as in Example 3. Example 3
Sample the bottom liquid of the product distillation column in the same manner as
Analysis of the deposited metal component was carried out, but in any of the examples, substantially no deposited metal component was present.

[0076]

According to the present invention described above, a high maintenance temperature of the reaction solution can be adopted without causing the isomerization reaction of the product, and therefore, the precipitation of the by-product polymer can be prevented, There is provided an industrially advantageous method for producing an α-olefin low polymer which can easily cope with a method of concentrating and separating a raw polymer and a catalyst component together.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeshi Okano 3-10, Ushidori, Kurashiki-shi, Okayama Prefecture Mitsubishi Chemical Mizushima Development Laboratory Co., Ltd.

Claims (11)

[Claims] In a low-polymerization reactor, low-polymerization of α-olefin is carried out in the presence of a chromium-based catalyst and a reaction solvent, and a part or all of the obtained reaction solution is supplied to a degassing column. A method for producing an α-olefin low polymer in which the reaction α-olefin is recovered, and then the reaction solution from the degassing column is supplied to a product distillation column, and the generated α-olefin low polymer is recovered as a distillate. In the process line from the outlet of the reactor to the inlet of the product distillation column, the temperature of the reaction solution is maintained in the range of 100 to 150 ° C., and is supplied to the degasification column and then supplied to the product distillation column. A method for producing an α-olefin low polymer, wherein the residence time of the reaction solution until the reaction is completed is within 1 hour. 2. At least a chromium compound (a), a nitrogen-containing compound (b), an alkylaluminum compound (c)
2. A chromium-based catalyst comprising a combination of
The production method described in 1. 3. The process according to claim 1, wherein a chromium-based catalyst comprising at least a combination of a chromium compound (a), a nitrogen-containing compound (b), an alkylaluminum compound (c), and a halogen-containing compound (d) is used. Method. 4. The molar ratio of the chromium compound (a), nitrogen-containing compound (b), alkylaluminum compound (c) and halogen-containing compound (d) (a) :( b) :( c):
3. The method according to claim 1, wherein (d) is 1: 1 to 50: 1 to 200: 1 to 50. 5. The low polymerization of α-olefin by contacting α-olefin with a chromium-based catalyst in such a manner that the chromium compound (a) and the alkylaluminum compound (c) do not come into contact in advance. The production method according to any one of the above. 6. The product distillation column according to claim 1, wherein the low α-olefin polymer produced is recovered as a distillate, and the by-product polymer and the catalyst component are both concentrated and recovered as a bottoms. The production method according to any one of the above. 7. The production method according to claim 6, wherein the α-olefin low polymer, the reaction solvent, the by-product polymer and the high boiling point component containing the catalyst component are separated by a single product distillation column. 8. A bottom product containing a by-product polymer and a catalyst component recovered from the product distillation column is supplied to a heating evaporator to recover a high-boiling component and further concentrate the by-product polymer and the catalyst component. The production method according to claim 6, wherein the recovery is performed by recovery. 9. The production method according to claim 8, wherein the heating evaporator is a monotube evaporator including a heating tube having a sufficient length and a collecting can capable of holding under reduced pressure. 10. The method according to claim 10, wherein the α-olefin is ethylene,
The process according to any one of claims 1 to 9, wherein the -olefin low polymer is mainly 1-hexene. 11. The process according to claim 6, wherein 1-hexene, a reaction solvent, and a high-boiling component containing a by-product polymer and a catalyst component are separated by a single product distillation column.