JPS61183231A - Production of isoamylene - Google Patents

Abstract

PURPOSE:To produce isoamylene efficiently at a low cost, by contacting unreacted hydrocarbon mixture recovered from the production process of polyisoprene with hydrogen in the presence of a catalyst, thereby selectively hydrogenating isoprene in the above mixture to isoamylene. CONSTITUTION:Isoamylene useful as a comonomer of petroleum resin, etc. is produced economically on an industrial scale, effectively utilizing the unreacted hydrocarbon mixture recovered from the polyisoprene production process, by the following steps comprising (I) the polymerization step to polymerize 1 isoprene 10 containing a small amount of isoamylene to produce polyisoprene, (II) the recovery step to recover 3 the hydrocarbon mixture 16 composed mainly of isoamylene and the unreacted isoprene from the step I, (III) the hydrogenation step to contact the hydrocarbon mixture 16 with hydrogen in the presence of a catalyst, and effect the selective hydrogenation 5 of isoprene in the hydrocarbon mixture 16 to isoamylene, and (IV) the separation step to separate 6 the isoamylene 20 from the product 18 of the step III.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing isoamylene, and more particularly, to a method for efficiently producing isoamylene from isoprene containing a trace amount of isoamylene.

(Prior Art) In recent years, inamicins, particularly 2-methyl-2-butene, have attracted attention as comonomers for petroleum resins. Conventionally known methods for producing it include a method of distilling isoamylene in the C5 fraction and a method of total hydrogenation of isoprene. However, these conventional methods have the following drawbacks due to their power.

In other words, in the distillation method, the content of isoamylene contained in the C5 fraction, which is the raw material, is low, so if you try to obtain high-purity isoamylene, a complicated process and a large amount of thermal energy are required, and the production cost is high. , it is hard to say that it is an industrially advantageous method.

In addition, the conventional hydrogenation method for isoprene uses high-purity isoprene, resulting in high raw material costs and cannot be called a geo-economical method.

(Problems to be Solved by the Invention) Therefore, as a result of intensive research in order to solve the above-mentioned drawbacks seen in the prior art, the present inventors have discovered that a large amount of unreacted isoamylene, which is a by-product from the polyisoprene manufacturing process, can be removed. It contains isoamylene, and when this fraction is subjected to a hydrogenation reaction, In7' is produced. It was discovered that V-n is selectively converted to isoamylene, and based on this finding, the present invention was developed.

(Means for Solving the Problems) Thus, according to the present invention, the polymerization step (I) of producing polyisogrene by polymerizing isoprene containing a trace amount of isoamylene, isoamylene and unreacted isoprene as main components from the polymerization step. A recovery step (■) 2 in which the recovered hydrocarbon mixture is brought into contact with hydrogen in the presence of a catalyst to selectively hydrogenate isoprene in the recovered hydrocarbon mixture to isoamylene. A process for producing isoamylene is provided, comprising a catalytic plow and a separation step for separating isoamylene from the output of the hydrogenation step.

In the present invention, isoprene containing a trace amount of isoamylene is used as a raw material for isoamylene. Specific examples of such surface isoprene include isoprene with a purity of 90% by weight or higher obtained from C5 fraction by extractive distillation, and is usually 2-methyl-2-butane O, 1 to 10% by weight, 2-methyl-2-butane O, 1 to 10% by weight, -1-butene O~3 weight i%, cis-pentene-20~2 hereditary, trans-pentene-2
0 to 2% by weight i is contained as an impurity.

In the present invention, such raw material isogrene is first supplied to the polymerization step (I), where a polymerization reaction using a polymerization catalyst is performed. The polymerization catalyst used may be any catalyst that can be used to produce rubbery or liquid isoprene polymer from isoprene; specific examples include:
For example, 4-Dollar type catalysts made of organic aluminum compounds and transition metal compounds, organic alkali metal compounds, etc. Specific examples include triisobutylaluminum-titanium tetrachloride, butyllithium, and the like.

Polymerization conditions are appropriately selected depending on the type of catalyst and the type of desired polymer, but usually the polymerization temperature is 0 to 100°C and the polymerization time is in the presence of a diluent such as butane, hexane, benzene, or toluene. For 10 minutes to 12 hours, the amount of catalyst used is 0.001 to 5% by weight (based on the amount of isoprene), and a rubbery or liquid isoprene polymer is produced by the polymerization reaction.

This polymerization reaction consumes most of isogrene, while hardly any isoamylene is consumed, so that the concentration of isoamylene in the unreacted mixture increases.

The product derived from the polymerization step is then sent to a recovery step (It), where the produced polymer is separated and the unreacted fraction is recovered. The processing conditions in this step are not particularly limited as long as they are the conditions normally used when producing isoprene polymers, and after adding a substance that deactivates the polymerization catalyst (e.g. alcohol, water, etc.), This is easily carried out by distilling off the fraction. Further, when a diluent is used in the polymerization step, the diluent is distilled off along with the unreacted fraction, but this diluent can usually be easily separated by simple distillation.

The unreacted fraction contains isoprene as its main component, but in the eastern process of refining isoprene, a fraction containing isoprene and isoamylene as its main components is obtained. This fraction has isoprene as its main component and usually contains about 5 to 30% by weight of isoamylene, but the concentration of isoamylene can be further increased by selecting distillation conditions.

In the present invention, the hydrocarbon mixture thus recovered is then fed to a hydrogenation step (to) where it is brought into contact with hydrogen in the presence of a hydrogenation catalyst to convert isoprene in the mixture into isoamylene. Selective hydrogenation is carried out. The reaction conditions at this time are not particularly limited as long as they can hydrogenate isoprene to isoamylene, such as palladium, platinum, ruthenium, nickel, etc.
In the presence of a catalyst based on Group II metals of the periodic table such as cobalt,
Reaction temperature: 0°C to 200°C, preferably 40°C to 150°C
The reaction pressure is 1 to 50 atm, preferably 6 to 40 atm.

Although it is desirable to reduce the amount of hydrogen used in the reaction as much as possible, it is preferable to add at least an equimolar amount of hydrogen to isoprene. In particular, it is preferable to use an equimolar amount to 20 times the molar amount.

The reaction is a well-known method and there are no particular restrictions, and either the patch type or fixed bed flow type may be used, and either the gas phase or the liquid phase may be used, but the fixed bed flow type is preferred in terms of operational simplicity and economic efficiency. Recommended by In the case of a fixed bed flow type, the flow of gas and liquid may be any of gas-liquid countercurrent, gas-liquid downward parallel flow, and gas-liquid upward parallel flow.

Also, when the reaction is carried out in the liquid phase, it is preferable to use all inert solvents in order to control the heat of reaction. Any non-reactive solvent that has solubility for the feedstock may be used. For example, alicyclic hydrocarbons such as tetrapane, butane, impentane, isoamylene, pentane, and hexane, aromatic hydrocarbons such as benzene, toluene, and xylene, and alicyclic hydrocarbons other than cyclohexane and cyclopentane. These hydrocarbon solvents may be used as a mixture of one or more kinds.

When the reaction format is a flow type, the liquid hourly space velocity of the isogrene raw material is carried out in the range of 0.2 to 10 volume times, preferably 1 volume to 5 volume times, relative to the catalyst capacity per hour.
In the case of patch type, the average residence time is 0.2 hours to 10 hours.
Implemented in hours.

Isoprene is easily converted to isoamylene by such hydrogenation reaction. At this time, isoamylene is also hydrogenated at the same time and isopentane is produced, but the reaction rate is slow compared to the hydrogenation reaction of imprene, so the loss of isoamylene remains within an acceptable range.

The hydrocarbon mixture derived from the hydrogenation step (a) is then fed to a separation step (conversion), where hydrogen and other impurities are separated. The separation means is not immediately limited, and can be carried out by general distillation (for example, simple distillation, precision distillation, etc.).

(Effects of the Invention) Thus, according to the present invention, isoamylene can be obtained at low cost and efficiently by effectively utilizing recovered unreacted hydrocarbons produced as a by-product from the isoprene polymer manufacturing process. That is, the recovered unreacted hydrocarbons, which are the raw materials for producing isoamylene, do not require any particular treatment and can be used as they are, and moreover, the isoamylene contained therein can be recovered without consuming them.

Next, one embodiment of the present invention will be described based on the drawings. In FIG. 1, first, isoprene diluted with a hydrocarbon solvent is supplied through a tube 10 to a polymerization vessel 1 (polymerization step), where a polymerization reaction is carried out.

After the polymerization reaction, the contents are sent to the coagulation tank 2 via the tube 12, and the coagulated isoplast polymer is sent to the drying system via the tube 22. On the other hand, the unreacted hydrocarbon mixture containing the hydrocarbon solvent is sent to the distillation column 3 via the pipe 14, and high purity isoprene is recovered from the top of the column via the pipe 24 and recycled to the polymerization process. The hydrocarbon mixture emerging from the bottom of the column is sent via pipe 26 to distillation column 4, where it is purified and then reused. Further, an isogrene fraction with a high concentration of isoamylene is extracted from the pipe 16 as a side stream of the distillation column 3 (recovery step).

This fraction is then fed to the hydrogenation reactor 5 and tube 3
After a hydrogenation reaction is carried out in the presence of hydrogen supplied from 0 (hydrogenation step), it is sent to the distillation column 6. A low-boiling fraction containing hydrogen is extracted from the top of the distillation column 6 via a pipe 32, and a high-boiling fraction is separated from the bottom of the column via a pipe 34. Distillate power/tube 20
It will be collected after all.

(Example) The present invention will be described in more detail with reference to Examples below. In addition, parts and percentages in the examples are based on weight unless otherwise specified.

Example 1 According to the flow sheet shown in FIG. 1, an experiment was conducted as follows. First, isoprene raw material 10 having the composition shown in Table 1
0 parts, triisobutylaluminum-titanium tetrachloride complex catalyst't 0.5 parts (relative to isoprene)
and xooo parts of toluene were supplied to the polymerization vessel. After polymerization was carried out at a reaction temperature of 40° C. and a residence time of 2 hours, the entire contents were transferred to a coagulation tank, and 50 parts of the in-prene polymer and the hydrocarbon mixture were completely separated. Next, after separating almost all of the toluene and unreacted isoprene from the bottom and top of the distillation column, isoamylene with a high isoamylene concentration is separated into 2 parts.
A portion was collected as a side stream. This isogrene fraction was supplied together with hydrogen to a hydrogenation reactor, where it was subjected to a liquid phase reaction in the presence of a palladium-tungsten catalyst under the conditions of 100°C, 23 atm, and liquid hourly space velocity W (LH8V) of 2.5 Hr. Thereafter, the reaction solution was supplied to the center of a distillation column with 100 plates, and distilled under the conditions of 65°C, 1 atm, and reflux ratio of 3, and from the 10th plate of the column, isoamide 771.8 with a purity of 93.6% was obtained. I got the department. The composition of the mixture in each step is shown in Table 1.

[Brief explanation of drawings]

FIG. 1 is a flow sheet showing one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Polymerization vessel, 2... Coagulation tank, 3... Distillation column, 4... Distillation column, 5... Hydrogenation reactor, 6...
distillation column.

Claims (1)

[Claims] 1. A polymerization step (I) of polymerizing isoprene containing a trace amount of isoamylene to produce polyisoprene; a recovery step (II) of recovering a hydrocarbon mixture mainly composed of isoamylene and unreacted isoprene from the polymerization step; A hydrogenation step (III) in which the recovered hydrocarbon mixture is brought into contact with hydrogen in the presence of a catalyst to selectively hydrogenate isoprene in the recovered hydrocarbon mixture to isoamylene, and a derivative of the hydrogenation step. A method for producing isoamylene, comprising a separation step (IV) of separating isoamylene from .