JPS6234018B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for separating each component in a C ₄ hydrocarbon fraction (hereinafter sometimes referred to as a C ₄ fraction).

The _C4 fraction is produced as a by-product during petroleum refining, for example, during the production of gasoline by catalytic cracking of petroleum, or during the production of olefins by thermal decomposition of petroleum. this
_C4 fractions are generally isobutylene, 1-butene and 2
- A mixture of _C4 hydrocarbons such as n-butenes and butanes, with a small amount of _C4 hydrocarbons,
It may also contain _C3 hydrocarbons, _C5 hydrocarbons, butadiene, etc. n separated from this _C4 fraction
- Each component such as butene and isobutylene is secondary butyl alcohol, methyl ethyl ketone, butyl rubber,
Demand is increasing for various raw materials such as polybutene and polyisobutylene. These chemical raw materials, isobutylene and n-butene, often need to be purified to a high degree of purity, and the basic technology for comprehensive utilization of _C4 fractions is to analyze each component, especially isobutylene and n-butene. Much attention has been paid to how these can be separated efficiently and industrially. However, since isobutylene and 1-butene have approximately the same vapor pressure, it is practically impossible to separate the components in the _C4 fraction by distillation alone, and various methods other than distillation have been proposed.

Conventionally, extraction separation using sulfuric acid has been adopted as a separation method for _C4 fraction, but there are problems with corrosion, requiring the use of expensive corrosion-resistant materials, and the reaction system is multi-stage and complex. However, several other separation methods have been proposed. For example, crystalline aluminosilicate was used to adsorb and separate 1-butene in the _C4 fraction (Japanese Patent Publication No. 52-21481, etc.), or 1-butene in the _C4 fraction was isomerized to 2-butene. Thereafter, the isobutylene is separated by distillation (Japanese Patent Publication No. 50-22005), or the 1-butene in the _C4 fraction is isomerized to 2-butene, and then the isobutylene is polymerized and removed (Japanese Patent Publication No. 51-1989). No. 8201) has been proposed, but there are still unresolved problems such as insufficient yield and purity of the target component, short catalyst life, and the inability to recover useful components by isomerization or polymerization. There is.

In recent years, as a method for separating _C4 fractions, isobutylene in _C4 fractions is reacted with methanol and water to intermediately produce methyl tertiary butyl ether (abbreviated as MTBE) and tertiary butyl alcohol (abbreviated as TBA). Many reports have been made on reaction separation methods that utilize However, there are several difficulties in almost completely separating and removing isobutylene from the _C4 fraction.

Since the MTBE method is a homogeneous reaction, C ₄
In order to remove trace amounts of isobutylene from the fraction, it is necessary to repeat the reaction and separation several times to shift the equilibrium and minimize the amount of unreacted isobutylene remaining, making the reaction system complex with multiple steps. Also
When decomposing MTBE to recover isobutylene, the loss of methanol due to dehydration condensation cannot be ignored, and methanol and ether are mixed into the separated components, making their separation difficult.

In the latter TBA method, water and the C ₄ fraction are not compatible, and in order to increase the reaction rate, it is necessary to add a polar solvent or surfactant to the system. In this case as well, it is necessary to repeat the reaction and separation several times to shift the equilibrium and increase the conversion rate, making the reaction multistage and complicated. Furthermore, it is difficult to separate the added polar solvent and surfactant, making the system complex. In the case of the TBA method, it has also been proposed to take advantage of the fact that water and the _C4 fraction are not compatible and bring the water and the _C4 fraction into countercurrent contact in the presence of a catalyst (Patent Publication No. 56-500087).
However, the ratio of the distribution ratio of the generated TBA to water and _C4 fraction is not so large, so the extraction effect is enhanced.
In order to almost completely remove isobutylene from the C ₄ fraction, the molar and volume ratios of water and isobutylene must be very high and a large amount of water must be used, which has the disadvantage of increasing heat loss. Furthermore, in order to reduce the amount of isobutylene remaining in the C ₄ fraction, this method is not efficient because the treated C ₄ fraction must be recycled to the reaction zone after removing the TBA contained therein. do not have. In addition, this method requires the linear velocity of the raw material to be extremely high, which requires the use of a huge reaction tower with a very high height, which poses a practical problem. Furthermore, when the present inventors tried this method again, the difference in specific gravity between the ascending flow layer and the descending flow layer was insufficient, and flooding was likely to occur, causing problems in operation (the amount of TBA produced and the distribution ratio to each layer). It was also found that the ratio of water and C ₄ fraction supply must be changed accordingly. Also, under the TBA law
TBA has the disadvantage that it is difficult to separate because it is azeotropic and compatible with water.

As a method similar to the TBA method, it is also possible to use ethylene glycol, which behaves very similar to water, instead of water, and remove isobutylene by reacting with the ethylene glycol. However, this method also has the same problems as the TBA method in batch methods and cocurrent contact methods. Furthermore, since ethylene glycol behaves very similarly to water, it is common knowledge that even if the C ₄ fraction is brought into countercurrent contact with ethylene glycol, the same problems as the TBA method will occur.

The present inventors conducted various studies to establish a method for separating and removing isobutylene from _C4 fractions, and found that although ethylene glycol is similar to water, _C4 fractions can be used in countercurrent flow with ethylene glycol under specific conditions. Contrary to expectations by contacting the above
The present invention was established based on the discovery that, unlike the MTBE method and the TBA method, isobutylene can be almost completely removed from a C ₄ fraction with great efficiency and industrial advantages. Conventionally, ethylene glycol is thought to behave similarly to water with respect to isobutylene, so it was completely unexpected that ethylene glycol was able to solve the problem that could not be solved using the TBA method using water. It was hot.

That is, the gist of the present invention is that isobutylene and n-
A C ₄ hydrocarbon fraction containing butene is mixed with ethylene glycol in the presence of a strongly acidic cation exchange catalyst having an average particle size of at least 1 mm at a temperature of 60 to 120°C.
C, the pressure is 5 to 70 Kg/cm ² , the liquid hourly space velocity of the C ₄ hydrocarbon fraction is 0.04 to 5 hr ^-1 , and the molar ratio of ethylene glycol to isobutylene is 20 mol/mol or more. The present invention relates to a method for separating isobutylene from a C ₄ hydrocarbon fraction, characterized in that the isobutylene in the C ₄ hydrocarbon fraction is separated by reacting with ethylene glycol.

In the present invention, the etherification catalyst used when bringing the _C4 fraction and ethylene glycol into countercurrent contact is a strongly acidic cation exchanger with an average particle size of at least about 1 mm or more (the particle size of 1 mm or more is preferable). (approximately 90% or more, preferably approximately 95% or more), preferably with an average particle size of approximately 2 to 5 mm (particle size 2 to 5 mm).
5 mm is about 90% or more, preferably about 95% or more. )belongs to. Examples of strong acid type cation exchangers include styrene sulfonic acid type cation exchange resins (sulfonated crosslinked copolymers of styrene and polyunsaturated compounds such as divinylbenzene), and phenolsulfonic acid type cation exchange resins. Sulfonic acids such as (phenolsulfonic acid condensed with formaldehyde), sulfonated coal, sulfonated asphalt, sulfonic acid-type cation exchange resins with sulfonate bound to fluororesin (for example, Nafion manufactured by Dupont, etc.) Some have groups. In order to be used for countercurrent contact in the present invention, the particle size must be large. If particles with a particle size too small are used, it is difficult to bring them into countercurrent contact, and particles with an extremely large particle size are difficult to obtain.

The _C4 fraction treated in the present invention is isobutylene and n
-butenes. When the isobutylene content in the C ₄ fraction is high, it is necessary to increase the amount of ethylene glycol supplied in order to almost completely remove isobutylene only by countercurrent contact.
Therefore, the _C4 fraction with a high content of isobutylene may be directly brought into countercurrent contact, but the _C4 fraction should be brought into contact with ethylene glycol at a temperature of 0 to 150°C before the countercurrent contact to substantially completely remove isobutylene. The isobutylene content is determined in advance by a method such as reacting isobutylene with ethylene glycol by contacting them in cocurrent or countercurrent in the presence of a strong acid type cation exchange catalyst at a molar ratio of ethylene glycol and isobutylene of about 1 to 5. It is desirable to keep it as low as about 5-25% by weight. The production reaction of glycol ether by the reaction of isobutylene in the _C4 fraction with ethylene glycol by cocurrent contact is described, for example, in U.S. Patent Nos. 2480940, 3170000, and 3288842.
For example, ethylene glycol and isobutylene are mixed in the presence of a strong acid type cation exchanger catalyst as described above at a temperature of 0 _to 150°C. molar ratio of 0.1 to 100 mol/mol, liquid hourly space velocity
It consists of co-current contact under conditions of 0.1 to 100 hr ^-1 and pressure of 1 to 70 Kg/cm ² .

The countercurrent contact of the _C4 fraction with ethylene glycol according to the invention is carried out using the large particle size catalyst described above and at a temperature of about 60-120°C, particularly preferably about 70-110°C, and a pressure of about 5-70 kg/ ^cm2, especially Preferably about 15-25Kg/cm ² ,
The liquid hourly space velocity of the _C4 fraction is about 0.04 to 5.0 hr ^-1 , particularly preferably about 0.07 to 2.0 hr ^-1 , and the molar ratio of the ethylene glycol fed to the isobutylene fed is about 20 mol/mol or more, particularly preferably about 25 to 2.0 hr -1. The reaction is carried out under conditions of 35 mol/mol by feeding the C ₄ fraction from the bottom of the reaction column and ethylene glycol from the top of the reaction column. In the reaction tower, isobutylene reacts with ethylene glycol to produce ethylene glycol monotertiary butyl ether (abbreviated as MBE) and a small amount of ethylene glycol ditertiary butyl ether (abbreviated as DBE), which are discharged from the bottom of the reaction tower. MBE is used in the ethylene glycol layer to be extracted.
and a small amount of C ₄ hydrocarbons are dissolved, and the treated C ₄ fraction layer taken out from the top of the reaction tower contains almost no isobutylene and the produced DBE is dissolved. The residual isobutylene content of the treated _C4 fraction is less than about 1% by weight, and can be less than about 0.5%, or even less than about 0.1% by weight. If the reaction temperature is too low than the above range, the reaction rate will be slow, which is disadvantageous, and if it is too high, side reactions such as olefin polymerization and DBE formation will occur, and the catalyst will be damaged. The reaction pressure must be such that the C ₄ fraction becomes a liquid phase, but if the pressure is too high, it is disadvantageous because the reaction system must be able to withstand the high pressure. In order to reduce the residual amount of isobutylene in the treated C ₄ fraction, it is necessary to make the molar ratio of the supplied ethylene glycol and the supplied isobutylene above a certain value and to make the liquid hourly space velocity of the C ₄ fraction below a certain value. be. If the molar ratio of ethylene glycol and isobutylene is too large, the increased effect will be almost useless, and if the feed rate of each raw material is too slow, uneven flow will occur and operation will become unstable, which is _{disadvantageous} . If the feed rate of the fraction is too fast, the efficiency of contact with the catalyst and ethylene glycol will decrease.

The _C4 fraction exiting from the top of the countercurrent catalytic reaction column is n-
Contains butenes, has little residual isobutylene, and has a very high recovery rate of n-butenes.
It can be used as a chemical raw material, such as a raw material for producing secondary butyl alcohol, or as a raw material for the production of 1-butene and 2-butyl alcohol.
-Each component such as butene can be separated and purified by distillation.

Ethylene glycol layer (contains MBE, dissolved if necessary) exiting from the bottom of the countercurrent contact reaction tower
Removes _C4 hydrocarbons. ) is used as it is or isobutylene is further added to the ethylene glycol layer containing the product of reacting ethylene glycol and isobutylene in the presence of a strong acid type cation exchanger catalyst (contains MBE and may also contain DBE. Dissolved C if necessary) ₄ Hydrocarbons may be removed by flushing, distillation, etc.), (a) MBE may be obtained as a product by distillation, or (b) MBE or MBE may be obtained by heating in the presence of a strong acid type cation exchange catalyst. DBE may be decomposed to recover isobutylene, or (c) MBE or MBE may be recovered by heating under pressure in the presence of a strong acid type cation exchanger catalyst.
Diisobutylene may be produced by decomposing DBE, or (d) tertiary butyl alcohol may be produced by decomposing MBE and DBE by adding water and heating in the presence of a strong acid type cation exchange catalyst. You can also. Preferred reaction conditions for obtaining isobutylene are a temperature of about 80 to 120°C, reduced pressure, and normal pressure to about 3 Kg/cm ²
Under pressure up to, the liquid hourly space velocity is approximately 0.5~2hr ^-1 ,
Particularly preferred reaction conditions for obtaining diisobutylene are a temperature of about 110 to 130°C, a pressure of about 4 to 10 Kg/cm ² , and a liquid hourly space velocity of about 0.2 to 1 hr ^-1 . Conditions are temperature approximately 90
-120°C, pressure 4-8 Kg/ ^cm2 , molar ratio of the mixture of MBE and DBE to water about 2-5 mol/mol, and liquid hourly space velocity of the raw material about 0.5-2 hr ^-1 . When obtaining isobutylene and diisobutylene, a small amount of water is added during the reaction, i.e. approximately 0.005 to 0.05 water per 1 part by weight of all raw materials.
Addition of parts by weight is useful for suppressing dehydration condensation of ethylene glycol. In the case of diisobutylene production, triisobutylene and higher oligomers are produced in very small quantities. The purity of the isobutylene thus obtained is usually 99.0% or higher, and it is also possible to obtain one with a purity of 99.5% or higher. The recovery rate of ethylene glycol is also very high.
For example, it is possible to set it to 99% or more or 99.5%.

Next, an embodiment of a method for separating a C ₄ fraction incorporating the method for treating a C ₄ fraction by countercurrent contact according to the present invention will be described with reference to a flow sheet of the drawings.

The C ₄ fraction from tube 1 is cocurrently treated with the ethylene glycol-containing fraction from tube 2 (which also contains MBE, DBE, dissolved C ₄ hydrocarbons, and ethylene glycol monosecondary butyl ether) to form a cation exchanger. It is introduced into the packed co-current reaction tower 3, and ethylene glycol and isobutylene are reacted. The reaction product withdrawn from the bottom of the reaction column 3 is introduced into a distillation column 5 through a pipe 4 to separate the C ₄ fraction and liquid components. The liquid components drawn out from the bottom of the distillation column 5 are composed of ethylene glycol, MBE, DBE, etc., and are sent through a pipe 6 to a decomposition step to be described later. The isobutylene content withdrawn from the top of the distillation column is
The C ₄ fraction reduced to about 10% by weight is introduced into the bottom of the countercurrent reaction tower 8 packed with a cation exchanger catalyst through a pipe 7, and then sent to the top of the countercurrent reaction tower 8 through a pipe 9 from the decomposition step described below. It is brought into countercurrent contact with the recovered ethylene glycol introduced in the countercurrent reaction tower 8. The C ₄ fraction withdrawn from the top of the reaction column 8 is introduced into a distillation column 11 via a pipe 10 to separate the C ₄ fraction and liquid components. The _C4 fraction drawn out from the top of the distillation column 11 through the pipe 12 mainly consists of n-butene and butane, and the residual amount of isobutylene is less than 0.5% by weight. The components withdrawn from the bottom of the distillation column 11 by pipe 13 are mainly MBE and DBE, together with the ethylene glycol layer consisting of ethylene glycol, MBE and dissolved _C4 fraction withdrawn from the bottom of countercurrent reaction column 8 by pipe 14. The ethylene glycol-containing fraction is recycled to the above-mentioned co-current reaction tower 3 via pipe 2. The distillation column 5
The liquid component withdrawn from the bottom of the tube consists of ethylene glycol, MBE, DBE, and a small amount of ethylene glycol monosecondary butyl ether, which is a reactant with n-butene, and is transferred via tube 6 to a decomposition packed with cation exchanger catalyst. Introduced from the top of the reaction column 15, MBE, DBE, and ethylene glycol monosecondary butyl ether are decomposed and converted into ethylene glycol, isobutylene, and 2-butene. The decomposition reaction product is drawn out from the bottom of the decomposition reaction tower 15 and introduced into a gas-liquid separator 17 through a pipe 16, where it is separated into gas and liquid components. The gaseous components withdrawn from the top of the separator 17 are introduced via a pipe 18 into a compressor 19 where they are liquefied and then introduced into a distillation column 20. Distillation column 2
At 0, n-butenes as impurities are drawn out from the bottom of the column through a pipe 21, and high-purity isobutylene with a purity of 99% or more is drawn out from the top of the column through a pipe 22. The liquid component withdrawn from the bottom of the gas-liquid separator 17 is introduced via a pipe 23 into a distillation column 24, where ethylene glycol is recovered. Distillation column 24
MBE that has not been decomposed in the decomposition reactor is withdrawn from the top of the decomposition reactor, and is recycled to the decomposition reactor 15 through a pipe 25. The recovered ethylene glycol withdrawn from the bottom of the distillation column 24 is recycled along with make-up ethylene glycol from line 26 to the top of the countercurrent reaction column 8 via line 9. (Reaction zone 15 may also be used for the production of diisobutylene or tertiary butyl alcohol.) Regarding the advantage of the process of the present invention, the C ₄ fraction is countercurrently contacted with ethylene glycol instead of water under specific conditions. As a result, isobutylene can be selectively and efficiently separated and removed from the C ₄ fraction, and a C ₄ hydrocarbon fraction containing n-butene and having an extremely small amount of residual isobutylene can be obtained in a one-stage reaction.
Furthermore, extremely high purity isobutylene, diisobutylene, tertiary butyl alcohol, and ethylene glycol monotertiary butyl ether can be obtained in good yield. The recovery rate of n-butenes and ethylene glycol is also very high. In the countercurrent catalytic reaction tower, ethylene glycol monotertiary butyl ether is selectively produced, and the amount of by-products of ethylene glycol ditertiary butyl ether and diisobutylene is extremely small.Furthermore, since the boiling point difference between ethylene glycol and MBE is large, the reaction product is Separating and purifying things is easy. In addition, in a countercurrent catalytic reaction tower, the difference in specific gravity between the upflow layer and the downflow layer is approximately 0.5, and flooding is unlikely to occur, so operation is easy, unlike in the case of the TBA method. Since the method of the present invention does not use sulfuric acid, there is no problem of corrosion as in the sulfuric acid method.

The present invention will be explained below with reference to Examples.

Example 1 About 650 c.c. of a strong acid type cation exchange resin (abbreviated as OMZ, provided by Organo Co., Ltd.) was placed in a reaction tower with a cross-sectional area of about 5 cm ² and a height of 1.5 m. Styrene and divinylbenzene were copolymerized, and then sulfone The grain size is 2.
~5mm. ₎ at 75℃ and 20Kg/ ^cm
27%, saturated _C4 hydrocarbons 38%, butadiene 1%,
The remainder consists of other _C2-5 hydrocarbons. ) is supplied from the lower nozzle of the reactor at a liquid hourly space velocity of 0.1 hr ^-1 ,
Ethylene glycol was fed from the reactor upper flange at a liquid hourly space velocity of 0.36 hr ^-1 (ethylene glycol to isobutylene molar ratio was 30:1).

The isobutylene concentration in the _C4 fraction distilled from the upper part of the reactor was 0.3wt%, with a very small amount of MBE,
It included DBE. The ethylene glycol distilled from the bottom of the reactor contained approximately 5 wt% MBE, but no DBE was observed. The amount of distillate obtained by removing gaseous components at room temperature from the upper distillate was approximately 1 wt% of the amount of lower distillate.

Example 2 The _C4 fraction was contacted with ethylene glycol in the same manner as in Example 1, except that the flow rate of ethylene glycol was varied to vary the molar ratio of ethylene glycol fed to isobutylene fed. When the molar ratio of ethylene glycol to isobutylene was 35, 25, and 15 mol/mol, the isobutylene content of the C ₄ fraction distilled from the top of the reactor was 0.2, 0.6, and 1.3 wt%, respectively.

Comparative Example 1 A reaction was carried out in the same manner as in Example 1 except that 0.36 hr ^-1 of water was supplied instead of 0.36 hr ^-1 of ethylene glycol. The isobutylene content of the C ₄ fraction distilled from the upper part of the reactor was 2.8 wt%.

Comparative Example 2 Same as Example 1 except that instead of feeding ethylene glycol 0.36hr ^-1 from the bottom of the reaction tube, methanol 0.36hr ^-1 was fed from the top of the reactor and brought into contact with the C ₄ fraction in parallel flow. The _C4 fraction was contacted with methanol. The isobutylene content of the C ₄ fraction distilled from the bottom of the reactor was 6.3 wt%.

Comparative Example 3 Same as Example 1 except that instead of feeding ethylene glycol from the bottom of the reactor, 0.36 hr ^-1 was fed from the top of the reactor and brought into contact with the C ₄ fraction in parallel flow.
The _C4 fraction was contacted with ethylene glycol. The isobutylene content of the _C4 fraction distilled from the bottom of the reactor is 5.9wt%, and the production ratio of MBE to DBE is 20/
It was 1wt/wt.

Example 3 The C ₄ fraction was brought into contact with ethylene glycol in the same manner as in Example 1 except that the reaction temperature was 65°C.
The isobutylene content of the C ₄ fraction distilled from the upper part of the reactor was 0.5 wt%.

Example 4 The _C4 fraction was brought into contact with ethylene glycol in the same manner as in Example 1, except that 0.36 hr ^-1 of recovered ethylene glycol containing 4.5 wt% MBE as an impurity was supplied instead of 0.36 hr ^-1 ethylene glycol. Ta. The results were slightly inferior to those of Example 1, and the isobutylene content of the C ₄ fraction distilled from the upper part of the reactor was 1.0 wt%.

Example 5 Lower distillate (MBE 5.8 wt% and ethylene glycol monosecondary butyl ether) distilled from the lower part of the countercurrent contact reaction tower obtained in Example 1.
Ethylene glycol solution containing 0.1wt%)
, strong acid type cation exchange resin Amberlyst 15
(Manufactured by Rohm and Haas. Sulfonated copolymer of styrene and divinylbenzene, exchange capacity 4.9 meq/g, particle size 0.3 to 1.0 mm.) In a reaction tube filled with 20 c.c. It was supplied at 110°C and a liquid hourly space velocity (LHSV) of 0.5 hr ^-1 . The MBE content in the distilled ethylene glycol solution is 0.75 mol%,
MBE conversion rate is 76%, ethylene glycol recovery rate is
The purity of isobutylene obtained by distilling the gaseous components separated from the distillate after liquefying the distillate was 99%, and the recovery rate of isobutylene was 99.2%.

In this reaction, when 0.01 part by weight of water was added to 1 part by weight of the raw material and the mixture was passed through a reaction tube, the ethylene glycol recovery rate was approximately 100%.

Example 6 The reaction pressure was 6.3Kg/cm ² and the liquid hourly space velocity of all raw materials was
The reaction was carried out in the same manner as in Example 5 except that the reaction time was 0.3 hr ^-1 . An ethylene glycol solution and a diisobutylene solution were separated and obtained as distillates. M.B.E.
Conversion rate 65.9%, ethylene glycol recovery rate 98%
The diisobutylene obtained after distillation purification had a purity of 99% and a yield of 86%.

Example 7 The lower distillate distilled from the lower part of the countercurrent contact reaction tower obtained in Example 1 was distilled under reduced pressure to recover MBE. The purity of the recovered MBE was 99.2% and the recovery rate was 98%.

Example 8 The MBE obtained in Example 7 was used as a raw material, and the molar ratio of water to MBE was 3.4:1, 100℃, 5.8Kg/
cm ² , LHSV of all raw materials was 1.2 hr ⁻¹ and fed into a reaction tube filled with 20 c.c. of catalyst Amberlyst 15.
The MBE conversion rate was 67% and the ethylene glycol recovery rate was 100%, and the product was subjected to a three-component azeotropic distillation operation to separate and recover TBA.

Example 9 According to the flow sheet shown in the drawing, _C4 fraction (composition is isobutylene 50wt%, 1-butene 25%,
Consists of 15% 2-butene, 9.5% saturated _C4 hydrocarbons, and the remainder other _C2-5 hydrocarbons. ) was separated.

The catalyst packed in reaction towers 3 and 15 was Amberlyst 15, and the catalyst packed in reaction tower 8 was OMZ. The reaction conditions in reaction column 3 are a temperature of 70°C;
Pressure 20Kg/cm ² , molar ratio of feed ethylene glycol to feed isobutylene 2.8:1, LHSV of all raw materials is
2.0 hr ^-1 , and the reaction conditions in reaction column 8 were: temperature 75°C, pressure 20 Kg/cm ² , molar ratio of ethylene glycol to isobutylene supplied 30:1, and C ₄ fraction supplied (isobutylene content 9.1 wt%). The cavity liquid hourly space velocity is 0.2 hr ^-1 , and the reaction conditions in the reaction column 15 are a temperature of 110°C, normal pressure, and a liquid hourly space velocity of all raw materials.
It was 1.0hr ^-1 . The isobutylene content of the _C4 fraction distilled from the top of the distillation column 11 is 0.3 wt%, n-
The butene recovery rate is 94%, and the isobutylene distilled from the top of the distillation column 20 has a purity of 99.6%, and the recovery rate is
It was 99.3%.

[Brief explanation of the drawing]

The drawing is a flow sheet showing one embodiment of the method of the present invention. 3... Co-current catalytic reaction tower, 8... Counter-current catalytic reaction tower, 15... Decomposition reaction tower.

Claims (1)

[Claims] 1 C ₄ containing isobutylene and n-butene
The hydrocarbon fraction is mixed with ethylene glycol in the presence of a strongly acidic cation exchange catalyst having an average particle size of at least 1 mm at a temperature of 60 to 120°C, a pressure of 5 to 70 Kg/cm ² , and a C ₄
The isobutylene in the _C4 hydrocarbon fraction is converted to ethylene by countercurrent contact under conditions where the liquid hourly space velocity of the hydrocarbon fraction is 0.04 to 5 hr ^-1 and the molar ratio of ethylene glycol to isobutylene is 20 mol/mol or more. A method for separating isobutylene from a _C4 hydrocarbon fraction, characterized by separating isobutylene by reaction with glycol.