JPH0257525B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for separating and recovering high-yield, high-purity butene-1 from a butane-butene fraction containing isobutylene and butene-1.

Butane-containing isobutylene and butene-1
In order to separate butene-1 from the butene fraction, the _C4 fraction other than butene-1 must be separated and removed by precision distillation, but in this case, isobutylene has a specific volatility that is very similar to butene-1. Therefore, high purity butene-1 cannot be separated and recovered simply by distillation. Therefore, in order to separate and recover high purity butene-1 from a butane-butene fraction containing isobutylene and butene-1, it is first required to almost completely remove isobutylene from this fraction.

Conventionally, there is a sulfuric acid extraction method as a method for separating isobutylene from a butane-butene fraction. However, this method requires the use of high-grade materials due to the corrosive nature of sulfuric acid, which imposes a heavy economic burden.
Another method for separating isobutylene is adsorption using zeolite, but this method does not sufficiently separate butene-1 and butene-2.

Generally, it is considered to dimerize or polymerize isobutylene by using an acidic catalyst and remove this polymer from the butane-butene fraction by distillation, but usually during this reaction, butene-1 is isomerized and the butene-1 isomerized. There is a strong tendency for it to be 2. Also butene-1
causes a copolymerization reaction with isobutylene. Therefore, in order to separate and recover butene-1 in high yield, it is necessary to suppress these side reactions as much as possible and increase the amount of isobutylene.

The present invention relates to a method for separating and recovering butene-1, which comprises separating and removing isobutylene by lowering isobutylene in a butane-butene fraction containing isobutylene and butene-1 through a reaction with special reaction conditions. This invention relates to a method for separating butene-1, characterized in that the butane-butene fraction contains 0.001 to 2% by weight of an alcohol having 1 to 9 carbon atoms.

That is, the present invention adds an alcohol having 1 to 9 carbon atoms to a butane-butene fraction containing 0.1 to 15% by weight of isobutylene and 10 to 50% by weight of butene-1.
A hydrocarbon fraction containing 0.001 to 2% by weight was placed in a reaction tower filled with strong acid type cation exchange resin particles with an average particle size of 0.2 to 10 mm at a temperature of 30 to 100°C and a liquid hourly space velocity of 0.1 to 1.
50 (1/hr) and a pressure of 1 to 50 atmospheres to underpolymerize isobutylene, and this low polymer is distilled to produce heavy hydrocarbons mainly containing low polymers of isobutylene and butane. High purity butene characterized by obtaining light hydrocarbons mainly containing butene, and further separating butene-1 from other _C4 hydrocarbons by precision distillation of the light hydrocarbons to obtain butene-1. The present invention relates to a method for separating and recovering -1 in high yield.

The starting material used in the present invention is isobutylene.
It is a butane-butene fraction containing 0.1 to 15% by weight and 10 to 50% by weight of butene-1. This raw material is usually obtained from the _C4 fraction produced when petroleum is thermally cracked, steam cracked, or catalytically separated, and it is usually used that has almost completely removed butadiene, for example, to 0.1% by weight or less.

These usually contain isobutylene, butene-1, butene-2, isobutane, and n-butane. If the isobutylene content is greater than 15% by weight, it will not be used effectively. 1 to 10% by weight of isobutylene and 20 to 40% by weight of butene-1 are preferred.

In the present invention, a _C4 hydrocarbon mixture obtained by separating and removing butadiene from a _C4 hydrocarbon fraction obtained by cracking petroleum as a raw material butane-butene fraction is polymerized using an aluminum chloride catalyst to form a liquid or semi-solid polymer. It is preferably employed to use an unreacted C ₄ hydrocarbon mixture in producing the coalescence. Conventional C ₄ with butadiene removed
It is known that a liquid or semi-solid polymer (polybutene) is produced by polymerizing a hydrocarbon mixture using an aluminum chloride catalyst as a raw material and polymerizing isobutylene mainly in a _C4 hydrocarbon mixture.
After this polymerization reaction, the unreacted _C4 hydrocarbon mixture has a reduced isobutylene content, but is still about 1
It contains up to 10% by weight, especially 2 to 6% by weight.
Distilling this unreacted _C4 hydrocarbon mixture as it is does not yield highly pure butene-1, and this mixture has generally been used as a fuel. In the present invention, it is very preferable to use this unreacted C ₄ hydrocarbon mixture as a starting material.

In addition, in the present invention, as a butane-butene fraction as a starting material, a C ₄ hydrocarbon mixture obtained by separating butadiene from a C ₄ hydrocarbon fraction obtained by cracking petroleum and methanol are mixed in the presence of an acidic catalyst. The unreacted C ₄ hydrocarbon mixture used in the reaction to produce methyl-tert-butyl ether can also be effectively used. A C ₄ hydrocarbon mixture from which butadiene has been separated and methanol are reacted in the presence of an acidic catalyst, such as a strong acid type cation exchange resin described below when used in the present application, and the isobutylene and methanol in the mixture are reacted to form a methyl tertiary compound. It is known to produce butyl ether, and the unreacted hydrocarbon mixture after this reaction still contains about 1 to 10% by weight of isobutylene, which is commonly used as a fuel. This unreacted C ₄ hydrocarbon mixture is also effectively used in the present invention.

In the present invention, the butane-butene fraction as a raw material is further obtained by decomposing petroleum.
Butadiene was separated and removed from the _C4 hydrocarbon fraction.
An unreacted C ₄ hydrocarbon mixture obtained when tert-butyl alcohol is produced by reacting a C ₄ hydrocarbon mixture with water in the presence of an acidic catalyst can also be effectively used. The C ₄ hydrocarbon fraction from which butadiene has been removed is reacted with water using an acidic catalyst such as sulfuric acid, hydrochloric acid, or a cation exchange resin similar to that used in this application, which will be described later, to hydrate the isobutylene in the fraction. It is known to produce tertiary butyl alcohol. The unreacted mixture in this reaction also contains 1 to 10% by weight of isobutylene, which is normally used as a fuel. In this application, this unreacted C ₄
Hydrocarbon mixtures can also be used to advantage.

The alcohol used in the present invention has 1 carbon number
~9, and their structures are not particularly limited. Among these alcohols, methanol,
Particularly preferred are ethanol, isopropanol and sec-butanol. If the alcohol has 10 or more carbon atoms, the effect of adding the alcohol in the present invention will hardly be observed.

The effect of adding alcohol in the present invention refers to the surprising effect that isomerization and polymerization of butene-1 can be significantly suppressed by adding alcohol. The amount of alcohol added varies depending on the isobutylene content in the butane-butene, but is 0.001 to 2% by weight in the butane-butene.
It is. If the amount of alcohol added is less than 0.001% by weight, no effect of alcohol addition will be observed, and if it is more than 2% by weight, the reaction rate of isobutylene will decrease, and the amount of ether having a tert-butyl group will not only increase, but also unreacted. An alcohol recovery tower is required. A particularly preferred range of the amount of alcohol added is 0.01 to 1% by weight.

In the present invention, a hydrocarbon fraction containing an alcohol having 1 to 9 carbon atoms is used in the above-mentioned raw material butane-butene fraction, and this is subjected to a reaction column filled with a strong acid type cation exchange resin as described below. .

In the present invention, it is possible to cause low polymerization of isobutylene by passing the butane-butene fraction through a fixed bed filled with a strong acid type cation exchange resin in a one-stage, one-pass system.
However, if no alcohol is present in the butane-butene fraction, if this step is continued for a long time, the activity gradually decreases. In that case, measures are taken to maintain the removal rate of isobutylene by low polymerization reaction above a certain value by raising the reaction temperature, but in this case, butene-1 undergoes isomerization and polymerization, and its content gradually decreases. A decreasing trend is observed. The butene-1 to be produced is maintained at a high purity of, for example, 99% by weight or more, and the residual rate of butene-1 at that time (residual rate refers to the butene-1 content after the reaction relative to the butene-1 content in the raw material). It is required to maintain a high residual ratio of butene-1) and, as a result, to maintain a high recovery rate of butene-1.

The present inventors have discovered that by incorporating a small amount of alcohol into the butane-butene fraction, the above-mentioned requirements can be met while the activity can be maintained for a long period of time, and thus the present invention has been developed.

When the butane-butene fraction is passed through a fixed bed packed with the ion exchange resin in the present invention,
Since the low polymerization reaction of isobutylene is an exothermic reaction, a temperature difference occurs between the inlet and the outlet of the reaction tower, and especially when the concentration of isobutylene in the butane-butene fraction is high, there is a temperature difference near the exit of the reaction tower. It gets quite hot. Such high temperatures must be avoided quite strictly from the viewpoint of increasing the loss of butene-1 in the raw material and deteriorating the catalyst. Therefore, in this case, it is necessary to equip the reactor with, for example, a special cooler, but due to the poor heat transfer of the ion exchange resin, a multi-tube cooling reaction type must be used. If this method is adopted, replacing the catalyst becomes complicated. Moreover, even in this case, the presence of localized high-temperature parts often occurs, which is disadvantageous. Therefore, if the reactor is not equipped with a special cooler or the like, the one-stage, one-pass method is preferably employed when the content of isobutylene in the butane-butene is 0.1 to 2% by weight. Isobutylene content is 2~
In the case of 15% by weight, the reaction column is divided into two stages, and in the first reaction column, the reaction mixture that has passed through the first reaction column is divided into two streams, and one stream is fed to the subsequent second reaction column. It is preferable to adopt a circulation supply system in which the other streams are directly circulated and supplied to the first reaction tower filled with the ion exchange resin. In this case, the amount of each flow is 1 to 1 for the former and 1 to 15 (parts by weight) for the latter (circulating amount), preferably 3 to 7. The second reaction column employs the usual one-pass method. In the case of a circulation system, the temperature within the reaction tower is maintained sufficiently uniform. However, in the one-stage circulation method, the reactivity is lower than in the isothermal one-pass method (piston flow method), so low polymerization of isobutylene can be suppressed, that is, the amount of isobutylene remaining after the reaction with isobutylene in the raw material. is increasing. For this purpose, the reaction conditions must be made harsh (e.g., raising the reaction temperature and lowering the liquid hourly space velocity). However, under such severe conditions, the amount of loss due to isomerization and polymerization of butene-1 increases, resulting in a decrease in the remaining amount of butene-1. Therefore, in the first stage, it is preferable to adopt a circulation system under conditions that suppress low polymerization of isobutylene to some extent (e.g., isobutylene reaction rate, e.g., 70 to 90% by weight), and to react the remaining isobutylene in the second stage reaction column. In the second stage, the isobutylene in the second stage raw material is further reduced, and the accumulation of reaction heat is also small, so the temperature difference between the inlet and outlet of the reaction column is small, and the reaction of butene-1 is minimized. For the purpose of suppression, the second stage reaction column adopts a one-pass system.

In the present invention, the reaction temperature is 30 to 100°C regardless of whether it is a one-stage method or a two-stage method.
Preferably it is carried out at 45-75°C. In any reaction tower, if the reaction temperature is lower than 30°C, the reaction rate will be low, resulting in insufficient separation of isobutylene.
Moreover, if the temperature is higher than 100°C, the reaction of butene-1 becomes radical and the amount of loss of butene-1 increases.

The reaction pressure in the present invention is 1 to 50 atm, preferably 50 atm, regardless of whether it is a one-step method or a two-step method.
~30 atm. If the reaction pressure is lower than 1 atm, the reaction system will be in a gas phase and the reaction will not be able to reach its full potential.
If the pressure is higher than the atmospheric pressure, the reaction vessel and its attached equipment must be made into strong pressure-resistant equipment, which is industrially disadvantageous.

The strong acid type cation exchange resin as used in the present invention is a cation exchange resin exhibiting strong acidity, and representative examples thereof include styrene sulfonic acid type resin and phenolsulfonic acid type resin. A styrene-based sulfonic acid type ion exchange resin is a sulfonated resin obtained by copolymerizing styrene and a polyunsaturated compound such as divinylbenzene, and is generally represented by the following formula.

Furthermore, the phenolsulfonic acid type resin is usually obtained by condensing phenolsulfonic acid with formaldehyde, and is usually represented by the following formula.

(m and n are positive integers) The above-mentioned strong acid type cation exchange resin is used as a catalyst in the present invention, and is used in the form of spherical or cylindrical particles with an average particle size of 0.2 to 10 mm.

The catalyst particles are packed into a pressure-resistant cylindrical reaction vessel to form a bed of a fixed bed.

The size of the fixed bed is not particularly limited.
Usually the height is 0.2m to 20m.

Butane-containing isobutylene and butene-1 from the top or bottom of the fixed bed, preferably from the top.
Continuously feed the butene fraction. The amount supplied is such that the liquid hourly space velocity is 0.1 to 50 (Kg/Kg x 1/hr = 1/hr), preferably 0.5 to 15 (1/hr). In the case of a one-stage process, the liquid hourly hourly (hr) is expressed as the weight of the stream fed to the reaction tower per kilogram of catalyst (Kg), and in the case of a two-stage process, the liquid hourly space velocity is expressed as hr), the weight (Kg) of the stream fed to the first reaction column per kg of catalyst (excluding the stream circulating through the first reaction column)
In the second reaction column, it is expressed as the weight (Kg) of the flow passing through the second reaction column per 1 kg of catalyst per hour (hr). The supply amount of butane-butene fraction is 0.1 (1/
If it is smaller than hr), the yield of the butane-butene fraction after isobutylene separation will be small, which is industrially disadvantageous. Furthermore, if the feed rate is greater than 50 (1/hr), sufficient separation of isobutylene will not be achieved.

In the present invention, when the isobutylene content in the butane-butene fraction is relatively small, the isobutylene content in the butane-butene fraction can be reduced by lowering most of the isobutylene by a one-step method. If the amount is relatively large, a two-stage method is used to underpolymerize 70 to 90% by weight of isobutylene in the butane-butene fraction of the raw material in the first reaction tower, and most of the remaining isobutylene is underpolymerized in the second reaction tower. The removal of isobutylene is thereby achieved.

The reaction mixture subjected to the above reaction is subjected to a distillation column, and heavy hydrocarbons mainly containing dimers and low polymers of isobutylene and a small amount of alcohol are obtained from the bottom of the column,
Light hydrocarbons containing mainly butane-butene are obtained from the top of the column. For this distillation, it is sufficient to carry out ordinary distillation using about 3 to 30 stages, for example, about 10 to 20 stages.

The light hydrocarbons obtained from the distillation are then further subjected to precision distillation. Usually, this precision distillation is carried out in two stages, and in the first precision distillation, isobutane is mainly separated and removed from the top of the column. The bottom stream is further subjected to precision distillation to mainly remove n-butane and butene-2 from the bottom, and high-purity product butene-1 is produced from the top of the column.
Separate and collect. Precision distillation usually takes 30~
Those with 150 stages, especially around 90 to 140 stages, are used.

In the case of the method of the present invention, a product isobutylene having a purity of 99% by weight or more, and further a purity of 99.5% by weight or more can be obtained. Of course, if higher product purity is not required, this can be achieved by making the reaction conditions milder or by relaxing the distillation operating conditions.

Next, in order to explain the method of the present invention in more detail, an example of the process will be explained with reference to the drawings.

In the case of the one-stage process, in Fig. 1, the butane-butene fraction as a raw material is fed through line 1, the alcohol consisting of 1 to 9 carbon atoms is fed through line 2, and both are fed through line 3 to heater E. ₁ and maintained at a predetermined temperature, it enters a fixed bed reaction tower R filled with strong acid type cation exchange resin particles. The pressure around the reaction tower R is controlled at a predetermined pressure by a pressure control valve PCV. The fluid exiting the reaction column R passes through a pipe 5, has its pressure reduced in the PCV, and enters the distillation column _D1 after being temperature-controlled by a heat exchanger _E2 as necessary. Isobutylene low polymers are separated from the bottom of the distillation column D ₁ , and a butane-butene fraction from which isobutylene has been removed is distilled from the top of the column, which enters the distillation column D ₂ via line 7 . Isobutane is separated off from the top of D ₂ and the bottom fraction enters distillation column D ₃ via line 9. High purity butene from the top of _D3
1 is separated and the remaining C ₄ fraction is removed from the bottom of the D ₃ column.

Regarding the process of the two-stage method, since the distillation system after passing through the reaction column is the same as that of the one-stage process, the explanation thereof will be omitted and a specific explanation of the surroundings of the reaction column will be given.

In FIG. 2, both the raw material butane-butene fraction and alcohol consisting of 1 to 9 carbon atoms are fed through pipe 1, heated by heater E ₁ through pipe 2, and maintained at a predetermined temperature. It enters a fixed bed reaction column _R1 packed with strong acid type cation exchange resin particles. The fluid leaving the reaction tower _R1 is divided into two streams, one stream is cooled by a cooler _E2 , then circulated by a circulation pump P, and the raw material is fed from line 1 via line 3. and is recycled to the reaction column _R1 .
The other stream of fluid leaving the reaction column _R1 passes through line 4 to the fixed bed reaction column R2, which is maintained at a predetermined temperature by a heat exchanger _E3 and filled with a strong acid type cation exchange resin _. to go into. The pressure around the reaction towers _R1 and _R2 is controlled at a predetermined pressure by a pressure control valve PCV. Fluid exiting the PCV is sent to the distillation system.

Next, the features of the present invention will be described in more detail with reference to Examples.

Example 1 A styrene-based sulfonic acid type ion exchange resin (containing about 20% by weight of divinylbenzene, acid amount
4.7meq/g average particle diameter 0.5mmφ) 40Kg of catalyst is packed. Butane-butene fraction (composition: 0.98% isobutylene (weight, same below), butane-butene fraction via pipe 1)
1 29.5%, butene-2 28.9%, isobutane 9.6
%, n-butane 31.0%) at a flow rate of 200 Kg/hr through line 2 and methanol at a flow rate of 0.5 Kg/hr. The liquid hourly space velocity of the raw material is 5.0 (1/hr).
The pressure inside the reaction system is 18Kg/cm ² G due to PCV operation.
is maintained. The inlet temperature of the reaction tower R is controlled by a heat exchanger _E1 to be 47°C. The outlet temperature of reaction tower R is 52°C, the residual rate of isobutylene in the fluid exiting R is 2.8% by weight, and the residual rate of butene-1 is
It is 91.5% by weight. This fluid passes through pipe 5 to the PCV
The pressure is reduced at , and it is sent to distillation column D ₁ . Isobutylene content 0.03% by weight from the top of the column, butene
A butane-butene fraction containing 1% by weight of 27.0% by weight is distilled out, and isobutylene oligomers are separated and removed from the bottom of the column. The fraction distilled from the top of distillation column D ₁ is precision distilled in precision distillation columns D ₂ and D ₃ each having 100 theoretical plates, and is passed through pipe 10 from the top of D ₃ to a distillate with a purity of 99.9% by weight. Butene-1 is separated at a flow rate of 53.8 Kg/hr.

Furthermore, even after 120 days, the residual rate of butene-1 is
90% weight was maintained.

Example 2 In FIG. 2, reaction towers R ₁ and R ₂ were
using the same styrene-type ion exchange resin catalyst.
Fill 50Kg and 29.2Kg. Butane-butene fraction (composition: isobutylene 3.5% (weight,
(same below), butene-1 30.1%, butene-2
25.8%, isobutane 9.5%, n-butane 31.1%)
3.1Kg/hr of isopropanol at a flow rate of 350Kg/hr
Inject at a flow rate of The liquid space velocity of the raw material is 7.0 (1/
hr). The pressure within the reaction system was maintained at 18 Kg/cm ² G by the operation of the PCV. This raw material joins the fluid flowing through the circulation pipe 3 and is sent to the reaction tower R ₁ through the pipe 2. The inlet temperature of the reaction tower _R1 is
The temperature is controlled by heat exchanger E ₁ to be 50℃. The fluid exiting the reaction tower _R1 is divided into two fluids, one flow is controlled by a circulation pump P so that the flow rate is 10 times the raw material charging flow rate (circulation ratio 10), and the new raw material is transferred through pipe 3. join with. The other stream leaving reaction column R ₁ is passed via line 4 to reaction column R ₂ . The residual rate of isobutylene in this fluid was 19.0% by weight, and the residual rate of butene-1 was 95.9% by weight (residual rate refers to the ratio to isobutylene or butene-1 contained in the raw material). The inlet temperature of R ₂ is controlled by heat exchanger E ₃ to be 50°C. The liquid hourly space velocity at R ₂ is 12 (1/hr). The residual rate of isobutylene in the fluid exiting the reaction column _R2 is 2.6% by weight, and the residual rate of butene-1 is 91.2% by weight. sent to ₁ . A butane-butene fraction containing 0.07% by weight of isobutylene and 26.0% by weight of butene-1 was distilled from the top of the column.
Isobutylene oligomers are separated and removed from the bottom of the column. The fraction distilled off from the top of distillation column D ₁ is precision distilled in precision distillation columns D ₂ and D ₃ each having 100 theoretical plates, and then passed from the top of D ₃ through pipe 10 to achieve purity.
99.6% by weight of butene-1 is separated at a flow rate of 95.8 Kg/hr.

Note that even after 120 days, the residual rate of butene-1 remained at 90% by weight.

Example 3 In FIG. 2, reaction towers R ₁ and R ₂ of Example 1
30Kg and 22.5Kg of similar catalysts are charged respectively. Obtained by decomposition of petroleum through pipe 1
_The butane-butene fraction (composition: _isobutylene 6.0
%, butene-1 35.3%, butene-2 32.5%,
180Kg/isobutane 5.9%, n-butane 20.3%)
hr flow rate (liquid hourly space velocity in reaction column R ₁ 6 (1/hr)
Sec-butanol is delivered at a flow rate of 0.3 Kg/hr, with a liquid hourly space velocity at R ₂ of 8 (1/hr). The inlet temperature of the reaction tower _R1 is 47°C, the circulation ratio is 10, and the inlet temperature of the reaction tower _R2 is 50°C. The reaction was the same as in Example 2 except for the above. The residual rate of isobutylene in the fluid passing through pipe 4 is 18.5% by weight, butene-1
The residual rate is 95.9% by weight, the residual rate of isobutylene in the fluid passing through the pipe 5 is 1.5% by weight, and the residual rate of butene-1 is 90.1% by weight. Isobutylene content 0.09% by weight from the top of distillation column D ₁ , butene-1
A butane-butene fraction containing 29.8% by weight is distilled out, and isobutylene oligomers are separated and removed from the bottom of the column. Pipe 10 from the top of precision distillation column D ₃
57.0Kg/hr of butene-1 with purity of 99.7% by weight
separated at a flow rate of

Note that even after 120 days, the residual rate of butene-1 remained at 88% by weight.

[Brief explanation of the drawing]

1 and 2 are flow diagrams showing an example of the process of the present invention. R...Reaction tower, _R1 ...First reaction tower, _E1 ...Heat exchanger,
E ₂ ...Heat exchanger, P...Pump, E ₃ ...Heat exchanger, R ₂
…Second reaction column, E ₄ …Heat exchanger, D ₁ …Distillation column, D ₂
…Precision distillation column, D ₃ …Precision distillation column, V ₁ …Valve,
V ₂ ...Valve, V ₃ ...Valve, V ₄ ...Valve, 1~1
1... Pipeline.

Claims (1)

[Claims] 1 Isobutylene 0.1-15% by weight, butene-1
Strong acid type cation exchange resin particles with an average particle size of 0.2 to 10 mm are mixed with a butane-butene fraction containing 10 to 50% by weight and a hydrocarbon fraction containing 0.001 to 2% by weight of alcohol having 1 to 9 carbon atoms. temperature in the packed reaction column
30~100℃, liquid space velocity 0.1~50 (1/hr), pressure 1
Isobutylene is underpolymerized by continuous passage at ~50 atmospheres, and this underpolymer is distilled to produce heavy hydrocarbons, mainly containing low polymers of isobutylene, and light hydrocarbons, mainly containing butane-butenes. By further precisely distilling the light hydrocarbon,
A method for separating and recovering high-purity butene-1 at a high yield, the method comprising separating butene-1 from other _C4 hydrocarbons to obtain butene-1.