JPS6043048B2 - Separation and recovery method of n-butene - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Background Technical Field of the Invention The present invention relates to a method for separating and recovering n-butene from a Co hydrocarbon mixture.

More specifically, isobutene is reacted with water from a Co hydrocarbon mixture to form tertiary butyl alcohol (TBA),
This invention relates to a method for separating and recovering n-butene by converting residual isobutene in an n-butene fraction from which generated TBA has been separated and removed into a low polymer using a solid catalyst. It is.
N-butene is used as a raw material for useful petrochemical products such as secondary butyl alcohol and methyl ethyl ketone, or as a copolymer component with α-olefins such as ethylene.

As a method for industrially producing n-butene, a method is known in which isobutene is recovered by a sulfuric acid method and then separated and recovered from an n-butene fraction. However, this method is not completely selective in the reaction of sulfuric acid to isobutene, so n-
Isobutene remains in the butene fraction, and it is difficult to completely remove this isobutene to obtain n-butene that does not contain isobutene. In addition, as a method for separating isobutene without using an aqueous sulfuric acid solution, for example, isobutene is separated as a low polymer by contacting a Co hydrocarbon mixture with a solid catalyst such as silica/alumina, molecular sieve, zeolite, activated clay, or acidic cation exchange resin. or Co
A hydrocarbon mixture is reacted with isobutene with water, alcohol, or organic acid in the presence of a solid acid catalyst such as a cation exchange resin, silica, alumina, or a phosphoric acid supported catalyst, or an acid aqueous solution, to produce TBA, tertiary butyl ether, or butyl ester. There are known methods of separating and recovering such substances.

The present inventors have already
No. 79671, No. 54-11044 proposes a method of hydrating isobutene in the presence of a solid catalyst and a neo-type polyhydric alcohol, an oxyacid, a sulfone, or a derivative thereof, and separating and recovering it as TBA.

However, the n-butene fraction obtained after separating and recovering these isobutenes also contains a small amount of isobutene, so when using n-butene as a petrochemical raw material as mentioned above, it is necessary to completely remove isobutene. There is a need to.

(B) Summary of the Invention The present invention is aimed at solving the above problems, and involves removing isobutene from a C4 hydrocarbon mixture containing isobutene and n-butene as TBA by reacting it with water. The remaining isobutene in the n-butene fraction is converted into a low polymer using a macroporous cation exchange resin and separated from the n-butene fraction, with the aim of recovering n-butene that does not contain isobutene.

In particular, the n-butene fraction obtained by reacting isobutene in a C4 hydrocarbon mixture with water in the presence of a solid catalyst and a neo-type polyhydric alcohol, oxyacid, sulfone or a derivative thereof to produce TBA, and then separating this. by contacting with a macroporous cation exchange resin, the n-
By polymerizing isobutene contained in the butene fraction and separating and removing it as a low polymer, it does not contain isobutene.
- The purpose is to separate and recover phthenes.

By carrying out the present invention, isobutene can be efficiently removed from an isobutene-containing C4 hydrocarbon mixture as a "MAl isobutene dimer," and n-butene containing no isobutene can be obtained. The various catalysts mentioned above can be used for hydration, but if hydration is carried out in the presence of a solid catalyst, particularly an acidic cation exchange resin, a neo-type polyhydric alcohol, an oxyacid, a sulfone, or a derivative thereof, side reactions will occur. The reaction rate and conversion rate can be significantly accelerated, and isobutene can be easily converted to TBA.

Therefore, it is possible to obtain an n-butene fraction suitable for the next step of low polymerization of isobutene. The low polymerization of isobutene proceeds almost selectively by using a solid acid catalyst, especially a macroporous cation exchange resin, so that n-butene is reduced regardless of the isobutene content in the n-butene fraction. Isobutene is polymerized to a low level with almost no loss, and isobutene can be separated as a low polymer.

In addition, in the isobutene low polymerization process, the presence of an appropriate amount of water can maintain the polymerization activity and improve the selectivity. TBA by sum reaction
An appropriate amount of TBA and water are present in the n-butene fraction from which the isobutene is removed, which plays the role of preventing catalyst activity deterioration and improving selectivity in the isobutene low polymerization step.

Therefore, by continuously performing this hydration-isobutene low polymerization separation step, n-butene with an extremely low isobutene content can be obtained from the C4 hydrocarbon fraction, eliminating the need for conventional multi-stage reactions and reducing the complexity of the process. is unnecessary and can save a large amount of energy. The n-butene separated in this way has extremely high purity, and the loss of n-butene is small, making it highly economical.

(C) Detailed Description of the Invention C4 Hydrocarbon Mixture In the present invention, the isobutene content in the C4 hydrocarbon mixture is not particularly limited.

The composition is mainly composed of isobutene, n-butene, butane, etc., and may contain some hydrocarbons having 3 or 5 carbon atoms. Industrially, isobutene-containing hydrocarbon mixtures obtained from thermal cracking, catalytic cracking, etc. of petroleum are used. - Hydration reaction step The hydration reaction of isobutene in the first step of the present invention can be achieved by using a mixture of a C4 hydrocarbon mixture and water as a solid catalyst for hydration.

At this time, adding the hydration solvent described below to the mixture of C4 hydrocarbon mixture and water not only increases the reaction rate of the hydration reaction but also shows effects such as suppressing the formation of by-products. Therefore, it was desired to use such a hydration solvent together. However, in the present invention, it is not absolutely essential to use a hydration solvent. Solvent for Hydration Examples of neo-type polyhydric alcohols or derivatives thereof used for hydration in the present invention include pentaerythritol, trimethylolpropane, trimethylolethane, neopentyl glycol, dipentaerythritol, dineopentyl glycol, etc. It will be done.

As neo-type polyhydric alcohol derivatives, esters or partially esterified products of the above-mentioned neo-type polyhydric alcohols can also be used. Oxyacids or derivatives thereof used in the present invention include oxyacetic acid, lactic acid, 3-oxypropionic acid, oxypivalic acid, γ-oxybutyric acid, β-proviolactone, β,β-dimethylproviolactone, γ
-Butyrolactone, γ-valerolactone, diglycolide, lactide, glycolic acid methyl ester, glycolic acid ethyl ester, and the like. Sulfones or derivatives thereof used in the present invention include sulfolane, sulfolene, dimethylsulfone, sulfonal, trional, diethylsulfone, ethylmethylsulfone, divinylsulfone, and the like.

These solvents are used in an amount of 5 to 3,000 parts by weight, preferably 10 to 200 parts by weight, per 10 parts by weight of water.

Solid catalyst for hydration The solid catalyst for hydration used in the present invention is preferably a strongly acidic cation exchange resin, for example, a copolymer of styrene and divinylbenzene as a core,
Polystyrene sulfonic acid type resin containing sulfonic acid groups, phenol sulfonic acid type resin containing sulfonic acid groups in the condensation of phenol and formaldehyde,
Or perfluorosulfonic acid resin, which is a copolymer of sulfonated vinyl ether and fluorocarbon, etc.
Gel type, macroporous type, giant reticular type, etc. are preferable.

Hydration Conditions In the hydration of the present invention, the molar ratio of water to isobutylene is preferably in the range of 1 to 10.

The reaction temperature is suitably 30 to 150°C, preferably 50°C.
~120°C. Although the reaction pressure may be normal pressure, it is preferable to operate under a pressure equal to or slightly higher than the vapor pressure of the raw material hydrocarbon mixture at the reaction temperature. The reaction time is usually the liquid hourly space velocity (LHS) of the hydrocarbon: 0.3 to 1011
A range of r-1 is preferred. Although the reactor may be of a batch type, it is usually a continuous type using a fixed bed of solid catalyst. If the amount of isobutene remaining in the C4 hydrocarbon mixture after the completion of the hydration reaction is too large, the burden of the next isobutene polymerization step will become large, which is undesirable, and it is usually 1% by weight.
The content is preferably 7% by weight or less.

TBA Separation Process The C4 hydrocarbon mixture that has undergone the hydration process is separated and removed from the TBA produced in the separation process.

As a separation method, an extraction separation method using water, an evaporation separation method, etc. can be adopted, but a method using distillation is usually used. Polymerization process of isobutene The C4 hydrocarbon mixture containing a small amount of isobutene remaining after the TBA separation process is then brought into contact with a macroporous cation exchange resin to selectively polymerize isobutene. It is a low polymer of isobutene.

Solid catalyst for isobutene low polymerization The macroporous cation exchange resin used in the isobutene low polymerization reaction is preferably a strongly acidic cation exchange resin, for example, a copolymer of styrene and divinylbenzene as a core, A sulfonated styrene-divinylbenzene copolymer containing a sulfonic acid group, a sulfonated phenol-formaldehyde resin containing a sulfonic acid group obtained by condensing phenol and formaldehyde, or a copolymer of fluorinated vinyl ether and fluorocarbon. It is a perfluorosulfonic acid resin with a sulfonic acid group in it, and from a geometrical structure point of view, it is a gel-type ion exchange resin with physical pores added, and in the swollen state, the resin is chemically It is a porous ion exchange resin that has a structural network (micropores) and physical pores (macropores).

The j-exchange capacity of macroporous cation exchange resins is the same as that of cation exchange resins, or is reduced only by the macropores, but the reaction rate (catalytic activity)
The reaction is very fast, the amount of catalyst used is small, the reactor can be made smaller, and the macrobore portion acts as a cushion for volume changes, so it has excellent physical durability.

This macroporous cation exchange resin has an exchange capacity of 2.0 meq'y (dry state) or more, preferably 3.0 meq'y or more.
0-6.0rT1eq1f1 Specific surface area (BET method) 0.
2dIy or more, preferably 0.5-600rr11y1 Pore volume 0.02mUy or more, preferably 0.1-0.7m
Preferably, it is 1 Iq. As described above, macroporous cation exchange resins have characteristics different from conventional gel type cation exchange resins. Typical commercially available macroporous cation exchange resins include:
Amperlyst 1 weight Amperlite 200C1 Our Barlite IR-252, Dowex MSC-1, Diaion HPK25, Diaion HPK4O (Amperlyst, Amperlite, Dowex, Diaion are trade names), and the like. Conditions for Isobutene Low Polymerization Reaction By bringing the n-butene fraction obtained in the hydration step into contact with a macroporous cation exchange resin, the isobutene in the n-butene fraction is selectively converted into dimers. Become.

Reaction temperature is 60-150°C, preferably 80-130°C
The reaction pressure is a pressure that can maintain the n-butene fraction in a liquid phase under the reaction conditions, and is usually preferably 5 to 50 kgId.

The reaction time is the liquid hourly space velocity (LHSV) of the hydrocarbon: 0.1
~10 hr-1 is preferred. Contact between the n-butene fraction supplied to the reactor and the macroporous cation exchange resin is usually carried out in a fixed bed system, but it can also be carried out in a moving bed system or a suspended bed system if necessary. The conversion rate of isobutene should be determined depending on the level of isobutene content in the target n-butene, but usually the isobutene content is 0.5 mol% or less based on n-butene, preferably The content is appropriately selected so as to be 0.3 mol% or less.

Separation and removal process of low polymers of isobutene The C4 hydrocarbon mixture obtained by polymerizing isobutene to form low polymers in the isobutene polymerization step is then subjected to distillation to separate and remove low polymers of isobutene, so that it contains almost no isobutene. - Obtaining a C4 hydrocarbon containing a butene fraction.

As described above, the present invention extremely easily converts isobutene-containing C4 hydrocarbon mixtures into isobutene by combining 1 hydration step, 2 TBA separation step, 3 isobutene polymerization step, and 4 isobutene low polymer separation step. It has been discovered that C4 hydrocarbons containing n-butene can be obtained with a small content of n-butene.

In particular, in the present invention, isobutene can be removed extremely economically by specifying the amount of isobutene in the C4 hydrocarbon fraction in the monohydration step and the triisobutene polymerization step.

In other words, it is difficult to remove most of the isobutene in the first hydration step with a single reaction, and normally two or three steps are required, but the method of the present invention removes most of the isobutene. The polymerization step is carried out in one step, the conversion rate of isobutene is lowered, and the amount of residual isobutene is kept at 10% or less, preferably 7%, and the remaining isobutene is polymerized in the next isobutene polymerization step to form a low polymer of isobutene. C with an isobutene content of 0.5% or less is separated by distillation.
Four hydrocarbon fractions can be obtained. FIG. 1 illustrates an example of the steps of the method of the present invention.

The method of the present invention will be explained below with reference to FIG.

A first hydration reactor 101 filled with a solid catalyst is supplied with an isobutene-containing C4 hydrocarbon mixture through a pipe 1, water through a pipe 2, and a recycle solvent aqueous solution through a pipe 3, respectively.

The reaction liquid is supplied from the bottom of the first hydration reactor 101 to the first decanter 102 through the pipe 4. The TBA and solvent aqueous solution generated in the lower layer of the first decanter 102 are transferred to the pipe 6
The azeotrope of TBA and water is taken out from the pipe 7 and supplied to the TBA distillation column 103. The aqueous solvent solution from which TBA has been separated is supplied to the second hydration reactor 104 through the pipe 8 together with the C4 hydrocarbon mixture containing isobutene from the pipe 5 in the upper layer of the first decanter 102. The second hydration reactor 104 is filled with the same solid catalyst as the first hydration reactor. The reaction liquid in the second hydration reactor is taken out from the pipe 9 and supplied to the second decanter 105. The TBA and solvent aqueous solution in the lower layer that have been left to stand and separate are recycled to the first hydration reactor via piping 11. The C4 hydrocarbon mixture containing a small amount of unreacted isobutene in the upper layer is fed to an isobutene low polymerization reactor 106 filled with a macroporous cation exchange resin. The reaction product is passed through the pipe 12 to C.
4 distillation column 107. N-butene and butane fractions from which isobutene has been completely removed are obtained from pipe 13 and sent to a butane and n-butene separation distillation column. On the other hand, the isobutene low polymer and the aqueous solvent solution are sent to the isobutene dimer separation column 108 through the pipe 14, and after the dimer is removed, they are recycled to the hydration reaction zone. Hereinafter, the present invention will be explained in more detail using specific examples.

Note that % indicates mol% unless otherwise specified. Example 1~
4 (Hydration reaction) Using an autoclave equipped with a stirrer, a C4 hydrocarbon is produced using a macroporous cation exchange resin of sulfonated styrene/divinylbenzene copolymer as a catalyst and an aqueous solution of water with a solvent added. Mixture (isobutene 41.
0%, n-butene 43.0%, butane 16.0%) The results of the hydration reaction are shown in Table 1.

Examples 5 to 9 (low polymerization reaction of isobutene) Next, the C4 hydrocarbon mixture used in Examples 1 to 4 (isobutene 41.0%, n-butene 43.0%, butane 16.0%
%) and a macroporous cation exchange resin of sulfonated styrene-divinylbenzene low polymer under various conditions, and TBA was distilled.
After removal, C4 hydrocarbon mixtures with different amounts of residual isobutene were obtained.

Next, this C4 hydrocarbon mixture was hydrated and fed to a vertical reactor filled with a macroporous cation exchange resin used to carry out a continuous low polymerization reaction of isobutene.
Table 2 shows the results measured 2 hours after the start of the reaction.
It was shown to. For comparison, the results obtained when a gel-type cation exchange resin was used are also listed in Table 2. Example 10 Using an apparatus with the flowchart shown in Figure 1, isobutene is continuously hydrated from a C4 hydrocarbon mixture and separated and recovered as TBA, while isobutene remaining in the unreacted hydrocarbon mixture is continuously reduced. A method for producing n-butene that is polymerized and separated is shown.

A raw material hydrocarbon mixture (41.0 mol% isobutene, 130.0 mol% butene, 210.0 mol% butene, 19.0 mol% butane) is fed from pipe 1 at a rate of 2139 mol/hour, and water is 1149 mol/hour. from pipe 2 at the speed of TB
A4. 1 mol %, water 67.3 mol %, and γ-butyrolactone 28.6 mol % were each supplied to the first hydration reactor 101 from the pipe 3 at a rate of 4888 mol/hour. The first hydration reactor is filled with macroporous cation exchange resin 200e of sulfonated styrene/divinylbenzene copolymer, and the temperature is 80°C.
A pressure of 30 kgIcj1 was maintained. The reactant was supplied to the first decanter 102 via the pipe 4.

Table 2 shows the composition of the reactant taken out from pipe 4.
The lower layer of the first decanter is a TBA recovery distillation column containing water and γ-
Butyrolactone is separated and TBA7O. A 7 mol% aqueous solution was recovered at a rate of 1129 mol/hour.

The γ-butyrolactone aqueous solution from the pipe 8 was supplied to the second hydration reactor 104 in the upper layer of the second decanter. It was filled with a macroporous cation exchange resin 100e similar to the second hydration reactor, and the conditions of temperature 70° C. and pressure 30 kgId were maintained.
3. The reaction mixture was supplied from the second hydration reactor to the second decanter 105 through the pipe 9. The composition of the pipe 9 is shown in Table 2. The upper layer of the second decanter 105 was supplied to the isobutene low polymerization reactor 106.

The isobutene low-heavy reactor was filled with the same macroporous cation exchange resin 1501 as in the first hydration reactor, and the conditions were maintained at a temperature of 110° C. and a pressure of 30 k91 cIt. The reactants were sent to a C4 distillation column 107 through pipe 12. Table 2 shows the composition of the pipe 12. C4 distillation column 1
At 07, the butane and butene fractions are separated from isobutene dimer, and 33.0% butane and 16.0% butane are delivered from pipe 13.
0%, butene-260.8%, isobutene 0.2% C
Four fractions were obtained at a rate of 1229 mol/h.

The isobutene dimer was separated in the isobutene dimer separation column 108 and recovered from the pipe 15 at a rate of 55 mol/hour.
BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings are a flowchart illustrating an example of a continuous implementation of the method of the present invention.

Claims (1)

[Claims] 1. The n-butene fraction containing residual isobutene obtained by reacting isobutene in a C_4 hydrocarbon mixture containing isobutene and n-butene with water and separating and removing it as tertiary butyl alcohol is further processed into a macroporous type. A method for separating and recovering n-butene, which comprises polymerizing isobutene contained in the n-butene fraction to form a low polymer by contacting it with a cation exchange resin, and then separating it from the n-butene fraction.