JPH1171310A - Production of 1,4-butanediol - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for effectively producing high-purity 1,4- butanediol, by simply purifying crude 1,4-butanediol containing impurities. SOLUTION: Crude 1,4-butanediol is purified by melt crystallization method comprising the following processes of (1) a crystallization process for letting a crude 1,4-butanediol melt flow on a wall face cooled to the freezing point of 1,4-butanediol or lower than it to give 1,4-butanediol crystal and (2) a recovery process for heating the wall face to the freezing point of 1,4-butanediol crystal or higher than it to recover 1,4-butanediol obtained by the crystallization process as a crystal melt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for purifying crude 1,4-butanediol (hereinafter sometimes abbreviated as "1,4-BG") by melt crystallization and a method for purifying the same. And a method for producing 1,4-butanediol using the same. 1,4-BG is an important compound as a synthetic raw material such as polyester resin, γ-butyrolactone, and tetrahydrofuran.

[0002]

2. Description of the Related Art As a method for producing 1,4-BG, a butadiene method for producing 1,4-BG by acetoxylation of butadiene with acetic acid and oxygen and then hydrolyzing diacetoxybutane obtained by hydrogenation (for example, , JP 52
-7909, 52-65208, 52-6520
9, No. 52-133912, etc.), a maleic anhydride method for hydrogenating maleic anhydride to produce 1,4-BG and γ-butyrolactone simultaneously (for example, JP-A-2-23362).
No. 7), 1,4-butenediol obtained by reacting acetylene and formaldehyde is hydrogenated to give 1,4
Acetylene method for producing BG (for example,
No. 91813) is known.

In these production methods, crude 1,4-
Purification of BG is usually performed by distillation, but crude 1,4-B
In G, impurities having a boiling point very close to 1,4-BG and 1,
Because it contains impurities that azeotrope with 4-BG, it is difficult to purify to high purity by simple distillation purification, and in order to increase the purity, the purification equipment becomes large-scale or large energy is required. was there.

[0004] Among the impurities contained in 1,4-BG, 1,2-diacetoxybutane (hereinafter referred to as "12
DAB "), 1,4-diacetoxybutane (hereinafter sometimes abbreviated as" 14DAB "), and 1,2-hydroxyacetoxybutane (hereinafter abbreviated as" 12HAB "). ), 1,4-hydroxyacetoxybutane (hereinafter referred to as "14HAB"
), Dibutylene glycol (hereinafter sometimes abbreviated as “DBG”), 2- (4 ′
-Hydroxybutoxy) tetrahydrofuran (hereinafter sometimes abbreviated as "BGTF"), 2- (4'-
Oxobutoxy) tetrahydrofuran (hereinafter referred to as "B
DTF "), 1,4-di- (2 '
-Tetrahydrofuroxy) butane (hereinafter referred to as “BGD
TF ") may be 1,4-B
When processed into a resin, fiber, or the like using G as a raw material, it causes coloring, thread breakage, and the like.

In order to remove these impurities, for example, Japanese Unexamined Patent Publication (Kokai) No. 61-197534 discloses a crude 1,4-B
A method for hydrotreating G, and a method for hydrotreating crude 1,4-BG after distilling and separating high boiling components has been proposed in JP-A-6-172235. However,
In these methods, distillation must be performed again after the hydrogenation treatment in order to separate impurities. For this reason,
As described above, there are problems such as a large-scale refining facility and a large amount of energy required, and it is not always an efficient method.

Although the structure and formation mechanism of all impurities in the crude 1,4-BG obtained by the respective production methods such as the butadiene method, the maleic anhydride method and the acetylene method have not been elucidated, Among them, BGTF, BDT
F, BGDTF, especially BGTF, has been found to be formed again in the distillation step. Therefore, as long as the distillation method is applied as a method for purifying crude 1,4-BG, there is a limit in removing impurities such as BGTF, and it is more difficult to remove impurities during continuous operation.

[0007] The following is an example of the 1,4-BG using the butadiene method.
The problems of the manufacturing method of the present invention will be described. In the current butadiene method, first, butadiene, acetic acid, and an oxygen-containing gas are reacted and then hydrogenated to produce diacetoxybutane (see FIG. 1). After hydrolyzing the diacetoxybutane thus obtained, a liquid raw material containing 1,4-BG as a hydrolysis reaction product, acetic acid and water are separated in a first distillation column, and then diacetoxybutane and hydroxyacetoxy are separated in a second distillation column. Butane and crude 1,4-BG are separated, the crude 1,4-BG and hydrogen gas are subjected to a hydrogenation reaction through a hydrogenation catalyst, THF is further concentrated in a third distillation column, and then the side stream is passed through a fourth distillation column. Alternatively, high-purity 1,4-BG is extracted from the bottom of the column (see FIG. 2).

Although very high purity 1,4-BG can be produced by this method, diacetoxybutane and hydroxyacetoxybutane must be separated twice, and the separation specifications are extremely strict. There are many problems that need to be improved, such as the large amount of by-products, and the fact that 1,4-BG and high boiling impurities are separated and concentrated at three places.

On the other hand, in the melt crystallization method, a high-purity organic compound (eg, 97% by weight) is further purified (eg, 9% by weight).
9.9% by weight). Specific examples of application of melt crystallization to industrial refining include bisphenol A and acrylic acid (JP-A-7-163802, JP-A-9-155101).
No.). Each of these compounds is a low-viscosity compound having a viscosity of several cp near the freezing point. On the other hand, 1,4-BG
Has a high viscosity of about 120 cp near the freezing point (20 ° C.), so it was expected that it would be extremely difficult to apply purification by the melt crystallization method. Further, as far as the present inventors know, it contains a relatively large amount of impurities having a significantly lower freezing point than the target organic compound, such as crude 1,4-BG, and is used for purification of a crude organic compound having a high viscosity near the freezing point. There were no examples using melt crystallization.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a crude 1,4-BG containing various impurities by-produced in a manufacturing process.
To provide a method for simply and efficiently purifying the compound without requiring a complicated process, and a method for producing a 1,4-BG capable of efficiently obtaining a high-purity 1,4-BG. .

[0011]

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above object, and as a result, have found that they contain a relatively large amount of impurities having an extremely low freezing point than 1,4-BG, and have a high viscosity near the freezing point. Was found to be able to be efficiently purified by melt crystallization. Furthermore, if the crude 1,4-BG obtained by hydrolyzing diacetoxybutane is melt-crystallized, the load on the distillation column can be reduced, and high purity 1,4-BG can be obtained.
It has been found that 4-BG can be efficiently obtained, and the present invention has been completed.

That is, the gist of the present invention is (1) a method for purifying crude 1,4-butanediol by melt-crystallization of crude 1,4-butanediol containing impurities.
According to a preferred embodiment of the present invention, (2) melt crystallization is carried out by flowing the crude 1,4-butanediol melt on the wall cooled to a temperature below the freezing point of 1,4-butanediol,
A crystallizing step for obtaining 1,4-butanediol crystals, a crystal melt obtained by heating the wall surfaces of the 1,4-butanediol crystals obtained in the crystallizing step to a temperature higher than the freezing point of the 1,4-butanediol crystals. A recovery step of recovering 1,4-butanediol as above, comprising the above-mentioned method performed by a wall melt crystallization method;

(3) Melt crystallization is carried out in the following step: The crude 1,4-butanediol melt is caused to flow on a wall cooled below the freezing point of 1,4-butanediol.
A crystallization step for obtaining 1,4-butanediol crystals, and removing the remaining mother liquor, which is a crude 1,4-butanediol melt, from the 1,4-butanediol crystals obtained in the crystallization step. By heating to the vicinity of the freezing point of the 1,4-butanediol crystal, the impurities in the 1,4-butanediol crystal are removed from the crystal as a sweat liquid. The 1,4-butanediol crystal obtained in the sweating step is
A method for recovering 1,4-butanediol as a crystal melt by heating the wall surface to a temperature higher than the freezing point of 1,4-butanediol crystals, the above-mentioned method performed by a wall surface melt crystallization method;

(4) The crystal film thickness in the crystallization step is 1 to 20 m
(5) The above method in which the crude 1,4-butanediol contains a total of 1% by weight or more of impurities. (6) The impurities have a freezing point of 0 ° C. or less. The above method, which is a compound;

(7) The impurities are 1,2-diacetoxybutane, 1,2-hydroxyacetoxybutane, 1,4-diacetoxybutane, 1,4-hydroxyacetoxybutane, dibutylene glycol, 2- (4'- (Hydroxybutoxy) tetrahydrofuran, 2- (4′-oxobutoxy) tetrahydrofuran, 1,4-di- (2′-tetrahydrofuroxy) butane, 2-methyl-1,4-butanediol, γ-butyrolactone, 2-hydroxy The above method is provided, wherein the method is at least one compound selected from tetrahydrofuran and 2-methylpentanediol.

According to another aspect of the present invention, (8) crude 1,4-butanediol obtained by hydrolyzing diacetoxybutane is prepared by any of the methods described in (1) to (7) above. A method for producing 1,4-butanediol by melt crystallization is provided. According to a preferred aspect of the present invention, (9) crude 1,4-butane from which low boiling components are removed from crude 1,4-butanediol obtained by hydrolyzing diacetoxybutane, The diol is melt-crystallized by any one of the methods (1) to (7) to recover 1,4-butanediol crystals,
Production of 1,4-butanediol by removing high-boiling components from the mother liquor from which 4-butanediol crystals have been separated, hydrogenating the high-boiling components-removed product obtained in the process, and supplying the hydride to the process A method is provided.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in more detail. (Crude 1,4-BG) Crude 1,4-BG containing impurities to be a target (raw material) of the purification method of the present invention may be produced by any method, for example, a butadiene method, maleic anhydride. It may be produced by any method known per se, such as a method, an acetylene method, and a propylene method.

Specifically, crude 1,4-BG before the purification step of 1,4-BG or 1,4-BG containing impurities after the distillation purification tower step is used as the crude 1,4-BG. be able to. As impurities contained in the crude 1,4-BG,
Even if the impurity forms a solid solution with 1,4-BG,
Although it may be an impurity which becomes eutectic with 1,4-BG,
Preferably, it is an impurity which becomes a eutectic system. Specifically, for example, 12HAB, 12DAB, 14HAB (freezing point-
65 ° C), 14 DAB, DBG, BGTF, BDTF,
BGDTF, 2-methyl-1,4-butanediol, γ
-Butyrolactone (freezing point -44 ° C), 2-hydroxytetrahydrofuran, 2-methylpentanediol and the like. The method of the present invention, among these impurities,
Preferably, 12HAB, 12DAB, 14HAB, 1
4DAB, DBG, BGTF, BDTF and BGDTF
BGTF, BDTF, B
Crude 1,4-BG containing GDTF is converted to BGTF
It is suitable for processing crude 1,4-BG containing.

In the method of the present invention, high-purity 1,4-BG can be obtained efficiently even when applied to the purification of crude 1,4-BG containing a relatively large amount of impurities having a low freezing point. . The freezing point of impurities contained in the crude 1,4-BG is not particularly limited, but is preferably 0 ° C or lower, more preferably -10 ° C or lower, and particularly preferably -30 ° C or lower. The content of impurities is not particularly limited,
The total amount is 1% by weight or more, usually up to about 15% by weight, preferably 1 to 10% by weight, more preferably 2 to 10% by weight, and particularly preferably about 3 to 10% by weight.

(Molten Crystallization Method) The melt crystallization method used in the present invention is not particularly limited, but a method including at least a crystallization operation is preferably used. Examples of the melt crystallization method include (i) a method of growing a purified crystal on a cooled wall surface (wall surface melt crystallization method), and (ii) cooling of a molten liquid to grow a purified crystal in the liquid to form a mother liquor. How to sweat after separation,
(Iii) Any method such as sweating after separating mother liquor by crystallization by applying pressure may be used, but preferably (i)
A wall melt crystallization method is suitable.

The wall surface crystallization method comprises the following steps. Walls cooled below the freezing point of 1,4-BG
A crystallization step in which a 1,4-BG crystal is obtained by flowing a BG melt; By heating the wall surface of the 1,4-BG crystal obtained in the crystallization step to a temperature higher than the freezing point of the 1,4-BG crystal,
A recovery step of recovering 1,4-BG as a crystal melt.

Further, a melt crystallization method comprising the following steps, in which a sweating step is added as an additional step, is more preferable. Walls cooled below the freezing point of 1,4-BG
A crystallization step in which a 1,4-BG crystal is obtained by flowing a BG melt; After removing the residual mother liquor, which is a crude 1,4-BG melt, from the 1,4-BG crystals obtained in the crystallization step,
By heating to around the freezing point of the 4-BG crystal,
A sweating step in which impurities in the 1,4-BG crystal are removed from the crystal as a sweat liquid. The 1,4-BG crystal obtained in the sweating process was
A recovery step of recovering 1,4-BG as a crystal melt by heating to a temperature higher than the freezing point of the 4-BG crystal.

In general, for the wall surface crystallization, a crystallizer is used in which a liquid raw material is allowed to flow on one side of a smooth plate or tube and cooled from the other side to precipitate crystals on the one side. More preferably, using a plurality of tanks, a mother liquor and a crystal melt when crystallization is performed on a liquid raw material in a certain tank, and if necessary, a perspiration liquid is sent to another tank, and the crystal melt is Further, a multi-stage crystallization method for performing crystallization is used.

The shape of the crystallizer may be any of a flat plate type, a tube type and other shapes, but a flat plate type is desirable in order to obtain a transmission surface efficiently. Hereinafter, a melt crystallization method using a flat plate type melt crystallization apparatus and, if necessary, passing through a sweating step will be described. In this case, the crystallization apparatus includes a crystallizer, a storage tank, and a liquid feed pump. The crystallizer is, for example, a plate for attaching crystals formed of a flat plate of stainless steel having a size of 2 m long × 1 m wide × 1 mm thick (hereinafter referred to as “crystallized plate”).
The crystallization plate is vertically arranged, and the upper end is bent to form an inclined surface.
A raw material supply device is provided on one side of the crystallizing plate via the inclined surface or a vertical surface continuous with the upper end of the inclined surface, serving as a raw material supply means for causing the liquid raw material to flow down in a thin film form. In the case of scale-up, the number of flat plate crystallization units is increased to increase the throughput and cope.

On the other side of the crystallization plate, there is provided a refrigerant supply pipe for supplying a refrigerant for causing a refrigerant having a temperature below the freezing point of the liquid raw material to flow down in a thin film form. This refrigerant supply pipe also serves as a heat medium supply pipe serving as a heat medium supply means for supplying a heat medium having a temperature near the freezing point of the liquid raw material to the other surface side of the crystallization plate. The liquid raw material is circulated by the liquid feed pump and supplied to one side of the crystallization plate, while the refrigerant is circulated to the other side of the crystallized plate through another liquid feed pump and a cooler to the refrigerant supply pipe. The supplied heat medium is circulated and supplied to a heat medium supply pipe (also serving as a refrigerant supply pipe) via another liquid supply pump and a heater.

As a temperature control medium such as a heat medium and a refrigerant used in the crystallizer, any solvent can be used as long as it can control the temperature from about -10 ° C. to + 30 ° C. Diols such as ethylene glycol; lower alcohols such as methyl alcohol and ethyl alcohol;
There may be used those known per se, such as water, and mixtures thereof.

Next, each step of melt crystallization will be described. Crystallization Step The crude 1,4-BG melt is circulated and supplied to one side of the crystallized plate to flow down in a thin film form, and the freezing point of 1,4-BG (19-20 ° C.) is transferred to the other side of the crystallized plate. A refrigerant having the following temperature is caused to flow down in a thin film form. Crystals do not precipitate unless they are supercooled to some extent, so the wall surface temperature of the crystallized plate is set to the nucleation start temperature (1,4-BG
(The temperature at which solidification starts). The nucleation start temperature changes depending on the purity of the crude 1,4-BG melt, the supply speed, and the like. The lower the purity and the faster the supply speed, the lower the nucleation start temperature.

The lower the wall temperature is, the faster the crystal growth is. However, in order to minimize the incorporation of impurities into the crystal during the crystal growth, it is preferable to reduce the crystal growth rate. For this purpose, the temperature of the wall surface is first reduced to 1,4-B
The crystallization is started by cooling to a temperature lower by about 8 ° C. at the maximum from the freezing point of G (wall temperature: about 11 ° C.), and as the crystal grows, the cooling medium temperature is gradually lowered to lower the wall temperature by 1,4 ° C. -Lowering from the freezing point of BG to a temperature lower by about 15 ° C. If the melt crystallization is performed in multiple stages, the method of decreasing the refrigerant temperature is, for example, the second stage is slower than the first stage, that is, the rate of decrease in the refrigerant temperature in the later crystallization step. Is performed in such a manner that the crystal growth rate in a later crystallization step can be reduced, and a crystal with less impurities can be obtained.

A crude 1,4-BG melt is provided on one side of the crystallization plate,
By causing the coolant to flow down to the other side, 1,4-BG crystals precipitate on one side of the crystallized plate. Crude 1,4-B
The supply temperature of the G melt is preferably 1,4 at the initial stage.
-Within a temperature range of about 5 ° C higher than the freezing point of BG, more preferably within a temperature range of about 1 ° C higher. Since the crystal surface cannot maintain the initial temperature due to a decrease in heat transfer efficiency due to heat of crystallization or crystal thickness, the temperature of the refrigerant is gradually lowered in consideration of a rise in crystal surface temperature. The upper limit of the flow rate of the crude 1,4-BG melt is not particularly limited as long as a thin film flow can be obtained. As the flow rate increases, the liquid film does not break, the heat transfer coefficient improves, and the processing speed increases. Should be as large as possible.

After the thickness of the 1,4-BG crystal layer reaches a predetermined value, the mother liquor is extracted from the circulation supply system. However, if the crystal layer is thin, impurities are easily taken in. On the other hand, if the crystal layer is too thick, the thermal conductivity deteriorates, and the crystallization time becomes long. Also, when combined with the sweating step, if the crystal layer is too thick, a long sweating time is required, and the separation between the crystal layer and the sweat liquid is also poor. Therefore, the thickness of the crystal layer is preferably 1 to 20 m
m, more preferably 3 to 15 mm, most preferably 5 to
A range of 10 mm is appropriate.

Sweating Step It is preferable to subject the 1,4-BG crystals obtained in the crystallization step to a sweating step as required. The sweating step is a step of melting and removing a liquid having a high impurity concentration taken between the precipitated crystals or attached to the crystal surface,
This is performed to further lower the impurity concentration of the crystal. Specifically, before the recovery step, the temperature close to the freezing point of the target pure substance, that is, the heat medium is allowed to flow down in the form of a thin film on the other surface side of the crystallized plate, and the wall temperature of the crystallized plate is aimed at. The temperature is controlled within ± 5 ° C., preferably ± 3 ° C. of the freezing point of the pure substance to be partially melted.
By this sweating step, the impurity concentration in the crystal can be further reduced.

The sweating time is not particularly limited and is usually about 30 minutes, but 1,4-BG has a viscosity of 77 cp (25
° C), which requires a sweating time of about 2 to 20 times (60 to 600 minutes).

Recovering Step The 1,4-BG crystal obtained through a crystallization step and, if necessary, a sweating step is then separated from the medium by a superheater.
Heating to a temperature above the freezing point of the 4-BG crystal to form a heating medium,
This heat medium is allowed to flow down to the other side of the crystallizing plate to form 1,4-BG
The crystals are melted and recovered. Also, when the 1,4-BG crystal melt already obtained is heated and allowed to flow down to one surface side of the crystallized plate, that is, to the crystal surface, along with the flow of the heat medium, 1,4-BG
Is heated from both sides and melts in a short time.

A crystallization step and, if necessary, a sweating step;
Although 1,4-BG with high purity can be obtained through melt crystallization including a recovery step, and further subjected to melt crystallization, 1,4-BG with higher purity can be obtained. Therefore, if the melt crystallization is performed in multiple stages, 1,4-BG of extremely high purity can be obtained.

Next, an outline of a multi-stage crystallization apparatus for performing a two-stage crystallization operation will be described with reference to FIG. V-
0 to V-4 are storage tanks, and V-5 is a circulation tank.
The fourth storage tank V-4 is a product storage tank for temporarily storing the product, 1,4-BG. V-0 is a mother liquor storage tank for temporarily storing a mother liquor obtained by crystallization using the lowest-purity liquid raw material, that is, obtained by crystallizing the liquid raw material in the storage tank 1. It is. In this apparatus, a liquid raw material is sent from V-2 into a circulation tank V-5, and flows through the crystallizer 1 to precipitate 1,4-BG crystals in the crystallizer 1 (crystallization step). .

The uncrystallized residual liquid (mother liquor) obtained in this step is collected in the circulation tank V-5 and sent to V-1. Subsequently, the aforementioned sweating operation is performed on the 1,4-BG crystals in the crystallizer 1, and the sweating liquid is stored in V-2 (a sweating step). Thereafter, the first-stage purified liquid obtained by melting 1,4-BG in the crystallizer 1 is sent to V-3 (recovery step). Next, the liquid in V-3 is sent to the circulation tank V-5, and is passed through the crystallizer 1 to precipitate 1,4-BG in the crystallizer (crystallization step). Subsequent to this operation, operations of the sweating step and the collecting step are performed. The storage tanks for returning the obtained mother liquor, perspiration liquid and purified liquid are shifted by one stage. That is, the melt in V-3 is supplied to the circulation tank V-
The mother liquor is stored in V-2, and the sweating liquid is stored in V-3. Then, the crystal melt is collected in the product storage tank V-4.

Following the crystallization operation of the melt in V-3, V-1
(Mother liquor obtained by crystallization operation of melt in V-2)
Is crystallized. This operation is exactly the same as the operation described above, and the obtained mother liquor is sent to the mother liquor storage tank V-0 outside the crystallizer, and the sweating liquid is sent to V-1. The melt recovered from the crystallizer 1 is stored in V-2. The mother liquor in V-0 is
It is collected again in the distillation column and one cycle is completed.

Further, in each recovery step, if the 1,4-BG melt already recovered as described above is allowed to flow down to the crystal surface, the crystal can be melted in a short time. As described above, the crude 1,4-BG used in the method of the present invention may be one produced by any of the production methods, and particularly, one produced by the butadiene method is suitably used.

Thus, the crude 1,4-BG produced by the butadiene method, which is another embodiment of the present invention, that is, by hydrolyzing diacetoxybutane, is subjected to the aforementioned melt crystallization, A method for producing 4-BG is provided. Hereinafter, the method for producing 1,4-butanediol of the present invention will be described. (Production method of 1,4-butanediol) Crude 1,4-BG
Is a reaction product obtained by hydrolyzing diacetoxybutane. Diacetoxybutane is usually obtained by hydrogenating diacetoxybutene obtained by reacting butadiene, acetic acid and oxygen in the presence of a palladium-based catalyst (Japanese Patent Publication Nos. 55-45051 and 55-16489;
No. 55-17016). FIG. 1 shows an outline of this manufacturing process.

The diacetoxybutane to be subjected to the hydrolysis reaction is mainly composed of 1,4-diacetoxybutane.
An isomer mixture of 4-diacetoxybutane and 1,2-diacetoxybutane, 1,3-diacetoxybutane and the like,
Further, those with monohydroxyacetoxybutane are also included. In some cases, a mixture of 1,4-diacetoxybutane, 1,4-monohydroxyacetoxybutane and 1,4-BG excluding water and acetic acid after the hydrolysis reaction is allowed to proceed to some extent can also be used. .

The use of a cation exchange resin as a catalyst in the hydrolysis reaction is suitable because the hydrolysis rate is high and by-products such as tetrahydrofuran (hereinafter sometimes abbreviated as "THF") are small. ing. In particular,
A sulfonic acid type strongly acidic cation exchange resin having a copolymer of styrene and divinylbenzene as a base is preferable, and a gel type resin or a porous type resin may be used.

As the sulfonic acid type strongly acidic cation exchange resin, a gel type resin such as SK1B, SK104, SK106, SK11 manufactured by Mitsubishi Chemical Corporation can be used.
0, SK112 is a porous type, PK20
8, PK216, PK228, RCP160H, RCP
170H, RCP145H and the like. The hydrolysis reaction is usually carried out at a temperature within the range of 30 to 110 ° C.
It is more preferable to carry out in the range of -90 ° C.

The reaction pressure is not particularly limited, and is usually from normal pressure to normal pressure.
It is performed within a range of 10 kg / cm ² G (0.1 to 1.08 MPa). The ratio of diacetoxybutane and water is such that water is used as a reaction raw material and at the same time acts as a solvent.
It is selected within the range of 2 to 100 mol, preferably 4 to 50 mol, per mol.

Although various reaction modes are conceivable, a method in which diacetoxybutane and water are flowed down to a fixed bed filled with an acidic cation exchange resin is usually employed. With respect to the hydrolysis reaction product obtained by the above method, a crude 1,4-BG is usually obtained by distilling and removing a light-boiling component and a high-boiling component, and these distillation separation methods are known per se. A commonly used method, for example, a method described in JP-A-6-172235 can be used.

However, in the distillation step used in the present invention, it is possible to reduce the number of distillation columns and the amount of reflux compared with the distillation step used in the conventional 1,4-BG production method, and to operate under more moderate distillation conditions. Can be. In the method of the present invention, a hydrogenation step for reducing impurities contained in crude 1,4-BG is not always necessary. Specifically, as shown in FIG. 3, a hydrolysis product obtained by hydrolyzing diacetoxybutane in a hydrolysis reactor is supplied to a distillation column. Light distillation components such as water, acetic acid, 12HAB, and 14HAB are distilled off in a distillation column, and a hydrolysis reaction product is extracted from the bottom or a side stream of the distillation column to obtain crude 1,4-BG. As for the low boiling point component, preferably, water and acetic acid are distilled off in the first distillation column 302 and 12HAB, 14HAB and the like are distilled off in the second distillation column 303 using two or more distillation columns.

In the method of the present invention, the crude 1,4-BG extracted from the bottom or side stream of the distillation column is directly subjected to melt crystallization by the above-mentioned method. For the melt crystallization, it is preferable to use a melt crystallization method comprising the above-mentioned crystallization step, if necessary, a sweating step and a recovery step.

In the method of the present invention, the crude 1,4-butanediol extracted from the bottom of the distillation column is subjected to melt crystallization without hydrogenation reaction, and the remaining liquid (mother liquor) in which no crystals are precipitated is obtained. Feed to another distillation column, dibutylene glycol,
After removing high-boiling components (impurities) such as dibutylene glycol monoacetate, dibutylene glycol diacetate, tribubutylene glycol, tributylene glycol monoacetate, and tributylene glycol diacetate, a hydrogenation reaction is performed. Preferably, a process of returning to the distillation column is performed (see FIG. 3). According to this method, a conventional THF concentration column (for example, the third and fourth distillation columns in FIG. 2)
Becomes unnecessary. Further, it is possible to relax the separation specification of 1,4-BG and hydroxyacetoxybutane in the distillation column. That is, in the process of purifying by the conventional distillation method (FIG. 2), the crude 1,4-
The impurities contained in BG are 0.5% by weight or less of 14HAB, 0.1% by weight or less of 12HAB, and 2.0% or less of BGTF.
It was necessary to reduce it to less than the weight%. However, in the process of purification by the melt crystallization method, the specifications of impurities contained in the crude 1,4-BG obtained from the second distillation column are 2% by weight or less of 14HAB, 0.4% by weight or less of 12HAB, and 8% by weight of BGTF. %, It is possible to obtain 1,4-BG having the same purity as that of the distillation method.

That is, in the conventional distillation method (FIG. 2),
The second distillation column 203 generally has 50 to 150 theoretical plates,
Top pressure 100-400mmHg, Top temperature 150-2
50 ° C, preferably 180-230 ° C, reflux ratio 10-2
An operation at 00, preferably 20-100 is required. However, in the method of the present invention, for example, the second distillation column 303 of FIG.
100, preferably 10 to 50 is suitable. As described above, in the method of the present invention, the operation can be performed under mild conditions in which the theoretical plate number and the reflux ratio of the distillation column are about half the values of the conventional distillation method.

[0049]

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples. In the following examples, “parts” and “%” indicate “parts by weight” and “% by weight”, respectively, unless otherwise specified. In addition, a series of values in the following examples indicate analysis values by gas chromatography for 5 days after the start of the steady operation unless otherwise specified.

Reference Example 1 Butadiene 1 was placed in an acetoxylation reactor 101 shown in FIG.
70 parts / hr, acetic acid 3000 parts / hr containing 0.8% 1,4-hydroxyacetoxybutane and 0.6% 1,2-hydroxyacetoxybutane as impurities, and oxygen 5
30 parts / hr, palladium 3%, tellurium 0.6
%, In the presence of a catalyst supported on activated carbon at 9 MPa, 100 MPa
After the reaction at ℃, degassing treatment was performed in the gas-liquid separator 102 to obtain a reaction product containing 12.5% of 1,4-diacetoxybutene.

The reaction product is supplied to the first distillation column 103 at 3100 parts / hr, and most of water and acetic acid are distilled off at the top of the column at 2500 parts / hr, and 1,4-diacetoxybutene 74. A bottom liquid containing 8% was withdrawn at 580 parts / hr.
The bottom product is charged to the second distillation column 104 (actual number of plates: 20) at 580.
Parts / hr and distilled under the conditions of a top pressure of 2.7 kPa and a reflux ratio of 0.5, and a liquid containing 75.5% of 1,4-diacetoxybutene was distilled at 550 parts / hr from the top of the column. Let out.

The obtained diacetoxybutene fraction was supplied to a hydrogenation reactor 105 filled with a palladium catalyst and a ruthenium catalyst, and under a hydrogen flow, a reaction pressure of 5 MPa and a temperature of 7 MPa.
A hydrogenation reaction was carried out at 0 ° C. to give 1,4-diacetoxybutane 7
A reaction solution containing 5.6% was obtained. After gas-liquid separation of the reaction solution,
The mixture was fed to the third distillation column 106 (actual number of plates: 20) at 550 parts / hr, and distilled under the conditions of a top pressure of 2.0 kPa and a reflux ratio of 0.25. A liquid containing 75.9% of diacetoxybutane was distilled at 520 parts / hr.

100 liters of cation exchange resin SK1
B (manufactured by Mitsubishi Chemical Corporation) was charged with the 1,4-diacetoxybutane-containing liquid having the composition shown in Table 1 above in a reactor.
The mixture was fed at 0 parts / hr and a 250% aqueous acetic acid solution at 250 parts / hr, and a hydrolysis reaction was carried out at a reaction temperature of 50 ° C. As a result, the composition of each component other than water contained in the hydrolysis reaction product was as shown in Table 1.

[0054]

[Table 1]

The hydrolysis reaction product was supplied to the first distillation column 302 shown in FIG. 3 and distilled. The first distillation column is SUS3
A packed tower of 200 mm in inner diameter made of SUS3
A 16-piece Raschig ring was filled to a height of 3000 mm. A liquid supply port was provided 500 mm below the top of the packed bed, the top pressure was 70 mmHg, the reflux ratio was 0.5, and the bottom temperature was 160 ° C
, Water, acetic acid and a trace amount of light substances were distilled off from the top of the column, and the bottom liquid was supplied to the second distillation column 303.

The second distillation column is made of SUS304 and has an inner diameter of 100 m.
m, packed with SUS304 McMahon Packing, packed bed height 50
It was filled to be 00 mm. 100 from the top of the packed bed
Provide a side drain outlet below 0 mm, and further 1000 m
m, a liquid supply port was provided. In addition, a vapor outlet was further provided 1000 mm below the liquid supply port. The bottom of the first distillation column was distilled by operating at a top pressure of 230 mmHg, a reflux ratio of 30, a bottom temperature of 200 ° C, and a top temperature of 155 ° C.

From the top of the column, 9.5% of 1,2-diacetoxybutane and 1,2-dihydroxyacetoxybutane 2
A fraction consisting of 5.2% and 65.3% of 1,2-butanediol was distilled off. From the sidestream, 1,2-diacetoxybutane 0.4%, 1,2-hydroxyacetoxybutane 0.9%, 1,2-butanediol 2.4%, 1,4-butanediol
Diacetoxybutane 15.9%, 1,4-hydroxyacetoxybutane 64.1%, 1,4-BG 11.4%
A fraction consisting of The fraction was circulated to the hydrolysis reaction zone as a part of the reaction raw material.

Further, the crude 1,4-B
G (1,4-BG 94.0% by weight, 14HAB 0.
02% by weight and 0.48% by weight of BGTF). Example 1 (1) Two-stage crystallization was performed using the crude 1,4-BG obtained in Reference Example 1 as a raw material (feed solution) using the crystallizer shown in FIG. 4 as an experimental apparatus. As a crystallizer, a vertical blade type shown in FIG. 4 was used. The size of the crystallizing plate made of stainless steel was 200 mm in width and 600 mm in height, and a transparent acrylic plate was installed on the front and upper parts of the crystallizer to make it visible.
As the refrigerant, a 30 to 40% ethylene glycol aqueous solution was used.

(2) Crude 1,4-BG 500 of crystallization raw material
g is supplied to the storage tank V-2. The raw material sent to the storage tank V-2 is sent to the circulation tank V-5, and further sent to the crystallizer 1. The raw material is circulated to the crystallizer under predetermined conditions to crystallize 450 g. The remaining 50 g of mother liquor is sent to storage tank V-1. Next, 200 g of the sweat is perspired for about 2 hours, the perspiration solution is sent to the storage tank V-2, and the melted first-stage crystallization melt is sent to the storage tank V-3.

(3) Next, the melt in the storage tank V-3 is
And further circulates through the crystallizer 1. According to the method described above, 10 g of mother liquor is stored in storage tank V-2, and 165 g of perspiration is stored in storage tank V-3.
Then, 75 g of the purified melt was sent to the storage tank V-4. (4) At this time, the purified melt in the storage tank V-4 is 1,4-BG
Was about 97.7% by weight (BGTF content 0.19% by weight).

Example 2 (1) Using the crystallizer shown in FIG. 4, two-stage crystallization was performed using the crude 1,4-BG obtained in Reference Example 1 as a raw material (feed solution). As a crystallizer, a vertical blade type shown in FIG. 4 was used. The size of the crystallization plate is 200mm wide and 600mm high
mm, and a transparent acrylic plate was installed on the front and upper parts of the crystallizer to make it visible. As the refrigerant, a 30 to 40% ethylene glycol aqueous solution was used.

(2) Crude 1,4-BG 500 of crystallization raw material
g is supplied to the storage tank V-2. The raw material sent to the storage tank V-2 is sent to the circulation tank V-5, and further sent to the crystallizer 1. The raw material is circulated to the crystallizer under predetermined conditions to crystallize 450 g. The remaining 50 g of mother liquor is sent to storage tank V-1. Next, 200 g is allowed to sweat for about 4 hours, the perspiration solution is sent to the storage tank V-2, and the melted first-stage crystallization melt is sent to the storage tank V-3.

(3) Next, the melt in the storage tank V-3 is
And further circulates through the crystallizer 1. According to the above-described method, 10 g of mother liquor is stored in storage tank V-2, and 185 g of perspiration is stored in storage tank V-3.
Then, 15 g of the purified melt was sent to the storage tank V-4. (4) At this time, the purified melt in the storage tank V-4 is 1,4-BG
Was about 99.7% by weight (BGTF content: 0.08% by weight).

Comparative Example 1 (Conventional Distillation Method) In the process shown in FIG. 2, 1,4-BG was produced from diacetoxybutane using a conventional distillation method. The composition of the crude 1,4-BG obtained from the side stream of the second distillation column 203 in FIG. 2 is 97.0% by weight of 1,4-BG, 14HAB 0.
5% by weight and 2.0% by weight of BGTF. 1000
The product obtained from the fourth distillation column 209 in FIG. 2 after continuous operation for a time is 99.7% by weight of the purity of 1,4-BG (BGTF
Was 0.25% by weight).

[0065]

According to the present invention, various impurities generated in the production process can be easily and efficiently separated and purified without taking complicated steps by using the purification method by melt crystallization. . In particular, B which is difficult to separate by distillation
GTF can be efficiently removed.

Further, by purifying crude 1,4-butanediol obtained by hydrolyzing diacetoxybutane using melt crystallization, the load on the distillation step and the hydrogenation step is reduced, and the efficiency is improved. High-purity 1,4-butanediol can be produced.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a process for producing diacetoxybutane.

FIG. 2 is an explanatory view showing a conventional production process for producing 1,4-BG from diacetoxybutane.

FIG. 3 is an explanatory view showing an example of the production process of the present invention for producing 1,4-BG from diacetoxybutane.

FIG. 4 is an explanatory view showing one example of a melt crystallization apparatus for carrying out the method of the present invention.

[Explanation of symbols]

 Reference Signs List 101 reactor 102 gas-liquid separator 103 first distillation column 104 second distillation column 105 hydrogenation reactor 106 third distillation column 201 hydrolysis reactor 202 first distillation column 203 second distillation column 204 fifth distillation column 205 1 hydrogenation reactor 206 second hydrogenation reactor 207 gas-liquid separator 208 third distillation column 209 fourth distillation column 301 hydrolysis reactor 302 first distillation column 303 second distillation column 304 melt crystallization device 305 third Distillation tower 306 First hydrogenation reactor 401 Crystallizer 402 Constant temperature water circulator V-0 Mother liquor storage tank V-1, V-2, V-3 Storage tank V-4 Product storage tank V-5 Circulation tank

Claims (9)

[Claims] 1. A method for purifying crude 1,4-butanediol, comprising melting and crystallizing crude 1,4-butanediol containing impurities. 2. The method according to claim 1, wherein the melt crystallization is performed by a wall surface melt crystallization method comprising the following steps. By flowing the crude 1,4-butanediol melt on the wall cooled below the freezing point of 1,4-butanediol,
A crystallization step for obtaining 1,4-butanediol crystals. A recovery step of recovering 1,4-butanediol as a crystal melt by heating the wall surface of the 1,4-butanediol crystal obtained in the crystallization step to a temperature higher than the freezing point of the 1,4-butanediol crystal. 3. The method according to claim 1, wherein the melt crystallization is performed by a wall melt crystallization method comprising the following steps. By flowing the crude 1,4-butanediol melt on the wall cooled below the freezing point of 1,4-butanediol,
A crystallization step for obtaining 1,4-butanediol crystals. After removing the remaining mother liquor, which is a molten liquid of 1,4-butanediol, from the 1,4-butanediol crystals obtained in the crystallization step, the wall surface is heated to around the freezing point of the 1,4-butanediol crystals. A perspiration step of removing impurities in the 1,4-butanediol crystals from the crystals as a perspiration liquid. The 1,4-butanediol crystals obtained in the sweating process are
A recovery step of recovering 1,4-butanediol as a crystal melt by heating the wall surface to a temperature higher than the freezing point of the 1,4-butanediol crystal. 4. The method according to claim 2, wherein the crystal thickness in the crystallization step is in the range of 1 to 20 mm. 5. A crude 1,4-butanediol having a total amount of 1
The method according to any one of claims 1 to 4, wherein the method comprises at least an impurity by weight. 6. The method according to claim 1, wherein the impurity is a compound having a freezing point of 0 ° C. or lower. 7. The method according to claim 1, wherein the impurity is 1,2-diacetoxybutane.
1,2-hydroxyacetoxybutane, 1,4-diacetoxybutane, 1,4-hydroxyacetoxybutane,
Dibutylene glycol, 2- (4'-hydroxybutoxy) tetrahydrofuran, 2- (4'-oxobutoxy) tetrahydrofuran, 1,4-di- (2'tetrahydrofuroxy) butane, 2-methyl-1,4-butane The method according to any one of claims 1 to 5, which is at least one compound selected from diol, γ-butyrolactone, 2-hydroxytetrahydrofuran, and 2-methylpentanediol. 8. A process for producing 1,4-butanediol, comprising subjecting crude 1,4-butanediol obtained by hydrolyzing diacetoxybutane to melt crystallization. 9. A low-boiling component is removed from crude 1,4-butanediol obtained by hydrolyzing diacetoxybutane, and the crude 1,4-butanediol from which low-boiling components have been removed is melt-crystallized. The 1,4-butanediol crystals are recovered, the high-boiling components are removed from the mother liquor from which the 1,4-butanediol crystals have been separated, and the high-boiling components removed in the process are hydrogenated, and the hydride is converted to a process. A method for producing 1,4-butanediol, which comprises supplying.