JP3572636B2 - Method for producing butanediol - Google Patents

Description

【００２５】
【発明の効果】
本発明の方法によれば、ジアセトキシブタンを加水分解してブタンジオールを製造する際に必要な水、酢酸を有効に回収利用しつつ、かつ、製品であるブタンジオールを高い品質に維持することができる。加水分解反応物より回収された水は、留出物としてではなく、単に軽沸物を留出カットする簡単な蒸留で精製することができるので、熱源負荷を大きくすることなく、極めて経済的な品質改良プロセスといえる。
【図面の簡単な説明】
【図１】本発明の実施態様の一例である。
【符号の説明】
１ アセトキシ化反応器
２，３，５，７，８，９ 蒸留塔
４ 水添反応器
６ 加水分解反応器
１０ 酢酸分離塔
１１ 分離器
１１ａ 油相
１１ｂ 水相
１２ 水精製塔[0001]
[Industrial applications]
The present invention relates to a method for producing butanediol by hydrolyzing diacetoxybutane.
[0002]
[Prior art]
As a typical production method of butanediol, particularly 1,4-butanediol useful as a raw material of a polyester resin, a method of producing butanediol by hydrolyzing diacetoxybutane is known.
Since the diacetoxybutane hydrolysis reaction product contains a large amount of acetic acid and water in addition to the target 1,4-butanediol, industrially, acetic acid and water are recovered by distillation. It is desirable to be able to reuse it.
[0003]
For example, Japanese Patent Publication No. 57-7609 discloses that butadiene is acetoxylated, and then the diacetoxybutane hydrolysis reaction product obtained by hydrogenation is distilled in a first distillation column to give a distillate containing water, acetic acid and butyl acetate. And distilling the fraction in a second distillation column to separate it into an oil phase and an aqueous phase, and circulating the aqueous phase to the hydrolysis reaction zone, while separating the acetic acid in the second distillation column. A method is described in which the bottoms are reused as a starting material for acetoxylation.
According to the publication, butyl acetate is contained in the acetic acid bottoms, and even if it is reused in the acetoxylation reaction, it has no effect on the reaction and has no effect on the life of the catalyst. I have. The aqueous phase also contains a small amount of butyl acetate, but this butyl acetate is also hydrolyzed to acetic acid and butanol, which does not affect the quality of 1,4-butanediol at all. I have.
[0004]
[Problems to be solved by the invention]
In recent years, application fields of 1,4-butanediol have been diversified, and higher quality has been required. Then, as a method of achieving an improvement in quality, improvement of the conditions of the hydrolysis reaction and the conditions of the distillation purification can be considered. However, what can be industrially adopted needs to be a more economical improvement method that minimizes the increase in product cost.
[0005]
[Means for Solving the Problems]
The present inventors acetoxylated butadiene and then hydrolyzed diacetoxybutane obtained by hydrogenation to produce butanediol. result of intensive studies on how to maintain the high quality, conventionally, it found that impurities in the recovered water which was used in the hydrolysis is largely influenced than expected quality of butanediol, the process improvements As a result, the present invention has been achieved. That is, according to the present invention , an acetic acid aqueous solution distilled and separated from a reaction product of hydrolysis of diacetoxybutane is supplied to an acetic acid separation column, and acetic acid is removed from the bottom of the column, while the distillate is separated into an oil phase and water. phases separated settling, the aqueous phase was supplied to the water purification column, by circulating purified water to Kande from the bottom while distilling off low-boiling point fraction from the top to the hydrolysis reaction zone, high High quality butanediol can be produced.
[0006]
The aqueous acetic acid solution separated by distillation from the reaction product of acetoxylation may be supplied to the acetic acid separation tower together with the aqueous acetic acid solution separated by distillation from the reaction product of hydrolysis of diacetoxybutane.
[0007]
Hereinafter, the present invention will be described in detail.
Diacetoxybutane is usually obtained by acetoxylation of butadiene followed by hydrogenation. The acetoxylation is usually carried out by reacting butadiene, acetic acid and oxygen in the presence of a palladium-based catalyst at a temperature of usually from 40 to 180 ° C under a pressure condition of normal pressure or higher. As a method of separating diacetoxybutene from the reaction product, first, water, acetic acid, and other light-boiling components are separated by distillation, and then, diacetoxybutene and a high-boiling substance are separately separated, and a method of separating again by distillation is preferable. .
[0008]
Further, as a method of hydrogenating diacetoxybutene, usually, diacetoxybutene is brought into contact with hydrogen in the presence of a noble metal catalyst such as palladium or ruthenium, and usually in a temperature range of 40 to 180 ° C and a pressure condition of normal pressure or higher. And the reaction is carried out. Preferably, the reactants are subjected to distillation to separate diacetoxybutane and high-boiling substances.
[0009]
Diacetoxybutane obtained by the above method is partially hydrogenated during hydrogenation, and usually contains about 0.1 to 5% of butyl acetate. For the hydrolysis reaction of diacetoxybutane, it is preferable to use a cation exchange resin as a solid acid catalyst because the hydrolysis rate is high and there are few by-products such as tetrahydrofuran. The reaction is usually carried out at a temperature of 30 to 110 ° C, preferably 40 to 90 ° C. Water is used in an amount of usually 2 to 100 mol, preferably 4 to 50 mol, per 1 mol of diacetoxybutane.
[0010]
The hydrolysis reaction product is separated and purified as follows. First, the reaction product is distilled in a distillation column, and a component containing 1,4-butanediol is removed from the bottom of the column, while water and acetic acid, that is, an aqueous solution of acetic acid is obtained as a distillate. The distillation conditions are usually selected from the range of a bottom temperature of 100 to 210 ° C. and a bottom pressure of 30 to 300 mmHg.
The recovered acetic acid aqueous solution is then supplied to an acetic acid separation column, where distillation is performed, acetic acid is removed from the bottom of the column, and water and other light boiling components are distilled off. In this case, the aqueous solution of acetic acid supplied to the acetic acid separation tower may include an amount separated and recovered from the acetoxylation reaction product. The operating conditions of the acetic acid separation column are usually selected from a range of 100 to 180 ° C. under normal pressure to slightly elevated pressure.
[0011]
Acetic acid is recovered as a bottom of the acetic acid separation tower. In the bottoms, in addition to acetic acid, reaction by-products such as butyl acetate and monoacetylbutene and water are contained. There is no problem in reusing it as a raw material for the acetoxylation reaction.
When the distillate from the acetic acid separation tower is introduced into a separator and allowed to stand, it separates into an oil phase and an aqueous phase. Of these, the oil phase is mainly composed of butyl acetate and monoacetoxybutene, and the separated oil phase may be circulated to the acetic acid separation tower or discharged outside the system. On the other hand, in the aqueous phase, components other than water are mainly acetic acid, and a small amount of slightly dissolved butyl acetate and the like is contained. Collected.
[0012]
Therefore, conventionally, this aqueous phase was circulated to the hydrolysis reaction zone and reused. In the present invention, this aqueous phase is further supplied to a water purification column, and purified from the bottom of the water purification column. It is characterized in that water is circulated to the hydrolysis reaction zone.
As the operating conditions of the water purification tower, the bottom temperature is usually set in the range of 70 to 110 ° C. under pressure conditions near normal pressure. In the water purification tower, it is not necessary to perform strict distillation as long as a small amount of light boilers in the aqueous phase can be distilled off, and there is no problem even if acetic acid in the aqueous phase cannot be separated.
[0013]
Although some components are detected as light boilers, specific examples thereof include n-butyl acetate, monoacetoxybutene, tetrahydrofuran, furan, n-butyraldehyde, and butanol. It has been hardly expected that each of these components adversely affects the quality of 1,4-butanediol during hydrolysis. However, in the case of industrial continuous operation, It is considered that there is an effect such as accumulation of each component in the reaction system or slight occurrence of a complicated side reaction.
[0014]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples. In the examples, “parts” indicates “parts by weight” and “%” indicates “% by weight”.
Example 1
A process for producing butanediol from butadiene and acetic acid raw materials shown in FIG. 1 will be described.
Butadiene, air and recovered acetic acid described below were supplied to the acetoxylation reactor 1 filled with a palladium-supported catalyst, and reacted at 90 KG and 100 ° C. After gas-liquid separation (not shown) of the reaction solution, acetic acid, water and other light boilers were distilled off in the distillation column 2 and diacetoxybutene was distilled off in the distillation column 3.
[0015]
Next, the diacetoxybutene distilled from the distillation column 3 was subjected to a hydrogenation reaction at a reaction pressure of 50 KG and a temperature of 90 ° C. in a hydrogenation reactor 4 filled with a palladium catalyst and a ruthenium catalyst under a hydrogen flow. Then, the reaction solution was subjected to gas-liquid separation and then distilled in the distillation column 5 to distill diacetoxybutane.
[0016]
Next, diacetoxybutane distilled from the distillation column 5 and the purified water to be described later are subjected to a hydrolysis reaction at 50 ° C. in a hydrolysis reactor 6 filled with a strongly acidic ion exchange resin, to give butanediol, hydroxyacetoxy. A reaction mixture containing butane and diacetoxybutane as main components was used. Acetic acid, water and other light boilers were distilled off from the hydrolyzed liquid in the distillation column 7. The bottom product of the distillation column 7 was supplied to the distillation column 8 to distill a low boiling point from the top of the column, diacetoxybutane and hydroxyacetoxybutane from the upper side stream, and butanediol from the middle side stream. Then, butanediol was rectified in the distillation column 9 and recovered as a product stream of butanediol.
[0017]
On the other hand, 29400 parts / hr of an acetic acid aqueous solution distilled and collected from the distillation column 2 of the acetoxylation reaction system and 10080 parts / hr of an acetic acid aqueous solution distilled and collected from the distillation column 7 of the hydrolysis reaction system are supplied to the acetic acid separation column 10, Distillation was performed under normal pressure and at a tower bottom temperature of 159 ° C.
The composition of the bottom liquid of the acetic acid separation column 10 was as follows, and was circulated to the acetoxylation reactor 1 at 33230 parts / hr.
[0018]
[Table 1]
Acetic acid 92.3%
1.5% water
3.8% of monoacetoxybutene
Diacetoxybutene 0.4%
Butyl acetate 0.7%
High boiling 1.3%
The composition of the distillate from the top of the acetic acid separation column 10 was as follows, and was supplied to the separator 11 at 28,900 parts / hr.
[0019]
[Table 2]
Water 25.3%
Monoacetylbutene 34.3%
Butyl acetate 35.8%
Acetic acid 0.3%
4.3% of light boilers
When the above distillate was separated by standing with a separator, the composition of the oil phase 11a and the aqueous phase 11b was as follows.
[0020]
[Table 3]
(Composition of oil phase)
Butyl acetate 47.6%
Monoacetylbutene 45.6%
1.1% water
Acetic acid 0.1%
5.7% light boiler
(Aqueous phase composition)
98.3% of water
Acetic acid 1.0%
Butyl acetate 0.2%
Monoacetylbutene 0.3%
Light boiler 0.2%
[0021]
Most of the oil phase 11a was returned to the acetic acid separation column 10, and a part (50 parts / hr) was discharged out of the system. On the other hand, the water phase 11b was supplied to the water purification tower 12 at 7000 parts / hr. Then, distillation was carried out under normal pressure at a column bottom temperature of 100 ° C. Then, 50 parts / hr of a distillate containing light boiling components is discharged out of the system, and 6950 parts / hr of purified water (water 99.0%, acetic acid 1.0%) discharged from the bottom of the column are hydrolyzed. Circulated to reactor 6.
[0022]
Table 1 shows the purity of the product stream of 1,4-butanediol distilled from the distillation column 9 after 5 days and 30 days of continuous operation of the above process.
It is considered that various aldehydes and acetals exist as trace impurities in 1,4-butanediol. It is also possible to use the carbonyl value as an index of the total content of these aldehydes and acetals. In Table 1, the carbonyl value is represented by a potentiometric titration value (mg · KOH / g) of the imine hydrochloride formed by the reaction of aldehyde and acetal with hydroxyamine hydrochloride using KOH. If the carbonyl value is high, problems such as coloring of products such as polyester resins using the 1,4-butanediol as a raw material occur, which is not preferable.
[0023]
Comparative Example 1
In Example 1, the results obtained when continuous operation was performed in the same manner as in Example 1 except that the aqueous phase from the separator 11 was circulated to the hydrolysis reactor 6 without purification in the water purification tower 12 are shown in Table 1. 1 is shown.
[0024]
[Table 4]

[0025]
【The invention's effect】
According to the method of the present invention, while water and acetic acid required for producing butanediol by hydrolyzing diacetoxybutane are effectively recovered and used, and the product butanediol is maintained at a high quality. Can be. The water recovered from the hydrolysis reaction product can be purified not by distillate but by simple distillation that simply distills off light boilers, so it is extremely economical without increasing the heat source load. This is a quality improvement process.
[Brief description of the drawings]
FIG. 1 is an example of an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Acetoxylation reactor 2,3,5,7,8,9 Distillation tower 4 Hydrogenation reactor 6 Hydrolysis reactor 10 Acetic acid separation tower 11 Separator 11a Oil phase 11b Water phase 12 Water purification tower

Claims (3)

In a method for producing butadiene by hydrolyzing diacetoxybutane obtained by acetoxylation of butadiene and then hydrogenation, an aqueous acetic acid solution distilled and separated from a reaction product of the hydrolysis is supplied to an acetic acid separation column, and acetic acid is supplied from the bottom of the column. While separating the distillate into an oil phase and an aqueous phase, feeding the aqueous phase to a water purification column, distilling off the light boiling components from the top and removing it from the bottom. A method for producing butanediol, wherein water is circulated to the hydrolysis reaction zone. In a method for producing butanediol by hydrolyzing diacetoxybutane obtained by acetoxylation of butadiene and then hydrogenation, an aqueous acetic acid solution obtained by distilling and separating an acetoxylation and hydrolysis reaction product is supplied to an acetic acid separation column, While distilling off acetic acid from the bottom of the column, the distillate is separated into an oil phase and an aqueous phase, and the separated aqueous phase is supplied to a water purification column. A method for producing butanediol, comprising circulating purified water discharged in the hydrolysis reaction zone. 3. The method for producing butanediol according to claim 1, wherein the bottom of the acetic acid separation tower is circulated to an acetoxylation reaction zone.

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