JPH0536423B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to the production of 1,4-butanediol.

[Prior art and its problems] 1,4-butanediol is useful as a raw material for producing polybutylene terephthalate, polyurethane, γ-butyrolactone, tetrahydrofuran, and the like.

Various methods for producing 1,4-butanediol using maleic anhydride as a raw material have been proposed so far, and the following method can be presented as a specific example.

(1) A method in which maleic anhydride and aliphatic alcohol are reacted at normal pressure without a catalyst to produce dialkyl maleate, which is then hydrogenated by a batch reaction (British Patent No. 1454440).

In this method, a large amount of maleic acid monoester, which is an acidic substance, remains after the esterification reaction, so the reaction product is washed with a large amount of water to remove this monoester before the next hydrogenation step. The production process is complicated, as it is necessary to refine the dialkyl maleate by distillation and then hydrogenate it.

(2) Maleic anhydride in the presence of a monohydric aliphatic alcohol as a solvent at 180-300°C and 250-350°C.
A method for continuously producing 1,4-butanediol in one step by hydrogenation using a copper-chromium fixed bed catalyst in a bar (Japanese Patent Application Laid-open No. 57528/1983).

According to this method, deactivation of the catalyst by acidic substances in a short period of time is unavoidable, and furthermore, the reaction efficiency is very low, as the feed rate of the reaction mixture is 0.18/h per catalyst.

(3) The maleic anhydride-containing gaseous reaction mixture obtained by air oxidation of the C ₄ - fraction,
A method of washing with a monohydric or dihydric aliphatic alcohol having a boiling point of 180° C. or higher, and then catalytically hydrogenating a mixture of this alcohol and maleic acid in the liquid phase (Japanese Patent Application Laid-open No. 156425/1983).

In this method as well, as in method (2) above, complete diesterification is impossible, and deactivation of the catalyst by unreacted monoester is unavoidable. Moreover, the average space-time yield of 1,4-butanediol is 40 g/h, which is very poor productivity.

(4) Maleic acid dialkyl ester was continuously hydrogenated in the gas phase using a copper-chromium catalyst to obtain 1,4
- A method for obtaining a mixture of butanediol and γ-butyrolactone (JP-A-61-22035).

Since this method is a gas phase reaction, it requires a vaporizer and is complicated in terms of equipment.

That is, in the conventionally known methods, (1) the acid value of the diester is high; therefore, a purification process such as water washing or distillation is necessary as a pretreatment for hydrogenation to remove the remaining monoester; .

(2) Since the diester has a high acid value, the activity of the hydrogenation catalyst is significantly reduced, resulting in low productivity.

(3) In the case of gas phase hydrogenation, the hydrogenation equipment is complicated.

There were various drawbacks such as, and it was industrially disadvantageous.

In addition to the high acid value of the diester mentioned above, possible causes for the deactivation of the hydrogenation catalyst include poisoning by mineral acids, organic acids, etc. used as catalysts for esterification. In addition, in the case of gas phase hydrogenation, it is thought that the deactivation of the catalyst due to the deposition of produced heavy components on the catalyst is significant.

The present inventors have conducted intensive studies to solve these drawbacks and develop a method for industrially advantageous production of 1,4-butanediol. (1) The dialkylation reaction of maleic anhydride was (2) A mixture of dialkyl fumarate and dialkyl maleate with a low acid value can be obtained by carrying out the reaction at high temperature, under pressure, and without a catalyst. (3) If this mixture is used as a raw material for the continuous hydrogenation reaction in the next step, hydrogenation can be carried out in a liquid phase fixed bed for a long time without deactivation of the catalyst; ,
The inventors have discovered that the desired 1,4-butanediol can be obtained with high selectivity, and have completed the present invention based on this finding.

That is, an object of the present invention is to provide an industrially excellent method for producing 1,4-butanediol.

[Means for Solving the Problems] The method for producing 1,4-butanediol according to the present invention involves hydrogenating a diester obtained from maleic anhydride and a monohydric aliphatic alcohol to produce 1,4-butanediol. The process is characterized in that a diester with an oxidation rate of 5 or less is obtained by esterification under pressure without using a catalyst, and this diester is continuously hydrogenated in a liquid phase.

Esterification process The esterification reaction according to the present invention is a non-catalytic reaction that does not use any catalyst that can poison the catalyst used in the hydrogenation reaction. ,
It is carried out under conditions of pressure.

In diesterification, in order to continuously distill the produced water out of the system, the monohydric aliphatic alcohol used is continuously supplied and the produced water is continuously distilled from the reaction vessel as steam. The extraction method is preferable, and the amount of alcohol charged is 0.2 to 1 hour per hour based on maleic anhydride.
A suitable amount is about 2.0 mol, preferably in the range of 0.4 to 1.0 mol. Below this range, the rate of diesterification becomes extremely slow, while above this range, there is an upper limit to the reaction rate, which is undesirable, as alcohol consumption becomes unnecessarily large.

As the reaction temperature, it is necessary to select a high temperature that is high enough to cause isomerization of monoalkyl maleate since there is no catalyst. Specifically, a temperature range of about 180°C to 280°C, preferably 200°C to 260°C, is appropriate; below 180°C, the amount of unreacted monoester increases, while above 280°C, the amount of unreacted monoester increases. There is a tendency that the reaction becomes significant and the yield of the desired diester decreases.

Although the reaction time varies depending on other conditions, in order to obtain a crude diester with a low acid value, a range of about 5 to 10 hours, preferably 7 to 8 hours is appropriate. The final crude product has an acid value of 5 or less. If the time is less than 5 hours, the reduction in the acid value is insufficient, and if the time is more than 10 hours, no further reduction in the acid value can be expected.

When a diester having an acid value exceeding 5 is used as a raw material for the next hydrogenation step, the life-extending effect of the hydrogenation catalyst inherent in the present invention is not observed.

The reaction pressure is suitably in the range of about 1 to 30 kg/cm ² G, particularly 3 to 15 kg/cm ² G, for the purpose of increasing the concentration of monohydric aliphatic alcohol in the liquid phase and increasing the esterification rate.

As the monohydric aliphatic alcohol, those having 1 to 6 carbon atoms can be used, and n-butanol is particularly preferred. n-Butanol forms an azeotrope with water produced by esterification, and since this azeotrope can be separated into layers, it can be easily separated from water. This separated n-butanol is easy and economical to reuse. Moreover, since the produced dibutyl fumarate and dibutyl maleate are liquid, they are easy to handle industrially. Furthermore, n-butanol is inexpensive and advantageous in terms of cost. on the other hand,
When it comes to long chain alcohols with carbon numbers of 7 or more,
It is disadvantageous because it is expensive, the esterification rate is slow, and the hydrogenation reaction of the produced diester is also extremely slow. Furthermore, the yield of 1,4-butanediol in the hydrogenation step is extremely reduced, resulting in poor production efficiency.

Hydrogenation process The hydrogenation reaction includes a one-step method in which diester as a raw material is hydrogenated to the target 1,4-butanediol in one step, and a dialkyl succinate intermediate in the first step, and then this intermediate is converted into 1,4-butanediol in the second step. , 4-butanediol, but either method is possible. As the diester serving as a reaction raw material, the crude product (acid value 5 or less) obtained in the previous step can be used directly as a raw material, and there is no need to wash with water or distill it.

The hydrogenation reaction method uses a copper-chromium catalyst as a catalyst, and a fixed bed liquid phase continuous reaction is industrially advantageous, and both the ascending method and the descending method are possible as a method for supplying raw materials and hydrogen gas. be.

Furthermore, since it is a liquid phase reaction, there is no deposition of heavy components on the catalyst, which is often observed in gas phase reactions, and the reaction can be carried out for a long period of time.

Suitable catalysts that can be used in the continuous hydrogenation reaction using a liquid-phase fixed bed of the present invention are commonly commercially available tablet-shaped copper-chromium catalysts, and catalysts modified with compounds such as manganese, calcium and barium. You can also use things. This catalyst is in the form of an oxide, and after being filled into a continuous hydrogenation reaction tower, it can be used as a hydrogenation catalyst for diesters by preliminary reduction with hydrogen gas.

The feeding rate of the raw material is preferably in the range of 0.2 to 2 diesters per hour of packed catalyst. If it is less than 0.2, production efficiency will be poor and by-products will increase. On the other hand, if it is 2 or more,
This is disadvantageous because the reaction rate of the raw materials tends to decrease.

In addition, in order to maintain the catalytic activity and remove the heat of reaction, it is preferable to add a monohydric aliphatic alcohol having 1 to 6 carbon atoms together with the raw material diester, and the amount added is 200 The amount is limited to about % by weight, and if the amount is more than necessary, production efficiency will decrease.

Hydrogenation pressure is 30 to 300Kg/in the case of one-stage method.
About cm ² G, preferably in the range of 100 to 200 Kg/cm ² G is appropriate. On the other hand, in the case of the two-stage method, the first stage is 10
The range of ~200Kg/ ^cm2G , especially 20~50Kg/ ^cm2G is preferable, and the latter stage is about 30~300Kg/ ^cm2G , especially
A range of 100 to 200 Kg/cm ² G is preferred.

On the other hand, as for the hydrogen gas flow rate, the space gas linear velocity is about 0.5 to 10 cm/sec, preferably 1 to 5 cm/sec.
A suitable range is cm/sec, and in these ranges there is a large excess amount relative to the raw material ester, and there is an advantage that physical damage to the copper-chromium catalyst packed therein is small.

The appropriate range of reaction temperature varies depending on the hydrogenation pressure, but is preferably about 160 to 260°C in a one-stage reaction. Below 160°C, residual unreacted dialkyl fumarate and dialkyl succinate become noticeable, and above 260°C, by-product tetrahydrofuran or n-butanol becomes noticeable. On the other hand, in the case of a two-stage reaction, the first stage is 80 to 220℃.
The temperature is preferably in the range of 120 to 180°C, and the temperature in the latter stage is about 160 to 260°C, preferably 180 to 230°C. In both the first and second stages, if the reaction is below the above-mentioned suitable range, unreacted substances will remain prominently, while if it is above the suitable range, by-products will be produced significantly, which is disadvantageous in both cases.

If it is desired to obtain γ-butyrolactone as the main product, the hydrogenation pressure may be lowered (approximately 30 to 50 kg/cm ² G) and the reaction temperature may be increased (approximately 220 to 260° C.) in the one-step reaction.

The final reaction product obtained by hydrogenation is separated by fractional distillation into the desired 1,4-butanediol and other components such as tetrahydrofuran, monohydric aliphatic alcohol, γ-butyrolactone, and unreacted succinic acid. Dialkyl can be separated and purified.

The alcohol added to sustain the activity of the catalyst and remove the heat of reaction and the alcohol constituting the diester can be recovered and reused. However, when both alcohols are the same, the system is simple and industrially advantageous.

[Example] Hereinafter, the present invention will be explained in detail by giving examples. Note that the composition determined by gas chromatography is based on weight.

Example 1 Maleic anhydride 15Kg (0.153kmol) and n-
11.3 kg (0.153 kmol) of butanol was charged into a pressure-resistant reaction vessel equipped with a stainless steel stirrer.
Start stirring after heating the mixture to 100°C.
Monobutyl maleate was obtained by reacting for 30 minutes.
After that, the temperature of the reaction system was raised to 240°C while stirring,
While maintaining the reaction pressure at 5 Kg/cm ² G, n-butanol was continuously supplied at a rate of 6.78 Kg/hour (0.092 kmol), and the produced water was continuously fed with n-butanol into the reactor equipped with a cooler at the top of the reactor. The dibutyl esterification reaction was carried out while drawing out the distillate from the distillation line. Eight hours after starting the supply of n-butanol, the heating and supply of n-butanol were stopped, and after purging the gas phase so that the pressure in the reactor was approximately 1 kg/cm ² G, the reaction mixture was Cool while stirring.

After cooling, the reaction mixture was extracted from the reaction vessel, and 31.4 kg of dibutyl ester crude material with an acid value of 1.5 was extracted.
(crude yield 90%). The composition of this crude product determined by gas chromatography was as follows.

n-Butanol 4.1% Dibutyl fumarate 89.9% Dibutyl maleate 3.0% High boiling point compounds 3.0% On the other hand, the amount of dibutyl fumarate and dibutyl maleate distilled out during the reaction together with n-butanol was 2.9 kg, so The total amount of the above diester was 34.3Kg (yield 98.3%).

Using the dibutyl ester as a raw material, a continuous fixed bed liquid phase one-stage hydrogenation reaction to 1,4-butanediol was carried out.

The reactor used was a cylindrical one made of stainless steel (SUS316) with an inner diameter of 25 mm and a tower length of 1000 mm.
37% by weight of manganese oxide, 2.0% by weight of manganese oxide, cylindrical molded product, 5 mm in diameter x 5 mm in height), and was previously subjected to reduction treatment to prepare a catalyst for hydrogenation reaction.

A mixture of raw material dibutyl ester (acid value 1.5) and the same weight of n-butanol [feed rate: 334 ml/h (space velocity 0.68/h)]
and hydrogen gas [introduction rate: 5Nm ³ /h (molar ratio to ester = 349:1)] were simultaneously supplied from the top of the column,
The reaction was carried out at 220° C. and 200 Kg/cm ² G, and a liquid reaction mixture was continuously extracted from the bottom of the column.

n by gas chromatography of the reaction mixture
The composition other than -butanol was 1,4-butanediol 93.0% dibutyl succinate 2.4% γ-butyrolactone 2.4% tetrahydrofuran 1.0% others 1.8%, and unreacted dibutyl fumarate and dibutyl maleate were not detected.

Furthermore, the reaction was continued for 1080 hours under the same conditions, but
No deactivation of the catalyst was observed.

Example 2 A two-stage hydrogenation reaction was carried out using the same apparatus, catalyst, and raw materials as in Example 1.

The first hydrogenation reaction was carried out using the same mixture of dibutyl ester and n-alcohol as in Example 1 [feed rate: 501 ml/h (space velocity 1.02/h)] and hydrogen gas [introduction rate: 4 Nm ² /h ( to ester molar ratio = 165:1)] were simultaneously fed from the bottom of the column, and
The reaction was carried out under conditions of 20 kg/cm ² G, and a liquid reaction mixture was continuously extracted from the top of the column.

n by gas chromatography of the reaction mixture
The composition other than -butanol was 94.9% dibutyl succinate, 1.0% 1,4-butanediol, 0.8% γ-butyrolactone, and 3.1% high boiling point compounds, and unreacted dibutyl fumarate and dibutyl maleate were not detected.

Furthermore, the subsequent hydrolysis reaction was carried out using the same apparatus and the same catalyst under the following conditions. The n-butanol solution of dibutyl succinate obtained in the previous step was used as the reaction raw material, and hydrogen gas was added at a rate of 501 ml/h (space velocity 1.02/·h) to 4 Nm ² /h.
h (molar ratio to ester = 165:1) was charged simultaneously from the bottom of the reaction tower, and the reaction was carried out at 200° C. and 200 Kg/cm ² G, and the liquid reaction mixture was continuously extracted from the top of the tower.

n by gas chromatography of the reaction mixture
The crude products other than -butanol were 1,4-butanediol 95.3% dibutyl succinate 3.0% γ-butyrolactone 0.7% tetrahydrofuran 0.6% high boiling point compounds 0.4%.

Furthermore, although the first stage reaction was carried out for 400 hours and the second stage reaction was carried out for 400 hours, no deactivation of the catalyst was observed.

Example 3 Maleic anhydride was diesterized in the same manner as in Example 1, except that ethanol was used as the monohydric aliphatic alcohol and the reaction pressure was 10 Kg/cm ² G.

The acid value of the resulting reaction crude product was 1.2, and its crude formation by gas chromatography was as follows.

Ethanol 3.2% Diethyl fumarate 90.5% Diethyl maleate 3.8% High-boiling point compounds 2.5% Using the above diethyl ester as a raw material, continuous liquid phase one-stage hydrogenation in a fixed bed was carried out using the same reactor and catalyst as in Example 1. Summer.

Example 1 A mixture of diethyl ester and the same weight of ethanol was added from the top of the column together with hydrogen gas.
Same speed as (raw material 334ml/, hydrogen gas 5Nm ² /
h) and reacted under the conditions of 210° C. and 200 Kg/cm ² G, and a liquid reactant was continuously extracted from the bottom of the column.

The composition of the reaction mixture other than ethanol was as follows.

1,4-Butanediol 93.5% Diethyl succinate 1.5% γ-Butyrolactone 2.0% Tetrahydrofuran 1.0% n-Butanol 0.8% Others 1.2% Furthermore, the reaction was continued for 920 hours under the same conditions.
No deactivation of the catalyst was observed.

Comparative Example 1 Hydrogenation was carried out in the same manner as in Example 1, except that a mixture of dibutyl fumarate and dibutyl maleate with a high acid value (7.0) obtained by non-catalytic esterification reaction was used as the raw material diester. As a result, the composition of the reaction crude product excluding n-butanol was 1,4-butanediol 92.5% dibutyl succinate 3.2% γ-butyrolactone 2.0% tetrahydrofuran 0.8% others 1.5%, which is almost the same result as Example 1. Ta.

However, when the reaction was further continued for 162 hours under the same conditions, the composition of the crude product was 1,4-butanediol 55.0% dibutyl succinate 38.1% γ-butyrolactone 3.5% tetrahydrofuran 1.8% others 1.6%, which clearly showed that the catalyst was not present. Deactivation was recognized.

Comparative Example 2 Diethyl fumarate (acid value 1.5) (space velocity: 360 ml/h)] and hydrogen gas [introduction rate: 15 Nm ³ /h (molar ratio to ester =
310:1)] were simultaneously supplied from the top of the tower, and the temperature was 175°C and 42°C.
Hydrogenation was carried out under gas phase conditions of Kg/cm ² G, and a liquid reactant was continuously extracted from the bottom of the column.

n of this reactant by gas chromatography
The composition excluding -butanol was 1,4-butanediol 73.8% diethyl succinate 7.9% γ-butyrolactone 15.5% tetrahydrofuran 2.7%. Furthermore, when the reaction was continued for 184 hours under the same conditions, the crude composition was 48.8% 1,4-butanediol, 27.9% diethyl succinate, 20.5% γ-butyrolactone, and 2.7% tetrahydrofuran, and clear deactivation of the catalyst was observed. .

Comparative Example 3 0.5% by weight of concentrated sulfuric acid was added to maleic anhydride as an esterification catalyst, and n-butanol was added to 120% by weight of maleic anhydride.
℃ for 8 hours according to a conventional method, then washed with water to obtain dibutyl maleate with an acid value of 1.5, and then hydrogenated according to Example 1 to prepare 1,4-butanediol. . As a result, the composition of the reaction crude product excluding n-butanol was 1,4-butanediol 91.3% diethyl succinate 3.9% γ-butyrolactone 2.1% tetrahydrofuran 0.9% others 1.8%, which is almost the same result as Example 1. It was hot.

However, when the reaction was further continued for 58 hours under the same conditions, the composition of the crude product was 1,4-butanediol 51.0% diethyl succinate 42.1% γ-butyrolactone 3.8% tetrahydrofuran 1.9% others 1.2%, which clearly showed that the catalyst was not present. It was also recognized that it was deactivated.

[Effects of the Invention] A crude diester with a low acid value can be obtained by esterifying maleic anhydride as a raw material and a monohydric aliphatic alcohol under pressure without a catalyst. This product can be used as a raw material for the next continuous hydrogenation reaction without the need for treatments such as water washing or distillation, so it can be used in high yields and with high efficiency.
Butanediol is obtained. Moreover, the hydrogenation catalyst does not show any decrease in activity over a long period of time, making it a very industrially advantageous method.

Claims (1)

[Claims] 1 When hydrogenating a diester obtained from maleic anhydride and a monovalent aliphatic alcohol to produce 1,4-butanediol, esterification is performed under pressure without using a catalyst to obtain a diester with an acid value of 5 or less. A method for producing 1,4-butanediol, which comprises continuously hydrogenating this diester in a liquid phase.