JPH09328451A - Method for producing carboxylic acid ester using HF catalyst - Google Patents

Abstract

(57) Abstract: In a method for producing a carboxylic acid ester from an olefin, carbon monoxide and an alcohol by using an HF catalyst, water is generated by a dehydration reaction of an unreacted alcohol and troubles due to residual acyl floyd are eliminated. Avoid,
Provided is a method for stably producing a high-quality carboxylic acid ester. SOLUTION: In a method for producing an acyl fluoride by reacting an olefin with carbon monoxide in the presence of HF, and reacting the obtained acyl fluoride with an alcohol to produce an ester, residual acyl fluoride is converted into an ester. On the other hand, esterification is performed so that the amount becomes 0.1 mol% or more and 5.0 mol% or less, the HF catalyst is separated, and then alcohol is added to esterify the residual acyl fluoride.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a carboxylic acid ester from an olefin, carbon monoxide and an alcohol using an HF catalyst.

[0002]

2. Description of the Related Art As a method for producing a carboxylic acid ester from an olefin using a strong acid catalyst, a so-called Koch reaction is used to carbonyl an olefin with carbon monoxide to form an acyl cation, which is then reacted with water to produce a carboxylic acid. It is known to obtain carboxylic acid ester by reacting with alcohol after obtaining.

Examples of the Koch reaction include the production of pivalic acid from isobutene and the production of C _{6 to} C ₁₁ carboxylic acids from C _{5 to} C ₁₀ olefins, and secondary or tertiary carboxylic acids are obtained by this reaction. ing. As a catalyst for carboxylic acid synthesis by Koch reaction, inorganic acids such as sulfuric acid, HF and phosphoric acid may be used alone or in combination with BF ₃ or SbF ₅ .
For example, HF · SbF ₅ or H ₃ PO ₄ BF ₃ is used, but since the product and the catalyst phase are separated by adding water in the latter half of the reaction, the catalyst diluted with water or the like is used. The problem is that you have to play.

In order to produce an ester from a carboxylic acid and an alcohol, for example, an inorganic acid such as sulfuric acid, HF, phosphoric acid or hydrochloric acid, an alkyl sulfonic acid such as methanesulfonic acid or trifluoromethanesulfonic acid, P-toluenesulfonic acid or the like. The reaction is carried out while removing water in the presence of a catalyst such as an aryl sulfonic acid, an alkoxy metal such as tetrabutoxy titanium, a Lewis acid such as boron fluoride ethylate, etc., but in the case of a secondary or tertiary branched carboxylic acid, esterification The reaction is slow and it has a difficult problem to carry out industrially.

On the other hand, in US Pat. No. 5,463,093, acyl fluoride is synthesized by carbonylation of an olefin using HF as an acid catalyst, and the acyl fluoride and alcohol are reacted in the presence of HF to form an ester. The method of obtaining is described. This method also facilitates catalyst recovery,
Moreover, the carbonylation reaction and the esterification reaction proceed extremely easily, and an ester having a branched acid structure can be easily obtained.

[0006]

The method using the HF catalyst of the above cited patent is an excellent method because the ester can be directly obtained without separating the carboxylic acid and the catalyst can be easily recovered. Carbonylation and esterification H
Since it is carried out in the presence of F, stoichiometric control of the acyl fluoride obtained by carbonylation and the alcohol is extremely important. That is, when the alcohol is added in excess to the acyl fluoride, the unreacted alcohol causes a dehydration reaction to produce water in the system. Especially, when a lower monohydric alcohol is used, this dehydration reaction easily proceeds, so caution is required. Since water and HF are difficult to separate because they form an azeotropic composition, not only water accumulates in the recovered HF within a short time to adversely affect the reaction, but it also causes significant corrosion of equipment materials, Stable operation becomes difficult.

When the amount of alcohol added is insufficient with respect to the acyl fluoride, unreacted acyl fluoride remains in the reaction product. This acyl fluoride is difficult to remove by a simple operation such as neutralization, so it remains with the product ester in a later step and is a fluorine-containing compound that is difficult to separate from the product ester under heating conditions such as distillation. Is produced, and this is mixed in the product as an impurity, which deteriorates the product purity.

In the method using the HF catalyst as described above,
Accurately controlling the stoichiometric amount from the beginning of the reaction, it is extremely important for industrial implementation to stably obtain conditions under which neither water is by-produced nor acylfluoride remains in the system. Although important, such an error-free operation is practically difficult, which often causes problems such as equipment corrosion troubles and the inclusion of fluorine-containing impurities in products.

An object of the present invention is a method for producing a carboxylic acid ester from an olefin, carbon monoxide and an alcohol using an HF catalyst, which causes problems such as water generation due to dehydration reaction of unreacted alcohol and residual acyl fluoride. It is another object of the present invention to provide a method for avoiding and stably producing a high-quality carboxylic acid ester.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above problems in the method for producing an ester using an HF catalyst, and as a result, have found that the ester formed in the esterification step after carbonylation is On the other hand, the ester was prepared by controlling the addition amount of alcohol so that the acyl fluoride remained at 0.1 to 5.0 mol%, and then the HF catalyst was separated, and the residual acyl was added in the presence of a new catalyst. It was found that esterification of fluoride with alcohol makes it possible to use a high-performance HF catalyst while avoiding the risk of water formation, and to stably produce an ester containing no fluorine-containing impurities in the product. Reached

That is, the present invention is a method for producing an acyl fluoride by reacting an olefin with carbon monoxide in the presence of HF, and reacting the obtained acyl fluoride with an alcohol to produce an ester. Fluoride is 0.1 mol% to 5.0 mol% with respect to the ester
The method for producing a carboxylic acid ester is characterized in that esterification is carried out within the following range, the HF catalyst is separated, and then alcohol is added to esterify the residual acyl fluoride.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The raw material olefin used in the present invention is not particularly limited and is selected from aliphatic chain olefins, alicyclic olefins and the like depending on the intended product. Examples of these olefins include propylene, butylene, isobutylene, pentene, hexene, octene, cyclohexene, cyclododecene and the like.

The carbonylation reaction of an olefin to produce an acyl fluoride by reacting an olefin with carbon monoxide is carried out under pressure of carbon monoxide in the presence of an HF catalyst. At this time, an inert gas such as nitrogen or methane may be contained, but the carbon monoxide partial pressure is 0.5 to 5 MPa,
The range is preferably 1 to 3 MPa. If the carbon monoxide partial pressure is too low, the carbonylation reaction will not proceed sufficiently and the polymerization reaction will occur at the same time, leading to a decrease in yield. Further, even if the carbon monoxide partial pressure is higher than this range, the merit in the reaction cannot be obtained, and a high pressure device is required, which causes a problem.

The HF catalyst used in the carbonylation reaction is substantially anhydrous. The amount of HF used is 3 to 25 times mol, preferably 5 to 20 times mol, of the raw material olefin. If the molar ratio of HF is too low, the carbonylation reaction does not proceed sufficiently as in the case where the carbon monoxide partial pressure is too low, and the polymerization reaction occurs concurrently, leading to a decrease in yield, and HF in an amount of 25 times or more moles is required. Even if it is used, the effect of improving the yield is small, the cost for separating HF increases, and the volumetric efficiency of the apparatus also decreases.

The reaction temperature for carbonylation is not particularly limited,
The highest yield condition may be appropriately selected depending on the type of olefin, but carbonylation of olefins using an HF catalyst is generally carried out in the temperature range of -40 ° C to 100 ° C. The form of the carbonylation reaction is not particularly limited, and any method such as a semi-continuous type or a continuous type may be used.

In the carbonylation reaction, a solvent which is soluble and inactive with the starting olefin, for example, a saturated aliphatic hydrocarbon such as hexane, heptane, decane or the like can be used as a reaction solvent. When a solvent is used, the polymerization reaction is further suppressed and the yield is often improved, but when used in a large amount, the volumetric efficiency of the device is lowered, and the energy unit consumption for separation is deteriorated. Whether or not to use and the amount to be used are appropriately selected.

The acyl fluoride prepared by the carbonylation reaction is subsequently reacted with an alcohol to give an ester.
At this time, the acyl fluoride may be separated once, and then esterified with the alcohol under the HF catalyst again.
A method in which the carbonylation reaction liquid containing the F catalyst is reacted with alcohol as it is to esterify it. The reaction temperature and reaction pressure at the time of esterification are not particularly limited, and are optimized depending on the type of the target ester, but generally, conditions near atmospheric pressure are selected in the temperature range of -40 to 70 ° C. It

The alcohol used for the esterification is not particularly limited, and is determined from a chain or alicyclic monohydric or polyhydric alcohol depending on the desired ester. These alcohols include methanol, ethanol, propanol, isopropanol, butanol, pentanol,
Hexanol, heptanol, octanol, ethylene glycol, propylene glycol, glycerol, sorbitol, neopentyl glycol, trimethylolethane, trimethylolpropane, pentaerythritol and the like are exemplified.

In the present invention, the amount of alcohol added in the esterification step is adjusted so that the acyl fluoride content is 0.1 mol% or more and 5.0 mol% or less, preferably 0.
It is important to allow it to remain in the range of 5 mol% to 3.0 mol%. By leaving unreacted acyl fluoride within this range, the by-product of water can be substantially reduced to zero. When it is attempted to reduce the residual acyl fluoride from the above range, water is easily produced as a by-product, and water accumulates in the system over time, increasing the risk of equipment corrosion. Since a non-esterified hydroxy group is likely to remain in the molecule, product yield and purity are reduced. If a large amount of acyl fluoride is left over the above range in the esterification step, the amount of fluorine-containing compounds that are difficult to separate from the product ester in the recovery step such as distillation of the HF catalyst will increase. It is not a good idea because it will not be possible to obtain a suitable product, and a load will be added to the step of recovering or removing the remaining residual acyl fluoride as an ester. When converting the residual acyl fluoride to an ester, HF is liberated by the reaction, which leads to an increase in wastewater treatment load.

From the esterification reaction liquid thus obtained, H
The F catalyst is separated by distillation or the like, and the separated HF is reused as a catalyst for carbonylation and esterification again. The esterification reaction liquid after the HF catalyst has been separated remains at 0.1 mol% or more and 5 mol% or less with respect to the product ester by adding alcohol to react in the presence of a new esterification catalyst. The acyl fluoride that had been formed reacts with the alcohol and is converted into an ester. This reaction is hereinafter referred to as "post-esterification".

In the post-esterification step, acyl fluoride can be recovered as a product ester by using the same alcohol as in the previous esterification step. Therefore, it is preferable to use the same alcohol as in the previous esterification step. However, the reaction is often difficult to proceed depending on the combination of acyl fluoride and alcohol. In this case, an ester that is easy to esterify and is easy to separate from the product ester is selected without using the same alcohol as in the esterification step. It In general, a lower monohydric alcohol has a higher activity and a higher activity in the order of primary>second> tertiary alcohol in the esterification reaction. The amount of alcohol added may be such that the acyl fluoride is substantially zero, and is usually selected in the range of 1.0 to 20.0 times the equivalent amount of the acyl fluoride.

The catalyst for the post-esterification step is not limited, and a catalyst used for ordinary esterification reaction can be used. For example, inorganic acids such as sulfuric acid, HF, phosphoric acid and hydrochloric acid, alkylsulfonic acids such as methanesulfonic acid and trifluoromethanesulfonic acid, arylisulfonic acids such as P-toluenesulfonic acid, and alkoxy metal catalysts such as tetrabutoxytitanium. Lewis acid catalysts such as boron fluoride ethylate may be mentioned. In the post-esterification step, the reaction is performed with an excess of alcohol, so that water is produced by the dehydration reaction of the alcohol, and thus the esterification catalyst is not usually recovered.
Therefore, since the residual esterification catalyst is discarded by neutralization after the reaction, it is preferable to use an inexpensive catalyst. The amount of the catalyst used is preferably as small as possible within the range where the reaction proceeds sufficiently, and it generally depends on the type of the catalyst, the amount of the acyl fluoride left and the combination of the acyl fluoride and the alcohol, but the reaction solution is generally used. To 0.001% to 2%
Used in the range.

The reaction temperature for the post-esterification is not particularly limited, but if it is 60 ° C. or lower, the reaction rate is slow and it is not practical.
It is desirable that the temperature be at least 60 ° C or higher. The pressure is not particularly limited. The reaction solution thus obtained has the catalyst removed by a conventional method such as neutralization, and is purified if necessary to obtain a product ester.

[0024]

EXAMPLES The present invention will be described in detail with reference to examples. However, the present invention is not limited by the following examples.

Example 1 A stainless steel autoclave having an internal volume of 4.5 liters, which is equipped with a Nak-drive type stirrer, three inlet nozzles at the top and one withdrawal nozzle at the bottom, and whose internal temperature can be controlled by a jacket, is used. An experiment was conducted. (Carbonylation step) First, after replacing the inside of the autoclave with carbon monoxide, anhydrous HF ( ² Kg, 100 mol) was introduced, the mixture was cooled to -20 ° C, and pressurized to 20 Kg / cm ^{2 with} carbon monoxide. While maintaining this temperature and pressure, 561 g (6.7 mol) of 1-hexene was fed from the top of the autoclave over about 60 minutes to synthesize acyl fluoride. 1
-After feeding hexene, stirring was continued for about 20 minutes until no carbon monoxide uptake was observed. The absorption amount of carbon monoxide at this time was 5.2 mol.

(Esterification step) Next, after depressurizing to atmospheric pressure to purge unreacted carbon monoxide, the reaction temperature was set to 0 ° C., and 163 g (5.1 mol) of methanol was added from the upper part of the autoclave for about 15 minutes. And fed for 1 hour to carry out esterification with stirring. When the amount of water in the recovered HF after removing the HF catalyst by distillation was measured, it was 220 ppm
Met. Further, four kinds of the obtained ester were produced by isomerization, but 2.1 mol% of acyl fluoride remained with respect to the total of these.

(Post-esterification step) Obtained ester 1
00 g (containing 0.015 mol of acyl fluoride) was placed in a 200 ml stainless steel container with a lid equipped with a reflux condenser, and 98% sulfuric acid was added with stirring so that the concentration was 0.2 wt% with respect to the ester. Then, the temperature was raised to 70 ° C. When 2 g (0.064 mol) of methanol was added thereto and the mixture was reacted for 30 minutes with stirring, all the acyl fluoride was esterified. The reaction solution was washed with a 2% caustic soda aqueous solution for neutralization, and then purified using a distillation column with 5 theoretical plates to 4
A mixture of seed esters was obtained. When the total fluorine content in this ester was measured, it was 5 ppm or less.

Example 2 The same operation as in Example 1 was carried out using a catalyst (water content 200 ppm) obtained by adding a loss of anhydrous HF to the HF catalyst recovered in Example 1. The residual amount of acyl fluoride in the esterification process is 1.6%, and the water content in the recovered HF is 180 ppm.
The total fluorine content in the product was 5 ppm or less. From this result, it is understood that according to the present invention, accumulation of water in the catalyst recovery system can be prevented and an ester having a low total fluorine content can be stably produced.

Comparative Example 1 Without post-esterification in Example 1, the esterification reaction liquid was washed with 2% aqueous caustic soda solution for neutralization and purified by distillation to obtain a mixture of 4 kinds of esters. Acyl fluoride was not detected in this ester, but the total fluorine content was as high as 860 ppm. The total fluorine content was high because a fluorine-containing compound that could not be separated by distillation was by-produced during the distillation from the acyl fluoride remaining at the time of esterification.

Comparative Example 2 In Example 1, 173 methanol was used in the esterification step.
g (5.4 mol) and no post-esterification was carried out. As a result, the same ester having a total fluorine content of 5 ppm or less as in Example 1 was obtained, but the amount of acyl fluoride remaining during esterification was lost (0.02% or less).
Unreacted alcohol caused a dehydration reaction, and the recovered HF catalyst contained 950 ppm of water.

Comparative Example 3 The same operation as in Comparative Example 2 was carried out using a catalyst (water content: 780 ppm) obtained by adding a loss of anhydrous HF to the HF catalyst recovered in Comparative Example 2. As a result, the total fluorine content in the product is 5
It was as low as ppm, but the water content in the recovered HF was 1330 ppm.
Up. It can be seen that water is accumulated in the catalyst recovery system when the alcohol is increased and the post-esterification is not performed.

Comparative Example 4 In Example 1, 140% of methanol in the esterification step was added.
g (4.4 mol), and the amount of methanol added in the post-esterification step was 12 g (0.375 mol). As a result,
The water content in the recovered HF was as low as 200 ppm, but the amount of acyl fluoride remaining in the esterification step was large (12%). No residual acyl fluoride was detected in the post-esterification treatment, but the total fluorine content of the product ester was reduced to only 100 ppm. This is because the amount of residual acyl fluoride at the time of esterification was large.
This is because a fluorine-containing compound that cannot be removed by post-esterification or distillation was by-produced during the recovery and distillation of the catalyst.

Example 3 1000 g of cyclododecene diluted with 600 g of heptane
(6.0 mol) using 2 kg of HF catalyst containing 500 ppm of water, reaction temperature -20 ° C, carbon monoxide pressure 2
Carbonylation at 0 Kg / cm ² revealed a carbon monoxide absorption of 3.2 mol. 141.6 g (3.0%) of ethanol was added to the reaction solution containing the obtained acyl fluoride.
(8 mol) was added for esterification, and 3.9 mol% of acyl fluoride remained with respect to the ester. The water content in the HF catalyst recovered by distillation was 230 p
It was decreasing to pm. To 100 g of crude ester (containing 0.01 mol of acyl fluoride) obtained by distilling off heptane, 0.7 wt% of paratoluenesulfonic acid was added with stirring, and the temperature was raised to 85 ° C., and ethanol 4. 6 g
When (0.1 mol) was added and post-esterification was carried out for 30 minutes under stirring, all the acyl fluoride was esterified. After washing the reaction solution with 2% aqueous sodium hydroxide solution for neutralization
A low-boiling fraction and a high-boiling fraction were separated by distillation to obtain an ethyl cyclododecacarboxylate fraction. When the total fluorine content in this ester was measured, it was 25 ppm.

Comparative Example 5 In Example 1, the post-esterification was not carried out, the crude ester was washed with a 2% aqueous solution of caustic soda to neutralize it, and then the low-boiling component and the high-boiling component were separated by distillation to obtain cyclododecacarboxylic acid. The ethyl fraction was obtained. When the total fluorine content in this ester was measured, it was 420 ppm.

[0035]

As is clear from the above examples, in the method for producing a carboxylic acid ester of the present invention, HF having a low water content is used.
Is recovered, and a product with extremely low fluorine content is obtained. Therefore, in the method of the present invention, a high-performance HF catalyst can be recycled and used while avoiding the risk of water formation, and the ester containing no fluorine-containing impurities in the product can be easily and stably produced. According to the present invention, a carboxylic acid ester can be industrially extremely advantageously produced from an olefin, carbon monoxide and an alcohol, and the industrial significance of the present invention is great.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication C07C 69/30 C07C 69/30 69/33 69/33 69/74 69/74 A 69/75 69 / 75 Z // C07B 61/00 300 C07B 61/00 300

Claims (1)

[Claims] 1. A method of producing an acyl fluoride by reacting an olefin with carbon monoxide in the presence of HF, and reacting the obtained acyl fluoride with an alcohol to produce an ester, wherein the residual acyl fluoride is an ester. To 0.1 mol% or more and 5.0 mol% or less, and after separating the HF catalyst, an alcohol is added to esterify the residual acyl fluoride. Method for producing acid ester.