JP4106494B2 - Method for producing carboxylic acid ester using HF catalyst - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a carboxylic acid ester from an olefin, carbon monoxide and alcohol using an HF catalyst.
[0002]
[Prior art]
As a method for producing a carboxylic acid ester from an olefin using a strong acid catalyst, an olefin is carbonylated with carbon monoxide by a so-called Koch reaction to generate an acyl cation, and then reacted with water to obtain a carboxylic acid. A method of reacting with an alcohol to obtain a carboxylic acid ester is known.
[0003]
Examples of the Koch reaction include production examples of pivalic acid from isobutene and C _{6 to} C ₁₁ carboxylic acid from C _{5 to} C ₁₀ olefins, and secondary and tertiary carboxylic acids are obtained by this reaction.
As a catalyst for carboxylic acid synthesis by the Koch reaction, an inorganic acid such as sulfuric acid, HF, phosphoric acid or the like, or in combination with BF ₃ or SbF ₅ , for example, HF · SbF ₅ or H ₃ PO ₄ · BF ₃ However, since the product and the catalyst phase are separated by adding water in the latter half of the reaction, there is a problem that the catalyst diluted with water or the like must be regenerated.
[0004]
In order to produce an ester from a carboxylic acid and an alcohol, for example, inorganic acids such as sulfuric acid, HF, phosphoric acid and hydrochloric acid, alkylsulfonic acids such as methanesulfonic acid and trifluoromethanesulfonic acid, and arylsulfones such as P-toluenesulfonic acid. The reaction is carried out while removing water under a catalyst such as an acid, an alkoxy metal such as tetrabutoxytitanium, or a Lewis acid such as boron fluoride ethylate. However, in the case of a secondary or tertiary branched carboxylic acid, the esterification reaction is slow. It has a difficult problem to implement industrially.
[0005]
In contrast, US Pat. No. 5,463,093 discloses a method of synthesizing an acyl fluoride by carbonylation of an olefin using HF as an acid catalyst and reacting the acyl fluoride with an alcohol in the presence of HF to obtain an ester. Are listed. In this method, the catalyst can be easily recovered, the carbonylation reaction and the esterification reaction proceed very easily, and an ester having a branched acid structure can be easily obtained.
[0006]
[Problems to be solved by the invention]
The method using the HF catalyst of the above cited patent is an excellent method because an ester can be obtained directly without separating the carboxylic acid and the catalyst can be easily recovered. However, carbonylation and esterification are carried out in the presence of HF. Therefore, the stoichiometric control of the acyl fluoride obtained by carbonylation and the alcohol is extremely important.
That is, when an excessive amount of alcohol is added to the acyl fluoride, unreacted alcohol causes a dehydration reaction to generate water in the system. In particular, when a lower monohydric alcohol is used, care must be taken because this dehydration reaction proceeds easily. Since water and HF form an azeotropic composition and are difficult to separate, water accumulates in the recovered HF within a short period of time and adversely affects the reaction, leading to significant corrosion of equipment materials, Stable operation becomes difficult.
[0007]
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 an operation such as simple neutralization, so it remains in a later step together with the product ester, and is a fluorine-containing compound that is difficult to separate from the product ester under heating conditions such as distillation operation. This is mixed with the product as an impurity and deteriorates the product purity.
[0008]
As described above, in the method using an HF catalyst, the stoichiometric amount is accurately controlled from the beginning of the reaction, and the conditions under which water and by-products are not generated in the system and no acyl fluoride is left stably are stably obtained. Obtaining it is extremely important for industrial implementation, but such an operation that does not allow errors is practically difficult, and therefore it often causes equipment corrosion problems and fluorine-containing impurities in the product. There is a problem of mixing.
[0009]
An object of the present invention is to avoid generation of water due to dehydration of unreacted alcohol and trouble due to residual acyl fluoride in a method for producing a carboxylic acid ester from olefin, carbon monoxide and alcohol using an HF catalyst, The object is to provide a method for stably producing a high-quality carboxylic acid ester.
[0010]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems in the method for producing an ester using an HF catalyst, the inventors have found that the acyl fluoride is 0.1% relative to the produced ester in the esterification step after carbonylation. An ester is prepared by controlling the amount of alcohol added so as to remain at ˜5.0 mol%, and after separating the HF catalyst, the remaining acyl fluoride is esterified with alcohol in the presence of a new catalyst. The inventors have found that it is possible to use a high-performance HF catalyst while avoiding the risk of water generation, and that it is possible to stably produce an ester containing no fluorine-containing impurities in the product, and the present invention has been achieved.
[0011]
That is, the present invention relates to a method for producing an acyl fluoride by reacting an olefin and carbon monoxide in the presence of HF, and producing an ester by reacting the obtained acyl fluoride with an alcohol. Esterification is performed in a range of 0.1 mol% to 5.0 mol% with respect to the ester, and after separating the HF catalyst, alcohol is added to esterify the remaining acyl fluoride. This is a method for producing a carboxylic acid ester.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The raw material olefin used in the present invention is not particularly limited, and is selected from an aliphatic chain olefin, an alicyclic olefin, and the like depending on a target product. Examples of these olefins include propylene, butylene, isobutylene, pentene, hexene, octene, cyclohexene, and cyclododecene.
[0013]
The olefin carbonylation reaction in which acyl fluoride is produced by reacting an olefin with carbon monoxide is carried out in the presence of an HF catalyst and under pressure of carbon monoxide. At this time, an inert gas such as nitrogen or methane may be contained, but the carbon monoxide partial pressure is in the range of 0.5 to 5 MPa, preferably 1 to 3 MPa. When the carbon monoxide partial pressure is too low, the carbonylation reaction does not proceed sufficiently, and the polymerization reaction occurs simultaneously, leading to a decrease in yield. Further, even if the carbon monoxide partial pressure is higher than this range, no merit in reaction is obtained, and problems such as the need for a high-pressure apparatus are caused.
[0014]
A substantially anhydrous HF catalyst is used in the carbonylation reaction. The usage-amount of HF is 3-25 times mole with respect to raw material olefin, Preferably it is 5-20 times mole. When 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, causing a polymerization reaction and a decrease in yield. Even if it is used, the improvement effect such as the yield is small, the cost for separating HF is increased, and the volumetric efficiency of the apparatus is also lowered.
[0015]
The reaction temperature for carbonylation is not particularly limited, and the conditions for the highest yield may be appropriately selected according to the type of olefin. However, the carbonylation of olefins using an HF catalyst is performed at a temperature range of -40 ° C to 100 ° C. It is common to implement.
The form of the carbonylation reaction is not particularly limited, and any method such as a semi-continuous method or a continuous method may be used.
[0016]
In the carbonylation reaction, a raw material olefin and a soluble and inert solvent, for example, saturated aliphatic hydrocarbons such as hexane, heptane, decane, and 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 apparatus is reduced, and the energy intensity for separation is deteriorated. Presence / absence of use and amount used are appropriately selected.
[0017]
The acyl fluoride prepared by the carbonylation reaction is subsequently reacted with alcohol to give an ester. At this time, the acyl fluoride may be once separated and then esterified with an alcohol again in the presence of an HF catalyst. Usually, a method of esterifying by reacting the carbonylation reaction solution containing the HF catalyst with the alcohol as it is is employed.
There are no particular restrictions on the reaction temperature and reaction pressure during esterification, and it is optimized according to the type of target ester. In general, conditions near atmospheric pressure are selected in the temperature range of -40 to 70 ° C. The
[0018]
The alcohol used for esterification is not particularly limited, and is determined from a chain or alicyclic monohydric or polyhydric alcohol depending on the target ester. These alcohols include methanol, ethanol, propanol, isopropanol, butanol, pentanol, hexanol, heptanol, octanol, ethylene glycol, propylene glycol, glycerol, sorbitol, neopentyl glycol, trimethylolethane, trimethylolpropane, pentaerythritol, etc. Illustrated.
[0019]
In the present invention, the amount of alcohol added in the esterification step is adjusted so that the acyl fluoride is 0.1 mol% or more and 5.0 mol% or less, preferably 0.5 mol% or more and 3.0 mol% relative to the ester. It is important to make it remain in the range. By leaving unreacted acyl fluoride within this range, water by-product can be made substantially zero.
If the residual acyl fluoride is reduced from the above range, water is easily produced as a by-product, moisture accumulates in the system over time, and the risk of equipment corrosion increases. Since the hydroxy group which is not esterified easily remains in the molecule, the product yield and purity are lowered.
When a large amount of acyl fluoride is left in the esterification process exceeding the above range, the amount of by-product of the fluorine-containing compound that is difficult to separate from the product ester increases in the recovery process such as by distillation of the HF catalyst. This is not a good idea because it results in a burden on the process of recovering or removing the next remaining acyl fluoride as an ester. When converting the remaining acyl fluoride into an ester, HF is liberated by the reaction, leading to an increase in wastewater treatment load.
[0020]
The HF catalyst is separated from the esterification reaction solution thus obtained by distillation or the like, and the separated HF is reused again as a catalyst for carbonylation and esterification.
The esterification reaction liquid after separation of the HF catalyst remains in a range of 0.1 mol% to 5 mol% with respect to the product ester by reacting with an alcohol in the presence of a new esterification catalyst. The acyl fluoride that has been reacted with alcohol is converted to an ester. This reaction is hereinafter referred to as “post-esterification”.
[0021]
In the post-esterification step, if the same alcohol as that used in the previous esterification step is used, the acyl fluoride can be recovered as a product ester. Therefore, it is preferable to use the same alcohol as that used in the previous esterification step. However, depending on the combination of acyl fluoride and alcohol, the reaction is often difficult to proceed. In this case, an ester that is easily esterified and easily separated from the product ester is selected without using the same alcohol as in the esterification step. The
In general, lower monohydric alcohols are more active and are more active against esterification reactions in the order of first>second> tertiary alcohol.
The addition amount of alcohol should just be added so that an acyl fluoride may become substantially zero, and the range of 1.0-20.0 times equivalent with respect to an acyl fluoride is normally selected.
[0022]
There is no restriction | limiting in the catalyst of a post-esterification process, The catalyst used for normal 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 tetrabutoxy titanium, Examples include Lewis acid catalysts such as boron fluoride ethylate.
In the post-esterification step, the reaction is carried out with an excess of alcohol, so that water is produced by the dehydration reaction of the alcohol, so that usually the esterification catalyst is not recovered. Therefore, since the remaining esterification catalyst is discarded by neutralization after the reaction, it is preferable to use an inexpensive catalyst. The amount of catalyst to be used is preferably as small as possible within the range in which the reaction proceeds sufficiently, and generally depends on the type of catalyst, the amount of acyl fluoride remaining and the combination of acyl fluoride and alcohol. Is used in the range of 0.001% to 2%.
[0023]
The reaction temperature for the post-esterification is not particularly limited. However, the reaction rate is slow and impractical at 60 ° C. or lower, so it is desirable that the reaction temperature be at least 60 ° C. or higher. The pressure is not particularly limited.
From the reaction solution thus obtained, the catalyst is removed by a conventional method such as neutralization and the product is purified as necessary to obtain a product ester.
[0024]
【Example】
Next, the present invention will be described specifically by way of examples. However, the present invention is not limited by the following examples.
[0025]
Example 1
An experiment was conducted using a stainless steel autoclave having a volume of 4.5 liters, which was equipped with a Nack drive type stirrer, three inlet nozzles at the top, and one extraction nozzle at the bottom, and the internal temperature could be controlled by a jacket.
(Carbonation step)
First, after replacing the inside of the autoclave with carbon monoxide, anhydrous HF 2 kg (100 mol) was introduced, cooled to −20 ° C., and pressurized with carbon monoxide to 20 kg / cm ² .
While maintaining this temperature and pressure, 561 g (6.7 mol) of 1-hexene was supplied over about 60 minutes from the top of the autoclave to synthesize acyl fluoride. After feeding 1-hexene, stirring was continued for about 20 minutes until no absorption of carbon monoxide was observed. At this time, the amount of carbon monoxide absorbed was 5.2 mol.
[0026]
(Esterification process)
Next, after dropping to normal pressure and purging unreacted carbon monoxide, the reaction temperature was set to 0 ° C., and 163 g (5.1 mol) of methanol was supplied from the upper part of the autoclave over about 15 minutes, followed by stirring for 1 hour. The esterification was performed below.
The amount of water in the HF recovered by removing the HF catalyst by distillation was 220 ppm. In addition, although four types of the obtained esters were produced by isomerization, 2.1 mol% of acyl fluoride remained based on the total of these esters.
[0027]
(Post-esterification process)
100 g of the obtained ester (containing 0.015 mol of acyl fluoride) is put into a 200 ml lidded stainless steel vessel equipped with a reflux condenser, and stirred so that 98% sulfuric acid is 0.2 wt% with respect to the ester. After adding below, the temperature was raised to 70 ° C. When 2 g (0.064 mol) of methanol was added to this and reacted with stirring for 30 minutes, all the acyl fluoride was esterified.
The reaction solution was washed with a 2% aqueous solution of caustic soda in neutralized water and purified using a distillation column having 5 theoretical plates to obtain a mixture of 4 types of esters. When the total fluorine content in this ester was measured, it was 5 ppm or less.
[0028]
Example 2
The same operation as in Example 1 was performed 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 step was 1.6%, the water content in the recovered HF was 180 ppm, and the total fluorine content in the product was 5 ppm or less. From this result, it can be seen that according to the present invention, accumulation of moisture in the catalyst recovery system is prevented, and an ester having a low total fluorine content can be produced stably.
[0029]
Comparative Example 1
Without post-esterification in Example 1, the esterification reaction solution was washed with 2% aqueous sodium hydroxide solution in neutralized water and purified by distillation to obtain a mixture of four esters.
No acyl fluoride was detected in this ester, but the total fluorine content was as high as 860 ppm. The reason why the total fluorine content was high was that a fluorine-containing compound that could not be separated by distillation was by-produced during distillation from the acyl fluoride remaining at the time of esterification.
[0030]
Comparative Example 2
In Example 1, 173 g (5.4 mol) of methanol in the esterification step was used, and post-esterification was not performed.
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 at the time of esterification disappeared (0.02% or less), so that the unreacted alcohol caused a dehydration reaction. The recovered HF catalyst contained 950 ppm of water.
[0031]
Comparative Example 3
The same operation as in Comparative Example 2 was performed using a catalyst obtained by adding a loss of anhydrous HF to the HF catalyst recovered in Comparative Example 2 (water content of 780 ppm).
As a result, the total fluorine content in the product was as low as 5 ppm, but the water content in the recovered HF increased to 1330 ppm. It can be seen that when the alcohol is increased and no post-esterification is performed, moisture accumulates in the catalyst recovery system.
[0032]
Comparative Example 4
In Example 1, the amount of methanol in the esterification step was 140 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 increased (12%). Residual acyl fluoride was not detected in the post-esterification treatment, but the total fluorine content of the product ester decreased only to 100 ppm.
This is because the amount of residual acyl fluoride at the time of esterification was large, and a fluorine-containing compound that cannot be removed by post-esterification or distillation was produced as a by-product during the recovery distillation of the HF catalyst.
[0033]
Example 3
Carbonyl monoxide was obtained by carbonizing 1000 g (6.0 mol) of cyclododecene diluted with 600 g of heptane at a reaction temperature of −20 ° C. and a carbon monoxide pressure of 20 kg / cm ² using 2 kg of HF catalyst containing 500 ppm of water. The absorption amount of was 3.2 mol.
When esterification was performed by adding 141.6 g (3.08 mol) of ethanol to the reaction solution containing the acyl fluoride obtained, 3.9 mol% of acyl fluoride remained with respect to the ester. . The water in the HF catalyst recovered by distillation was reduced to 230 ppm.
To 100 g of crude ester obtained by distilling off heptane (containing 0.01 mol of acyl fluoride), 0.7 wt% of paratoluenesulfonic acid was added with stirring, the temperature was raised to 85 ° C., and ethanol 4. When 6 g (0.1 mol) was added and esterification was performed for 30 minutes with stirring, all the acyl fluoride was esterified.
The reaction solution was washed with a 2% aqueous solution of caustic soda in neutralized water, and then the low and high boiling components were separated by distillation to obtain an ethyl cyclododecacarboxylate fraction. The total fluorine content in this ester was measured and found to be 25 ppm.
[0034]
Comparative Example 5
In Example 1, the post-esterification was not performed, and the crude ester was washed with a 2% aqueous solution of caustic soda in neutralized water, and then the low and high boiling points were separated by distillation to obtain an ethyl cyclododecacarboxylate fraction. . When the total fluorine content in this ester was measured, it was 420 ppm.
[0035]
【The invention's effect】
As is clear from the above examples, the carboxylic acid ester production method of the present invention recovers HF with a low water content and provides a product with a very low fluorine content.
Therefore, in the method of the present invention, it is possible to circulate and use a high-performance HF catalyst while avoiding the risk of water generation, and it is possible to easily and stably produce an ester containing no fluorine-containing impurities in the product.
According to the present invention, a carboxylic acid ester can be produced industrially from olefin, carbon monoxide, and alcohol very advantageously, and the industrial significance of the present invention is great.

Claims (4)

In the method of producing an acyl fluoride by reacting an olefin and carbon monoxide in the presence of substantially anhydrous HF, and reacting the resulting acyl fluoride with an alcohol to produce an ester, the remaining acyl fluoride is an ester. The esterification reaction liquid after the esterification was performed so as to be 0.1 mol% or more and 5.0 mol% or less, and the substantially anhydrous HF catalyst was separated by distillation , and then the HF catalyst was separated A method for producing a carboxylic acid ester, wherein an alcohol is added to the residual ester to esterify the remaining acyl fluoride to obtain a high-quality carboxylic acid ester . The method for producing a carboxylic acid ester according to claim 1, wherein the total fluorine content of the high-quality carboxylic acid ester is 25 ppm or less. The method for producing a carboxylic acid ester according to claim 1 or 2, wherein the separated substantially anhydrous HF catalyst is reused again for the production of acyl fluoride and the production of an ester. The method for producing a carboxylic acid ester according to any one of claims 1 to 3, wherein the substantially anhydrous HF catalyst is an HF catalyst containing water of 500 ppm or less.