JPS5938936B2 - Method for producing acrylic ester or methacrylic ester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing higher acrylates or higher methacrylates by transesterification of lower alkyl esters of acrylic acid or methacrylic acid with higher alcohols.

It is known to produce higher acrylates or higher methacrylates by transesterification.

Catalysts commonly used at this time include acids such as sulfuric acid and para-toluenesulfonic acid, and alkali metal alcoholades.
Alcolades such as aluminum Alcolade and titanium Alcolade are known. however,
These catalysts have various problems.

That is, when an acid catalyst such as sulfuric acid is used, the reaction rate is slow and the production of polymers increases. Further, when a primary alcohol is used as a raw material, ether is produced, and when a secondary alcohol is used as a raw material, it is partially dehydrated to produce an olefin. In addition, there are other drawbacks such as corrosion of the equipment.
On the other hand, when an alkali metal alcoholade such as sodium methylate is used as a catalyst, it has the disadvantage of causing undesirable side reactions such as by-products of addition reactants, by-products of alkali metal salts, and anionic polymerization. In addition, the catalyst deactivates over time, so it must be added continuously, and the catalyst deactivates by reacting with moisture in the reaction system, so complicated operations such as sufficient dehydration in advance are necessary. I need. Furthermore, the catalyst must be removed by washing with water to prevent polymerization before the obtained product is taken out by distillation or the like, which makes the process complicated and further requires a wastewater treatment process.
In addition, in the case of aluminum and titanium alcolades, in addition to the drawbacks of deactivation over time like alkali metal alcolades and deactivation due to the influence of moisture, their catalytic activity is lower than that of alkali metal alcolade catalysts. is low, and the amount of catalyst must be increased or the reaction time must be lengthened.

Therefore, no matter which catalyst is used, there are various industrial problems. The present inventors have fully considered these various problems and conducted intensive research to find a completely new catalyst. As a result, the present inventors have found that a catalyst for transesterifying lower alkyl esters of acrylic acid or methacrylic acid with higher alcohols has been developed. As a result, they discovered that a β-diketone chelate compound of iron has a catalytic effect on this reaction and also produces good results, leading to the completion of the present invention.

That is, the present invention is a transesterification process characterized in that a β-diketone chelate compound of iron is used as a catalyst when producing a higher acrylate or higher methacrylate by a transesterification reaction between a lower alkyl ester of acrylic acid or methacrylic acid and a higher alcohol. It is the law.

The raw material lower alkyl ester of acrylic acid or methacrylic acid used in the present invention is generally a lower alkyl ester having fewer carbon atoms than the raw material alcohol, and is preferably a methyl or ethyl ester.

The raw material higher alcohol used in the present invention has a higher boiling point than the alcohol produced by the transesterification reaction, and alcohols having 4 or more carbon atoms are particularly preferred.

Specific examples include n-, i-, t-butanol, 2-ethylhexanol, lauryl alcohol, stearyl alcohol, cyclohexyl alcohol, and the like.

These alcohols can be used as they are without dehydration.
Further, as the iron β-diketone chelate compound used in the present invention, iron acetylacetonate, 2,4-hexanedionate, 3,5-heptanedionate, 3-phenylacetylacetonate, 2,2, Examples include 6,6-tetramethyl 3,5-heptanedionate, 1,1,1-trifluoro2,4pentanedionate,
According to the present invention, iron acetylacetonate is the most preferred when considering price as well as catalytic activity.

In this reaction, an inert solvent can be used to form an azeotrope with the alcohol produced in the transesterification reaction. Examples include hexane, benzene, and cyclohexane. This reaction is preferably carried out in the presence of a polymerization inhibitor since it involves handling substances that are generally prone to polymerization.

Therefore, hydroquinone, hydroquinone monomethyl ether, di-t-butylcatechol, phenothiazine, p
- Phenylene diamine, methylene blue, etc. are typically used. In the present invention, the molar ratio of the raw material lower alkyl ester of acrylic acid or methacrylic acid to the higher alcohol is 1.0 to 10 mol relative to the alcohol, preferably 1.1 to 5.0 mol. It is.

Of course, it may be outside this range, but it will be disadvantageous when economic efficiency is considered from an industrial standpoint. The catalyst may be added in its entirety from the beginning, added at regular intervals, or added continuously; however, from an operational point of view, it is preferable to charge the entire amount from the beginning.

Although the amount used can vary considerably, it is generally from 0.0001 to 1.0 mol, preferably from 0.0005 to 0.05 mol, based on the raw material higher alcohol.

It is desirable that the transesterification reaction be carried out at a temperature of 30°C to 150°C, preferably 60°C to 140°C. Moreover, it can also be carried out under reduced pressure if necessary. The present invention will be specifically explained below with reference to Examples and Reference Examples. However, in Examples and Reference Examples, unreacted raw materials and reaction products were determined by gas chromatography, and the conversion rate of raw alcohol and the yield of the target ester were expressed based on the higher alcohol raw material.

That is, it was calculated using equations (1) and (2). Example 1 74.1f (1.0 mol) of n-butanol was added to a 11-content flask equipped with a stirrer, thermometer, and fractionator.
0.71 f (0.002 mol) of iron acetylacetonate and 0.287 mol of hydroquinone monomethyl ether were added, and the mixture was heated and stirred.

A mixture of methanol and methyl methacrylate is obtained from the fractionator section, which is azeotropically produced at a reflux ratio of 2 to 1.
The reaction proceeded continuously by taking out the solution at zero. The reaction is 3
Time passed. During this period, the tower top temperature was 65°C to 70°C, and the pot temperature was 104°C to 130°C. The reaction results obtained were n-
The conversion rate of butanol was 99.4%, and the yield of n-butyl methacrylate was 97.9%. When this reaction solution was directly distilled, 1367 fractions having a temperature of 80 m, 71 LHg and 93 to 94°C were obtained. This was determined to be n-butyl methacrylate by gas chromatography, and the yield was 95%.
．． It was 6%. Therefore, it is clear that distillation can be carried out as is without any steps such as washing with water. Example 2 Using the apparatus described in Example 1, n-butanol was heated to 74.
17 (1.0 mol), methyl acrylate 172.27
(2.0 mol), iron acetylacetonate 1,06y (
0.003 mol) and 0.2f7 of hydroquinone monomethyl ether were added, and the reaction proceeded in the same manner as in Example 1.

The reaction lasted for 3 hours. The results obtained were a conversion rate of n-butanol of 99.0% and a yield of n-butyl acrylate of 98%.
．． It was 0%. Further, when this ester was distilled in the same manner as in Example 1, it was recovered with a yield of 971%. Example 3 Using the apparatus described in Example 1, 130.2y (1.0 mol) of 2-ethylhexanol, 250.27 (2.5 mol) of methyl methacrylate, and 0.717 (0.7 mol) of iron acetylacetonate were prepared. 0.002 mol) and 0.28 y of hydroquinone monomethyl ether were added, and the reaction was proceeded in the same manner as in Example 1.

The reaction lasted for 3 hours. The results obtained were a conversion rate of 2-ethylhexanol of 99.3% and a yield of 2-ethylhexyl methacrylate of 98.5%. Further, when this ester was distilled in the same manner as in Example 1, it was recovered with a yield of 97.7%. In all of the reactions described in Examples 1 to 3, no dehydration operation was performed before the reaction, and 0.005 to 0.007 mol of water was mixed per 1 mol of raw material higher alcohol. had no effect, and all achieved sufficiently high results.

Therefore, it is clear that the dehydration operation before the reaction can be omitted, and there is no by-product of acrylic acid or methacrylic acid due to hydrolysis, which has a remarkable effect on simplifying the reaction process. Reference Example 1 In the apparatus described in Example 1, n-butanol 74.17 (1
．． 0 mol), methyl methacrylate 250.2f (2.
5 mol), hydroquinone monomethyl ether 0.25
7. 2.45 f (0.025 mol) of concentrated sulfuric acid was added thereto, and the reaction proceeded in the same manner as in Example 1.

The reaction lasted for 6 hours. The reaction results obtained were a conversion rate of n-butanol of 96.5% and a yield of n-butyl methacrylate of 91.2%. However, gas chromatography revealed that high-boiling by-products were present, and methacrylic acid was 0.004 mol (26 mol based on n-butyl methacrylate).
60 ppm) was produced as a by-product. When this reaction solution was directly distilled in the same manner as in Example 1, the methyl methacrylate fraction polymerized after completion of distillation, and butyl methacrylate could not be recovered.

After the reaction was completed, the reaction solution was washed with 507 10% caustic soda water, and this process was repeated twice.

Thereafter, distillation was performed in the same manner as in Example 1, and 1227 butyl methacrylate fractions were obtained. Therefore, the yield is 8
It remained at 5.8%. Reference Example 2 In a flask with 11 contents equipped with a stirrer, a thermometer, and a fractionating column, n-butanol 74.17 (1.0 mol), methyl methacrylate 250.27 (2.5 mol), and n-hexane 187 y (2 mol) were added. 0.18 mol) and 0.177 mol of hydroquinone monomethyl ether were added, and the mixture was heated and stirred for one hour under total reflux to remove water from the reaction system.

As a result, the amount of water in the reaction solution was 0.001 mol. Thereafter, 0.0035 mol of sodium methylate was added as a catalyst, and the mixture was heated and stirred.

Claims (1)

[Scope of Claims] 1. The invention is characterized in that an iron β-diketone chelate compound is used as a catalyst when producing a higher acrylate or higher methacrylate through a transesterification reaction between a lower alkyl ester of acrylic acid or methacrylic acid and a higher alcohol. A method for producing higher acrylate or higher methacrylate. 2 The amount of catalyst used is 0.0001 per higher alcohol.
The manufacturing method according to claim 1, characterized in that the amount is 1.0 mol to 1.0 mol. 3. The production method according to claim 1, which uses iron acetylacetonate as a catalyst.