JP2003292473A - Method for producing methacrylic ester - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a methacrylic ester. <P>SOLUTION: The method for producing the methacrylic ester which is an important raw material for a synthetic resin, with good reproducibility by regulating pH in preparation of a gold catalyst, the method producing the methacrylic ester by reacting methacrolein, an alcohol and oxygen in the presence of a gold catalyst obtained by supporting chloroauric acid on a carrier, reducing with a reducing agent and then regulating the pH at 5-7, methanol is preferred as the alcohol and silica is preferred as the carrier. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a methacrylic acid ester, which is important as a raw material for synthetic resins.

[0002]

2. Description of the Related Art Conventionally, methacrolein and alcohol are
A method for producing a methacrylic acid ester by reacting palladium with a base metal such as lead, mercury or thallium in the presence of an intermetallic compound catalyst is disclosed (Japanese Patent Publication No. 57-358).
No. 56). However, in order to reproduce high performance, it was necessary to precisely adjust an intermetallic compound of palladium and a base metal such as lead, mercury or thallium as described in JP-A 09-29096 (catalyst). X-ray diffraction angle of 3
(A catalyst that satisfies the range of 8.55 to 38.70 and the composition ratio of palladium to lead in the catalyst Pd / Pb = 3 / 0.7 to 3 / 1.3 is required). Therefore, there has been a demand for the development of a single metal catalyst which is easier to prepare a catalyst, and a method using a gold catalyst has been disclosed so far (Japanese Patent Laid-Open No. 2000-1).
54164).

[0003]

However, depending on the conditions for adjusting the gold catalyst, side reactions such as acetalization or addition of alcohol to the olefin site proceed, and it cannot be said that the method is necessarily sufficient for industrial production. It was a thing.

[0004]

The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems, and as a result, by controlling the pH when adjusting the gold catalyst, the methacrylic acid ester can be produced more reproducibly. They have found that they can be manufactured and have reached the present invention.

That is, the present invention is characterized by supporting chloroauric acid on a carrier, reducing it with a reducing agent, and then reacting methacrolein, alcohol, and oxygen in the presence of a gold catalyst adjusted to pH 5 to 7. A method for producing a methacrylic acid ester is provided.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The gold catalyst preparation method consists of the following 5 steps. Gold chloride loading step, reduction step, pH adjustment step, filtration step, drying step.

The gold chloride supporting step is carried out by adding a carrier to an aqueous solution of chloroauric acid, which is a commercially available product, and stirring it. Examples of the carrier generally include silica, alumina, silica-alumina, zirconia, titania, zeolite, activated carbon and the like, but silica is preferable. The amount used is usually in the range of 1 to 1000 mol times, preferably 10 to 100 mol times, relative to chloroauric acid. The pH is not particularly limited, but is preferably in the range of 1-9. Temperature is usually 5
Is in the range of -100 ° C, preferably 20-80 ° C. Water is usually used as the solvent, but preferably,
Ion-exchanged water may be used. The amount of water used is not particularly limited, but it is preferable to use water having a solubility higher than that of chloroauric acid.

The reducing step is carried out by adding a reducing agent to the slurry obtained in the chloroauric acid supporting step and then stirring the mixture. As the reducing agent, usually a reducing agent such as formalin (formaldehyde aqueous solution), hydrazine, sodium borohydride can be used, but formalin is preferable. The formaldehyde concentration in formalin is not particularly limited, but a 37% product, which is easily commercially available, is preferably used. The amount used is usually in the range of 0.1 to 100 mol times, preferably 1 to 50 mol times, relative to chloroauric acid. The pH is not particularly limited, but is preferably in the range of 1-9. Temperature is usually 5
Is in the range of -100 ° C, preferably 20-80 ° C.

The pH adjusting step is carried out by adjusting the pH of the slurry obtained in the reducing step with an alkali or an acid. The pH is usually adjusted in the range of 5 to 7, preferably in the range of 5.5 to 6.5. However, when the pH is controlled within the control value in the step of or, the pH adjusting step can be omitted. Examples of the alkali include alkali metal hydroxides or carbonates such as sodium hydroxide, potassium hydroxide, sodium hydrogen carbonate, sodium carbonate, potassium hydrogen carbonate and potassium carbonate, or magnesium hydroxide, calcium hydroxide, magnesium carbonate and carbonate. Examples thereof include alkaline earth metal hydroxides or carbonates such as calcium, but sodium hydroxide is preferable. The alkali may be used either as an aqueous solution or as a powder, but it is preferably used as an aqueous solution.
Examples of the acid generally include inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid and nitric acid. The temperature of the pH adjusting step is usually 5 to 100
C., preferably in the range of 20 to 50.degree.

The filtration step is a step of separating the catalyst from the aqueous solution by filtering the slurry obtained in the pH adjusting step. The filtration method is usually vacuum filtration,
It is pressure filtration, centrifuge filtration or the like and is not particularly limited. The temperature is usually in the range of 5 to 100 ° C, preferably 20 to 80 ° C. The cake thus obtained may not be washed, but it is preferable to wash it with water. The amount of the washing solution used is usually 0.1 to 100 times by weight, preferably 1 to 10 times by weight, the amount of the carrier.

The drying step is a step of removing water from the cake obtained by the filtration step. The method includes, but is not particularly limited to, a method under reduced pressure or a method under normal pressure nitrogen stream. The temperature is usually 5 to 1000
C., preferably in the range of 20 to 500.degree.

The amount of gold supported on the catalyst thus obtained is usually 0.01 to 20% by weight, preferably 0.1.
It is in the range of 10% by weight.

Next, a method for producing a methacrylic acid ester by reacting methacrolein, alcohol, and oxygen using the above gold-supported catalyst will be described.

Methacrolein can usually be produced by oxidizing isobutene, but is not limited to this method. When it is produced by a method of oxidizing isobutene, it becomes a mixture with methacrylic acid, but it is not necessary to remove methacrylic acid and it can be used as it is for the reaction.

The amount of gold catalyst is usually 0.001 mol% or more, preferably 0.01 mol% or more, based on methacrolein. The upper limit is not particularly limited, but is usually 10 mol% or less for economic reasons.

The reaction system may be either a batch system or a continuous system.

The alcohol is usually methanol,
Ethanol, n-propanol, isopropanol, n
-Butanol, sec-butanol, ter-butanol and the like can be mentioned, and preferably methanol can be mentioned. The amount of alcohol used is usually 0.01 to 100 mol times, preferably 0.1 to 50, times that of methacrolein.
It is in the range of molar times.

The reaction temperature is usually -100 to 200 ° C, preferably 0 to 100 ° C.

Oxygen is usually used as pure oxygen, air or a mixture of oxygen and an inert gas. The inert gas is usually a single gas selected from nitrogen, argon, helium or the like or a mixed gas of two or more kinds, but nitrogen is preferable. The oxygen concentration in the oxygen-containing gas is usually 0.
1 to 99.9% by volume, more preferably 1 to 20 in terms of safety
It is in the range of volume%.

The pressure of the gas phase in the reaction system is usually from atmospheric pressure to
It is in the range of 10 MPa, preferably atmospheric pressure to 1 MPa.

The reaction may be carried out without a solvent or, for example, the following solvents may be mentioned. Halogenated hydrocarbons, hydrocarbons,
A single solvent of ketones, nitriles or water or a mixed solvent of two or more thereof is used, but preferably,
From the viewpoint of production efficiency, solvent-free or water can be used.
Examples of the halogenated hydrocarbon include dichloromethane and 1,2-dichloroethane, and examples of the hydrocarbons include hexane and heptane.
Examples of ketones include acetone and 4-methyl-2.
-Pentanone and the like, and examples of the nitriles include acetonitrile and the like. The amount used is not particularly limited.

After completion of the reaction, the methacrylic acid ester can be usually obtained by distillation.

Typical examples of the methacrylic acid ester thus obtained are, for example, methyl methacrylate,
Examples thereof include ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, sec-butyl methacrylate, ter-butyl methacrylate and the like.

[0024]

According to the production method of the present invention, methacrylic acid ester can be produced industrially advantageously.

[0025]

The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto.

Example 1 80 g of ion-exchanged water and 0.70 g of chloroauric acid were placed in a 200 cc four-necked flask and stirred to dissolve chloroauric acid. After the temperature was raised to 60 ° C., 5.56 g of silica was added and the temperature was kept for 3 hours. The pH at this time was 1.6. After cooling to room temperature, 2 mL of formalin was added and stirred for 2 hours. The pH at this time was 1.6.
Then, 9.8 g of 1N aqueous sodium hydroxide solution was added to adjust the pH to 6.4, and the mixture was stirred for 16 hours. After filtration, the gold-supported catalyst 5.8 was obtained by drying under reduced pressure at 50 ° C.
g was obtained. The gold content was 6.2%.

Example 2 80 g of ion-exchanged water and 0.70 g of chloroauric acid were placed in a 200 cc four-necked flask, and the chloroauric acid was dissolved by stirring. After that, a 1N aqueous sodium hydroxide solution was added to adjust the pH to 6.7. Adjusted to. After the temperature was raised to 60 ° C., 5.56 g of silica was added and the temperature was kept for 3 hours. During this time, the pH was controlled within the range of 6 to 7. After cooling to room temperature, 2 mL of formalin was added and stirred for 2 hours. During this time, the pH is 6 to
It was managed in the range of 7. After filtration, it was dried at 50 ° C. under reduced pressure to obtain 5.3 g of a gold-supported catalyst. The gold content was 6.2%.

(Example 3) The same procedure as in Example 1 was carried out except that the pH was adjusted to 5.9 instead of the pH of 6.4. The gold content was 5.6%.

Example 4 In a 120 cc autoclave, 1.71 g of the gold catalyst obtained in Example 1 and 0.86 water.
g, methanol 17.0 g, methacrolein / methanol mixed solution 20.0 g (methacrolein / methanol weight ratio = 4.5 / 25), and after purging with nitrogen, pressurize with nitrogen to 0.40 MPa to adjust the internal temperature. The temperature was raised to 40 to 50 ° C. At this time, the total pressure in the reaction system rose to 0.42 MPa. Then, pure oxygen was introduced into the reaction system from an oxygen cylinder to bring the total pressure in the reaction system to 0.47 MPa (oxygen partial pressure in the reaction system:
(0.05 MPa) and then kept at the same temperature for 16 hours. At that time, the oxygen consumption was replenished from the oxygen cylinder so that the total pressure in the reaction system was always 0.47 MPa (oxygen partial pressure: 0.05 MPa). After the heat retention was completed, the pressure in the reaction system was restored, the atmosphere was replaced with nitrogen, and then the reaction solution was taken out and analyzed by gas chromatography. The conversion of methacrolein is 32.9% and the selectivity of methyl methacrylate is 86.
It was 5% (to methacrolein).

(Example 5) The same as Example 4 except that the catalyst obtained in Example 2 was used as the gold catalyst in place of the catalyst obtained in Example 1 in Example 4. Went to. The conversion of methacrolein was 39.1% and the selectivity of methyl methacrylate was 84.1% (to methacrolein).

Example 6 In Example 4, 1.71 g (gold amount: 0.106) of the catalyst obtained in Example 1 was used as the gold catalyst.
g) Instead of using the catalyst obtained in Example 3, 1.
The same procedure as in Example 4 was performed except that 89 g (gold amount: 0.106 g) was used. The conversion rate of methacrolein is 2
8.4%, methyl methacrylate selectivity 87.4%
(Vs methacrolein).

Reference Example 1 The procedure of Example 1 was repeated except that the pH was adjusted to 7.5 instead of the pH of 6.4. The gold content was 5.5%.

Reference Example 2 The procedure of Example 1 was repeated except that the pH was adjusted to 4.2 instead of the pH of 6.4. The gold content was 3.7%.

Reference Example 3 The procedure of Example 1 was repeated except that the pH of Example 1 was adjusted to 9.3 instead of 6.4. The gold content was 4.7%.

(Comparative Example 1) In Example 4, 1.71 g (gold amount: 0.106) of the catalyst obtained in Example 1 was used as the gold catalyst.
g) Instead of using the catalyst obtained in Reference Example 1, 1.
The same procedure as in Example 4 was carried out except that 93 g (gold amount: 0.106 g) was used. The conversion rate of methacrolein is 3
6.8%, methyl methacrylate selectivity 63.5%
(Vs methacrolein).

(Comparative Example 2) In Example 4, 1.71 g (gold amount: 0.106) of the catalyst obtained in Example 1 was used as the gold catalyst.
g) Instead of using the catalyst obtained in Reference Example 2, 2.
The same procedure as in Example 4 was performed except that 90 g (gold amount: 0.107 g) was used. The conversion rate of methacrolein is 1
The selectivity was 8.7% and methyl methacrylate was 2.6% (to methacrolein).

(Comparative Example 3) In Example 4, 1.71 g (gold amount: 0.106) of the catalyst obtained in Example 1 was used as the gold catalyst.
g) Instead of using the catalyst obtained in Reference Example 3, 2.
The same procedure as in Example 4 was performed except that 25 g (gold amount: 0.106 g) was used. The conversion rate of methacrolein is 7
3.5%, methyl methacrylate selectivity 26.9%
(Vs methacrolein).

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Claims (3)

[Claims] 1. Methacrylic acid characterized by supporting chloroauric acid on a carrier, reducing with a reducing agent, and then reacting methacrolein, alcohol and oxygen in the presence of a gold catalyst adjusted to pH 5 to 7. Method for producing ester. 2. The production method according to claim 1, wherein the alcohol is methanol. 3. The method according to claim 1, wherein the carrier is silica.