JP2001220367A - Method and catalyst for producing carboxylic acid ester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a carboxylic acid ester characteristically using a catalyst containing relatively inexpensive ruthenium among metal species instead of an expensive palladium catalyst in producing a carboxylic acid ester by reacting an aldehyde with an alcohol and to obtain a catalyst for producing a carboxylic acid ester useful in the method for producing the carboxylic acid ester. SOLUTION: The carboxylic acid ester can be industrially advantageously produced in an extremely excellent economic efficiency. This inexpensive catalyst for producing the carboxylic acid ester can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a carboxylic acid ester in one step by oxidizing an aldehyde and an alcohol with molecular oxygen, and more particularly, to performing the reaction in the presence of a specific catalyst. The present invention relates to an industrially advantageous method for producing a carboxylic acid ester, and also relates to a catalyst for producing a carboxylic acid ester used in the method for producing a carboxylic acid ester.

[0002]

2. Description of the Related Art Conventionally, as a method for producing a carboxylic acid ester from an aldehyde, a method in which an aldehyde is once oxidized to a carboxylic acid, and the carboxylic acid is reacted with an alcohol in another step to esterify the carboxylic acid to obtain a carboxylic acid ester. Met. However, this method has the drawback that the reaction requires two steps, and the step of oxidizing the aldehyde is generally a high-temperature gas phase reaction, so that there is a limit in improving the yield. Further, when an unsaturated bond is present in the aldehyde molecule, polymerization and other side reactions are apt to occur, and there is a problem that the operation operation becomes complicated.

In order to solve such a problem, a method has been proposed in which an aldehyde and an alcohol are reacted to produce a carboxylic acid ester in one step. Among them, palladium and compounds containing palladium are variously studied as catalysts. For example, according to Japanese Patent Publication No. 45-34368, a catalyst in which palladium is supported on a carrier such as diatomaceous earth or activated carbon is suspended in a mixture of aldehyde and alcohol, and a molecular oxygen-containing gas is added thereto under pressure. To oxidize the aldehyde and simultaneously esterify it to produce a carboxylic acid ester. However, this method has a problem that various side reactions occur in parallel with the desired carboxylic acid ester formation reaction. In particular, when an unsaturated aldehyde is used as a raw material, the unsaturated bond present in the aldehyde molecule may cause an acetal of the unsaturated aldehyde, an alkoxy compound in which an alcohol is added to the unsaturated bond, or an unsaturated acid. Many by-products are produced, and furthermore, carbon dioxide, carbon monoxide, and the like, which are final oxidation products, are also generated.

Therefore, in order to solve these problems, various improvements in new palladium and catalysts containing palladium have been studied. For example, Japanese Patent Publication No. 62-007902
According to the publication, a catalyst containing an intermetallic compound containing palladium and at least one element selected from lead, mercury, bismuth, or thallium, or the intermetallic compound and an alkali metal compound or an alkaline earth metal The use of a catalyst comprising a compound suppresses the formation of the by-products in question, and enables the production of a carboxylic acid ester in high yield. Further, for example, JP-A-09-029099 and JP-A-09-192495
Similarly, Japanese Patent Application Laid-Open No. 10-263399 discloses various studies of a catalyst containing palladium as an essential component.

As described above, it has been considered that the production of a carboxylic acid ester requires the presence of a catalyst containing palladium. Since palladium has high reactivity, it is widely used in chemical industrial processes as an oxidation reaction, a reduction reaction, a hydrogenation reaction, or a purification catalyst for automobile exhaust gas. However, in recent years, the unit price of palladium has risen remarkably due to these demands, and the economic burden due to the increase in cost in the production of industrial catalysts and the like is large, and it is becoming difficult to say that it is industrially advantageous. Therefore, at present, there is a strong demand for the development of a catalyst which can be newly substituted for palladium, which is excellent in economic efficiency and industrially advantageous.

[0006]

According to the present invention, an aldehyde is reacted with an alcohol and molecular oxygen by using an inexpensive and economical metal active species as a catalyst instead of expensive palladium. An object of the present invention is to provide a method for producing a carboxylic acid ester which solves the problem and is industrially advantageous, and a catalyst used therefor.

[0007]

In order to solve the above-mentioned problems, the present inventors have found that in producing carboxylic acid esters by oxidizing aldehydes and alcohols with molecular oxygen, it is possible to obtain a carboxylic acid ester in one step with a high yield and economic efficiency. Surprisingly, as a result of intensive research to improve the performance, the above problem was solved by a catalyst containing ruthenium, which is inexpensive to palladium at a unit price of about 1/10, and the carboxylic acid ester was converted. It has been found that they can be manufactured, and the present invention has been accomplished.

According to the production method of the present invention, it has been found that when oxygen is molecularly supplied to a reactor containing aldehyde and alcohol in a catalyst made of ruthenium not containing palladium, a carboxylic acid ester is formed. Was. Furthermore, they have found that the addition of at least one element of lead, mercury, bismuth, and thallium to the catalyst results in a further increase in the yield of the carboxylate. Furthermore, in this reaction, the production of a dimer or a polymer compound caused by an acetal or an unsaturated aldehyde is almost controlled, showing a very revolutionary reaction behavior, which is extremely industrially advantageous. Suggest that. Further, the present invention is a carboxylic acid ester production catalyst for producing a carboxylic acid ester by reacting an aldehyde and an alcohol in the presence of molecular oxygen, comprising ruthenium, and further, the catalyst is ruthenium and It is a catalyst for producing carboxylate esters comprising at least one element of lead, mercury, bismuth, thallium and these compounds.

Hereinafter, the present invention will be described in detail. The aldehyde used in the production of the carboxylic acid ester according to the present invention includes, for example, an aliphatic saturated aldehyde having 1 to 10 carbon atoms such as formaldehyde, acetaldehyde, propionaldehyde, isobutyraldehyde, glyoxal; acrolein, methacrolein, crotonaldehyde and the like. C3-10 aliphatic unsaturated aldehydes; C7-2 carbon atoms such as benzaldehyde, tolylaldehyde, benzylaldehyde and phthalaldehyde
0 aromatic aldehydes; and derivatives of these aldehydes. Among them, preferred are highly reactive aliphatic unsaturated aldehydes, and more preferred are acrolein and methacrolein. These aldehydes can be used alone or as a mixture of two or more kinds.

In the production of the carboxylic acid ester according to the present invention, the alcohol includes, for example, an aliphatic saturated alcohol having 1 to 10 carbon atoms such as methanol, ethanol, isopropanol and octanol; and 2 to 2 carbon atoms such as ethylene glycol and butanediol. 10 diols;
3 carbon atoms such as allyl alcohol and methallyl alcohol
Aliphatic unsaturated alcohols having 10 to 10; aromatic alcohols having 6 to 20 carbon atoms, such as benzyl alcohol. Among these, a lower aliphatic saturated alcohol having higher reactivity is preferable, and among them, methanol is more preferable. These alcohols can be used alone or as a mixture of two or more kinds.

The amount of the aldehyde and the alcohol used in the reaction of the present invention is 3 in a molar ratio of aldehyde / alcohol.
The range is preferably 0.5 to 10/10, more preferably 2 to 0.5 / 10. When the molar ratio exceeds 3/10, decomposition of aldehyde and other side reactions become remarkable, and the selectivity of the reaction is lowered.
If it is less than 10, the reaction between alcohols becomes remarkable and the selectivity of the reaction is lowered, which is not preferable. The oxygen used in the present invention can be in the form of molecular oxygen, that is, oxygen gas itself or a mixed gas obtained by diluting oxygen gas with a diluent inert to the reaction, for example, nitrogen or carbon dioxide gas, and using air. You can also. The amount of oxygen to be present in the reaction system is not less than the stoichiometric amount necessary for the reaction, preferably 2 stoichiometric amounts.
More than double is enough.

When acrolein or methacrolein is used as the aldehyde as the carboxylic acid ester obtained by the reaction of the present invention, an acrylate ester or a methacrylic ester corresponding to the alcohol used is obtained. It is essential that the catalyst used in the present invention is composed of ruthenium, and at least one of lead, mercury, bismuth, thallium and these compounds as described above. Thus, a carboxylic acid ester can be produced with high activity and high selectivity.

Further, as a different element, for example, tellurium,
Nickel, chromium, cobalt, indium, tantalum,
Copper, zinc, zirconium, hafnium, tungsten,
Manganese, silver, rhenium, antimony, tin, iridium, gold, bismuth, titanium, aluminum, boron, silicon and the like may be contained. In addition, these heterogeneous element compounds and the like may penetrate a small amount between crystal lattices, or may be substituted for a part of the crystal lattice metal, and may be directly added to the reaction system. As the carrier, silica, alumina,
It can be widely selected from silica-alumina, magnesia, silica-alumina-magnesia, magnesium hydroxide, titania, calcium carbonate, activated carbon, and the like, and more preferably, silica-alumina and silica-alumina-magnesia.

The composition ratio of the catalyst depends on the type and amount of the reaction raw material,
It can be arbitrarily changed according to the method of adjusting the catalyst, operating conditions, and the like, and is not particularly limited.
0% by weight, more preferably 2 to 20% by weight. Since the activity cannot be sufficiently obtained if the amount supported is small, the weight ratio is required to be 2 to 5 times as much as the supported amount of palladium. However, as described above, the unit price of ruthenium is 1/10 compared with palladium. Therefore, this can be said to be sufficiently industrially advantageous. The amount of lead carried is not particularly limited, and is usually 0.1 to
It is 10% by weight, preferably 1 to 5% by weight. The amount of the catalyst to be used relative to the starting aldehyde is not particularly limited, but is usually about 1/1000 to 5 times by weight. However, the present invention is not limited to this range, and is not particularly limited in the case of a flow reaction system.

[0015] The reaction temperature is preferably in the range of 10 to 300 ° C, particularly preferably in the range of 30 to 200 ° C.
The pressure is not particularly limited, but is usually 1 to 100 atm, particularly 1
A range of -70 atm is preferred. Further, the present invention can be carried out by any conventionally known method such as a gas phase reaction, a liquid phase reaction, and a perfusion solution. For example, when the reaction is carried out in the liquid phase, any reactor type such as a bubble column reactor, a draft tube type reactor, a stirred tank type reactor and the like can be used. Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In the examples, "%" indicates "% by weight" unless otherwise specified.

[0016]

Example 1 A commercially available 10% ruthenium-alumina (manufactured by NE Chemcat Co.) was used as a catalyst in an amount of 24 g as a catalyst, and a catalyst separator was provided. Carried out. 32.
48 g / h of a 5% methacrolein-methanol solution
r, a 0.2-0.5% caustic soda-methanol solution was continuously supplied to the reactor at a rate of 4 g / hr for pH adjustment (the methacrolein concentration of the above two solutions was 30).
%), A reaction temperature of 80 ° C. and a reaction pressure of 0.5 MPa, and a production reaction of methyl methacrylate was carried out while adjusting the amount of air so that the inlet oxygen concentration was 4.0% by volume. Reactor pH
The caustic soda concentration supplied to the reactor was adjusted so as to be 6.2 to 6.4. The reaction product was continuously withdrawn from the reactor outlet by overflow. Analysis of the withdrawn liquid after elapse of 20 hours revealed that the conversion of methacrolein was 22.5% and the yield of methyl methacrylate was 11.5%.
(Selectivity 51.1%).

[0017]

COMPARATIVE EXAMPLE 1 A reaction was carried out using 24 g of 3% palladium-silica supported as a catalyst in the same apparatus, under the same conditions and under the same method as in Example 1, and as a result, the conversion of methacrolein was 26.4%. Although the yield was higher than that of the ruthenium-alumina catalyst, the yield of methyl methacrylate was 11.3% (selectivity 42.9%).

COMPARATIVE EXAMPLE 2 Using the same apparatus, under the same conditions, and the same method as in Example 1, 24% of a catalyst supported on 5% platinum-silica was used.
As a result of using g, the conversion of methacrolein was 4.9%, but no formation of methyl methacrylate was observed.

COMPARATIVE EXAMPLE 3 A reaction was carried out using 24 g of a catalyst supported by 5% rhodium-silica as a catalyst in the same apparatus, under the same conditions and under the same method as in Example 1, and as a result, the conversion of methacrolein was 5.6%. However, production of methyl methacrylate was not observed at all.

[0018]

Example 2 The same apparatus and the same method as in Example 1 were used to supply a lead acetate-methanol solution at a rate of 4 g / hr (lead was equivalent to 100 ppm of the total supply amount including methacrolein), and the reaction was carried out. The conversion of methacrolein increased to 45.2% and the yield of methyl methacrylate reached 40.7% (selectivity 90.0%).

Comparative Example 4 A reaction was carried out using 24 g of 3% palladium-silica supported catalyst as a catalyst in the same apparatus, under the same conditions and under the same conditions as in Example 2, and as a result, the conversion of methacrolein was 50.2%. And the yield of methyl methacrylate was 42.8.
% (Selectivity 85.2%).

[0019]

Example 3 The reaction was carried out in the same apparatus and in the same manner as in Example 1, except that the catalyst was used in an amount 1.5 times the amount of 36 g. As a result, the conversion of methacrolein was increased to 55.6%, and the yield of methyl methacrylate was increased. The rate reached 49.0% (selectivity 88.1%).

Example 4 As a result of carrying out a reaction using the same apparatus and the same method as in Example 1 at a reaction pressure of 0.6 MPa, the conversion of methacrolein was increased to 62.5% and the yield of methyl methacrylate was 59%. 0.1% (selectivity 94.5%).

[0020]

As described above, according to the present invention, when an aldehyde and an alcohol are reacted with molecular oxygen to produce a carboxylic acid ester, an expensive palladium catalyst which has been considered to be essential is replaced with a low-priced catalyst. Use of a ruthenium catalyst is very economical and industrially advantageous. It is expected that further optimization of the reaction conditions and the like will greatly improve both the conversion and the selectivity.

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[Procedure amendment]

[Submission date] February 29, 2000 (200.2.2
9)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0002

[Correction method] Change

[Correction contents]

[0002]

2. Description of the Related Art Conventionally, as a method for producing a carboxylic acid ester from an aldehyde, a method in which an aldehyde is once oxidized to a carboxylic acid, and the carboxylic acid is reacted with an alcohol in another step to esterify the carboxylic acid to obtain a carboxylic acid ester. Met. However, this method has the drawback that the reaction requires two steps, and the step of oxidizing the aldehyde is generally a high-temperature gas phase reaction, so that there is a limit in improving the yield. In addition, when an unsaturated bond is present in the aldehyde molecule, polymerization and other side reactions are liable to occur, and there is a problem that the operation operation is complicated.

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Claims (6)

[Claims] 1. A method for producing a carboxylic acid ester, wherein a catalyst comprising ruthenium is used in producing a carboxylic acid ester by reacting an aldehyde and an alcohol in the presence of molecular oxygen. 2. The method according to claim 1, wherein the catalyst comprises ruthenium and at least one element of lead, mercury, bismuth, thallium and these compounds. 3. The aldehyde is an unsaturated aldehyde,
The method for producing a carboxylic acid ester according to claim 1, wherein the alcohol is an aliphatic saturated alcohol, and the carboxylic acid ester is an unsaturated carboxylic acid ester. 4. The process for producing a carboxylic acid ester according to claim 3, wherein the unsaturated aldehyde is methacrolein, the aliphatic saturated alcohol is methanol, and the unsaturated carboxylic acid ester is methyl methacrylate. 5. A catalyst for producing a carboxylic acid ester, comprising ruthenium and reacting an aldehyde and an alcohol in the presence of molecular oxygen to produce a carboxylic acid ester. 6. The catalyst for producing a carboxylate according to claim 5, wherein the catalyst comprises ruthenium and at least one element of lead, mercury, bismuth, thallium and these compounds.