JPH08337553A - Method for producing carboxylic acid ester - Google Patents

Abstract

(57) [Summary] [Object] To provide a method for producing a carboxylic acid ester using an alkyl titanate / silica catalyst, which is excellent in catalyst loading stability. [Structure] Carboxylic acid and / or its anhydride and alcohol are reacted using a catalyst in which an alkyl titanate is supported on silica to produce a carboxylic acid ester. Production of a carboxylic acid ester using a catalyst having a range of 5 angstroms or more and 150 angstroms or less, and an alkyl titanate supported on silica with an average bond coordination number of 2.8 or more and less than 4 Method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a carboxylic acid ester used as a plasticizer or the like.

[0002]

2. Description of the Related Art Conventionally, as a method for industrially producing a carboxylic acid ester such as a phthalic acid ester, a method of esterifying a carboxylic acid and an alcohol in the presence of a strong acid catalyst such as sulfuric acid or paratoluenesulfonic acid has been used. Used to be
There is a problem such as deterioration of the quality of carboxylic acid ester due to by-products, and currently, a tetraalkyl titanate catalyst that can obtain a high quality product is widely used. However, in the production of a carboxylic acid ester using this homogeneous tetraalkyl titanate catalyst, it is necessary to add water after the esterification reaction to decompose the catalyst and separate the decomposition product. Since it becomes a viscous gel that is difficult to separate by filtration, it is difficult to separate and remove it, which hinders the improvement of productivity. Further, it is inevitable that the titanium component is mixed into the carboxylic acid ester which is a product, which may cause a problem in the quality of the product.

In order to improve such problems, some methods using a catalyst in which an alkyl titanate is supported on a carrier have been reported. JP-A-52-75684 discloses that an excess amount of a tetraalkoxide such as titanium or zirconium with respect to an effective surface hydroxyl group of a hydroxylic carrier is supported by heating in an inert hydrocarbon solvent in the presence of water. The use of such catalysts is disclosed. JP-A-62-140651 discloses the use of a catalyst supporting polytitanic acid polymerized by reacting alkoxytitanium with water in the presence of a carrier such as diatomaceous earth and subjecting it to dealcoholization. ing. In addition, Japanese Patent Application Laid-Open No. 2-62849 discloses silica.
After supporting the alkyl titanate on the magnesia carrier,
A method for producing an aromatic carboxylic acid ester using methyl titanate or a polymer thereof which has been subjected to alkoxy exchange by adding methanol is disclosed.

When these catalysts are used, they show a catalytic activity equivalent to that of the homogeneous tetraalkyl titanate catalysts used industrially, but the desorption of the alkyl titanate from the carrier proceeds rapidly. However, the catalyst performance is significantly deteriorated over time, and it is not industrially satisfactory.

[0005]

An object of the present invention is to use a catalyst in which an alkyl titanate is supported on silica (hereinafter referred to as "alkyl titanate / silica catalyst"), which is excellent in catalyst loading stability. It is to provide a method for producing a carboxylic acid ester.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that an alkyl titanate is bound to a silica carrier having a specific average pore diameter with an average bond coordination number. The present inventors have found that an alkyl titanate / silica catalyst supported in a range of 2.8 or more and less than 4 has excellent alkyl titanate loading stability, and arrived at the present invention.

That is, the gist of the present invention is to react a carboxylic acid and / or its anhydride with an alcohol by using a catalyst in which an alkyl titanate is supported on silica to produce a carboxylic acid ester as a carrier. The silica used has an average pore diameter of 5 angstroms or more, 15
A catalyst having an alkyl titanate in the range of 0 angstroms or less and an average value of the bond coordination number of silica (hereinafter referred to as “average bond coordination number”) of 2.8 or more and less than 4 is used. It exists in the manufacturing method of the carboxylic acid ester characterized by using.

The present invention will be described in detail below. In the present invention, an alkyl titanate is used as a catalyst in silica having an average pore diameter of 5 angstroms or more and 150 angstroms or less and an average bond coordination number of 2.8.
The alkyl titanate / silica catalyst is used in the range of not less than 4 and less than 4, preferably not less than 2.8 and not more than 3.5. Furthermore, the lower limit of the average pore diameter as a carrier is preferably
By using a catalyst using silica having a thickness of 10 angstroms or more, preferably 100 angstroms or less, and more preferably 50 angstroms or less, esterification can be rapidly progressed, and the carrying stability is further improved. .

The average pore diameter of silica is 5 angstroms.
If it is less than 100 m, it is difficult to carry the alkyl titanate,
When it exceeds 150 angstrom, it is difficult to re-bond when the bond between the alkyl titanate and silica is partially dissociated. In addition, when the average number of bond coordination sites is less than 2.8,
When the supported alkyl titanate is easily released, and when the average bond coordination number is 4, there is no alkoxy-exchangeable group.

The above silica may be prepared by a known method, or a commercially available silica may be used. The silica may contain a metal oxide such as alumina, titania or zirconia, but the amount thereof is preferably 5% by weight or less.
The average pore diameter of silica can be determined by a known method such as BET method,
It is obtained from the desorption curve of nitrogen at the liquid nitrogen temperature by the T-plot method. When this silica is used, it may be used as it is, but when water is adsorbed on the silica, it is removed at a temperature of 100 ° C or higher, preferably at a temperature of 120 to 500 ° C at which the pore structure is not destroyed. , 0.
It is preferable to heat-treat in air for 5 to 3 hours or to vacuum-dry under heat. When water is adsorbed on silica, the adsorbed water and the alkyl titanate may react with each other to hydrolyze the alkyl titanate.

The alkyl titanate used in the present invention is not particularly limited, but a tetraalkyl titanate having an alkyl group having 1 to 10 carbon atoms is easily available and is generally used. Examples of these include tetraethyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, tetra-n-hexyl titanate and the like. It is also possible to use oligomers of these tetraalkyl titanates.

The amount of alkyl titanate supported on silica is calculated from the amount of surface hydroxyl groups of silica (calculated from the ignition loss (JI
SK1150-1994)), usually 1/100 to 1/3 equivalent,
Preferably 1/100 to 1/5 equivalent, more preferably 1/100 to
1/8 equivalent is good. The amount of alkyl titanate is 1 /
If it is less than 100 equivalents, the supported amount may be small and the catalytic activity may decrease, and if it exceeds 1/3 equivalents, the average bond coordination number may be less than 2.8. Furthermore, alkyl titanium
The amount of the salt is 0.1 to 20% by weight with respect to silica, preferably 1 to
10% by weight is good. The solvent used for the supporting treatment is not particularly limited, but a hydrocarbon solvent such as pentane, hexane, cyclohexane or heptane is usually used. It is also possible to carry out alkoxy exchange of the alkyl titanate by adding alcohol to the obtained alkyl titanate / silica catalyst and heating and refluxing after the supporting treatment. Examples of the method for preparing the above-mentioned alkyl titanate / silica catalyst include the following methods. First, 5 angstroms vacuum dried at 50-100 ° C
Silica having an average pore diameter of not less than 150 Å and not more than 150 Å is immersed in an organic solvent, then a solution of alkyl titanate is added dropwise, and the mixture is uniformly stirred by heating at 80 to 120 ° C. under heating. After the solvent was filtered off and washed, an organic solvent was added again to the obtained alkyl titanate / silica catalyst to obtain 80 to 12
Heat at reflux at 0 ° C. The solvent washing and filtration are repeated 3 to 4 times to remove the unsupported alkyl titanate and the alkyl titanate desorbed from the silica. Next, it is heated to 60 to 70 ° C. and dried under reduced pressure to obtain the alkyl titanate / silica catalyst of the present invention.

By following the above preparation method, an alkyl titanate / silica catalyst having an average bond coordination number of 2.8 or more and less than 4 can be obtained. The average bond coordination number between titanium and silica of the obtained alkyl titanate / silica catalyst was calculated from the value obtained by analyzing the element content of the catalyst, C / Ti.
It can be calculated from the value of (molar ratio). For example, when the number of carbon atoms in the alkyl group of alkyl titanate is n, C / Ti = m
Then, the average bond coordination number is calculated as 4-m / n.

In the present invention, alkyl titanate /
A silica catalyst is used to produce a carboxylic acid ester by reacting a carboxylic acid and / or an anhydride thereof with an alcohol. The method for producing a carboxylic acid ester of the present invention is particularly excellent in carrying stability of the catalyst. It is suitable for producing an ester of an aromatic carboxylic acid having high acidity among acids. As the carboxylic acid, a monovalent carboxylic acid, a polyvalent carboxylic acid and / or their anhydrides are used. To exemplify these, benzoic acid, toluic acid,
α- and β-naphthoic acid, o-, m- and p-ethylbenzoic acid, o-, m- and p-phenylbenzoic acid and other aromatic monovalent carboxylic acids having 7 to 30 carbon atoms, adipic acid, Azelaic acid,
Aromatic divalent carboxylic acids such as sebacic acid, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, trimesic acid, trimellitic acid, trimellitic anhydride, pyromellitic acid and pyromellitic anhydride carboxylic acid,
Other examples include polyvalent carboxylic acids having 6 to 30 carbon atoms and / or their anhydrides. Examples of alcohols include monohydric alcohols having 1 to 20 carbon atoms and polyhydric alcohols such as dihydric or trihydric alcohols. Examples of these are methanol, ethanol, propanol, isopropanol, n-
Butanol, isobutanol, t-butanol, isoamyl alcohol, n-hexanol, 2-ethylhexanol, n-octanol, n-decanol, isodecanol,
Aliphatic monohydric alcohols such as capryl alcohol, lauryl alcohol and stearyl alcohol, aromatic alcohols such as phenol and benzyl alcohol, ethylene glycol, 1,3-butanediol, 1,4-butanediol, 1,
Aliphatic polyhydric alcohols such as 4-pentanediol, trimethylolpropane, sorbitol, glycerol and the like can be mentioned.

The esterification reaction is carried out by the above-mentioned carboxylic acid and / or
Alternatively, 1.0 to 1.5 equivalents of alcohol to carboxylic acid is added to the anhydride under an inert gas atmosphere, and about 0.1 mol% of alkyl titanate / silica catalyst is added to the carboxylic acid, usually as Ti. , 150-250
It is carried out at a temperature of ° C under normal pressure or reduced pressure. The produced water is usually removed from the system by azeotropic distillation with the raw material alcohol.
After the reaction, the alkyl titanate / silica catalyst is easily separated and recovered by filtration or the like.

[0016]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist of the invention. <Examples 1 to 4 and Comparative Examples 1 to 4> (Synthesis of catalyst) 10 g of silica having an average pore diameter of 150 angstrom and 25 ml of n-hexane previously vacuum dried at 90 ° C. for 3 hours were placed in a flask under a nitrogen stream, 50
Heated to ° C. Next, tetra-n-butyl titanate 1.71
A solution of 10 g of n-hexane dissolved in 10 ml of n-hexane was gradually added with stirring by a dropping funnel. After the dropping is completed,
After heating up and refluxing for 2 hours, the solvent was filtered off. To the obtained white solid, 40 ml of toluene was added, and the mixture was heated and refluxed again for 2 hours. After the toluene was filtered off, the obtained white solid was washed 3 times with n-hexane and then dried under reduced pressure at 70 ° C. to obtain an alkyl titanate / silica catalyst. This was used as the catalyst of Example 1. Catalysts of Examples 2 to 4 and Comparative Examples 1 to 4 were obtained in the same manner except that the average pore diameter of silica and the type of alcohol shown in Table 1 were used. From the obtained alkyl titanate / silica catalyst carbon-sulfur analyzer (EMIA-520SPFA model manufactured by Horiba, Ltd.) and the Ti amount analysis value measured by a fluorescent X-ray analyzer (3370 model manufactured by Rigaku), alkyl titanate The average bond coordination numbers of silica and silica were determined and are shown in Table 1.

(Synthesis of Carboxylic Acid Ester) Under a nitrogen atmosphere, 0.5 mol of phthalic anhydride and 1.25 mol of 2-ethylhexanol were placed in a flask equipped with a reflux condenser, an esterification tube (water divider), a stirrer and a thermometer. Alkyl titanate / silica catalyst 0.5 mmol (as Ti equivalent) was added, and under normal pressure
The reaction was carried out for 1 hour while maintaining the temperature at 210 ° C and removing the produced water outside the system. Then gradually increase the pressure reduction (at 560 mmHg
0.5 hour, 0.5 hour at 460mmHg, 0.5 hour at 360mmHg
Time), the reaction was terminated, and the amount of di-2-ethylhexyl phthalate (DOP) produced was determined by acid value measurement and liquid chromatography. The yield was as shown in Table 1. . The Ti elution amount obtained by measuring the reaction solution with an inductively coupled plasma atomic emission spectrometer (ICP-AES: JY-38S manufactured by JOBINYVON) was as shown in Table 1.

[0018]

[Table 1] * 1: Angstrom * 2: Alkyl group * 3: n-Butyl * 4: Methyl

[0019]

EFFECTS OF THE INVENTION According to the present invention, a carboxylic acid ester can be obtained which is easy to separate from the catalyst and which does not contain a titanium component.

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display area C07C 69/80 9546-4H C07C 69/80 A

Claims (7)

[Claims] 1. Mean pores of silica used as a carrier in producing a carboxylic acid ester by reacting a carboxylic acid and / or its anhydride with an alcohol using a catalyst in which silica is supported by an alkyl titanate. Diameter is 5
A catalyst having a carbon number in the range of angstrom or more and 150 angstrom or less, and an alkyl titanate supported on silica in the range of 2.8 or more and less than 4 in average bond coordination number is used. Method for producing acid ester. 2. The method for producing a carboxylic acid ester according to claim 1, wherein the carboxylic acid is an aromatic carboxylic acid. 3. The carboxylic acid is phthalic acid, trimellitic acid,
The method for producing a carboxylic acid ester according to claim 1 or 2, which is one kind or a mixture of two or more kinds of pyromellitic acid and anhydrides thereof, and isophthalic acid and terephthalic acid. 4. The method for producing a carboxylic acid ester according to claim 1, wherein the alcohol is an aliphatic monohydric alcohol having 1 to 20 carbon atoms. 5. The method for producing a carboxylic acid ester according to claim 1, wherein the alkyl group of the alkyl titanate has 1 to 10 carbon atoms. 6. The average pore diameter of silica is 10 angstroms.
The method for producing a carboxylic acid ester according to any one of claims 1 to 5, wherein the carboxylic acid ester is in the range of 100 to 100 angstroms. 7. The method for producing a carboxylic acid ester according to claim 1, wherein the amount of the alkyl titanate supported on the silica is 0.1 to 20% by weight based on the silica.