JPH11140026A - Production of carboxylic acid ester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a carboxylic acid ester in a high yield giving little by-product(s) and capable of recycling a catalyst used. SOLUTION: The method is provided by using a titanosilicate catalyst having mesoporous structure in a process where a carboxylic acid ester is produced by the reaction of a carboxylic acid and/or its anhydride with an alcohol, wherein the titanosilicate having mesoporous structure gives a peak corresponding to a lattice distance of 20-80 Å in the powder X-ray diffraction analysis, the carboxylic acid is phthalic acid, and the alcohol is a 1-18C aliphatic monovalent alcohol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a carboxylic acid ester. More specifically, the present invention relates to a method for producing a carboxylic acid ester used as a plasticizer such as a vinyl chloride resin or a vinyl acetate resin.

[0002]

2. Description of the Related Art Conventionally, when a plasticizer such as dialkyl phthalate is industrially produced by esterifying (anhydrous) phthalic acid and an aliphatic alcohol, sulfuric acid and paratoluenesulfonic acid are used as a catalyst for the esterification reaction. And other strong acids and tetraalkyl titanates. In particular, tetraalkyl titanates are widely used because they have less side reactions such as dehydration of alcohols than strong acid catalysts and can provide high-quality carboxylic esters without coloring.

[0003] However, since tetraalkyl titanate is a homogeneous catalyst, there is a problem that it is difficult to separate the product ester from the product. That is, since it is difficult to distill and separate a high boiling point carboxylic acid ester such as dialkyl phthalate, a method of hydrolyzing and depositing the catalyst after the reaction is completed, and then a method of separating by filtration is generally used. However, there has been a problem that the catalyst is not recovered and reused, and the hydrolyzed tetraalkyl titanate becomes a viscous gel, so that it takes a long time for filtration and separation.

To solve such problems, various heterogeneous titanium catalysts such as supported alkyl titanate catalysts and titanium-containing metal oxide catalysts have been proposed. Supported alkyl titanate catalysts are those in which an alkyl titanate is supported using an inorganic compound having a hydroxyl group on the surface as a carrier. For example, JP-A-52-75684 discloses a catalyst in which a tetraalkyl titanate is supported on silica or alumina. Are disclosed. In addition, Japanese Patent Application Laid-Open No. 2-628
No. 49 discloses a methyl titanate catalyst supported on silica magnesia. These catalysts exhibit an activity comparable to that of the homogeneous titanate catalyst, but have a problem in that titanium is eluted because the bond between the carrier and the titanate is weak. Particularly when used in the production of phthalic diesters, which are mainly used as plasticizers for plastic products, the elution of titanium causes a reduction in the volume resistivity of the product, which may adversely affect the quality of the final product such as poor insulation. Is not preferred.

[0005] On the other hand, various studies have been made on the esterification reaction using a titanium-containing metal oxide catalyst, mainly on titania and silica titania. However, in general, the activity is insufficient, and In the case of a catalyst having a high esterification activity, such as titania, it is possible to use the method described in Collect. Cz
ech. Chem. Commun. , 49 (1), (1
984), 253, as in the case of the supported alkyl titanate catalyst, there was a problem that a large amount of titanium was eluted. Also, JP-A-7-275
No. 701 discloses that a silica titania catalyst obtained by a method of co-precipitating a titanium compound and a silicon compound under a high acid concentration shows high esterification activity, but the activity decreases over time. There is a problem in that occurs. Also, US Pat. No. 5,502,240 describes that titanium in the zeolite skeleton is an effective catalyst for the esterification reaction, but the activity is insufficient as will be shown later in Comparative Examples. Microporous titanosilicate such as TS-1 and mesoporous titanosilicate such as Ti-HMS are the same in that titanium in a silicate matrix is used as an active site. The catalytic activity exerted is often very different. Particularly in a reaction system in the presence of water, mesoporous titanosilicate has lower activity than microporous titanosilicate. For example, Appl. Catal.
A. , 128 (1995) 231, microporous titanosilicates exhibit excellent catalytic activity in the oxidation of primary amines with hydrogen peroxide, whereas mesoporous titanosilicates have significantly lower activity. Only show. These phenomena are generally explained as being due to the hydrophilic nature of the mesoporous titanosilicate, which is susceptible to active site poisoning by water. JP-A-8-92166 and JP-A-8-198817 disclose that mesoporous titanosilicate is an effective catalyst for producing a carbonate ester, but the form of the reaction does not produce water as a by-product. Limited to transesterification. As described above, it was not expected that mesoporous titanosilicate which is susceptible to water poisoning would show excellent catalytic activity in the esterification reaction in which water is produced as a by-product.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high ester yield, a small amount of by-products, and a catalyst recovery / recovery method.
An object of the present invention is to provide a method for producing a carboxylic acid ester which can be reused.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above problems, and as a result, when producing a carboxylic acid ester by reacting a carboxylic acid and / or an anhydride thereof with an alcohol, It has been found that the object is achieved by using a titanosilicate having a mesoporous structure as a catalyst, and the present invention has been completed.

That is, the gist of the present invention is to use a titanosilicate catalyst having a mesoporous structure in producing a carboxylic acid ester by reacting a carboxylic acid and / or an anhydride thereof with an alcohol. The present invention relates to a method for producing an acid ester.

[0009]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, a titanosilicate catalyst having a mesoporous structure is used, and the form of the catalyst will be described in detail below. As the mesoporous titanosilicate catalyst in the present invention, Ti-HMS (W
O96 / 29297 patent) and Ti-MCM-41 (J. Ch.
em. Soc., Chem. Commun., (1994) 147), Ti-MSU-1
(Science, 269, (1995) 1242). Especially T
i-HMS is excellent as an industrial catalyst in that alkylamine, which is a catalyst mold agent, is inexpensive, does not require hydrothermal treatment, and requires a short time for preparation.

[0010] The mesoporous titanosilicate catalyst of the present invention preferably has a peak corresponding to a plane spacing of 20 to 80 ° in powder X-ray diffraction analysis.
A surface spacing of 5-60 ° is desirable. If the interplanar spacing is too small, the pore diameter becomes small and the esterification activity decreases. On the other hand, if the surface spacing is too large, the wall portion tends to increase. As a result, the proportion of titanium that cannot enter the wall portion to exhibit its activity increases, resulting in a decrease in activity.

The mesoporous titanosilicate catalyst of the present invention is effective when the specific surface area is 500 m2 / g or more. The molar ratio of titanium to silicon in the mesoporous titanosilicate is “titanium / silicon” = 0.1 / 99.9-
A range of 10/90, preferably 0.5 / 99.5 to 5/95 is suitable. If the molar ratio of titanium / silicon is too small, sufficient activity cannot be obtained because the density of titanium, which is an active site, becomes low. Also, if the molar ratio of titanium / silicon is too large, titanium is aggregated out of the skeleton of the silicate matrix to form titanium having a six-coordinated structure. As a result, the activity decreases.

The mesoporous titanosilicate catalyst of the present invention can be synthesized by the method described in WO 96/29297. The form of the catalyst to be provided to the reaction system may be a powdered product immediately after the synthesis of mesoporous titanosilicate, or a tablet directly formed without adding a binder, or a tablet formed by adding a binder such as silica sol, or It may be extruded.

In the present invention, the reason why the mesoporous titanosilicate catalyst gives excellent results in both the activity and the selectivity in the esterification reaction is unknown, but the substrate is easily the active site because of its large pore size. This is thought to be due to the accessibility to the coordinating structure titanium and the lack of strong acid sites that make it difficult for alcohol dehydration to occur.

Next, a method for producing a carboxylic acid ester using the catalyst of the present invention will be described. The carboxylic acid and / or its anhydride are mixed with the alcohol under an inert gas atmosphere, and the silica titania catalyst obtained as described above is added thereto.
７760 mmHg, set according to the vapor pressure of the alcohol used. ) At a temperature of 60-250 ° C., preferably 100
The esterification reaction is performed at a temperature of 220 ° C. The generated water is removed from the reaction system by azeotropy with the alcohol. At this time, it is also possible to use an azeotropic agent such as toluene.

The carboxylic acid in the present invention includes benzoic acid, toluic acid, α- and β-naphthoic acid, o- and m-
-And monovalent aromatic carboxylic acids having 7 to 30 carbon atoms such as p-ethylbenzoic acid, o-, m- and p-phenylbenzoic acid; and aliphatic divalent acids such as adipic acid, azelaic acid and sebacic acid. Carboxylic acid, phthalic acid, isophthalic acid,
And aromatic polycarboxylic acids such as terephthalic acid, trimesic acid, trimellitic acid, and pyromellitic acid. Particularly, (phthalic anhydride), (trimellitic anhydride), and adipic acid are useful as a raw material of the plasticizer and are preferably used in the present invention.

Examples of the alcohol include methanol, ethanol, propanol, isopropanol, n-butanol, t-butanol, isoamyl alcohol, n-hexanol, 2-ethylhexanol, n-octanol, n-decanol, isodecanol, 2-octanol, lauryl. Examples include aliphatic saturated monohydric alcohols such as alcohol and stearyl alcohol, and aliphatic polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, pentanediol, trimethylolpropane, sorbitol, glycerol, and pentaerythritol. Further, a mixture of these alcohols may be used. Among them, carbon number 1-1
An aliphatic monohydric alcohol having 8 is preferable, and an aliphatic saturated monohydric alcohol having 4 to 10 carbon atoms alone or as a mixture is useful as a raw material for a plasticizer. In particular, the above-mentioned carboxylic acid esters obtained from phthalic acid (anhydride), trimellitic acid (anhydride) or adipic acid and the above-mentioned alcohols alone or in a mixture are preferably used as a plasticizer.

In such a case, the molar ratio of alcohol / carboxylic acid (including its anhydride) is usually from 1/1 to 10 /.
1, preferably in the range of 2/1 to 5/1. If the value of the molar ratio is too small, the conversion of carboxylic acid and / or its anhydride into an ester is difficult to increase, while if the value is too large, the amount of unreacted alcohol increases and burdens the circulation system. This is not desirable.

The titanosilicate catalyst can be easily separated from the product by filtration, and the filtered catalyst can be reused as it is. Therefore, the esterification reaction can be carried out not only by a batch method but also by a continuous method.

[0019]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples unless it exceeds the gist thereof. Example 1 (Preparation of mesoporous titanosilicate catalyst) The catalyst was prepared basically according to the method described in WO96 / 29297. Under a nitrogen atmosphere, 62.5 g of tetraethoxysilane (300
(Mmol) and 115 ml of ethanol in a flask (500 ml) and 300 rpm
And stirred. 2.56 g (9 mmol) of tetra-i-propyl titanate and isopropyl alcohol 4
Six milliliters of the mixture was added over 10 minutes at room temperature. The mixture was then heated to 70 ° C. and held for 3 hours before cooling to room temperature.

While 115 ml of water and 15.0 g of dodecylamine were weighed into a separable flask (1 liter) and stirred at 400 rpm, the bimetallic alkoxide solution prepared above was added over about 1 hour. Then, after stirring was continued for 4 hours, the mixture was allowed to stand for about 1 day. The resulting precipitate is filtered off, washed once with water, and then washed with water.
It dried under reduced pressure at 0 degreeC. The resulting solid is placed under a stream of nitrogen 500
C. for 1 hour, followed by baking at 650.degree. C. for 4 hours under a stream of air to give mesoporous titanosilicate 18.1.
g was obtained. Powder X-ray diffraction analysis (using Rigaku RINT 1500) indicated that the catalyst had a peak corresponding to a 36.0 ° plane spacing as shown in FIG. The specific surface area of this catalyst was measured by the nitrogen adsorption method (Okura Riken AMS-80
As a result, the weight was 781 m2 / g. When the pore distribution of this catalyst was measured by a nitrogen adsorption method (using Omnisorp 100CX manufactured by Coulter Inc.), it was found that the catalyst had an average pore diameter around 17 ° as shown in FIG.

(Synthesis of carboxylic acid ester) In a flask equipped with a stir bar, a thermometer, a reflux tube and an ester tube, 37 g (0.25 mol) of phthalic anhydride and 81.4 g (0.625 mol) of 2-ethylhexanol were placed. ) Was added and kept at 210 ° C. under a normal pressure and a nitrogen atmosphere to remove the water from the system while removing the generated water outside the system.
The reaction was performed for 5 hours. At this time, the conversion of phthalic anhydride was measured by measuring the NMR (nuclear magnetic resonance spectrum analysis: using UNITY-300 manufactured by Varian Co., Ltd.), the acid value and the reaction rate by liquid chromatography (using LC-6A manufactured by Shimadzu Corporation). The yield was 100%, and the yield of dioctyl phthalate (DOP) was 68%. Next, the mesoporous titanosilicate catalyst 1 obtained as described above was used.
After reacting at normal pressure for 1 hour while maintaining the temperature at 210 ° C. again, the degree of decompression was gradually increased (at 560 Torr to 0.1 g).
5 hours, 0.5 hours at 460 Torr, and 360 T
(0.5 hours at orr). Dioctyl phthalate (DO) was determined by acid value measurement and liquid chromatography.
The yield of P) was found to be 99.9%. Further, it was found by gas chromatography that octene was formed as a by-product with a selectivity of 0.02% (based on the charged 2-ethylhexanol).

Example 2 18.2 g of mesoporous titanosilicate was obtained in exactly the same manner as in Example 1 except that octadecylamine was used instead of dodecylamine. Example 1 using this as a catalyst
When the esterification reaction was performed in exactly the same manner as in
The yield of P was 99.8%. The octene by-product rate was 0.02%.

Example 3 16.8 g of mesoporous titanosilicate was obtained in the same manner as in Example 1 except that octylamine was used instead of dodecylamine. When the esterification reaction was carried out in the same manner as in Example 1 using this as a catalyst, the yield of DOP was 99.6%. The octene by-product rate was 0.03%.

Example 4 The procedure was the same as in Example 1 except that 0.85 g (3 mmol) of tetra-i-propyl titanate was used and the ratio of titanium to silicon was changed to “titanium / silicon” = 1/100. As a result, 18.1 g of mesoporous titanosilicate was obtained. When an esterification reaction was carried out in the same manner as in Example 1 using this as a catalyst, the yield of DOP was 98.8%.
Met. The octene by-product rate was 0.01% (detection limit) or less.

Comparative Example 1 (in the case of microporous titanosilicate) TS-1 which is a microporous titanosilicate was synthesized by the method described in US Pat. No. 4,410,501, and the procedure of Example 1 was repeated except that this was used as a catalyst. When the esterification reaction was performed in exactly the same manner, the yield of DOP was 93.2%.
Met. Octene by-product rate is 0.01% (detection limit)
It was below.

Comparative Example 2 (in the case of amorphous silica titania) 60.6 g of tetraethoxysilane (29
(1 mmol) and 150 ml of ethanol were weighed into a separable flask (1 liter), and 300 r at room temperature.
Stirred at pm. Next, a previously prepared alcoholic dilute hydrochloric acid solution (3.03 g of 35 wt% hydrochloric acid, 20 g of demineralized water, and 5 ml of ethanol) was added thereto over 30 minutes by a dropping funnel to hydrolyze tetraethoxysilane. After stirring for another 30 minutes, tetra-n
A mixture of 3.1 g (9 mmol) of butyl titanate and 20 ml of ethanol was added dropwise over 30 minutes. After continuing stirring for further 30 minutes, a mixed solution of 3 ml of 28 wt% ammonia water and 20 ml of demineralized water was added over 30 minutes to gel. Then, the gel was aged by allowing to stand for 7 days. The obtained precipitate was separated by filtration, washed with water until chloride ions and ammonium ions were not detected in the filtrate, and dried under reduced pressure at 70 ° C. The obtained solid was calcined at 400 ° C. for 3 hours under flowing air to obtain 18.0 g of silica titania. The result of powder X-ray diffraction showed that this solid was silica titania in an amorphous state. When an esterification reaction was carried out in exactly the same manner as in Example 1 except that this was used as a catalyst, the yield of DOP was 99.9%, but the by-product rate of octene was 0.1%.
It was 54%.

[0027]

According to the present invention, the production of by-products can be suppressed, and a high-quality carboxylic acid ester can be obtained with high yield and high selectivity. Further, the used catalyst can be reused.

[Brief description of the drawings]

FIG. 1 is a powder X-ray diffraction diagram of a mesoporous titanosilicate catalyst obtained in Example 1.

FIG. 2 is a pore distribution diagram of the mesoporous titanosilicate catalyst obtained in Example 1.

Claims (4)

[Claims] 1. A method for producing a carboxylic acid ester by reacting a carboxylic acid and / or an anhydride thereof with an alcohol, comprising using a titanosilicate catalyst having a mesoporous structure. 2. The method for producing a carboxylic acid ester according to claim 1, wherein the titanosilicate having a mesoporous structure has a peak corresponding to a plane spacing of 20 to 80 ° in powder X-ray diffraction analysis. 3. The method for producing a carboxylic acid ester according to claim 1, wherein the carboxylic acid is phthalic 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 18 carbon atoms.