JP4838538B2 - Method for producing unsaturated carboxylic acid ester and method for producing catalyst therefor - Google Patents

Description

The present invention relates to a method for producing an unsaturated carboxylic acid ester and a method for producing a catalyst therefor .

  Conventionally, by transesterification of unsaturated carboxylic acid esters such as methyl methacrylate and methyl acrylate with alcohols such as butyl alcohol and 2-ethylhexyl alcohol, butyl methacrylate, 2-ethylhexyl methacrylate, butyl acrylate, acrylic In the case of producing an unsaturated carboxylic acid ester having a large number of carbon atoms such as 2-ethylhexyl acid, an acid catalyst such as sulfuric acid and a catalyst such as tetraalkoxytitanium and dibutyltin oxide have been used. However, since these catalysts are dissolved in the reaction solution, it is difficult to recover and reuse them.

  As a means for solving this problem, it has been proposed to use an inorganic solid catalyst in which an active component such as titanium or tin is insolubilized. For example, Patent Literature 1 describes that an oligomer is formed in advance by reacting a transition metal alkoxide with water and a catalyst produced by mixing with a solid support having a surface hydroxyl group is used. Describes that a catalyst obtained by reacting alkoxytitanium with water in the presence of a carrier such as diatomaceous earth and then dealcoholizing is used. Patent Document 3 describes the use of a catalyst in which an alkyl titanate is supported on silica having an average pore diameter of 5 angstroms or more and 150 angstroms or less, and Patent Document 4 and Non-Patent Document 1 describe alkoxy on silica. The use of a catalyst carrying a titanium derivative is described.

  Further, Patent Document 4 and Patent Document 5 describe using a catalyst carrying a tin compound using a silane coupling agent.

  However, in the method described in the above literature, when the catalyst is recycled, the activity is greatly reduced, and the catalyst cannot be recycled.

JP-A-6-9495 JP-A-62-140651 JP-A-8-337553 JP 11-255782 A JP 2001-506661 A Catal. Lett. 43, 1/2, 139-142 (1997)

  The present invention has been made in view of the current state of the prior art described above, and by improving the activity of the catalyst or restoring the catalyst activity that has been reduced by use, the catalyst can be reused or continuously used. It is an object of the present invention to provide a production method capable of producing an unsaturated carboxylic acid ester stably over a long period of time or repeatedly.

That is, the present invention in which the above-described problems, first the presence of a catalyst, 100Ppm～180ppm the water content of the reaction mixture at the start of the reaction, the reaction temperature 95 ° C. or more conditions carrying the titanium emission of compounds on a carrier Then, a first transesterification reaction is carried out between the raw material unsaturated carboxylic acid ester and the raw material alcohol for 0.1 to 50 hours to prepare a second catalyst, and in the presence of the second catalyst, In this method, an unsaturated carboxylic acid ester is produced by performing a second transesterification reaction between the saturated carboxylic acid ester and the raw material alcohol.
Further, the present invention is a method for producing a catalyst for producing an unsaturated carboxylic acid ester performed transesterification between a raw material unsaturated carboxylic acid ester and the starting alcohol, a titanium emissions of compounds on a carrier In a method comprising treating a supported material in a liquid containing a raw material unsaturated carboxylic acid ester having an initial water content of 100 ppm to 180 ppm and a raw material alcohol at 95 ° C. or more for 0.1 to 50 hours. is there.

  According to the production method of the present invention, by preparing a catalyst under specific conditions, the activity of the catalyst can be improved, or the catalytic activity that has been reduced by use can be restored. And even when unsaturated carboxylic acid ester is produced repeatedly or continuously, the catalytic activity can be maintained, and the unsaturated carboxylic acid ester can be produced stably over a long period of time. That is, the catalyst can be recycled or continuously used.

In the present invention, the titanium or tin compound used for the catalyst refers to a titanium compound or tin compound having a substituent such as an alkyl group or an alkoxy group.
The first catalyst used in the present invention is prepared by mixing the titanium or tin compound, the support and the solvent, and heating them.

Examples of titanium or tin compounds that can be used in the present invention include compounds such as alkoxy titanium and alkyl tin.
As alkoxytitanium, for example, tetrabutoxytitanium, tetraisopropyloxytitanium, and tetraoctyloxytitanium are preferable because a highly active catalyst can be obtained.
Examples of the alkyl tin include dibutyl tin oxide, monobutyl tin oxide, di-n-butyl tin dilaurate, tributyl tin hydride, tin (IV) t-butoxide, and derivatives thereof.

In the present invention, either an inorganic carrier or an organic carrier can be used as a carrier for supporting these titanium or tin compounds.
Examples of the inorganic carrier include silica, alumina, titania, magnesia, zirconia, CaO, ZnO, silica-alumina, zeolite, activated clay, diatomaceous earth, clay (for example, kaolin, montmorillonite, vermiculite, chlorite) and the like. Among these inorganic carriers, it is composed of silica and alumina such as silica, alumina, silica-alumina, activated clay, and diatomaceous earth because the bond with titanium or tin compound is strong and titanium and tin compounds do not elute. An inorganic carrier is preferred, and silica-alumina is more preferred because the effect of improving the catalytic activity is remarkable. In view of good catalytic activity, the Si / Al atomic ratio of silica-alumina is preferably 1-8, more preferably 2-7, and even more preferably 4-6.

  Since the titanium or tin compound is supported in the pores formed in the carrier, and the raw material unsaturated carboxylic acid ester or raw material alcohol needs to enter the pores, the carrier has an average pore diameter of 1 nm or more. Those are preferred. Since the raw material unsaturated carboxylic acid ester and the raw material alcohol can move more freely in the pores, it is more preferable that the carrier has an average pore diameter of 2 nm or more. In addition, since the strength of the carrier tends to decrease when the pore diameter becomes too large, the average pore diameter is preferably 30 nm or less, and more preferably 15 nm or less.

  The amount of titanium or tin compound supported when preparing the first catalyst is preferably 0.1 to 30% by mass relative to the support. From the viewpoint of the activity of the catalyst, the supported amount is more preferably 5% by mass or more, and further preferably 10% by mass or more based on the carrier. From the viewpoint of preventing the loading efficiency of the titanium or tin compound and blocking the pores of the carrier, the loading amount of the titanium or tin compound is more preferably 25% by mass or less with respect to the carrier, and 20% by mass or less. Is more preferable.

  The organic solvent used for preparing the first catalyst is not particularly limited. For example, hydrocarbon solvents such as pentane, hexane, heptane, octane, isooctane, cyclopentane, cyclohexane, benzene, toluene, methanol, ethanol N-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, t-butyl alcohol, isobutyl alcohol, n-amyl alcohol, isoamyl alcohol, n-to Xyl alcohol, n-heptyl alcohol, n-octyl alcohol, n-nonyl alcohol, n-decyl alcohol, lauryl alcohol, cetyl alcohol, stearyl alcohol, benzyl alcohol, tri Phenylcarbinol, ethylene glycol, 1,2-propanediol Alcohol, 1,3-propanediol, 1,4-butanediol, cresol, phenol, xylenol and other alcohol solvents, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, tetrahydrofuran, Examples include ether solvents such as diethyl ether, diisopropyl ether, and methyl-tert-butyl ether; ketone solvents such as acetone and methyl ethyl ketone; and chlorine solvents such as carbon tetrachloride, chloroform, and methylene chloride. Two or more of the above solvents may be mixed and used. If necessary, water may be added to these solvents.

  When a catalyst is prepared by supporting alkoxytitanium such as tetrabutoxytitanium or tetraisopropyloxytitanium on the support surface, if a highly polar organic solvent is used, the adsorption of the solvent to the support surface becomes stronger, and the alkoxytitanium Adsorption may be hindered and loading may not be successful. In this case, it is preferable to use a low-polarity solvent such as the hydrocarbon solvent, diethyl ether, diisopropyl ether, or methyl-tert-butyl ether when preparing the first catalyst.

  If the amount of the solvent in preparing the first catalyst is too large, the progress of the supporting reaction tends to be slow, and if it is too small, the reaction control tends to be difficult, so 1 to 100 times the mass of the titanium or tin compound It is preferable to be 2-20 mass times.

If the temperature of the system for preparing the first catalyst is too low, the supporting reaction tends to be incomplete, and if it is too high, the catalytic activity tends to decrease. ° C is more preferable, and 50 to 100 ° C is particularly preferable.
Although the preparation time of a 1st catalyst is not specifically limited, 10 minutes-5 hours are preferable and 30 minutes-3 hours are more preferable.

  Since the above titanium or tin compounds are unstable at high temperatures, after preparing the first catalyst by supporting these compounds on a support, treatment such as drying at high temperatures may be performed to remove moisture in the catalyst. difficult. For example, a catalyst in which titanium or a tin compound such as alkoxy titanium or alkoxy tin or alkyl tin oxide is supported on a carrier is decomposed by the high temperature treatment, and the activity is remarkably lowered. Further, hydration water such as polytitanic acid supported on a carrier cannot be completely removed unless heated at several hundred degrees. When treated at such a temperature, it becomes titanium oxide or the like, and the activity is significantly reduced. Therefore, it is preferable not to add water. In the case of adding water, the amount used is preferably less than 15-fold mol, more preferably less than 1-fold mol, and less than 0.1-fold mol relative to titanium or tin compound. Further preferred.

  The method of taking out the first catalyst after supporting the titanium or tin compound on the carrier is not particularly limited, and can be performed by a known method such as filtration or concentration. The taken out first catalyst may be used as it is, or may be used after drying under heating normal pressure or heating reduced pressure. The drying conditions are not particularly limited as long as the temperature and pressure at which the solvent evaporates can be set. If the drying temperature is too high, the activity may decrease, and if it is too low, the solvent may remain, so 0 to 200 ° C is preferable, more preferably 30 to 180 ° C, and even more preferably 50 to 150 ° C. is there.

In the presence of the first catalyst, a first transesterification reaction is performed for 0.1 to 50 hours between the raw material unsaturated carboxylic acid ester and the raw material alcohol to prepare a second catalyst.
At that time, at least the amount of water in the reaction liquid at the start of the first transesterification reaction (hereinafter simply referred to as “reaction liquid”) improves the activity of the catalyst or restores the catalytic activity that has been reduced by use. , 180 ppm or less, and the reaction temperature is 95 ° C. or more.
Furthermore, in order to avoid fluctuations in the catalyst activity and perform stable production, the water content of the reaction solution is set to 100 ppm or more.

The reaction time for performing the first transesterification reaction varies depending on conditions such as the raw material and the activity of the catalyst, but is preferably 0.1 to 50 hours, and from the viewpoint of operation, it is 0.5 hours or more. More preferably, it is more preferably 1 hour or longer. From the viewpoint of suppressing the time required for the treatment and energy consumption, the reaction time is more preferably 30 hours or less, and even more preferably 10 hours or less.
In the continuous reaction apparatus, the reaction may be continuously performed without a stop period between the first transesterification reaction and the second transesterification reaction.
From the viewpoint of the activity of the second catalyst, the temperature of the first transesterification reaction is preferably 100 ° C. or higher, and more preferably 105 ° C. or higher. In addition, from the viewpoint of stability of the active site of the second catalyst and suppression of side reactions, the temperature is preferably 170 ° C. or lower, and more preferably 150 ° C. or lower. Although the temperature may be temporarily lower than 95 ° C. in the initial stage or in the middle of the first transesterification reaction, it is not preferable because the activity is greatly reduced.

  Since the solvent sold in general contains water, and the amount of water increases when the container is opened, it is preferable to perform a dehydration treatment when using the solvent. Examples of the dehydration method include known methods such as a method of using a water absorbent such as molecular sieve, a method of separating and removing water using Dean Stark and the like, and a method of removing water by distillation. . Further, since the dehydrated solvent may increase the amount of water even if it is sealed, it is preferably stored in a container purged with a desiccator or dry air.

Even if the amount of water in the liquid has exceeded 180 ppm in the initial stage or in the middle of the first transesterification reaction, for example, a dehydration treatment is performed using a water separator such as Dean Stark, and the reaction liquid The activity of the catalyst can be improved by adjusting the amount of water to 180 ppm or less and performing the first transesterification reaction again for 0.1 to 50 hours.
The usage form of the first and second catalysts can be selected arbitrarily such as suspension type, fluidized bed type, fixed bed type.
As an example of a continuous use method of the first and second catalysts, for example, raw materials are continuously supplied to a fixed bed type or fluidized bed type catalyst layer, and the reaction liquid that has passed through the catalyst layer is recovered. There is a way. In addition, a circulation system that removes by-produced alcohol from the reaction solution that has once passed through the catalyst layer and supplies it again to the catalyst layer can be used.
Moreover, as an example of the method of repeatedly using the first and second catalysts, for example, after supplying and reacting new raw materials for each batch, the operation of separating the catalyst and collecting the reaction liquid is repeated. There is a way.

  In the present invention, the carbon number of the raw material alcohol to be used is not limited, but an alcohol having a carbon number larger than that of the alkoxy group of the raw material unsaturated carboxylic acid ester is preferably used.

  Examples of the raw material alcohol include ethanol, propanol, isopropanol, n-butanol, t-butanol, n-pentanol, 2-ethylhexanol, lauryl alcohol, stearyl alcohol and other alkyl alcohols, 2-methoxyethanol, 2-ethoxy Alkoxyalkyl alcohols such as ethanol, 1-methoxy-2-propanol, 1-methoxy-2-butanol, phenoxyalkyl alcohols such as 2-phenoxyethanol, 1-phenoxy-2-propanol, cyclohexanol, cyclopentanol, cyclo Cycloalkyl alcohols such as octanol, haloalkyl alcohols such as 2-chloroethanol and 2-bromoethanol, ethanolamine, N, N-dimethylethanolamine Amino alkyl alcohols, ethylene glycol, propylene glycol, trimethylene glycol, polyhydric alcohols such as glycerol, benzyl alcohol and the like. Among these alcohols, those having 2 to 18 carbon atoms are preferred from the viewpoint of transesterification reactivity.

  On the other hand, the raw material unsaturated carboxylic acid ester is not particularly limited, and examples thereof include methyl methacrylate, methyl acrylate, ethyl methacrylate, ethyl acrylate, butyl methacrylate, and butyl acrylate.

  In the presence of the first catalyst, the feed ratio of the raw material unsaturated carboxylic acid ester and the raw material alcohol when performing the first transesterification reaction between the raw material unsaturated carboxylic acid ester and the raw material alcohol is not particularly limited, The amount of raw material unsaturated carboxylic acid ester used relative to 1 mol of raw material alcohol is preferably 0.05 to 20 mol, more preferably 0.1 to 10 mol in view of the balance between yield and productivity.

In the first transesterification reaction, a solvent may be added. The solvent that can be added is not particularly limited as long as it does not contain water, for example, hydrocarbon solvents such as pentane, hexane, heptane, octane, isooctane, cyclopentane, cyclohexane, benzene, toluene, Diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, tetrahydrofuran, diethyl ether, diisopropyl ether, ether solvents such as methyl tert-butyl ether, ketone solvents such as acetone and methyl ethyl ketone, carbon tetrachloride, Chlorinated solvents such as chloroform and methylene chloride. Two or more of these solvents may be mixed or used.
The amount of these solvents used is not particularly limited, but if the amount is too small, the dehydration effect may be lost. If the amount is too large, the productivity may decrease. 0-20 times capacity is more preferable.
The produced second catalyst may be recovered and used for the second transesterification reaction, or may not be recovered and used for the second transesterification reaction.

  Since the target unsaturated carboxylic acid ester can be obtained by a short-time reaction, the present invention is suitable for producing an α, β-unsaturated carboxylic acid ester having high polymerization among the unsaturated carboxylic acid esters. In particular, transesterification reactions are carried out with ethyl alcohol, butyl alcohol, 2-ethylhexyl alcohol and other alcohols using unsaturated carboxylic acid esters such as methyl methacrylate and methyl acrylate, which are industrially inexpensive and easily available. It is suitable for producing the target methacrylic acid ester and acrylic acid ester.

  The production method of the unsaturated carboxylic acid ester of the present invention includes a production method by a batch operation in which a raw material is supplied and reacted to separate a catalyst by batch using a batch type reaction apparatus such as a suspension type or a fluidized bed type, or a fixed type. Any production method such as a production method by continuous operation using a floor-type continuous reaction apparatus or the like may be used. It is preferable that the reactor takes measures to prevent moisture from entering from outside the system. In addition to the liquid phase reaction, it is also possible to carry out the reaction in a gas phase reaction or a gas-liquid mixed system.

  In the presence of the second catalyst prepared in the first transesterification reaction, an unsaturated carboxylic acid ester is produced by performing a second transesterification reaction between the raw material unsaturated carboxylic acid ester and the raw material alcohol. The feed ratio of the raw material unsaturated carboxylic acid ester and the raw material alcohol at that time is not particularly limited, but the amount of the raw material unsaturated carboxylic acid ester used with respect to 1 mol of the raw material alcohol is preferably 0.05 to 20 mol, and the yield and productivity. Is more preferably 0.1 to 10 mol in view of

  The amount of the second catalyst used can be appropriately determined from the activity of the catalyst, the production process of the unsaturated carboxylic acid ester, the amount of production, etc., but the number of moles of titanium or tin supported on the carrier is the mole of the raw alcohol. The amount that is 0.000001 to 1 times the mole is preferable with respect to the number, and the amount that is 0.00001 to 0.5 times the mole is preferable in terms of cost and reactivity.

When the raw material unsaturated carboxylic acid ester may cause a polymerization reaction, for example, in the case of a methacrylic acid ester or an acrylic acid ester, it is preferable that a polymerization inhibitor is present in the reaction system. The polymerization inhibitor is not particularly limited as long as it has a desired function, but those that can be used for the transesterification reaction using alkoxytitanium, dibutyltin oxide, and the like exhibit a good effect. Examples include phenolic compounds such as hydroquinone and paramethoxyphenol, N, N′-diisopropylparaphenylenediamine, N, N′-di-2-naphthylparaphenylenediamine, N-phenyl-N ′-(1,3- (Dimethylbutyl) amine compounds such as paraphenylenediamine and phenothiazine, 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine And N-oxyl compounds such as -N-oxyl. These polymerization inhibitors may be used alone or in combination of two or more.
When performing the second transesterification reaction, a solvent may be used as in the first transesterification reaction.

  In general, the reaction temperature for performing the second transesterification reaction is preferably 95 to 200 ° C. In view of the activity of the catalyst, the reaction temperature is more preferably 100 ° C. or higher, and further preferably 105 ° C. or higher. The reaction temperature is preferably 170 ° C. or lower, more preferably 150 ° C. or lower, from the viewpoint of stability of the active site of the catalyst and suppression of side reactions. Although the temperature may be lower than 95 ° C. in the initial stage or in the middle of the reaction, the activity is greatly reduced when the temperature is lower than 95 ° C. Therefore, it is preferable to maintain the temperature range during the reaction.

The reaction time for performing the second transesterification reaction varies depending on conditions such as the raw material and the activity of the catalyst, but is preferably 0.1 to 50 hours in the case of a batch-type reaction apparatus. Therefore, the reaction time is more preferably 0.5 hours or more, and even more preferably 1 hour or more. From the viewpoint of productivity, the reaction time is more preferably 30 hours or less, and further preferably 10 hours or less. In the case of a continuous reaction apparatus such as a flow type, the contact time is preferably 0.000001 to 0.1 second · g / ml, and from the viewpoint of operation, the contact time is 0.00001 second · g / ml. More preferably, it is more than ml, and further more preferably 0.0001 second · g / ml. From the viewpoint of productivity, the contact time is more preferably 0.01 seconds · g / ml or less, and further preferably 0.005 seconds · g / ml or less.
The reaction time performed in the continuous reaction apparatus is preferably 3 hours or more, more preferably 5 hours or more, and particularly preferably 10 hours or more in order to sufficiently improve the activity.

  The reaction pressure can be processed at any pressure, but when the reaction is carried out in the liquid phase, it is preferable to adjust the pressure so that the reflux temperature of the raw materials, the solvent and the like is within the above temperature range.

  During the reaction, it is preferable to remove the alcohol derived from the starting carboxylic acid ester as a by-product from the reaction system because the reverse reaction can be suppressed and the reaction time can be shortened.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.
In the examples, the water content of the reaction solution was measured using a Karl Fischer moisture meter. The composition of the raw material liquid and the reaction liquid was analyzed using gas chromatography (represented as GC), and the conversion rate (%) of the raw material alcohol was determined by the number of moles of raw material alcohol (N _al ) It calculated by the following formula from the measured value of the number of moles of saturated carboxylic acid ester (N _es ).
Conversion (%) = 100 × N _es / [N _al + N _es ]
The activity of the catalyst was evaluated by the conversion rate of n-butanol 90 minutes after the start of the first transesterification reaction.

[Example 1]
Preparation of First Catalyst Tetra-n-butyl titanate 8.36 g (12.3 mol) was dissolved in 121 g of toluene and vacuum-dried at 150 ° C. for 12 hours. 42 g) (a ratio = 5.5, average pore diameter 4.4 nm) was added little by little with stirring to obtain a slurry. The slurry was heated to 60 ° C. and stirred for 2 hours, and then the solvent was distilled off with an evaporator having a bath temperature of 60 ° C. and vacuum dried at 130 ° C. for 12 hours to obtain a first catalyst.

Preparation of second catalyst ( first transesterification reaction)
902 g of methyl methacrylate (MMA) dehydrated with molecular sieves in a 2 L glass four-necked flask equipped with a 20-stage Older Show, Dean Stark, and a catalyst container made of 100 mesh SUS mesh holding the catalyst. 9.0 mol), 370 g (5.0 mol) of n-butanol similarly dehydrated, and 0.15 g of 2,2,6,6-tetramethyl-4-acetaminopiperidine-N-oxyl as a polymerization inhibitor. The mixture was heated in an oil bath to azeotrope MMA and water, and dewatered by removing water with Dean Stark.
Dehydration treatment was performed while supplementing the extracted MMA and butanol, and the water content in this liquid was analyzed. When the water content in the liquid reached 30 ppm, this dehydration operation was terminated. 10 g of the first catalyst obtained above was introduced into a catalyst container provided in the four-necked flask, and the water content of the reaction liquid at the start of the first transesterification reaction was measured and found to be 32 ppm. Then, the reaction liquid was heated in an oil bath, and the first transesterification reaction was performed at a flask internal temperature of 103 to 135 ° C. while extracting by-product methanol. After 140 minutes, the conversion of n-butanol reached 99%. The reaction was terminated. After cooling the reaction solution, the second catalyst was recovered by taking out the catalyst container and dried in a desiccator. The composition of the reaction solution was analyzed by gas chromatography (GC). The conversion rate of n-butanol 90 minutes after the start of the first transesterification reaction is shown in Table 1 (repeated operation number 1).

Second transesterification reaction Next, using the second catalyst prepared above, the same operation as the first transesterification reaction is repeated to perform the second transesterification reaction (repeated operation number 2). ), And the catalyst was recovered. The same second transesterification reaction was repeated three times using the recovered catalyst. The water content of the reaction liquid at the start of the second transesterification reaction in each operation and the conversion rate of n-butanol 90 minutes after the start of the reaction are summarized in Table 1 (repeated operation numbers 2 to 5).

As the reaction was repeated, the conversion of n-butanol was improved 90 minutes after the start of the reaction.

[Comparative Example 1]
The first catalyst prepared in Example 1 was used as the catalyst, the raw material was not dehydrated, the water content of the reaction solution at the start of the reaction was 230 ppm, and the reaction time was 180 minutes (the conversion rate of n-butanol was The first transesterification reaction was carried out in the same manner as in Example 1 except that the second catalyst was reached, and the reaction solution was analyzed. Further, the second transesterification reaction was repeated four times in the same manner as the first transesterification reaction.
Table 2 summarizes the water content of the reaction liquid at the start of the reaction and the conversion rate of n-butanol 90 minutes after the start of the reaction in each operation.

[Example 2]
The first catalyst was adjusted and the first transesterification was carried out in the same manner as in Example 1 except that the catalyst recovered in the repeated operation number 5 of Comparative Example 1 was used. Further, the second transesterification reaction was repeated four times in the same manner as in Example 1.
Table 2 summarizes the water content of the reaction liquid at the start of the reaction and the conversion rate of n-butanol 90 minutes after the start of the reaction in each operation.

  As shown in Table 2, according to the method of the present invention, not only the activity decreased due to the influence of moisture in the reaction solution but also the activity of the catalyst could be greatly improved. On the other hand, in the method of Comparative Example 1, the activity of the catalyst decreased as the transesterification reaction was repeated.

[Example 3]
A first catalyst was prepared in the same manner as in Example 1 except that silica-alumina having a particle diameter of 1 mm (Si / Al atomic ratio = 2.2, average pore diameter 5.6 nm) was used. Further, using this catalyst, the water content of the reaction solution at the start of the reaction was 35 ppm, and the reaction time was 150 minutes (the conversion of n-butanol reached 99%). A dehydration treatment was performed, a first transesterification reaction was performed, and a second catalyst was prepared. The second transesterification reaction was repeated 4 times in the same manner as in Example 1 using the obtained second catalyst.
Table 3 summarizes the water content of the reaction solution at the start of the reaction and the conversion rate of n-butanol 90 minutes after the start of the reaction in each operation.

[Example 4]
A first catalyst was prepared in the same manner as in Example 3 except that silica having a particle diameter of 1 mm (average pore diameter of 10 nm) was used. Further, using this catalyst, a first transesterification reaction was carried out in the same manner as in Example 3 to prepare a second catalyst. The second transesterification reaction was repeated 4 times in the same manner as in Example 3 using the obtained second catalyst.
Table 4 summarizes the water content of the reaction solution at the start of each reaction and the conversion rate of n-butanol 90 minutes after the start of the reaction.

[Example 5]
The first catalyst prepared in Example 1 was used as the catalyst, except that the water content of the reaction liquid at the start of the reaction was 142 ppm, and the reaction time was 155 minutes (the conversion of n-butanol reached 99%). Was carried out in the same manner as in Example 1 to carry out a first transesterification reaction to prepare a second catalyst. The second transesterification reaction was repeated 4 times in the same manner as in Example 1 using the obtained second catalyst.
Table 5 summarizes the water content of the reaction liquid at the start of the reaction and the conversion rate of n-butanol 90 minutes after the start of the reaction in each operation.

  As described above, according to the production method of the present invention, it is possible to improve the activity of the catalyst or restore the catalyst activity which has been lowered by use and maintain high activity. Thereby, the unsaturated carboxylic acid ester can be stably produced over a long period of time repeatedly or continuously.

Claims (2)

First in the presence of a catalyst a titanium emission reduction compound was supported on a carrier, 100Ppm～180ppm the water content of the reaction at the start of the reaction solution at a reaction temperature 95 ° C. above conditions, the raw material unsaturated carboxylic acid ester and the starting alcohol The first transesterification reaction is performed for 0.1 to 50 hours to prepare a second catalyst, and in the presence of the second catalyst, between the raw material unsaturated carboxylic acid ester and the raw material alcohol A method for producing an unsaturated carboxylic acid ester by performing a second transesterification reaction. A process for preparing a catalyst for producing an unsaturated carboxylic acid ester performed transesterification between a raw material unsaturated carboxylic acid ester and the starting alcohol, the the titanium emission of compounds those supported on a carrier, the initial A method comprising treating at 95 ° C. or more for 0.1 to 50 hours in a liquid containing a raw material unsaturated carboxylic acid ester having a water content of 100 ppm to 180 ppm and a raw material alcohol.