JP2000319225A - Production of methacrylic acid alkyl ester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently obtain the subject compound at a high reaction rate by carrying out a transesterification reaction while distilling a by-product alcohol. SOLUTION: In this method for producing the objective compound by performing the transesterification reaction of a methacrylic acid ester with an alkyl alcohol by a batch operation, a vapor rate of by-product alcohol defined by the equation [L/h.nol]=(D+Q)/MROH×R×T/(P×F) D is mass [g/h] of the by-product alcohol in a distillate per unit; Q is mass [g/h] of the by- product in a reflux per unit; MROH is molecular weight [g/mol] of by-product alcohol; R is a gas constant (8.31) [J/mol.K]; T is a temperature [K] of the top of the column; P is pressure [kPa] at the top of the column; F is a fed mol amount [mol] of the raw material alcohol) is 25-200 L/h.mol is 25-200 L/h.mol to perform the reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing an alkyl methacrylate by a transesterification reaction between a methacrylate and an alkyl alcohol.

[0002]

2. Description of the Related Art In a method for producing an alkyl methacrylate by subjecting an ester of a lower aliphatic alcohol of methacrylic acid and an alkyl alcohol to a transesterification reaction in the presence of a catalyst, a lower alcohol produced as a by-product (in the present invention, a by-product) is produced. Methods for distilling alcohols) have been described in the literature. Further, when the by-product alcohol and the raw material methacrylate form an azeotropic composition,
The azeotropic composition having an azeotropic temperature lower than the azeotropic temperature of the azeotropic composition is subjected to azeotropic distillation using a solvent that forms with the by-product alcohol, thereby distilling the by-product alcohol out of the reaction system. Methods for producing the desired alkyl methacrylate are also described in the literature.

[0003] Such prior art documents include, for example, JP-A-58-170730 and JP-A-61-5094.
0, JP-A-61-56155, JP-A-63-56155
JP-287748, JP-A-2-101042, JP-A-2-01043, JP-A-6-949
No. 5, JP-A-6-256260, JP-A-9-206
No. 183751 and the like.

[0004] Also, Japanese Patent Application Laid-Open No. 2-101444 discloses that
It is described that, for the purpose of improving the reaction rate of the transesterification reaction which is an equilibrium reaction, a predetermined amount or more of evaporation is secured to reduce by-product alcohol in the reactor.

[0005]

It is very important to shorten the operation time by increasing the reaction rate in order to reduce the production cost. However, Japanese Patent Application Laid-Open No. 2-101444 discloses extraction of by-product alcohol. There is no description of the conditions for adjusting the amount or withdrawal amount. Therefore, the operation conditions of the reaction have to rely on the feeling of the operator, and the operation has not been performed under the optimal conditions for efficiently performing the transesterification at a high reaction rate.

Accordingly, an object of the present invention is to provide a method for producing an alkyl methacrylate in which a transesterification reaction between a methacrylate and an alkyl alcohol is carried out in a batch operation to efficiently produce an alkyl methacrylate at a high reaction rate. It is to provide a method.

[0007]

According to the present invention, there is provided a method for producing an alkyl methacrylate in which a transesterification reaction between a methacrylic ester and an alkyl alcohol is carried out in a batch operation. This is a method for producing an alkyl methacrylate, wherein a transesterification reaction is performed while distilling a by-product alcohol at a rate of 25 to 200 L / h · mol. By-product alcohol vapor rate [L / h · mol] = (D + Q) / M _ROH × R × T / (P × F) (1) D: Mass of by-product alcohol in distillate per unit time [g / h] Q: Mass of by-product alcohol in reflux liquid per unit time [g / h] M _ROH : Molecular weight of by-product alcohol [g / mol] R: Gas constant (8.31) [J / mol · K] T: overhead temperature [K] P: overhead pressure [kPa] F: charged molar amount of raw material alcohol [mol]

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the methacrylic acid ester as a raw material for a transesterification reaction is not particularly limited as long as it can be transesterified with an alkyl alcohol as another raw material. Is used. Examples of such a methacrylate include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, and the like, with methyl methacrylate being particularly preferred.

As the alkyl alcohol which is a raw material for the transesterification reaction, one corresponding to the target alkyl methacrylate is used. For example, when producing isobutyl methacrylate, isobutyl alcohol, 2
-When producing ethylhexyl methacrylate, 2-
When producing ethylhexyl alcohol and cyclohexyl methacrylate, cyclohexyl alcohol is used.

The amount of the methacrylic acid ester to be used is generally 1 to 10 moles, preferably 1.2 to 5 moles, per mole of the alkyl alcohol. As the amount of methacrylate increases, the reaction rate increases, and as the amount decreases, the productivity per reactor volume increases.

Usually, a catalyst is used in the transesterification reaction. Examples of such a catalyst include tetramethoxytitanium, dibutyltin oxide, dioctyltin oxide and the like. The amount of the catalyst used is usually 0.01% of the total mass of the methacrylic acid ester and the alkyl alcohol.
To 2%, preferably 0.02 to 1%.

In the present invention, the type of the reaction apparatus used for the transesterification reaction is not particularly limited as long as the reaction can be carried out in a batch operation and distillation can be carried out during the reaction.
As such a reaction apparatus, for example, a batch-type reaction tank equipped with a distillation column can be mentioned. The type of the distillation column is not particularly limited, and a tray type, a packed column type, or the like can be used.

The reaction pressure of the transesterification reaction may be any of reduced pressure, normal pressure and increased pressure, but is preferably reduced pressure, particularly preferably 10 to 100 kPa, in order to suppress polymerization or side reactions. The reaction temperature is determined by the boiling point of the reaction system at the reaction pressure, and is preferably 333K to 423K.

In the present invention, the by-product alcohol is removed by distillation during the transesterification reaction. In this case, the by-product alcohol is defined by the above formula (1) which is an index of the rate at which the by-product alcohol is removed from the reaction system. The by-product alcohol vapor rate to 25
It is important to set it to ２００200 L / h · mol. In order to remove the by-product alcohol from the reaction system so as not to hinder the progress of the reaction, the vapor speed of the by-product alcohol is 30 L /
h · mol or more is preferable. However, if the vapor rate of the by-product alcohol is higher than the rate of production of the by-product alcohol produced by the reaction, the reaction is in a rate-limiting state, and not only the by-product alcohol but also the raw material components may be removed from the reaction system. Since the equipment for removing raw alcohol becomes excessively large, the vapor speed of by-product alcohol is 150 L /
h · mol or less is preferable.

The vapor speed of the by-product alcohol can be determined by changing the size or capacity of the distillation column, for example, by the above formula (1).
The parameters D, Q, T and P can be adjusted by increasing or decreasing.

In the distillation, when the by-product alcohol and the unreacted raw material methacrylate form an azeotropic composition, the by-product alcohol may be taken out of the system by azeotropic distillation. A solvent that forms an azeotropic composition with the by-product alcohol at a temperature can be added and removed as an azeotrope outside the reaction system.

In the transesterification reaction, a polymerization inhibitor is usually added to suppress the polymerization of the reaction system. The polymerization inhibitor is not particularly limited, and examples thereof include hydroquinone, hydroquinone monomethyl ether, phenothiazine, N, N'-di-2-naphthyl-p-phenylenediamine (hereinafter, referred to as NF). The addition amount of the polymerization inhibitor is preferably 0.001 to 2% of the mass of the reaction solution. If the amount of the polymerization inhibitor is too small, the effect of inhibiting the polymerization is not sufficient.If the amount is too large, the polymerization inhibitor cannot be sufficiently separated from the target product alkyl methacrylate, and the obtained alkyl methacrylate is used as a raw material of the polymer. When used as a monomer, it has adverse effects such as inhibition of polymerization.

When oxygen or a mixture of oxygen and an inert gas, such as air, a mixed gas of oxygen and argon, or the like is introduced into the reaction solution and / or the surface of the reaction solution over the entire reaction time, the starting material methacrylate or The effect of inhibiting polymerization of the resulting alkyl methacrylate is further improved.

[0019]

The present invention will be described in more detail with reference to the following examples. The mass of each compound in the reaction mixture was analyzed using gas chromatography. The by-product alcohol vapor rate was as described above, and the conversion was determined by the following equation. Conversion [%] = {1- (C _ROH / M _ROH ) / (C _ROH / M
_ROH + C _RMA / M _RMA )｝ × 100 C _ROH : Ratio of raw material alcohol in reaction liquid [% by mass] C _RMA : Ratio of alkyl methacrylate in reaction liquid [% by mass] M _ROH : Molecular weight of raw material alcohol [ g / mol] M _RMA : molecular weight of alkyl methacrylate [g / mol]
mol]

Example 1 444.7 g (6.0 mo) of isobutyl alcohol (hereinafter referred to as IBOH) as a raw material in a glass 3L flask equipped with a stirring blade and a thermometer.
l) and 1201.4 g of methyl methacrylate (hereinafter referred to as MMA), 0.516 g of tetramethoxytitanium as a catalyst, and 0.1% of NF as a polymerization inhibitor.
085 g was added, and the flask was attached to a distillation column equipped with a distillation column, a cooling device, and a liquid distributor. The distillation column has an inner diameter of 3
A 5 mm glass 20-stage Oldershaw distillation column was used.

The reaction was started by heating the flask with an oil bath. The reaction was performed at atmospheric pressure. The methanol (molecular weight 32.04 g / mol) generated in the system was adjusted to a reflux ratio of 1 to 20 so that the 10th stage from the bottom of the distillation column became 338 K to 343 K, and methanol and methyl methacrylate were co-existed from the top of the column. The boil was distilled off. IBOH conversion of 9
It takes 2 hours from the start of the reaction to reach 9%. At that time, the composition of the reaction solution is 0.4% by mass of methanol, 40% by mass of MMA, 0.3% by mass of IBOH, and isobutyl methacrylate (hereinafter referred to as IBMA) 59.3. % By mass. The mass of by-product methanol in the distillate per unit time during the reaction was 92 g / h, the mass of by-product methanol in the reflux solution per unit time was 198 g / h, and the top temperature of the distillation column was 3 g / h.
At 37.6 K, the overhead pressure was 100 kPa, and the vapor rate of by-product methanol was 42 L / h · mol. The average composition of the azeotrope of methanol and methyl methacrylate distilled from the top was 77.2% by mass of methanol, M
MA was 22.8% by mass.

Example 2 The reaction was carried out in the same manner as in Example 1 except that the distillation column was replaced with one having an inner diameter of 40 mm.
One hour from the start of the reaction even though the conversion of OH exceeds 99% 4
It took 5 minutes, and the composition of the reaction solution at that time was 0.1 ml of methanol.
5% by mass, MMA 39.2% by mass, IBOH 0.2% by mass, and IBMA 60.1% by mass. The amount of by-product methanol in the distillate per unit time during the reaction was 105 g /
h, the by-product methanol mass in the reflux liquid per unit time is 279 g / h, the top temperature of the distillation column is 337.5 K, the top pressure is 100 kPa, and the vapor rate of by-product methanol is 56 L / h · mol. Met. The average composition of the azeotrope of methanol and methyl methacrylate distilled from the top was 77.9% by mass of methanol and 22.1% by mass of MMA.
Met.

Comparative Example 1 The reaction was carried out in the same manner as in Example 1 except that the distillation column was replaced with one having an inner diameter of 25 mm.
It took 4 hours from the start of the reaction for the conversion of OH to exceed 99%, at which time the composition of the reaction solution was 0.5% by mass of methanol, 38.8% by mass of MMA, 0.3% by mass of IBOH,
BMA was 60.4% by mass. The amount of by-product methanol in the distillate per unit time during the reaction was 46 g / h, and the amount of by-product methanol in the reflux liquid per unit time was 77 g / h.
h, the top temperature of the distillation column is 337.6 K, and the top pressure is 10
0 kPa, and the vapor speed of by-product methanol was 18 L /
h · mol. The average composition of the azeotrope of methanol and methyl methacrylate distilled off from the top was 76.6% by mass of methanol and 23.4% by mass of MMA.

[Example 3] A glass lining equipped with a stirring blade and a thermometer was applied, and a 200 was equipped with a steam jacket.
23.6 kg (318 mol) of IBOH and 63.7 kg of MMA were charged into the reactor L, 54.7 g of tetramethoxytitanium as a catalyst, and NF as a polymerization inhibitor.
4 g were added. The reactor was equipped with a distillation tower, a cooling device, and a liquid distributor. The distillation column is made of glass 20 with an inner diameter of 100 mm.
A staged Oldershaw distillation column was used.

The reaction vessel was heated by steam to start the reaction. When the reaction was carried out in the same manner as in Example 1, IBOH
It takes 2 hours and 15 minutes from the start of the reaction for the conversion of the compound to exceed 99%, at which time the composition of the reaction solution is 0.2% by mass of methanol, 39.4% by mass of MMA, 0.2% by mass of IBOH,
BMA was 60.2% by mass. The by-product methanol in the distillate per unit time during the reaction was 4400 g / h,
The by-product methanol mass in the reflux liquid per unit time is 11
900 g / h, the top temperature of the distillation column was 337.6 K, the top pressure was 100 kPa, and the vapor rate of by-product methanol was 45 L / h · mol. The average composition of the azeotrope of methanol and methyl methacrylate distilled from the top was 77.4% by mass of methanol and 22.6% by mass of MMA.
Met.

Comparative Example 2 The reaction was carried out in the same manner as in Example 3 except that the distillation column was replaced with one having an inner diameter of 50 mm.
It took 8 hours from the start of the reaction for the conversion of OH to exceed 99%, at which time the composition of the reaction solution was 0.3% by mass of methanol, 39.0% by mass of MMA, 0.2% by mass of IBOH,
BMA was 60.5% by mass. The amount of by-product methanol in the distillate per unit time during the reaction was 1200 g / h,
The by-product methanol mass in the reflux liquid per unit time is 24
00 g / h, the top temperature of the distillation column was 337.5 K, the top pressure was 100 kPa, and the vapor rate of by-product methanol was 10 L / h · mol. The average composition of the azeotrope of methanol and methyl methacrylate distilled from the top was 76.7% by mass of methanol and 23.3% by mass of MMA.
Met.

Example 4 2-Ethylhexyl alcohol (hereinafter referred to as EHOH) 4 was placed in a 200 L reaction vessel.
1.4 kg (318 mol) and 63.7 kg of MMA
And tetramethoxy titanium 54.7 as a catalyst
g, 3.3 g of NF as a polymerization inhibitor
When the reaction was carried out in the same manner as in
%, It takes 2 hours and 30 minutes from the start of the reaction. At that time, the composition of the reaction solution is methanol 0.1% by mass, MMA3
0.4% by mass, 0.2% by mass of EHOH, and 69.3% by mass of 2-ethylhexyl methacrylate (hereinafter, EHMA). The amount of by-product methanol in the distillate per unit time during the reaction was 4000 g / h, the amount of by-product methanol in the reflux liquid per unit time was 12000 g / h, the top temperature of the distillation column was 337.7 K, The top pressure was 100 kPa, and the vapor speed of by-product methanol was 39 L / h · mol. The average composition of the azeotrope of methanol and methyl methacrylate distilled from the top of the column was methanol 76.3.
% By mass and 23.7% by mass of MMA.

Comparative Example 3 The reaction was carried out in the same manner as in Example 4 except that the distillation column was replaced with one having an inner diameter of 50 mm.
It took 7 hours and 30 minutes from the start of the reaction for the conversion of EHOH to exceed 99%. At that time, the composition of the reaction solution was 0.1% by mass of methanol, 31.6% by mass of MMA, and 0.3% by mass of EHOH.
% By mass and 68.0% by mass of EHMA. The by-product methanol in the distillate per unit time during the reaction was 130
0 g / h, the by-product methanol in the reflux liquid per unit time was 3100 g / h, and the top temperature of the distillation column was 337.7.
K, the overhead pressure was 100 kPa, and the vapor rate of by-product methanol was 12 L / h · mol. The average composition of the azeotrope of methanol and methyl methacrylate distilled from the tower top was 77.3% by mass of methanol and 22.
It was 7% by mass.

Example 5 A 200 L reactor was charged with cyclohexyl alcohol (hereinafter referred to as CHOH) 31.9.
kg (318 mol) and 63.7 kg of MMA were added, and 218.8 g of tetramethoxytitanium was added as a catalyst, and 2.8 g of NF was added as a polymerization inhibitor, and the reaction was carried out in the same manner as in Example 3. It takes 5 hours from the start of the reaction to exceed 99%, at which time the composition of the reaction solution is 1.1% by mass of methanol, 34.7% by mass of MMA,
0.3% by mass of CHOH and 63.9% by mass of cyclohexyl methacrylate (hereinafter referred to as CHMA).
The amount of by-product methanol in the distillate per unit time during the reaction was 1400 g / h, the amount of by-product methanol in the reflux liquid per unit time was 12000 g / h, the top temperature of the distillation column was 337.8 K, The top pressure was 100 kPa, and the vapor rate of by-product methanol was 37 L / h · mol.
The average composition of the azeotrope of methanol and methyl methacrylate distilled from the top of the column was 73.8% by mass of methanol,
MMA was 26.2% by mass.

Comparative Example 4 The reaction was carried out in the same manner as in Example 5 except that the distillation column was replaced with one having an inner diameter of 50 mm.
It took 14 hours from the start of the reaction for the conversion of OH to exceed 99%, at which time the composition of the reaction solution was 1.1% by mass of methanol, 34.5% by mass of MMA, 0.3% by mass of CHOH,
CHMA was 64.1% by mass. The by-product methanol in the distillate per unit time during the reaction was 700 g / h,
The by-product methanol mass in the reflux liquid per unit time is 56
00 g / h, the top temperature of the distillation column was 337.8 K, the top pressure was 100 kPa, and the vapor rate of by-product methanol was 17 L / h · mol. The average composition of the azeotrope of methanol and methyl methacrylate distilled from the top was 72.7% by mass of methanol and 27.3% by mass of MMA.
Met.

[0031]

According to the present invention, in a method for producing an alkyl methacrylate by a transesterification reaction between a methacrylate and an alkyl alcohol, the alkyl methacrylate can be efficiently produced at a high reaction rate. .

Claims (2)

[Claims] 1. A method for producing an alkyl methacrylate in which a transesterification reaction between a methacrylic acid ester and an alkyl alcohol is carried out by a batch operation,
The by-product alcohol vapor rate defined by 25 to 200 L /
A method for producing an alkyl methacrylate, wherein a transesterification reaction is carried out while distilling a by-product alcohol under a condition of h · mol. By-product alcohol vapor rate [L / h · mol] = (D + Q) / M _ROH × R × T / (P × F) (1) D: Mass of by-product alcohol in distillate per unit time [g / h] Q: Mass of by-product alcohol in reflux liquid per unit time [g / h] M _ROH : Molecular weight of by-product alcohol [g / mol] R: Gas constant (8.31) [J / mol · K] T: overhead temperature [K] P: overhead pressure [kPa] F: charged molar amount of raw material alcohol [mol] 2. The method for producing an alkyl methacrylate according to claim 1, wherein the alkyl alcohol is at least one selected from the group consisting of isobutyl alcohol, 2-ethylhexyl alcohol and cyclohexyl alcohol.