JPH10259164A - Continuous production of dialkyl or diallyl carbonate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for easily producing a dialkyl or diallyl carbonate continuously at high reaction rate and in high yield from urea and an inexpensive alcohol. SOLUTION: This dialkyl or diallyl carbonate is obtained by the following process: a continuous multistate reactor is continuously fed with an alcohol of the general formula ROH (R is a 2-6C aliphatic lower alkyl group of allyl group), urea and a catalyst; ammonia formed by the reaction is continuously withdrawn in a gaseous state via the top of the reactor, while a high-boiling product containing the aimed dialkyl or diallyl carbonate is continuously withdrawn in a liquid state via the bottom.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a continuous process for producing dialkyl or diallyl carbonate. Specifically, a method for continuously producing a dialkyl or diallyl carbonate by reacting an alcohol represented by the general formula ROH (where R is a C ₂ -C ₆ aliphatic lower alkyl group and an allyl group) with urea. It is about. Dialkyl or diallyl carbonate is an important substance as a solvent for resins and paints, an alkylating agent, or a carbonylating agent.

[0002]

2. Description of the Related Art As a method for producing a dialkyl carbonate from an alcohol and urea, Japanese Patent Publication No. 62-54297
Is known as a basic patent, but according to the method described in this example, the reaction time is as long as 8.5 hours, the yield is as low as 41 to 87.9% based on urea, and Is only higher alcohols having 8 or more carbon atoms. Also, JP-A-8-1
No. 19907, methanol or ethanol and urea,
A method for producing dimethyl carbonate or diethyl carbonate by reaction with methyl carbamate or ethyl carbamate has been proposed. The yield of dimethyl carbonate is 0.96 to 4.1% in a reaction time of 5 hours, and a yield of 104 hours in a reaction time of 104 hours. It is extremely low at 18.5%, which is not practical.

[0003]

The above-mentioned method for producing dialkyl carbonate relates to a batch method, and no continuous production method has been known so far. An object of the present invention is to provide a method for easily producing a dialkyl or diallyl carbonate from an inexpensive alcohol and urea continuously at a high reaction rate and a high yield.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, when reacting alcohol and urea in the presence of a catalyst, a continuous multistage reactor was used. At the same time as carrying out the reaction, it was found that dialkyl or diallyl carbonate can be produced continuously at a high reaction rate and high yield by continuously extracting ammonia produced by the reaction from the upper part of the reactor. Reached.

That is, the present invention relates to a method for producing a dialkyl or diallyl carbonate by reacting an alcohol represented by the general formula ROH (where R is a C ₂ -C ₆ aliphatic alkyl group and an allyl group) with urea. ,
The alcohol, urea and catalyst are continuously supplied to the continuous multi-stage reactor, and the ammonia generated in the reaction is continuously extracted in gaseous form from the upper stage of the continuous multi-stage reactor, and the high boiling products containing dialkyl or diallyl carbonate are extracted from the lower stage. This is a continuous method for producing dialkyl or diallyl carbonate, which is continuously extracted in a liquid state.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The continuous multistage reactor used in the present invention is a tank-type or tower-type reactor having two or more reactor stages. Examples of the tower-type reactor include, for example, a bubble tray, a perforated plate tray, a bubble tray, a counter-flow tray, a tray column type using Raschig ring, a pole ring, a bell saddle, a Dexon packing, a McMahon packing, A packed tower type packed with various packing materials such as a helipack, a sulzer packing and the like is used. The number of reactor stages is usually 2
Ｌ10. When the number of stages is 2 or less, ammonia generated in the reaction is dissolved in a large amount in the reaction mixture, so that
The reaction rate and yield are very low. It is not economical to have more stages than necessary.

The reaction of the present invention is usually carried out by continuously supplying a mixture of alcohol, urea and a catalyst to the upper stage of the reactor set at a predetermined temperature and pressure. A method in which part or all of the alcohol is supplied to the lower stage of the reactor, also serving as stripping of ammonia generated in the lower stage of the reactor, is effective.

The general formula ROH of the present invention (where R is C ₂
-C ₆ aliphatic lower alkyl group and allyl group), for example, ethanol, n-
Propanol, n-butanol, isobutanol, 1-
Pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2,2-dimethyl-1-propanol, 1-hexanol, 2-methyl-1-pentanol, 3-methyl-1-pentanol , 4-methyl-1-
Pentanol, 2,2-dimethyl-1-butanol,
2,3-dimethyl-1-butanol, 3,3-dimethyl-1-butanol, 2-ethyl-1-butanol, 3-
It is an aliphatic primary alcohol such as ethyl-1-butanol and allyl alcohol. The ratio of alcohol to urea is usually 2 to 10 moles per 1 mole of urea. When the molar ratio of alcohol to urea is less than 2, selectivity to dialkyl or diallyl carbonate is reduced due to a side reaction of urea itself.

Although the catalyst in the present invention is not limited, a catalyst composed of a simple substance or a compound selected from zinc, magnesium, lead, calcium, titanium, and tin is particularly preferable. , Oxides, hydroxides, inorganic salts, carbonates, basic carbonates, organic acid salts, and the like. Further, the catalyst in the present invention, these zinc,
A single metal or compound of magnesium, lead, calcium, titanium and tin may be reacted with an organic compound present in the reaction system, for example, alcohol, urea, dialkyl or diallyl carbonate. These metals alone or compounds may be used alone or in combination with two or more. Further, these catalysts can be used by mixing them with a compound or a carrier inert to the reaction, or by supporting them on these. The amount of the catalyst used is not particularly limited, but is usually 0.000 per mol of urea.
An amount ranging from 0.01 to 10 mol, preferably from 0.001 to 1 mol, is used.

In the present invention, since the reaction is usually carried out in an alcohol excess system, a solvent is not particularly required. However, when an alkylene carbonate is used as a solvent, a high reaction rate can be obtained and it is effective. Examples of the alkylene carbonate used for the solvent include ethylene carbonate,
Propylene carbonate and the like. Although the amount of the solvent used is not particularly limited, it is usually 0.1 to 10 per mol of urea.
The amount is in the range of moles, preferably in the range of 0.5 to 5 moles.

In the present invention, in a plurality of stages in a continuous multi-stage reactor, alcohol and urea react in the presence of a catalyst to produce ammonia and dialkyl or diallyl carbonate. If ammonia is dissolved in a large amount in the reaction mixture, the reaction rate will be low and the yield will be low. Therefore, it is necessary to make the ammonia concentration in the lower stage of the continuous multistage reactor as low as possible. In order to remove ammonia from the reaction mixture, there is a method in which an inert gas under the reaction conditions is introduced into the reaction solution during the reaction.However, instead of the inert gas, the reaction is carried out under boiling of the raw alcohol. Is more effective.

Among the ammonia and dialkyl or diallyl carbonate formed in the present invention, ammonia is separated from the reaction mixture in a gaseous state, passes through a reflux condenser installed at the top of the reactor for gas-liquid separation, and is separated from the reaction system. Continuously discharged to Since ammonia is dissolved in the reflux liquid, a system in which a part is returned to the reactor and a part is extracted may be considered, but it is not particularly necessary in the present invention. Ammonia discharged to the outside of the reaction system may be used alone, may be a mixture with alcohol, or may contain a small amount of high-boiling substances.

[0013] Among the ammonia and the dialkyl or diallyl carbonate produced in the present invention, the dialkyl or diallyl carbonate is continuously withdrawn in a liquid state from the lower stage of the continuous multistage reactor. In this case, the withdrawn liquid is a mixture of small amounts of ammonia, alcohol, dialkyl or diallyl carbonate, solvents, catalysts and other high boiling products. The dialkyl or diallyl carbonate is separated from the dialkyl or diallyl carbonate-containing liquid thus obtained. As a method for separating dialkyl or diallyl carbonate, a distillation method is usually used, and a substance having a lower boiling point than the dialkyl or diallyl carbonate and a substance having a higher boiling point than the catalyst are recycled to the reaction system and reused.

The reaction temperature in the present invention is from 140 to 270.
° C. When the reaction temperature is low, the reaction rate becomes extremely slow. Since the reaction pressure is restricted by the boiling temperature of the reaction composition solution, a pressurized system is particularly preferable to increase the reaction temperature. The pressure in this case depends on the composition of the reaction solution and the reaction temperature, but is usually in the range of 0 to 3 MPa (gauge pressure), and a pressure that causes boiling at the reaction temperature is appropriately selected. The residence time of the reaction solution in the continuous multistage reactor varies depending on the reaction conditions, the type of the continuous multistage reactor and the number of stages, but is usually 1 to 10 hours.

FIG. 1 is an explanatory view of the present invention in a tank type reactor and a column type reactor. FIG. 1 shows a case of a two-stage tank reactor, in which a mixture of alcohol, urea and a catalyst as raw materials is
The liquid is supplied from the flow path 5 to the first reaction tank 1, and the product liquid from the first reaction tank is further introduced into the second reaction tank 2. The high-boiling products containing dialkyl or diallyl carbonate from the second reaction vessel are continuously withdrawn in a liquid form from the channel 7. On the other hand, the ammonia generated by the reaction is supplied to the first reaction tank and the second reaction tank.
Continuously withdraw from the upper stage of the reaction vessel in gaseous form,
Then, it is continuously discharged from the flow path 6 to the outside of the reaction system through the reflux condenser 4. FIG. 2 shows the case of a tower reactor, in which the raw material liquid is supplied from a flow path 5 to a stage tower 8 (tower reactor), and ammonia produced by the reaction is continuously extracted in gaseous form from the upper stage. It is continuously discharged out of the reaction system through the reflux condenser 4. In addition, a high-boiling product containing dialkyl or diallyl carbonate is continuously withdrawn in a liquid form from the flow path 7 from the lower stage.

[0016]

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.

EXAMPLE 1 A stirrer shown in FIG. 1, a 20 mmφ × 300 mm packed packing column equipped with a reflux condenser at the top, and a 500 ml S column equipped with a pressure control valve at the top of the reflux condenser.
Using two tanks made of US316 tank-type reactors, two tanks were continuously reacted under pressure. Under pressure of 0.6 MPa (gauge pressure) with nitrogen, 264.5 g (3.00 mol) /60.05 g of isoamyl alcohol / urea / zinc oxide was introduced from the raw material inlet of the first reaction tank.
A composition solution having a ratio of 1 g (1.00 mol) /1.5 g was used in an amount of 163.1 g /
hr and heated. The pressure in the reaction system was maintained at 0.6 MPa (gauge pressure) by discharging ammonia generated in the reaction in a gaseous state by a pressure control valve to the outside of the reaction system. On the other hand, the reaction product liquid was transferred to the second reaction tank. In the second reaction tank, the produced ammonia was introduced into the lower part of the packed tower of the first reaction tank, and the reaction product liquid was extracted from the lower part of the second reaction tank to the outside of the reaction system. The liquid level was adjusted so that the residence time of the reaction liquid in the first and second reaction tanks was 3 hours each. The reaction temperature at the time of equilibrium is 198 ° C. in the first reaction tank and 223 ° C. in the second reaction tank.
° C. The reaction product liquid extracted from the lower part of the second reaction tank was 148.5 g / hr, and the composition of the reaction solution was analyzed by gas chromatography to find that diisoamyl carbonate in the reaction solution was 88.9 g. The diisoamyl carbonate yield based on the charged urea is 87.9%.

Example 2 A reaction was carried out in the same manner as in Example 1 except that the reaction was carried out at normal pressure. The reaction temperature at equilibrium was 146 ° C. in the first reaction tank and 150 ° C. in the second reaction tank. The reaction product withdrawn from the lower part of the second reaction tank was 150.0 g / hr, and the composition of the reaction solution was analyzed by gas chromatography to find that the reaction solution contained 33.2 g of diisoamyl carbonate. Diisoamyl carbonate yield based on charged urea is 32.8%
It is.

COMPARATIVE EXAMPLE 1 A single tank continuous reaction was carried out under pressure in the same manner as in Example 1 except that the second reaction tank was not provided. The reaction pressure was 0.6 MPa (gauge pressure) as in Example 1, and the reaction solution residence time was 6 hours. The reaction temperature at equilibrium was 208 ° C. The reaction product withdrawn from the lower part of the reaction tank was 153.1 g / hr, and the composition of the reaction solution was analyzed by gas chromatography to find that the diisoamyl carbonate in the reaction solution was 14.4 g.
Met. The diisoamyl carbonate yield based on the charged urea is 14.2%.

Example 3 As shown in FIG. 2, the inner diameter is 30 mm, the length is 1 m, and the number of steps is 2.
A multi-stage continuous reaction was performed under pressure using a zero-stage SUS316 column tower. Under a pressure of 0.8 MPa (gauge pressure) with nitrogen, 2 parts of n-propyl alcohol / urea / lead acetate / solvent (propylene carbonate) were fed from the raw material inlet at the top of the tower.
40.4 g (4.00 mol) /60.1 g (1.00 mol) / 3.
81.lg of a composition solution having a ratio of 0 g / 102.1 g (1.00 mol)
/ Hr and heated. The ammonia generated in the reaction is discharged out of the reaction system in a gaseous state by a pressure control valve installed at the top of the tower reflux, thereby reducing the pressure in the reaction system to 0.8 MPa.
a (gauge pressure). Further, the reaction product liquid was drawn out of the reaction system from the lower part of the tower. The temperature in the tower at the time of equilibrium
The temperature was 69 ° C and the bottom 202 ° C. The reaction product liquid extracted from the bottom of the column was 74.7 g / hr, and the composition of the reaction solution was analyzed by gas chromatography to find that the dipropyl carbonate in the reaction solution was 26.5 g. The yield of dipropyl carbonate based on urea charge is 90.8%.

Example 4 From 373.5 g of the reaction product solution obtained in Example 2 for 5 hours, n-propyl alcohol and dipropyl carbonate were separated by distillation, and 117.6 g of a catalyst-containing high boiling portion was recovered. . 240.4 g of n-propyl alcohol was added to this solution.
(4.00 mol) and 60.1 g (1.00 mol) of urea were added to prepare 418.lg of the raw material liquid. 83.
The reaction was carried out in the same manner as in Example 2, except that 6 g / hr was used. The temperature in the column at the time of equilibrium was 170 ° C. at the top and 204 ° C. at the bottom. The reaction product liquid extracted from the bottom of the column is 7
When the composition of the reaction solution was analyzed by gas chromatography, the amount of dipropyl carbonate in the reaction solution was 28.4 g. The dipropyl carbonate yield based on freshly supplied urea is 97.2%.

Example 5 Using the same apparatus as in Example 3, a multistage continuous reaction was carried out under pressure. Under pressure of 0.8 MPa (gauge pressure) with nitrogen, 232.3 g of allyl alcohol / urea / zinc oxide / solvent (propylene carbonate) was fed from the raw material inlet at the top of the tower.
(4.00 mol) /60.lg (1.00 mol) /3.0 g / 1
39.8 g / hr of a composition liquid having a ratio of 2.1 g (1.00 mol)
And heated. Ammonia produced by the reaction was discharged out of the reaction system in a gaseous state by a pressure control valve installed at the top of the tower reflux to keep the pressure in the reaction system at 0.8 MPa (gauge pressure). Further, the reaction product liquid was drawn out of the reaction system from the lower part of the tower. The temperature in the tower at the time of equilibrium was 157
° C and the bottom of the column was 183 ° C. The reaction product liquid extracted from the bottom of the column was 36.9 g / hr, and the composition of the reaction liquid was analyzed by gas chromatography. As a result, dipropyl carbonate in the reaction liquid was 12.3 g. The yield of diallyl carbonate based on the charged urea is 86.4%.

[0023]

As is clear from the above examples, according to the method of the present invention, dialkyl or diallyl carbonate is easily produced continuously from alcohol and urea at a high reaction rate and a high yield. I can do it. Therefore, the present invention is an industrially superior method for producing a dialkyl or diallyl carbonate.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a two-tank continuous reactor, and FIG. 2 is an explanatory view of a multi-stage continuous reactor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st reaction tank 2 2nd reaction tank 3 Packing tower 4 Reflux cooler 5 Raw material introduction port 6 Ammonia gas discharge flow path 7 Reaction product liquid extraction flow path 8 stage tower (tower reactor)

Claims (3)

[Claims] An alcohol represented by the general formula ROH (where R is a C ₂ -C ₆ aliphatic alkyl group and an allyl group) is reacted with urea to produce a dialkyl or diallyl carbonate. Urea and a catalyst are continuously supplied to a continuous multistage reactor, and ammonia generated in the reaction is continuously extracted in gaseous form from an upper stage of the continuous multistage reactor, and a high-boiling product containing dialkyl or diallyl carbonate is converted to a liquid state from a lower stage. A method for continuously producing dialkyl or diallyl carbonate, wherein the method is continuously withdrawn. 2. The process for continuously producing dialkyl or diallyl carbonate according to claim 1, wherein the reaction is carried out under pressure using a continuous multistage reactor having two or more stages. 3. The dialkyl or diallyl according to claim 1 or 2, wherein the dialkyl or diallyl carbonate is separated from the product liquid extracted from the lower stage of the continuous multistage reactor, and then the high-boiling product containing the catalyst is recycled to the reaction system. A continuous method for producing carbonate.