JP2006022067A - System for producing dimethyl carbonate, method for producing dimethyl carbonate, and compound - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a system for industrially mass-producing dimethyl carbonate at low cost in an energy-saving way, and to provide a method for producing dimethyl carbonate. <P>SOLUTION: In the system 10, dimethyl carbonate is produced using an acetal and carbon dioxide as raw materials. In this system 10, by-products formed in producing the dimethyl carbonate are reacted with methanol to regenerate the acetal as one of the raw materials for the dimethyl carbonate. This system 10 works as follows: Carbon dioxide left unreacted in a mixture of the dimethyl carbonate and the by-products produced in a reactor 20 and an unreacted acetal is removed under high pressures by a CO<SB>2</SB>separator 30, and thereafter the dimethyl carbonate and the by-products are separated by a DMC refining column 40. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a dimethyl carbonate production system, a dimethyl carbonate production method, and the like.

Conventionally, MTBE (Methyl Tertiary Butylether) has been used as a gasoline additive for improving gasoline combustibility, so-called octane booster. However, due to its harmfulness, etc., there is a trend to restrict its use in the United States.
As an alternative to MTBE, DMC (Dimethyl Carbonete: hereinafter, dimethyl carbonate) has attracted attention.

  As a method for producing dimethyl carbonate, there is a method in which methanol and carbon dioxide are reacted using tetraalkoxytitanium, diazabicycloalkenes and a methylating agent, an alkoxy compound of tin, zirconium, titanium, or the like (for example, , See Patent Document 1).

  In addition, a method for producing dimethyl carbonate using acetals, carbon dioxide and the like has also been proposed (see, for example, Non-Patent Document 1).

Japanese Patent Laid-Open No. 11-80096 Toshiyasu Sakakura, “Conversion of supercritical carbon dioxide and liquefied propane by molecular catalyst”, Chemical Equipment, Industrial Research Committee, February 1999, p. 54, FIG.

  However, in the technique described in Patent Document 1, materials with poor environmental properties such as tetraalkoxy titanium and titanium alkoxy compounds are used. If you try to mass-produce dimethyl carbonate, you will discharge a lot of substances with poor environmental properties. For this reason, this method is not suitable for mass production.

On the other hand, the technique described in Non-Patent Document 1 is excellent in environmental properties and inexpensive, and is suitable for mass production of dimethyl carbonate, which may contribute to the spread of dimethyl carbonate. .
However, this technology is currently at an experimental level, and Non-Patent Document 1 does not mention any industrialization method for mass-producing dimethyl carbonate.
For example, in this technique, ketone (acetone) or aldehyde is produced as a by-product during the production of dimethyl carbonate. By treating these compounds with alcohol, they can be easily returned to the raw material acetals, which can be a very economical technology. There is no mention of any configuration for the purpose. In addition, it is necessary to reliably separate unreacted substances and by-products from dimethyl carbonate before finally removing only dimethyl carbonate. However, these specific means are not disclosed at all. Absent.

In addition, when industrially mass-producing dimethyl carbonate, it is very important to suppress costs and energy consumption. Unless this can be solved, it is not industrially feasible.
The present invention has been made on the basis of such a technical problem. A dimethyl carbonate production system capable of industrially mass-producing dimethyl carbonate and achieving low cost and energy saving is disclosed. It aims at providing a manufacturing method etc.

In view of the above problems, the present inventors have intensively studied.
As a result, in the dimethyl carbonate production system using acetals shown in Non-Patent Document 1, dimethyl carbonate and other by-products and unreacted substances are separated using a separation device such as a distillation tower, and dimethyl carbonate We have devised a method for continuously synthesizing.

  The distillation column is used for separating a target substance from a mixture. The liquid phase component of the mixture introduced into the distillation tower is heated with a boiler or the like. Then, it evaporates from a substance with a low boiling point among mixtures. As a result, a concentration distribution in which the concentration of a substance having a low boiling point in the mixture is high on the upper side of the distillation column and the concentration of a substance having a high boiling point is increased on the lower side is generated. A substance having a low boiling point can be recovered by discharging steam from the upper part of the distillation column and condensing the discharged steam. On the other hand, a substance having a high boiling point in the mixture can be recovered by recovering the substance in a liquid state from the lower part of the distillation column.

  For example, as shown in [Chemical Formula 1], when acetone dimethyl acetal as an acetal and carbon dioxide are reacted in a reactor, a mixture of dimethyl carbonate and acetone (dimethyl ketone) as a by-product is generated. When this mixture is introduced into the distillation column as described above, acetone vapor and carbon dioxide are discharged from the upper portion of the distillation column, and dimethyl carbonate can be recovered in a liquid state from the lower portion of the distillation column. At this time, acetone vapor and carbon dioxide discharged from the upper part of the distillation column are partially condensed by the cooler and returned to the distillation column.

  However, in order to make the above operation industrially feasible, acetone discharged from the distillation column is recovered, methanol is added thereto, and as shown in [Chemical Formula 2], acetone dimethyl acetal used as a raw material for dimethyl carbonate. Is an essential condition. For this purpose, carbon dioxide discharged together with acetone from the distillation column needs to be separated from acetone.

In general, in a distillation column, water is usually used as a cooling source in a cooler in terms of economy. For this reason, the cooling temperature in the cooler is around 45 ° C., but acetone vapor containing a large amount of carbon dioxide cannot be condensed. This is because the vapor pressure of acetone at 45 ° C. is high and a large amount of non-condensable carbon dioxide is mixed.
Here, in order to separate carbon dioxide and acetone at a cooling temperature of 45 ° C., it is necessary to perform the above separation operation under a high pressure suitable for this. On the other hand, it is not practical to use a distillation column at a very high pressure because the distillation column is generally a large-sized device.

The present inventors who have found such a problem have obtained the present invention through repeated studies.
That is, the dimethyl carbonate production system of the present invention comprises a reactor for reacting acetals with carbon dioxide to produce dimethyl carbonate, dimethyl carbonate produced in the reactor, by-products in the reactor, and unreacted in the reactor. A first separation device for separating and removing carbon dioxide from a mixture of acetals and carbon dioxide in the reaction; and a second separation device for separating and removing dimethyl carbonate from the mixture from which carbon dioxide has been removed by the first separation device. And a separation device.
Thus, carbon dioxide can be separated from the mixture discharged from the reactor by first separating carbon dioxide and then separating dimethyl carbonate and by-products.

The carbon dioxide taken out by the first separation device can be supplied to the reactor through the carbon dioxide supply path. Thereby, carbon dioxide can be recycled. At this time, it is necessary to compress the carbon dioxide with a compressor or the like and increase the pressure to a pressure suitable for the reaction.
In the first separation device, it is preferable to separate and remove carbon dioxide from the mixture under a pressure higher than normal pressure. This is because, as described above, when compressing carbon dioxide, the required energy is less when compressed from a high pressure state. The high-pressure state referred to here does not need to be the same pressure as the high-pressure state when the reaction is performed in the reactor, and may be a pressure suitable for carbon dioxide separation.
In the second separator, dimethyl carbonate can be separated and taken out from the mixture at a lower pressure than the first separator.

  Further, an acetal generator that produces acetals by reacting methanol with a by-product remaining after separating dimethyl carbonate in the second separator, and an acetal supply path that supplies the acetals to the reactor, In addition, acetals can be recycled.

The present invention provides a reactor for obtaining dimethyl carbonate by reacting acetals and carbon dioxide under a first pressure higher than normal pressure, and under a second pressure higher than normal pressure and lower than first pressure. CO ₂ stripper or flash tank consisting of a CO ₂ stripper or flash tank that separates and removes carbon dioxide from the mixture of dimethyl carbonate produced in the reactor, by-products produced in the reactor, and unreacted acetals and carbon dioxide in the reactor. A carbon separator, a distillation column that separates the mixture that has passed through the carbon dioxide separator into dimethyl carbonate and by-products at a pressure lower than that of the carbon dioxide separator, that is, a pressure lower than the second pressure, and is discharged from the distillation column. An acetal regenerator that regenerates acetals by reacting by-products with methanol, carbon dioxide extracted from the carbon dioxide separator, and A supply path for supplying acetals reproduced by the tar reproducing apparatus as a raw material to the reactor, it may be regarded as dimethyl carbonate production system, characterized in that it comprises a.

The method for producing dimethyl carbonate of the present invention includes a reaction step of reacting acetals with carbon dioxide to obtain dimethyl carbonate, dimethyl carbonate obtained in the reaction step, by-products generated in the reaction step, and reaction step. A carbon dioxide separation step for separating and removing carbon dioxide from a mixture of unreacted acetals and carbon dioxide, and a dimethyl carbonate separation step for separating and removing dimethyl carbonate from the mixture that has undergone the carbon dioxide separation step. It can also be a feature.
In this case, in the reaction step, dimethyl carbonate is obtained by reacting under a pressure higher than normal pressure. In the carbon dioxide separation step, carbon dioxide is separated from the mixture at a pressure higher than normal pressure and lower than the reaction step. In the dimethyl carbonate separation step, it is preferable to separate and remove dimethyl carbonate from the mixture at a lower pressure than in the carbon dioxide separation step.
Further, in the dimethyl carbonate separation step, a by-product remaining by separating dimethyl carbonate is reacted with methanol to regenerate the acetals, the acetals regenerated in the acetal regeneration step, and the carbon dioxide separation step It is also preferable to further include a circulation step of circulating the carbon dioxide taken out in step 1 to the reaction step.

The present invention can also be understood as a compound produced by the above system and method.
That is, the compound of the present invention removes unreacted carbon dioxide contained in the reaction product from the reaction product obtained by reacting acetals with carbon dioxide, and further removes by-products from the reaction product. It is characterized by being generated by.
Dimethyl carbonate can be obtained by removing carbon dioxide from the reaction product obtained by reacting acetals and carbon dioxide, and further removing by-products. It is allowed to contain not only the additives but also additives that are appropriately added during the process.
Such compounds can be used as gasoline additives. In addition to this, the compound of the present invention can also be used for other uses such as a raw material for polycarbonate, which is an engineering plastic, or a carbonylating agent, a raw material for a fuel cell.

  According to the present invention, dimethyl carbonate can be industrially mass-produced at low cost and with reduced energy consumption.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
In the following description, acetone dimethyl acetal is used as the acetal, and acetone is used as a by-product in the reaction process, but the material is not limited to this material.
FIG. 1 is a diagram for explaining a configuration of a dimethyl carbonate production system 10 in the present embodiment.
As shown in FIG. 1, a dimethyl carbonate production system 10 includes a reactor 20, a CO ₂ separation device (first separation device, carbon dioxide separation device) 30, a DMC purification tower (second separation device, distillation column). 40, an acetal regenerator (acetal generator) 50, and a dehydrator 60 are provided.

In the reactor 20, high-pressure liquid carbon dioxide pressurized to a pressure higher than normal pressure, for example, 30 MPa, and acetone dimethyl acetal in the same high-pressure state are combined and mixed in advance and vaporized and introduced. Is done.
In the reactor 20, CO ₂ is reacted with acetone dimethyl acetal under a predetermined catalyst under a predetermined pressure (first pressure) higher than normal pressure, for example, 30 MPa. In such a reaction by the catalyst, in the reactor 20, dimethyl carbonate (compound) is generated (synthesized), and acetone is generated as a by-product (reaction process).

  As such a catalyst, for example, a dibutyltin catalyst can be used. However, dibutyltin catalysts are not toxic because they are highly toxic, relatively expensive, and the reaction conditions are severe. Therefore, it is preferable to use a catalyst in which a strong acid is supported on a carrier made of a compound having a solid acid point.

In this case, a compound having a solid acid site, various solid, especially metal oxides _{(Al 2 O 3, V 2} O 5 , etc.), sulfides (ZnS, etc.), sulfate (NiSO _4, CuSO ₄ Etc.), phosphates (AlPO ₄ , Ti phosphates, etc.), chlorides (AlCl ₃ , CuCl ₂ etc.), clay minerals, zeolites, etc., and solid acids that perform acid-base catalysis. In the present embodiment, it is particularly preferable to use ZrO ₂ , Al ₂ O ₃ , or TiO ₂ .
Further, it is preferable to use SO ₄ ^2- or PO ₄ ^3- as the strong acid to be supported. However, other strong acids can be supported on the carrier. As SO ₄ ²⁻ or PO ₄ ³⁻ , those derived from H ₂ SO ₄ , H ₃ PO ₄ , (NH ₄ ) ₂ SO ₄ , (NH ₄ ) ₃ PO ₄ can be used.

The mixture of dimethyl carbonate and acetone discharged from the reactor 20 is sent to the CO ₂ separation device 30 in a high pressure state. At this time, unreacted acetone dimethyl acetal and carbon dioxide are mixed in the reactor 20. Yes.
In the CO ₂ separator 30, carbon dioxide is separated from dimethyl carbonate and acetone at a predetermined pressure (second pressure) higher than normal pressure and lower than the pressure at which the reaction is performed in the reactor 20, for example, 4 MPa. (Carbon dioxide separation step).
As such a CO ₂ separation device 30, a CO ₂ stripper provided with a heat source 31 for heating a liquid or a flash tank can be suitably used.
The CO ₂ stripper has a configuration similar to that of a so-called tray type or packed type distillation column, and a mixture of dimethyl carbonate, acetone, and carbon dioxide is sprinkled under high pressure, and liquid components such as dimethyl carbonate and Acetone remains as it is, and only carbon dioxide rises. Then, at a predetermined pressure, for example, 4 MPa, only carbon dioxide is separated and discharged from the top of the CO ₂ stripper, and dimethyl carbonate and acetone are discharged from the bottom in a liquid state and sent to the DMC purification tower 40. .
The flash tank is a device that evaporates high-pressure liquid and separates it into low-pressure steam and low-pressure condensate. Like the CO ₂ stripper, it separates carbon dioxide and purifies DMC with dimethyl carbonate and acetone in the liquid state. Send to tower 40.

As the DMC purification column 40, a so-called tray type or packed type distillation column can be adopted. In the DMC purification tower 40, when the mixed liquid of dimethyl carbonate and acetone is introduced, the mixed liquid at the bottom of the tower is heated by the reboiler 41 and returned to the DMC purification tower 40. Thereby, it evaporates from a substance with a low boiling point among the liquid mixture in the DMC purification tower 40, and raises the inside of a tower. The liquid mixture newly introduced into the DMC purification tower 40 and falling inside the tower comes into vapor-liquid contact with the rising steam.
As a result, a concentration distribution occurs in which the concentration of acetone, which is a substance having a low boiling point, of the mixed liquid is increased on the upper side of the DMC purification tower 40 and the concentration of DMC, which is a substance having a high boiling point, is increased on the lower side. And acetone can be collect | recovered in a liquid state by discharging | emitting the vapor | steam of acetone from the upper part of the DMC refinement | purification tower 40, and condensing the discharged | emitted vapor | steam with the cooler 42. FIG. On the other hand, dimethyl carbonate can be recovered in a liquid state from the lower part of the DMC purification tower 40 (dimethyl carbonate separation step).

The acetone discharged from the DMC purification tower 40 is mixed with methanol supplied from the outside and introduced into the acetal regenerator 50. By reacting acetone and methanol in the acetal regenerator 50, acetone dimethyl acetal and water are generated.
The mixed solution of acetone dimethyl acetal and water discharged from the acetal regenerator 50 is sent to the dehydrator 60.
In the dehydrator 60, water is discharged from the lower part, and acetone dimethyl acetal condensed by the condenser 61 is discharged from the upper part. A part of the condensed acetone dimethyl acetal is circulated to the dehydrator 60. The remainder of the acetone dimethyl acetal is pressurized by the compressor 62, is brought to a high pressure state of about 30 MPa, for example, and is circulated to a circulation path (acetal supply path, carbon dioxide supply path, supply path) 70 connected to the reactor 20.
Further, the high-pressure carbon dioxide discharged from the CO ₂ separation device 30 is also circulated through the circulation path 70.
Here, the carbon dioxide is compressed to a predetermined pressure. For this, a plurality of stages of compressors 71, 72, etc. may be used as necessary.

The dimethyl carbonate production system 10 as described above can produce dimethyl carbonate using acetone dimethyl acetal and carbon dioxide as raw materials. At this time, no toxic substances are used as raw materials. Acetone, which is a by-product in producing dimethyl carbonate, is reacted with methanol to obtain acetone dimethyl acetal as a raw material for dimethyl carbonate, and in that case, water is produced. In this way, the discharge is water, and no harmful substances are discharged. By producing dimethyl carbonate in this way, there is no environmental problem in mass production.
In addition, since the entire reaction system is only supplied with carbon dioxide and methanol, dimethyl carbonate can be produced at low cost.
The dimethyl carbonate production system 10 including the reactor 20, the CO ₂ separation device 30, the DMC purification tower 40, the acetal regenerator 50, and the dehydrator 60 can realize the dimethyl carbonate production method at an industrial level. Industrialization of dimethyl carbonate can be achieved.

The carbon dioxide remaining in an unreacted state in the mixture of dimethyl carbonate and acetone produced in the reactor 20 was removed by the CO ₂ separation device 30. Moreover, by separating carbon dioxide under high pressure, the separation can be performed regardless of the temperature of the cooling water. Further, in the DMC purification tower 40 on the downstream side, when separating dimethyl carbonate and acetone, the cooling temperature can be 45 ° C. when water is used as a refrigerant.
By the way, since the carbon dioxide discharged from the CO ₂ separation device 30 maintains a high pressure, the degree of pressure increase is small when it is circulated to the reactor 20. That is, the energy required for the compressors 71 and 72 used for boosting is significantly less than when boosting from normal pressure. Since acetone and acetone dimethyl acetal are in a liquid state, even if the pressure is increased, less energy is required for compression than gas.
Thus, when manufacturing dimethyl carbonate, energy required can be suppressed, and this also provides the effects of cost saving and suppression of environmental deterioration.

In the above embodiment, any catalyst or the like for reacting acetone dimethyl acetal and carbon dioxide in the reactor 20 may be used. For example, an existing technique may be employed, or a new one may be newly used. The developed technology may be adopted.
In addition to this, as long as it does not depart from the gist of the present invention, the configuration described in the above embodiment can be selected or changed to another configuration as appropriate.

It is a figure which shows the structure of the dimethyl carbonate manufacturing system in this Embodiment.

Explanation of symbols

10 ... dimethyl carbonate production system 20 ... reactor, 30 ... CO ₂ separator (first separator, the carbon dioxide separation device), 40 ... DMC purification column (the second separator, a distillation column), 50 ... acetal Regenerator (acetal generator), 60 ... dehydrator, 70 ... circulation path (acetal supply path, carbon dioxide supply path, supply path)

Claims (11)

A reactor for reacting acetals with carbon dioxide to produce dimethyl carbonate;
A first separation device for separating and removing carbon dioxide from dimethyl carbonate produced in the reactor, by-products in the reactor, and a mixture of unreacted acetals and carbon dioxide in the reactor;
A second separator for separating and taking out dimethyl carbonate from the mixture from which carbon dioxide has been taken out by the first separator;
A dimethyl carbonate production system comprising: In the reactor, dimethyl carbonate is obtained by reacting under a pressure higher than normal pressure,
2. The dimethyl carbonate production system according to claim 1, wherein the first separation device separates and extracts carbon dioxide from the mixture under a pressure higher than normal pressure.   The dimethyl carbonate production system according to claim 1 or 2, wherein the second separator separates and removes dimethyl carbonate from the mixture at a pressure lower than that of the first separator. An acetal generator for producing acetals by reacting methanol with a by-product remaining by separating dimethyl carbonate in the second separator;
An acetal supply path for supplying the acetals generated in the acetal generator to the reactor;
The dimethyl carbonate production system according to claim 1, further comprising:   The dimethyl carbonate production system according to any one of claims 1 to 4, further comprising a carbon dioxide supply path for supplying carbon dioxide taken out by the first separation device to the reactor. A reactor that reacts acetals with carbon dioxide to produce dimethyl carbonate under a first pressure higher than normal pressure;
Under a second pressure higher than normal pressure and lower than the first pressure, dimethyl carbonate produced in the reactor, a by-product of the reactor, and a mixture of unreacted acetals and carbon dioxide in the reactor A carbon dioxide separator comprising a CO ₂ stripper or a flash tank for separating and taking out carbon dioxide,
A distillation column for separating the mixture having passed through the carbon dioxide separator at a pressure lower than the second pressure into dimethyl carbonate and by-products;
An acetal regenerator that regenerates acetals by reacting by-products discharged from the distillation column with methanol;
A supply path for supplying carbon dioxide extracted from the carbon dioxide separator and acetals regenerated by the acetal regenerator as raw materials to the reactor;
A system for producing dimethyl carbonate, comprising: A reaction step of reacting acetals with carbon dioxide to obtain dimethyl carbonate;
A carbon dioxide separation step for separating and taking out carbon dioxide from dimethyl carbonate obtained in the reaction step, a by-product of the reaction step, and a mixture of unreacted acetals and carbon dioxide in the reaction step;
A dimethyl carbonate separation step of separating and taking out dimethyl carbonate from the mixture that has undergone the carbon dioxide separation step;
A process for producing dimethyl carbonate, comprising: In the reaction step, dimethyl carbonate is obtained by reacting under a pressure higher than normal pressure,
In the carbon dioxide separation step, carbon dioxide is separated and taken out from the mixture under a pressure higher than normal pressure,
The method for producing dimethyl carbonate according to claim 7, wherein in the dimethyl carbonate separation step, dimethyl carbonate is separated and taken out from the mixture at a pressure lower than that in the carbon dioxide separation step. An acetal regeneration step of regenerating acetals by reacting methanol with a by-product remaining by separating dimethyl carbonate in the dimethyl carbonate separation step;
A circulation step of circulating the acetals regenerated in the acetal regeneration step and the carbon dioxide taken out in the carbon dioxide separation step to the reaction step;
The method for producing dimethyl carbonate according to claim 7 or 8, further comprising:   It is produced by removing unreacted carbon dioxide contained in the reaction product from a reaction product obtained by reacting acetals and carbon dioxide, and further removing by-products from the reaction product. A compound.   The compound according to claim 10, which is used as a gasoline additive.

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