KR20060040210A - Reactive distillation process for the continuous preparation of dimethyl carbonate and ethylene glycol using pre-reactor - Google Patents

Abstract

The present invention relates to a method for preparing dimethyl carbonate and ethylene glycol by using a pre-reactor, and more particularly, dimethyl carbonate (ethylene carbonate) and methanol (methanol) by reacting in a reaction distillation column In the continuous process of combining dimethyl carbonate and ethylene glycol, conventional reaction by reacting ethylene carbonate and methanol as reactants in a pre-reactor that can easily change the reaction conditions such as temperature before the reaction distillation column It is possible to improve the production speed of the product by supplementing the disadvantages of the distillation method, as well as to properly distribute the amount of unreacted methanol circulated to the pre-reactor and the reaction distillation column, which is improved to enable the optimal production of dimethyl carbonate and ethylene glycol. Dimethylcarbone using reactor It relates to a process for the production of whey and ethylene glycol.

Dimethyl carbonate, ethylene glycol, reaction distillation, pre-reactor, reaction temperature

Description

Reactive distillation process for the continuous preparation of dimethyl carbonate and ethylene glycol using pre-reactor}             

1 is a block diagram of a manufacturing process for combining dimethyl carbonate and ethylene glycol using a conventional reaction distillation method.

2 is a block diagram of a manufacturing process for co-existing dimethyl carbonate and ethylene glycol using the reaction distillation method of the present invention improved by the use of a pre-reactor.

3 is a graph of equilibrium conversion of ethylene carbonate in a 100 ° C. pre-reactor.

Figure 4 is a graph showing the change in the reaction rate (conversion) when changing the ratio of ethylene carbonate and methanol in the reaction distillation column.

FIG. 5 is a graph showing the change in the reaction rate according to the ratio of the amount distributed to the pre-reactor in the total unreacted methanol.

<Description of Drawing Abbreviation>

EC: ethylene carbonate, MeOH: methanol, DMC: dimethyl carbonate

EG: ethylene glycol

The present invention relates to a method for preparing dimethyl carbonate and ethylene glycol by using a pre-reactor, and more particularly, dimethyl carbonate (ethylene carbonate) and methanol (methanol) by reacting in a reaction distillation column In the continuous process of combining dimethyl carbonate and ethylene glycol, conventional reaction by reacting ethylene carbonate and methanol as reactants in a pre-reactor that can easily change the reaction conditions such as temperature before the reaction distillation column It is possible to improve the production speed of the product by supplementing the disadvantages of the distillation method, as well as to properly distribute the amount of unreacted methanol circulated to the pre-reactor and the reaction distillation column, which is improved to enable the optimal production of dimethyl carbonate and ethylene glycol. Dimethylcarbone using reactor It relates to a process for the production of whey and ethylene glycol.

Dimethylcarbonate is an environmentally friendly substance that can replace toxic phosgene, which can be used as an intermediate in the synthesis or pharmaceutical process of polymers such as polycarbonate, and can also act as a methylating agent or carbonylating agent. Its application range is very wide. In the meantime, various researches have been conducted on the preparation method of dimethyl carbonate, and there is a method of obtaining dimethyl carbonate and ethylene glycol by transesterification of ethylene carbonate and methanol as shown in Scheme 1 below.

(CH ₂ O) ₂ CO + 2CH ₃ OH → (CH ₃ O) ₂ CO + (CH ₂ OH) ₂

The transesterification reaction of Scheme 1 is usually carried out in the presence of a catalyst, the catalyst may be used both a homogeneous catalyst and a heterogeneous catalyst. Homogeneous catalysts include KOH, NaOH, alkaline earth metal halides, phosphine compounds, tin alkoxides, and the like, and heterogeneous catalysts include Group 5 and Group 6 oxides or ion exchange resins. Has been. As can be seen in U.S. Patent Nos. 5,847,189, 5,359,118, 5,231,212 and the like, the use of homogeneous catalysts such as NaOH and KOH during the transesterification reaction results in high conversion and selectivity even at relatively low temperatures (below 150 ° C). Has However, if a homogeneous catalyst is used, it is necessary to separate the catalyst after use, and facility costs may additionally occur due to corrosion of the reaction apparatus. US Patent No. 6,207,850 uses pseudoboehmite alumina, US Patent No. 5,436,362 uses ion exchange zeolites substituted with alkali or alkaline earth metals, and Japanese Patent Application Laid-Open No. 8-59560. In this paper, a technique using zinc oxide has been proposed. The present inventors have developed and applied for a patent on a magnesium oxide catalyst carrying potassium which can be used in the process of reacting ethylene carbonate and methanol in a reaction distillation column to combine dimethyl carbonate and ethylene glycol. [Korean Patent Laid-Open No. 2004-34183 ].

For the reaction of ethylene carbonate and methanol, (1) a liquid ash reactor, (2) a flow reactor, (3) a distillation column on a liquid ash reactor, and (4) a reaction distillation column are used. There is a way. Among these methods, a method using a reaction distillation column as a reactor is known to be the most efficient, and the patent documents thereof include Japanese Patent Application Laid-Open No. 5-213830, Japanese Patent Application Laid-open No. 4-198141, US Patent No. 5,231,212, US Patent No. 5,359,118 and the like. The reaction distillation method uses a reaction distillation column as a reactor and simultaneously performs reaction and distillation. The reaction distillation method can overcome the limitation of equilibrium, recover heat of reaction and improve productivity by reducing equipment and facility cost. There is an advantage to this.

The combined process for producing dimethyl carbonate and ethylene glycol by reaction distillation is generally as shown in FIG. 1. At the top of the reaction distillation column, ethylene carbonate, which is a reactant, is added, and methanol, which is another reactant, is added to the bottom. The method of adding the catalyst differs depending on whether it is a homogeneous system or a heterogeneous system. When using a homogeneous catalyst such as KOH, the catalyst is dissolved in ethylene glycol and introduced into the upper part of the reaction distillation column. The catalyst is charged inside the distillation column. After the reaction proceeds, the product dimethyl carbonate forms a low boiling point azeotrope with methanol and is discharged to the column top, another product ethylene glycol is discharged to the column bottom together with the unreacted ethylene carbonate. The reaction distillation method has the advantage of overcoming the limitations of the reaction equilibrium because the reaction and distillation are performed at the same time, but it is difficult to operate and control because the reaction temperature is not easily changed and the reaction conditions change according to the distillation conditions. have.

Several techniques for improving the reaction distillation method have been proposed. Japanese Patent Laid-Open No. 16-131394, Japanese Patent Laid-Open No. 15-342209, Japanese Patent Laid-Open No. 15-300936, Japanese Patent Laid-Open No. 14-308804, Japanese Patent Laid-Open No. 9-278689, US Patent No. 6,479,689 In B1 and the like, methanol and dimethyl carbonate contained in the mixture discharged to the bottom of the column are separated from the high boiling point ethylene carbonate and ethylene glycol using another distillation column and circulated to the bottom of the reaction distillation column, and unreacted ethylene carbonate is It suggests ways to decompose. In addition, Japanese Patent Application Laid-Open No. 9-194435 discloses an appropriate range of the amount of dimethyl carbonate contained therein when circulating the unreacted methanol discharged with dimethyl carbonate in another distillation column and then circulating it to the reaction distillation column. Patent No. 6,346,638B1 proposes a range of proper flow rates in a distillation column.

In the above reaction distillation method, since the reaction and distillation of the reactants are performed in one apparatus, reaction conditions such as temperature cannot be easily changed. In order to improve the reaction speed and shorten the production time of the product, it is desirable to raise the reaction temperature. To this end, it is desirable to increase the pressure of the reaction distillation tower. However, when the pressure of the reaction distillation tower is increased, the unreacted ethylene carbonate is converted into ethylene oxide in the reboiler. The reaction to decompose into and carbon dioxide gas is accelerated, affecting the yield of the product. In particular, when the temperature of the column bottom is 140 ° C. or more and a catalyst such as KOH is used, a considerable amount of ethylene carbonate is decomposed. As the pressure of the reaction distillation column increases, the concentration of dimethyl carbonate decreases in the azeotropic composition of dimethyl carbonate and methanol, which lowers the dimethyl carbonate composition of the product discharged to the column top of the distillation column. Let's go. Therefore, when the reaction distillation method is used, the operating pressure of the reaction distillation column is about atmospheric pressure, the reaction temperature in the distillation column is 60 to 90 ° C., and there is a limit in that the reaction temperature can not be increased any longer in order to increase the reaction speed.

In order to solve the problem of the reaction distillation method, Japanese Patent Application Laid-Open No. 9-176061 and Japanese Patent Application Laid-open No. 4-23023 inject the liquid inside the distillation column into a plurality of reactors attached to the outside of the distillation column, and then circulate it to the distillation column. To improve the reaction rate. However, this method is difficult to apply industrially because the operation is very complicated and the operating conditions are not constant. Since the composition and flow rate in the distillation column can change continuously, it is impossible to expect stable operation in the reactor and the distillation column. .

Therefore, the present inventors have studied and tried to solve the above-mentioned problems. As a result, the ethylene carbonate and methanol, which are reactants, were added to the reaction distillation column, respectively, to simultaneously react and distill, and to control the reaction conditions. After the reaction, the reaction temperature can be added to the reaction distillation column to adjust the reaction temperature to improve the reaction rate, and the unreacted methanol can be added to the pre-reactor and the reaction distillation column so that the amount of unreacted methanol re-injected for each process step can be properly adjusted. It was found that the optimum production of dimethyl carbonate and ethylene glycol was possible to complete the present invention.

Therefore, in the continuous process of reacting ethylene carbonate and methanol in a reaction distillation column to combine dimethyl carbonate and ethylene glycol, the present invention is carried out in a pre-reactor such as a continuous rotary reactor or a circulation reactor before the ethylene carbonate and methanol are introduced into the reaction distillation column. It is an object of the present invention to provide a method for preparing dimethyl carbonate and ethylene glycol by using a pre-reactor including the step of reacting and appropriately dispensing unreacted methanol into the pre-reactor and the reaction distillation column.

A continuous process of reacting ethylene carbonate and methanol in a reaction distillation column to combine dimethyl carbonate and ethylene glycol, comprising: a first step of reacting ethylene carbonate and methanol in a pre-reactor; A second step of adding the reaction product of the first step to the upper portion of the reaction distillation column, recovering and reacting with the unreacted methanol circulated and distilling; And Method for producing dimethyl carbonate and ethylene glycol using a pre-reactor comprising a third step of distributing the unreacted methanol discharged to the top or bottom of the reaction distillation column to the pre-reactor and the bottom of the reaction distillation column It is characterized by.

The present invention will be described in more detail as follows.

In the present invention, ethylene carbonate (EC) and methanol (MeOH) are reacted in a reaction distillation column to combine dimethyl carbonate (DMC) and ethylene glycol (EG). By reacting in a pre-reactor that can easily change the reaction conditions such as temperature beforehand, it is possible to improve the production rate of the product by compensating the disadvantages of the conventional reaction distillation method, and to increase the amount of unreacted methanol circulated to the pre-reactor and the reaction distillation column. The present invention relates to a process for preparing dimethyl carbonate and ethylene glycol using a pre-reactor, which can be appropriately distributed and improved to enable optimal production of dimethyl carbonate and ethylene glycol.

One embodiment of the combined process of the present invention is shown in FIG. It is an important feature of the present invention to include the step of reacting ethylene carbonate and methanol in a pre-reactor. In the present invention, the reactants are not added to the reaction distillation tower, but are reacted in advance in the reactor to reach an equilibrium, and then they are added to the reaction distillation tower. As the pre-reactor, a continuous stirred tank reactor or a flow reactor may be used. The catalysts that can be used in the pre-reactor can be either homogeneous or heterogeneous catalysts and do not necessarily have to match the catalysts used in the reaction distillation tower. Therefore, the heterogeneous catalyst can be used in the pre-reactor and the homogeneous catalyst in the reaction distillation column. . In addition, unlike the reaction distillation column, the pre-reactor is a device that reacts only until the reaction material reaches equilibrium, so that the reaction temperature can be increased to increase the reaction speed, and can be stably operated separately from the process in the reaction distillation tower.

The prereactor is fed with ethylene carbonate, equivalents of methanol and some of the unreacted methanol. The unreacted methanol is a mixture of a low boiling point azeotrope of dimethyl carbonate and methanol discharged to the top of the reaction distillation column by reaction and distillation in the reaction distillation column and ethylene glycol, a small amount of dimethyl carbonate and a small amount of methanol discharged to the bottom of the reaction distillation column. It is preferable that dimethyl carbonate is contained at a concentration of 10% by weight or less as it is left after separating the dimethyl carbonate and ethylene glycol through a fractionation apparatus. In the combined process of dimethyl carbonate and ethylene glycol, unreacted ethylene carbonate is not likely to be discharged due to the excessive input of methanol, but unreacted ethylene carbonate may be discharged to the bottom together with ethylene glycol in abnormal operation or if necessary. .

The reaction product of the pre-reactor is then added to the top of the reaction distillation column to react with the unreacted methanol introduced into the bottom of the reaction distillation column and distilled off according to the difference in boiling point. That is, in the reaction distillation column, the reaction takes place and distillation occurs. At atmospheric pressure, the boiling point of ethylene carbonate is 243 ° C, the boiling point of methanol is 64 ° C, the boiling point of dimethyl carbonate is 90 ° C, and the boiling point of ethylene glycol is 197 ° C, so methanol and dimethyl carbonate are unreacted at the top depending on the boiling point. It can be separated into ethylene carbonate and ethylene glycol, but methanol and dimethyl carbonate form low boiling azeotropes, so they are discharged in the form of azeotrope.

The operating temperature of the reaction distillation column varies depending on the reaction pressure and the composition of the mixture in the distillation column, but the reaction product methanol should be present in the liquid phase. At the bottom, a small amount of dimethyl carbonate and methanol are discharged together with ethylene glycol. In order to separate dimethyl carbonate and ethylene glycol, which are products from the mixture discharged from the column top and the bottom, a separate separator (usually using a distillation column) can be used and unreacted methanol is circulated through the reaction distillation column and reused.

The process in the reaction distillation column of the present invention is different from the conventional method in the following points. In the conventional reaction distillation method, as shown in FIG. 1, ethylene carbonate is added to the upper part of the reaction distillation column and methanol is added to the lower part, and the reaction distillation is simultaneously performed in the reaction distillation column. Dimethyl carbonate, ethylene glycol, and unreacted substances produced by the reaction in advance in the reactor are added to the upper part of the reaction distillation column, and circulated unreacted methanol is added to the lower part of the reaction distillation column to perform countercurrent contact reaction and distillation. The countercurrent contact allows the unreacted ethylene carbonate to react completely with the reintroduced methanol to increase the reaction rate.

The amount of unreacted methanol added to the bottom of the reaction distillation column may be adjusted according to the amount of unreacted methanol added to the reactor beforehand. Excessive addition of unreacted methanol to the pre-reactor can improve the conversion of ethylene carbonate, but the amount of methanol supplied to the bottom of the reaction distillation column is reduced, so the conversion rate in the reaction distillation column is reduced. It was confirmed by the present inventors that the ratio of the unreacted methanol introduced into the pre-reactor in the total unreacted methanol circulated is preferably 0.5 or less, and the ratio can be changed by the pre-reactor, the reaction distillation column, and the attached distillation column. Properly distributing the amount of unreacted methanol circulated in the above range may improve productivity of dimethyl carbonate and ethylene glycol as described below.

As the top of the reaction distillation column, dimethyl carbonate and unreacted methanol are discharged in a composition close to azeotropic composition (about 30% by weight of dimethyl carbonate at atmospheric pressure). In the step of obtaining dimethyl carbonate by separating a mixture of dimethyl carbonate and unreacted methanol discharged to the top of the reaction distillation column, methanol may be recovered in a composition having a concentration of dimethyl carbonate of 10 wt% or less using a dividing column or the like. have.

Factors affecting the production of the combined acid process can be various, such as the reaction and operating conditions of the pre-reactor, the reaction and operating conditions of the reaction distillation column, the reaction and operating conditions of the accessory distillation column. In the present invention, by introducing a pre-reactor and at the same time by adjusting the distribution ratio of the unreacted methanol circulated in the pre-reactor and the lower part of the reaction distillation column to enable optimal production.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to Examples.

Experimental Example 1 Reaction Rate and Equilibrium Conversion Rate in Pre-Reactor

The reaction rates and equilibrium conversions of the reactions occurring in the reactor were checked to determine the optimal distribution ratio of the unreacted methanol circulated. The pre-reactor used a stainless steel autoclave (200 mL) and stirred using a magnetic stirrer. Ethylene Carbonate (Acros Organic, 99% purity), Methanol (JT Baker, HPLC, 99.99% purity), Dimethylcarbonate (Acros Organic, 99% purity) and Ethylene Glycol (Acros Organic, 99 purity) % Or more) was used to determine the reaction order, reaction rate constant depending on the reaction temperature under KOH (JT Baker, purity more than 90%) catalyst. The analysis of the reactants and products was carried out using gas chromatography (Gas Chromatography, Gow-Mac, 550P), the detector was used the Thermal Conductivity Detector (TCD), and the column was 10% Carbowax (1/8 in. ㅧ 2). m, Chrom W-HP, 80/100) was used. In addition, a GC mass spectrometer (GC mass spectrometer, HP Co., 5890, 5971A mass detector) was used for component analysis. In the experiment using KOH as a catalyst, the reaction rate equation can be expressed as the following Reaction Equation 2, and the reaction order and rate constant values are summarized in Table 1.

In Reaction Scheme 2, -r _EC is the reaction rate of ethylene carbonate (mol / l / min), k _forward and k _backward are reaction rate constants of forward and reverse reaction, respectively, and C _MeOH , C _EC , C _DMC and C _EG are methanol, respectively. , Ethylene carbonate, dimethyl carbonate and ethylene glycol concentration (mol / l).

reaction Reaction order Speed constant Forward a = 0, b = 0.87 18.1 e ^{-12734.2 / RT} Backward c = 1.25, d = 0.9 2457.5 e ^{-29276.6 / RT}  R is gas constant (8.3 J / mol-K), T is absolute temperature

The ethylene carbonate conversion rate (EC equilibrium conversion rate) at the equilibrium according to the change in the initial molar concentration ratio of ethylene carbonate and methanol from Scheme 2 and Table 1 is calculated as shown in FIG. It is an advantage of the pre-reactor that the reaction rate can be increased by increasing the internal temperature, but the temperature of the pre-reactor is generally preferably about 80 to 140 ° C. In this experiment, the equilibrium conversion at 100 ° C. was calculated.

As can be seen in Figure 3, when recovering and circulating the unreacted methanol in the present invention, if a part of the pre-reactor in the reactor, the conversion of ethylene carbonate increases with the addition of methanol.

Experimental Example 2 Change in the Reaction Rate in the Reaction Distillation Column According to the Ratio of Ethylene Carbonate and Methanol

As a preliminary experiment to determine how much unreacted methanol of the present invention should be added to the lower part of the pre-reactor and the reaction distillation column, the reaction rate changes according to the input ratio of ethylene carbonate and methanol using a conventional reaction distillation method saw. The reaction distillation experiment was carried out using a distillation column of 3 inches in diameter and 5 meters in height, and was filled with a 1/4 inch size Raschig ring. The tower top was equipped with a condenser and the bottom was equipped with a reboiler equipped with an electric heater. Ethylene carbonate containing 2% by weight of KOH catalyst was charged 2.1 mole per hour at a point below the top of the tower condenser (top of the reactor distillation column) and methanol at a point above the tower bottom (bottom of the reactor tower). Was added. The operating pressure of the reaction distillation column was adjusted to 0.8 atm (absolute pressure) and the temperature in the distillation column was maintained at about 80 ℃. The other factors that may affect the combined acid process were fixed at a constant, and the change in reaction rate (conversion) when changing only the input ratio of ethylene carbonate and methanol in the reaction distillation column is shown in FIG. 4.

As can be seen in Figure 4, the higher the ratio of methanol to ethylene carbonate (MeOH / EC), the higher the conversion rate (EC conversion) of ethylene carbonate in the reaction distillation column, the ratio of methanol to ethylene carbonate is 9 or more When the reaction rate (conversion rate) is 100%, it can be seen that it is no longer necessary to add methanol.

Experimental Example 3 Estimation of Optimum Magnification Distributing to the Pre-Reactor in All Unreacted Methanol

3 and 4, the higher the ratio of methanol to ethylene carbonate, the higher the conversion rate in the pre-reactor and the reaction distillation column. That is, it is necessary to appropriately distribute the methanol introduced as a raw material and the unreacted methanol circulated in the process to the pre-reactor and the reaction distillation column. This optimal distribution ratio can be changed according to the reaction and operating conditions of the pre-reactor, reaction distillation column, and accessory distillation column, and thus cannot be obtained without research and experiment on reaction and distillation characteristics.

In order to confirm the conditions under which unreacted methanol was properly distributed at the bottom of the pre-reactor and the reaction distillation column to enable optimal production, the parallel process was reviewed using the reaction distillation method applying the pre-reactor of the present invention.

Ethylene carbonate and methanol, the reaction raw materials, were added to the pre-reactor at 4 equivalent and 8 moles per hour, respectively, in an equivalence ratio (methanol / ethylene carbonate mole ratio = 2/1). Conversion rate in the pre-reactor where the reaction equilibrium was made at ℃ can be seen in FIG.

In the reaction distillation column, unreacted ethylene carbonate introduced from the top and methanol introduced from the bottom are in countercurrent contact, and distillation is performed simultaneously with the reaction, and dimethyl carbonate and unreacted methanol are discharged to the top. At this time, since the azeotrope is formed, its composition is changed according to the operating pressure conditions, and it is assumed that dimethyl carbonate may be included in the range of 20 to 30% by weight and 30% by weight in the preliminary calculation. If a separate distillation apparatus is used to recover unreacted methanol from this mixture and to separate the product dimethyl carbonate, the methanol recovered depending on the operating conditions may contain 0 to 10% by weight dimethyl carbonate and in this precalculation 5 weight % Is assumed to be included.

As described above, the concentration of dimethyl carbonate in the mixture discharged from the column top of the reaction distillation column is 30% by weight, and this is separated from the accessory distillation column to discharge the unreacted methanol mixture containing 5% by weight of dimethyl carbonate to the column bottom. Assuming that 100% of dimethyl carbonate is emitted, the amount of methanol in the circulated unreacted methanol mixture is about 30 moles, which is distributed to the pre-reactor and the reaction distillation column.

According to the ratio of distributing the circulated unreacted methanol to the pre-reactor and the reaction distillation column, the expected total conversion is calculated as shown in FIG. 5.

When all of the circulated unreacted methanol is added to the lower part of the reaction distillation column without allocating to the pre-reactor, as shown in FIG. 3, about 34% of the ethylene carbonate is converted in the pre-reactor. When 4 mol and 8 mol of ethylene carbonate and methanol were added to the pre-reactor, respectively, the amount of unreacted ethylene carbonate was 2.64 mol. At this time, when the mixture containing unconverted ethylene carbonate is introduced into the upper part of the reaction distillation column and all of the unreacted methanol (30 mol) circulated is returned to the lower part of the reaction distillation column, the molar ratio of MeOH / EC in the reaction distillation column is 30 / 2.64 = 11.4 and the conversion rate in the reaction distillation column is 100% as can be seen in FIG.

When 5 moles, 10 moles, 15 moles, and 20 moles of unreacted methanol (30 moles) circulated in the same manner are allocated to the pre-reactor and the remainder is added to the reaction distillation column, the reaction rate of the pre-reactor is as shown in FIG. 40%, 43%, 47% and 50%, and the conversion rates in the reaction distillation column are 100%, 96%, 83% and 68% as shown in FIG. Therefore, when calculating the total conversion considering the pre-reactor and the reaction distillation column will change to 100%, 98%, 91% and 81%, respectively, as shown in FIG.

As shown in FIG. 5, the total reaction rate (conversion rate) is 100% until the unreacted methanol distribution ratio to the pre-reactor reaches about 0 to about 0.3, but when the distribution ratio to the pre-reactor is 0.3 or more, It can be seen that the amount decreases and the efficiency of the reaction distillation tower is lowered and the overall reaction rate is lowered. As shown in FIG. 4, since the ratio of methanol to ethylene carbonate in the reaction distillation column is 9 or more, the reaction rate (conversion) is 100%, and thus the distribution ratio of methanol circulated according to the amount of unreacted ethylene carbonate in the pre-reactor You must decide.

Therefore, in this precalculation, the optimum ratio 0.3 distributed in the pre-reactor among the unreacted methanol circulated was most preferred. In the case of 0.3 or more, as shown in FIG. 5, the total conversion rate is lowered to 100% or less, and in the case of 0.3 or less, the total conversion rate is 100%, and there is no difference in conversion rate, but a part of the amount of unreacted methanol injected into the bottom of the reaction distillation column is This is because it is inefficient because the proper ratio of methanol / ethylene carbonate in the reaction distillation column is exceeded.

As described above, the optimum distribution ratio may vary depending on the reaction and operating conditions of the pre-reactor, the reaction distillation column, and the accessory distillation column, and thus may be determined by the above method in consideration of these conditions.

For example, when the molar ratio of methanol / ethylene carbonate is 6 or more in the pre-reactor, the rate of increase of the equilibrium reaction rate decreases. The methanol / ethylene carbonate molar ratio fed to the pre-reactor under the conditions of the reaction raw materials (ethylene carbonate 4 mol / hour, methanol 8 mol / hour) and the unreacted methanol circulation (30 mol / hour), as described above, may be The distribution ratio of unreacted methanol of was calculated to be about 0.53 (= (24-8) / 30). In addition, it was confirmed that the ratio of methanol / ethylene carbonate to obtain a 100% conversion by increasing the reflux ratio in the reaction distillation column should be 8 or more, and the distribution ratio (allocation to the pre-reactor) was 0.47. It is estimated that the reaction rate in the pre-reactor is about 50%, and the amount of unreacted ethylene carbonate introduced into the reaction distillation column is 2 moles per hour, so the amount of circulation of the unreacted methanol to be supplied to the reaction distillation tower is 8 times 16 moles, which is distributed to the pre-reactor. The amount is 14 moles per hour and the distribution ratio is calculated as 14/30 = 0.47. Therefore, the ratio of circulating unreacted methanol distributed to the pre-reactor is suitably about 0.5 or less.

Example

Dimethyl carbonate and ethylene glycol were combined together using a pre-reactor according to the present invention and a conventional reaction distillation method.

As a pre-reactor, a 1.2 liter continuous rotary reactor was used, and the reaction distillation column was a distillation column having a diameter of 3 inches and a height of 5 meters. The distillation column was filled with a 1/4 inch Raschig ring. The tower top was equipped with a condenser and the bottom was equipped with a reboiler equipped with an electric heater. The feed rates of ethylene carbonate and methanol, which were added to the reactor, were 4 mol (352 g) and 8 mol (512 g) per hour, respectively, and were added together with a small amount of KOH (less than 0.2 wt% of the reactant). The expected amount of methanol mixture circulated from the mass balance was about 870 g per hour, of which 260 g per hour (30%) was added to the pre-reactor and the remainder was added to the bottom of the reaction distillation column, respectively. The reaction product discharged from the pre-reactor was introduced into the upper part of the reaction distillation tower (1 m lower point from the top) and the methanol mixture introduced into the reaction distillation tower was introduced into the lower part of the reaction distillation tower (1 m upper point from the bottom) to check the performance of the reaction distillation tower. The experiment was carried out in the same manner. The prereactor was operated at 3 atm and 100 ° C. The distillation column at 0.8 atm had a temperature of 80 ° C and a reboiler at 110 ° C. The heating amount of the reaction distillation column reboiler was operated at 1.7 kWh.

As illustrated in the present invention, when the pre-reactor and the reaction distillation column were used simultaneously, the conversion rate of ethylene carbonate was 99% or more.

Comparative example

In the same apparatus as in Example, the conversion rate of ethylene carbonate was 95% or less when the reaction raw material ethylene carbonate and the catalyst were added to the upper part of the reaction distillation column and the reaction raw material methanol and the circulating methanol were added to the lower part.

As described above, the method for producing dimethyl carbonate and ethylene glycol by using the pre-reactor of the present invention by reacting ethylene carbonate and methanol in a reaction distillation column, dimethyl carbonate and ethylene glycol ( In the continuous process of ethylene glycol) co-existing, the ethylene carbonate and methanol are reacted in a pre-reactor that can easily change the reaction conditions such as temperature before the reaction distillation column to compensate for the shortcomings of the conventional reaction distillation method In addition to improving productivity, the amount of unreacted methanol re-introduced into the pre-reactor and the reaction distillation column can be appropriately distributed, thereby enabling the optimum production of dimethyl carbonate and ethylene glycol.

Claims (6)

In a continuous step of reacting ethylene carbonate and methanol in a reaction distillation column to co-exist dimethyl carbonate and ethylene glycol, A first step of reacting ethylene carbonate and methanol in a pre-reactor; A second step of adding the reaction product of the first step to the upper portion of the reaction distillation column, recovering and reacting with the unreacted methanol circulated and distilling; And A third step of distributing unreacted methanol discharged to the top of the reaction distillation column or the bottom of the reaction distillation to the lower portion of the pre-reactor and the reaction distillation column Method for producing dimethyl carbonate and ethylene glycol using a pre-reactor characterized in that it comprises a. The method of claim 1, wherein dividing the mixture of dimethyl carbonate and unreacted methanol discharged to the top of the reaction distillation column between the second step and the third step to obtain dimethyl carbonate and ethylene discharged to the bottom of the reaction distillation column A process for producing dimethyl carbonate and ethylene glycol using a pre-reactor further comprising the step of classifying a mixture of glycol, a small amount of dimethyl carbonate and a small amount of unreacted methanol to obtain ethylene glycol. The method of claim 1 or 2, wherein when the unreacted methanol discharged to the top or bottom of the reaction distillation column is recovered and re-injected into the pre-reactor and the reaction distillation column, the ratio of re-introduction into the pre-reactor is 0.5 or less. Method for producing dimethyl carbonate and ethylene glycol using a pre-reactor characterized in. The method for producing dimethyl carbonate and ethylene glycol using a pre-reactor according to claim 1 or 2, wherein the reaction temperature of the pre-reactor is 60 to 140 ° C. The method for producing dimethyl carbonate and ethylene glycol using a pre-reactor according to claim 1 or 2, wherein the reaction temperature of the reaction distillation column is 60 to 100 ° C. The method of claim 1 or 2, wherein the pre-reactor is a continuous rotary reactor or a flow reactor, the method for producing dimethyl carbonate and ethylene glycol using a pre-reactor.

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