TWI642660B - Manufacturing methods and manufacturing apparatuses of propylene carbonate and dimethyl carbonate - Google Patents

Abstract

The invention provides a method and a device for producing propylene carbonate and dimethyl carbonate. The method for producing propylene carbonate includes the following steps. Urea and excess propylene glycol are respectively entered into the first part of the distillation system, so that urea and propylene glycol are reacted and separated in the first part to form a first product including ammonia and a second product including propylene glycol and propylene carbonate. The second product is passed into the second part of the distillation system to separate the second product to form a third product including propylene glycol and a fourth product including propylene carbonate. The first part and the second part are two distillation columns connected to each other.

Description

Method and device for producing propylene carbonate and dimethyl carbonate

The present invention relates to a method and device for manufacturing propylene carbonate and dimethyl carbonate, and more particularly, to a method and device for manufacturing propylene carbonate and dimethyl carbonate by urea indirect alcoholysis.

Dimethyl carbonate (DMC) is a basic chemical raw material with low toxicity, low pollution and environmental friendliness. Dimethyl carbonate can be subjected to carbonylation, methylation, methylation, and transesterification to generate many important chemical products. On the other hand, dimethyl carbonate can be used as a raw material to develop and prepare a variety of high-value-added precision chemicals, and has been widely used in medicine, agriculture, dyes, lubricant additives, food flavoring agents, and electronic chemicals. . In this way, how to manufacture dimethyl carbonate with a method and a device with low manufacturing cost and high conversion rate has become one of the important topics in the field.

The invention provides a method for manufacturing propylene carbonate and a device for manufacturing propylene carbonate, which have higher product conversion rate and lower manufacturing cost.

The invention provides a method for manufacturing dimethyl carbonate and a device for manufacturing dimethyl carbonate, which have higher product conversion rate and lower manufacturing cost.

The method for producing propylene carbonate of the present invention includes the following steps. Urea and excess propylene glycol are respectively entered into the first part of the distillation system, so that urea and propylene glycol are reacted and separated in the first part to form a first product including ammonia and a second product including propylene glycol and propylene carbonate. The second product is passed into the second part of the distillation system to separate the second product to form a third product including propylene glycol and a fourth product including propylene carbonate. The first part and the second part are two distillation columns connected to each other.

In an embodiment of the present invention, the first part is a first reactive distillation column and the second part is a first distillation column. The first product and the second product are the top product and the bottom product of the reactive distillation column, respectively. The third product and the fourth product are the top product and the bottom product of the first distillation column, respectively.

In an embodiment of the present invention, the method for manufacturing propylene carbonate further includes heat-exchanging the bottom liquid of the first reactive distillation column and the top gas of the first distillation column in a first heat exchange device. Reflux to the bottom of the first reactive distillation column and the top of the first distillation column, respectively.

In an embodiment of the present invention, the first distillation column may include an upper stage column, a lower stage column, and a gas compression device, so that the top gas of the lower stage column enters the gas compression device to generate a compression product, and the compression product enters the upper stage. The tower produces the top product of the upper tower. The top product of the upper column is the top product of the first distillation column.

In an embodiment of the present invention, the bottom liquid of the first reactive distillation column and the top gas of the upper column may be heat-exchanged in the first heat exchange device and then refluxed to the first reactive distillation column, respectively. The bottom of the column and the top of the upper column of the first distillation column.

In an embodiment of the present invention, a part of the gas in the top of the upper tower and the bottom liquid in the lower tower are heat-exchanged in the second heat exchange device, and then return to the top of the upper tower and the tower respectively. The bottom of the lower tower.

The method for producing dimethyl carbonate of the present invention includes the following steps. Excess methanol and the fourth product mentioned above are passed into the second reactive distillation column, so that methanol and propylene carbonate in the fourth product are reacted and separated in the second reactive distillation column, and formed on the top of the second reactive distillation column A fifth product including methanol and dimethyl carbonate. The fifth product and the extractant are passed into a second distillation column to form a sixth product including methanol and a seventh product including dimethyl carbonate at the top and bottom of the second distillation column, respectively.

In an embodiment of the present invention, the seventh product further includes an extractant, and the method for manufacturing dimethyl carbonate further includes passing the seventh product into a third distillation column to make the dimethyl carbonate in the seventh product It is separated from the extractant in a third distillation column to form an eighth product including dimethyl carbonate and a ninth product including an extractant.

The apparatus for producing propylene carbonate of the present invention includes a distillation system. The distillation system has a first part and a second part. The first part and the second part are two distillation columns connected to each other. Urea and excess propylene glycol are reacted and separated in the first part to form a first product including ammonia and a second product including propylene glycol and propylene carbonate. Propylene glycol and propylene carbonate in the second product enter the second part and are separated to form a third product including propylene glycol and a fourth product including propylene carbonate.

In an embodiment of the present invention, the first part is a first reactive distillation column and the second part is a first distillation column. The first product and the second product are the top product and the bottom product of the reactive distillation column, respectively. The third product and the fourth product are the top product and the bottom product of the first distillation column, respectively.

In an embodiment of the present invention, the above-mentioned propylene carbonate manufacturing apparatus further includes a first heat exchange apparatus. The first heat exchange device is connected between the first reactive distillation column and the first distillation column, so that the bottom liquid of the first reactive distillation column and the top gas of the first distillation column perform heat exchange in the first heat exchange device. After that, it was refluxed to the bottom of the first reactive distillation column and the top of the first distillation column, respectively.

In an embodiment of the present invention, the first distillation column may include an upper column, a lower column, and a gas compression device. The gas compression device is connected between the upper stage tower and the lower stage tower, so that the top gas of the lower stage tower enters the gas compression unit to generate a compression product, and the compressed product enters the bottom of the upper stage tower to generate the top stage product of the upper stage tower. The top product of the upper column is the top product of the first distillation column.

In an embodiment of the present invention, the bottom liquid of the first reactive distillation column and the top gas of the upper column may be heat-exchanged in the first heat exchange device and then refluxed to the first reactive distillation column, respectively. The bottom of the column and the top of the upper column of the first distillation column.

In an embodiment of the present invention, the above-mentioned propylene carbonate manufacturing apparatus may further include a second heat exchange apparatus. Part of the gas in the top of the upper tower and the liquid in the bottom of the lower tower undergo heat exchange in the second heat exchange device, and then return to the top of the upper tower and the bottom of the lower tower, respectively.

The dimethyl carbonate production apparatus of the present invention includes the above-mentioned distillation system, a second reactive distillation column, and a second distillation column. The methanol and propylene carbonate in the fourth product described above are reacted and separated in a second reactive distillation column, and a fifth product including methanol and dimethyl carbonate is formed on the top of the second reactive distillation column. The fifth product is separated from the extractant in a second distillation column to form a sixth product including methanol and a seventh product including dimethyl carbonate.

In an embodiment of the present invention, the seventh product further includes the extractant, and the dimethyl carbonate manufacturing apparatus further includes a third distillation column. The dimethyl carbonate in the seventh product is separated from the extractant in the third distillation column to form an eighth product including the dimethyl carbonate and a ninth product including the extractant.

Based on the above, urea and excess propylene glycol respectively enter a distillation system of a propylene carbonate production device to perform a reaction to produce propylene carbonate. In addition, propylene glycol can be separated from propylene carbonate as a product in a distillation system. Therefore, the purity of propylene carbonate as a product can be improved, and the conversion rate of propylene carbonate can be improved. In this way, the method and device for producing dimethyl carbonate by using propylene carbonate of higher purity as a reactant can also have a higher product conversion rate.

In some embodiments, the propylene carbonate distillation system may include two first reactive distillation columns and a first distillation column that are interconnected. In addition, by setting a first heat exchange device connected between the first reactive distillation column and the first distillation column, the thermal energy at the top of the first distillation column can be used to heat the bottom of the first reactive distillation column. Therefore, the energy consumption required for the first reactive distillation column can be reduced.

In order to make the above features and advantages of the present invention more comprehensible, embodiments are hereinafter described in detail with reference to the accompanying drawings.

FIG. 1A is a flowchart of a method for manufacturing propylene carbonate and dimethyl carbonate according to a first embodiment of the present invention. FIG. 1B is a schematic diagram of an apparatus for manufacturing propylene carbonate and dimethyl carbonate according to the first embodiment of the present invention.

A method for producing dimethyl carbonate includes first producing propylene carbonate, and then producing dimethyl carbonate from the propylene carbonate. In other words, the method for producing dimethyl carbonate includes a method for producing propylene carbonate. Similarly, the production apparatus of dimethyl carbonate includes a production apparatus of propylene carbonate.

In the method for producing propylene carbonate of this embodiment, the following steps S100 to S104 are performed by the propylene carbonate production apparatus 10 shown in FIG. 1B.

Referring to FIG. 1A and FIG. 1B, step S100 is performed to make carbon dioxide and ammonia react in the reaction system 100 to generate urea. In addition, the reaction product of carbon dioxide and ammonia gas may further include water. The product water can be discharged from the outlet 101.

Step S102 is performed to allow urea and excess propylene glycol to enter the first portion 102a of the distillation system 102, respectively. The distillation system 102 includes a first portion 102a and a second portion 102b. In some embodiments, the first portion 102a and the second portion 102b of the distillation system 102 are a first reactive distillation column 104 and a first distillation column 114, respectively. The first reactive distillation column 104 and the first distillation column 114 are connected to each other. A catalyst may be provided in the first reactive distillation column 104 (for example, a diagonal line region in the first reactive distillation column 104 shown in FIG. 1B). For example, the catalyst material may include metal oxides such as zinc chloride, zinc oxide, magnesium oxide, lead oxide, and calcium oxide. Urea and propylene glycol are reacted and separated in the first part 102a (ie, the first reactive distillation column 104) to form a first product including ammonia gas and a second product including propylene glycol and propylene carbonate. The first product may be an overhead product of the first reactive distillation column 104 and may flow from the overhead of the first reactive distillation column 104 to a partial condenser 106. The ammonia gas can be returned to the reaction system 100 from a part of the condenser 106 for recycling. A small amount of propylene glycol and propylene carbonate are condensed into a liquid by a partial condenser 106 and stored in a reflux tank 108, and can be refluxed to the first reactive distillation column 104. The second product may be a bottom product of the first reactive distillation column 104 and may enter the reboiler 110. After the second product is heated in the reboiler 110, it may be partially refluxed into the first reactive distillation column 104.

Step S104 is performed to allow a portion of the second product to enter the second portion 102 b of the distillation system 102. The second product is separated in a second portion 102b (ie, the first distillation column 114) to form a third product including propylene glycol and a fourth product including propylene carbonate. In some embodiments, the third product is an overhead product of the first distillation column 114 and may flow from the overhead of the first distillation column 114 to the condenser 116. The third product may be stored in the reflux tank 118 after being condensed in the condenser 116. The third product condensed in the reflux tank 118 may be refluxed to the first distillation column 114 and may be refluxed to the first reactive distillation column 104 for recycling. In some embodiments, part of the propylene glycol from the reflux tank 118 may be fed to the first reactive distillation column 104 through the same feed port as urea produced by the reaction system 100, and another part of the propylene glycol from the reflux tank 118 may be passed through another A feed port is fed to the first reactive distillation column 104. The fourth product is a bottom product of the first distillation column 114 and may enter the reboiler 120. After the fourth product is heated in the reboiler 120, a part of the fourth product may be refluxed into the first distillation column 114. In addition, the propylene carbonate in the fourth product of the other part can be used as a product of the method for producing propylene carbonate in this embodiment.

Propylene glycol and propylene carbonate easily generate azeotrope under low pressure (for example, the pressure is less than 0.12 atm), and it is difficult to separate the two. Therefore, in some embodiments, the pressure of the first distillation column 114 may be increased to prevent propylene glycol and propylene carbonate from forming an azeotrope on the top of the first distillation column 114.

The method for manufacturing dimethyl carbonate of this embodiment includes the above-mentioned steps S100 to S104, and further includes a fourth product obtained in step S104, followed by steps S106 to S110 described below.

Step S106 is performed to allow excess methanol and a portion of the fourth product to enter the second reactive distillation column 124. A catalyst may be provided in the second reactive distillation column 124 (for example, a diagonal line region in the second reactive distillation column 124 shown in FIG. 1B). For example, the catalyst material may include sodium methoxide or organic non-ionic super strong base (proazaphosphatrane). The methanol and propylene carbonate in the fourth product are reacted and separated in the second reactive distillation column 124, and a fifth product including methanol and dimethyl carbonate is formed on the top of the second reactive distillation column 124. The fifth product may flow from the top of the second reactive distillation column 124 to the condenser 126. The fifth product may be stored in the reflux tank 128 after being condensed in the condenser 126. The condensed methanol and dimethyl carbonate in the reflux tank 128 may be partially refluxed to the second reactive distillation column 124. In some embodiments, the fourth product may further include a small amount of propylene glycol. In this way, the propylene glycol in the fourth product can form a bottom product at the bottom of the second reactive distillation column 124 and can enter the reboiler 130. A part of the bottom product of the second reactive distillation column 124 is heated in the reboiler 130 and then may be refluxed to the second reactive distillation column 124. In addition, another part of the bottom product of the second reactive distillation column 124 may be refluxed into the first reactive distillation column 104 for recycling.

Step S108 is performed to allow a part of the fifth product and the extractant to enter the second distillation column 134. Methanol and dimethyl carbonate in the fifth product can form an azeotrope. The extractant can be applied to change the relative volatility of methanol and dimethyl carbonate, that is, to separate methanol from dimethyl carbonate in the fifth product. For example, the extractant may include phenol, aniline, ethylene glycol monoethyl ether or 4-methyl-2-pentanone, and the like. As such, the fifth product can be separated in the second distillation column 134 to form a sixth product including methanol and a seventh product including dimethyl carbonate. The sixth product may be an overhead product of the second distillation column 134 and may flow from the top of the second distillation column 134 to the condenser 136. The sixth product can be stored in the reflux tank 138 after being condensed in the condenser 136. The condensed methanol in the reflux tank 138 may be partially refluxed to the second distillation column 134 and may be partially refluxed to the second reactive distillation column 124 for recycling. The seventh product may be a bottom product of the second distillation column 134 and may enter the reboiler 140. After the seventh product is heated in the reboiler 140, it may be partially refluxed into the second distillation column 134.

Step S110 may be performed to make the seventh product enter the third distillation column 144. In some embodiments, the seventh product may further include an extractant. The dimethyl carbonate and the extractant in the seventh product can be separated in the third distillation column 144 to form an eighth product including dimethyl carbonate fingers and a ninth product including the extractant. The eighth product may be an overhead product of the third distillation column 144 and may flow from the top of the third distillation column 144 to the condenser 146. The dimethyl carbonate in the eighth product can be stored in the reflux tank 148 after being condensed. The dimethyl carbonate condensed in the reflux tank 148 may be partially refluxed to the third distillation column 144, and another portion of the dimethyl carbonate may be used as a product of the dimethyl carbonate manufacturing method of this embodiment. The ninth product may be a bottom product of the third distillation column 144 and may be partially refluxed to the second distillation column 134 for recycling, while another portion may enter the reboiler 150 and be refluxed into the third distillation column 144.

Next, the propylene carbonate manufacturing apparatus 10 and the dimethyl carbonate manufacturing apparatus 10a of this embodiment are demonstrated using FIG. 1B.

The propylene carbonate manufacturing apparatus 10 of this embodiment includes a distillation system 102 and may further include a reaction system 100. Carbon dioxide and ammonia can be reacted in the reaction system 100 to produce urea. Propylene glycol and urea produced in the reaction system 100 described above can be used as feed to the distillation system 102. The distillation system 102 includes a first portion 102a and a second portion 102b. In some embodiments, the first portion 102a and the second portion 102b are a first reactive distillation column 104 and a first distillation column 114 that are connected to each other, respectively. Urea and excess propylene glycol are reacted and separated in a first reactive distillation column 104 to form a first product including ammonia and a second product including propylene glycol and propylene carbonate. The first product may be a top product of the first reactive distillation column 104, and the second product may be a bottom product of the first reactive distillation column 104. The second product enters the first distillation column 114 and is separated to form a third product including propylene glycol and a fourth product including propylene carbonate. The third product may be a top product of the first distillation column 114, and the fourth product may be a bottom product of the first distillation column 114.

The dimethyl carbonate manufacturing apparatus 10a of this embodiment includes a propylene carbonate manufacturing apparatus 10, and further includes a second reactive distillation column 124 and a second distillation column 134. Methanol and the aforementioned fourth product are reacted and separated in a second reactive distillation column 124, and a fifth product including methanol and dimethyl carbonate is formed on the top of the second reactive distillation column 124. The fifth product is separated in a second distillation column 134 having an extractant to form a sixth product including methanol and a seventh product including dimethyl carbonate.

In some embodiments, the seventh product may further include an extractant. In addition, the dimethyl carbonate production apparatus 10 a may further include a third distillation column 144. The dimethyl carbonate in the seventh product is separated from the extractant in the third distillation column 144 to form an eighth product including the dimethyl carbonate and a ninth product including the extractant.

Based on the above, urea and propylene glycol enter the distillation system 102 of the propylene carbonate manufacturing apparatus 10, respectively, to perform a reaction to generate propylene carbonate. In addition, propylene glycol and propylene carbonate as products can be further separated in the distillation system 102. Therefore, the purity of the propylene carbonate as a product can be improved, and the method and device for manufacturing the propylene carbonate of this embodiment can have a high product conversion rate. In this way, the method and apparatus for producing dimethyl carbonate by using propylene carbonate of higher purity as a reactant can also have a higher product conversion rate.

Next, a method for manufacturing propylene carbonate and a device for manufacturing the second to fourth embodiments of the present invention will be described with reference to FIGS. 2 to 4. The components in FIG. 2 to FIG. 4 that are the same as or similar to those in FIG. 1B are described with the same reference numerals, and their effects or functions are not described herein again. In addition, for simplicity, the reaction system 100 is omitted in FIGS. 2 to 4.

2A to 2C are schematic diagrams of an apparatus for manufacturing propylene carbonate according to a second embodiment of the present invention.

Please refer to FIG. 1A, FIG. 1B and FIG. 2A. The manufacturing method of the propylene carbonate of the second embodiment is similar to the manufacturing method of the propylene carbonate of the first embodiment. The difference between the two lies in that the method for producing propylene carbonate in this embodiment further includes heat-exchanging the bottom liquid of the first reactive distillation column 104 and the top gas of the first distillation column 114 in the first heat exchange device 112. And refluxed to the bottom of the first reactive distillation column 104 and the top of the first distillation column 114, respectively.

In some embodiments, the liquid bottom product (ie, the second product) of the first reactive distillation column 104 may flow from the bottom of the first reactive distillation column 104 to the reboiler 110, the first distillation column 114, and First heat exchange device 112. In addition, the top product (ie, the third product) of the gaseous first distillation column 114 may flow from the top of the first distillation column 114 to the first heat exchange device 112, and in the first heat exchange device 112, The liquid bottom product of the reactive distillation column 104 is subjected to heat exchange. The liquid bottom product of the first reactive distillation column 104 can be refluxed into the first reactive distillation column 104 after being heated to provide a part of the thermal energy required by the first reactive distillation column 104. Therefore, the energy consumption required for the reboiler 110 can be reduced. In other embodiments, the top gas of the first distillation column 114 can even provide all the thermal energy required by the first reactive distillation column 104, so the reboiler 110 provided to heat the first reactive distillation column 104 can be omitted. On the other hand, the gaseous overhead product of the first distillation column 114 can enter the reflux tank 118 after being condensed in the first heat exchanging device 112, so the installation of the overhead product to condense the overhead product of the first distillation column 114 can be omitted. Condenser.

Referring to FIG. 1B and FIG. 2A, the propylene carbonate manufacturing apparatus 20a of this embodiment is similar to the propylene carbonate manufacturing apparatus 10 of the first embodiment. The difference between the two is that the propylene carbonate manufacturing apparatus 20 a of this embodiment further includes a first heat exchange apparatus 112. The first heat exchange device 112 is connected between the first reactive distillation column 104 and the first distillation column 114, so that the liquid in the first reactive distillation column 104 and the gas in the first distillation column 114 are in the first heat exchange device 112. After heat exchange is performed in the medium, the mixture is refluxed to the first reactive distillation column 104 and the first distillation column 114, respectively.

Referring to FIG. 2B, in some embodiments, the first distillation column 114 of the propylene carbonate manufacturing device 20b may further include an upper column 114a, a lower column 114b, and a gas compression device 114c. The gas compression device 114c is connected between the upper column 114a and the lower column 114b, so that the gas in the lower column 114b enters the gas compression device 114c to generate a compressed product, and the compressed product is allowed to enter the upper column 114a to generate a first distillation column 114. Top product. The gas compression device 114c can increase the temperature and pressure of the gas, so the temperature and pressure of the upper stage tower 114a can be higher than the temperature and pressure of the lower stage tower 114b. In this way, propylene glycol and propylene carbonate can be prevented from forming an azeotrope in the upper column 114a, and the lower column 114b can be maintained at a relatively low temperature and pressure, thereby reducing the energy consumption of the reboiler 120.

In addition, the top gas of the upper column 114a and the bottom liquid of the first reactive distillation column 104 are heat-exchanged in the first heat exchange device 112, and then returned to the top of the upper column 114a and the first reactive distillation column 104 respectively. The bottom of the tower. Because the upper column 114a has a relatively high temperature and pressure, the first reactive distillation column 104 can obtain more thermal energy from the upper column 114b of the first distillation column 114 through heat exchange. Therefore, the energy consumption required for the reboiler 110 can be reduced.

Please refer to FIG. 2C. In some embodiments, the propylene carbonate manufacturing device 20 c may further include a second heat exchange device 113. Part of the gas in the top of the upper column 114a of the first distillation column 114 and the bottom liquid of the lower column 114b can be heat-exchanged in the second heat exchange device 113 and then returned to the top of the upper column 114a and the lower column respectively. 114b's bottom. In this way, the lower stage tower 114b can obtain sufficient thermal energy from the upper stage tower 114a by heat exchange, so the reboiler 120 can be omitted.

In summary, urea and excess propylene glycol respectively enter the distillation system of a propylene carbonate manufacturing device to perform a reaction to produce propylene carbonate. In addition, propylene glycol can be separated from propylene carbonate as a product in a distillation system. Therefore, the purity of propylene carbonate as a product can be improved, and the conversion rate of propylene carbonate can be improved. In this way, the method and device for producing dimethyl carbonate by using propylene carbonate of higher purity as a reactant can also have a higher product conversion rate.

In some embodiments, the propylene carbonate distillation system may include two first reactive distillation columns and a first distillation column that are interconnected. In addition, by setting a first heat exchange device connected between the first reactive distillation column and the first distillation column, the thermal energy at the top of the first distillation column can be used to heat the bottom of the first reactive distillation column. Therefore, the energy consumption required for the first reactive distillation column can be reduced.

Although the present invention has been disclosed as above with the examples, it is not intended to limit the present invention. Any person with ordinary knowledge in the technical field can make some modifications and retouching without departing from the spirit and scope of the present invention. The protection scope of the present invention shall be determined by the scope of the attached patent application.

10, 20a, 20b, 20c ‧‧‧ propylene carbonate production equipment

10a‧‧‧Dimethyl carbonate manufacturing equipment

100‧‧‧ reaction system

101‧‧‧ exit

102‧‧‧Distillation system

102a‧‧‧Part I

102b‧‧‧Part II

104‧‧‧The first reactive distillation column

104a‧‧‧Upper Tower

104b‧‧‧lower tower

104c‧‧‧Gas compression device

106‧‧‧Partial condenser

108, 118, 128, 138, 148‧‧‧ return tank

110, 120, 130, 140, 150‧‧‧ reboilers

112‧‧‧The first heat exchange device

113‧‧‧Second heat exchange device

114‧‧‧The first distillation column

116, 126, 136, 146‧‧‧ condenser

124‧‧‧Second reactive distillation column

134‧‧‧Second distillation column

144‧‧‧The third distillation column

S100, S102, S104, S106, S108, S110‧‧‧ steps

FIG. 1A is a flowchart of a method for manufacturing propylene carbonate and dimethyl carbonate according to a first embodiment of the present invention. FIG. 1B is a schematic diagram of an apparatus for manufacturing propylene carbonate and dimethyl carbonate according to the first embodiment of the present invention. 2A to 2C are schematic diagrams of an apparatus for manufacturing propylene carbonate according to a second embodiment of the present invention.

Claims (14)

A method for manufacturing propylene carbonate, comprising: separately introducing urea and excess propylene glycol into a first part of a distillation system, so that urea and propylene glycol are reacted and separated in the first part to form a first product including ammonia and propylene glycol And a second product of propylene carbonate; and passing the second product into a second part of the distillation system to separate the second product to form a third product including propylene glycol and a fourth product including propylene carbonate Product, wherein the first part and the second part are two distillation columns connected to each other, the second part is a first distillation column, and the third product and the fourth product are the first A top product and a bottom product of a distillation column, wherein the first distillation column includes an upper column, a lower column, and a gas compression device, so that the top gas of the lower column enters the gas compression device to generate a compressed product, And making the compressed product enter the bottom of the upper column to produce a top product of the upper column, and the top product of the upper column is the first distillation The top product. The method for manufacturing propylene carbonate according to item 1 of the scope of patent application, wherein the first part is a first reactive distillation column, and the first product and the second product are the tops of the reactive distillation column, respectively. Product and bottom product. The method for producing propylene carbonate according to item 2 of the scope of the patent application, further comprising performing the bottom liquid of the first reactive distillation column and the top gas of the first distillation column in a first heat exchange device. After the heat exchange, they are respectively refluxed to the bottom of the first reactive distillation column and the top of the first distillation column. The method for producing propylene carbonate according to item 1 of the scope of patent application, wherein the bottom liquid of the first reactive distillation column and the top gas of the upper column are heat-exchanged in the first heat exchange device. Then, it is refluxed to the bottom of the first reactive distillation column and the top of the upper column of the first distillation column, respectively. The method for manufacturing propylene carbonate according to item 1 of the scope of patent application, wherein a part of the gas in the top of the upper column and the bottom liquid in the lower column are subjected to heat exchange in a second heat exchange device, Return to the top of the upper tower and the bottom of the lower tower respectively. A method for manufacturing dimethyl carbonate, comprising: passing an excess of methanol and a fourth product according to any one of claims 1 to 5 into a second reactive distillation column, so that methanol and the first reactive distillation column The propylene carbonate in the fourth product is reacted and separated in the second reactive distillation column, and a fifth product including methanol and dimethyl carbonate is formed on the top of the second reactive distillation column; and The five products and the extractant enter the second distillation column to form a sixth product including methanol and a seventh product including dimethyl carbonate at the top and bottom of the second distillation column, respectively. The method for manufacturing dimethyl carbonate according to item 6 in the scope of the patent application, wherein the seventh product further includes the extractant, and the method for manufacturing the dimethyl carbonate further includes allowing the seventh product to enter A third distillation column to separate the dimethyl carbonate in the seventh product from the extractant in the third distillation column to form an eighth product including dimethyl carbonate and an The ninth product. A device for producing propylene carbonate, comprising a distillation system, wherein the distillation system has a first part and a second part, the first part and the second part are two distillation columns connected to each other, and the second part is In a first distillation column, urea and propylene glycol are reacted and separated in the first part to form a first product including ammonia and a second product including propylene glycol and propylene carbonate. The propylene glycol and propylene carbonate in the second product enter The second part is separated to form a third product including propylene glycol and a fourth product including propylene carbonate, and the third product and the fourth product are an overhead product and a column of the first distillation column, respectively. A bottom product, wherein the first distillation column includes an upper stage column, a lower stage column, and a gas compression device, and the gas compression device is connected between the upper stage column and the lower stage column so that the top gas of the lower stage column Enter the gas compression device to produce a compressed product, and cause the compressed product to enter the bottom of the upper column to produce a top product of the upper column, so The overhead section of the column is the product of the first distillation column overhead product. The device for manufacturing propylene carbonate according to item 8 of the scope of the patent application, wherein the first part is a first reactive distillation column, and the first product and the second product are the tops of the reactive distillation column, respectively. Product and bottom product. The propylene carbonate manufacturing device according to item 9 of the scope of patent application, further comprising a first heat exchange device, wherein the first heat exchange device is connected to the first reactive distillation column and the first distillation column. Between the bottom liquid of the first reactive distillation tower and the top gas of the first distillation tower in the first heat exchange device, and then return to the first reactive distillation tower respectively And the top of the first distillation column. The device for producing propylene carbonate according to item 8 of the scope of application, wherein the bottom liquid of the first reactive distillation column and the top gas of the upper column perform heat exchange in the first heat exchange device. Then, it is refluxed to the bottom of the first reactive distillation column and the top of the upper column of the first distillation column, respectively. The propylene carbonate manufacturing device according to item 8 of the scope of patent application, further comprising a second heat exchange device, wherein a part of the gas in the top of the upper column and the liquid in the bottom of the lower column are in the first After performing heat exchange in the two heat exchange devices, they are respectively returned to the top of the tower in the upper stage and the bottom of the tower in the lower stage. A device for manufacturing dimethyl carbonate, comprising: the distillation system according to any one of items 8 to 12 in the scope of patent application; a second reactive distillation column, in which methanol and the eighth to the seventh in scope of patent application The propylene carbonate in the fourth product according to any one of 12 items is reacted and separated in the second reactive distillation column, and the top of the second reactive distillation column is formed to include methanol and dimethyl carbonate A fifth product; and a second distillation column, wherein the fifth product is separated from an extractant in the second distillation column to form a sixth product including methanol and a seventh product including dimethyl carbonate. The dimethyl carbonate manufacturing apparatus according to item 13 of the scope of the patent application, wherein the seventh product further includes the extractant, and the dimethyl carbonate manufacturing apparatus further includes a third distillation column, the The dimethyl carbonate in the seventh product is separated from the extractant in the third distillation column to form an eighth product including dimethyl carbonate and a ninth product including the extractant.