Method for removing carbon tetrachloride from phosgene and application thereof

Abstract

The invention discloses a method for removing carbon tetrachloride from phosgene and application of the method. According to the method for removing carbon tetrachloride from phosgene, a phosgene raw material is purified through a carbon tetrachloride removal tower, and carbon tetrachloride is removed. Wherein the number of theoretical tower plates in the tower body is 23 to 30; the material inlets are positioned at the 11th to 15th tower plates from bottom to top; the reflux ratio in the tower body is 0.5-0.7. In the treated phosgene, the content of carbon tetrachloride is less than 15 ppm. And the content of carbon tetrachloride in the phosgene raw material is effectively reduced. The method for removing the carbon tetrachloride from the phosgene is applied to a TDI (toluene diisocynate) production process, and the phosgene raw material is subjected to carbon tetrachloride removal before synthesis, so that the subsequent separation difficulty is avoided, and the quality of a TDI product is improved.

Description

Technical Field

[0001] This invention relates to the field of chemical wastewater treatment, and in particular to a method for removing carbon tetrachloride from phosgene and its application. Background Technology

[0002] Toluene diisocyanate (TDI) is a diisocyanate derivative of toluene, mainly existing in two isomers: 2,4-TDI and 2,6-TDI. Chemically, TDI is highly reactive, particularly with compounds containing active hydrogen atoms (such as alcohols and amines) to form polyurethane. Therefore, it is an ideal raw material for the production of polyurethane materials and enjoys broad market demand.

[0003] Currently, the industrial production of TDI mainly employs phosgenation technology. During the generation of phosgene, a small amount of methane reacts with liquid chlorine to produce carbon tetrachloride, which, along with other byproducts, accumulates in the reaction system. This carbon tetrachloride is a major impurity in the TDI production process, leading to delayed decomposition of TDI intermediates, causing side reactions, increasing the difficulty of subsequent purification, and reducing TDI yield. Therefore, carbon tetrachloride content is a crucial indicator of TDI product quality. Given the impact of carbon tetrachloride on TDI product performance, it is necessary to reduce its content during production. Summary of the Invention

[0004] The purpose of this invention is to address the technical deficiencies in existing technologies by providing a method for removing carbon tetrachloride from phosgene. The method involves purifying the phosgene feedstock using a carbon tetrachloride removal tower to remove carbon tetrachloride. The tower has 23-30 theoretical plates; the material inlet is located at the 11th-15th plate from the bottom; and the reflux ratio within the tower is 0.5-0.7. The treated phosgene contains less than 15 ppm of carbon tetrachloride, effectively reducing the carbon tetrachloride content in the phosgene feedstock.

[0005] Another object of the present invention is to provide the application of the above method in the TDI production process.

[0006] Another objective of this invention is to provide a TDI production process that removes carbon tetrachloride from phosgene raw materials before synthesis, thereby avoiding subsequent separation difficulties and improving the quality of TDI products.

[0007] The technical solution adopted to achieve the purpose of this invention is: A method for removing carbon tetrachloride from phosgene involves purifying the phosgene feedstock by passing it through a carbon tetrachloride removal tower to remove carbon tetrachloride. The carbon tetrachloride removal tower includes a tower body, a tower bottom, a top condenser, and a tower bottom reboiler; The theoretical number of trays in the tower body is 23-30; a material inlet is provided on the tower body; the material inlet is located at the 11th-15th tray from bottom to top; The top of the tower body is provided with a top gas outlet and a condensate return port; the top gas in the tower body enters the top condenser through the top gas outlet and is condensed to form condensate, which then flows back to the tower body through the condensate return port. The top of the tower is also equipped with a phosgene extraction outlet for extracting phosgene that has been dechlorinated with carbon tetrachloride; The column reboiler is provided with a column reboiler liquid outlet and a reboiler liquid reflux port; the column reboiler liquid in the column reboiler flows out through the column reboiler liquid outlet and enters the column reboiler, and after being heated and reboiled, it flows back into the column reboiler through the reboiler liquid reflux port. The reflux ratio inside the tower is 0.5-0.7; The reboiler is also equipped with a reboiler liquid outlet for extracting a mixture of phosgene and carbon tetrachloride.

[0008] In the above technical solution, the theoretical number of trays in the tower body is 23.

[0009] In the above technical solution, the material inlet is located at the 11th tray from bottom to top.

[0010] In the above technical solution, the reflux ratio inside the tower is 0.5.

[0011] In the above technical solution, the carbon tetrachloride content in the phosgene extracted from the phosgene extraction outlet is less than 15 ppm.

[0012] Another aspect of the present invention is the application of the above method in the TDI production process.

[0013] Another aspect of the present invention is a TDI production process, comprising the aforementioned carbon tetrachloride removal tower, reaction vessel, photochemical tower, decoking tower, and refining tower.

[0014] In the above technical solution, the phosgene outlet of the carbon tetrachloride removal tower is connected to the feed inlet of the reaction tank so that the phosgene that has removed carbon tetrachloride can enter the reaction tank for reaction. The reaction vessel is connected to the photochemical tower and is used to remove phosgene from the crude TDI generated by the reaction. The photochemical tower is connected to the decoking tower and is used to decoke the crude TDI product after removing phosgene. The decoking tower is connected to the refining tower and is used to refine the decoked TDI to obtain qualified products.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. The method for removing carbon tetrachloride from phosgene provided by this invention involves purifying the phosgene feedstock by passing it through a carbon tetrachloride removal tower to remove carbon tetrachloride. The tower has 23-30 theoretical plates; the material inlet is located at the 11th-15th plate from the bottom; and the reflux ratio within the tower is 0.5-0.7. The treated phosgene contains less than 15 ppm of carbon tetrachloride, effectively reducing the carbon tetrachloride content in the phosgene feedstock.

[0016] 2. The TDI production process provided by this invention removes carbon tetrachloride from the phosgene raw material before synthesis, avoiding subsequent separation difficulties and improving the quality of TDI products. Attached Figure Description

[0017] Figure 1 The diagram shown is a schematic of the carbon tetrachloride removal tower. In the diagram: 1-tower body, 1-1-material inlet, 1-2-top gas outlet, 1-3-condensate reflux port, 1-4-phosgene outlet, 2-tower bottom, 2-1-bottom liquid outlet, 2-2-reboiler bottom liquid reflux port, 2-3-bottom liquid outlet, 3-top condenser, 4-bottom reboiler. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0019] Example 1

[0020] A method for removing carbon tetrachloride from phosgene involves purifying the phosgene feedstock by passing it through a carbon tetrachloride removal tower to remove carbon tetrachloride; wherein the phosgene feedstock contains 90 ppm carbon tetrachloride and 30 ppm chlorine.

[0021] The carbon tetrachloride removal tower, such as Figure 1 As shown, it includes a column body 1, a column bottom 2, a column top condenser 3, and a column bottom reboiler 4; The theoretical number of trays in the tower body is 23; the tower body has a material inlet 1-1; the material inlet 1-1 is located at the 11th tray from bottom to top; the feed temperature of the phosgene feedstock is 66 ℃, the feed pressure is 0.3 MPaG, and the feed rate is 6500 kg / h.

[0022] The top of the tower body is provided with a top gas outlet 1-2 and a condensate return port 1-3; the top gas in the tower body enters the top condenser 3 through the top gas outlet 1-2 and is condensed to form condensate, which then flows back to the tower body 1 through the condensate return port 1-3. The column reboiler 2 is provided with a column reboiler liquid outlet 2-1 and a reboiler liquid reflux port 2-2; the column reboiler liquid in the column reboiler 2 flows out through the column reboiler liquid outlet 2-1 and enters the column reboiler 4, and after being heated and reboiled, it flows back into the column reboiler 2 through the reboiler liquid reflux port 2-2. The reflux ratio inside the tower is 0.7; The top of the tower is also equipped with phosgene outlets 1-4 for collecting phosgene that has been dechlorinated to remove carbon tetrachloride. The collected phosgene contains 10 ppm carbon tetrachloride and 30 ppm chlorine, meeting production requirements. The bottom of the tower is also equipped with bottom liquid outlets 2-3 for collecting a mixture of phosgene and carbon tetrachloride, wherein the phosgene content is approximately 27% and the carbon tetrachloride content is approximately 73%.

[0023] Comparative Example 1

[0024] A method for removing carbon tetrachloride from phosgene involves purifying the phosgene feedstock by passing it through a carbon tetrachloride removal tower to remove carbon tetrachloride; wherein the phosgene feedstock contains 90 ppm carbon tetrachloride and 30 ppm chlorine.

[0025] The carbon tetrachloride removal tower includes a tower body, a tower bottom, a top condenser, and a tower bottom reboiler; The theoretical number of trays in the tower body is 20; a material inlet is provided on the tower body; the material inlet is located at the 11th tray from bottom to top; the feed temperature of the phosgene feedstock is 66 ℃, the feed pressure is 0.3 MPaG, and the feed rate is 6500 kg / h.

[0026] The top of the tower body is provided with a top gas outlet and a condensate return port; the top gas in the tower body enters the top condenser through the top gas outlet and is condensed to form condensate, which then flows back to the tower body through the condensate return port. The column reboiler is provided with a column reboiler liquid outlet and a reboiler liquid reflux port; the column reboiler liquid in the column reboiler flows out through the column reboiler liquid outlet and enters the column reboiler, and after being heated and reboiled, it flows back into the column reboiler through the reboiler liquid reflux port. The reflux ratio inside the tower is 0.7; The top of the tower is also equipped with a phosgene outlet for collecting phosgene that has been dechlorinated. The collected phosgene contains 20 ppm of carbon tetrachloride and 30 ppm of chlorine. The carbon tetrachloride content is still relatively high, which is not conducive to subsequent production. The bottom of the tower is also equipped with a bottom liquid outlet for collecting a mixture of phosgene and carbon tetrachloride, in which the phosgene content is approximately 30% and the carbon tetrachloride content is approximately 70%.

[0027] Example 2

[0028] A method for removing carbon tetrachloride from phosgene involves purifying the phosgene feedstock by passing it through a carbon tetrachloride removal tower to remove carbon tetrachloride; wherein the phosgene feedstock contains 100 ppm carbon tetrachloride and 35 ppm chlorine.

[0029] The carbon tetrachloride removal tower, such as Figure 1 As shown, it includes the column body, column bottom, top condenser, and column bottom reboiler; The theoretical number of trays in the tower body is 30; a material inlet is provided on the tower body; the material inlet is located at the 15th tray from bottom to top; the feed temperature of the phosgene feedstock is 66 ℃, the feed pressure is 0.3 MPaG, and the feed rate is 6500 kg / h.

[0030] The top of the tower body is provided with a top gas outlet and a condensate return port; the top gas in the tower body enters the top condenser through the top gas outlet and is condensed to form condensate, which then flows back to the tower body through the condensate return port. The column reboiler is provided with a column reboiler liquid outlet and a reboiler liquid reflux port; the column reboiler liquid in the column reboiler flows out through the column reboiler liquid outlet and enters the column reboiler, and after being heated and reboiled, it flows back into the column reboiler through the reboiler liquid reflux port. The reflux ratio inside the tower is 0.5; The top of the tower is also equipped with a phosgene outlet for extracting phosgene that has been dechlorinated with carbon tetrachloride. The extracted phosgene contains 8 ppm carbon tetrachloride and 30 ppm chlorine, meeting production requirements. The bottom of the tower is also equipped with a bottom liquid outlet for extracting a mixture of phosgene and carbon tetrachloride, wherein the phosgene content is approximately 26% and the carbon tetrachloride content is approximately 74%.

[0031] Comparative Example 2 A method for removing carbon tetrachloride from phosgene involves purifying the phosgene feedstock by passing it through a carbon tetrachloride removal tower to remove carbon tetrachloride; wherein the phosgene feedstock contains 100 ppm carbon tetrachloride and 35 ppm chlorine.

[0032] The carbon tetrachloride removal tower, such as Figure 1 As shown, it includes the column body, column bottom, top condenser, and column bottom reboiler; The theoretical number of trays in the tower body is 30; a material inlet is provided on the tower body; the material inlet is located at the 15th tray from bottom to top; the feed temperature of the phosgene feedstock is 66 ℃, the feed pressure is 0.3 MPaG, and the feed rate is 6500 kg / h.

[0033] The top of the tower body is provided with a top gas outlet and a condensate return port; the top gas in the tower body enters the top condenser through the top gas outlet and is condensed to form condensate, which then flows back to the tower body through the condensate return port. The column reboiler is provided with a column reboiler liquid outlet and a reboiler liquid reflux port; the column reboiler liquid in the column reboiler flows out through the column reboiler liquid outlet and enters the column reboiler, and after being heated and reboiled, it flows back into the column reboiler through the reboiler liquid reflux port. The reflux ratio inside the tower is 0.4; The top of the tower also has a phosgene outlet for collecting phosgene that has been dechlorinated. The collected phosgene contains 18 ppm of carbon tetrachloride and 30 ppm of chlorine. The carbon tetrachloride content is still relatively high, which is not conducive to subsequent production. The bottom of the tower also has a bottom liquid outlet for collecting a mixture of phosgene and carbon tetrachloride, in which the phosgene content is approximately 29% and the carbon tetrachloride content is approximately 71%.

[0034] Example 3

[0035] A method for removing carbon tetrachloride from phosgene involves purifying the phosgene feedstock by passing it through a carbon tetrachloride removal tower to remove carbon tetrachloride; wherein the phosgene feedstock contains 95 ppm carbon tetrachloride and 32 ppm chlorine.

[0036] The carbon tetrachloride removal tower, such as Figure 1 As shown, it includes the column body, column bottom, top condenser, and column bottom reboiler; The theoretical number of trays in the tower body is 23; a material inlet is provided on the tower body; the material inlet is located at the 13th tray from bottom to top; the feed temperature of the phosgene feedstock is 66 ℃, the feed pressure is 0.3 MPaG, and the feed rate is 6500 kg / h.

[0037] The top of the tower body is provided with a top gas outlet and a condensate return port; the top gas in the tower body enters the top condenser through the top gas outlet and is condensed to form condensate, which then flows back to the tower body through the condensate return port. The column reboiler is provided with a column reboiler liquid outlet and a reboiler liquid reflux port; the column reboiler liquid in the column reboiler flows out through the column reboiler liquid outlet and enters the column reboiler, and after being heated and reboiled, it flows back into the column reboiler through the reboiler liquid reflux port. The reflux ratio inside the tower is 0.5; The top of the tower is also equipped with a phosgene outlet for extracting phosgene that has been dechlorinated with carbon tetrachloride. The extracted phosgene contains 10 ppm carbon tetrachloride and 32 ppm chlorine, meeting production requirements. The bottom of the tower is also equipped with a bottom liquid outlet for extracting a mixture of phosgene and carbon tetrachloride, wherein the phosgene content is approximately 26% and the carbon tetrachloride content is approximately 74%.

[0038] Comparative Example 3 A method for removing carbon tetrachloride from phosgene involves purifying the phosgene feedstock by passing it through a carbon tetrachloride removal tower to remove carbon tetrachloride; wherein the phosgene feedstock contains 95 ppm carbon tetrachloride and 32 ppm chlorine.

[0039] The carbon tetrachloride removal tower, such as Figure 1 As shown, it includes the column body, column bottom, top condenser, and column bottom reboiler; The theoretical number of trays in the tower body is 23; a material inlet is provided on the tower body; the material inlet is located at the 10th tray from bottom to top; the feed temperature of the phosgene feedstock is 66 ℃, the feed pressure is 0.3 MPaG, and the feed rate is 6500 kg / h.

[0040] The top of the tower body is provided with a top gas outlet and a condensate return port; the top gas in the tower body enters the top condenser through the top gas outlet and is condensed to form condensate, which then flows back to the tower body through the condensate return port. The column reboiler is provided with a column reboiler liquid outlet and a reboiler liquid reflux port; the column reboiler liquid in the column reboiler flows out through the column reboiler liquid outlet and enters the column reboiler, and after being heated and reboiled, it flows back into the column reboiler through the reboiler liquid reflux port. The reflux ratio inside the tower is 0.5; The top of the tower also has a phosgene outlet for collecting phosgene that has been dechlorinated. The collected phosgene contains 23 ppm of carbon tetrachloride and 32 ppm of chlorine. The carbon tetrachloride content is still relatively high, which is not conducive to subsequent production. The bottom of the tower also has a bottom liquid outlet for collecting a mixture of phosgene and carbon tetrachloride, in which the phosgene content is approximately 28% and the carbon tetrachloride content is approximately 72%.

[0041] The above description is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for removing carbon tetrachloride from phosgene, characterized in that, The phosgene feedstock is purified by passing it through a carbon tetrachloride removal tower to remove carbon tetrachloride. The carbon tetrachloride removal tower includes a tower body, a tower bottom, a top condenser, and a tower bottom reboiler; The theoretical number of trays in the tower body is 23-30; a material inlet is provided on the tower body; the material inlet is located at the 11th-15th tray from bottom to top; The top of the tower body is provided with a top gas outlet and a condensate return port; the top gas in the tower body enters the top condenser through the top gas outlet and is condensed to form condensate, which then flows back to the tower body through the condensate return port. The top of the tower is also equipped with a phosgene extraction outlet for extracting phosgene that has been dechlorinated with carbon tetrachloride; The column reboiler is provided with a column reboiler liquid outlet and a reboiler liquid reflux port; the column reboiler liquid in the column reboiler flows out through the column reboiler liquid outlet and enters the column reboiler, and after being heated and reboiled, it flows back into the column reboiler through the reboiler liquid reflux port. The reflux ratio inside the tower is 0.5-0.7; The reboiler is also equipped with a reboiler liquid outlet for extracting a mixture of phosgene and carbon tetrachloride.

2. The method as described in claim 1, characterized in that, The theoretical number of plates inside the tower is 23.

3. The method as described in claim 2, characterized in that, The material inlet is located at the 11th tray from the bottom.

4. The method as described in claim 3, characterized in that, The reflux ratio inside the tower is 0.

5.

5. The method as described in claim 1, characterized in that, The phosgene extracted from the phosgene extraction outlet contains less than 15 ppm of carbon tetrachloride.

6. The application of the method as described in claim 1 in the TDI production process.

7. A TDI production process, characterized in that, Includes the carbon tetrachloride removal tower, reaction vessel, photochemical tower, decoking tower, and purification tower as described in any one of claims 1-6.

8. The TDI production process as described in claim 7, characterized in that, The phosgene outlet of the carbon tetrachloride removal tower is connected to the feed inlet of the reaction vessel so that the phosgene that has been dechlorinated with carbon tetrachloride can enter the reaction vessel for reaction. The reaction vessel is connected to the photochemical tower and is used to remove phosgene from the crude TDI generated by the reaction. The photochemical tower is connected to the decoking tower and is used to decoke the crude TDI product after removing phosgene. The decoking tower is connected to the refining tower and is used to refine the decoked TDI to obtain qualified products.

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