CN107540518B - Hydrogen recycling method in production process of chlorotrifluoroethylene - Google Patents
Hydrogen recycling method in production process of chlorotrifluoroethylene Download PDFInfo
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Abstract
The invention discloses a hydrogen recycling method for chlorotrifluoroethylene production, which is characterized in that a crude product containing chlorotrifluoroethylene and hydrogen sequentially undergoes steps of water-alkali washing, water removal, compression and condensation, and is circulated back to a reactor to continuously participate in reaction when the mass percent of oxygen is lower than 0.2%. The method provided by the invention not only realizes the recycling of hydrogen, but also can improve the utilization rate of raw materials and the yield of products.
Description
Technical Field
The invention relates to a hydrogen recycling method, in particular to a hydrogen recycling method in a chlorotrifluoroethylene production process.
Background
Chlorotrifluoroethylene, also known as chlorotrifluoroethylene, is an important fluorine-containing polymeric monomer and can be used for manufacturing fluorine resins, fluororubbers, fluoroplastics, and the like.
For the preparation of chlorotrifluoroethylene, two methods exist in the existing industrial production, namely a zinc powder reduction method process taking trichlorotrifluoroethane (CFC-113) as a raw material and a solid-phase hydrogenation dechlorination process taking trichlorotrifluoroethane (CFC-113) as a raw material gas.
The gas-solid phase hydrogenation dechlorination process using the trichlorotrifluoroethane (CFC-113) as the raw material has the advantages of environmental protection, high efficiency, low cost and the like, thereby having wider industrial development value. However, in the process, in order to improve the service life of the catalyst in the gas-solid phase catalytic hydrodechlorination link, a larger hydrogen/trifluorotrichloroethane ratio is usually adopted, and excessive hydrogen is difficult to recover, so that not only is a large amount of hydrogen raw materials wasted, but also partial chlorotrifluoroethylene products are carried in the hydrogen discharge, and the product yield is low.
Therefore, it is very necessary to develop a hydrogen recycling method suitable for the production process of chlorotrifluoroethylene to improve the utilization rate of raw materials and the yield of products.
Disclosure of Invention
The invention aims to provide a hydrogen recycling method suitable for the production process of chlorotrifluoroethylene, which can improve the utilization rate of raw materials and the yield of products.
The invention provides the following technical scheme:
a hydrogen reuse process for chlorotrifluoroethylene production, the process comprising:
(1) feeding a crude product 8 containing chlorotrifluoroethylene and hydrogen into an acid remover 2 for water and alkali washing to reduce the acidity of a material flow 9 to 15-300 ppm;
(2) enabling the material flow 9 to enter a dehydrator 3 for dehydrating, and reducing the water content of the material flow 10 to 50-500 ppm;
(3) enabling the material flow 10 to enter a compressor 4 for compression, and enabling the formed material flow 11 to enter a condenser 5 for condensation, wherein the condensation temperature is-25-0 ℃, and the material flow 12 is formed;
(4) when the mass percentage of oxygen in stream 12 is lower than 0.2%, it is returned to reactor 1; when the mass percentage of oxygen in stream 12 is higher than 0.2%, it is fed to the three-waste system as stream 13.
In the hydrogen recycling method provided by the invention, in the step (1), the alkali used in the water alkali washing can be an alkali commonly used in the field. From the viewpoint of availability and economy, it is preferable that the base is selected from sodium hydroxide and/or potassium hydroxide. The concentration of the base is not particularly required in the present invention. Preferably, the alkali is present at a mass concentration of 2% to 10%.
In the hydrogen recycling method provided by the invention, in the step (1), the water and alkali washing comprises water washing and alkali washing. The water washing can be one-stage or multi-stage water washing. The alkaline washing can be one-stage or multi-stage alkaline washing. The number of stages of water washing and alkali washing can be selected according to actual requirements.
According to the hydrogen recycling method provided by the invention, in the step (1), acid in a crude product containing chlorotrifluoroethylene and hydrogen is removed through water and alkali washing, so that a material flow 9 is obtained. Preferably, the acidity of said stream 9 is less than 300 ppm. It is further preferred that the acidity of said stream 9 is less than 200 ppm.
In the hydrogen recycling method provided by the invention, in the step (2), the water removal method may be at least one selected from freeze drying, solid caustic soda drying and molecular sieves.
When the freeze drying method is used for removing water, the freeze drying method preferably uses low-temperature water with the temperature of 0-5 ℃.
When the solid caustic drying method is used for removing water, it is preferable that the base used for the solid caustic drying is selected from sodium hydroxide and/or potassium hydroxide.
When a molecular sieve process is used to remove water, it is preferred that the molecular sieve is a silicate.
In the hydrogen recycling method provided by the invention, in the step (2), water in the material flow 9 is removed through water removal, so that a material flow 10 is obtained. Preferably, the moisture of the stream 10 is less than 200 ppm.
In the hydrogen recycling method provided by the invention, in the step (3), the material flow 10 is compressed by the compressor 4, and then the material flow 11 is condensed by the condenser 5 to obtain the material flow 12.
Preferably, the compression pressure of the compressor 4 is 1.0 to 3.5 MPa.
Preferably, the condensing temperature of the condenser 5 is-20 to-5 ℃.
The condenser 5 may be condensed using a condensing medium commonly used in the art. Preferably, the condenser 5 uses brine or HCFC-22 with the temperature of-15 ℃ to-30 ℃ for condensation.
The oxygen content of the material flow 12 obtained after condensation by the condenser 5 is measured by the oxygen measuring instrument 6. If the mass percent of oxygen in stream 12 is less than 0.2%, it is returned to reactor 1 and continues to participate in the reaction. If the mass percentage of oxygen in stream 12 is higher than 0.2%, it is fed to the three wastes system as stream 13.
Drawings
Fig. 1 is a process flow diagram of a hydrogen recycling method in a chlorotrifluoroethylene production process, wherein:
equipment: 1 is a reactor, 2 is an acid remover, 3 is a water remover, 4 is a compressor, 5 is a condenser, and 6 is an oxygen meter;
logistics: 7 is a stream with oxygen mass percentage lower than 0.2%, 8 is a crude product containing chlorotrifluoroethylene and hydrogen, 9 is a stream after water-alkali washing, 10 is a stream after water removal, 11 is a stream after compression, 12 is a stream after condensation, and 13 is a stream with oxygen mass percentage higher than 0.2%.
Detailed Description
The present invention is further illustrated by the following examples, which are not intended to limit the invention to these embodiments. It will be appreciated by those skilled in the art that the present invention encompasses all alternatives, modifications and equivalents as may be included within the scope of the claims.
Example 1
After the crude product 8 containing chlorotrifluoroethylene and hydrogen, which is subjected to hydrodechlorination in the reactor 1, is subjected to water-alkali washing in the acid remover 2 to remove hydrogen chloride, the acidity of the obtained material flow 9 is 35ppm, and the hydrogen content in the material flow 9 is about 70 percent, and the chlorotrifluoroethylene content is about 30 percent. Stream 9 is passed on to dehydrator 3 for dehydration to give stream 10 having a moisture content of 150 ppm. And (3) enabling the material flow 10 to enter a compressor 4 for compression, and then entering a condenser for condensation at the temperature of 5-23 ℃ to obtain a material flow 12. The stream 12 is a non-condensable gas with a hydrogen content of 95%. Oxygen content detection of stream 12 using an oxygen meter 6, returning it to reactor 1 as stream 7 when the mass percentage of oxygen in stream 12 is lower than 0.2%; when the mass percentage of oxygen in stream 12 is higher than 0.2%, it is fed to the three-waste system as stream 13.
Fresh hydrogen and R113 are added in the reactor 1, and the raw material ratio H is kept2: r113 is 3:1, fresh hydrogen: 1:2 of recycled hydrogen and stable reaction system. The yield of the chlorotrifluoroethylene product after 24 hours in the reaction system can reach 95 percent.
Example 2
After the crude product 8 containing chlorotrifluoroethylene and hydrogen, which is subjected to hydrodechlorination in the reactor 1, is subjected to water-alkali washing in the acid remover 2 to remove hydrogen chloride, the acidity of the obtained material flow 9 is 30ppm, and the hydrogen content in the material flow 9 is about 68 percent, and the chlorotrifluoroethylene content is about 32 percent. Stream 9 is passed on to dehydrator 3 for dehydration to give stream 10 having a moisture content of 70 ppm. And (3) enabling the material flow 10 to enter a compressor 4 for compression, and then entering a condenser for condensation at the temperature of 5-23 ℃ to obtain a material flow 12. The stream 12 is a non-condensable gas with a hydrogen content of 97%. Oxygen content detection of stream 12 using an oxygen meter 6, returning it to reactor 1 as stream 7 when the mass percentage of oxygen in stream 12 is lower than 0.2%; when the mass percentage of oxygen in stream 12 is higher than 0.2%, it is fed to the three-waste system as stream 13.
Fresh hydrogen and R113 are added in the reactor 1, and the raw material ratio H is kept2: r113 is 3:1, fresh hydrogen: 1:2 of recycled hydrogen and stable reaction system. The yield of the chlorotrifluoroethylene product after 24 hours of the reaction system can reach 95.5 percent.
The stable production is continued for 5000h under the system, the yield of the chlorotrifluoroethylene product is 95%, and the total yield and the catalyst life of the reaction are close to those of the reaction with the fresh hydrogen.
Claims (9)
1. A hydrogen recycling method in the process of producing trifluorochloroethylene by using trichlorotrifluoroethane CFC-113 as a raw material gas through solid phase hydrogenation and dechlorination is characterized by comprising the following steps:
step (1), feeding a crude product 8 containing chlorotrifluoroethylene and hydrogen into an acid remover 2 for water and alkali washing, and reducing the acidity of a material flow 9 to 15-300 ppm;
step (2), enabling the material flow 9 to enter a dehydrator 3 for dehydrating, and reducing the water content of the material flow 10 to 50-500 ppm;
step (3), enabling the material flow 10 to enter a compressor 4 for compression, wherein the compression pressure is 1.0-3.5 Mpa, and enabling the formed material flow 11 to enter a condenser 5 for condensation, wherein the condensation temperature is-25-0 ℃, so as to form a material flow 12;
step (4) when the mass percentage of oxygen in stream 12 is lower than 0.2%, it is returned to reactor 1; when the mass percentage of oxygen in stream 12 is higher than 0.2%, it is fed to the three-waste system as stream 13.
2. The hydrogen recycling method according to claim 1, wherein in the step (1), the acidity of the crude product containing chlorotrifluoroethylene and hydrogen is reduced to 15-200 ppm, and the alkali used in the water alkali washing is selected from sodium hydroxide and/or potassium hydroxide.
3. The method for recycling hydrogen according to claim 2, wherein in the step (1), the mass concentration of the alkali used in the water alkali washing is 2-10%.
4. The hydrogen recycling method according to claim 1, wherein in the step (1), the water-alkali washing comprises water washing and alkali washing, the water washing comprises one-stage or multi-stage water washing, and the alkali washing comprises one-stage or multi-stage alkali washing.
5. The hydrogen recycling method according to claim 1, wherein in the step (2), the water content of the stream 10 is reduced to 50-200 ppm.
6. The method for recycling hydrogen according to claim 1, wherein in the step (2), the water is removed by at least one method selected from the group consisting of freeze drying, solid-base drying and molecular sieves.
7. The hydrogen recycling method according to claim 6, characterized in that in the step (2), the freeze drying uses low-temperature water with the temperature of 0-5 ℃, the alkali used in the solid alkali drying is selected from sodium hydroxide and/or potassium hydroxide, and the molecular sieve is silicate.
8. The hydrogen recycling method according to claim 1, characterized in that in the step (3), the formed material flow 11 enters a condenser 5 for condensation, the condensation temperature is-20 to-5 ℃, and the material flow 12 is formed.
9. The method for recycling hydrogen according to claim 8, wherein in the step (3), the condenser 5 is condensed by using brine or HCFC-22 at a temperature of-15 ℃ to-30 ℃.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102863313A (en) * | 2011-07-06 | 2013-01-09 | 中化蓝天集团有限公司 | Resource utilization method of tail gas from trifluoroethylene production |
| CN104140356A (en) * | 2014-07-16 | 2014-11-12 | 常熟三爱富氟化工有限责任公司 | Novel preparation method for green CTFE |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US7723552B2 (en) * | 2008-08-08 | 2010-05-25 | Honeywell International Inc. | Process for making chlorotrifluoroethylene from 1,1,2-Trichlorotrifluoroethane |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102863313A (en) * | 2011-07-06 | 2013-01-09 | 中化蓝天集团有限公司 | Resource utilization method of tail gas from trifluoroethylene production |
| CN104140356A (en) * | 2014-07-16 | 2014-11-12 | 常熟三爱富氟化工有限责任公司 | Novel preparation method for green CTFE |
Non-Patent Citations (1)
| Title |
|---|
| 国外三氟氯乙烯制备工艺路线的研究;陈祥俭等;《有机氟工业》;19901231(第1期);第52-55页 * |
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