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CN-122010678-A - HFC-23 and CHCl3Method for producing HCFC-22 and HCFC-21 as raw materials

CN122010678ACN 122010678 ACN122010678 ACN 122010678ACN-122010678-A

Abstract

The invention discloses a method for producing HCFC-22 and HCFC-21 by taking HFC-23 and CHCl 3 as raw materials, belonging to the technical field of fluorine chemical industry, improving the single pass conversion rate and reducing the reaction carbon deposition rate. HFC-23 and CHCl 3 are taken as raw materials, the raw materials are preheated and mixed and then are sent into a first reactor containing a catalyst for fluorine-chlorine exchange reaction, the raw materials which are still unreacted after the reaction are separated out by condensation separation and rectification, then the raw materials are sent into a second reactor containing the catalyst for continuous reaction, the reaction temperature of the fluorine-chlorine exchange reaction in the first reactor and the second reactor is 150-330 ℃, and products obtained by the two reactors are subjected to mixed rectification by utilizing a multi-step rectifying tower, so that the products HCFC-22 and HCFC-21 are obtained.

Inventors

  • SHAO CHUNTAO
  • ZHAO JINGPING
  • WANG ZHANGMING
  • CUI SHIWEI
  • ZHAN XIAODONG
  • ZHU XIAOMING

Assignees

  • 金华永和氟化工有限公司

Dates

Publication Date
20260512
Application Date
20260415

Claims (10)

  1. 1. A process for preparing HCFC-22 and HCFC-21 from HFC-23 and CHCl 3 includes such steps as preheating HFC-23 and CHCl 3 , mixing, loading in the first reactor containing catalyst, exchange reaction between fluorine and chlorine, condensing, separating HFC-23 and CHCl 3 , rectifying, and loading in the second reactor containing catalyst; The reaction temperature of the fluorine-chlorine exchange reaction in the first reactor and the second reactor is 150-330 ℃, and products obtained by the two reactors are subjected to mixed rectification by utilizing a multi-step rectifying tower to obtain products HCFC-22 and HCFC-21.
  2. 2. The method for producing HCFC-22 and HCFC-21 from HFC-23 and CHCl 3 as raw materials according to claim 1, wherein the temperature at which HFC-23 and CHCl 3 are pre-heated and mixed is 150 to 300 ℃, the reaction temperature at which the fluorine-chlorine exchange reaction is performed in the first reactor is 250 to 330 ℃, and the reaction temperature at which the fluorine-chlorine exchange reaction is performed in the second reactor is 150 to 250 ℃.
  3. 3. The method for producing HCFC-22 and HCFC-21 by using HFC-23 and CHCl 3 as raw materials according to claim 1, wherein the residence time of the raw materials in the first reactor is 0.5-5 s, and/or the residence time of the raw materials in the second reactor is 5-140 s, and/or the reaction pressure of the fluorine-chlorine exchange reaction in the first reactor and the second reactor is 0-0.7 mpa.
  4. 4. The method for producing HCFC-22 and HCFC-21 by using HFC-23 and CHCl 3 as raw materials according to claim 1, wherein the molar ratio of HFC-23 and CHCl 3 in the raw materials is 1 (1-3), and/or the acid value in CHCl 3 in the raw materials is controlled within the range of 0-50 ppm.
  5. 5. The method for producing HCFC-22 and HCFC-21 by using HFC-23 and CHCl 3 as raw materials according to claim 1, wherein the multi-step rectifying tower comprises a rectifying tower 1 and a rectifying tower 2, products after reaction in the reactor are separated in the rectifying tower 1, the HFC-23 is separated from the tower top, the purity is more than 98%, the HCFC-22 and HCFC-21 at the tower bottom are sent to the rectifying tower 2 for further separation, and the HCFC-22 and HCFC-21 at the tower top and the tower bottom are respectively recovered in the rectifying tower 2.
  6. 6. The method for producing HCFC-22 and HCFC-21 by using HFC-23 and CHCl 3 as raw materials according to claim 5, wherein the temperature of the top of the rectifying tower 1 is-40 to-10 ℃, the temperature of the bottom of the rectifying tower 1 is 0-20 ℃, the pressure of the rectifying tower 1 is 0.8-2.2 MPa, and/or the temperature of the top of the rectifying tower 2 is 30-50 ℃, the temperature of the bottom of the rectifying tower 2 is-30 to-5 ℃, and the pressure of the rectifying tower 2 is 0.5-1.5 MPa.
  7. 7. The method for producing HCFC-22 and HCFC-21 by using HFC-23 and CHCl 3 as raw materials according to claim 1, wherein after passing through a first reactor, unreacted raw materials HFC-23, CHCl 3 and products HCFC-22, HCFC-21 and HCl are condensed and separated from gas and liquid, the condensed CHCl 3 is fed into a CHCl 3 intermediate buffer tank, and after passing through a second reactor, unreacted raw materials HFC-23, CHCl 3 and products HCFC-22, HCFC-21 and HCl are condensed and separated from gas and liquid, and the condensed CHCl 3 is fed into a chloroform raw material tank for collection.
  8. 8. The method for producing HCFC-22 and HCFC-21 from HFC-23 and CHCl 3 as raw materials of claim 7, wherein after the reaction in the reactor, unreacted CHCl 3 is separated by a multi-stage cyclone separator, and the purity of separated CHCl 3 is controlled to be more than 99.5%.
  9. 9. The method for producing HCFC-22 and HCFC-21 by using HFC-23 and CHCl 3 as raw materials according to claim 7, wherein the products obtained by the reaction in the reactor are subjected to condensation and gas-liquid separation, the low boiling point products are subjected to acid removal and water removal by a solid alkali dryer, and the products are compressed and then enter a multi-step rectifying tower for rectification.
  10. 10. The method for producing HCFC-22 and HCFC-21 by using HFC-23 and CHCl 3 as raw materials according to claim 1, wherein the catalyst comprises a main catalyst and metal auxiliary components, the active components of the main catalyst are one or more than two of corresponding oxides or fluorides of chromium, aluminum and magnesium metals, the metal auxiliary components are any one or two of metals W, mo, V, nb, and the total mass content of the metal auxiliary components is 0.1-10% of the total mass of the catalyst.

Description

Method for producing HCFC-22 and HCFC-21 by taking HFC-23 and CHCl 3 as raw materials Technical Field The application belongs to the technical field of HFC-23 recycling conversion, and in particular relates to a method for producing HCFC-22 and HCFC-21 by taking HFC-23 and CHCl 3 as raw materials. Background At present, high-temperature incineration is an HFC-23 disposal technology, and the method has high operation cost and can cause the waste of fluorine resources. Therefore, the development of a suitable recycling conversion method of HFC-23, which is converted into a useful product, has practical significance. The prior reported HFC-23 resource utilization methods are more. For example, patent US3009966A discloses a method for preparing tetrafluoroethylene and hexafluoropropylene by thermal cracking at 700-1090 ℃, patent US2003/0166981 discloses a method for preparing pentafluoroethane, heptafluoropropane and the like by catalytic cracking with HFC-22 at 690-775 ℃, patent WO96/29296 discloses a method for preparing macromolecular fluoroalkyl by co-cracking with fluoroalkyl and the like. However, these methods are difficult to realize industrial application due to the severe reaction conditions, low product selectivity, short catalyst life and the like. The patents CN112979410A and CN116037165A disclose a method for recycling HFC-23 into HCFC-22 and HCFC-21 by using a fixed bed reactor and using HFC-23 and CHCl 3 as raw materials under the catalysis of a catalyst, and the method has the advantages of mild reaction conditions and simple product composition, but no specific production process is mentioned. CN120229988 describes a technological process for preparing HCFC-22 and HCFC-21 by using HFC-23 and CHCl 3 fluorochloro exchange reaction, after preheating and mixing HFC-23 and CHCl 3, making them be fed into reactor to make intermolecular fluorochloro exchange reaction, and the unreacted raw material and product HCFC-22 and HCFC-21 are passed through the processes of condensation separation, and the HFC-23, HCFC-22 and a small quantity of HCFC-21 are fed into condenser from top of tower to make condensation, and the separated low-boiling HCFC-21 and CHCl 3 are fed into liquid-phase fluorination reactor for producing HCFC-22 so as to continuously make reaction so as to obtain the product HCFC-22. The HFC-23 and HCFC-22 are refined and separated, and the separated HFC-23 is recycled to the reactor for continuous reaction. The single-pass conversion rate of HFC-23 is lower in the above scheme, and is only less than 30%, so that a large amount of HFC-23 needs to be circularly operated, thereby increasing energy consumption, increasing equipment load and reducing process efficiency. In addition, as the HCFC-22 production system is a process system with a larger risk, the process stability of the original system can be influenced after the HCFC-22 production system is coupled with the existing HCFC-22 production process, so that the production risk of the original system is increased. Moreover, CHCl 3, which is heated by a high-temperature reactor and washed with water, is decomposed to some extent, resulting in an increase in acidity and a decrease in purity of the raw material, and the raw material, which is used again as the HCFC-22 reactor, may affect the index control of the HCFC-22 production process. The prior HFC-23 conversion process has few reports, and the problems of high reaction temperature, serious carbon deposition of the catalyst, low HFC-23 conversion rate, poor product selectivity and the like are generally reported. Therefore, the problems of lowering the activation temperature of HFC-23, improving the selectivity of the product and separating reactants from the product are the core problems of HFC-23 resource utilization, are the most critical technologies and are the technical difficulties in the field. Disclosure of Invention Aiming at the defects of the prior art, the application provides a method for producing HCFC-22 and HCFC-21 by taking HFC-23 and CHCl 3 as raw materials, which improves the single pass conversion rate and reduces the reaction carbon deposition rate. In order to solve the technical problems, the application adopts the following technical scheme: A process for preparing HCFC-22 and HCFC-21 from HFC-23 and CHCl 3 includes such steps as preheating, mixing, loading in the first reactor containing catalyst, exchange reaction between fluorine and chlorine, condensing, separating HFC-23 from CHCl 3, rectifying, and loading in the second reactor containing catalyst; The reaction temperature of the fluorine-chlorine exchange reaction in the first reactor and the second reactor is 150-330 ℃, and products obtained by the two reactors are subjected to mixed rectification by utilizing a multi-step rectifying tower to obtain products HCFC-22 and HCFC-21. Preferably, the preheating and mixing temperature of HFC-23 and CHCl 3 is 150-300 ℃, the reaction temperature for performing t