Method for producing HCFC-22 and HCFC-21 by using HFC-23 and CHCl3 as raw materials

Abstract

The invention discloses a method for producing HCFC-22 and HCFC-21 by using HFC-23 and CHCl3 as raw materials, belongs to the technical field of fluorine chemical industry, and aims to improve the conversion per pass and reduce the reaction carbon deposition rate. The method comprises the following steps of: preheating and mixing HFC-23 and CHCl3 which are used as raw materials, feeding into a first reactor containing a catalyst to carry out fluorine-chlorine exchange reaction, condensing, separating and rectifying the unreacted raw materials after the reaction to separate out the HFC-23 and CHCl3, and feeding into a second reactor containing the catalyst to continue the reaction; the reaction temperature of the fluorine-chlorine exchange reaction in the first reactor and the second reactor is 150-330 DEG C, and the products obtained by the two reactors are mixed and rectified by using a multi-step rectifying tower to obtain the products HCFC-22 and HCFC-21.

Description

Technical Field

[0001] This application belongs to the field of resource conversion technology of HFC-23, specifically relating to a method for producing HCFC-22 and HCFC-21 using HFC-23 and CHCl3 as raw materials. Background Technology

[0002] Currently, high-temperature incineration is the primary technology for HFC-23 disposal. However, this method is costly to operate and wastes fluorine resources. Therefore, developing suitable resource-based conversion methods for HFC-23 to transform it into useful products is of practical significance.

[0003] Currently, there are numerous reported methods for the resource utilization of HFC-23. For example, patent US3009966A discloses a method for preparing tetrafluoroethylene and hexafluoropropylene through thermal cracking at 700-1090℃; patent US2003 / 0166981 discloses a method for preparing pentafluoroethane and heptafluoropropane through catalytic cracking with HFC-22 at 690-775℃; and patent WO96 / 29296 discloses a method for preparing macromolecular fluoroalkanes through co-cracking with fluoroalkanes. However, these methods are difficult to industrialize due to harsh reaction conditions, low product selectivity, and short catalyst lifetime. In contrast, patents CN112979410A and CN116037165A disclose a method using a fixed-bed reactor and a catalyst to convert HFC-23 into HCFC-22 and HCFC-21 products from HFC-23 using CHCl3 as raw materials. The reaction conditions are mild, and the product composition is simple, but the specific production process is not mentioned.

[0004] CN120229988 describes a process for preparing HCFC-22 and HCFC-21 through the fluorine-chlorine exchange reaction of HFC-23 and CHCl3. HFC-23 and CHCl3 are preheated and mixed before entering a reactor for intermolecular fluorine-chlorine exchange. Unreacted raw materials and products HCFC-22 and HCFC-21 are separated by condensation. HFC-23, HCFC-22, and a small amount of HCFC-21 are condensed from the top of the column. The separated low-boiling-point HCFC-21 and CHCl3 are sent to a liquid-phase fluorination reactor for HCFC-22 production to continue the reaction, yielding HCFC-22. HFC-23 and HCFC-22 are then purified and separated, with the separated HFC-23 recycled back to the reactor for further reaction. However, this method results in a low single-pass conversion rate of HFC-23, less than 30%, requiring a large amount of HFC-23 to be recycled, leading to increased energy consumption, heavier equipment load, and decreased process efficiency. Furthermore, since the HCFC-22 production system is a high-risk process, coupling it with the existing HCFC-22 production process will affect the process stability of the original system and increase its production risk. Moreover, CHCl3 undergoes a certain degree of decomposition after being heated in the high-temperature reactor and subjected to alkaline washing, leading to increased acidity and decreased purity of the raw material. Using this raw material again in the HCFC-22 reactor may affect the control of parameters in the HCFC-22 production process.

[0005] Currently, there are few reports on HFC-23 conversion processes, and those that are reported generally suffer from problems such as high reaction temperatures, severe catalyst carbon buildup, low HFC-23 conversion rates, and poor product selectivity. Therefore, reducing the HFC-23 activation temperature, improving product selectivity, and solving the separation problem between reactants and products are the core issues, the most critical technologies, and the technical challenges in this field for the resource utilization of HFC-23. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this application provides a method for producing HCFC-22 and HCFC-21 using HFC-23 and CHCl3 as raw materials, thereby improving the single-pass conversion rate and reducing the rate of carbon deposition in the reaction.

[0007] To solve the above-mentioned technical problems, this application adopts the following technical solution: A method for producing HCFC-22 and HCFC-21 using HFC-23 and CHCl3 as raw materials involves using HFC-23 and CHCl3 as raw materials, which are preheated and mixed before being fed into a first reactor containing a catalyst for a fluorine-chlorine exchange reaction. The raw materials that have not yet reacted after the reaction are then separated by condensation and distillation to separate the raw materials HFC-23 and CHCl3, and then fed into a second reactor containing a catalyst to continue the reaction. The reaction temperature for the fluorine-chlorine exchange reaction in the first and second reactors is 150–330°C. The products obtained from the two reactors are mixed and distilled using a multi-step distillation column to obtain products HCFC-22 and HCFC-21.

[0008] Preferably, the preheating temperature of HFC-23 and CHCl3 is 150-300°C, the reaction temperature of the fluoride-chlorine exchange reaction in the first reactor is 250-330°C, and the reaction temperature of the fluoride-chlorine exchange reaction in the second reactor is 150-250°C.

[0009] Preferably, the residence time of the raw materials in the first reactor is 0.5 to 5 s; and / or, the residence time of the raw materials in the second reactor is 5 to 140 s; and / or, the reaction pressure of the fluoride-chlorine exchange reaction in the first reactor and the second reactor is 0 to 0.7 MPa.

[0010] Preferably, the molar ratio of HFC-23 to CHCl3 in the raw material is 1:(1-3); and / or, the acid value of the raw material CHCl3 is controlled within the range of 0-50ppm.

[0011] Preferably, the multi-step distillation column includes distillation column 1 and distillation column 2. The product after the reactor reaction is separated in distillation column 1. HFC-23 is separated at the top of the column with a purity of over 98%. HCFC-22 and HCFC-21 at the bottom of the column are sent to distillation column 2 for further separation. HCFC-22 and HCFC-21 products at the top and bottom of the column are recovered in distillation column 2, respectively.

[0012] Preferably, the temperature at the top of distillation column 1 is -40 to -10°C, the temperature at the bottom of distillation column 1 is 0 to 20°C, and the pressure of distillation column 1 is 0.8 to 2.2 MPa; and / or, the temperature at the top of distillation column 2 is 30 to 50°C, the temperature at the bottom of distillation column 2 is -30 to -5°C, and the pressure of distillation column 2 is 0.5 to 1.5 MPa.

[0013] Preferably, after passing through the first reactor, the unreacted raw materials HFC-23 and CHCl3 and the products HCFC-22, HCFC-21 and HCl are condensed and separated into gas and liquid components, with the condensed CHCl3 entering the CHCl3 intermediate buffer tank; after passing through the second reactor, the unreacted raw materials HFC-23 and CHCl3 and the products HCFC-22, HCFC-21 and HCl are condensed and separated into gas and liquid components, with the condensed CHCl3 entering the chloroform raw material tank for collection.

[0014] Preferably, after the reactor reaction, the unreacted CHCl3 is separated by a multi-stage cyclone separator, and the purity of the separated CHCl3 should be controlled above 99.5%.

[0015] Preferably, after the product from the reactor reaction is condensed and separated into gas and liquid, the low-boiling-point product is deacidified and dehydrated using a solid alkali dryer, and then compressed before entering a multi-step distillation column for distillation.

[0016] Preferably, the catalyst comprises a main catalyst and a metal promoter component. The active component of the main catalyst is one or more of the corresponding oxides or fluorides of chromium, aluminum, and magnesium metals. The metal promoter component is selected from any one or two of the metals W, Mo, V, and Nb, and the total mass content of the metal promoter is 0.1% to 10% of the total catalyst.

[0017] This application uses HFC-23 and CHCl3 in the presence of a catalyst to carry out a series reaction in a series reactor to continuously prepare products HCFC-22 and HCFC-21. This not only converts most of HFC-23 into products HCFC-22 and HCFC-21, but also achieves effective separation of the products through simple separation and purification techniques. The reaction has a high single-pass conversion rate, high product selectivity, and a simple process.

[0018] Compared with the prior art, this application has the following beneficial effects: 1. Using HFC-23 and CHCl3 as raw materials to produce high-value-added HCFC-22 and HCFC-21 products promotes the resource utilization of the by-product trifluoromethane, generating significant economic and social benefits.

[0019] 2. This application utilizes a conversion process that combines a series reactor (a first reactor and a second reactor connected in series) with separation and purification (the product after the reaction in the first reactor is separated and purified so that the unreacted raw material can enter the second reactor to continue the reaction), which significantly improves the single-pass conversion rate of HFC-23, reduces raw material recycling, reduces equipment load, and improves process efficiency.

[0020] 3. The series reactor process technology used in this application can greatly reduce the reaction temperature of a single reactor. The reaction temperature of the second reactor is only 150-250℃, which is significantly lower than the 300-400℃ of the existing single-stage reactor technology. This reduces the requirements for equipment, significantly reduces the rate of carbon deposition, and greatly improves the service life of the catalyst.

[0021] 4. This application reduces side reactions and improves the selectivity of the target products HCFC-22 and HCFC-21 by using reasonable and effective acid removal and trace CHCl3 removal processes. Simultaneously, by controlling the acidity of the raw materials, carbon buildup in the reaction is significantly reduced, and the catalyst lifespan is extended. Compared to existing technologies that use oxidizing gases such as oxygen to extend catalyst lifespan, this reduces the difficulty of post-processing and improves the safety of the equipment.

[0022] 5. Since the reaction between HFC-23 and CHCl3 is an equilibrium reaction, excessive HCFC-22 in HFC-23 will hinder the conversion of HFC-23. To ensure efficient HFC-23 conversion, the purity of HFC-23 separated from distillation column 1 should be controlled above 98%, which will benefit the continued reaction in the second reactor and improve the HFC-23 conversion rate. Furthermore, the purity of the unreacted CHCl3 after separation using a multi-stage cyclone separator should be controlled above 99.5%, which will also benefit the reaction in the second reactor and improve the HFC-23 conversion rate.

[0023] The specific technical solution and its beneficial effects of this application will be described in detail below with reference to the accompanying drawings. Attached Figure Description

[0024] The present application will be further described below with reference to the accompanying drawings and specific embodiments: Figure 1 This is a flowchart of the production method of this application. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0026] like Figure 1 As shown, this application provides a method for producing HCFC-22 and HCFC-21 using HFC-23 and CHCl3 as raw materials, including the following steps: HFC-23 and CHCl3 are stored in the HFC-23 raw material tank and the CHCl3 storage tank, respectively. Using HFC-23 and CHCl3 as raw materials, the raw materials are preheated and mixed in a mixing preheater and then sent to the first reactor containing the catalyst for fluorine-chlorine exchange reaction. After condensation and distillation, the raw materials HFC-23 and CHCl3 are separated and sent to the second reactor containing the catalyst for further reaction. The products obtained from the two reactors are mixed and distilled in a multi-step distillation column to obtain products HCFC-22 and HCFC-21, which are sent to the HCFC-22 storage tank and the HCFC-21 storage tank, respectively.

[0027] The specific reaction equation is shown below: CHF3 + CHCl3 → CHClF2 + CHCl2F This application uses HFC-23 and CHCl3 in the presence of a catalyst to convert most of HFC-23 into products HCFC-22 and HCFC-21 through a series reactor. The products are effectively separated by a simple separation and purification technique. The reaction has a high single-pass conversion rate, high product selectivity, and a simple process.

[0028] The specific process is as follows: Step 1: After preheating and mixing, raw materials HFC-23 and CHCl3 are fed into the first reactor containing the fluorine-chlorine exchange reaction catalyst to react and obtain products HCFC-22 and HCFC-21. The conversion rate of HFC-23 in the first reactor is more than 35%, and the total selectivity of the main products HCFC-22 and HCFC-21 is ≥99.9%.

[0029] After passing through the reactor, the unreacted raw materials HFC-23 and CHCl3 and the products HCFC-22, HCFC-21, and HCl are condensed and separated into gas and liquid components. Most of the condensed CHCl3 is sent to the CHCl3 intermediate buffer tank. The low-boiling-point HFC-23, HCFC-22, HCFC-21, and HCl are dried with solid alkali, cooled, and compressed by a compressor before entering distillation column 1 for separation. HFC-23 is separated at the top of the column with a purity of over 98%. HCFC-22 and HCFC-21 at the bottom of the column are sent to distillation column 2 for further separation. In distillation column 2, the top and bottom products HCFC-22 and HCFC-21 are recovered, respectively.

[0030] Step 2: The CHCl3 in the intermediate buffer tank is separated into HFC-23 by a pump and distillation column 1. After being preheated and mixed, it enters the second reactor containing the fluorine-chlorine exchange reaction catalyst to continue the reaction, producing products HCFC-22 and HCFC-21. The conversion rate of HFC-23 in the second reactor is over 45%, and the total selectivity of the main products HCFC-22 and HCFC-21 is ≥99.9%.

[0031] After passing through the reactor, the unreacted raw materials HFC-23 and CHCl3 and the products HCFC-22, HCFC-21 and HCl are condensed and separated into gas and liquid components. Most of the condensed CHCl3 is collected in the chloroform feed tank. The low-boiling-point HFC-23, HCFC-22, HCFC-21 and HCl are dried, cooled and compressed again before entering distillation column 1 and distillation column 2 for recycling and separation, and the products HCFC-22 and HCFC-21 are recovered.

[0032] This application utilizes HFC-23 and CHCl3 as raw materials to produce high-value-added HCFC-22 and HCFC-21 products, promoting the resource utilization of the byproduct trifluoromethane and generating significant economic and social benefits. This application employs a conversion process combining a series reactor and separation and purification, significantly improving the single-pass conversion rate of HFC-23, reducing raw material recycling, alleviating equipment load, and enhancing process efficiency.

[0033] Since the reaction between HFC-23 and CHCl3 is an equilibrium reaction, excessive HCFC-22 in HFC-23 will hinder the conversion of HFC-23. To ensure efficient conversion of HFC-23, the purity of HFC-23 separated from distillation column 1 should be controlled above 98%, preferably above 99%.

[0034] Because CHCl3 has poor stability and decomposes into HCl at high temperatures, it must first be removed by alkaline washing to prevent equipment corrosion. Although most of the CHCl3 can be separated through cooling and gas-liquid separation, trace amounts of CHCl3 will still remain in the high-boiling-point substances. Due to dissolved air and other factors during conventional alkaline washing, the high air content during the crude product's alkaline washing process can cause CHCl3 to decompose into COCl2 and CO2. These impurities, when entering the next reactor, will promote the reaction and generate byproducts such as CO and CFC-12, leading to reduced reaction selectivity, thus affecting product quality and increasing separation costs. Therefore, this step uses a solid alkali dryer to remove water and HCl. The packing material in the solid alkali dryer is one or more of potassium hydroxide, sodium hydroxide, and calcium oxide, preferably sodium hydroxide flakes. This step can effectively control the air content.

[0035] When the acid value of the raw material CHCl3 is high, free radicals Cl and free H... +Accelerating catalyst carbon buildup leads to a decrease in catalyst lifespan. Therefore, the acid value of the feedstock CHCl3 needs to be controlled within the range of 50 ppm, and more preferably within the range of 0–20 ppm, such as 1 ppm, 5 ppm, 10 ppm, 15 ppm, and 20 ppm. By simultaneously controlling the feedstock acidity index and employing reasonable and effective acid removal and separation processes, the occurrence of side reactions is effectively reduced, and the selectivity of the target products HCFC-22 and HCFC-21 is improved, enabling the HFC-23 conversion catalyst of this application to maintain good activity, selectivity, and stability.

[0036] The catalyst for the fluoride-chloride exchange reaction comprises a main catalyst and a metal promoter component. The active component of the main catalyst is one or more of the corresponding oxides or fluorides of chromium, aluminum, and magnesium metals commonly used in fluoride-chloride exchange reactions. The catalyst promoter is selected from one or more metal oxides or chlorides of W, Mo, Nb, or V. The total mass content of the catalyst promoter is 0.1% to 10% of the total catalyst mass. The metal promoter component can be added using conventional methods for catalyst preparation, such as physical grinding with the main catalyst, or by co-precipitation, wet mixing with a metal salt solution precursor, or impregnation followed by calcination.

[0037] In some embodiments, the catalyst has a composition of M / Cr x O3-Al y O3, where x+y=2. Among them, Cr x O3-Al y O3 is the main catalyst, obtained by ball milling and calcining Cr2O3 and Al2O3. M represents the metal auxiliary component. The inventors discovered that in the fluoride-chloride exchange reaction of HFC-23 and CHCl3, the L acidic sites of the catalyst are the active centers of the reaction, and the number of L acidic sites is crucial to the catalyst activity. The inventors also found that the products of the fluoride-chloride exchange reaction readily undergo disproportionation reactions on the catalyst surface, leading to carbon deposition. Therefore, the larger the catalyst surface area and the more active sites, the higher the activity, the stronger the ability to accommodate carbon deposits, and the better the stability. Al2O3 catalysts have high reactivity but poor stability, and Al2O3 is difficult to exist stably in the reaction, gradually being fluorinated to AlF3, causing a significant decrease in specific surface area, thus resulting in poor catalyst stability. Cr2O3, on the other hand, has a stable structure in the fluoride-chloride exchange reaction, and even in the presence of pure HF, it is difficult to form CrF3. However, it has fewer surface acidic sites and exhibits almost no reactivity in the HFC-23 and CHCl3 fluoride-chloride exchange reaction. Therefore, this application synthesizes Cr-doped Al2O3 material by ball milling, fully utilizing the structural characteristics of Cr2O3 and Al2O3. Through the synergistic effect of Cr2O3 and Al2O3, the structural transformation of Al2O3 is effectively suppressed. Furthermore, this application further modulates the surface acidity distribution and the number of surface acid sites of the catalyst by impregnating this material with loading additives, resulting in a catalyst with high catalytic activity and stability.

[0038] The preparation method of the main catalyst includes: adding Al2O3 nanoparticles and Cr2O3 nanoparticles to deionized water, stirring slowly until homogeneous, then transferring to a ball mill and ball milling for a period of time. The ball-milled slurry is then dried, and the dried solid is calcined in a muffle furnace. After cooling, Cr2O3 is obtained. x O3-Al y O3 solid.

[0039] The mass ratio of Al2O3 nanoparticles to Cr2O3 nanoparticles is 1:(0.01~1), preferably 1:(0.1~0.5), for example 1:0.1, 1:0.5, 1:0.3. Under this mass ratio, the prepared Cr-doped Al2O3 catalyst has a suitable specific surface area and structure, can effectively suppress the structural transformation of Al2O3 in the reaction, and has good stability.

[0040] The mass ratio of the deionized water to the total mass of Al2O3 nanoparticles and Cr2O3 nanoparticles is 1:(0.5~1), preferably 1:(0.5~0.8), for example 1:0.5, 1:0.6, 1:0.7, 1:0.8. Under this mass ratio, the two nanoparticles can be better combined, and the resulting catalyst is more uniform.

[0041] The Cr2O3 and Al2O3 nanoparticles are spherical particles with a particle size of 20-200 nm, such as 20 nm, 50 nm, 100 nm, 150 nm, and 200 nm. The average particle size of the Cr2O3 nanoparticles is preferably 50-100 nm, such as 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, and 100 nm. The average particle size of the Al2O3 nanoparticles is preferably 20-50 nm, such as 20 nm, 30 nm, 40 nm, and 50 nm.

[0042] The ball milling mixture is carried out using a ball mill with a rotation speed of 100–500 r / min and a milling time of 2–10 h. Preferably, the ball mill rotation speed is 300–400 r / min and the milling time is 4–6 h; the ball mill rotation speed is 300 r / min and the milling time is 6 h; the ball mill rotation speed is 400 r / min and the milling time is 4 h; and the ball mill rotation speed is 350 r / min and the milling time is 5 h.

[0043] The drying temperature of the slurry is 100-180℃, preferably 120-140℃, for example 120℃, 130℃, or 140℃, and the drying is carried out in an oven.

[0044] The calcination is carried out in an air atmosphere at a temperature of 400–700°C, preferably 500–600°C, for a duration of 5–15 hours. For example, a calcination temperature of 500°C for 15 hours, a calcination temperature of 5600°C for 5 hours, or a calcination temperature of 550°C for 10 hours are all examples of calcination.

[0045] The inventors discovered through research that the mechanical ball milling method provided in this application, used to prepare the composite catalyst, utilizes the mechanical force generated during the high-speed operation of the machine to cause Cr2O3 and Al2O3 particles to break and refine under high-energy collisions. This leads to lattice distortion in alumina, allowing some Cr atoms to enter the Al2O3 lattice and replace Al atoms, ultimately resulting in a structurally stable Cr2O3 lattice. x O3-Al y O3. Research has found that only under specific ratios of Cr and Al, specific water content, and specific energy levels can Al2O3 undergo lattice distortion, allowing Cr atoms to replace Al atoms and thus yield structurally stable Cr. x O3-Al y O3.

[0046] In some embodiments, the preheating mixing temperature of HFC-23 and CHCl3 is 150–300°C, for example, 150°C, 200°C, 250°C, or 300°C. The reaction temperature of the fluorine-chlorine exchange reaction is 150–330°C, wherein the reactor reaction temperature in step 1 is 250–330°C, and the reactor reaction temperature in step 2 is 150–250°C. More preferably, the reactor reaction temperature in step 1 is 280–300°C, for example, 280°C, 290°C, or 300°C, and the reactor reaction temperature in step 2 is 180–220°C, for example, 180°C, 200°C, or 220°C. Compared with the reaction temperature of 250–400°C in the prior art for fluorine-chlorine exchange reactions, the reaction temperature is significantly reduced, the requirements for equipment are lowered, the rate of carbon deposition is significantly reduced, and the service life of the catalyst is greatly improved.

[0047] In some embodiments, the reaction pressure of the fluorine-chlorine exchange reaction is 0–0.7 MPa. More preferably, the reaction pressure is 0.1–0.3 MPa, for example, 0.1 MPa, 0.2 MPa, or 0.3 MPa.

[0048] In some embodiments, the residence time of the fluorine-chlorine exchange reaction is 0.5–140 s. Specifically, the residence time of the raw materials in the reactor during step 1 is 0.5–5 s, and the residence time of the raw materials in the reactor during step 2 is 5–140 s. More preferably, the residence time of the raw materials in the reactor during step 1 is 1–4 s, for example, 1 s, 2 s, 3 s, or 4 s; and the residence time of the raw materials in the reactor during step 2 is 24–100 s, for example, 24 s, 35 s, 50 s, 70 s, or 100 s.

[0049] In some embodiments, the molar ratio of HFC-23 to CHCl3 is 1:(1 to 3). More preferably, the molar ratio of HFC-23 to CHCl3 is 1:(1.5 to 2.5), for example, 1:1.5, 1:2, or 1:2.5.

[0050] In some embodiments, the condensation employs multi-stage condensation, more preferably two-stage condensation, with the temperature of the first stage condensation being 30~55℃, for example 30℃, 45℃, 55℃; and the temperature of the second stage condensation being 25~50℃, for example 25℃, 35℃, 50℃.

[0051] In some embodiments, the gas-liquid separation is performed using a multi-stage cyclone separator, more preferably a two-stage cyclone separator. The purity of the collected unreacted raw material CHCl3 should be controlled to be above 99.5%.

[0052] In some embodiments, the temperature at the top of the distillation column 1 is -40 to -10°C, more preferably -35 to -25°C, for example -35°C, -30°C, or -25°C. The temperature at the bottom of the distillation column 1 is 0 to 20°C, more preferably 5°C to 15°C, for example 5°C, 10°C, or 15°C. The pressure of the distillation column 1 is 0.8 to 2.2 MPa, more preferably 1.2 to 2 MPa, for example 1.2 MPa, 1.6 MPa, or 2 MPa. The purity of HFC-23 separated by the distillation column 1 should be controlled above 98%.

[0053] To ensure that distillation column 2 separates HCFC-22 and HCFC-21 products with a purity of 99.9% or higher, the top temperature, bottom temperature, and pressure of the distillation column must meet the following conditions: The top temperature of distillation column 2 is 30–50°C, more preferably 35°C–45°C, for example, 35°C, 40°C, or 45°C. The bottom temperature of distillation column 2 is -30–-5°C, more preferably -20–-10°C, for example, -20°C, -15°C, or -10°C. The pressure of distillation column 2 is 0.5–1.5 MPa, more preferably 0.8–1.2 MPa, for example, 0.8 MPa, 1 MPa, or 1.2 MPa.

[0054] Example 1: (1) Raw materials CHCl3 and HFC-23 were sent to a preheater for preheating at a temperature of 260°C, and then entered the first reactor for reaction at a concentration of 5% W / Cr. x O3-Al y The fluorine-chlorine exchange reaction, catalyzed by O3, yields HCFC-22 and HCFC-21. The reaction temperature is 300℃, the pressure is 0.2MPa, the residence time is 4s, and the ratio of HFC-23 to CHCl3 is 1:2. After passing through the reactor, the unreacted raw materials HFC-23 and CHCl3, and the products HCFC-22, HCFC-21, and HCl, are separated by a two-stage condenser and a two-stage cyclone separator. Most of the condensed CHCl3 is sent to a CHCl3 intermediate buffer tank. The low-boiling-point HFC-23, HCFC-22, HCFC-21, and HCl are dried in a solid alkali dryer to remove HCl. After cooling, they are compressed by a compressor and sent to distillation column 1 for separation. The top of the column separates low-boiling-point HFC-23 with a purity of over 98%, which is then sent to the next reactor for further reaction. The bottom products HCFC-22 and HCFC-21 of the distillation column are sent to distillation column 2 for further separation. In distillation column 2, the top and bottom products HCFC-22 and HCFC-21 are recovered and sent to the product tank for storage.

[0055] (2) The CHCl3 in the intermediate buffer tank and the HFC-23 separated from distillation column 1 are sent together to the preheater for preheating at a temperature of 160°C, and then enter the second reactor for reaction at 5% W / Cr x O3-Al y The fluorine-chlorine exchange reaction, catalyzed by O3, yields products HCFC-22 and HCFC-21. The reaction temperature is 180℃, the pressure is 0.2MPa, the residence time is 80s, and the ratio of HFC-23 to CHCl3 is 1:2. After passing through the reactor, the unreacted raw materials HFC-23 and CHCl3, and the products HCFC-22, HCFC-21, and HCl, are condensed in a two-stage condenser and separated by a two-stage cyclone separator. Most of the condensed CHCl3 is returned to the CHCl3 feed tank. The low-boiling-point HFC-23, HCFC-22, HCFC-21, and HCl are dried in a solid alkali dryer to remove HCl, cooled, and then compressed by a compressor before being fed into distillation columns 1 and 2 for mixed circulation and separation.

[0056] Step (1) The HFC-23 conversion rate was 35.5%, and the total selectivity of HCFC-22 and HCFC-21 was 99.9%.

[0057] Step (2): HFC-23 conversion rate was 54.3%, and the total selectivity for HCFC-22 and HCFC-21 was 99.9%. Total HFC-23 conversion rate was 70.8%, and the total selectivity for HCFC-22 and HCFC-21 was 99.9%.

[0058] The HFC-23 conversion catalyst remained stable after a single-pass reaction of 3870 h, with an average total HFC-23 conversion rate of 67.5% and a total selectivity of 99.8% for HCFC-22 and HCFC-21.

[0059] Example 2: (1) Raw materials CHCl3 and HFC-23 were sent together to a preheater for preheating at a temperature of 260°C, and then entered the first reactor for reaction at a concentration of 5% W / Cr. x O3-Al yThe fluorine-chlorine exchange reaction, catalyzed by O3, yields HCFC-22 and HCFC-21. The reaction temperature is 280℃, the pressure is 0.2 MPa, the residence time is 4 s, and the ratio of HFC-23 to CHCl3 is 1:2. After passing through the reactor, the unreacted raw materials HFC-23 and CHCl3, and the products HCFC-22, HCFC-21, and HCl, are separated by a two-stage condenser and a two-stage cyclone separator. Most of the condensed CHCl3 is sent to a CHCl3 intermediate buffer tank. The low-boiling-point HFC-23, HCFC-22, HCFC-21, and HCl are dried in a solid alkali dryer to remove HCl, cooled, and then compressed before entering distillation column 1 for separation. The top of the column separates low-boiling-point HFC-23 with a purity exceeding 98%, which is then sent to the next reactor for further reaction. The bottom products HCFC-22 and HCFC-21 of the distillation column are sent to distillation column 2 for further separation. In distillation column 2, the top and bottom products HCFC-22 and HCFC-21 are recovered and sent to the product tank for storage.

[0060] (2) The CHCl3 in the intermediate buffer tank and the HFC-23 separated from distillation column 1 are sent together to the preheater for preheating at a temperature of 160°C, and then enter the second reactor for reaction at 5% W / Cr x O3-Al y The fluorine-chlorine exchange reaction, catalyzed by O3, yields HCFC-22 and HCFC-21. The reaction temperature is 200℃, the pressure is 0.2MPa, the residence time is 80s, and the ratio of HFC-23 to CHCl3 is 1:2. After passing through the reactor, the unreacted raw materials HFC-23 and CHCl3, and the products HCFC-22, HCFC-21, and HCl, are condensed in a two-stage condenser and separated by a two-stage cyclone separator. Most of the condensed CHCl3 is returned to the CHCl3 feed tank. The low-boiling-point HFC-23, HCFC-22, HCFC-21, and HCl are dried in a solid alkali dryer to remove HCl, cooled, and then compressed before being fed into distillation columns 1 and 2 for mixed circulation and separation.

[0061] Step (1) The HFC-23 conversion rate was 30.3%, and the total selectivity of HCFC-22 and HCFC-21 was 99.9%.

[0062] Step (2) The HFC-23 conversion rate was 58.5%, the total selectivity of HCFC-22 and HCFC-21 was 99.9%, the total HFC-23 conversion rate was 71.1%, and the total selectivity of HCFC-22 and HCFC-21 was 99.9%.

[0063] Example 3: (1) Raw materials CHCl3 and HFC-23 were sent together to a preheater for preheating at a temperature of 260°C, and then entered the first reactor for reaction at a concentration of 5% W / Cr.x O3-Al y The fluorine-chlorine exchange reaction, catalyzed by O3, yields HCFC-22 and HCFC-21. The reaction temperature is 280℃, the pressure is 0.2 MPa, the residence time is 5 s, and the ratio of HFC-23 to CHCl3 is 1:2. After passing through the reactor, the unreacted raw materials HFC-23 and CHCl3, and the products HCFC-22, HCFC-21, and HCl, are separated by a two-stage condenser and a two-stage cyclone separator. Most of the condensed CHCl3 is sent to a CHCl3 intermediate buffer tank. The low-boiling-point HFC-23, HCFC-22, HCFC-21, and HCl are dried in a solid alkali dryer to remove HCl, cooled, and then compressed before entering distillation column 1 for separation. The top of the column separates low-boiling-point HFC-23 with a purity of over 98%, which is then sent to the next reactor for further reaction. The bottom products HCFC-22 and HCFC-21 of the distillation column are sent to distillation column 2 for further separation. In distillation column 2, the top and bottom products HCFC-22 and HCFC-21 are recovered and sent to the product tank for storage.

[0064] (2) The CHCl3 in the intermediate buffer tank and the HFC-23 separated from distillation column 1 are sent together to the preheater for preheating at a temperature of 160°C, and then enter the second reactor for reaction at 5% W / Cr x O3-Al y The fluorine-chlorine exchange reaction, catalyzed by O3, yields products HCFC-22 and HCFC-21. The reaction temperature is 200℃, the pressure is 0.2MPa, the residence time is 70s, and the ratio of HFC-23 to CHCl3 is 1:2. After passing through the reactor, the unreacted raw materials HFC-23 and CHCl3, and the products HCFC-22, HCFC-21, and HCl, are condensed in a two-stage condenser and separated by a two-stage cyclone separator. Most of the condensed CHCl3 is returned to the CHCl3 feed tank. The low-boiling-point HFC-23, HCFC-22, HCFC-21, and HCl are dried in a solid alkali dryer to remove HCl, cooled, and then compressed by a compressor before being mixed and circulated into distillation columns 1 and 2 for further separation.

[0065] Step (1) The HFC-23 conversion rate was 38.2%, and the total selectivity of HCFC-22 and HCFC-21 was 99.9%.

[0066] Step (2) The HFC-23 conversion rate was 53.4%, the total selectivity of HCFC-22 and HCFC-21 was 99.9%, the total HFC-23 conversion rate was 71.2%, and the total selectivity of HCFC-22 and HCFC-21 was 99.9%.

[0067] Example 4: (1) Raw materials CHCl3 and HFC-23 were sent together to a preheater for preheating at a temperature of 260°C, and then entered the first reactor for reaction at a concentration of 5% W / Cr. x O3-Al y The fluorine-chlorine exchange reaction, catalyzed by O3, yields HCFC-22 and HCFC-21. The reaction temperature is 300℃, the pressure is 0.2MPa, the residence time is 5s, and the ratio of HFC-23 to CHCl3 is 1:1.8. After passing through the reactor, the unreacted raw materials HFC-23 and CHCl3, and the products HCFC-22, HCFC-21, and HCl, are separated by a two-stage condenser and a two-stage cyclone separator. Most of the condensed CHCl3 is sent to a CHCl3 intermediate buffer tank. The low-boiling-point HFC-23, HCFC-22, HCFC-21, and HCl are dried in a solid alkali dryer to remove HCl, cooled, and then compressed before entering distillation column 1 for separation. The top of the column separates low-boiling-point HFC-23 with a purity of over 98%, which is then sent to the next reactor for further reaction. The bottom products HCFC-22 and HCFC-21 of the distillation column are sent to distillation column 2 for further separation. In distillation column 2, the top and bottom products HCFC-22 and HCFC-21 are recovered and sent to the product tank for storage.

[0068] (2) The CHCl3 in the intermediate buffer tank and the HFC-23 separated from distillation column 1 are sent together to the preheater for preheating at a temperature of 160°C, and then enter the second reactor for reaction at 5% W / Cr x O3-Al y The fluorine-chlorine exchange reaction, catalyzed by O3, yields products HCFC-22 and HCFC-21. The reaction temperature is 200℃, the pressure is 0.2MPa, the residence time is 70s, and the ratio of HFC-23 to CHCl3 is 1:1.8. After passing through the reactor, the unreacted raw materials HFC-23 and CHCl3, and the products HCFC-22, HCFC-21, and HCl, are condensed in a two-stage condenser and separated by a two-stage cyclone separator. Most of the condensed CHCl3 is returned to the CHCl3 feed tank. The low-boiling-point HFC-23, HCFC-22, HCFC-21, and HCl are dried in a solid alkali dryer to remove HCl, cooled, and then compressed by a compressor before being fed into distillation columns 1 and 2 for mixed circulation and separation.

[0069] Step (1) The HFC-23 conversion rate was 36.2%, and the total selectivity of HCFC-22 and HCFC-21 was 99.9%.

[0070] Step (2) The HFC-23 conversion rate was 51.4%, the total selectivity of HCFC-22 and HCFC-21 was 99.9%, the total HFC-23 conversion rate was 69%, and the total selectivity of HCFC-22 and HCFC-21 was 99.9%.

[0071] Comparative Example 1: The operation of this example is the same as that of Example 1, the main difference being that the low-boiling HFC-23 separated at the top of distillation column 1 has a purity of 96%.

[0072] Step (1): HFC-23 conversion rate 35.5%, total selectivity of HCFC-22 and HCFC-21 99.5%. Step (2): HFC-23 conversion rate 39.4%, total selectivity of HCFC-22 and HCFC-21 99.5%, total HFC-23 conversion rate 60.9%, total selectivity of HCFC-22 and HCFC-21 99.5%.

[0073] Comparative Example 1 illustrates that when the purity of the low-boiling HFC-23 separated from the top of distillation column 1 decreases, the conversion rate of HFC-23 and the selectivity of the target products HCFC-22 and HCFC-21 also decrease. Therefore, in order to ensure a sufficiently high conversion rate and selectivity, the purity of HFC-23 separated from distillation column 1 should be controlled above 98%.

[0074] Comparative Example 2: The operation of this example is the same as that of Example 1. The main difference is that after the product from the reactor passes through a two-stage condenser and a two-stage cyclone separator, the low-boiling-point HFC-23, HCFC-22, HCFC-21 and HCl are removed by conventional water washing and alkaline washing steps.

[0075] Step (1) The HFC-23 conversion rate was 34.8%, and the total selectivity of HCFC-22 and HCFC-21 was 96.6%.

[0076] Step (2) The HFC-23 conversion rate was 53.4%, the total selectivity of HCFC-22 and HCFC-21 was 96.9%, the total HFC-23 conversion rate was 69.6%, and the total selectivity of HCFC-22 and HCFC-21 was 96.8%.

[0077] Comparative Example 2 demonstrates that removing the HCl generated during the reaction using conventional water and alkali washing steps results in lower selectivity for the target products HCFC-22 and HCFC-21. In contrast, removing HCl using the solid alkali dryer method described in Example 1 improves product selectivity.

[0078] Comparative Example 3: The operation of this example is the same as that of Example 1, the main difference being that the acid value of the raw material CHCl3 used in the HFC-23 conversion reaction is 200ppm.

[0079] Step (1): HFC-23 conversion rate 34.4%, total selectivity of HCFC-22 and HCFC-21 99.2%. Step (2): HFC-23 conversion rate 54.2%, total selectivity of HCFC-22 and HCFC-21 99.3%, total HFC-23 conversion rate 70%, total selectivity of HCFC-22 and HCFC-21 99.3%.

[0080] The HFC-23 conversion catalyst was deactivated after 890 hours of single-pass reaction, with an average total HFC-23 conversion rate of 30.4% and a total selectivity of 99.3% for HCFC-22 and HCFC-21.

[0081] Comparative Example 3 demonstrates that when the acid value of the feedstock CHCl3 is high in the HFC-23 conversion reaction, the selectivity of the target products HCFC-22 and HCFC-21 is reduced, and the catalyst lifespan is also significantly shortened.

[0082] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Those skilled in the art should understand that this application includes, but is not limited to, the content described in the above specific embodiments. Any modifications that do not depart from the functional and structural principles of this application will be included within the scope of the claims.

Claims

1. A method for producing HCFC-22 and HCFC-21 using HFC-23 and CHCl3 as raw materials, characterized in that, Using HFC-23 and CHCl3 as raw materials, after preheating and mixing, the mixture is fed into a first reactor containing a catalyst for fluorine-chlorine exchange reaction. The raw materials that have not yet reacted are then separated by condensation and distillation to separate the raw materials HFC-23 and CHCl3, and then fed into a second reactor containing a catalyst to continue the reaction. The reaction temperature for the fluorine-chlorine exchange reaction in the first and second reactors is 150–330°C. The products obtained from the two reactors are mixed and distilled using a multi-step distillation column to obtain products HCFC-22 and HCFC-21.

2. The method for producing HCFC-22 and HCFC-21 using HFC-23 and CHCl3 as raw materials according to claim 1, characterized in that, The preheating temperature of HFC-23 and CHCl3 is 150-300℃, the reaction temperature of the fluoride-chlorine exchange reaction in the first reactor is 250-330℃, and the reaction temperature of the fluoride-chlorine exchange reaction in the second reactor is 150-250℃.

3. The method for producing HCFC-22 and HCFC-21 using HFC-23 and CHCl3 as raw materials according to claim 1, characterized in that, The residence time of the raw materials in the first reactor is 0.5 to 5 s; and / or, the residence time of the raw materials in the second reactor is 5 to 140 s; and / or, the reaction pressure of the fluoride-chlorine exchange reaction in the first reactor and the second reactor is 0 to 0.7 MPa.

4. The method for producing HCFC-22 and HCFC-21 from HFC-23 and CHCl3 as raw materials according to claim 1, characterized in that, The molar ratio of HFC-23 to CHCl3 in the raw material is 1:(1-3); and / or, the acid value of the raw material CHCl3 is controlled within the range of 0-50ppm.

5. The method for producing HCFC-22 and HCFC-21 from HFC-23 and CHCl3 as raw materials according to claim 1, characterized in that, The multi-step distillation column includes distillation column 1 and distillation column 2. The product after the reactor reaction is separated in distillation column 1. HFC-23 is separated at the top of the column with a purity of over 98%. HCFC-22 and HCFC-21 at the bottom of the column are sent to distillation column 2 for further separation. HCFC-22 and HCFC-21 products at the top and bottom of the column are recovered in distillation column 2.

6. The method for producing HCFC-22 and HCFC-21 from HFC-23 and CHCl3 as raw materials according to claim 5, characterized in that, The temperature at the top of distillation column 1 is -40 to -10°C, the temperature at the bottom of distillation column 1 is 0 to 20°C, and the pressure of distillation column 1 is 0.8 to 2.2 MPa; and / or, the temperature at the top of distillation column 2 is 30 to 50°C, the temperature at the bottom of distillation column 2 is -30 to -5°C, and the pressure of distillation column 2 is 0.5 to 1.5 MPa.

7. The method for producing HCFC-22 and HCFC-21 using HFC-23 and CHCl3 as raw materials according to claim 1, characterized in that, After passing through the first reactor, the unreacted raw materials HFC-23 and CHCl3 and the products HCFC-22, HCFC-21 and HCl are condensed and separated into gas and liquid components. The condensed CHCl3 is then sent to the CHCl3 intermediate buffer tank. After passing through the second reactor, the unreacted raw materials HFC-23 and CHCl3 and the products HCFC-22, HCFC-21 and HCl are condensed and separated into gas and liquid components. The condensed CHCl3 is then sent to the chloroform raw material tank for collection.

8. A method for producing HCFC-22 and HCFC-21 from HFC-23 and CHCl3 as raw materials according to claim 7, characterized in that, After the reactor reaction, the unreacted CHCl3 is separated by a multi-stage cyclone separator, and the purity of the separated CHCl3 should be controlled above 99.5%.

9. A method for producing HCFC-22 and HCFC-21 from HFC-23 and CHCl3 as raw materials according to claim 7, characterized in that, After the products from the reactor reaction are condensed and separated into gas and liquid, the low-boiling-point products are deacidified and dehydrated using a solid alkali dryer, and then compressed before entering a multi-step distillation column for distillation.

10. A method for producing HCFC-22 and HCFC-21 from HFC-23 and CHCl3 as raw materials according to claim 1, characterized in that, The catalyst comprises a main catalyst and a metal promoter component. The active component of the main catalyst is one or more of the corresponding oxides or fluorides of chromium, aluminum, and magnesium metals. The metal promoter component is selected from any one or two of the metals W, Mo, V, and Nb, and the total mass content of the metal promoter is 0.1% to 10% of the total catalyst mass.

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