Method for preparing 1-chloro-1, 1-difluoroethane and co-producing 1, 1-difluoroethylene

Abstract

The invention discloses a method for preparing 1-chloro-1, 1-difluoroethane and co-producing 1, 1-difluoroethylene, which comprises the following steps: mixing 1, 1-difluoroethane, chlorine and a hot substance, preheating, introducing into a reactor, and carrying out thermal chlorination reaction to obtain 1-chloro-1, 1-difluoroethane and 1, 1-difluoroethylene, wherein the reaction temperature of the thermal chlorination reaction is 300-600 DEG C, and the reaction retention time is less than or equal to 150s. The hot substance is introduced in the hot chlorination reaction process to take away the heat of the reaction system, so that the temperature rise of the reaction system is prevented from being too fast, the reaction temperature is easy to control, and the yield of the target product is improved. Besides, the method avoids the use of a catalyst, can co-produce the downstream product 1, 1-difluoroethylene of the 1-chloro-1, 1-difluoroethane, has the advantages of simple process, high production efficiency, low production cost, continuous production and the like, and is a feasible industrial route for production.

Description

Technical Field

[0001] The invention belongs to the field of fluorine chemical industry, and specifically relates to a method for preparing 1-chloro-1,1-difluoroethane and co-producing 1,1-difluoroethylene. Background Art

[0002] 1,1-Difluoro-1-chloroethane (HCFC-142b, abbreviated as R142b) has the molecular formula CClF2CH3 and a boiling point of -9.2°C. It is a colorless gas at room temperature and is an important organic intermediate. Its main use is as a raw material for vinylidene fluoride monomer (VDF), which is an indispensable monomer for the preparation of fluororubber and polyvinylidene fluoride (PVDF) resin. Related downstream products are widely used in the automotive industry, aerospace industry, petrochemical industry and other fields.

[0003] There are three main methods for synthesizing HCFC-142b: (1) direct fluorination; (2) vinylidene chloride fluorination addition; (3) 1,1-difluoroethane chlorination.

[0004] (1) Direct fluorination method

[0005] The direct fluorination method is a process that uses 1,1,1-trichloroethane and hydrogen fluoride as raw materials to undergo a fluorination reaction under specific conditions to obtain 1,1-difluoro-1-chloroethane. The reaction equation is as follows:

[0006] CH3CCl3+HF→CH3CFCl2+HCl

[0007] CH3CFCl2+HF→CH3CF2Cl+HCl

[0008] CH3CClF2+HF→CH3CF3+HCl

[0009] Patent CN1030746A publicly reports the use of 1,1,1-trichloroethane or 1,1-dichloro-1-fluoroethane and hydrofluoric acid as raw materials, and perfluoroalkylsulfonic acid (trifluoromethanesulfonic acid) as a catalyst to carry out a liquid phase fluorination reaction to prepare 1,1-difluoro-1-chloroethane. Using this catalyst, the conversion rate of the raw material 1,1,1-trichloroethane is 98.5%, and the selectivity of 1,1-difluoro-1-chloroethane is 64.4%. In this method, since the trichloromethyl group of 1,1,1-trichloroethane itself is very active, fluorination reaction can occur even without a catalyst, so the degree of reaction is difficult to control. If the reaction does not use a catalyst, the required reaction temperature is too high; excessive hydrogen fluoride will result in excessive by-products in the reaction product; too little hydrogen fluoride will result in a reduced reaction rate and prolonged reaction time.

[0010] (2) Vinylidene chloride fluorination addition method

[0011] The vinylidene chloride fluorination addition process is a process that uses 1,1-dichloroethylene (VDC) and hydrogen fluoride as raw materials to perform an addition fluorination reaction under specific conditions to obtain 1,1-difluoro-1-chloroethane. The process can be divided into a one-step process and a two-step process, and the equation is as follows:

[0012] CH2=CCl2+HF→CH3CCl2F

[0013] CH3CCl2F+HF→CH3CF2Cl+HCl

[0014] CH3CClF2+HF→CH3CF3+HCl

[0015] Patent CN1171837C discloses a method for preparing R124b by a one-step liquid phase reaction using VDC and hydrogen fluoride as raw materials and SnCl4 and CF3(CF2)3COF as catalysts. The selectivity of R142b in this method reaches 95.2%, but the heat release is intense during the experiment and the utilization rate of hydrogen fluoride is low.

[0016] Patent US5159126 reported that HCFC-142b was synthesized in liquid phase using VDC and hydrogen fluoride as raw materials and tin tetrachloride as catalyst. The mixture of VDC and HF was heated to 60°C in an autoclave to generate 64.8% HCFC-141b, 26.7% HCFC-142b, 2.1% HFC-143a, 0.8% 1,1,1-trichloroethane and 1.4% oligomers by mass fraction, and 4.2% unreacted VDC. This method has obvious defects in industrial implementation. The main reason is that under the reaction conditions, the raw material VDC is very easy to polymerize and crack, generating a large amount of polymers and tar-like substances, resulting in a decrease in reaction yield and a rapid decrease in catalyst activity, resulting in the interruption of the production process.

[0017] (3) 1,1-Difluoroethane chlorination method

[0018] HCFC-142b is produced by chlorination of 1,1-difluoroethane (152a) in the gas phase or liquid phase. The reaction proceeds according to the free radical process and is often catalyzed by heat, light and free radicals. It is an exothermic reaction.

[0019] CH3CHF2+Cl2→CH3CF2Cl+HCl

[0020] Patent CN116023230A discloses a method for preparing 1-chloro-1,1-difluoroethane by gas phase catalysis, wherein 1,1-difluoroethane and chlorine are used as raw materials, and 1-chloro-1,1-difluoroethane is prepared by gas phase chlorination reaction under the action of Lewis acid catalyst, wherein the conversion rate of 1,1-difluoroethane is 95%, and the selectivity of R142b is 93.5%. The catalyst is prone to deactivation and carbon deposition in this method.

[0021] Patent CN101456788A discloses a method for preparing difluoromonochloroethane using a photocatalytic reactor, which includes mixing chlorine and difluoroethane and then entering a photocatalytic reactor to react to generate a crude difluoromonochloroethane product; then washing with water, alkali washing, degassing, distillation, and drying to obtain the finished difluoromonochloroethane. The photocatalytic reactor used in the reaction includes a cylinder with a heat exchange jacket on the outer wall and an inner wall lined with an anti-corrosion material, the top and bottom of the cylinder are provided with a material port, the top of the cylinder is provided with a spray device, and the part below the spray device is assembled by connecting four tower sections up and down, and each tower section is provided with four ultraviolet lamps arranged up and down; three temperature measuring ports arranged up and down and a liquid difluoroethane feed port. However, this method has a large reactor amplification effect and is limited in production scale. Summary of the invention

[0022] In order to solve the deficiencies of the prior art, the present invention provides a method for preparing 1-chloro-1,1-difluoroethane and simultaneously producing 1,1-difluoroethylene. The present invention adopts a thermal chlorination method to prepare the above-mentioned substance, which has simple process, convenient operation, high production efficiency and can be produced continuously.

[0023] A method for preparing 1-chloro-1,1-difluoroethane and co-producing 1,1-difluoroethylene comprises the following steps:

[0024] 1,1-difluoroethane and chlorine are mixed with a hot substance and preheated, and then introduced into a reactor for a thermal chlorination reaction to obtain 1-chloro-1,1-difluoroethane and 1,1-difluoroethylene, wherein the reaction temperature of the thermal chlorination reaction is 300-600°C, the reaction residence time is ≤150s, and the reaction equation is as follows:

[0025] CF2HCH3+Cl2→CF2ClCH3+HCl

[0026] CF2HCH3+Cl2→CF2=CH2+HCl

[0027] Chlorine generates chlorine radicals under high temperature initiation, and the chlorine radicals attack the hydrogen on 1,1-difluoroethane, and the reaction generates 1,1-difluoroethane radicals and hydrogen chloride. The 1,1-difluoroethane radicals react with chlorine to generate 1-chloro-1,1-difluoroethane and chlorine radicals, or continue to dehydrogenate to generate 1,1-difluoroethylene. The present invention directly adopts the method of thermal chlorination to prepare 1-chloro-1,1-difluoroethane, which avoids the adverse effects that the use of catalysts may bring to the reaction, and at the same time, by introducing a hot substance to take away the heat of the reaction system, it is avoided that the temperature rise of the reaction system is too fast, so that the reaction temperature is easy to control, thereby improving production efficiency, so that production can be carried out continuously. In addition, in the reaction process of the present invention, part of 1,1-difluoroethane can be converted in one step to directly generate 1,1-difluoroethylene (vinylidene fluoride monomer, downstream product of 1-chloro-1,1-difluoroethane), without the need to be prepared by 1-chloro-1,1-difluoroethane, which simplifies the process flow and reduces production costs.

[0028] Preferably, the reaction residence time is 1 to 60 seconds. If the time is too short, the reaction time of 1,1-difluoroethane is short and the conversion rate is low. If the time is too long, there will be more side reactions and the selectivity will decrease.

[0029] Further preferably, the reaction temperature of the thermal chlorination reaction is 350-450°C, and the reaction residence time is 10-30s. Under these conditions, the thermal chlorination reaction can be fully carried out, with fewer side reactions, and the total selectivity of 1-chloro-1,1-difluoroethane and 1,1-difluoroethylene is more than 90%.

[0030] Preferably, the thermal chlorination reaction pressure is 0 to 1 MPa. More preferably, the thermal chlorination reaction pressure is 0 to 0.6 MPa.

[0031] Preferably, the molar ratio of chlorine to 1,1-difluoroethane is 0.3 to 1.5:1. Because too low a chlorine ratio will result in a low conversion rate of 1,1-difluoroethane, which is not conducive to industrialization, and too high a chlorine ratio will increase by-products and reduce selectivity. More preferably, the molar ratio of chlorine to 1,1-difluoroethane is 0.7 to 1.2:1.

[0032] Preferably, the heat-carrying substance is selected from one of 1-chloro-1,1-difluoroethane, hydrogen chloride, 2-chloro-1,1-difluoroethane, nitrogen, dichlorodifluoroethane, trichlorodifluoroethane, etc. The heat-carrying substance of the present invention is a product of the reaction, which can not only take away part of the heat during the reaction, prevent overheating, and improve the yield of the target product, but also avoid adding additional separation steps.

[0033] Preferably, the mass of the heat-carrying substance is 20-40% of the mass of 1,1-difluoroethane. Too little heat-carrying substance will cause the reaction temperature to run away, causing the reaction temperature to rise and aggravate the side reactions, while too much heat-carrying substance will increase the separation cost.

[0034] Preferably, the preheating temperature is 80-150° C. More preferably, the preheating temperature is 100-130° C.

[0035] Preferably, the reactor is a kettle or tubular reactor. The material of the reactor can be selected from glass, nickel alloy, ceramic, stainless steel (such as 316L, 304, etc.), Hastelloy, inconel alloy (inconel600) or silicon carbide. Preferably, the material of the thermal chlorination reactor is nickel alloy or glass.

[0036] More preferably, the molar ratio of chlorine gas to 1,1-difluoroethane is 1 to 1.2:1, the heat-carrying substance is 1-chloro-1,1-difluoroethane, the mass of 1-chloro-1,1-difluoroethane is 30 to 35% of the mass of 1,1-difluoroethane, the temperature of the chlorination reaction is 350 to 450°C, the reaction pressure is 0 to 0.6 MPa, and the reaction residence time is 10 to 20 seconds. Under these reaction conditions, the conversion rate of 1,1-difluoroethane can reach more than 88 wt%, the total selectivity of 1-chloro-1,1-difluoroethane and 1,1-difluoroethylene is more than 90%, and the yield of the obtained products 1-chloro-1,1-difluoroethane and 1,1-difluoroethylene is relatively high.

[0037] Compared with the prior art, the present invention has at least the following beneficial effects:

[0038] (1) The present invention prepares 1-chloro-1,1-difluoroethane and simultaneously produces 1,1-difluoroethylene through a thermal chlorination reaction. A heat-carrying substance is introduced during the thermal chlorination reaction to take away the heat of the reaction system, thereby preventing the temperature of the reaction system from rising too fast, and making the reaction temperature easy to control. The method of the present invention has a simple process, high production efficiency, can be produced continuously, and is easy to apply industrially.

[0039] (2) The heat-carrying substance of the present invention is a product of a thermal chlorination reaction, which can not only take away part of the heat during the reaction to prevent overheating and increase the yield of the target product, but also avoid adding an additional separation process.

[0040] (3) The present invention adopts a direct thermal chlorination method to prepare 1-chloro-1,1-difluoroethane, thereby avoiding the adverse effects of using a catalyst on the reaction, and can co-produce 1,1-difluoroethylene, a downstream product of 1-chloro-1,1-difluoroethane, thereby reducing production costs and improving production efficiency. DETAILED DESCRIPTION

[0041] The present invention is further described in detail below in conjunction with examples, but the present invention is not limited to the following examples.

[0042] Example 1

[0043] In this embodiment, a nickel alloy reaction tube with an inner diameter of 6 mm and a length of 700 mm is used as a thermal chlorination reactor. The molar ratio of the reaction raw materials chlorine and 1,1-difluoroethane is 1:1. 1-Chloro-1,1-difluoroethane is used as a heat-carrying substance, and its addition amount is 30% of the mass of 1,1-difluoroethane. Chlorine, 1,1-difluoroethane and 1-chloro-1,1-difluoroethane are mixed and preheated to 100° C., and then introduced into the thermal chlorination reactor for reaction. The reaction temperature is controlled to be 350° C., the reaction pressure is 0.3 MPa, and the residence time is 10 s. The reaction product is washed with water alkali, dried, and then sampled and analyzed, and the conversion rate of 1,1-difluoroethane is 88.3%, the selectivity of 1-chloro-1,1-difluoroethane is 84.1%, and the selectivity of 1,1-difluoroethylene is 8.6%.

[0044] Example 2

[0045] In this embodiment, a nickel alloy reaction tube with an inner diameter of 6 mm and a length of 700 mm is used as a thermal chlorination reactor. The molar ratio of the reaction raw materials chlorine and 1,1-difluoroethane is 1:1. 1-chloro-1,1-difluoroethane is used as a heat-carrying substance, and its addition amount is 35% of the mass of 1,1-difluoroethane. Chlorine, 1,1-difluoroethane and 1-chloro-1,1-difluoroethane are mixed and preheated to 120° C., and then introduced into the thermal chlorination reactor for reaction. The reaction temperature is controlled to be 400° C., the reaction pressure is 0.3 MPa, and the residence time is 10 s. The reaction product is washed with water alkali, dried, and then sampled and analyzed, and the conversion rate of 1,1-difluoroethane is 95.4%, the selectivity of 1-chloro-1,1-difluoroethane is 77.5%, and the selectivity of 1,1-difluoroethylene is 15.7%.

[0046] Example 3

[0047] In this embodiment, a nickel alloy reaction tube with an inner diameter of 6 mm and a length of 700 mm is used as a thermal chlorination reactor. The molar ratio of the reaction raw materials chlorine and 1,1-difluoroethane is 0.7:1. 1-chloro-1,1-difluoroethane is used as a heat-carrying substance, and its addition amount is 35% of the mass of 1,1-difluoroethane. Chlorine, 1,1-difluoroethane and 1-chloro-1,1-difluoroethane are mixed and preheated to 120° C., and then introduced into the thermal chlorination reactor for reaction. The reaction temperature is controlled to be 400° C., the reaction pressure is 0 MPa, and the residence time is 20 s. The reaction product is washed with water alkali, dried, and then sampled and analyzed, and the conversion rate of 1,1-difluoroethane is 64.7%, the selectivity of 1-chloro-1,1-difluoroethane is 73.7%, and the selectivity of 1,1-difluoroethylene is 16.6%.

[0048] Example 4

[0049] In this embodiment, a nickel alloy reaction tube with an inner diameter of 6 mm and a length of 700 mm is used as a thermal chlorination reactor. The molar ratio of the reaction raw materials chlorine and 1,1-difluoroethane is 1:1. 1-chloro-1,1-difluoroethane is used as a heat-carrying substance, and its addition amount is 30% of the mass of 1,1-difluoroethane. Chlorine, 1,1-difluoroethane and 1-chloro-1,1-difluoroethane are mixed and preheated to 110° C., and then introduced into the thermal chlorination reactor for reaction. The reaction temperature is controlled to be 350° C., the reaction pressure is 0.6 MPa, and the residence time is 20 s. The reaction product is washed with water alkali, dried, and then sampled and analyzed, and the conversion rate of 1,1-difluoroethane is 94.5%, the selectivity of 1-chloro-1,1-difluoroethane is 80.1%, and the selectivity of 1,1-difluoroethylene is 12.3%.

[0050] Example 5

[0051] In this embodiment, a nickel alloy reaction tube with an inner diameter of 6 mm and a length of 700 mm is selected as a thermal chlorination reactor. The molar ratio of chlorine and 1,1-difluoroethane as the reaction raw materials is 1.1:1. 1-Chloro-1,1-difluoroethane is used as a heat-carrying substance, and its addition amount is 30% of the mass of 1,1-difluoroethane. Chlorine, 1,1-difluoroethane and 1-chloro-1,1-difluoroethane are mixed and preheated to 120° C. and introduced into the thermal chlorination reactor for reaction. The reaction temperature is controlled to be 450° C., the reaction pressure is 0.3 MPa, and the residence time is 10 s. The reaction product is washed with water alkali, dried, and then sampled and analyzed, and the conversion rate of 1,1-difluoroethane is 96.3%, the selectivity of 1-chloro-1,1-difluoroethane is 65.4%, and the selectivity of 1,1-difluoroethylene is 27.8%.

[0052] Example 6

[0053] In this embodiment, a nickel alloy reaction tube with an inner diameter of 6 mm and a length of 700 mm is selected as a thermal chlorination reactor. The molar ratio of the reaction raw materials chlorine and 1,1-difluoroethane is 1.2:1. 1-Chloro-1,1-difluoroethane is used as a heat-carrying substance, and its addition amount is 30% of the mass of 1,1-difluoroethane. Chlorine, 1,1-difluoroethane and 1-chloro-1,1-difluoroethane are mixed and preheated to 120° C., and then introduced into the thermal chlorination reactor for reaction. The reaction temperature is controlled to be 450° C., the reaction pressure is 0 MPa, and the residence time is 10 s. The reaction product is washed with water alkali, dried, and then sampled and analyzed, and the conversion rate of 1,1-difluoroethane is 97.3%, the selectivity of 1-chloro-1,1-difluoroethane is 70.2%, and the selectivity of 1,1-difluoroethylene is 23.4%.

[0054] Example 7

[0055] In this embodiment, a nickel alloy reaction tube with an inner diameter of 6 mm and a length of 700 mm is selected as a thermal chlorination reactor. The molar ratio of the reaction raw materials chlorine and 1,1-difluoroethane is 1:1. 2-chloro-1,1-difluoroethane is used as a heat-carrying substance, and its addition amount is 30% of the mass of 1,1-difluoroethane. Chlorine, 1,1-difluoroethane and 1-chloro-1,1-difluoroethane are mixed and preheated to 130° C., and then introduced into the thermal chlorination reactor for reaction. The reaction temperature is controlled to be 450° C., the reaction pressure is 0 MPa, and the residence time is 10 s. The reaction product is washed with water alkali, dried, and then sampled and analyzed, and the conversion rate of 1,1-difluoroethane is 91.2%, the selectivity of 1-chloro-1,1-difluoroethane is 71.4%, and the selectivity of 1,1-difluoroethylene is 20.7%.

[0056] Example 8

[0057] In this embodiment, a nickel alloy reaction tube with an inner diameter of 6 mm and a length of 700 mm is selected as a thermal chlorination reactor. The molar ratio of the reaction raw materials chlorine and 1,1-difluoroethane is 1.1:1. 1-Chloro-1,1-difluoroethane is used as a heat-carrying substance, and its addition amount is 35% of the mass of 1,1-difluoroethane. Chlorine, 1,1-difluoroethane and 1-chloro-1,1-difluoroethane are mixed and preheated to 100° C. and introduced into the thermal chlorination reactor for reaction. The reaction temperature is controlled to be 600° C., the reaction pressure is 0.1 MPa, and the residence time is 1 s. The reaction product is washed with water alkali, dried, and then sampled and analyzed, and the conversion rate of 1,1-difluoroethane is 83.5%, the selectivity of 1-chloro-1,1-difluoroethane is 73.1%, and the selectivity of 1,1-difluoroethylene is 16.3%.

[0058] Example 9

[0059] In this embodiment, a nickel alloy reaction tube with an inner diameter of 6 mm and a length of 700 mm is selected as a thermal chlorination reactor. The molar ratio of the reaction raw materials chlorine and 1,1-difluoroethane is 1.1:1. 1-Chloro-1,1-difluoroethane is used as a heat-carrying substance, and its addition amount is 35% of the mass of 1,1-difluoroethane. Chlorine, 1,1-difluoroethane and 1-chloro-1,1-difluoroethane are mixed and preheated to 120° C. and introduced into the thermal chlorination reactor for reaction. The reaction temperature is controlled to be 400° C., the reaction pressure is 0.1 MPa, and the residence time is 60 s. The reaction product is washed with water alkali, dried, and then sampled and analyzed, and the conversion rate of 1,1-difluoroethane is 94.7%, the selectivity of 1-chloro-1,1-difluoroethane is 64.2%, and the selectivity of 1,1-difluoroethylene is 19.1%.

[0060] Example 10

[0061] In this embodiment, a nickel alloy reaction tube with an inner diameter of 6 mm and a length of 700 mm is selected as a thermal chlorination reactor. The molar ratio of the reaction raw materials chlorine and 1,1-difluoroethane is 1:1. 1-Chloro-1,1-difluoroethane is used as a heat-carrying substance, and its addition amount is 30% of the mass of 1,1-difluoroethane. Chlorine, 1,1-difluoroethane and 1-chloro-1,1-difluoroethane are mixed and preheated to 150° C. and introduced into the thermal chlorination reactor for reaction. The reaction temperature is controlled to be 300° C., the reaction pressure is 0 MPa, and the residence time is 120 s. The reaction product is washed with water alkali, dried, and then sampled and analyzed, and the conversion rate of 1,1-difluoroethane is 95.3%, the selectivity of 1-chloro-1,1-difluoroethane is 60.1%, and the selectivity of 1,1-difluoroethylene is 15.6%.

[0062] Embodiment 11

[0063] In this embodiment, a nickel alloy reaction tube with an inner diameter of 6 mm and a length of 700 mm is selected as a thermal chlorination reactor. The molar ratio of the reaction raw materials chlorine and 1,1-difluoroethane is 1.2:1. 1-Chloro-1,1-difluoroethane is used as a heat-carrying substance, and its addition amount is 30% of the mass of 1,1-difluoroethane. Chlorine, 1,1-difluoroethane and 1-chloro-1,1-difluoroethane are mixed and preheated to 120° C., and then introduced into the thermal chlorination reactor for reaction. The reaction temperature is controlled to be 450° C., the reaction pressure is 0 MPa, and the residence time is 150 s. The reaction product is washed with water alkali, dried, and then sampled and analyzed, and the conversion rate of 1,1-difluoroethane is 94.2%, the selectivity of 1-chloro-1,1-difluoroethane is 45.3%, and the selectivity of 1,1-difluoroethylene is 15.3%.

[0064] Comparative Example 1

[0065] In this comparative example, a nickel alloy reaction tube with an inner diameter of 6 mm and a length of 700 mm is used as a thermal chlorination reactor. The molar ratio of the reaction raw materials chlorine and 1,1-difluoroethane is 0.5:1. The reaction raw materials are mixed and preheated to 120° C., and then introduced into the thermal chlorination reactor for reaction. The reaction temperature is controlled to be 250° C., the reaction pressure is 0 MPa, and the residence time is 10 s. The reaction product is washed with water alkali, dried, and then sampled and analyzed, and the conversion rate of 1,1-difluoroethane is 15.3%, the selectivity of 1-chloro-1,1-difluoroethane is 88.5%, and the selectivity of 1,1-difluoroethylene is 4.3%.

Claims

1. A method for preparing 1-chloro-1,1-difluoroethane and co-producing 1,1-difluoroethylene, characterized in that: The method comprises the following steps: mixing 1,1-difluoroethane and chlorine with a hot substance, preheating the mixture, and then introducing the mixture into a reactor for a thermal chlorination reaction to obtain 1-chloro-1,1-difluoroethane and 1,1-difluoroethylene, wherein the reaction temperature of the thermal chlorination reaction is 300-600° C., and the reaction residence time is ≤150s.

2. The method according to claim 1, characterized in that The reaction residence time is 1 to 60 seconds.

3. The method according to claim 1, characterized in that The reaction temperature of the thermal chlorination reaction is 350-450° C., and the reaction residence time is 10-30 seconds.

4. The method according to claim 1, characterized in that: The molar ratio of chlorine to 1,1-difluoroethane is 0.3-1.5:

1.

5. The method according to claim 4, characterized in that The molar ratio of chlorine to 1,1-difluoroethane is 0.7-1.2:

1.

6. The method according to claim 1, characterized in that The heat-carrying substance is selected from one of 1-chloro-1,1-difluoroethane, hydrogen chloride, 2-chloro-1,1-difluoroethane, nitrogen, dichlorodifluoroethane or trichlorodifluoroethane.

7. The method according to claim 6, characterized in that The mass of the heat-carrying substance is 20-40% of the mass of 1,1-difluoroethane.

8. The method according to claim 1, characterized in that The preheating temperature is 80-150°C.

9. The method according to claim 1, characterized in that: The reactor is a kettle type or a tubular type reactor.

10. The method according to claim 9, characterized in that The material of the reactor is selected from one of glass, nickel alloy, ceramic, stainless steel, Hastelloy, inconel alloy or silicon carbide.

11. The method according to any one of claims 1 to 10, characterized in that The molar ratio of chlorine to 1,1-difluoroethane is 1-1.2:1, the heat-carrying substance is 1-chloro-1,1-difluoroethane, the mass of 1-chloro-1,1-difluoroethane is 30-35% of the mass of 1,1-difluoroethane, the reaction temperature of the thermal chlorination reaction is 350-450° C., and the reaction residence time is 10-20 seconds.