JPH09504544A - Method for producing trichlorotrifluoroethane - Google Patents

Abstract

(57) [Summary] A method for producing a reaction product consisting of C ₂ Cl ₃ F ₃ substantially free of 1,2-dichlorotetrafluoroethane is disclosed. The process consists essentially of a compound of the formula C ₂ Cl _4-x F _{2 + x,} where x is 0 or 1 and has a C ₂ Cl ₄ F ₂ content of said C ₂ Cl _4-x , F is between about 10 to 90 mol% of _{2 + x,} and CCl ₃ CClF ₂ and CCl ₂ FCCl ₂ F and the molar ratio of the total amount of CCl ₂ FCClF ₂ with respect to the total amount of CCl ₃ CF ₃ is at least about 1: 9 Is contacted with an isomerization catalyst, and there is less than about 50,000 parts by weight of CCl ₂ FCCl ₂ F and CCl ₂ FCClF ₂ per million parts by weight of CCl ₃ CClF ₂ and CCl ₃ CF ₃ in total. To produce an isomerized product. The isomerized product is contacted with HF at an Atsushi Nobori of 400 ° C. or less selected in the presence of a wax hydrogenation catalyst comprising trivalent chromium at the gas phase, CCl ₂ FCCl ₂ F against CCl ₃ CClF ₂ ratios and CCl ₃ ratio of CCl ₂ FCClF ₃ against CF ₂ is greater respectively than their ratio in the isomerization product, and the molar ratio of CClF ₂ CClF ₂ against CCl ₂ FCClF ₂ is about 1: less than 9, C A fluorinated product containing ₂ Cl ₂ F ₄ , C ₂ Cl ₃ F ₃ and between about 10 and 90% C ₂ Cl ₄ F ₂ is provided from the isomerization product, C ₂ Cl ₂ F ₄ and C ₂ A first portion of Cl ₃ F ₃ is recovered from the fluorinated product; and a _{second portion} of C ₂ Cl ₄ F ₂ and C ₂ Cl ₃ F ₃ from the fluorinated product is added in step (iii). at least 1 of the amount of C ₂ Cl ₂ F ₄ and C ₂ Cl ₃ F ₃ is recovered Ku, which is recycled along with _{C 2 Cl 4-x F 2} + x with respect to C ₂ Cl ₂ F ₂ of desired sufficient additional amount to give a raw material mixture ratio of CCl ₂ FCCl ₂ F in step (i).

Description

Detailed Description of the Invention                  Method for producing trichlorotrifluoroethane   Field of the invention   The present invention is C₂Cl_FourF₂C from a mixture of isomers₂Cl_ThreeF_ThreeMethod for producing reaction product , And more particularly substantially CClF₂CCIF₂Not including C₂Cl_ThreeF_ThreeReaction Regarding the manufacture of goods.   background   Tetrachlorodifluoroethane can be easily converted into trichlorodifluoroethane using conventional fluorination. Lifluoroethane (C₂Cl_ThreeF_Three) Is converted to. C₂Cl_ThreeF_ThreeThe product is typically Is more than 98% of the more symmetrical isomer, CCl₂FCClF₂(CFC-113) including. CFC-113 uses an aluminum trihalide catalyst and is less Isomer, CCl_ThreeCF_ThreeIt can be easily isomerized to (CFC-113a). Also C FC-113a is 1,1-dichlorotetrafluoroethane by ordinary fluorination. (Ie CCl₂FCF_ThreeOr it may be converted to CFC-114a).   CCl₂FCF_ThreeIs the catalytic hydrogen of its carbon-chlorine bond using supported metal hydrogenation catalysts 1,1,1,2-tetrafluoroethane (ie C F_ThreeCH₂Of interest as intermediates to F or HFC-134a) (eg For example, C.I. Gervasutti et al., J. Fluorine Chem., 1981/82, 19, 1-20 Page). HFC-134a is regarded as related to the decomposition of stratospheric ozone Chlorofluorocarbon (ie CFC) refrigerants, blowing agents, aerosols It is a potential environmentally acceptable alternative to propellants and sterilants. HFC-1 To 34a 1,1-dichlorotetrafluoroethane used in the hydrogenation route Due to the presence of CFC-114, 1,1,2,2-tetrafluoroethane (ie CH F₂CHF₂Or HFC-134) production can occur, It is highly desirable to have a much lower content of 1,2-dichlorotetrafluoroethane Shii [eg J. L. Bitner et al. S. Dep. Comm. Off. Tech. Serv. Rep. 13 6732, (1958), page 25]. HF mixed in HFC-134a C-134 is inconvenient for some applications depending on the concentration and Separation of high-purity isomers is difficult because the body boils only at 7 ° C.   A process useful in the preparation of CFC-114a substantially free of its isomers, especially conventional There is a need for a method by which the gas phase fluorination technique of can be used. This is 1,2-jik Method for producing trichlorotrifluoroethane without producing lorotetrafluoroethane Including the law.   SUMMARY OF THE INVENTION   The process according to the invention is substantially free of 1,2-dichlorotetrafluoroethane. C₂Cl_ThreeF_ThreeA method for producing a reaction product comprising This method consists of (i) essentially the formula C₂Cl_4-xF_{2 + x}(Wherein X is 0 or 1), and C₂Cl_Four F₂The content is C₂Cl_4-XF_{2 + X}Between about 10 and 90 mol% of CC, and CC l_ThreeCCIF₂And CCl_ThreeCF_Three(Ie the more asymmetric C₂Cl_4-XF_{2 + X}Isomer ) To the total amount of CCl₂FCCl₂F and CCl₂FCClF₂(Ie more symmetrical Sex C₂Cl_4-XF_{2 + X}Raw material mixture having a total molar ratio of (isomers) of at least about 1: 9. The compound is contacted with an isomerization catalyst, and CCl_ThreeCCIF₂And CCl_ThreeCF_ThreeTotal of 100 Less than about 50,000 parts by weight per 10,000 parts by weight CCl₂FCCl₂F and And CCl₂FCClF₂(Ii) isomerization The product was selected in the gas phase in the presence of a fluorination catalyst containing trivalent chromium at 400 ° C. Contact with HF under the following high temperature, CCl_ThreeCCIF₂Against CCl₂FCCl₂ Ratio of F and CCl_ThreeCF₂Against CCl₂FCClF_ThreeIn the isomerization product Greater than that ratio, and CCl₂FCClF₂Against CClF₂CCIF₂of Molar ratio less than about 1: 9, C₂Cl₂F_Four, C₂Cl_ThreeF_ThreeAnd about 10 to 90% Between C₂Cl_FourF₂A fluorinated product containing from the isomerized product; (iii) C₂ Cl₂F_FourAnd C₂Cl_ThreeF_ThreeRecover the first portion of the fluorinated product; and (i v) C from fluorinated products₂Cl_FourF₂And C₂Cl_ThreeF_ThreeThe second part of step (i ii) C recovered in₂Cl₂F_FourAnd C₂Cl_ThreeF_ThreeAt least equal to C₂Cl_4-XF_{2 + X}C for₂Cl_FourF₂Is sufficient to give the raw material mixture ratio of Additional amount of CCl₂FCCl₂Recycling with F to step (i).   Brief description of the drawings   FIG. 1 illustrates an embodiment of the present invention.   Detailed Description of the Invention   The method of the present invention is a method for the gas phase contacting of a mixture of tetrachlorodifluoroethane isomers. Including categorization. Substantially CClF₂CCIF₂CCl without₂FCClF₂Reaction An object is produced. C₂Cl_FourF₂Is a halogenated hydrocarbon used during the fluorination process CFC-11 to CFC-112a of about 19: 1 to 1:19 in a mixture of primes. Present in a molar ratio of 2. Preferably, CFC-112 to CFC-112a Ratio is less than about 1: 1 and more preferably less than about 1: 9. The present invention According to fluorination Is the actual CClF₂CCIF₂Is not generated (for example, about 400 ° C or higher). Under high temperature). Substantially CClF₂CCIF₂Is not generated in this specification CCl in fluorinated products₂FCClF₂Against CClF₂CCIF₂No Means a ratio of less than about 1: 9. Preferably, C in the fluorinated product Cl₂FCClF₂Against CClF₂CCIF₂Molar ratio of less than about 1:19 , And more preferably less than about 1:99. The fluorination method according to the present invention is However, it is generally used in the art when conducting a catalytic gas phase fluorination reaction. It is continuously carried out by a known method.   C₂Cl_FourF₂The mixture is reacted with hydrogen fluoride using a catalyst containing trivalent chromium . In addition to a catalytically effective amount of trivalent chromium, such fluorination catalysts have catalytic activity and / or Or other components such as one or more divalent metals to increase life. It may contain cations such as zinc, magnesium and / or cobalt. Three No valent chromium catalyst is supported (eg Cr₂O_Three) Or supported (eg alumina) , Aluminum fluoride, magnesium fluoride or on carbon).   Suitable gas phase fluorination catalysts include trivalent chromium halides supported on carbon (eg For example CrCl_ThreeAnd / or CrF_Three) Is included. Supported on carbon for suitable catalysts U.S. Patent No. CrF disclosed in 3,632,834_ThreeThere is. Any suitable carbon support Although preferred, a suitable carbon support is acid washed prior to the precipitation of trivalent chromium on it. It is. Suitable trivalent chromium catalysts are those which use carbon as an acid carrier, preferably two species. It can be produced by treating with acid. Typically deionized after acid treatment of carrier Washed with water And then dry; then deposit the chromium halide in a precipitation technique well known in the art (eg, For example, see US Pat. No. 3,632,834, Example 1) You. Preferably, the chromium content (CrCl_ThreeRepresents about the carbon supported catalyst. It is 5 to 50% by weight.   An acid other than hydrofluoric acid is typically used for the acid treatment. Preferred for acid treatment Acids do not contain either phosphorus or sulfur. Used for the first acid wash during the catalyst preparation process Examples of acids that can be used are organic acids such as acetic acid and inorganic acids such as HCl or HNO._ThreeBut included. Preferably hydrochloric acid or nitric acid is used. If the second acid treatment is performed, It is advantageous to use hydrofluoric acid. Normally, carbon is about 0.1% by weight after treatment Treat with acid to contain less ash.   Commercially available carbon that can be treated with acid to provide a suitable support is sold under the following trademarks: Includes: Darco^TM, Nuchar^TM, Columbia SBV^TM, Columbia MBV^TM, C olumbia MBQ^TM, Columbia JXC^TM, Columbia CXC^TM, Calgon PCB^TM, Norit^TMas well as Barnaby Cheny NB^TM. Carbon carrier is in the form of powder, granules, extrudates or pellets possible.   Acid treatment can be accomplished in several ways. A suitable method is as follows. Carbon carrier Soak overnight in 1 molar solution of acid prepared in deionized water with gentle stirring I do. Then the carbon support is separated and deionized until the pH value of the washing solution is about 3. Wash with water. Preferably, the carbon support is then treated with an acid prepared in deionized water. Soak again in a 1 molar solution for 12-24 hours with gentle stirring. Then carbon support When tested by standard methods, the wash solution contains substantially no acid anion (eg Cl^-Ma Or NO_Three ^-) Finally, wash with deionized water until free. Then carbon support To separate And it dries at about 120 degreeC. Then wash the washed carbon into deionized water if necessary Immerse in the prepared 1 molar HF for about 48 hours at room temperature with occasional stirring. Carbon bearing Separate the body and repeat with deionized water until the pH of the wash solution is above 4. Wash back. The carbon support is then dried, followed by air before its use as a support. Bake at about 300 ° C. for about 3 hours. For the production of acid washed carbon catalysts See US Pat. No. 5,136,113 for further details.   For continuous processes, the fluorination reaction is generally performed in the reaction zone for fluorination . The reaction zone has more than one reactor, multiple feed lines, and intercooling or It may include heating, addition of reactants, diluents, recycle streams and the like. For example, multi-stage The reactor can be used to control the degree of fluorination, and therefore excessive temperature Rise and perfluorination are avoided. Reaction products are usually collected at the end of the reaction zone. It is. If desired, reaction products, intermediates and / or by-products may be present in various reaction zones. Can be removed at different stages and recycled to different parts of the reaction zone if desired. . For example, HF and CFC-113a may be fed into the reaction zone at more than one feed location. Can be paid. CFC-114a is generally recovered from the end of the reaction zone.   Suitable fluorination reaction temperatures are usually about 250-400 ° C. The preferred temperature range is 275-375 ° C, with a temperature range of 300-350 ° C being particularly preferred. HF: C₂Cl_ThreeF_ThreeThe ratio is usually 0.2: 1 to 4: 1 and preferably 0.25: 1. The range is ~ 2: 1 and the pressure is not critical. Atmospheric pressure and superatmospheric pressure (for example, about 100 to about 7,000 kPa) is most convenient and is therefore preferred. Above reaction change Is CCl in the fluorinated product with catalyst loading₂FCF_Three 10 per million copies From 000 parts by weight Less CClF₂CCIF₂Is balanced with others so that there is You. Those familiar with this field will find high temperatures and high HF: C.₂Cl_ThreeF_ThreeRatio is altitude It will be appreciated that there is an advantage in the incarnation. Thus, the amount of perfluorination is low HF: C₂ Cl_ThreeF_ThreeIt can be reduced by providing ratios and / or lower temperatures. In addition, catalyst contact The touch time can be adjusted in a conventional manner to control the fluorination.   The product mixture from fluorination is C₂Cl_ThreeF_Three(Mostly mainly CCl₂FCClF₂ ), A small amount of CClF₂CF_Three(CFC-115), CClF₂CCIF₂, CCl₂ FCF_Three(CFC-114a), unreacted C₂Cl_FourF₂Isomers and HF and HCl Usually a mixture of The fluorinated product is C in the product mixture.₂Cl_ThreeF_Three(And yes Slightly C₂Cl₂F_Four) Part is C in this₂Cl_FourF₂Separated to be separated from I do. Typically, conventional fractionation using one or more distillation columns (s) Use separation. Also, the separation is one or more decanters (plural). May be contained. During the separation by distillation, low-boiling substances (eg HF, HCl, CFC) -115) is separated from the CFC-112 isomer. HF and various halocarbon examples For example CCl₂FCCl₂F, CCl_ThreeCCIF₂, CCl_ThreeCF_Three, And CCl₂FC F_ThreeIt is noted that an azeotrope with can be formed during distillation.   CFC-112 isomers from fluorinated products (selective fluoride of CFC-112a Normally enriched in CFC-112 as a result of digestion) and CFCs from fluorinated products A portion of the -113 isomer was fed to the isomerization zone along with additional CFC-112, This substantially converts CFC-112 to CFC-112a. HF is an isomer catalyst C before contact with₂Cl_FourF₂From Should be removed. C supplied to the isomerizer₂Cl_ThreeF_ThreeAnd C₂Cl_FourF₂Mixture of C that exists in₂Cl_ThreeF_ThreeIs CCl₂FCCl₂Gives a melting point below the melting point of F, Helps in the desired isomerization. Preferably, C₂Cl_FourF₂Content is isomerization process C supplied₂Cl_4-xF_{2 + x}Between about 10 and 75 mol%; and better More preferably C₂Cl_FourF₂The content is between about 10 and 50 mol% thereof. CFC- 112 is chloride chloride as disclosed in Example IV of US Pat. No. 2,598,411. Recycled C with Luminium catalyst₂Cl_ThreeF_ThreeCFC-112a in the presence of Is isomerized to. CCl recycled₂FCClF₂Isomerization of CFC-112 Can be accomplished in an isomerization reactor similar to that used for isomerization to CFC-112a . However, according to the invention, the C fed to the isomerization zone₂Cl_ThreeF_ThreeAgainst C₂Cl_FourF₂The molar ratio of is at least about 1: 9. Compound supplied to isomerization (CCl_ThreeCF_Three+ CCl_ThreeCCIF₂) To (CCl₂FCClF₂+ C Cl₂FCCl₂The molar ratio of F) is generally at least about 1: 9. A lot of aluminum Aluminum trihalides can be used. Suitable catalyst is about 0.8 m²/ G is larger than Finely ground to give surface area (ie crushing, ball milling, rod milling Mechanically crushed by a ring, crushing, etc.), and 1 g of aluminum trichloride At least about 10 g of CCl₂FCClF₂And active by treating under stirring Is anhydrous aluminum trichloride. Further discussion of finely ground catalysts See joint application US Patent Application Publication No. 08 / 117,379 for I want to. CFC-112a is recycled to the fluorination process according to the present invention.   Also, as disclosed in Example I of US Pat. No. 2,598,411, CFC-113 recovered from the separation zone is CF using an aluminum chloride catalyst. It can be isomerized to C-113a. As mentioned above, the preferred catalyst is about 0.8 m.²/ G Includes activated finely ground anhydrous aluminum trichloride with a larger surface area .   CFC-113a from the isomerization zone readily reacts with HF in the reaction zone , High purity CFC-114a. Next, the latter compound is hydrolyzed CH, a non-destructive refrigerant₂FCF_Three(HCF-134a).   The use of the present invention is further illustrated by reference to FIG. 1, where substantially CF C including C-112₂Cl_FourF₂Optional C including isomers and substantially CFC-113₂ Cl_ThreeF_ThreeIsomers (ie, the ratio of CFC-113 to CFC-113a is 100. 1) (> 1) mixture through line (211) to isomerizer (210). Pay. C mainly including CFC-112a₂Cl_FourF₂Isomers and mainly CFC-11 Any time including 3a C₂Cl_ThreeF_ThreeThe isomerizer effluent consisting of a mixture of isomers Feed into the fluorination reactor (220) through 212). HF line (221 ) To the reactor (220). Unreacted CCl₂FCClF₂, Unreacted C₂ Cl_FourF₂, HF and HCl and mainly CCl₂FCF_ThreeIncluding C at any time₂Cl₂F_FourDifference The fluorination reactor effluent containing the solids is passed through a line (222) to a distillation column (23 0). C₂Cl_ThreeF_ThreeIsomers, HF and HCl and optionally C₂Cl₂F_FourDifference The sex is collected at the top of the column and collected through line (232). Kara C-112-rich C from the bottom of the membrane (230)₂Cl_FourF₂Isomer and CFC -113 rich in C₂Cl₂F_ThreeAdditional CF through line (213) With C-112 To the isomerizer (210) via line (231). Reactor line up Its auxiliary supply line, effluent line and auxiliary equipment are hydrogen fluoride, hydrogen chloride and It should be manufactured from materials that are chlorine resistant. Well known in the fluorination field One of the typical manufacturing materials is especially austenite type stainless steel. And well-known high-nickel alloys Is commonly used as a lining for polytrifluorochloroethylene and It is a polymeric plastic such as ritetrafluoroethylene.   The practice of the invention will be more apparent from the following non-limiting examples.   Example   General reaction method And heated in a nitrogen stream (25 ml / min) at 300 ° C. for about 20 hours Was. The temperature was reduced to 175 ° C. and a 2: 1 molar ratio of nitrogen and HF was charged to the reactor. The flow started (total flow rate 100 ml / min). After 1 hour under these conditions, The nitrogen molar ratio was adjusted to 1: 3, and the temperature was gradually increased to 400 over 2 hours. ° C. The reactor is then brought back to the desired operating temperature, the nitrogen flow is stopped and the reaction is Started supplying body flow.   General analysis method   Krytox reactor effluent on inert carrier^TMLength 2 including perfluorinated polyether 0 ft (6.1 m), 1/8 inch (0.32 cm) diameter column and 3 flow rates Hewlett Packard HP 5890 gas chromatograph using 5 ml / min helium. Sampled online at Gask The chromatographic conditions are 70 ° C for 3 minutes, then 6 ° C / min up to 180 ° C. A temperature program was performed. % In the table is mol%.   Example 1   Fluorination of CCl ₂ FCCl ₂ F / CCl ₂ FCClF ₂ mixture   Carbon supported 29% CrCl_ThreeCatalyst (10.8g, 25ml), CCl₂FCCl₂ F (64.7%), CCl₂FCClF₂(35.1%), and CCl_ThreeCF_Three(0. 2%) in a 1 molar composition of chlorofluorocarbons (CFCs), 2: 1 H F: CFCs molar ratio and contact time of 30 seconds according to general reaction method went. The reaction was carried out at atmospheric pressure. The results at various temperatures are shown in Table 1.   Other products identified are CF_ThreeCF_Three, CCl₂= CClF, CCl_ThreeCCl₂F And CCl₂= CCl₂Was included.   Example 2   Fluorination of CCl ₃ CClF ₂ / CCl ₂ FCClF ₂ mixture   Carbon supported 29% CrCl_ThreeCatalyst (10.8g, 25ml), CCl_ThreeCCIF₂( 63.8%), CCl₂FCClF₂(35.8%), and CCl_ThreeCF_Three(0.2% 1 mole composition of chlorofluorocarbons (CFCs) containing 2: 1 HF: CFCs molar ratio and contact time of 30 seconds were used according to the general reaction method. Was. The reaction was carried out at atmospheric pressure. The results at various temperatures are shown in Table 2. 112 / a is CCl₂FCCl₂F + CCl_ThreeCCIF₂Is (C₂Cl_FourF₂Different The sex could not be revealed using the above analytical method. In this example, raw The product is essentially CCl_ThreeCCIF₂It is considered to consist of).   Other identified products are CCl₂= CClF and CCl₂= CCl₂Contains Was.   Specific examples of the present invention are shown in the examples. Other embodiments are novel to the present invention. Familiar with the art from consideration of the specification or practice without departing from the spirit and scope of various concepts. It will be clear to the one who makes it happen. Furthermore, the present invention is directed to the specific formulas and embodiments presented herein. Including, but not limited to, such improved forms thereof as set forth in the following claims. It will be appreciated.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Office reference number FI // C07B 61/00 300 7419-4H C07B 61/00 300

Claims (1)

[Claims] 1. (I) consists essentially of a compound of formula C ₂ Cl _4-X F _{2 + X} , wherein X is 0 or 1 and the C ₂ Cl ₄ F ₂ content is C ₂ Cl _4-X F _{2 + X} between about 10 and 90 mol% and the molar ratio of the total amount of CCl ₂ F CCl ₂ F and CCl ₂ FCClF _{2 to} the total amount of CCl ₃ CClF ₂ and CCl ₃ CF ₃ is at least about 1: 9. A feed mixture is contacted with an isomerization catalyst and there is less than about 50,000 parts of CCl ₂ FCCl ₂ F and C Cl ₂ FCClF ₂ per million parts of total CCl ₃ CClF ₂ and CCl ₃ CF _3. (Ii) contacting the isomerization product with HF at a high temperature of 400 ° C. or lower selected in the presence of a fluorination catalyst containing trivalent chromium in the gas phase, C Cl ₂ FCCl ₂ F ratio and for CCl ₃ CClF ₂ CCl ₃ The ratio of CCl ₂ FCClF ₂ with respect to CF ₂ is greater respectively than their ratio in the isomerization product, and the molar ratio of C ClF ₂ CClF ₂ against CCl ₂ FCClF ₂ is about 1: less than 9, C ₂ Cl Giving from the isomerization product a fluorinated product containing ₂ F ₄ , C ₂ Cl ₃ F ₃ and between about 10 and 90% C ₂ Cl ₄ F ₂ ; (iii) C ₂ Cl ₂ F ₄ and C A first portion of ₂ Cl ₃ F ₃ is recovered from the fluorinated product; and (iv) a C ₂ Cl ₄ F ₂ and a _{second portion} of C ₂ Cl ₃ F ₃ from the fluorinated product are treated with a step ( iii) at least equal to the amount of C ₂ Cl ₂ F ₄ and C ₂ Cl ₃ F ₃ recovered in, and the feed mixture ratio of C ₂ Cl ₄ F _{2 to} C ₂ Cl _4-x F _{2 + x} is Consisting of recycling to step (i) with an additional amount of CCl ₂ FCCl ₂ F sufficient to give A method for producing a reaction product consisting of C ₂ Cl ₃ F ₃ substantially free of CClF ₂ CClF ₂ . 2. The method of claim 1 wherein the fluorination catalyst comprises trivalent chromium supported on acid washed carbon. 3. The method of claim 2 wherein the fluorination catalyst is a chromium halide supported on acid washed carbon. 4. A process according to claim ₃ , wherein the chromium content of the catalyst is 5 to 50% by weight, expressed as CrCl ₃ . 5. The method of claim 1 wherein the C ₂ Cl ₄ F ₂ content of the feed mixture is between about 10 and 75 mol% of the C ₂ Cl _4-X F _{2 + X} therein. 6. The method of claim 1 wherein the C ₂ Cl ₄ F ₂ content of the feed mixture is between about 10 and 50 mol% of the C ₂ Cl _4-x F _{2 + x} therein. 7. The method of claim 1 wherein the fluorination reaction temperature is about 250-350 ° C. 8. The method according to claim 1, wherein the HF: C ₂ Cl ₄ F ₂ ratio in the fluorination step is 0.2: 1 to 4: 1. 9. The molar ratio of CClF ₂ CClF ₂ against CCl ₂ FCClF ₂ of the fluorination product is less than about 1:19 method according claim 1, wherein. Ten. The molar ratio of CClF ₂ CClF ₂ against CCl ₂ FCClF ₂ of the fluorination product is less than about 1:99, the method according claim 1, wherein.