US005254772A United States Patent (19) 11) Patent Number: 5,254,772 Dukat et al. (45) Date of Patent: Oct. 19, 1993

(54) CHEMICAL PROCESS FOREIGN PATENT DOCUMENTS (75) Inventors: Wolfgang W. Dukat, Konigstein, Fed. Rep. of Germany; John H. 705927 3/1965 Canada ...... 570/170 Holloway, Leicester; Eric G. Hope, 0164798 12/1985 European Pat. Off. . Warwickshire, both of England; Primary Examiner-Alan Siegel Matthias Rieland, Hanover, Fed. Attorney, Agent, or Firm-Cushman, Darby & Cushman Rep. of Germany; Paul J. Townson, Lancashire; Richard L. Powell, 57) ABSTRACT Cheshire, both of England A process for the preparation of an alkane containing fluorine by contacting a halogenated alkane containing 73) Assignee: Imperial Chemical Industries PLC, at least one hydrogen atom and at least one halogen London, England atom selected from chlorine, bromine and iodine with a (21) Appl. No.: 849,604 transition metal fluoride selected from osmium hexaflu oride, iridium hexafluoride, rhenium hexafluoride, ru (22) Filed: Mar. 12, 1992 thenium pentafluoride, chromium pentafluoride, vana (30) Foreign Application Priority Data dium pentafluoride, rhenium heptafluoride and uranium Mar. 12, 1991 GB United Kingdom ...... 9105167 hexafluoride, whereby to replace at least one hydrogen atom or at least one chlorine, bromine or iodine atom in 51 Int. Cl...... CO7C 17/20; CO7C 17/00 said halogenated alkane starting material by a fluorine 52 U.S.C...... 570/170; 570/123 58) Field of Search ...... 570/170, 168, 123 atom. Use of certain of the defined transition metal fluorides, 56) References Cited e.g. Osf6, Irfs and ReF6 allows the selective replace U.S. PATENT DOCUMENTS ment of halogen by fluorine, while others, e.g. UF6, 2,423,045 9/1943 Passino et al. . VFs and ReF, allow selective replacement of hydrogen 2,759,026 2/1950 McCleary . by fluorine. 3,235,608 3/1962 Gibbs. 3,972,953 8/1976 Lyons . 8 Claims, No Drawings 5,254,772 1 2 The proportions of halogenated alkane and transition CHEMICAL PROCESS metal fluoride are not critical; either may be in excess over stochiometric, if desired. Thus, for example, the This invention relates to a process for the fluorination proportion of halogenated alkane to transition metal of aliphatic compounds, and more particularly to a 5 fluoride may be in the range from about 50:1 to about process for the replacement by fluorine of at least one l:50, and preferably in the range from about 20:1 to hydrogen atom and/or at least one halogen atom other about 1:20 of the stoichiometrically required propor than fluorine in aliphatic compounds. tion, although these ranges are given merely by way of It is already known to manufacture aliphatic com guidance and are in no way limiting on the process of pounds containing fluorine by reacting aliphatic chloro O the present invention. Hydrogen fluoride may also be carbons or chlorohydrocarbons with fluorinating included in the reaction mixture as a fluorinating agent, agents such as antimony pentafluoride. In many cases, the metal fluoride then optionally being employed in a however, known fluorinating agents do not give en catalytic amount. tirely satisfactory results, being somewhat deficient in In operating the process of the invention, whether at activity and/or in product selectivity. 15 least one hydrogen atom or at least one halogen atom It has now been found that certain transition metal other than fluorine, or both hydrogen and halogen in fluorides are useful fluorinating agents capable of selec the halogenated alkane is/are replaced by fluorine may tively replacing by fluorine one or more hydrogen depend to a large extent on the particular halogenated atoms and/or one or more halogen atoms other than alkane and on the particular transition metal fluoride fluorine in aliphatic compounds. 20 used. According to the present invention there is provided Where it is desired to replace at least one halogen a process for the preparation of an alkane containing atom in the halogenated alkane, the preferred transition fluorine which comprises contacting a halogenated metal fluorides are Oss, Irf6 and ReF6. The use of alkane containing at least one hydrogen atom and at these particular fluorides allows the replacement of 25 halogen atom other than fluorine in the halogenated least one halogen atom selected from chlorine, bromine alkane by fluorine with a selectivity which may be as and iodine with a transition metal fluoride selected from high as 80% and even as high as 95%, in particular osmium hexafluoride, iridium hexafluoride, rhenium where Oss is used. w hexafluoride, ruthenium pentafluoride, chromium pen Where it is desired to replace a hydrogen atom in the tafluoride, vanadium pentafluoride, rhenium heptafluo 30 halogenated alkane and the halogenated alkane is a ride and uranium hexafluoride, and replacing at least chlorinated alkane, the preferred transition metal fluo one hydrogen atom or at least one one chlorine, bro rides are UF6, VFs and ReF7. The use of these particu mine or iodine atom in said halogenated alkane by a lar fluorides allows the replacement of at least one hy fluorine atom. drogen atom by fluorine with a selectivity which may Halogenated alkanes which may be employed in the 35 be as high as 80% and even as high as 95%, in particular process of the invention may contain one or more car where UF6 is used, bon atoms, for example, typically up to 6 carbon atoms, Furthermore, certain of the transition metal fluorides, and have at least one hydrogen atom and at least one for example Rufs, may selectively replace at least one replaceable halogen atom selected from chlorine, bro hydrogen atom in certain halogenated alkanes, for ex mine and iodine. Other atoms, for example fluorine, ample CF3CH2Cl, yet selectively replace at least one may also be present. halogen atom other than fluorine in other halogenated Especially useful halogenated alkanes include hydro alkanes, for example in dichloromethane. CrFs may chlorocarbons and chlorofluorohydrocarbons. selectively replace at least one hydrogen atom although Specific examples of halogenated alkanes which may the selectivity may be better with certain halogenated be used include dichloromethane, chlorofluorome 45 alkane starting materials than with others; for example thane, dibromomethane, bromofluoromethane, and 2 high selectivity is obtained with CrFs for the replace chloro-1,1,1-trifluoroethane from which the products ment of hydrogen in CFCH2Cl although selectivity may be respectively difluoromethane, and 1,1,1,2-tetra may not be as high with CH2Cl2. In addition, ReF may fluoroethane. selectively replace at least one hydrogen atom where In operating the process of the invention, the haloge the halogenated alkane is a chlorinated alkane, but may nated alkane may be contacted with the transition metal selectively replace at least one halogen atom where the fluoride at a temperature at which the halogenated halogenated alkane is a brominated alkane. alkane is in the liquid phase or the vapour phase but The process of the invention is of particular value for conveniently the liquid phase. Accordingly the temper the preparation of difluoromethane from dichlorometh ature may be from about -80 to about 25' C. depending 55 ane or chlorofluoromethane and accordingly in a pre upon the boiling point of the halogenated alkane, al ferred aspect of the invention there is provided a pro though the reaction proceeds, and may be conducted at, cess for the preparation of difluoromethane which pro temperatures higher than 25 C., for example up to 100 cess comprises contacting dichloromethane or chloro C., in which case the halogenated alkane may be in the fluoromethane with a transition metal fluoride selected vapour phase. The process of the invention is preferably from Osfs, Irfs, ReF6 and RuFs and maintaining the operated under substantially anhydrous conditions, and contact until at least a portion of the dichloromethane is conveniently operated at atmospheric pressure, al or chlorofluoromethane has been converted to di though superatomospheric or subatmospheric pressures fluoromethane. The reaction mixture may, if desired, may be employed, if desired. also contain hydrogen fluoride. The transition metal fluoride may, at the reaction 65 The process of the invention is also of particular temperature, be present in the reaction vessel in the value for the preparation of 1,1,1,2-tetrafluoroethane solid or vapour phase, and may be supported on a sub from 2-chloro-1,1,1-trifluoroethane and accordingly in strate, for example aluminium fluoride or carbon. a further aspect of the invention there is provided a 5,254,772 3 4. process for the preparation of 1,1,1,2-tetrafluoroethane T-piece were evacuated, passivated with R2 and re which comprises contacting 2-chloro-1,1,1-trifluoroe evacuated. thane with a transition metal fluoride selected from 236 mg, 2.78 mmol of CH2Cl2 was sublined into the Osfs, Irf6, and ReF6 and maintaining the contact until FEP tube cooled to -196° C. in liquid nitrogen. The at least a portion of the 2-chloro-1,1,1-trifluoroethane PTFE valve was closed and the reaction mixture al has been converted to 1,1,1,2-tetrafluoroethane. The lowed to warm slowly to -78 C. in a dry-ice-acetone reaction mixture may, if desired, also contain hydrogen bath and then to room temperature (20', C.) with fre fluoride. quent shaking. After 1 hour the solution had turned The process of the invention is also of particular from its original yellow colour to black and there was a value for the preparation of dichlorofluoromethane by 10 black precipitate. The FEP tube and PTFE valve were contacting dichloromethane with ReF7, UF6 or VFs taken off the vacuum line and re-weighed. and of 2-chloro-1,1,1,2-tetrafluoroethane by contacting The FEP reaction tube and a second FEP tube were 2-chloro-1,1,1-trifluoroethane with Rufs, ReF, Crfs, connected to the vacuum line via a PTFE T-piece, and VF5 or UF6 and these processes represent further par the connectors and T-piece were evacuated, passivated ticular embodiments of the invention. 15 with F2 and re-evacuated. The second FEP tube was The invention is illustrated by the following examples cooled to -196' C. in liquid nitrogen, the PTFE valves in which the organic materials were handled in a vac opened and the volatile product from the reaction tube uum line made from stainless steel tubing with stainless was allowed to sublime into the second FEP tube. The steel valves and the metal fluorides were handled in involatile precipitate in the reaction tube was taken for satellite lines made from PTFE. Reactions were con 20 elemental analysis, and was determined to be OsCls. ducted in FEP tubes (copolymer of HFP and TFE) The FEP tube containing the volatile product was which could be sealed thermally in a small ring furnace kept cold at -196° C. and was placed in a small ring after reaction had reached completion and could be furnace and heated gently to form a vacuum and pres inserted into a standard precision 5 mm n.m.r. glass tube sure tight seal. The n.m. r. spectra of the volatile product with a thin film of the lock substance-d6 acetone placed 25 was run at 298 K. between the tubes. To obtain a reliable integration of H The results are shown in Table 1. From these results against 19F signals, CF3CH2OH (33% w/v) was added it was calculated that the replacement of chlorine by fluorine was 87% selective and that the overall yield of to the lock substance. fluorinated products was 88%. All equipment was seasoned with fluorine gas at a 30 pressure of 700-800 mbar for about 16 hours. The tran EXAMPLE 2 sition metal fluorides were prepared by conventional literature methods and were stored in F2 passivated Ni Fluorination of CH2Cl2 by IrF6 cylinders. The procedure described in example 1 was followed The products were analysed by n,m, r. spectroscopy 35 except that 39.2 mg, 0.128 mmol of IrF6 (prepared as on a Bruker FT spectrometer AM 300 (H at 3000 described in J. Chem Physics., 1970, 53, 1411) and 190 MHz, 19F at 282.4 MHz) with a 5 mm bore selective mg, 2.23 mmol of CH2Cl2 were sublimed into the reac probe. tion tube. The results are shown in Table 1. From these results EXAMPLE 1. it was calculated that the replacement of chlorine by Fluorination of CH2Cl2 by OsR6 fluorine was 78% selective. A 15 cm longX4 mm diameter (outside diame EXAMPLE 3 ter)x0.5 mm wall thickness FEP tube was connected via a PTFE valve (supplied by Production Techniques) Fluorination of CH2Cl2 by ReF6 to an all metal vacuum line, evacuated to <10 Torr, 45 The procedure described in example 1 was followed passivated with F2 gas (400 Torr) for 20 minutes, and except that 32.2 mg, 0.107 mmol of ReF6 (prepared as re-evacuated. The valve was closed and the weight of described in J. ChemSoc. Dalton Trans., 1988, 1341) the valve and tube measured. and 475 mg, 5.6 mmol of CH2Cl2 were sublimed into the 37.9 mg (0.125 mmol) of Osfs (prepared in accor reaction tube. The reaction was allowed to run for 5 dance with J. Chem Soc., Dalton Trans., 1988, 1341) SO days before analysis by nimr. was carried out. Further was condensed from the nickel storage cylinder into the more, after 5 days no precipitate had formed and the pre-fluorinated FEP tube by vacuum transfer at -196' FEP reaction tube itself was sealed as described in ex C. as follows. The Nistorage container and FEP tube ample 1 without transferring the volatile products to a were connected to the vacuum line. The connections second FEP tube, were evacuated, passivated with F2 gas and re 55 The results are shown in Table 1. From these results evacuated. The FEP tube was cooled to -196° C. in it was calculated that the replacement of chlorine by liquid nitrogen and the valves to the FEP tube and Ni fluorine was 88.5% selective and that the overall yield storage container were opened to allow the Osfs to of fluorinated products was 95%. sublime into the FEP tube. The valve to the storage EXAMPLE 4 container was closed and the apparatus was re evacuated, the valve to the FEP tube closed and the Fluorination of CH2Cl2 by RuFs FEP tube allowed to warm to room temperature. The The procedure described in example 1 was followed FEP tube and valve were taken off the vacuum line and except that 60.8 mg 0.310 mmol of solid RuFs (pre re-weighed. 65 pared as described in J. Chem Soc., 1963, 527) was The FEP tube containing Osfs and a glass storage loaded into the pre-fluorinated weighed FEP tube in a vessel containing dried CH2Cl2 were connected to the dry box (<1 ppm H2O, supplied by Vacuum Atmo vacuum line via a PTFE T-piece. The connectors and spheres Ltd) and 647 mg, 7.614 mmol of CH2Cl2 were 5,254,772 5 6 sublimed into the reaction tube. The reaction tube was and the HF and organic layers were separated by freez allowed to warm up to 10' C. ing the organic layer at -196' C. and vacuum sublim The results are shown in Table 1. From these results ing the HF layer into a further FEP tube. The organic it was calculated that the replacement of chlorine by phase was then warmed up to room temperature and fluorine was 96.5% selective. vacuum sublined into a third FEP tube. The FEP tubes EXAMPLE 5 containing the organic phase and HF phases were then heat sealed and taken for n.m.r. analysis. Fluorination of CH2Cl2 by UF6 The results are shown in Table 1. The results show The procedure described in example 1 was followed that the fluorination of CH2Cl2 using Crfs is not selec except that 415.0 mg, 1.179 mmol of UF6 (prepared as O tive. described in DOKLAKAD NAUK SSSR, 1962, 143) and 1317 mg, 15.5 mmol of CH2Cl2 were sublimed into EXAMPLE 9 the reaction tube. The reaction was allowed to proceed Fluorination of CH2Br2 by ReF for 5 days before analysis by n,m.r. was carried out. The involatile precipitate was determined to be UFs. 15 The procedure described in example 1 was followed The results are shown in Table 1. From these results except that 49.0 mg, 0.1535 mmol of ReF, and 854.3 mg, it was calculated that the replacement of hydrogen by 4.91 mmol of CH2Br2 were sublimed into the reaction fluorine was 99.9% selective. tube. The reaction was allowed to run for 1 day before analysis by n.m.r. was carried out. Furthermore, after 1 EXAMPLE 6 20 day no precipitate had formed and the FEP reaction Fluorination of CH2Cl2 by VFs tube itself was sealed as described in example 1 without The procedure described in example 1 was followed transferring the volatile products to a second FEP tube. except that 190.5 mg, 1.305 mmol of VFs (prepared as The results are shown in Table 2. From these results described in J. Chem Soc., 1949, 2979) and 942.5 mg, 25 it was calculated that the replacement of bromine by 11.09 mmol of CH2Cl2 were sublimed into the reaction fluorine was 98.0% selective. tube. The FEP tube was allowed to warm up to 0 C. The reaction was allowed to proceed for 2 hours before EXAMPLE 10 carrying out analysis by nimr. The involatile product Fluorination of CH2Br2 by UF6 was determined to be VF4. 30 The procedure described in example 1 was followed The results are shown in Table 1. From these results except that 217.5 mg, 0.618 mmol of UF6 and 1142 mg, it was calculated that the replacement of hydrogen by 6.57 mmol of CH2Br2 were sublimed into the reaction fluorine was 92.0% selective. tube. The reaction was allowed to proceed for 14 days EXAMPLE 7 before analysis by n.m.r. was carried out. 35 The results are shown in Table 2. From these results Fluorination of CH2Cl2 by ReF, it was calculated that the replacement of hydrogen by The procedure described in example 1 was followed except that 207.3 mg, 0.649 mmol of ReF7 (prepared as fluorine was 100.0% selective. described in J. Inorg Nucl Chem., 1961, 20, 189) and EXAMPLE 11 1061.3 mg, 12.5 mmol of CH2Cl2 were sublimed into the reaction tube. The reaction was allowed to run for 1 day Fluorination of CFCH2Cl by VFs before analysis by nimr, was carried out. Furthermore, The procedure described in example 1 was followed after 1 day no precipitate had formed and the FEP except that 93.3 mg, 0.639 mmol of VFs and 464.0 mg, reaction tube itself was sealed as described in example 1 3.916 mmol of CF3CH2Cl were sublimed into the reac without transferring the volatile products to a second 45 tion tube, and the reaction was allowed to proceed for FEP tube. 4 days. The results are shown in Table 1. From these results The results are shown in Table 3. From these results it was calculated that the replacement of hydrogen by it was calculated that the replacement of hydrogen by fluorine was 96.0% selective. fluorine was 100% selective and that the yield of fluori EXAMPLE 8 nated products was 70%. Fluorination of CH2Cl2 by Crfs EXAMPLE 12 This reaction was carried out in the presence of HF as Fluorination of CF3CH2Cl by ReF, solvent. The procedure of example 1 was followed except that 205.4 mg, 1.397 mmol of Crfs (prepared as 55 The procedure described in example 1 was followed described in J. Inorg Chem, 1985, 24, 2286) was loaded except that 151.5mg, 0.475 mmol of ReF7 and 443.7 mg, into a large (10 cm x 10 mm outside diameterX 1 mm 3.74 mmol of CF3CH2Cl were sublimed into the reac wall thickness) FEP reaction tube in a dry box. Dry HF tion tube. The reaction was allowed to run for 1 day was then sublimed into the reaction tube and the mix before analysis by n.m.r. was carried out. Furthermore, ture of Crs and HF was stirred for 18 hours to allow 60 after 1 day no precipitate had formed and the FEP dissolution of Crfs in the HF.2086 mg, 24.55 mmol of reaction tube itself was sealed as described in example 1 CHCl2 were then sublimed into the reaction vessel and without transferring the volatile products to a second the reaction mixture was stirred at room temperature FEP tube. for 2 hours. After 2 hours, all the volatile products from 6S The results are shown in Table 3. From these results the reaction tube were allowed to condense in a large it was calculated that the replacement of hydrogen by FEP tube which was at -196° C. The volatile products fluorine was 100% selective and that the yield of fluori were warmed up to -78 C. in a dry-ice acetone bath nated products was 26%. 5,254,772 7 8 osmium hexafluoride, iridium hexafluoride, rhenium EXAMPLE 13 hexafluoride, ruthenium pentafluoride, vanadium penta Fluorination of CFCH2Cl by RuFs fluoride and rhenium heptafluoride, and replacing at The procedure described in example 1 was followed least one hydrogen atom or at least one chlorine, bro except that 200.0 mg, 1.02 nmol of solid Rufs was mine or iodine atom in said halogenated alkane by a loaded into the pre-fluorinated weighed FEP tube in a fluorine atom. dry box (<1 ppm H2O, supplied by Vacuum Atmo 2. A process as claimed in claim 1 in which the halo spheres Ltd) and 906.9 mg, 7.653 mmol of CF3CH2Cl genated alkane comprises a hydrochlorocarbon or chlo were sublimed into the reaction tube. Reaction was rofluorohydrocarbon. allowed to proceed for 2 hours. 10 3. A process as claimed in claim 2 in which the halo The results are shown in Table 3. From these results genated alkane is selected from the group consisting of it was calculated that the replacement of hydrogen by dichloromethane, chlorofluoromethane, dibronometh fluorine was 43% selective. The large amount of CHF3 ane, bromofluoromethane, and 2-chloro-1,1,1-tri produced resulted from the fluorination by Rufs of fluoroethane. CHF2Cl which was present as a reactive contaminant in 4. A process as claimed in claim 1 wherein the haloge the CF3CH2Cl used. nated alkane is contacted with Osf6, IrF6 or ReF6 and at least one chlorine, bromine or iodine atom in said TABLE 1. PRODUCTS OF FLUORINATION OF CH2Cl2. TM FLUORDE. ReF ReF6 OsF6 IrF6 UF6 RuFs VFs CrFs PRODUCTS. MOLE 2. (Moles.) CHCIF. 1.2 85, 22, 42.0 37.4 2.0 27.8 (0.5) (0.17) (0.03) CH2F 3.44 54.8 29.3 59, 2.6 (0.01) (0.21) CHCl2F 43.2 4, 11.1 99.9 1.68 9.9 8.17 (0.03) (1.18) (1.18) CHCIF. 0.6 3.2 1.3 10,2 1.2 6.2 2.5 (0.01) (0.01) (0.08) CHF 7.92 7.4 0.6 3.0 (0.02) CF2Cl2 0.26 2.0 CF3C 1.67 2.4 (0.004) CF4. 4.4 HF. 54.7 4. 12.5 (0.03) (0.1)

TABLE 2 40 PRODUCTS OF FLUORINATION OF CH2Br2. PRODUCTAMole %. halogenated alkane is replaced by a fluorine atom. CH2BrF CH2F2 CHBr2F CHBrF2 5. A process as claimed in claim 1 in which the halo TM FLUORIDE genated alkane is contacted with VF5 or ReF, and at -ReF. A A 40.1 58.2 0.38 1.2 45 least one hydrogen atom in said halogenated alkane is UF6. 85.5 4.5 replaced by a fluorine atom. 6. A process for the preparation of difluoromethane which process comprises contacting dichloromethane TABLE 3 or chlorofluoromethane with a transition metal fluoride PRODUCTS OF FLUORINATION OF CF3CH2C. 50 selected from Osfs, IrF6, ReF6 and RuFs and maintain TM FLUORDE. ing the contact until at least a portion of the dichloro VFs. ReF. RuFs. methane or chlorofluoromethane has been converted to PRODUCTAMole %. difluoromethane. (No. of Moles). e 2 7. A process for the preparation of 1,1,1,2-tetra CFCHFCl. 100 100 43.0 55 fluoroethane which comprises contacting 2-chloro (0.111) (0.0299) 1,1,1-trifluoroethane with a transition metal fluoride CFCFCl2. 4.8 selected from Osfs, Irfs, and ReF6 and maintaining the SESHCl: : contact until at least a portion of the 2-chloro-1,1,1-tri 31, fluoroethane has been converted to 1,1,1,2-tetrafluoroe 60 thane. We claim: 8. A process as claimed in any one of claims 1 to 7 1. A process for the preparation of an alkane contain which comprises contacting the transition metal fluo ing fluorine which comprises contacting a halogenated ride with the halogenated alkane in the liquid or vapour alkane containing at least one hydrogen atom and at phase at a temperature in the range from about -80 C. least one halogen atom selected from chlorine, bromine to about 100 C. and iodine with a transition metal fluoride selected from 65