3,287,426 United States Patent Office Patented Nov. 22, 1966

2 satisfactory results when used at moderate temperature 3,287,426 rangeS. FLUORINATION WITH SiF The temperatures at which the fluorination reactions Karl O. Christe and Attila E. Pavlath, Berkeley, Calif., can be carried out rely heavily on the reactivity of the assignors to Stauffer Chemical Company, New York, exchangeable chlorines and the thermal stability of the N.Y., a corporation of Delaware chlorinated organic compound. Actually, reaction Will No Drawing. Filed July 1, 1963, Ser. No. 292,100 occur at any temperature, however, to be economically 2 Claims. (C. 260-653.8) feasible the higher temperatures are favored. It is there This invention relates to a new process for preparing fore not practical to operate below about 300° C. in this fluorine-containing organic compounds utilizing silicon invention. To obtain practical conversions to the desired tetrafluoride as the fluorinating agent. In particular, it 10 products, it is preferred to work within the approximate relates to a new process for the replacement of chlorine range of 400° C. to 900 C. atoms by fluorine atoms in certain selected chlorine-con Since the reaction is carried out in a heated tubular taining organic compounds. Because of the temperature reactor at atmospheric pressure, this invention has a dis range of the reaction it is necessary to limit this invention tinct advantage of being easily adaptable to a continuous to those organic compounds whose thermal stability will 15 flow system. The retention time is not critical. Satisfact enable them to withstand this high temperature. Specifi tory results are obtained with retention times of 5 to 60 cally, these organic compounds will work: perhalometh seconds. Our preferred range is from 5 to 20 Seconds. anes, chloroform, tetrachloroethylene and hexachloropro More specifically, if we consider the fluorination of pene. 20 carbon tetrachloride carried out with silicon tetrafluoride The utilization of the fluorine values of silicon tetra according to the present invention, we will see the effect fluoride as a fluorinating agent is very useful, since the of temperature on the product. This reaction results silicon tetrafluoride is produced as a gaseous by-product in a mixture of mono-, di- and trifluorochloromethanes in the industrial superphosphate plants. This provides a in quantitative yields and conversions of 60 to 80% per source for inexpensive silicon tetrafluoride. Previously 25 pass. The composition of the reaction products can be the utilization of the silicon tetrafluoride required the changed easily by variation of the reaction temperature. absorption of the gas in water and thus form fluosilicic At lower temperature a higher yield of monofluorotri acid, which was converted by neutralization with sodium chloromethane is observed. Whereas, at higher tempera hydroxide solution to sodium fluosilicate. The sodium ture a higher yield of difluorodichloro- and trifluoromono fluosilicate was then used in certain fluorination reactions 30 chloromethane are obtained. at high pressure and high temperature. We propose the If we use a trihalomethane, as chloroform, we find the use of gaseous silicon tetrafluoride. effect of temperature on the thermal stability of the The fluorine perhalomethanes, i.e., dichlorodifluoro compound quite dominate. The upper limit for this type methane and trichloromonofluoromethane, are extremely of compound is 650° C. where an undesirable amount valuable compounds. They find extensive use as refrig 35 of decomposition and disproportionation takes place. erant liquids, as dielectric fluids, and as propellants in This effect will be demonstrated in Example III involving aerosols. chloroform. Therefore, the desirable range for this com This invention has as an object a new process for pre pound is 450-600 C. paring fluorine-containing compounds utilizing the fluorine Fluorination of activated CCl3-groups, for example values of silicon tetrafluoride. 40 in hexachloropropene, can be carried out easily due to This object is accomplished by the present invention of the activation of the allylic chlorines. Whereas, in try a process which comprises reacting silicon tetrafluoride ing to replace the vinylic chlorines of tetrachloroethylene with selected chlorine-containing organic compounds, e.g., we find a greater resistance to exchange. carbon tetrachloride, chloroform, tetrachloroethylene, The following examples illustrate the present inven hexachloropropene, at a temperature within the range 45 tion. 400 C. to about 900 C. and isolating the fluorine-con Example 1.--A gas mixture consisting of silicon tetra taining compounds formed. fluoride and carbon tetrachloride in a ratio of 2:1 was The respective proportions of the chlorine-containing passed through an electrically heated quartz tube at 600 organic compound and silicon tetrafluoride are not criti C. The quartz, tube was filled with surface active quartz cal. However, it is desirable to use the two reactants in 50 granules. A retention time of 10 seconds was achieved such ratio that there is present in the reaction tube at least by regulating the silicon tetrafluoride gas flow through one gram atom of fluorine for each gram atom of chlorine the carbon tetrachloride container. present in the organic compound. The proportion of The above example is Example 1 of Table I below, fluorine has been increased, i.e., amount of silicon tetra which includes the results of a similar reaction carried fluoride, in certain reactions where the advantage as a car 55 rier gas was to be utilized. In the cases where the chlo out at 800° C., all other conditions being equal. The rine-containing organic compound is a liquid excess sili results are of the gaseous reaction products, after removal con tetrafluoride was used as a carrier gas to carry the of excess silicon tetrafluoride and unreacted carbon tetra material into the heated reaction zone. The organic chloride. The effect of temperature can clearly be seen compound was placed in a flask adjacent to the reactor in the preparation of chlorofluoromethanes by the present tube and warmed to a sufficient temperature which would 60 invention. TABLE. I.-PREPARATION OF CHIOROFLUOROMETH. give a satisfactory vapor pressure and likewise the desir ANES FROM CARBON TETRACEORIDE AND SILICON able ratio of reactants. Our preferred ratio is two gram TETRAFLUORIDE atoms of fluorine per gram atom of chlorine. Percent. Yield of The reactants are passed through a heated tubular re 65 Example Tempara- Percent Con actor, the material of construction of which is not impor ture, C. version of tant; metal, quartz, or equivalent reaction tubes may be CC CF3C CF2Cl2 CFCs used. Although not essential for reaction, but desirable 1------600 57.8 ------18.9 81. for proper heat transport and better yields, the use of a 2------800 77.1 17.2 51.3 31, 5 packing was employed in the reactor. The nature of the 70 packing similarly is not important. We found the use of Example 3-A gaseous mixture of chloroform and a quartz tube with high surface quartz granules produced silicon tetrafluoride in the ratio of 1:5 was passed through 3,287,426 3 4. a quartz tube at 450° C. The tube was packed with high surface active quartz granules. The reaction temperature surface quartz granules. The retention time was 10 was 520 C. The retention time was 10 seconds. The seconds. Analysis of the obtained organic product analysis of the reaction products gave a conversion to showed it contained on a molar basis, 1.5% monofluoro fluorinated products of 87%. The main product of the dichloromethane and 96.8% chloroform. This repre resulting compounds was CFCl-CCI FCC in a yield sented a starting material conversion of 3.2% and a yield of 56.8%. of 47% of the monofluoro compound. Various changes and modifications may be made in the The above example is Example 3 of Table II below, process described herein as will be apparent to those which gives examples of several other temperatures used skilled in the chemical arts. It is accordingly intended in the reaction of chloroform and silicon tetrafluoride. 0. that the present invention shall only be limited by the All other conditions were kept constant except for the scope of the appended claims. reaction zone temperature. The composition of the re We claim: action products was figured after removal of excess sili 1. A process for the preparation of halogenated organ con tetrafluoride. ic compounds in which at least one halogen atom is fluo 5 rine and any other halogen is chlorine, which comprises TABLE II-PREPARATION OF CHF Cls FROM CHIC AND bringing a chlorinated organic compound starting ma SiFi. terial, selected from the group consisting of perhalometh anes, chloroform, tetrachloroethylene and hexachloro Mol Percent Percent Percent propene, in contact at a temperature of at least 300° C. Example Tempera- Composition Conver- Yield of 20 ture, C. of Products sion of CHFC with silicon tetrafluoride, and isolating said fluorine-con CEICl3 taining organic compound formed by this substitution re action. 3------450 .5 CHF Cl2------3.2 47.0 2. A process for the preparation of fluorochlorometh 1.7 Unidentified 96.8 CHC3 anes comprising bringing carbon tetrachloride and silicon 4------500 1.5 CHFC2- 4.25 34.7 25 tetrafluoride in contact at a temperature of at least 300° C. 2.7 Unidentified 95.8 CEICls 5------550 2.2 CHF.C.--- 7.1 31. References Cited by the Examiner 4.9 Unidentified 92.9 CHC3 UNITED STATES PATENTS. 30 2,757,214 7/1956 Muetterties ------260-544X Example 6.-In the same manner as Example 1, a 2,935,531 5/1960, Dahmlos ------260-544 gas mixture of perchloroethylene and silicon tetrafluoride FOREIGN PATENTS in the ratio of 2:5 was passed through a packed quartz 623,358 7/1961 Canada. tube heated to 800° C. The retention time was 6 seconds. The analysis of the reaction products gave the following OTHER REFERENCES results: 2.4% monofluorotrichloroethylene, 0.4% carbon Bennett: "Chemical and Technical Dictionary," p. 792 tetrachloride, 0.08% chlorine and the remainder was (1962). starting materials. The recovered starting material mix Mellor: “Comprehensive Treatise on Inorganic and ture could be recycled. Theoretical Chemistry,” vol. 6 (1925), pp. 936-937. Example 7.-A gas mixture of hexachloropropene and 40 silicon tetrafluoride in the ratio 1:7 was passed through LORRAINE A. WEINBERGER, Primary Examiner. an electrically heated quartz tube which was filled with R. K. JACKSON, Examiner.