United States Patent Office Patented Mar
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3,373,000 United States Patent Office Patented Mar. 2, 1968 2 3,373,000 monofluoride is also an economical reactant, since it is PROCESS FOR PREPARING TETRAFLUORDES conveniently prepared by the disproportionation of ele AND HEXAFLUOR DES mental chlorine in liquid hydrogen fluoride, thereby avoid James J. Pitts, West Haven, and Albert W. Jache, North ing the use of expensive elemental fluorine. The selective Haven, Conn., assignors to Olin Mathieson Chemical fluorination process of this invention is particularly Sur Corporation, a corporation of Virginia prising and unexpected in view of the prior art which No Drawing. Filed Nov. 1, 1966, Ser. No. 591,079 teaches that chlorine monofluoride adds to a wide variety 9 Claims. (Cl. 23-352) of compounds, thereby acting as a chloro-fluorinating agent. For instance, U.S. Patent 3,035,893 discloses the 10 preparation of sulfur chloride pentafluoride from Sulfur ABSTRACT OF THE DISCLOSURE tetrafluoride and chlorine monofluoride. The tetrafluorides and hexafluorides of sulfur, selenium According to the process of this invention, the tetra and tellurium are provided by reacting chlorine mono fluorides and hexafluorides of sulfur, selenium and tel fluoride with sulfur, selenium, tellurium, metal sulfides, lurium are provided by reacting chlorine monofluoride metal selenides or metal tellurides. The hexafluorides of 15 with a material selected from the group consisting of Sul tungsten, molybdenum and uranium are provided by the fur, selenium, tellurium, metal sulfides, metal selenides reaction of chlorine monofluoride with the metals, their and metal tellurides. The hexafluorides of tungsten, oxides, sulfides and salts containing the metallate anion. molybdenum and uranium are provided by reacting These tetrafluorides and hexafluorides are well-known chlorine monofluoride with a material selected from the compounds, useful as fluorinating agents, gaseous di 20 group consisting of tungsten; molybdenum, uranium; the electrics, sources of high purity metallic powders, etc. oxides of tungsten, molybdenum and uranium; the sul fides of tungsten, molybdenum and uranium; uranium -mass skirm carbides and salts containing the metallate anion of tung This invention relates to a process for preparing the sten, molybdenum and uranium. tetrafluorides and hexafluorides of sulfur, selenium and 25 While any of the metals and metal compounds illus tellurium by the reaction of chlorine monofluoride with trated above can be utilized in the process of this in the elements sulfur, selenium and tellurium and with the vention, preferred embodiments employ sulfur, selenium, metal sulfides, selenides and tellurides. It also relates to a tellurium, the Group VI-B metal sulfides, molybdenum, process for preparing the hexafluorides of tungsten, tungsten, uranium, the oxides of molybdenum, tungsten molybdenum and uranium by the reaction of chlorine 30 and uranium, the alkali metal molybdates and tungstates, monofluoride with the metals, their oxides, sulfides and lead molybdate and lead tungstate in the reaction with salts containing the metallate anion. chlorine monofluoride to provide the corresponding tetra The tetrafluorides and hexafluorides of sulfur, selenium, fluorides and hexafluorides. tellurium, tungsten, molybdenum and uranium have been Illustrative of the Group VI-B sulfides are molybdenum previously prepared and described in the literature. For ex disulfide, tungsten sulfide, and the uranium sulfides, for ample, D. Yost and W. Calusen in J. Am. Chem. Soc., 55,- example, uranium disulfide and uranium sesquisulfide. 885 (1933) discloses the reaction of sulfur and selenium These Group VI-B sulfides generally provide the hexa with elemental fluorine to provide sulfur tetrafluoride, fluorides of the Group VI-B element in addition to sulfur sulfur hexafluoride, selenium tetrafluoride and Selenium tetrafluoride and sulfur hexafluoride, and thus are par hexafluoride, while the reaction of tellurium with fluorine 40 ticularly suitable for the simultaneous preparation of to provide tellurium hexafluoride is reported by H. Moissan several of the compounds of this invention. Other suit and P. Lebeau in Compt. Rend., 130, 965 (1900). Fluori able metal sulfides include the alkali metal sulfides, i.e., fluorine to provide the respective hexafluorides is de sodium sulfide, potassium sulfide, lithium sulfide and the scribed by Edwards et al., J. Chem Soc. 4486, (1962). like. Calcium sulfide, aluminum selenide and aluminum However, elemental fluorine is costly, corrosive and diffi telluride are also useful in preparing the tetrafluorides and cult to handle. Furthermore, it is such a vigorous fluori hexafluorides of this invention. nating agent that stringent process conditions are essen Molybdenum trioxide, tungstic oxide and the uranium tial, thereby hindering efficient commercial operations. oxides such as uranium dioxide, uranium trioxide and It is also known to prepare various tetrafluorides and pitch-blend are illustrative of the oxides suitable for use hexafluorides employing chlorine trifluoride as the fluori 50 in the preparation of the hexafluorides of molybdenum, nating agent. For instance, F. Nyman and H. Roberts in tungsten and uranium. Exemplificative of salts of tung J. Chem. Soc., 3180, (1962) report the reaction of sulfur sten, molybdenum and uranium containing the respective with chlorine trifluoride to provide sulfur tetrafluoride. metallate anions are the alkali metal molybdates, ammo The efficacy of chlorine trifluoride as a fluorinating agent nium molybdate and lead molybdate; the alkali metal is attributed to the highly oxidized state of the chlorine, 55 tungstates, calcium tungstate and lead tungstate; and which readily releases fluorine, making it available to re uranous uranate. Minerals such as huebernite (MnWO4), act with the metal to form the tetrafluoride. However, ferberite (FeWO), wolframite (Fe, Mn)WO and chlorine trifluoride is such a powerful fluorinating agent carnotite KO-2VOVO, which contain metallate that cumbersome process controls such as dilution with anions, also react readily with chlorine monofluoride to 60 provide the desired tetrafluorides and hexafluorides. inert gases or cooling to the liquid state are necessary. The compounds of this invention are obtained at various Furthermore, chlorine trifluoride is synthesized from ele temperatures within the range of about -50 to about mental fluorine and chlorine, and therefore processes em 600 C., depending on the particular tetrafluoride or hexa ploying it as a fluorinating agent are uneconomical. fluoride being provided. Thus sulfur tetrafluoride is obtain Now it has been found that chlorine monofluoride ed from the reaction of chlorine monofluoride with sulfur unexpectedly acts as a selective fluorinating agent over 65 or an appropriate sulfide at temperatures from about a wide temperature range and in the presence of a variety -50 to 100° C. while the hexafluoride is obtained at of metals. Furthermore, it is readily utilized in its gaseous temperatures above 100° C. The tetrafluorides of selenium state without dilution or other process controls, thereby and tellurium are provided over a temperature range of obviating the above-mentioned difficulties encountered -50 to 200° C., while the corresponding hexafluorides when chlorine trifluoride is employed in the preparation 70 are obtained at temperatures above 200° C. Tungsten of metal tetrafluorides and metal hexafluorides. Chlorine hexafluoride and molybdenum hexafluoride are formed 3,373,000 3 4 at any temperatures within the broad range, while tem Infrared analysis of a sample of the product revealed peratures above about 75° C. provide uranium hexa the characteristic tungsten hexafluoride bands at 6.85, 7.35, fluoride. 12.45, 14.00 and 14.10u. The process of this invention is carried out under sub Example 4 stantially anhydrous conditions in a sealed reaction vessel. A wide range of pressures can be employed, but it is Chlorine monofluoride (1.5 grams) was reacted with a feature of this invention that the process can be carried powdered molybdenum (1.0 gram) following the pro out advantageously around atmospheric pressure. The cedure of the previous examples. Liquid chlorine was desired tetrafluorides and hexafluorides are easily isolated vacuum distilled from the reaction mixture at -78 C. from the reaction mixture by conventional techniques such 10 Infrared analysis of the remaining gaseous product as vacuum distillation. showed molybdenum hexafluoride bands at 6.80, 7.25, The tetrafluorides and hexafluorides provided by the 12.85, 13.10 and 13.50a. process of this invention are known compounds having a wide variety of useful applications. Thus, the tetrafluorides Example 5 of sulfur, selenium and tellurium are well-known spe 15 Chlorine monofluoride (2.0 grams) was reacted with cialized fluorinating agents in the field of organo-fluorine tungsten trioxide (1.5 grams) following the procedure of chemistry. Sulfur hexafluoride is a commercially avail Example 1. Chlorine and oxygen were distilled from the able gaseous dielectric, commonly used in X-ray equip reaction mixture at -78 C. Infrared analysis of the ment, transformers, circuit breakers, wave guides and product showed characteristic tungsten hexafluoride bands other electrical and electronic equipment, and tellurium 20 at 6.85, 7.35, 12.45, 14.00 and 14.10u. hexafluoride possesses similar dielectric properties. The hexafluorides of tungsten and molybdenum can be reduced Example 6 in a process for obtaining high