United States Patent Office Patented May 9, 1961 1
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2,983,583 United States Patent Office Patented May 9, 1961 1. 2 of the tube and drained into the hot Zone. Most of the 2,983,583 silicon tetrachloride was recovered unchanged. 0.43 millimole of BCls were obtained. Based on the SiCl4 METHOD OF PREPARNG BORON TRICHLORDE consumed, the yield of boron trichloride was about 70% FROM BORIC OXDE AND SILICON TETRA 5 based on Equation 2. CHLORDE Example III-In another experiment, conducted in William H. Schechter, Bradford Woods, Pa., assignor to a manner similar to those above, 10.0 millimoles of S2Cl2 Callery Chemical Company, Pittsburgh, Pa., a corpor was heated with 5.04 millimoles of BOs at 800° C. for ration of Pennsylvania 10 minutes. Boron trichloride and sulfur dioxide were O obtained in the volatile products, and a yellow solid, be No Drawing. Filed Mar. 28, 1958, Ser. No. 725,471 lieved to be sulfur, formed in the tube. 2 Claims. (CI. 23-205) Example IV.-9.32 millimoles of PC were passed over excess BO heated to 800° C. for 10 minutes. The vola This invention relates to the preparation of boron tri 15 tile products formed were analyzed with an infrared spec chloride and more particularly to the preparation of trometer and found to be predominantly BCl3. Some boron trichloride from boric oxide and non-metallic orange colored solids also formed in the reactor during chlorides. the reaction. The non-metallic chlorides which have been found Boron trichloride, BC, is used in several processes to useful in the practice of this invention are all volatile prepare other boron compounds, as a catalyst, and, in 20 liquids, at ordinary temperatures, and their reaction with general, is regarded as a basic boron compound. There molten boric oxide may be carried out in any manner or fore, although several methods of preparing it are known, apparatus suitable for effecting high-temperature reac there is continuing interest in the boron chemical in tions. in the laboratory, it has been found convenient dustry directed toward the finding of new and improved to carry out the reactions in sealed tubes on a batch basis, preparative methods. 25 as described in connection with the examples given above. It is an object of this invention to provide a new meth In larger scale applications, it may be desirable to use od of preparing boron trichloride from boric oxide and other methods, such as stirred pots, flow systems, or certain non-metallic liquid chlorides. fluidized bed techniques wherein the chloride is entrained Other objects will become apparent from the following on an inert gas carrier. Similarly, inert solvents or dis specification and claims. - 80 persion media may be used if desired. This invention is based upon the discovery that boric The boron trichloride which is formed in the foregoing oxide will react at elevated temperatures with certain reactions is often obtained as a mixture with unreacted non-metallic chlorides to produce boron trichloride. The chloride, as well as with other volatile products in some chlorides which have been found to react with boric oxide instances. The boron trichloride may be separated and in this manner include carbon tetrachloride, silicon tetra 85 recovered by fractional condensation, selective absorp chloride, phosphorus trichloride, and sulfur monochloride. tion, gas chromatography, or any other method which Although the reaction mechanism in each instance is not may ordinarily be used to separate such mixtures. fully understood, the primary reactions are believed to According to the provisions of the patent statutes, I correspond to the following equations: have explained the principle and mode of practicing my 40 invention, have described what I now consider to be its best embodiments. However, I desire to have it under stood that within the scope of the appended claims, the described.invention may be practiced otherwise than as specifically The reaction in each case takes place upon contacting 45 I claim: the reactants at elevated temperatures. The temperatures 1. A method of preparing boron trichloride, BC, which may be used depend to some extent upon the par which comprises contacting boric oxide, B2O3, with silicon ticular chloride used, and further, upon the method used tetrachloride, SiCl4, while maintaining said boric oxide to carry out the reaction, i.e., static system, flow system, at a temperature from about 600° C. to about 1000 C., or other. In general, however, temperatures of from 50 and recovering the boron trichloride formed. about 600 C. to 1000 C. may be used. 2. A method according to claim 1 in which the tem The following examples illustrate the invention de perature is about 800 C. scribed herein. Example I.-An Alundum boat containing 5.29 milli 55 References Cited in the file of this patent moles of B2O3 was placed in one end of Wycor tube, UNITED STATES PATENTS which was then placed in a furnace heated to 700° C. 9.85 millimoles of CCI was allowed to reflux over the 2,097,482 Weber ----------------- Nov. 2, 1937 heated boric oxide for 15 minutes. The volatile portions 2,369,212 Cooper ---------------- Feb. 13, 1945 of the reaction mixture were then distilled out of the tube 2,369,214 Cooper ---------------- Feb. 13, 1945 and analyzed. Substantial amounts of boron trichloride 60 2,446,221 Ferguson --------------- Aug. 3, 1948 were identified in the reaction products by infrared ab 2,770,526 Lander ---------------- Nov. 13, 1956 sorption analysis. The overall reaction appears to be more complex than is indicated by Equation 1 above, OTHER REFERENCES since in addition to carbon dioxide, some carbon mon- 65 Mellor: "Comprehensive Treatise on Inorganic and oxide and phosgene were found among the products, Theoretical Chemistry," vol. 8, pp. 1011 and 1016, 1928; along with unreacted carbon tetrachloride. vol. 5, 1924, p. 130. Example II-A tube containing 9.57 millimoles of Weber: "Uber das Bortrichlorid,” pp. 10 and 11, 1934. BO was charged with 7.93 millimoles of SiCl4. The Friend: Textbook of Inorganic Chemistry (1926), lower portion of the tube, containing the B2O3, was main to Charles Griffin and Co., Ltd., London, vol. 5, pages 95, tained at 800° C. for 15 minutes, whereupon the SiCl4 96, 195 and 196; vol. 6, part 2, page 93; vol. 7, part 2, continually vaporized, condensed on the cooler portion page 79. .