Patented Nov. 1, 1938 2,135,460

UNITED STATES PATENT OFFICE 2,135,460 PREPARATION OF BORON FLUOR DE Donald J. Loder, Wilmington, Del, assignor to E. I. du Pont de Nemours & Company, Will mington, Del, a corporation of Delaware No Drawing. Application August 5, 1936, Serial No. 94,337 8 Claims. (C. 23-88) This invention relates to a process for the After the removal of the by distillation or preparation of boron- compounds and other means there remains the metal halide more particularly to the preparation of boron boron-halogen complex. If the metal halide em . ployed is an alkaline earth halide or an alkaline An object of the present invention is to provide earth Salt or oxide, such, for example, as 5 a process for the separation of constituents from carbonate, and the like which re complexes containing the same and more partic act with a boronhalide to form an alkaline earth ularly to the separation of boron fluoride from halide, the boron-halogen constituent can be ob its complex. Another object of the invention is tained in a substantially anhydrous form by 0 to provide a process wherein a boron-halogen simply heating the complex to a temperature of 10 containing compound is separated from its com from 150 to 300° C. plex with water. A further object of the inven The metal halides which have been found par tion is to provide a process wherein an alkaline ticularly well adapted for replacing water from earth metal halide is added to a complex, com complexes containing them and a boron-halogen 5 pound, mixture, or solution of water and boron containing compound include, for example, cal- 5 fluoride; the water is removed and the boron cium fluoride, zinc fluoride, aluminum fluoride, fluoride recovered in the anhydrous form. A aluminum chloride, cuprous chloride, lead chlo more Specific object of the invention is to provide ride, iron chloride, tin chloride, , a process wherein complexes containing boron barium chloride, and analogous metal , 20, fluoride, and water may be so treated that the chlorides, bromides, and iodides. While metal. 20 anhydrous boron fluoride is freed from the water. halides will replace the water in a complex con Other objects and advantages of the invention taining it and a boron-halogen constituent, such will hereinafter appear. as borontrifluoride, I have found in addition that I have found that if a boron-halogen-water the alkaline earth halides and more especially complex, compound, mixture, or solution is the alkaline earth fluorides form a complex or 25 treated with a metal halide the water will be set Compound with boron fluoride from which the free, leaving a compound formed between the boron fluoride or other analogous, easily volatil metal halide and the boron-halogen constituent. ized, halogen-containing compound may be re Moreover, if alkaline earth metal halides are covered by heating. The alkaline earth halides, 30 employed, the alkaline earth metal halide-boron such, for example, as the fluorides, chlorides, and 30 halide reaction product will, upon heating, give bromides of calcium, barium or strontium, and up the boron halide it contains leaving the alka salts thereof which react with boron halides to line earth halide as a residue. Accordingly when form alkaline earth, halides likewise have the employing alkaline earth metal halides it is ability to not only displace the Water from its possible to recover the boron-halogen-contain complex with a boron halide, but also to permit 35 ing constituent from water. the recovery of the boron halide from the alka Boron fluoride, and analogous boron-halogen line earthhalide. Compounds, form with water and other com The advantages of my process for the prepara pounds an association that has been generally tion of anhydrous volatile halides from complexes Called in the literature a "complex.' In this containing them can be readily appreciated. 40 Specification and the claims appended thereto. For example, hydrated boron fluoride can be this association will be referred to as a “complex' prepared by interacting anhydrous hydrofluoric altho this term will be understood to include acid with solid orthoboric acid, boric anhydrides Water and a boron halogen compound whether, or borates. The reaction may be effected by the they are present as a solution, mixture, com addition of the anhydrous to 45 pound, or complex, or whatever may be the man the solid orthoboric acid, boric anhydride or ner of their association. borate which comprises essentially a hydrated Generally, my process is effected in the follow . To this product calcium flu ing manner; a metal halide is added to the com oride is added, water is liberated and can be re 50 plex containing water and a boron-halogen Con moved by a simple heating operation to a tem- 50 stitueat and apparently due to the fact that perature of about 110° C. thereby leaving as a the boron-halogen constituent reacts more readily residue a compound containing calcium fluoride with the metal halide, a complex is preferentially and boron fluoride. By heating this substan formed between the metal halide and the boron tially anhydrous material to a higher tempera halogen constituent, thereby freeing the water. ture, say form 170 to 500 C., usually a tempera- 55 2 a,185,460 ture of 250 C. is sufficient for satisfactory recov densing agent can be recovered and used over ery, the boron fluoride can be driven of in a sub and over again the sole loss in catalyst occurring stantially anhydrous form leaving calcium fluo from usual physical operating causes rather than ride as the residue. from loss due to byproduct formation. I shall now illustrate by Way of examples meth From a consideration of the above specification ods of preparing boron fluoride from various com it will be appreciated that many changes may be plexes containing it but it will be distinctly under made in the process herein described without Stood that the invention will not be limited spe departing from the Scope of the inventio or sac cifically to the details of the examples. rificing any of the advantages that may be de 10 Eacample 1.-12.8 grams of (H2O)3.BF3 (1. rived therefrom. 10 mol) is treated with 45 grams CaF2 (.58 mol) in I claim: a flask attached to a short fractionation column. 1. In a process for the preparation of boron The mixture is heated in an oil bath to not more fluoride and steps which comprise reacting a than 150 C. at one atmosphere pressure, during metal halide with a water-boron fluoride complex 5 Which the water and a small amount of boron and subsequently separating from the resulting 5 fluoride is distilled out. The distillation can be metal halide-boron fluoride complex the boron effected at atmospheric or reduced pressures. fluoride. v. Subsequent heating of the solid residue, which 2. A process for the preparation of boron fluo consists mainly of Ca (BF4)2, to temperatures be ride which comprises reacting a compound se 20 tween 300° C., and 500 C, resulted in the evo lected from the group consisting of an alkaline lution of boron fluoride according to the equa earth halide and an alkaline earth salt that will tion: Ca (BF4)2->CaF2--2BFs. Temperatures be form a halide when reacted with a boron halogen low and above those given may be used but the compound with a Water-bOron fluoride complex range given is preferred. and subsequently removing from the resulting 25 EacGimple 2-51.9 grams of (H2O)2BE (5 mol) complex the boron fluoride in a substantially 25 is treated With 25 grams NaF (.6 mol) in a flask anhydrous form. attached to a short fractionation column. The 3. A process for the preparation of a boron mixture is heated in an oil bath to approxi fluoride which comprises reacting a boron fluoride mately 150 C., during which time water is associated with water with calcium fluoride, heat 30 evolved. The distillation can be conducted at ing and evaporating the Water from the result 30 atmospheric or reduced pressures. The BF ing mixture, and subsequently, at a higher tem can be recovered by heating the solid, which con perature driving off the boron fluoride. sists mainly of NaBF4, to higher temperatures. 4. A process for the preparation of boron fluo Eacample 3. About 60.9 grams (H2O)3.BF3 (.5 ride which comprises reacting a complex of water : 35 mol) was treated with 60 grams NaCl (1 mol) in and boron fluoride with calcium fluoride, heating 35 a flask attached to a short fractionating column. and evaporating the Water from the resulting The mixture was heated in an oil bath to not mixture, and subsequently, at a higher tempera more than 150 C., to drive of the water. The ture driving of the boron fluoride. distillation can be carried out at atmospheric or 5. A process for the preparation of boron tri 40 reduced pressures. fluoride which comprises reacting a water-boron The boron fluoride can be separated from the trifluoride complex with calcium fluoride, heat solid residue (NaCl.BFs) by further heating to ing and removing all the water, and subsequently, from 300-500° C. at a higher temperature, driving off the boroa If desired the condensate obtained by heating trifluoride. 45 the mixture containing the water, boron fluoride, 6. A process for the preparation of boron tri and a metal halide can be distilled to give a resi fluoride which comprises reacting a mixture con due containing substantially all of the boron taining one mol of a boron trifluoride water com fluoride originally present in the condensate. plex with approximately one-half mol of calcium This residue may be combined with the next fluoride, heating and removing the water and 50 batch of water-boron fluoride to be treated there subsequently, at a higher temperature, driving by providing a method of substantially complete of the boron trifluoride. - recovery of the boron fluoride. 7. In a process for the preparation of a boron My process is particularly well adapted for luoride the steps which comprise reacting a com use in Separation of a boron-halogen constituent pound selected from the group consisting of an 55 from addition compounds containing it and water alkaline earth metal fluoride and an alkaline 55 and more particularly such addition compounds compound that Will form a fluoride when reacted in which the halogen constituent is a highly vola with a boron fluoride, with a Water-boron fluoride tile halide, such, for example, as the fluorides, complex and subsequently separating from the chlorides, bromides, and iodides of boron. Cal resulting metal halide-boron fluoride complex the 60 cium fluoride is particulary well adapted for use boror fluoride. 60 in a process for Separating not only, the water 8. In a process for the preparation of a boron from a Water-boron fluoride complex, but to fluoride compound the steps which comprise add separate the calcium fluoride-boron fluoride ing an alkaline earth metal halide to a Water complex formed into boron fluoride and calcium boron fluoride complex and subsequently sepa 65 fluoride. It Will be appreciated that when en rating from the resulting alkaline earth metal 5 ploying boron fluoride as a condensing agent in halide-borOn fluoride complex the boron fluoride organic acid reactions the use of calcium fluoride by heat. is particularly useful for the reason that the con DONAD J, ODER. CERTIFICATE OF coRRECTION. Patent No. 2,135,260. November 1, 1938. DONALD J. LODER. It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, second column, line 13, claiml, for the word "and" read the ; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office Signed and sealed this 20th day of December, A. D. l958. Hen ry War Arsdale

(Seal) Acting Commissioner of Patents,