Abstract: Starting from pegmatitic sand, the invention provides a method of purifying quartz sand, in which the amount of iron is reduced to less than 0.3 ppm, the amount of zircon to less than 1 ppm, and the amount of phosphor to less than 0.2 ppm. Gas nuclei are also removed. The method is carried out by washing with solution which contains at least 15% by weight of HF in water until at least 40% by weight of the quartz sand is dissolved, and washing with a solution which contains at least 20% by weight of HCl in water at a temperature from 5.degree. to 95.degree. C. for at least 30 minutes. In this method, the grains of the sand are freely suspended in an upward stream of the acid. Such quartz sand can suitably be used for the manufacture of very pure quartz glass for use in mercury discharge lamps, in glass fibers for telecommunication purposes (cladding glass), or in semiconductor arrangements.

Abstract: The invention relates to the selective and sequential reduction of halodisilanes by reacting these compounds at room temperature or below with trialkyltin hydrides or dialkyltin dihydrides without the use of free radical intermediates. The alkyltin hydrides selectively and sequentially reduce the Si-Cl, Si-Br or Si-I bonds while leaving intact the Si-Si and Si-F bonds present.

Abstract: A method is disclosed for increasing the fluosilicic acid (FSA) recovered from a wet process phosphoric acid manufacturing process. The filtrate obtained by washing a filter cake is pumped to a stripper and reacted with H.sub.2 SO.sub.4 to converting the dissolved FSA to gaseous SiF.sub.4. A defoamer is added to the acid-filtrate mixture to reduce the foam produced by the reaction and increase the amount of gaseous SiF.sub.4 recovered from the reaction. The gaseous SiF.sub.4 is recovered from the acid-filtrate reaction mixture and converted to FSA for commercial use.

Abstract: A method for the selective removal of boron halides and other Lewis acid-type impurities from silicon halides is disclosed. Treatment of contaminated silicon halides with siloxanes, which react with the impurities, allow the distillation of silicon halide which is virtually free from contamination within extremely low limits of detectability.

Abstract: Method for treating waste slurries containing solid impurities, e.g. in the form of metal chlorides, and silicon tetrachloride and trichlorosilane by evaporation and separation techniques to recover more of the silicon tetrachloride and trichlorosilane.

Abstract: Disclosed is a process for the cleavage of chlorosiloxanes in the gas phase at temperatures between 350 and 1450.degree. C. to form chlorosilanes and silicon dioxide as reaction products. The claimed process is preferably performed in the presence of metallic silicon or ferrosilicon. The procedure can be combined with the large-scale technical production of chlorosilanes by the chlorination or hydrochlorination of silicon. The inventive process makes it possible to perform the chlorination or hydrochlorination of silicon with the formation of chlorosilanes in an increased yield while reducing the formation of by-products.

Abstract: A method of separating HF from a mixture including HF and HCl is disclosed wherein the mixture is contacted with silica causing the HF to react with the silica to form SiF.sub.4. The concentration of HCl is increased thereby increasing the relative volatility of SiF.sub.4 /HCl. The SiF.sub.4 is then removed as an aqueous distillate. The concentration of the HCl can be increased by various methods including adding gaseous or concentrated HCl to the mixture or by distilling off a portion of the water to thereby increase the concentration of the HCl. This method provides an efficient method of removing SiF.sub.4 and HF from HCl.

Abstract: Chlorosilanes contaminated with boron-containing impurities can be purified by passing the chlorosilane vapor through a silica fixed bed. Normally the boron level in trichlorosilane is reduced by about 90-99+% by the use of this process. The capacities of the silica columns for the purification of trichlorosilane generally are in the range of 1500-2000 pounds trichlorosilane per pound of silica. The purified chlorosilane is particularly well suited for the production of polycrystalline silicon. Polycrystalline silicon containing 0.03 ppba (parts per billion atomic) has been prepared from trichlorosilane purified with this process.

Abstract: A silicon fiber which has a structure expressed by (SiF.sub.2).sub.n where n is greater than 1 and where the fiber may be 1 mm or less in diameter.

Abstract: A process for producing silicon tetrafluoride by hydrolysis of gases containing silicon fluoride, the hydrolysate being reacted with sodium fluoride, potassium fluoride and/or barium fluoride and the reaction product obtained decomposed thermally, thereby forming silicon tetrafluoride.

Abstract: The process of disproportionation of chlorosilanes in the presence of a dried catalyst which is dried by heating up to 200.degree. C. under vacuum starting from a water-containing anion exchange cross-linked resin matrix containing as a functional group and said resin matrix stable at temperatures up to about 200.degree. C. without separation of the functional group from the resin matrix to produce the disproportionated product of high purity, semiconductor grade, without any contamination from the catalyst.

Abstract: The invention relates to the preparation of silicon tetrachloride by reacting material containing SiO.sub.2 with chlorine in the presence of carbon and metal halides and especially chlorides of the fifth main or subsidiary group of the Periodic Table at temperatures in the range of from 500.degree. to 1200.degree. C. The material containing SiO.sub.2 has a BET surface area of at least 0.1 m.sup.2 /g and the carbon has a BET surface area of at least 0.5 m.sup.2 /g.

Abstract: A process is disclosed for recovering cobalt in a relatively pure form from an impure cobalt bearing material. The process involves digesting the material in hydrochloric acid to form a solution essentially all of the cobalt and some impurities and insoluble material containing the remainder of the impurities, separating the solution from the insolubles, adding an oxalate producing compound in an amount sufficient to subsequently convert essentially all of the cobalt to cobalt oxalate to the solution, adjusting the pH of the oxalate treated solution to from about 1.5 to about 2.0 with a base to precipitate the cobalt, and finally separating the precipitate from the resulting mother liquor.

Abstract: Irradiation of a siloxane derives SiO at low temperatures and forms the basis for a closed cycle reforming the siloxane that decomposes water to produce H.sub.2 and O.sub.

Abstract: A process for the beneficiation of an iron-containing material is carried out by first chlorinating the iron-containing material. Oxidation of ferrous chloride in the effluent gas from the chlorination is carried out under controlled conditions of oxygen supply so that more than 50% but less than 100% of the ferrous chloride is oxidized. In this way chlorine gas is separated from the process stream in a relatively pure form which can be utilized in a continuous process by recycle to another chlorination.

Abstract: Silane, SiH.sub.4, and diochlorosilane, particularly suitable for the preparation of silicon are readily obtained by disproportionating trichlorosilane to dichlorosilane and, ultimately silane by reacting:(a) a silane containing at least one Si-H bond, of the general formula R.sub.n H.sub.m SiX.sub.4-(n+m) wherein R represents an alkyl or aryl group, x represents a halogen or an alkoxy group, n is an integer equal to 0, 1, 2 or 3 and m is an integer equal to 1, 2 or 3, and(b) a catalyst system comprising an ionic inorganic salt of the formula M.sup.+ A.sup.- and a compound capable of at least partially dissociating the salt by complexing its cation M.sup.+.

Abstract: An improved process is disclosed for the high pressure plasma hydrogenation of silicon tetrachloride. Hydrogen and silicon tetrachloride are reacted in the presence of a high pressure plasma and further in the presence of a boron catalyst to form trichlorosilane and dichlorosilane. By adding the boron catalyst the overall conversion efficiency is increased and the dichlorosilane content in the reaction effluent is increased.

Abstract: A method for separating and recovering substantially pure aluminum, iron and silica from fly ash, a by-product of coal combustion, includes reacting the fly ash with aqueous fluosilicic acid and aqueous hydrogen fluoride at temperatures sufficiently high to form aqueous silicon fluoride vapor and fluorides and fluosilicate of aluminum and iron, separating the aluminum and iron fluorides and fluorosilicates from the aqueous silicon fluoride vapor, hydrolizing the silicon fluoride vapor to form silicon dioxide in substantially pure form and hydrogen fluoride, recovering and recycling the hydrogen fluoride for reuse in the process, and separating the aluminum and iron fluorides and fluosilicates from one another, and recovering substantially pure aluminum fluoride, substantially pure iron and other substantially pure metals, by electroplating or otherwise.

Abstract: Provided is an olefin-polymerization catalyst comprising the combination of the following components [I] and [II]:[I] a solid component obtained by intercontacting and reacting the following components (1) through (4):(1) a compound obtained by treating an oxide of an element of Groups II-IV in the Periodic Table with a compound represented by the general formula R.sup.1.sub.m Si(OR.sup.2).sub.n.sup.X.sub.4-m-n wherein R.sup.1 and R.sup.2 are each a hydrocarbon radical having 1 to 24 carbon atoms, a hydrocarbon radical containing oxygen, sulfur or nitrogen, or hydrogen, X is a halogen atom, m is 0.ltoreq.m<4 and n is 0.ltoreq.n.ltoreq.4, provided 0.ltoreq.m+n.ltoreq.4,(2) a reaction product obtained by the reaction of a magnesium halide and a compound represented by the general formula Me(OR.sup.3).sub.n.sup.X.sub.z-n wherein Me is an element of Groups I-VIII in the Periodic Table, with the limitation that silicon, titanium and vanadium are excluded, R.sup.

Abstract: A method for preparing a chlorosilane sample to enable colorimetric detection of the presence of minute amounts of boron impurities is provided. Detection of boron impurities below five parts per billion is contemplated.

Abstract: The invention provides a method for manufacturing boron-free SiO.sub.2 by purification of hexafluorosilicic acid. In this case, an aqueous solution of the boron-containing hexafluorosilicic acid is transferred to the organic phase by treatment with organic compounds immiscible with water and subsequently the organic phase is converted to boron-free hexafluorosilicic acid by means of fluid-fluid extraction in the alkaline or acid medium. Particularly, complex-forming compounds, such as tri-iso-octylamine, and organic solvents, such as xylol, are used as organic compounds. The method produces SiO.sub.2 with a boron content of less than 1 ppm and is usable for manufacturing silicon for solar cells.

Abstract: Perchloroethylene, phosgene, and silicon tetrachloride are coproduced by passing vaporous carbon tetrachloride into contact with porous silica at a temperature of 800.degree. to 950.degree. C. The silica is disposed as a bed of granules have a surface area of from 0.1 to 30 m.sup.2 /g. It should be at least 90 percent pure and free of elemental carbon. Molecular oxygen and water vapor are excluded. The carbon tetrachloride is supplied in a proportion more than two mols per mol of silica consumed.

Abstract: A process is provided for recovering fluorine from dilute hydrofluoric acid solutions, such as waste scrubber solution obtained in the treatment of phosphates. The dilute solution is used to react with oxidic titanium material to solubilize the contained titanium and subsequently form, in the presence of potassium ions, crystals of K.sub.2 TiF.sub.6 which are commercially useful as a grain-refining agent in the manufacture of aluminum alloys.

Abstract: Silicon tetrachloride is effectively and efficiently produced at a relatively low temperature and at a high yield by (1) feeding a mixture of a silicon dioxide containing substance and carbon to the top of a reactor in which a reaction mixture forms a downwardly flowing moving bed, (2) feeding gaseous boron trichloride to an intermediate portion of the reactor, (3) feeding gaseous chlorine to a portion of the reactor located below the boron trichloride feed portion, and (4) feeding an inert gas to a portion of the reactor located below the chlorine feed portion, whereby a silicon tetrachloride formation reaction is carried out in the moving bed and the formed silicon tetrachloride is recovered from a gas mixture discharged from the top of the reactor.

Abstract: Silicon tetrafluoride gas is produced by reacting aqueous fluosilicic acid and concentrated sulfuric acid in a vertical column. The fluosilicic acid is fed to an intermediate point of the column and the sulfuric acid to the top of the column. Silicon dioxide, both dissolved and suspended, is fed with fluosilicic acid in some forms so as to produce a by-product acid substantially free of silicon and fluoride values.

Abstract: There is described a method for extracting fluoride ions from a nuclear fuel solution which comprises treating said solution with a solid phase from hydrated silica, such as silica gel and/or silicic acid, to bind the fluorine to the silicium, said solid phase then being separated from said solution.

Abstract: SiF.sub.4 gas containing oxygen-containing silicofluoride(s) typified by (SiF.sub.3).sub.2 O as impurity can be refined to extremely high purity by making the SiF.sub.4 gas contact with HF in the presence of a liquid medium having strong affinity for water such as sulfuric acid or phosphoric acid. By reaction with HF, the impurity such as (SiF.sub.3).sub.2 O is converted to SiF.sub.4, while the liquid medium absorbs water formed by the reaction to thereby prevent a reverse reaction between SiF.sub.4 and H.sub.2 O to form (SiF.sub.3).sub.2 O.

Abstract: A process for preparing high purity silicon metal from Na.sub.2 SiF.sub.6 (sodium fluosilicate). The sodium fluosilicate is heated to decomposition temperature to form NaF, which retains most of the impurities, and gaseous SiF.sub.4. The SiF.sub.4 is then reduced by the bomb reduction method using a reductant having a low packing density.

Abstract: A process is disclosed for the purification of trichlorosilane and other silicon source materials. Trace impurities of boron and phosphorous are removed from trichlorosilane or dichlorosilane by reacting small amounts of oxygen with the trichlorosilane or dichlorosilane at a temperature between about 60.degree. C. and 300.degree. C. The oxygen reacts with the Si--H bond in HSiCl.sub.3 or H.sub.2 SiCl.sub.2 to form a "SiOH" species which in turn complexes impurities such as BCl.sub.3 or PCl.sub.3 present in the chlorosilane. Purification of the chlorosilane is then easily accomplished during a subsequent distillation step which separates the purified chlorosilane from the less volatile complexed boron or phosphorous compounds.

Abstract: Silicon tetrafluoride is reacted with sodium hydride in a cyclic ether reaction medium such as tetrahydrofuran or 1,4-dioxane or in dimethoxyethane. Sodium aluminum hydride is dissolved in the solvent and catalyzes the reaction in amounts of 4-25%, by weight of combined sodium hydride and sodium aluminum hydride.

Abstract: The dismutation/redistribution of halogenosilanes into silane is carried out by contacting at least one halogenosilane comprising at least one Si-H function with a compound comprising at least one .alpha.-oxoamine group, then by contacting the products of such reaction with a compound also comprising at least one .alpha.-oxoamine group, to selectively dissolve all products of reaction except for the silane therein, and then separating the desired silane therefrom.

Abstract: Polyvinyl cyclic tertiary amine hydrocarbons having nitrogen in the ring as catalysts for chlorosilane disproportionation. The catalysts are suitable for continuous flow processes redistributing any one or more of SiHCl.sub.3, SiH.sub.2 Cl.sub.2, and SiH.sub.3 Cl.

Abstract: A process of preparing silicon tetrafluoride by introducing hydrogen fluoride gas into a dispersion of powdery silicon oxide material, which needs not to be pure SiO.sub.2, in sulfuric acid not lower than 65% in the concentration of H.sub.2 SO.sub.4. The reaction takes place even at room temperature. By using amorphous silicon oxide material, the rate of reaction can be enhanced with better yield. Preferably, the concentration of H.sub.2 SO.sub.4 in the liquid phase of the reaction system is maintained above 80% to obtain SiF.sub.4 containing little (SiF.sub.3).sub.2 O.

Abstract: What is disclosed is a method of forming silicon from the degradation of polychlorosilanes, a method of coating a substrate with said silicon and a product of said coating method. The method of forming silicon consists essentially of pyrolyzing said polychlorosilanes in an inert atmosphere or in a vacuum at a temperature of 500.degree. C. to 1450.degree. C.

Abstract: Tri- and dichlorosilanes formed by hydrogenation in the course of the reaction of metallurgical silicon, hydrogen and recycle silicon tetrachloride are employed as feed into a separation column arrangement of sequential separation columns and redistribution reactors which processes the feed into ultrahigh purity silane and recycle silicon tetrachloride. A slip stream is removed from the bottom of two sequential columns and added to the recycle silicon tetrachloride process stream causing impurities in the slip streams to be subjected to reactions in the hydrogenation step whereby waste materials can be formed and readily separated.

Abstract: A method for preparing cyclotetrasiloxane, aliphatic chlorides and/or acyl chlorides from a chlorosilane and an acyloxy compound is disclosed. The chlorosilane and the acyloxy compound may be present as substantially equimolar amounts of separate compounds or they may be present in the same molecule in equimolar amounts. The reactants are merely heated sufficiently, with or without a soluble halide salt catalyst, to form the products. Advantageously this method can provide cyclotetrasiloxanes having water-sensitive radicals such as silicon-bonded chlorine atoms and/or silicon-bonded acyl chloride radicals.

Abstract: A method for preparing cyclotetrasiloxane, aliphatic chlorides and/or acyl chlorides from a cyclotrisiloxane, a chlorosilane and an acyloxy compound is disclosed. The chlorosilane and the acyloxy compound may be present as substantially equimolar amounts of separate compounds or they may be present in the same molecule in equimolar amounts. The reactants are merely heated sufficiently, with or without a soluble halide salt catalyst, to form the products. Advantageously this method can provide cyclotetrasiloxanes having water-sensitive radicals such as silicon-bonded chlorine atoms and/or silicon-bonded acyl chloride radicals. This method also provides a method for preparing cyclotetrasiloxanes having either one type of siloxane unit (non-mixed cyclotetrasiloxanes) or more than one type of siloxane unit (mixed cyclotetrasiloxanes).

Abstract: The chlorides of elements of Groups III, IV and V of the Periodic Table, such as, boron trichloride, silicon tetrachloride, zirconium tetrachloride and vanadium tetrachloride are prepared by heating activated carbon particles having a supported aqueous solution of compounds of the elements of Groups III, IV and V of the Periodic Table thereon at a temperature of from 300.degree. through 1000.degree. C. and, then, reacting the resultant activated carbon particles with chlorine.

Abstract: Raw wet phosphoric acid which has been extracted from the solvent and regenerated with water according to the process of U.S. Pat. No. 3,607,029 is subsequently subjected to treatment with steam or a hot gas to afford concentrated phosphoric acid with a F/P.sub.2 O.sub.5 ratio of less than 10 ppm. The acid obtained is suitable for use in the food industry.

Abstract: Hydrofluoric acid is recovered from fluosilicic acid by reacting fluosilicic acid with sodium sulfate to form sodium fluosilicate. The sodium fluosilicate is reacted with a sodium-containing compound to form an alkaline aqueous slurry comprising silica and dissolved sodium fluoride. The reaction occurs under such conditions that the slurry contains precipitated amorphous silica. The precipitated amorphous silica is separated from the alkaline aqueous slurry leaving an aqueous solution of sodium fluoride. Sodium fluoride is recovered from the aqueous solution and reacted with sulfuric acid to produce hydrogen fluoride.

Abstract: A hydrolysis method of purifying silicon tetrachloride is shown that reduces losses in optical fibers made from silica produced therefrom. Water is added to impure liquid silicon tetrachloride, which forms a gel which is then separated from the remaining SiCl.sub.4. Metal impurities, OH-containing impurities, and SiHCl.sub.3 are removed by this process. In a preferred embodiment, the water is added by bubbling a wet gas through the SiCl.sub.4. A residual amount of OH containing impurities and HCl is left after the hydrolysis, which impurities may be further removed by a refluxing technique.

Abstract: Alkali metal fluosilicate is used as an intermediate reactant in a process for the production of hydrochloric acid and an alkali metal sulfate from sulfuric acid and an alkali metal chloride. The process includes the reaction of alkali metal fluosilicate with sulfuric acid to produce alkali metal sulfate and H.sub.2 SiF.sub.6, the latter being reacted with alkali metal chloride to produce HCl and alkali metal fluosilicate. The resulting hydrochloric acid may be converted to anhydrous hydrogen chloride. A continuous process for the production of hydrochloric acid and of alkali metal sulfate such as potassium sulfate from an alkali metal fluosilicate material is also disclosed.

Abstract: A fluosilicate material is added to a suspension of lime in water heated to a temperature at or near its boiling point to form a solid calcium fluoride product in which the silicon present in the fluosilicate material is in chemical combination with calcium. The amount of calcium in the suspension is in excess of stoichiometric for conversion of CaF.sub.2 of all of the fluorine in the fluosilicate and is sufficient to form chemical compounds of calcium and silicon from silicon in the fluosilicate.

Abstract: A process is described for the production of dense metastable phases of carbon which have characteristics similar to diamond. Particulates of the metastable carbon are produced by reacting silicon carbide or a silicon carbide precursor, such as a silane or silicon metal, with a fluorocarbon, such as carbon tetrafluoride at a temperature greater than about 800.degree. C. A preferred range is from about 900.degree. C. to 1200.degree. C. The reaction may be carried out in a high voltage electrical diacharge, or other plasma, or in a furnace. The presence of a "promoter" metal, such as nickel and iron, increases the reaction rate and the quantity of the metastable carbon phases. Relatively large quantities of these diamond-like particulates are produced, and their properties are such as to make them useful for many of the same applications for which commercial diamonds are utilized. They are also useful in numerous high temperature applications.

Abstract: Hydrofluoric acid is recovered from fluosilicic acid by reacting fluosilicic acid with sodium sulfate to form sodium fluosilicate. The sodium fluosilicate is reacted with sodium hydroxide to form a first slurry having a pH of from about 11 to about 14, the first slurry containing sodium metasilicate and precipitated sodium fluoride. Sodium fluoride is recovered from the first slurry leaving a first solution which is reacted with sodium fluosilicate or fluosilicic acid or both to form a second slurry comprising silica and dissolved sodium fluoride. The reaction occurs under such conditions that the second slurry contains precipitated amorphous silica. The precipitated amorphous silica is separated from the second slurry leaving a second solution of sodium fluoride. Sodium fluoride is recovered from the second solution. Recovered sodium fluoride is reacted with sulfuric acid to produce hydrogen fluoride.

Abstract: Dry granular silicon acid, an organic polyol and a silicon tetrahalide are mixed simultaneously to produce an organic halosilicon acid resinous product.

Abstract: Crude sodium hexafluorosilicate containing gypsum and various metal phosphates is refined into highly pure and sufficiently large crystals. First, the crude fluorosilicate is treated with a sodium chloride solution to dissolve gypsum. Then the solid phase is reconstituted into an aqueous slurry in which the concentration of Na is limited. This slurry is acidified and maintained at temperatures not lower than 80.degree. C. with continued stirring to cause recrystallization of sodium hexafluorosilicate.

Abstract: Crude sodium hexafluorosilicate containing gypsum as a principal impurity can be refined economically with a minimized loss of fluorine by first making the crude fluorosilicate in the form of an aqueous slurry react with an alkali metal compound such as sodium carbonate or sodium hydroxide to form a soluble sulfate, and then treating the solid component of the reaction product with an acid solution in the presence of sodium ion, preferably at elevated temperatures near boiling point, to form a soluble calcium salt and crystallize sodium hexafluorosilicate. Sea water may be used both as the aqueous medium for the slurry in the first step and as the source of the sodium ions in the second step.

Abstract: A new and useful pigment is prepared by reacting an inorganic silicofluoride and an inorganic calcium compound selected from the group consisting of calcium oxide, calcium hydroxide and calcium carbonate. The product is especially useful in protective coating compositions which are applied to metals in order to enhance adherence to and corrosion resistance of metals such as aluminum, zinc, magnesium, steel and alloys of said metals.

Abstract: Co-current absorber for recovering inorganic compounds from plant effluents, particularly useful for recovery of fluorine values as low phosphorus fluosilicic acid from phosphate plant effluents. Improved co-current absorber utilizing multiple cyclonic entrainment separators, co-current flow and renewed droplet surfaces.