Hydrogen fluoride production

Production. Global hydrogen fluoride production capacity in 1992 was estimated to be 875,000 metric tons. An additional 204,000 metric tons was used captively for production of aluminum fluoride. Worldwide capacity is tabulated in Table 5 (38). Pricing for hydrogen fluoride in 1990 was about 1.52/kg (39). 

North America accounts for about 38% of the worldwide hydrogen fluoride production and 52% of the captive aluminum fluoride production. Table 6 (38) summarizes North American capacity for hydrogen fluoride as weU as this captive capacity for aluminum fluoride production. In North America, HF is produced in the United States, Canada, and Mexico, but represents a single market, as weU over 90% of the consumption is in the United States. 

A.queous and yinhjdrous Hydrogen Fluoride product specifications, AUied-Signal Inc., Morristown, N.J., 1991. 

Hydrogen Fluoride Product Data Brochure, Pemi valt Chemical Corporation, Philadelpliia, July 1979. 

The reaction of solid fluorspar with liquid sulfuric acid produces a solid (calcium sulfate) and a gaseous (hydrogen fluoride) product. The reaction passes through a paste-like phase. Many reactor modifications have been developed to attain an optimal reaction in this phase. The aim is thorough mixing of this phase, which is achieved by internal fittings in the rotary tube (e.g. paddles) or by kneading the reaction mixture in a kneader. 

Silicon tetrafluoride is a colourless gas, b.p. 203 K, the molecule having, like the tetrahalides of carbon, a tetrahedral covalent structure. It reacts with water to form hydrated silica (silica gel, see p. 186) and hexafluorosilicic acid, the latter product being obtained by a reaction between the hydrogen fluoride produced and excess silicon tetrafluoride ... 

Anhydrous hydrogen fluoride (as distinct from an aqueous solution of hydrofluoric acid) does not attack silica or glass. It reacts with metals to give fluorides, for example with heated iron the anhydrous iron(II) fluoride is formed the same product is obtained by displacement of chlorine from iron(II) chloride ... 

By far the largest use of hydrogen fluoride is in the manufacture of fluorocarbons which find a wide variety of uses including refrigerants, aerosol propellants and anaesthetics. Hydrogen fluoride is also used in the manufacture of synthetic cryolite, Na3AIFg, and the production of enriched uranium. 

The cr-complexes (iv) are thus the intermediates corresponding to the substitution process of hydrogen exchange. Those for some other substitutions have also been isolated in particular, benzylidyne trifluoride reacts with nitryl fluoride and boron trifluoride at — ioo°C to give a yellow complex. Above — 50 °C the latter decomposes to hydrogen fluoride, boron trifluoride, and an almost quantitative yield of tn-nitrobenzylidyne trifluoride. The latter is the normal product of nitrating benzylidyne trifluoride, and the complex is formulated as... 

Secondary smoke is produced mosdy by the condensation of water in humid or cold air. The presence of hydrogen chloride or hydrogen fluoride in the combustion products increases the extent and rate of condensation. Composition modifications to reduce primary smoke may reduce secondary smoke to some extent, but complete elimination is unlikely. The relatively small amount of smoke produced in gun firings by modem nitrocellulose propellants, although undesirable, is acceptable (102—109). 

Fluorine reacts with ammonia in the presence of ammonium acid fluoride to give nitrogen trifluoride, NF. This compound can be used as a fluorine source in the high power hydrogen fluoride—deuterium fluoride (HF/DF) chemical lasers and in the production of microelectronic siUcon-based components. 

Production of hydrogen fluoride from reaction of Cap2 with sulfuric acid is the largest user of fluorspar and accounts for approximately 60—65% of total U.S. consumption. The principal uses of hydrogen fluoride are ia the manufacture of aluminum fluoride and synthetic cryoHte for the Hall aluminum process and fluoropolymers and chlorofluorocarbons that are used as refrigerants, solvents, aerosols (qv), and ia plastics. Because of the concern that chlorofluorocarbons cause upper atmosphere ozone depletion, these compounds are being replaced by hydrochlorofluorocarbons and hydrofluorocarbons. 

The balance of hydrogen fluoride is used ia appHcations such as stainless steel pickling inorganic fluoride production, alkylation (qv), uranium enrichment, and fluorine production. Hydrogen fluoride is used to convert uranium oxide to UF which then reacts with elemental fluorine to produce volatile UF. ... 

The manufacture of cryoHte is commonly iategrated with the production of alumina hydrate and aluminum trifluoride. The iatermediate stream of sodium aluminate from the Bayer alumina hydrate process can be used along with aqueous hydrofluoric acid, hydrogen fluoride kiln gases, or hydrogen fluoride-rich effluent from dry-process aluminum trifluoride manufacture. 

Properties. Antimony pentafluoride [7783-70-2], SbF, is a colorless, hygroscopic, very viscous liquid that fumes ia air. Its viscosity at 20°C is 460 mPa-s(=cP) which is very close to the value for glycerol. The polymerization of high purity SbF at ambient temperature can be prevented by addition of 1% anhydrous hydrogen fluoride, which can be removed by distillation prior to the use of SbF. The pure product melts at 7°C (11), boils at 142.7°C,... 

Economic Aspects. Pertinent statistics on the U.S. production and consumption of fluorspar are given in Table 4. For many years the United States has rehed on imports for more than 80% of fluorspar needs. The principal sources are Mexico, China, and the Repubflc of South Africa. Imports from Mexico have declined in part because Mexican export regulations favor domestic conversion of fluorspar to hydrogen fluoride for export to the United States. 

Analytical Methods. Fluorite is readily identified by its crystal shape, usually simple cubes or interpenetrating twins, by its prominent octahedral cleavage, its relative softness, and the production of hydrogen fluoride when treated with sulfuric acid, evidenced by etching of glass. The presence of fluorite in ore specimens, or when associated with other fluorine-containing minerals, may be deterrnined by x-ray diffraction. 

Specifications, Shipping, and Analysis. Hydrogen fluoride is shipped in bulk in tank cars (specification 112S400W) and tank tmcks (specification MC312). A small volume of overseas business is shipped in ISO tanks. Bulk shipments are made of anhydrous HF as well as 70% aqueous solutions. A small amount of aqueous solution may be shipped as 50%. Cars and tmcks used for anhydrous HF transport are of carbon steel constmction. It is possible to ship 70% aqueous in steel from a corrosion standpoint however, mbber lining is commonly used to eliminate iron pickup, which is detrimental to product quaUty in a number of appHcations. Hydrogen fluoride of less than 60% strength must always be shipped in lined containers. 

Anhydrous hydrogen fluoride is also available in cylinders, and aqueous hydrogen fluoride, either 50% or 70%, is also shipped in polyethylene bottles and carboys. Typical product specifications and analysis methods are given in Table 4. 

Asian production of hydrogen fluoride is concentrated in Japan. The Japanese are leaders in the production of high quaHty HP. Hashimoto has the capacity for 3000 t/yr of ultrahigh purity product. Por the future, increased production in many of the developing Asian nations is likely. 

Fluorspar Supply. Production costs of hydrogen fluoride are heavily dependent on raw materials, particularly fluorspar, and significant changes have occurred in this area. Identified world fluorspar resources amount to approximately 400 x 10 metric tons of fluorspar (40). Of these 400 X 10 t, however, only 243 x 10 t are considered reserves and an additional 93 x 10 t is considered reserve base, ie, recoverable at higher market... 

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