Refrigerants hydrofluorocarbons

Magnesium forms a highly stable fluoride film and, consequently, has good resistance to hot fluorine gas, HF solutions, and fluorinated hydrocarbons, such as refrigerants. Hydrofluorocarbons have recently been found to not only be noncorrosive at room and elevated temperatures, but very... 

High-purity grades of trichloroethylene are used as a feedstock in the synthesis of the refrigerant hydrofluorocarbon 134a. In this process, the trichloroethylene molecule is destroyed to form the new fluorinated compound. It also is used in the production of such chlorinated end products as polychlorinated aliphatics and flame-retardant chemicals. In polyvinyl chloride (PVC) manufacture, trichloroethylene is used as a molecular weight control agent. 

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. 

A leader in the refrigerants industry, we manufacture and supply customers with economical chlorofluorocarbon (CFC) replacements and non-ozone depleting hydrofluorocarbon (HFC) refrigerants for automotive, home, commercial and transportation uses. In the Americas and Asia, you can find these products under the Genetron name and in Europe and the Middle East under Honeywell Refrigerants. 

As you know, most countries are phasing out certain refrigerants to lessen damage to the ozone layer. The chemicals being phased out are chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). Replacements are hydrofluorocarbons (HFCs) and certain blends. The DuPont web site (www.dupont.com) gives the handy Table I of recommended replacement refrigerants for various applications. 

Standley LJ, TL Bott (1998) Trifluoroacetate, an atmospheric breakdown product of hydrofluorocarbon refrigerants biomolecular fate in aquatic organisms. Environ Sci Technol 32 469-475. 

Chloroflnorocarbons have been replaced with hydrofluorocarbons in refrigerators and air conditioners becanse of CEC s potential to —... 

Substitutes for CFCs are available, but none provide a completely satisfactory alternative. Hydrofluorocarbons (HFCs) are organic compounds that behave like CFCs, but do not harm the ozone layer. For example, 1,1,1,2-tetrafluoroethane and 1,1-difluoroethane are HFCs that can be used to replace CFCs in refrigerators and air conditioners. Unfortunately, HFCs are also greenhouse gases. 

This would have results in 77 hits from l,2-[propadiene, 1,1,2,2-tetrafluoro-] with a boiling point of —38 °C, to [propane, l,l,l,2,3,3,3-heptafluoro-2-(trifluoromethyl)-] with a boiling point of 0 °C. Out of 77 hits, 49 of them contain elements that include B, Si, N, P, As, O, S, Cl, Br, and I, and perhaps too toxic to be considered as refrigerants seriously. There are 11 hits that are hydrocarbons, such as butane, which would be too flammable to be considered. Perhaps we would eliminate the six hits that have double or triple bonds, as they tend to be less stable and could polymerize. The remaining ones are all hydrofluorocarbons (HECs) without chlorine, and the prime candidates are C2H2E4, C3H3E5, and C4F10. 

Hydrofluorocarbon 134a (1,1,1,2-tetrafluoroethane) is used as a replacement for Freon 12 (see Problem 4.2) for refrigeration applications. (Why is such a replacement necessary and what is the advantage of HFC-134a from an environmental... 

Refrigeration technology is moving into a new phase with the introduction of hydrofluorocarbons that combine the safety of chlorofluorocarbons with a much lower environmental impact The considerable care bemg taken to choose the new refrigerants under the close scrutiny of the public and regulatory bodies will ensure that the new products will benefit mankind for years to come... 

Within the family of halocarbon refrigerants are compounds that contain chlorine, fluorine, and carbon, the chlorofluorocarbons (CFCs). Hydrochlorofluorocarbons (HFCs) contain chlorine, fluorine, carbon and hydrogen. Halocarbons that contain only carbon, fluorine, and hydrogen are called hydrofluorocarbons (HFCs). 

Various other workers have reported on the determination of volatile organic compounds in soils [186,187] and landfill soils [188]. Soil fumigants such as methyl bromide have also been determined by this technique [189]. Trifluoroacetic acid is a breakdown product of hydrofluorocarbons and hydrochlorofluorocarbon refrigerant products in the atmosphere and, as such, due to the known toxicity of trifluoroacetic acid, it is important to be able to determine it in the atmosphere, water and in soil from an environmental point of view [190]. In this method the trifluoroacetic acid is extracted from the soil sample by sulfuric acid and methanol, which is then followed by the derivatisation of it to the methyl ester. The highly volatile methyl ester is then analysed with a recovery of 87% using headspace gas chromatography. Levels of trifluoroacetic acid in soil down to 0.2 ng/g can be determined by the procedure. 

In the early 1990s, chlorofluorocarbon refrigerants and propellants were largely replaced by hydrofluorocarbons and hydrochlorofluorocarbons in order to reduce stratospheric ozone depletion. The hydrochlorofluorocarbons and hydrofluorocarbons, unlike the older chlorofluorocarbons, are unstable in the... 

Tetrafluoroethane is a hydrofluorocarbon (HFC) or hydro-fluoroalkane (HFA) aerosol propellant (contains hydrogen, fluorine, and carbon) as contrasted to a CFC (chlorine, fluorine, and carbon). The lack of chlorine in the molecule and the presence of hydrogen reduces the ozone depletion activity to practically zero. Hence tetrafluoroethane can be considered as an alternative to CFCs in the formulation of metered-dose inhalers (MDIs). It has replaced CFC-12 as a refrigerant since it has essentially the same vapor pressure. Its very low Kauri-butanol value and solubility parameter indicate that it is not a good solvent for the commonly used surfactants for MDIs. Sorbitan trioleate, sorbitan sesquioleate, oleic acid, and soya lecithin show limited solubility in tetrafluoroethane and the amount of surfactant that actually dissolves may not be sufficient to keep a drug readily dispersed. 

Alkyl halides are widely used as refrigerants. Unhl the late 1980s, alkyl halides called chlorofluorocarbons (CFCs) were widely used in refrigerators and air-conditioning systems. Because of their potential to damage Earth s ozone layer, CFCs have been replaced by HFCs, hydrofluorocarbons, which contain only hydrogen and fluorine atoms bonded to carbon. One of the more common HFCs is 1,1,2-trifluoroethane, also called R134a. 

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