Hydrofluorocarbons HFCs

The 1990 Clean Air Act regulates the production and use of CFCs, hydrochlorocarbons, hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbon (HFC) substitutes. CFC and halon (Class I substances) usage is to be phased out in steps until total phaseout occurs on January 1,... 

In this sequence the Cl also acts as a catalyst and two molecules are destroyed. It is estimated that before the Cl is finally removed from the atmosphere in 1—2 yr by precipitation, each Cl atom will have destroyed approximately 100,000 molecules (60). The estimated O -depletion potential of some common CFCs, hydrofluorocarbons, HFCs, and hydrochlorofluorocarbons, HCFCs, are presented in Table 10. The O -depletion potential is defined as the ratio of the emission rate of a compound required to produce a steady-state depletion of 1% to the amount of CFC-11 required to produce the 1% depletion. The halons, bromochlorofluorocarbons or bromofluorocarbons that are widely used in fire extinguishers, are also ozone-depleting compounds. Although halon emissions, and thus the atmospheric concentrations, are much lower than the most common CFCs, halons are of concern because they are from three to ten times more destmctive to O, than the CFCs. 

Table 2. Physical Properties of Aliphatic Hydrofluorocarbons (HFCs) ...

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. 

Hexamethylphosphoramide (HMPT), 185 HFBPA-based poly(arylene ether)s, 362 HFCs. See Hydrofluorocarbons (HFCs) High-impact polystyrene (HIPS), 219 High-melting polymers, 33 High-melting-point fiber-forming polyesters, 19... 

Wallington TJ, OJ Nielsen (2002) Atmospberic chemistry and environmental impact of hydrofluorocarbons (HFCs) and hydrofluoroethers (HFEs). Handbook Environ Chem 3N 85-102. 

Very powerful greenhouse gases that are not naturally occurring include hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6), which are generated in a variety of industrial processes. 

Submarine Exposure Guidance Levels for Selected Hydrofluorocarbons HFC-236fa, HFC-23, and HFC-404a (2000)... 

Radicals derived from hydrofluorocarbons (HFCs) as well as hydrofluo-roethers (HFE) are often destabilized with respect to the methyl radical [51, 57,68,70,79-82], The low stability of these radicals implies that the C-H bonds in the corresponding closed shell parent compounds are comparatively strong and thus rather unreactive towards attack of oxidizing reagents. This latter property is of outstanding importance for the use of these compounds in a variety of technical applications, in which thermally stable, non-oxidizable, non-flammable compounds are needed. However, with respect to the environmental fate of these compounds high C-H bond energies... 

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. 

The task facing CFC producers, therefore, is to develop alternatives with all the positive properties associated with CFCs, but with no adverse effect on the ozone layer. The new compounds are hydrofluorocarbons (HFCs). They... 

The study of several hydrofluorocarbons (HFC) and fluorocarbons (FC) and their binary mixtures that have no ozone-depleting ability is being carried out in the frame-... 

Chlorinated alkanes were used in the production of chlorofluoroalkanes (CFCs).188 Because of their atmospheric ozone-depleting ability, the use of CFCs is being phased out. Hydrochlorofluorocarbons, containing at least one hydrogen atom (HCFCs), are introduced as safer alternatives.189 190 In the long run, however, hydrofluorocarbons (HFCs) will be the ideal substitutes to CFCs.190... 

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