CFC replacements

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. 

Graepel, P. and D.J.Alexander. 1991. CFC replacements safety testing, approval for use in metered dose inhalers. J. Aerosol Med. 4 193-200. 

Perfluorocarbons are chemically inert, are nonflammable and have low toxici-ties. Unlike the halofluorocarbons, perfluorocarbons are not ozone-depleting and have been used as CFC replacements [7], However, perfluorocarbons have very long lifetimes in the atmosphere (>2000 years) [8] and this has consequences for their use as solvents since any process has to take into account the fact that any loss of solvent to the atmosphere is extremely undesirable. 

In short, a number of the rate constants for the reactions of OH with HFCs, HCFCs, and other potential CFC replacements such as partially fluorinated... 

TABLE 13.7 Typical Organic Products of the Tropospheric Oxidation of Some of the CFC Replacement Compounds... 

The effects on human health of trifluoroacetic acid (TFA) from the oxidation of HFC-134a, halothane (l,l,l-trifluoro-2-bromo-2-chloroethane, used as an anesthetic), and some of the other CFC replacements, such as HCFC-123 and HCFC-124, have been of some... 

Kanakidou et al. (1995) have carried out three-dimensional modeling studies of the global tropospheric fates of HFC-134a and other HCFCs using projected emissions and the chemistry described earlier. Table 13.9 shows their calculated lifetimes for some of the CFC replacements with respect to oxida-... 

The reason that the ODPs of these CFC replacements are much smaller than those of the original CFCs is the presence of an abstractable hydrogen with which OH can react. However, this also means that they can also contribute to ozone formation in the troposphere. Hayman and Derwent (1997) have used their photochemical trajectory model to calculate tropospheric ozone-forming potentials of some of these CFC replacements. Table 13.10 summarizes these relative ozone-forming potentials, expressed taking that for ethene as 100. Clearly, although they react in the troposphere, their contribution to tropospheric ozone formation is expected to be very small. 

While we have focused here on CFC replacements, similar chemistry applies to replacements for the bromine-containing halons. For example, CF2 BrH is a potential halon substitute that will react with OH in the troposphere (DeMore et al., 1997). Through the subsequent reaction with 02 and then NO, the alkoxy radical CF2BrO is formed. This decomposes via scission of the weak C-Br bond to form COF2 (Bilde et al., 1996). 

While the tropospheric concentrations of CFCs and halons are not increasing as rapidly in the past due to controls outlined in the Montreal Protocol and subsequent amendments, those of the CFC replacements are increasing. However, due to their different structures and reactivities, the ozone depletion potentials associated with these compounds are significantly less that those of the compounds they replace. This truly represents a success story in terms of application of atmospheric chemistry to the development of effective control strategies. 

Hayman, G. D., and R. G. Derwent, Atmospheric Chemical Reactivity and Ozone-Forming Potentials of Potential CFC Replacements, Enriron. Sci. Techno/., 31, 327-336 (1997). 

Wallington, T. J., D. R. Worsnop, O. J. Nielsen, J. Sehested, W. J. Debruyn, and J. A. Shorter, The Environmental Impact of CFC Replacements—HFCs and HCFCs, Enriron. Sci. Technol., 28, 320A-326A (1994a). 

Chlorofluorocarbon (CFC) replacements have recently been used for their lower stability and because they have carbon-hydrogen bonds, which means that their atmospheric lifetime is expected to be much shorter than those of CFCs. The adsorption properties of l,l,2-trichloro-l,2,2-trifluoroethane (CFC 113) and its replacement compounds, l,l-dichloro-2,2,2-trifluoroethane (HCFC123), 1,1-dichloro-l-fluoroethane (HCFC141b), and l,l-dichloro-l,2,2,3,3-pentafluoropropane (HCFC225ca) on four kinds of activated carbons were investigated. The adsorption isotherms of inhalational anesthetics (halothane, chloroform, enflurane, isoflurane, and methoxyflurane) on the activated carbon were measured to evaluate the action mechanism of inhalational anesthesia. The anesthesia of CFC replacements can be estimated by the Freundlich constant N of the adsorption isotherms (Tanada et al., 1997). 

Cooper, D.L., Cunningham, T.P., Allan, N.L., McCulloch, A. (1992) Tropospheric lifetimes of potential CFC replacements Rate coefficients for reaction with the hydroxyl radical. Atmos. Enrivon. 26A, 133-1334. 

The CFC replacements need to be nontoxic, nonflammable and have significantly lower, or zero ozone depletion potentials. Many organic- and aqueous-based systems, that do not contain chlorine or fluorine, have been developed for some applications while others use hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs). Unlike hydrocarbon catalysis, the presence of hydrogen, chlorine and fluorine in the same molecule creates a very large number of... 

Drucker s examples are health, dining and food, care for environment, class structure and feminism. There are many chemical examples here particularly under care for the environment e.g. CFCs replacements, unleaded petrol, City diesel, solar electricity and fuel cells. 

Supercritical fluids were identified in early 1989 as a possible CFC replacement for certain niche applications at Honeywell Space Systems. At that time there was very limited data on either the application of supercritical fluids for precision cleaning or compatibility studies with materials common to the aerospace industry. 

The impact of deposition on global distribution has been noted for the CFC replacements hydro-chlorofluorocarbons (HCFCs), the chlorinated solvents tetrachloroethene (PCE), and trichloro-ethene (TCE), as these compounds undergo gas phase oxidation and photochemical degradation, resulting in the formation of carbonyl halides (e.g., CCI2O) and haloacetyl halides (e.g., bromo-, chloro-, and fluoroacetates). As these compounds are polar and water soluble, they are transported via aerosols, rain, and fog, which impacts their tropospheric lifetime and depositional fluxes (Rompp et al., 2001 de Bmyn et al., 1995). It is not clear whether and to what extent there is evidence of latitudinal fractionation of these compounds. 

The three surfactants commonly used in chlorofluro-carbon (CFC)-based MDI formulations are insoluble in the CFC-replacement propellants, hydrofluoroalk-ane (HFA) 134a and HFA 227. Possible formulation alternatives involve the use of an adjuvant such as ethanol to aid dissolution of the surfactant or a novel surfactant. Several companies have investigated novel materials among which are fluorosurfactants, poly-oxyethylenes and drugs coated with surfactant. ... 

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