CFC alternatives

HCFCs, originally developed as a less harmful class of CFC alternatives, will be phased out by 2020 in industrial countries, with some provisions for servicing equipment to 2030. Developing countries are to freeze consumption by 2016 (base year 2015) and phase out use by 2040. 

Ishikawa, N Ed The Technologies Coping with C h C/Hulon Issue I CFC Alternatives and Recovery/Ret ycle Technologies (Jap ) CMC Tokyo ... 

J. C.Ravensberg, D.J.Alexander, D.Borkhataria, G.M.Rusch, and B.Schmit. 2000. Human safely and pharmacokinetics of the CFC alternative propellants HFC 134a (1,1,1,2-tetrafluoroethane) and HFC 227 (1,1,1,2,3,3,3-heptafluoropropane) following whole-body exposure. Regul. Toxicol. Pharmacol. 32 22-35. 

Midgley, 1998). It might be expected that the tropospheric concentrations of these CFC alternatives would therefore increase, and this is indeed the case (e.g., see Montzka et al., 1993, 1994, 1996a, 1996b Irion et al., 1994 Schauffler et al., 1995 Simmonds et al., 1998b and Miller et al., 1998). 

Energy and Global Warming Impacts of CFC Alternative Technologies, AFEAS Report, U.S. Department of Energy, Washington, D.C., 1991, pp. 

P. M. Norling, "Accessing Technology from External Sources Using External Sources for CFC Alternatives," Industrial Research Institute Roundtable, Washington, D.C., July 28,1994. 

Testing of a number of the chlorofluorocarbon (CFC) alternatives indicates that most of these chemicals have low acute toxicity, and low to moderate chronic toxicity. Some chemicals, originally proposed as alternatives, have been dropped from consid-... 

A comprehensive assessment of the environmental impact of any CFC alternative should be made in weighing its relative benefits and liabihties. The magnitude, impact, and disposition of all waste sneams should be evaluated. Differences in safety and toxicity need to be considered. Energy requirements may vary substantially, resulting in environmental as well as economic impact. 

As 2-chloro-l,l,l-trifluoroethane (HCFC-133b) and 2,2-dichIoro-l,l,l-trifluoroethane (HCFC-123b) are industrially produced CFC alternatives, the original academic oxidative reaction to produce them is now of technical importance 7 a thermal oxidation method for 2.2-dichloro-l,1,l-trifluoroethane that is attractive from an industrial point of view has been developed7 and high yields of trifluoroacetic acid were obtained in a continuous process in addition, minor products were characterized. The acid is formed by continuous hydrolysis of the reaction mixture.7... 

The Technologies Coping with CFCjHalon Issue I. CFC Alternatives and Recovery Recycle Technologies (Published in Japanese) Ishikawa, N., Ed. CMC Tokyo, 1988. 

In this section, we briefly summarize current synthetic methods to CFC alternatives. More comprehensive reviews with many examples have been published... 

The major source for atmospheric FCO is expected to be photolysis of CF20 and CFCIO, but the advent of hydrofluorocarbons, such as CF3CFH2 (HFC-134a), as CFC-alternatives now provides an additional source by means of hydrogen-atom abstraction from CHFO by OH, F or Cl. Yet another source is addition of atomic fluorine to carbon monoxide. 

S. K. Fischer, P. J. jHughes, P. D. Fairchild, C. L. Kusik, J. T. Dieckmann, E. M. McMahon and N. Hobday, Energy and Global Warming Impacts of CFC Alternative Technologies, Alternative Fluorocarbons Environmental Acceptability Study, Washington, D. C., 1991. 

The development of CFC alternatives has focused on non-chlorinated compounds, such as hydrofluorocarbons (HFCs), which have similar physical properties, but break down in the lower atmosphere.110 111 Consequently, hydrodechlorination is a simple method for the production of HFCs and also for destruction of CFCs108,109,112-114. Palladium is unique among the catalytic metals for its activity and selectivity in this process,102-108,115,116 but using Pd-Au/SiC>2 (Pd Au = 60 40) increased the selectivity for difluoromethane from difluorodichloromethane (CFC-12) shown by Pd/Si02 at 453 K from 40 to 95%.109,112-114... 

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