Chlorofluorocarbon alternatives development

Apart from these synthetically impractical examples of hydrolysis of chloro-fluorocarbons, there are useful applications converting some chlorofluorocarbons to fluonnated carboxylic acids. As an alternative to the use of the highly corrosive fuming sulfuric acid, normally used in batch processes, a continuous hydrolytic process for converting 1,1,1-trichlorotrifluoroethane (CFC-113a), available by isomerization of CFC-113 [44], to trifluoroacetic acid has been developed [45] (equation 45). It uses metal chloride catalysts deposited on high-surface-area supports Unreacted CFC-113a can be recycled. 

Hydrofluorocarbons (HFCs), including 1,1,1,2-tetrafluoroethane (HFC-134a), have been developed as alternatives to chlorofluorocarbons (CFCs), which are known to contribute to the breakdown of ozone to oxygen in the stratosphere. HFCs do not contribute to the destruction of stratospheric ozone, but some HFCs have global warming potential. They primarily serve as replacements for CFCs in refrig... 

In this chapter, recent advances in our understanding of catalytic fluorination under heterogeneous conditions are surveyed from the standpoint of catalyst properties, including developments based on the use of mixed metal fluorides having different structural types, and reaction mechanisms. Much of the newer work has been the result of the need to replace chlorofluorocarbons (CFCs) by alternatives, hydrofluorocarbons (HFCs) or, more controversially, hydrochlorofluorocarbons (HCFCs), following adoption of the Montreal and successor Protocols [2,3]. Where relevant, aspects of catalytic hydrogenolysis, where fluorides have been used as replacement supports in the conventional palladium/carbon catalysts, and isomerization reactions are included. 

The most significant developments in metered-dose inhaler technology to occur since the early 1990s have been the introduction of hydrofluoroalkane (HFA) systems as alternatives to chlorofluorocarbon (CFC) systems [174]. This has largely been caused by the link between the use of CFC systems and ozone depletion in the upper atmosphere [152,175]. Albuterol and beclomethasone have been reformulated in HFA products, but as yet the CFC products are still subject to an annually renewable medical exemption. The Food and Drug Administration has recently published its position on alternative propellant formulations, which should initiate the phase-out of CFCs [176]. In the meantime, a number of generic CFC products of albuterol have been manufactured. The opportunity for reformulation of products as they come of patent is likely to increase research and development in this area in the near future. New formulation opportunities will also arise from these developments, including solutions [177], micellar [178,179], and microemulsion [180]. 

Methods for determining TPH in aqueous samples are discussed above in Section 3.3.1. The overall method includes sample collection and storage, extraction, and analysis steps. Sampling strategy is an important step in the overall process. Care must be taken to assure that the samples collected are representative of the environmental medium and that they are collected without contamination. There are numerous modifications of the EPA, American Public Health Association (APHA), and American Society for Testing and Materials (ASTM) methods discussed above. Most involve alternate extraction methods developed to improve overall method performance for TPH or replacement of the chlorofluorocarbon solvents. SPE techniques have been applied to water samples (Schrynemeeckers 1993). Solvent extraction methods with hexane (Murray and Lockhart 1981 Picer and Picer 1993) or methylene chloride (Mushrush et al. 1994) have been reported as well. 

For the last two decades, attention has been focused on redressing the ozone depletion in the earth s protective layer. It is believed that chlorine radicals dissociated from chlorofluorocarbons (CFCs), upon irradiation of sun s UV in the stratosphere, promotes the ozone depletion. Hence, in addition to development of CFC alternatives there is an urgent need for the safe disposal of CFCs. Several processes such as pyrolysis, incineration, photocatalysis, oxidative destruction over metal oxide or zeolite catalysts and destruction at very high temperatures ( by plasma technique ) are reported in the literature for the disposal of CFCs[ 1-5]. But all these processes yield harmful products like CO, HF/F2 etc. Catalytic conversion of chlorinated organics in presence of hydrogen seems to be a better technique as it yields either hydrofluorocarbons(HFCs) or hydrochlorofluorocarbons(HCFCs) whose ozone depletion potential is either zero or very low and yet most of these products act as CFC alternatives. 

K. Ahmed, Technological Development and Pollution Abatement. A Study of How Enterprises Are Finding Alternatives to Chlorofluorocarbons, Technical Paper No. 271, Wmld Bank, Washington, DC (1995). 

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