Page 226 - Chemical and process design handbook

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CHLOROFLUOROCARBONS

Chlorofluorocarbons (CFCs) are manufactured by reacting hydrogen fluoride
and carbon tetrachloride in the presence of a partially fluorinated antimony
pentachloride catalyst in a continuous, liquid-phase process.
2CCl + 3HF + SbCl F → CC1 F + CC1 F+ 3HCl
4 2 2 2 2 3
The products dichlorodifluoromethane and trichlorofluoromethane are
also known as CFC-12 and CFC-11, respectively.
There are common abbreviations and a numbering system for chlorofluo-
rocarbons and related compounds. The original nomenclature developed in
the 1930s is still employed and uses three digits. When the first digit is 0, it is
dropped. The first digit is the number of carbon atoms minus 1, the second
digit is the number of hydrogen atoms plus 1, and the third digit is the num-
ber of fluorine atoms. All other atoms filling the four valences of each carbon
are chlorine atoms. Important nonhydrogen-containing chlorofluorocarbons
®
(Freons ) are:
CCl F (CFC-12) CCl F (CFC-11) CCl FCClF (CFC-113)
2 2 3 2 2
Halons, a closely related type of chemical that also contains bromine, are
used as fire retardants. Numbering here is more straightforward: first digit,
number of carbons; second digit, number of fluorine atoms; third digit, num-
ber of chlorines; and fourth digit, number of bromines.
Common Halons are: Halon 1211 (CF BrCl), 1301 (CF Br), and Halon
2 3
2402 (C F Br).
2 4
Compared to the same size hydrocarbons, fluorocarbons have higher
volatility and lower boiling points, unusual for halides. They are less reac-
tive, more compressible, and more thermally stable than hydrocarbons.
They also have low flammability and odor.
Common uses for the fluorocarbons are as refrigerants, foam-blowing
agents, solvents, and fluoropolymers. Recent environmental legislation
has restricted or banned the use of chlorofluorocarbons.

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