1852
PASHKEVICH et al.
Table 4. Composition of gaseous products of reaction of
fluorine with graphite in the steady-state mode as influ-
enced by temperature. Contact time 3 s, fluorinating mix-
ture composition 40% F2 + 60% N2
ate to perform the decomposition of the synthesized
polyfluoride in the absence of fluorine in the decom-
position zone.
CONCLUSIONS
CF4
C2F6
C2F4
C3F8
C3F6 C4F10
T, C
(1) The major gaseous products of graphite fluori-
nation are CF , C F , C F , and C F ; the amounts
vol %
4
2 6
3 8
4 10
of C F and C F do not exceed 2.0 wt %.
2 4
3 6
580
590
75.43 13.9
75.65 14.18
0.02
0.06
7.37
6.72
0.57
0.4
2.49
2.99
(2) At 550 600 C, the composition of the reaction
products is as follows (wt %): 40 45 CF , 20 25
4
C F , 20 25 C F , and 10 15 C F .
2 6
3 8
4 10
increased, the product composition changes: the
(3) Synthesis of CF , C F , C F , and C F
4 10
4
2 6
3 8
amount of CF increases, and that of the other fluoro-
4
involves intermediate formation of (CF ) followed by
x n
carbons decreases.
its thermal decomposition.
This experimental fact can be explained as follows.
Two reaction zones can be distinguished in the reac-
tion unit: the zone of the fluorine uptake in which
solid carbon polyfluoride is formed and the zone of
the carbon polyfluoride decomposition yielding gase-
ous perfluorocarbons. In a reactor with a circulating
fluidized bed, the zone of decomposition of carbon
polyfluoride occupies the whole reactor volume,
whereas the zone of formation of carbon polyfluoride
occupies only its part. These zones overlap (Fig. 3),
and thermal decomposition of carbon polyfluoride
occurs in a medium containing gaseous fluorine.
(4) At temperatures above 550 C, solid carbon
polyfluoride does not accumulate in the laboratory
reactor.
(5) To increase the yield of perfluorocarbons con-
taining more than one carbon atom, it is appropriate
to perform the decomposition of (CF ) with x
under the isothermal conditions in the absence of
fluorine.
1
x n
REFERENCES
1. Maksimov, B.N., Barabanov, V.G., Serushkin, I.L.,
et al., Promyshlennye ftororganicheskie produkty:
Spravochnoe izdanie (Commercial Organofluorine
Products: Handbook), St. Petersburg: Khimiya, 1996.
As the fluorine concentration in the fluorinating
mixture is increased, the height of the zone of the
fluorine uptake increases. Apparently, under the ex-
perimental conditions the gaseous fluorocarbons react
with fluorine to give lower-molecular-weight perflu-
oro compounds. Therefore, at increased fluorine con-
2. RF Patent 2117652.
3. Trukshin, I.G., Vishnyakov, V.M., and Fedorova, S.G.,
Abstracts of Papers, 2-ya Mezhdunarodnaya konferen-
tsiya Khimiya, tekhnologiya i primenenie ftorsoedi-
nenii v promyshlennosti (2nd Int. Conf. Chemistry,
Technology, and Industrial Applications of Fluorine
Compounds ), St. Petersburg (Russia), September 23
26, 1997, p. 35.
tent in the fluorinating mixture, the yield of CF is
4
higher.
Thus, to increase the yield of perfluorocarbons
containing more than one carbon atom, it is appropri-
(a)
(b)
4. Asovich, V.S., Kornilov, V.V., Kostyaev, R.A., et al.,
Abstracts of Papers, 1-ya Mezhdunarodnaya konferen-
tsiya Khimiya, tekhnologiya i primenenie ftorsoedi-
nenii v promyshlennosti (1st Int. Conf. Chemistry,
Technology, and Industrial Applications of Fluorine
Compounds ), St. Petersburg (Russia), May 30
June 3, 1994, p. 15.
5. Kaurova, G.I., Nikiforov, B.L., Nekrashevich, A.Yu.,
et al., Abstracts of Papers, 3-ya Mezhdunarodnaya
konferentsiya Khimiya, tekhnologiya i primenenie
ftorsoedinenii v promyshlennosti (3rd Int. Conf.
Chemistry, Technology, and Industrial Applications
of Fluorine Compounds ), St. Petersburg (Russia),
June 6 9, 2001, p. 155.
Fig. 3. Scheme of the distribution of the reaction zones
in the reactor channel: (1) zone of fluorine uptake and
(2) zone of decomposition of carbon polyfluoride. Fluorine
concentration, %: (a) 20 and (b) 40.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 77 No. 11 2004