1070-4272/01/7407-1151$25.00C2001 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 74, No. 7, 2001, pp. 1151!1155. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 7,
2001, pp. 1120!1124.
Original Russian Text Copyright + 2001 by Pashkevich, Mukhortov, Alekseev, Asovich, Rozhdestvenskaya.
AND INDUSTRIAL ORGANIC CHEMISTRY
Gas-Phase Fluorination of Fluoroethanes
with Elemental Fluorine
D. S. Pashkevich, D. A. Mukhortov, Yu. I. Alekseev,
V. S. Asovich, and O. V. Rozhdestvenskaya
Prikladnaya Khimiya Russian Scientific Center, St. Petersburg, Russia
Received May 22, 2000; in final form, February 2001
Abstract-Scientific basis for industrial gas-phase fluorination of fluoroethanes with elemental fluorine
allowing production of higher-fluorinated fluoroethanes from lower-fluorinated compounds is developed.
Fluorine is extremely reactive and its reactions are
highly exothermic. Therefore, at present preparation
of fluorinated organic compounds using fluorine has
almost no industrial application.
Fluorine is commercially available, and its utili-
zation for production of valuable fluorinated prod-
ucts is rather urgent. These products include a series
of fluoroethanes, e.g., 1,1-difluoroethane (DFE,
R152a), 1,1,2-trifluoroethane (R143a), 1,1,1,2-tetra-
fluoroethane (TFE, R134a), pentafluoroethane (PFE,
R125), and hexafluoroethane (HFE, R116), which are
widely used as refrigerants, propellants, fire ex-
tinguishers, reagents for plasmochemical production
of superlarge integrated circuits, gas dielectrics, etc.
. The world’s consumption of these compounds
reaches tens thousands tons per year.
The modern industrial process for production of
fluoroethanes is based on catalytic fluorination of
fluorochloroethanes and ethylenes with hydrogen
fluoride. The initial chlorinated materials used in this
case are ozone-dangerous, and, in accordance with the
Montreal Protocol, their production should be ter-
minated. Moreover, this process yields significant
amounts of hydrogen chloride (by-product) and re-
quires periodical replacement and utilization of the
spent chromium3manganese fluoride catalyst. Thus,
development of alternative procedures for synthesis of
fluoroethanes is urgent. One of such procedures can
be synthesis of higher-fluorinated ethanes by gas-
phase fluorination of lower-fluorinated compounds
with elemental fluorine.
The first data on the gas-phase fluorination are
given in . In particular, the gas-phase fluorina-
tion of ethane with fluorine was studied and the pos-
sibility of preparing HFE was confirmed. However,
the corresponding industrial procedures still are not
The kinetics of 1,1,1,2-TFE fluorination was
studied in ; it was found that industrial synthesis in
the steady-state thermal mode is unsuitable. As shown
in , industrial fluorination of fluoroethanes should
be carried out in the nonstationary thermal mode
(wave or combustion modes). In this case fluoro-
methanes are not formed in noticeable amounts at the
initial concentration of fluorine lower than 30 vol %.
Development of the industrial process for fluorina-
tion of fluoroethanes requires understanding of the
principles of scaling the reactor for gas-phase fluorina-
tion operating in the wave mode.
One of the features of combustion is that the reac-
tion profile in a laminar torch comprises tenth frac-
tions of millimeter. In tunnel jets conversion of com-
pounds in the turbulent torch reaches 80% within the
length of five diameters of the crater . Such a struc-
ture of the turbulent torch suggests that, if the thermal
radiation of the gas is negligible, the main conversion
of compounds proceeds at temperature fairly close to
adiabatic. In this case the composition of the products
of 1,1,1,2-TFE gas-phase fluorination in the mode of a
steady-state self-propagating wave should be indepen-
dent of the diameter of the reaction unit and of the gas
flow mode (without taking into account thermal de-
composition of fluoroethanes outside the fluorination
zone). To verify this assumption, we performed a
series of tests with reactors of various diameters.
The tests we carried out using changeable tubes
with an internal diameter of 10, 4, 3, and 2 mm at
flow rates of the cold reaction mixture providing con-
stant velocities of the gas flow. To eliminate the