Synthesis of Hexafluoroacetone by Catalytic Oxidation of Hexafluoropropylene

Article abstract of DOI:10.1023/A:1012741226948

Oxidation of hexafluoropropylene with molecular oxygen in a fixed bed of a catalyst (activated carbon promoted with alkali metal fluorides) was studied.

Full text of DOI:10.1023/A:1012741226948

Russian Journal of Applied Chemistry, Vol. 74, No. 1, 2001, pp. 170 171. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 1,
2001, pp. 164 165.
Original Russian Text Copyright
2001 by Igumnov, Lekontseva, Shipigusev, Gomzyakova, Soshin.
BRIEF
COMMUNICATIONS
Synthesis of Hexafluoroacetone by Catalytic Oxidation
of Hexafluoropropylene
S. M. Igumnov, G. I. Lekontseva, A. A. Shipigusev,
O. D. Gomzyakova, and V. A. Soshin
Perm Branch, Prikladnaya Khimiya Russian Scientific Center, Perm, Russia
Received May 17, 1999; in final form, August 2000
Abstract Oxidation of hexafluoropropylene with molecular oxygen in a fixed bed of a catalyst (activated
carbon promoted with alkali metal fluorides) was studied.
Catalytic oxidation of hexafluoropropylene (HFP)
is a most promising route to hexafluoroacetone (HFA).
In known procedures oxidation is carried out using as
catalysts oxides of tin, iron, and indium [1] or fluori-
nated aluminum oxide [2], which in some cases is
activated with water (0.001 0.003 mol per mole HFP
[3]). Catalytic oxidation of HFP in the presence of
palladium, platinum, rhodium, ruthenium, and iridium
deposited on activated carbon was studied in [4].
The required catalysts were prepared using a
BAU-A brand crushed activated carbon with a particle
size of 1.5 2.0 mm. In the tests the content of alkali
metal fluorides was varied within 5 60 wt %; in this
range the yield of HFA was almost constant. It was
found that at the content of alkali metal fluoride
smaller than 5 wt % the yield of HFA decreases,
whereas the increase to more than 60 wt % is prac-
tically unfeasible. Oxidation at temperatures higher
than 300 C and the HFP : O molar ratio greater than
1 : 10 causes more profound oxidation of HFP yield-
In this work we found that the oxidation of HFP
to HFA proceeds on a catalyst (activated carbon pro-
moted with alkali metal fluorides NaF, KF, CsF, or
2
ing predominantly COF .
2
RbF) at 50 300 C and the HFP : O molar ratio of
1 : (0.1 10.0):
The catalyst activity remains stable for 1500 h.
During this period the particle size also remains con-
stant (1.5 2.0 mm). At longer operation the catalysts
in question partially lose their activity because of
changes in the grain-size distribution. The conditions
of catalytic oxidation and experimental results are
listed in the table.
2
C
/MF,
act
CF3CF=CF2 + 1/2O2
(CF3)2C=O. (1)
The reaction probably proceeds with intermediate
formation of a carbanion generated by reaction with
fluoride ion on the catalyst surface:
EXPERIMENTAL
CF3CF=CF2 + F
(CF3)2CF + O2 (CF3)2C=O + F .
3
A tubular reactor (0.3 dm ) equipped with an elec-
Appearance of COF in the reaction products is
due to more profound oxidation:
2
trical heater, a thermocouple, and pipes to supply the
initial components and O and remove the oxidation
2
3
products was filled with a catalyst (0.25 dm ). The
CF3CF=CF2 + 1.5O2
3COF2.
(2)
catalyst was activated carbon with 1.0 1.5 mm par-
ticle size, promoted with alkali metal fluorides. The
catalyst was preliminarily activated by heating in a
flow of dry nitrogen at 180 200 C for 4 h. Then the
catalyst was cooled to the required temperature and
HFP and O were supplied at a rate of 1.0 3.0 l h
in the required molar ratio.
Formation of 1,1,1,2,3,3,3-heptafluoropropane is
probably due to partial hydrolysis of COF with resid-
ual moisture on the catalyst and further addition of
hydrogen fluoride to HFP:
2
1
2
COF2 + H2O
CO2 + 2HF,
CF3CFHCF3.
(3)
(4)
The gas mixture from the reactor was condensed in
a trap cooled to 90 C and analyzed by gas liquid
CF3CF=CF2 + HF
1070-4272/01/7401-0170$25.00 2001 MAIK Nauka/Interperiodica

SYNTHESIS OF HEXAFLUOROACETONE BY CATALYTIC OXIDATION
Catalytic oxidation of hexafluoropropylene*
171
Composition of reaction product, %
B
Catalyst,
wt %
HFP : O2
molar ratio
T, C
HFP
HFA
COF2
Freon 227
%
50 KF
25 CsF
30 KF
10 RbF
5 NaF
100
220
180
250
300
1 : 3
1 : 2
1 : 1
1 : 7
1 : 10
11.8
13.1
7.8
19.2
17.5
55.4
48.4
51.9
44.6
45.2
29.3
36.1
37.9
31.7
32.5
2.5
2.4
2.4
4.5
4.8
62.8
55.7
56.3
55.1
54.7
88.2
86.8
92.2
80.7
82.4
* (B) yield of HFA based on converted HFP; ( ) conversion.
chromatography. The individual components were
recovered by low-temperature fractional distillation.
(2) The main reaction is accompanied by side oxi-
dation of hexafluoropropylene to CO and 1,1,1,2,3,-
2
3,3-heptafluoropropane.
The components were identified by IR and NMR
spectroscopy. The yield of HFA was 55 62%, and
conversion, 90%.
REFERENCES
CONCLUSIONS
1. JPN Patent 60-55049.
2. JPN Patent 58-22017.
3. JPN Patent 58-23856.
(1) Procedure was developed for preparing hexa-
fluoroacetone by catalytic oxidation of hexafluoropro-
pylene using activated carbon promoted with alkali
metal fluorides.
4. Kurosaki, A. and Okazaki, S., Chem. Lett., 1988, no. 1,
p. 17.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 74 No. 1 2001