622
BARABANOV et al.
[
8]. Polymeric sulfuric anhydride is considerably less re-
okhrom-80 (fraction 0.160–0.2 mm) as stationary phase.
The carrier gas was helium (flow rate 20 mL min ).
A flame ionization detector was used.
–
1
active than the monomeric form [5]. In addition, sulfuric
anhydride undergoes polymerization in pipelines and
fittings, plugging them, which can lead to accidents; the
probability of accidents increases with increasing scale
of the sultone or isomer production. Also, the procedure
eliminates an environmental problem:After distillation of
sulfuric anhydride from oleum (the main source of sulfu-
ric anhydride in laboratory and semicommercial practice),
large amounts (1.5–3.5 kg per kilogram of distilled-off
sulfuric anhydride) of lean (10–18%) oleum remain, and
its utilization is often difficult. To eliminate this problem,
it is possible to use sulfur dioxide for preparing the sultone
and isomer. Catalytic oxidation of SO to SO has been
Synthesis of tetrafluoroethane-β-sultone by the
reaction of tetrafluoroethylene with freshly distilled
sulfuric anhydride. Freshly distilled sulfuric anhydride
–1
was fed from a dropping funnel at a rate of 4 g min into
a tubular reactor (volume 130 mL) made of Teflon, Pyrex
glass, or 12Cr18Ni10Ti steel and heated to 80°С. TFE
was fed simultaneously to this reactor at 80°С (flow rate
–1
5
.25 g min ). The reaction products were collected in a
trap cooled to –30°С. In 1 h, 545 g of the crude sultone
was obtained. GLC analysis of the product, %: sultone
99.8, isomer 0.04, and TFE 0.16.
2
3
the subject of numerous studies and is well understood.
Sulfuric anhydride prepared by oxidation of sulfur dioxide
can contain up to 3% SO and up to 40% O [8, 9].
Synthesis of tetrafluoroethane-β-sultone using sul-
fur dioxide. Into a tubular Nichrome reactor of volume
2
2
2
50 mL, packed with SVD vanadium catalyst [9] and
As we found, under the conditions of the synthesis of
the sultone and isomer, sulfur dioxide and oxygen do not
react with tetrafluoroethylene and can be readily separated
from the reaction mixture after the synthesis.
heated to 440°С, a 1 : 1 mixture of SO and O was fed at
2
2
–1
a rate of 2.4 L min . The mixture was cooled to 50°C in
a cooler made of 12Cr18Ni10Ti steel and fed to the syn-
thesis reactor of volume 130 mL, made of 12Cr18Ni10Ti
steel and heated to 80°С. Tetrafluoroethylene was fed si-
Preparation of sulfuric anhydride by oxidation of sul-
fur dioxide with oxygen is also appropriate on enlarged
scale, e.g., in semicommercial production, because the
problems related to the use of oleum are thus eliminated.
–1
multaneously to this reactor at a rate of 1.25 L min . The
reaction products were condensed in a coil trap cooled
to –45°С. The unchanged oxygen was separated. In 1 h,
4
92 g of the crude sultone was obtained. The installation
We studied the synthesis of the isomer by the reaction
scheme is shown in Fig. 1. GLC analysis of the reaction
mixture, %: sultone 97.02, isomer 0.12, TFE 0.22, O2
of SO with TFE at 50–60°С. Sulfuric anhydride was
3
prepared by oxidation of SO with oxygen at 420–450°С
2
0
.89, SO 1.6, and СOF 0.15.
2 2
on SVD vanadium catalyst. The maximal content of the
isomer in the reaction mixture (97.44 wt %) is attained
when the oxidation of SO to SO is performed at 440°С.
Synthesis of fluorocarbonyldifluoromethanesulfo-
nyl fluoride by the reaction of tetrafluoroethylene with
freshly distilled sulfuric anhydride. Into a tubular reac-
tor of volume 130 mL, made of 12Cr18Ni10Ti steel and
heated to 80°С, freshly distilled sulfuric anhydride was
fed at a rate of 4.5 g min , and tetrafluoroethylene was fed
simultaneously to this reactor at a rate of 60 g min . The
process occurred at atmospheric pressure. The reaction
products were cooled to 50°C in a heat exchanger made
of 12Cr18Ni10Ti steel and were then fed to a reactor of
volume 160 mL, made of 12Cr18Ni10Ti steel, heated to
50–60°С, equipped with an electric heater, a manometer,
and a heat exchanger to remove heat from the reaction
zone, and packed with BAU-2 activated carbon. The
carbon was preliminarily dried in a vacuum with intermit-
tent nitrogen purging at 180°С for 6 h. After the constant
weight of the activated carbon was attained, the reactor
was cooled to 50–60°С. The reaction products were
collected in a coil trap cooled to –30°С, weighed, and
analyzed by GLC. In 1 h, 621 g of the product contain-
2
3
Using the continuous scheme, we prepared the sultone
by preliminary oxidation of sulfur dioxide with oxygen,
followed by the reaction with tetrafluoroethylene. The
–1
reaction of SO with TFE was performed at 70–80°С.
3
–1
Sulfuric anhydride was prepared by oxidation of SO2
with oxygen at 420–450°С on SVD vanadium catalyst.
The maximal sultone content of the reaction mixture
(
97.17 wt %) is reached when the oxidation of SO to
2
SO is performed at 450°С.
3
EXPERIMENTAL
The reaction products were analyzed by gas chro-
matography. Gas-chromatographic separation of the
substances was performed on a Tsvet 800 chromatograph
using a 2 m long steel column, 3 mm i.d., with trifluoro-
propylmethylsilicone (SKTFT-50-kh) supported on Sfer-
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 87 No. 5 2014