ISSN 0023-1584, Kinetics and Catalysis, 2017, Vol. 58, No. 4, pp. 392–396. © Pleiades Publishing, Ltd., 2017.
Original Russian Text © R.V. Petrov, A.A. Zirka, S.I. Reshetnikov, 2017, published in Kinetika i Kataliz, 2017, Vol. 58, No. 4, pp. 410–414.
Pretreatment Effect on the Properties of the Cr–Mg Catalyst
for the Gas-Phase Hydrofluorination of Perchloroethylene
R. V. Petrov*, A. A. Zirka, and S. I. Reshetnikov
Boreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
Received November 30, 2016
Abstract⎯The effect of the temperature of thermal pretreatment of the precursors of the Cr–Mg catalyst on
its physicochemical properties (specific surface area and elemental composition) and catalytic properties has
been experimentally investigated. The dehydration of the precursor takes place up to a temperature of
~500°С, making it possible to tune the catalyst composition by varying the heat-treatment temperature. The
samples prepared from precursors with various compositions differ in their specific surface area and catalytic
activity. The highest activity is shown by the catalyst prepared by heat treatment of the precursor at 330°С.
Keywords: gas-phase hydrofluorination, pentafluoroethylene, chromium–magnesium catalyst
Halogenated hydrocarbons are employed as refrig-
erants, propellants, cleansers, etc. At present, in pur-
suance of the Montreal Protocol, which bans the
application of the substances that deplete the ozone
layer, chlorofluorohydrocarbons are BEING replaced
with ozone-friendly fluorohydrocarbons [1–3]. In
this context, a promising fluorohydrocarbon is penta-
, which is mainly used as a
refrigerant (R-125). Fluorohydrocarbons with a high
fluorine content are commonly synthesized by cata-
lytic gas-phase hydrofluorination in which a haloge-
nated hydrocarbon is reacted with hydrogen fluoride
in a catalyst bed [1, 4–7].
The most efficient catalysts for the synthesis of
refrigerants by this method are chromium ones, both
bulk and supported on Mg or Аl oxide or fluoride [1,
8–11]. The activity and selectivity of the catalysts for
pentafluoroethane synthesis by gas-phase perchloro-
ethylene (PCE) hydrofluorination depend both on
the composition of their precursor and on the condi-
tions under which the sample was pretreated prior to
being used in the reaction (primarily on the heat-
treatment temperature). One way of improving the
properties of the catalyst is by optimizing the heat-
treatment conditions. However, this issue has been
the subject of very few studies.
Here, we report the effect of thermal pretreatment
of the Cr–Mg catalyst in air on its physicochemical
and catalytic properties.
The catalyst precursor was prepared by adding a
О solution to dry MgF
followed by stirring
the mixture and by granulating, and drying the prod-
uct in air at 70–150°С. The dry sample was crushed
down to a particle size of 0.25–0.5 mm. Before per-
forming catalytic tests, the precursor was subjected to
the following in situ two-step pretreatment in the reac-
tor: (1) heat treatment in air at various temperatures;
(2) treatment with an HF + N
mixture under gradual
elevation of the temperature from 120 to 390°С.
Thereafter, the HF + C
reaction was carried out
over the catalyst.
Methods of Investigation
Thermal analysis (TA) was carried out on an STA-
449 synchronous thermal analyzer (NETZSCH, Ger-
many) while heating the sample from room tempera-
ture to 600°С at a rate of 5 deg/min in air flowing at a
rate of 30 cm
/min. The sample weight was 40 mg.
Specific surface areas (S
/g) were deter-
mined by the BET method from thermal argon
The article is based on the proceedings of the 4th Young
Researchers’ School and Conference in memoriam of
L.N. Kurina, “Catalysis: From Science to Industry” (Tomsk,
Russia, October 23–27, 2016).