Gas-phase oxidation of propylene into acetone on a V2O5/TiO2 catalyst: Effect of pressure and role of water

Article abstract of DOI:10.1134/S1070427217090105

The effect of pressure and role of water on gas-phase oxidation of propylene into acetone on a V₂O₅/TiO₂ catalyst were investigated. A positive effect of increasing the pressure and water content in the reaction mixture in the oxidative conversion of propylene into acetone on a V₂O₅/TiO₂ catalyst was observed. The results showed that the reaction occurred via intermediate formation of isopropanol, which was produced in situ as a result of the acid-catalyzed hydration of propylene and, under certain conditions, may be the main product.

Full text of DOI:10.1134/S1070427217090105

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2017, Vol. 90, No. 9, pp. 1439−1442. © Pleiades Publishing, Ltd., 2017.
Original Russian Text © A.N. Chernov, V.I. Sobolev, K.Yu. Koltunov, 2017, published in Zhurnal Prikladnoi Khimii, 2017, Vol. 90, No. 9, pp. 1183−1186.
CATALYSIS
Gas-Phase Oxidation of Propylene into Acetone
on a V2O5/TiO2 Catalyst: Effect
of Pressure and Role of Water
A. N. Chernova, V. I. Soboleva, and K. Yu. Koltunova,b*
a Boreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences,
pr. Akademika Lavrent’eva 5, Novosibirsk, 630090 Russia
b Novosibirsk State University, Novosibirsk, 630090 Russia
*e-mail: koltunov@catalysis.ru
Received October 20, 2017
Abstract—Positive effect of raising the pressure and water content in the reaction mixture in the oxidative con-
version of propylene into acetone on a V2O5/TiO2 catalyst was observed. It was shown that the reaction occurs
via intermediate formation of isopropanol, which id produced in situ as a result of the acid-catalyzed hydration
of propylene and, under certain conditions, may be the main product.
DOI: 10.1134/S1070427217090105
More than one fourth of the basic products of the
chemical industry are obtained with the use of catalytic
oxidative processes, the share of which is steadily increas-
ing. Molecular oxygen (air) is the most readily available,
inexpensive, and ecologically safe chemical oxidizing
agent, and oxidation catalysts are most-in-demand and
surpass in application even polymerization catalysts.
The oxidative conversion of propylene into acetone is of
particular interest as an atomically efficient way to obtain
this compound and markedly surpasses in this regard the
conventional cumene method [1]. It is known that pro-
pylene reacts with molecular oxygen in a flow-through
gas-phase mode on supported heteropolyacid catalysts
under atmospheric pressure and temperature of 150 to
190°C [2, 3]. However, the achievable selectivity of the
reaction toward acetone (84%) at a propylene conversion
of less than 18% is of no practical significance because of
the low output capacity of the process.Amore successful
case was the application of a supported oxide vanadium
catalyst V2O5/TiO2. This provides under the optimal con-
ditions a selectivity of 94% toward acetone at a propylene
conversion of 32% [4]. It has also been shown that, as
the content of water in the reaction mixture is raised to
~20%, the yield of acetone grows and the decrease in the
catalytic activity with the process duration is slower [5].
The positive effect of water was attributed to its direct
involvement in the hydration of propylene to give isopro-
panol, which is rapidly oxidized to acetone in the second
stage of the reaction (see scheme). Indeed, isopropanol
was found among the reaction products in trace amounts
[4, 5]. It should be noted in this context that V2O5/TiO2
is not only an efficient oxidation catalyst [6, 7], but can
also be regarded as a solid acid [8]. It is also known that
the acid-catalyzed hydration of propylene is a reversible
reaction in the inert atmosphere and a shift of the reaction
equilibrium toward formation of isopropanol is promoted
by an increase in pressure [9].
The scheme of the supposed sequence of stages in
the oxidative conversion of propylene into acetone is as
follows
1439

1440
С, %
CHERNOV et al.
S, %
Acetone
Isopropanol
P, MPa
P, MPa
Fig. 1. Conversion C of propylene vs. the gas mixture pressure
P. Starting mixture C3H6/O2/H2O/N2 in ratio of 6 : 4 : 10 :
80 vol %. R (°C): (1) 179, (2) 180, (3) 190, (4) 205, (5) 215.
Fig. 2. Selectivity S toward reaction products vs. pressure P.
T = 190°C, starting mixture C3H6/O2/H2O/N2 in ratio of 6 : 4 :
10 : 80 vol %.
It would be reasonable to assume that the intensification
of the first stage of the reaction by raising the pressure
and optimizing the relative amounts of propylene and
water will, on the whole, positively affect the oxidative
conversion of propylene into acetone. In reversible
processes, such as hydration of alkenes, raising the
pressure can shift the chemical equilibrium in accordance
with the Le Chatelier principle and accelerate the
successive reactions, which are exceedingly slow at low
pressures.Another important consequence of an increase
in pressure is that the concentration of gaseous reagents
grows, which favors a faster rate of their interaction and,
on the whole, makes higher the specific output capacity
of a catalyst.
by X-ray diffraction (XRD) analysis, IR spectroscopy,
temperature-programmed reduction of H2, and differential
dissolution method [10].
The reactions of gas-phase oxidation of propylene
were performed in a tubular steel reactor with inner
diameter of 10 mm in the flow-through mode with a
fixed catalyst bed (sample volume 2 mL). The volumetric
delivery rate of the C3H6/O2/H2O/N2 mixtures of various
compositions was 4500 h–1. The temperature within the
reactor was measured (with accuracy of ±1°) with a
thermocouple placed in the catalyst bed.
Prior to measuring the kinetic characteristics of the
reactions, we activated the catalyst for 1 h in the reactor
at 400°C in a flow of O2/He (1 : 3). Then, the reaction
mixture was passed for 1 h through the reactor cooled to
the required temperature to reach steady-state conditions.
The goal of our study was to evaluate the influence
exerted by the pressure and the reaction mixture
composition on the course of the reaction of propylene
with oxygen and water on the V2O5/TiO2 catalyst.
Based on published data [2–5], we performed the
catalytic reactions with propylene in the temperature
range 170–215°C. The total pressure of the gas mixture
was varied from 0.2 to 2.2 MPa. The reaction mixtures
were subjected to an on-line chromatographic analysis, as
this was done in [11, 12]. The absence of a homogeneous
oxidation of propylene under these conditions was
confirmed by runs in a reactor having no catalyst.
EXPERIMENTAL
A sample with 20% V2O5/TiO2 (SBET = 111 m2 g–1)
was produced by impregnation of TiO2 (anatase, Alfa
Aesar, Germany, specific surface area 350 m2 g–1) with
an aqueous solution of vanadyl oxalate, prepared from
V2O5 (>99.6%, Reakhim, Russia) and oxalic acid (>97%,
Reakhim, Russia), followed by drying in air at 110°C for
24 h and calcination in a flow of air (50 mL min–1) for
4 h at 400°C. The resulting catalyst was characterized
RESULTS AND DISCUSSION
Figure 1 shows how the conversion of propylene
depends on pressure at varied temperature for the starting
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 90 No. 9 2017

GAS-PHASE OXIDATION OF PROPYLENE INTO ACETONE
1441
S, %
Y, %
Acetone
Acetone
Isopropanol
Isopropanol
T, °C
P, MPa
Fig. 3. Selectivity S toward reaction products vs. temperature
T, P = 1.1 MPa. Starting mixture C3H6/O2/H2O/N2 in ratios
(vol %): (1) 6/4/10/80, (2) 6/4/30/60, (3) 6/4/50/40; the same
for Fig. 4.
Fig. 4. Yield Y of reaction products vs. temperature T, P =
1.1 MPa.
gas mixture C3H6/O2/H2O/N2 in a 6 : 4 : 10 : 80 vol %
ratio, respectively. Figure 2 shows the selectivities toward
the main reaction products in relation to pressure at a
temperature of 190°C, which seems to be the optimal
temperature for obtaining acetone under the chosen
conditions. These data show that the conversion of
propylene grows with pressure increasing to 1.1 MPa at
an insignificant decrease in the selectivity toward acetone.
Raising the pressure further, to 2.2 MPa, results in a
general fall of the values of both parameters. Despite this
circumstance, the output capacity of the reaction in terms
of acetone at 2.2 MPa is, on average, 1.5 times that for
a pressure of 1.1 MPa. Carbon oxides, CO and CO2, are
formed as by-products. The formation of isopropanol for
the given starting mixture is at zero point, in agreement
with the result of a similar reaction under atmospheric
pressure [4, 5].
the selectivity toward isopropanol substantially decreases
with increasing temperature, and a proportional rise in the
reaction selectivity toward acetone is observed. It is also
remarkable that the maximum reaction selectivity toward
acetone is also observed at high temperatures (>200°C)
as the content of water is raised to 50 vol %, which is due
to the suppression of reactions of deep oxidation to COx.
On the whole, raising the concentration of water in
the starting mixture favors a rise in the yield of acetone
with increasing temperature (Fig. 4). Nevertheless, it
follows from Fig. 4 that the optimal, as regards the yield of
acetone, concentration of water for the whole temperature
range under study is 30%.
In conclusion, it should be noted that raising the
reaction temperature further and making larger the
fraction of oxygen in the starting mixture leads to a sharp
rise in the yield of by-products, mostly COx. Therefore,
changing these reaction parameters is inadvisable from
a practical standpoint.
The effect of water on the oxidative conversion of
propylene was studied for the pressure of 1.1 MPa.
Figure 3 shows a temperature dependence of the selec-
tivity of the reaction toward acetone and isopropanol for
three reaction mixtures with different concentrations of
water: 10, 30, and 50 vol %. It is remarkable that, as the
concentration of water increases at temperatures below
200°C, the mixture outflowing from the reactor contains
a substantial amount of isopropanol. Apparently, the in-
crease in the concentration of water promotes hydration
of propylene, but hinders the subsequent oxidation of
isopropanol. Possibly, this is due to the competitive ad-
sorption of water on the catalyst surface [8]. Nevertheless,
CONCLUSIONS
(1) The effect of the total pressure in the range
0.2–2.2 MPa on the course of the oxidative conversion
of propylene into acetone on a supported oxide catalyst
of composition V2O5/TiO2 was studied at temperatures of
170 to 213°C in reaction mixtures containing propylene,
oxygen, water, and nitrogen in various ratios.
(2) It was shown that, in the general case, raising
the pressure to 1.1 MPa leads to a rise in the degree of
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1442
CHERNOV et al.
Commun., 2003, vol. 4, pp. 281–285.
propylene conversion and in the yield of acetone, whereas
further increase in pressure leads to a decrease in these
parameters. Simultaneously, the increase in pressure
favors formation of deep-oxidation products, CO and
CO2.
3. Li, M., Shen, J., Ge, X., and Chen, X., Appl. Catal., A,
2001, vol. 206, pp. 161–169.
4. Li, M. and Shen, J., React. Kinet. Catal. Lett., 2001, vol. 72,
pp. 263–267.
5. Li, M. and Shen, J., Appl. Catal., A, 2003, vol. 246,
(3) Raising the concentration of water in the
starting mixture promotes the first stage of the reaction,
conversion of propylene into isopropanol, and suppresses
deep oxidation processes, which on the whole favors an
increase in the yield of acetone.
pp. 351–363.
6. Rodella, C.B. and Mastelaro, V.R., J. Phys. Chem. Solids,
2003, vol. 64, pp. 833–839.
7. Andrushkevich, T.V. and Ovchinnikova, E.V., Cat. Rev.
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ACKNOWLEDGMENTS
vol. 466, pp. 45–50.
9. Mahajani, S.M., Sharma, M.M., and Sridhar, T., Chem.
Eng. Sci., 2002, vol. 57, pp. 4877–4882.
The study was carried out under a State assignment
to the Institute of Catalysis, Siberian Branch, Russian
Academy of Sciences (project no. 0303-2016-0006).
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