V. I. Sobolev et al.
trans-2-butenes) has attracted much attention as a prom-
ising alternative approach to produce BD [3–6]. Indeed,
ODH reactions are thermodynamically favorable and offer
significant savings of energy and cost [7–10]. Therefore,
considerable efforts have been made to find an appropriate
catalyst for the ODH of n-butenes. To date, bismuth molyb-
dates with various metal components have proved to be the
most efficient catalysts for this reaction [11–18].
with an Optima 4300 DV spectrometer (Perkin Elmer, US)
with an accuracy of 0.01–0.05%.
XRD studies were conducted using a D8 diffractometer
(Bruker, Germany) with monochromatic CuKα radiation in
0.05° steps with a counting time of 5 s per data point in
the 2θ=15°–90° range. According to XRD data, the cata-
lyst consisted of multiphase system of iron, cobalt, nickel,
and bismuth molybdates (Fe2Mo3O12, α,β-CoMoO4, α,β-
NiMoO4 α-Bi2Mo3O12) and phase of MoO3.
Furthermore, it is important that, commercial value of
the BD production through the ODH reaction can be much
enhanced on condition that mixtures of light hydrocarbons,
such as BBF (butane-butene fraction), C4-raffinates, and
other available row materials are used as a significant and
cheap source of n-butenes [19]. In that case, however, the
accompanying hydrocarbons can affect negatively the tar-
get reaction. Moreover, even though only n-butenes are
present in the feed gas, their integral reactivity may not be
the same as the sum of the original reactivities of the three
isomers. In fact, cis- and trans-2-butenes are noticeably less
inclined to ODH than 1-butene [15, 20, 21]. Therefore, it
is not improbable that 2-butenes will exert a suppressing
effect on the reactivity of 1-butene and vice versa. It should
be noted also that the promotion or inhibition effects of iso-
meric 2-butenes, BD and water on the ODH of 1-butene
have been studied earlier, but the conclusions drawn by the
authors were controversial [20, 22, 23].
The specific surface area of the catalyst (SBET) was
determined by argon thermal desorption at 77 K on a
SORBI-M instrument (META, Russia) using four points of
the sorption equilibrium. The measured BET surface area
was 29 m2/g.
1-Butene (Sigma-Aldrich Inc., 99%), isobutene (Sigma-
Aldrich Inc., 99%), 2-butenes (a ~1:2 mixture of cis- and
trans-isomers, ABCR GmbH & Co. KG, 99%), propylene,
butane, isobutane, oxygen and He were used for prepara-
tion of gas mixtures by using mass flow controllers.
The temperature programmed gas-phase reactions
were performed in a quartz tube flow reactor with an
internal diameter of 6 mm using shaped catalyst granules
(d=0.25–0.5 mm; 1.64 g, ca. 2 mL). The reactive gas mix-
tures were fed (30 mL min−1) into the reactor filled with
the catalyst; the reactor was operated under atmospheric
pressure. The reaction temperature ( 1 °C) was meas-
ured inside the reactor using a thermocouple inserted into
the catalyst bed. The heating rate was 0.5 °C min−1. Dur-
ing the catalytic runs, gas samples were analyzed periodi-
cally by integrated online gas chromatography (GC, gas
chromatograph Tsvet-500; 30 m×0.32 mm monolithic
poly(divinylbenzene) capillary column; 170 °C) with a
flame-ionization detector for determination of organics.
For determination of CO and CO2, they were preliminarily
separated on a 1.5 m×3 mm steel column filled with Pora-
pak Q at 20 °C followed by methanation and analysis with
a flame-ionization detector.
In view of these considerations, we decided to investi-
gate the influence of selected light hydrocarbons, such as
n-butane, isobutane, propylene, 2-butenes, and isobutene
on the ODH of 1-butene over a typical multicomponent
Bi-Mo catalyst. Also, the main aim of this study was to elu-
cidate the possible reasons of such a potential influence.
2 Experimental
The multicomponent 50% K0.1Ni3.5Co5.0Fe2.0Bi2.0P0.5Mo12
Ox/50% SiO2 catalyst denoted as MCC was prepared by
mixing the aqueous solution of ammonium paramolybdate
[(NH4)6Mo7O24·7H2O] with 40% silica sol (particle size of
20 nm, Nalco 2327, US) under vigorous stirring at room
temperature followed by successive introduction of aque-
ous solutions of KNO3, Fe(NO3)3·9H2O, Ni(NO3)2·6H2O,
Co(NO3)2·6H2O, Bi(NO3)2·5H2O and H3PO4 (reagent
grade materials purchased from Aldrich or Merck). All
the solutions had a concentration of 90–150 g/L counting
on the corresponding metal. The suspension obtained was
spray dried on the Spay Drier (Buchi B-290, Germany),
then dried in the dry-box at 110°C for 12 h and calcined in
air at 550°C for 4 h.
Prior to the kinetic measurements, the catalyst was acti-
vated in the reactor at 400°C in a flow of O2/He (1:3) for
1 h. The reactor was then cooled to 200°C and the feed was
switched at this temperature to the reactive gas mixture for
20–30 min in order to reach steady state initial conditions.
The catalytic reactions of 1-butene and isobutene under
reduced pressure were carried out in a vacuum static setup.
The setup was made of stainless steel with a small quartz
reactor and was described elsewhere [24]. The setup was
equipped with an on-line mass-spectrometer (SRS RGA
200) to analyze the gas phase composition. The reactor
loaded with the catalyst sample (0.5 g) can be isolated from
the rest of the setup. This ensures substitution of the gas
phase in the setup at a closed reactor. Prior to the experi-
ments, the catalyst was subjected to a standard pretreatment
in vacuum, then in oxygen (1 Torr) at 500°C for 1 h and
Atomic adsorption spectrometry was used to determine
the concentrations of the chemical elements in the catalyst
1 3