656
Russian Chemical Bulletin, International Edition, Vol. 55, No. 4, pp. 656—660, April, 2006
Transformations of cyclohexane and benzene on the bimetallic
Ru—Pt oxide catalysts
O. V. Masloboishchikova, E. G. KhelkovskayaꢀSergeeva, V. I. Bogdan, T. V. Vasina, and L. M. Kustovꢀ
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
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7 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (495) 135 5328. Eꢀmail: lmk@ioc.ac.ru
The bimetallic RuꢀPt/Al O catalysts with an overall metal content of 1 wt. % and Pt : Ru
2
3
weight ratios from 1 : 3 to 3 : 1 were studied. The catalytic activity for cyclohexane and benzene
transformations, including hydrogenation, hydrogenolysis, and skeletal isomerization of the
initial substrates and products of intermediate transformations, was studied at temperatures
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80—350 °C and H2 pressures from 1.0 to 5.0 MPa. The maximum yield of nꢀhexane from
cyclohexane and benzene was obtained on the catalysts with a ruthenium content of 0.75—1.0%,
being ~29—30 wt.% at 40% selectivity. The selectivity to form nꢀhexane decreases with an
increase in the cyclohexane conversion and is almost independent of the composition of the
Ru—Pt system. On the catalysts under study, benzene is converted to the same products but at
temperatures by 60 °C lower as compared to cyclohexane conversion.
Key words: bimetallic catalysts, platinum, ruthenium, cyclohexane, benzene, nꢀhexane,
ring opening, hydrogenation, hydrogenolysis.
Stringent levels imposed on the content of aromatic
conditions of preliminary activation.9—13 For instance, in
terms of activity in methylcyclopentane (MCP) hydroꢀ
genolysis, the bimetallic Pt—Ru system is substantially
hydrocarbons, in particular, benzene, in motor fuels can
only be met by improving the quality of fuels. One of the
ways to solve this problem can be the selective ring openꢀ
ing of aromatic and naphthenic hydrocarbons to form
alkanes with the same number of carbon atoms as in the
initial hydrocarbon.
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different from the monometallic Ru/Al O catalyst, beꢀ
2
3
cause the introduction of Pt decreases the formation of
light hydrocarbons, namely, the predominant direction of
MCP conversion on Ru/Al O .
2
3
It has previously been shown1—4 that the reaction of
cyclohexane ring opening forming nꢀhexane occurs, unꢀ
der certain conditions, on the oxide catalysts containꢀ
ing Rh, Ru, or Pt. The sixꢀmembered ring opening
on the Ru catalyst occurs at much lower temperaꢀ
The present work is aimed at enhancing the selectivity
of the Ru catalyst in the reaction of sixꢀmembered ring
opening. For this purpose, we studied the influence of the
second metal (Pt) in the bimetallic Ru—Pt/Al O cataꢀ
lysts with different compositions on the regularities of
nꢀhexane formation by cyclohexane hydrogenolysis and
benzene hydrogenation followed by the hydrogenolysis of
cyclohexane.
2
3
tures (210—230 °C) than on the Rh and Pt catalysts
2
(
350—400 °C). However, the Ruꢀoxide systems are charꢀ
acterized by high activity in the hydrogenolysis of alkanes
and naphthenes forming methane and other low alkanes.
The activity of the Ru catalysts depends, to a great extent,
on the initial compound from which Ru is introduced and
Experimental
2
,5,6
on the support nature (SiO , Al O , TiO , ZrO ).
The support for catalysts was γꢀAl O (Haldor Topsoe, Denꢀ
2 3
2
2
3
2
2
2
–1
The properties of the Ru catalysts also change considꢀ
erably when the second metal is introduced, for instance,
Pt, Pd, Ir, or Re. The influence of the structure of the
bimetallic Ru—Pt system on its catalytic activity and seꢀ
lectivity has been studied earlier for the deep hydroꢀ
genolysis of alkanes and naphthenes, hydrogenation of
mark) with the specific surface Ssp = 250—300 m g . Metals
(Ru, Pt) were introduced from dilute 1 М aqueous solutions
of H PtCl , Ru(CH COO) , or RuCl (analytical grade). To
2
6
3
3
3
prepare the bimetallic catalysts, first Pt and after drying Ru
were introduced. The support was impregnated at 20 °C, the
solvent was removed on a rotary evaporator, and the samples
were dried at 130 °C. Before experiments, the catalysts were
reduced for 3 h in a hydrogen flow at 450 °C. The content of the
metals in the monometallic samples and the total content of Pt
and Ru in the bimetallic systems was 1 wt.% at the metal ratio
Pt : Ru equal to 1 : 3, 1 : 1, and 3 : 1. The metal content was
7
—12
benzene, and isomerization of hexanes.
The properꢀ
ties of the bimetallic Ru—Pt catalysts depend strongly on
the nature of the support and the initial salt (chlorides or
ammoniates), a sequence of introduction of metals, and
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 633—637, April, 2006.
066ꢀ5285/06/5504ꢀ0656 © 2006 Springer Science+Business Media, Inc.
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