ISSN 0036ꢀ0236, Russian Journal of Inorganic Chemistry, 2012, Vol. 57, No. 12, pp. 1540–1544. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © O.N. Krasnobaeva, I.P. Belomestnykh, T.A. Nosova, T.A. Elizarova, G.V. Isagulyants, V.P. Danilov, 2012, published in Zhurnal Neorganicheskoi Khimii,
012, Vol. 57, No. 12, pp. 1639–1643.
2
SYNTHESIS AND PROPERTIES
OF INORGANIC COMPOUNDS
CopperꢀContaining Catalysts for the Oxidative
Dehydrogenation of Organic Compounds
a
b
a
a
O. N. Krasnobaeva , I. P. Belomestnykh , T. A. Nosova , T. A. Elizarova ,
b
a
G. V. Isagulyants , and V. P. Danilov
a
Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia
Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, Leninskii pr. 47, Moscow, 119991 Russia
b
eꢀmail: danilov@igic.ras.ru
Received January 24, 2012
Abstract—A method of doping magnesium aluminum hydrotalcites, which are precursors for oxidative dehyꢀ
drogenation oxide catalysts of various compositions, with copper(II) was developed, and copper(II)ꢀcontainꢀ
ing oxide catalyst samples were synthesized. The catalytic properties of these catalysts were studied in the oxiꢀ
dative dehydrogenation of ethane, propane, and hexane. The conversion of ethane into ethylene on the copꢀ
perꢀcontaining catalysts was established to proceed with high selectivities (90–97%) and at low temperatures
(400–450
°C).
DOI: 10.1134/S003602361212011X
This work continues studies of the effect of the The resulting precipitate was washed with water
composition of hydrotalciteꢀlike hydroxosalts used as from potassium ions on a Nutsche filter until the
catalyst precursors on the catalytic properties of the washings gave negative reaction to tetraphenylboꢀ
resulting catalysts for oxide catalysts of oxidative rate. According to chemical and Xꢀray diffraction
dehydrogenation of organic compounds.
analyses, the precipitate represented a ternary magꢀ
nesium copper aluminum hydrotalciteꢀlike hydroxꢀ
In our earlier works [1–8], we synthesized different
MgꢀAl, MgꢀNiꢀAl, MgꢀNiꢀCoꢀAl, MgꢀAlꢀCr, and
osalt [AlMg Cu0.125–0.02(OH)5.25–5.04][(CO )
⋅ nH O],
3 0.5 2
(
2
isomorphous to various binary and ternary hydrotalꢀ
citeꢀlike hydroxosalts synthesized by us earlier [1–5].
To accomplish anion exchange with a partial substituꢀ
MgꢀAlꢀFe) hydroxosalts containing nitrate, carbonꢀ
ate, decavanadate, paramolybdate, metatungstate,
hexaniobate, and pentatantalate ions in their anionic
interlayers. The oxide catalysts prepared from them
were highly selective and provided high yields of target
products in the oxidative dehydrogenation of some
organic compounds.
The objective of our work was to develop a method
of doping the catalysts with copper(II) and to study its
effect on the properties in these catalysts the oxidative
dehydrogenation of alkanes.
6
–
tion of decavanadate (V O ) , paramolybdate
(
10 28
6–
6–
Mo O ) , and metatungstate (H W O ) ions for
7 24 2 12 40
the carbonate ions of a hydroxosalt, the paste obtained
after precipitation and washing was diluted with water
to the ratio solid (S) : liquid (L) = 1 : 2; then, a solution
of potassium decavanadate (0.15 mol/L), ammonium
paramolybdate (0.15 mol/L), or sodium tungstate
(
0.5 mol/L) was added in a necessary amount dependꢀ
ing on the required final composition. The pulp was
stirred for 10 min, then nitric acid (0.2 M) was added
to it drop by drop until pH became 4.5 in order to
exchange the carbonate ion for the decavanadate or
paramolybdate ions [9, 10] and until pH became 5.0 in
order to exchange the carbonate ion for the metatungꢀ
state ion [11]. After keeping the mixture at required
pH for 10 min to exchange the carbonate ion for the
decavanadate and paramolybdate ions and for 30 min
to exchange the carbonate ion for the metatungstate
ion, the precipitate was filtered off and washed with
water from potassium, ammonium, and sodium ions.
EXPERIMENTAL
Precursors were synthesized via the reaction of a
solution of magnesium, aluminum, and copper(II)
nitrates with a solution of potassium hydroxide and
potassium carbonate and subsequent anion exchange
of nitrate and carbonate ions for different polyoxometꢀ
alate ions, in the following way.
To a solution of aluminum (0.3 mol/L), magneꢀ
sium (0.6 mol/L), and copper (0.005–0.04 mol/L)
nitrates, a solution of potassium hydroxide and potasꢀ
sium carbonate (2 mol/L KOH + 1 mol/L K CO ) was
To perform the anion exchange of the carbonate
2
3
slowly added drop by drop (1 drop per 3 s) under conꢀ ion of the MgꢀCuꢀAl hydroxosalt for the polyoxonioꢀ
8
6 19 5 16
–
7–
tinuous stirring at 60°С
until pH changed from 1 to 10. bate [Nb O ] and polyoxotantalate [Ta O ] ions,
1540