Praseodymium-containing catalysts for oxidative dehydrogenation of organic compounds

Article abstract of DOI:10.1134/S0036023617070129

A method is developed for incorporating praseodymium into magnesium–aluminum hydrotalcites, which are precursors for oxide catalysts for oxidative dehydrogenation (ODH) of alkanes. Oxide catalyst samples that contain praseodymium and various combinations of magnesium, aluminum, chromium, vanadium, molybdenum, and niobium are prepared. The catalytic properties of the prepared catalysts in ethane, propane, and butane ODH reactions are studied. Into some of our studied multicomponent catalysts, the incorporation of praseodymium enhances the reaction selectivity and increases yields of desired products.

Full text of DOI:10.1134/S0036023617070129

ISSN 0036-0236, Russian Journal of Inorganic Chemistry, 2017, Vol. 62, No. 7, pp. 879–885. © Pleiades Publishing, Ltd., 2017.
Original Russian Text © O.N. Krasnobaeva, I.P. Belomestnykh, T.A. Nosova, D.F. Kondakov, T.A. Elizarova, V.P. Danilov, 2017, published in Zhurnal Neorganicheskoi Khimii,
2017, Vol. 62, No. 7, pp. 897–904.
SYNTHESIS AND PROPERTIES
OF INORGANIC COMPOUNDS
Praseodymium-Containing Catalysts for Oxidative Dehydrogenation
of Organic Compounds
O. N. Krasnobaevaa, I. P. Belomestnykhb, T. A. Nosovaa, D. F. Kondakova,
T. A. Elizarovaa, and V. P. Danilova, *
aKurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia
b Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninskii pr. 47, Moscow, 119991 Russia
*e-mail: vpdanilov@igic.ras.ru
Received October 27, 2016
Abstract—A method is developed for incorporating praseodymium into magnesium–aluminum hydrotal-
cites, which are precursors for oxide catalysts for oxidative dehydrogenation (ODH) of alkanes. Oxide catalyst
samples that contain praseodymium and various combinations of magnesium, aluminum, chromium, vana-
dium, molybdenum, and niobium are prepared. The catalytic properties of the prepared catalysts in ethane,
propane, and butane ODH reactions are studied. Into some of our studied multicomponent catalysts, the
incorporation of praseodymium enhances the reaction selectivity and increases yields of desired products.
DOI: 10.1134/S0036023617070129
The work we report here is a continuation of the (mol/mol) was dropped at 60°С under stirring until
studies intended to elucidate the influence of the com-
position of multicomponent hydrotalcite-like hydroxo
salts used as catalyst precursors on the catalytic prop-
erties of the catalysts for oxidative dehydrogenation
(ODH) of organic compounds.
pH changed from 1 to 10. The thus-obtained precipi-
tate was washed with water from potassium ions
according to the tetraphenyl borate test. Chemical
analysis and X-ray powder diffraction showed that,
depending on the initial solution composition, the
precipitate was either the hydrotalcite-like alumi-
num–magnesium–praseodymium hydroxo salt
[Al0.8–0.83Pr0.09–0.2Mg1.67–1.92(OH)5.34–5.84][(CO3)0.5
nH2O], or the hydrotalcite-like aluminum–magne-
sium–praseodymium–chromium hydroxo salt
[Al0.83Cr0.08Pr0.09Mg1.92(OH)5.84][(CO3)0.5 · nH2O].
Earlier [1–13] we prepared a large set of complex
hydroxo salts having the hydrotalcite layered structure
where the metal–hydroxyl cationic layers contained
magnesium, aluminum, nickel, chromium, iron,
cobalt, copper, gallium, indium, samarium, and euro-
pium atoms in various combinations and the anionic
interlayers contained nitrate, carbonate, decavana-
date, paramolybdate, metatungstate, hexaoxoniobate,
·
As probed by X-ray powder diffraction, these salts
and pentaoxotantalate ions. Some of the oxide cata- were isostructural to the hydrotalcite-type complex
lysts prepared from those salts had high selectivities
and provided high yields of desired products in the
ODH of lower alkanes and alcohols.
hydroxo salts we prepared earlier [1–13].
In order to accomplish anion exchange to replace
carbonate ions in hydroxo salts by decavanadate ions
(V10O28)6– or paramolybdate ions (Mo7O24)6–, we
diluted the paste obtained after precipitation and
washing with water to S : L = 1 : 2, and then added a
set amount of a solution of potassium decavanadate
(0.15 M) and ammonium paramolybdate (0.15 M).
The slurry was stirred for 10 min, and nitric acid
(0.2 M) was then added to adjust pH to 4.5 in order to
provide the necessary conditions for anion exchange
to occur [14–16]. After the mixture was exposed for
10 min at pH of 4.5, the precipitate was filtered and
washed with water from potassium and ammonium
This study is targeted at developing a method to
incorporate praseodymium(III) into catalysts and elu-
cidate how it influences the properties of catalysts in
the ODH of alkanes.
EXPERIMENTAL
The praseodymium-containing hydroxo salts to be
used as catalyst precursors were prepared by the fol-
lowing protocol. To a solution containing aluminum,
magnesium, praseodymium, and chromium nitrates
in set amounts, a solution containing potassium
hydroxide and potassium carbonate in the ratio 2 : 1 ions according to the tetraphenyl borate test.
879

880
KRASNOBAEVA et al.
1
10
8
2
3
4
6
4
2
0
15
30
[OH], mg-eq
Fig. 1. Potentiometric titration curves for (1) praseodymium, (2) praseodymium–magnesium, (3) praseodymium–magnesium–
aluminum, and (4) praseodymium–aluminum–chromium–magnesium nitrate solutions.
In order to introduce niobium into hydroxo salts, the hydroxo salt in 2 weeks upon exposure to 50°C
К2СО3 was alloyed with Nb2O5 in the ratio 10 : 1 (Fig. 2); aluminum precipitated at pH 3–3.5 as a
hydroxo salt of variable composition Al(OH)n(NO3)3 – n
the resulting solution (pH 13) was used to accomplish mH2O, which is described in [1]; chromium precipi-
the exchange of carbonate ions for polyoxoniobate
·
(mol/mol) [16], the alloy was dissolved in water, and
tated in the form of chromium hydroxide at pH 4.5–
ions [Nb6O19]8– [7, 16]. The anion exchange lasted 6 h; 5.0; and magnesium precipitated at pH 10–10.5 in the
form of well-crystallized MgOH(NO3) · mH2O, which
we described earlier [1].
then, the precipitates were washed with water from
potassium ions.
From a solution containing praseodymium and
magnesium nitrates, amorphous praseodymium
hydroxide first precipitated at рН 6–6.5, then crystal-
line MgOH(NO3) · mH2O precipitates at рН 9–10
(Fig. 1, curve 2; Fig. 3, curve 1) [1]. From a solution
containing praseodymium, aluminum, and magne-
sium nitrates, amorphous aluminum hydroxonitrate
first precipitated at pH 3–3.5, followed by the precip-
itation of amorphous praseodymium hydroxide at рН
6–7, and then well-crystallized hydrotalcite-like alu-
minum–praseodymium–magnesium hydroxonitrate
of variable composition precipitated at рН 8–9
(Fig. 1, curve 3; Fig. 3, curve 2). We precipitated sam-
ples of two compositions: [Al0.5Pr0.5Mg3(OH)8][(NO3) ·
nH2O] and [Al0.5Pr0.5Mg2(OH)6][(NO3) · nH2O].
The phase and chemical compositions of the pre-
pared hydroxo salts were determined by chemical
analysis and X-ray powder diffraction (DRON-2.0
diffractometer, CuKα radiation). The salt formation
conditions were determined by potentiometric titra-
tion of solutions on a RADELKIS OR-208 precision
digital pH meter. The determination methods for all
elements, except for praseodymium, are found in [12].
The praseodymium was determined by titrating an ali-
quot with Trilon Bat at pH of 5.5–6.5 in the presence
of pyridine with arsenazo as an indicator, with alumi-
num masked by 0.1 M sulfosalicylic acid.
RESULTS AND DISCUSSION
Figure 1 shows potentiometric titration curves for
magnesium, praseodymium, chromium, aluminum
nitrates and their mixtures with aqueous potassium
hydroxide. Praseodymium was found to precipitate
from metal nitrate solutions at pH 6–7 as amorphous
praseodymium hydroxide Pr(OH)3 (Fig. 1, curve 1),
which crystallized to Pr(OH)3 with an admixture of
From a solution containing aluminum, praseo-
dymium, chromium, and magnesium nitrates, amor-
phous aluminum hydroxonitrate first precipitated at
pН 2.5–3, followed by the precipitation of amorphous
chromium hydroxide and praseodymium hydroxide at
рН 4–6, and then well-crystallized hydrotalcite-like
aluminum—praseodymium–chromium–magnesium
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY
Vol. 62
No. 7
2017

PRASEODYMIUM-CONTAINING CATALYSTS
881
10
20
30
40
50
60
2θ, deg
Fig. 2. X-ray diffraction pattern of crystalline Pr(OH) with admixtures of a hydroxo salt and praseodymium.
3
2
1
10
20
30
40
50
60
2θ, deg
Fig. 3. X-ray diffraction patterns of (1) amorphous praseodymium hydroxide and crystalline MgOH(NO ) · nH O and (2) hydro-
3
2
talcite-like aluminum–praseodymium–magnesium hydroxonitrate [Al Pr Mg (OH) ][(NO ) · nH O.
0,5 0,5
2
6
3
2
hydroxonitrate (isomorphous to aluminum–praseodym- bate and aluminum–praseodymium–magnesium
ium–magnesium hydroxonitrate) precipitated at рН 8–
8.5 (Fig. 1, curve 4). We precipitated a sample of compo-
sition [Al0.33Cr0.33Pr0.33Mg2.5(OH)6.97][(NO3) · nH2O].
hydroxocarbonate that contained decavanadate and
paramolybdate ions (Table 2, sample 1). To prepare
sample 3 (Table 1), we used a mixture of aluminum–
praseodymium–chromium–magnesium hexaniobate
and aluminum–praseodymium–chromium–magne-
sium hydroxocarbonate that contained decavanadate
and paramolybdate ions (Table 2, sample 2).
In order to elucidate how praseodymium influ-
ences the catalytic properties of an oxide catalyst in
alkane ODH reactions, we prepared samples of a pra-
seodymium-containing catalyst precursor. For this
purpose, we first prepared ternary and quaternary
hydroxocarbonates and then introduced decavanadate
and paramolybdate ions into them by anion exchange
(Table 1, samples 2 and 3). In preparing precursors for
ODH catalysts that contained hexaniobate ions
together with decavanadate and paramolybdate ions,
we had to use a mixture of two isomorphous phases for
the reason that decavanadate and paramolybdate ions
substitute for interlayer carbonate ions of hydrotalcite-
like hydroxo salts at pH 4.5 and hexaniobate ions do it
at pH 13. To prepare the precursor whose composition
corresponds to sample 2 (Table 1), we used a mixture
Those mixtures were prepared by stirring the two
initial hydroxo salts in the weight ratio 1 : 1 in aqueous
medium with S : L = 1 : 2 for 2 h (to attain homogene-
ity). The mixtures were sufficiently homogeneous, as
verified by their sedimentation character and the
chemical analysis of the slurry sampled from the upper
and lower portions of the sedimentation column (the
samples had the same ratios Al : Nb, Al : Mo, and Al : V).
The compositions of the thus-prepared precursor
samples are listed in Table 1.
Compounds 1–3 in Table 1 and compounds 1 and
of aluminum–praseodymium–magnesium hexanio- 2 in Table 2 were prepared by us for the first time.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 62 No. 7 2017

882
KRASNOBAEVA et al.
Table 1. Praseodymium-containing hydrotalcite-like salts used as precursors for alkane ODH catalysts
Sample no.
Precursor
1
2
3
[Al0.8Pr0.2Mg1.8(OH)5.6][CO3)0.5 · nH2O]
[Al0.82Pr0.18Mg1.67(OH)5.34][(CO3)0.412(Mo7O24)0.02(V10O28)0.004(Nb6O19)0.004 · nH2O]
[Al0.83Cr0.08Pr0.09Mg1.92(OH)5.84][(CO3)0.409(Mo7O24)0.02(V10O28)0.005(Nb6O19)0.004 · nH2O]
Table 2. Isomorphous hydrotalcite-like hydroxo salts that were mixed in the weight ratio 1 : 1 to produce precursors for
alkane ODH catalysts (see Table 1, samples 2 and 3)
Molybdenum-and-vanadium-containing
Sample no.
1
Niobium-containing hydroxo salt
hydroxo salt
[Al0.82Pr0.18Mg1.67(OH)5.34
]
[Al0.82Pr0.18Mg1.67(OH)5.34
]
[(CO3)0.468(Nb6O19)0.008 · nH2O]
[(CO3)0.356(Mo7O24)0.04(V10O28)0.008 · nH2O]
2
[Al0.83Cr0.08Pr0.09Mg1.92(OH)5.84
]
[Al0.83Cr0.08Pr0.09Mg1.92(OH)5.84
]
[(CO3)0.468(Nb6O19)0.008 · nH2O]
[(CO3)0.35(Mo7O24)0.04(V10O28)0.01 · nH2O]
To convert as-prepared precursor samples (Table 1) reaction temperature, the hydrocarbon flow rate, and
to oxide catalysts, we heat-treated them. Heat treat-
the hydrocarbon/oxygen/carbon dioxide ratio in the
ment consisted in drying a precipitate at 100–120°С to batch were varied widely. Reaction products were ana-
a water content of 40%, pelletizing, calcining in a muf-
fle in flowing air with a constant rise of temperature to
500°С at 100 K/h, and then exposing to this tempera-
ture for 4–5 h.
lyzed by liquid chromatography using a column filled
with Porapak Q.
The contact gas was analyzed for the unreacted
hydrocarbon (ethane, propane, or isobutane), dehy-
drogenation product (ethylene, propylene, or isobuty-
lene), СО2, and СО. The results of experiments were
used to calculate the conversion of the initial com-
pound, reaction selectivity, and the yield of desired
The catalytic properties of the thus-produced
materials were studied in a flow-through silica glass
reactor charged with 1–2 mL of the catalyst. The oxi-
dizing agents were atmospheric air and carbon diox-
ide. For maintaining isothermicity, the catalyst was
mixed with an equal volume of ground silica. The products:
Conversion, % = [converted hydrocarbon/admitted hydrocarbon, mols × 100];
Selectivity, % = [produced hydrocarbon/converted hydrocarbon, mols × 100];
Yield, % = [produced hydrocarbon/admitted hydrocarbon, mols × 100].
The catalysts prepared from samples 1–3 (Table 1) tively). When chromium is introduced into the praseo-
were used in the oxidative dehydrogenation of ethane,
propane, and isobutane.
dymium-containing catalyst in addition to molybde-
num, vanadium, and niobium (Table 1, sample 3), the
yield at 450°C rises considerably (30.7%) with the high
selectivity maintained (99.0%). At 650°C, the ethylene
yield for this sample is 34.3% and the selectivity is
80.0%.
An analysis of the results of catalytic studies shows
that ethane-to-ethylene conversion over praseodym-
ium-containing catalysts occurs at low temperatures
(450°С).
Over the Pr-Al-Mg-O catalyst (Table 1, sample 1)
When oxygen is introduced into the reaction mix-
ethane oxidation occurs with high selectivity (93.1%),
but with low yield (17.6%) (Table 3). When molybde- ture in addition to carbon dioxide in the ratio 1/1/1,
num, vanadium, and niobium are entered into the cat-
alyst (Table 1, sample 2), selectivity increases (97.6%)
and the ethylene yield increases to 23.0%.
(we used a chromium-containing catalyst under these
conditions; see Table 3, sample 3), the yield increases
to become 35.2% at 450°C and 42.6% at 600°C.
When the temperature rises to 650°C, the yields
over samples 1 and 2 become higher (Table 3),
increasing to 21.5 and 30.6%, respectively, but selec-
We also studied the catalytic activity of a Pr-Cr-Al-
Mg-Nb-Mo-V-О catalyst (Table 1, sample 3) in pro-
tivities decline considerably (72.0 and 80.0% respec- pane ODH reactions (Table 4).
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY
Vol. 62
No. 7
2017

PRASEODYMIUM-CONTAINING CATALYSTS
Table 3. Results of ethane ODH over praseodymium-containing catalysts
883
C2H6/CO2/O2
batch
С2Н6
conversion, %
С2Н4
yield, %
С2Н4
selectivity, %
Sample
no. s
Temperature,
Catalyst
Pr-Al-Mg-O
°C
1
2
3
1/0.3/0
1/0.3/0
1/0.3/0
450
600
650
18.9
25.3
29.9
17.6
19.5
21.5
93.1
77.2
72.0
Pr-Al-Mg-Nb-V-Mo-O
1/0.3/0
1/0.3/0
1/0.3/0
450
600
650
23.6
25.4
38.3
23.0
22.6
30.6
97.6
89.0
80.0
Pr-Cr-Al-Mg-Nb-V-Mo-O
1/0.3/0
1/0.3/0
1/1/1
450
650
450
600
31.0
42.9
36.8
50.7
30.7
34.3
35.2
42.6
99.0
80.0
95.7
84.0
1/1/1
Table 4. Results of propane ODH over a Pr-Cr-Al-Mg-Nb-V-Mo-O catalyst (the batch: C3H8/CO2/O2 = 1/1/0.5)
С3Н8 conversion, %
С3Н6 yield, %
С3Н6 selectivity, %
Sample no.
Temperature, °C
1
2
450
600
25.0
49.0
19.25
33.8
77
69
Propylene yields at temperatures in the range 450– results in ethane ODH (at 450°C, the yield was 30.7%
600°С were 19.25–33.8% with 77–69% selectivities,
respectively.
We also studied the catalytic activity of this catalyst
in isobutane ODH (Table 5) at various temperatures
and various batch compositions.
The isobutylene yield was found to increase as tem-
perature rises and the amount of oxygen in the batch
increases. At 450°C and iso-С4Н10/СО2/O2 = 1/1/0,
the isobutylene yield was 27.0% and the selectivity was
93.0%; for the same batch composition at 600°C, the
yield was 39.5% and the selectivity was 76.0%. When
the oxygen amount was increased to iso-
C4H10/CO2/O2 = 1/1/1, the isobutylene yield at 450°C
was 32.2% and the selectivity was 87.0%; at 600°C, the
yield was 45.9% and the selectivity was 74.0%.
and the selectivity was 99.0%). In isobutane ODH at
450°C, the yield was 27.0% and the selectivity was
93.0%; in propane ODH at 450°C, the yield was
19.25% and the selectivity was 77%.
Comparing the catalytic activities of catalysts that
contained a rare-earth element (samarium, europium,
or praseodymium) [12, 13] together with vanadium,
molybdenum, and niobium, we found that chromium
additions noticeably improved ethylene yields in the
ethane ODH reaction: 24.3% for the samarium-con-
taining catalyst, 26.2% for the europium-containing
catalyst, and 30.7% for the praseodymium-containing
catalyst with a high selectivity (93.7, 97.0, and 99.0%,
respectively).
Table 6 shows a comparison of the catalytic proper-
Comparing the catalytic activities of the chro- ties of various catalyst compositions containing vana-
mium-containing catalyst (Table 1, sample 3) in eth- dium, molybdenum, niobium, and chromium in eth-
ane, propane, and isobutane ODH, we see the best ane ODH reactions. One can infer from Table 6 that
Table 5. Results of isobutane ODH over a Pr-Cr-Al-Mg-Nb-V-Mo-O catalyst at various temperatures and various batch
compositions
Batch,
iso-C4H10/CO2/O2
iso-С4Н10
conversion, %
iso-С4Н8
yield, %
iso-С4Н8
selectivity, %
Sample no.
Temperature, °C
1
2
3
4
5
6
1/1/0
1/1/0
1/1/0.5
1/1/0.5
1/1/1
450
600
450
600
450
600
29.0
52.0
32.0
60.0
37.0
62.0
27.0
39.5
29.4
45.0
32.2
45.9
93.0
76.0
92.0
75.0
87.0
74.0
1/1/1
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 62 No. 7 2017

884
KRASNOBAEVA et al.
Table 6. Comparison of the results of ethane ODH over various chromium-containing catalyst compositions
С2Н6
conversion, %
С2Н4
yield, %
С2Н4
selectivity, %
Sample no.
1
Catalyst
Temperature, °C
In-Cr-Al-Mg-Nb-V-Mo-O
450
650
20.0
35.7
19.14
30.3
95.7
85.0
2
3
Ga-Cr-Al-Mg-Nb-V-Mo-O
Sm-Cr-Al-Mg-Nb-V-Mo-O
450
20.4
19.5
95.7
450
650
26.0
40.0
24.3
32.0
93.7
80.0
4
5
Eu-Cr-Al-Mg-Nb-V-Mo-O
Pr-Cr-Al-Mg- Nb-V-Mo-O
450
650
27.0
41.0
26.2
33.2
97.0
81.0
450
650
31.0
42.9
30.7
34.3
99.0
80.0
Table 7. Comparison of the results of ethane ODH over various catalyst compositions
С2Н6 conversion, %
С2Н4 yield, %
С2Н4 selectivity, %
Sample no.
Catalyst
Temperature, °C
1
2
3
4
5
6
7
8
9
Pr-Al-Mg-Nb-V-Mo-O
Eu-Al-Mg-Nb-V-Mo-O
Sm-Al-Mg-Nb-V-Mo-O
In-Al-Mg-Nb-V-Mo-O
Ga-Al-Mg-Nb-V-Mo-O
Nb-Al-Mg-V-Mo-O
Ta-Al-Mg-V-Mo-O
Ni-Al-Mg-V-Mo-W-O
Fe-Al-Mg-V-Mo-W-O
450
450
450
450
450
450
500
550
550
23.6
20.6
20.0
20.7
20.4
19.0
17.5
6.9
23.0
19.8
19.14
19.7
19.5
17.9
15.95
2.67
3.32
97.6
95.6
95.7
95.0
95.7
94.0
91.15
38.7
44.6
7.45
Table 8. Comparison of the results of propane ODH over various catalyst compositions
С3Н8
conversion, %
С3Н6
selectivity, %
С3Н6 yield, %
Sample no.
Catalyst
Temperature, °C
1
2
3
4
5
6
7
8
In-Cr-Al-Mg-Nb-V-Mo-O
Ga-Cr-Al-Mg-Nb-V-Mo-O
Sm-Cr-Al-Mg-Nb-V-Mo-O
Pr-Cr-Al-Mg-Nb-V-Mo-O
Eu-Cr-Al-Mg-Nb-V-Mo-O
Cu-Al-Mg-V-Mo-O
450
450
450
450
450
450
450
450
26.6
60.0
20.0
25.0
25.0
38.3
21.1
11.9
23.9
20.2
19.14
19.25
17.5
14.3
8.0
90
33.7
95.7
77.0
70.0
37.3
37.9
36.0
Bi-Al-Mg-V-Mo-O
Ni-Al-Mg-V-Mo-O
4.3
the praseodymium-containing catalyst gives the best selectivity: 97.6%). The europium-, samarium-,
indium-, and gallium-containing catalysts perform
almost equally given that they contain niobium, vana-
dium, and molybdenum: yields are 19.14–19.8% and
selectivities are 95.0–95.7%. The Nb-Al-Mg-V-Mo-O
catalyst shows slightly worse results: the yield is 17.9%
and the selectivity is 94.0%. The Ta-Al-Mg-V-Mo-O
catalyst shows even worse results: the yield is 15.95%
results; ethylene yield increases noticeably over all cat-
alysts as temperature rises from 450 to 650°С, but
selectivity declines.
Table 7 shows a comparison of ethane ODH cata-
lytic activities for various chromium-free catalysts.
From Table 7, one can infer that the praseodymium-
containing catalyst gives the best results (yield: 23.0%; and the selectivity is 91.15%.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY
Vol. 62
No. 7
2017

PRASEODYMIUM-CONTAINING CATALYSTS
885
Table 9. Comparison of the results of isobutane ODH over various catalyst compositions
Sample
nos.
Isobutane
conversion, %
Isobutylene
yield, %
Isobutylene
selectivity, %
Catalyst
Temperature, °C
1
2
3
4
5
Pr-Cr-Al-Mg-Nb-V-Mo-O
In-Cr-Al-Mg-Nb-V-Mo-O
Eu-Cr-Al-Mg-Nb-V-Mo-O
Ga-Cr-Al-Mg-Nb –V-Mo-O
Sm-Cr-Al-Mg-Nb-V-Mo-O
450
450
450
450
450
29.0
26.6
26.0
60.0
24.1
27.0
23.94
23.9
20.2
17.4
93.0
90.0
92.0
33.7
72.2
Over Ni-Al-Mg-V-Mo-W-O and Fe-Al-Mg-V-
Mo-W-O catalysts, ethane ODH virtually does not
occur (Table 7, samples 8 and 9): yields are 2.7–3.3%,
and selectivities are 39–45%.
ACKNOWLEDGMENTS
This study was supported by the Presidium of the
Russian Academy of Sciences through the fundamen-
tal research program of “Development of Methods for
Preparing Chemical Materials and Materials Design”
and “Targeted Synthesis of Inorganic Compounds
Having Tailored Properties and Design of Functional
Materials on Their Base” (project no. 8P6).
Table 8 shows a comparison of the propane OHD
catalytic properties of various catalyst compositions.
One can infer from Table 8 that the indium-containing
catalyst gives the best results: the yield is 23.9%, and
selectivity is 90%. The yield further systematically
drops from the gallium-containing catalyst to the
europium-containing one, from 20.2 to 17.5%,
respectively. For the praseodymium-containing cata-
lyst, the yield is 19.25% and the selectivity is 77.0%.
The other catalysts show lower yields and selectivities
(yields are 14.3–4.3%; selectivities are 36–38%).
REFERENCES
1. O. N. Krasnobaeva, I. P. Belomestnykh, G. V. Isaguly-
ants, et al., Russ. J. Inorg. Chem. 49, 1482 (2004).
2. O. N. Krasnobaeva, V. P. Danilov, I. P. Belomestnykh,
et al., Russ. J. Inorg. Chem. 50, 1295 (2005).
3. O. N. Krasnobaeva, I. P. Belomestnykh, G. V. Isaguly-
Table 9 shows a comparison of the performances of
various catalyst compositions in isobutane ODH reac-
tions. The praseodymium-containing catalyst gives
the best results: the yield is 23.9% and selectivity is
93.0% at 450°C. For europium- and indium-contain-
ing catalysts, the yield is 23.9% and the selectivity is
92.0 and 90.0%, respectively. For gallium- and samar-
ium-containing catalysts, the ODH results are notice-
ably worse: yields are 20.2 and 17.4%, and selectivities
are 33.7 and 72.2%, respectively.
ants, et al., Russ. J. Inorg. Chem. 52, 141 (2007).
4. O. N. Krasnobaeva, I. P. Belomestnykh, G. V. Isaguly-
ants, et al., Russ. J. Inorg. Chem. 53, 1176 (2008).
5. O. N. Krasnobaeva, I. P. Belomestnykh, G. V. Isaguly-
ants, et al., Russ. J. Inorg. Chem. 54, 495 (2009).
6. O. N. Krasnobaeva, I. P. Belomestnykh, G. V. Isaguly-
ants, et al., Russ. J. Inorg. Chem. 54, 1862 (2009).
7. O. N. Krasnobaeva, I. P. Belomestnykh, T. A. Nosova,
et al., Russ. J. Inorg. Chem. 56, 168 (2011).
8. O. N. Krasnobaeva, I. P. Belomestnykh, T. A. Nosova,
et al., Russ. J. Inorg. Chem. 56, 1012 (2011).
In summary, we have developed a method to intro-
duce praseodymium to catalysts that contain Mg, Al,
Cr, V, Mo, and Nb in various proportions. We have
prepared new hydroxo salts having hydrotalcite-type
9. O. N. Krasnobaeva, I. P. Belomestnykh, T. A. Nosova,
et al., Russ. J. Inorg. Chem. 57, 1540 (2012).
10. O. N. Krasnobaeva, I. P. Belomestnykh, T. A. Nosova,
et al., Russ. J. Inorg. Chem. 58, 644 (2013).
layered structure, namely, [Al1 – nPrnMgm(OH)3 + 2m – 1
]
11. O. N. Krasnobaeva, I. P. Belomestnykh, V. M. Kogan,
[A · qH2O] and [Al1 – (n + m) PrnCrmMgp(OH)3 + 2p – 1][A ·
qH2O] where A = (NO3) or (СО3)0.5. Similar hydroxo-
carbonates were subjected to a partial anion exchange
of (СО3) for (Mo7O24)6–, (V10O28)6–, and (Nb6O19)8–
to be subsequently used as precursors for alkane ODH
catalysts.
et al., Russ. J. Inorg. Chem. 59, 693 (2014).
12. O. N. Krasnobaeva, I. P. Belomestnykh, T. A. Nosova,
et al., Russ. J. Inorg. Chem. 60, 409 (2015).
13. O. N. Krasnobaeva, I. P. Belomestnykh, T. A. Nosova,
et al., Russ. J. Inorg. Chem. 60, 1074 (2016).
14. The Analytical Chemistry of Vanadium, Ed. by
Yu. A. Zolotov (Nauka, Moscow, 1981) [in Russian].
We studied the catalytic properties of the prepared
catalysts in ethane, propane, and isobutane ODH reac-
tions. Praseodymium when introduced into catalysts
enhances the selectivity and final product yields in eth-
ane and isobutane ODH reactions. The praseodymium-
containing catalyst gives the best results in ethane and
isobutane ODH among the М-Cr-Al-Mg-Nb-V-Mo-O
catalysts where М = Pr, Eu, Sm, In, or Ga.
15. T. Kwon, G. A. Tsigdinnos, and T. J. Pinnavaia, J. Am.
Chem. Soc. 110, 3653 (1988).
16. The Analytical Chemistry of Niobium and Tantalum, Ed.
by A. P. Vinogradov (Nauka, Moscow, 1976) [in Rus-
sian].
Translated by O. Fedorova
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 62 No. 7 2017