Catalytic Materials Based on Hydrotalcite-Like Aluminum, Magnesium, Nickel, and Cobalt Hydroxides: Effect of the Nickel/Cobalt Ratio on the Results of Partial Oxidation and Dry Reforming of Methane to Synthesis Gas

Article abstract of DOI:10.1134/S0965544120020048

Abstract: Catalysts for the partial oxidation and dry reforming of methane based on hydroxo salts [AlMg₂Ni_xCo_y(OH)_6.08][(NO₃) ? nH₂O], where x, y = 0, 0.005, 0.01, 0.02, 0.03, 0.035, and 0.04, with a hydrotalcite-like structure and a total Ni and/or Co content of no more than 2 wt % have been synthesized. It has been shown that Ni–Co catalysts with x = 0.03–0.035 and y = 0.005–0.01 provide a synthesis gas yield of 97–99% in both processes. At a low cobalt loading, the catalysts hardly form carbon nanotubes or other carbon depos-its.

Full text of DOI:10.1134/S0965544120020048

ISSN 0965-5441, Petroleum Chemistry, 2020, Vol. 60, No. 2, pp. 194–203. © Pleiades Publishing, Ltd., 2020.
Russian Text © The Author(s), 2020, published in Neftekhimiya, 2020, Vol. 60, No. 2, pp. 214–224.
Catalytic Materials Based on Hydrotalcite-Like Aluminum,
Magnesium, Nickel, and Cobalt Hydroxides:
Effect of the Nickel/Cobalt Ratio on the Results of Partial Oxidation
and Dry Reforming of Methane to Synthesis Gas
A. G. Dedova, b, d, A. S. Loktev
a, b, d,
* **, V. P. Danilov , O. N. Krasnobaeva , T. A. Nosova ,
,
b
b
b
a
b
c
c
a, b, d
I. E. Mukhin , A. E. Baranchikov , Kh. E. Yorov , M. A. Bykov , and I. I. Moiseev
a
Gubkin State University of Oil and Gas (National Research University), Moscow, 119991 Russia
b
Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Moscow, 117901 Russia
c
Moscow State University, Moscow, 119991 Russia
d
Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Moscow, 119991 Russia
*
e-mail: al57@rambler.ru
*e-mail: genchem@gubkin.ru
Received October 7, 2019; accepted October 14, 2019
*
Abstract—Catalysts for the partial oxidation and dry reforming of methane based on hydroxo salts [AlMg2
-
Ni Co (OH) ][(NO ) ⋅⋅nH O], where x, y = 0, 0.005, 0.01, 0.02, 0.03, 0.035, and 0.04, with a hydrotalcite-
x
y
6.08
3
2
like structure and a total Ni and/or Co content of no more than 2 wt % have been synthesized. It has been
shown that Ni–Co catalysts with x = 0.03–0.035 and y = 0.005–0.01 provide a synthesis gas yield of 97–99%
in both processes. At a low cobalt loading, the catalysts hardly form carbon nanotubes or other carbon
deposits.
Keywords: synthesis gas, partial oxidation of methane, dry reforming of methane, cobalt, nickel, Al–Mg
hydrotalcite
DOI: 10.1134/S0965544120020048
The production of synthesis gas (syngas) from nat- cobalt catalysts, are prone to losing activity owing to
ural gas is an important high-cost stage in the conver- the blocking of the active sites by surface carbon or the
sion of gas feedstocks to petrochemicals. In addition, interaction of nickel with the support, which leads to
hydrogen contained in syngas is thought of as an envi- the formation of inactive compounds. Doping of
ronmentally friendly fuel [1–6]. Promising processes nickel-containing catalysts with platinum-group met-
of syngas production by the partial oxidation of meth- als provides a decrease in the degree of coking of the
ane (POM) and the dry reforming of methane (DRM)
are the closest competitors to the currently available
method of the steam reforming of methane. The
advantages of POM include the process exothermicity
catalysts; the selection of an optimum support con-
tributes to the stabilization of the nickel active sites
[
1–6]. Cobalt additives also decrease the degree of
coking of the catalyst [8].
and the formation of syngas with H /CO = 2, which
2
It is generally believed that a cause of the deactiva-
tion of alumina-supported nickel catalysts is the for-
provides the Fischer–Tropsch synthesis of hydrocar-
bons and methanol. The DRM process (H /CO = 1)
2
mation of the NiAl O spinel [1–4]. However, in the
is attracting increasing attention as a method to utilize
2
4
carbon dioxide, which is the main greenhouse gas. In case of mixed aluminum–magnesium supports, nickel
addition, a renewable raw material—biogas—can be does not undergo deactivation [9–11] and the charac-
used for this process [7].
teristics of the synthesized catalysts are frequently
superior to the characteristics of catalysts containing
platinum-group metals. It is assumed that the reduc-
Oxide-supported nickel, cobalt, platinum group
metals, and various combinations of them are known
as effective catalysts for syngas production [1–6]. The
tion of the NiAl O spinel contributes to the formation
2
4
use of platinum group metals is constrained by their of stable and active nickel particles [9], while magne-
high cost. Nickel-based catalysts, which are signifi- sium oxide provides a uniform dispersion of nickel
cantly more active at relatively low temperatures than owing to the inhibition of the formation of the
194

CATALYTIC MATERIALS
195
NiAl O spinel and owing to the formation of a NiO–
A probable cause of the catalyst stability in POM
and DRM is the small sizes of the resulting nickel par-
ticles, which do not give reflections in X-ray diffrac-
tion patterns. A similar effect was observed in DRM in
the presence of aluminum–magnesium hydrotalcite
catalysts containing 10% of nickel. At a nickel particle
size of less than 15 nm, the catalyst coking ceases [17].
2
4
MgO solid solution [11].
It was found that an effective support for nickel and
cobalt POM and DRM catalysts is oxide systems
based on a layered material, namely, an Al–Mg hydro-
talcite [12–26]. The high parameters—reactant con-
version, selectivity, stability of syngas formation, and
coking resistance—are attributed to the formation of
nanosized nickel particles and the presence of magne-
sium oxide and an aluminum–magnesium spinel. In
some cases, the addition of cobalt to nickel-containing
catalysts leads to a decrease in the degree of coking of
the catalysts. Most of the described catalysts of this
type contain a significant amount of nickel and/or
cobalt and, in general, are not free from coking. The
known DRM catalysts based on aluminum–magne-
sium hydrotalcites containing less than 5 wt % of
Taking into account the fact that mixed nickel–
cobalt catalysts did not undergo coking during DRM
and the published data on the activity of cobalt-con-
taining catalysts based on aluminum–magnesium
hydrotalcites in POM and DRM, it was of interest to
study the effect of the nickel/cobalt ratio in alumi-
num–magnesium catalysts based on an aluminum–
magnesium hydrotalcite on the occurrence of POM
and DRM.
The aim of this study was (i) to synthesize and test
POM and DRM catalysts based on nickel–cobalt alu-
nickel provide a methane and СО conversion of less
2
than 90% with a significant coking [15]. The introduc- minum–magnesium hydroxo salts of a hydrotalcite-
tion of lanthanum into a 2% nickel catalyst provided a like structure with a total content of a nickel–cobalt
methane and CO conversion of about 90%; however, mixture of 2 wt % under variation in the nickel/cobalt
2
it did not eliminate the formation of carbon nanofi- ratio; (ii) determine the effect of the nickel/cobalt
bers and nanotubes [23, 24].
ratio in the synthesized catalysts on the POM and
DRM results; and (iii) compare the POM and DRM
results with the results obtained earlier [27].
Catalysts synthesized by the thermolysis of hydroxo
salts with
a
general formula of [AlMg Ni
2 x-
The use of these POM and DRM catalysts with a
varying nickel/cobalt ratio at a total content of Ni and
Co of no more than 2 wt % has not yet been described.
Co (OH) ][(NO ) ⋅ nH O], where x = 0, 0.02, 0.04
y
6.08
3
2
and y = 0, 0.02, 0.04, have been developed; the cata-
lysts precursors have a hydrotalcite-like structure
and a total content of Ni and/or Co of no more than
2
wt % [27]. Nickel-containing catalysts provide a syn-
EXPERIMENTAL
gas yield of 90 and 97% in POM and DRM, respec-
tively. In addition, during DRM, a trace amount of
carbon nanotubes is formed, whereas the simultane-
ous presence of nickel and cobalt in the catalyst com-
position completely eliminates the formation of car-
bon nanotubes in DRM. At the same time, the catalyst
containing 1 wt % Ni and 1 wt % Co was less active in
DRM; the catalyst containing only 2 wt % of cobalt
showed unsatisfactory results [27].
Nickel–cobalt aluminum–magnesium hydroxo
salts used as catalyst precursors were synthesized in
accordance with the following procedure: at 60°C,
under stirring, a solution containing potassium
hydroxide and potassium carbonate in a molar ratio of
2
: 1 was dropwise added to a solution containing alu-
minum, magnesium, cobalt, and nickel nitrates in
predetermined amounts to change the pH value from
1
to 10. The resulting precipitate was washed with
After a short-term heating to 950°C in a methane–
water to remove potassium ions (until a negative
sodium tetraphenylborate test). The phase and chem-
ical composition of the synthesized hydroxo salts was
determined by chemical analysis and X-ray diffraction
oxygen mixture stream (CH /O = 2; feed space
4
2
velocity of 12 L/(g h)), the catalyst containing 2% Ni
cat
still exhibits a stable on-stream behavior in POM at
9
00°C for 50 h and provides a high syngas yield (more
(XRD) methods (DRON-2.0 diffractometer, CuK
α
than 90%) [28]. Micrographs of the catalyst after
POM do not show any signs of cocking.
radiation); conditions for the formation of the hydroxo
salts were controlled by pH-metric titration of solu-
tions using a Radelkis OP-208 precision digital pH
meter (Hungary). Element determination procedures
are described in [29]. According to chemical analysis
and XRD, the resulting four single-phase samples of
hydrotalcite-like hydroxo salts had the following com-
positions:
The same catalyst exhibits a stable on-stream
behavior in DRM for 60 h and provides a high syngas
yield (more than 95%). Microphotographs of the cat-
alyst surface after DRM show fragmentary clusters of
nickel or nickel oxide particles and the resulting negli-
gible carbon deposits. The X-ray diffraction patterns
of the catalyst after POM and DRM are identical and
show the formation only of MgO and spinel phases
that contain, along with aluminum, magnesium or
nickel.
(
(
(
1) [AlMg Ni0.01Co (OH) ][(NO ) · nH O],
2 0.03 6.08 3 2
2) [AlMg Ni Co (OH) ][(NO ) · nH O],
2
0.03
0.01
6.08
3
2
3) [AlMg Ni Co (OH) ][(NO ) · nH O],
2
0.005
0.035
6.08
3
2
and (4) [AlMg Ni0.035Co0.005(OH)6.08][(NO ) · nH O].
2 3 2
PETROLEUM CHEMISTRY Vol. 60 No. 2 2020

1
96
DEDOV et al.
3
000
000
2
1000
0
10
20
2
30
40
50
60
θ (Coupled 2θ/θ) WL = 1.54060
Fig. 1. Example of an X-ray powder diffraction pattern of synthesized [AlMg Ni0.01Co0.03(OH)6.08][(NO )nH O] hydroxo salt
2
3
2
sample no. 1; samples nos. 2–4 are isomorphic to sample no. 1.
The synthesized hydroxo salts were heated from 20 (ESB) at an accelerating voltage of 7 and 1 kV, respec-
to 400°C at a rate of 100 deg/h and then held at 400°C tively, and a magnification of up to 200000×.
for 2 h and at 500°C for 2 h.
The materials of a complex oxide structure synthe-
sized by the thermolysis of the respective hydroxo salts
and used in POM and DRM catalysis are character-
ized by the following molar ratio of metal ions con-
tained in them:
The catalytic properties of the samples in POM and
DRM were studied in a heated flow-type quartz reac-
tor with a thermocouple pocket. The end of the ther-
mocouple was located in the middle of the catalyst
bed. The catalyst precursor powders were pelletized
and ground to select a fraction with a grain size of 0.5–
(
1) Al : Mg : Ni : Co = 1 : 2 : 0.01 : 0.03 (hereinafter
referred to as Ni0.01Co0.03HT),
2) Al : Mg : Ni : Co = 1 : 2 : 0.03 : 0.01 (hereinafter
referred to as Ni0.03Co0.01HT),
3) Al : Mg : Ni : Co = 1 : 2 : 0.005 : 0.035 (hereinafter
referred to as Ni0.005Co0.035HT), and
(
1
mm. The catalyst (weight, 0.2 g; bed height, 1 mm)
was placed on a quartz fiber substrate. For the POM
reaction, the free volume of the reactor was filled with
quartz chips. The reactor was fed with CH –O or
(
4
2
(
4) Al : Mg : Ni : Co = 1 : 2 : 0.035 : 0.005 (hereinafter
referred to as Ni0.035Co0.005HT).
CH –CO mixtures undiluted with an inert gas (man-
4
2
ufactured at OAO Moscow Gas Refining Plant; purity
of 99.9%) at ratios of CH /O = 2 and CH /CO = 1
4
2
4
2
For comparison, results of previous tests on POM
and a space velocity of 11–12 and 15–16 L/(g h), and DRM were used; in those tests, materials synthe-
cat
respectively; the catalyst was heated to a predeter- sized in accordance with a similar procedure had the
mined temperature. After analysis, the temperature following molar ratio of metal ions contained in them
was adjusted to predetermined values. Product com- [27]:
position was analyzed by gas chromatography as
described in [5, 8].
Al : Mg : Ni = 1 : 2 : 0.04 (hereinafter referred to as
NiHT),
Al : Mg : Ni : Co = 1 : 2 : 0.02 : 0.02 (hereinafter
referred to as Ni0.02Co0.02HT), and
Al : Mg : Co = 1 : 2 : 0.04 (hereinafter referred to as
CoHT).
The phase composition of the catalysts after POM
and DRM was studied by powder XRD on a Rigaku
MiniFlex 600 diffractometer (Japan) equipped with a
detector with a graphite monochromator and a copper
anticathode using CuK radiation at λ = 1.54187 Å;
α
the International Center for Diffraction Data (ICDD)
database was used.
RESULTS AND DISCUSSION
The interplanar distances of d = 1.49(113),
Catalyst morphology after POM and DRM was 1.51(110), 1.98(018), 2.33(015), 2.59(009), 3.88(006),
studied using a Carl Zeiss NVision 40 scanning elec- and 7.76(003) Å determined by XRD for the feed
tron microscope (SEM) equipped with secondary (SE hydroxo salts are characteristic of a classical hydrotal-
or InLens) and backscattered electron detectors cite-like compound that crystallizes in the hexagonal
PETROLEUM CHEMISTRY
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No. 2
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CATALYTIC MATERIALS
197
2
000
900
800
700
600
500
400
300
200
100
000
00
00
00
00
00
00
00
00
1
1
1
1
1
1
1
1
1
1
9
8
7
6
5
4
3
2
1
00
0
10
20
30
40
50
60
2
θ (Coupled 2θ/θ) WL = 1.54060
Fig. 2. Example of an X-ray powder diffraction pattern of calcined [AlMg Ni0.01Co0.03(OH)6.08][(NO ) · nH O] hydroxo salt
2
3
2
sample no. 1; samples nos. 2–4 are isomorphic to sample no. 1.
system with unit cell parameters of c = 23.28 Å and a = methane–oxygen mixture at 950°С (Table 1, tests 15,
3
.02 Å (Fig. 1).
According to XRD (Fig. 2), after calcining at
30) [27]. The methane conversion and the syngas yield
were low and considerably decreased with decreasing
temperature. This fact suggested that cobalt-contain-
ing catalysts based on an aluminum–magnesium
hydrotalcite that contain 2 wt % Co or 1 wt % Co and
5
00°С, all the samples are a mixture of poorly crystal-
lized and amorphous phases, presumably Al O ,
2
3
MgO, NiO, CoO, and Co O . It is difficult to reliably
2
3
1
wt % Ni are inefficient in POM [27].
detect the last three oxides by XRD, because their
content in the samples is low.
At the same time, the Ni0.035Co0.005HT catalyst
Table 1 shows results of POM in the presence of the
synthesized Ni0.035Co0.005HT, Ni0.03Co0.01HT,
Ni0.01Co0.03HT, and Ni0.005Co0.035HT catalysts
synthesized in this study, which contained 1.75% Ni
and 0.25% Co (heated to 900°С in a methane–oxygen
mixture for 1 h), showed a high methane conversion
(
tests 5–14, 20–29). For comparison, the table shows
(
(
86%) and a high yield of hydrogen (71%) and CO
results of previous tests in the presence of the NiHT,
Ni0.02Co0.02HT, and CoHT catalysts [27] (tests 1–4,
80%) even at 900°C (Table 1, test 5). With an increase
in temperature (Table 1, tests 6, 7), the methane con-
version and the hydrogen and CO yield increased; at
1
5–19, 30–34). The catalysts are arranged in decreas-
ing order with respect to nickel content and increasing
9
1
50°C, these parameters achieves values close to
order with respect to cobalt content.
00%. The subsequent decrease in temperature
The nickel/cobalt ratio in the catalyst composition (Table 1, tests 8, 9) led to a decrease in the parameters;
significantly affects the POM results (Table 1). The
cobalt-free NiHT catalyst (tests 1–4) heated to 950°С
in a methane–oxygen mixture for 1 h did not show a
high syngas yield initially (test 1). However, after hold-
ing at 950°С (test 2), the methane conversion and the
syngas yield increased to 89–90% and did not signifi-
cantly decrease even with a decrease in the tempera-
ture in the catalyst bed (tests 3, 4). The nickel-free
however, even at 850°C, the values remained high: a
methane conversion of 96%, a hydrogen yield of 91%,
and a CO yield of 93%. Thus, the introduction of a
small amount of cobalt (Ni/Co = 7), at a total nickel
and cobalt content of 2 wt %, positively affects the
POM results.
Under the same conditions, the Ni0.03Co0.01HT
CoHT catalyst and the Ni0.02Co0.02HT catalyst con- catalyst containing 1.5% Ni and 0.5% Co (Ni/Co = 3)
taining equimolar amounts of nickel and cobalt showed similar results (Table 1, tests 10–14). It is evi-
(
Table 1, tests 30–34, 15–19) exhibited low activity in dent that an increase in the cobalt content from 0.25 to
POM even in the case of a long-term contact with a 0.5 wt % with a simultaneous decrease in the nickel
PETROLEUM CHEMISTRY Vol. 60 No. 2 2020

1
98
DEDOV et al.
content from 1.75 to 1.5 wt % does not lead to a dete- Table 1. Results of POM
rioration in the POM results.
Methane
t, °C conversion,
Yield, %
Test
number
However, it should be noted that a further increase
in the cobalt content with a simultaneous decrease in
the nickel content significantly worsens the POM
results. The catalysts containing 1 wt % Co and 1 wt %
Ni (Ni0.02Co0.02HT, Table 1, tests 15–19), 1.5% Co
and 0.5% Ni (Ni0.01Co0.03HT, Table 1, tests 20–24),
and 1.75% Co and 0.25% Ni (Ni0.005Co0.035HT,
Table 1, tests 25–29), in common with nickel-free
CoHT, showed a low methane conversion and syngas
yield.
CO
H2
CO2
С2+
%
NiHТ*
1
2
3
4
950
950
920
900
34
90
89
89
7
90
89
89
14
16
9
0
0
0
90 Traces
89 Traces
89 Traces
Ni0.035Co0.005HТ
The SEM and XRD studies of the catalysts with a
varying nickel/cobalt ratio after POM (Fig. 3) showed
that the texture and phase composition of the catalysts
are approximately identical: a layered structure with
occasional inclusions on the surface of particles con-
taining nickel or cobalt, apparently, in the form of
oxides. The formation of MgO and spinel phases con-
taining, along with aluminum, magnesium and, possi-
bly, nickel and cobalt was recorded. The silica phase is
attributed to the particles of the silica fiber substrate.
The absence of reflections of metallic nickel and
cobalt and their oxides in the X-ray powder diffraction
patterns can be associated with the small particle sizes
and the catalyst cooling procedure in a mixture with a
high oxygen content. The incorporation of nickel and
cobalt into the structure of spinels that are isomorphic
to an aluminum–magnesium spinel is also possible.
5
6
7
8
9
900
920
950
900
850
86
99
100
99
80
96
98
95
93
71
95
6
1
0
0
0
0
0
98 Traces
95 Traces
91
96
1
Ni0.03Co0.01HТ
1
0
900
920
950
900
850
77
97
99
99
97
70
95
98
97
95
60
6
0
0
0
0
0
11
93 Traces
99
94 Traces
1
2
0
1
3
14
89
1
Ni0.02Co0.02HТ*
1
5
950
920
900
850
800
36
32
28
23
23
7
6
5
3
3
15
14
12
6
16
18
17
17
17
8
6
5
4
3
1
6
Thus, the observed differences in the catalytic
properties are apparently determined by the presence
of a nonoptimal excess of cobalt with respect to the
amount of nickel, which worsens the POM results
probably because of the high oxidative activity of
cobalt oxides in the presence of oxygen fed to the reac-
tor along with methane.
1
7
18
19
6
Ni0.01Co0.03HТ
33
23
37
37
31
20
900
920
950
900
850
0
0
2
1
0
5
8
17
13
4
27
20
30
32
27
6
3
2
3
4
2
1
Table 2 shows results of DRM in the presence of the
synthesized Ni0.035Co0.005HT, Ni0.03Co0.01HT,
Ni0.01Co0.03HT, and Ni0.005Co0.035HT catalysts
22
2
2
3
4
(
tests 6–17, 24–34). For comparison, the table shows
results of previous tests on DRM in the presence of the
NiHT, Ni0.02Co0.02HT, and CoHT catalysts [27] (tests
Ni0.005Co0.035HТ
1
–5, 18–23, 35–38). The catalysts are arranged in
25
26
27
28
900
920
950
900
850
34
34
38
36
35
2
1
5
3
9
12
17
14
8
26
29
28
29
30
4
3
1
2
3
decreasing order with respect to nickel content and
increasing order with respect to cobalt content.
In DRM, in common with the POM tests, the
nickel/cobalt ratio in the catalyst composition signifi-
cantly affects the results. The cobalt-free NiHT cata-
lyst was heated in a DRM reactant stream to 800°C;
after that, the temperature was gradually increased to
29
1
CoHТ*
30
950
920
900
850
800
33
32
30
25
25
5
3
2
2
2
13
10
8
6
6
19
20
21
19
21
8
7
6
4
2
9
50°C and then decreased to 850°C. At 800 and
50°C, the catalyst was inactive; however, upon
3
1
8
achieving 900°C, it abruptly improved the DRM
results (Table 2, tests 1, 2). With a further increase in
temperature, the DRM results were improved. The
32
33
4
3
conversion of methane (95%) and CO (99%) and the
2
yields of CO and hydrogen (97 and 95%, respectively) * Data of [27].
PETROLEUM CHEMISTRY
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CATALYTIC MATERIALS
Ni0.035Co0.005HT
199
MgAl2O4
MgO
SiO2
1
00
8
0
0
0
0
0
6
4
2
200 nm
1
0
15 20 25 30 35 40 45 50 2θ
Ni0.03Co0.01HT
00
MgAl2O4
MgO
1
8
0
0
0
0
0
6
4
2
200 nm
10
15 20 25 30 35 40 45 50 2θ
Ni0.01Co0.03HT
MgAl2O4
MgO
100
8
0
0
0
0
0
6
4
2
200 nm
10
15 20 25 30 35 40 45 50 2θ
Ni0.005Co0.035HT
00
MgAl2O4
MgO
SiO2
1
8
0
0
0
0
0
6
4
2
200 nm
10
15 20 25 30 35 40 45 50 2θ
Fig. 3. (left) Scanning electron microscopy micrographs and (right) X-ray powder diffraction patterns after POM catalysis.
PETROLEUM CHEMISTRY Vol. 60 No. 2 2020

2
00
DEDOV et al.
Table 2. Results of DRM
Conversion, %
NiHТ*
Yield, %
Test number
t, °C
CH4
CO2
CO
H2
1
2
3
4
5
850
1
93
94
95
89
11
93
94
99
89
5
92
94
97
89
1
93
94
95
89
900
920
950
850
Ni0.035Co0.005HТ
6
7
8
9
900 (30 min)
900 (50 min)
14
31
97
97
98
96
93
15
92
95
97
94
90
17
92
96
99
95
85
94
95
96
93
90
920
950
900
850
1
0
1
1
Ni0.03Co0.01HТ
1
2
900 (50 min)
80
97
93
96
96
90
84
97
97
98
98
93
68
96
92
97
97
91
47
97
91
99
99
88
1
3
920
900
920
950
850
1
4
1
5
1
6
1
7
Ni0.02Co0.02HТ*
1
8
800
850
900
920
950
850
6
14
18
30
45
85
83
3
3
12
28
83
81
Traces
1
9
6
14
28
81
79
2
6
18
81
79
2
0
2
1
2
2
3
2
Ni0.01Co0.03HТ
24
25
26
27
28
900
920
950
900
850
1
8
14
11
10
7
18
29
24
20
0
3
2
9
16
13
7
11
6
1
Ni0.005Co0.035HТ
2
9
0
900
920
950
920
900
850
3
9
10
0
4
3
9
3
22
37
45
25
10
3
1
20
28
9
16
28
3
15
18
8
32
33
34
4
0
3
CoHТ*
3
5
6
950 (40 min)
28
27
24
13
47
42
40
26
29
28
23
13
22
18
22
12
3
920
900
850
3
7
38
*
Data of [27].
at 950°С (test 4) did not differ significantly from the stream to 850°С did not provide a detectible formation
results obtained at 900 and 920°С (Table 2, tests 2, 3). of active metal sites; the active DRM sites formed at a
higher temperature were efficient even after subse-
The subsequent decrease in the DRM temperature
quent cooling.
to 850°С (Table 2, test 5) did not cause an abrupt
decrease in the reactant conversion and the syngas
With allowance for these results, the cobalt-doped
yield: these parameters were 89%; this value is signifi- Ni0.035Co0.005HT catalyst containing 1.75% Ni and
cantly higher than the results obtained at the same 0.25% Co (Ni/Co = 7) was heated in a methane–car-
temperature under catalyst heating conditions. Appar- bon dioxide mixture immediately to 900°С; the for-
ently, the heating of the NiHT catalyst in the reactant mation of syngas was recorded as early as 30 min after
PETROLEUM CHEMISTRY
Vol. 60
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2020

CATALYTIC MATERIALS
Ni0.035Co0.005HT
201
MgAl2O4
100
MgO
Ni(Co)
SiO
8
0
0
0
0
0
2
6
4
2
200 nm
10
15 20 25 30 35 40 45 50 2θ
Ni0.03Co0.01HT
MgAl2O4
100
MgO
Ni(Co)
SiO2
8
0
0
0
0
0
6
4
2
2
00 nm
10
15 20 25 30 35 40 45 50 2θ
Ni0.01Co0.03HT
MgAl2O4
MgO
100
8
0
0
0
0
0
6
4
2
200 nm
10
15 20 25 30 35 40 45 50 2θ
Ni0.005Co0.035HT
MgAl2O4
MgO
SiO2
1
00
8
0
0
0
0
0
6
4
2
200 nm
1
0
15 20 25 30 35 40 45 50 2θ
Fig. 4. (left) Scanning electron microscopy micrographs and (right) X-ray powder diffraction patterns after DRM catalysis.
PETROLEUM CHEMISTRY Vol. 60 No. 2 2020

2
02
DEDOV et al.
heating (Table 2, test 6). After 50 min, the methane and 12 nm for Ni0.035Co0.005HT and
and CO conversion achieved 94 and 97%, respec- Ni0.03Co0.01HT, respectively (particle sizes were
2
tively; the hydrogen and CO yield was 92% (Table 2, determined using the Scherrer equation). The cata-
test 7). With a further increase in temperature lysts exhibiting low activity in DRM do not contain
(
Table 2, tests 8, 9), the methane and СО conversions metal particles detectable by SEM and XRD methods.
2
According to XRD, triangular crystals of cobalt
and/or nickel oxides are present on the surface of the
Ni0.005Co0.035HT catalyst.
and the hydrogen and CO yields increased; at 950°С,
these parameters achieved values close to 100%.
The subsequent decrease in temperature (Table 2,
tests 10, 11) led to a slight decrease in the parameter
Thus, the DRM-active catalysts doped with a small
values; however, even at 850°C, high conversions of amount of cobalt are not prone to forming surface car-
methane (96%) and CO (93%) and high hydrogen bon and contain active metal sites smaller than 15 nm,
2
(
85%) and CO yields (93%) were observed. Thus, the which do not undergo coking [17]. These catalysts can
catalyst with a total content of nickel and cobalt of 2 wt be more stable in DRM and POM than the cobalt-free
at Ni/Co = 7 showed the DRM results that were not NiHT catalyst, which showed stable results in POM
%
inferior to the results obtained in the presence of the and DRM, yet contained a small amount of carbon
cobalt-free counterpart.
decrease in the Ni/Co ratio to
nanotubes on the surface after DRM [28].
A
3
(
Ni0.03Co0.01HT catalyst) did not lead to a signifi-
CONCLUSIONS
cant decrease in the methane and СО conversion and
2
Catalysts based on hydroxo salts [AlMg Ni
2
x-
the hydrogen and CO yields (Table 2, tests 12–17).
Co (OH) ][(NO ) ⋅ nH O], where x, y = 0.005, 0.01,
y
6.08
3
2
However, at Ni/Co = 1 (Table 2, tests 18–23), sig- 0.03, and 0.035, with a hydrotalcite-like structure have
nificant DRM results were achieved only at 950°C been synthesized and tested in the POM and DRM
(Table 2, test 22); they remained almost unchanged reactions. The total content of Ni and Co in the cata-
with a decrease in temperature to 850°C (Table 2, lysts (2 wt %) is lower than that in most of the
test 23). That is, Ni0.02Co0.02HT, which hardly cat- described similar works. It has been shown that the
alyzed the POM reaction, proved to be a significantly Ni–Co catalysts with x = 0.03–0.035 and y = 0.005–
more efficient DRM catalyst, although it was inferior 0.01 (Ni/Co = 3–7) provide a syngas yield of 97–99%
to catalysts with a lower cobalt content. Apparently, in in both POM and DRM. The obtained POM and
the absence of oxygen in the feed gas mixture, the DRM results are superior to the parameters achieved
active metal sites of the catalysts are more stable in the presence of a similar cobalt-free catalyst studied
despite the high content of cobalt capable of supplying previously [27, 28]. The synthesized POM and DRM
active lattice oxygen.
catalysts do not form carbon nanotubes or other car-
bon deposits.
With a further decrease in the nickel content in the
Ni0.01Co0.03HT catalyst (Ni/Co = 0.33), even at
950°С, it was impossible to achieve high reactant con-
FUNDING
version and syngas yield values (Table 2, tests 24–28).
However, at lower ratios—Ni/Co = 0.17 and 0—the
DRM reaction at 900–950°С still occurred to a con-
siderable extent (Table 2, tests 25–34). The CO yields
were significantly higher than the yields in the case of
using the same catalysts in POM. Thus, a high cobalt
content (Ni/Co < 1) and even the complete absence of
nickel are factors that hinder the formation of active
metal sites in DRM catalysts; however, they do not
suppress it.
This work was supported by the Presidium of the Rus-
sian Academy of Sciences (program no. 14 “Physical
Chemistry of Adsorption Phenomena and Actinide
Nanoparticles”) and the Ministry of Education and Science
of the Russian Federation in the framework of the state task,
topic no. FSZE-2017-0008 (project no. 4.6718.2017/VU).
CONFLICT OF INTEREST
The authors declare that there is no conflict of interest
According to SEM and XRD, carbon nanotubes regarding the publication of this manuscript.
were not formed on the surface of the cobalt-contain-
ing catalysts after use in DRM (Fig. 4), whereas a
REFERENCES
1. Hydrogen and Syngas Production and Purification Tech-
nologies, Ed. by K. Liu, C. Song, and V. Subramani
(Wiley–AIChE, Hoboken, NJ, 2009).
small amount of carbon nanotubes was found in the
places of localization of nickel-containing particles on
the NiHT catalyst after DRM [28]. Micrographs of
the catalysts showed fragments associated with the
presence of nickel and cobalt particles on the catalyst
2. A. Holmen, Catal. Today 142, 2 (2009).
surface. According to XRD, the MgAl O spinel is
2
4
3. B. C. Enger, R. Lodeng, and A. Holmen, Appl. Catal.,
present in the structure of all the catalysts after DRM.
After DRM, the catalysts with a low cobalt content
comprised phases of metal particles with a size of 14
A 346, 1 (2008).
4. S. Zeng, X. Zhang, X. Fu, et al., Appl. Catal., B 136–
137, 308 (2013).
PETROLEUM CHEMISTRY
Vol. 60
No. 2
2020

CATALYTIC MATERIALS
203
5
6
. A. G. Dedov, A. S. Loktev, D. A. Komissarenko, et al., 18. A. I. Tsyganok, T. Tsunoda, S. Hamakawa, et al., J.
Fuel Process. Technol. 148, 128 (2016).
Catal. 213, 191 (2003).
9. Z. Hou and T. Yashima, Appl. Catal., A 261, 205
2004).
1
. N. Ya. Usachev, V. V. Kharlamov, E. P. Belanova, et al.,
(
Pet. Chem. 51, 96 (2011).
20. O. W. Perez-Lopez, A. Senger, N. R. Marcilio, and
7. B. Zhenghong and Y. Fei, Adv. Bioenergy 3, 43 (2018).
M. A. Lansarin, Appl. Catal., A 303, 234 (2006).
8
. A. G. Dedov, A. S. Loktev, V. K. Ivanov, et al., Dokl.
Phys. Chem. 461, 73 (2015).
21. A. Serrano-Lotina, L. Rodriguez, G. Muñoz, and
L. Daza, J. Power Sources 196, 4404 (2011).
9. J. R. Rostrup-Nielsen and J. H. Bak Hansen, J. Catal.
2
2. A. Serrano-Lotina, A. J. Martin, M. A. Folgado, and
1
44, 38 (1993).
L. Daza, Int. J. Hydrogen Energy 37, 12342 (2012).
10. F. Basile, L. Basini, M. D’Amore, et al., J. Catal. 173, 23. A. Serrano-Lotina and L. Daza, J. Power Sources 238,
247 (1998).
81 (2013).
1
1. Q. Yejun, C. Jixiang, and J. Zhang, J. Fuel Chem. 24. A. Serrano-Lotina and L. Daza, Appl. Catal., A 474,
Technol. 34, 450 (2006).
2. K. M. Lee and W. Y. Lee, Catal. Lett. 83, 65 (2002).
3. K. Takehira, T. Shishido, P. Wan, et al., J. Catal. 221,
3 (2004).
4. T. P. Maniecki, K. Bawolak-Olczak, P. Mierczyński,
et al., Chem. Eng. J. 154, 142 (2009).
5. J. Guo, H. Lou, H. Zhao, et al., Appl. Catal., A 273, 75
2004).
107 (2014).
2
2
2
2
5. G. De Souza, C. Ruoso, N. R. Marcilio, and O. W. Pe-
1
1
rez-Lopez, Chem. Eng. Commun. 203, 783 (2016).
6. C. Tanios, S. Bsaibes, C. Gennequin, et al., Int. J. Hy-
4
drogen Energy 42, 12818 (2017).
1
7. A. G. Dedov, A. S. Loktev, V. P. Danilov, et al., Pet.
Chem. 58, 418 (2018).
1
8. A. G. Dedov, A. S. Loktev, I. E. Mukhin, et al., Pet.
(
Chem. 59, 385 (2019).
16. A. Bhattacharyya, V. W. Chang, and D. J. Schumacher, 29. O. N. Krasnobaeva, I. P. Belomestnykh, G. V. Isaguly-
Appl. Clay Sci. 13, 317 (1998).
ants, et al., Russ. J. Inorg. Chem 52, 141 (2007).
1
7. T. Shishido, M. Sukenobu, H. Morioka, et al., Catal.
Lett. 73, 21 (2001).
Translated by M. Timoshinina
PETROLEUM CHEMISTRY Vol. 60 No. 2 2020