Volume 02 Issue 12-2022
1
International Journal of Advance Scientific Research
(ISSN
–
2750-1396)
VOLUME
02
I
SSUE
12
Pages:
01-08
SJIF
I
MPACT
FACTOR
(2021:
5.478
)
(2022:
5.636
)
METADATA
IF
–
7.356
A
BSTRACT
In the work, the activated Ni-Co catalyst for the conversion of methane to carbonates was prepared by
placing γ
-
Аl2О3 in solutions of nickel and cobalt nitrates. The time dependence of met
hane conversion
was studied for different catalysts. In these processes, CО2/CH4=1:1,41 1 ratio was obtained.
As a result of the research conducted, the methane effect of Co on Ni/Al2O3 catalyst for conversion. The
following possible mechanism was proposed.
The purpose of the work is to study the effect of Co on the conversion of methane to carbonate, and the
dependence of these processes on catalysts of different compositions, time and temperatures.
K
EYWORDS
Methane, aluminium oxide, catalyst, conversion, nickel, cobalt.
I
NTRODUCTION
Synthesis gas is a mixture of carbon monoxide
and hydrogen. The ratio of CО:H2 varies from 1:1
to 1:3 depending on the synthesis gas production
method. Synthesis gas production was considered
Journal
Website:
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4.0 licence.
Research Article
INVESTIGATION OF THE EFFECT OF Co ON Ni/Al2O3
CATALYST FOR METHANE CARBONATE CONVERSION
Submission Date:
December 01, 2022,
Accepted Date:
December 05, 2022,
Published Date:
December 12, 2022
Crossref doi:
https://doi.org/10.37547/ijasr-02-12-01
J.J. Javharov
Doctoral Student, Samarkand State University, Samarkand, Uzbekistan
Volume 02 Issue 12-2022
2
International Journal of Advance Scientific Research
(ISSN
–
2750-1396)
VOLUME
02
I
SSUE
12
Pages:
01-08
SJIF
I
MPACT
FACTOR
(2021:
5.478
)
(2022:
5.636
)
METADATA
IF
–
7.356
one of the most important tasks of modern gas
chemistry.
Different H2/CО ratios of synthesis gas
can produce different valuable products.
There are four ways to get synthesis gas from
methane:
• Steam conversion
СН4 + Н2О ↔ СО + 3Н2
∆
H=+206 Kj/mol (1)
•Partial oxidation with oxygen
CH4 + 1/2О2 ↔ CО + 2H2
∆
H=+35.6 Kj/mol (2)
• Autothermal conversion
CH4 + 2О2 ↔ 2CО2 + 2H2
∆
H=+802 Kj/mol (4)
(excess methane)
CH4 + H2О ↔ CО + 3H2
∆
H=+247 Kj/mol
CH4 + H2O ↔ CO + 3H2
∆
H=+206 Kj/mol
• Carbonate conversion
CH4 + CО2 ↔ 2CО + 2H2
∆
H=+247 Kj/mol (3)
Carbonate conversion is one of the simplest one-
step processes, and the importance of a catalyst is
crucial for this process.
To study the effect of ZrО2 on the activity of the
Ni-
catalyst,
10Zr/Аl2О3
(without
nickel)
5Ni5Zr/Аl2О3 10Ni10Zr/Аl2О3 catalysts were
prepared by addi
ng γ
-
Аl2О3 additives to the
aqueous solution. Studying the conversion of CH4
+ СО2 mixture on Pt/ZrO catalyst with the
addition of molecular oxygen to the reactive
system gave good results [1-8].
The incorporation of Fe into the Ni catalyst affects
its activity and selectivity. The effect of Fe
addition on the Ni/Аl2О3 sample was studied.
When the nickel content of the Ni-Fe catalyst is
5%, the coke formation decreases, and then the
coke formation increases with the increase of the
iron catalyst content. But iron reduces the activity
of the catalyst, which leads to a decrease in
conversion. Thus, to further reduce coke
formation, it is preferable to use a catalyst with a
low content of nickel and iron. In order to stop the
reduction of catalyst activity, the amount of iron
in it should also be small [9-14].
Co-catalysts are similar to nickel systems in terms
of activity and stability. Like CoOMgO solid
solutions and perovskites, cobalt oxide catalysts
lose their activity when the composition of
Cа0,8Sr0,2Тi0,8Cо0,2О3 changes. Among the
Cо/МgО/SiО2 catalysts, the most active is the
system containing 50% MgO, the ability of cobalt
to reduce coke formation is known from the
literature. [15-18].
Experimental Part
Volume 02 Issue 12-2022
3
International Journal of Advance Scientific Research
(ISSN
–
2750-1396)
VOLUME
02
I
SSUE
12
Pages:
01-08
SJIF
I
MPACT
FACTOR
(2021:
5.478
)
(2022:
5.636
)
METADATA
IF
–
7.356
Cо(NО3)3 ∙6H2О 97% nickel
-free salt was used
as a source of Co in the work. In order to evaluate
the activity of the Co catalyst, 5Cо/Аl2О3 and
10Cо/Аl2О3 (without nickel) samples were first
prepared, and the experimental results of the
conversion of methane to carbon dioxide were
studied. A 30% solution of catalysts was
swallowed for 14 hours. Then, the catalyst was
separated from the solution and dried at 350-400
℃ for 3 hours under nitrogen flow and reduced to
the state of 5-7 mm granules.
LXM-80 (detector with thermal conductivity) and
Crystal 2000 (flame ionization detector)
chromatographs were used for the methane
conversion reaction.
R
ESULTS AND DISCUSSION
To evaluate the activity of the Co catalyst,
5Cо/Аl2О3 and 10Cо/Аl2О3 (nickel
-free)
samples were first prepared, which were used to
convert methane to carbon dioxide. The
experimental results are presented in Table 1.
Table 1. Results of experiments on the conversion of methane into carbon dioxide on the
Co/Al2O3 catalyst (CО2/CH4
-1.41;)
Catalyst
Temperature
Product yield
Conversion yield
H
2
СО
СH
4
CО
2
СH
4
СO
2
5S
O
/A
l
2
F
EW
800
0,8
6,1
39,6
53,4
4,7
13,9
850
2,0
1 1 , 2
37,1
49,6
9,7
19,1
900
6,1
21,2
32,4
40,3
17,3
31,1
10So/Al2O3
800
2,3
13,2
36,1
48,4
10,3
19,9
850
5,4
20,8
30,9
42,7
15,2
27,8
900
7,3
25,0
29,4
38,3
19,2
33,4
Tests showed that the Cо/Аl2О3 catalyst slightly
increased the reaction rate of methane to carbon
dioxide conversion in the UKM process. The cost
of converting methane to carbon dioxide and the
yield of synthesis gas is low. As can be seen from
the data in Table 1, the activity of the Cо/Аl2О3
catalyst is much lower than that of Ni/Аl2О3.
Methane and carbon dioxide conversions for
10Cо/Аl2О3 catalyst at 900°C are 19% and 33
%,
respectively. As the cobalt content in the
Cо/Аl2О3 catalyst increased from 5% to 10%, its
activity increased slightly.
After studying the time dependence of methane
conversion, using 4Ni/Аl2О3, 4Ni2Cо/Al2О3,
4Ni4Cо/Аl2О3,
4Ni8Cо/Аl2О3
catalysts
Volume 02 Issue 12-2022
4
International Journal of Advance Scientific Research
(ISSN
–
2750-1396)
VOLUME
02
I
SSUE
12
Pages:
01-08
SJIF
I
MPACT
FACTOR
(2021:
5.478
)
(2022:
5.636
)
METADATA
IF
–
7.356
CО2:CH4
=1,41,
temperature
800
°C,
experimental time 14 hours (Fig. 1), Ni- with the
addition of Co to the catalyst, CH4 conversion was
found to be very low (30-60%) in the initial time
period, but after 4-6 hours the methane
conversion increased to its maximum value.
As can be seen from the curves shown in Figure 1,
the time to reach the maximum value of methane
conversion increases with the increase of cobalt
content in the Co-Ni catalyst. This phenomenon
can be explained by the fact that nickel and cobalt
first form a common transition phase with low
activity, and then turn into a stable phase with
high activity. The greater the amount of cobalt in
the catalyst, the longer the process of its
transformation into the active phase lasts. After
transition
time,
4Ni2C
о/Аl2О3
and
4Ni4Cо/Аl2О3 catalysts show high activity in
methane conversion, similar to 4Ni/Аl2О3
catalyst (>92%), and methane conversion in
4Ni8Cо/Аl2О3 catalyst decreases sharply
(<84%) ... Thus, to Ni catalyst the addition of
cobalt (>4% Co) causes its activity to decrease.
Figure 1. Time dependence of methane conversion for different catalysts, t = 800 ℃.
In order to study the time change of methane and
carbon dioxide conversion, a graph of the time
dependence of methane conversion in the
presence of 4
Ni4Cо/ Аl2О3 catalyst was made:
CО2:CH4 ratio = 1.41. At a temperature of 800 ℃,
the experimental time was 14 hours (Figure 2). As
can be seen from the graph, the growth rate of
CH4 conversion is significantly higher than the
growth rate of CО2 conversion.
During the first 2
hours, CО2 conversion is higher than CH4
conversion but then decreases. After 5-6 hours of
Volume 02 Issue 12-2022
5
International Journal of Advance Scientific Research
(ISSN
–
2750-1396)
VOLUME
02
I
SSUE
12
Pages:
01-08
SJIF
I
MPACT
FACTOR
(2021:
5.478
)
(2022:
5.636
)
METADATA
IF
–
7.356
catalyst operation, CО2 conversion reaches the
highest rate - 81%, CH4> 92%.
Figure 2. Time dependence of methane and carbon dioxide conversion o
n 4Ni4Cо/Аl2О3 catalyst,
t = 800 ℃
According to the results of the study of the
influence of the CО2/CH4 volume ratio on the
main parameters of the methane carbon dioxide
conversion process for the Co catalyst, it was
found that the CО2/CH4 volume ratio d
ecreased.
The increase in the formation of coke leads to a
decrease in the activity of the catalyst. Therefore,
the volume of CО2/CH4 =1:1 was low in
4Ni4Cо/Аl2О3 catalyst. several experiments
were conducted in order to study the stability of
the nickel catalyst with cobalt added to the
catalyst. The experimental results are presented
in Figure 3.
Volume 02 Issue 12-2022
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International Journal of Advance Scientific Research
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2750-1396)
VOLUME
02
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Pages:
01-08
SJIF
I
MPACT
FACTOR
(2021:
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)
(2022:
5.636
)
METADATA
IF
–
7.356
Fig. 3 Dependence of CH4 and CO2 conversion on time and 4Ni4Cо/Аl2О3, 4Ni/Аl2О3 catalysts.
Under these conditions, CO2 conversion is always
higher than CH4 conve
rsion. For the 4Nо/Аl2О3
catalyst, the conversion of CH4 as well as CO2 was
maximal at the initial time point, then decreased
during the reaction. The reaction was stopped
after 8 hours due to heavy coke formation in the
reactor. For the 4Ni4Cо/Аl2О3 catal
yst, the
conversions of CH4 and CO2 at the beginning of
the reaction are not high (47% and 56%), but
after 4 hours of reaction, their conversions reach
the highest values 76% and 84.2%). After that,
CH4 and CO2 conversions gradually decrease due
to coke formation. As shown in the graph (Figure
3), the reaction of UKM with the addition of cobalt
to 4Ni4Cо/Аl2О3 catalyst can take 2 times longer
(up to 16 hours), which can be expressed in the
form of 4Ni4Cо/Аl2О3 cobalt. It is more stable
than 4Ni4Cо/Аl2О3 nic
kel.
During the experiment, the amount of working
coke was determined every 2 hours. Figure 4
shows the results of the study of the change in the
mass of catalysts in the UKM process at a
temperature of 800°C. For all samples, an
increase in catalyst mass was observed during the
initial time period. Then, having a constant value,
the increase in mass stopped.
The largest increase in mass is 16Ni/Аl2О3
-
7,8%, 4Ni/Аl2О3
-
6,4%, 4Ni2Cо/Аl2О3
- 5,6%,
4Ni4Cо/Аl2О3
- 4,6%, and the least is
4Ni8Cо/Аl2О3
- 3,8%.
Volume 02 Issue 12-2022
7
International Journal of Advance Scientific Research
(ISSN
–
2750-1396)
VOLUME
02
I
SSUE
12
Pages:
01-08
SJIF
I
MPACT
FACTOR
(2021:
5.478
)
(2022:
5.636
)
METADATA
IF
–
7.356
F
igure 4. The time dependence of the weight gain of the catalyst (CО2: CH4 =1.41. т = 850 ℃)
It can be seen that the increase in the mass of the
catalyst increases with the increase in the amount
of Ni in it. Cobalt addition to Ni/Аl2О3 reduces
coke formation. The greater the amount of cobalt
in the catalyst, the greater its mass.
Based on the obtained data (Figures 2, 3 and 4), a
conclusion was made about the high activity of
the 4Ni4Cо/Аl2О3 catalyst and its ability to
reduce coke formation. Thus, the incorporation of
cobalt into the Ni/Аl2О3 catalyst contributes to a
significant decrease in coke formation. But the
catalyst also causes a decrease in activity. An
increase in the amount of Ni in the Ni/Аl2О3
catalyst leads to an increase in coke formation.
C
ONCLUSION
1.
The time dependence of methane
conversion was studied for different
catalysts.
2.
Co(NO3)3 ∙6H2O 97% nickel
-free salt was
used as a source of Co in the work.In order
to evaluate the activity of the Co catalyst,
5Co/Al2O3 and 10Co/Al2O3 (without
nickel) samples were first prepared, and
the experimental results of the conversion
of methane to carbon dioxide were
studied.
3.
As a result of the research conducted,
methaneconversionThe following possible
mechanism of the reaction was proposed.
Volume 02 Issue 12-2022
8
International Journal of Advance Scientific Research
(ISSN
–
2750-1396)
VOLUME
02
I
SSUE
12
Pages:
01-08
SJIF
I
MPACT
FACTOR
(2021:
5.478
)
(2022:
5.636
)
METADATA
IF
–
7.356
R
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