Effect of Temperature and Pressure on Conversion of Methane and Lifetime of the Catalyst in the Catalytic Decomposition of Methane

Article abstract of DOI:10.1134/S1070427220070022

The effect of temperature and pressure on conversion of CH₄ and the catalyst lifetime during the catalytic decomposition of CH₄ with the formation of H₂ and nanofibrous carbon on a Ni–Cu catalyst was investigated. The pressure varied in the range of 1–10 atm at the temperatures of 600°C and 675°C. Results revealed that when increasing pressure, the total yield of H₂ increased from the start of synthesis to the deactivation of the catalyst. This effect was manifested the stronger, the higher the temperature of process. Also, increasing pressure allowed temperature range expansion of the process without reducing the total yield of useful products.

Full text of DOI:10.1134/S1070427220070022

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2020, Vol. 93, No. 7, pp. 954–959. © Pleiades Publishing, Ltd., 2020.
Russian Text © The Author(s), 2020, published in Zhurnal Prikladnoi Khimii, 2020, Vol. 93, No. 7, pp. 938–944.
CATALYSIS
Effect of Temperature and Pressure on Conversion of Methane
and Lifetime of the Catalyst in the Catalytic
Decomposition of Methane
M. V. Popova,b,c,*, A. G. Bannovb, A. E. Bresterb,
and P. B. Kurmashovb
a Zelinsky Institute of Organic Chemistry of Russian Academy of Sciences, Moscow, 119991 Russia
b Novosibirsk State Technical University, Novosibirsk, 630073 Russia
c Mendeleev University of Chemical Technology of Russia, Moscow, 125047 Russia
*e-mail: popovmaxvik@gmail.com
Received November 13, 2019; revised February 6, 2020; accepted February 21, 2020
Abstract—The results of studying the effect of temperature and pressure on conversion of methane and the catalyst
lifetime during the catalytic decomposition of methane with the formation of hydrogen and nanofibrous carbon
on a Ni–Cu catalyst are presented. The pressure varied in the range of 1–10 atm at the temperatures of 600 and
675°C. It was found that when increasing pressure, the total yield of hydrogen increases from the start of synthesis
to the deactivation of the catalyst. This effect is manifested the stronger, the higher the temperature of process.
It is shown that increasing pressure allows expanding the temperature range of the process without reducing the
total yield of useful products.
Keywords: hydrogen energy, nanofibrous carbon, methane-hydrogen mixture, pressure effect, conversion, yield
of hydrogen, methane decomposition
DOI: 10.1134/S1070427220070022
Replacing traditional fuels with alternative hydrogen-
containing fuel mixtures can increase efficiency and
reduce emissions of gas-piston thermal power plants,
autonomous power plants, automobile and other types
of transport [1, 2]. One of the promising methods for
producing pure hydrogen and hydrogen-containing
mixtures is the catalytic decomposition of light
hydrocarbons [3, 4]. This process is described by the
reaction:
Despite a significant number of works devoted to
the catalytic decomposition of methane, there is no
consensus among researchers on the process conditions,
such as the composition of catalyst, temperature,
pressure, allowing to obtain maximum yields of reaction
products. An analysis of the published data shows that
nickel-containing catalysts of various ratios Ni : Me :
support (Me is a promoting additive) are mainly used
for the process under study, which usually allows to
increase the lifetime of nickel catalyst [9], the optimal
temperature range of the process established by the
researchers is 550–700°С [10–13]. However, there are
no comprehensive studies of the effect of pressure on the
catalytic decomposition of methane.
CH4 → C(solid) + 2H2, ΔH° = 75.6 kJ mol–1,
which proceeds over the catalyst at temperatures from
500 to 800°C.
The purpose of this work is to expand our understanding
of the process of catalytic decomposition of methane
into hydrogen and carbon nanofibers, carried out under
pressure from 1 to 10 atm at temperatures of 600 and
675°C over a Ni–Cu catalyst.
In addition to hydrogen, a valuable product is formed
during the reaction, carbon nanofibers, which can be used,
for example, as a filler in composite materials [5, 6], as a
reagent for the synthesis of refractory materials (boron
carbide, chromium, zirconium, vanadium, titanium) [7, 8].
954

EFFECT OF TEMPERATURE AND PRESSURE ON CONVERSION OF METHANE
955
Back pressure
regulator
Bursting disc
Pressure
gauge
Filter 2
Reactor
Filter 1
Isothermal cabinet
AMFC
Chromatograph
Water lock
Exhaust
Fig. 1. Schematic diagram of the laboratory setup. (1) Catalyst bed, (2) quartz substrate.
EXPERIMENTAL
The substrate was a quartz glass tube of 210 mm
long and a 10 mm external diameter. There was a special
partition in the tube where the catalyst was placed, and
holes were made in it through which gas penetrated the
substrate and interacted with the catalyst.
The experiments were performed using an Autoclave
Engineers BTRS-Jn flow catalytic system. The scheme
of experimental setup is shown in Fig. 1.
Pure methane 99.99 vol % was used as the initial
hydrocarbon gas. Gases were supplied to the reactor
from cylinders through a reducing valve; the flow rate
of the source gas supplied to the reactor was controlled
by an automatic multichannel flow controller (AMFC).
The reactor was placed in a tubular electric furnace. The
temperature was maintained with an accuracy of 1°C.
The catalyst fell onto the substrate inside the reactor. The
system with a catalyst was heated to a predetermined
reaction temperature in argon, followed by switching to
methane. The pressure in the system was regulated and
controlled with an accuracy of 0.14 atm by a back pressure
regulator with a manometer.
The main parameters characterizing the thermocatalytic
decomposition of methane are: conversion of methane
XCH4, catalyst lifetime t, and specific yield of hydrogen
yH2. Based on the equations of mass balance and data of
chromatographic analysis, conversion of methane (%)
and specific yield of hydrogen were calculated as follows:
cC0H  cCi H
4
4
XCH

100,
cC0H (1  cCi H
)
4
4
4
MH2
yCH

,
4
MHcat
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POPOV et al.
where c0CH is the initial concentration of methane; ciCH
is the current concentration of methane; Mcat is the mass
of the catalyst; MH2 is the amount of hydrogen resulting
from the reaction.
of this mixture to a temperature of 150°C, the formation
of a solid solution of anhydrous nitrates and their partial
decomposition occurred. Then, when the temperature was
increased to 400°C (heating rate 15 deg min–1), the final
removal of nitrogen oxides was conducted by reactions
4
4
The concentrations of the reaction products in the
exhaust gases were measured by gas chromatography on
a CHROMOS GC-1000 chromatograph.
2Cu(NO3)2 → 2CuO + 4NO2 + O2,
2Ni(NO3)2 → 2NiO + 4NO2 + O2
The resulting catalyst was investigated using the
method of low-temperature nitrogen adsorption on a
Quantachrome NOVA1000e instrument. Before studying
the texture characteristics, the samples were degassed in
vacuum at 300°С for 6 h to remove physically adsorbed
gases and water.
with the formation of porous, easily crushed structure.
The resulting mass was cooled to room temperature with
a cooling rate of the furnace and ground to powder.
In the next step, the obtained powder was impregnated
with a solution of tetraethoxysilane (ethyl silicate-40) in
an organic solvent and the resulting mass was thoroughly
mixed. Then this mass was dried at 100°С for 2 h and cal-
cined for 2 h at 400°С, the heating rate was 10 deg min–1.
Then, the powder was restored in a hydrogen flow with
a flow rate of 50 mL min–1 at a temperature of 600°С for
4 h, after which hydrogen was replaced by argon (flow
rate 20 mL min–1), and the resulting catalyst was cooled
to room temperature.
An analysis of the texture properties was carried out
at a temperature of 77 K and relative pressures p/p0 of
the adsorbent (nitrogen) gas in the range 0.005–0.995 to
construct complete adsorption and desorption isotherms.
The specific surface area was calculated by the Brunauer–
Emmet–Teller (BET) method. To obtain the size
distribution of mesopores, the Barrett–Joyner–Hallenda
method was used.
Micrographs of the samples were taken on a Hitachi-
3400N scanning electron microscope at an accelerating
voltage of 20 kV and a working distance of 10 mm. For
registration of images, a secondary electron detector and
a backscattered electron detector were used.
RESULTS AND DISCUSSION
As the pore diameter of the catalyst decreases, the rate
of the process increases until diffusion inhibition takes
effect, therewith the decrease in the degree of use of the
surface area of catalyst grain was somewhat compensated
by the increasing it with diminishing pore diameter [14].
Thus, the activity of catalyst directly depends on the
surface area and pore volume. This can be explained by
the fact that the activity of the catalyst increases due to
the large number of pores and free access of the contacted
gas to active sites on the inner surface of the pores in the
entire volume of catalyst.
Elemental analysis of the samples was performed
using an attachment of an energy dispersive spectrometer
for scanning electron microscope (Oxford Instruments).
EDX spectra were processed by the INCA Energy
software. Samples were applied to conductive carbon
tape, and stuffed into a mesh for elemental analysis.
The catalyst prepared by the method of alloying metal
salts contained, wt %: Ni 82, Cu 8, SiO2 10.
Initial components for the preparation of the catalyst,
such as Ni(NO3)2·6H2O (analytical grade) according
to State Standard GOST 4055–78, Cu(NO3)2·3H2O
(analytical grade) according to Technical Specification
TU 2622-003- 62931140–2015, ethyl silicate-40
(premium) in accordance with TU 2435-427-05763441-
2004, were purchased from OJSC Reaktiv (Novosibirsk).
The synthesized catalyst has a high specific surface
area of 132 m2 g–1 with a pore volume of 0.13 cm3 g–1,
and the average pore diameter of the catalyst is close to
the micropore range (3.9 nm).
From the adsorption isotherm and the type of
hysteresis, the type and shape of pores can be one can
determined [15, 16]. The hysteresis loop (Fig. 2) of
the adsorption and desorption isotherms indicates the
presence of mesopores, and the sample has a large number
of deaf bottle-shaped pores with very large radii of wide
parts and narrow throats. The main part of the catalyst
(Fig. 3) is nickel with a small amount of copper, which
The required weights of crystalline hydrates of
copper and nickel salts were calculated in terms of
pure nickel. The salts were mixed in a ceramic cup and
slowly heated. When increasing temperature, the salts
began to melt in their own crystallization water until a
homogeneous mixture was formed. Whenfurther heating
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EFFECT OF TEMPERATURE AND PRESSURE ON CONVERSION OF METHANE
Adsorbate volume, cm3 g–1
957
Element
Content, wt %
Fig. 2. Adsorption and desorption isotherms of the 82Ni–8Cu/
SiO2 catalyst (wt %).
50 μm
confirms the expected composition of the samples, the
ratio of nickel to copper is ~10 : 1.
Fig. 3. SEM images of the 82Ni–8Cu/SiO2 catalyst (wt %) and
its elemental composition.
The initial conversion of methane was 37% (Fig. 4) at
a temperature of 600°C and atmospheric pressure, while
the catalyst had a lifetime of 17 h. When increasing the
pressure to 10 atm, the initial conversion of methane
dropped to 20%, and the catalyst had a lifetime of
more than 40 h. When increasing the temperature to
675°С and pressure up to 10 atm, the catalyst lifetime
changed insignificantly and amounted to ~40 h (Fig. 4).
At a temperature of 675°C, conversion of methane is
on average 10% higher than at a temperature of 600°C,
(a)
1 atm
5 atm
10 atm
–1
and the total maximum yield of hydrogen is 54 mol g
cat
(Fig. 5). Thus, the yield of hydrogen achieved at a
pressure of 10 atm during the catalyst deactivation period
at 675°C is higher than at 600°C.
Reaction time, h
(b)
It should be noted that the effect of pressure on the
total yield of hydrogen manifests itself more significantly
at elevated temperatures, when the rate of catalyst
deactivation at atmospheric pressure increases sharply.
Indeed, at 600°C, the total specific yield of hydrogen does
not change significantly with increasing pressure in the
region above 3 atm, while at 675°C the specific yield of
hydrogen increases by more than 10 times with increasing
pressure from atmospheric to 10 atm.
1 atm
5 atm
10 atm
The increase in the total yield of hydrogen can be
explained by the fact that, with increasing pressure, the
phenomenon of catalyst deactivation is compensated
by an increase in the catalyst lifetime. The latter is due
to a rise in the partial pressure of hydrogen as a result
of an increase in the total pressure, despite the fact that
this process is accompanied by a shift in the reaction
equilibrium to the left, towards a relative decrease in the
hydrogen concentration in the reactor.
Reaction time, h
Fig. 4. Conversion of methane vs. the reaction time at various
pressures and temperature (a) 600, (b) 675°C.
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POPOV et al.
temperature variation is limited by the area of intensive
deactivation of the catalyst. Obviously, the transition
to higher pressures extends the temperature range of
effective process proceeding.
During the catalytic decomposition of methane,
the catalyst is deactivated due to the encapsulation of
the catalyst by the formation of carbon nanofiber on
its surface [18]. In the course of the work, electron
micrographs of the spent catalyst were obtained (Fig. 6).
In the mode of detection of backscattered electrons, it was
possible to see particles of a metal catalyst in the bulk of
carbon formed. It was shown that the ratio of the formed
carbon nanofiber to the amount of catalyst involved is
quite large.
Pressure, atm
Fig. 5. Specific yield of hydrogen vs. pressure at the
temperatures of 600 and 675°C.
CONCLUSIONS
With increasing pressure, the total yield of hydrogen
rises for the period of catalyst deactivation during
the catalytic decomposition of methane. This effect
is manifested the stronger, the higher the process
temperature. The method used to prepare the catalyst, the
alloying the nickel and copper salts, is technologically
simple enough and can be implemented both on a
laboratory and industrial scale. It is shown that increasing
pressure allows expanding the temperature range of
the process without reducing the total yield of useful
products.
5 μm
CONFLICT OF INTEREST
The authors declare no conflict of interest requiring
disclosure in this article.
REFERENCES
1. Pevnev, N.G. and Ponamarchuk, V.V., Vestn. Sib. Gos.
Avtomobil’no-dorozhnogo Univ., 2017, vol. 55, no. 3,
pp. 99–105.
5 μm
Fig. 6. SEM images of the deactivated catalyst.
2. Karim, G.A., Wierzba, I., and Al-Alousi, Y., Int. J.
Hydrogen Energy, 1996, vol. 21, no. 7, pp. 625–621.
https://doi.org/10.1016/0360-3199(95)00134-4
It can be expected that a further increase in pressure
will make it possible to carry out the process quite
efficiently at even higher temperatures, that may be
useful from the point of view of controlling the properties
of the resulting carbon nanofiber. Indeed, temperature
is one of the main parameters affecting the structure
and morphology of carbon nanofiber, produced on the
basis of the catalytic decomposition of hydrocarbons
[17]. However, at atmospheric pressure, the range of
3. Kuvshinov, G.G., Mogilnykh, Yu.I., Kuvshinov, D.G.,
Yermakov, D.Y., Yermakova, M.A., Salanov, A.N., and
Rudina, N.A., Carbon, 1999, vol. 37, no. 8, pp. 1239–
1246.
https://doi.org/10.1016/S0008-6223(98)00320-0
4. Ashik, U.P.M., Wan Daud, W.M.A., Abbas, H.F., Renew
Sust. Energ. Rev., 2015, vol. 44, pp. 221–256.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 93 No. 7 2020

EFFECT OF TEMPERATURE AND PRESSURE ON CONVERSION OF METHANE
959
https://doi.org/10.1016/j.rser.2014.12.025
Zhao, L., Chen, H., Wang, H., and Peng, S., Fusion Eng.
Des., 2017, vol. 125, pp. 593–602.
https://doi.org/10.1016/j.fusengdes.2017.05.040
5. Bannov, A.G., Uvarov, N.F., Shilovskaya, S.M., and
Kuvshinov, G.G., Nanotechnologies in Russia, 2012,
vol. 7, nos. 3–4, pp. 169–177.
12. Shen, Y. and Lua, A., Appl. Catal. B: Environmental,
2015, vol. 164, pp. 61–69.
https://doi.org/10.1134/S1995078012020048
https://doi.org/10.1016/j.apcatb.2014.08.038
6. Bannov, A.G., Uvarov, N.F., and Kuvshinov, G.G., The
8 Int. Forum on Strategic Technologies, IFOST 2013,
vol. 1, pp. 194–199.
13. Li, J., Xiao, C., Xiong, L., Chen, X., Zhao, L., Dong, L.,
Du, Y., Yang, Y., Wang, H., and Peng, S., RSC Adv., 2016,
vol. 6, no. 57, pp. 52154–52163.
https://doi.org/10.13140/2.1.1986.0481
https://doi.org/10.1039/c6ra05782a
7. Krutskii, Y.L., Tyurin, A.G., Popov, M.V.,
Maksimovskii, E.A., and Netskina, O.V., Steel in
Translation, 2018, vol. 48, no. 4, pp. 207–213.
14. Mukhlenov, I.P., Dobkina, E.I., Deryuzhkina, V.I., and
Soroko, V.E., Tekhnologiya katalizatorov (Catalysits
Technology), Leningrad: Khimiya, 1979.
https://doi.org/10.3103/S096709121804006X
15. Lowell, S., Shields, J.E., Thomas, M.A., and Thommes,
M., Characterization of Porous Solids and Powders:
Surface Area, Pore Size and Density, Netherlands:
Springer, 2006.
8. Krutskii, Y.L., Popov, M.V., Cherkasova, N.Y.,
Kvashina, T.S., Chushenkov, V.I., Smirnov, A.I.,
Felof’yanova, A.V., Aparnev, A.I., Maksimovskii, E.A.,
and Netskina, O.V.., Russ. J. Appl. Chem., 2018, vol. 91,
no. 3, pp. 428–435.
https://doi.org/10.1007/978-1-4020-2303-3
https://doi.org/10.1134/S107042721803014X
16. Karnaukhov, A.P., Adsorbtsiya. Tekstura dispersnykh i
poristykh materialov (Texture of Dispersed and Porous
Materials), Novosibirsk: Izd. SO RAN, 1999.
9. Qian, J.X., Chen, T.W., Enakonda, L.R., Liu, D.B.,
Mignani, G., Basset, J.-M., and Zhou, L., Int. J. Hydrogen
Energ., 2020, vol. 45, no. 15, pp. 7981–8001.
17. Ermakova, M.A., Ermakov, D.Yu., Chuvilin, A.L.,
Kuvshinov, G.G., J. Catal., 2001, vol. 201, no. 2,
pp. 183–197.
https://doi.org/10.1016/j.ijhydene.2020.01.052
10. García-Sancho, C., Guil-López, R., Pascual, L., Maireles-
Torres, P., Navarro, R.M., and Fierro, J.L.G., Appl. Catal.
A: General, 2017, vol. 548, pp. 71–82.
https://doi.org/10.1006/jcat.2001.3243
18. Chesnokov, V.V. and Buyanov, R.A., Russ. Chem. Rev.,
2000, vol. 69, no. 7, pp. 623–638.
https://doi.org/10.1016/j.apcata.2017.07.038
11. Li, J., Gong, Y., Chen, C., Hou, J., Yue, L., Fu, X.,
https://doi.org/10.1070/RC2000v069n07ABEH000540
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 93 No. 7 2020