Novel catalysts for conversion of liquid hydrocarbon

Article abstract of DOI:10.1134/S107042721412009X

A catalytic system NiO-Al₂O₃ of conversion of C₆₊ hydrocarbon fractions obtained after separation of the target natural raw materials was improved by a method of mechanical activation and modification of CeO₂. The resulting modified catalyst system of a NiO-BaO-CoO₂-Al₂O₃ structure is characterized by high activity and stability during operation and also it demonstrates an oxidative activity. Structural characteristics and morphology of the modified catalytic system of hydrocarbon conversion were analyzed by adsorption methods, scanning electron microscopy, laser-dispersive and X-ray analysis.

Full text of DOI:10.1134/S107042721412009X

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2014, Vol. 87, No. 12, pp. 1849−1857. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © N.V. Lisitsyn, D.Yu. Murzin, E.A. Vlasov, A.Yu. Postnov, M.M. Sychev, S.V. Myakin, L.A. Nefedova, 2014, published in Zhurnal Prikladnoi
Khimii, 2014, Vol. 87, No. 12, pp. 1769−1778.
PROCESSES AND EQUIPMENT
OF CHEMICAL INDUSTRY
Novel Catalysts for Conversion of Liquid Hydrocarbon
N. V. Lisitsyn, D. Yu. Murzin, E. A. Vlasov, A. Yu. Postnov,
M. M. Sychev, S. V. Myakin, and L. A. Nefedova
St. Petersburg State Technological Institute (Technical University),
Moskovskii pr. 26, St. Petersburg, 190013 Russia
e-mail: ap1804@yandex.ru
Received December 12, 2014
Abstract—A catalytic system NiO–Al2O3 of conversion of C6+ hydrocarbon fractions obtained after separation
of the target natural raw materials was improved by a method of mechanical activation and modification of CeO2.
The resulting modified catalyst system of a NiO–BaO–CoO2–Al2O3 structure is characterized by high activity and
stability during operation and also it demonstrates an oxidative activity. Structural characteristics and morphol-
ogy of the modified catalytic system of hydrocarbon conversion were analyzed by adsorption methods, scanning
electron microscopy, laser-dispersive and X-ray analysis.
DOI: 10.1134/S107042721412009X
and synthesis gases with high efficiency and operational
stability.
Fractions of alkanes C6+ after the target separation of
natural raw materials on gas and oil refineries are usually
burned in boiler furnaces or in flares thereby polluting the
atmosphere with combustion products, Implementation
of the technology for processing this part of the raw
material formed after fractionation and separation of a
mixture of C1–C5 paraffins and petroleum gases after the
catalytic reforming of gas condensates to synthesis gas or
a methane–hydrogen mixture is prospective as from the
standpoint of the environmental protection and in terms
of increasing the depth of processing of hydrocarbons
[1–3]. The involvement of a part of a kerosene fraction
of the straight distillation of crude oil containing up to
47 wt % of alkanes expands the raw material resource
base of this technology.
EXPERIMENTAL
Catalysts were prepared by mixing powders of
pseudoboehmite (9 h, 16.5 wt % in term of Al2O3)
and γ-Al2O3 (18 h, 75.0 wt %) of 3–5 μm dispersion
obtained by a preliminary grinding in a ball mill with salts
Ce(NO3)·6H2O (7.5 wt % of CeO2) and Ba(CH3COO)2
(1.0 wt % of BaO), followed by homogenization for
1 h in a ball mill filled with ceramic balls of a diameter
0.04 m and a weight of 0.07 kg. A mechanochemical
activation of the mixture of powders was performed in
a ball mill for 8 h in an acidic liquid medium (HNO3 +
H3PO4) at a ratio of material : balls : water = 1 : 7 : 1.
After activation for gelling a solution of ammonia water
(25 wt %) was added to the slurry till pH 7.2–7.4. Then
in the mixture Ni-containing component [nickel nitrate,
MkhA-1 and MkhA-2 samples; basic nickel carbonate,
samples of MKhA-3 and MKhA-4; basic nickel carbonate
thermally decomposed at 250–400°C (Ta) for 0.2–2.0 h
(τa), samples NS-1–NS12] was introduced in term of
10.0 wt % NiO, followed by stirring for 0.5 h. After
drying at 70–80°C for 6 h the resulting mass was extruded
through spinnerets of a diameter 5 mm, the granules were
Steam, oxygen or carbon dioxide conversion of
methane and its homologues is performed on Ni-
containing catalysts supported on α-Al2O3 [4, 5].
However, with increasing a length of a hydrocarbon chain
in the processed liquid alkanes the catalyst undergoes
rapid deactivation due to the formation of free carbon
on the surface [6].
The aim of the study is to optimize the structure of
oxide aluminum-nickel catalysts for the implementation
of the conversion of C6+ in a mixture of hydrocarbon
1849

1850
LISITSYN et al.
Table 1. Structural and strength parameters of MKhA samples
dtrue
δ
VΣ,
Sample
requiv, nm
Ssp, m2 g–1
Pe, MPa
8.2
Т, °C
cm3 g–1
g cm–3
MKhA-1
MKhA-2
MKhA-3
MKhA-4
2.786
3.025
3.190
3.340
1.77
1.82
1.38
1.32
0.27
0.26
0.43
0.46
60–85; 135–203
123–190; 300–520
5–15; 50–70
124
57
600
1000
600
11.8
6.9
160
98
54–63; 150–180
12.6
1000
dried at 100°C for 4 h and calcined at 600°C (MKhA-1
and MKhA-3) and 1000°C (MKhA-2 and MKhA -4).
reforming reaction of n-heptane as a model substance of
a series of alkanes at a flow rate 2285–2900 h–1, a ratio
of steam : heptane = 11 : 1, a pressure of 1 atm, a volume
of a catalyst of fraction 3–4 mm = 20 cm3, the process
temperature Tp= 380–470°C, and a testing time τt = 0.5–
18 h in the oxidation reaction of hydrogen with air oxygen
at a rate of gas-air flow of 27 000 h–1 (a concentration of
hydrogen in the air about 3%, a volume of the catalyst
of 3–4 mm fraction 4 cm3). Analysis of gas mixtures
and condensate was carried out on a chromatograph
Tsvet-500. The catalytic activity of the samples was
Porous structure of the synthesized samples was
analyzed using pycnometry methods (a true density dtrue
was determined based on benzene, an apparent density
δ, based on mercury), a porosimetry instrument PA-3M
(pore radius requiv was calculated from the differential
curve of a change in pore volume relative to radius),
and adsorption methods (a specific surface area Ssp of
samples was measured chromatographically by a thermal
desorption of nitrogen) [7]. The total pore volume was
calculated according to the equation VΣ = 1/δ – 1/d.
evaluated by a conversion X (%) of n-heptane [X = (c0C7
–
cC7) × 100/c0C7, where c0C7 and cC7 are concentrations of
n-heptane at the inlet and outlet of a reactor] and by a
volume V and composition (H2, CO, CO2, CH4) of dry
gas at the reactor outlet.
X-ray diffraction (XRD) patterns were analyzed
on a DRON-3M (CuKα-radiation and Ni-filter). To
calculate the parameters of the unit cell 12–20 reflexes
and the program PDWIN were used; the accuracy of
determination was 0.0002 nm. Infrared spectra (IR)
were recorded on an automatic spectrophotometer
Shimadzu FTIR-460 S in the region of 400–1700 cm–1;
samples were prepared as tablets with KBr. Texture of
the surface of the catalysts was studied by a scanning
electron microscope VEGA 3 TESCAN, a disperse
composition of the products of thermal decomposition
was examined by a laser dispersion analyzer Microtrac
Nanotrac S 3500 and a scanning electron microscope
JSM-35CF (company JEOL), a completeness of salt
decomposition was determined by chemical analysis and a
total weight of nickel (ZGNi) in the product; a distribution
of the acid-base sites by the strength was studied on
a spectrophotometer SF-46, and the Hammett acidity
function HoI was determined from pH-metric curves [8].
A mechanical crushing strength on the end face Pe and
along loading line Pl were evaluated using an average
value of crushing strength of the granules from a selection
of 30 pieces and by a device MP-2S.
The analysis of the electronic images demonstrates
that by using nickel nitrate the catalyst surface is
composed of closely packed quasi-globular aggregates
(average size of the individual agglomerate 2–3 μm)
(Figs. 1a, 1b). Application of the basic nickel carbonate
generates more structural defects (Fig. 1d) in comparison
with Ni(NO3)2. Samples MKhA-3 and MKhA-4 (Table 1)
are of an average pore radius of 5–15, 50–70, and
54–63, 150–180 nm and, consequently, of more fine
pore structure as compared with the catalysts MKhA-1
and MKhA-2. Application of basic nickel carbonate at
a calcination temperature of 600°C has increased the
specific surface area of samples up to 160 m2 g–1 at the
satisfactory (6.9 MPa) crushing strength of the granules.
In samples MKhA-1 and MKhA-2 prepared from
nickel nitrate XRD and IR spectroscopy detected
together with NiO a significant amount of NiAl2O4,
and demonstrated that an increase in T from of 600 to
1000°C leads to the formation of a new phase of spinel
NiO·5Al2O3, and α-Al2O3. In the MKhA-3 sample
synthesized from basic nickel carbonate the presence of
The catalytic activity of synthesized samples was
determined on installations of a flow type on a steam
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NOVEL CATALYSTS FOR CONVERSION OF LIQUID HYDROCARBON
(b)
1851
(a)
5 μm
20 μm
(c)
(d)
2 μm
2 μm
Fig. 1. Electronic photographs of the surface of catalysts MKhA-1 (a), MKhA-2 (b), MKhA-3 (c), MKhA-4 (d).
NiO up to 5.10 wt %, NiAl2O4, and traces of Ni2O3 were
found. Therewith samples MKhA-3 and MKhA-4 are
less crystallized than samples MKhA-1 and MKhA-2,
and aluminum-nickel spinel is detected in the IR spectra
of the samples MKhA-1 and MkhA-2: 583, 579, 533,
529 cm–1 (Fig. 2 ).
deactivation of nickel due to the spinel formation in
the case of using nickel nitrate in the synthesis of the
catalysts.
Thermal activation of basic nickel carbonate.
Electronic photographs of texture (Fig. 3) of starting
NiCO3·Ni(OH)2 showed the presence of agglomerates
with a pronounced inner structure, which is formed from
spheroidal particles ranging in size from 80 to 300 nm.
According to XRD and IR spectroscopy salt is X-ray
amorphous, absorption maxima at 662, 703, and 832 cm–1
are assigned to the stretching vibrations of O–Ni–O
in carbonate–hydroxide structures, and those at 1072,
1376, 1595 cm–1 characterize the stretching vibrations
of monodentate carbonate ion. Derivatografic analysis
of basic nickel carbonate identified two specific intervals
of weight loss during decomposition: 60–140°C—at
removing of hydration water the weight loss was
The catalytic activity of samples of the MKhA
series. The catalyst of MKhA-3 synthesized using a basic
nickel carbonate and obtained at 600°C shows the best
performance in the conversion of n-heptane (Table. 2).
The sample gives the conversion X up to 55% that is
greater by 15% the conversion of an industrial catalyst
GIAP-8 and therewith a flow of the gas mixture at the
outlet is up to 0.0315 m3 h–1 that is by more than 3 times
larger than this value for GIAP-8 (at T = 470°C). Samples
of MKhA-1 and MKhA-2 were inactive during n-heptane
conversion, this fact is associated with almost complete
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1852
LISITSYN et al.
MKhA-1
MKhA-2
A
MKhA-3
MKhA-3
Fig. 2. IR absorption spectra of the samples MKhA-1–MKhA-4. (ν) wavenumber, cm–1.
10 μm
1 μm
Fig. 3. Electronic photographs of microstructure of basic nickel carbonate.
19.1–22.3 wt %; 260–315°C—in the decomposition of
the hydroxide component and the partial destruction of
the carbonate component the weight loss was 40 wt %
(Fig. 4). The final decomposition of the salt completes
already at 400°C. Therefore, the NiCO3·Ni(OH)2 heat
treatment regime in the temperature range of 300–400°C
enables: (a) adjusting the pore structure due to changes
in the intensity of the decomposition of the carbonate
component of salt; (b) changing acid-base and donor-
acceptor properties of active sites on the catalyst surface
by changing in the rate of solid phase reactions. The
last statement is based on the theory of topochemical
processes, according to which in the intradiffusion field a
rate of thermal decomposition is inversely proportional to
the square of the radius of the particles that can be realized
by slow decomposition of carbonate and removal of CO2
without destroying the original agglomerates.
However, during ignition of the catalyst the thermal
decomposition of NiCO3·Ni(OH)2 is advantageously to
carry out at a maximum rate for the formation of nano-
sized NiO, therewith kinetic or external diffusion region
of the process may occur, where the decomposition rate
is inversely proportional to the radius of the particle.
Accounting for that the source nickel carbonate is
of a polydisperse composition, variation in a ratio of
nanosized NiO and larger particles of NiO formed in the
preparation stage of the precursor enables controlling the
properties of the catalyst as a whole.
X-ray diffraction and chemical analysis showed
that the decomposition of the carbonate and hydroxide
component of the salt passes through the formation of
X-ray amorphous phases of NiOOH and Ni2O2(OH)4, and
also of NiO, the presence of which is detected only at a
concentration of Ni more than 65 wt % in the products
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NOVEL CATALYSTS FOR CONVERSION OF LIQUID HYDROCARBON
1853
Table 2. Activity of cata;ysts MKhA-3 and MKhA-4 on steam
conversion of n-heptane
Table 3. Disperse composition of basic nickel carbonate
Parameter Value
According to data of SEM, JSM-35 CF (JEOL)
Fraction, μm < 5 5–10 10–15 15–20 20–35
Proportion of fraction, vol % 25 30 20 10 15
According to data of Microtrac Nanotrac S 3500
Composition of fry gas
V,
m3 h–1
Τexp,
h
mp, °С
X, %
H2 CO CH4 CO2
MKhA-3
380 76.45 1.90 0.40 21.25
5
0.0054
Fraction, μm
Proportion of fraction, vol %
2.6
46
1.8
54
420 77.15 2.15 0.52 20.18 25 0.0144
450 77.30 2.20 0.55 19.95 34 0.0260
470 78.10 1.63 0.47 19.80 55 0.0315
4
4
samples HoI increases (from 8.4 to 9.3).
MKhA-4
A gradual growth of the amount of CeO2 of cubic
system upon the increase in ZGNi was found in the ranks
of NS-1 → NS-6 and NS-7 → NS-12 (Table 4). This
fact indicates a change in priorities of the distribution
of cerium cations that is the hallmark of the conversion
catalyst obtained according to the proposed technology.
380 75.67 2.79 1.37 20.17
420 76.91 2.23 0.79 20.07
450 77.48 2.11 0.52 19.89
470 77.95 2.24 0.61 19.20
2
5
7
8
0.0015
0.0015
0.0017
0.0019
The average size of coherent scattering of particles
of cubic NiO increases with increasing temperature
from 600 to 1000°C and in the rank of NS-1 (22 nm) →
NS-12 (60 nm), i.e., with increasing crystallinity of the
decomposition product. Figure 5 shows photographs of
a microstructure of the catalyst sample NS-6, Table 5
lists the elemental composition of the samples in the
selected locations. The presence of areas with both low
and high contents of nickel and cerium can be ascertained
in the structure of the compositions. Zones with high
concentration of nickel and cerium are demonstrated
by ellipsoidal formations of light range, the average
distribution of which in the catalyst bed is fairly
evenly. Therewith an association of nickel- and cerium-
containing phases in such separate agglomerates shows
of thermolysis, that just determines the character of the
formation of disperse composition of product.
In the case of the constant time of decomposition (τa =
0.2 h) with increasing temperature (Ta = 300 → 350 →
400°C) there occurs a change in the particles size and the
fraction ratio 0.5–1.0 μm (30%) and 1.0–5.0 μm (70%) →
<0.1 μm (28%), 0.5–1.0 μm (30%) and 1.0–5.0 μm
(42%) → <0.1 μm (5%), 0.5–1.0 μm (35%) and 1.0–
5.0 mm (60% ).At the constant temperature (Ta = 350°C)
and increase in τa up to 1.0 h the following relations were
set: 0.5–1.0 μm (60%) and 1.0–5.0 μm (40%).
In general, the character of the topochemical processes
proceeding at a final heat treatment of the catalyst
synthesized using carbonate or products of its thermolysis
can determine essential differences in structural and
strength properties of the catalysts and activity in the
conversion processes.
TG
The structural and strength properties of the granules of
the catalysts prepared by MKhAtechnology using nickel
carbonate thermally decomposed at 250 (53.35 wt %
of NiO) and 400°C (72.60 wt % of NiO) with a final
treatment temperature of 600 and 1000°C were studied.
Table 4 demonstrates that with increasing the NiO
proportion a decreases in the pore volume occurs from
0.45 to 0.34 (T = 600°C) and from 0.43 to 0.29 cm3 g–1
(T = 1000°C) and also the strength of granules grows from
5.7 to 13.3 MPa (T = 600°C) and from 6.3 to 28.0 MPa
(T = 1000°C), moreover, a basicity of the surface of the
DTA
T
T
Fig. 4. Derivation basic nickel carbonate. (T) temperature (°C).
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LISITSYN et al.
Table 4. Structural and strength parameters of NS catalysts
Pe
Pl
d,
VΣ,
requiv
nm
,
Ssp,
Sample
Та, °C
250
300
350
400
350
400
τа, h
ZGNi, wt %
53.35
Т, °C
HоI
g cm–3
cm3 g–1
m2 g–1
MPa
NS-1
NS-7
NS-2
NS-8
NS-3
NS-9
NS-4
NS-10
NS-5
NS-11
NS-6
NS-12
600
1000
600
3.37
3.45
3.35
3.40
3.43
3.16
3.43
3.43
3.42
3.45
3.21
3.38
0.45
0.43
0.43
0.41
0.38
0.37
0.38
0.36
0.35
0.34
0.34
0.29
4.8
9.7
4.4
8.2
4.5
8.7
4.3
8.0
4.6
8.5
4.3
8.2
138
87
5.7
6.3
2.2
2.7
2.6
2.9
3.4
4.4
3.4
5.3
3.7
6.0
4.4
6.7
8.4
8.5
8.4
8.6
8.5
9.0
8.3
9.1
8.5
9.2
8.4
9.3
0.8
160
77
6.5
53.75
1000
600
7.6
125
65
12.1
16.2
12.1
17.3
12.3
20.4
13.3
28.0
1.0
0.8
60.50
1000
600
147
62
60.00
1000
600
141
64
67.65
1000
600
2.0
157
71
72.60
1000
the deformation vibrations of hydronium ion that indicates
the appearance of new surface active sites of sorption in
the course of thermolysis of NiCO3·nNi(OH)2·mН2O.
Peaks at 660–680 cm–1 characterize stretching vibrations
of NiO bond possessing a high dispersion.
likely their specific diffusive interaction, which should
have a decisive effect on the catalyst operation in the
target process.
XRD identifies only a small amount of nickel
aluminates compared with catalysts synthesized without
thermal decomposition of the active component. In the IR
spectra of NS-4 (Ta = 400°C, τa = 0.8 h) and NS-6 (τa =
2.0 h) a band appears at 1745 cm–1, which is responsible for
The catalytic activity of samples of the NS series.
Parameters of the catalytic activity of the samples
calcined at 600°C are much higher than the data of
catalysts thermally treated at 1000°C. With increasing
ZGNi (Table 6) the conversion and the amount of the gas
mixture at the outlet increase. However, the selectivity
of the catalysts (T = 600°C) from NS-1 (Ta = 250°C) to
NS-6 (Ta = 400°C) varies in the direction of increasing the
Spectrum 1
Spectrum 3
Spectrum 4
Spectrum 5
Spectrum 2
Fig. 6.Agglomerates of coke formed on the the R-67-7N catalyst
surface after 4 hours of operation under specified conditions of
steam reforming of n-heptane.
Fig. 5. Electronic photographs of microstructure of sample
NS-6.
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NOVEL CATALYSTS FOR CONVERSION OF LIQUID HYDROCARBON
1855
Table 5. The elemental composition of the sample
Content of element, wt %
Localization
O
Al
Si
P
Ni
Ba
Ce
Spectrum 1
Spectrum 2
Spectrum 3
Spectrum 4
Spectrum 5
33.82
53.79
52.47
45.64
55.22
33.11
40.52
41.14
42.23
39.96
0.59
0.58
0.92
1.00
0.35
0.22
0.18
0.13
0.26
0.13
22.34
1.77
1.79
3.59
1.32
0.30
0.44
0.67
0.82
0.46
9.63
2.72
2.88
6.46
2.56
amount of methane (H2 → CH4) in a production mixture.
Catalysts NS-1 and NS-6 are of an increased stability:
even after 36 h of operation the conversion parameters
achieved the have not changed, and the formation of
carbon are not observed. The results of similar tests
carried out for industrial catalysts of grades GIAP-8,
R-67-7H, and KATALCOJM 57-4Q demonstrated intense
coking of a surface after 1.5–3.0 h (Table 7, Fig. 6).
electron acceptor Lewis sites and the main Bronsted sites,
which dissociate with a cleavage of a proton and setting
+
–
→
←
of equilibrium M–OH
H + M–O , was found. With
increasing Ta of the salt decomposition from 300 to 400°C
the cs of the acid-base sites of pKa –4.4…–1.3 decreases
(from 0.382 to 0.085 μmol m–2 at T = 600°C for NS-2 →
NS-8 and from 0.600 to 0.0796 μmol m–2 at T = 1000°C
for NS-6 → NS-12) the concentration of sites of pKa 2.1
increases from 0.0022 to 0.0105 μmol m–2 at T = 600°C
and from 0.0013 to 0.0017 μmol m–2 at T = 1000°C.
In the spectrophotometric determination of the
concentration cs and distribution of acid-base surface
sites by the strength for the synthesized samples no
correlation was found between the catalytic activity in the
conversion reaction of n-heptane and a concentration of
electron donor Lewis acid-base sites with pKa values in a
range of –4.4…–1.3; but the presence of sites of pKa < 0
representing Lewis acid sites formed by oxygen atoms was
determined. The correlation between the catalytic activity
and the content of sites with pKa 2.1, which are formed by
By increasing the treatment temperature of alumina
systems from 600 to 1000°C the concentration of acid
sites is usually reduced and the content of base sites
increases. However, when basic nickel carbonate with
Ta = 300°C is used in the synthesis of X-ray amorphous
product decomposition, the concentration of acid sites
with increasing T rises and only at Ta = 400°C the
concentration of base sites begins to rise. Dependences,
Table 6. Activity of the NS catalysts in the process of steam reforming of n-heptane. Total test time 36 h
Composition of dry gas, vol %
ZGNi, wt % mp, °С
X, %
V, m3 h–1
τexp, h
H2
CO
CH4
NS-1
CO2
53.35
72.6
380
420
450
470
78.59
78.15
76.20
74.87
1.26
1.53
2.34
3.28
0.36
1.46
1.55
1.90
19.79
18.86
19.91
19.95
2
0.0019
0.0220
0.0313
0.0343
40
69
62
3.0
NS-6
380
420
450
470
56.08
56.67
55.74
55.46
1.65
2.64
4.07
4.76
22.27
20.89
20.42
20.08
20.00
19.80
19.77
19.70
80
0.0300
0.0414
0.0450
0.0514
1.5
2.0
100
100
100
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LISITSYN et al.
Table 7. Activity of industrial catalysts in steam reforming of n-heptane
Composition of dry gas, vol %
mp, °С
X, %
V, m3 h–1
τexp, h
H2
CO
CH4
CO2
R-67-7Н (NiO/MgAl2O4, Tfin= 1200°С, ZGNiO ≈ 15 wt %)
380
420
450
470
62.35
61.91
56.37
55.97
1.00
2.12
2.34
3.64
16.32
17.15
22.79
23.39
20.33
18.82
18.50
17.00
60
99
99
99
0.0209
0.0383
0.0439
0.0500
3
1.5
1.5
1.5
KATALCOJM 57-4Q (NiO/mCaO·nAl2O3)
380
420
450
470
–
9
0.0036
0.0058
0.0072
0.0073
3
77.07
75.68
74.59
1.19
2.32
3.00
0.13
0.21
0.35
21.61
21.79
22.06
15
24
28
1.5
1.5
1.5
GIAP-8 (NiO/Al2O3, Tfin = 1100°С, ZGNiO ≈ 10 wt %)
380
420
450
470
77.18
77.39
77.49
80.03
0.40
0.60
1.39
2.37
0.32
0.61
1.53
2.50
22.10
21.50
19.59
15.10
19
23
34
40
0.0040
0.0076
0.0086
0.0108
4
4
4
4
which were obtained for the first time, show that the
growth in X occurs due to both the Lewis and Bronsted
sites of pKa 2.1 providing an effective cleavage of
hydrocarbon molecules owing to detachment of protons
from molecules of n-heptane at the optimum acidity and
binding them into molecules H2 with protons splitting
off from the main Bronsted sites. There is a significant
decrease in the concentration of sites of pKa –5…0
when approaching the decomposition product by its
composition to NiO (Ta = 400°C in the catalysts NS-6 and
NS-12). However, a clear correlation with the selectivity
is observed for a narrow range of the Bronsted sites of
pKa < 1.25. The concentration of these adsorption sites is
minimal on the catalyst NS-6, which provides the greatest
amount of methane in the production gas mixture.
acid-base sites.
From the analysis of data on texture scanning and
elemental composition of synthesized samples the
presence of ellipsoidal formations was found, which are
characterized by high concentrations of Ni and Ce and
fairly evenly distributed in the structure. The presence of
such mixed phases activates the catalysts in the conversion
and oxidation processes. It should be noted that in the
catalysts with T = 600°C nickel component prevails in the
ellipsoidal formations (15–16 wt % for NS-2), while for
compositions with T = 1000°C Ce components prevails
(12–13 wt % for NS-8). The concentration of Ni in these
formations greatly increases (up to 22–26 wt % in NS-6)
for the catalyst in the synthesis of which a precursor of
ZGNi = 72.60 wt % (Ta = 400°C) was used that indicates
a change in the localization of active sites.
All the catalysts of series NS-1–NS-6 and NS-7–NS-
12 exhibit the increased activity relative to oxidation of
hydrogen (at 140–160°C the conversion of hydrogen
reaches 95–98%). For sites of pKa –4.4…–1.3 and 2.1
approximating equations of the form X = A1cs + B1 and X =
A2ln cs + B2 were derived (Table 8) with a high criterion
validity allowing performance of a rapid analysis of the
catalytic properties using the known concentration of the
CONCLUSIONS
(1) The modified catalyst NiO–BaO–CeO2–Al2O3
synthesized using basic nickel carbonate (sample
MKhA-3, the calcination temperature 600°C) provides
the conversion of n-heptane up to 55% at 470°C with a
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 87 No. 12 2014

NOVEL CATALYSTS FOR CONVERSION OF LIQUID HYDROCARBON
1857
Table 8. Constants of approximation equations (criterion
concentrations of the surface sites.
ACKNOWLEDGMENTS
reliability R2i )
Acid-base sites
The work was performed as part of state contract
awarded on the basis of a grant of the Government of
the Russian Federation for support of scientific research
conducted under the supervision of leading scientists
at Russian institutions of higher education, research
institutions of State Academies of Sciences and state
research centers of the Russian Federation on March 19,
2014, no. 14.Z50.31.0013.
mp, °С
рKа –4.4…–1.3
А1 В1
R12
380 –89.16 56.29 0.85
рKа 2.1
А2
В2
R12
32.26 225.49 0.871
420 –112.32 70.49 0.937 33.81 277.12 0.826
470 –113.20 79.37 0.867 36.45 269.43 0.753
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RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 87 No. 12 2014