Effect of immobilized carbon nanoparticles on the activity of zeolites in the oxidative dehydrogenation of 4-vinylcyclohexene and ethylbenzene to styrene

Article abstract of DOI:10.1134/S0965544112010021

The results of studies on the oxidative dehydrogenation of 4-vinylcyclohexene to ethylbenzene and styrene and ethylbenzene to styrene on nanocomposite systems prepared by the immobilization of carbon nanoparticles on the H forms of zeolites and the modifi

Full text of DOI:10.1134/S0965544112010021

ISSN 0965ꢀ5441, Petroleum Chemistry, 2012, Vol. 52, No. 2, pp. 97–104. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © Kh.M. Alimardanov, A.A. Alieva, S.I. Abasov, M.F. Abbasov, A.D. Kuliev, 2012, published in Neftekhimiya, 2012, Vol. 52, No. 2, pp. 116–123.
Effect of Immobilized Carbon Nanoparticles on the Activity
of Zeolites in the Oxidative Dehydrogenation of 4ꢀVinylcyclohexene
and Ethylbenzene to Styrene
Kh. M. Alimardanov, A. A. Alieva, S. I. Abasov, M. F. Abbasov, and A. D. Kuliev
Mamedaliev Institute of Petrochemical Processes, National Academy of Sciences of Azerbaijan, Baku, 370025 Azerbaijan
eꢀmail: mayabdullayeva@rambler.ru; alreyhan@yahoo.com
Received May 16, 2011
Abstract—The results of studies on the oxidative dehydrogenation of 4ꢀvinylcyclohexene to ethylbenzene
and styrene and ethylbenzene to styrene on nanocomposite systems prepared by the immobilization of carꢀ
bon nanoparticles on the H forms of zeolites and the modification of the resulting samples with platinum,
gallium, and gadolinium are given. The activities of these catalysts are compared, and the synergism of the
action of zeolite and carbon nanoparticles under the conditions of dehydrogenation is established. The
immobilization of carbon nanoparticles into zeolite matrices contributes to an increase in their activity and
stability and also to a decrease in the reaction temperature. The high yields of 4ꢀvinylcyclohexene and ethylꢀ
benzene dehydrogenation products are reached at 425 and 470°C, respectively.
DOI: 10.1134/S0965544112010021
The targetꢀoriented conversion of hydrocarbon raw styrene. For the industrial implementation of this proꢀ
materials into necessary products in the presence of cess, it is necessary to develop catalytic systems that
nanocomposite systems, in particular, those prepared are more efficient and provide high selectivity at either
based on materials with zeolite or zeoliteꢀlike strucꢀ of the stages because of the presence of considerable
tures, is a priority trend in the development of presentꢀ 1,3ꢀbutadiene resources in the pyrolysis products of
day petroleum chemistry. It is well known that pentaꢀ petroleum fractions.
sils and mesoporous zeoliteꢀlike systems modified
with Pt, Ga, and Gd exhibit high activity and selectivꢀ
ity in the aromatization, oligomerization, and alkylaꢀ
tion of lowꢀmolecularꢀweight saturated and unsaturꢀ
ated hydrocarbons [1–6]; the conversion of methanol
into aliphatic and aromatic hydrocarbons [7, 8]; the
alkylation of benzene with propane [9] or isopropanol
[10]; the dehydrodisproportionation [11] and dehyꢀ
droalkylation of alkylꢀsubstituted С7–С8 cyclohexꢀ
anes with methanol [12, 13]; etc. However, there is
almost no data on the use of these catalysts in the
dehydrogenation reactions of hydrocarbons, in particꢀ
ular, ethylbenzene conversion into styrene, although
other modified forms of different zeoliteꢀcontaining
catalysts are widely used in reactions for the producꢀ
tion of styrene and its methyl derivatives by the dehyꢀ
drogenation of ethylbenzene [14–16], the dehydraꢀ
tion of methylꢀ and dimethylphenyl carbinols [17, 18],
and the alkylation of alkenylbenzenes [19, 20] and tolꢀ
uene [21, 22] with methanol.
The dehydrogenation of 4ꢀvinylcyclohexene in the
presence of wellꢀknown catalytic systems occurs with
the predominant formation of ethylbenzene [25, 27]
or a mixture of ethylbenzene and styrene with the preꢀ
dominance of the former [23, 24]. In this case, the
ratio between the resulting reaction products—ethylꢀ
benzene and styrene—depends on the time of catalyst
operation and changes significantly in the course of
the process.
This work is the development of studies on the oxiꢀ
dative dehydrogenation of 4ꢀvinylcyclohexene and
ethylbenzene in the presence of zeolites TsVM modiꢀ
fied with Pt and Ga. Here, we report the main experiꢀ
mental results of studying changes in the activity and
selectivity of nanocomposite systems prepared based
on these zeolites and carbon nanoparticles immobiꢀ
lized in them in the test reaction.
EXPERIMENTAL
The butadiene method implemented with the parꢀ
The experiments were conducted on a laboratory
ticipation of oxide and zeoliteꢀcontaining catalysts setup at 0.1 MPa. A 3ꢀg sample (fraction of 0.5–1 mm)
[23–26] is currently considered an alternative method of a catalyst, which was granulated without a binding
for expanding the range of raw materials for styrene agent, mixed with quartz grains in a ratio of 1 : 2 was
production. This method is performed in the following loaded in a flow reactor and thermally treated at 500–
two stages: the dimerization of butadiene to 4ꢀvinylcyꢀ 550 С for 3–4 h in a flow of air. The hydrogen forms
°
clohexene and the dehydrogenation of the latter to of HNaꢀmordenite (HNaM, SiO2/Al2O3 =
x = 10),
97

98
ALIMARDANOV et al.
The Xꢀray diffraction patterns of the prepared catꢀ
alysts were taken on a DRONꢀ3M diffractometer
using CuK
radiation with a Ni filter. The sizes of carꢀ
α
bon nanoparticles in a zeolite matrix were determined
on an NCꢀAFM scanning atomic force microscope.
The parent substances were 4ꢀvinylcyclohexene,
which was prepared in accordance with a wellꢀknown
procedure [29], and chemically pure ethylbenzene.
The physicochemical constants of these substances
were consistent with reference data [30].
Z
nm
X
nm
40
20
1600
1200
0
Y
nm
1600
The reaction products were analyzed by GLC with
a flameꢀionization detector: a
packed with 10 wt % SEꢀ30 on Chromosorb W (Tcol
140°C and inj = 180°C) and with 12 wt % bis(2ꢀcyaꢀ
6
×
2400 mm column
800
1200
=
T
800
400
noethyl) sulfide on the adsorbent Chromaton N AWꢀ
DMCS. Standard reference compounds were used for
the identification of the products of catalysis.
400
0
0
Fig. 1. AFM 3D image of the Pt, Ga, Gd/HNaꢀTsVM +
20% immobilized carbon nanoparticles.
RESULTS AND DISCUSSION
Previously, we found that the samples of HNaꢀTsVM
modified with Pt, Ga, Gd, and potassium at 470–
485 С exhibited high activity in the oxidative dehyꢀ
HNaꢀTsVM (x = 30), and HNaY (x = 4.8) were used
°
as parent zeolites. The degree of decationation was
75 wt %. The immobilization of carbon nanoparticles
was performed by the in situ precipitation of them
onto the zeolite. For obtaining the carbon nanopartiꢀ
cles, CCl4 taken in an excess amount was stirred with
aluminum metal chips in a glass reactor at 75–76°C.
At the instant of carbon formation according to the
equations
drogenation of 4ꢀvinylcyclohexene to ethylbenzene
and styrene [31]. Further studies showed that the yield
of dehydrogenation products on a freshly prepared
sample initially increased in the course of the process
and then somewhat decreased. The activity and stabilꢀ
ity of spent samples after their treatment in a flow of air
at 450–500 С for 4 h were much higher than data
°
obtained on the freshly prepared catalysts; this fact
suggests the participation of specific reaction mixture
components in the formation of the active centers of
the catalyst. Analogous regularity was observed previꢀ
ously [1, 6] for the aromatization of С3⎯С5 paraffins
on Ga and Pt, Ga pentasils. Dergachev et al. [1, 6]
proposed the treatment of gallosilicates and galloaluꢀ
minosilicates in a flow of hydrogen or water vapor in
order to accelerate the stabilization of activity. On the
other hand, such a change in the activity of oxide and
zeolite catalysts in the oxidative dehydrogenation [32,
33] and alkylation [34] reactions of alkylaromatic
hydrocarbons can be a consequence of the accumuꢀ
lated carbon deposits on their surface. To study the
effect of carbonꢀcontaining deposits on the activity of
zeolites in the oxidative dehydrogenation reaction of
4ꢀvinylcyclohexene and ethylbenzene, we preliminarꢀ
ily investigated systems based on immobilized carbon
nanoparticles containing modified forms of zeolites
(HNaY, HNaM, and HNaꢀTsVM) with different conꢀ
centrations of carbon nanoparticles in wide ranges of
2Al + 3CCl4
→
2AlCl3 + C2Cl6 + C
2AlCl3 + 2C
2Al + C2Cl6
→
decationized zeolite was added to the mixture, and the
stirring was continued until the complete consumpꢀ
tion of aluminum for 2–8 h. The carbonized samples
were separated from the mixture by filtration with the
use of a Buchner funnel. Then, the precipitate was
washed with CCl4, dried at 80–120
nitrogen, and thermally treated at 200–250
°
C
in a flow of
until
°
C
the complete cessation of the release of HCl and the
sublimation of AlCl3. The specified degree of zeolite
carbonization was reached by varying the amount of
aluminum metal and the duration of stirring. Ga, Gd,
and Pt were introduced into the composition of the H
form of zeolites with immobilized carbon nanopartiꢀ
cles by impregnation with the aqueous solutions of Ga
and Gd nitrates and ammonium hexachloroplatinate
followed by heat treatment according to the known
method [28]. Catalyst samples containing 3.0 wt %
Ga2O3, 2.0 wt % Gd2O3, and 0.5 wt % Pt were used in
the experiments. For the comparison of activities, Pt–
Ga–Gd samples supported on immobilized carbon
nanoparticles without a zeolite matrix and on zeolite
that did not contain immobilized carbon nanopartiꢀ
cles were also prepared.
temperatures (320–525
ities (
°
С), hydrocarbon space velocꢀ
v
= 0.5–3 h–1), and 4ꢀvinylcyclohexene (ethylꢀ
benzene) : О2 molar ratios (0.2–1.5). The relief of carꢀ
bon nanoparticles in the prepared samples was studied
on a scanning atomic force microscope (Figs. 1 and 2).
Carbonization mainly occurs on the surface of a zeoꢀ
lite matrix. The sizes of the resulting carbon nanoparꢀ
ticles were as great as 30–67 nm. The atomic force
PETROLEUM CHEMISTRY Vol. 52
No. 2
2012

EFFECT OF IMMOBILIZED CARBON NANOPARTICLES ON THE ACTIVITY
99
microscopic analysis of the samples revealed morphoꢀ
Exit
2200
2000
1800
1600
1400
1200
1000
800
logically diverse surface structures. Xꢀray diffraction
analysis demonstrated that the major portion of
immobilized carbon nanoparticles was highly disꢀ
persed carbonꢀcontaining mass. As a rule, peaks due
to carbon in the diffractograms merged into a wide
nm
halo with characteristic maximums at
d = 3.41–
3.42 Å.
According to Xꢀray diffraction data, the structure
of zeolites remained almost unchanged upon carbonꢀ
ization and impregnation with corresponding salt
solutions. Only a decrease in crystallinity was observed
in HNaY samples. Tables 1 and 2 compare results conꢀ
cerning catalyst activity. As can be seen in Table 1, the
introduction of immobilized carbon nanoparticles
into the composition of zeolites had almost no effect
on the qualitative composition of the liquid products
of catalysis. The ratios between and the yields of the
dehydrogenation products of 4ꢀvinylcyclohexene
(ethylbenzene and styrene) depend on structure and
the degree of carbonization of zeolites. Of zeolite catꢀ
alysts, the greatest amounts of ethylbenzene and styꢀ
600
400
200
nm
0
10 20 30 40 50 60 70
, nm
Z
Roughness Average 7.78 nm
Root Mean Square 9.93 nm
Fig. 2. Bar diagram of the distribution of carbon nanoparꢀ
ticles on the surface of a zeolite matrix.
rene in a nonꢀsteady state at 470 С were obtained on
°
Pt, Ga, Gd/HNaY (51.9%) and Pt, Ga, Gd/HNaM
(20.4%), respectively. The presence of immobilized
carbon nanoparticles (INCs) in the composition of
zeolite catalysts contributes to an increase in
their dehydrogenating activity. However, from
data in Table 1, it follows that the yields of ethylbenꢀ
zene and styrene upon the oxidative dehydrogenation
of 4ꢀvinylcyclohexene on Pt, Ga, Gd/INC were lower
than those on the zeolite catalysts containing no
immobilized carbon nanoparticles by a factor of
almost 1.5. It is also of interest that the activity of Pt,
Ga, Gd/INC was twice as high as the activity of the Pt,
Ga, Gd/AGꢀ3 sample prepared based on AGꢀ3 carꢀ
bon.
hydrocarbons, increases. It is likely that this is responꢀ
sible for the observed high selectivity of the process for
the target products.
Our studies performed using zeolite samples modiꢀ
fied with Pt, Ga, and Gd with different degrees of
dealumination of mordenite (Al2O3/SiO2 =
x =
10 17; TsVM, = 33–50) showed that the dealumiꢀ
⎯
х
nation of zeolites in the specified range had almost no
effect on the activity of the used catalysts.
We chose Pt, Ga, Gd/HNaTsVM samples containꢀ
ing 5 and 20 wt % immobilized carbon particles for the
subsequent studies of catalytic properties.
A somewhat different behavior was observed in the
oxidative dehydrogenation of ethylbenzene on these
samples. An increase in the amount of immobilized
carbon nanoparticles to 5 wt % (Table 2) had almost
no effect on the activity of the catalysts, although it
facilitated an increase in selectivity for styrene from
82.0 to 88.0%. A further increase in the amount of
immobilized carbon nanoparticles in the composition
of a catalyst led to a decrease in its activity, whereas the
selectivity remained almost unchanged.
The ratios between and the yields of the oxidative
dehydrogenation products of 4ꢀvinylcyclohexene and
ethylbenzene with the participation of this
sample depend on both the conditions of catalysis
(Tables 3, 4) and the hydrocarbon : oxygen molar ratio
(Figs. 3a, 3b). For the comparison of results, Tables 3
and 4 also summarize data obtained on noncarbonized
TsVM and immobilized carbon nanoparticles conꢀ
taining corresponding amounts of Pt, Ga, and Gd. It
is well known that, on the decationized forms of zeoꢀ
It is likely that the chemical modification of zeoꢀ lites like mordenite and pentasil modified with the
lites with nanosized carbon particles leads to their oxides of polyvalent metals in the range of 250–
accumulation in the channels of the structure and, 340
C, the sequential displacement of multiple bonds
°
thus, in the blocking of the accessibility of active cenꢀ mainly occurs in the ring and from the side vinyl
ters to a reactant with these particles. Furthermore, group toward the ring until their conjugation occurs
this nanocomposite system can facilitate a redistribuꢀ according to the following scheme: 4ꢀvinylcyclohexꢀ
tion of metal cations into surface sites accessible to ene
hydrocarbons upon the modification of this system ene
→
3
ꢀvinylcyclohexene
→
3ꢀethylidenecyclohexꢀ
→
ethylꢀ1,2ꢀcyclohexadiene isomers [23]. The
with Ga, Gd, and Pt compounds. As a result, ionicꢀ isomerization of 4ꢀvinylcyclohexene in the presence
type side reactions (isomerization and disproportionꢀ of the above catalysts precedes the dehydrogenation
ation) are inhibited and selectivity for radical–ion reaction; this is likely due to its lower activation
reactions, including the oxidative dehydrogenation of energy. In this case, the dehydrogenation of the above
PETROLEUM CHEMISTRY Vol. 52
No. 2
2012

100
ALIMARDANOV et al.
Table 1. Oxidative dehydrogenation of 4ꢀvinylcyclohexene on zeolites with different concentrations of immobilized carbon
nanoparticles (
T
= 470
°
C;
v
4ꢀvinylcyclohexene, 1 h–1; molar ratio 4ꢀvinylcyclohexene : O2 = 1 : 0.3)
Composition of liquid products of catalysis, wt %
Amount
of immobiꢀ
lized carbon
nanopartiꢀ
cles, wt %
Yield, %
C6⎯C8 cyꢀ
clanes and
cyclenes
C8H12 4ꢀVinylcyꢀ Benzene, Xylene Ethylbenꢀ
Styrene
Ethylbenꢀ
Styrene
dienes * clohexene toluene
isomers
zene
zene
Pt, Ga, Gd/HNaY
–
2
1.2
2.0
2.4
1.8
10.6
11.6
9.0
12.2
9.4
9.4
9.9
5.5
4.4
5.0
4.5
1.7
1.6
1.0
0.4
53.6
53.5
55.0
60.6
15.2
17.5
18.2
15.3
51.9
51.8
53.2
58.7
15.0
17.3
18.0
15.1
5
20
7.5
Pt, Ga, Gd/HNaM
–
2
3.7
2.8
2.1
2.5
12.0
12.3
10.0
9.1
9.4
10.4
11.2
12.4
3.0
3.6
3.0
3.4
1.0
0.8
0.9
0.6
50.2
51.0
51.7
55.4
20.7
19.1
21.1
16.6
48.5
49.4
50.0
55.6
20.4
18.8
20.8
16.4
5
20
Pt, Ga, Gd/HNaTsVM
–
2
2,5
1,8
1,7
3,2
14.8
12.0
10.5
7.0
13.2
10.9
13.2
11.5
4.1
4.7
2.2
2.9
1.7
1.8
1.5
1.0
42.8
44.1
46.3
49.4
20.9
24.7
24.6
25.0
40.2
42.7
44.8
47.8
19.6
24.4
24.3
24.7
5
20
Pt, Ga, Gd/ICN
2.5 0.5
Pt, Ga, Gd/AG
1.0
–
0.6
5.3
35.6
38.6
24.3
16.9
6.9
37.4
24.0
16.7
7.0
–
0.9
4.0
62.9
–
* Ethylidene and ethylcyclohexadiene isomers.
Table 2. Oxidative dehydrogenation of ethylbenzene on zeolites with different concentrations of immobilized carbon
nanoparticles (
T
= 470
°
C;
v
ethylbenzene, 1 h–1; molar ratio ethylbenzene : O2 = 1 : 0.5)
Composition of liquid products of catalysis, wt %
Amount of immobiꢀ
lized carbon nanoꢀ
particles, wt %
Ethylbenꢀ Selectivity
zene converꢀ for styrene,
Zeolite
Light hyꢀ Benzene,
drocarbons toluene
Ethylbenꢀ
zene
Xylene
Styrene
sion, %
%
–
1.0
0.9
0.5
0.2
0.6
0.4
0.5
0.4
0.4
0.4
0.3
0.3
0.3
–
7.8
5.6
6.2
3.6
6.7
5.8
6.3
2.4
5.2
2.8
2.3
2.5
1.5
0.9
4.2
4.7
3.4
3.0
3.2
4.0
3.2
2.2
2.6
2.3
2.2
2.0
1.2
0.8
30.4
33.5
32.5
41.3
35.1
34.0
36.2
43.8
41.4
40.0
42.3
47.4
57.6
81.4
56.6
55.3
57.4
51.9
54.4
55.8
53.8
51.2
50.0
54.5
52.9
47.8
39.4
16.9
70.5
67.5
68.5
59.9
66.7
67.0
64.9
58.4
59.8
61.2
59.0
55.0
44.1
22.7
79.4
81.0
82.9
85.6
81.5
82.3
82.0
84.9
82.0
88.0
88.7
84.3
88.3
78.6
Pt,Ga,Gd/HNaY
Pt,Ga,Gd/HNaM
2
5
20
–
2
5
20
–
Pt,Ga,Gd/HNaTsVM
–
2
5
20
Pt,Ga,Gd/ICN
Pt,Ga,Gd/AGꢀ3
PETROLEUM CHEMISTRY Vol. 52
No. 2
2012

EFFECT OF IMMOBILIZED CARBON NANOPARTICLES ON THE ACTIVITY
101
Table 3. Effect of temperature on the yield of products in the oxidative dehydrogenation of 4ꢀvinylcyclohexene in the presꢀ
ence of Pt, Ga, Gd/HNaTsVM with immobilized carbon nanoparticles (
v
4ꢀvinylcyclohexene, 1 h–1; molar ratio 4ꢀvinylcycloꢀ
hexene : O2 = 1 : 0.3)
Composition of liquid products of catalysis, wt %
4ꢀVinylcyꢀ Yield of oxiꢀ
Ethylbenꢀ
clohexene dative dehyꢀ
zene : styrene
T, °C
C6⎯C8 cyꢀ
clanes and
cyclenes
converꢀ
drogenation
C8H12*ꢀ 4ꢀvinylcyꢀ Benzene, Xylene Ethylꢀ
dienes clohexene toluene isomers benzene
molar ratio
Styrene
sion**, % products, %
Pt, Ga, Gd/HNaTsVM + 5% immobilized carbon nanoparticles
320
345
370
400
425
470
500
0.7
0.7
1.2
2.0
2.0
1.7
2.2
13.2
14.0
10.2
10.0
13.1
10.5
7.7
73.7
65.0
58.2
35.0
19.0
13.2
10.7
1.0
1.0
1.5
2.5
3.0
2.2
4.0
–
11.4
18.3
24.2
34.8
41.1
46.3
50.8
–
1.0
14.8
23.4
35.0
57.7
70.1
78.0
83.2
11.3
19.1
27.1
47.7
60.2
69.1
70.3
–
–
18 : 1
6.3 : 1
2.4 : 1
1.9 : 1
1.85 : 1
2.2 : 1
1.0
1.5
1.5
1.5
1.6
3.7
14.2
20.7
24.6
23.0
Pt, Ga, Gd/HNaTsVM + 20% immobilized carbon nanoparticles
320
345
370
400
425
470
500
0.5
0.6
1.1
2.4
2.4
3.2
2.0
11.7
12.0
10.5
9.2
77.8
70.5
58.4
34.4
27.2
11.5
14.9
–
–
–
10.0
15.8
26.3
38.6
40.0
49.4
49.2
–
0.6
12.3
20.0
34.5
59.0
65.7
82.8
79.9
9.9
16.2
28.9
50.0
55.8
72.5
66.8
–
0.5
0.8
1.6
2.4
2.9
3.5
–
–
2.9
9 : 1
3 : 1
2.3 : 1
1.9 : 1
2.3 : 1
1.0
1.1
1.0
1.4
12.8
17.3
25.0
20.9
9.6
7.0
8.1
Pt, Ga, Gd/HNaTsVM
320
345
370
400
425
470
500
2.0
3.6
7.8
5.9
6.1
6.2
1.0
17.5
17.2
14.5
15.6
16.1
13.4
4.4
79.3
71.4
49.6
40.1
21.8
10.9
6.3
–
–
1.2
7.8
–
–
5.1
14.1
39.2
48.1
64.7
77.2
90.2
1.2
7.7
–
–
–
–
2.5
4.8
4.8
4.5
3.0
0.5
1.3
0.9
1.3
0.9
20.0
23.3
37.3
42.8
54.8
5.2
22.6
28.8
43.8
59.8
70.4
3.9 : 1
2.6 : 1
2.9 : 1
2.05 : 1
1.85 : 1
9.0
13.0
20.9
29.6
Pt, Ga, Gd/ICN
320
345
370
400
425
470
500
–
3.4
3.5
6.4
7.3
7.1
6.0
4.8
90.2
87.3
73.1
56.6
40.8
31.3
32.2
–
–
–
6.4
9.2
–
–
8.3
11.9
24.5
39.9
54.3
65.3
66.1
6.3
9.1
–
–
–
–
0.5
2.8
3.0
4.2
2.2
1.1
1.4
2.0
2.5
2.7
–
16.4
23.0
33.1
38.6
41.0
2.5
18.7
30.5
46.2
54.1
54.3
6.5 : 1
2.7 : 1
2.4 : 1
2.2 : 1
2.5 : 1
0.6
0.6
0.5
1.0
8.3
13.4
16.9
16.1
* Ethylidene and ethylcyclohexadiene isomers. ** In the calculation of conversion, the migration of double bonds in the 4ꢀvinylcycloꢀ
hexene molecule was ignored.
PETROLEUM CHEMISTRY Vol. 52
No. 2
2012

102
ALIMARDANOV et al.
Table 4. Temperature effect on the conversion of ethylbenzene and the yield of styrene in the oxidative dehydrogenation of
ethylbenzene on Pt, Ga, Gd/HNaTsVM with immobilized carbon nanoparticles (
v
ethylbenzene, 1 h–1; molar ratio ethylbenꢀ
zene : O2 = 1 : 0.5)
Composition of liquid products of catalysis, wt %
Ethylbenzene Selectivity
conversion, % for styrene, %
T, °C
Light
benzene,
toluene
xylenes
ethylbenzene
styrene
hydrocarbons
Pt,Ga,Gd/HNaTsVM + 5% immobilized carbon nanoparticles
370
400
430
470
500
525
–
1.0
1.0
1.2
2.3
3.0
4.6
1.0
1.0
1.2
2.2
2.7
2.8
91.6
85.3
75.9
42.3
40.1
38.7
6.4
12.7
21.5
52.9
53.7
52.1
11.1
19.0
27.9
59.0
61.9
64.0
56.7
64.9
74.6
88.7
89.1
81.8
–
0.2
0.3
0.5
1.8
Pt,Ga,Gd/HNaTsVM + 20% immobilized carbon nanoparticles
370
400
430
470
500
525
–
1.0
1.2
0.8
2.5
3.4
5.2
1.0
1.0
1.1
2.0
2.0
2.4
93.8
88.1
77.6
47.4
46.8
46.5
4.2
9.7
7.1
14.5
24.7
55.0
55.5
56.8
59.6
65.9
80.8
84.3
82.1
74.0
–
0.3
0.3
0.7
1.6
20.2
47.8
47.1
44.3
Pt,Ga,Gd/ICN
350
370
430
470
500
530
0.1
0.2
0.4
0.3
0.7
0.9
–
–
97.4
94.7
74.8
57.6
56.6
56.3
2.5
5.1
3.5
7.2
72.9
71.6
82.9
88.3
81.3
72.5
–
–
1.0
1.5
2.1
5.0
0.8
1.2
0.9
1.6
23.0
39.4
39.7
36.2
27.4
44.1
46.8
47.6
intermediates also leads to the formation of a mixture of this system is low and the maximum yield of styrene
does not exceed 39.0% (at 470°С).
of ethylbenzene and styrene. Therefore, we did not
take into account the migration of double bonds in the
calculation of the conversion of 4ꢀvinylcyclohexene.
According to the results given in Tables 1–4, it is
possible to conclude that the immobilization of carꢀ
bon nanoparticles on the zeolite HNaꢀTsVM matrix
leads to the synergism of their action. This is likely due
to their mutual influence on the distribution of metal
cations in the process of modification.
As can be seen in Table 3, unlike noncarbonized Pt,
Ga, Gd/HNaTsVM, the oxidative dehydrogenation of
4ꢀvinylcyclohexene on the carbonized samples begins
at a lower temperature (320–340 С). In this case, the
°
The dehydrogenation of 4ꢀvinylcyclohexene on
noncarbonized samples is accompanied by the
isomerization and disproportionation of the initial
substances and dehydrogenation products in signifiꢀ
cant amounts. The isomerization of 4ꢀvinylcyclohexꢀ
ene occurs by the migration of multiple bonds in the
molecule without changes in the structure of the initial
hydrocarbon and leads to the formation of a mixture of
3ꢀethylideneꢀ1ꢀcyclohexene and ethylꢀ1,3ꢀcycloꢀ
hexadienes. These latter are easily dehydrogenated to
ethylbenzene and styrene. The disproportionation of
the dehydrogenation products occurs more intensely
main product of 4ꢀvinylcyclohexene dehydrogenation
is ethylbenzene. Styrene is formed starting from
370
°
С
, and its buildup is intensified at 400–425 С.
°
The maximum yields of ethylbenzene and styrene
(39.8–44.8 and 20.4–22.3%, respectively) are reached
on the nanocomposite Pt, Ga, Gd/HNaTsVM system
containing 5 wt % immobilized carbon nanoparticles
at 425–470
genation of ethylbenzene begins at a temperature of
370 and the highest yield of styrene (52.5–55.2%)
with 88.7–89.1% selectivity is reached at 470–500
°
С. On this system, the oxidative dehydroꢀ
°
С
°
С
(Table 4). Note that the dehydrogenation of ethylbenꢀ
zene on the zeoliteꢀcontaining Pt, Ga, Gd/ICN samꢀ
ple, as in the case of 4ꢀvinylcyclohexene, begins at a
as the temperature is increased from 470 to 525 С and
leads to the accumulation of an amount of benzene
and toluene in the products of catalysis. As the amount
°
lower temperature (320–350°С); however, the activity of immobilized carbon nanoparticles in the composiꢀ
PETROLEUM CHEMISTRY Vol. 52
No. 2
2012

EFFECT OF IMMOBILIZED CARBON NANOPARTICLES ON THE ACTIVITY
103
90
80
70
60
50
40
mol %
100
(a)
1
1
2
3
4
90
80
70
60
50
40
2
2
'
'
5
1
2
4
6
8
10 20 22 24
, h
τ
1 : 0.3
1 : 0.7
1 : 1.2
4ꢀVinylcyclohexene : O molar ratio
Fig. 4. Effect of catalyst operation time on catalyst activity
in the oxidative dehydrogenation of 4ꢀvinylcyclohexene
2
mol %
100
(at 425°C; 4ꢀvinylcyclohexene : O = 1 : 0.5). Catalysts:
(b)
2
(
1
) Pt, Ga, Gd/HNaTsVM + 5% immobilized carbon
nanoparticles; (
Ga, Gd/HNaY + 5% immobilized carbon nanoparticles;
) Pt, Ga, Gd/HNaTsVM; and ( ) Pt, Ga, Gd/ICN.
2) Pt, Ga, Gd/HNaTsVM + 20%; (3) Pt,
90
80
70
60
50
40
(
4
5
3
3
4
'
'
cyclohexene. Note that the same regularity was also
observed on Pt, Ga, Gd/ICN.
The yield of the dehydrogenation products of
4ꢀvinylcyclohexene and ethylbenzene substantially
depends on the operation time of the above catalysts
(Figs. 4, 5). As a rule, in all of the zeolite catalysts
modified with immobilized carbon nanoparticles, an
increase in the yield of the main products (ethylbenꢀ
zene and styrene) was observed upon the oxidative
dehydrogenation of 4ꢀvinylcyclohexene for 4–6 h
(Fig. 4). Pt, Ga, Gd/HNaꢀTsVM and Pt, Ga,
Gd/ICN exhibited the same properties. In all cases,
an increase in the yield of target products during the
indicated period occurred due to an increase in the
reaction selectivity (from 74.3 to 93%) with a simultaꢀ
neous decrease in the conversion of 4ꢀvinylcyclohexꢀ
ene and in the yields of byꢀproducts—disproportionꢀ
4
1 : 0.3
1 : 0.7
1 : 1.2
Ethylbenzene : O molar ratio
2
Fig. 3. Dependence of the conversion of (a) 4ꢀvinylcycloꢀ
hexene (at 425 ) and (b) ethylbenzene (at 470 ) and
selectivity for dehydrogenation products on the hydrocarꢀ
bon : oxygen : ( ) Pt, Ga, Gd/(HNaTsVM + 5% immoꢀ
bilized carbon nanoparticles) or ( '– ) Pt, Ga, Gd/ICN
catalyst molar ratios: ( ') 4ꢀvinylcyclohexene converꢀ
sion, ( ') selectivity for ethylbenzene + styrene, ( ')
ethylbenzene conversion, and ( ') selectivity for styrene.
°
С
°С
1–4
(
1 4'
1, 1
2,
2
3, 3
4, 4
tion of a catalyst is increased, the benzene and toluene
content of the liquid reaction products decreases. As
noted above, this is likely due to the fact that, upon the
immobilization of carbon on the surface of a zeolite
matrix, its localization preferably occurs at strong acid
sites, which are responsible for the occurrence of ionꢀ
type reactions, in particular, the disproportionation of
the alkyl derivatives of benzene [35].
ation (benzene and toluene) and deep oxidation (CО2
products. After reaching a maximum, the yield of
dehydrogenation products remained almost
)
unchanged for ~20 h. The exception is provided by the
Pt, Ga, Gd/HNaY + 5% immobilized carbon nanoꢀ
particles and Pt, Ga, Gd/HNaTsVM samples, whose
activity gradually decreased. According to atomic
force microscopic data, the structure of immobilized
carbon nanoparticles and the sizes of the carbon nanoꢀ
particles underwent considerable changes upon the
operation of the carbonized forms of zeolites for 10 h.
The yield of products of the oxidative dehydrogeꢀ
nation of 4ꢀvinylcyclohexene and ethylbenzene on Pt,
Ga, Gd/HNaTsVM + 5% immobilized carbon nanoꢀ
particles initially increased with the hydrocarbon :
oxygen molar ratio (Figs. 3a, 3b) to reach maximum
values at 1 : 0.9–1.1 or 1 : 0.5 for 4ꢀvinylcyclohexene
or ethylbenzene, respectively, but then decreased. This
was due to the fact that the products of the deep and
partial oxidation of hydrocarbons increased with the
concentration of oxygen in the initial mixture; this
The sizes of the carbon nanoparticles reached 80–
90 nm. In this case, the structure of HNaTsVM
remained almost unchanged (according to Xꢀray difꢀ
fraction data). A decrease in the crystal structure was
observed in the carbonized Pt, Ga, Gd/HNaY sample.
Approximately the same behavior was observed in
the oxidative dehydrogenation of ethylbenzene
more intensely manifested itself in the case of 4ꢀvinylꢀ (Fig. 5); however, in this case, unlike 4ꢀvinylcyclohexꢀ
PETROLEUM CHEMISTRY Vol. 52
No. 2
2012

104
70
ALIMARDANOV et al.
9. C. Bigey and B. ꢀL. Su, J. Mol. Catal. A 209, 179
(2004).
1
10. S. Gnanapragasam, V. Krishnasamy, and V. Mohan,
Indian J. Chem., Sect. A: Inorg., Bioinorg., Phys.,
Theor. Anal. Chem. 40, 947 (2001).
60
50
40
30
20
10
2
4
5
11. Kh. M. Alimardanov, S. I. Abasov, A. F. Abdullaev,
et al., Pet. Chem. 41, 431 (2001).
3
12. Kh. M. Alimardanov, L. A. Tairova, and S. I. Abasov,
Pet. Chem. 43, 403 (2003).
13. Kh. M. Alimardanov, F. M. Velieva, L. A. Dadasheva,
and M. I. Rustamov, Pet. Chem. 46, 353 (2006).
14. N. S. Nesterenko, O. A. Ponomerova, V. V. Yuschenko,
et al., Appl. Catal. A: Gen/ 254, 261 (2003).
15. SheꢀTin Wong, HongꢀPing Lin, and ChungꢀYuan
2
4
6
8
10 20 22 24 26 28
Mou, Appl. Catal. A: Gen. 198, 103 (2000).
τ
, h
16. Y. Qiao, C. Miao, Y. Yue, et al., Micropor. Mezopor.
Mater. 119, 150 (2009).
Fig. 5. Effect of the catalyst onꢀstream time on catalyst
17. I. G. Shmelev, A. A. Lamberov, and R. G. Romanova,
in Modern Problems of Theoretical and Experimental
Chemistry (2001) [in Russian], p. 69.
activity in the oxidative dehydrogenation of ethylbenzene
(at 470°C; ethylbenzene : O = 1 : 0.5).
2
18. E. M. Mamedov, M. A. Gagarin, and Kh. E. Kharlamꢀ
pidi, Zh. Prikl. Khim. 75, 599 (2002).
ene, the catalyst activity slowly increased for 10–15 h,
and then it was stabilized. It is likely that the catalytic
properties of these systems changed in the course of
the process due to the additional modification of their
surface by coke deposits, whose composition was difꢀ
fered from the composition of immobilized carbon
nanoparticles. The greatest coke deposition was
observed in the oxidative dehydrogenation of 4ꢀvinylꢀ
cyclohexene.
19. O. A. Ponomareva, I. F. Moskovskaya, and B. V. Roꢀ
manovskii, Pet. Chem. 41, 257 (2001).
20. O. A. Ponomareva, I. F. Moskovskaya, and B. V. Roꢀ
manovskii, Pet. Chem. 39, 83 (1999).
21. Yu. I. Sidorenko, P. N. Galich, V. S. Gutyrya, et al.,
Dokl. Akad. Nauk SSSR 173, 132 (1967).
22. K. I. Patrilyak, Yu. I. Sidorenko, and V. A. Bortyꢀ
shevskii, Alkylation on Zeolites (Naukova Dumka, Kiev,
1991) [in Russian].
Thus, the modification of pentasil zeolites with
immobilized carbon nanoparticles leads to an increase
in their activity and selectivity in radical–ion reacꢀ
tions, in particular, the oxidative dehydrogenation of
4ꢀvinylcyclohexene and ethylbenzene. The introducꢀ
tion of immobilized carbon nanoparticles facilitates
the blocking of strong acid sites in the catalysts, the
highly dispersed redistribution of metal cations, and
an increase in the stability of the catalyst.
23. Kh. M. Alimardanov and A. F. Abdullaev,
Neftekhimiya 35, 526 (1995).
24. Y. S. Choi, Y.ꢀK. Park, J.ꢀS. Chang, et al., Catal. Lett.
69, 93 (2000).
25. J.ꢀS. Chang, S.ꢀE. Park, Q. Gao, et al., Chem. Comꢀ
mun., 859 (2001).
26. R. Neumann and I. Dror, Appl. Catal. 172, 67 (1998).
27. G. G. Garifzyanov, I. Kh. Bikbulatov, and R. B. Valitov,
Neftekhimiya 10, 28 (1970).
28. Kh. M. Minachev and Ya. I. Isakov, Preparation, Actiꢀ
vation, and Regeneration of Zeolite Catalysts (TsNIꢀ
ITENeftekhimii, Moscow, 1971) [in Russian].
REFERENCES
1. Kh. M. Minachev and A. A. Dergachev, Izv. Akad.
Nauk SSSR, Ser. Khim., No. 6, 1018 (1993).
2. D. Seddon, Catal. Today, No. 6, 351 (1998).
29. I. E. Maxwell, R. S. Downing, and S. A. J. van Langen,
J. Catal. 61, 485 (1980).
30. R. C. Weast and M. J. Astle, Handbook of Data on
Organic Compounds (CRC, Boca Raton, 1985), Vol. 1.
3. V. R. Choudhary, P. Devadas, S. Banerjee, and
A. K. Kinage, Microporous Mezoporous Mater. 47
,
253 (2001).
31. Kh. M. Alimardanov, A. A. Alieva, and S. I. Abasov, Pet.
Chem. 50, 124 (2010).
4. V. R. Choudhary, S. Banerjee, and P. Devadas, J. Catal.
205, 398 (2002).
32. T. G. Alkhazov and A. E. Lisovskii, Oxidative Dehydroꢀ
genation of Hydrocarbons (Khimiya, Moscow, 1980) [in
Russian].
5. R. V. Dmitriev, D. P. Shevchenko, E. S. Shpiro, et al.,
Stud. Surf. Sci. Catal. 69, 381 (1991).
33. O. V. Krylov, Heterogeneous Catalysis (Akademkniga,
6. A. L. Lapidus, A. A. Dergachev, V. A. Kostina, and
Moscow, 2004) [in Russian].
A. A. Silakova, Pet Chem. 48, 83 (2008).
34. S. J. Kulkarni, H. Hattori, and K. Tanabe, Appl. Catal.
7. D. Freeman, R. P. K. Wells, and G. J. Hutschings,
49, 27 (1989).
J. Catal. 205, 358 (2002).
8. O. A. Sinitsyna, V. N. Chumakova, and I. F. Moskꢀ 35. P. A. Jacobs, Carboniogenic Activity of Zeolites (Elsevier,
ovskaya, Neftekhimiya 27, 194 (1987). Amsterdam, 1977; Khimiya, Moscow, 1983).
PETROLEUM CHEMISTRY Vol. 52
No. 2
2012