The transformations of toluene on alumina and bifunctional catalysts

Article abstract of DOI:10.1134/S003602440604011X

The activity of Pt, Rh, and Ni catalysts deposited on Al₂O ₃ and tungsten-containing catalysts 20% H₄SiW ₁₂O₄₀/ZrO₂ and 15% WO_x/ZrO ₂ in the hydrogenation of toluene and toluene ring opening and isomerization in the presence of hydrogen was studied. Under experimental conditions (160-360°C, 2.2 MPa), the main reactions on Rh/Al ₂O₃ were the hydrogenation of toluene into methylcyclohexane, hydrogenolysis into isoheptanes, and hydrocracking into alkanes C₁-C₆. On Pt, Rh, and Ni catalysts on carriers with strong acid properties, the isomerization of the six-membered into five-membered ring followed by hydrogenolysis (hydrocracking) of alkylcyclopentanes occurred. The yield of heptane isomers, however, did not exceed 13%. The activity of Pt and Rh catalysts on a high-acidity carrier (WO_x/ZrO₂) in hydrocracking was much higher than that of catalysts based on deposited heteropoly acid. The yields of hydrogenolysis (hydrocracking) products on Ni/WO_x/ZrO₂ were much lower than on Pt(Rh)/WO_x/ZrO₂. The highest yield of ring opening products (isoheptanes and n-heptane) was obtained with layered loading of two catalysts; it reached 58 wt % at 300°C and a 2.2 MPa pressure, which was 4.5 and 2 times higher than the yield obtained on Ni-Pt/WO_x/ZrO ₂ and 2% Rh/Al₂O₃ catalysts. Hydrodemethylation was not the main direction of toluene transformations on any of the catalysts studied. Pleiades Publishing, Inc., 2006.

Full text of DOI:10.1134/S003602440604011X

ISSN 0036-0244, Russian Journal of Physical Chemistry, 2006, Vol. 80, No. 4, pp. 551–556. © Pleiades Publishing, Inc., 2006.
Original Russian Text © O.V. Masloboishchikova, E.G. Khelkovskaya-Sergeeva, V.I. Bogdan, T.V. Vasina, L.M. Kustov, 2006, published in Zhurnal Fizicheskoi Khimii, 2006,
Vol. 80, No. 4, pp. 646–652.
CHEMICAL KINETICS
AND CATALYSIS
The Transformations of Toluene
on Alumina and Bifunctional Catalysts
O. V. Masloboishchikova, E. G. Khelkovskaya-Sergeeva, V. I. Bogdan,
T. V. Vasina, and L. M. Kustov
Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, Leninskii pr. 47, Moscow, 119991 Russia
E-mail: lmk@ioc.ac.ru
Received July 18, 2005
Abstract—The activity of Pt, Rh, and Ni catalysts deposited on Al O and tungsten-containing catalysts 20%
2
3
H SiW O /ZrO and 15% WO /ZrO in the hydrogenation of toluene and toluene ring opening and isomer-
4
12 40
2
x
2
ization in the presence of hydrogen was studied. Under experimental conditions (160–360°ë, 2.2 MPa), the
main reactions on Rh/Al O were the hydrogenation of toluene into methylcyclohexane, hydrogenolysis into
2
3
isoheptanes, and hydrocracking into alkanes ë –ë . On Pt, Rh, and Ni catalysts on carriers with strong acid
1
6
properties, the isomerization of the six-membered into five-membered ring followed by hydrogenolysis (hydro-
cracking) of alkylcyclopentanes occurred. The yield of heptane isomers, however, did not exceed 13%. The
activity of Pt and Rh catalysts on a high-acidity carrier (WO /ZrO ) in hydrocracking was much higher than
x
2
that of catalysts based on deposited heteropoly acid. The yields of hydrogenolysis (hydrocracking) products on
Ni/WO /ZrO were much lower than on Pt(Rh)/WO /ZrO . The highest yield of ring opening products (isohep-
x
2
x
2
tanes and n-heptane) was obtained with layered loading of two catalysts; it reached 58 wt % at 300°ë and a
2
.2 MPa pressure, which was 4.5 and 2 times higher than the yield obtained on Ni-Pt/WO /ZrO and 2%
x 2
Rh/Al O catalysts. Hydrodemethylation was not the main direction of toluene transformations on any of the
2
3
catalysts studied.
DOI: 10.1134/S003602440604011X
INTRODUCTION
cyclohexane occurs on Pt catalysts at low temperatures
of 50–100°ë [9]. The hydrodemethylation of toluene
into benzene at temperatures above 380°ë was studied
in [10–12]. Group VIII metals form the series Ni > Rh >
Ir > Ru > Pt > Pd in order of decreasing activity in
hydrodemethylation [10]. The selectivity of C–C bond
breaking between the methyl group and ring in toluene
on Rh/Al O is almost 20 times higher than the selec-
Changes in the requirements imposed on the content
of aromatic hydrocarbons in fuels have increased the
interest of researchers in catalytic hydrodearomatiza-
tion. Transformations of benzene on bifunctional cata-
lysts in the presence of hydrogen are widely covered in
the literature [1–5]. The hydrogenation of benzene or
its deeper transformations with breaking ring C–C
bonds occur depending on reaction conditions. The
main reaction direction on Rh and Ir deposited on
Al O at elevated pressures is ring opening with the for-
mation of n-hexane. The isomerization of the six- into
five-membered ring followed by the hydrogenolysis
into 2- and 3-methylpentanes and n-hexane occurs on
Pt and Rh catalysts with strong acid centers [1, 5]. The
following types of toluene transformations on metal
oxide catalysts are discussed in the literature: hydroge-
nation, hydrodemethylation, and disproportionation.
The hydrogenation of toluene on Pt and Rh was consid-
ered in [6, 7]. It was shown that the activity of aromatic
2
3
tivity of breaking ring C–C bonds [11]. Ring opening
with the formation of MCH occurs on Ir/Al O along
2
3
with hydrodemethylation of toluene into benzene [13].
2
3
The purpose of this work was to study the influence
of the nature of metals (Pt, Rh, and Ni) and carrier acid
properties (Al O , H SiW O /ZrO , and WO /ZrO )
2
3
4
12 40
2
x
2
on the types of toluene transformations under the con-
ditions that made six-membered ring opening possible.
EXPERIMENTAL
We used Pt, Rh, and Ni catalysts on the following
hydrocarbons (benzene, toluene, and p-xylene) in carriers: γ-Al O with specific surface area S =
2
3
sp
2
hydrogenation decreased as the number of methyl sub- 250–300 m /g, ZrO (prepared from Zr(OH) with S =
2
4
sp
2
stituents increased [6]. According to the thermody- 150 m /g), and 15% WO /ZrO
and 20%
x
2
namic data [8], an equilibrium mixture of toluene and H SiW O /ZrO (WO /ZrO and HSiWO/ZrO in
4
12 40
2
x
2
2
methylcyclohexane (MCH) contains equal amounts what follows). The preparation of WO /ZrO and
x
2
(
2
~50%) of the components at atmospheric pressure and HSiWO/ZrO was described in [5]. The metals (Pt, Rh,
2
80°ë. At lower temperatures, MCH, and at higher, tol- and Ni) were introduced in the form of dilute aqueous
uene, prevail. The hydrodemethylation of toluene into solutions of H PtCl , RhCl , and Ni(NO ) . The sam-
2
6
3
3 2
5
51

5
52
MASLOBOISHCHIKOVA et al.
x, % respectively. The concentrations of Pt and Rh in the cat-
y, wt %
00
2% Rh/Al O
2
3
alysts were 1–2 wt %, and that of Ni, 6 wt %. Bimetallic
Ni–Pt catalysts were prepared by successively impreg-
nating carriers with solutions of Ni(NO ) and H PtCl .
1
100
80
60
40
20
0
1
3
2
2
6
8
6
4
2
0
0
0
0
0
4
The bimetallic catalysts contained 6 wt % Ni and
0
.2 wt % platinum.
Toluene transformations were studied in a flow reac-
tor at 160–360°ë and a 2.2 MPa pressure. The volume
3
of catalyst loads was 3 cm , the rate of supplying tolu-
–1
ene was 2 h , and the hydrogen : hydrocarbon molar
ratio was 10 : 1. The products were analyzed by gas-liq-
uid chromatography on a column 3 m long packed with
2
3
1
5% PFMS/Celite and a capillary column 25 m long
2
00
240
280
t, °C
320
360
with SE-30. The activity of the catalysts was estimated
from the yield of ring opening products (isoheptanes
and n-heptane) and selectivity of their formation. Selec-
tivity was calculated as the ratio between the yield of
ring opening products and the total yield of ring opening
products, hydrocracking, and hydrodealkylation.
Fig. 1. Temperature dependences of toluene conversion (x)
and major product yields (y) on the 2% Rh/Al O catalyst at
a 2.2 MPa pressure: (1) methylcyclohexane, (2) isoheptanes
and n-heptane, (3) cyclohexane, and (4) ë –ë alkanes.
2
3
1
5
RESULTS AND DISCUSSION
ples were dried at 130°ë. Prior to experiments, cata-
lysts on Al O were reduced in a flow of H at 450°ë
2
3
2
On the basis of literature data, we suggest the fol-
lowing scheme of toluene transformations on bifunc-
were calcined in a flow of air for 3 h at 350 and 500°ë, tional catalysts in the presence of hydrogen:
for 3 h, and catalysts on çSiWO/ZrO and WO /ZrO
2
x
2
C –C -alkanes
1
6
This scheme includes the isomerization of MCH other hand, hydrodealkylation of toluene occurs on
into dimethyl- and ethylcyclopentanes on catalysts with Rh/Al O at high temperatures and atmospheric pres-
2
3
strong acid properties such as Pt/SO /ZrO [14]. The sure [11].
4
2
ëç –ëç bonds in alkylcyclopentanes (AlkCP) pref-
2
2
The temperature dependences of the yields of the
erably experience hydrogenolysis on Pt, Rh, Ni, Ru,
and Ir catalysts [15]. The selective hydrogenolysis of
ëç –ëç bonds was also described for MCH [8].
main toluene transformation products on 2% Rh/Al O
2
3
are shown in Fig. 1. The conversion of toluene over the
temperature range studied (180–360°ë) at a 2.2 MPa
2
2
As is known, Rh catalysts on Al O and SiO are pressure was 98–100% (Fig. 1, Table 1). Figure 1
2
3
2
active and selective in cyclohexane and benzene ring shows that toluene is only hydrogenated to MCH at low
opening with the formation of n-hexane [5]. On the temperatures (up to 200°ë). Above 200°ë, we observe
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY Vol. 80 No. 4 2006

THE TRANSFORMATIONS OF TOLUENE ON ALUMINA AND BIFUNCTIONAL CATALYSTS
553
Table 1. Influence of reaction temperature on toluene transformation product yields (y, wt %) on 2% Rh/Al O (molar ratio
2
3
–
1
H : C H = 10 : 1, p = 2.2 MPa, v = 2 h )
2
7
8
vol
y(I)
y(II)
y(III)
y(IV)
y(V)
t, °C
x, %
Cyclohex-
ane
CH –C H
MP
n-C H
DMP
MH
n-C H
AlkCP
MCH
4
5
12
6
14
7
16
2
3
3
60
00
20
99.9
99.9
99.4
0.4
2.8
13.7
17.1
0.1
0.7
1.6
0.2
1.2
2.0
14.3
29.1
29.6
0.1
0.4
0.6
0.2
0.8
1.5
0.2
0.7
1.4
81.4
50.5
41.1
2.1
5.0
Note: I, hydrocracking; II, ring opening; III, ring isomerization; IV, hydrodealkylation; V, hydrogenation; vvol is the toluene volume feed-
ing rate; x is the conversion of toluene; MP stands for 2- and 3-methylpentanes; DMP, for dimethylpentanes; MH, for 2- and 3-meth-
ylhexanes; MCP is methylcyclopentane; AlkCP denotes dimethylcyclopentanes and ethylcyclopentane; and MCH is methylcyclo-
hexane. The yield of C8+ is 0.2–0.9 wt %.
the formation of six-membered ring opening products, hydrocarbons to aromatic hydrocarbons on Pt catalysts
2
- and 3-methylhexanes and n-heptane. Their total [8]. On the other hand, Pt/HSiWO/ZrO might be deac-
2
yield passes a maximum as the temperature increases tivated, because the yields of ë hydrocarbons likely
8+
and equals 29 wt % at 300°ë. The yield of isohexanes formed as a result of disproportionation, transalkyla-
increases at 250–340°ë simultaneously with the yield tion, and other secondary reactions increased on this cat-
of isoheptanes. Isohexanes are probably formed as a alyst at high temperatures (Table 2). The predominant
result of the splitting off of the ëç group from the cor- reactions at 160–260°ë on both catalysts were the
3
responding methylheptanes (Table 1). At 360°ë, tolu-
hydrogenation of toluene to MCH and its isomerization
into alkylcyclopentanes (AlkCP), including 1,1-, 1,2-,
and 1,3-dimethylcyclopentanes and ethylcyclopentane.
The highest yield of AlkCP was 37.5 wt % on
ene fully transforms into ë –ë alkanes. According to
1
3
Table 1, the hydrodemethylation of toluene occurs to an
insignificant extent at 260–300°C (the yields of cyclo-
hexane and the product of its hydrogenolysis (n-hex-
ane) are lower than 1.5%). Alkylcyclopentanes are also
formed in insignificant amounts, and their yields do not
exceed 1%. It follows that the predominant types of tol-
uene transformations on 2% Rh/Al O at temperatures
Pt/HSiWO/ZrO and 46 wt % on the Rh catalyst. Ring
2
opening products (dimethylpentanes, methylhexanes,
and n-heptane) are formed at 220°ë and above. The
yield of ë –ë alkanes also increases substantially at
1
6
2
3
these temperatures. A small yield of heptane isomers,
.6 wt %, was observed on the Pt catalyst at 260°ë; on
up to 300°ë are its hydrogenation to MCH and the
hydrogenolysis of the latter to 2- and 3-methylhexanes.
The yield of ring opening products from toluene is,
however, approximately half that from benzene [5].
The contribution of secondary reactions such as
hydrocracking to lower alkanes, the formation of ë8+
hydrocarbons, and skeletal isomerization increases at
6
the Rh catalyst, this yield was 11.3 wt % at 320°ë.
Hydrocracking reactions make a substantial contribu-
tion at these temperatures, and the yields of ë –ë
1
5
y, wt %
00
x, %
100
3
20–340°ë.
1
1
1'
It is known from the literature [1, 4] that the isomer-
2
'
ization of six-membered into five-membered rings is
only possible in the presence of Broensted acid centers,
whereas, in the presence of only Lewis acid centers,
cyclopentane hydrocarbons do not form. We showed
1
1
% Pt/HSiWO/ZrO2
8
0
80
60
40
20
0
2
% Rh/HSiWO/ZrO2
60
[
5] that methylcyclopentane and its hydrogenolysis
products (isohexanes and n-hexane) were predomi-
nantly formed from benzene under certain conditions
on Pt and Rh catalysts deposited on carriers with strong
acid properties, WO /ZrO and HSiWO/ZrO . We stud-
4
2
0
0
0
3
3
'
5
x
2
2
5
'
4
ied toluene transformations on these catalysts. The tem-
perature dependences of the yields of the main toluene
4
'
1
80
220
260
300
340
transformation products on 1% Pt/HSiWO/ZrO and
2
t, °C
1
% Rh/HSiWO/ZrO are presented in Fig. 2 and Table 2.
2
The conversion of toluene on 1% Rh/HSiWO/ZrO was
2
Fig. 2. Influence of the nature of metals on toluene con-
version (x) and major product yields (y) on the catalysts
close to 100% over the temperature range studied (160–
3
40°ë), and that on the Pt catalyst decreased to 95% as
(
1–5) 1% Pt/HSiWO/ZrO ) and (1'–5') 1% Rh/HSiWO/ZrO
2
2
the temperature increased to 300°ë (Fig. 2). The reason
at 2.2 MPa; (1, 1') conversion, (2, 2') MCH, (3, 3') AlkCP,
(4, 4') isoheptanes and n-heptane, and (5, 5') C –ë alkanes.
for this may be easy dehydrogenation of naphthene
1
5
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY Vol. 80 No. 4 2006

5
54
MASLOBOISHCHIKOVA et al.
Table 2. Influence of the acidic properties of carriers on the yields of the major toluene transformation products (y, wt %) on
–
1
Pt and Rh catalysts (molar ratio H : C H = 10 : 1, p = 2.2 MPa, v = 2 h )
2
7
8
vol
y(I)
y(II)
MH n-C H
16
y(III)
y(IV)
y(V)
t, °C
x, %
y''(C )
8+
DMB
Cyclo-
hexane
CH –C H
n-C H
DMP
MCP AlkCP
MCH
4
5
12
6
14
7
+
MP
1
% Pt/HSiWé/ZrO2
2
2
00 100
60 100
2.8
0.1 + 0.3
0.9 + 2.4
0.1
0.6
0.2
1.0
1.3
4.6
0.3
1.0
0.7
4.2
37.5
29.5
0.2
1.2
54.9
28.2
1.6
20.7
5.7
1
% Rh/HSiWO/ZrO2
2
2
3
00 100
60 100
0.2
2.3
traces
traces traces
0.2
3.0
7.5
0.1
0.7
2.0
0.1
0.7
3.4
33.8
46.0
33.0
traces
0.2
65.2
44.4
21.9
0.4
1.4
3.4
0.1 + 0.3
0.7 + 2.1
0.1
0.8
0.8
1.8
20
99.8
22.6
0.6
1
% Pt/WO /ZrO
x 2
2
2
2
00 100
20 100
60 100
5.9
15.7
68.0
0.2 + 0.6
0.5 + 1.2
1.9 + 3.4
0.2
0.3
1.1
2.2
3.2
1.6
5.9
8.1
4.2
1.1
1.7
0.9
1.0
1.7
2.0
31.4
27.4
7.7
0.4
0.7
0.6
49.3
36.8
7.5
1.8
2.7
1.1
1
% Rh/WO /ZrO
x 2
2
2
00 100
60 100
0.5
0.1
traces
0.3
0.4
3.0
1.7
8.8
0.3
2.0
0.1
1.2
38.0
34.0
0.1
0.3
58.3
33.4
0.5
2.4
13.2
0.4 + 1.0
Note: See Table 1 for notation.
alkanes amount to 21–23 wt % (Fig. 2). Hydrodealky- patterns on catalysts deposited on WO /ZrO are simi-
x
2
lation product yields are insignificant (Table 2). A com- lar to those observed for catalysts HSiWO/ZrO . As
2
parison of Pt and Rh catalysts showed that the same tol- with the heteropoly acid catalysts, all reactions on
uene hydroconversion reactions occur on them, but the Pt/WO /ZrO occur at lower temperatures than on
x
2
temperature is lower by 50–60°ë on the Pt catalyst Rh/WO /ZrO . As distinct from heteropoly acid cata-
x
2
(
Fig. 2).
lysts, the hydrogenolysis and hydrocracking of MCH
and AlkCP on Pt and Rh catalysts deposited on
The results obtained for toluene transformations on
% Rh/WO /ZrO and 1% Pt/WO /ZrO are presented
WO /ZrO , which is characterized by stronger acid
1
x
2
x
2
x
2
properties [16], occur at temperatures lower by 40–
0°ë and to deeper transformation degrees. The highest
in Fig. 3 and Table 2. The main toluene transformation
6
yield of ring opening products on Pt/WO /ZrO is
x
2
higher than that on Pt/HSiWO/ZrO and equals 13 wt %.
y, wt %
2
3
1
% Pt/WZR
The maximum yield on Rh/WO /ZrO is 13.8 wt %,
x
2
8
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
1
1
'
'
1% Rh/WZR
3'
which is commensurate with the yield obtained on
Rh/HSiWO/ZrO2.
It follows that the hydrogenation of toluene into
MCH and isomerization of MCH into AlkCP fol-
lowed by the hydrogenolysis (hydrocracking) of
cyclic structures largely occur in the presence of Pt
and Rh deposited on acid carriers under the condi-
tions studied. The direction of toluene transforma-
tions strongly depends on the strength of the acid
properties of carriers.
2
2
4
4
'
The shortcoming of catalysts containing noble met-
als is their irreversible poisoning with small amounts of
sulfur [3]. The hydrodearomatization of oil fractions is
performed using Ni–W catalysts [17] more stable
toward the action of sulfur and cheaper than Pt and
Rh catalysts. The temperature dependences of the
yields of the main toluene transformation products on
6% Ni/WO /ZrO are shown in Fig. 4. We see that tol-
1
80
220
260
300
t, °C
Fig. 3. Influence of the nature of metals on the yields of
major toluene transformation products (y) on the catalysts
(
1–4) 1% Pt/WO /ZrO and (1'–4') 1% Rh/WO /ZrO at a
x 2 x 2
2
.2 MPa pressure; (1, 1') MCH, (2, 2') AlkCP, (3, 3' ) ë –ë
1 5
alkanes, and (4, 4') isoheptanes and n-heptane.
x
2
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY Vol. 80 No. 4 2006

THE TRANSFORMATIONS OF TOLUENE ON ALUMINA AND BIFUNCTIONAL CATALYSTS
555
y, wt %
y, wt %
00
(‡)
x, %
(
b)
1
6
2
8
4
0
4
5
'
'
1
100
6
% Ni/WZR
1'
2
'
0
.2%Pt–6% Ni/WZR
8
6
4
2
0
0
0
0
0
80
1
2
1 60
40
3
3
20
4
5
'
0
2
00
240
280
320 t, °C
220
260
300
340
t, °C
Fig. 4. Temperature dependences of toluene conversion (x) and major product yields (y) on the catalysts (1–5) 6% Ni/WO /ZrO
x
2
and (1'–5') 0.2% Pt–6% Ni/WO /ZrO at a 2.2 MPa pressure; (a) (1, 1') conversion, (2, 2') MCH, and (3, 3') AlkCP and (b) (4,
x
2
4
') C –ë alkanes and (5, 5') isoheptanes and n-heptane.
1 5
uene conversion on this catalyst is 100% at tempera- individual Ni–Pt/WO /ZrO and two times larger than
x
2
tures up to 300°ë and rapidly decreases at higher tem- on 2% Rh/Al O . Simultaneously, a fairly high yield of
2
3
peratures. This can be related to the deactivation of the isohexanes is obtained at 300–320°ë. The yield of ë1–
catalyst by compaction products, as follows from the ë alkanes does not exceed 18 wt % even at 320°ë. It
5
presence of ë hydrocarbons in reaction products. The follows that joint use of two catalysts may provide the
8
+
yield of ë8+ hydrocarbons reaches 4–5 wt % at 300– highest yield of ring opening products and a high ratio
3
40°ë (Table 3). Platinum (0.2 wt %) was introduced between disubstituted and monosubstituted heptane
into the Ni catalyst to increase its stability. The major isomers.
toluene transformation products on Ni and Ni–Pt cata-
lysts are MCH and AlkCP (Fig. 4, Table 3). The highest
yield of AlkCP is 47–48 wt % (260–300°ë); this is
higher than the yields obtained on the Pt and Rh cata-
lysts. As distinct from the Pt and Rh catalysts, ring
Using the data on toluene transformations on metal
oxide and bifunctional catalysts and the scheme of tol-
uene transformations given above, the following main
toluene reactions can be specified: (1) hydrogenation
into methylcyclohexane, (2) isomerization of the six-
into five-membered ring, (3) ring opening with the for-
mation of mono- and disubstituted heptane isomers,
and (4) hydrocracking of naphthene hydrocarbons and
ë ç into ë –ë alkanes.
opening occurs on Ni–Pt/WO /ZrO at higher tempera-
x
2
tures, and the yield of isoheptanes does not exceed
1 wt %. The yield of hydrocracking products on
Ni−Pt/WO /ZrO is much lower compared with
1
x
2
7
16
1
6
Pt(Rh)/WO /ZrO .
x
2
The hydrogenation of toluene into MCH is observed
As is shown in [5, 18], aromatic and naphthene on all catalysts under the conditions studied (160–
hydrocarbons can transform into branched alkanes with 360°ë, 2.2 MPa). At temperatures up to 180°ë, MCH
the number of carbon atoms equal to that in the initial is the major product. The isomerization of the six- into
substance when two catalysts are used simultaneously. five-membered ring only occurs on catalysts with
In order to increase the yield of ring opening products Broensted acid sites (Pt, Rh, and Ni on WO /ZrO or
x
2
(
isoheptanes) from the hydrogenolysis of toluene, we HSiWO/ZrO ). A comparison of the Pt, Rh, and Ni cat-
2
tested combined catalysts comprising two fractions, alysts shows that the isomerization of toluene into alky-
6
% Ni–0.2% Pt/WO /ZrO and 2% Rh/Al O (Table 3). lcyclopentanes occurs on Pt catalysts at temperatures
x 2 2 3
The volume of catalyst loads remained the same as pre- 50–60°ë lower than those characteristic of the Rh and
3
viously (3 cm ), and the volume ratio between the two Ni catalysts. The yield of AlkCP increases as the tem-
fractions was 1 : 1. Close results were obtained no mat- perature grows and passes a maximum. Both the nature
ter whether catalysts were loaded in layers or mixed of the metal and the acidity of the carrier play important
(
Fig. 5). The hydrogenation of toluene and isomeriza- roles in ring opening reactions with the formation of
tion of the six- into five-membered ring occurred on the isoheptanes. The contribution of the ring opening reac-
acid component of combined catalysts (6% Ni–0.2% tion increases as the temperature grows. The hydro-
Pt/WO /ZrO ), and MCH and AlkCP underwent hydro- genolysis of the six-membered ring gives monosubsti-
x
2
genolysis with the formation of methylhexanes and tuted isoheptanes, and five-membered ring opening
dimethylpentanes on the metal oxide component largely results in the formation of disubstituted iso-
(
Table 3). The total yield of heptanes reaches 52–58 wt % mers. The yield of isoheptanes decreases in the series
at 300–320°ë, which is 4.5 times larger compared with Pt ≅ Rh > Ni for catalysts deposited on WO /ZrO . The
x
2
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY Vol. 80 No. 4 2006

5
56
MASLOBOISHCHIKOVA et al.
Table 3. Yields of the major toluene transformation products (y, wt %) on Ni-containing catalysts (molar ratio H : C H =
2
7
8
–
1
3
1
0 : 1, p = 2.2 MPa, vvol = 2 h , catalyst load volume 3 cm )
y(I)
y(II)
y(III)
y(IV)
y(V)
t, °C
x, %
y(C )
8+
DMB
MP
Cyclo-
hexane
CH –C H
n-C H
DMP
MH n-C H
MCP AlkCP
MCH
4
5
12
6
14
7
16
+
6
% Ni/WO /ZrO
x
2
2
3
60 100
2.2
5.2
0.1 + 0.3
0.2 + 0.6
0.1
0.2
0.2
0.5
1.3
0.3
0.9
0.7
1.8
47.7
48.3
0.1
0.3
44.9
34.6
2.1
4.0
00
99.8
3.2
6
% Ni–0.2% Pt/WO /ZrO
x 2
2
3
3
60 100
0.6
3.8
0.1
Traces
0.3
0.2
1.3
1.8
1.1
4.9
7.2
0.3
0.3
1.9
3.6
47.7
47.8
40.9
0.1
0.4
0.7
49.1
35.9
27.3
0.5
1.3
2.5
00
20
99.9
99.7
0.3 + 0.8
0.8 + 1.9
1.2
1.9
10.4
0.7
*
6
% Ni–0.2% Pt/WO /ZrO + 2% Rh/Al O
x
2
2
3
2
3
3
60 100
0.9
9.4
0.1 + 0.6
0.7 + 8.1
0.1
1.2
6.4
20.5
18.1
10.5
0.7
2.4
1.8
0.2
36.5
7.7
0.1
0.3
0.3
43.3
12.8
5.5
0.6
1.4
1.7
00
20
99.9
99.8
35.4
31.6
0
0
17.9
1.6 + 14.6
2.0
4.7
3
*
Two-layer catalyst loading, layer volumes 1.5 cm . See Table 1 for notation.
activity of Pt/HSiWO/ZrO in ring opening is half that
REFERENCES
2
of Pt/WO /ZrO with stronger carrier acidity. The yield
of isoheptanes on acid catalysts does not exceed 13 wt %.
x
2
1. K. Shimizu, T. Sunagawa, C. R. Vera, and K. Ukegawa,
Appl. Catal., A 206, 79 (2001).
2
3
. O. Cairon, K. Thomas, A. Chambellan, and T. Chevreau,
Cracking to ë –ë alkanes becomes predominant on all
1
6
Appl. Catal., A 236, 167 (2003).
catalysts studied at high temperatures. The yield of
hydrocracking products may be as high as 100% on the
. M. A. Arribas, F. Marquez, and A. Martinez, J. Catal.
1
90, 309 (2000).
Rh/Al O and Me/WO /ZrO (Me is Pt or Rh) catalysts.
2
3
x
2
4. J. Wang, H. Y. Chen, and Q. Z. Li, React. Kinet. Catal.
Hydrodemethylation is not the main direction of tolu-
ene transformations on any of the catalysts studied.
Lett. 69 (2), 277 (2000).
5
6
7
. E. G. Khelkovskaya-Sergeeva, O. V. Masloboishchikova,
V. I. Bogdan, et al., Katal. v Promyshlennosti (in press).
. J. Volter, M. Hermann, and K. Heise, J. Catal. 12, 307
Methylcyclohexane
Alkylcyclopentanes
Isoheptanes and n-C H
(1968).
. S. D. Lin and M. A. Vannice, J. Catal. 143, 554 (1993).
7
16
8. C. G. Walter, B. Cog, F. Figueras, and M. Boulet, Appl.
CH –C H
Catal., A 133, 95 (1995).
Y, wt %
4
4
10
9
. G. Lietz and J. Volter, J. Catal. 45, 121 (1976).
6
5
4
3
2
1
0
0
0
0
0
0
0
300°C
300°C
1
0. D. C. Grenoble, J. Catal. 56, 32 (1979).
11. D. Duprez, A. Miloudi, G. Delahay, and R. Maurel,
3
20°C
320°C
J. Catal. 90, 292 (1984).
1
1
1
1
1
1
2. V. N. Mozhaiko, G. L. Rabinovich, G. N. Maslyanskii,
and L. P. Erdyakova, Neftekhimiya, No. 1, 95 (1975).
3. J. P. Boitiaux, J. Cosyns, and A. K. Joesoef, Appl. Catal.,
A 3, 89 (1982).
4. F. Figueras, B. Cog, C. Walter, and J.-Y. Carriat, J. Catal.
169, 103 (1997).
5. G. B. McVicker, M. Daage, M. S. Touvelle, et al.,
J. Catal. 210, 137 (2002).
I
II
III
IV
6. A. V. Ivanov and L. M. Kustov, Ross. Khim. Zh., No. 2,
2
1 (2000).
Fig. 5. Yields of major toluene transformation products on
catalysts loaded in layers and as a mixture; I, Ni–
7. M. D. Navalikhina and O. V. Krylov, Usp. Khim.,
No. 67, 656 (1998).
Pt/WO /ZrO + Rh/Al O (layered loading); II, Ni–
x
2
2 5
Pt/WO /ZrO (mixture); III, Ni–Pt/WO /ZrO ; and
18. U.S. Patent No. 5382731; Chem. Abstr. 122, 293888h
x
2
3
x
2
IV, Rh/Al O .
(1995).
2
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