Transformations of β-alkylcyclohexane hydrocarbons on modified pentasils with participation of methanol and oxidants

Article abstract of DOI:10.1134/S0965544106050094

The reactions of dehydroalkylation of methylcyclohexane, ethylcyclohexane, and methylcyclohexene isomers and toluene alkylation with methanol on platinum-and gallium-modified pentasil in the presence of an O ₂-CO₂ mixture was studied. Optimum conditions were found for the one-step dehydroalkylation of methylcyclohexane on the ring. Under these conditions, the degree of conversion of methylcyclohexane and methylcyclohexene isomers into xylene isomers is above that of toluene alkylation to afford xylene. According to the discussed reaction mechanism, the dehydroalkylation of cyclohexane hydrocarbons on Pt, Ga-pentasil involves both the steps of formation of unsaturated intermediates and toluene in status nascendi. Nauka/Interperiodica 2006.

Full text of DOI:10.1134/S0965544106050094

ISSN 0965-5441, Petroleum Chemistry, 2006, Vol. 46, No. 5, pp. 353–361. © Pleiades Publishing, Inc., 2006.
Original Russian Text © Kh.M. Alimardanov, F.M. Velieva, L.A. Dadasheva, M.I. Rustamov, 2006, published in Neftekhimiya, 2006, Vol. 46, No. 5, pp. 381–390.
Transformations of b-Alkylcyclohexane Hydrocarbons
on Modified Pentasils with Participation
of Methanol and Oxidants
Kh. M. Alimardanov, F. M. Velieva, L. A. Dadasheva, and M. I. Rustamov
Institute of Petrochemical Processes, National Academy of Sciences of Azerbaijan, Baku, Azerbaijan
e-mail: hafizalimardanov@yahoo.com
Received April 6, 2006
Abstract—The reactions of dehydroalkylation of methylcyclohexane, ethylcyclohexane, and methylcyclohex-
ene isomers and toluene alkylation with methanol on platinum- and gallium-modified pentasil in the presence
of an O2–CO2 mixture was studied. Optimum conditions were found for the one-step dehydroalkylation of
methylcyclohexane on the ring. Under these conditions, the degree of conversion of methylcyclohexane and
methylcyclohexene isomers into xylene isomers is above that of toluene alkylation to afford xylene. According
to the discussed reaction mechanism, the dehydroalkylation of cyclohexane hydrocarbons on Pt, Ga-pentasil
involves both the steps of formation of unsaturated intermediates and toluene in status nascendi.
DOI: 10.1134/S0965544106050094
Despite the advances in the production of aromatic
hydrocarbons, the search for new alternative sources of
raw materials and nontraditional methods of their con-
version into polyalkylated benzenes remains a topical
problem of modern petroleum chemistry.
EXPERIMENTAL
Methylcyclohexane and ethylcyclohexane used as
reactants were obtained via the hydrogenation of tolu-
ene and ethylbenzene (reagent grade), respectively, in
the presence of nickel supported on kieselguhr at 160–
180°C and a pressure of 9–10 MPa; 1-, 3-, and
4-MCHE were obtained by the dehydration of 2- and
4-methylcyclohexanols on γ-Al2O3 at 250°ë. The
hydrocarbons were isolated from the catalyzate by rec-
tification on a column with a number of theoretical
plates of 20 and subsequent distillation over sodium
metal. The purity of 1-MCHE was 99.0–99.6 wt %,
3-and 4-MCHE was used as a mixture (33 wt %
3-MCHE + 67 wt % 4-MCHE).
Catalyst specimens were prepared as described previ-
ously [17]. As catalysts, HNa-TsVM zeolites—high-sil-
ica zeolites having the ZSM-5 structure (SiO2/Al2O3 =
ı = 30 or 43.5)—modified with gallium, iron, zinc neody-
mium, and phosphorus oxides, as well as platinum,
Ga-Fe-Nd-P-O-, Zn-Ga-Nd-P-O-, and Pt-Ga-Nd-P-
O/HNa-TsVM, were used. The amount of gallium, iron,
zinc neodymium, and phosphorus oxides varied from 1.5
to 3.0 wt %, and that of platinum was 0.005–0.5 wt %.
The experiments were carried out in a laboratory
unit with a flow reactor in the presence and in the
absence of carrier gas at a pressure of 0.1 MPa and tem-
peratures of 380–600°ë. To prevent the homogeneous
transformations of hydrocarbons, a catalyst in the reac-
tor was placed in quartz packing. While studying the
catalytic transformations of each hydrocarbon, the cat-
alyst activity was checked by periodically returning to
the initial conditions.
The research in this area mainly deals with naturally
occurring raw materials—-crude oil, natural gas, and
coal processing products. Along with modernization of
pyrolysis and catalytic reforming as traditional indus-
trial processes for the manufacture of aromatic hydro-
carbons, the reactions of toluene disproportionation [1–
5], benzene and toluene alkylation with low saturated
and unsaturated hydrocarbons [6, 7] and alcohols [8–
10], and aromatization of ë1–ë4 hydrocarbons [11, 12]
and methanol [13, 14] are the subjects of current stud-
ies. The use of ë1– ë4 hydrocarbons and alcohols in the
alkylation of aromatic hydrocarbons promotes the com-
prehensive utilization of feedstocks of different origin.
In light of the foregoing, the preparation of industrially
important aromatic hydrocarbons, such as isomers of
xylene, ethyltoluene, diethylbenzene, and other polyalkyl
benzenes, from alicyclic hydrocarbons that are present in
considerable amounts in straight-run gasoline fractions
[15–16] or from ë1–ë3 monohydric alcohols is of
undoubted scientific and practical interest. However,
unlike the case of alkylation of toluene and other aromatic
hydrocarbons, information in the literature on this line of
research is insufficient. In this work, we studied the dehyd-
roalkylation of methylcyclohexane (MCH) and ethylcy-
clohexane (ECH), as well as the isomers of methylcyclo-
hexene (1- and 3-MCHE) with methanol on the H-form of
pentasil modified with transition and nontransition metal
oxides, as well as the influence of é2 and ëé2 on the reac-
tion selectivity.
Before use, catalyst specimens were activated for
4 h at 500°C in a stream of air and then in a stream of
353

354
ALIMARDANOV et al.
oxygen-free nitrogen. Kinetic studies were carried out However, we observed a significant increase in the degree
in a laboratory unit with a gradientless reactor at tem- of dehydrogenation (DH) and dehydrodisproportionation
peratures of 430–530°ë.
(DD) of MCH and ECH, a result that is obviously due to a
high rate of reduction of Ga3+ to Ga+ cations on gallium-
pentasil after its additional modification with platinum.
The same effect was noted earlier by Minachev and Der-
gachev [12] in the aromatization reaction of ë3ç8 and n-
ë4ç10, who explained the phenomenon by the spillover of
highly reactive hydrogen atoms in the Pt–Ga3+ system.
The introduction of oxygen or ëé2 into the reaction zone
results in the intensification of MCH transformation via
disproportionation and dehydroalkylation. The obtained
results are given in Tables 2 and 3.
The product composition was determined by GLC
analysis on Tsvet-100 and KhL-3 chromatographs. Gas-
eous products were analyzed using the stationary phase
triethylene glycol butyrate (TEGB, 15 wt %) supported on
firebrick (INZ-600) and liquid products were analyzed on
Chromosorb W coated with bis(2-dicyanoethyl)sulfide
(12 wt %) or polyethylene glycol succinate (PEGC). The
composition of ë8ç10 aromatic hydrocarbons (ArH) was
refined on a Benton-245 column.
RESULTS AND DISCUSSION
The MCH dehydration and dehydrodisproportion-
ation degrees presented in Tables 2 and 3 were calcu-
lated in terms of toluene and benzene yields, respec-
tively, assuming the following reactions:
The dehydroalkylation of MCH and ECH with
methanol on pentasil has some specific features
depending on the nature of the modifiers used. Its main
distinguishing feature is a significant amount of unsat-
urated hydrocarbons (UHC) in the products obtained
on pentasil modified with gallium and iron oxides. The
yield of MCH and dimethylcyclopentene isomers in the
presence of Ga-Fe-P-O/HNa-TsVM at 430–470°C was
4.1–4.8% in terms of feedstock supplied (Table 1). An
increase in temperature and a decrease in the feedstock
space velocity lead to a decrease in the relative amount
of cyclohexene homologues and other unsaturated
hydrocarbons in the catalyzate.
Earlier, we noted that MCHE isomers are the most
likely intermediate products of the MCH dehydroalky-
lation reaction with methanol on Ga-Fe-P-O/HNa-
TsVM [17]. Thus, it was assumed that the alkylation of
cyclohexane derivatives on this contact catalyst pro-
ceeds predominantly through the stages of dehydroge-
nation of both hydrocarbon and alcohol followed by the
reaction of the formed unsaturated compounds with
formaldehyde adsorbed on the catalyst surface.
2ëç3ë6ç11 + 3é2
2ëç3ë6ç11 + 3é2
2ëç3ë6ç5 + 6ç2é,
ë6ç4(ëç3)2 + ë6ç6 + 6ç2é.
In this case, we admitted that methanol yields prac-
tically no benzene on pentasil-type zeolites [13] and the
degree of MCH dehydrodemethylation and toluene
demethylation on them is very low [20]. To simplify the
calculations, we also ignored the disproportionation of
forming xylenes into toluene and isomers of trialkyl-
benzene.
The most significant promoting effect was exerted
by a mixture of oxygen and carbon dioxide. For exam-
ple, at a temperature of 460°C, the yield of dialkyl- and
polyalkylbenzenes was 18.8–20.5% at an MCH conver-
sion of 59.4–62.5%. It is interesting that the amount of
MCH isomers in the catalyzate also increases under the
same conditions on Ga-Fe-P-O/HNa-TsVM. As fol-
lows from the data presented in Table 2, when oxygen
The presence of a significant amount of unsaturated is introduced into the reaction zone, the dehydrodispro-
hydrocarbons with cyclic structure in the catalyzate is portionation of MCH prevails over its dehydroalkyla-
explained by the high rate of their desorption from the tion on the gallium–zinc and gallium–platinum sys-
active sites of the zeolite surface at which coordination- tems, in contrast to the gallium–iron-containing speci-
unsaturated Ga3+ and Fe3+ cations are mainly localized mens. As the main part of oxygen is replaced by carbon
[12]. However, the introduction of platinum or zinc dioxide (é2 : ëé2 = 0.05 : 1.0–1.5), the degree of dehy-
instead of iron cations into this catalyst sharply decreases drodisproportionation and dehydroalkylation increases
the amount of unsaturated hydrocarbons in the alkylate. and the degree of its dehydrogenation remains practi-
The main liquid products are benzene, toluene, xylenes, cally unchanged in the range 31.1–36.7%. It is known
and ë9 ArH, as well as a small amount of ë5–ë7 paraffin that the abstraction of hydrogen atoms from MCH and
and isoparaffin hydrocarbons (ë5–ë7 AliphH). The degree ëç3éç molecules proceeds with the participation of
of dehydroalkylation of MCH in the presence of platinum- nucleophilic surface oxygen (O2–) [21, 22]. Then, the
and zinc-containing catalysts slightly differs from analo- formed carbanions are stabilized on metal cations and
gous data obtained on Ga-Fe-P-O/HNa-TsVM [18, 19]. reduce them:
OH
OH
.
–
Pt…OGaOxZ + CH3C6H11
Pt…OGaOxZ + CH3OH
[Pt…GaOxZ]+C6H10CH3
OH
[Pt…GaOxZ]C6H10CH3
OH
[Pt…GaOxZ]C6H9CH3,
[Pt…GaOxZ]CH2O.
.
[Pt…GaOxZ]+CH3O–
[Pt…GaOxZ]CH3O
PETROLEUM CHEMISTRY Vol. 46 No. 5 2006

TRANSFORMATIONS OF β-ALKYLCYCLOHEXANE HYDROCARBONS
355
Table 1. Dehydroalkylation of methyl- and ethylcyclohexanes with methanol on modified forms of pentasil (hydrocarbon :
CH3OH = 2 : 1, ν = 0.5 h–1)
Yield in terms of reactant feed, wt %
Yield, wt %
Selectivity
for dehy-
droalkyla-
tion product,
%
Hydrocar-
bon conver-
sion, %
Tempera-
Hydrocarbon
MCH
ture, °C
liquid
gas
coke and loss
ArH
cycloolefins
products
Catalyst Ga-Fe-P-O/HNa-TsVM
430
470
500
530
570
430
470
500
530
570
12.0
20.2
31.2
52.0
58.9
13.5
20.0
26.6
40.5
48.9
90.2
87.2
85.7
84.0
83.6
93.5
91.3
88.0
87.2
87.3
7.3
10.0
10.3
11.8
12.0
4.8
2.5
2.8
4.0
4.2
4.4
1.7
1.5
2.1
4.0
5.2
9.8
17.4
29.6
49.4
54.9
12.1
16.7
21.6
36.4
40.5
4.8
4.1
2.2
2.0
2.5
3.6
4.4
4.5
2.2
2.4
6.0
9.2
13.0
17.7
24.7
4.0
ECH
4.9
7.1
6.2
11.7
13.0
16.4
11.4
10.4
Catalyst Zn-Ga-Nd-P-O/HNa-TsVM
MCH
ECH
430
470
500
530
570
430
470
500
530
570
11.0
32.1
38.4
52.6
66.0
12.3
19.0
28.5
55.7
66.1
89.4
87.5
87.0
84.0
80.3
91.7
90.8
90.0
91.2
88.3
7.4
8.3
3.2
4.2
4.6
4.5
5.1
2.6
2.6
3.1
3.3
3.5
9.5
25.2
28.2
39.0
48.4
10.1
14.3
23.6
42.1
52.4
0.4
0.5
–
2.1
6.2
8.4
12.5
15.5
18.1
3.6
11.5
14.6
5.7
–
–
0.3
–
6.6
4.5
6.9
–
9.6
5.5
–
16.8
19.7
8.2
–
Catalyst Pt-Ga-Nd-P-O/HNa-TsVM
MCH
ECH
430
450
470
500
430
450
470
500
21.4
36.1
41.4
54.0
17.2
19.2
19.0
34.6
92.6
92.5
91.5
87.4
93.6
91.8
90.0
90.4
5.5
5.9
5.5
9.8
4.6
6.4
7.8
7.0
1.9
1.6
3.0
2.8
1.8
1.8
2.2
2.6
18.4
30.9
34.5
45.0
14.1
15.9
15.0
27.7
0.6
0.7
0.3
–
6.2
9.8
11.8
19.4
4.0
0.3
–
4.1
–
4.4
–
12.7
PETROLEUM CHEMISTRY Vol. 46 No. 5 2006

356
ALIMARDANOV et al.
Table 2. Dehydroalkylation of methylcyclohexane with methanol on modified forms of pentasil in an air stream (MCH :
CH3OH = 2 : 1, MCH : O2 = 1 : 0.2)
Conversion
Alkylate composition, wt %
C5–C6
ν,
MCH DH MCH DD MCH DA
degree, % degree, % degree,%
T, °C
aliphat-
h–1
C6–C7
UHCs
CH3OH MCH ic hy-
benzene toluene C8 ArH C9 ArH
drocar-
bons
Catalyst Ga-Fe-P-O/HNa-TsVM
0.5
0.5
0.5
0.5
1.0
2.0
420
440
460
500
460
460
82.0
88.1
95.7
21.6
24.0
32.5
38.6
28.2
25.0
–
4.6
5.9
2.3
3.0
4.0
3.5
1.2
3.8
5.1
6.0
5.0
2.6
83.1
74.5
67.5
62.3
68.1
76.6
8.0
12.6
17.1
20.4
18.0
13.7
3.1
3.0
7.4
8.0
4.6
3.6
17.6
17.5
21.5
24.0
19.6
19.6
0.6
2.3
3.6
5.5
3.1
1.5
2.1
2.8
6.2
8.5
4.9
3.6
0.2
0.6
1.2
0.3
–
100
84.5
79.6
Catalyst Zn-Ga-Nd-P-O/HNa-TsVM
0.5
0.5
0.5
1.0
2.0
400
430
460
460
460
93.0
100.0
100.0
100.0
89.7
31.6
34.8
40.2
36.0
29.7
1.2
0.5
1.0
0.6
0.6
1.8
0.6
–
2.0
3.6
6.4
5.8
4.0
84.8
81.1
83.9
76.3
82.7
6.8
9.0
3.4
5.2
6.0
4.8
3.1
28.5
28.2
29.7
27.5
24.6
1.5
3.1
6.0
4.9
2.8
2.2
3.6
4.9
4.1
2.4
12.7
12.5
9.2
–
0.4
Catalyst Pt-Ga-Nd-P-O/HNa-TsVM
0.5
0.5
0.5
0.5
1.0
2.0
400
420
440
460
440
440
83.6
92.2
100
29.6
38.3
44.5
52.6
36.0
29.2
–
0.7
–
3.4
4.7
6.0
8.1
4.3
3.1
83.3
80.7
71.8
65.6
82.9
86.5
9.7
11.0
18.4
21.6
10.2
8.3
2.9
3.2
3.2
4.7
2.0
1.8
23.9
30.9
31.9
33.1
29.8
25.2
2.4
4.2
2.7
3.6
6.8
8.3
2.8
2.0
0.4
0.6
1.4
0.3
–
–
6.3
100
–
10.5
3.6
86.0
81.5
0.3
0.3
2.1
The increase in the concentration of polyalkylbenzenes dehydroalkylation of MCH by methanol with an admix-
ture of water (Table 3) should be considered. The stability
of the formed carbonate complexes correlates with the
oxidation number of the modifying additives. Slightly
adsorbed forms of carbon dioxide are the most active [7].
in the catalyzate indicates that é2 and ëé2 play different
roles in this process. For example, oxygen is needed
mainly for the oxidation of reduced catalyst sites respon-
sible for MCH dehydrogenation, in particular, Ga+ to Ga3+
in the Pt–Ga+ system, whereas ëé2 and ç2é released in
the course of the reaction react with metal cations and
enrich the zeolite surface with additional Bronsted acid
sites according to the known scheme Pt…O–GaOxZ +
Based on the data presented in Tables 2 and 3, one
can suppose that another dehydrogenation product, tol-
uene, also (along with the reactant MCH) undergoes
subsequent transformation in status nascendi on the
platinum-gallium-containing specimen into xylene iso-
mers via disproportionation and alkylation. However,
experiments to corroborate this assumption showed
that, during the alkylation of toluene with methanol
(Table 4) on this catalytic system under the same con-
ditions over a wide temperature range, the degrees of
toluene disproportionation and alkylation, as well as
H2O + CO2
[Pt…O–GaOxZ + H2CO3]
Pt…O–
GaOxZëé3 + 2ç+ [7, 23]. It is these acid sites that are
responsible for the disproportionation and alkylation of
MCH dehydrogenation products with methanol or formal-
dehyde and it is from this point of view that the higher
yields of xylene and ë9 aromatic hydrocarbons during the
PETROLEUM CHEMISTRY Vol. 46 No. 5 2006

TRANSFORMATIONS OF β-ALKYLCYCLOHEXANE HYDROCARBONS
357
Table 3. Dependence of dehydroalkylation of methylcyclohexane on Pt-Ga-Nd-P-O/HNa-TsVM on the molar ratio of
MCH : O2 : CO2 (MCH : CH3OH = 2 : 1, T = 460°C, νMCH = 0.5 h–1)
Conversion, %
Yield, wt %
MCH : O2 : CO2
molar ratio
MCH DH MCH DD MCH DA
degree, % degree, % degree, %
C9–C10 di- and
benzene toluene xylenes; polyalkylben-
zenes
CH3OH
MCH
1 : 0.2* no CO2
1 : 0.1 : 0.1
100
100
100
100
100
100
100
57.6
49.7
49.4
45.0
46.8
51.7
54.2
59.4
62.5
48.7
33.1
32.0
32.0
31.2
31.7
33.2
31.1
34.0
36.7
29.5
10.5
7.7
8.3
9.5
4.2
3.2
2.8
3.1
3.1
3.0
4.1
5.0
5.6
2.6
31.4
29.4
30.1
29.3
29.7
31.2
29.2
32.6
34.4
28.2
12.7
9.0
2.1
1.7
2.0
2.0
2.2
3.1
5.4
5.5
4.9
3.6
1 : 0.05 : 0.1
1 : 0.01 : 0.1
1 : 0.05 : 0.2
1 : 0.05 : 0.5
1 : 0.05 : 1
7.0
7.0
9.4
7.2
6.3
9.0
7.3
7.4
10.0
11.3
13.4
15.0
16.5
11.0
7.0
9.6
9.6
12.3
12.4
12.8
10.0
1 : 0.05 : 1.5
1 : 0.05 : 1.5**
98.4
12.4
14.1
6.4
97.3
97.4
MCH : CO2 =
1 : 1.5, no O2
* The diluent was nitrogen, O : N = 1 : 4.
2
2
** Methanol contained 0.5 wt % H O.
2
the conversion and the yields of xylenes, were signifi- lium-containing pentasil by the action of carbon diox-
cantly lower than those obtained in MCH transforma- ide and released water catalyze the disproportionation
tion (Table 3), although the yields of xylene isomers are and alkylation of both intermediate unsaturated hydro-
about two times those obtained in the toluene alkylation carbons and toluene that appears in a metastable state at
with methanol on platinum-free GaGdPO/HNa-TsVM the moment of its formation (corresponding aromatic
[17].
Another situation is observed when MCHE isomers
carbocation [24, 25]).
The extent of these transformations along with other
are used a feedstock. As follows from the data given in factors also depends on the ratio of deposited active
Table 5, at a molar ratio of MCHE : ëç3éç = 2 : 1, the components (Fig. 1). For example, a decrease in the
yield of xylene isomers was 9.3–22.2 wt % even at 380– platinum loading from 0.5 to 0.005 wt % (the amount
420°C and increased to 21.4–27.1 wt % at 460°C. Fur- of other components was constant at a level of 3.0 wt %)
thermore, the yield and isomeric composition of decreased the yield of toluene, the product of MCH
xylenes strongly depends on the structure of the reac- dehydrogenation; simultaneously, the selectivity for
tant MCHE. For example, the catalyzate contains xylene isomers increased.
mainly the m- and o-isomers when 1-MCHE is used
and the relative amount of p-xylenes in the mixture of
the produced ë8ç10 aromatic hydrocarbons increases to
become as high as 40.7–44.0% in the case of 3-MCHE.
An increase in the amount of ëç3éç in the reaction
mixture decreases the yield of xylenes; however, the
proportion of other dialkylbenzenes, in particular,
ethyl- and isopropyltoluenes, in the catalyzate
increases under these conditions.
It is noteworthy that the activity of the Pt-Ga-Nd-P-
O/HNa-TsVM catalyst pretreated in a dry ëé2 stream
at a temperature of 600–650°C for 5 h significantly
decreased during the MCH dehydroalkylation reaction
and, especially, the alkylation of toluene with methanol
under the aforementioned conditions. However, after
2.5−3-h operation under catalysis conditions, its activ-
ity is restored. On the basis of the obtained results, the
conversion of an MCH– ëç3éç mixture on platinum–
Thus, taking into account these data, it becomes gallium pentasil in a ëé2 stream containing 2.4–3.6 wt %
obvious that protonic sites produced on platinum–gal- é2 can be described by the following scheme:
PETROLEUM CHEMISTRY Vol. 46 No. 5 2006

358
ALIMARDANOV et al.
CH3
+CH3OH, O2
CH3
+ 3H O
2
CH3
CH3
O2
0.5
CH3
CH3
+ 0.5
+ 2H O
2
CH3
CH3
CH3
H+
+H2
CH3
CH3
CH3
CH3
+CH3OH
CH3 + H O
2
H
H
⊕
CH3
0.5
+ 0.5
CH3
which substantially differs from the scheme suggested through the intermediate step of formation of aromatic
earlier [18]. These transformations occur on different
active sites of the catalyst. This scheme does not take
into account the routes of buildup of other polyalky-
lated benzenes. Most likely, these hydrocarbons are the
products of subsequent transformations of xylenes (or
other dialkylbenzenes, in particular, ethyltoluene iso-
mers [20]) that are formed via the reaction
carbonium ions [24], it may be assumed that the forma-
tion of carbocations from unsaturated intermediates
occurs with a higher probability in comparison with
their formation from stable molecules of toluene and
other aromatic hydrocarbons on the gallium–iron sys-
tem. The introduction of platinum instead of iron into
pentasil decreases this probability, and xylenes are
formed as a result of both MCH dehydroalkylation and
toluene alkylation. Hence, it is resonable to use the
technical mixture of MCH and toluene as a feedstock in
the process on Pt, Ga-Nd-P-O/HNa-TsVM.
H+
C6H4(CH3)2 + CH3OH
C6H3(CH3)3 + H2O,
H+
C6H4(CH3)2
C6H5CH3 + C6H3(CH3)3
or
As the isomers of MCHE and methylcyclohexadi-
ene under the aforementioned conditions are intermedi-
ate products in the reactions of MCH dehydrodispro-
portionation and dehydroalkylation to xylene and other
alkyl derivatives of benzene and the isomers of dimeth-
ylcyclopentene can be considered intermediate com-
pounds responsible for coke formation (from dimethyl-
cyclopentadiene) and destructive degradation [26], we
omitted some reaction routes from the description of
the reaction kinetics according to the following
H+
CH3C6H4C2H5
C6H3(CH3)3 .
The yield of polyalkylbenzenes under the aforemen-
tioned conditions is lower than that of dialkylbenzenes.
The same situation is observed when the mixture of
xylene and methanol is passed over Pt, Ga-Nd-P-
O/HNa-TsVM (Fig. 2). The main routes of conversion
of Ó- and p-xylene are their isomerization and dispro-
portionation. Since both the disproportionation and
alkylation reactions of aromatic hydrocarbons proceed scheme.
PETROLEUM CHEMISTRY Vol. 46 No. 5 2006

TRANSFORMATIONS OF β-ALKYLCYCLOHEXANE HYDROCARBONS
359
+O2
3-C6H9CH3
+CH3OH, O2
–H2O, –H2
+CH3OH
–H2O
C6H5CH3
C6H11CH3
C6H6(CH3)2
C1–C6, CO2
C6H4(CH3)2
1-C6H9CH3
+CH3OH
+O2
+O2
C6H3(CH3)3
+O2
+O2
On the basis of the given material, we chose the follow- ential technique [27]. In the selection of rate equations
ing set of independent reaction routes:
CH3C6H11 + CH3OH + 1.5O2
C6H4(CH3)2 + 4H2O,
on the basis of the available experimental material, the
rate of destructive MCH transformation via route (8)
was ignored, since r8 ꢀ r7.
(1)
k1[PCH C H ][PCH OH][PO ]
3
6
11
3
2
r = -----------------------------------------------------------------------------------------------
, (9)
1
2CH3C6H11 + 3O2
1 + Kα[PH O] + Kβ[PCH OH] + Kγ [PCO
]
2
3
2
C H (CH ) + C H + 6H O
,
(2)
(3)
6
4
3
6
6
2
2
k2[PCH C H ]2[PO ]
r2 = ----------------------------------------------------------------------------------------------- , (10)
1 + Kα[PH O] + Kβ[PCH OH] + Kγ [PCO
3
6
11
2
CH3C6H11 + 1.5O2
C6H5CH3 + CH3OH
C6H5CH3 + 3H2O,
]
2
3
2
H+
C6H4(CH3)2 + H2O , (4)
(5)
k3[PC H CH ][PO ]
6
5
3
2
r3 = ----------------------------------------------------------------------------------------------- , (11)
1 + Kα[PH O] + Kβ[PCH OH] + Kγ [PCO
]
H+
2
3
2
2C6H5CH3
C6H4(CH3)2 + C6H6 ,
k4[PC H CH ][PCH OH
]
6
5
3
3
H+
r4 = ----------------------------------------------------------------------------------------------- , (12)
2C6H4(CH3)2
C6H5CH3 + C6H3(CH3)3 , (6)
1 + Kα[PH O] + Kβ[PCH OH] + Kγ [PCO
]
2
3
2
2
(CH3OH + O2)
C1–C4 hydrocarbons,
k5[PC H CH
]
6
5
3
(7)
r5 = ----------------------------------------------------------------------------------------------- , (13)
carbon oxides, (CH3)2O, H2O.
1 + Kα[PH O] + Kβ[PCH OH] + Kγ [PCO
]
2
3
2
2
To determine the kinetic constants for these reaction
routes, we calculated the initial rates from the rate
curves of buildup of the desired products by the differ-
k6[PCH C H
]
3
6
11
r6 = ----------------------------------------------------------------------------------------------- , (14)
1 + Kα[PH O] + Kβ[PCH OH] + Kγ [PCO
]
2
3
2
Table 4. Alkylation of toluene with methanol on Pt–Ga–Nd–P–O/HNa TsVM (CH3C6H5 : CH3OH = 2 : 1, CH3C6H5 : O2 :
CO2 = 1 : 0.05 : 1.5)
Reaction
Conversion, %
C8H10 aromatic hydrocarbons composition, %
Toluene Toluene dispro-
conditions
alkylation
degree, %
portionation
degree, %
T, °C ν, h–1 CH3OH CH3C6H5
p-xylene
m-xylene
o-xylene ethylbenzene
350
400
450
500
500
500
500
1.0
1.0
1.0
1.0
0.5
2.0
3.0
77.4
85.8
5.2
8.6
3.0
4.1
1.2
2.3
4.8
7.4
9.1
8.0
6.3
36.8
38.2
30.7
28.0
26.4
31.4
33.0
46.3
42.0
50.6
51.7
50.5
48.3
46.0
16.0
18.1
17.8
19.0
22.4
18.0
20.0
0.9
1.7
0.9
1.3
0.7
2.3
1.0
100.0
100.0
100.0
100.0
98.2
20.7
31.4
35.2
30.0
22.7
12.7
18.3
19.3
16.4
11.6
PETROLEUM CHEMISTRY Vol. 46 No. 5 2006

360
ALIMARDANOV et al.
Table 5. Dehydroalkylation of methylcyclohexene isomers with methanol on Pt, Ga-Nd-P-O/HNa-TsVM (MCH : CH3OH =
2 : 1, MCH : O2 : CO2 = 1 : 0.05 : 1.5)
Reaction
Composition of C8H10 aromatic
hydrocarbons, %
Conversion, %
MCHE DH MCHE DD MCHE DA
conditions
degree,%
degree,%
degree,%
T, °C ν, h–1 CH3OH MCHE
p-xylene m-xylene o-xylene ethylbenzene
1-Methylcyclohexene
340
380
420
460
500
420
420
0.5
0.5
0.5
0.5
0.5
1.0
2.0
54.2
74.5
43.6
51.0
60.6
66.1
74.3
57.0
53.1
19.0
24.2
24.6
29.6
32.8
28.1
24.0
4.2
8.1
1.8
6.9
35.0
32.5
28.4
28.0
26.4
31.0
33.5
40.5
46.3
51.0
51.2
48.8
48.7
46.4
24.5
20.4
19.6
19.1
21.0
19.0
20.1
–
0.8
1.0
1.7
3.8
1.3
–
87.1
11.0
13.5
17.1
9.8
10.2
14.6
19.7
9.7
100.0
100.0
86.0
82.2
8.0
8.2
4- and 3-methylcyclohexenes
340
380
420
460
420
420
0.5
0.5
0.5
0.5
1.0
2.0
52.7
75.1
48.4
57.2
70.0
82.1
69.2
63.0
21.4
27.3
33.4
35.4
29.0
27.6
2.8
6.0
2.0
8.1
38.3
44.0
40.7
33.6
43.0
41.6
34.3
33.7
39.2
44.9
37.6
39.4
27.4
22.3
19.3
20.0
18.4
19.0
–
–
85.0
18.4
21.4
17.0
13.8
13.0
18.7
12.4
9.7
0.8
1.5
1.0
–
100.0
100.0
94.0
k7[PO ]2
ciative CH3OH adsorption, and äγ is the ëO2 chemi-
2
sorption constant.
r7 = ----------------------------------------------------------------------------------------------- , (15)
1 + Kα[PH O] + Kβ[PCH OH] + Kγ [PCO
]
The rates of reactant hydrocarbon conversion and
product buildup relevant to the above reaction routes
were calculated by the following equations:
2
3
2
where r1–r7 are the rates of reactions (1)–(7), k1–k7 are
the reaction rate constants, äα is the constant of disso-
ciative adsorption of H2é, äβ is the constant of disso-
wCH C H = –r1 – 2r2 – r3 – r8 ,
(16)
(17)
(18)
(19)
(20)
(21)
(22)
3
6
11
wC H (CH ) = r1 + r2 + r4 + r5 – 2r6 ,
6
4
3
2
wC H CH = r3 – r4 – 2r5 + r6 ,
%
6
5
3
70
1
wC H = r2 + r5 ,
1
1
6
6
60
50
40
30
20
10
0
1
wC H (CH ) = r6 ,
6
3
3
3
2
wC –C = r7 + r8 ,
2
2
1
4
2
3
3
wCH OH = –r1 – r4 – r7 .
3
3
3
4
4
4
4
The rate constants were calculated with a personal
computer using a modified Matlab-6.5 program.
I
II
III
IV
With the values of the constants thus found,
–1
cat
k1 = 2738.5 exp(–90968/RT), l2
h–1mol–2,
g
Fig. 1. Dependence of the yield of aromatic hydrocarbons
on the platinum loading of platinum–gallium pentasil (í =
460°ë, MCH : ëç éç = 2 : 1, MCH : é : ëé = 1 : 0.05 :
–1
cat
k2 = 585.78 exp(–81668/RT), l2
h–1mol–2,
g
3
2
2
–1
1.5; ν = 0.5 h ): (1) MCH conversion, (2) toluene yield, (3)
–1
k3 = 2044.7 exp(–87050/RT), l g h–1 mol–1,
yield of ë ç aromatic hydrocarbons, and (4) yield of
8
10
cat
ë −ë aromatic hydrocarbons. The amount of Pt intro-
9
10
–1
duced into Ga-Nd-P-O/HNa-TsVM is (I) 0.005, (II) 0.01,
(III) 0.1, and (IV) 0.5 wt %.
k4 = 508.41 exp(–81506/RT), l g h–1 mol–1,
cat
PETROLEUM CHEMISTRY Vol. 46 No. 5 2006

TRANSFORMATIONS OF β-ALKYLCYCLOHEXANE HYDROCARBONS
361
2. J. Kim, S. Namba, and T. Yasima, Appl. Catal. 83, 51
%
20
(1992).
(‡)
3. J. Kochi, J. Organomet. Chem. 653, 11 (2002).
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No. 2001107838/04, Russia (2001).
5. J. Cejka, A. Krejci, N. Zilkova, et al., in Proceedings of
2 International Symposium on Mesoporous Molecular
Sieves, Quebec City, 2001, p. 499.
1
15
10
1
1
1
3
3
2
3
2
5
0
3
2
2
4
6. S. I. Abasov, F. A. Babayeva, R. R. Zarbaliyev, et al.,
4
4
4
Appl. Catal., A 251, 267 (2003).
7. Ya. I. Isakov, Neftekhimiya 38, 404 (1998) [Pet. Chem.
38, 372 (1998)].
I
II
III
IV
8. N. Ya. Usachev, A. L. Lapidus, O. N. Usacheva, et al.,
20
15
10
5
1
Neftekhimiya 33, 305 (1993).
(b)
3
9. A. Vos, X. Rozanska, Schoonheydt, et al., J. Am. Chem.
1
Soc. 123, 2799 (2001).
1
1
3
10. S. Nojima, T. Yasutake, and T. Imai, J. Chem. Soc. Jpn.,
No. 6, 345 (2001).
11. Yuing Shu and M. Ichikawa, Catal. Today 71, 55 (2001).
12. Kh. M. Minachev andA. A. Dergachev, Izv. Akad. Nauk,
Ser. Khim., No. 6, 1018 (1993).
3
2
3
2
2
2
4
4
4
4
0
I
II
III
IV
13. Kh. M. Minachev and D. A. Kondrat’ev, Usp. Khim. 52,
1921 (1983).
Fig. 2. Activity of Pt, Ga-Nd-P-O/HNa-TsVM in the reac-
tion of (a) o-xylene and (b) p-xylene with methanol
(ë ç (ëç ) : ëç éç = 2 : 1, ë ç (ëç ) : é : ëé =
1 : 0.05 : 1.5): (1) xylene conversion, (2) degree of dispro-
portionation, (3) degree of isomerization, and (4) degree of
alkylation. The reaction temperature was (I) 460, (II) 480,
(III) 500, or (IV) 530°C.
14. O. A. Sinitsyna, V. I. Chumakova, and I. F. Mos-
6
4
3 2
3
6
4
3 2
2
2
kovskaya, Neftekhimiya 27, 194 (1997).
15. T. N. Maslyanskii and R. I. Shapiro, in Catalytic Reform-
ing of Naphthas (Khimiya, Leningrad, 1965) [in Rus-
sian].
16. F. I. Samedova, Azerbaijanian Crude Oils and Their
Component Composition (Elm, Baku, 2002) [in Rus-
sian].
–1
cat
k5 = 4469.10 exp(–72486/RT), l g h–1 mol–1,
17. Kh. M. Alimardanov, L. A. Tairova, and S. I. Abasov,
Neftekhimiya 43, 443 (2003) [Pet. Chem. 43, 404
(2003)].
18. Kh. M. Alimardanov, F. M. Velieva, E. T. Suleimanova,
et al., Neftekhimiya 45, 115 (2005) [Pet. Chem. 45, 96
(2005)].
19. H. Alimardanov, F. Veliyeva, and L. Tairova, in Proceed-
ings of 13 International Congress on Catalysis, Paris,
2004, Book 2, p. 216.
–1
cat
k6 = 1290.3 exp(–70480/RT), l g h–1 mol–1,
–1
k7 = 354.46 exp(–68010/RT), l g h–1 mol–1,
cat
Kα = 1.1817 × 10–6 exp(70751/RT), l mol–1,
Kβ = 7.36 × 10–7 exp(73402/RT), l mol–1,
Kγ = 9.037 × 10–8 exp(88798/RT), l mol–1,
where R is the universal gas constant (8.3144 J/(mol K)),
the best fit of the rates calculated by Eqs. (1)–(7) for the
dehydroalkylation reactions of cyclohexane hydrocar-
bons with the experimentally determined values was
obtained. The standard deviation for principal reaction
route (1) was 8.1%, and that for routes (2)–(5) and (6)–
(8) was 10–12 and 12–15%, respectively.
In summary, the catalysts prepared via the introduc-
tion of platinum (0.01–0.1 wt %) into gallium-pro-
moted pentasil exhibit a high activity in both the dehy-
droalkylation of cyclohexane and cyclohexene hydro-
carbons and the alkylation of toluene at the ring.
20. Ya. I. Isakov, T. A. Isakova, Kh. M. Minachev, and
B. A. Lipkind, Neftekhimiya 26, 335 (1986).
21. G. I. Golodets, Teor. Eksp. Khim. 18, 37 (1982).
22. Kh. M. Alimardanov, E. T. Suleimanova, A. A. Akhun-
dov, and V. S. Mekhtiev, Neftekhimiya 31, 814 (1991).
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Ser. Kinet. Katal. 13, 3 (1984).
24. P. A. Jacobs, Carbonic Activity of Zeolites (Elsevier,
Amsterdam, 1977), p. 141.
25. P. Vogel, Stud. Org. Chem. 21, 596 (1985).
26. Yu. N. Usov, E. V. Skvortsova, G. G. Nasledskova, et al.,
Neftekhimiya 7, 172 (1967).
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PETROLEUM CHEMISTRY Vol. 46 No. 5 2006