DIMERIZATION OF α-METHYLSTYRENE IN THE PRESENCE OF MORDENITE
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with unmodified mordenite. For example, at a constant
temperature of 80°C, the conversion of α-methylstyrene is
68.7 wt % irrespective of the reaction time. Experiments
performed for 600 h proved that the selectivity with
respect to liquid dimers remained essentially unchanged,
97–98 wt %.
Table 2. Parameters of α-methylstyrene dimerization at
various temperatures
The temperature dependence of α-methylstyrene
dimerization in the presence of modified mordenite is
presented in Table 2.
Table 2 shows that, starting from 80°C, dimerization
of α-methylstyrene becomes intense, and at 90°C the
yield of dimers II and III reaches 80 wt %. However,
starting from 100°C, the selectivity with respect to liquid
dimers starts to decrease, and on reaching 120°C the
weight fraction of crystalline dimer IV and of trimers
dramatically increases. It should be noted that the yields
of α-methylstyrene trimers and tetramers on this catalyst
at temperatures of up to 90°C do not exceed 2 wt %. This
phenomenon confirms the coarsely porous structure of
the treated catalyst (mordenite), because α-methylstyrene
dimerization in the system is kinetically controlled with
no diffusion hindrance.
of the integral intensities of these signals is 10 : 1 : 3 : 6,
suggesting the presence of 20 protons in the molecule of
the linear dimer.
An increase in the yield of liquid dimer IIIwith
an increase in the time of contact of α-methylstyrene
with the catalyst and in the temperature shows that, in
dimerization of α-methylstyrene, α-isomer of linear
dimer II is formed first, and the β-isomer is formed by its
isomerization.
The presence of a conjugated vinylphenyl group in the
molecule of the liquid dimer is well confirmed by the UV
spectrum of this compound, in which we found a band at
λ = 0.251 nm, disappearing upon hydrogenation of dimers
II and III.
The synthesized α-methylstyrene dimers were analyzed
by GLC. As references we used individual dimers
synthesized according to [12].
Thus, the developed heterogeneous catalyst can be
suggested for an environmentally safe, power-saving,
and highly efficient procedure of the synthesis of the
linear dimer, 2,4-diphenyl-4-methyl-1(2)-pentene, from
α-methylstyrene with a small number of process steps.
With the aim to decrease the hygroscopicity of liquid
dielectrics, improve their gas resistance, and reduce
tarring of the base of transformer oils, we examined
α-methylstyrene dimerization products (mixture of
II–IV).
The structure of the unsaturated linear dimers prepared
was studied by IR, UV, and 1H NMR spectroscopy. In the
IR spectrum of 2,4-diphenyl-4-methyl-1(2)-pentene, along
with the bands at 3070, 3020, 765, and 705 cm–1, belonging
to two phenyl groups, we found absorption bands at 3090
and 855 см–1, characteristic of the substituted C=C double
bond. The structure of 2,4-diphenyl-4-methyl-1(2)-pentene
is well consistent with the 1Н NMR spectrum in which we
observed the following signals: a multiplet at 7.09 ppm
belonging to ten protons of two phenyl rings; a singlet at
6.0 ppm, characteristic of the single proton at the multiple
bond (=СН–); a singlet at 1.53 ppm, belonging to three
protons of the methyl group at the C=C double bond (СН3–
СН=СН–); and, finally, a singlet at 1.1 ppm, belonging to
six protons of the remaining two methyl groups. The ratio
The structural-group compositions of a mixture of
α-methylstyrene dimers II–IV and of typical commercial
oilsaregiveninTable3.Thepropertiesandphysicochemical
parameters of commercial transformer oils TK, T-750, and
GK are described in detail in [13].
Table 3 shows that the mixture of α-methylstyrene
dimers is a highly aromatized oil. Therefore, synthetic
hydrocarbon oils based on α-methylstyrene dimers II–IV
are low-viscosity light yellow mobile liquids, resistant to
oxidation and nonhygroscopic. These oils are compatible in
definite ratios with functional and nonfunctional oligomeric
and polymeric substances, solvents, and plasticizers. They
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 82 No. 2 2009