Russian Journal of Applied Chemistry, 2013, Vol. 86, No. 1, pp. 116−118.
Pleiades Publishing, Ltd., 2013.
Original Russian Text © S.E. Mamedov, I.Sh. Gendzhalieva, N.F. Akhmedova, 2013, published in Zhurnal Prikladnoi Khimii, 2013, Vol. 86, No. 1, pp. 127−129.
Selective Conversion of Methanol to p-Xylene
on Modiﬁ ed High-Silica Zeolites
S. E. Mamedov, I. Sh. Gendzhalieva, and N. F. Akhmedova
Baku State University, Baku, Azerbaijan
Received October 5, 2012
Abstract—A procedure was proposed for preparation of p-xylene from a nonhydrocarbon material, methanol,
in the presence of a modiﬁ ed ultrasil. It was shown that ultrasils modiﬁ ed by multiple-charge cations actively
catalyze synthesis of xylenes from methanol at atmospheric pressure, and their properties can be controlled by
varying the nature, charge, and size, as well as the procedure of introduction of the modiﬁ er cation. Modiﬁ cation of
H-ultrasil with gallium led to enhanced para-selectivity (70%) of the catalysts, which was attributed to an increase
in the ratio of the Lewis to Brønsted acid sites and to a decrease in the effective channel diameters of the zeolite.
High-silica (HS) zeolites have become the subject of
much recent investigation due to their unique catalytic
properties, in particular, suitability for catalyzing the
synthesis of oleﬁ n and aromatic hydrocarbons from a
nonhydrocarbon material, methanol [1, 2]. At the same
time, the possibility of selective synthesis of p-xylene
from methanol in the presence of modiﬁ ed HS-zeolites
still remains to be explored.
Here, we examined how the nature, concentration,
and procedure of introduction of the modiﬁ ers affect the
acidity and selectivity of high-silica zeolites in the reac-
tion of p-xylene formation from methanol.
The experiments were carried out on a ﬂ ow-type setup
with a ﬁ xed catalyst bed (catalyst volume 4 cm
) in a plug-
ﬂ ow reactor at atmospheric pressure in the temperature
range 300–450°C. The space velocity of methanol was
, and the time of the experiments, 0.5 h.
We used a high-silica zeolite of ultrasil type with molar
= 61. The cationic forms of the ultrasil
were obtained by the ion-exchange procedure described
in [3, 4]. The catalysts modiﬁ ed with 1.0–10.0 wt% gal-
lium were prepared by impregnation of H-ultrasil with a
gallium nitrate solution, followed by drying initially in air
and subsequently in an oven at 110°C and calcination in
a mufﬂ e furnace at 550°C for 4 h to achieve the conver-
sion to Ga-H-ultrasil.
The IR spectra were measured on a Spekord spec-
trophotometer, to which end the zeolites were pressed
into thin pellets, 6–8 mg cm
, which were treated in a
vacuum for 2 h at 500°C prior to adsorption . Adsorp-
tion of pyridine was carried out at room temperature and
atmospheric pressure of saturated vapor. The adsorption
examinations followed the technique described in .
As known, the methanol conversion on zeolite-con-
taining catalysts proceeds by the following scheme :
In the temperature range 350–400°C, the degree of
methanol conversion is 100% both for the initial Na-form
of zeolite and the ion-exchanged zeolite samples. The
main products of methanol conversion are oleﬁ n С
(30–40%), aliphatic С
(15–20%), and aromatic С
(25–40%) hydrocarbons. The yield of С