1070-4272/02/7511-1812$27.00C2002 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 75, No. 11, 2002, pp. 1812!1815. Translated from Zhurnal Prikladnoi Khimii, Vol. 75, No. 11,
2002, pp. 1847!1850.
Original Russian Text Copyright + 2002 by Grigor’eva, Bikbaev, Kutepov, Apkarimova, Makhamatkhanov.
Effect of Thermal Treatment on the Acidity and Catalytic
Properties of Pentasil-Containing Catalysts
N. G. Grigor’eva, R. T. Bikbaev, B. I. Kutepov,
G. I. Apkarimova, and R. A. Makhamatkhanov
Institute of Petrochemistry and Catalysis, Academy of Sciences of the Republic of Bashkortostan
and Ural Scientific Center, Russian Academy of Sciences, Ufa, Bashkortostan, Russia
Received May 27, 2002
Abstract-The effect of thermal treatment of zeolite-containing catalysts on their acid and catalytic properties
in aromatization of the long distillate of light hydrocarbons was studied.
One of application fields of Pentasil-containing
catalysts is conversion of saturated hydrocarbons into
aromatic compounds [1, 2]. These processes are
carried out at 3403420 (aromatization of benzine frac-
tions) or 5003600oC (conversion of C
with the catalyst gradually deactivated by coking. To
restore its catalytic properties, the catalyst is subjected
to oxidizing regeneration at temperatures exceeding
550oC. During regeneration, zones with higher tem-
perature may appear, and dehydroxylation, dealumina-
tion, and even disintegration of the crystalline frame-
work of the zeolite are possible . Therefore, one
of the most important characteristics of catalysts is
their thermal stability, which is largely determined
by the SiO
molar ratio in the zeolite.
This study is concerned with the effect of thermal
treatment on the acid and catalytic properties of cata-
lysts synthesized on the basis of Pentasils of varied
composition in aromatization of the long distillate of
light hydrocarbons (LDLH).
The starting zeolites of mixed structure, ZSM-5/11,
molar ratios of 30 and 60 were syn-
thesized in the sodium form by crystallization of alka-
line aluminosilicate hydrogels under hydrothermal
conditions (pressure 5 atm, temperature 1303150oC,
duration 94396 h) using monoethanolamine as an
organic template. The samples obtained were dried
at 150oC for 3 h and calcined in air at 540oC for 16 h.
The hydrogen form of Pentasils was obtained by treat-
ing the samples with NH
at 60oC to residual
O content of 0.1 wt % and less, with subsequent
conversion of the NH
form into the H form (thermal
treatment in air flow at 540oC for 4 h). Catalyst sam-
ples were prepared by mixing 70 wt % Pentasils ob-
tained with 30 wt % pseudoboehmite in a mixer and
paste forming into sticks. It has been shown previous-
ly  that the presence of up to 40 wt % Al
catalysts of this kind has no noticeable effect on the
activity and selectivity of a catalyst in aromatization
To study the thermal stability, the catalyst samples
were calcined in air at 600, 650, and 700oC for 63
24 h. The catalyst containing Pentasil with the molar
= 30 is denoted by TsSK, and that
= 60, by TsSK(M).
Transformations of LDLH were studied on a flow-
through installation under atmospheric pressure in
the temperature range 3203550oC and feed space
velocity w of 0.5 h
. The working cycle comprised
a 8-h experiment and 3-h catalyst regeneration with
air at 5503580oC. The reaction products formed were
analyzed by gas3liquid chromatography.
The LDLH characteristics are as follows: density
at 20oC 0.675 g cm
, initial boiling point 27oC, final
boiling point 185oC; content (wt %): n-paraffins 36.9,
isoparaffins 43.8, naphthenes 16.8, and arenes 2.5.
The acid properties of the catalysts were studied
by temperature-programmed desorption of ammonia
on a Quarta Chrom instrument. The samples were
heated in a helium flow to 600oC, kept at this tem-
perature for 2 h, and then cooled to room temperature
and saturated with ammonia. Thermal desorption of
was done at 1003575oC after removal of physi-
cally adsorbed ammonia.
The IR spectra were recorded on a UR-20 instru-
ment. Samples for measurement of IR spectra of the