1070-4272/03/7605-0719$25.00C2003 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 76, No. 5, 2003, pp. 719!722. Translated from Zhurnal Prikladnoi Khimii, Vol. 76, No. 5,
2003, pp. 747!750.
Original Russian Text Copyright + 2003 by Asnin, Fedorov.
AND ION-EXCHANGE PROCESSES
Adsorption of Chlorobenzene on C-Al
by Calcination of Boehmite at Various Temperatures
L. D. Asnin and A. A. Fedorov
Institute of Technical Chemistry, Ural Division, Russian Academy of Sciences, Perm, Russia
Received July 22, 2002
Abstract-The influence exerted by the temperature of boehmite calcination in air within the range
4503 600oC on the adsorption properties of the resulting g-Al
with respect to chlorobenzene was studied.
is frequently used as support for catalysts
for deep oxidation of chlorobenzene . The con-
centration of surface OH groups, which largely deter-
mines the sorption properties of a support, may vary
widely with synthesis and working temperatures of
these catalysts (these temperatures are limited to the
existence range of the g phase, up to 900oC [5, 6]).
The influence exerted by the concentration of surface
OH groups on the sorption characteristics of oxide
supports has been studied extensively . For
example, it is known that step-by-step removal of
chemisorbed water from the Al
surface leads to
an increase in its hydrophilicity . By contrast, it
has been established for the example of ZnO that the
heat of adsorption of benzene, toluene, and chloro-
benzene decreases with decreasing number of surface
OH groups . A similar pattern has been observed
for silica gel . Presumably, such a behavior will
be observed for aromatic compounds on oxides of
other elements (Al, Ti). Kiselev and Lygin  attri-
buted this to a decrease in the number of surface OH
groups interacting with the aromatic ring. Nagao et al.
[10, 12] pointed to a decreasing probability of two-
center adsorption of chlorobenzene on the dehydroxy-
lated surface of oxides.
Less unambiguous is the influence exerted on the
sorption capacity of oxide supports by dehydration.
This is so because the calcination conditions affect not
only the content of structural water, but also the
support texture. However, a general pattern can be
revealed in this case also. For example, it was shown
in [9, 10] that the fraction of aromatic compounds
irreversibly sorbed on TiO
and ZnO is the lowest for
hydrated oxides and increases for dehydrated oxides.
A detailed study of the influence exerted by condi-
tions of thermal treatment of aluminum hydroxides on
the texture characteristics of the oxides obtained was
reported in .
Thus, some aspects of the influence of calcination
on the adsorption properties of alu-
minum oxide can be predicted qualitatively. It is of
interest to evaluate the extent of this influence on
the chlorobenzene adsorption. The present study is
concerned with chlorobenzene adsorption on g-Al
samples obtained by calcination of boehmite at 450
(OA1) and 600oC (OA2) in air for 5 h.
The boehmite used to obtain aluminum oxide was
synthesized by a procedure described in . The
phase composition of the samples was determined by
X-ray phase analysis on a DRON-2 diffractometer.
Adsorption isotherms were measured chromatographi-
cally  in the temperature range 1903300oC; the
apparatus used and experimental conditions were
described in . The same equipment was used to
determine by the method of frontal chromatography
the sorption capacity of the samples for chlorobenzene
at 50 and 100oC. The working gas-and-vapor mixture
was prepared by saturating the carrier gas (nitrogen,
flow rate 25 cm
) with chlorobenzene vapor in a
glass saturator with constant evaporation area at room
temperature (vapor concentration 43346 mgcm
The dead time was determined for methane. The
specific surface area S
of the samples was found by
the method of thermal desorption of nitrogen, and the
content of structural water, by calcination at 1000oC
of samples preliminarily dried at 300oC. The pore
was found from the weight gain of samples
after their saturation with benzene vapor in a desic-
cator at room temperature. The characteristics of the
samples are listed in Table 1.