ISSN 1070-4272, Russian Journal of Applied Chemistry, 2006, Vol. 79, No. 9, pp. 1453!1457. + Pleiades Publishing, Inc., 2006.
Original Russian Text + A.A. Lamberov, E.V. Dement’eva, Kh.Kh. Gil’manov, S.R. Egorova, N.V. Romanova, 2006, published in Zhurnal Prikladnoi
Khimii, 2006, Vol. 79, No. 9, pp. 1469!1473.
Effect of the Paste Molding Pressure on the Mechanical
Strength of an Iron Oxide Catalyst in the Dehydrogenation
A. A. Lamberov, E. V. Dement’eva, Kh. Kh. Gil’manov,
S. R. Egorova, and N. V. Romanova
Kazan State University, Kazan, Tatarstan, Russia
Nizhnekamskneftekhim Open Joint-Stock Company, Nizhnekamsk, Tatarstan, Russia
Kazan State Technological University, Kazan, Tatarstan, Russia
Received December 27, 2005; in final form, May 2006
Abstract-The effect of the paste molding pressure on the physicomechanical and texture characteristics
of catalysts was studied. An indirect criterion is suggested to evaluate the molding pressure in industrial
extruders, whose optimal value ensures good physicomechanical properties of the catalysts and kinetic control
over the catalyzed reaction. The results obtained were verified in paste molding on various industrial
extruders, and this enabled the optimal choice of the molding equipment.
The preceding paper was concerned with the effect
of the molding pressure on the activity of catalysts in
the dehydrogenation of methylbutenes. It was shown
that the molding pressure of the catalyst paste can
predetermine the limiting stage of the process. An as-
sumption was made that the dehydrogenation reaction
mostly proceeds within the [working] pores of the
catalyst, which have radii in the range from 15 to
50 nm. This is indicated by the correlation between
the conversion of methylbutenes and the specific sur-
face area S
in this range. An increase in the molding
pressure results in that S
grows in the pore radius
range 5315 nm, which gives rise to steric hindrance
caused by the formation of a large number of pores
of size smaller than the [working] value and shifts
the process from kinetic to diffusion control mode.
Pores with radii exceeding 3.5 mm have no significant
effect on the reaction control mode, but can determine
the physicomechanical properties of the catalyst.
Iron oxide catalysts are used under industrial condi-
tions in reactors with large unit power and charges
exceeding 60 t. Therefore, one of the most important
parameters of a catalyst is its mechanical strength,
which is known to be determined by the chemical
composition and pore structure. The latter, in turn,
depends on the molding pressure of the catalyst paste,
which can hardly be found for domestic industrial
The aims of this study were as follows: to find out
how the molding pressure affects the pore structure
and mechanical strength of iron oxide catalysts; to
reveal an indirect criterion for evaluating the molding
pressure in industrial extruders and substantiate its
optimal values; and to verify the reliability of the
results under industrial process conditions.
Catalyst samples were synthesized by [wet] mix-
ing  of the starting components containing iron
oxide and compounds of potassium, magnesium, cal-
cium, and other metals. Then the suspensions obtained
were dried at 1503200oC, after which the powder
was moistened and molded on a Maekawa Testing
Machine MFG hydraulic press at pressures of 50, 150,
and 275 MPa and on extruders of various types.
The samples having the same chemical composition
were calcined in air under identical conditions.
The cleavage strength was determined with a
PPK-1 semiautomatic device with a knife with a blade
width of 0.1 mm . The cleavage strength coefficient
was calculated as the ratio of the breaking load to
grain diameter or height of a catalyst pellet.
The texture characteristics of the catalysts were
studied by mercury porosimetry (MP) on a Micro-
meritics Auto-Pore 9200 instrument (the United