Russian Journal of Applied Chemistry, 2012, Vol. 85, No. 10, pp. 1524−1530.
Pleiades Publishing, Ltd., 2012.
Original Russian Text © A.S. Savenkov, S.I. Avina, V.A. Loboyko, 2012, published in Zhurnal Prikladnoi Khimii, 2012, Vol. 85, No. 10, pp. 1587−1594.
AND INDUSTRIAL INORGANIC CHEMISTRY
Kinetics of Loss of Platinum Group Metals
in Catalytic Oxidation of Ammonia
A. S. Savenkov, S. I. Avina, and V. A. Loboyko
National Technical University Kharkiv Polytechnic Institute, Kharkiv, Ukraine
Received December 19, 2011
Abstract—Basic characteristics of ammonia oxidation catalysts based on platinum metals, their composition,
wire diameter, and speciﬁ c mass are presented. An irrecoverable loss of the catalyst in manufacture of regular
nitric acid is demonstrated. The loss of catalysts based on platinum-group metals and the effect of various factors
on this loss are considered. The effect of various parameters on the ammonia oxidation process is analyzed and
an equation describing the process in which platinum-group metals are lost is derived.
Regular nitric acid is a large-tonnage product widely
used to manufacture mineral fertilizers. The industrial
production of nitric acid is based on catalytic oxidation
of ammonia by atmospheric oxygen, with subsequent
absorption of nitrogen(IV) oxides by water .
At present, ammonia is oxidized to nitrogen(II)
oxide on catalyst gauzes based on platinum-group
metals (platinum, palladium, rhodium, etc.). Among
speciﬁ c features of a catalyst of this kind are its high
selectivity with respect to nitrogen(II) oxide and stable
activity and mechanical strength during a long time at
high temperatures and elevated pressures. The catalyst
is used as a packet of gauzes, which makes it possible to
manufacture nitric acid in the simplest type of catalytic
apparatus [2, 3].
In CIS countries, nitric acid is produced with a 95%
Pt + 5% Rh alloy whose characteristics are listed in
Table 1. The catalyst package based on platinum-group
metals is constituted by 5 to 14 gauzes, with the gauze
wire diameter being 0.076 to 0.082 mm.
World’s leaders in manufacture of catalysts based
on platinum-group metals are Umicore (Germany),
EZOTsM (Russia), and Johnson Matthey (Great Britain).
The last company holds the patent for production of
woven catalytic gauzes . In the last decade, knitted
gauzes have been used in the world in apparatus for
production of nitric acid .
Earlier, the process of ammonia oxidation was studied
under elevated pressures of 4.5, 11, 16, 21, and 31 atm
on woven catalysts based on platinum-group metals .
Recently, knitted catalytic gauzes have come into use in
the nitric acid technology. However, experimental data
on how widely varied technological parameters (linear
gas ﬂ ow velocity, contact time, O
temperature) affect the degree of ammonia oxidation are
lacking. The advantages of knitted gauzes over those of
the woven type is in the larger surface area per 1 kg of
gauze, lowered expenditure of platinum, longer catalyst
life, and low gas ﬂ ow resistance . Therefore, it became
necessary to carry out studies on this catalyst under the
pressure P = 0.716 MPa, widely used in manufacture of
regular nitric acid in CIS countries.
We determined the degree of ammonia oxidation
to give nitrogen(II) oxide on a knitted catalyst (95%
Pt, 5% Rh) at a constant pressure P = 0.716 MPa and
ammonia concentration of 10.5–10.8 vol % in relation
to temperature, K: 1023–1173–1203; linear gas ﬂ ow
velocity, m s
: 1–3–5–78; number of gauzes: 4–6–8–
10–12–14; and contact duration, τ × 10
The oxidation of ammonia is one of fast and selective
catalytic processes. The degree of ammonia conversion