1070-4272/02/7503-0402$27.00C2002 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 75, No. 3, 2002, pp. 402! 407. Translated from Zhurnal Prikladnoi Khimii, Vol. 75, No. 3,
2002, pp. 413!418.
Original Russian Text Copyright + 2002 by Zakharchenko.
AND ION-EXCHANGE PROCESSES
Recovery of Platinum with Calcium Oxide Sorbent
in Ammonia Oxidation
N. I. Zakharchenko
Zhukovsky Aerospace University, Kharkov, Ukraine
Received June 26, 2001
Abstract-The reaction of granulated CaO sorbent with platinum lost in high-temperature oxidation of
ammonia was studied. Physicochemical properties of the product and conditions and mechanism of its forma-
tion are considered.
Catalytic oxidation of ammonia to nitrogen(II)
oxide is the key stage in industrial synthesis of nitric
acid . Commercial catalysts (Pt, Rh, and Pd alloys)
undergo physicochemical transformations in the proc-
ess, with their surface structure and chemical com-
position changed . A set of transformations of
this kind results in loss of deficient and expensive
platinum-group metals. An effective way to reduce
the loss of platinum metals is their partial recovery
by sorbents mainly based on calcium oxide [1, 7315].
The mechanism of platinum recovery by calcium-
containing sorbents and the chemical aspect of the
process are debated in the scientific literature. Atro-
shchenko et al.  came to a conclusion that platinum
is bound on the surface of the oxide sorbent to form
an xCaO.yPt compound. In other studies [10, 11],
platinum was found in the sorbent bulk as 4CaO. PtO
compounds. In [12, 16], platinum com-
pounds in the sorbent bulk were identified as Ca
This study is concerned with recovery by calcium
oxide of platinum lost in high-temperature oxidation
of ammonia and with identification of products
formed in the reaction of the lost platinum with cal-
The calcium oxide sorbent was prepared as fol-
lows. As starting compound served calcium oxide of
chemically pure grade, which was treated with 80%
ethanol (233% relative to sorbent weight) and com-
pacted into pellets under a pressure of 150 MPa. Step-
like thermal treatment of the sorbent was done in a
muffle furnace in air at 473, 673, 873, and 1073 K
(for 2 h in each stage). The sorbent was crushed into
grains, and fraction with a grain size of (233)0
m was selected.
Since the lost platinum is mainly caught by the sur-
face layer of sorbents [1, 7314, 17], sorbent grains
were ground and subjected to additional forming and
thermal treatment in inert medium (argon) following
the above scheme in order to intensify the process and
raise the yield of the chemical compounds obtained.
The processes of platinum recovery were studied
on a flow-through installation with a quartz reactor
5 0 10
m in diameter. As catalyst was used platinum
in the form of a package of five meshes with a wire
diameter of 7.5 0 10
m (industrial platinoid alloy
nos. 1 and 5 were not used, because Rh and Pd con-
tained in these alloys in addition to Pt would com-
plicate the interpretation of the experimental results).
A bed of sorbent grains, of height 1.7 0 10
placed directly after the catalyst meshes at a distance
of 8.0 0 10
m from them.
The temperature of catalytic oxidation of ammonia
was maintained at 1073 K, and the pressure in the
system, at 0.101 MPa. The content of ammonia in the
air3ammonia mixture (AAM) was about 11.5 vol %.
The linear flow velocity of AAM was 0.40 m s
X-ray phase analysis of the compounds obtained
was carried out on a Siemens D-500 diffractometer
radiation and graphite monochromator
used to analyze the diffracted beam. The phases ob-
served in the diffraction patterns were identified using
the JCPDS file contained in the mathematical soft-
ware package of the diffractometer; some X-ray dif-
fraction pattern were compared with the data of the
ASTM file .
IR absorption spectra were measured on a Perkin3
Elmer 577 spectrometer in the range 20032000 cm
with CsI pellets used as matrices.
Differential thermal analysis was made on an