INORGANIC SYNTHESIS AND INDUSTRIAL
Russian Journal of Applied Chemistry, 2011, Vol. 84, No. 2, pp. 173−178.
Pleiades Publishing, Ltd., 2011.
Original Russian Text © A.G. Okunev, A.I. Lysikov, 2011, published in Zhurnal Prikladnoi Khimii, 2011, Vol. 84, No. 2, pp. 177−182.
Effect Exerted by Texture of Calcined Calcium Oxide
on Its Sorption Capacity
in the CO
A. G. Okunev and A. I. Lysikov
Boreskov Institute of Catalysis, Russian Academy of Sciences, Siberian Branch, Novosibirsk, Russia
Received November 24, 2010
Abstract—The dynamic capacity of a set of sorbents prepared by calcination of different precursors was studied
in multiple СО
sorption-regeneration cycles. The effect exerted by type of a precursor and calcination temperature
on the steady state value of the dynamic capacity attained after several tens of cycles was determined. A model
was suggested for estimate of the sorption capacity of CaO sintered above the Tammann temperature from data
on the mercury porosimetry.
Global warming has stimulated the search for new
cost-effective technologies for CO
separation and con-
centration. One promising approach may be the use of
regenerated high-temperature CaO sorbents for carbon
dioxide by the reaction
CaO + CO
which is efﬁ cient up to 750–800°C.
According to probable scheme of the process, the sor-
bent circulates between the fuel reactor of deep oxidation
and the regenerator, where СО
is evolved in a reverse
reaction (1) at elevated temperature in a ﬂ ow of water
vapor [1–3]. For ssuccessful implementation of the pro-
cess, the key factor is high and stable capacity of CaO
for carbon dioxide over a large number of cycles. It was
shown previously that the dynamic capacity of sorbents,
obtained by calcining fossil limestones, is about 7 wt%
in multicycle tests [4, 5]. More impressive results have
demonstrated some synthetic materials [3, 6–9], but the
high cost prevents their use in large-tonnage processes .
The mechanism for sintering sorbent in the СО
absorption-regeneration cycles has been suggested in
, consisting in multiple decomposition of calcium
carbonate and its further reaction with СО
to form me-
chanically stable СаО skeleton, with sorption capacity
determined by its reactive outer surface and further sin-
tering impeded. Based on this approach, a cheap thermal
method, calcination of calcium salts above a Tammann
temperature of CaO (1154°C), has been developed for
preparing stable CO
sorbents with high dynamic capac-
ity. The high-temperature treatment accelerates sintering
of primary particles and assists the formation of stable
In the study, the correlation between the texture and ca-
pacity of the calcined sorbents under the conditions of high-
temperature processes of СО
.removal was determined.
We used in the study several types of СаО precursors
of different chemical nature: specially pure (98.5%) cal-
cium carbonate powder, analytically pure (99%) calcium
nitrate, analytically pure (99%) calcium hydroxide, and
optically transparent monocrystalline calcium carbonate.
Cleaved piece of a single crystal was crushed and sieved
to obtain 80–100-μm fraction. The remaining reagents
were used without preliminary treatment.