1070-4272/01/7403-0378$25.00C2001 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 74, No. 3, 2001, pp. 378!380. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 3,
2001, pp. 371!374.
Original Russian Text Copyright + 2001 by Vigranenko, Gavrilova, Gvozdovskii.
AND INDUSTRIAL INORGANIC CHEMISTRY
Kinetics of Formation of Cobalt Carbonyls from Aqueous
Solution of Cobalt Acetate in the Presence of Cyclohexanone
in the Liquid!Liquid!Gas Heterogeneous System
Yu. T. Vigranenko, V. M. Gavrilova, and G. N. Gvozdovskii
VNIINeftekhim Joint-Stock Company, St. Petersburg, Russia
Received September 7, 2000; in final form, December 2000
Abstract-Cobalt carbonyls was prepared from an aqueous solution of cobalt acetate containing or not con-
taining pyridine in the presence of the organic solvent immiscible with water. The product in the form of an
organic solution can be used as hydroformylation catalyst. The kinetic equation taking into account the
distribution of the reagents between the three phases was derived. The apparent rate constants and activation
energies were calculated.
Industrial preparation of aldehydes form olefins
and a CO + H
gas mixture is performed by hydrofor-
One of the steps of this process is preparation of
the catalyst. The most suitable procedure for preparing
cobalt carbonyls from solutions of cobalt salts is
based on the reaction
+ 16CO + 5H
+ 8RCOOH. (2)
We used cobalt acetate as the precursor since it is
available and the resulting catalyst can be readily sepa-
rated from the reaction products. Cyclohexanone was
the solvent. Data on the kinetics of formation of cobalt
carbonyls from an aqueous solution of Co(OAc)
the presence of organic solvent in the liquid3liquid3
gas system are lacking. It is only reported  that
cobalt carbonyl is formed in a Co(OAc)
mixture. This reaction is heterogeneous and is con-
trolled by diffusion. In this work we studied the kinet-
ics of cobalt carbonyl formation in the above system.
Synthesis of cobalt carbonyls was studied in a 0.5-l
ideal mixing batch reactor of the Vishnevskii screw
type . The unit consists also of high-pressure surge
tanks for hydrogen, carbon oxide, and their mixture
and a 0.25-l high-pressure charger for introducing
the components of the reaction mixture into the reac-
tor. The reactor purged with carbon monoxide was
charged with cyclohexanone. A CO + H
fed at a pressure of 9.0 MPa, and stirring and heating
were switched on. An aqueous solution of Co(OAc)
was poured into the charger. When pyridine was used
it was introduced in the reactor with the organic solv-
ent. The mixture was heated to the required tempera-
ture with stirring, and the Co(OAc)
solution was fed
by the synthesis gas into the reactor. In the course of
the synthesis the samples of the liquid were taken, and
the aqueous and organic phases were separated. The
cobalt(II) content was determined spectrophotometri-
cally ; and the content of cobalt carbonyls, by
iodometric titration .
Since cobalt acetate is practically nonvolatile, reac-
tion (2), apparently, does not occur in the gas phase.
The general kinetic equation of the reaction in the
system of two immiscible liquid is as follows:
W = 3aÄÄÄÄÄÄÄÄÄÄÄ 3 (1 3a)ÄÄÄÄÄÄÄÄÄÄÄ, (3)
where a and (1 3a) are the volume fraction of the first
(aqueous) and second (organic) phases, respectively.
is insoluble in cyclohexanone,
= 0. Hence Eq. (3) can be written as
W = 3aÄÄÄÄÄÄÄÄÄÄÄ.
In accordance with the law of mass action
W = ak[Co(OAc)
, and n
are the reaction orders with re-
spect to Co(OAc)
, and CO, respectively.