1070-4272/05/7806-0912 + 2005 Pleiades Publishing, Inc.
Russian Journal of Applied Chemistry, Vol. 78, No. 6, 2005, pp. 912!916. Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 6, 2005,
Original Russian Text Copyright + 2005 by Dobrovinskaya, Dobkina, Kuznetsova.
Study of the Stability of Catalysts for Decomposition
of Spent Sulfuric Acid
N. A. Dobrovinskaya, E. I. Dobkina, and S. M. Kuznetsova
St. Petersburg State Technological Institute, St. Petersburg, Russia
Received November 15, 2004
Abstract-The influence of various factors on the stability of operation of heterogeneous catalysts for de-
composition of spent sulfuric acid is analyzed.
The stability of operation of a catalyst  in de-
composition of spent sulfuric acid (SSA) containing
organic admixtures is strongly affected by several
factors, including the mechanical action associated
with the mode of the boiling bed and a long exposure
to a high temperature. The first factor can promote
destruction of the support and removal of active com-
ponents. The second can diminish the catalytic activ-
ity through a transformation of the porous structure
that leads to a decrease in the specific surface area.
This study is devoted to examination and analysis of
the effect of these factors on the catalyst.
We used as real sulfuric acid waste to be subjected
to decomposition the SSA formed in alkylation and in
manufacture of methyl ethyl ketone. These two kinds
of waste are representatives of concentrated and diluted
SSA containing small amounts of organic admixtures
(Table 1). The admixtures have a complex chemical
composition including components of initial raw
materials and products of target and side reactions. In
view of the difficulties in determining such a com-
position, we estimated the amount of organic admix-
tures in SSA by a conventional method , by their
sum in terms of carbon.
The abrasion resistance was estimated directly
under conditions of SSA decomposition on an instal-
lation with a boiling-bed reactor (Fig. 1). The catalyst
bed was poured on a porous quartz partition situated
in the middle of a heated reactor 1 and brought into
a fluidized state with air whose flow rate was meas-
ured with a rheometer 2. Spent sulfuric acid was de-
livered by a mechanical batcher 3 into the catalyst
bed through a side capillary built into a condenser 4
to prevent the catalyst coking. The loss of substance
from the bed was judged from the increase in the mass
of a trap 5 filled with fiberglass. To prevent condensa-
tion of sulfuric acid, the trap was placed in a furnace 6
which maintained its temperature at 300oC. To make
a control measurement of the substance removal,
the entire bed was additionally weighed every 10 h
during the test.
The catalyst activity was estimated by the degree of
SSA decomposition, b. It was studied on the same
installation as the mechanical strength after dismantl-
ing the trap 5 and furnace 6. A cooled gas mixture
from the reactor 1 was analyzed by chromatography
after removing SO
and water vapor.
The degree of SSA decomposition is the ratio be-
tween the amount of sulfur dioxide contained in
the gas phase after the reactor and the total amount of
sulfur dioxide in the SSA fed into the reactor.
The completeness of burning-out of organic ad-
mixtures was determined from the content of carbon
oxide in gaseous decomposition products.
The wear resistance of the samples was studied in
situ in the natural mode of the thermocatalytic decom-
position of SSA. The samples were tested for 100 h
Table 1. Composition of industrial SSA
³ in terms of carbon
Alkylation ³ 85.0 ³ 3.0
Manufacture of ³ 73.0 ³ 1.5
methyl ethyl ketone ³³