Hydrogen sulfide oxidation by ozone on sorbents-catalysts

Article abstract of DOI:10.1134/S1070427210090089

Effect of the sorbents SK-2001, SK-2002, SK-1138, SK-498, SK-8, SK-174, SK-57, SK-458, SK-455, SK-19, and SK-72 based on a KhIPEK synthetic ceramics on the oxidation of hydrogen sulfide by ozone was studied. The sorbents that catalyze the reaction of hydrogen sulfide oxidation by ozone were determined.

Full text of DOI:10.1134/S1070427210090089

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2010, Vol. 83, No. 9, pp. 1548–1552. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © Yu.A. Aleksandrov, A.V. Belyaev, A.Yu. Sozin, M.F. Churbanov, 2010, published in Zhurnal Prikladnoi Khimii, 2010, Vol. 83,
No. 9, pp. 1448–1452.
PHYSICOCHEMICAL STUDIES
OF SYSTEMS AND PROCESSES
Hydrogen Sulfide Oxidation by Ozone on Sorbents-Catalysts
Yu. A. Aleksandrova, A. V. Belyaeva, A. Yu. Sozinb, and M. F. Churbanovb
a Lobachevsky State University, Nizhni Novgorod, Russia
b Institute of Chemistry of High-Purity Substances, Russian Academy of Sciences, Nizhni Novgorod, Russia
Received February 15, 2010
Abstract—Effect of the sorbents SK-2001, SK-2002, SK-1138, SK-498, SK-8, SK-174, SK-57, SK-458, SK-
455, SK-19, and SK-72 based on a KhIPEK synthetic ceramics on the oxidation of hydrogen sulfide by ozone
was studied. The sorbents that catalyze the reaction of hydrogen sulfide oxidation by ozone were determined.
DOI: 10.1134/S1070427210090089
Hydrogen sulfide is used or formed in a number of
chemical industries and is one of the main products in
such processes as biomass rotting and volcanic
eruptions. Hydrogen sulfide is highly toxic. Therefore,
purification of air to remove hydrogen sulfide is a
topical task in a number of cases. A promising method
for air purification to remove hydrogen sulfide is its
oxidation with ozone.
It should be emphasized that the rate constant is
small at room temperature. Therefore, it seems promis-
ing to oxidize hydrogen sulfide with ozone in the
presence of sorbents that raise the reactant concentra-
tions on their surface and thereby make higher the
process rate.
The aim of the study was to examine whether the
sorbents can be used to accelerate the reaction of
hydrogen sulfide oxidation by ozone.
It is known [1] that ozone is widely used for
sanitary purification and deodorization of air.
However, this process is insufficiently effective in the
homogeneous mode of air purification to remove
ecologically hazardous chemical compounds with low
or extremely low maximum permissible concentrations
(MPCs) in air and, in particular, hydrogen sulfide.
EXPERIMENTAL
Experiments were carried out with sorbents based
on a KhIPEK synthetic ceramics (SC) [5, 6]. The
KhIPEK sorbents are based on natural clays. Ceramic
materials of acid and alkaline nature were used. The
acid nature of a ceramic was provided by introduction
of H3PO4 into the raw material. The composition of the
stock for the acid ceramic was varied by changing the
proportion of the introduced amount of natural clays
with addition of an anticorrosive cement and wood
flour. In calcination of the sorbents, the wood flour
burns out and makes the sorbents porous. The alkaline
nature of a ceramic was provided by introducing
powdered aluminum, oxides of alkaline-earth metals
into the stock and using a high-modulus liquid glass as
a stock binder. In this study, some separate
components of the stock were also used to study the
behavior of ozone and oxidation of hydrogen sulfide.
It is known that, in the gas phase, one molecule of
ozone reacts with one molecule of hydrogen sulfide to
give sulfur dioxide and water [2]. However, the
relevant kinetic data are contradictory. Studies of this
reaction in flow conditions demonstrated that its order
with respect to ozone is 1.5 and that with respect to
hydrogen sulfide is “zero” [3] or 0.5 [4]. It was found
in [3] that the rate constant k [M–1/2 s–1] of the reaction
between ozone and hydrogen sulfide is described by
the equation
log k = 6.9 – 8300/2.3RT,
(1)
where k(25°C) = 8.5 ± 2 M–1/2 s–1, R is the universal
gas constant (1.987 cal mol–1 K–1), and T is the
absolute temperature (K).
The following sorbents were used: SK-2001, SK-
2002, SK-1138, SK-498, SK-8, SK-174, SK-57, SK-
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HYDROGEN SULFIDE OXIDATION BY OZONE ON SORBENTS-CATALYSTS
Table 1. Characteristics of the sorbents used
458, SK-455, SK-19, and SK-72. The characteristics of
these sorbents are listed in Table 1.
Sorbent
Ssp, m2 g–1
Nature of a sorbent
The behavior of ozone in the presence of an SC was
examined as follows: the ozone concentration in the
gas phase was measured at the outlet of a flow-through
reactor when passing an ozone–oxygen mixture
(OOM) with and without a sorbent. A flow-through
tubular Pyrex-glass reactor with a length of 50 mm and
diameter of 9.5 mm was charged with a fraction of
sorbent grains with a diameter of 1.0–1.5 mm. The
ozone concentration in the OOM was determined
spectrophotometrically on an SF-46 spectrophotometer
in a gas-flow cuvette 50 mm long and 12 mm in
diameter. The measurements were made at a wave-
length of 254 nm. The molar extinction coefficient of
ozone was taken to be 3033 M–1 cm–1 [7]. The spec-
trophotometric cuvette was made of a fluoroplastic and
had quartz windows. The OOM was delivered into the
reactor at a rate of 100 ml min–1, the experiments were
carried out at a temperature of 20 ± 0.5°C. The ozone
concentration in the gas phase at the reactor inlet was
(3.3 ± 0.1)×10–5 M. The installation for analysis of the
ozone decomposition is shown schematically in Fig. 1.
The ozone concentration in the gas phase at the reactor
inlet was measured when the OOM passed through
reactor 1 at closed valves 2 and 3 and open valve 4.
The ozone concentration in the gas phase at the reactor
outlet was measured when the OOM was passed
through the reactor at open valves 2 and 3 and closed
valve 4. First, the ozone concentration at the reactor
SK-174
SK-458
SK-72
1.30
0.20
0.60
4.50
1.60
1.86
0.60
16.00
11.80
11.50
1.10
Acid
The same
''
Alkaline
Acid
SK-19
SK-8
SK-455
SK-2001
SK-2002
SK-498
SK-1138
SK-57
The same
''
''
''
Alkaline
The same
inlet was measured. Then valve 4 was closed, valves 2
and 3 were open, and the ozone concentration in the
gas phase was measured at the reactor outlet as a
function of the time of OOM blowing-through. The
time of the OOM contact with the sorbent was
calculated as the ratio between the sorbent-free volume
of the reactor and the OOM delivery rate. This ratio
was 1.0 ± 0.1 s in all the experiments.
Hydrogen sulfide was oxidized with ozone in the
same reactor as that used for analysis of the ozone
decomposition. The kinetics of hydrogen sulfide
oxidation by zone was studied with pulsed introduction
Fig. 1. Schematic of the installation for studying the kinetics of ozone decomposition on SCs. (1) Reactor, (2–4) fluoroplastic
valves, (5) cylinder with oxygen, (6) drying columns with molecular sieves and phosphorus pentoxide, (7) gas flow controlling unit,
(8) ozonizer, and (9) spectrophotometric cuvette.
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ALEKSANDROV et al.
1
15
12
6
16
5
14
10
17
7
3
2
13
8
11
4
9
Fig. 2. Schematic of the installation for studying the oxidation of hydrogen sulfide. (1) Ozonizer, (2) reactor, (3) cylinder with dried
air, (4) spectrophotometric cuvette, (5–8, 12) fluoroplastic valves, (9) feed chamber, (10) standard vacuum gage, (11) cylinder with
a mixture of H2S (0.25 vol %) with air, (13) cylinder with oxygen, (14) drying columns with molecular sieves and phosphorus
pentoxide, (15, 16) gas flow controlling units, and (17) roughing pump.
of the reagent into the reactor. The installation used for
this purpose is shown schematically in Fig. 2. The
experiment was carried out as follows: an ozonized
flow of oxygen at the outlet of ozonizer 1 was
permanently mixed, before being fed into the reactor,
with a flow of air from cylinder 3, which carries
hydrogen sulfide. After passing through the sorbent
bed in reactor 2, the mixture was delivered to
spectrophotometric cuvette 4, in which the ozone
concentration was measured.
wavelength of 254 nm: 1.8 [8], 40 [9], and 4.2 M–1 cm–1
[10], respectively. Because of the extinction coef-
ficients are small, the additive contribution of
hydrogen sulfide and products of its oxidation to the
optical density of ozone can be neglected. The ozone
concentration in a pulse at the outlet of the reactor with
a sorbent was used to calculate the loss X (%) of ozone
by the formula
D0 −D
× 100,
(2)
X =
D0
A prescribed amount of hydrogen sulfide was
introduced into the air line as follows: air was
evacuated at closed valves 5 and 6 and open valves 7
and 8 from feed chamber 9, with the process monitored
with a standard vacuum gage 10. Further, a mixture of
hydrogen sulfide and air from cylinder 11 was let in
until the atmospheric pressure was attained. After that
valves 7 and 8 were closed. Hydrogen sulfide was
delivered into the reactor by opening valves 5 and 6
and closing valve 12. Air from the bypass channel
transferred hydrogen sulfide from feed chamber 9 to
the reactor inlet, where it was mixed with the OOM.
where D0 and D are the optical densities of ozone in a
“pulse” at the inlet and outlet of the tube with a
sorbent.
Experiments aimed to study the behavior of ozone
on SCs yielded typical kinetic curves describing the
dependence of the optical density D of the OOM at the
outlet of the reactor packed with a sorbent on the time
τ of OOM blowing-through (Fig. 3).
The region delimited by curves 3 and 4 and line 1
corresponds to displacement of air by the ozone–
oxygen mixture from a reactor with quartz crumb
(material hardly causing any decomposition of ozone
under the experimental conditions). The sharp decline
and rise in the optical density of ozone in displacement
of air from the reactor packed with quartz make it
possible to use curves 3 and 4, with the “boundary”
diffusion and mixing neglected, in interpretation of
kinetic curves obtained with sorbents.
The concentrations of hydrogen sulfide and ozone
in the reaction mixture before the reactor were
(5.5 ± 0.1)×10–5 M. The delivery rates of the OOM and
air carrying a “pulse” of hydrogen sulfide were
50 ml min–1. The total rate of reactant delivery into the
reactor was 100 ml min–1. The temperature during the
experiment was 20 ± 0.5°C. The time of contact
between hydrogen sulfide and a sorbent was 1.0 ± 0.1 s
in all the experiments. Hydrogen sulfide and its
oxidation products, sulfur dioxide and trioxide, have
the following molar extinction coefficients at a
The region delimited by curves 2 and 3 and line 1
reflects the fact that, in addition to the displacement of
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HYDROGEN SULFIDE OXIDATION BY OZONE ON SORBENTS-CATALYSTS
6
1
2
3
4
5
6
7
8
D
4
1
2
2
9
3
4
20
60
100
τ, s
Fig. 4. Variation of the concentration c of ozone in the case
when a hydrogen sulfide pulse passed through the reactor
with (1) SK-2001, (2) SK-72, (3) SK-458, (4) SK-57,
(5) quartz, (6) SK-498, (7) SK-174, and (8) SK-19.
(τ) Time during which the mixture is passed through the
reactor. (9) Ozone concentration at the inlet of the reactor.
τ, s
Fig. 3. Typical dependences of the optical density D of the
OOM at (1) inlet and (2–4) outlet of the reactor with a
sorbent on the time τ of OOM blowing-through.
air from the reactor, there occurs consumption of
ozone as a result of its interaction with the sorbent.
Figure 4 shows curves of how ozone is consumed
when hydrogen sulfide is passed through an SC bed.
The curves of ozone consumption on the sorbents
SK-72, SK-2001, and SK-458 are identical to the curve
of ozone consumption on quartz. This suggests that
these materials have no significant influence on the
consumption of ozone.
The calculated loss of ozone in a “pulse” at the
outlet of the reactor with a sorbent is presented in
Table 2. The loss of ozone from the mixture,
calculated for a reaction mixture passed through a
quartz crumb bed (X = 6%), was used to evaluate the
efficiency of the sorbents in acceleration of the
reaction of hydrogen sulfide by ozone. With the
sorbents SK-2001, SK-498, SK-57, and SK-19, no
ozone is observed at the instant when the OOM–H2S
mixture leaves the reactor. The acceleration of the
oxidation of hydrogen sulfide by ozone in the presence
The consumption of ozone on the sorbents SK-498,
SK-8, SK-174, SK-57, SK-455, and SK-19 is des-
cribed by a kinetic curve similar to curve 2 in Fig. 3,
which suggests that ozone interacts with these sorbents.
With the sorbents SK-2002 and SK-1138, no ozone
was detected by the instrument during 5 min. This is
indicative of a catalytic effect of the sorbent in ozone
decomposition or a large surface area of the sorbent
(Table 1) and, accordingly, a large number of reaction
centers on the sorbent surface, which have not enough
time to be noticeably consumed in the reaction with
ozone in 5 min. The data on decomposition of ozone
on SK-2002 and SK-1138 suggest that these sorbents
can be regarded as promising materials for
decomposition of ozone.
Table 2. Loss of ozone from a hydrogen sulfide pulse in its
passing from a sorbent bed
Sorbent mass Sorbent area
Loss of
Sorbent
m in the
S in the
ozone, X, %
reactor, g
reactor, m2
Quartz crumb
SK-2001
SK-498
SK-174
SK-57
–
–
6±2
99±1
99±1
28±5
99±1
26±5
99±1
4±2
3.77
2.60
2.08
0.95
2.37
1.02
2.75
2.26
30.68
2.70
1.05
0.47
4.59
1.65
The heterogeneous oxidation of hydrogen sulfide
by ozone was studied using SK-72, SK-2001, and SK-
458 (comparatively inert toward ozone) and SK-57,
SK-498, SK-174, and SK-19, “passivated” with ozone
until its consumption in blowing-through the OOM
through the rector with a sorbent ceased. When an
ozone pulse mixed with the OOM is passed through
the reactor under the experimental conditions, ozone is
only consumed for the reaction with hydrogen sulfide.
SK-458
SK-19
SK-72
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ALEKSANDROV et al.
of SK-57 and SK-19 can be attributed to the alkaline
nature of the sorbent, owing to which hydrogen sulfide
is actively bound as an acid with the sorbent surface.
In the presence of SK-498, the oxidation of hydrogen
sulfide is possibly provided by its larger surface area,
compared with the rest of the sorbents.
REFERENCES
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vol. 14, no. 3, pp. 462–468.
The results obtained indicate that SK-2001, SK-57,
SK-19, and SK-498 are promising sorbents for
accelerating the reaction of hydrogen sulfide oxidation
by ozone.
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CONCLUSIONS
7. Molina, L.T. and Molina, M.J., J. Geophys.Res., 1986,
(1) A procedure for evaluating the activity of
sorbents as catalysts for oxidation of hydrogen sulfide
by ozone and catalysts for ozone decomposition was
developed.
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(2) It was found that the sorbents SK-2001, SK-57,
SK-19, and SK-498 catalyze the oxidation of hydrogen
sulfide by ozone, and the sorbents SK-2002 and SK-
1138 catalyze the decomposition of ozone.
10. Robinson, T.W., Schofield, D.P., and Kjaergaard, H.G.,
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