Complexes of Copper(I) with Dimercapto Compounds as Catalysts for Oxidation of Mercaptans and Hydrogen Sulfide with Molecular Oxygen in Aqueous Solutions

Article abstract of DOI:10.1023/A:1023300101895

The conditions for formation of complexes of copper(I) with mercapto compounds in aqueousalkaline solutions and the catalytic activity of these complexes in oxidation of mercaptans and hydrogen sulfide was studied. The kinetic characteristics of these catalysts were compared with those of catalysts based on cobalt phthalocyanines. A method was proposed for suppressing formation of the thiosulfate ion in oxidation of H₂S to elemental sulfur.

Full text of DOI:10.1023/A:1023300101895

Russian Journal of Applied Chemistry, Vol. 76, No. 1, 2003, pp. 88 94. Translated from Zhurnal Prikladnoi Khimii, Vol. 76, No. 1,
003, pp. 90 96.
Original Russian Text Copyright
2
2003 by Bagiyan, Koroleva, Soroka, Ufimtsev.
CATALYSIS
Complexes of Copper(I) with Dimercapto Compounds
as Catalysts for Oxidation of Mercaptans and Hydrogen Sulfide
with Molecular Oxygen in Aqueous Solutions
G. A. Bagiyan, I. K. Koroleva, N. V. Soroka, and A. V. Ufimtsev
Konstantinov Institute of Nuclear Physics, Russian Academy of Sciences, Gatchina, Leningrad oblast, Russia
Received September 2, 2002
Abstract The conditions for formation of complexes of copper(I) with mercapto compounds in aqueous-
alkaline solutions and the catalytic activity of these complexes in oxidation of mercaptans and hydrogen
sulfide was studied. The kinetic characteristics of these catalysts were compared with those of catalysts based
on cobalt phthalocyanines. A method was proposed for suppressing formation of the thiosulfate ion in oxida-
tion of H S to elemental sulfur.
2
Catalytic oxidation of mercaptans plays a key part
in industrial processes for purification of hydrocarbon
raw materials to remove sulfur compounds [1] impair-
ing the quality of motor fuels and poisoning catalysts
in various stages of manufacture of synthetic rubber.
The content of mercaptan sulfur in the raw materials
is within the range from hundredths to tenths of a
percent. Extraction of hydrogen sulfide from natural
gas containing 1 (Orenburg gas field) to 25% (Astra-
has monofunctional mercaptans as ligands [4]. The
+
formation constants of Cu complexes with thiol com-
+
pounds are so high that the concentration of free Cu
10
ions in aqueous solutions does not exceed 10
17
10
M, depending on the pH of the medium at total
concentration of copper compounds in solution in the
range 10 4 10 M [5]:
6
RSH
RS + H,
(3)
(4)
(5)
(6)
khan gas field) H S and its subsequent oxidation to
2
elemental sulfur involves numerous catalytic stages
aimed to convert the maximum possible amount of the
RS + Cu2+
RSSR + Cu+,
2
initial H S into sulfur [2]. Cobalt phthalocyanines
2RS + Cu+
RS + Cu+
2
[Cu(SR) ] ,
2
(
CoPC), proposed in the 1960s, proved to be the most
effective catalysts for oxidation of mercaptans into
disulfides. In the years that passed, a great number of
CoPC derivatives have been tested: from water-solu-
ble mononuclear complexes intended for oxidation of
mercaptans in the bulk of an aqueous-alkaline solution
formed in Merox extraction process to polynuclear
CuSR .
Hence follows that the catalytic properties of copper(I)
in oxidation of thiol compounds are due to complex
+
species rather than to Cu aqua ions.
A study of the catalytic oxidation of thiol com-
pounds in relation to their structure in aqueous solu-
tions revealed that the rate of oxidation of difficultly
oxidized aliphatic mercaptans in aqueous-alkaline
solutions increases dramatically [6] if into their solu-
(
M > 5000 Da) complexes acting as catalysts at the
interface between the aqueous and organic phases in
Merox demercaptanization of naphthas [3]:
2
RSH + O2
RSSR + H O ,
(1)
(2)
2
2
+
tions, along with Cu , minor amounts of readily oxi-
4RSH + O2
2RSSR + 2H O.
dizable dimercapto compounds (DMCs) (I) are intro-
duced, such as dimercaptopropionic, dimercaptosuc-
cinic, and dimercaptopropanesulfonic acids and dimer-
captopropylamine (Fig. 1):
2
It is known that, in aqueous-alkaline solutions in an
2+
excess of thiol compounds, Cu ions are reduced to
Cu , and further, thiolate anions form either soluble
complexes with Cu (if additional hydrophilic func-
tional groups are present in a thiol compound) or
+
+
CH CH CH SO H
HOOC CH CH2
SH SH
2
2
3
+
+
poorly soluble Cu mercaptides in the case when Cu
SH SH
1
070-4272/03/7601-0088$25.00 2003 MAIK Nauka/Interperiodica

COMPLEXES OF COPPER(I) WITH DIMERCAPTO COMPOUNDS
89
CH CH CH NH
HOOC CH CH COOH
SH SH
CO2, M
2
2
2
SH SH
+
In this case, Cu mercaptides are dissolved and
the previously inert mercaptans start to oxidize with
kinetic characteristics typical of DMC oxidation. This
effect can be used to develop novel catalysts for mer-
captan oxidation, which have not been used previ-
ously in purification of petroleum products to re-
move mercaptans. Here, the main components of the
,
min
catalyst are DMCs and their complexes with copper
+
Fig. 1. Catalytic oxidation of butyl mercaptan BuSH.
(c ) Oxygen concentration and ( ) reaction time. Solution
composition (M): (1) CuSO , 1.25 10 ; BuSH , 1 10
(
DMC + Cu ), introduced into an alkaline solution. In
+
O
2
this case, the catalyst complex DMC + Cu does not
require development of any special flowsheet in puri-
fication of hydrocarbon raw materials to remove mer-
captans, being totally compatible with the flowsheets
employing CoPC.
6
2
,
4
0
4
pH 11; (2) 1 + unithiol, 1 10
.
with heavy metals. Therefore, a catalyst on its base is,
in principle, of interest for demercaptanization of
hydrocarbons. The mechanism of the catalytic action
of DMC + Cu catalysts is based on two conjugated
reactions: DMC oxidation by molecular oxygen in the
The scheme of this process is as follows: hydrocar-
bon raw materials are brought in contact in an ex-
tractor, in a counterflow, with an alkaline (15 20%
NaOH) solution of the catalyst, and mercaptans,
+
+
coordination sphere of Cu ions and thiol disulfide
which are weak acids (pK 10 10.5) pass in the form
exchange, which occurs outside the coordination
sphere of the Cu ion and results in that mercaptans
a
+
of anions, mercaptides, into the aqueous-alkaline solu-
tion. In this solution, when it comes in contact with
atmospheric oxygen in the regeneration apparatus,
mercaptides are oxidized to disulfides. The disulfides,
which are insoluble in aqueous solutions, are extracted
from the aqueous phase in the settling apparatus,
being accumulated in a small volume of the upper
organic layer and then removed from the system [7].
dissolved in the alkaline medium are converted into
disulfides and DMCs oxidized in the first reaction
pass into their original reduced form. At relatively low
+
Cu concentrations the occurring reactions can be
represented by Scheme 1.
Effective homogeneous catalysts for mercaptan
oxidation must be characterized by high catalytic ac-
tivity and long-term stability in 15 20% alkali solu-
tions. The kinetics of butyl mercaptan oxidation in the
presence of a complex of unithiol with copper(I) was
studied in most detail: the dependence of the rate of
mercaptan oxidation on the unithiol concentration,
The DMCs mentioned differ only slightly in their
catalytic properties in oxidation of mercaptans in the
+
presence of Cu ions, but only dimercaptopropanesul-
fonic acid (unithiol) is manufactured in Russia on the
industrial scale for use in medicine to cure poisoning
Scheme 1
CH2 CH CH2 SO3
_
_
2_
_
2_
.
.
CH2 CH CH2 SO3
CH2 CH CH2 SO3
+
+ O
2
+
Cu
_
_
_
_
_
_
S
S
S
S
S
S
Cu+
CH2 CH CH2 SO3
+
Cu
O
.
.
_
2
_
2
+
+
Cu + (O ) ,
2
S
S
_
_
_
CH2 CH CH2 SO3
CH2 CH CH2 SO3
_
CH2 CH CH2 SO3
_
_
+
RS
+ RS
_
_
+ RSSR.
S
S
S
S
S
S
SR
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 76 No. 1 2003

90
BAGIYAN et al.
blade impeller stirrer, bubbler for oxygen supply,
10 , mol l min 1
2
1
V
reflecting partitions, reflux condenser, and contact
thermometer connected to an electric relay. To main-
tain the temperature at the required level, a cooling
finger was inserted into the vessel, and the reactor
itself was heated with a Nichrome coil. The tempera-
ture was controlled to within 0.5 C, the stirrer rota-
tion rate was 2700 rpm. Kinetic curves of butyl mer-
captan oxidation were recorded at 20 C. The concen-
6
tration of copper(I) ions was varied between 1.0 10
5
and 1.0 10 M, and that of unithiol, between 1.0
3
2
10
and 1.0 10 M. The initial concentration of
mercaptides in the alkaline solution was varied bet-
ween 0.690 and 0.082 M. The solution of mercaptides
was prepared by mixing appropriate amounts of fresh-
ly distilled butyl mercaptan with a 10% solution of
NaOH. The catalyst complex was prepared separately
by dissolving weighed portions of unithiol and
CuSO 5H O in distilled water. The mercaptide
and catalyst solutions were mixed and the reaction
mixture was thermostated directly in the reaction
vessel in an atmosphere of argon. Oxygen was fed
into the vessel at 20 C; the reaction time was counted
from the beginning of oxygen supply into the reactor.
The oxidation course was monitored by the content of
mercaptides in the alkaline solution, by sampling the
reaction mixture at certain intervals of time. The
content of mercaptides in the reaction mixture was
determined by potentiometric titration with 0.01 N
cBuSH, M
Fig. 2. BuSH oxidation rate V at relatively low Cu(I) con-
centrations in the catalyst solution. Concentration: BuSH
0
1
3
1
.75 10 and unithiol 4 10 . (c
) BuH concentra-
BuSH
1
tion; the same for Fig. 4. Cu(I) concentration, g-ion l
:
4
2
6
6
6
6
(
(
1) 2.5 10 , (2) 2.0 10 , (3) 1.60 10 , (4) 1.25 10 ,
6
7
5) 1.0 10 , and (6) 6.25 10 .
content of copper(I) ions in solution, and concentra-
tion of butyl mercaptan was analyzed.
EXPERIMENTAL
A procedure for determining the catalytic activity
was chosen with account taken of the conditions in
which the oxidation is kinetically controlled. The
most adequate in this regard is the technique described
in [8]. The oxidation was done with technical-grade
oxygen under atmospheric pressure in an alkaline
solution of the catalyst in a batch installation. The
reactor was a 0.5-l glass vessel equipped with a three-
[
Ag(NH ) ]NO3 in conformity with GOSTs (State
3 2
Standards) 22985 78 and 17323 71.
The graphical dependence of the oxidation rate on
the mercaptan concentration at different reagent con-
centrations in solution is shown in Figs. 2 4. It can
c
, M
10 , mol l min 1
2
1
BuSH
V
,
min
cBuSH, M
Fig. 3. BuSH oxidation kinetics at varied initial con-
Fig. 4. BuSH oxidation rate V at varied unithiol concentra-
centrations of mercaptan. Concentration: Cu(I) 1.25
tion in the catalyst solution. Concentration, M: BuSH
0
6
1
3
1
6
1
0
g-ion l and unithiol 4 10 M. (c
) BuSH con-
1.75 10 and CuSO 1.25 10 . Unithiol concentration,
4
BuSH
2
3
3
3
centration and ( ) reaction time. Initial BuSH concentration,
M: (1) 1 10 , (2) 5 10 , (3) 3.5 10 , (4) 2.2 10 ,
(
3
4
1
1
5) 1.5 10 , and (6) 8 10 .
M: (1) 6.5 10 and (2) 3.2 10
.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 76 No. 1 2003

COMPLEXES OF COPPER(I) WITH DIMERCAPTO COMPOUNDS
91
be seen that the reaction kinetics is described by
the Michaelis equation [9, 10]
first-order at very low mercaptan concentrations and
zero-order at a sufficiently high concentration. It is
the latter case that occurs in catalytic oxidation of
V = d[RSH]/dt = Vmax[RSH]/([RSH] + Km), (7)
mercaptans in high-sulfur raw materials. Therefore,
1
the quantity
(
, reciprocal of the time of conversion
where V is the reaction rate, [RSH] is the mercaptan
concentration, and Vmax and Km are constants.
1
e.g., 95% oxidation), can serve as a measure of the
catalyst performance. Let us consider how the reaction
rate depends on the concentrations of the catalyst
components. The rate is virtually independent of the
unithiol concentration in a wide range (Fig. 4). As for
the dependence of the reaction rate on the copper(I)
concentration, the situation is complicated by the fol-
lowing circumstance. As shown previously [6], the
complex of copper(I) with unithiol exists in two
forms, monomeric and dimeric, characterized by dif-
ferent catalytic activities. In the dimeric complex, the
With increasing mercaptan concentration, the reac-
tion rate does not grow unlimitedly, but tends to a
value Vmax reached at the highest concentrations of
the catalytically active complex species. The physical
meaning of the Michaelis constant K is as follows: If
m
the mercaptan concentration is chosen to be [RSH] =
Km, then the reaction rate is equal to half the maxi-
mum possible value, i.e., V = d[RSH]/dt = Vmax/2.
Such a dependence means that the reaction rate is
limited by the concentration of the catalytically active
complex species. Their concentration becomes the
O molecule is a bridging ligand, in which connection
2
the steady-state concentration of the catalytically
active oxygen-containing complex is higher for the
dimeric form of the complex, compared to its mono-
meric form:
highest at mercaptan concentrations of about K , and
m
then it no longer depends on the mercaptan concentra-
tion because of the saturation. Thus, this reaction is
_
_
_
4_
_
2_
.
+
O3S CH2 CH
CH2
S
Cu
S
CH2
CH CH2 SO3
CH2 CH CH2 SO3
_
_
_
_
_
+
2
(8)
S
Cu
S
S
S
Cu+
Therefore, the mechanism of oxidation of coordi-
nated dimercapto compounds in such a dimeric com-
plex differs from the scheme presented for the mono-
meric form of the complex: electrons pass from four
captans. For example, Co disulfophthalocyanine oxi-
dizes butyl mercaptan 4.5 times faster than ethyl
mercaptan, which, in turn, is oxidized several times
faster than the sulfide ion. Moreover, in contrast to the
kinetic characteristics of the DMC + Cu systems, the
reaction is first-order with respect to the catalyst and
mercaptan concentrations [11].
+
thiolate anions to the bridging O molecule, and water
2
molecule, rather than the O2 anion, is the reduction
2
product in this case (Scheme 2). At low copper(I)
concentrations, the reaction is first-order with respect
to copper(I), since the dimeric complex is mainly dis-
sociated; whereas at sufficiently high copper(I) con-
centrations the reaction order must be 0.5, i.e., the
reaction rate is to be proportional to a square root of
the copper concentration. It is this behavior that is
observed experimentally (Fig. 5).
In view of the fundamentally different kinetic char-
acteristics of the catalysts compared, the time neces-
sary for 95% oxidation of butyl mercaptan with the
initial concentration of 0.2 M was chosen as a cata-
lytic activity criterion.
Experiments demonstrated that butyl mercaptan is
9
5% oxidized in an alkaline solution at copper(I) and
6
As shown by experiments, the oxidation rates of
butyl and ethyl mercaptans are the same under com-
parable conditions, and that of the sulfide ion is half
the oxidation rate of mercaptans, which would be ex-
pected since the sulfide ion loses two times greater
number of electrons in oxidation, compared to the
mercaptide ion. By contrast, in the presence of CoPC
catalysts, high-molecular-weight mercaptans are oxi-
dized more readily than low-molecular-weight mer-
unithiol concentrations of, respectively, 5 10 and
4
3
5
10
5
10 M in 35 40 min, whereas the in-
dustrial Co disulfophthalocyanine ensures the same
conversion in 100 min at a concentration in solution of
6
5
10 M. With Co polyphthalocyanine, 95% con-
version of butyl mercaptan into disulfide is reached
in 20 min. It is noteworthy that the activity of the
+
catalyst based on Cu and dimercaptopropionic acid
ensures the same conversion in 20 min. Thus, compar-
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 76 No. 1 2003

92
BAGIYAN et al.
Scheme 2
_
_
4_
_
3
+
_
_
O3S CH2 CH
S
Cu
S
CH2
CH2 CH CH SO
+
2
2
Cu
+ 2
_
_
_
_
Cu+
CH2
S
CH CH2 SO3
4_
S
S
CH2
S
_
_
+
_
O3S CH2 CH
S
Cu
..
S
.
.
+
O
2
O
2
_
_
_
+
CH2
S
Cu
S
CH CH2 SO3
_
.
.
+
0
O3S CH2 CH
S
Cu
S
CH2
_
+
CH2 CH CH SO3
2
+
4H
+
2
Cu + 2
+ 2H O.
2
2
H O
2
S
S
.
.
_
+
CH2
S
Cu
+
S
CH CH2 SO3
ison of the activity of DMC + Cu catalysts with that
of the industrially used CoPC catalysts shows that the
unithiol-based system is 2.5 times more active than
Co diphthalocyanine and 1.5 times less active than
Co polyphthalocyanine, and the system based on Cu
and dimercaptopropionic acid exhibits higher activity
than Co polyphthalocyanine.
catalyst solutions. The initial concentrations (M) of
the catalysts compared were the same as those in in-
4
dustrial processes, i.e., 3 10 disulfophthalocyanine,
.5 1 03 polyphthalocyanine, and 5 10 3 unithiol +
4
1
1
+
10 CuSO . The variation of the activity of the
4
catalyst solutions with time is shown in Fig. 6. It can
be seen that after 7 days the activity of the DMC +
The above data on the catalytic activity are an im-
portant, but insufficient characteristic of the catalysts,
since, at their close catalytic activities, of key im-
portance for the effective industrial use of the cata-
lysts must be their stability in alkaline solutions. That
is why experiments were performed on prolonged
keeping of the catalysts in a 10% NaOH solution,
with periodic sampling to measure the dependence of
the catalytic activity on the time of keeping of the
+
Cu , disulfophthalocyanine, and polyphthalocyanine
catalysts decreased by, respectively, factors of 1.4,
7, and 60. After 2 weeks the respective figures were
.5, 120, and 120. In subsequent sampling, the ac-
tivity was only measured for the DMC + Cu catalyst,
to decrease 5-fold in 6 weeks, compared with that
of a freshly prepared solution. Thus, it was established
1
2
+
+
that the DMC + Cu catalysts much better retain their
1
2
1
02 [min]
10 [min]
1
1
1
,
days
0
.5
3
1
c
10 , g-ion l
Cu(I)
Fig. 6. Variation of the catalytic activity of the complexes
Fig. 5. BuSH oxidation rate vs. concentration c
Cu(I) ions in the catalyst solution at high Cu(I) concentra-
of
in prolonged keeping in a 10% NaOH solution. ( ) Time
Cu(I)
1
of 95% conversion and ( ) time of keeping in an alkali
1
tions. ( ) Time of 95% conversion. Concentrations: BuSH
solution. Catalyst (g l ): (1) disulfophthalocyanine, 2.0;
0
1
3
6
1
1
.75 10 M, unithiol 4 10 M, Cu(I) 4 10
6
(2) polyphthalocyanine, 1.0; (3) complex of copper
5
1
1
1
0
g-ion l
.
(0.17 g l CuSO ) with unithiol, 1 g
.
4
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 76 No. 1 2003

COMPLEXES OF COPPER(I) WITH DIMERCAPTO COMPOUNDS
activity in prolonged storage in alkaline solutions R(S) R S6 + RSSR.
93
(14)
8
than the CoPC catalysts do [12, 13].
The undesirable appearance of radicals can be
prevented by introducing effective radical scavengers
into the system. For example, 0.2 1 M ammonium
thiosulfate and 0.03 3 M elemental sulfur are intro-
duced, together with CoPC, into the absorbing solu-
tion. However, these measures ensure quantitative
It is known that CoPC catalysts cannot sustain
elevated temperatures in alkaline solutions: their ac-
tivity falls dramatically at 70 80 C. The DMC + Cu
catalysts show no changes in catalytic activity on
being kept for 1 h in a 10% NaOH solution at 95 C
and subsequent cooling of the solution to 20 C. The
same result was obtained on heating a DMC + Cu
catalyst solution in a 20% diethanolamine solution
at 107 C for 1.5 h.
+
+
conversion of H S into sulfur at H S concentration in
2
2
2
solution not exceeding 2 10 M in 3 20 min [16]
and, therefore, cannot be used in processing of gases
with high H S content. In the present study, an amino-
2
It was of interest to test the capabilities of DMC +
+
disulfide, (H NCH CH S ) , cystamine, manufac-
2
2
2
2
Cu catalysts in a more intensive process involving
tured in Russia industrially, was used to effectively
purification of natural gas to remove hydrogen sulfide,
with elemental sulfur obtained simultaneously. Most
suppress radical-chain reactions in H S oxidation.
2
Aminodisulfides are known to be, together with ami-
nothiols, active scavengers of many kinds of radicals.
Here, it should be emphasized once more that the oxi-
dation of both mercaptans and hydrogen sulfide oc-
curs in the thiol disulfide reaction, including that
with active short-chain polysulfides, rather than in the
coordination sphere of the complex. Thus, it would be
expected that, as a result of consecutive reactions,
these active polysulfide species will be transformed
into R(S) R species, which are inert toward O . With
frequently, natural gas with high H S content ( 1.5%)
is purified in the industry by intensive processes
2
associated with preliminary H S absorption by ethan-
2
olamine solutions, subsequent desorption of H S from
2
ethanolamine solutions at 120 C, and its oxidation
in a flow of O to elemental sulfur (Claus process).
2
This technique has an important disadvantage, high
sorbent loss of up to 100 g of ethanolamine per ton of
natural gas. All other wet methods for H S oxida-
2
tion do not compare in intensity with this process and
n
2
the chain of sulfur atoms growing, as a result of these
reactions, to R(S) R or R(S) R, 6- and 8-membered
can only be used at low H S content in natural gas
2
(
<0.5%), because Na CO solutions should not be
8
10
2
3
sulfur rings are formed from them. Indeed, the pres-
ence in the absorbing solution of cystamine with con-
strongly saturated with hydrogen sulfide. Such a satu-
ration could lead to predominant formation of thiosul-
fate and sulfate ions in the solutions, with the H2S
absorption capacity of the solutions decreasing in
proportion to this accumulation [14]. Preliminarily,
+
centration of 1 1.5 M, in addition to DMC + Cu ,
totally suppresses formation of oxygen-containing
sulfur compounds in oxidation of 1.5 M S2 with half-
3
the oxidation of H S to polysulfides and elemental
oxidation time of 6 min in the presence of 2 10
M
2
unithiol and 4 10 g-ion l 1 Cu .
4
+
sulfur in sodium carbonate solutions in the presence
+
of DMC + Cu catalysts was studied and it was es-
Thus, the system proposed ensures a two orders of
magnitude more intensive process than that in the
above-considered conventional technique with CoPC.
Analysis for the content of thiosulfate ions in solu-
tions shows that their concentration does not exceed
1%. The difficulty of analysis of thiosulfate ions in
the presence of a large excess of cystamine gives no
way of determining with sufficient accuracy in labora-
tory conditions how much less than 1% is the amount
of thiosulfate ions formed in the system. This could
be done reliably in experiments on a continuous pilot
installation from the extent of preservation of the
buffer capacity of the absorbing solution in the stage
tablished that, in H S oxidation, elemental sulfur is
2
not the only and even not the major reaction product.
Indeed, experiments aimed to determine the stoi-
chiometry of H S (1.5 M) oxidation in Na CO solu-
2
2
3
3
4
tions containing 2 10 M unithiol and 4 10
M
+
Cu demonstrated that elemental sulfur and thiosulfate
ions are formed in a 1 : 4 molar ratio. The short-chain
polysulfides formed in the catalytic stage react outside
the coordination sphere of the complex with excess
O by the radical-chain mechanisms, finally yielding
2
thiosulfate ions [15]:
HS + RSSR
RSSH
RSSH + RS ,
RSS + H+,
(9)
(10)
(11)
(12)
of H S absorption.
2
RSS + RSSR
RSS + RSSSR
RSSSR + RS ,
RSSSSR + RS ,
Calculations show that, if by-product thiosulfate
ions are formed in amount less than 0.1%, the catalyt-
ic system developed is more attractive economically
than separate ethanolamine treatment of natural gas to
RSS + R(S) R
R(S) R + RS ,
(13)
7
8
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 76 No. 1 2003

94
BAGIYAN et al.
remove H S with elemental sulfur subsequently ob-
2. Agaev, G.A. and Chernomyrdin, V.S., Tekhnicheskii
progress v ochistke prirodnogo gaza ot serovodoroda
okislitel’nymi metodami (Technical Progress in Puri-
fication of Natural Gas To Remove Hydrogen Sulfide
by Oxidative Techniques), Moscow: Mingazprom,
1980.
2
tained by the Claus method. An additional advantage
of cystamine introduction into the catalytic system is
that cystamine as a base can also be employed as an
effective absorbent binding the H S acid from the gas
2
flow, instead of using the conventional ethanolamine,
and can perform, in the stage of catalytic interaction
between H S and O , a second important function by
3. Sharipov, A.Kh. and Kovtunenko, S.V., Neftekhimiya,
1997, vol. 37, no. 6, pp. 563 567.
2
2
suppressing the undesirable radical-chain reactions.
4
5
. Hemmerich, P. and Sigwart, C., Experientia, 1963,
vol. 19, no. 2, pp. 488 492.
CONCLUSIONS
. Bagiyan, G.A., Valeev, A.K., Koroleva, I.K., and
Soroka, N.V., Zh. Neorg. Khim., 1983, vol. 28, no. 8,
pp. 2016 2025.
(1) New effective catalysts for oxidation of mer-
captans and hydrogen sulfide are proposed, based on
complexes of copper(I) with dimercapto compounds,
which can be used in purification of the wide fraction
of light hydrocarbons to remove mercaptans and in
purification of natural gas to remove hydrogen sulfide,
with elemental sulfur obtained simultaneously.
6
7
. Bagiyan, G.A., Koroleva, I.K., Soroka, N.V., and
Ufimtsev, A.V., in Breslerovskie chteniya (Bresler
Readings), St. Petersburg: Peterb. Inst. Yadernoi Fizi-
ki, Ross. Akad. Nauk, 2002, pp. 270 290.
. Ivanova, N.N., Pavlova, V.V., Glebova, N.A., et al.,
Seroochistka legkogo uglevodorodnogo syr’ya (Puri-
fication of Light-Hydrocarbon Raw Materials To
Remove Sulfur), Moscow: TsNIITEneftekhim, 1975.
(2) A study of the kinetic characteristics of the
new catalysts demonstrated that the catalytically ac-
tive species in the practically important range of con-
centrations is the dimeric form, which binds more
effectively an oxygen molecule in the coordination
sphere of copper(I).
8
9
. Fomin, V.A. and Mazgarov, A.M., Neftekhimiya,
1
978, vol. 18, no. 3, pp. 298 303.
. Panchenkov, G.M. and Lebedev, V.P., Khimicheskaya
kinetika i kataliz (Chemical Kinetics and Catalysis),
Moscow: Khimiya, 1974.
(
3) In oxidation of H S to elemental sulfur, the
2
undesirable formation of a by-product, thiosulfate
ions, was suppressed by introducing cystamine into
the catalyst solution, with the high intensity of catalyt-
1
1
1
0. Bresler, S.E., Vvedenie v molekulyarnuyu biologiyu
Introduction to Molecular Biology), Moscow: Nauka,
966.
(
1
ic oxidation of H S into elemental sulfur preserved.
2
1. Fomin, V.A., Liquid-Phase Catalytic Oxidation of
Mercaptans with Molecular Oxygen, Cand. Sci. Dis-
sertation, Kazan, 1980.
ACKNOWLEDGMENTS
2. USSR Inventor’s Certificate no. 869300.
The authors are grateful to A.V. Ilatovskii for as-
sistance in preparing the manuscript.
13. USSR Inventor’s Certificate no. 908069.
1
1
4. USSR Inventor’s Certificate no. 1401665.
REFERENCES
5. Simonov, A.D., Keier, N.P., and Kundo, N.N., Kinet.
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. Borisenkova, S.A., Neftekhimiya, 1991, vol. 31, no. 3,
pp. 391 408.
16. USSR Inventor’s Certificate no. 1510898.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 76 No. 1 2003