i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 4 0 ( 2 0 1 5 ) 9 9 8 9 e1 0 0 0 1
Available online at www.sciencedirect.com
ScienceDirect
journal homepage: www.elsevier.com/locate/he
Selective catalytic oxidation of H2S to elemental
sulfur over titanium based TieFe, TieCr and TieZr
catalysts
H.Mehmet Tasdemir*, Sena Yasyerli, Nail Yasyerli
Department of Chemical Engineering, Gazi University, 06570 Ankara, Turkey
article info
abstract
Article history:
In this study, titanium oxide catalyst was incorporated with iron, chromium and zirconium
Received 23 January 2015
to improve catalytic activity for selective catalytic oxidation of H2S to elemental sulfur.
Received in revised form
Equimolar titanium based iron (TieFe), chromium (TieCr) and zirconium (TieZr) catalysts
8 June 2015
were synthesized by the complexation method and tested in oxidation between the tem-
Accepted 10 June 2015
perature range of 200e300 C and using different O2/H2S ratios. TieFe catalyst with Fe2TiO5
Available online 2 July 2015
crystalline phase and TieCr catalyst with mainly Cr2O3 crystalline phase showed complete
conversion of H2S and high sulfur selectivity (close to one) at 250 C. TieZr catalyst having
Keywords:
relatively high surface and small pore diameter could not prevent sulfur deposition on the
Hydrogen sulfide
surface and lost in catalytic activity at the same temperature. TieFe catalyst had high
Selective catalytic oxidation
activity with 100% conversion and sulfur selectivity in the reaction period of an experi-
Elemental sulfur
mental run (150 min) even at lower oxidation temperature (200 C). It was concluded that
Titanium
incorporation of iron into TieFe catalyst structure improved the redox ability and surface
Iron
acidity of the catalyst. Fe2TiO5 mixed metal oxide in the TieFe catalyst was responsible and
Chromium
active phase resulting in complete conversion of H2S and high sulfur selectivity in the
selective oxidation of H2S to elemental sulfur.
Copyright © 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights
reserved.
Introduction
Due to environmental concerns and economic considerations,
sulfur recovery from hydrogen sulfide has attracted significant attention by researchers and fuel producers. High
amount of H2S is produced as a side product, in the operation
of an integrated gasification combined cycle system (IGCC)
power plant as well as during gasification of fossil fuels and
also in petroleum refinery. The integrated gasification combined cycle, which is an environmentally clean sustainable
technology, involves coal gasifier, acid gas cleanup unit, and
power generation facilities. Sulfur in fuel can be converted to
H2S due to reducing atmosphere during coal gasification.
Hydrogen sulfide is usually removed from the sour gas by
absorption in ammonia, alkanolamine or alkaline salts. The
main disadvantages of the removal of H2S by absorption are
its relatively high cost and the use of solvent/sorbent [1e3].
Claus process is a well-known process to convert H2S from tail
gases to elemental sulfur. There are a number of publications
in the literature on the modeling of the Claus process [4,5]. In
the study of Jones et al., the modified Claus Process, when part
of IGCC power plant, was proposed to destroy ammonia
completely and recover sulfur thoroughly from a relatively
* Corresponding author. Tel.: þ90 312 582 3516; fax: þ90 312 230 8434.
E-mail addresses: [email protected] (H.Mehmet Tasdemir), [email protected] (S. Yasyerli), [email protected] (N. Yasyerli).
http://dx.doi.org/10.1016/j.ijhydene.2015.06.056
0360-3199/Copyright © 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
9990
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 4 0 ( 2 0 1 5 ) 9 9 8 9 e1 0 0 0 1
low purity acid gas stream [6]. In the conventional Claus
process, 1/3 of the H2S in the feed gas is burned to SO2 (R1
denoted as thermal oxidation) at high temperatures,
H2S þ 3/2 O2 / SO2 þ H2O
(R1)
SO2 is then reacted with the unburned H2S to produce
elemental sulfur at lower temperatures (R2 donated as catalytic step or Claus reaction)
2 H2S þ SO2 / 3/n Sn þ 2 H2O
(R2)
The main disadvantage of Claus process is thermodynamic
restriction (97e98%) in the catalytic step (R2). Catalytic selective oxidation of H2S is an attractive alternate to conventional
Claus process, to produce elemental sulfur in a single step
(R3).
H2S þ 1/2 O2 / 1/nSn þ H2O
(200 C T 350 C)
(R3)
Direct oxidation of H2S (R3) does not have any equilibrium
limitations and it is essentially irreversible. Some side reactions may reduce elemental sulfur yield; such as deep
oxidation of H2S (R4) and oxidation of produced sulfur (R5).
2 H2S þ 3 O2 / 2 SO2 þ 2 H2O
(R4)
1/n Sn þ O2 / SO2
(R5)
Therefore, development of a selective catalyst for selective
oxidation of H2S to elemental sulfur is crucial in producing
elemental sulfur with a high yield.
A number of investigations have been focused in the
literature on the development of active, selective and stable
catalyts for catalytic selective oxidation of H2S. Iron-, titanium-, chromium-, and vanadium based catalysts have been
reported to have high potential in catalytic oxidation of H2S to
produce elemental sulfur [7e10]. Also, catalysts with different
types of supports (for example, MCM-41, SBA-15, alumina,
actived carbon, alumina intercalated laponite etc.) have been
tried to improve catalytic activity in a single step catalytic
oxidation of H2S [11e15]. Iron oxide, which is Super-Claus
catalyst, is known one of the oldest catalysts tested in oxidation of H2S. Also, its lower cost and availability are advantages
of iron oxide catalyst. Additionaly, relatively high activity of
iron based catalyst for oxidation of H2S was reported in the
literature. However, iron oxide catalyst requires excess
amount of oxygen in order to obtain elemental sulfur [16].
Number investigations were tried to modify iron oxide catalyst to achieve high sulfur selectivity. Nguyen et al. studied on
thermal conductivity of silicon carbide (b-SiC) supported Fe2O3
catalyst. They have also reported silica supported Fecontaining catalysts [17,18]. Our previous study showed that
sulfur selectivity and stability of iron oxide catalyst could be
significantly enhanced by the incorporation of cerium into the
catalyst structure [16]. Vanadium based catalysts with good
redox properties are also known to be highly active in partial
oxidation of hydrocarbon and selective oxidation of hydrogen
sulfide. Our earlier studies indicated that oxidation state of
vanadium in the catalyst structure had a major role to achieve
high sulfur yield. Bimetallic CueV catalysts (Cu/V ratio of 1/1)
containing partially reduced vanadium in Vþ4 state were
highly selective to elemental sulfur. However, elemental sulfur yield was significantly decreased when catalyst was in Vþ5
state [19,20]. In the study performed by Barba et al., catalytic
performances of vanadium-based materials, supported on
mixed metal oxides (CeO2, TiO2, CuFe2O4) were investigated
for partial selective oxidation of H2S, at low temperatures
(50e250 C). In that study, high H2S conversion was obtained
with V2O5/CeO2 and V2O5/CuFe2O4 catalysts [21]. In the recent
work of Palma and Barba, V2O5/CeO2 catalysts were investigated for low temperature catalytic oxidation of H2S. They
proposed possible surface reaction mechanism for H2S
oxidation to sulfur [22]. In another work of Tan et al., a series
of Mn-substituted LaCrO3 were prepared by self combustion
technique and tested as sulfur tolerant anode catalysts in
solid oxide fuel cell using fuel gas containing H2S [23].
It was reported by Mobil Oil researchers that TiO2-based
catalysts can be used to oxidize H2S to elemental sulfur using
stoichiometric amount of O2 in the MODOP (Mobil Direct
Oxidation Process). However, this type catalyst was reported
to deactivate in the presence of water [17]. In addition to the
catalysts mentioned above, chromium oxide based catalysts
which were industrially used in dehydrogenation reaction
[24,25], may also have some potential in this reaction. In the
literature, studies with the titanium based catalysts are quite
limited, as compared to iron and vanadium based catalysts,
for selective oxidation of H2S to elemental sulfur [8,10].
The objective of the present study is to improve the
selectivity and catalytic performance of titanium dioxide
based catalysts with the aid of the synergistic effects of
bimetallic titanium/iron, titanium/chromium and titanium/
zirconium. New bimetallic catalysts, namely TieFe, TieCr,
and TieZr were synthesized by the complexation method and
their catalytic performances were investigated in selective
catalytic oxidation of H2S to elementel sulfur, in the temperature range of 200e300 C and at different O2/H2S ratios.
Experimental method
Catalyst preparation and characterization
In this study, titanium based iron (TieFe), chromium (TieCr)
and zirconium (TieZr) catalysts, having equimolar ratios
were synthesized by the modification of complexation
method, which was originally described by Marcilly et al. [26].
In this synthesis method, equimolar ratio of citric acid and
metal salt were mixed in a solution, where ethanol (Merck)
was used as solvent. Then, this solution was evaporated at
65 C for about 3 h, with continuosly stirring, until its viscosity
had noticeable increased. Evaporation time of solution is
markedly decreased due to the use of ethanol. In the second
step of synthesis, dehydration was completed in an oven at
65 C, by placing the viscous solution as a thin layer in a glass
dish. The solid foam formed in this step was then calcined at
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 4 0 ( 2 0 1 5 ) 9 9 8 9 e1 0 0 0 1
550 C for 8 h. In this synthesis route, titanium isopropoxide
(C12H28O4Ti, %98, Merck), iron (III) nitrate nanohydrate (Fe
(NO3)3.9H2O, %99, Merck), chromium (III) nitrat nanohydrate
(Cr (NO3)3.9H2O), %98, Merck), zirkonium (IV) oxide chloride
decahydrate ((ZrOCl2.8H2O), %99, Merck) were used as titanium, iron, chromium and zirconium sources, respectively.
Citric acid monohydrate was used as the complexation agent.
The catalysts synthesized in this work were characterized by
X-ray powder diffraction (XRD, Riguka D/MAX 2200 employing a Cu KR radiation source), N2 adsorption-desorption
(Quantachrome Autosorbe1), temperature programmed
reduction (TPR, Quantachrome Chembet 3000), scanning
electron microscopy (SEM, JEOL), energy dispersive X-ray
spectroscopy (EDS, JEOL, JSMe6400), and X-ray photoelectron
spectroscopy (XPS, SPECS), techniques. Fourier Transform
Infrared (FT-IR) analyses of pyridine adsorbed catalysts were
performed by using a Perkin Elmer Spectrum One instrument,
scanned from 1690 to 1390 cm1. Before this analysis, the
samples were dried at 110 C for 12 h. Pyridine adsorbed
samples were than kept at 40 C for 2 h before obtaining the
FT-IR spectra. Differences of the spectra obtained with and
without pyridine adsorbtion were than analyzed for the
characterization of the acid sites of the catalysts.
Catalytic tests
H2S selective oxidation experiments were carried out in a fixedbed quartz reactor having a 0.6 cm inside diameter. In all experiments, total flow rate of the gas mixture was kept constant
at 100 cm3/min (measured at 25 C) and helium was used as the
carrier gas. 0.2 g catalyst, which was supported by quartz wool
from both sides, was placed into the quartz tubular reactor. H2S
concentration was kept as 1%, in all experiments. Experiments
were performed with different O2/H2S ratios, ranging between
0 and 2, in a temperature range of 200e300 C. The effluent
stream was continuously analyzed by an FT-IR (PerkineElmer
Spectrum One, containing a flow gas cell) spectrophotometer,
connected online to the exit of the reactor. A sulfur condenser
was placed between the reactor and the FT-IR, to collect most of
the produced elemental sulfur. The temperature between
reactor and sulfur condenser was maintained at about 200 C,
to prevent sulfur condensation. Similarly, the temperature
between sulfur condenser to FT-IR was adjusted to about 100 C
to prevent water condensation. The analysis procedure and the
reaction system were detailed in the earlier study of Yasyerli
et al. [19]. The conversion of H2S and sulfur selectivity were
defined as follows;
Conversion of H2 S ð%Þ ¼
Sulfur Selectivity ð%Þ ¼
½H2 Sinlet ½H2 Soutlet
100
½H2 Sinlet
½H2 Sinlet ½H2 Soutlet ½SO2 outlet
100
½H2 Sinlet ½H2 Soutlet
Results and discussion
Characterization of fresh catalysts
Nitrogen adsorption-desorption isotherms of fresh TieFe,
TieCr and TieZr catalysts are given in Fig. 1.
9991
The isotherms of TieFe and TieCr are consistent with type
IV according to IUPAC classification, which are typical for
mesoporous materials with ordered pore structure. These two
isotherms show H1 type adsorption hysteresis [27]. The
isotherm of TieZr shows some difference from the other two
catalysts. Absence of the major hysteresis loop in the
isotherm of TieZr catalyst is an indication of loss of longrange order of mesopores in the synthesized material. Some
physical properties of the catalysts prepared by complexation
method are given in Table 1.
TieZr catalyst has the highest surface area among the
others due to its microporous structure and smaller average
pore diameter (about 2.4 nm) compared to the other catalysts.
XRD patterns of TieFe, TieCr, and TieZr catalysts prepared
by the complexation method are shown in Fig. 2. As seen in
Fig. 2a, XRD pattern of fresh TieZr catalyst showed a broad
peak between 25 and 35 . No sharp peaks were observed
corresponding to the Ti and/or Zr oxides. However, as reported by Stefanic et al., x-ray diffraction pattern scanned
over the Bragg angle (2q) range from 26 to 38 , should contains
the most prominent diffraction lines of m-, t-, c-ZrO2 [29]. This
result indicated that metal oxides in the structure of the TieZr
catalyst might have small particles (<5 nm), which is not
detectable by the XRD analysis or they are in amorphous form.
In the case of TieCr mixed oxide catalyst, mainly the Cr2O3
crystalline phase was observed in the XRD pattern of fresh
TieCr catalyst, given in Fig. 2c. In the same XRD pattern, some
small peaks corresponding to TiO2 (rutile) phase were also
observed. However, XRD pattern of the fresh TieFe catalyst
(Fig. 2e) indicated the formation of mixed metal oxide, in the
Fe2TiO5 (Pseudo brookite) crystalline phase, with sharp peaks
[30].
Fig. 3 shows TPR profiles of fresh TieFe, TieCr and TieZr
catalysts (gas mixture: 5% H2e95% N2). The reduction of TieFe
catalyst started at about 250 C and mainly occurred in three
steps (Fig. 3a). The maximum of the first TPR peak, the second
peak and the third peak were observed at about 450 C, 570 C
and 680 C, respectively.
In the literature, it was reported that the reduction of iron
oxide can be considered to be due to Fe2O3 / FeO /Fe in the
temperature range of 350e660 C [31]. The broad and poor
reduction peak for single TiO2 was reported as 575 and 615 C,
in the literature [32e35]. TPR reduction peaks of TieFe catalyst
can be mainly attributed to the iron in catalyst structure.
There is no sharp reduction peaks in the TPR profiles of TieCr
and TieZr catalysts. TieCr catalyst gave only one reduction
peak at about 360 C, corresponding to the reduction from Crþ3
to Crþ2 in agreement with the literature [36,37]. In the TPR
profiles of TieZr catalyst, there is only very slight reduction
peak at about 485 C. According to hydrogen consumption in
TPR profiles of all catalysts, the TieFe catalyst has better redox
ability than the others, due to the presence of iron.
In order to investigate the acidic properties of the catalysts,
FT-IR study was performed by using pyridine adsorbed fresh
TieFe, TieCr, TieZr catalysts, in the range of 1390 cm-1 and
1690 cm-1 bands (Fig. 4).
In the literature, the peaks observed at 1540 cm1 and
1640 cm1 are assigned to a pyridinium ion bonded to Bronsted acid sites. Lewis acid sites were observed at about
1600e1630 cm1 and 1445-1450 cm1 infrared bands,
9992
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 4 0 ( 2 0 1 5 ) 9 9 8 9 e1 0 0 0 1
140
Ti-Cr
Adsorbed Volume (cc/g)
120
100
Ti-Fe
80
60
40
20
(a)
0
0.0
0.2
0.4
0.6
0.8
1.0
P/P0 , Relative Pressure
Adsorbed Volume (cc/g)
140
120
100
80
Ti-Zr
60
40
(b)
20
0
0.0
0.2
0.4
0.6
0.8
1.0
P/P0,Relative Pressure
Fig. 1 e Nitrogen adsorptionedesorption isotherms of a) TieFe, TieCr b) TieZr catalysts.
corresponding to physisorbed pyridine. The peak observed at
about 1490 cm1 is assigned to both type of acidity. Sharp
adsorption bands were observed at about 1445, 1490 and
1610 cm1 in the infrared spectra of pyridine adsorbed TieFe
and TieCr catalysts, as seen in Fig. 4. Additionaly, the broad
adsorption band observed at about 1545 cm-1 indicated the
presence of Bronsted acid sites on these catalysts. However, in
the infrared spectrum of TieZr catalyst, intensities of all corresponding bands were lower. According to pyridine adsorbed
FT-IR analysis, TieFe and TieCr catalysts have higher Bronsted and Lewis acidity than TieZr catalyst. Additionaly,
adsorption peak at about 1545 cm1 (Bronsted acid sites) in the
FT-IR spectrum of TieFe catalyst is slightly greater than the
corresponding peak in the FT-IR spectrum of TieCr catalyst.
Pyridine adsorbed FT-IR analysis indicated that TieFe catalyst
has more acidic surface than TieCr and TieZr catalysts.
In order to see the morphology of catalysts, typical SEM
photographs of fresh TieFe and TieCr catalysts samples were
given in Fig. 5.
SEM photographs show quite different morphology of
TieFe and TieCr catalysts. In the SEM photograph of TieFe
catalyst small particles were mainly observed. However,
TieCr catalyst was in the non-uniform rod-like structure.
Catalytic activity tests of catalysts
Hydrogen sulfide selective oxidation experiments of TieFe,
TieCr and TieZr catalysts were first carried out using a feed
Table 1 e Some physical properties of the synthesized catalysts.
Catalyst
TieFe
TieCr
TieZr
a
BET surface
area, m2/g
45
52
169
Average pore
diameter, nm
11.6
11.6
2.4
Average pore
volume, cm3/g
0.14
0.21
0.10
Evaluated from: L ¼ K l/(B cosq) (Scherrer equation; K ¼ 0.89 [28]).
Ti/(Fe or Cr or Zr)
Molar ratio
In solution
EDS
1.0
1.0
1.0
0.9
1.1
1.0
Crystallite
sizea, nm
Crysitalline phase
25
16 for Cr2O3
e
Fe2TiO5
Cr2O3, TiO2 (Rutile)
Amorphous
9993
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 4 0 ( 2 0 1 5 ) 9 9 8 9 e1 0 0 0 1
Ti-Fe
A
A
A
A
C
C
S
A
A
A
A
A
A C AA
Intensity
A
A
AC
A
A
AC
A
A
A
C
(f)
A
A
A
AA
C
AA
A
A
A C
C
0
5
10
15
20
25
30
35
40
45
50
AA
A
A
55
60
65
A A
70
75
B
B C
(e)
C
80
85
90
2 theta
Ti-Cr
B
B
B
Intensity
B
B
B
C
C
B
B
(d)
B
B
B
0
5
10
15
20
25
C
B
B
B
30
35
40
B
B
B
45
50
55
60
65
C
70
B
B C
75
(c)
80
85
90
2 theta
Ti-Zr
Intensity
(b)
(a)
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
2 theta
Fig. 2 e XRD patterns of fresh and used catalyst at a stoichiometric ratio of O2/H2S and 250 C. [a,c,e: Fresh Catalysts and
b,d,f: Used Catalysts] (A: Fe2TiO5, B:Cr2O3, C: Rutile TiO2, S: Sulfur).
stream containing stoichiometric ratio of O2/H2S, in the fixedbed reactor, at 250 C. Fractional conversion of H2S and sulfur
selectivity values obtained with these catalysts are shown in
Fig. 6a and b, respectively.
As seen in Fig. 6, TieFe catalyst showed complete conversion of H2S and very high sulfur selectivity close to one (0.98).
Fractional conversion and selectivity values obtained with
this catalyst remained constant and no deactivation was
9994
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 4 0 ( 2 0 1 5 ) 9 9 8 9 e1 0 0 0 1
Hydrogen Consum ption
(a) Ti-Fe
200
300
400
500
600
700
800
Hydrogen Consumption
Temperature, °C
(b) Ti-Cr
200
300
400
500
600
700
800
Hydrogen Consumption
Temperature, °C
( c) Ti-Zr
200
300
400
500
600
700
800
Temperature, °C
Fig. 3 e Hydrogen TPR Profiles of (a) TieFe catalyst (b) TieCr catalyst (c) TieZr catalyst.
observed during the reaction period of 150 min. TieCr catalyst
also showed complete conversion of H2S, but selectivity value
(0.97) was slightly lower than the corresponding value obtained with TieFe catalyst. In the case of TieZr mixed oxide
catalyst, a significant activity loss was observed during the
selective oxidation run. The stability of this catalyst was less
than the other two catalytic materials. For TieZr catalyst, H2S
fractional conversion decreased from 1.00 to about 0.65 within
the first 35 min of the reaction period and then it become
stable at this value. The decrease of H2S fractional conversion
with rection time is illustrated in Fig. 6a. Although TieZr
catalyst showed lower H2S conversion, there was no SO2
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 4 0 ( 2 0 1 5 ) 9 9 8 9 e1 0 0 0 1
Lewis
1446
LB
1490
9995
Bronsted
1637
Bronsted
1545
Lewis
1598
Ti-Zr
Bronsted
1640
Transmittance
Ti-Cr
Lewis
1611
Ti-Fe
Lewis
1610
1390
1440
1490
1540
1590
1640
1690
Wavenumber, cm-1
Fig. 4 e FT-IR of adsorbed pyridine on equimolar TieFe, TieCr and TieZr mixed oxide catalysts.
Fig. 5 e SEM photographs of (a) TieFe catalyst (b) TieCr catalyst.
detected by FT-IR in the reactor exit stream. Therefore, TieZr
catalyst gave the highest sulfur selectivity (1.00).
In order to understand the stability behavior of titania
based catalysts, XRD patterns and Nitrogen adsorption/
desorption isotherms of the used catalysts were also
measured and compared with the corresponding characterization results of the fresh catalysts. XRD patterns of fresh and
used TieFe, TieCr and TieZr catalysts were compared in
Fig. 2. Results indicated that there was no big differences in
the XRD patterns of all fresh and used titania based catalyst.
This result showed that the bulk structure of the catalysts did
not change after selective oxidation runs. Also, the BET surface areas of the used TieFe and TieCr catalyst did not change
(Table 2).
However, a significant decrease of BET surface area of
TieZr catalyst was found after the selective oxidation run. It
decreased from 169 m2/g to 77 m2/g, after the reaction test.
The decrease of surface area of the used TieZr catalyst was
about 55% with respect to its initial value. The EDS analysis of
the used catalysts after selective oxidation runs were also
obtained and reported in Table 2. Also, the typical steady state
fractional conversion and sulfur selectivity values obtained
with these catalysts (at the stoichiometric ratio of O2/H2S) are
reported in this table. For TieZr catalyst, the atomic ratio of
sulfur to total metal (Ti þ Zr) was 0.104. On the other hand, for
other catalysts, the values of the sulfur atomic ratio were
much smaller than corresponding value of used TieZr catalyst. Sulfur over the TieZr catalyst could not be observed in
the XRD pattern of used catalyst due to its amorphous structure. Sulfur is probably deposited in pore volume of TieZr
catalyst and causes pore plugging due to its smaller pore sizes.
Therefore, sulfur deposition is the main reason of decrease of
surface area of TieZr, and hence decrease of the catalytic
activity of this material as a function of reaction time.
Selective catalytic oxidation experiments were then
continued with TieFe and TieCr catalysts, which showed
more stable catalytic performance, giving complete conversion at 250 C with a stochiometric ratio of O2/H2S. In order to
see catalytic activity at lower and higher temperatures, selective oxidation runs were repeated at 200 and 300 C, with
9996
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 4 0 ( 2 0 1 5 ) 9 9 8 9 e1 0 0 0 1
Ti-Fe Catalyst
Ti-Cr Catalyst
Fractional Conversion of H2S
1.2
Ti-Zr Catalyst
1
0.8
0.6
0.4
0.2
0
(a)
0
30
60
90
120
150
time, min
Ti-Fe Catalyst
1.05
Ti-Cr Catalyst
Ti-Zr Catalyst
Sulfur Selectivity
1
0.95
0.9
0.85
(b)
0.8
0
30
60
90
120
150
time, min
Fig. 6 e (a) Fractional conversion of H2S and (b) sulfur selectivity values obtained with titanium-based catalysts at 250 C and
a stoichiometric feed stream.
these two catalysts. Steady state H2S conversion and sulfur
selectivity values obtained with TieFe and TieCr catalysts
using stoichiometric feed ratio of O2/H2S are shown in Fig. 7.
TieFe and TieCr catalyst showed quite different catalytic
performance by changing reaction temperatures between
200 C and 300 C. TieFe catalyst showed complete H2S conversion at all temperatures, while the conversion obtained
with the TieCr catalyst significantly decreased at 200 C and
300 C. TieCr catalyst did not show a higher activity compared
Table 2 e H2S conversion and sulfur selectivity values,
EDS results and BET surface area of used catalysts after
150 min of time on stream at 250 C.
Catalyst
TieFe
TieCr
TieZr
a
Fractional
SMolar ratio BET surface
conversion selectivity (S/Tiþa Me) area, m2/g
of H2S
1.00
1.00
0.65
Me: Fe, Cr and Zr metals.
0.98
0.97
1.00
0.034
0.032
0.104
43
51
77
with activity of TieFe catalyst for selective oxidation of H2S to
elemental sulfur. On the other hand, SO2 formation was not
observed in reactor exit stream at 200 and 300 C using the
TieCr catalyst. So, sulfur selectivity obtained with the TieCr
catalyst was found as 100% at 200 C and 300 C oxidation
temperatures. Sulfur selectivities obtained with TieFe catalyst
were found as 100% at 200 C, 98% at 250 C and 93% at 300 C
(Fig. 7). It was observed that sulfur selectivity slightly decreases in increasing of oxidation temperature. These results
showed that TieFe and TieCr catalyst could prevent the
importance of side reactions such as deep oxidation of H2S
(H2S þ 3/2 O2 / SO2þ H2O) or oxidation of produced sulfur
(S þ O2 / SO2) during selective oxidation of H2S at 200 C.
However, higher catalytic activity of TieFe catalyst with
respect to H2S conversion was observed at three oxidation
temperatures. FT-IR spectrum of pyridine adsorbed TieFe
catalyst showed the presence of acidic sites, which may
contribute to the high catalytic activity. In the work of Chun
et al., it was reported that selective oxidation to elemental
sulfur over TiO2/SiO2 is proceded on acidic sites and single
step selective catalytic oxidation reaction is dominant [8]. In
the other work performed by Zhang et al., iron oxide
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 4 0 ( 2 0 1 5 ) 9 9 8 9 e1 0 0 0 1
Fractional Conv- Selectivity
1
9997
Conversion of Ti-Fe Catalyst
Selectivity of Ti-Fe catalyst
Conversion of Ti-Cr Catalyst
0.8
Selectivity of Ti-Cr Catalyst
0.6
0.4
0.2
0
200°C
1
250°C
2
300°C
3
Fig. 7 e Fractional conversion of H2S and sulfur selectivity values obtained with TieFe and TieCr catalysts at different
temperatures after 150 min of time on stream. (1H2S%-0.5%O2eHe).
supported on alumina-intercalated laponite clay catalysts for
selective oxidation of H2S were reported. The authors
emphasized that strong acidity of catalysts was beneficial to
the oxidation reaction [14]. XRD patterns of the used TieFe
catalysts in the temperature range of 200e300 C were shown
in Fig. 8.
There was no significant change in the bulk structure of
used TieFe catalyst compared with fresh the TieFe catalyst.
Small sulfur peak was observed at 200 C reaction temperature
as mentioned before for reaction run at 250 C.
In order to understand the differences of catalytic performances of these materials, further characterization of used
catalysts were carried out using XPS and EDS analysis. XPS
results of fresh and used TieCr catalyst at different oxidation
temperatures were given Fig. 9.
XPS analysis of fresh and used TieCr catalyst showed that
titanium was in the oxidation state of þ4 in all of them. This
result indicated that oxidation state of titanium did not
change after selective oxidation run. The binding energy
observed at around 576.8 eV showed that most of chromium
was in þ3 oxidation state in fresh TieCr catalyst. After
oxidation, there was no shift in the binding energy of 576 eV
and some decrease in the intensity of corresponding signal.
Also, the characteristic sulfur peak (S 2p3) observed at 169 eV
clearly showed that the formation of sulfide layer on the
catalyst surface. Quantative analysis of the XPS results
indicated a Cr/Ti atomic ratio of about 1.18. After oxidation
runs at different temperature, the Cr/Ti atomic ratios on the
surface of used catalysts at 200, 250 and 300 C were found as
0.73, 1.18 and 0.83, respectively. Sulfur deposition on the
chromium of the catalyst surface result in the change in the
molar ratio of Cr/Ti after selective oxidation reaction at 200
and 300 C. In the literature [38,39], it was reported that the
chromiumesulfur system was complex and Cr2S3 could be
made by the action of H2S on Cr2O3. Additionaly, nonstochiometric chromium sulphides have been investigated
under various condition of temperature and pressure of S2.
Sulfur molar ratios determined by XPS and EDS techniques
for each used catalyst were given in Table 3.
High amount of sulfur deposition might be another reason
for decrease in fractional conversion obtained with TieCr at
200 C. At the same reaction condition, almost half amount of
sulfur on TieFe catalyst was detected. However, this amount
of sulfur on TieFe catalyst did not effect on the catalytic activity during oxidation run. At 250 C reaction temperature,
both catalysts have the almost the same sulfur deposition.
Sulfur on surface determined by XPS results of used TieFe and
TieCr catalysts confirm the sulfur deposition detected by the
EDS technique. Especially, TieCr catalyst did not prevent
amount of sulfur deposition over the chromium at the 200 C
and 300 C. The difference between amount of sulfur deposited at 200 C and 300 C oxidation temperatures may be an
Intensity
(d) After reaction, 300°C
s
(c) After reaction, 250°C
s
(b) After reaction, 200°C
(a) Fresh
10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90
2 theta
Fig. 8 e XRD Patterns of TieFe catalyst before and after the reaction at a stochiometric feed stream composition.
9998
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 4 0 ( 2 0 1 5 ) 9 9 8 9 e1 0 0 0 1
Fig. 9 e XPS result of fresh and used TieCr catalyst at different temperature with a stoichiometric ratio. a) Fresh catalyst b)
200 C c) 250 C d) 300 C.
indication of a shift in the reaction mechanism at higher
temperatures.
In order to give further inside about the progress of the
reaction, sulfidation experiments were repetead using single
TiO2 and TieFe mixed metal oxide catalysts in the absence of
oxygen (1% H2SeHe). H2S breakthrough curves obtained with
these catalysts are given in Fig. 10.
Sulfur retention capacities of TieFe and TiO2 catalysts were
determined using breakthrough curves obtained in the
absence of gas phase oxygen. Sulfur retention capacities of
these catalysts were found as 0.033 g S/g catalyst for TieFe and
0.006 g S/g catalyst for TiO2. As expected, TieFe catalyst
showed longer breakthrough time due to the presence of iron.
Iron oxide is well known desulfurization sorbent for H2S
removal [40,41] due to non-catalytic reaction between H2S and
iron-oxides. In a reducing atmosphere, it is expected that
metallic iron or iron oxide (Fe2O3 or/and FeO) react with H2S to
Table 3 e Sulfur molar ratios of used catalysts determined
by XPS and EDS techniques after oxidation reactions.
Temperature, Catalyst EDS (molar ratio),
C
S/Tiþ(Fe or Cr)
200
250
300
TieFe
TieCr
TieFe
TieCr
TieFe
TieCr
0.102
0.231
0.034
0.032
0.048
0.033
XPS
(molar ratio),
S/Tiþ(Fe or Cr)
No result
0.083
0.056
0.041
No result
0.074
form metal sulfide. Our previous results [16] showed that
sulfur retention capacities of mixed metal oxide of FeeCe and
FeeO catalysts prepared by complexation method were found
as 0.06 g S/g catalyst and 0.056 g S/g catalyst, respectively.
Comparison of the sulfur retention capacities of TieFe and
FeeCe mixed metal oxides, TieFe catalyst had a lower sulfur
retention capacity. This result indicated that sulfur retention
capacity of TieFe mixed metal oxide should be improved for
hot gas desulfurization as a sorbent. In the work of Zeng et al.,
FeeMn based sorbents with different mole ratios were prepared by coprecipitation method and their sulfur retention
capacities were determined at high temperature desulfurization (850 C). They reported zero effective sulfur capacity of Fe
sorbent at high temperature desulfurization [42]. In this work,
H2S sorption was completed within a time period of about
10 min with TieFe catalyst. SO2 formation was not observed
during sulfidation with mixed metal oxide TieFe catalyst and
TiO2 catalyst. In our previous studies, SO2 formation in the
initial stages of sulfidation was observed with single or mixed
metal oxide sorbents due to contribution of lattice oxygen of
metal oxide at reducing athmosphere [16,43,44]. It could be
said that oxygen mobility of TieFe mixed metal oxide catalyst
to form SO2 from H2S is lower. These results showed that
TieFe mixed metal oxide does not permit to contribute the
lattice oxygen in the structure during sulfidation. The EDS
analysis of the used catalyst in sulfidation showed the molar
ratio of sulfur to (Ti þ Fe) of 0.031. It is interestingly seen that
amounts of sulfur deposition on TieFe catalyst used in sulfidation (1% H2SeHe) and oxidation (1%H2S-0.5% O2eHe) are
almost the same. Also, EDS analysis of the used TiO2 catalyst
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 4 0 ( 2 0 1 5 ) 9 9 8 9 e1 0 0 0 1
9999
Ti-Fe
TiO2
1.2
CH2Sout/CH2Sin
1
0.8
0.6
0.4
0.2
0
0
10
20
30
40
50
time, min
Fig. 10 e H2S breakthrough curves obtained with TiO2 and TieFe catalysts at 250 C.
after sulfidation experiment showed no sulfur deposition and
SO2 formation at 250 C and 200 C, as expected. EDS analysis
showed that TiO2 catalyst did not permit sulfur deposition on
surface, which is the main reason for deactivation of catalyst
in sulfur recovery process.
The XPS results of fresh and used TieFe catalysts are
shown in Fig. 11.
The XPS peak observed at binding energy values of 711 eV
and 724 eV, which correspond 2p3/2 and 2p1/2, showed
presence of þ3 oxidation state of iron in the fresh catalyst. In
the same XPS spectrum, peaks observed at binding energy
values of 465 eV and 459 indicated that titanium was in þ4
oxidation state. After selective oxidation run (1% H2S, 0.5%O2
in He, 250 C), there was almost no change in the XPS spectrum of used TieFe catalyst. Small sulfur peak at about
168 eV was observed in the XPS spectrum used TieFe catalyst. In the XRD pattern of used catalyst in oxidation run,
small sulfur peak at about 23 was also observed as given
before (Fig. 2f). The atomic ratio of Fe to Ti on the surface of
fresh catalyst was found as 0.84. The corresponding value of
used catalyst is about 0.68. There is a small reduction in
atomic ratio of Fe to Ti on the surface of used catalyst after
the oxidation run. This result together with sulfidation run
might be an indication that sulfur was deposited or adsorbed
as elemental sulfur on iron oxide in the catalyst structure.
This type of sulfur did not cause major decrease in catalytic
activity during selective oxidation of H2S. Therefore, it can be
concluded that Fe2TiO5 mixed metal oxide was quite stable
and it is the active phase for selective oxidation of H2S to
elemental sulfur.
Selective oxidation runs at different O2 concentrations in
the feed stream were repeated using the best catalyst (TieFe)
catalyst, at a temperature of 200 C. H2S conversion and sulfur
selectivity obtained with TieFe catalyst were given in Table 4.
Fig. 11 e XPS result of fresh and used TieFe catalyst at different temperature with a stoichiometric ratio. a) Fresh catalyst b)
250 C.
10000
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 4 0 ( 2 0 1 5 ) 9 9 8 9 e1 0 0 0 1
Table 4 e H2S conversion and sulfur selectivity over TieFe catalyst at different oxidation temperatures and O2/H2S ratios.
O2/H2S: 0.5
Temperature
O2/H2S: 1.0
O2/H2S: 2.0
H2S conversion
Sulfur selectivity
H2S conversion
Sulfur selectivity
H2S conversion
Sulfur selectivity
1.00
1.00
1.00
1.00
0.98
0.94
1.00
1.00
1.00
0.88
0.58
0.56
1.00
1.00
1.00
0.87
0.53
0.14
200 C
250 C
300 C
As seen in Table 4, complete conversion was achieved at all
feed stream compositions and oxidation temperatures.
Highest sulfur selectivity was observed with the stochiometric
feed ratio of selective oxidation reaction at 200 C. While oxygen concentration in feed stream increases, sulfur selectivity
drops due to the formation of SO2. At different oxygen concentrations, the variations of SO2 concentration in the reactor
exit stream versus time gave further inside about the progress
of the reaction (Fig. 12). An increase oxygen concentration in
the feed stream resulted in a decrease in sulfur selectivity, as
expected.
Results reported in Fig. 12 gave significant variations of SO2
concentration in the reactor exit stream during the first
100 min after which a steady state reached at above stochiometric O2/H2S ratio of selective oxidation reaction. In our
earlier studies, CueV and CueVeMo catalysts also showed
similar behavior at higher oxidation temperatures [19]. This
study showed that the formation of active phase for selective
oxidation of H2S was started at initial reaction period and was
completed when the steady state is reached.
catalysts due to sulfur deposition in its relatively small pore
diameters. TieCr and TieFe catalysts showed complete conversion of H2S and high sulfur selectivity at 250 C. On the
other hand, when the conversion of H2S and selectivity of
elemental sulfur values of all three catalysts were compared,
it was found that the most active catalyst was TieFe catalyst
for selective catalytic oxidation of H2S to elemental sulfur
reaction between 200 and 300 C and a ratio of O2/H2S is 0.5.
Fe2TiO5 crystalline phase of TieFe catalyst is stable during
selective oxidation and responsible for high activity and
selectivity even at 200 C oxidation temperatue.
Acknowledgment
The Scientific and Technological Research Council of Turkey
(TUBITAK) and Gazi University Research Funds (Grant BAP 06/
_
2011-56) and TUBITAK Scholarship Programme (BIDEB
2211)
are greatfully acknowledged.
references
Conclusion
In this work, titanium based iron (TieFe), chromium (TieCr)
and zirconium (TieZr) mixed metal oxide catalysts having
equimolar ratios were prepared by the complexation method
and tested for selective oxidation of H2S to elemental sulfur.
As a result of XRD patterns of the catalysts, only TieFe catalyst
gave complex compound as Fe2TiO5 in its structure. TieZr
catalyst showed lowest catalytic activity at 250 C in all
O2/H2S:0
O2/H2S:0.5
O2/H2S:1.0
O2/H2S:2.0
1
CSO2 out/CH2S in
0.8
0.6
0.4
0.2
0
0
30
60
90
120
150
time, min
Fig. 12 e SO2 exit concentrations of TieFe catalyst at 200 C
with different O2/H2S ratios.
[1] Ferguson PA. Hydrogen sulfide removal from gases, air, and
liquids. 1st. ed. New Jersey: Noyes Data Corp.; 1975.
[2] Wu X, Schwartz V, Overbury SH, Armstrong TR.
Desulfurization of gaseous fuels using activated carbons as
catalysts for the selective oxidation of hydrogen sulfide.
Energy Fuels 2005;19:1774e82.
[3] Lee JD, Park NK, Han KB, Ryu SO, Lee TJ. Influence of reducing
power on selective oxidation of H2S over V2O5 catalyst in
IGCC system. Stud Surf Sci Catal 2006;159:425e8.
[4] Bhattacharya D, Turton R, Zitney SE. Steady-state simulation
and optimization of an integrated gasification combined
cycle power plant with CO2 capture. Ind Eng Chem Res
2011;50:1674e90.
[5] Puchyr DM, Mehrotra AK, Behie LA, Kalogerakis N.
Hydrodynamic and kinetic modelling of circulating fluidized
bed reactors applied to a modified claus plant. Chem Eng Sci
1996;51:5251e62.
[6] Jones D, Bhattacharya D, Turton R, Zitney SE. Rigorous
kinetic modelling and optimization study of a modified claus
unit for an integrated gasification combined cycle (IGCC)
power plant with CO2 capture. Ind Eng Chem Res
2012;51:2362e75.
[7] Li KT, Yen CS, Shyu NS. Mixed-metal oxide catalysts
containing iron for selective oxidation of hydrogen sulfide to
sulfur. Appl Catal A 1997;156:117e30.
[8] Chun SW, Jang JY, Park DW, Woob HC, Chung JS. Selective
oxidation of H2S to elemental sulfur over TiO2/SiO2 catalysts.
Appl Catal B 1998;16:235e43.
[9] Uhm JH, Shin MY, Zhidong J, Chung JS. Selective oxidation of
H2S to elemental sulfur over chromium oxide catalysts. Appl
Catal B 1999;22:293e303.
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 4 0 ( 2 0 1 5 ) 9 9 8 9 e1 0 0 0 1
[10] Shin MY, Park DW, Chung JS. Development of vanadiumbased mixed oxide catalysts for selective oxidation of H2S to
sulfur. Appl Catal B 2001;30:409e19.
[11] Carmona AR, Soriano MD, Nieto JML, Jones DJ, Jimenez JJ,
Lopez AJ, et al. Iron-containing SBA-15 as catalyst for partial
oxidation of hydrogen sulfide. Catal Today 2013;210:117e23.
[12] Bineesh KV, Kim MI, Park MS, Lee KY, Park DW. Selective
catalytic oxidation of H2S over V2O5-supported Fe-pillared
montmorillonite clay. Catal Today 2011;175:183e8.
[13] Fang HB, Zhao JT, Fang YT, Huang JJ, Wang Y. Selective
oxidation of hydrogen sulfide to sulfur over activated
carbon-supported metal oxides. Fuel 2013;108:143e8.
[14] Zhang X, Dou G, Wang Z, Li L, Wang Y, Wang H, et al.
Selective catalytic oxidation of H2S over iron oxide supported
on alumina-intercalated laponite clay catalysts. J Hazard
Mater 2013;260:104e11.
[15] Sisani E, Cinti G, Discepoli G, Penchini D, Desideri U,
Marmottini F. Adsorptive removal of H2S in biogas conditions
for high temperature fuel cell systems. Int J Hydrog Energy
2014;39:21753e66.
[16] Eslek DD, Yasyerli S. Selectivity and stability enhancement of
ıron oxide catalyst by ceria incorporation for selective
oxidation of H2S to sulfur. Ind Eng Chem Res 2009;48:5223e9.
[17] Nguyen P, Edouard D, Nhut JM, Ledoux MJ, Pham C, Huu CP.
High thermal conductive b-SiC for selective oxidation of H2S:
a new support for exothermal reactions. Appl Catal B
2007;76:300e10.
[18] Nguyen P, Nhut JM, Edouard D, Pham C, Ledoux MJ, Huu CP.
Fe2O3/b-SiC: a new high efficient catalyst for the selective
oxidation of H2S into elemental sulfur. Catal Today
2009;141:397e402.
[19] Yasyerli S, Dogu G, Ar I, Dogu T. Dynamic analysis of removal
and selective oxidation of H2S to elemental sulfur over Cu-V
and Cu-V-Mo mixed oxide in a fixed bed reactor. Chem Eng
Sci 2004;59:5206e14.
[20] Yasyerli S, Dogu G, Dogu T. Selective oxidation of H2S to
elemental sulfur over CeeV mixed oxide and CeO2 catalysts
prepared by the complexation technique. Catal Today
2006;117:271e8.
[21] Barba D, Palma V, Ciambelli P. Screening of catalysts for H2S
abatement from biogas to feed molten carbonate fuel cells.
Int J Hydrog Energy 2013;38:328e35.
[22] Palma V, Barba D. Low temperature catalytic oxidation of H2S
over V2O5/CeO2 catalysts. Int J Hydrog Energy
2014;39:21524e30.
[23] Tan W, Zhong Q, Xu D, Yan H, Zhu X. Catalytic activity and
sulfur tolerance for Mn-substituted La0.75Sr0.25CrO3±d in gas
containing H2S. Int J Hydrog Energy 2013;38:16656e64.
[24] Gaspar AB, Dieguez LC. Distribution of chromium species in
catalysts supported on ZrO2/Al2O3 and performance in
dehydrogenation. J Catal 2003;220:309e16.
[25] Karamullaoglu G, Dogu T. Oxidative dehydrogenation of
ethane over chromium-vanadium mixed oxide and
chromium oxide catalysts. Ind Eng Chem Res
2007;46:7079e86.
[26] Marcilly C, Courty P, Delmon B. Preparation of highly
dispersed mixed oxides and oxide solid solutions by
[27]
[28]
[29]
[30]
[31]
[32]
[33]
[34]
[35]
[36]
[37]
[38]
[39]
[40]
[41]
[42]
[43]
[44]
10001
pyrolysis of amorphous precursors. J Am Ceram Soc
1970:53e6.
Lowell S, Shield J. Powder surface area and porosity. 2nd ed.
New York: Chapman and Hall; 1984.
Brundle CR, Evans CA. Materials characterization series. In:
Wachs IE, editor. Characterization of catalytic materials.
Boston: Manning Publications Co.; 1992. p. 6.
Stefanic G, Grzeta B, Music S. Influence of oxygen on the
thermal behavior of the ZrO2-Fe2O3 system. Mater Chem Phy
2000;65:216e21.
Selected powder diffraction data for minerals. 1st ed. 1974.
Pennsylvania.
Liao SJ, Chen T, Miao CX, Yang WM, Xie ZK, Chen QL. Effect
of TiO2 on the structure and catalytic behavior of
ironepotassium oxide catalyst for dehydrogenation of
ethylbenzene to styrene. Catal Commun 2008;9:1817e21.
Zhu H, Qin Z, Shan W, Shen W, Wang J. Pd/CeO2eTiO2
catalyst for CO oxidation at low temperature: a TPR study
with H2 and CO as reducing agents. J Catal 2004;225:267e77.
Kim M, Ju WD, Kim KH, Park DW, Hong SS. Selective
oxidation of hydrogen sulfide to elemental surfur and
ammonium thiosulfate using VOx/TiO2 catalysts. Stud Surf
Sci Catal 2006;159:225e8.
Pereira CAS, Gonzales EAU. Reduction of NO with CO on CuO
or Fe2O3 catalysts supported on TiO2 in the presence of O2,
SO2 and water steam. Fuel 2014;118:137e47.
Caceres CV, Fierro JL, Agudo AL, Soria J. Effect of support on
the surface characteristics of supported molybdena
catalysts. J Catal 1990;122:113e25.
Ilieva LI, Andreeva DH. Investigation of the chromium oxide
system by means of temperature-programmed reduction.
Thermochim Acta 1995;265:223e31.
Ayari F, Mhamdi M, Rodriguez JA, Ruiz ARG, Delahay G,
Ghorbel A. Ammoxidation ethylene over low and overexchanged Cr-ZSM-5 catalysts. Appl Catal A
2012;415e416:132e40.
Satake M, Mido Y. Chemistry of transition elements. 1st ed.
New Delhi: Discovery Publishing House; 1994.
Johnson BFG. Inorganic chemistry of the transition elements,
4th Vol.. Cambridge: Royal Society of Chemistry; 1976.
Pan YG, Perales JF, Velo E, Puigjaner L. Kinetic behaviour of iron
oxide sorbent in hot gas desulfurization. Fuel 2005;84:1105e9.
Tamhankar SS, Hasatani M, Wen CY. Kinetic studies on the
reactions involved in the hot gas desulfurization using a
regenerable iron oxide sorbent. Chem Eng Sci
1981;36:1181e91.
Zeng B, Yue H, Liu C, Huang T, Li J, Zhao B, et al.
Desulfurization behavior of Fe-Mn-based regenerable
sorbents for high etemperature H2S removal. Energy Fuels
2015;29:1860e7.
Yasyerli S, Dogu G, Ar I, Dogu T. Activities of copper oxide
and Cu-V and Cu-Mo mixed oxides for H2S removal in the
presence and absence of hydrogen and predictions of a
deactivation model. Ind Eng Chem Res 2001;40:5206e14.
Yasyerli S, Dogu G, Ar I, Dogu T. Breakthrough analysis of
H2S removal on Cu-V-Mo, Cu-V and Cu-Mo mixed oxides.
Chem Eng Commun 2003;190:1055e72.
本文献由“学霸图书馆-文献云下载”收集自网络，仅供学习交流使用。
学霸图书馆（www.xuebalib.com）是一个“整合众多图书馆数据库资源，
提供一站式文献检索和下载服务”的24 小时在线不限IP 图书馆。
图书馆致力于便利、促进学习与科研，提供最强文献下载服务。
图书馆导航：
图书馆首页
文献云下载
图书馆入口
外文数据库大全
疑难文献辅助工具