Materials Sciences and Applicatio ns, 2011, 2, 49-52
doi:10.4236/msa.2011.21007 Published Online January 2011 (http://www.SciRP.org/journal/msa)
49
Activated Carbons Containing Dispersed Metal
Oxide Particles for Removal of Methyl Mercaptan
in Air
Hisashi Tamai*, Miki Nakamori, Masayoshi Nishikawa, Takeshi Shiono
Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, Higashi-hiroshima, Japan.
Received October 15th, 2010; revised December 21st, 2010; accepted January 6th, 2011.
ABSTRACT
Activated carbons containing dispersed metal oxide particles were prepared by carbonization of phenol resin contain-
ing metal compounds followed by steam activation. Acetylacetonates of Fe, Mn and V, and Cu nitrate were used as the
sources of metals. The removal of a small amoun t of methyl mercaptan (CH3SH) in air with these activated carbons was
tested in a flow system. Compared with activated carbons without metal oxides, the carbons exhibited high activity for
the removal of CH3SH in air. In particular, activated carbon obtained from Novolac containing 5 wt% Cu showed ex-
cellent behavior over a long time.
Keywords: Activated Carbon, Methyl Mercaptan, Adsorption, Metal Oxide, Oxidation
1. Introduction
Methyl mercaptan (CH3SH) is an odorous gas emitted to
the atmosphere. Even a very small amount of CH3SH in
air makes life uncomfortable, and its removal is impor-
tant. For the removal of CH3SH, various procedures have
been investigated and applied. For instance, the adsorp-
tive removal of CH3SH by activated carbon is one of the
effective methods, because activated carbons with large
specific surface area have high adsorption ability for a
very low concentration of harmful gases. In practice,
activated carbons have been widely used for the removal
of odorous gases [1-6]. However, in most cases, their
adsorption activity is lost due to saturated adsorption.
This limitation suggests th at they are inefficient for prac-
tical use for a long period. On the other hand, it is known
that some metal oxides po ssess high catalytic activity for
oxidative decomposition of organic compounds such as
odorous substances [7-10]. From this point of view, re-
garding the limitation of activated carbons and the cata-
lytic activity of metal oxides, it is expected that metal
oxide particles dispersed in activated carbons may have
improved functions both for adsorption and oxidative
decomposition. As a result, these hybrid materials are
expected to be very effective for the removal of CH3SH
in air for long times.
Activated carbons containing metal oxides are gener-
ally manufactured by impregnation metal compounds
into activated carbons. However, this method decreases
the surface area of the activated carbon, that is, the depo-
sition of metal oxide particles on the pores lowers ad-
sorption capacity. In addition, the supporting of metal
oxide particles on the surface of the activated carbons is
often irregular and the size of metal oxide particles is not
necessarily uniform. Here, the simple preparation of
metal oxides dispersed on activated carbons was investi-
gated. The removal of a small amount of CH3SH in air
by the activated carbons obtained was tested using
CH3SH/air mixed gas in a flow method.
2. Experimental
Metal oxides dispersed in activated carbons were pre-
pared by carbonization of phenol resins containing metal
compounds followed by activation. Acetylacetonates of
Fe, Mn, and V, and Cu nitrate were used. Phenol resins
containing metal compounds were prepared by mixing a
methanol solution of Novolac with metal compounds
dissolved in methanol. After mixing, methanol was re-
moved by flash distillation and then cured at 170˚C for 1
h. The cured mixtures were carbonized in Ar atmosphere
at 800˚C for 1h, and then activated at 900˚C for 1 h. Ac-
tivation was conducted with N2 gas saturated with steam.
The pore characteristics were determined from N2 ad-

Activated Carbons Containing Dispersed Metal Oxide Particles for Re mova l of Met hy l Mercaptan in Air 50
sorption/desorption isotherms using a Quantachrome
NOVA 3200 apparatus. Metal contents in the activated
carbons were determined by particle induced X-ray
emission analysis (PIXE). The kinds of metal oxides
were determined by X-ray diffraction (XRD). Metal ox-
ides in the activated carbons were observed by transmis-
sion electron microscopy (TEM) and electron probe mi-
croanalysis (EPMA).
The test for the removal of CH3SH in air was con-
ducted by flowing air containing CH3SH through acti-
vated carbon powder in a quartz tube of inner diameter of
4 mm. Typically 10 mg of activated carbon was placed in
the tube. The inlet concentration of CH3SH in the air was
10 ppm. The amounts of CH3SH adsorbed and oxidized
were obtained from the differences between the inlet
concentration of CH 3SH and the outlet one.
3. Results and Discussion
Various activated carbons were prepared from Novolac
containing 1.0 wt% of Fe (AC-Fe-1), 1.0 wt% of V
(AC-V-1), and 1.0 wt% of Mn (AC-Mn-1), and various
wt% of Cu (AC-Cu-1 , -2, -5, and -10). Th e N2 adso rptio n
and desorption isotherms of the activated carbons ob-
tained are shown in Figure 1 and Figure 2, respectively.
Figure 1 also shows the isotherm of the activated carbon
obtained from metal-free phenol resin (AC). As shown in
Figure 1, the major uptake of N2 on AC occurs at rela-
tively low relative pressure (< 0.2). This indicates that
AC is microporous. On the other hand, in the case of
AC-Fe-1, AC-V-1, and AC-Mn-1, the amounts of N2
adsorbed gradually increase with increasing relative
pressure at relative pressure above 0.3, and a hysteresis
was observed between the adsorption and desorption
isotherms of N2. In addition, in the case of AC-Mn-1, a
steep increase in the amount of N2 adsorbed was ob-
served at a high relative pressure of 0.8 ~ 1.0. The for-
mation of macropores is indicated in AC-Mn-1. These
00.2 0.40.60.8
0
200
400
600
800
1200
1.0
1000
P/ P 0[ -]
N
2
V
o
l
u
m
e
(
c
m
3/
g
)
Figure 1. N2 adsorption/desorption isotherms of activated
carbons obtained from phenol resin containing metal com-
pounds. ○: AC, ▲: AC-Fe-1, ■: AC-V-1, ◆: AC-Mn-1.
0
100
200
300
400
500
600
700
800
900
0.0 0.5 1.
N
2
v
o
l
u
m
e
[
c
m
3
/
g
]
P /P o [-]
N
2 volume (cm3/g)
0
Figure 2. N2 adsorption/desorption isotherms of activated
carbons obtained from phenol resin containing Cu(NO3)2. -:
AC, ▲: AC-Cu-1, ■: AC-Cu-2, □: AC-Cu-10.
results suggest that the activated carbons obtained from
phenol resin containing metal compounds are mesopor-
ous and macroporous. We have earlier reported the
preparation of mesoporous activated carbons by car-
bonization of polymer materials containing metal com-
plexes followed by activation, and metal oxide particles
in carbonaceous materials play an important role in
mesopore formation [11]. Similarly to those results,
mesopores seem to be formed by metal oxide particles in
carbonaceous materials. However, in the case of AC-Cu
shown in Figure 2, an increase in the amounts of N2 ad-
sorbed at a relative pressure above 0.3 and a hysteresis
between the adsorption and desorption isotherms were
not observed, in spite of the increase in Cu content in
phenol resin. AC-Cu are thought to be microporous.
Table 1 shows the pore characteristics. BET specific
surface areas decreased by the addition of metal com-
pounds to phenol resin. This is especially noticeable in
AC-Fe-1. It is supposed that the decrease in BET specific
surface area is attributed to the catalytic effect of metal
oxide particles for steam activation. That is, the catalytic
effect of metal oxides for steam activation excessively
accelerate the activation, and as a result, pores formed in
the carbons are lost by activation. The BET specific sur-
face area of AC-Cu decreased with an increase in Cu
content in Novolac. Table 1 also shows metal contents
and metal species in the activated carbons. 3.8-6.0 wt%
of metal is contained in the activated carbons obtained
from phenol resin containing 1.0 wt% of metal. These
metal contents, determined by PIXE analysis, are com-
parable to the amounts calculated from the carbon yields
N
2 volume (cm3/g)
after carbonization and activation. Cu contents in AC-Cu
increased with increasing Cu content in the phenol resin.

Activated Carbons Containing Dispersed Metal Oxide Particles for Re mova l of Met hy l Mercaptan in Air 51
Table 1. Characteristics of activated carbons containing dispersed metal oxide particles.
Sample Metal amount
in novolac (wt%) Metal amount in AC (wt%) Metal species BET-SA (m2/g) Total porevolume
(cm3/g)
AC - - - 2597 1.20
AC-Fe-1 1.0 3.8 Fe2O3 441 0.58
AC-V-1 1.0 4.5 VO2 1610 1.00
AC-Mn-1 1.0 6.0 MnO, MnO2 1670 1.60
AC-Cu-1 1.0 4.1 CuO, Cu2O 2160 1.00
AC-Cu-2 2.0 4.5 CuO, Cu2O 0.73
AC-Cu-5 5.0 16.4 CuO, Cu2O 0.48
AC-Cu-10 10.0 34.0 Cu, CuO, Cu2O 0.35
These results suggest that the amounts of metal contained
in phenol resin are retain ed in the ACs even after activa-
tion. Metal species formed in the activated carbons were
determined by XRD. The formation of metal oxides was
observed (XRD profiles are not shown). Fe2O3 in
AC-Fe-1, VO2 in AC-V-1, MnO and MnO2 in AC-Mn-1,
CuO and Cu2O in AC-Cu-1. The dispersion of metal ox-
ide particles in activated carbons was observed by TEM
and EPMA. Figure 3 shows the TEM and EPMA images
of AC-Cu-5. The TEM image suggests that large copper
oxide particles, greater than 50 ~ 100 nm, are present.
However, the EPMA image indicates that copper was
uniformly dispersed in the activated carbon. It is sup-
posed that various sizes of copper oxide particles are
dispersed and very fine copper oxide particles which
cannot be resolved by TEM are present in the activated
carbon. Regarding the other metal compounds, similar
results to copper were observed.
The removal of CH3SH in air was tested. Figure 4
shows the removal of CH3SH from air as a function of
flow time of CH3SH/air gas mixture at 200 ml/min flow
speed. Initially, CH3SH was efficiently removed. How-
ever, removal steeply decreased after 200 min flow time.
This seems to be due to saturated adsorption of the AC.
On the other hand, activated carbons with dispersing
metal oxide particles, AC-Fe-1, AC-V-1, and AC-Mn-1,
exhibited higher removal activities than AC over a long
time. Figure 5 shows the removal of CH3SH from air by
AC-Cu, as a function of flow time at 40 ml/min flow
speed. The removal ratios by AC-Cu-1, AC-Cu-2, and
(A) (B)
(C)
Figure 3. TEM, SEM, and EPMA images of AC-Cu-5.
(a): TEM , (b): SEM, (c): EPMA.
0200 400 600 80010001200
0
10
20
30
40
Time (min)
R
e
m
o
v
a
l
(
%
)
Removal (%)
Figure 4. Removal of methyl mercaptan(CH3SH) in air by
activated carbons containing dispersed metal oxide parti-
cles. Flow rate of CH3SH/Air mixed gas: 200 ml/min. ○: AC,
▲: AC-Fe-1, ◇: AC-V-1, ■: AC-Mn-1.
0500 1000
0
20
40
60
80
100
Time (min)
R
e
m
o
v
a
l
(
%
)
Removal (%)
Figure 5. Removal of methyl mercaptan(CH3SH) in air by
activated carbons containing dispersed copper oxide parti-
cles. Flow rate of CH3SH/Air mixed gas: 40 ml/min. -: AC,
◆:AC-Cu-1, ●: AC-Cu-2, □: AC-Cu-5, △: AC-Cu-10.
AC-Cu-5 increased with increase in Cu amount. These
removal ratios of CH3SH by AC-Cu are far higher than
that by metal-free AC. Furthermore, it should be noted
that AC-Cu-5, prepared from phenol resin containing 5.0
wt% of Cu, exhibited the highest removal activity and
CH3SH in air was completely removed after 24 h flow
time. On the relationship between surface areas of acti-
vated carbons and Cu contents in phenol resin, BET spe-
cific surface area decreased with increasing content of
Cu, as shown in Table 1. These results suggest that the
removal of CH3SH in air is due to oxidative decomposi-
tion of CH3SH by copper oxide particles, in addition to
(a) (b)
(c)

Activated Carbons Containing Dispersed Metal Oxide Particles for Re mova l of Met hy l Mercaptan in Air 52
adsorption by the activated carbon. It has been reported
that metal oxides catalyze the oxidation of CH3SH to
dimethyl disulfide [8,9]. Therefore, copper oxide parti-
cles dispersed in the activated carbons prepared in this
work seem to have an extremely high efficiency for the
oxidative decomposition of CH3SH in air. As a result,
activated carbons with dispersed copper oxide particles
are supposed to exhibit high activities for the removal of
a small amount of CH3SH in air.
4. Conclusions
Activated carbons containing a fine dispersion of metal
oxide particles were prepared by carbonization of phenol
resin containing metal compounds followed by steam
activation. These materials exhibited high activity for the
oxidative removal of a small amount of CH3SH in air. In
particular, the activity of activated carbon containing
dispersed copper oxides was very high over a long time.
REFERENCES
[1] T. Sakano, H. Tamon and M. Okazaki, “Selective Re-
moval of Methyl Mercaptan Coffee Aroma Using Oxi-
dized Microporous Carbon,” Journal of Chemical Engi-
neering of Japan, Vol. 32, No. 5, 1999, pp. 701-704.
doi:10.1252/jcej.32.701
[2] A. K. Dalai, E. L. Tollefson, A. Yang and E. Sasaoka,
“Oxidation of Methyl Mercaptan over an Activated Car-
bon in a Fixed-Bed Reactor,” Industrial & Engineering
Chemistry Research, Vol. 36, No. 11, 1997, pp. 4726-
4733.
doi:10.1021/ie9701231
[3] S. Bashkova, A. Bagreev and T. J. Bandosz, “Adsorption
of Methyl Mercaptan on Activated Carbons,” Environ-
mental Science & Technology, Vol. 36, No. 12, 2002, pp.
2777-2782.
doi:10.1021/es011416v
[4] S. Bashkova, A. Bagreev and T. J. Bandosz, “Effect of
Surface Characteristics on Adsorption of Methyl Mer-
captan on Activated Carbons,” Industrial & Engineering
Chemistry Research, Vol. 41, No. 17, 2002, pp. 4346-
4352.
doi:10.1021/ie020137t
[5] S. Bashkova, A. Bagreev and T. J. Bandosz, “Adsorp-
tion/Oxidation of CH3SH on Activated Carbons Contain-
ing Nitrogen,” Langmuir, Vol. 19, No. 15, 2003, pp.
6115-6121.
doi:10.1021/la0300030
[6] A. Bagreev, J. A. Menendez, I. Dukhno, Y. Tarasenko
and T. J. Bandoz, “Oxidative Adsorption of Methyl Mer-
captan on Nitrogen-Enriched Bituminous Coal-Based Ac-
tivated Carbon,” Carbon, Vol. 43, No. 1, 2005, pp. 195
-213.
doi:10.1016/j.carbon.2004.09.003
[7] A. H. Miguel, D. F. S. Natusch, R. L. Tanner and J. L.
Hudson, “Adsorption and Catalytic Conversion of Thiol
Vapors by Activated Carbon and Manganese Dioxide,”
Atmospheric Environment, Vol. 10, No. 2, 1976, pp. 145
-150.
doi:10.1016/0004-6981(76)90232-8
[8] C. J. Heyes, J. G. Irwin, H. A. Johnson and R. L. Moss,
“The Catalytic Oxidation of Organic Air Pollutants. Part
1. Single Metal Oxide Catalysts,” Journal of Chemical
Technology & Biotechnology, Vol. 32, No. 12, 1982, pp.
1025-1033.
doi:10.1002/jctb.5030320746
[9] C. J. Heyes, J. G. Irwin, H. A. Johnson and R. L. Moss,
“The Catalytic Oxidation of Organic Air Pollutants. Part
2. Cobalt Molybdate and Copper Chromite Catalysts,”
Journal of Chemical Technology & Biotechnology, Vol.
32, No. 12, 1982, pp. 1034-1041.
[10] M. Nozawa, K. Tanigawa, M. Hosomi, T. Chikusa and E.
Kawada, “Removal and Decomposition of Malodorants
by Using Titanium Dioxide Photocatalyst Supported on
Fiber,” Water Science and Technology, Vol. 44, No. 9,
2001, pp. 127-133.
[11] H. Tamai, T. Kakii, Y. Hirota, T. Kumamoto and H. Ya-
suda, “Synthesis of Extremely Large Mesoporous Acti-
vated Carbon and Its Unique Adsorption for Giant Mole-
cules,” Chemistry of Materials, Vol. 8, No. 2, 1996, pp.
454-462.
doi:10.1021/cm950381t