Synthesis of a Highly Active and Stable Pt/Co3O4 Catalyst and Its Application for the Catalytic Combustion of Toluene

Article abstract of DOI:10.1002/ejic.201900372

Catalytic combustion has become one of the most economical, feasible and effective tools for the abatement of VOCs. However, it is difficult to prepare supported Pt catalysts possessing both excellent catalytic activity and stability by traditional preparation methods, such as incipient-wetness impregnation method and nanoparticle loading method. In this work, we prepared Pt/Co₃O₄ catalyst with high catalytic activity and stability for the catalytic combustion of toluene by galvanic displacement method. As comparing, additional reference samples were prepared using incipient-wetness impregnation method and nanoparticle loading method, respectively. All of the samples were characterized by XRD, TEM, H₂-TPR, O₂-TPD and XPS techniques. The catalyst prepared by galvanic displacement method exhibited the best catalytic activity with the temperature of 90 % toluene conversion about 150 °C (T₉₀ = 150 °C) and outstanding stability reflected in a continuous 100 h on-stream toluene combustion lifetime experiment without catalytic activity decline at the GHSV = 60 000 mL g^–1 h^–1 compared to which prepared by traditional methods. These results are attributed to the excellent oxygen mobility, the high surface chemisorbed oxygen species concentration and the strong interaction between Pt and support Co₃O₄. Therefore, our work provided a universal strategy for designing high-efficiency and stable catalyst for the abatement of VOCs at low temperature.

Full text of DOI:10.1002/ejic.201900372

DOI: 10.1002/ejic.201900372
Full Paper
Catalytic Combustion of VOCs
Synthesis of a Highly Active and Stable Pt/Co3O4 Catalyst and
Its Application for the Catalytic Combustion of Toluene
Xuefeng Hu,[a,b][‡] Zeshu Zhang,[a,c][‡] Yibo Zhang*[a] Liwei Sun,[a,c] Heyuan Tian,[a,c] and
Xiangguang Yang*[a,c]
Abstract: Catalytic combustion has become one of the most and XPS techniques. The catalyst prepared by galvanic displace-
economical, feasible and effective tools for the abatement of ment method exhibited the best catalytic activity with the tem-
VOCs. However, it is difficult to prepare supported Pt catalysts perature of 90 % toluene conversion about 150 °C (T90 = 150 °C)
possessing both excellent catalytic activity and stability by tra- and outstanding stability reflected in a continuous 100 h on-
ditional preparation methods, such as incipient-wetness im- stream toluene combustion lifetime experiment without cata-
pregnation method and nanoparticle loading method. In this lytic activity decline at the GHSV = 60 000 mL g–1 h–1 compared
work, we prepared Pt/Co3O4 catalyst with high catalytic activity to which prepared by traditional methods. These results are
and stability for the catalytic combustion of toluene by galvanic attributed to the excellent oxygen mobility, the high surface
displacement method. As comparing, additional reference sam- chemisorbed oxygen species concentration and the strong in-
ples were prepared using incipient-wetness impregnation teraction between Pt and support Co3O4. Therefore, our work
method and nanoparticle loading method, respectively. All of provided a universal strategy for designing high-efficiency and
the samples were characterized by XRD, TEM, H2-TPR, O2-TPD stable catalyst for the abatement of VOCs at low temperature.
Introduction
tivity of supported Pd catalysts are higher for catalytic combus-
tion of short-chain hydrocarbons while supported Pt catalysts
are more active for long-chain hydrocarbons and aromatics.[9]
So we chose noble metal Pt as the active component of the
supported catalyst for toluene combustion. Zhang et al.[5b] pre-
pared Pt/HPMOR for toluene combustion with T90 = 190 °C the
GHSV at the GHSV = 60 000 mL g–1 h–1. Chen et al.[10] prepared
0.82Pt@MCr2O3 and found that the T90 was equal to 154 °C
with the GHSV of 60 000 mL g–1 h–1. CeO2,[11] SiO2,[8] Al2O3,[12]
The emissions of volatile organic compounds (VOCs), such as
formaldehyde, benzene, ethylbenzene and toluene, have be-
come an increasingly serious problem owing to its huge harm
to both the environment and human body.[1] To eliminate the
emissions of VOCs, many researchers have tried hard to develop
the VOCs abatement technologies, such as thermal burning,[2]
absorption,[3] photocatalytic degradation[4] and catalytic com-
bustion.[5] Among those VOCs abatement technologies, cata-
lytic combustion technology has caused so much attention due
to its high efficiency, economic feasibility, and eco-friendli-
ness.[6]
For catalytic combustion, the key point is to improve the
catalytic activity as much as possible. Although transition metal
oxides (e.g., Ni, Co, and Mn)[7] possess good catalytic perform-
ance, supported noble-metal catalysts, especially Pt and Pd, are
the most ideal catalyst in the matter of low temperature cata-
lytic activity for VOCs combustion.[8] Generally, the catalytic ac-
[13]
[14]
MnO2
and Co3O4
are the common supports of noble-
metal catalysts for the abatement of VOCs. Among all, Co3O4
shows great effective and active on account of its weaker Co–
O bond and higher oxygen binding rate.[15] Bai et al.[16] found
that the porous Co3O4-HT-CTAB catalyst exhibited an excellent
catalytic activity and the T90 value was 215 °C for the combus-
tion of toluene with the GHSV = 20 000 mL g–1 h–1. Liu et al.[17]
prepared 6.5 Au/meso-Co3O4 and the catalyst gave the T90 of
138 °C, 162 °C and 189 °C for the catalytic combustion of tolu-
ene, o-xylene and benzene with the GHSV = 20 000 mL g–1 h–1,
respectively. Beyond that, the preparation methods of the cata-
lysts exerted a crucial influence on the performance of the cata-
lysts.[18] However, supported Pt catalysts prepared with tradi-
tional preparation methods, such as incipient-wetness impreg-
nation method, nanoparticle loading method and so on, have
two serious problems including the poor catalytic activity that
cannot meet current expectations and the worse stability for
the combustion of VOCs.
[a] State Key Laboratory of Rare Earth Resource Utilization,
Jilin Province Key Laboratory of Green Chemistry and Process,
Changchun Institute of Applied Chemistry,Chinese Academy of Sciences,
Changchun 130022, China
E-mail: xgyang@ciac.ac.cn
yibozhang@ciac.ac.cn
[b] University of Chinese Academy of Sciences,
Beijing 100190, China
[c] University of Science and Technology of China,
Hefei 230026, China
[‡] These authors contributed equally to this work.
Supporting information and ORCID(s) from the author(s) for this article are
available on the WWW under https://doi.org/10.1002/ejic.201900372.
In order to improve the catalytic activity and stability, the
galvanic displacement method is taken as an alternative
method. The galvanic displacement method is a facile one and
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Scheme 1. Synthetic process by galvanic displacement reaction.
widely used in preparing bimetallic heterostructures with core– 2000ppm toluene gas and air with a total flow of 100 mL min–1,
shell, hollow, and nanocage structures.[19] Thus, it can be used which made sure the GHSV of 60 000 mL g–1 h–1 over 100 mg
to deposit noble metal on the support to obtain a tight interfa- catalyst. Figure 1 shows that the toluene conversion increased
cial interaction between two metal components. Our group[20] with the temperature rising. For convenience, the catalytic ac-
prepared PdNi/Al2O3 catalyst with galvanic displacement tivity of toluene combustion over the catalysts was represented
method and then found the catalytic activity and stability both by T90, as shown in Table S1. As can be seen from Figure S1
were excellent for methane combustion. Xu et al.[21] also used and Table S1, the catalytic activity of toluene combustion over
the galvanic displacement method to prepare Pd-CuO/γ-Al2O3 Pt/Co3O4-GD prepared at different calcination temperatures
catalyst with notable catalytic activity and stability for the com- from 400 °C to 700 °C increased in the following order:
plete oxidation of benzene.
Pt/Co3O4-GD-400 °C(T90 = 179 °C) < Pt/Co3O4-GD-700 °C(T90 =
164 °C) < Pt/Co3O4-GD-500 °C(T90 = 157 °C) < Pt/Co3O4-
600 °C(T90 = 150 °C). Thus we chose to use an optimum calcina-
tion temperature of 600 °C during the catalysts preparation
process with different methods including wetness impregnation
and nanoparticle loading methods. The results in Figure 1 and
In this work, we used Co3O4 as the support to prepare
Pt/Co3O4 catalyst via galvanic displacement method (donated
as Pt/Co3O4-GD). The synthetic process by galvanic displace-
ment reaction is shown in Scheme 1. Firstly, Co3O4 was reduced
by H2 at 250 °C for 0.5 h to obtain Co0 nanoparticles on the
surface of the support. Then Pt0 nanoparticles deposited on
the surface of the support by a displacement reaction at room
temperature for 2 h as follows: Co0 + Pt2+ → Co2+ + Pt0. Finally,
the sample was calcined in air at 600 °C for 5 h to obtain Pt/
Co3O4-GD catalyst. As a contrast, Pt/Co3O4 were prepared by
incipient-wetness impregnation method (donated as Pt/Co3O4-
WI) and nanoparticle loading method (donated as Pt/Co3O4-
NPs), respectively. All of the catalysts were further applied for
the consumption of toluene, which was one of the typical VOCs,
and characterized by the powder X-ray diffraction (XRD), trans-
mission electron microscopy (TEM), hydrogen temperature-
programmed reduction (H2-TPR), oxygen temperature-pro-
grammed desorption (O2-TPD) and X-ray photoelectron spectro-
scopy (XPS). The experiment results indicated that the catalytic
activity of Pt/Co3O4-GD was much higher than Pt/Co3O4-WI and
Pt/Co3O4-NPs for complete oxidation of toluene. Besides, the
results of a lifetime experiment revealed that Pt/Co3O4-GD pos-
sessed excellent stability. According to catalysts characterization
results, the superior catalytic activity and stability of Pt/Co3O4-
GD were due to its excellent oxygen mobility, high surface
chemisorbed oxygen species concentration and the strong in-
teraction between Pt and support Co3O4.
Table S1 show that the catalytic activity of Pt/Co3O4-GD(T90
=
150 °C) prepared by galvanic displacement method was much
better than Pt/Co3O4-NPs (T90 = 207 °C), Pt/Co3O4-WI (T90
228 °C) and the support Co3O4 (T90 = 238 °C).
=
Figure 1.Toluene conversion over Pt/Co3O4-GD, Pt/Co3O4-WI, Pt/Co3O4-NPs
and Co3O4. Reaction conditions:100 mg catalyst, 2000ppm toluene, air, total
flow rate = 100 mL min–1, GHSV = 60 000 mL g–1 h–1
.
Results and Discussion
Toluene combustion has been researched over catalysts pre-
Table S1 summarizes the catalytic activity for toluene com-
pared with different methods under a mixed gas consisting of bustion over a variety of catalysts that was reported in the refer-
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ences. Comparing to the other catalysts reported in the referen-
ces, the catalytic activity of Pt/Co3O4-GD (T90 = 150 °C) in this
work showed an excellent performance.
The XRD patterns of Co3O4 and Pt/Co3O4 prepared by three
methods are shown in Figure 2. For each sample, the diffraction
peaks at 19.00°, 31.27°, 36.85°, 44.81°, 55.66°, 59.36°and 65.24°
were observed, which were assigned to the (111), (220), (311),
(400), (422), (511) and (440) planes of the Co3O4 phase (JCPDS
42–1467) with a space group of Fd3m. In addition, no Pt diffrac-
tion peaks could be observed in the XRD patterns of the sam-
ples and the reason should be the low loading of noble metal
Pt and the high dispersion of Pt NPs.
Figure 3. Representative TEM and HRTEM images of Pt/Co3O4-GD (a,b,c), Pt/
Co3O4-WI (e,d,f), Pt/Co3O4-NPs (g,h,i) samples and corresponding size distri-
butions of Pt clusters.
had two reduction peaks at the temperature of 281 °C and
338 °C, which indicated the reduction reaction from Co3O4 to
CoO and finally to metallic Co.[25] After the incorporation of Pt
species, it was observed from the H2-TPR results in Figure 4 that
the reduction peaks of Pt/Co3O4-GD, Pt/Co3O4-WI and Pt/Co3O4-
NPs shifted to much lower temperature comparing with sup-
port Co3O4. The decrease of reducing peaks temperature of
Pt/Co3O4 catalysts was probably attributed to the spillover of
H2 from Pt to Co3O4.[26] Therefore, the incorporation of Pt spe-
cies was beneficial to improve the redox property of catalysts,
which was related to the catalytic performance of toluene com-
bustion reaction.
Figure 2. XRD pattern of Co3O4 and Pt/Co3O4 prepared by three methods.
Figure 3 shows representative TEM and HRTEM images of
Pt/Co3O4 catalysts prepared with three methods. All of the
Pt/Co3O4 catalysts exhibited surface lattice spacings of
0.244 nm and 0.227 nm, which corresponded to (311) crystal
planes of Co3O4 and (111) crystal planes of Pt, respectively. The
metal Pt NPs of Pt/Co3O4-GD possessed an average particle size
at 1.91 nm while that of Pt/Co3O4-WI had an average particle
size at 1.32 nm. For Pt/Co3O4-NPs, the Pt NPs were too small to
be seen in the TEM and HRTEM images, which maybe resulted
from the redispersion behavior of Pt on support.[22] The average
size of Pt NPs of Pt/Co3O4 catalysts increase in the following
order: Pt/Co3O4-NPs < Pt/Co3O4-WI < Pt/Co3O4-GD, which indi-
cated that the catalytic activity of catalysts got stronger when
the Pt NPs increased within certain limits. Chen et al.[23] re-
searched the size effect over Pt/ZSM-5 and found that the pro-
file between the catalytic performance for toluene combustion
and the Pt NPs size presented volcanic distribution and the
optimal average size of Pt NPs was 1.9 nm. Peng et al.[24] came
to a similar conclusion about the size effect over Pt/CeO2 for
toluene combustion and the optimal average size of Pt NPs was
1.8 nm. Therefore, for Pt NPs supported on Co3O4, it probably
existed an optimal average size of Pt NPs and 1.91 nm was the
nearest one to the optimal average size among the three kinds
of Pt/Co3O4 catalysts.
Figure 4. H2-TPR of Co3O4 and Pt/Co3O4 prepared by three methods.
The H2-TPR of support Co3O4, Pt/Co3O4-GD, Pt/Co3O4-NPs
Generally, the desorption of oxygen with the increase of
and Pt/Co3O4-WI were shown in Figure 4. The support Co3O4 temperature by the following process: physically adsorbed oxy-
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–
gen (O2)→chemically adsorbed oxygen (O2 ,O–)→lattice oxy-
gen (O2–) and the physically adsorbed oxygen was easiest to
desorb while the lattice oxygen was the most difficult to de-
sorb.[27] The temperature-programmed desorption of oxygen
(O2-TPD) curves of a series of Pt/Co3O4 and Co3O4 support are
presented in Figure 5 and include three peaks (α,ꢀ,γ), described
to the desorb of physically adsorbed oxygen, chemically ad-
sorbed oxygen and lattice oxygen. For Pt/Co3O4-GD, the peak
position of ꢀ peak and γ peak (289 °C, 650 °C) were lower than
that of the other samples. That is to say, the mobility of chemi-
cally adsorbed oxygen and lattice oxygen, which was beneficial
to the exchange and transfer of different oxygen species,[15b]
was the best among these catalysts.
The XPS technique was carried out to research the surface
compositions, oxygen species and metal oxidation states of
support Co3O4, Pt/Co3O4-GD, Pt/Co3O4-NPs and Pt/Co3O4-WI.
Figure 6 showed the O 1s, Co 2p, Pt 4f XPS spectra of these
samples.
Figure 5. O2-TPD of the samples.
Figure 6. O 1s(a), Co 2p(b), Pt 4f(c) XPS spectra of the samples.
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The O 1s XPS spectra of the catalysts are shown in Figure 6a,
Moreover, as suggested by the catalytic mechanism shown
which were fitted into three component peaks. The deconvolu- in Figure 7, C7H8 preferentially dissociates into CHn and OH spe-
tion of O 1s showed peaks at 529.6eV, 531.3eV and 533.0eV, cies on the surface of PtOx, and its own valence state decreases
ascribed to the lattice oxygen (Olat), chemisorbed oxygen spe- to PtOx-1. And then these species react with chemisorbed oxy-
–
cies (Oads, such as O2 ,O– and O22–) and adsorbed molecular gen species (Oads) species which migrate from Co3O4 surface to
water or hydroxyl groups, respectively.[28] As shown in Table 1, Pt-Co3O4 interface to form CO2 and H2O. On the other hand,
the molar ratio of Oads/(Oads + Olat + Owater) increased as this The Oads species migrate from the support to Pt-Co3O4 interface
follow: Co3O4 (31.8 %) < Pt/Co3O4-WI (36.1 %) < Pt/Co3O4-NPs to re-oxidize PtOx-1 to PtOx and transform to lattice oxygen spe-
(39.3 %) < Pt/Co3O4-GD (47.6 %). Such results were consistent cies (OL). Thus, the oxygen mobility and Oads species have great
with the increasing order of catalytic activity of the catalysts. effect on the overall catalytic circus. The mobility of oxygen
The higher ratio of chemisorbed oxygen species (Oads) signifies species is more excellent and the Oads species concentration is
more oxygen vacancies, which can absorb and activate the gas higher, and the catalytic rate can be more efficient.
phase oxygen molecules to enhance catalytic activity of the
catalysts for toluene combustion.
Table 1. XPS data measured for Co3O4 and Pt/Co3O4 catalysts.
Catalyst
Co3O4
Pt/Co3O4-WI 36.1 %
Pt/Co3O4-NPs 39.3 %
Pt/Co3O4-GD 47.6 %
Oads/(Oads + Olat + Owater
)
Co3+/(Co2++Co3+
)
BE value of Pt 4f7/2
31.8 %
64.1 %
58.3 %
54.1 %
47.8 %
–
74.2eV
74.3eV
74.5eV
The Co 2p XPS spectra of the catalysts were shown in
Figure 6b, which had two peaks, ascribed to Co 2p3/2 and Co
2p1/2. The Co 2p3/2 peak can be fitted at 779.5eV and 780.8eV,
which could be attributed to Co3+ and Co2+, respectively.[29] For
Co 2p1/2 peak, the Co3+ and Co2+ were marked at 794.4eV and
796.1eV, respectively. As summarized in Table 1, the molar ratio
of Co3+/(Co2++Co3+) decreased as this follow: Co3O4 (64.1 %) >
Pt/Co3O4-WI (58.3 %) > Pt/Co3O4-NPs (54.1 %) > Pt/Co3O4-GD
(47.8 %). That is to say, the lower proportion of Co3+, the higher
the catalytic activity. The proportion of Co3+ was negative corre-
late to the proportion of oxygen vacancies, so the conclusion
resulted from the Co 2p XPS spectra was similar to that of O 1s
XPS spectra.
Figure 7. Probable catalytic mechanism.
Conclusions
In this work, the catalysts of Pt/Co3O4 were prepared by the
galvanic displacement method (Pt/Co3O4-GD), the nanoparticle
loading method (Pt/Co3O4-NPs), and the incipient-wetness im-
pregnation method (Pt/Co3O4-WI). Pt/Co3O4-GD exhibited the
best catalytic activity (T90 = 150 °C) relative to Pt/Co3O4-NPs
(T90 = 207 °C), Pt/Co3O4-WI (T90 = 228 °C), and Co3O4 (T90
=
238 °C) at GHSV = 60 000 mL g–1 h–1. According to the charac-
terization results of the catalysts, the catalytic performance of
these catalysts was related to the oxygen mobility, the surface
chemisorbed oxygen species, and the interaction between Pt
and Co3O4. The Pt/Co3O4-GD exhibited the best catalytic activ-
ity because it had the most distinguished oxygen mobility, the
highest surface chemisorbed oxygen species concentration and
the strongest interaction between Pt and support Co3O4 among
all of the Pt/Co3O4 catalysts. Moreover, The Pt/Co3O4-GD had
outstanding stability reflected in a continuous 100 h on-stream
toluene combustion lifetime experiment without catalytic activ-
ity decline. In summary, the Pt/Co3O4-GD prepared with the
galvanic displacement method possessed excellent catalytic ac-
tivity and stability for toluene combustion at low temperature
as compared to traditional catalyst preparation methods, and
the galvanic displacement method can be applied to prepare
other catalysts to obtain outstanding catalytic performance in
the future.
The Pt 4f XPS spectra of the samples were shown in Fig-
ure 6c. The band energy value of Pt 4f7/2 increased as this fol-
low: Pt/Co3O4-WI (74.2eV) < Pt/Co3O4-NPs (74.3eV) < Pt/Co3O4-
GD (74.5eV). This indicated that the Pt/Co3O4-GD catalyst had
a strongest interaction between Pt and support Co3O4 via elec-
tron density transferring from the PtOx nanoparticles to the
support Co3O4, followed by Pt/Co3O4-NPs and Pt/Co3O4-WI,
which can be described as the reaction Pt0
+ =
Co3+
Ptδ++Co2+ [9c]
.
Therefore, the Pt/Co3O4-GD catalyst possessed
the highest Oads/(Oads + Olat + Owater) molar ratio, highest band
energy (BE) value of Pt 4f7/2 and lowest Co3+/(Co2++Co3+) molar
ratio compared with the others. So, the Pt/Co3O4-GD exhibited
the best catalytic activity among all samples.
Lifetime experiment was carried out over Pt/Co3O4-GD at
150 °C for continuous 100 h to test the stability of the catalyst.
As shown in Figure S3, the catalytic activity of Pt/Co3O4-GD
still kept 100 % conversion of toluene during the period of time,
which showed an excellent stability of Pt/Co3O4-GD. The XRD
patterns of the fresh and used Pt/Co3O4-GD are shown in Figure
S2, which indicated that the structure remained unchanged
after being used. The TEM results of the used Pt/Co3O4-GD (Fig-
ure S4) revealed that the size of Pt nanoparticles was almost
equal to that of the unused.
Experimental Section
Chemicals: Cobalt(II) nitrate hexahydrate (Co(NO3)2·6H2O), sodium
hydroxide(NaOH) and toluene(C7H8) were purchased from Aladdin.
Platinum(II) nitrate solution,(Pt(NO3)2 (Pt mass concentration: 19 %)
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)were purchased from Sino-Platinum Metals Co. Ltd. All regents (30 mL min–1) at 200 °C for 1 h to remove water. After cooling to
were used without further purification.
40 °C, the quartz tube reactor with a 50 mg sample was flowed
with a mixture gas of 5vol.-% O2/Ar mixed gas for 30 min and then
pure He gas was switched to purge unabsorbed O2 molecules for
1 h. In the end, the sample was heated from 40 °C to 700 °C in He
Preparation of Co3O4: Co(NO3)2·6H2O(0.06 mmol, 17.46 g) was dis-
solved in 50 mL deionized water. The aqueous solution was added
dropwise excess 3 M NaOH aqueous solution and stirred for 1 h
subsequently. The solid was centrifuged, washed with deionized
water for several times, dried at 80 °C overnight and calcined in air
at 600 °C for 5 h to obtain black powder.
gas atmosphere (30 mL min–1) at a heating rate of 10 °C min–1
.
X-ray photoelectron spectroscopy (XPS) was conducted on a VG
Thermo ESCALAB 250 spectrometer with a focused monochromatic
Al Kα X-ray(1486.7eV) source which was operated at 120 W and
500 μm-diameter beams. For known standards, the carbon C 1s at
284.8eV was used to calibrate the binding energy scale. The decon-
volution of XPS peak was performed with XPSPEAK.
Preparation of Pt/Co3O4-GD: 400 mg Co3O4 was added into
a U-type tube with a flow of 5 % H2/Ar mixed gas at 250 °C for
0.5 h. After cooling to room temperature, the 5 % H2/Ar mixed gas
was replaced by high-purity Ar gas and then a mixed solution con-
sisting of 100 mg Pt(NO3)2 aqueous solution(Pt mass concentration:
19 %) and 10 mL deionized water was added into the U-type tube
to make the power immerse in the liquid completely. After mag-
netic stirring for 2 h, the black solid was filtered, washed with deion-
ized water for several times to remove the residual Pt2+, dried at
80 °C overnight and finally calcined in air at 600 °C for 5 h. The
accurate Pt loading was determined to be 3.5w% according to
ICP-OES analyses (Thermo Scientific ICAP6000, USA). For the sake
of contrast, the Pt loading of Pt/Co3O4-WI and Pt/Co3O4-NPs were
both consistent with Pt/Co3O4-GD (3.5w%).
Measurement of Catalytic Activity: The catalytic activity was
measured in a fixed-bed quartz tubular microreactor (i.d., 6 mm;
length, 350 mm) with 100 mg catalyst. A flow of air (20vol.-%O2,
80vol.-%N2) passed through a volumetric flask filled with toluene in
an ice-bath kept at 0 °C to generated and then injected toluene
gas. A compounded reactant gas consisting of 2000ppm toluene
and air was formed by introducing another balanced air and the
total flow of mixture reactant gas was kept at 100 mL min–1 to
afford a gas hourly space velocity (GHSV) of 60 000 mL g–1 h–1
.
The gas types and concentrations of reactants and products were
continuously monitored by an on-line quadrupole mass spectrome-
ter (QIC-20, Hiden) from 30 °C to 300 °C at a heating rate of 1 °C
min–1. The ion peaks (m/z) of substances were determine as follows:
91 toluene, 44 CO2, 18 H2O, 28 N2, 32 O2.
Preparation of Pt/Co3O4-WI: The Pt/Co3O4-WI was prepared by in-
cipient-wetness impregnation method. Typically, Co3O4, a certain
amount of Pt(NO3)2 aqueous solution (Pt mass concentration: 19 %)
and deionized water were mixed with magnetic stirring at 80 °C
until the liquid evaporated to dryness. Then the solid was dried at
80 °C overnight and calcined in air at 600 °C for 5 h to obtain 3.5w%
Pt/Co3O4-WI catalyst.
Acknowledgments
We would like to acknowledge the financial support from the
National Key Research and Development Program of China
(2016YFC0204301) and the National Natural Science Foundation
of China (21872133). We also gratefully acknowledge the finan-
cial support provided by the Youth Innovation Promotion Asso-
ciation, CAS, China (2018263).
Preparation of Pt/Co3O4-NPs: The Pt/Co3O4-NPs was prepared by
nanoparticle loading method. For the first step, it is necessary to
synthesize Pt nanoparticles.[23,30] Typically, a 12.5 mL ethylene
glycol solution containing 250 mg H2PtCl6·6H2O was added in an-
other 12.5 mL ethylene glycol NaOH solution(0.5 M). The mixture
solution was heated at 160 °C for 3 h with pure N2 gas atmosphere
and then added 1 mL HCl solution (2 M) to precipitate the nano-
particles. After all, Pt nanoparticles were centrifuged and then dis-
persed in ethanol which contained 12.2 mg PVP (Mw = 29 000).
Keywords: Platinum · Cobalt · Heterogeneous catalysis ·
Catalytic combustion · Toluene
For Pt/Co3O4-NPs, Co3O4 and a certain amount of Pt colloid solution
mixed together and then supersonic for 0.5 h. The rest of the syn-
thetic process was same as that of preparation of Pt/Co3O4-WI.
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14977–14980; b) J. H. Park, A. H. Goldstein, J. Timkovsky, S. Fares, R.
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[2] S. Salvador, J. M. Commandre, Y. Kara, Appl. Therm. Eng. 2006, 26, 2355–
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Catalyst characterization: The powder X-ray diffraction (XRD) was
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Received: April 3, 2019
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Catalytic Combustion of VOCs
X. Hu, Z. Zhang, Y. Zhang,*
L. Sun, H. Tian, X. Yang* .................. 1–8
Synthesis of a Highly Active and Sta-
ble Pt/Co3O4 Catalyst and Its Appli-
cation for the Catalytic Combustion
of Toluene
A Pt/Co3O4 catalyst was prepared by and outstanding stability reflected in
the galvanic displacement method, a continuous 100 h on-stream toluene
which exhibited excellent catalytic ac- combustion lifetime experiment with-
tivity for toluene combustion (T90
=
out loss in catalytic activity.
150 °C at GHSV = 60 000 mL g–1 h–1)
DOI: 10.1002/ejic.201900372
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