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CeO2–ZrO2–SnO2 catalyst supported on mesoporous silica SBA-16
Accepted Manuscript Title: Liquid-phase oxidation of phenol in facile condition using Pt/CeO2 –ZrO2 –SnO2 catalyst supported on mesoporous silica SBA-16 Authors: Abdul Rohman Supandi, Naoyoshi Nunotani, Nobuhito Imanaka PII: DOI: Reference:
S2213-3437(17)30376-7 http://dx.doi.org/doi:10.1016/j.jece.2017.07.072 JECE 1787
To appear in: Received date: Revised date: Accepted date:
22-4-2017 27-7-2017 28-7-2017
Please cite this article as: Abdul Rohman Supandi, Naoyoshi Nunotani, Nobuhito Imanaka, Liquid-phase oxidation of phenol in facile condition using Pt/CeO2–ZrO2–SnO2 catalyst supported on mesoporous silica SBA-16, Journal of Environmental Chemical Engineeringhttp://dx.doi.org/10.1016/j.jece.2017.07.072 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Liquid-phase oxidation of phenol in facile condition using Pt/CeO 2–ZrO2–SnO2 catalyst
supported on mesoporous silica SBA-16
Abdul Rohman Supandi, Naoyoshi Nunotani, and Nobuhito Imanaka*
Department of Applied Chemistry, Faculty of Engineering, Osaka University,
2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan
Corresponding author: [email protected]
Tel. +81-6-6879-7352; Fax. +81-6-6879-7354
GRAPHICAL ABSTRACT
Highlights The oxygen release and storage abilities of CZ/SBA were enhanced by doping SnO2. Phenol was effectively removed by Pt/CZSn/SBA at 80 °C under atmospheric pressure. Phenol removal percentage reached up to 91% by Pt/CZSn/SBA after 6 h reaction.
1
Abstract A Pt/CeO2–ZrO2–SnO2/SBA-16 catalyst was prepared by using co-precipitation and impregnation methods for
removing phenol through liquid-phase oxidation at moderate condition. The platinum active catalyst with a
CeO2–ZrO2–SnO2 oxygen promoter loaded on mesoporous silica Santa Barbara Amorphous No. 16 (SBA-16) possesses
the large surface area with appropriate pore size and high oxygen release and storage abilities, caused by synergistically
reduction of Ce4+ to Ce3+ with Sn4+ to Sn2+. This catalyst was effective in removing phenol at moderate temperature of
80 °C under atmospheric pressure without supplying any oxidants or applying photo-irradiation, wherein the phenol
removal percentage reached up to 91%.
Keywords:
Catalyst, Liquid-phase oxidation, Phenol, Rare earth oxide, Ceria, Fluorite-type
1.
Introduction
The increasing attention towards the environment is important for the sustainable development of the industrial
sector, where many harmful compounds are generated as byproduct and/or the excess raw material. Many organic
pollutants are disposed as wastewater from industrial processes. Phenol is one of the most common organic pollutants
encountered in the wastewater, because it has been used as raw material in many kinds of industries for the production,
such as bisphenol A, phenol resins, and acetyl-salicylic acid [1–3]. However, phenol is toxic compound for human
health and may affect kidney, heart, and the nervous center system [4–5]. It is also lethal to aquatic life even at low
concentration [6–8]. Therefore, there is a requirement to develop an applicable process for phenol removal from 2
wastewater stream.
Several phenol removal methods, including biological treatment [7–8] and activated carbon adsorption [9–10],
have been developed; however, these processes have problems, e.g. control of pH and temperature for
microorganisms and replacement of activated carbon. Although the oxidation processes were reported by using
strong oxidizing additives, such as hydrogen peroxide [15] and peroxymonosulfate [16], they require constant supply
of hazardous oxidants. Hence, we focused on a catalytic liquid-phase oxidation using oxygen gas supply (catalytic
wet air oxidation), because this process has many benefits, such as a simple, sustainable, and environmental friendly
procedure [11–14]. In this method, promoters are used to storage oxygen species from dissolved oxygen gas in the
liquid-phase and release it toward a catalyst activator. CeO2–ZrO2 solid solution is well-known as an oxygen
promoter in automotive exhaust catalysts, because it has high oxygen release and storage abilities, due to easy
reversible process of redox reaction of Ce4+/Ce3+ couple [17–20]. To date, it is reported that 92% of phenol was
removed by using platinum supported on CeO2–ZrO2 after the reaction at high operational temperature (160 °C) and
high oxygen partial pressure (2 MPa) [14]. Thus, it still remains the challenging task to remove phenol at the
moderate reaction conditions, i.e., at lower temperatures (below 100 °C) and under atmospheric pressure.
In order to solve problem mentioned above, we introduced SnO2 into the CeO2–ZrO2 lattice resulting CeO2–ZrO2–SnO2 solid solution. The introduction of SnO2 enhances the oxygen storage and release abilities due to
the valence change of Sn4+/2+ [21–23]. In addition, surface area is also an important issue in catalyst field, because the
catalyst with large surface area possesses high amount of active site. Here, we selected a mesoporous silica SBA-16
(Santa Barbara Amorphous No. 16) as the catalyst support, which has large surface area with cage-like mesoporous
structure that may immobilize the catalyst and promoter particles [24–26]. From these concepts, we prepared the 3
catalyst, that consists of the platinum activator and the CeO2–ZrO2–SnO2 promoter supported on SBA-16, to remove
phenol in facile operating conditions (operating temperature was less than 100 °C and under atmospheric pressure)
without any oxidant supply. For this catalyst, we investigated the catalytic activity for phenol removal in the
liquid-phase.
2.
Material and method
2.1. Catalyst preparation
SBA-16 was prepared via a hydrothermal reaction by modifying preparation method reported in the studies [24–26]. Pluronic F-127 (1.6 g) was dissolved into hydrochloric acid 0.2 mol·L−1 (90 mL), and then
1,3,5–trimethylbenzene (1.1 mL) was added. The mixture was stirred at 35 °C for 3 h. Subsequently, tetraethyl
orthosilicate (7.1 mL) was added into the mixture, and further stirred for 20 h. The mixture was heated inside the
Teflon bottle in sealed brass vessel at 140 °C for 24 h. The precipitated product was separated by filtration and dried at room temperature for a day. The dried sample was then calcined at 400 °C for 4 h with air gas flow (20 mL·min−1).
16 wt% CeO2–ZrO2–SnO2/SBA-16 was prepared by co-precipitation method. The composition of each metal oxide was adjusted to be Ce0.68Zr0.17Sn0.15O2 by mixing 1.0 mol∙L−1 Ce(NO3)3 solution (0.85 mL), 0.1 mol∙L−1
ZrO(NO3)2 solution (2.13 mL), and SnC2O4 powder (38.75 mg). The mixture of solution was previously stirred at
room temperature for 30 min before adding the SBA-16 powder (1.055 g) and further stirred for 30 min. The pH of
mixture was adjusted to be 11 by dropwise addition of 5.6% ammonia solution. Afterwards, the mixture was stirred at
room temperature for 12 h. The precipitated product was separated by filtration and then calcined at 900 °C for 1 h.
Pt was loaded on 16 wt% CeO2–ZrO2–SnO2/SBA-16 by impregnation method. The platinum in ethanol stabilized 4
with polvinylpyrrolidone (Pt-PVP, Pt: 4.0 wt%) was mixed with 16 wt% CeO2–ZrO2–SnO2/SBA-16, wherein the
amount of loaded platinum was adjusted to be 7 wt%. The mixture was sequentially stirred at room temperature for 6
h and then the solvent was vaporized at 180 °C. The dried sample was calcined at 500 °C for 4 h. For comparison, we
also prepared 7 wt% Pt/ 16 wt% Ce0.8Zr0.2O2/SBA-16 and 7 wt% Pt/SBA-16 by similar procedure. Hereafter, we
denote 7 wt% Pt/ 16 wt% Ce0.68Zr0.17Sn0.15O2/SBA-16, 7 wt% Pt/ 16 wt% Ce0.8Zr0.2O2/SBA-16, 7 wt% Pt/SBA-16, and
SBA-16 as Pt/CZSn/SBA, Pt/CZ/SBA, Pt/SBA, and SBA, respectively.
2.2. Catalyst Characterization
The prepared catalysts were analyzed by X-ray powder diffraction and small angle X-ray scattering (XRD and
SAXS; SmartLab, Rigaku) with Cu-Kα radiation in the 2Ө range 10–70° and 0.1–1.5°, respectively. The X-ray
fluorescent (XRF, supermini 200 ZSX100, Rigaku) analysis was carried out to confirm the exact composition of
catalysts. The N2 gas adsorption-desorption measurements (Tristar 3000, Micromeritics) were carried out at −196 °C
to measure the Brunauer-Emmett-Teller (BET) surface area and the porosity of the catalysts. Temperature program reduction (TPR) was carried out in a 5 vol% H2−Ar flow (50 mL·min−1) with a heating rate of 5 °C·min−1 (Belcat-B,
Bel Japan). This TPR experiment was followed by the oxygen storage capacity (OSC) measurement using pulse
injection method at 500 °C.
2.3. Catalytic performance test
The catalytic liquid-phase oxidation of phenol was carried out in the oil bath using a 300 cm3 three necked flask
equipped with an opened condenser at 80 °C in the atmospheric pressure and magnetically stirred (500 rpm). An 5
aqueous solution of phenol 1000 ppm (10 mL) and the catalyst (0.4 g) were mixed in the flask. After the reaction, the
aliquot was separated by using centrifuge with rotating speed 14000 rpm for 10 min (Allegra 64R centrifuge,
Beckman Coulter). Representative samples after reaction were sequentially withdrawn and mixed with naphthalene
solution in methanol (1000 ppm) as the internal standard substance with a volume ratio of 1:1. The mixture of solution
was then analyzed by using gas chromatography-mass spectrometry (GC-MS; GCMS-QP2010 Plus, Shimadzu) to
evaluate the phenol removal percentage. The phenol removal percentage was calculated using the following equation: (Phenol removal percentage)
C0 C
100%
C0
where C0 and C are phenol concentration before and after reaction, respectively. In addition, we also determined the rate constant by plotting the −ln[C/C0] vs. the reaction time (t). The rate
constant (k) was calculated as pseudo-first-order reaction using the following equation: dC dt
3.
k C0 .
Results and discussion
3.1. Characteristic of catalysts
Fig. 1 shows XRD patterns of the CZ/SBA and CZSn/SBA oxygen promoters, and the Pt/CZSn/SBA, Pt/CZ/SBA,
and Pt/SBA catalysts. The XRD patterns of Pt/CZSn/SBA and Pt/CZ/SBA were indexed as the fluorite-type structure
which can be observed in XRD patterns of CZ/SBA and CZSn/SBA, platinum, and SBA, and no impurity phase was
observed. After the introduction of SnO2 into the CZ lattice, the diffraction peaks of fluorite-type structure were
slightly shifted to higher angle as shown in magnified XRD patterns of CZ/SBA and CZSn/SBA at angular position of
54–60°, i.e., the lattice parameter decreases. This lattice shrinkage was caused by the replacement of Ce4+ ion (ionic 6
radius: 0.097 nm [27]) and Zr4+ ion (0.084 nm [27]), by the smaller ionic-size Sn4+ ion (0.081 nm [27]).
The compositions measured by XRF and the surface areas of the catalysts are shown in Table 1. The measured
compositions of the prepared catalysts are in good agreement with the feed compositions within experimental errors. While the prepared SBA support has large surface area of 668 m2·g−1, the insertion of platinum and/or fluorite-type
oxides led the decrease of surface area, suggesting that platinum and/or fluorite-type oxides were inserted into the
SBA support.
Fig. 2 shows the SAXS patterns of the catalysts. These patterns confirmed the regular arrangement of
mesoporous SBA before and after the insertion of platinum and/or fluorite-type oxides. Two diffraction peaks were
observed in SBA pattern at angular position of 0.47° and 0.89°, correspond to (110) and (200) porous planes,
respectively [24–26]. After the insertion of platinum and/or fluorite-type oxides into mesoporous SBA, the diffraction
peaks were shifted to the higher angle and their intensities were also decreased, indicating the decrease of the pore size
and the slight loss of the periodicity of pores. Therefore, platinum and/or fluorite-type oxides were successfully
inserted into mesoporous SBA. These results are supported by the pore size distribution and N 2 adsorption–desorption
isotherm analysis as shown in Fig. 3. The N2 adsorption–desorption isotherm patterns of SBA showed the
distinctiveness of hysteresis curve, classified to the type IV in IUPAC classification, which is typical for the
mesoporous material [28]. After Pt and/or oxygen promoters loading, the similar hysteresis shapes were obtained,
indicating that the mesoporous structure was still maintained. In addition, the decrease of the intensity of adsorbed
volume corresponds to the decreasing of pore size, as shown in inset of Fig. 3, due to the insertion of Pt and/or oxygen
promoters [21].
7
3.2. Catalytic performance evaluation
The catalytic performance tests of liquid-phase oxidation of phenol were carried out by using the Pt/CZSn/SBA,
Pt/CZ/SBA, and Pt/SBA catalysts at 80 °C under atmospheric pressure as reaction time function. From the GC-MS
spectra (Fig. S1), the phenol removal percentages were calculated and the results are shown in Fig. 4(a). In order to
investigate the evaporated phenol and adsorbed phenol into the mesoporous SBA, liquid-phase oxidation of phenol in
the absence of catalyst and using SBA were also carried out. In the absence of catalyst, ca. 15% phenol was removed, in
other words, evaporated. Whereas, by using SBA, the phenol removal percentage was slightly higher than the absence
case, indicating that ca. 4% of phenol was adsorbed into the SBA support. For Pt/CZSn/SBA, Pt/CZ/SBA, and Pt/SBA,
the phenol removal percentage was increased with increasing the reaction time during the catalytic reaction process. By
using oxygen promoters of CZ and CZSn, the catalytic activities enhanced compared to that of Pt/SBA. The presence of
oxygen promoters inside the catalyst well provided oxygen species to Pt for oxidizing phenol. In the presence of oxygen
promoter, the introduction of SnO2 into the CZ lattice successfully enhanced the catalyst activity, and the phenol
removal percentage using Pt/CZSn/SBA reached up to 91% after the reaction for 6 h. This enhancement in catalytic
activity is attributed to the enhanced oxygen release and storage abilities by introducing SnO 2. Furthermore, the phenol
removal percentage using Pt/CZSn/SBA is comparable with that of the previous Pt/CZ sample (~92%), whose reaction
conditions were extremely severe (160 °C, 2 MPa) [14]. For Pt/CZSn/SBA after the reaction, the collapse of the crystal
structure and the leaching of metal from Pt/CZSn/SBA were not observed (Fig. S2 and Table S1). In addition, the
reproducibility of the catalytic activity was confirmed as shown in Fig. S3.
Fig. 4(b) depicts the plot of −ln (C/C0) vs. the reaction times. Since the graphic curves are almost linear, the phenol
removal reaction would proceed by pseudo-first-order reactions. These results are appropriate with previous study, in 8
which it is reported that the phenol degradation using heterogeneous catalyst followed first-order reaction [16]. Based
on the first-order reaction power law, we estimated the rate constant of phenol oxidation using the catalysts; i.e., 0.39 h−1, 0.31 h−1, and 0.24 h−1 for Pt/CZSn/SBA, Pt/CZ/SBA, and Pt/SBA, respectively. Thus, liquid-phase oxidation of
phenol using a Pt/CZSn/SBA occurs faster than those using Pt/CZ/SBA and Pt/SBA.
The H2–TPR measurement of CZSn/SBA was carried out to investigate the reason of the high activity of
Pt/CZSn/SBA, and the result is shown in Fig. 5, with the data of CZ/SBA and SBA. There was not any peak in TPR
profile of SBA at temperatures lower than 500 °C, suggesting that SBA has no reduction activity at those temperatures.
Whereas, the presence of CZ over SBA-16 started to be reduced at 346 °C. Furthermore, the introduction of SnO 2 into
the CZ lattice drastically decreased the reduction temperature which started to be reduced at 220 °C and reached the
peak at 288 °C, likely due to the surface reduction of Ce4+ to Ce3+. This decrease of reduction temperature was caused
by synergistically reduction of Ce4+ to Ce3+ with Sn4+ to Sn2+ [19–21]. Additionally, another reduction peak was also
observed at 370 °C, which might correspond to the bulk reduction of the CZSn promoter over SBA-16. The oxygen
vacancy, formed by the reduction of Sn4+ to Sn2+, took part in increasing the oxygen mobility in the bulk structure of the
CZSn promoter. As shown in the inset of Fig. 5, the oxygen storage ability was also drastically increased by doping
SnO2, and the value was ca. three times higher than that of CZ/SBA. These properties of oxygen promoters took part in
providing the oxygen species to the platinum activator for oxidizing phenol.
In addition, we also investigated the presence of intermediate compounds in aliquot which are produced after
reaction for 6 h by GC-MS measurement (Fig. S1). After the reaction using Pt/SBA for 6 h, we found the acetic acid in
low concentration (~172 ppm), whereas this acetic acid was not detected when using Pt/CZ/SBA and Pt/CZSn/SBA. In
the case of Pt/CZSn/SBA, benzoquinone was detected as intermediate compound, while its concentration (~42 ppm) 9
was lower than the case for Pt/CZ/SBA (~82 ppm) and Pt/SBA (~100 ppm).
4.
Conclusion The Pt/CeO2–ZrO2–SnO2/SBA-16 catalyst has been successfully synthesized by dispersing platinum and
CeO2–ZrO2–SnO2 into the SBA-16 support, with the large surface area and the appropriate pore size. CeO2–ZrO2–SnO2/SBA-16 has the high reduction activity and oxygen storage ability compared to CeO2–ZrO2/SBA-16
and SBA-16, due to the synergistically redox reaction of Ce4+/3+ and Sn4+/2+. This property can be utilized in promoting
the oxidation on platinum as the active catalyst. The liquid-phase oxidation of phenol using the various catalysts were
carried out at 80 °C under atmospheric pressure without any other oxidant additives. The 7 wt% Pt/ 16 wt%
Ce0.68Zr0.17Sn0.15O2-δ/SBA-16 catalyst revealed the remarkable activity in removing phenol, and the phenol removal percentage reached up to 91% after 6 h reaction due to the effective supply of oxygen from the CeO 2–ZrO2–SnO2
promoter and the large surface area. The phenol removal mechanism was fitted as the pseudo-first-order reaction with rate constant of 0.39 h−1.
10
Acknowledgements
We would like to thank to Lake Biwa-Yodo River water Quality Preservation Organization for financially supporting
this work.
11
References [1] C. Ayral, C.J. Lebigue, F. Stüber, A.M. Wilhelm, H. Delmas, Catalytic wet air oxidation of phenolic compounds and mixtures over activated carbon: conversion, mineralization, and catalyst stability, Ind. Eng. Chem. Res. 49 (21) (2010) 10707–10714. [2] Z.P.G. Masende, B.F.M. Kuster, K.J. Ptasinski, F.J.J.G. Janssen, J.H.Y. Katima, J.C. Sxhouten, Platinum catalyzed wet oxidation of phenol in a stirred slurry reactor: A practical operation window, Appl. Catal. B: Environ. 41 (2003) 247–267. [3] Institute for Health and Consumer Protection European Chemicals Bureau, European Union risk assessment report: phenol, volume 64, revised edition. https://echa.europa.eu/documents/10162/3e04f30d-9953-4824-ba04-defa32a130fa, 2006 (accessed 17.02.17). [4] S.J. Kulkarni, J.P. Kaware, Review on research for removal of phenol from wastewater, Int. J. Sci. Res. Pub. 3 (4) (2013) 654–658. [5] S. Yang, W. Zhu, J. Wang, Z. Chen, Catalytic wet air oxidation of phenol over CeO2-TiO2 catalyst in the batch reactor and the packed-bed reactor, J. Hazard. Mater. 153 (2008) 1248–1253. [6] V.M. Brown, D.H.M. Jordan, B.A. Tiller, The effect of temperature on the acute toxicity of phenol to rainbow trout in hard water, Water Res. 1 (8-9) (1967) 587–594. [7] T-P. Chung, H-Y. Tseng, R-S. Juang, Mass transfer effect and intermediate detection for phenol degradation in immobilized Pseudomonas putida systems, Process Biochem. 38 (10) (2003) 1497–1507. [8] M. Kibert, W. Somitsch, K-H. Robra, Characterization of a phenol degrading mixed population by enzyme assay, Water Res. 34 (4) (2000) 1127–1134. [9] R.R. Karri, N.S. Jayakumar, J.N. Sahu, Modelling of fluidised-bed reactor by differential evolution optimization for phenol removal using coconut shells based activated carbon, J. Mol. Liq. 231 (2017) 249–262. [10] G.S. dos Reis, M.A. Adebayo, C.H. Sampaio, E.C. Lima, P.S. Thue, I.A.S. de Brum, S.L.P. Dias, F.A. Pavan, Removal of Phenolic Compounds from Aqueous Solutions Using Sludge-Based Activated Carbons Prepared by Conventional Heating and Microwave-Assisted Pyrolysis, Water Air Soil Poll. 228 (33) (2017) 1–17. [11] S. Keav, A. Martin, J. Barbier Jr., D. Duprez, Deactivation and reactivation of noble metal catalysts tested in the Catalytic Wet Air Oxidation of phenol, Catal. Today 151 (2010) 143–147. 12
[12] S. Keav, A.E. de los Monteros, J. Barbier Jr., D. Duprez, Wet air oxidation of phenol over Pt and Ru catalysts supported on cerium-based oxides: resistance to fouling and kinetic modelling, Appl. Catal. B: Environ. 150–151 (2014) 402–410. [13] A.E. de los Monteros, G. Lafaye, A. Cervantes, G.D. Angel, J. Barbier Jr, G. Torres, Catalytic wet air oxidation of phenol over metal catalyst (Ru, Pt) supported on TiO2–CeO2 oxides, Catal. Today 258 (2015) 564–569. [14] S. Nousir, S. Keav, J. Barbier Jr., M. Bensitel, R. Brahmi, D. Duprez, Deactivation phenomena during catalytic wet air oxidation (CWAO) of phenol over platinum catalysts supported on ceria and ceria–zirconia mixed oxides, Appl. Catal. B: Environ. 84 (2008) 723–731. [15] J. Guo, M. Al-Dahhan, Catalytic wet oxidation of phenol by hydrogen peroxide over pillared clay catalyst, Ind. Eng. Chem. Res. 42 (12) (2003) 2450–2460. [16] S. Muhammad, E. Saputra, H. Sun, H-M. Ang, M.O. Tade,́ S. Wang, Heterogeneous catalytic oxidation of aqueous phenol on red mud supported cobalt catalysts, Ind. Eng. Chem. Res. 51 (2012) 15351−15359. [17] S. Bedrane, C. Descorme, D. Duprez, Investigation of the oxygen storage process on ceria- and ceria–zirconia-supported catalysts, Catal. Today 75 (2002) 401–405. [18] P. Fornasiero, R. Dimonte, G.R. Rao, J. Kašpar, S. Meriani, A. Trovarelli, M. Graziani, Rh-loaded CeO2-ZrO2 solid-solutions as highly efficient oxygen exchangers: dependence of the reduction behavior and the oxygen storage capacity on the structural-properties, J. Catal. 151 (1995) 168–177. [19] C.E. Hori, H. Permana, K.Y. Simon Ng, A. Brenner, K. More, K.M. Rahmoeller, D. Belton, Thermal stability of oxygen storage properties in a mixed CeO2-ZrO2 system, Appl. Catal. B: Environ. 16 (1998) 105–117. [20] J. Kašpar, P. Fornasiero, M. Graziani, Use of CeO2-based oxides in the three-way catalysis, Catal. Today 50 (2) (1999) 285–298. [21] P.G. Choi, N. Nunotani, N. Imanaka, High catalytic efficiency in liquid-phase oxidation of 1,4-dioxane using a Pt/CeO2-ZrO2-SnO2/SBA-16 catalyst, Int. J. Appl. Ceram. Technol. 14 (2017) 9–15. [22] Q. Dong, S. Yin, C. Guo, T. Sato, Ce0.5Zr0.4Sn0.1O2/Al2O3 catalysts with enhanced oxygen storage capacity and high CO oxidation activity, Catal. Sci. Technol. 2 (2012) 2521–2524. [23] K. Yasuda, A. Yoshimura, A. Katsuma, T. Masui, N. Imanaka, Low-temperature complete combustion of volatile organic compounds over novel Pt/CeO2-ZrO2-SnO2/γ-Al2O3 catalysts, Bull. Chem. Soc. Jpn. 85 (2012) 522–526. 13
[24] H. Yotou, T. Okamoto, M. Ito, T. Sekino, S-I. Tanaka, Novel method for insertion of Pt/CeZrO 2 nanoparticles into mesoporous SBA-16 using hydrothermal treatment, Appl. Catal. A: Gen. 458 (2013) 137–144. [25] D. Zhao, Q. Huo, J. Feng, B.F. Chmelka, G.D. Stucky, Nonionic triblock and star diblock copolymer and oligomeric surfactant syntheses of highly ordered, hydrothermally stable, mesoporous silica structures, J. Am. Chem. Soc. 120 (24) (1998) 6024–6036. [26] S. Zuo, F. Liu, J. Tong, C. Qi, Complete oxidation of benzene with cobalt oxide and ceria using the mesoporous support SBA-16, Appl. Catal. A: Gen. 467 (2013) 1–6. [27] R.D. Shannon, Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides, Acta. Crystallogr. A32 (1976) 751–767. [28] K.S.W. Sing, D.H. Evereet, R.A.W. Haul, L. Moscou, R. Pierotti, J. Rouquerol, T. Siemieniewska, Reporting physisorption data for gas/solid systems with special reference to the determination of surface area and porosity, Pure Appl. Chem. 57 (4) (1985) 603–619.
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Figure captions Fig. 1. XRD patterns of CZ/SBA, CZSn/SBA, Pt/SBA, Pt/CZ/SBA, and Pt/CZSn/SBA. Fig. 2. SAXS patterns of SBA support, Pt/SBA, Pt/CZ/SBA, and Pt/CZSn/SBA catalysts. Fig. 3. N2 adsorption-desorption isotherms of SBA support, Pt/SBA, Pt/CZ/SBA, and Pt/CZSn/SBA catalysts. The BJH pore size distribution profiles are shown in the insets. Fig. 4. (a) Phenol removal percentage as reaction time function, (b) reaction rate constants of phenol oxidation by using the catalysts with error bars. Each solid line in Fig. 4(b) represents the regression line. Fig. 5. H2–TPR profiles of SBA support, CZ/SBA, and CZSn/SBA promoters.
15
Figure 1. A.R. Supandi et al.
16
Figure 2. A.R. Supandi et al.
17
Figure 3. A.R. Supandi et al.
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Figure 4. A.R. Supandi et al.
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Figure 5. A.R. Supandi et al.
List of Table Table 1. The measured compositions and surface areas of prepared catalysts Surface area Catalyst
Measured composition (m2∙g−1)
SBA
-
668
Pt/SBA
7 wt% Pt/SBA-16
507
Pt/CZ/SBA
6.8 wt% Pt/ 16 wt% Ce0.80Zr0.2O2-δ/SBA-16
280
Pt/CZSn/SBA
6.8 wt% Pt/ 16 wt% Ce0.69Zr0.17Sn0.14O2-δ/SBA-16
283
20
S2213-3437(17)30376-7 http://dx.doi.org/doi:10.1016/j.jece.2017.07.072 JECE 1787
To appear in: Received date: Revised date: Accepted date:
22-4-2017 27-7-2017 28-7-2017
Please cite this article as: Abdul Rohman Supandi, Naoyoshi Nunotani, Nobuhito Imanaka, Liquid-phase oxidation of phenol in facile condition using Pt/CeO2–ZrO2–SnO2 catalyst supported on mesoporous silica SBA-16, Journal of Environmental Chemical Engineeringhttp://dx.doi.org/10.1016/j.jece.2017.07.072 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Liquid-phase oxidation of phenol in facile condition using Pt/CeO 2–ZrO2–SnO2 catalyst
supported on mesoporous silica SBA-16
Abdul Rohman Supandi, Naoyoshi Nunotani, and Nobuhito Imanaka*
Department of Applied Chemistry, Faculty of Engineering, Osaka University,
2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan
Corresponding author: [email protected]
Tel. +81-6-6879-7352; Fax. +81-6-6879-7354
GRAPHICAL ABSTRACT
Highlights The oxygen release and storage abilities of CZ/SBA were enhanced by doping SnO2. Phenol was effectively removed by Pt/CZSn/SBA at 80 °C under atmospheric pressure. Phenol removal percentage reached up to 91% by Pt/CZSn/SBA after 6 h reaction.
1
Abstract A Pt/CeO2–ZrO2–SnO2/SBA-16 catalyst was prepared by using co-precipitation and impregnation methods for
removing phenol through liquid-phase oxidation at moderate condition. The platinum active catalyst with a
CeO2–ZrO2–SnO2 oxygen promoter loaded on mesoporous silica Santa Barbara Amorphous No. 16 (SBA-16) possesses
the large surface area with appropriate pore size and high oxygen release and storage abilities, caused by synergistically
reduction of Ce4+ to Ce3+ with Sn4+ to Sn2+. This catalyst was effective in removing phenol at moderate temperature of
80 °C under atmospheric pressure without supplying any oxidants or applying photo-irradiation, wherein the phenol
removal percentage reached up to 91%.
Keywords:
Catalyst, Liquid-phase oxidation, Phenol, Rare earth oxide, Ceria, Fluorite-type
1.
Introduction
The increasing attention towards the environment is important for the sustainable development of the industrial
sector, where many harmful compounds are generated as byproduct and/or the excess raw material. Many organic
pollutants are disposed as wastewater from industrial processes. Phenol is one of the most common organic pollutants
encountered in the wastewater, because it has been used as raw material in many kinds of industries for the production,
such as bisphenol A, phenol resins, and acetyl-salicylic acid [1–3]. However, phenol is toxic compound for human
health and may affect kidney, heart, and the nervous center system [4–5]. It is also lethal to aquatic life even at low
concentration [6–8]. Therefore, there is a requirement to develop an applicable process for phenol removal from 2
wastewater stream.
Several phenol removal methods, including biological treatment [7–8] and activated carbon adsorption [9–10],
have been developed; however, these processes have problems, e.g. control of pH and temperature for
microorganisms and replacement of activated carbon. Although the oxidation processes were reported by using
strong oxidizing additives, such as hydrogen peroxide [15] and peroxymonosulfate [16], they require constant supply
of hazardous oxidants. Hence, we focused on a catalytic liquid-phase oxidation using oxygen gas supply (catalytic
wet air oxidation), because this process has many benefits, such as a simple, sustainable, and environmental friendly
procedure [11–14]. In this method, promoters are used to storage oxygen species from dissolved oxygen gas in the
liquid-phase and release it toward a catalyst activator. CeO2–ZrO2 solid solution is well-known as an oxygen
promoter in automotive exhaust catalysts, because it has high oxygen release and storage abilities, due to easy
reversible process of redox reaction of Ce4+/Ce3+ couple [17–20]. To date, it is reported that 92% of phenol was
removed by using platinum supported on CeO2–ZrO2 after the reaction at high operational temperature (160 °C) and
high oxygen partial pressure (2 MPa) [14]. Thus, it still remains the challenging task to remove phenol at the
moderate reaction conditions, i.e., at lower temperatures (below 100 °C) and under atmospheric pressure.
In order to solve problem mentioned above, we introduced SnO2 into the CeO2–ZrO2 lattice resulting CeO2–ZrO2–SnO2 solid solution. The introduction of SnO2 enhances the oxygen storage and release abilities due to
the valence change of Sn4+/2+ [21–23]. In addition, surface area is also an important issue in catalyst field, because the
catalyst with large surface area possesses high amount of active site. Here, we selected a mesoporous silica SBA-16
(Santa Barbara Amorphous No. 16) as the catalyst support, which has large surface area with cage-like mesoporous
structure that may immobilize the catalyst and promoter particles [24–26]. From these concepts, we prepared the 3
catalyst, that consists of the platinum activator and the CeO2–ZrO2–SnO2 promoter supported on SBA-16, to remove
phenol in facile operating conditions (operating temperature was less than 100 °C and under atmospheric pressure)
without any oxidant supply. For this catalyst, we investigated the catalytic activity for phenol removal in the
liquid-phase.
2.
Material and method
2.1. Catalyst preparation
SBA-16 was prepared via a hydrothermal reaction by modifying preparation method reported in the studies [24–26]. Pluronic F-127 (1.6 g) was dissolved into hydrochloric acid 0.2 mol·L−1 (90 mL), and then
1,3,5–trimethylbenzene (1.1 mL) was added. The mixture was stirred at 35 °C for 3 h. Subsequently, tetraethyl
orthosilicate (7.1 mL) was added into the mixture, and further stirred for 20 h. The mixture was heated inside the
Teflon bottle in sealed brass vessel at 140 °C for 24 h. The precipitated product was separated by filtration and dried at room temperature for a day. The dried sample was then calcined at 400 °C for 4 h with air gas flow (20 mL·min−1).
16 wt% CeO2–ZrO2–SnO2/SBA-16 was prepared by co-precipitation method. The composition of each metal oxide was adjusted to be Ce0.68Zr0.17Sn0.15O2 by mixing 1.0 mol∙L−1 Ce(NO3)3 solution (0.85 mL), 0.1 mol∙L−1
ZrO(NO3)2 solution (2.13 mL), and SnC2O4 powder (38.75 mg). The mixture of solution was previously stirred at
room temperature for 30 min before adding the SBA-16 powder (1.055 g) and further stirred for 30 min. The pH of
mixture was adjusted to be 11 by dropwise addition of 5.6% ammonia solution. Afterwards, the mixture was stirred at
room temperature for 12 h. The precipitated product was separated by filtration and then calcined at 900 °C for 1 h.
Pt was loaded on 16 wt% CeO2–ZrO2–SnO2/SBA-16 by impregnation method. The platinum in ethanol stabilized 4
with polvinylpyrrolidone (Pt-PVP, Pt: 4.0 wt%) was mixed with 16 wt% CeO2–ZrO2–SnO2/SBA-16, wherein the
amount of loaded platinum was adjusted to be 7 wt%. The mixture was sequentially stirred at room temperature for 6
h and then the solvent was vaporized at 180 °C. The dried sample was calcined at 500 °C for 4 h. For comparison, we
also prepared 7 wt% Pt/ 16 wt% Ce0.8Zr0.2O2/SBA-16 and 7 wt% Pt/SBA-16 by similar procedure. Hereafter, we
denote 7 wt% Pt/ 16 wt% Ce0.68Zr0.17Sn0.15O2/SBA-16, 7 wt% Pt/ 16 wt% Ce0.8Zr0.2O2/SBA-16, 7 wt% Pt/SBA-16, and
SBA-16 as Pt/CZSn/SBA, Pt/CZ/SBA, Pt/SBA, and SBA, respectively.
2.2. Catalyst Characterization
The prepared catalysts were analyzed by X-ray powder diffraction and small angle X-ray scattering (XRD and
SAXS; SmartLab, Rigaku) with Cu-Kα radiation in the 2Ө range 10–70° and 0.1–1.5°, respectively. The X-ray
fluorescent (XRF, supermini 200 ZSX100, Rigaku) analysis was carried out to confirm the exact composition of
catalysts. The N2 gas adsorption-desorption measurements (Tristar 3000, Micromeritics) were carried out at −196 °C
to measure the Brunauer-Emmett-Teller (BET) surface area and the porosity of the catalysts. Temperature program reduction (TPR) was carried out in a 5 vol% H2−Ar flow (50 mL·min−1) with a heating rate of 5 °C·min−1 (Belcat-B,
Bel Japan). This TPR experiment was followed by the oxygen storage capacity (OSC) measurement using pulse
injection method at 500 °C.
2.3. Catalytic performance test
The catalytic liquid-phase oxidation of phenol was carried out in the oil bath using a 300 cm3 three necked flask
equipped with an opened condenser at 80 °C in the atmospheric pressure and magnetically stirred (500 rpm). An 5
aqueous solution of phenol 1000 ppm (10 mL) and the catalyst (0.4 g) were mixed in the flask. After the reaction, the
aliquot was separated by using centrifuge with rotating speed 14000 rpm for 10 min (Allegra 64R centrifuge,
Beckman Coulter). Representative samples after reaction were sequentially withdrawn and mixed with naphthalene
solution in methanol (1000 ppm) as the internal standard substance with a volume ratio of 1:1. The mixture of solution
was then analyzed by using gas chromatography-mass spectrometry (GC-MS; GCMS-QP2010 Plus, Shimadzu) to
evaluate the phenol removal percentage. The phenol removal percentage was calculated using the following equation: (Phenol removal percentage)
C0 C
100%
C0
where C0 and C are phenol concentration before and after reaction, respectively. In addition, we also determined the rate constant by plotting the −ln[C/C0] vs. the reaction time (t). The rate
constant (k) was calculated as pseudo-first-order reaction using the following equation: dC dt
3.
k C0 .
Results and discussion
3.1. Characteristic of catalysts
Fig. 1 shows XRD patterns of the CZ/SBA and CZSn/SBA oxygen promoters, and the Pt/CZSn/SBA, Pt/CZ/SBA,
and Pt/SBA catalysts. The XRD patterns of Pt/CZSn/SBA and Pt/CZ/SBA were indexed as the fluorite-type structure
which can be observed in XRD patterns of CZ/SBA and CZSn/SBA, platinum, and SBA, and no impurity phase was
observed. After the introduction of SnO2 into the CZ lattice, the diffraction peaks of fluorite-type structure were
slightly shifted to higher angle as shown in magnified XRD patterns of CZ/SBA and CZSn/SBA at angular position of
54–60°, i.e., the lattice parameter decreases. This lattice shrinkage was caused by the replacement of Ce4+ ion (ionic 6
radius: 0.097 nm [27]) and Zr4+ ion (0.084 nm [27]), by the smaller ionic-size Sn4+ ion (0.081 nm [27]).
The compositions measured by XRF and the surface areas of the catalysts are shown in Table 1. The measured
compositions of the prepared catalysts are in good agreement with the feed compositions within experimental errors. While the prepared SBA support has large surface area of 668 m2·g−1, the insertion of platinum and/or fluorite-type
oxides led the decrease of surface area, suggesting that platinum and/or fluorite-type oxides were inserted into the
SBA support.
Fig. 2 shows the SAXS patterns of the catalysts. These patterns confirmed the regular arrangement of
mesoporous SBA before and after the insertion of platinum and/or fluorite-type oxides. Two diffraction peaks were
observed in SBA pattern at angular position of 0.47° and 0.89°, correspond to (110) and (200) porous planes,
respectively [24–26]. After the insertion of platinum and/or fluorite-type oxides into mesoporous SBA, the diffraction
peaks were shifted to the higher angle and their intensities were also decreased, indicating the decrease of the pore size
and the slight loss of the periodicity of pores. Therefore, platinum and/or fluorite-type oxides were successfully
inserted into mesoporous SBA. These results are supported by the pore size distribution and N 2 adsorption–desorption
isotherm analysis as shown in Fig. 3. The N2 adsorption–desorption isotherm patterns of SBA showed the
distinctiveness of hysteresis curve, classified to the type IV in IUPAC classification, which is typical for the
mesoporous material [28]. After Pt and/or oxygen promoters loading, the similar hysteresis shapes were obtained,
indicating that the mesoporous structure was still maintained. In addition, the decrease of the intensity of adsorbed
volume corresponds to the decreasing of pore size, as shown in inset of Fig. 3, due to the insertion of Pt and/or oxygen
promoters [21].
7
3.2. Catalytic performance evaluation
The catalytic performance tests of liquid-phase oxidation of phenol were carried out by using the Pt/CZSn/SBA,
Pt/CZ/SBA, and Pt/SBA catalysts at 80 °C under atmospheric pressure as reaction time function. From the GC-MS
spectra (Fig. S1), the phenol removal percentages were calculated and the results are shown in Fig. 4(a). In order to
investigate the evaporated phenol and adsorbed phenol into the mesoporous SBA, liquid-phase oxidation of phenol in
the absence of catalyst and using SBA were also carried out. In the absence of catalyst, ca. 15% phenol was removed, in
other words, evaporated. Whereas, by using SBA, the phenol removal percentage was slightly higher than the absence
case, indicating that ca. 4% of phenol was adsorbed into the SBA support. For Pt/CZSn/SBA, Pt/CZ/SBA, and Pt/SBA,
the phenol removal percentage was increased with increasing the reaction time during the catalytic reaction process. By
using oxygen promoters of CZ and CZSn, the catalytic activities enhanced compared to that of Pt/SBA. The presence of
oxygen promoters inside the catalyst well provided oxygen species to Pt for oxidizing phenol. In the presence of oxygen
promoter, the introduction of SnO2 into the CZ lattice successfully enhanced the catalyst activity, and the phenol
removal percentage using Pt/CZSn/SBA reached up to 91% after the reaction for 6 h. This enhancement in catalytic
activity is attributed to the enhanced oxygen release and storage abilities by introducing SnO 2. Furthermore, the phenol
removal percentage using Pt/CZSn/SBA is comparable with that of the previous Pt/CZ sample (~92%), whose reaction
conditions were extremely severe (160 °C, 2 MPa) [14]. For Pt/CZSn/SBA after the reaction, the collapse of the crystal
structure and the leaching of metal from Pt/CZSn/SBA were not observed (Fig. S2 and Table S1). In addition, the
reproducibility of the catalytic activity was confirmed as shown in Fig. S3.
Fig. 4(b) depicts the plot of −ln (C/C0) vs. the reaction times. Since the graphic curves are almost linear, the phenol
removal reaction would proceed by pseudo-first-order reactions. These results are appropriate with previous study, in 8
which it is reported that the phenol degradation using heterogeneous catalyst followed first-order reaction [16]. Based
on the first-order reaction power law, we estimated the rate constant of phenol oxidation using the catalysts; i.e., 0.39 h−1, 0.31 h−1, and 0.24 h−1 for Pt/CZSn/SBA, Pt/CZ/SBA, and Pt/SBA, respectively. Thus, liquid-phase oxidation of
phenol using a Pt/CZSn/SBA occurs faster than those using Pt/CZ/SBA and Pt/SBA.
The H2–TPR measurement of CZSn/SBA was carried out to investigate the reason of the high activity of
Pt/CZSn/SBA, and the result is shown in Fig. 5, with the data of CZ/SBA and SBA. There was not any peak in TPR
profile of SBA at temperatures lower than 500 °C, suggesting that SBA has no reduction activity at those temperatures.
Whereas, the presence of CZ over SBA-16 started to be reduced at 346 °C. Furthermore, the introduction of SnO 2 into
the CZ lattice drastically decreased the reduction temperature which started to be reduced at 220 °C and reached the
peak at 288 °C, likely due to the surface reduction of Ce4+ to Ce3+. This decrease of reduction temperature was caused
by synergistically reduction of Ce4+ to Ce3+ with Sn4+ to Sn2+ [19–21]. Additionally, another reduction peak was also
observed at 370 °C, which might correspond to the bulk reduction of the CZSn promoter over SBA-16. The oxygen
vacancy, formed by the reduction of Sn4+ to Sn2+, took part in increasing the oxygen mobility in the bulk structure of the
CZSn promoter. As shown in the inset of Fig. 5, the oxygen storage ability was also drastically increased by doping
SnO2, and the value was ca. three times higher than that of CZ/SBA. These properties of oxygen promoters took part in
providing the oxygen species to the platinum activator for oxidizing phenol.
In addition, we also investigated the presence of intermediate compounds in aliquot which are produced after
reaction for 6 h by GC-MS measurement (Fig. S1). After the reaction using Pt/SBA for 6 h, we found the acetic acid in
low concentration (~172 ppm), whereas this acetic acid was not detected when using Pt/CZ/SBA and Pt/CZSn/SBA. In
the case of Pt/CZSn/SBA, benzoquinone was detected as intermediate compound, while its concentration (~42 ppm) 9
was lower than the case for Pt/CZ/SBA (~82 ppm) and Pt/SBA (~100 ppm).
4.
Conclusion The Pt/CeO2–ZrO2–SnO2/SBA-16 catalyst has been successfully synthesized by dispersing platinum and
CeO2–ZrO2–SnO2 into the SBA-16 support, with the large surface area and the appropriate pore size. CeO2–ZrO2–SnO2/SBA-16 has the high reduction activity and oxygen storage ability compared to CeO2–ZrO2/SBA-16
and SBA-16, due to the synergistically redox reaction of Ce4+/3+ and Sn4+/2+. This property can be utilized in promoting
the oxidation on platinum as the active catalyst. The liquid-phase oxidation of phenol using the various catalysts were
carried out at 80 °C under atmospheric pressure without any other oxidant additives. The 7 wt% Pt/ 16 wt%
Ce0.68Zr0.17Sn0.15O2-δ/SBA-16 catalyst revealed the remarkable activity in removing phenol, and the phenol removal percentage reached up to 91% after 6 h reaction due to the effective supply of oxygen from the CeO 2–ZrO2–SnO2
promoter and the large surface area. The phenol removal mechanism was fitted as the pseudo-first-order reaction with rate constant of 0.39 h−1.
10
Acknowledgements
We would like to thank to Lake Biwa-Yodo River water Quality Preservation Organization for financially supporting
this work.
11
References [1] C. Ayral, C.J. Lebigue, F. Stüber, A.M. Wilhelm, H. Delmas, Catalytic wet air oxidation of phenolic compounds and mixtures over activated carbon: conversion, mineralization, and catalyst stability, Ind. Eng. Chem. Res. 49 (21) (2010) 10707–10714. [2] Z.P.G. Masende, B.F.M. Kuster, K.J. Ptasinski, F.J.J.G. Janssen, J.H.Y. Katima, J.C. Sxhouten, Platinum catalyzed wet oxidation of phenol in a stirred slurry reactor: A practical operation window, Appl. Catal. B: Environ. 41 (2003) 247–267. [3] Institute for Health and Consumer Protection European Chemicals Bureau, European Union risk assessment report: phenol, volume 64, revised edition. https://echa.europa.eu/documents/10162/3e04f30d-9953-4824-ba04-defa32a130fa, 2006 (accessed 17.02.17). [4] S.J. Kulkarni, J.P. Kaware, Review on research for removal of phenol from wastewater, Int. J. Sci. Res. Pub. 3 (4) (2013) 654–658. [5] S. Yang, W. Zhu, J. Wang, Z. Chen, Catalytic wet air oxidation of phenol over CeO2-TiO2 catalyst in the batch reactor and the packed-bed reactor, J. Hazard. Mater. 153 (2008) 1248–1253. [6] V.M. Brown, D.H.M. Jordan, B.A. Tiller, The effect of temperature on the acute toxicity of phenol to rainbow trout in hard water, Water Res. 1 (8-9) (1967) 587–594. [7] T-P. Chung, H-Y. Tseng, R-S. Juang, Mass transfer effect and intermediate detection for phenol degradation in immobilized Pseudomonas putida systems, Process Biochem. 38 (10) (2003) 1497–1507. [8] M. Kibert, W. Somitsch, K-H. Robra, Characterization of a phenol degrading mixed population by enzyme assay, Water Res. 34 (4) (2000) 1127–1134. [9] R.R. Karri, N.S. Jayakumar, J.N. Sahu, Modelling of fluidised-bed reactor by differential evolution optimization for phenol removal using coconut shells based activated carbon, J. Mol. Liq. 231 (2017) 249–262. [10] G.S. dos Reis, M.A. Adebayo, C.H. Sampaio, E.C. Lima, P.S. Thue, I.A.S. de Brum, S.L.P. Dias, F.A. Pavan, Removal of Phenolic Compounds from Aqueous Solutions Using Sludge-Based Activated Carbons Prepared by Conventional Heating and Microwave-Assisted Pyrolysis, Water Air Soil Poll. 228 (33) (2017) 1–17. [11] S. Keav, A. Martin, J. Barbier Jr., D. Duprez, Deactivation and reactivation of noble metal catalysts tested in the Catalytic Wet Air Oxidation of phenol, Catal. Today 151 (2010) 143–147. 12
[12] S. Keav, A.E. de los Monteros, J. Barbier Jr., D. Duprez, Wet air oxidation of phenol over Pt and Ru catalysts supported on cerium-based oxides: resistance to fouling and kinetic modelling, Appl. Catal. B: Environ. 150–151 (2014) 402–410. [13] A.E. de los Monteros, G. Lafaye, A. Cervantes, G.D. Angel, J. Barbier Jr, G. Torres, Catalytic wet air oxidation of phenol over metal catalyst (Ru, Pt) supported on TiO2–CeO2 oxides, Catal. Today 258 (2015) 564–569. [14] S. Nousir, S. Keav, J. Barbier Jr., M. Bensitel, R. Brahmi, D. Duprez, Deactivation phenomena during catalytic wet air oxidation (CWAO) of phenol over platinum catalysts supported on ceria and ceria–zirconia mixed oxides, Appl. Catal. B: Environ. 84 (2008) 723–731. [15] J. Guo, M. Al-Dahhan, Catalytic wet oxidation of phenol by hydrogen peroxide over pillared clay catalyst, Ind. Eng. Chem. Res. 42 (12) (2003) 2450–2460. [16] S. Muhammad, E. Saputra, H. Sun, H-M. Ang, M.O. Tade,́ S. Wang, Heterogeneous catalytic oxidation of aqueous phenol on red mud supported cobalt catalysts, Ind. Eng. Chem. Res. 51 (2012) 15351−15359. [17] S. Bedrane, C. Descorme, D. Duprez, Investigation of the oxygen storage process on ceria- and ceria–zirconia-supported catalysts, Catal. Today 75 (2002) 401–405. [18] P. Fornasiero, R. Dimonte, G.R. Rao, J. Kašpar, S. Meriani, A. Trovarelli, M. Graziani, Rh-loaded CeO2-ZrO2 solid-solutions as highly efficient oxygen exchangers: dependence of the reduction behavior and the oxygen storage capacity on the structural-properties, J. Catal. 151 (1995) 168–177. [19] C.E. Hori, H. Permana, K.Y. Simon Ng, A. Brenner, K. More, K.M. Rahmoeller, D. Belton, Thermal stability of oxygen storage properties in a mixed CeO2-ZrO2 system, Appl. Catal. B: Environ. 16 (1998) 105–117. [20] J. Kašpar, P. Fornasiero, M. Graziani, Use of CeO2-based oxides in the three-way catalysis, Catal. Today 50 (2) (1999) 285–298. [21] P.G. Choi, N. Nunotani, N. Imanaka, High catalytic efficiency in liquid-phase oxidation of 1,4-dioxane using a Pt/CeO2-ZrO2-SnO2/SBA-16 catalyst, Int. J. Appl. Ceram. Technol. 14 (2017) 9–15. [22] Q. Dong, S. Yin, C. Guo, T. Sato, Ce0.5Zr0.4Sn0.1O2/Al2O3 catalysts with enhanced oxygen storage capacity and high CO oxidation activity, Catal. Sci. Technol. 2 (2012) 2521–2524. [23] K. Yasuda, A. Yoshimura, A. Katsuma, T. Masui, N. Imanaka, Low-temperature complete combustion of volatile organic compounds over novel Pt/CeO2-ZrO2-SnO2/γ-Al2O3 catalysts, Bull. Chem. Soc. Jpn. 85 (2012) 522–526. 13
[24] H. Yotou, T. Okamoto, M. Ito, T. Sekino, S-I. Tanaka, Novel method for insertion of Pt/CeZrO 2 nanoparticles into mesoporous SBA-16 using hydrothermal treatment, Appl. Catal. A: Gen. 458 (2013) 137–144. [25] D. Zhao, Q. Huo, J. Feng, B.F. Chmelka, G.D. Stucky, Nonionic triblock and star diblock copolymer and oligomeric surfactant syntheses of highly ordered, hydrothermally stable, mesoporous silica structures, J. Am. Chem. Soc. 120 (24) (1998) 6024–6036. [26] S. Zuo, F. Liu, J. Tong, C. Qi, Complete oxidation of benzene with cobalt oxide and ceria using the mesoporous support SBA-16, Appl. Catal. A: Gen. 467 (2013) 1–6. [27] R.D. Shannon, Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides, Acta. Crystallogr. A32 (1976) 751–767. [28] K.S.W. Sing, D.H. Evereet, R.A.W. Haul, L. Moscou, R. Pierotti, J. Rouquerol, T. Siemieniewska, Reporting physisorption data for gas/solid systems with special reference to the determination of surface area and porosity, Pure Appl. Chem. 57 (4) (1985) 603–619.
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Figure captions Fig. 1. XRD patterns of CZ/SBA, CZSn/SBA, Pt/SBA, Pt/CZ/SBA, and Pt/CZSn/SBA. Fig. 2. SAXS patterns of SBA support, Pt/SBA, Pt/CZ/SBA, and Pt/CZSn/SBA catalysts. Fig. 3. N2 adsorption-desorption isotherms of SBA support, Pt/SBA, Pt/CZ/SBA, and Pt/CZSn/SBA catalysts. The BJH pore size distribution profiles are shown in the insets. Fig. 4. (a) Phenol removal percentage as reaction time function, (b) reaction rate constants of phenol oxidation by using the catalysts with error bars. Each solid line in Fig. 4(b) represents the regression line. Fig. 5. H2–TPR profiles of SBA support, CZ/SBA, and CZSn/SBA promoters.
15
Figure 1. A.R. Supandi et al.
16
Figure 2. A.R. Supandi et al.
17
Figure 3. A.R. Supandi et al.
18
Figure 4. A.R. Supandi et al.
19
Figure 5. A.R. Supandi et al.
List of Table Table 1. The measured compositions and surface areas of prepared catalysts Surface area Catalyst
Measured composition (m2∙g−1)
SBA
-
668
Pt/SBA
7 wt% Pt/SBA-16
507
Pt/CZ/SBA
6.8 wt% Pt/ 16 wt% Ce0.80Zr0.2O2-δ/SBA-16
280
Pt/CZSn/SBA
6.8 wt% Pt/ 16 wt% Ce0.69Zr0.17Sn0.14O2-δ/SBA-16
283
20