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Chinese Journal of Catalysis
2014, Vol. 35, No. 8
Online: 01 August 2014


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Rare earths are very important precious resources that have limited supplies. The high efficiency and high quality application of rare earths, especially the light rare earth elements (La, Ce, Pr, and so on) which are more abundant, as catalytic materials is a key requirement. To show the latest progress on rare earth catalysis and promote the development of the rare earth catalytic materials, we are pleased to invite a number of scientists to present their recent work on rare earth catalysis. This special issue consists of 2 reviews, 1 communication, and 13 articles, which described work related to environmental, organic and energy catalysis, and density functional theory studies.

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Table of Contents for VOL.35 No.8 2014, 35 (8):  0-0.  Abstract ( 118 )   PDF (2167KB) ( 662 )

Editorial

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Preface to Special Issue on Rare Earth Catalysis Guanzhong Lu 2014, 35 (8):  1237-1237.  DOI: 10.1016/S1872-2067(14)60188-1 Abstract ( 194 )   [Full Text(HTML)] () PDF (240KB) ( 619 )

Reviews

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Current status and perspectives of rare earth catalytic materials and catalysis Wangcheng Zhan, Yun Guo, Xueqing Gong, Yanglong Guo, Yanqing Wang, Guanzhong Lu 2014, 35 (8):  1238-1250.  DOI: 10.1016/S1872-2067(14)60189-3 Abstract ( 1060 )   [Full Text(HTML)] () PDF (1227KB) ( 2259 )   Rare earth elements possess 4f orbitals without full electron occupancy and lanthanide contraction. This characteristic results in their unique catalytic performance when they are used as active components or as catalyst supports. Research into and the development of rare earth catalytic materials will significantly promote the high-efficiency utilization of abundant rare earth elements, such as lanthanum and cerium. Currently, rare earth catalytic materials play an important role in such areas as the petroleum chemical industry, the catalytic combustion of fossil fuels, automotive emissions control, the purification of industrial waste air, and solid solution fuel cells. In this paper, we review the application of and recent research progress that has been made on rare earth catalytic materials, including relative theoretical research. The effects of rare earth elements on the structure, activity, and stability of the catalysts of interest are described.

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The use of ceria for the selective catalytic reduction of NOx with NH3 Wenpo Shan, Fudong Liu, Yunbo Yu, Hong He 2014, 35 (8):  1251-1259.  DOI: 10.1016/S1872-2067(14)60155-8 Abstract ( 393 )   [Full Text(HTML)] () PDF (726KB) ( 1023 )   The selective catalytic reduction of NOx with NH3 (NH3-SCR) is one of the widely used NOx control strategies for stationary sources (particularly for power plants) and mobile sources (particularly for diesel vehicles). The application is aimed at meeting the increasingly stringent standards for NOx emissions. Recently, ceria has attracted much attention for its applications in NH3-SCR catalysts owing to its unique redox, oxygen storage, and acid-base properties. In this article, we comprehensively review recent studies on ceria for NH3-SCR catalysts when used as support, promoter, or the main active component. In addition, the general development of ceria for NH3-SCR catalysts is discussed.

Communications

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Oxidative dehydrogenation of ethane to ethylene in the presence of HCl over CeO2-based catalysts Fengchi Yu, Xuejiao Wu, Qinghong Zhang, Ye Wang 2014, 35 (8):  1260-1266.  DOI: 10.1016/S1872-2067(14)60152-2 Abstract ( 368 )   [Full Text(HTML)] () PDF (546KB) ( 839 )   This article reports a new catalytic route for the oxidative dehydrogenation of ethane to ethylene in the presence of HCl at moderate temperatures. CeO2 was found to be the most efficient catalyst for the production of ethylene from the variety of metal oxides examined in this work. CeO2 nanocrystals with rod and cube morphologies showed higher ethane conversions and ethylene selectivities than CeO2 nanoparticles. The modification of CeO2 by MnOx further enhanced the catalytic performance. Ethane conversion of 94% and ethylene selectivity of 69% were obtained after 2 h of reaction at 723 K over an 8 wt% MnOx-CeO2 catalyst. This catalyst was stable and the ethylene yield could be sustained at 65%-70% over 100 h of reaction. The presence of HCl played a key role in the selective production of C2H4, and some of the C2H4 was probably formed from chloroethane by dehydrochlorination.

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Effects of the addition of small quantities of ceria on the catalytic behavior of Pd-only close-coupled catalysts during automobile exhaust elimination Xue Yang, Linyan Yang, Siyu Lin, Renxian Zhou 2014, 35 (8):  1267-1280.  DOI: 10.1016/S1872-2067(14)60157-1 Abstract ( 252 )   [Full Text(HTML)] () PDF (1343KB) ( 1072 )   A series of La-Al2O3 supported Pd-Ce close-coupled catalysts were synthesized by a co-adsorption impregnation method and subsequently investigated. In the case of fresh catalysts, the presence of an optimal concentration of ceria obviously promoted the catalytic activity during HC and NOx eliminations, owing to the interaction between the palladium oxide species (PdOx) and CeO2 that improves the oxidation of Pd0 to PdO and enhances the adsorption of nitrite/nitrates and isocyanate intermediate species on the support under reaction conditions. Pd-Ce(2.0)/La-Al2O3 catalyst (where 2.0 is the wt% of CeO2) exhibited the highest catalytic activity for HC and NO eliminations. Following aging at 1100 ℃, the operational window for HC and NOx conversions was broadened and the thermal stability of the catalysts was also improved as a result of the presence of an appropriate quantity of ceria (2.0-4.0 wt%). The enhanced interactions between PdOx and CeO2 evidently led to the formation of a Pd-O-Ce system, stabilizing PdOx species with smaller particle sizes at high temperatures. This result is significant since it suggests a means of improving the catalytic performance of Pd-only close-coupled catalysts during automobile exhaust elimination.

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Tailored temperature window of MnOx-CeO2 SCR catalyst by addition of acidic metal oxides Jiuyuan Nie, Xiaodong Wu, Ziran Ma, Tengfei Xu, Zhichun Si, Lei Chen, Duan Weng 2014, 35 (8):  1281-1288.  DOI: 10.1016/S1872-2067(14)60106-6 Abstract ( 276 )   [Full Text(HTML)] () PDF (688KB) ( 769 )   A MnOx-CeO2 catalyst was modified with various acidic metal oxides (Nb2O5, WO3, and MoO3) using a sol-gel method. The activities of the obtained catalysts were measured for the selective catalytic reduction (SCR) of NOx with NH3 to screen suitable acidic metal oxides for different temperature windows. The catalytic activities for NO and NH3 oxidation were also evaluated. The catalysts were characterized by X-ray diffraction, N2 adsorption, H2 temperature-programmed reduction, NH3/NOx temperature-programmed desorption analyses, and infrared spectroscopic measurements of NH3/NOx adsorption. The MnOx-CeO2 catalyst exhibited the greatest low-temperature (100-150 ℃) activity. The addition of acidic metal oxides weakened the redox properties of the catalyst, resulting in inhibition of the partial oxidation of the adsorbed NH3 and NO2-assisted fast SCR reactions. Meanwhile, the oxidation of NH3 at relatively high temperatures (250-350 ℃) was suppressed, and the adsorption of NH3 on Brönsted and Lewis acid sites was strengthened. Consequently, the temperature window of SCR reaction shifted to higher temperatures in the order Nb2O5< WO3< MoO3.

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In situ IR studies of selective catalytic reduction of NO with NH3 on Ce-Ti amorphous oxides Qian Li, Huachun Gu, Ping Li, Yuhao Zhou, Ying Liu, Zhongnan Qi, Ying Xin, Zhaoliang Zhang 2014, 35 (8):  1289-1298.  DOI: 10.1016/S1872-2067(14)60154-6 Abstract ( 256 )   [Full Text(HTML)] () PDF (944KB) ( 654 )   A series of in situ infrared (IR) studies of the selective catalytic reduction (SCR) of NOx with NH3 on the short-range ordered structure Ce-O-Ti sites in amorphous Ce-Ti mixed oxides were performed. Under the reaction conditions, the catalyst surface was mainly covered by NH3 ad-species and no NOx ad-species were detected. The reaction order of 0.5-0.6 with respect to NO confirmed a hybrid Langmuir-Hinshelwood and Eley-Rideal mechanism. A possible route may involve the reaction of NH3 ad-species and weakly adsorbed NOx to form an active intermediate, NHyNO3 (y = 0-4); this was confirmed by GAUSSIAN calculations and the in situ IR results. The Ce-O-Ti structure, with Ce-Ti interactions on the atomic scale, enhanced the redox properties in the active temperature window of the SCR reactions.

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(La0.8A0.2)MnO3 (A = Sr, K) perovskite catalysts for NO and C10H22 oxidation and selective reduction of NO by C10H22 Anne Giroir-Fendler, Sonia Gil, Alexandre Baylet 2014, 35 (8):  1299-1304.  DOI: 10.1016/S1872-2067(14)60173-X Abstract ( 232 )   [Full Text(HTML)] () PDF (734KB) ( 711 )   In this work, we studied the catalytic activity of LaMnO3 and (La0.8A0.2)MnO3 (A = Sr, K) perovskite catalysts for oxidation of NO and C10H22 and selective reduction of NO by C10H22. The catalytic performances of these perovskites were compared with that of a 2 wt% Pt/SiO2 catalyst. The La site substitution increased the catalytic properties for NO or C10H22 oxidation compared with the non-substituted LaMnO3 sample. For the most efficient perovskite catalyst, (La0.8Sr0.2)MnO3, the results showed the presence of two temperature domains for NO adsorption: (1) a domain corresponding to weakly adsorbed NO, desorbing at temperatures lower than 270 ℃ and (2) a second domain corresponding to NO adsorbed on the surface as nitrate species, desorbing at temperatures higher than 330 ℃. For the Sr-substituted perovskite, the maximum NO2 yield of 80% was observed in the intermediate temperature domain (around 285 ℃). In the reactant mixture of NO/C10H22/O2/H2O/He, (La0.8Sr0.2)MnO3 perovskite showed better performance than the 2 wt% Pt/SiO2 catalyst: NO2 yields reaching 50% and 36% at 290 and 370 ℃, respectively. This activity improvement was found to be because of atomic scale interactions between the A and B active sites, Sr2+ cation and Mn4+/Mn3+ redox couple. Thus, (La0.8Sr0.2)MnO3 perovskite could be an alternative free noble metal catalyst for exhaust gas after treatment.

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DFT + U study of the CO + NOx reaction on a CeO2(110)-supported Au nanoparticle Jie Zhang, Xueqing Gong, Guanzhong Lu 2014, 35 (8):  1305-1317.  DOI: 10.1016/S1872-2067(14)60168-6 Abstract ( 349 )   [Full Text(HTML)] () PDF (1060KB) ( 1153 )   The adsorption and reactions of CO and NOx on a Au6 nanoparticle supported on the CeO2(110) surface have been studied using density functional theory calculations corrected by on-site Coulomb interactions (DFT + U). The results show that CO can strongly adsorb on the top site of the Au nanoparticle with an adsorption energy of ~1.2 eV, while the adsorption of NO on both the Au nanoparticle and the interface between the nanoparticle and the CeO2 support is generally much weaker. However, at the interface, formation of the N2O2 dimer followed by cleavage of the terminal N-O bond is an effective way to decompose NOx. For the complete process, the first step of the CO + N2O2 reaction can readily occur in Langmuir-Hinshelwood mode with an activation energy of only ~0.4 eV, leading to the formation of N2O and CO2 via an intermediate ONNOCO species. In contrast, the second step to eliminate N2O requires a rather high energy barrier of ~1.8 eV through a Eley-Rideal type collision reaction. Further analyses show that the unique electronic properties of Ce can induce the electron transfer and localization from supported Au to surface Ce cations, which then promotes the formation of negatively charged N2O2. Moreover, the structural flexibility of the Au nanoparticle also facilitates the adsorbed CO to approach and react with N2O2 at the interface.

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Acidity characterization of rare-earth-exchanged Y zeolite using 31P MAS NMR Shanqing Yu, Huiping Tian 2014, 35 (8):  1318-1328.  DOI: 10.1016/S1872-2067(14)60149-2 Abstract ( 323 )   [Full Text(HTML)] () PDF (803KB) ( 659 )   Detailed qualitative and quantitative information on the effects of rare-earth (RE) cations on the types (Brönsted and Lewis), strengths, and distributions of acid sites on Y zeolite was studied by solid-state 31P magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy, using adsorbed trimethylphosphine oxide (TMPO) and tributylphosphine oxide (TBPO) as probe molecules. A total of seven 31P resonance peaks, with 31P NMR/TMPO chemical shifts at δ = 78, 70, 65, 62, 58, 55, and 53, corresponding to sites with different acid strengths, were identified. The peaks at δ = 78 and 70 arose from external and internal acid sites, the peaks at δ = 65, 62, 58, and 53 were from internal Brönsted acid sites, and the peak at δ = 55 was from internal Lewis acid sites. With increasing RE content, the number of medium strength Brönsted acid sites (δ = 62 and 58) increased significantly, whereas those of strong Brönsted acid sites (δ = 65) and weak Lewis acid sites (δ = 55) decreased. These experimental results were explained in terms of the influence of framework Al, extra-framework Al, and RE cations on the Y zeolite acidity.

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Insights into the vanadia catalyzed oxidative dehydrogenation of isobutane with CO2 Ruixue Yuan, Yang Li, Haobing Yan, Huan Wang, Jian Song, Zhongshen Zhang, Weibin Fan, Jiangang Chen, Zhongwen Liu, Zhaotie Liu, Zhengping Hao 2014, 35 (8):  1329-1336.  DOI: 10.1016/S1872-2067(14)60180-7 Abstract ( 355 )   [Full Text(HTML)] () PDF (686KB) ( 688 )   Vanadia-based catalysts were prepared using the sol-gel method and were subjected to the oxidative dehydrogenation of isobutane with CO2. The materials were extensively characterized by using X-ray diffraction, N2 adsorption-desorption, O2-temperature programmed oxidation, temperature programmed surface reaction, and in situ Fourier transform infrared techniques. Catalytic results indicate that a high selectivity toward total C4 olefins over 85% was obtained over all of the catalysts. On the contrary, the highest conversion of isobutane was observed over 12 wt% V2O5/Ce0.6Zr0.4O2(7 wt%)-Al2O3, and a more stable performance was achieved over 6 wt% V2O5-Ce0.6Zr0.4O2(7 wt%)-Al2O3. The catalytic activity for the titled reaction was found to be dependent on the dispersion and crystallinity of the VOx species over the catalyst, and the deposition of the heavier coke over the catalyst was revealed to be the main reason for the catalyst deactivation. Moreover, the benefit of CO2 toward the titled reaction was clearly revealed from TPSR results, and the reaction was confirmed to follow the redox mechanism.

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Self-cleaning perovskite type catalysts for the dry reforming of methane Marí Natividad Pérez-Camacho, Jehad Abu-Dahrieh, Alexandre Goguet, Kening Sun, David Rooney 2014, 35 (8):  1337-1346.  DOI: 10.1016/S1872-2067(14)60187-X Abstract ( 237 )   [Full Text(HTML)] () PDF (1432KB) ( 690 )   Gas-to-liquid processes are generally used to convert natural gas or other gaseous hydrocarbons into liquid fuels via an intermediate syngas stream. This includes the production of liquid fuels from biomass-derived sources such as biogas. For example, the dry reforming of methane is done by reacting CH4 and CO2, the two main components of natural biogas, into more valuable products, i.e., CO and H2. Nickel containing perovskite type catalysts can promote this reaction, yielding good conversions and selectivities; however, they are prone to coke laydown under certain operating conditions. We investigated the addition of high oxygen mobility dopants such as CeO2, ZrO2, or YSZ to reduce carbon laydown, particularly using reaction conditions that normally result in rapid coking. While doping with YSZ, YDC, GDC, and SDC did not result in any improvement, we show that a Ni perovskite catalyst (Na0.5La0.5Ni0.3Al0.7O2.5) doped with 80.9 ZrO2 15.2 CeO2 gave the lowest amount of carbon formation at 800 ℃ and activity was maintained over the operating time.

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Comparative study on the catalytic CO oxidation properties of CuO/CeO2 catalysts prepared by solid state and wet impregnation Jingfang Sun, Lei Zhang, Chengyan Ge, Changjin Tang, Lin Dong 2014, 35 (8):  1347-1358.  DOI: 10.1016/S1872-2067(14)60138-8 Abstract ( 565 )   [Full Text(HTML)] () PDF (786KB) ( 1116 )   A series of CuO/CeO2 catalysts were prepared by solid state impregnation (SSI) and wet impregnation (WI) methods and characterized by X-ray diffraction, H2 temperature-programmed reduction (H2-TPR), laser Raman spectroscopy (LRS), in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS), and X-ray photoelectron spectroscopy (XPS). XPS and H2-TPR results showed that SSI increased the dispersion of the copper species on the catalyst surface, which benefited the reduction of CuO species. LRS results indicated that a higher concentration of oxygen vacancies was obtained by the SSI method unlike the WI method. CO oxidation results showed that at a given CuO loading, the activity of the catalysts prepared by SSI was higher than that of their counterparts prepared by WI. Based on the combined characterization results, it was suggested that the enhanced activity was closely related to the higher concentrations of oxygen vacancies and Cu+-CO species on the catalysts. Last, a possible synergetic mechanism was proposed for CO oxidation over the CuO/CeO2 catalysts.

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Effect of KCl on the performance of Cu-K-La/γ-Al2O3 catalyst for HCl oxidation Kanka Feng, Chenwei Li, Yanglong Guo, Wangcheng Zhan, Binquan Ma, Binwu Chen, Maoquan Yuan, Guanzhong Lu 2014, 35 (8):  1359-1363.  DOI: 10.1016/S1872-2067(14)60166-2 Abstract ( 246 )   [Full Text(HTML)] () PDF (520KB) ( 589 )   Cu-K-La/γ-Al2O3 catalysts prepared by the incipient wetness impregnation for the catalytic oxidation of HCl to Cl2 at atmospheric pressure were investigated for the effect of KCl on the catalyst performance. Cu-K-La/γ-Al2O3 catalyst with 5 wt% KCl loading showed good activity and stability due to the promotion by KCl. It gave good activity over a wide range of space velocity of the feed gas and conversion of HCl above 85%, and it was nearly unchanged in activity after 100 h reaction at the conditions of 0.1 MPa, 360 ℃, space velocity of 450 L/(kg-cat·h), and HCl/O2 molar ratio = 2:1. X-ray diffraction results indicated that Cu, K, and La species were highly dispersed on the surface of the γ-Al2O3 support. H2 temperature-programmed reduction results indicated that the addition of KCl favored the reduction of Cu2+ to Cu+ and improved the activity of the active sites of Cu2+ species for HCl oxidation.

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Redox properties and CO2 capture ability of CeO2 prepared by a glycol solvothermal method Chuncheng Li, Xiaohui Liu, Guanzhong Lu, Yanqin Wang 2014, 35 (8):  1364-1375.  DOI: 10.1016/S1872-2067(14)60163-7 Abstract ( 461 )   [Full Text(HTML)] () PDF (1583KB) ( 725 )   CeO2 nanocrystals with plentiful oxygen vacancies were synthesized by a glycol solvothermal method (CeO2-GST) using the strong reducibility of glycol. For comparison, CeO2 nanorods (CeO2-nanorods) and CeO2 nanoparticles (CeO2-CA) were also prepared. The samples were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, H2 reduction-O2 oxidation cycle experiments and in situ CO2 infrared spectroscopy. The CeO2-GST sample exposed mainly (111) facets with abundant Ce3+ ions on its surface, and it gave excellent reversible redox behavior and high oxygen storage capacity. After seven H2 reduction-O2 oxidation cycles, the oxygen storage capacity became stable. The CeO2-GST sample also had a high CO2 adsorption capacity of 149 μmol/g at 50 ℃ by forming bidentate and bridge carbonates on the CeO2 surface. These carbonate species were less stable than the unidentate carbonate, bicarbonate and formate species, thus adsorbed CO2 was released easily. On reduced CeO2 nanorod, CO2 formed the stable unidentate carbonate and formate species, which is unfavorable for the release of adsorbed CO2.

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Gadolinia-doped ceria barrier layer produced by sputtering and annealing for anode-supported solid oxide fuel cells Weiming Wu, Zhongbo Liu, Zhe Zhao, Xiaomin Zhang, Dingrong Ou, Baofeng Tu, Da'an Cui, Mojie Cheng 2014, 35 (8):  1376-1384.  DOI: 10.1016/S1872-2067(14)60137-6 Abstract ( 265 )   [Full Text(HTML)] () PDF (698KB) ( 540 )   We prepared gadolinia-doped ceria (GDC) barrier layers by sputtering and annealing at various temperatures. We then investigated the effects of the GDC barrier layers on the performance of anode-supported solid oxide fuel cells. Sputtering at 200 ℃ readily produced a uniform, thin layer of cubic GDC. Sputtering and annealing at 900-1100 ℃ formed uniform, thin, dense films, which effectively prevented the reaction between the yttria-stabilized zirconia electrolyte and the Ba0.5Sr0.5Co0.8Fe0.2O3-δ cathode. The single cells assembled with the thin, dense GDC barrier layers sputtered at 200 ℃ and annealed at 900-1000 ℃ exhibited excellent electrochemical performance.

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18O isotopic study of photo-induced formation of peroxide species on cubic Nd2O3 Xiaolian Jing, Wenyu She, Weizheng Weng, Jianmei Li, Wensheng Xia, Huilin Wan 2014, 35 (8):  1385-1393.  DOI: 10.1016/S1872-2067(14)60153-4 Abstract ( 285 )   [Full Text(HTML)] () PDF (657KB) ( 619 )   Photo-induced formation of peroxide species on cubic Nd2O3 was studied by in situ microprobe Raman spectroscopy using 18O as a tracer and a 325-nm laser as an excitation source. The results confirmed that the peroxide ions were formed through photooxidation of the lattice oxygen species in neodymium sesquioxide by molecular oxygen species. Under UV excitation (λ = 325 nm), the reaction between O2 and O2- could take place at room temperature. A fast oxygen exchange between the peroxide ions and the lattice oxygen species in Nd2O3 took place under the experimental conditions studied. Also, bulk lattice oxygen species in Nd2O3 could migrate to the surface layer and participate in the formation of peroxide ions. The migration of lattice oxygen species and the oxygen exchange between lattice oxygen and peroxide ions were promoted by UV laser irradiation.

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Polyol-synthesized Pt2.6Sn1Ru0.4/C as a high-performance anode catalyst for direct ethanol fuel cells Qi Wang, Xing Lu, Qin Xin, Gongquan Sun 2014, 35 (8):  1394-1401.  DOI: 10.1016/S1872-2067(14)60063-2 Abstract ( 309 )   [Full Text(HTML)] () PDF (853KB) ( 533 )   PtSnRu/C catalysts with different atomic ratios and metal loadings were prepared using a polyol process to improve the performance of direct ethanol fuel cells (DEFCs). The catalysts were characterized using transmission electron microscopy and X-ray photoelectron spectroscopy. The DEFC performance was evaluated using a single-cell test. The ethanol electro-oxidation process and anode products were analyzed using in situ Fourier-transform infrared spectroscopy (FTIRS), gas chromatography, and neutralization titration. The performance of the Pt2.6Sn1Ru0.4/C catalyst was better than those of the Pt3Sn1/C and Pt2Sn1Ru1/C catalysts. The carbon-supported Pt2.6Sn1Ru0.4 catalyst with a 60 wt% metal loading gave a maximum power density of 121 mW/cm2 at 90 ℃. In situ FTIRS and anode product analysis indicated that ethanol was electro-oxidized to acetaldehyde, acetic acid, ethyl acetate, and CO2. The ethanol oxidation efficiency on the Pt2.6Sn1Ru0.4/C catalyst was higher than that on the Pt3Sn1/C catalyst. The activation energy of ethanol electro-oxidation at the anode and surface composition analysis indicated that interactions among the surface elements resulted in a lower apparent activation energy and greater ethanol electro-oxidation efficiency on the Pt2.6Sn1Ru0.4/C catalyst.

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Synthesis of high-surface-area Co-O-Si complex oxide for skeletal isomerization of 1-hexene and hydrodesulfurization of thiophene Yu Zhao, Jun'en Wang, Hui Chen, Xiaoyan Zhang, Yuchuan Fu, Jianyi Shen 2014, 35 (8):  1402-1409.  DOI: 10.1016/S1872-2067(14)60074-7 Abstract ( 247 )   [Full Text(HTML)] () PDF (1025KB) ( 633 )   The coprecipitation of sodium silicate with cobalt nitrate, combined with an n-butanol drying process, led to the formation of a Co-O-Si complex oxide (Co/Si atomic ratio ≈ 0.65) with atomically dispersed Co and Si atoms. The complex oxide had a high surface area (562 m2/g) and strong surface acidity. Sulfidation resulted in the formation of highly dispersed cobalt sulfide, which had high activity in the hydrodesulfurization (HDS) of thiophene (99.4%) and skeletal isomerization of 1-hexene (35%) at 573 K. The HDS activity was as high as that of the industrial catalyst Co-Mo/γ-Al2O3, although no Mo was present. The material could therefore be used for the skeletal isomerization of linear olefins during deep HDS of gasoline to reduce octane number loss caused by olefin saturation.

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Photodegradation of rhodamine B and methyl orange by Ag3PO4 catalyst under visible light irradiation Ming Ge 2014, 35 (8):  1410-1417.  DOI: 10.1016/S1872-2067(14)60079-6 Abstract ( 408 )   [Full Text(HTML)] () PDF (654KB) ( 993 )   A visible-light-driven Ag3PO4 catalyst was successfully synthesized by a facile ion-exchange route. The as-synthesized Ag3PO4 was characterized by X-Ray diffraction (XRD), field-emission scanning electron microscopy, N2 adsorption-desorption, UV-Vis diffuse reflectance spectroscopy and Fourier transform infrared spectroscopy. Under visible light irradiation, the Ag3PO4 catalyst showed excellent photocatalytic activity for rhodamine (RhB) degradation, but was poor at degrading methyl orange (MO) because of lower adsorption of MO molecules onto the surface of the Ag3PO4. The photodegradation of RhB and MO was achieved by holes and O2·- radical attack in the Ag3PO4 suspension. The photodegradation of MO over the Ag3PO4 catalyst was greatly enhanced in the presence of RhB owing to greater production of O2·- radicals.

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Structural changes of Rh-Mn nanoparticles inside carbon nanotubes studied by X-ray absorption spectroscopy Hongliang Bao, Xueping Sun, Zheng Jiang, Yuying Huang, Jianqiang Wang 2014, 35 (8):  1418-1427.  DOI: 10.1016/S1872-2067(14)60081-4 Abstract ( 341 )   [Full Text(HTML)] () PDF (766KB) ( 611 )   Supported Rh-based catalysts such as Rh-Mn nanoparticles (NPs) have potential use in the synthesis of ethanol from syngas. The structure of Rh-Mn NPs in multi-walled carbon nanotubes under different atmospheres and temperatures was studied by X-ray absorption spectroscopy (XAS). TEM images showed that the NPs dispersed in the carbon nanotubes had a uniform size of 2 nm. XAS data revealed that the Rh-Mn NPs before reduction were composed of Rh2O3 clusters and mixed Mn oxide species. After reduction in a 10% H2-90% He atmosphere, the mixed Mn oxides were converted into nearly pure MnO. In contrast, the Rh2O3 clusters were easily decomposed to metallic Rh clusters even under a He atmosphere at 250 ℃. The Rh clusters remained in the metal state under the next reduction atmosphere, but their dispersion in the Rh-Mn NPs increased with increasing temperature. No significant Mn-Rh or Mn-O-Rh interaction in the reduced NPs was observed in the extended X-ray absorption fine structure analysis. The results showed that there was no interaction between the MnO particles and Rh clusters and the role of the Mn promoter was mainly to improve Rh dispersion.