oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Simultaneous catalytic removal of NOx and diesel soot particulate over perovskite-type oxides and supported Ag catalysts
LIU Zhi-ming,HAO Zheng-ping,GUO Yun,Zhuang Ya-hui,
LIU Zhi-ming
,HAO Zheng-ping,GUO Yun,ZHUANG Ya-hui

环境科学学报(英文版) , 2002,
Abstract: A series of perovskite type oxides and supported Ag catalysts were prepared, and characterized by X ray diffraction (XRD) and X ray photoelectron spectroscopy (XPS). The catalytic activities of the catalysts as well as influencing factors on catalytic activity have been investigated for the simultaneous removal of NOx and diesel soot particulate. An increase in catalytic activity for the selective reduction of NOx was observed with Ag addition in these perovskite oxides, especially with 5% Ag loading. This catalyst could be a promising candidate of catalytic material for the simultaneous elimination of NOx and diesel soot.
Catalytic reduction of nitric oxide with carbon monoxide on copper-cobalt oxides supported on nano-titanium dioxide

CHEN Xi,ZHANG Junfeng,HUANG Yan,TONG Zhiquan,HUANG Ming,

环境科学学报(英文版) , 2009,
Abstract: A series of copper-cobalt oxides supported on nano-titanium dioxide were prepared for the reduction of nitric oxide with carbon monoxide and characterized using techniques such as XRD, BET and TPR. Catalyst CuCoOx/TiO2 with Cu/Co molar ratio of 1/2, Cu- Co total loading of 30% at the calcination temperature of 350°C formed CuCo2O4 spinel and had the highest activity. NO conversion reached 98.9% at 200°C. Mechanism of the reduction was also investigated, N2O was mainly yielded below 100°C, while N2 was produced instead at higher temperature. O2 was supposed to accelerate the reaction between NOx and CO for its oxidation of NO to give more easily reduced NO2, but the oxidation of CO by O2 to CO2 decreased the speed of the reaction greatly. Either SO2 or H2O had no adverse impact on the activity of NO reduction; however, in the presence of both SO2 and H2O, the catalyst deactivated quickly.
Heterogeneous Photooxidation of Phenol by Catalytic Membranes
Enrica Fontananova,Enrico Drioli,Laura Donato,Marcella Bonchio,Mauro Carraro,Gianfranco Scorrano,
Enrica Fontananova
,Enrico Drioli,Laura Donato,Marcella Bonchio,Mauro Carraro,Gianfranco Scorrano

过程工程学报 , 2006,
Abstract: In this work the heterogenization in polymeric membranes of decatungstate, a photocatalyst for oxidation reactions,was reported. Solid state characterization techniques confirmed that the catalyst structure was preserved within the polymeric membranes. The catalytic membranes were successfully applied in the aerobic photo-oxidation of phenol, one of the main organic pollutants in wastewater, providing stable and recyclable photocatalytic systems. The dependence of the phenol degradation rate by the catalyst loading and transmembrane pressure was shown. By comparison with homogeneous reaction,the catalyst heterogenized in membrane appears to be more efficient concerning the rate of phenol photodegradation and mineralization.
Sol-Gel Synthesized Semiconductor Oxides in Photocatalytic Degradation of Phenol  [PDF]
Maria K. Cherepivska,Roman V. Prihod’ko
ISRN Physical Chemistry , 2014, DOI: 10.1155/2014/724095
Abstract: Effectiveness of photocatalytic degradation of phenol in aqueous solution using semiconductor oxides (SO) prepared by a sol-gel method was examined. The physical and chemical properties of synthesized catalysts were investigated by X-ray diffraction (XRD), diffuse reflectance UV-Vis spectroscopy (DRS), and N2-adsorption measurements. The optimal conditions of the photocatalytic degradation of phenol using prepared titanium dioxide sample were defined. 1. Introduction Heterogeneous photocatalysis on the semiconductors allows achieving complete mineralization of the various classes toxic and biorefractory organic substances [1, 2]. Recently, the photocatalytic degradation of toxicants became one of the most promising directions of “green chemistry” [3]. The use of nanosized SO presents a great interest due to their outstanding optical, magnetic, catalytic, and sensing properties [4, 5]. The phenolic compounds contained in the wastewater of chemical, petrochemical, and pharmaceutical industries are hazardous carcinogenic and mutagenic pollutants [6, 7]. Furthermore, the oxidation of these substances in water bodies leads to decrease in dissolved oxygen required for normal functioning of animals and plants. Finding effective methods for the protection of water systems from phenols contamination is an important aim to ensure environmental safety [8, 9]. Among SO photocatalysts (PC) high activity have Fe2O3, WO3, ZnO and TiO2. Iron oxide polymorphs of hematite (α-Fe2O3) are nontoxic, cheap, and stable to photocorrosion material intensively absorbs radiation in the range from 295 to 600?nm. The semiconductor properties of α-Fe2O3 are the same as WO3, which can be seen in the position of band gaps relative to the standard hydrogen electrode. WO3 has chemical stability in acidic medium and electrolyte solutions as well as photoactivity in the near ultraviolet and blue regions of solar spectrum [10]. According to Daneshvar et al. nanosized ZnO is a suitable alternative to TiO2 due to the band gap energy. Dinda and Icli found that ZnO was as reactive as TiO2 for the photocatalytic degradation of phenol under concentrated sunlight [11]. Figure 1 shows a scheme of the energy levels of the studied semiconductor oxides relative to the standard hydrogen potential [12]. Several authors have associated the efficiency of semiconductor photocatalysts with electronic, structural, and morphological properties of the material such as band gap energy, crystalline structure, surface area, particle size [13]. Figure 1: Energy band gap of investigated semiconductor oxides. The
Mesoporous SiO2-Supported Pt Nanoparticles for Catalytic Application  [PDF]
Yingze Cao,Wentao Zhai,Xiang Zhang,Shuxi Li,Lin Feng,Yen Wei
ISRN Nanomaterials , 2013, DOI: 10.1155/2013/745397
Abstract: SiO2 nanoparticles have been synthesized by combining Stober’s method and nonsurfactant process. The diameters and pore sizes can be controlled by altering the template and its concentration. Mesoporous SiO2 obtained this way has extremely large surface area compared with most oxide supports, which benefits the catalytic performance. Pt nanoparticles were in situ grown on and in mesoporous SiO2 nanoparticles with low amount of the metal and high load ratio. Furthermore, we firstly developed a novel route, called “one-pot” method, to prepare Pt/SiO2 catalyst where mesoporous silica preparing and Pt loading occurred in one step. This method is more efficient in saving reagent, since it can prevent Pt loss. In the meantime, it enables the template to reduce agent. The catalytic activity of Pt/SiO2 samples was measured by CO oxidation. It is indicated that the supporting silica with mesopores is more active than silica with micropores. 1. Introduction With the acceleration of industrialization and the increase of pollution, new catalysts development becomes very important. It is especially true when it comes to catalysts used to process gases from the incomplete combustion [1]. The incomplete combustion occurs in gasoline engine mainly discharges three kinds of harmful emissions: carbon monoxide (CO), unburned hydrocarbon emissions, and nitrogen oxides (NOx) [2]. With the establishment of stricter exhaust standards, together with the limit reserves and high cost of rare metals, preparing efficient catalyst with trace rare metals becomes the focus of study [3]. Three-way catalysis (TWC) which is a revolution can simultaneously converse the three major emissions into CO2, H2O, and N2. The active substance of TWC is usually made of Pt, Pd, and Rh loaded on oxide supporting [2]. Recently, many researches have been developed around oxide supporting such as ceria, zirconia, alumina, and composite ceria-zirconia supporting [4–11]. Silica has also been used for supporting noble metals. For example, mixed oxide catalysts silica-ceria have been prepared through coprecipitation after hydrothermal synthesis for reduction and oxygen storage. The noble metals were loaded after calcination of the supports. The catalyst was fairly active. The full CO oxidation conversion was about 400°C, and the calcination limited the oxygen storage [12]. Also the catalytic performances of noble metals supported on mesoporous silica MCM-41 were investigated for the hydrodesulfurization of benzothiophene. MCM-41 was made by the surfactant method and had been treated at a very high
氧化铁负载铂纳米簇催化卤代硝基苯本体氢化性质研究
Catalytic Properties of Platinum Nanoclusters Supported on Iron Oxides for the Solvent-Free Hydrogenation of Halonitrobenzene
 [PDF]

连超,张垲,王远,()
- , 2017, DOI: 10.3866/PKU.WHXB201702084
Abstract: 复相金属催化剂中的载体效应研究具有重要意义。我们以结构不同的氧化铁载体吸附“非保护型”Pt金属纳米簇制备了具有相同Pt纳米簇的Pt/Fe3O4、Pt/γ-Fe2O3和Pt/α-Fe2O3催化剂,考察了其在无溶剂条件下(本体条件)催化邻氯硝基苯(o-CNB)选择性氢化反应的性能,发现三种铂/氧化铁催化剂的催化选择性远高于商购铂/碳催化剂,Pt/γ-Fe2O3和Pt/α-Fe2O3的催化选择性明显高于Pt/Fe3O4,而Pt/Fe3O4的催化活性较Pt/α-Fe2O3高50%。铂/氧化铁对不同卤代硝基苯的本体选择性氢化反应表现出优良的催化性能,相应卤代苯胺产物的选择性均可达到99%以上。考察了温度、氢气压力对Pt/Fe3O4催化o-CNB本体氢化性能的影响。本工作为理解氧化铁负载金属纳米簇催化剂的特殊催化性质,进而发展高效金属纳米簇基催化体系提供了新的基础。
It is of significance to investigate the support effect in heterogeneous metal catalysts. Pt/Fe3O4, Pt/ γ-Fe2O3, and Pt/α-Fe2O3 nanocomposites with the same Pt nanoclusters were prepared by adsorbing Pt colloidal particles stabilized with simple ions and solvent molecules on different iron oxide supports. The catalytic performances over the as-prepared catalysts for the selective hydrogenation of o-chloronitrobenzene (o-CNB) in the absence of solvent were evaluated. It was found that the catalytic activity and selectivity over the prepared iron oxide-supported Pt nanocluster catalysts were higher than those of a commercial Pt/C catalyst. The selectivity towards o-chloroaniline over Pt/γ-Fe2O3 or Pt/α-Fe2O3 was higher than that over Pt/Fe3O4, while the catalytic activity over Pt/Fe3O4 was 50% higher than that over Pt/α-Fe2O3. The Pt/iron oxide catalysts also exhibited excellent catalytic properties for the solvent-free selective hydrogenation of other tested halonitrobenzenes, with the selectivity to corresponding haloanilines being > 99%. In addition, the influences of temperature and hydrogen pressure on the solvent-free selective hydrogenation of o-CNB over Pt/Fe3O4 were studied. This work is helpful in understanding the superior properties of iron oxide-supported metal nanocluster catalysts and provides a foundation for further developing highly efficient catalytic systems based on metal nanoclusters
Preparation and catalytic properties of ZrO2-Al2O3 composite oxide supported nickel catalysts for methane reforming with carbon dioxide
HAO Zheng-ping,HU Chun,Jiang Zheng,GQLU,
HAO Zheng-ping
,HU Chun,JIANG Zheng,G. Q. LU

环境科学学报(英文版) , 2004,
Abstract: ZrO 2-Al 2O 3 composite oxides and supported Ni catalysts were prepared, and characterized by N 2 adsorption /desorption, X-ray diffraction(XRD) an d X-ray photoelectron spectroscopy(XPS) techniques. The catalytic performance and carbon deposition was also investigated. This mesoporous composite oxide is shown to be a promising catalyst support. An increase in the catalytic activity and stability of methane and carbon dioxide reforming reaction was resulted from the zirconia addition, especially at 5wt% ZrO 2 content. The Ni catalyst supported ZrO 2-Al 2O 3 has a strong resistance to sintering and the carbon deposition in a relatively long-term reaction.
First-principles theoretical evaluation of crystalline zirconia and hafnia as gate oxides for Si microelectronics  [PDF]
V. Fiorentini,G. Gulleri
Physics , 2002, DOI: 10.1103/PhysRevLett.89.266101
Abstract: Parameters determining the performance of the crystalline oxides zirconia (ZrO_2) and hafnia (HfO_2) as gate insulators in nanometric Si electronics are estimated via ab initio calculations of the energetics, dielectric properties, and band alignment of bulk and thin-film oxides on Si (001). With their large dielectric constants, stable and low-formation-energy interfaces, large valence offsets, and reasonable (though not optimal) conduction offsets (electron injection barriers), zirconia and hafnia appear to have a considerable potential as gate oxides for Si electronics.
Precursor type affecting surface properties and catalytic activity of sulfated zirconia
Zarubica Aleksandra R.,Bo?kovi? Goran C.
Acta Periodica Technologica , 2007, DOI: 10.2298/apt0738105z
Abstract: Zirconium-hydroxide precursor samples are synthesized from Zr-hydroxide, Zr-nitrate, and Zr-alkoxide, by precipitation/impregnation, as well as by a modified sol-gel method. Precursor samples are further sulphated for the intended SO4 2- content of 4 wt.%, and calcined at 500-700oC. Differences in precursors’ origin and calcination temperature induce the incorporation of SO4 2- groups into ZrO2 matrices by various mechanisms. As a result, different amounts of residual sulphates are coupled with other structural, as well as surface properties, resulting in various catalytic activities of sulphated zirconia samples. Catalyst activity and selectivity are a complex synergistic function of tetragonal phase fraction, sulphates contents, textural and surface characteristics. Superior activity of SZ of alkoxide origin can be explained by a beneficial effect of meso-pores owing to a better accommodation of coke deposits.
Electrochemical Study of Iodide in the Presence of Phenol and o-Cresol: Application to the Catalytic Determination of Phenol and o-Cresol  [PDF]
Lida Fotouhi,Mahsa Ganjavi,Davood Nematollahi
Sensors , 2004, DOI: 10.3390/s41100170
Abstract: The electrochemical oxidation of iodide in the presence of phenol and o-cresol was investigated at a glassy carbon electrode in buffered media by cyclic voltammetry, linear sweep voltammetry and controlled–potential coulometry. The experimental results indicate that the phenol and o-cresol convert to their derivatives after participating in a halogenation coupled reaction (quasi-catalytic reaction) following the oxidation of iodide to iodine. The concentrations of phenol and o-cresol have been determined in aqueous solutions according to the linear dependence of quasi-catalytic peak currents with the concentration. The calibration graphs show two linear sections of 0.0 to 1.0×10-4 M and 2.0×10-4 to 1.0 ×10-3 M for phenol and 4.2×10-5 to 1.0×10-4 M and 2.0×10-4 to 1.0×10-3 M for o-cresol. The theoretical detection limits and the relative standard deviations for ten measurements of phenol and o-cresol are 1.125×10-5 M, 1.06% and 4.201×10-5 M, 1.44%, respectively.
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.