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    Chinese Journal of Catalysis
    2010, Vol. 31, No. 11
    Online: 12 November 2010

    Cover:

    In their article on pages 1307–1315, LI Xuemei et al. give an overview on monolayer-protected gold (MPG) nanoparticle surface-bound catalysts with special focus on their preparation, catalytic properties, and characteristics of both a homogeneous and heterogeneous catalyst. The scheme illustrates the structure of an MPG-surface bound catalyst system including catalytic ligands and reactions.

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    Summary
    Monolayer-Protected Gold Nanoparticle Surface-Bound Catalysts: Preparation and Application
    JIA Lifeng, HE Tao*, LI Zhipeng, LI Xue-Mei*
    2010, 31 (11):  1307-1315.  DOI: 10.1016/S1872-2067(10)60118-0
    Abstract ( 3082 )   [Full Text(HTML)] () PDF (604KB) ( 1260 )  
    Precious metal nanomaterials have shown significantly different reactivity and catalytic activity because of their small-size effects. In this report, we focused on gold nanoparticle-based catalysts, especially gold nanoparticle surface-bound catalysts, their preparation and application. Because of its special surface properties, gold can form stable bonds with sulfur containing molecules including sulfides and thiols. These molecules form well ordered self-assembled monolayers on gold nanoparticles, which render monolayer-protected gold nanoparticles (MPGs) with good solubility, easy characterization, extraordinary stability, and versatility. With attached functional groups, we used MPGs as surface-bound catalysts. These catalysts show the combined characteristics of a homogeneous and a heterogeneous catalyst, which is critical for theoretical aspects and in the development of new types of surface-bound catalysts.
    Research Briefing
    An Efficient Protocol for a Pd(OAc)2-Catalyzed Ligand-Free Suzuki Reaction in Toluene
    LIU Ning, LIU Chun*, JIN Zilin
    2010, 31 (11):  1316-1320.  DOI: 10.1016/S1872-2067(10)60119-2
    Abstract ( 3056 )   [Full Text(HTML)] () PDF (284KB) ( 1228 )  
    An efficient protocol for a Pd(OAc)2-catalyzed ligand-free Suzuki reaction of aryl bromides with arylboronic acids in the presence of K3PO4·7H2O in toluene under mild and aerobic conditions afforded cross-coupling products in good to excellent yields. Under the optimized reaction conditions (i.e., 0.5 mmol ArBr, 0.75 mmol ArB(OH)2, 1 mol% Pd(OAc)2, 1.0 mmol K3PO4·7H2O, 2 ml toluene), the Suzuki reaction between 4-nitrobromobenzene and phenylboronic acid afforded a 99% isolated yield in 5 min at 75 °C and a TOF of up to 1 188 h-1.
    Research papers
    Amorphous Mesoporous Iron Aluminophosphate Catalyst for the Synthesis of 1,5-Benzodiazepines
    A. V. VIJAYASANKAR1, S. DEEPA1, B. R. VENUGOPAL2, N. NAGARAJU1,*
    2010, 31 (11):  1321-1327.  DOI: 10.1016/S1872-2067(10)60120-9
    Abstract ( 2570 )   [Full Text(HTML)] () PDF (298KB) ( 1141 )  
    A simple and versatile method for the synthesis of 1,5-benzodiazepines from o-phenylenediamine and ketones in the presence of solvents and under solvent-free conditions that used an amorphous mesoporous iron aluminophosphate as catalyst was developed. High yields with excellent selectivity were obtained with a wide variety of ketones under mild reaction conditions. The catalyst had the advantages of ease of preparation, ease of handling, simple recovery, reusability, non toxicity, and being inexpensive.
    Synthetic CeO2 Nanoparticle Catalysis of Methylene Blue Photodegradation: Kinetics and Mechanism
    H. R. POURETEDAL1,*, A. KADKHODAIE2
    2010, 31 (11):  1328-1334.  DOI: 10.1016/S1872-2067(10)60121-0
    Abstract ( 3855 )   [Full Text(HTML)] () PDF (293KB) ( 4138 )  
    CeO2 nanocrystals were synthesized by a simple precipitation method and calcination at 600 °C. (NH4)2Ce(NO3)6 and ammonia were used as precursors. The CeO2 nanoparticles were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and N2 adsorption. The photodegradation of methylene blue catalyzed by CeO2 nanoparticles was studied under UV and sunlight irradiation. The highest degradation was obtained with 1.0 g/L CeO2 at pH 11 within 125 min. The pseudo first order rate constants of dye bleaching were calculated as 16.2x10-3 and 15.7x10-3 min-1 under UV and sunlight irradiation, respectively. The effect of iso-PrOH, iodide ion, and H2O2 was studied to predict the pathway of dye degradation. The obtained results indicate the effect of photogenerated holes in the degradation mechanism of the dye. Also, the photocatalytic activity of the prepared photocatalyst was studied in the presence of several negative ions.
    57Fe Mössbauer Spectroscopy of Ir-Fe Catalysts for Preferential CO Oxidation in H2
    LIU Kuo1,2, ZHANG Wansheng1, WANG Junhu1, WANG Aiqin1, HUANG Yanqiang1, JIN Changzi1, SHEN Jianyi3,#, ZHANG Tao1,*
    2010, 31 (11):  1335-1341.  DOI: 10.1016/S1872-2067(10)60122-2
    Abstract ( 3177 )   [Full Text(HTML)] () PDF (652KB) ( 1100 )  
    New insights on the interaction between Ir and Fe oxide are reported. Three Ir-Fe catalysts were prepared by different impregnation sequences of an Al2O3 support. Co-impregnation gave a better catalyst for the preferential CO oxidation in H2 (PROX) reaction. Microcalorimetry data showed that the adsorption of CO and H2 were different. Quasi in situ Mössbauer data of the three catalysts after reduction, reoxidation, and PROX reaction showed that a strong interaction between Ir and Fe affected the redox properties of the Ir-Fe catalysts. CO conversion was proportional to the concentration of the Fe2+(a) species, thus, Fe2+(a) was an active site in the PROX reaction. The impregnation sequence influenced the interaction between Ir and Fe and consequently, the amount of the active Fe2+(a) species. A strong Ir-Fe interaction stabilized the active Fe2+ sites for activating O2.
    The Effect of Preparation Procedure on the Performance of Pd-SiW12/SiO2 Catalysts for the Direct Oxidation of Ethylene to Acetic Acid
    XU Shuliang1,2, CHU Wenling2,*, YANG Weishen2,#
    2010, 31 (11):  1342-1346.  DOI: 10.1016/S1872-2067(10)60123-4
    Abstract ( 2834 )   [Full Text(HTML)] () PDF (464KB) ( 841 )  
    Pd-SiW12/SiO2 catalysts were investigated to elucidate the effect of preparation procedure on the direct oxidation of ethylene to acetic acid. Pd-SiW12/SiO2 catalysts with a fixed amount of Pd and SiW12 were prepared in various ways. The order in which Pd and SiW12 were loaded on the SiO2 support and the treatment conditions for the supported Pd have a significant influence on the dispersion of Pd on the Pd-SiW12/SiO2 catalysts, but no influence on the concentration of B acid sites. The Pd-SiW12/SiO2 catalyst prepared by simultaneously loading Pd and SiW12 on the SiO2 support showed the best catalytic activity. The dispersion of Pd was the main factor in the catalytic activity.
    Catalytic Oxidation of Sulfides to Sulfoxides by Poly(4-vinyl pyridinium nitrate), Silica Sulfuric Acid and Ammonium Bromide as a Catalyst
    Arash GHORBANI-CHOGHAMARANI1,*, Sara SARDARI2
    2010, 31 (11):  1347-1350.  DOI: 10.1016/S1872-2067(10)60124-6
    Abstract ( 3087 )   [Full Text(HTML)] () PDF (267KB) ( 1119 )  
    A new catalytic procedure for the chemoselective oxidation of sulfides to sulfoxides was studied. A variety of aliphatic and aromatic sulfides were subjected to sulfoxidation by combining poly(4-vinyl pyridinium nitrate), silica sulfuric acid (SiO2-OSO3H), and catalytic amounts of ammonium bromide in CH2Cl2 in the presence of a few drops of water at room temperature. Excellent yields were obtained.
    Electrochemical Oxidation of Saccharose on Copper (Hydr)oxide- Modified Electrode in Alkaline Media
    Majid JAFARIAN1,*, Mehdi RASHVAND AVEI1, Iman DANAEE2, Fereydoon GOBAL3, Mohammad G. MAHJANI1
    2010, 31 (11):  1351-1357.  DOI: 10.1016/S1872-2067(10)60125-8
    Abstract ( 2954 )   [Full Text(HTML)] () PDF (640KB) ( 1366 )  
    A stable copper (hydr)oxide-modified electrode was prepared in 0.5 mol/L NaOH solution by cyclic voltammetry in the range of -250 to 1 000 mV. It can be used for electrochemical studies in the range of -250 to 1 000 mV without interfering peaks because there is no oxidation of copper. During an anodic potential sweep, the electro-oxidation of saccharose on Cu occurred by the formation of CuIII and this reaction also occurred in the early stages of the reversed cycle until it is stopped by the negative potentials. A mechanism based on the electro-chemical generation of CuIII active sites and their subsequent consumption by saccharose was proposed, and the rate law and kinetic parameters were obtained. The charge transfer resistance from theoretical and impedance studies was used to verify the mechanism. Under chronoamperometry regimes, the reaction followed Cottrellian behavior. The transfer of up to 21 electrons was observed in further investigations of the electro-oxidation of saccharose on a (hydr)oxide Cu rotating disk electrode.
    Influence of Nickel Precursors on Catalytic Activity of Non-supported Ni for Methane Decomposition
    ZHANG Wei1,2, GE Qingjie1,*, XU Hengyong1,*
    2010, 31 (11):  1358-1362.  DOI: 10.3724/SP.J.1088.2010.00430
    Abstract ( 2809 )   [Full Text(HTML)] () PDF (493KB) ( 1031 )  
    Non-supported nickel oxide catalyst samples were prepared by precipitation using different nickel precursors. The influence of nickel precursors on catalyst behavior was investigated by X-ray diffraction, H2 temperature-programmed reduction, CH4 temperature-programmed surface reaction, and methane decomposition stability tests. The results showed that the particle size of the NiO sample prepared from a nickel acetate precursor (named NiO-A) was smaller than that of the NiO sample prepared from nickel nitrate (NiO-N). NiO-A could be reduced more easily than NiO-N, and the activity of the reduced NiO-A sample (Ni-A) for methane decomposition was higher than that of the reduced NiO-N sample (Ni-N). The complexation of nickel acetate with glycol was the key factor leading to the smaller NiO particles. The results of the catalytic stability tests showed that the Ni-A catalyst exhibited higher stability than the Ni-N catalyst.
    Methane Combustion over Pd/Al2O3 Catalyst: Effect of Calcination Temperature
    GAO Diannan1, WANG Sheng1, LIU Ying1,2, ZHANG Chunxi1, WANG Shudong1,*
    2010, 31 (11):  1363-1368.  DOI: 10.3724/SP.J.1088.2010.00417
    Abstract ( 2768 )   [Full Text(HTML)] () PDF (715KB) ( 1023 )  
    The effect of calcination temperature for the support and catalyst on the catalytic properties of the Pd/Al2O3 catalyst for lean methane combustion was investigated. The Pd/Al2O3 catalyst was prepared by the impregnation method using Al2O3 support calcined at 500–1 300 °C. All catalyst samples were characterized by X-ray diffraction, transmission electron microscopy, surface area measurements, temperature-programmed desorption of NH3, and temperature-programmed oxidation of O2. Calcination temperature significantly affected the catalyst activity and stability. As the calcination temperature increased, the structure of the support and the amount and intensity of the acid sites changed obviously, and the dispersion of the active component and the interaction between the support and active component decreased. The proper calcination temperature for the Al2O3 support was 1 100 °C, and the optimal calcination temperature for the Pd/Al2O3 was 200 °C. This catalyst showed high thermal stability and catalytic activity.
    Selective Oxidation of Benzyl Alcohol Catalyzed by Pd/PMO-SBA-15 Catalyst
    LIU Cheng1, TAN Rong1,*, YIN Donghong1,2,*, YU Ningya1, ZHOU Yuxu
    2010, 31 (11):  1369-1373.  DOI: 10.3724/SP.J.1088.2010.00447
    Abstract ( 2885 )   [Full Text(HTML)] () PDF (472KB) ( 970 )  
    Pd nanoparticles were successfully captured by tetraimine groups incorporated into the channel of periodic mesoporous organosilica (PMO-SBA-15), yielding a Pd-containing mesoporous organosilica catalyst (Pd/PMO-SBA-15). N2 adsorption-desorption, X-ray diffraction, and transmission electron microscopy confirmed that the Pd nanoparticles were well stabilized and dispersed uniformly inside the channel of the PMO with average particle size of 1.8 nm. The Pd/PMO-SBA-15 was used as a catalyst for selective oxidation of benzyl alcohol with H2O2 as oxidant in water. The effects of various nanoparticles, H2O2 amount, reaction temperature, and reaction time on the oxidation were investigated. The benzyl alcohol conversion of 97.1% with the selectivity for benzaldehyde of 100.0% was obtained when the reaction was carried out in water with 0.05 g of 2%Pd/PMO-SBA-15 and 1.5 ml of H2O2 at 80 oC for 4 h. Furthermore, the Pd/PMO-SBA-15 could be conveniently recovered for recycle use. The conversion of benzyl alcohol decreased with the increase of reuse times.
    Preparation of SBA-15-Supported β-Mg2V2O7 Catalysts and Their Properties in Oxidative Dehydrogenation of Propane
    ZHANG Shenghong, ZHANG Hongpeng, SUN Jiying, LIU Haichao*
    2010, 31 (11):  1374-1380.  DOI: 10.3724/SP.J.1088.2010.00451
    Abstract ( 2281 )   [Full Text(HTML)] () PDF (577KB) ( 998 )  
     β-Mg2V2O7 catalysts supported on MgO-modified SBA-15 with V surface density of 4.1-8.5 nm-2 were synthesized by impregnation of the support with a pre-prepared aqueous solution of ammonium metavanadate, citric acid, and magnesium nitrate. The structure and reducibility of the catalysts were characterized by X-ray diffraction, Raman spectroscopy, diffuse reflectance UV-Vis spectroscopy, and temperature-programmed reduction in H2. For oxidative dehydrogenation (ODH) of propane, bulk β-Mg2V2O7 phase was much less active and selective than α-Mg2V2O7 although they have the same dimeric tetrahedral VO4 units connected by bridging V-O-V bonds. Compared to the bulk phase, the greater accessibility of V sites on the supported β-Mg2V2O7 catalysts led to an increase in not only the initial propane ODH rates by about 20 times but also the initial propene selectivity from 88.3 to 94.1%, as high as that for α-Mg2V2O7 (94.6%) that has been considered as the most selective Mg-V-O phase for propane ODH reactions. The selectivity results are consistent with those reflected by the two kinetic parameters, k1/k2 and k3/k1, which represent the ratios of the rate constants for primary propane ODH (k1) to propane combustion (k2) and that for secondary propene combustion (k3) to k1. Such understanding on the intrinsic catalytic properties of the bulk and supported Mg2V2O7 catalyst provides useful information for design of new Mg-V-O-based catalysts, for example, dispersed α-Mg2V2O7 catalyst with high activity and selectivity for propane ODH reactions under mild conditions.
    Preparation, Charaterization, and Photocatalytic Activity of TiO2/Mo-TiO2
    LIU Xingping, JIANG Rongying, LIU Song*
    2010, 31 (11):  1381-1387.  DOI: 10.3724/SP.J.1088.2010.00432
    Abstract ( 2473 )   [Full Text(HTML)] () PDF (656KB) ( 1116 )  
    Mo-doped TiO2 photocatalysts (Mo-TiO2) were prepared by the traditional sol-gel method using (NH4)6Mo7O24?4H2O and tetrabutyl titanate (Ti(OC4H9)4) as the raw materials. TiO2/Mo-TiO2 composite photocatalysts were prepared by mixing TiO2 sol with sol-gel derived Mo-TiO2 powder followed by drying and calcination. The samples were used as catalysts for methyl orange photodegradation in aqueous suspension under UV irradiation, which was used as a probe reaction. X-ray diffraction patterns showed that particles were in the form of anatase and there was no change in crystal structure except a slight variation in crystallite size. The photocatalytic activity of the Mo-TiO2 photocatalysts was lower than that of undoped TiO2, and the photodegradation rate decreased with an increase in the level of molybdenum doped (on TiO2). The reduced activity can be explained by the fact that dopants act more as recombination centers than as trap sites for charge transfer at the interface, especially for the samples with higher molybdenum ion dopant concentration. The TiO2/Mo-TiO2 composite photocatalysts have the n-n heterojunction and have a higher photocatalytic destruction rate than the Mo-TiO2 photocatalysts and undoped TiO2, which is mainly ascribed to the electrostatic-field-driven electron-hole separation in the TiO2/Mo-TiO2 composite photocatalysts. The best TiO2/Mo-TiO2 composite with TiO2:2mol% Mo-TiO2 mass ratio of 10:1 shows 1.57 times the photocatalytic activity of undoped TiO2.
    Preparation of Ordered Mesoporous Organometallic Pd(II) and Its Catalytic Performance for Suzuki Reactions in Water Medium
    ZHU Fengxia, YANG Xushi, YANG Didi, LI Hexing*
    2010, 31 (11):  1388-1392.  DOI: 10.3724/SP.J.1088.2010.00525
    Abstract ( 2620 )   [Full Text(HTML)] () PDF (522KB) ( 1030 )  
    Ordered mesoporous Pd(II) organometallic catalyst Pd(II)-PMO(Et) was synthesized by surfactant-directed co-polymerization of ethyl- and Pd(II) organometal-bridged silanes, and was characterized by Fourier transform infrared spectroscopy, NMR, X-ray powder diffraction, transmission electron microscopy, and nitrogen sorption techniques. Compared with the as-prepared Pd(II)-PMO(Et)-G by the grafting method, Pd(II)-PMO(Et) catalyst showed high dispersion of Pd(II) active sites and reduced diffusion limit. Moreover, this catalyst exhibited similar activity to the corresponding Pd(PPh3)2Cl2 homogeneous catalyst in water-medium Suzuki reactions. This can be attributed to the high dispersion of Pd(II) active sites, ordered mesoporous channels, and strong surface hydrophobicity resulted from ethyl fragments embedded in silica walls, the facilitating diffusion and adsorption of organic molecules onto the catalyst in aqueous solution. The Pd(II)-PMO(Et) could be used repeatedly and showed excellent durability, which can be attributed to the effective inhibition of Pd(II) leaching and the high hydrothermal stability of the mesoporous structure.
    Effect of Carbon Promoters on the Performance of Cu-Zn-Al Catalyst Prepared by Complete Liquid-Phase Technology
    HUANG Wei*, LI Wenhui, SUN Jingxiao, YIN Lihua
    2010, 31 (11):  1393-1398.  DOI: 10.3724/SP.J.1088.2010.00464
    Abstract ( 2502 )   [Full Text(HTML)] () PDF (615KB) ( 823 )  
    Cu-Zn-Al slurry catalysts were prepared by a complete liquid-phase technology and characterized by X-ray diffraction, N2 adsorption, H2 temperature-programmed reduction, and NH3 temperature-programmed desorption. The effects of carbon nanotubes and carbon microspheres as promoters on catalyst performance for alcohol synthesis were investigated. The results indicated that the Cu-Zn-Al methanol synthesis catalysts showed activity for the synthesis of higher alcohols and hydrocarbons. Cu0 particles with larger grain size were conducive to the growth of carbon chains. Adding carbon microspheres can significantly decrease the size of Cu0 particles and improve the selectivity for methanol.
    Photocatalytic Activity of Fe-Doped Titania Hollow Spheres Prepared by Hydrothermal Precipitation
    KUANG Jidong, LIN Bizhou*, CHEN Yilin, PIAN Xuetao, ZHANG Kezhi, ZHANG Ou
    2010, 31 (11):  1399-1404.  DOI: 10.3724/SP.J.1088.2010.00514
    Abstract ( 3129 )   [Full Text(HTML)] () PDF (852KB) ( 1470 )  
    Fe-doped titania hollow spheres (Fe-TiO2) with different dopant contents have been prepared by a hydrothermal precipitation method with carbon spheres as the template. The phase structure, morphology, composition, and crystalline grain size were characterized by X-ray powder diffraction, scanning electron microscopy, infrared spectroscopy, thermogravimetry/differential scanning calorimetry. The as-prepared hollow spheres were anatase with 0.5–3.20 mm in diameter, 30–60 nm in thickness, and 150–300 m2/g in specific surface area. With increasing dopant content, Fe-TiO2 exhibited an intense absorption in the visible light region. Fe-TiO2 exhibited photocatalytic activity for the degradation of methylene blue under visible light irradiation, and the degradation rate of methylene blue over 0.5% Fe-TiO2 hollow spheres was about 75% in 80 min. The catalytic reaction mechanism was discussed.
    Preparation, Characterization and Application of Cyclopentadiene-Containing Mesoporous Ethanesilica
    ZHOU Yuan, GAO Pengfei, ZHANG Tieming, WANG Yongzhao, ZHAO Yongxiang*
    2010, 31 (11):  1405-1410.  DOI: 10.3724/SP.J.1088.2010.00518
    Abstract ( 2521 )   [Full Text(HTML)] () PDF (792KB) ( 727 )  
    By adjusting the prehydrolysis time of (2-(cyclopenta-1,3-dienyl)ethyl)triethoxysilane (TEECp), cyclopentadiene-containing mesoporous ethanesilica (Cp-PMO) was synthesized through the co-condensation of 1,2-bis(triethoxysilyl)ethane (BTEE) and TEECp using triblock PEO-PPO-PEO copolymer P123 as the structure-directing agent. The prepared material samples were characterized by X-ray diffraction, N2 adsorption-desorption, transmission electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The results showed that cyclopentadiene was successfully incorporated into the material, which had highly ordered hexagonal mesostructure. With increasing cyclopentadiene loading, the mesostructure order, pore size, BET surface area, and pore volume of Cp-PMO decreased, while the pore wall widths increased. The Cp-PMO with 30% cyclopentadiene loading showed high activity in the transesterification of ethyl acetate and n-butanol to n-butyl acetate and its yield was 10.6%.
    Activity of Monolith Cu-ZSM-5 Catalyst for Selective Catalytic Reduction of NO with NH3
    ZHANG Qiulin, QIU Chuntian, XU Haidi, LIN Tao, GONG Maochu, CHEN Yaoqiang*
    2010, 31 (11):  1411-1416.  DOI: 10.3724/SP.J.1088.2010.00524
    Abstract ( 2902 )   [Full Text(HTML)] () PDF (551KB) ( 1335 )  
    A series of Cu-ZSM-5 catalyst samples with different Cu contents were prepared by an incipient wetness impregnation method and were used for selective catalytic reduction (SCR) of NO with NH3. The results showed that the Cu-ZSM-5 with 8% Cu loading had the highest catalytic activity. The conversion of NO was above 80% at 198–440 oC, and the highest conversion was 97% at a space velocity of 30 000 h–1. The space velocity had less influence on the catalytic activity, and the catalytic activity temperature window was still wide at a space velocity of 60 000 h–1. After hydrothermal aging, the catalytic activity of the Cu-ZSM-5 was significantly higher than that of the commercial V-based catalyst. The addition of H2O and SO2 lead to the reduced activity; however, the catalytic activity was still good. X-ray diffraction and NH3 temperature-programmed desorption results indicated that more Cu immigrated into the cation sites of ZSM-5 and the active sites of the catalyst increased when the Cu content reached 8%. Moreover, the Cu-ZSM-5 had more surface acidity centers and surface acidity, which were beneficial to SCR reaction.