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Chinese Journal of Catalysis
2013, Vol. 34, No. 11
Online: 18 October 2013


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This special issue is dedicated to Professor Yi Chen in honor of his 80th birthday for his outstanding contributions to the development of research on catalysis and to chemistry and chemical education in China. We sincerely wish him good health and happiness!

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Table of Contents for Vol. 34 No. 11 2013, 34 (11):  0-0.  Abstract ( 203 )   PDF (2750KB) ( 692 )

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Preface to Special Issue of Chinese Journal of Catalysis in Honor of the 80th Birthday of Professor Yi Chen Weiping Ding, Wenhua Hou, Lin Dong 2013, 34 (11):  1961-1963.  DOI: 10.1016/S1872-2067(12)60725-6 Abstract ( 479 )   [Full Text(HTML)] () PDF (417KB) ( 632 )

Reviews

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Progress in organic reactions catalyzed by bimetallic nanomaterials Shuangfei Cai, Dingsheng Wang, Zhiqiang Niu, Yadong Li 2013, 34 (11):  1964-1974.  DOI: 10.1016/S1872-2067(12)60701-3 Abstract ( 699 )   [Full Text(HTML)] () PDF (729KB) ( 1544 )   Nanocatalysis, which is also known as semi-heterogeneous catalysis, sits at the boundary between homogeneous catalysis and heterogeneous catalysis and has been the subject of increasing interest during the course of the last few years. Significant progress has recently been made towards the catalytic applications of bimetallic nanomaterials, which show high levels of activity, selectivity and recyclability. This review provides a summary of bimetallic nanomaterial-catalyzed organic transformations, including selective oxidation, hydrogenation, and coupling reactions, as well as dechlorination, amidation, reductive amination, and hydrogenolysis reactions, and the asymmetric 1,4-addition reactions of arylboronic acids to enones. The complex organic molecules using bimetallic nanocatalysis would be anticipated soon. There is significant scope for bimetallic nanocatalysts to be further developed in terms of our general understanding of their fundamental properties and practical applications. Future development may benefit from the rational design and controllable synthesis of bimetallic nanomaterials, as well as a deeper understanding of their reaction mechanisms and further progress towards the development of sophisticated computational studies involving catalysis, which would require interdisciplinary collaborations.

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The application of incorporation model in γ-Al2O3-supported single and dual metal oxide catalysts：A review Xiaojiang Yao, Fei Gao, Lin Dong 2013, 34 (11):  1975-1985.  DOI: 10.1016/S1872-2067(12)60708-6 Abstract ( 480 )   [Full Text(HTML)] () PDF (1184KB) ( 858 )   The investigation of the interaction between the surface dispersed components and the supports is the key to understand the nature of catalytic reactions. A single metal oxide (CuO) and dual metal oxides (CuO-Mn2O3, CuO-CoO, etc.) were supported on γ-Al2O3 to produce model catalysts. The dispersion behavior of these metal oxides on the surface of γ-Al2O3 and some physicochemical properties were explained using the Incorporation Model. These properties were considered together with their catalytic performances in CO+O2 and NO+CO model reactions to explore "composition-structure-property" relationships. A possible reaction mechanism involving surface synergetic oxygen vacancy on the supported dual metal oxide catalysts was proposed to approach the nature of NO reduction by CO.

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A mini review on carbon-based metal-free electrocatalysts for oxygen reduction reaction Lijun Yang, Yu Zhao, Shen Chen, Qiang Wu, Xizhang Wang, Zheng Hu 2013, 34 (11):  1986-1991.  DOI: 10.1016/S1872-2067(12)60713-X Abstract ( 453 )   [Full Text(HTML)] () PDF (548KB) ( 1109 )   Exploration of low-cost and high-performance oxygen reduction reaction (ORR) electrocatalysts to replace Pt-based catalysts is now undergoing fast and dynamic development. Metal-free carbon-based ORR electrocatalysts have interesting catalytic activities, high stabilities, and good CO and methanol tolerances, and their constituents are abundantly available. They are therefore potential alternatives to Pt-based catalysts. This paper briefly reviews the main progress in this emerging field, in combination with studies performed by our group. Special attention is paid to electron-rich N or electron-deficient B mono-/co-doped carbon nanostructures, and the correlation between the ORR activity and the electronic structure of the sp2 carbon material. The bright perspectives are speculated for this new kind of promising metal-free ORR electrocatalysts.

Communications

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Performance of polyaniline-derived Fe-N-C catalysts for oxygen reduction reaction in alkaline electrolyte Xiang-Hui Yan, Gui-Rong Zhang, Bo-Qing Xu 2013, 34 (11):  1992-1997.  DOI: 10.1016/S1872-2067(12)60714-1 Abstract ( 489 )   [Full Text(HTML)] () PDF (928KB) ( 1086 )   Without the presence of any precious metal, Fe-N-C materials derived from pyrolysis of polyaniline (PANI)/carbon/FeCl3 mixtures are recognized as new catalysts for cathodic oxygen reduction reaction (ORR) in acidic electrolyte. How these Fe-N-C catalysts would perform in an alkaline electrolyte remains yet unknown. Reported here are assessments of the ORR performance of two Fe-N-C catalysts (Fe content: 3.4% and 5.9%) in auqeous KOH by rotating disk electrode methods. Both Fe-N-C catalysts were found much more active than those metal-free N-doped carbon materials in literature. Moreover, the ORR onset and half-wave potentials over both Fe-N-C catalysts were respectively within 60 and 40 mV from those delivered by conventional Pt/C catalyst and both Fe-N-C catalysts even showed much superior catalytic stability in chronoamperometric measurement. ORR on the present Fe-N-C catalysts proceeded predominantly via a four-electron transfer mechanism. This work would shed a light on Fe-N-C materials for ORR catalysis in alkaline fuel cells.

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Cu nanoclusters supported on Co nanosheets for selective hydrogenation of CO Dong Lü, Yan Zhu, Yuhan Sun 2013, 34 (11):  1998-2003.  DOI: 10.1016/S1872-2067(12)60649-4 Abstract ( 392 )   [Full Text(HTML)] () PDF (885KB) ( 716 )   Cu nanoclusters supported on Co nanosheets (denoted Cu/Co) were prepared using lysine as a surfactant template. The shape of the Cu/Co catalyst promotes selective hydrogenation of CO, enhancing CO conversion and the selectivity for higher alcohols, and decreasing methane selectivity, which is in marked contrast to current Cu-Co bimetallic nanoparticle catalysts. The distinct functional interface of the Cu(111) surface with face-centered cubic structure with the Co(100) surface with hexagonal closed-packed structure in the Cu/Co catalyst provides a breakthrough in understanding the catalytic nature of metal-metal interactions. The design of this bimetallic catalyst bridges the gap between model catalysts and realistic catalytic applications, and will ultimately allow us to gain a fundamental understanding of the mechanism of syngas conversion to higher alcohols.

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Fluoride-free synthesis of anatase TiO2 crystals rich in (001) facets in the presence of cationic polymer Weiwei Chang, Yan Liu, Qi Sun, Xiangju Meng, Feng-Shou Xiao 2013, 34 (11):  2004-2008.  DOI: 10.1016/S1872-2067(12)60679-2 Abstract ( 339 )   [Full Text(HTML)] () PDF (826KB) ( 687 )   Controllable syntheses of anatase TiO2 rich in (001) facets have attracted much attention because of the excellent photocatalytic activity of this material in dye degradation. These syntheses are normally performed in the presence of fluoride, which is environmentally unfriendly. In this study, anatase TiO2 crystals rich in (001) facets were successfully synthesized in the presence of a cationic polymer and characterized using X-ray diffraction, scanning electron and transmission electron microscopies, and ultraviolet-visible spectroscopy. Photocatalytic tests showed that this material is very active in the degradation of methyl orange compared with conventional anatase TiO2 crystals and a commercial P25 photocatalyst. The high activity is attributed to the rich (001) facets translation.

Articles

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Selection of oxide supports to anchor desirable bimetallic structures for ethanol reforming and 1, 3-butadiene hydrogenation Tiefeng Wang, William Lonergan, Jingguang G. Chen 2013, 34 (11):  2009-2017.  DOI: 10.1016/S1872-2067(12)60715-3 Abstract ( 343 )   [Full Text(HTML)] () PDF (664KB) ( 646 )   Ethanol reforming and 1,3-butadiene hydrogenation reactions were studied on Pt-Ni bimetallic and monometallic catalysts supported on several supports, including γ-Al2O3, SiO2, TiO2, CeO2, and high surface area (HSA) and low surface area (LSA) ZrO2, to elucidate the effect of oxide supports on the bimetallic structures and catalytic activity. The catalysts were prepared by co-impregnation and were characterized by pulse CO chemisorption, transmission electron microscopy, and extended X-ray absorption fine structure. Reactions were carried out in a Fourier transform infrared batch reactor. The supports strongly affected the catalytic activity. For ethanol reforming, the activities of the Pt-Ni bimetallic catalysts were in the order TiO2 > SiO2 > γ-Al2O3 ≈ LSA-ZrO2 > CeO2 > HSA-ZrO2; while for 1,3-butadiene hydrogenation, the order was SiO2 > CeO2 > γ-Al2O3 > LSA-ZrO2 > HSA-ZrO2 ≈ TiO2. For the hydrogenation reaction, the Pt-Ni bimetallic catalysts outperformed the Pt and Ni monometallic catalysts; in contrast, for the reforming reaction, synergetic bimetallic effects were only found on SiO2, TiO2, and HSA-ZrO2.

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Hydrogenation of p-chloronitrobenzene on La-doped NiMoB nanocluster catalysts Der-Shing Lee, Yu-Wen Chen 2013, 34 (11):  2018-2028.  DOI: 10.1016/S1872-2067(12)60687-1 Abstract ( 329 )   [Full Text(HTML)] () PDF (1476KB) ( 634 )   Mo and La have been independently reported to be good promoters of NiB nanocluster in the hydrogenation of para-chloronitrobenzene (p-CNB). However, a bi-promoter effect of Mo and La in NiB catalysts has not previously been investigated. In this work, a series of La-Mo-doped, nanosized NiB catalysts with different La contents were prepared by chemical reduction and were characterized by X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. The liquid-phase hydrogenation of p-CNB was carried out in a batch reactor at 333 K, 1.2 MPa H2 pressure and at a spinning rate of 500 r/min. Even doping a small amount of La in NiMoB had a significant effect on its activity and selectivity to p-chloroaniline. The addition of an appropriate amount of La suppressed the growth and long-range order of NiMoB and helped the NiMoB maintain its amorphous state. La was determined to be present in its oxide form and to act as a spacer, preventing NiMoB from sintering and aggregation. However, a high amount of La had an opposite effect, and the optimum ratio of La:Ni was 0.2.

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Nanosized FeOx overlayers on Pt-skin surfaces for low temperature CO oxidation Hong Xu, Qiang Fu, Xinhe Bao 2013, 34 (11):  2029-2035.  DOI: 10.1016/S1872-2067(12)60673-1 Abstract ( 454 )   [Full Text(HTML)] () PDF (607KB) ( 599 )   Pt-Cu/carbon black catalysts were prepared by an impregnation-reduction method followed by acid leaching. The structure and composition of Pt-Cu nanoparticles treated under different conditions were investigated by inductively coupled plasma atomic emission spectrometry, X-ray diffraction, and X-ray photoelectron spectroscopy. PtCu3 alloy formed upon annealing Pt-Cu/carbon black catalysts in H2. Acid leaching produced Pt-Cu nanoparticles consisting of Pt-skeleton surface structure and PtCu3 alloy core. The Pt-skeleton could be transformed to well-defined Pt-skin structure through further annealing the leached Pt-Cu nanoparticles in H2. Decorating the Pt-skin surfaces with Fe oxide nanopatches resulted in enhanced reactivity in the preferential oxidation of CO in excess H2. The tri-component Pt-Cu-Fe catalysts exhibited comparable activity to the bi-component Pt-Fe catalysts but used much less Pt.

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Time-resolved infrared spectroscopic investigation of roles of valence states of Cr in (La, Cr)-doped SrTiO3 photocatalysts Shuai Shen, Yushuai Jia, Fengtao Fan, Zhaochi Feng, Can Li 2013, 34 (11):  2036-2040.  DOI: 10.1016/S1872-2067(12)60702-5 Abstract ( 483 )   [Full Text(HTML)] () PDF (536KB) ( 664 )   The kinetics of photogenerated electrons in SrTiO3(La,Cr) pretreated with either H2 or O2 were studied using time-resolved infrared spectroscopy. The X-ray photoelectron and Raman spectra showed that the Cr cations in the sample reduced with H2 were all in Cr3+, whereas those oxidized with O2 were in mixed of Cr3+ and Cr6+. Electrons excited with 355 and 532 nm light pulses showed the absorption of mid-IR light, and this was traced as a function of the time delay in a microsecond domain. The time-resolved results revealed that the decay rate of the photoinduced electrons with Cr3+ was slower than that with Cr6+, implying that trivalent Cr contributed more to retarding recombination of photoinduced electrons and holes, and enhanced photocatalytic H2 production activity.

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Catalytic conversion of Jerusalem artichoke stalk to ethylene glycol over a combined catalyst of WO3 and Raney Ni Likun Zhou, Jifeng Pang, Aiqin Wang, Tao Zhang 2013, 34 (11):  2041-2046.  DOI: 10.1016/S1872-2067(12)60686-X Abstract ( 336 )   [Full Text(HTML)] () PDF (744KB) ( 706 )   Jerusalem artichoke stalk (JAS) was employed as the feedstock for the production of ethylene glycol (EG) with a combined catalyst comprising commercial WO3 and Raney Ni. The raw JAS contains 51.6 wt% cellulose, 10.3 wt% hemicellulose, 17.2 wt% lignin, 1.7 wt% ash, and 19.2 wt% water-soluble substances. It was found that the lignin component in the JAS had little effect on the conversion of hemicellulose while the water-soluble substances caused a negative effect, which led to an EG yield of only 29.9%. After a simple hot water pretreatment, most of the water-soluble substances were removed, and the EG yield was increased to 37.6%. Moreover, the hot water pretreatment also led to an improvement in the durability of the catalyst. The effects of reaction temperature and reaction duration were also investigated.

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Catalytic conversion of methyl chloride to lower olefins over modified H-ZSM-34 Ting Xu, Hang Song, Weiping Deng, Qinghong Zhang, Ye Wang 2013, 34 (11):  2047-2056.  DOI: 10.1016/S1872-2067(12)60681-0 Abstract ( 281 )   [Full Text(HTML)] () PDF (632KB) ( 703 )   Among several typical zeolites, H-ZSM-34 was found to be an efficient catalyst for the conversion of methyl chloride to lower olefins, i.e., ethylene, propylene, and butenes. Treatment of H-ZSM-34 with a Na2H2EDTA (EDTA = ethylenediaminetetraacetate) aqueous solution followed by ion exchange and calcination enhanced the catalytic performance significantly. The selectivity to lower olefins increased significantly for certain Na2H2EDTA aqueous solution concentrations; when the H-ZSM-34 catalyst was treated with a 0.1 mol/L Na2H2EDTA solution, the selectivity and yield of C2-C4 olefins reached 82% and 61%, respectively, at 673 K and a CH3Cl partial pressure of 9.2 kPa. The modification of H-ZSM-34 with Ce ions improved C2-C4 olefin selectivity and yield. Catalyst characterization suggests that treatment with Na2H2EDTA or modification by Ce decreases the acidity of H-ZSM-34. The weakened acidity of the treated or modified H-ZSM-34 may suppress the hydrogen transfer reaction and prevent lower olefins from further transformation to paraffins.

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One-pot synthesis of primary amides on bifunctional Rh(OH)x/TS-1@KCC-1 catalysts Honggen Peng, Darui Wang, Le Xu, Peng Wu 2013, 34 (11):  2057-2065.  DOI: 10.1016/S1872-2067(12)60670-6 Abstract ( 422 )   [Full Text(HTML)] () PDF (1876KB) ( 939 )   A new microporous/mesoporous composite with a core-shell structure, TS-1@KCC-1, was fabricated in a microemulsion system by coating flower-like mesoporous silica (KCC-1) on the crystal surface of TS-1 zeolite. The synthesis conditions and a possible formation mechanism were studied in detail for the TS-1@KCC-1 material. A suitable temperature and assembly time were found to be 373-393 K and 4 h, respectively. The shell thickness of TS-1@KCC-1 was conveniently tuned in the range 25-80 nm. Rh(OH)x species were supported on TS-1@KCC-1, giving rise to a novel bifunctional tandem catalyst Rh(OH)x/TS-1@KCC-1, which effectively catalyzed the one-pot synthesis of primary amides directly from aldehydes, ammonia, and hydrogen peroxide.

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Efficient catalytic hydrogenolysis of glycerol using formic acid as hydrogen source Jing Yuan, Shushuang Li, Lei Yu, Yongmei Liu, Yong Cao 2013, 34 (11):  2066-2074.  DOI: 10.1016/S1872-2067(12)60656-1 Abstract ( 493 )   [Full Text(HTML)] () PDF (685KB) ( 781 )   We describe a sustainable, cost-effective, and highly efficient H2-free protocol for catalytic hydrogenolysis of glycerol to 1,2-propanediol (1,2-PDO) using formic acid (FA) as the H2 source. The process is catalyzed by an earth-abundant and robust Cu-based metal oxide catalyst, in which the high performance of the Cu catalyst for the in situ generation of H2 gas in the system by highly selective decomposition of FA in an aqueous medium is essential. The activity test results showed that a synergy effect of well-dispersed Cu and amphoteric ZrO2 is essential for FA decomposition as well as for glycerol conversion to 1,2-PDO. The Cu content of the Cu/ZrO2 catalyst prepared by the oxalate gel method has a significant role in the FA-mediated glycerol conversion to 1,2-PDO, and a Cu content of 20 wt% on ZrO2 was identified as the optimum Cu content. Moreover, the creation and maintenance of high component dispersion is essential for high glycerol hydrogenolysis activity of the Cu/ZrO2 system. Because selective hydrogenolysis with minimum use of external fossil-fuel H2 is a critical issue in the realization of biorefinery concepts, the procedure described here is expected to be of broad applicability in biomass use.

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Evolution of surface and bulk structures of CexTi1-xO2 oxide composites Jun Fang, Fucheng Shi, Huizhi Bao, Kun Qian, Zhiquan Jiang, Weixin Huang 2013, 34 (11):  2075-2083.  DOI: 10.1016/S1872-2067(12)60667-6 Abstract ( 408 )   [Full Text(HTML)] () PDF (908KB) ( 722 )   A series of CexTi1-xO2 oxide composites were synthesized using a coprecipitation method, and their structures were investigated using X-ray diffraction, N2 adsorption-desorption isotherms, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, H2 temperature-programmed reduction, selective chemisorption of methyl orange, and isoelectric point measurements. The selective chemisorption of methyl orange and isoelectric point measurements successfully characterized the outmost surface structures of the CexTi1-xO2 oxide composites, and the term "equivalent CeO2 surface coverage" in a monolayer was introduced to describe the outmost surface compositions. CexTi1-xO2 oxide composites with x ≥ 0.7 form a cubic fluorite phase solid solution, the Ce0.3Ti0.7O2 oxide composite is a pure monoclinic compound, and the other oxide composites have mixed phase structures. The outmost surface structure evolves in a different way from the bulk structure. A cubic fluorite Ce0.7Ti0.3O2 solid solution partially undergoes cubic fluorite solid solution-to-monoclinic Ce0.3Ti0.7O2 phase transition on its outmost surface, and Ce0.3Ti0.7O2 on the outmost surface of Ce0.7Ti0.3O2 grows from the surface to the bulk. Cubic fluorite CexTi1-xO2 solid solutions exhibit good reducibilities at relatively low temperatures, whereas Ce0.3Ti0.7O2 exhibits good reducibility at relatively high temperatures. These results provide comprehensive and in-depth structural information for important CexTi1-xO2 oxide composites.

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Synthesis of in-situ surfactant-free Pd nanoparticle catalysts for the synthesis of aromatic azo compounds and for unsaturated bond hydrogenation by hydrogen transfer Xin Wang, Jiaqing Wang, Fenqiang Qi, Lei Hu, Xinming Li, Xueqin Cao, Hongwei Gu 2013, 34 (11):  2084-2088.  DOI: 10.1016/S1872-2067(12)60665-2 Abstract ( 508 )   [Full Text(HTML)] () PDF (476KB) ( 734 )   We developed a simple and efficient method to synthesize aromatic azos by hydrogen transfer using palladium(Ⅱ) acetylacetonate as a catalyst and isopropyl alcohol as a hydrogen source. Furthermore, this system also showed catalytic potential for the hydrogenation of carbonyl groups or C=C bonds with yields up to ~97%.

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S-doped HTiNbO5 nanosheets：A novel efficient visible-light photocatalyst Lihong Zhang, Chenhui Hu, Liyuan Cheng, Weiping Ding, Wenhua Hou, Jing Chen 2013, 34 (11):  2089-2097.  DOI: 10.1016/S1872-2067(12)60692-5 Abstract ( 385 )   [Full Text(HTML)] () PDF (865KB) ( 931 )   S-doped HTiNbO5 nanosheets were prepared via an exfoliation-flocculation-calcination process using layered HTiNbO5 as the starting material and thiourea as the S source. The resulting catalyst had higher surface area and visible-light absorption than did unexfoliated HTiNbO5 or HTiNbO5 nanosheets. The adsorption and photodegradation of rhodamine B were evaluated under visible-light irradiation on the obtained catalysts. Both HTiNbO5 nanosheets and S-doped HTiNbO5 nanosheets showed enhanced adsorption capacity and a high visible-light photodegradation rate. However, a much higher degree of mineralization (41%) was achieved using the S-doped HTiNbO5 nanosheets, compared with almost no mineralization for the HTiNbO5 nanosheets, indicating that S doping can effectively improve the photocatalytic activity of nanosheets. The possible photodegradation mechanisms are also discussed.

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Synthesis and catalytic activity of M@SiO2 (M=Ag, Au, and Pt) nanostructures via “core to shell” and “shell then core” approaches Shengchao He, Zhaoyang Fei, Lei Li, Bo Sun, Xinzhen Feng, Weijie Ji 2013, 34 (11):  2098-2109.  DOI: 10.1016/S1872-2067(12)60716-5 Abstract ( 471 )   [Full Text(HTML)] () PDF (851KB) ( 1097 )   M@SiO2 (M = Ag, Au, and Pt) core-shell nanostructures were prepared by the "core to shell" and "shell then core" approaches. In the former, the metal core size could be controlled in the 6-9 nm range with a narrow size distribution, and the shell porosity was tunable. The preparation was straightforward and efficient, without requiring specialized high-speed centrifugation. Au@SiO2 containing mesoporous SiO2 shells (Au@meso-SiO2) exhibited good thermal stability and high CO oxidation activity (T100 = 235 ℃) even after being subjected to calcination in air at 550 ℃. In the latter approach, the core size could be controlled at < 10 nm with a narrow size distribution, and the shell porosity was tunable to a fine degree. 4-Nitrophenol was readily reduced at room temperature in the presence of Au@meso-SiO2 obtained through the "shell then core" approach. The SiO2 shell mesoporosity minimized the diffusion limitation of 4-nitrophenol. The core-shell structures from both approaches were uniformly dispersed. Employing Si sources with differing functionality allowed the SiO2 shell and metal core properties to be modified in these approaches, which is beneficial for application.

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Effect of acidic promoters on the titania-nanotubes supported V2O5 catalysts for the selective oxidation of methanol to dimethoxymethane Jingxuan Cai, Yuchuan Fu, Qing Sun, Minhui Jia, Jianyi Shen 2013, 34 (11):  2110-2117.  DOI: 10.1016/S1872-2067(12)60690-1 Abstract ( 300 )   [Full Text(HTML)] () PDF (1344KB) ( 686 )   The effect of acidic promoters on the titania-nanotubes (TNT) supported V2O5 catalysts (VTNT) was investigated. The structure of TNT was quite stable after the treatment with sulfuric, phosphoric, and phosphotungstic acids, respectively. The acid-modified VTNT catalysts were tested for the selective oxidation of methanol to dimethoxymethane (DMM). It was found that only the VTNT modified with sulfuric acid followed by calcination at 673 K exhibited the significantly enhanced selectivity to DMM with high methanol conversions. The calcination created some sulfate groups strongly interacted with vanadium species, which enhanced the strengths of surface acidity without weakening the redox ability of vanadium sites. The addition of phosphoric and phosphotungstic acids might enhance the surface acidity of V2O5/TiO2, but weakened its redox ability, and therefore had the negative effect for the target reaction.

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Direct hydroxylation of benzene to phenol with hydrogen peroxide catalyzed by a quinine-heteropolyacid hybrid Pingping Zhao, Yu Zhou, Yangqing Liu, Jun Wang 2013, 34 (11):  2118-2124.  DOI: 10.1016/S1872-2067(12)60631-7 Abstract ( 428 )   [Full Text(HTML)] () PDF (1035KB) ( 844 )   A new heterogeneous hybrid catalyst designed for direct hydroxylation of benzene to phenol was prepared through modification of Keggin-structured phosphovanadomolybdate with quinine. The structure of the catalyst was fully characterized by Fourier transform infrared and ultraviolet-visible spectroscopies, X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, nitrogen sorption experiments, and CHN elemental analysis. The results indicated that the hybrid catalyst was a semi-amorphous heteropolyacid salt with high thermal stability, surface area, and pore volume. The catalytic activity of the hybrid for the hydroxylation of benzene with H2O2 was assessed. The hybrid catalyst forms a liquid-solid biphasic system and exhibits high activity, convenient recovery, and reusability. The strong electronic interactions and hydrogen bonding networks formed between the π-electron-rich quinine framework and heteropolyanions are responsible for the solid nature and insolubility of the catalyst. The high surface area and improved redox properties of the Keggin heteropolyacid account for its excellent catalytic performance. The results of this work reveal a new, more facile way to prepare an efficient polyoxometalate-based catalyst for heterogeneous hydroxylation of benzene to phenol.

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Degradation of methylene blue with H2O2 over a cupric oxide nanosheet catalyst Maiyong Zhu, Dehai Meng, Chengjiao Wang, Jian Di, Guowang Diao 2013, 34 (11):  2125-2129.  DOI: 10.1016/S1872-2067(12)60717-7 Abstract ( 391 )   [Full Text(HTML)] () PDF (1363KB) ( 1374 )   Cupric oxide (CuO) nanosheets were prepared by the hydrothermal method with the use of cetyltrimethylammonium bromide (CTAB) and were used as the catalyst for the oxidation degradation of methylene blue with H2O2. The effects of temperature, oxidant concentration, and catalyst dosage were evaluated. The catalytic reaction obeyed first order kinetics, and the activation energy was 54 kJ/mol. Although the CuO nanosheets show high activity, their stability and reusability still need improvement.

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Pathways between superoxide and peroxide species on small La-O clusters Wensheng Xia, Da Zhang, Weizheng Weng, Huilin Wan 2013, 34 (11):  2130-2137.  DOI: 10.1016/S1872-2067(12)60694-9 Abstract ( 318 )   [Full Text(HTML)] () PDF (640KB) ( 583 )   Density functional theory calculations were used to investigate the connection between superoxide and peroxide species on La-O clusters. In the singlet state, a superoxide species can transition into a peroxide species by moving through a substantial energy barrier via a series of ozonides. In the triplet state, there is no connection between the two species, although there are two paths (singlet and triplet) that allow the interaction and subsequent transformation of two superoxide molecules on a La-O cluster. The superoxide species readily transitions to a peroxide species through a triplet pathway (O2-+ O2-↔O22 - + O2), in which the superoxide species undergoes rapid exchange with the peroxide. In the singlet path, however, the superoxide species must move through a pronounced energy barrier to change into a peroxide species, demonstrating that these oxygen species are highly stable in the singlet state.

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Nitrogen-doped graphene/CdS hollow spheres nanocomposite with enhanced photocatalytic performance Qian Mi, Daiquan Chen, Juncheng Hu, Zhengxi Huang, Jinlin Li 2013, 34 (11):  2138-2145.  DOI: 10.1016/S1872-2067(12)60641-X Abstract ( 439 )   [Full Text(HTML)] () PDF (1043KB) ( 1056 )   A novel N-doped graphene/CdS hollow sphere nanocomposite photocatalyst was synthesized by a simple, template-free one-pot method. The samples were characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, N2 adsorption-desorption, photoluminescence spectroscopy, and X-ray photoelectron spectroscopy. Photocatalytic degradations of methylene blue and salicylic acid were carried out to evaluate the photocatalytic activity of the nanocomposites under visible light irradiation. The N-graphene/CdS nanocomposites exhibited excellent stability and high photocatalytic activity, exceeding those of graphene oxide/CdS hollow sphere nanocomposites and pure CdS hollow spheres. This excellent photocatalytic activity of the nanocomposite was due to N-graphene acting as an excellent electron acceptor and transporter, thus reducing charge carrier recombination. It was also found that ·OH acted as the main reactive species in the degradation of methylene blue under visible-light irradiation.

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AlCl3 catalyzed conversion of hemicellulose in corn stover Jian Yi, Ting He, Zhicheng Jiang, Jianmei Li, Changwei Hu 2013, 34 (11):  2146-2152.  DOI: 10.1016/S1872-2067(12)60718-9 Abstract ( 359 )   [Full Text(HTML)] () PDF (774KB) ( 801 )   The selective conversion of the hemicellulose in corn stover (stalk) by AlCl3 as catalyst under hydrothermal conditions at low temperature was investigated. The effect of reaction temperature, reaction time, and AlCl3 amount was investigated. The biomass samples before and after reaction were characterized by chemical titration, X-ray diffraction, and scanning electron microscopy. The conversion of the hemicellulose in the corn stover at 140 ℃ for 1 h reached 85.1%, while keeping a high proportion of the cellulose and lignin components unreacted with the conversions of 10.7% and 23.9%, respectively. Xylose and a small amount of acetic acid, and furfural were obtained from the filtrate from the hemicellulose conversion. Further reaction of the filtrate significantly improved the conversion of xylose. This was performed in a H2O-tetrahydrofuran solvent system, and large amounts of levulinic acid, formic acid, and furfural were obtained. The γ-Al2O3/SO42- solid acid catalyst selectively promoted the formation of furfural in the H2O-tetrahydrofuran solvent system.

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Synergism between the Lewis and Brönsted acid sites on HZSM-5 zeolites in the conversion of methylcyclohexane Chenhai Song, Meng Wang, Li Zhao, Nianhua Xue, Luming Peng, Xuefeng Guo, Weiping Ding, Weimin Yang, Zaiku Xie 2013, 34 (11):  2153-2159.  DOI: 10.1016/S1872-2067(12)60721-9 Abstract ( 594 )   [Full Text(HTML)] () PDF (1568KB) ( 939 )   Catalytic conversion of methylcyclohexane was studied on four specially designed HZSM-5 zeolites. A careful steam treatment was used to produce pair-sites composed of a Lewis acid site, due to extra-framework Al species from the dealumination by steaming, and a Brö -nsted acid site, due to bridging hydroxyl in the steamed HZSM-5. The spatial proximity of these component acid sites of the pair-site was verified by 1H double quantum magic spinning NMR. Product selectivities of methylcyclohexane conversion showed the same trend for all the samples, which indicated that the pores of the zeolites were not changed by the steam treatment. The Lewis acid site that was created, however, gave a synergistic effect with the Brönsted acid site in the pair-site, which gave higher conversions and cracking rates of methylcyclohexane. The rate of methylcyclohexane conversion increased with increased concentration of extra-framework Al, which gave more pair-sites.