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  • Light-Driven Low-Temperature Syngas Production from CH3OH and H2O over Pt@SrTiO3 Photothermal Catalyst
    Catal. Sci. Technol. (IF 5.773) Pub Date : 2018-04-20
    Xiaoguang Han, Lizhu Song, Hua Xu, Shuxin Ouyang

    Under light irradiation, the Pt@SrTiO3 photothermal catalyst can realize efficient steaming reforming of CH3OH and H2O at a low temperature as low as 150oC. During 15-min light irradiation, an optimal catalyst achieved a high methanol conversion of 95.5% and a selectivity of 94.4% for syngas production.

    更新日期:2018-04-20
  • Mechanistic Insights Into 4-Nitrophenol Degradation and Benzyl Alcohol Oxidation Pathways Over MgO/g-C3N4 Model Catalyst Systems
    Catal. Sci. Technol. (IF 5.773) Pub Date : 2018-04-20
    P V R K Ramacharyulu, SK JAHIR ABBAS, Smruti R. Sahoo, Shyue-Chu Ke

    A series of g-C3N4 based visible light active photocatalysts was prepared by using melamine as a precursor and MgO as a dopant. The composites exhibited excellent photocatalytic activities in the degradation of 4-nitrophenol and selective oxidation of benzyl alcohol in aqueous media under a low power visible LED light source. The composites oxidized benzyl alcohols to benzaldehydes with better selectivity and conversion efficiency in mild acidic conditions (pH 5-6) than over in neutral conditions. When compared against pure g-C3N4, the as synthesized MgO/g-C3N4 composites showed about five-fold enhancements in photocatalytic activities. EPR spectroscopic results revealed identical EPR signal from both g-C3N4 and MgO/g-C3N4 composites, thus confirming the presence of unpaired electrons with C2p character. Introduction of MgO into gC3N4 resulted in an increased number of electrons trapped in the C2p states of g-C3N4, which manifested as an enhancement in the EPR signal intensity. The difference in the light and dark EPR spectral signal intensity verified the efficient charge separation in the as-synthesized MgO/g-C3N4 catalysts. Moreover, the double integral values of the visible and dark EPR spectral signal difference intensities matched well with the 4-nitrophenol degradation rate constants. This further confirms the importance of trapped electrons in C2p states responsible for the observed higher photocatalytic activities. Radical scavenging experiments evidenced electrons as the dominant active species responsible for 4-nitrophenol degradation. Whereas, both electrons and holes were observed to participate in the selective oxidation of benzyl alcohol. Furthermore, the scavenging experiments ruled out the possibility of either hydroxyl or singlet oxygen radicals influencing the rate of oxidation. This study demonstrates MgO/g-C3N4 as a viable photoactive material for environmental pollution abatement related applications. The photoactive nature of the catalysts in aqueous media under low powered visible LED light source further signifies its economic and ecological aspects, which can be exploited for other applications as well.

    更新日期:2018-04-20
  • An artificial metalloenzyme for carbene transfer based on a biotinylated dirhodium anchored within streptavidin
    Catal. Sci. Technol. (IF 5.773) Pub Date : 2018-04-16
    Jingming Zhao, Daniel G. Bachmann, Markus Lenz, Dennis G. Gillingham, Thomas R. Ward
    更新日期:2018-04-20
  • Gold‐Catalyzed Oxidative Cyclization of Tryptamine Derived Enynamides: A Stereoselective Approach to Tetracyclic Spiroindolines
    Adv. Synth. Catal. (IF 5.646) Pub Date : 2018-04-20
    Meijun Lin; Lei Zhu; Jiajin Xia; Yinghua Yu; Jianxin Chen; Zhifeng Mao; Xueliang Huang
    更新日期:2018-04-20
  • Diastereospecific Bis‐alkoxycarbonylation of 1,2‐Disubstituted Olefins Catalyzed by Aryl α‐Diimine Palladium(II) Catalysts
    Adv. Synth. Catal. (IF 5.646) Pub Date : 2018-04-20
    Diego Olivieri; Francesco Fini; Rita Mazzoni; Stefano Zacchini; Nicola Della Ca'; Gilberto Spadoni; Bartolo Gabriele; Raffaella Mancuso; Valerio Zanotti; Carla Carfagna
    更新日期:2018-04-20
  • Multigram Scale Enzymatic Synthesis of (R)‐1‐(4′‐Hydroxyphenyl)ethanol Using Vanillyl Alcohol Oxidase
    Adv. Synth. Catal. (IF 5.646) Pub Date : 2018-04-20
    Tom A. Ewing; Jasmin Kühn; Silvia Segarra; Marta Tortajada; Ralf Zuhse; Willem J. H. van Berkel
    更新日期:2018-04-20
  • Construction of All‐Carbon Quaternary Stereocenters via Asymmetric Cyclopropanations: Synthesis of Chiral Carbocyclic Pyrimidine Nucleosides
    Adv. Synth. Catal. (IF 5.646) Pub Date : 2018-04-20
    Hai‐Xia Wang; Fang‐Juan Guan; Ming‐Sheng Xie; Gui‐Rong Qu; Hai‐Ming Guo
    更新日期:2018-04-20
  • 更新日期:2018-04-20
  • Isocoumarins: General Aspects and Recent Advances in their Synthesis
    Adv. Synth. Catal. (IF 5.646) Pub Date : 2018-04-20
    Pallabi Saikia; Sanjib Gogoi
    更新日期:2018-04-20
  • Electrodimerization of N‐Alkoxyamides for Zinc(II) Catalyzed Phenolic Ester synthesis under mild reaction conditions
    Adv. Synth. Catal. (IF 5.646) Pub Date : 2018-04-19
    Kripa Subramanian; Subhash Laxman Yedage; Bhalchandra Bhanage

    An electrochemical On‐Off method for phenolic ester synthesis from N‐alkoxyamides has been reported. This one‐pot protocol begins with rapid and selective electrodimerization of the amide using n‐Bu4NI (TBAI) as an electrocatalyst. The reaction proceeds further in the absence of current via Zn catalyzed C‐N bond activation of the amide dimer followed by its coupling with phenol to form the ester. The present methodology is ligand‐free and takes place under mild reaction conditions. This transformation incorporates a wide variety of phenols and amide substrates leading to the formation of functionalized esters highlighting its versatility.

    更新日期:2018-04-20
  • 更新日期:2018-04-20
  • Iron-Catalyzed Direct Olefin Diazidation via Peroxyester Activation Promoted by Nitrogen-Based Ligands
    ACS Catal. (IF 10.614) Pub Date : 2018-04-19
    Shou-Jie Shen, Cheng-Liang Zhu, Deng-Fu Lu, Hao Xu
    更新日期:2018-04-20
  • Selective synthesis of the human drug metabolite 5’-hydroxypropranolol by an evolved self-sufficient peroxygenase
    ACS Catal. (IF 10.614) Pub Date : 2018-04-19
    Patricia Gomez de Santos, Marina Canellas, Florian Tieves, Sabry H.H. Younes, Patricia Molina-Espeja, Martin Hofrichter, Frank Hollmann, Victor Guallar, Miguel Alcalde

    Propranolol is a widely used beta-blocker that is metabolized by human liver P450 monooxygenases into equipotent hydroxylated human drug metabolites (HDMs). It is paramount for the pharmaceutical industry to evaluate the toxicity and activity of these metabolites but unfortunately, their synthesis has hitherto involved the use of severe conditions, with poor reaction yields and unwanted byproducts. Unspecific peroxygenases (UPOs) catalyze the selective oxyfunctionalization of C-H bonds and they are of particular interest in synthetic organic chemistry. Here, we describe the engineering of UPO from Agrocybe aegerita for the efficient synthesis of 5´-hydroxypropranolol (5´-OHP). We employed a structure-guided evolution approach combined with computational analysis, with the aim of avoiding unwanted phenoxyl radical coupling without having to dope the reaction with radical scavengers. The evolved biocatalyst showed a catalytic efficiency enhanced by two orders of magnitude and 99% regioselectivity for the synthesis of 5´-OHP. When the UPO mutant was combined with an H2O2 in situ generation system using methanol as sacrificial electron donor, total turnover numbers of up to 264,000 were achieved, offering a cost-effective and readily scalable method to rapidly prepare 5´-OHP.

    更新日期:2018-04-20
  • Absorbed hydrogen enhances the catalytic hydrogenation activity of Rh-based nanocatalysts
    Catal. Sci. Technol. (IF 5.773) Pub Date : 2018-04-19
    Franck Morfin, Lucie Blondeau, Karine Provost, Abdelmalek Malouche, Laurent Piccolo, Claudia Zlotea

    Carbon supported Rh-based nanoparticles with an average size of 1.0 nm have been tested for the hydrogenation of butadiene in two different forms: either metal Rh or hydride RhHx nanoparticles. Laboratory tests demonstrated that the Rh hydride nanocatalyst is more active than the metal counterpart, irrespective of the gas feed composition and temperature. Moreover, this difference is significantly more important at the initial stage of the reaction as compared to quasi-stationary conditions. However, the reaction mechanisms appear similar for metal and hydride nanocatalysts, as suggested by the similar selectivities to butenes, apparent reaction energies, and reaction orders. The local structures of both Rh and RhHx nanocatalysts were studied by operando XAS under stationary conditions. The EXAFS analyses confirm that RhHx and Rh catalysts preserve their structure during the reaction as either hydride or metal phase, respectively. We suggest that the Mars-van Krevelen mechanism might occur at the initial stage but becomes progressively less predominant. Under quasi-stationary conditions only electronic effects might be invoked to explain the activity difference between the hydride and the metal phases. We hypothesize that the stabilization of Rh-H bonds at the surface in the presence of subsurface hydrogen, consistently with previous theoretical findings, explains the higher activity of the hydride catalyst.

    更新日期:2018-04-19
  • A PGM-free NOx adsorber + selective catalytic reduction catalyst system (AdSCR) for trapping and reducing NOx in lean exhaust streams at low temperature
    Catal. Sci. Technol. (IF 5.773) Pub Date : 2018-04-04
    Tommaso Selleri, Federica Gramigni, Isabella Nova, Enrico Tronconi, Simone Dieterich, Michel Weibel, Volker Schmeisser
    更新日期:2018-04-19
  • Design Strategy toward Recyclable and Highly Efficient Heterogeneous Catalysts for the Hydrogenation of CO2 to Formate
    ACS Catal. (IF 10.614) Pub Date : 2018-04-19
    Gunniya Hariyanandam Gunasekar, Jeongcheol Shin, Kwang-Deog Jung, Kiyoung Park, Sungho Yoon
    更新日期:2018-04-19
  • 更新日期:2018-04-19
  • Aluminium Chloride‐Mediated Synthesis of 1‐Chloro‐2,2,2‐Trifluoroethylidene‐Substituted Pyrrolidones
    Adv. Synth. Catal. (IF 5.646) Pub Date : 2018-04-19
    Zeng Wang; Zihang Yuan; Xiaoyan Han; Zhiqiang Weng
    更新日期:2018-04-19
  • An Industrial Perspective on Counter Anions in Gold Catalysis: Underestimated with Respect to “Ligand Effects”
    Adv. Synth. Catal. (IF 5.646) Pub Date : 2018-04-19
    Jasmin Schießl; Jürgen Schulmeister; Angelino Doppiu; Eileen Wörner; Matthias Rudolph; Ralf Karch; A. Stephen K. Hashmi
    更新日期:2018-04-19
  • Catalytic Dehydrogenation of (Di)Amine-Boranes with a Geometrically Constrained Phosphine-Borane Lewis Pair
    ACS Catal. (IF 10.614) Pub Date : 2018-04-18
    Maxime Boudjelel, E. Daiann Sosa Carrizo, Sonia Mallet−Ladeira, Stéphane Massou, Karinne Miqueu, Ghenwa Bouhadir, Didier Bourissou
    更新日期:2018-04-19
  • 更新日期:2018-04-19
  • Mechanistic Understanding of Alloy Effect and Water Promotion for Pd-Cu Bimetallic Catalysts in CO2 Hydrogenation to Methanol
    ACS Catal. (IF 10.614) Pub Date : 2018-04-18
    Xiaowa Nie, Xiao Jiang, Haozhi Wang, Wenjia Luo, Michael J. Janik, Yonggang Chen, Xinwen Guo, Chunshan Song

    Density functional theory (DFT) calculations on Pd-Cu bimetallic catalysts reveal that the stepped PdCu(111) surface with coordinatively unsaturated Pd atoms exposed on the top is superior for CO2 and H2 activation and for CO2 hydrogenation to methanol than the flat Cu-rich PdCu3(111) surface. The energetically preferred path for CO2 to CH3OH over PdCu(111) proceeds through CO2*HCOO*HCOOH*H2COOH*CH2O*CH3O*CH3OH*. CO formation from CO2 via reverse water-gas shift (RWGS) proceeds faster than CH3OH formation in terms of kinetic calculations, in line with experimental observation. A small amount of water, which is produced in-situ from both RWGS and CH3OH formation, can accelerate CO2 conversion to methanol by reducing the kinetic barriers for O-H bond formation steps and enhancing the TOF. Water participation in reaction alters the rate-limiting step according to the degree of rate control (DRC) analysis. Compared to CO2, CO hydrogenation to methanol on PdCu(111) encounters higher barriers, thus is slower in kinetics. Complimentary to the DFT results, CO2 hydrogenation experiments over SiO2-supported bimetallic catalysts show that the Pd-Cu(0.50) that is rich in PdCu alloy phase is more selective to methanol than the PdCu3-rich Pd-Cu(0.25). Moreover, advanced CH3OH selectivity is also evidenced on Pd-Cu(0.50) at specific water vapor concentration (0.03 mol%), whereas that of Pd-Cu(0.25) is not comparable. The present work clearly shows that the PdCu alloy surface structure has a major impact on the reaction pathway, and the presence of water can substantially influence the kinetics in CO2 hydrogenation to methanol.

    更新日期:2018-04-19
  • A Mononuclear Tungsten Photocatalyst for H2 Production
    ACS Catal. (IF 10.614) Pub Date : 2018-04-18
    Aron J Huckaba, Hunter Pratt Shirley, Robert Lamb, Steve Guertin, Shane A. Autry, Hammad Cheema, Kallol Talukdar, Tanya C. Jones, Jonah W Jurss, Amala Dass, Nathan I Hammer, Russell H. Schmehl, Charles Edwin Webster, Jared H. Delcamp

    We report herein a mononuclear non-sensitized homogeneous photocatalyst for H2 production with sunlight for the first time. The synthesis and characterization of a (pyridyl)-N-heterocyclic carbene tungsten tetracarbonyl complex W(pyNHC)(CO)4 is described, and its application as a pre-catalyst for the electrocatalytic and non-photosensitized photocatalytic generation of H2 is evaluated. Through electrochemical studies, the complex was found to produce hydrogen from a relatively high pKa (27.2), dilute proton source (100 mM PhOH) in MeCN. The catalyst is photocatalytically active without a photosensitizer with a turnover number (TON) >17 in three hours of reaction time, which compares favorably to the only non-photosensitized (multinuclear) homogeneous photocatalyst (4 TON). Photonic energy was found to be necessary at multiple points in the catalytic cycle, and a mechanism is detailed based on a combined photophysical and computational approach.

    更新日期:2018-04-19
  • Genesis of Strong Brønsted Acid Sites in WZr-KIT-6 Catalysts and Enhancement of Ethanol Dehydration Activity
    ACS Catal. (IF 10.614) Pub Date : 2018-04-18
    Hongda Zhu, Anand Ramanathan, Jianfeng Wu, Bala Subramaniam

    Using a one-pot synthesis technique, tungsten and zirconium were simultaneously incorporated into ordered mesoporous KIT-6 framework. A series of such materials, denoted as WZr-KIT-6, were synthesized with W and Zr loadings ranging from 0 mol % to 10 mol % each. At sufficiently high Zr loadings, ssNMR spectra of neat as well as pyridine-adsorbed catalyst confirm that the fresh WZr-KIT-6 materials exhibit Brønsted acid sites of high strength resulting in correspondingly high ethylene yields during ethanol dehydration. Such yields surpass those observed on Wx-KIT-6 and Zry-KIT-6 materials with identical W and Zr loadings as in WxZry-KIT-6. Interestingly, air regeneration of the spent WZr-KIT-6 catalyst further enhances ethanol dehydration activity, with ethylene yields approaching those reported with HZSM-5 and SAPO-34 catalysts at similar operating conditions. This enhancement correlates with ssNMR evidence of the formation of additional strong Brønsted acid sites following the regeneration step, presumably from the water produced during combustion of the coke deposits. Based on ssNMR characterization of acid strength, these acidic protons are assigned to the hydroxyl groups bound to metals in W-O-Zr structures and to the stronger acidic protons on heteropolytungstate structures. The formation of strong Brønsted acid sites, comparable to those observed in H-ZSM-5 and H-Beta, in mesoporous WZr-KIT-6 materials should be particularly attractive for reactions that are prone to rapid deactivation by coking in microporous catalysts.

    更新日期:2018-04-19
  • Visible-Light-Driven Photoreduction of CO2 to CH4 over N,O,P-Containing Covalent Organic Polymer Submicrospheres
    ACS Catal. (IF 10.614) Pub Date : 2018-04-18
    Shien Guo, Hongye Zhang, Yu Chen, Zhenghui Liu, Bo Yu, Yanfei Zhao, Zhenzhen Yang, Buxing Han, Zhimin Liu

    Solar energy-driven photoreduction of CO2 to hydrocarbon fuels is an interesting and challenging topic, which gener-ally requires the photocatalysts with the capability to capture and photoreduce CO2 simultaneously. Herein, we demonstrate that a N,O,P-containing covalent organic polymer (NOP-COP) prepared via condensation of hexachloro-cyclotriphosphazene with barbituric acid can capture CO2 and further photocatalyze its reduction to CH4 under visible-light irradiation. The characterization information indicates that the incorporation of phosphorus in the skeleton of NOP-COP promoted the absorption of visible light and improved the lifetime of the photoinduced carriers. As a result, NOP-COP exhibited enhanced efficiency for photoreduction of CO2 compared to the N,O-containing polymer, afford-ing CH4 as the sole carbonaceous product with a rate of 22.5 μmol gcat−1 h−1 and selectivity over 90%. This work provides insight into designing and fabricating polymeric photocatalysts for CO2 photoreduction to fuels.

    更新日期:2018-04-19
  • A Side Arm Twist on Zn-Catalyzed Hydrosilylative Reduction of CO2 to Formate and Methanol Equivalents with High Selectivity and Activity
    ACS Catal. (IF 10.614) Pub Date : 2018-04-18
    Guoqin Feng, Chongyang Du, Li Xiang, Iker del Rosal, Guangyu Li, Xuebing Leng, Eugene Y.-X. Chen, Laurent Maron, Yaofeng Chen

    Reductive hydrosilylation of CO2 by catalysts based on environmentally benign metals such as zinc still presents an unmet challenge in terms of catalyst selectivity and activity. Here we show that tetra-coordinated neutral zinc siloxide complexes supported by the β-diketiminato ligand bearing a pendant amine arm exhibit unprecedentedly high catalytic activity towards the selective reduction of CO2 by a hydrosilane to silyl formate. More significantly, this zinc catalyst system can also effectively catalyze the subsequent reduction of silyl formate into methoxysilane in quantitative yield. To understand the mechanism of the CO2 hydrosilylation and the influence of the side arm, a series of catalytic active species (or intermediates), zinc hydrides and formates, has been synthesized and structurally characterized; the relevant stoichiometric reactions and kinetic study were performed. DFT calculations were also carried out to determine the reaction profiles for the CO2 hydrosilylation and to explain the relative activity of the zinc catalysts employed in this study. This combined experimental and theoretical study gives insights into the critical effects of the pendant amine donor arm and the size of the alkyl group of the amine on the relative energetics of the species involved in the proposed catalytic cycle. KEYWORDS: CO2 reduction, DFT, hydrosilylation, zinc catalyst, pendant donor

    更新日期:2018-04-19
  • FeOx/Al2O3 catalysts for high-temperature decomposition of N2O under conditions of NH3 oxidation in nitric acid production
    Catal. Sci. Technol. (IF 5.773) Pub Date : 2018-04-18
    Galina Sadovska, Edyta Tabor, Milan Bernauer, Petr Sazama, Tomaš Kmječ, J. Kohout, Karel Zaveta, Vlastimil Fila, Věnceslava Tokarová, Z Sobalik

    The catalytic activity of a series of FeOx/Al2O3 prepared under various conditions was evaluated for high temperature decomposition of N2O (HT-deN2O) in the complex gas mixture produced by oxidation of ammonia. Thus the relevant step in the industrial nitric acid production process was simulated. The catalyst stability during a long exposure (12 days) to reaction conditions relevant to HT-deN2O was studied. Both fresh and aged FeOx/Al2O3 exhibited more than 90 % conversion of N2O in the 750-900 °C temperature range. Structural analysis showed that prepared FeOx/Al2O3 catalysts contained various proportions of δ, θ and α alumina phases and up to four individual iron speciations. In the δ and θ Al2O3 phases well stabilized Fe(III) in Td or Oh coordination were identified as the active species in HT-deN2O.

    更新日期:2018-04-18
  • 更新日期:2018-04-18
  • Synthesis and photocatalytic activity of BiOBr nanosheets with tunable crystal facets and sizes
    Catal. Sci. Technol. (IF 5.773) Pub Date : 2018-04-18
    Yuwei Mi, Haiping Li, Yongfang Zhang, Na Du, Wan Guo Hou

    Crystal facet engineering is one of the most important ways to enhance the photoactivity of photocatalysts, but it remains challenging so far. In addition, the effects of exposed facets and crystallite sizes on the photoactivity for BiOX (X = Cl, Br, or I) nanosheets have been widely investigated. However, it is still unclear that which one of exposed facets and crystallite sizes are more important for photoactivity of BiOX nanosheets. In this work, a series of BiOBr nanosheets with tunable exposed facets and crystallite sizes were solvothermally synthesized in a mixed solvent of n-propanol, water, and acetic acid. The regulation of the exposed facets and crystallite sizes was achieved simply by changing the n-propanol/water volume ratios (Rp/w, 0/30−30/0) of the mixed solvent. At low n-propanol contents (Rp/w < 15/15), the obtained BiOBr nanosheets expose dominantly (001) facets, while at high n-propanol contents (Rp/w > 20/10), they expose dominantly (010) facets. With increasing Rp/w, the lateral size and thickness of the BiOBr nanosheets all decrease, from 1700 to 174 nm and from 156 to 17 nm, respectively. The effects of exposed facets and thicknesses of BiOBr nanosheets on the photocatalytic activity, evaluated by degradation of salicylic acid and Rhodamine B under visible-light irradiation, were investigated. The exposed facet and thickness of BiOBr nanosheets are both important for their photocatalytic performance. The (001) facts exhibit a higher photocatalytic activity than the (010) facets. For the BiOBr nanosheets with the same (001 or 010) exposed facets, the photocatalytic activity increases with a decrease in their thickness. This study provides a new facile way to adjust the exposed facets and crystallite sizes of BiOX, and the finding may give guidance for crystal facet engineering of other photocatalysts.

    更新日期:2018-04-18
  • Cobalt–nickel alloy catalysts for hydrosilylation of ketones synthesized by utilizing metal–organic framework as template
    Catal. Sci. Technol. (IF 5.773) Pub Date : 2018-04-12
    Niklas R. Bennedsen, Søren Kramer, Jerrik J. Mielby, Søren Kegnæs
    更新日期:2018-04-18
  • Supported ionic liquid phase (SILP) facilitated gas-phase enzyme catalysis – CALB catalyzed transesterification of vinyl propionate
    Catal. Sci. Technol. (IF 5.773) Pub Date : 2018-04-05
    Changhee Lee, Bernhard Sandig, Michael R. Buchmeiser, Marco Haumann
    更新日期:2018-04-18
  • 更新日期:2018-04-18
  • Efficient C–C coupling of bio-based furanics and carbonyl compounds to liquid hydrocarbon precursors over lignosulfonate derived acidic carbocatalysts
    Catal. Sci. Technol. (IF 5.773) Pub Date : 2018-04-02
    Lakhya Jyoti Konwar, Ajaikumar Samikannu, Päivi Mäki-Arvela, Jyri-Pekka Mikkola
    更新日期:2018-04-18
  • Well-Defined β-Diketiminatocobalt(II) Complexes for Alkene Cyclohydroamination of Primary Amines
    ACS Catal. (IF 10.614) Pub Date : 2018-04-18
    Clément Lepori, Pablo Gómez-Orellana, Allissa Ouharzoune, Régis Guillot, Agusti Lledós, Gregori Ujaque, Jérôme Hannedouche
    更新日期:2018-04-18
  • Low-Energy Electrocatalytic CO2 Reduction in Water over Mn-Complex Catalyst Electrode Aided by a Nanocarbon Support and K+ Cations
    ACS Catal. (IF 10.614) Pub Date : 2018-04-18
    Shunsuke Sato, Kenichiro Saita, Keita Sekizawa, Satoshi Maeda, Takeshi Morikawa
    更新日期:2018-04-18
  • 更新日期:2018-04-18
  • One‐pot Construction of Difluorinated Pyrrolizidine and Indolizidine Scaffolds via Copper‐Catalyzed Radical Cascade Annulation
    Adv. Synth. Catal. (IF 5.646) Pub Date : 2018-04-18
    Xiaoyang Wang; Miao Li; Yanyan Yang; Minjie Guo; Xiangyang Tang; Guangwei Wang
    更新日期:2018-04-18
  • NHC‐catalyzed Enantioselective [4 + 3] Cycloaddition of ortho‐Hydroxyphenyl Substituted para‐Quinone Methides with Isatin‐Derived Enals
    Adv. Synth. Catal. (IF 5.646) Pub Date : 2018-04-17
    Wenjun Li; Huijun Yuan; Zhantao Liu; Zhongyin Zhang; Yuyu Cheng; Pengfei Li

    The first enantioselective cycloaddition of ortho‐hydroxyphenyl substituted para‐quinone methides has been established by employing isatin‐derived enals as suitable 3C‐synthons under chiral N‐heterocyclic carbene catalysis. By using this strategy, biologically important ε‐lactones have been prepared in good yields (up to 89 %) and excellent asymmetric inductions (up to >99 % ee, > 20:1 dr). Notably, this methodology opens a direct [4 + 3] annulation entry for the asymmetric synthesis of spirobenzoxopinones bearing an oxindole moiety connected through the spirocenter.

    更新日期:2018-04-18
  • Direct Deuteration of Acrylic and Methacrylic Acid Derivatives Catalyzed by Platinum on Carbon in Deuterium Oxide
    Adv. Synth. Catal. (IF 5.646) Pub Date : 2018-04-17
    Kwihwan Park; Takumi Matsuda; Tsuyoshi Yamada; Yasunari Monguchi; Yuka Sawama; Naoki Doi; yasushi Sasai; Shin-ichi Kondo; Yoshinari Sawama; Hironao Sajiki

    The platinum on carbon (Pt/C)‐catalyzed deuteration of acrylic and methacrylic acid derivatives in deuterium oxide (D2O) efficiently proceeded to give the corresponding acrylic acid‐d3 and methacrylic acid‐d5 derivatives. The olefinic functionality as well as the methyl group on the unsaturated functionality of the substrate were satisfactorily deuterated via the hydrogen (H)‐deuterium (D) exchange reaction. The obtained deuterated compounds are useful building blocks and efficiently converted to the corresponding desired products including a polymer without the degradation of the original deuterium contents.

    更新日期:2018-04-18
  • Revealing Janus character of the coke precursor in the propane direct dehydrogenation on Pt catalysts from the kMC simulation
    ACS Catal. (IF 10.614) Pub Date : 2018-04-18
    Zan Lian, Sajjad Ali, Tian-Fu Liu, ChaoWei Si, Bo Li, Dang Sheng Su

    As the commercial catalyst in propane direct dehydrogenation (PDH) reaction, one of the biggest challenges of Pt catalysts is the coke formation which severely reduce the activity and stability. In this work, first principle DFT based kinetic Monte Carlo simulation (kMC) is performed to understand the origin of the coke formation and the effective method is proposed to curb coke. The conventional DFT calculations give a complete description of reaction pathway of dehydrogenation to propylene, deep dehydrogenation, and C-C bond cracking. The rate limiting step is identified as the dissociative adsorption of propane. Moreover, the comparison between different exchange-correlation functional indicates the importance of van der Waals corrections for the adsorption of propane and propylene. The lateral interactions between the surface adsorbates are significant which implies that the mean field microkinetic modeling might not adequately describe the reaction process. There are two distinct stages in PDH which are quick deactivation and steady state respectively revealed from kMC simulation. The precursor of coke mainly formed during the quick deactivation. The calculations indicate that the geometry of the active sites for the dehydrogenation and deep reactions are different. Therefore, the availability of the surface sites is a crucial factor to the propylene formation and side products. The occupation of the active sites from quick activation is mainly C2/C1 species which is hard to remove. On the other hand, the left surface sites are mainly active towards to the dehydrogenation to propylene due to the geometry constrain. Therefore, a stable activity and selectivity is reached. Furthermore, the effect of hydrogen molecule in the input stream is also explored. The calculations indicate that the inclusion of hydrogen in PDH reactants not only enhances the forward reactions to the propylene formation but also reduces the consumption of the resulted propylene during the reaction. Therefore, the hydrogen is very helpful to the selectivity increase in PDH besides other effects. Overall, the current study lays out a solid base for the future optimization of the Pt catalysts in PDH and we propose that the fine control of the surface sites on Pt has paramount importance to reduce the coke formation.

    更新日期:2018-04-18
  • Identifying Catalytically Active Mononuclear Peroxoniobate Anion of Ionic Liquids in the Epoxidation of Olefins
    ACS Catal. (IF 10.614) Pub Date : 2018-04-17
    Wenbao Ma, Haiyang Yuan, Haifeng Wang, Qingqing Zhou, Kang Kong, Difan Li, Yefeng Yao, Zhenshan Hou

    The organic carboxylic acid-coordinated monomeric peroxoniobate-based ionic liquids (ILs) designated [TBA][NbO(OH)2(R)] (TBA= tetrabutylammonium; R=lactic acid (LA), glycolic acid (GLY) or malic acid (MA)) were prepared and fully characterized by elemental analysis, NMR, IR, Raman, TGA, 93Nb-NMR, and HRMS. These IL catalysts exhibited not only high catalytic activity for the epoxidation of olefins under very mild reaction conditions as the turnover frequency of [TBA][NbO(OH)2(LA)] reached up to 110 h-1 but also satisfactory recyclability in the epoxidation by using only one equivalent of hydrogen peroxide as an oxidant. Meanwhile, this work revealed that the ILs underwent structural transformation from [NbO(OH)2(R)]- to [Nb(O-O)2(R)]- (R=LA, GLY, MA) in the presence of H2O2 by the subsequent activity evaluation, characterization and the first-principles calculations. Moreover, the organic carboxylic acid-coordinated monomeric peroxoniobate-based ILs were investigated using density functional theory (DFT) calculations, which identified that [Nb(O-O)2LA]- was more advantageous than [Nb(O-O)2(OOH)2]- for the epoxidation of olefins. Due to the coordination between the -hydroxy acids and the monomeric peroxoniobate anions, the functionalized ILs can efficiently catalyze the epoxidation of a wide range of olefins and allylic alcohols under very mild conditions. Additionally, the effect of solvents on the reaction is illustrated. It was found that methanol can lower the epoxidation barriers by forming a hydrogen bond with a peroxo ligand attached to the niobium center.

    更新日期:2018-04-18
  • Three-Dimensional Pd3Pb Nanosheet Assemblies: High-Performance Non-Pt Electrocatalysts for Bifunctional Fuel Cell Reactions
    ACS Catal. (IF 10.614) Pub Date : 2018-04-17
    Lingzheng Bu, Chongyang Tang, Qi Shao, Xing Zhu, Xiaoqing Huang

    Even though extensive efforts have been devoted to pursue the promising electrocatalysts, the design of high-efficiency and low-cost electrocatalysts continues to be a formidable challenge for commercializing the electrochemical energy technologies. Herein, we report the successful creation of a class of three-dimensional ordered Pd3Pb nanosheet assemblies (NSAs) via a wet-chemical approach. Such controlled nanostructures with ordered phase and highly open structure exhibit enhanced electrochemical activity and durability for both anodic methanol oxidation reaction (MOR) and cathodic oxygen reduction reaction (ORR). In particular, the ordered Pd3Pb NSAs show the ORR mass and specific activities of 0.697 A mgPd-1 and 0.989 mA cm-2 at 0.90 V versus reversible hydrogen electrode (RHE), which are 8.3 (10.9) and 7.5 (6.4) times higher than those of the commercial Pt/C (Pd/C), respectively, making them among the most efficient catalyst ever achieved in the Pd-based ORR catalysts to date. In addition, the ordered Pd3Pb NSAs can even sustain at least 20000 potential cycles with limited activity decay and structure change.

    更新日期:2018-04-18
  • Role of Lattice Oxygen Participation in Understanding Trends in the Oxygen Evolution Reaction on Perovskites
    ACS Catal. (IF 10.614) Pub Date : 2018-04-17
    Jong Suk Yoo, Xi Rong, Yusu Liu, Alexie M Kolpak

    This study demonstrates the importance of considering lattice oxygen participation in understanding trends in the oxygen evolution reaction (OER) on ABO3 (A = lanthanum or strontium, B = transition metal) perovskites. Using density functional theory, we show that the lattice oxygen mechanism (LOM) can lead to higher OER activity than the conventional adsorbate evolving mechanism (AEM) by minimizing the thermodynamically required overpotential. We also show that the OER activity volcano for AEM is universal for all perovskites, whereas that for LOM depends on the identity of the A cation in ABO3. This explains experimental observations that perovskites such as Pr0.5Ba0.5CoO3–δ and SrCoO3–δ show higher OER activities than the conventionally predicted optimum compounds such as LaNiO3 and SrCoO3. Furthermore, we show that LOM is preferred to AEM in achieving bifunctional catalysts capable of promoting both OER and ORR. Using our overall activity volcano, we finally suggest several candidate materials that are predicted to be highly active for OER via LOM.

    更新日期:2018-04-18
  • Deeper mechanistic insight into Ru pincer-mediated acceptorless dehydrogenative coupling of alcohols: exchanges, intermediates and deactivation species
    ACS Catal. (IF 10.614) Pub Date : 2018-04-17
    Duc Hanh Nguyen, Xavier Trivelli, Frederic Capet, Youssef Swesi, Alain Favre-Réguillon, Laurent Vanoye, Franck Dumeignil, Régis M. Gauvin

    The mechanism of acceptorless dehydrogenative coupling reaction (ADC) of alcohols to esters catalyzed by aliphatic pincer PHNP ruthenium complexes was experimentally studied. Relevant intermediate species involved into the catalytic cycle were isolated and structurally characterized by single crystal X-ray diffraction studies, and their reactivity (including towards substrates related to the catalytic process) was probed. VT NMR studies unveiled several chemical exchanges connecting the Ru amido hydride, the Ru alkoxide and the alcohol substrate. Under catalytic conditions, in-situ IR spectroscopy monitoring demonstrated the production of ester via aldehyde as intermediate. Tishchenko-like pathway is proposed as the main path for the production of ester from aldehyde, involving alkoxide and hemiacetaloxide Ru species (the latter being identified in the reaction mixture by NMR). Catalytic system deactivation under base free conditions was found to be related to water traces in the reaction medium (either as impurity or derived from aldol reactions) that lead to the formation of catalytically inactive acetato Ru complexes. These react with alkali metal alkoxides to afford catalytically active Ru species. In line with this observation, running the ADC reaction in the presence of water scavengers or alkoxides allows maintaining sustained catalytic activity.

    更新日期:2018-04-18
  • Trace Level Co-N Doped Graphite Foams as High-Performance Self-Standing Electrocatalytic Electrodes for Hydrogen and Oxygen Evolution
    ACS Catal. (IF 10.614) Pub Date : 2018-04-17
    Yue Tong, Xiaowen Yu, Haiyan Wang, Bowen Yao, Chun Li, Gaoquan Shi

    The development of eco-friendly electrocatalysts with high performance and low cost for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is significant for renewable energy storage. Here, trace level (0.11~0.18 wt%) Co-N doped graphite foam (Co-N/GF) was reported to work as a bifunctional high-performance and self-standing electrode for both HER and OER in alkaline electrolyte. The catalytic activities of Co-N/GFs with different annealing temperatures (600, 700, 800, 900 and 1000 ºC) were carefully studied. Among them, Co-N/GF-900 exhibited the best HER activity and Co-N/GF-700 showed the best OER activity, achieving the current density of 10 mA cm−2 at low overpotentials of 165 and 313 mV, respectively. In addition, both of these electrodes exhibited long-term durability. Co-N/GF electrodes were further constructed as a catalytic cathode and anode couple (Co-N/GF-900||Co-N/GF-700) for overall water splitting, exhibiting a low cell voltage of 1.68 V and good long-term stability. Our work reveals that introducing a trace level of Co-N into graphite foam can significantly enhance its electrocatalytic activity and stability for both HER and OER.

    更新日期:2018-04-18
  • Cross-Coupling of Phenol Derivatives with Umpolung Aldehydes Catalyzed by Nickel
    ACS Catal. (IF 10.614) Pub Date : 2018-04-17
    Leiyang Lv, Dianhu Zhu, Jianting Tang, Zihang Qiu, Chen-Chen Li, Jian Gao, Chao-Jun Li

    A nickel-catalyzed cross-coupling to construct C(sp2)-C(sp3) bond was developed from two sustainable biomass-based feedstocks: phenol derivatives with umpolung aldehydes. This strategy features the in situ generation of moisture/air stable hydrazones from naturally abundant aldehydes, which act as alkyl nucleophiles under catalysis to couple with readily available phenol derivatives. The avoidance of using both halides as the electrophiles and organometallic or organoboron regents (also derived from halides) as the nucleophiles make this method more sustainable and renewable. Water tolerance, great functional group (ketone, ester, free amine, amide etc) compatibility and late-stage elaboration of complex biological molecules exemplified its practicability, unique chemo-selectivity over organometallic reagents.

    更新日期:2018-04-18
  • Carboxymethyl-β-cyclodextrin functionalization of TiO2 doped with lanthanum: Characterization and photocatalytic activity enhance
    Catal. Sci. Technol. (IF 5.773) Pub Date : 2018-04-17
    Gustavo Lopes Colpani, Jessica Taísa Zanetti, Fabiele Cecchin, Adrieli Dal'Toé, Márcio Antônio Fiori, Regina F.P.M. Moreira, Cintia Soares

    In this paper was proposed the surface functionalization with carboxymethyl-β-cyclodextrin (CMCD) of TiO2 nanoparticles doped with lanthanum to increase the photocatalytic activity in the organic molecules degradation, since CMCD has the feature of capture these compounds, increasing their density on the catalyst surface and approaching them from hydroxyl radicals formed. Moreover, the doping with lanthanum can generate superficial defects that capture the formed electrons, avoiding the recombination or increasing the density of –OH groups or water molecules attached to the surface of the catalyst, potentiating the formation of hydroxyl radicals. From the FT-IR, XPS, DTA, TGA characterizations was possible to verify the inclusion of the elements on the TiO2 surface and to propose a mechanism responsible to the lanthanum and CMCD inclusion. The kinetics evaluations shown an increase in the constants after the inclusion of the organic and inorganic molecules with a 99% degradation of the contaminant after 25 min.

    更新日期:2018-04-18
  • TEOA-induced in situ formation of wurtzite and zinc-blende CdS heterstructures as a high-active and long-lasting photocatalyst for converting CO2 into solar fuel
    Catal. Sci. Technol. (IF 5.773) Pub Date : 2018-04-17
    Yao Chai, Jiaxue Lu, Li Li, Deli Li, Meng Li, Jun Liang

    The wurtzite and zinc-blende CdS heterostructures are designed and in situ synthesized by tuning triethanolamine (TEOA) usage in a mild hydrothermal condition. The as-prepared samples were systematically characterized by XRD, SEM, TEM, UV-vis DRS, XPS, PL, and Mott-Schottky. It is realized that a further increase in used amount of TEOA promote the CdS phase transformation from hexagonal wurtzite to cubic zinc-blende during hydrothermal process, and detailed investigations indicate that the heteronanoparticles possess explicit heterointerfaces and strong light absorption as well as tunable band gaps. Especially when used as photocatalyst toward reduction of CO2 to CO and CH4 in the presence of H2O, the heterostructured CdS hybrids display not only better photocatalytic CH4-/CO-producing activity under visible-light irradiation than that of isolated CdS phase, but also unprecedented cycling stability, without hardly deactivation over 100 h. The remarkable improvement of photoactivity and stability over CdS-based hybrid can be attributed to better electron-hole pair separation and migration owing to junctions formed by coexistence of wurtzite and zinc-blende in the CdS nanohybrids, according to the physicochemical characterization. Additionally, the role of the junctions endowed by wurtzite/zinc-blende CdS in the process of the CO2 photoreduction is evaluated by using transient photocurrents and electrochemical impedance spectra (EIS) analysis, illustrating its fast-interfacial charge transfer. This work would provide a significant avenue to effectively photocatalytic conversion CO2 using rationally designed CdS-based surface phase junctions engineering at nanoscale.

    更新日期:2018-04-18
  • Rhodium‐Catalyzed Chemo‐ and Enantioselective Hydrogenation of Alkynyl‐Aryl Hydrazones
    Adv. Synth. Catal. (IF 5.646) Pub Date : 2018-04-17
    Dongyang Fan; Yanhua Hu; Feng Jiang; Zhenfeng Zhang; Wanbin Zhang
    更新日期:2018-04-18
  • 更新日期:2018-04-18
  • Biocatalytic Process for (‐)‐Ambrox Production Using Squalene Hopene Cyclase
    Adv. Synth. Catal. (IF 5.646) Pub Date : 2018-04-17
    Eric Eichhorn; Esther Locher; Sabrina Guillemer; Denis Wahler; Laurent Fourage; Boris Schilling

    <i>Alicyclobacillus acidocaldarius</i> Squalene Hopene Cyclase was evolved to a biocatalyst suitable for (‐)‐Ambrox production at industrial scale. One round of random mutagenesis led to the identification of three variants with (<i>E,E</i>)‐homofarnesol conversion properties improved about 1.5‐ to 10‐fold over that of the wild type enzyme. Eight distinct amino acid mutations were identified overall; only one mutation was at the active site of the enzyme. Each of the three variants contained only two or three mutations over the 631 amino acids of the <i>Alicyclobacillus acidocaldarius</i> Squalene Hopene Cyclase polypeptide chain. Mutations responsible for improved (<i>E,E</i>)‐homofarnesol conversion were identified. Investigations on reaction conditions led to the selection of one variant, with which reaction parameters were optimized towards process‐relevant conditions. A whole cell biotransformation process is presented in which <i>Escherichia coli</i> cells producing an improved Squalene Hopene Cyclase variant allows the conversion of 125 g/L (<i>E,E</i>)‐homofarnesol in ≤ 72 hours. The developed process for the production of the fragrance ingredient (‐)‐Ambrox as Ambrofix® expands the biocatalysis toolbox by setting out a general basis for biocatalytic Squalene Hopene Cyclase cyclization reactions at industrial scale.

    更新日期:2018-04-18
  • Evaluation of Natural and Synthetic Phosphate Donors for the Improved Enzymatic Synthesis of Phosphate Monoesters
    Adv. Synth. Catal. (IF 5.646) Pub Date : 2018-04-17
    Gabor Tasnadi; Wolfgang Jud; Mélanie Hall; Kai Baldenius; Klaus Ditrich; Kurt Faber

    Undesired product hydrolysis along with large amounts of waste in form of inorganic monophosphate by‐product are the main obstacles associated with the use of pyrophosphate in the phosphatase‐catalyzed synthesis of phosphate monoesters on large scale. In order to overcome both limitations, we screened a broad range of natural and synthetic organic phosphate donors with several enzymes on a broad variety of hydroxyl‐compounds. Among them, acetyl phosphate delivered stable product levels and high phospho‐transfer efficiency at the lower functional pH‐limit, which translated into excellent productivity. The protocol is generally applicable to acid phosphatases and compatible with a range of diverse substrates. Preparative‐scale transformations using acetyl phosphate synthesized from cheap starting materials yielded multiple grams of various sugar phosphates with up to 433 g L‐1 h‐1 space‐time yield and 75% reduction of barium phosphate waste.

    更新日期:2018-04-18
  • Copper Mediated Three‐Component Reactions of Alkynes,Azides, and Propargylic Carbonates: Synthesis of 5‐Allenyl‐1,2,3‐Triazoles
    Adv. Synth. Catal. (IF 5.646) Pub Date : 2018-04-17
    Wanzhi Chen; Feifei Wu; Wei Zhou; Kai Chen; Miaochang Liu; Huayue Wu

    A copper‐mediated one‐pot sequential reaction of terminal alkynes, azides, and propargylic carbonates is reported. The three component reaction occurs readily at room temperature to afford a 5‐allenyl‐1,2,3‐triazoles in high yields, providing a straightforward approach to 1,3,5‐trisubstituted triazoles using easily available Cu(I) reagent.

    更新日期:2018-04-18
  • Effect of the morphology on the vapor phase benzene catalytic hydrogenation over Pd/CeO2 catalyst
    Catal. Commun. (IF 3.33) Pub Date : 2018-04-12
    Tao Li, Deping Xia, Guilin Zhou, Hongmei Xie, Zhaojie Jiao, Xianming Zhang

    CeO2 nanorods and nanocubes, which were used as supports to Pd (3.0 wt.%)/CeO2 catalysts, which were prepared by hydrothermal method. TEM, HRTEM, XRD, and H2-TPD were used to study the physic-chemical properties of the Pd/CeO2 catalysts. The Pd/CeO2 catalysts were applied to investigate the vapor phase benzene catalytic hydrogenation reaction under atmospheric pressure at the temperature of 100–200 °C. Results show that the Pd/CeO2 catalysts exhibit morphology-dependent catalytic activity. The Pd/CeO2 nanorod catalyst (PC100) has a superior vapor phase benzene catalytic hydrogenation performance. The benzene catalytic hydrogenation conversion and cyclohexane selectivity are 96.4% and 100% at 200 °C, respectively.

    更新日期:2018-04-17
  • Zeolite Y encapsulated Cu (II) and Zn (II)-imidazole-salen catalysts for benzyl alcohol oxidation
    Mol. Catal. Pub Date : 2018-04-11
    Fuhai Li, Dairong Hu, Yahui Yuan, Binbin Luo, Yibing Song, Songtao Xiao, Guanghui Chen, Yiwen Fang, Fushen Lu
    更新日期:2018-04-17
  • Tailoring the properties of oxygenated graphene with different oxidation degrees for noble-metal-free photocatalytic hydrogen evolution
    Catal. Today (IF 4.636) Pub Date : 2018-04-12
    Lutfi K. Putri, Boon-Junn Ng, Kok Hong Tan, Fang Sheng Lim, Wee-Jun Ong, Wei Sea Chang, Siang-Piao Chai

    This present work demonstrates the integration of oxygen atoms into the graphene matrix to develop graphene oxide (GO) with tailored oxidation degrees which render them as photoactive materials for hydrogen (H2) evolution. GO photocatalysts derived from the modified Hummer’s method can endow tunable optical and electronic properties by varying the oxidation level into three increasing degrees GO-0.33, GO-0.47 and GO-0.53. Absorption spectroscopy revealed the increasing band gap of GO with respect to increasing oxygen contents and XRD, Raman and AFM studies revealed transformation in properties with increasing degree of oxygenated graphene. As opposed to graphite or graphene which is not photoresponsive, all GO samples exhibited photocatalytic activity towards H2 generation in sacrificial systems containing 0.1 M Na2S/Na2SO3. Among the studied samples, GO with intermediate O/C ratio of 0.47 (GO-0.47) exhibited the highest H2 photoactivity of 1104.3 μmolg-1h-1 after of light irradiation, owing to the presence of optimal oxygen loading content in GO. The study reveals that mere chemical modification by oxygen groups on the graphene can confer photocatalytic properties whose activity is further adjustable by modification in the oxygen level.

    更新日期:2018-04-17
  • Selective oxidation of o-xylene to phthalic anhydride on tungsten, tin, and potassium promoted VOx on TiO2 monolayer catalysts
    Catal. Today (IF 4.636) Pub Date : 2018-04-12
    P. Eversfield, T. Lange, M. Hunger, E. Klemm

    VOx monolayer on TiO2 catalysts have been prepared by grafting and subsequently promoted with tungsten, tin, and potassium by impregnation. The samples have been characterized through N2 physisorption at 77 K, PXRD, Raman spectroscopy, H2-TPR, and 1H Solid State NMR spectroscopy with NH3 as probe molecule. Catalytic measurements have been performed in an isothermal fixed bed reactor at 350 °C with 1.5 vol.% o-xylene in air. Space velocities were varied to get selectivity-conversion-diagrams for CO2 and maleic anhydride as side products as well as phtalic anhydride, toluyl aldehyde and phthalide as value products. The selectivity-conversion diagrams of the unpromoted sample clearly indicate a direct pathway from o-xylene and/or toluylaldehyde towards phthalic anhydride. Tungsten, tin and potassium promoted samples were compared with unpromoted samples. It was found that optimum accessibility and acidity of the promoted VOx monolayer can explain the observed promoter effects. Tungsten as promoter decreases MA selectivities and increases PA selectivities at an optimum loading of 0.12 wt.% WO3. Tin was detrimental at all loadings because acidities seem to be too high causing too strong adsorption and condensation reactions of o-xylene. With potassium as promoter lowest acidities and highest V accessibilities were reached which correlates with the increase of activity and PA selectivity. In contrast to potassium, tungsten and tin move significantly into the TiO2 support during calcination which was proven by XPS measurements on sputtered probes. This might explain why potassium acts more efficiently as promoter already at low promoter levels.

    更新日期:2018-04-17
  • Enhanced molecular oxygen activation of Ni2+-doped BiO2-x nanosheets under UV, visible and near-infrared irradiation: Mechanism and DFT study
    Appl. Catal. B Environ. (IF 9.446) Pub Date : 2018-04-12
    Jun Li, Jia Wang, Gaoke Zhang, Yuan Li, Kai Wang

    Although molecular oxygen activation plays a significant role in photocatalytic process for pollutants removal, it is still challenging to activate molecular oxygen into superoxide radical (•O2-) by photocatalysts under near-infrared (NIR) light irradiation. Herein, we successfully synthesized Ni2+-doped BiO2-x nanosheets, which could efficiently achieve the molecular oxygen activation into •O2- under UV, visible and NIR irradiation. Meanwhile, we found the doping Ni2+ facilitated the formation of BiO2-x nanosheets. More importantly, the contribution of doping Ni2+ to full spectrum molecular oxygen activation over Ni2+-doped BiO2-x was further confirmed by experiments and density functional theory (DFT) study. The introduction of Ni2+ into BiO2-x structure resulted in the formation of a new doping energy level band between the valence band (VB) and conduction band (CB) of Ni2+-doped BiO2-x, which contributed to the faster separation of carriers and highly efficient full spectrum driven molecular oxygen activation under UV, visible and NIR irradiation, especially with the irradiation of NIR light as compared to BiO2-x. In addition, the doping Ni2+ promoted the optical absorption property of BiO2-x with narrowing band gap and the up-shift position of VB and CB. As expected, the Ni2+-doped BiO2-x nanosheets exhibited enhanced photocatalytic activity for rhodamine B (RhB) degradation under UV, visible and NIR irradiation than pure BiO2-x nanosheets. The photocatalyst still revealed high photocatalytic activity even after five cycles. Finally, a possible photocatalytic mechanism of the degradation processes by Ni2+-doped BiO2-x was proposed. This work not only confirmed Ni2+ doping could promote the formation of BiO2-x nanosheets and enhance their full spectrum driven molecular oxygen activation ability, but also presented an in-depth understanding on the mechanism of full spectrum driven molecular oxygen activation.

    更新日期:2018-04-17
  • Exceptionally Stable Rh-based Molecular Catalyst Heterogenized on a Cationically charged Covalent Triazine Framework Support for Efficient Methanol Carbonylation
    Catal. Sci. Technol. (IF 5.773) Pub Date : 2018-04-17
    Kwangho Park, Sangyup Lim, Joon Hyun Baik, Honggon Kim, Kwang-Deog Jung, Sungho Yoon

    Direct carbonylation of methanol into methyl acetate and acetic acid using Rh-based heterogeneous catalysis is of great interest due to the effective levels of activity and stability. Here, a Rh-based molecular catalyst heterogenized on a charged 1, 3-bis(pyridyl) imidazolium-based covalent triazine framework (Rh-bpim-CTF) was synthesized and characterized to have a single-site distribution of metal molecular species throughout the support by its ligation to abundant N atom sites. Methanol carbonylation was performed using the Rh-bpim-CTF catalyst in plug-flow reaction in a gas phase, affording a turnover frequency up to 3693 h-1 and productivity of 218.9 mol kg-1 h-1 for acetyl products with high stability.

    更新日期:2018-04-17
  • Selective synthesis of the resveratrol analogue 4,4′-dihydroxy-trans-stilbene and stilbenoids modification by fungal peroxygenases
    Catal. Sci. Technol. (IF 5.773) Pub Date : 2018-04-17
    Carmen Aranda, René Ullrich, Jan Kiebist, Katrin Scheibner, José C. del Río, Martin Hofrichter, Angel T. Martínez, Ana Gutiérrez
    更新日期:2018-04-17
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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