Catalytic Behaviour of Mesoporous Cobalt-Aluminum Oxides for CO Oxidation

Ordered mesoporous materials are promising catalyst supports due to their uniform pore size distribution, high specific surface area and pore volume, tunable pore sizes, and long-range ordering of the pore packing. The evaporation-induced self-assembly (EISA) process was applied to synthesize mesoporous mixed oxides, which consist of cobalt ions highly dispersed in an alumina matrix. The characterization of the mesoporous mixed cobalt-aluminum oxides with cobalt loadings in the range from 5 to 15 wt% and calcination temperatures of 673, 973, and 1073 K indicates that Co2+ is homogeneously distributed in the mesoporous alumina matrix. As a function of the Co loading, different phases are present comprising poorly crystalline alumina and mixed cobalt aluminum oxides of the spinel type. The mixed cobalt-aluminum oxides were applied as catalysts in CO oxidation and turned out to be highly active.Fil: Bordoloi, Ankur. Indian Institute of Petroleum; IndiaFil: Sanchez, Miguel Dario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Noei, Heshmat. Research Group X-Ray Physics and Nanoscience Deutsches Elektronen-Synchrotron; AlemaniaFil: Kaluza, Stefan. Fraunhofer Institute of Environmental, Safety, and Energy Technology; AlemaniaFil: Großmann, Dennis. Ruhr Universität Bochum; AlemaniaFil: Wang, Yuemin. Ruhr Universität Bochum; AlemaniaFil: Grünert, Wolfgang. Ruhr Universität Bochum; AlemaniaFil: Muhler, Martin. Ruhr Universität Bochum; Alemani

A general electro-synthesis approach to amaryllidaceae alkaloids

Amaryllidaceae alkaloids appeal to organic chemists with their attractive structures and their impressive antitumor and acetylcholinesterase inhibitory properties. We demonstrate a highly versatile access to this family of natural products. A general protocol with high yields in a sustainable electro-organic key transformation on a metal-free anode to spirodienones facilitates functionalization to the alkaloids. The biomimetic syntheses start with the readily available, inexpensive biogenic starting materials methyl gallate, O-methyl tyramine, and vanillin derivatives. Through known dynamic resolutions, this technology provides access to both enantiomeric series of (epi-)martidine, (epi-)crinine, siculine, and galantamine, clinically prescribed for the treatment of Alzheimer's disease

OpenLB User Guide: Associated with Release 1.6 of the Code

OpenLB is an object-oriented implementation of LBM. It is the first implementation of a generic platform for LBM programming, which is shared with the open source community (GPLv2). Since the first release in 2007, the code has been continuously improved and extended which is documented by thirteen releases as well as the corresponding release notes which are available on the OpenLB website (https://www.openlb.net). The OpenLB code is written in C++ and is used by application programmers as well as developers, with the ability to implement custom models OpenLB supports complex data structures that allow simulations in complex geometries and parallel execution using MPI, OpenMP and CUDA on high-performance computers. The source code uses the concepts of interfaces and templates, so that efficient, direct and intuitive implementations of the LBM become possible. The efficiency and scalability has been checked and proved by code reviews. This user manual and a source code documentation by DoxyGen are available on the OpenLB project website

Methanol synthesis over Cu/ZnO aggregates encapsulated in carbon nanotubes and mesoporous silica

Methanol ist eine der wichtigsten Grundchemikalien in der Industrie. Trotz jahrelanger Forschung sind die aktiven Spezies von Cu/ZnO basierten MeOH-Synthesekatalysatoren bis heute nicht endgültig identifiziert. Wenn auch der Einfluß des ZnO als essentiell bezeichnet wird, so bleibt die Frage nach dem tatsächlichen Zustand ungeklärt. Ziel dieser Arbeit war die Herstellung und Charakterisierung von Cu/ZnO basierten Modellkatalysatoren auf verschiedenen Trägern und deren Testung in der MeOH-Synthese um Aussagen über die aktiven Spezies zu erhalten. Die Strategie CNTs als Trägermaterial zu verwenden um Messing-Nanopartikel zu erzeugen war zunächst erfolgreich, es konnten aber aus bisher nicht eindeutig identifizierten Gründen nur sehr geringe Aktivitäten bestimmt werden. Die weiteren Ergebnisse zeigen allerdings, dass sich die Wechselwirkung zwischen metallischem Kupfer und einem partiell reduzierten ZnO positiv auf die katalytische Aktivität von SBA-15 geträgerten Katalysatoren auswirkt

"Dirty nanostructures" : aerosol-assisted synthesis of temperature stable mesoporous metal oxide semiconductor spheres comprising hierarchically assembled zinc oxide nanocrystals controlled via impurities

Structural disintegration or the loss of accessible surfaces of functional nanostructures due to processes involving mass transport (e.g. sintering) is a serious problem for any application of these materials at elevated temperatures, like in heterogeneous catalysis or chemical sensing. Phases with low sintering temperatures, e.g. some metals or metal oxides like zinc oxide (ZnO), are very sensitive in this respect. Therefore, it is not only relevant to prepare important materials with refined morphologies, but the desired features need to be stable under real conditions. In this study, we describe the preparation of mesoporous ZnO nano-/microspheres by means of a template-assisted aerosol technique. Furthermore, by intentional introduction of impurity elements as dopants, specific surface areas and porosities of the prepared materials can be increased significantly. The impurities also strongly improve the thermal stability of the described ZnO nanostructures against thermal sintering. Although the pure ZnO material suffers from a complete loss of porosity, the structures of the impure (”dirty”) materials change only negligibly. Even at 500 °C morphology and porosity are preserved. The latter advantageous property was used for testing the novel nanocatalysts in heterogeneous catalysis

Surface Alloy or Metal–Cation Interaction-The State of Zn Promoting the Active Cu Sites in Methanol Synthesis Catalysts

Model catalysts containing disordered CuO and ZnO species in the pores of SBA-15 were reduced under different conditions (standard: H2, 513 K; severe: CO/H2, 673 K), studied by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) including operando work and used as catalysts for methanol synthesis at pressures up to 8 bar, where they were comparable with a commercial reference in terms of reaction rates related to Cu surface area. Severe reduction caused significant activation of the Cu sites beyond the sizeable level achieved already after standard reduction. In XRD, which failed to detect most of the active components, owing to small particle sizes, weak indications of alloy formation were found after severe reduction. XAFS, which averages over all species present, showed the interaction of Cu with zinc ions to increase by severe reduction, while formation of Zn0 was below detection limit. On this basis, the promoting interaction of Zn to Cu was ascribed to an interaction of zinc cations with Cu0

Communicating unknown objects to robots through pointing gestures

Delegating tasks from a human to a robot needs an efficient and easy-to-use communication pipeline between them - especially when inexperienced users are involved. This work presents a robotic system that is able to bridge this communication gap by exploiting 3D sensing for gesture recognition and real-time object segmentation. We visually extract an unknown object indicated by a human through a pointing gesture and thereby communicating the object of interest to the robot which can be used to perform a certain task. The robot uses RGB-D sensors to observe the human and find the 3D point indicated by the pointing gesture. This point is used to initialize a fixation-based, fast object segmentation algorithm, inferring thus the outline of the whole object. A series of experiments with different objects and pointing gestures show that both the recognition of the gesture, the extraction of the pointing direction in 3D, and the object segmentation perform robustly. The discussed system can provide the first step towards more complex tasks, such as object recognition, grasping or learning by demonstration with obvious value in both industrial and domestic settings

How Different Characterization Techniques Elucidate the Nature of the Gold Species in a Polycrystalline Au/TiO2Au/TiO_{2} Catalyst

$TiO_{2}$-supported gold species were prepared via the deposition-precipitation route, with conservation of the initial speciation by freeze-drying. The structural and electronic properties of the Au species were investigated by X-ray absorption spectroscopy, electron microscopy, and IR spectroscopy of adsorbed CO in four states. Exclusively $Au^{III}$ was deposited on the $TiO_{2}$ surface in patches ranging from isolated Au ions to three-dimensional clusters. This paper illustrates in detail the unique contributions of all characterization techniques to this structural model

Tieftemperatur-CO-Oxidation mit Au3+Au^{3+}-Ionen auf TiO2TiO_{2}

$Au/TiO_{2}$-Katalysatoren, die durch das “Deposition-Precipitation”-Verfahren hergestellt und ohne Kalzinierung eingesetzt wurden, erreichten in der CO-Oxidation hohe, weitgehend temperaturunabhängige Umsätze. Dagegen erschien nach thermischen Vorbehandlungen, z. B. in He bei 623 K, die Umsatz-Temperatur-Charakteristik in der bekannten S-Form, mit Aktivierungsenergien nahe $30 kJ mol^{−1}$. Charakterisierung der Proben durch XAFS und HAADF-STEM sowie eine Tieftemperatur-IR-Studie von Adsorption und Oxidation des CO zeigten, dass letzteres am frisch präparierten (gefriergetrockneten) Katalysator, der Gold ausschließlich als $Au^{3+}$ enthielt, bereits bei 90 K durch Gasphasensauerstoff oxidiert wurde. Nach Aktivierung im Reaktantenstrom geht der CO-Umsatz bei niedrigen Reaktionstemperaturen auf Zentren zurück, die $Au^{III}$ enthalten, bei höheren Temperaturen wird er von $Au^{0}$ getragen. Nach thermischen Behandlungen wird CO im ganzen Temperaturbereich an Zentren umgesetzt, die ausschließlich metallisches Gold enthalten