Development and testing of a combined catalyst/sorbent core-in-shell material for the production of high concentration hydrogen

A combined catalyst and sorbent for the production of hydrogen from CH4 or CO was developed and tested. The combined catalyst and sorbent was a spherical multi-layered material having a CaO-based sorbent core and an outer shell composed mainly of alumina. The CaO sorbent core was employed to absorb CO2, one of the reaction products. The alumina shell protected the friable CaO core and also supported a Ni catalyst. The development of the material focused separately on the development of the core and shell. First, since the CO2 absorption capacity of CaO-based sorbents diminishes as they are repeatedly used and regenerated, the development of a more stable CaO-based sorbent was investigated. Both the addition of MgO, which acted as a sintering inhibitor, and severe initial calcination conditions for the CaO precursor limestone produced a more stable CaO sorbent. Second, an alumina-based material with good physical strength and high surface area was developed to serve as the shell of the core-in-shell material. The addition of either fine particle limestone or lanthanum oxide to the alumina shell formulation produced a material with enhanced physical strength, which was most likely due to the formation of a binding aluminate phase. Reaction testing of the core-in-shell pellets with a 3:1 molar ratio of H2O:CH4 in the feed produced a high concentration of H2 via simultaneous application of the steam-methane reforming reaction, the water-gas shift reaction and the reaction of CO2 with CaO. This testing was conducted with a tubular fixed bed reactor over a temperature range of 550-650yC and a pressure range of 1.0-10.0 atm. The rapid absorption of CO2 by CaO produced CH4 and CO conversions greater than would have been possible without a sorbent. Lifecycle testing determined that a high concentration of H2 could be produced over 10 cycles of H2 production and sorbent regeneration. However, the length of time that H2 was produced diminished with each cycle due to a loss of CO2 absorption capacity by the CaO sorbent. Physical characterization of the pellets after lifecycle testing also revealed that some pellets fractured during lifecycle testing and that the Ni catalyst sintered. Core-in-shell pellets with alternate shell formulations were also tested in the fixed bed reactor for the production of high concentrations of H2 from a mixture of CO and steam via the water-gas shift reaction. Three alumina shell formulations were tested: a formulation with mostly alumina in the shell, a formulation with 10 wt% Fe2O3 added to the alumina shell formulation and a formulation with Ni impregnated onto the shell. The rapid absorption of CO2 by the sorbent allowed for a high concentration of H2 to be produced and a high CO conversion to be achieved between 550-600yC at 1.0 atm with any of these formulations. However, once the CaO sorbent became loaded, only the formulation with Ni present converted CO to reaction equilibrium levels. On the other hand, by absorbing CO2 the formulation with mainly alumina in the shell appeared to be an attractive material for the production of H2 from syngas. Furthermore, this formulation would be resistant to sulfurous gases that might be present

Ab initio study of semiconducting carbon nanotubes adsorbed on the Si(100) surface: diameter- and registration-dependent atomic configurations and electronic properties

We present a first-principles study of semiconducting carbon nanotubes adsorbed on the unpassivated Si(100) surface. We have found metallicity for the combined system caused by n-doping of the silicon slab representing the surface by the SWNT. We confirm this metallicity for nanotubes of different diameters and chiral angles, and find the effect to be independent of the orientation of the nanotubes on the surface. We also present adsorption energetics and configurations which show semiconducting SWNTs farther apart from the surface and transferring less charge, in comparison with metallic SWNTs of similar diameter.Comment: Replaces old (Jan 2006) version; more supporting material. 11 pages, 8 figures, 7 table

How a dinosaur transformed into an e-commerce giant : the digital transformation of the Otto Group

Over the past few years, the topic of digital transformation has become more relevant for many companies. The ever-accelerating dynamics and rapidly emerging technologies represent significant challenges for many companies and require them to digitally transform. Many researchers have already studied several different factors that come along with the topic of digital transformation. Nevertheless, there is a lack of case studies that contain real-world examples illustrating how companies could digitally transform. For this reason, the teaching case on the digital transformation of the Otto Group, with special emphasis on its subsidiary OTTO, was developed. The purpose of this teaching case is to illustrate the challenges that the group faced as well as the success factors that played a major role during the transformation. Also, the case demonstrates how the company has changed over the years. Furthermore, this case shows how the Otto Group succeeded in constantly developing new business models. In the end, the results achieved through the digital transformation are demonstrated and a glimpse into the future of the company will be given. The Otto Group Case exemplifies what an important role corporate culture plays in the context of digital transformation. With the help of the cultural change at the Otto Group and the full commitment of the executive board, which could be seen, among other aspects, in the large investments made in the context of the change process, the group was able to carry out the digital transformation.Nos últimos anos, o tema da transformação digital tornou-se mais relevante para muitas empresas. A dinâmica cada vez mais acelerada e as tecnologias rapidamente emergentes representam desafios significativos para muitas empresas e exigem que elas se transformem digitalmente. Muitos investigadores já estudaram vários fatores diferentes que acompanham o tópico da transformação digital. No entanto, há uma falta de exemplos do mundo real que ilustrem como as empresas se podem transformar digitalmente. Por essa razão, foi desenvolvido o estudo de caso sobre a transformação digital do Grupo Otto, com especial destaque para a sua filial OTTO. O objetivo deste caso pedagógico é ilustrar os desafios que o grupo enfrentou, bem como os fatores de sucesso que desempenharam um papel chave durante a transformação. Além disso, o caso demonstra como a empresa mudou ao longo dos anos. Adicionalmente, este caso demonstra mostra como o Grupo Otto conseguiu constantemente desenvolver novos modelos de negócios. No final, são apresentados os resultados alcançados através da transformação digital e um vislumbre do futuro da empresa será dado. O caso Otto Group exemplifica o importante papel que a cultura corporativa desempenha no contexto da transformação digital. Com a ajuda da mudança cultural no Grupo Otto e o total compromisso da comissão executiva, que se verificou, entre outros aspectos, nos grandes investimentos realizados no contexto de mudança cultural processo, o grupo foi capaz de mudar a sua cultura corporativa e, assim, realizar a transformação digital

Der UN-Standort Österreich und der außenpolitische Status Österreichs nach 1945

Die hier vorliegende Arbeit beschäftigt sich mit der Etablierung des UNO-Standortes Österreich unter Rücksichtnahme auf die außenpolitische Ausgangssituation nach 1945 sowie die durch den Kalten Krieg gegebenen geopolitischen Umstände. Wesentlich ist hierbei die österreichische Neutralität sowie die Handlungsoptionen, die sich boten. Als neutraler Kleinstaat suchte Österreich früh Anbindung an die Vereinten Nationen um seine Souveränität zu festigen. Die Bemühungen, sich auch in ernsten Situationen als verlässlicher Partner zu erweisen, lassen sich sehr gut anhand des österreichischen Engagements bei diversen UN-Friedensmissionen darstellen. Nicht vernachlässigt wird im Zuge dieser Arbeit die rechtliche und vor allem neutralitätspolitische Komponente dieses Engagements. Besonderes Augenmerk gilt dem Bau des UN-Standortes Wien, der sogenannten UNO-City. Hier stehen vor allem die baulichen Aspekte, noch mehr aber der kontroverse innenpolitische Diskurs im Vordergrund, bei dem es vordergründig um Unregelmäßigkeiten bei der Auftragsvergabe sowie Kostenfragen ging. Als wichtiger Punkt gestalten sich jedoch auch die wirtschaftlichen und politischen Auswirkungen des Standortes Wien sowie die Reaktionen des Nachbarlandes Schweiz, das seine historische Rolle als neutraler Sitzstaat im Herzen Europas gefährdet sah. Das letzte Kapitel versucht einen aktuelleren Bezug herzustellen, das heißt es werden die veränderten geopolitischen Bedingungen nach Ende des Kalten Krieges sowie der geänderte Status Österreichs auch aufgrund seines Beitrittes zur Europäischen Union berücksichtigt. Besonderes Augenmerk gilt hier der Neutralität, die als deutlich geschwächt betrachtet werden kann. Die Frage, ob der UN-Standort aus diesem Grund oder auch aufgrund des entfallenden Ost-West-Gegensatzes an Bedeutung verloren hat, kann mit Nein beantwortet werden. Österreich hat sich als Amtssitz fest etabliert und übt diese Rolle bis heute entsprechend aus