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Two zeolitic imidazolate frameworks, ZIF-9 and ZIF-71, are evaluated by adsorption experiments and molecular simulations with respect to their potential towards olefin/paraffin separation. Pure component adsorption isotherms are measured and compared to grand-canonical Monte-Carlo (GCMC) simulations. The experiments show that the adsorption of the paraffin is favorable over the olefin in both structures. Whereas the isotherms are predicted well by simulations for ZIF-71, in case of ZIF-9 only the saturation loading could be computed accurately because the latter material seems to undergo a so-called gate-opening effect upon adsorption of guest molecules; ZIF-71 does not show this effect. Both structures show promising results with respect to olefin/paraffin separation. [ABSTRACT FROM AUTHOR]

Diffusion in nanoporous host–guest systems is often considered to be too complicated to comply with such “simple” relationships as Fick's first and second law of diffusion. However, it is shown herein that the microscopic techniques of diffusion measurement, notably the pulsed field gradient (PFG) technique of NMR spectroscopy and microimaging by interference microscopy (IFM) and IR microscopy (IRM), provide direct experimental evidence of the applicability of Fick's laws to such systems. This remains true in many situations, even when the detailed mechanism is complex. The limitations of the diffusion model are also discussed with reference to the extensive literature on this subject. [ABSTRACT FROM AUTHOR]

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Methodological advances in quantum chemistry and classical molecular simulation combined with the ever increasing speed of computers allow for approaching chemical accuracy in the prediction of thermodynamic and kinetic parameters of zeolite catalyzed hydrocarbon reactions. In this account, progress in the area of multiscale modeling is illustrated by two examples taken from the authors' recent work and needs for further developments are identified. [ABSTRACT FROM AUTHOR]

Bubble columns equipped with an vibration exciter, which pulsates with a frequency between 40 and 400 Hz, show significantly improved mass transfer rates. This results from a reduction of bubble size by cleavage, the associated increase in surface area and, additionally, an intensive movement at the bubble interface. The observed phenomena are explained based on flow simulations. The energy required for a oscillating bubble column is less than for a gassed stirred tank. [ABSTRACT FROM AUTHOR]

Knowledge about the structural elements of skin and its appendices is an essential prerequisite for understanding their complex functions and interactions. The hence necessary morphological description across several orders of scale not only requires the investigation at the light microscopic level but also ultrastructural investigation, ideally on the identical sample. For a correlative and multimodal observation one unique preparation protocol is mandatory. As a compromise between sample sizes of >500 μm in diameter on the one hand and optimal preservation of antigenicity and morphology on the other, we developed a new preparation protocol that allows (i) 3D reconstruction of the resin-embedded sample by confocal light microscopy prior to (ii) direct immunolocalization of target proteins within selected sample planes by light and fluorescence microscopy or transmission electron microscopy. Alternatively, (iii) serial cryosections of the frozen sample can be taken for characterizing the sample in toto. With this unique approach we were able to fully demonstrate the structural complexity of axillary skin samples, increasing the structural resolution from 3D reconstruction of the whole gland up to ultrastructural investigations at the subcellular level. We could demonstrate that axillary sweat glands are not separately distributed, as has been assumed to date; instead, they seem to be intricately twisted into one another. This promotes the concept of a complex axillary sweat gland organ instead of single sweat gland entities. [ABSTRACT FROM AUTHOR]

Designing the pore network structure is an effective approach to improve the performance of industrial catalyst particles, although it receives less attention than designing catalytic surfaces or active sites. This work presents a first example of the optimization of catalyst pore network structures in the presence of deactivation by coke formation, using a three‐dimensional pore network model. Propane dehydrogenation in a Pt‐Sn/Al2O3 catalyst particle is taken as the model reaction system. Catalyst particles with unimodal and bimodal pore‐size distributions are investigated, both being commonly used in industry. The porosity, connectivity, pore size, and their spatial distributions are optimized under two separate assumptions: constant intrinsic activity per unit catalyst weight and constant intrinsic activity per unit internal surface area. The optimized catalyst shows up to 14‐fold improvement in the time‐averaged propene formation rate, when compared to a benchmark catalyst. This significant improvement is primarily because of reductions in diffusion resistance and pore blockage. [ABSTRACT FROM AUTHOR]