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排序方式: 共有159条查询结果,搜索用时 31 毫秒
41.
Xinwei Ye Dr. Joel E. Schmidt Ru-Pan Wang Ilse K. van Ravenhorst Dr. Ramon Oord Prof. Dr. Tiehong Chen Prof. Dr. Frank de Groot Dr. Florian Meirer Prof. Dr. Bert M. Weckhuysen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(36):15740-15747
To gain insight into the underlying mechanisms of catalyst durability for the selective catalytic reduction (SCR) of NOx with an ammonia reductant, we employed scanning transmission X-ray microscopy (STXM) to study Cu-exchanged zeolites with the CHA and MFI framework structures before and after simulated 135 000-mile aging. X-ray absorption near-edge structure (XANES) measurements were performed at the Al K- and Cu L-edges. The local environment of framework Al, the oxidation state of Cu, and geometric changes were analyzed, showing a multi-factor-induced catalytic deactivation. In Cu-exchanged MFI, a transformation of CuII to CuI and CuxOy was observed. We also found a spatial correlation between extra-framework Al and deactivated Cu species near the surface of the zeolite as well as a weak positive correlation between the amount of CuI and tri-coordinated Al. By inspecting both Al and Cu in fresh and aged Cu-exchanged zeolites, we conclude that the importance of the preservation of isolated CuII sites trumps that of Brønsted acid sites for NH3-SCR activity. 相似文献
42.
Capturing the Genesis of an Active Fischer–Tropsch Synthesis Catalyst with Operando X‐ray Nanospectroscopy
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Ilse K. van Ravenhorst Charlotte Vogt Heiko Oosterbeek Koen W. Bossers José G. Moya‐Cancino Dr. Ir. Alexander P. van Bavel Ad M. J. van der Eerden Dr. David Vine Prof. Dr. Frank M. F. de Groot Dr. Florian Meirer Prof. Dr. Ir. Bert M. Weckhuysen 《Angewandte Chemie (International ed. in English)》2018,57(37):11957-11962
A state‐of‐the‐art operando spectroscopic technique is applied to Co/TiO2 catalysts, which account for nearly half of the world's transportation fuels produced by Fischer–Tropsch catalysis. This allows determination of, at a spatial resolution of approximately 50 nm, the interdependence of formed hydrocarbon species in the inorganic catalyst. Observed trends show intra‐ and interparticular heterogeneities previously believed not to occur in particles under 200 μm. These heterogeneities are strongly dependent on changes in H2/CO ratio, but also on changes thereby induced on the Co and Ti valence states. We have captured the genesis of an active FTS particle over its propagation to steady‐state operation, in which microgradients lead to the gradual saturation of the Co/TiO2 catalyst surface with long chain hydrocarbons (i.e., organic film formation). 相似文献
43.
The aim of this work was to quantify the content of elements present in textile materials since it is known that textiles containing metals may represent a health hazard to consumers. Determination of metal content can be also useful to the textile industry since some metals present in textiles may contribute to problems during textile production. Extraction of metals from different textile materials was performed in an artificial acidic sweat solution according to the Öko Tex standard for materials coming into direct contact with the skin. After extraction from textile products made of cotton, flax, wool, silk, viscose, and polyester materials, all elements were determined by means of inductively coupled plasma-optical emission spectrometry (ICP-OES). Results in the sweat extracts (minimum-maximum in μg/mL) were: Al 0.11-1.58, Cd 0.02-0.05, Cr 0.01-0.32, Cu 0.05-1.95, Mn 0.01-2.17, and Ni 0.05-0.10. Concentrations of other elements were bellow detection limits. The total amount of metals present was determined after microwave assisted acidic digestion of textile materials with 7 M nitric acid. According to the results, the majority of the detected elements were below the concentration limits given by the Öko Tex, and for this reason the textile materials investigated do not represent a health hazard to consumers. 相似文献
44.
Van den Brande J. Weuts Ilse Verreck G. Peeters J. Brewster M. Van den Mooter G. 《Journal of Thermal Analysis and Calorimetry》2004,77(2):523-530
Thermal analysis was performed on the anti-HIV agent loviride in order to test its suitability to be processed using hot-melt
extrusion. Temperature characteristic parameters of crystallization were determined to quantify the stability of amorphous
loviride. The present study has shown that cooling and heating loviride at different rates influenced its thermal stability.
At high cooling rates melted loviride did not crystallize during cooling, and formed a glass that recrystallized during reheating.
Very low cooling rates resulted in significant decomposition of the drug. The glass transition temperature was found to increase
as a function of increasing heating rates and the activation energy for the transition from the glassy to the super-cooled
liquid state was relatively high, indicating good stability of the glass.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
45.
W. Pilz und Ilse Johann 《Fresenius' Journal of Analytical Chemistry》1966,218(6):426-436
Zusammenfassung Nach einer kritischen Betrachtung der bisher bekannten Methoden zur Bestimmung wäßriger Substrate von Estern langkettiger Fettsäuren wird eine neue Methode beschrieben, die auf dem bereits früher bekannt gegebenen Prinzip der Bestimmung von Estern langkettiger Fettsäuren beruht. Speziell wurde der Einfluß von Wassermenge und Emulgatoren untersucht. Die Bereitung von Substraten wird genau beschrieben, eine Arbeitsvorschrift mit Faktorbestimmungen und Beleganalysen wird gebracht. Als Anwendungsbeispiel wird die Bestimmung des Optimums der Kettenlänge der Triglyceridspaltung durch menschliche Milz und das pH-Optimum der Spaltung von Tween 80 durch Pancreatin beschrieben.
V. Mitt.: Pilz, W., I. Johann u. E. Stelzl: diese Z. 215, 260 (1966). 相似文献
Summary Following a critical consideration of the known methods of determining aqueous substrates of long-chain fatty acid esters, a new method is described which is based on the same principle of determination of long-chain fatty acid esters as was reported earlier. Especially the influence of emulsifiers and the amount of water is investigated. The preparation of substrates is described exactly, an operation formula with factor determination and proof analyses is produced. The determination of optimum chain length for splitting triglycerides by the human spleen and the optimum pH for the splitting of Tween 80 by pancreatin are described as examples of application.
V. Mitt.: Pilz, W., I. Johann u. E. Stelzl: diese Z. 215, 260 (1966). 相似文献
46.
Zusammenfassung Es wird über die Verwendung von Enaminoketonen zur Synthese von Pyrazolo[3,4-b]pyridinderivaten aus Aminopyrazolen berichtet. Mit Aminomethylencyclohexanon wird ein Pyrazolo[3,4-c]isochinolin erhalten. IR- und NMR-Spektren sowie Vergleiche mit bereits bekannten Substanzen bestätigen die Strukturen.
The application of enaminoketones in the synthesis of pyrazolo[3,4-b]pyridine derivatives from aminopyrazoles is reported. With aminomethylenecyclohexanone a pyrazolo[3,4-c]isoquinoline is obtained. The structures are proofed by IR- and NMR-spectra and by comparison with known substances.相似文献
47.
48.
Zusammenfassung Die Verteilung einer Reihe von Jodidkomplexen zwischen mineralsauren Lösungen verschiedener Molarität, die 0,1-m an KJ waren, und einer 2%igen Lösung des langkettigen, sekundären Amingemisches Amberlite LA-2 in Xylol wurde untersucht. Auf Grund der erhaltenen Verteilungsverhältnisse wird eine Anzahl von Trennungen verschiedener Elemente vorgeschlagen.
Herrn Professor Dr.Hans Lieb in Verehrung zum 80. Geburtstag gewidmet. 相似文献
Summary A study has been made of the distribution of a series of iodide complexes between mineral acid solutions of various molarity, that were 0.1M with respect to KI, and a 2% solution in xylene of the mixture of long chain secondary amines known as Amberlite LA-2. A number of separations of various elements is suggested on the basis of the partition coefficients obtained.
Herrn Professor Dr.Hans Lieb in Verehrung zum 80. Geburtstag gewidmet. 相似文献
49.
Alison T Ung Karl Schafer Karl B Lindsay Stephen G Pyne Kitti Amornraksa Ria Wouters Ilse Van der Linden Ilse Biesmans Anne S J Lesage Brian W Skelton Allan H White 《The Journal of organic chemistry》2002,67(1):227-233
An efficient method for preparing conformationally restricted cyclopentenyl-glutamate analogues in a regioselective and diastereoselective manner has been developed using a formal [3 + 2] cycloaddition reaction of dehydroamino acids. Methods for preparing optically active versions of these compounds have also been devised. Of these compounds, (S)-2 is an agonist at the mGlu5 (EC(50) 18 microM) and mGlu2 (EC(50) 45 microM) receptors. 相似文献
50.
The vibrational behaviour of the cyclic carboxylic acid dimer is modelled through the scaled quantum mechanical (SQM) force field of the cyclic formic acid dimer. The results indicate that the SQM force field technique is very well applicable to hydrogen bonded molecules. The frequency shifts observed on hydrogen bonding can be related to the shifts observed on lowering the temperature. This study also confirms that a clear distinction between cyclic carboxylic acid dimers and catamers can be made through the difference between infrared and Raman frequencies, and it is proved here that these conditions are also valid for weaker hydrogen bonded cyclic carboxylic acid dimers. 相似文献