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61.
Navneet K. Gupta Dr. Anastasia Pashigreva Dr. Evgeny A. Pidko Prof. Emiel J. M. Hensen Prof. Leslaw Mleczko Dr. Stefan Roggan Dr. Erika E. Ember Prof. Johannes A. Lercher 《Angewandte Chemie (International ed. in English)》2016,55(5):1728-1732
Active sites in carbon‐catalyzed phosgene synthesis from gaseous CO and Cl2 have been identified using C60 fullerene as a model catalyst. The carbon atoms distorted from sp2 coordination in non‐planar carbon units are concluded to generate active Cl2. Experiments and density functional theory calculations indicate the formation of a surface‐bound [C60???Cl2] chlorine species with radical character as key intermediate during phosgene formation. It reacts rapidly with physisorbed CO in a two‐step Eley–Rideal‐type mechanism. 相似文献
62.
Li Y Xia H Fan F Feng Z van Santen RA Hensen EJ Li C 《Chemical communications (Cambridge, England)》2008,(6):774-776
For the first time an ordered mesoporous silica (Fe-Al-SBA-15) with catalytically active isolated Fe surface species for the hydroxylation of benzene with nitrous oxide is prepared by introduction of Fe3+ in the synthesis gel of Al-SBA-15. 相似文献
63.
Maxence Valla James W. Harris Rajamani Gounder William N. P. van der Graaff Evgeny A. Pidko Emiel J. M. Hensen Paola Ferrini Jan Dijkmans Bert Sels Ive Hermans Christophe Copéret 《Helvetica chimica acta》2016,99(12):916-927
In recent years, various protocols on preparing Lewis acidic Sn‐β zeolite hydrothermally and postsynthetically have been reported. However, very little is known about the effects of different synthesis protocols on the Sn(IV) speciation in the final material. Even the effects of individual synthesis parameters within a certain preparation method have not been studied systematically. Here, we demonstrate that hydrothermally synthesized Sn‐β zeolites prepared via very similar recipes show significantly different 119Sn‐NMR spectra, suggesting different Sn site speciation. Among postsynthetically prepared Sn‐β zeolites, less variation in the resulting 119Sn‐NMR spectra have been observed, indicating a more reproducible synthesis procedure compared to hydrothermal synthesis in fluoride media. This work highlights the importance of 119Sn‐NMR measurements to elucidate the precise local geometry of the Sn heteroatoms in Sn‐β, and the need to quantify the number of reactive Sn sites on each sample that participate in a given catalytic reaction, in order to accurately compare materials prepared by different routes. 相似文献
64.
65.
Meiling Guo Prof. Dr. Zhaochi Feng Dr. Guanna Li Dr. Jan P. Hofmann Dr. Evgeny A. Pidko Dr. Pieter C. M. M. Magusin Qiang Guo Prof. Dr. Bert M. Weckhuysen Prof. Dr. Emiel J. M. Hensen Dr. Fengtao Fan Prof. Dr. Can Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(38):12078-12084
The mechanism of crystallization of microporous titanosilicate ETS‐10 was investigated by Raman spectroscopy combined with 29Si magic‐angle spinning (MAS) NMR spectroscopy, DFT calculations, and SEM imaging. The formation of three‐membered ring species is shown to be the key step in the hydrothermal synthesis of ETS‐10. They are formed by means of a complex process that involves the interaction of silicate species in the reaction mixture, which promotes the dissolution of TiO2 particles. These insights into the mechanism of ETS‐10 growth led to the successful development of a new synthesis route to the vanadosilicate AM‐6 that involves the use of intermediates that contain three‐membered ring species as an initiator. 相似文献
66.
E. Garralaga Rojas B. Terheiden H. Plagwitz J. Hensen C. Baur G.F.X. Strobl R. Brendel 《Electrochemistry communications》2010,12(2):231-233
We produce uniform mesoporous single- and multilayers on 4 in. p-type Ge wafers by means of electrochemical etching in highly concentrated HF-based electrolytes. Pore formation by anodic etching in germanium leads to a constant dissolution of the already formed porous layer plus substrate. Alternating the etching bias from anodic to cathodic bias enhances the passivation of the pore walls and substrate. The formation of porous multilayers is possible, since the starting layer is not dissolved during the formation of the separation layer. We report on the production of mesoporous double layers in Ge with different porosities. The change in the porosity of the porous layers is achieved by varying the anodic etching current and the HF concentration of the electrolyte. Porosities in the range of 25–65% are obtained for etching current densities of 1–15 mA cm?2 with the specific resistivity of the Ge substrates lying in the (0.020–0.032) Ω cm range and electrolyte HF concentrations in the range of 35–50 wt.%. 相似文献
67.
68.
Ivo A. W. Filot Prof. Dr. Rutger A. van Santen Prof. Dr. Emiel J. M. Hensen 《Angewandte Chemie (International ed. in English)》2014,53(47):12746-12750
Microkinetics simulations are presented based on DFT‐determined elementary reaction steps of the Fischer–Tropsch (FT) reaction. The formation of long‐chain hydrocarbons occurs on stepped Ru surfaces with CH as the inserting monomer, whereas planar Ru only produces methane because of slow CO activation. By varying the metal–carbon and metal–oxygen interaction energy, three reactivity regimes are identified with rates being controlled by CO dissociation, chain‐growth termination, or water removal. Predicted surface coverages are dominated by CO, C, or O, respectively. Optimum FT performance occurs at the interphase of the regimes of limited CO dissociation and chain‐growth termination. Current FT catalysts are suboptimal, as they are limited by CO activation and/or O removal. 相似文献
69.
Ligthart DA van Santen RA Hensen EJ 《Angewandte Chemie (International ed. in English)》2011,50(23):5306-5310