scholarly journals Fullerene Black: Relationship between Catalytic Activity in n-alkanes Dehydrocyclization and Reactivity in Oxidation, Bromination and Hydrogenolysis

2017 ◽  
Vol 3 (2) ◽  
pp. 131 ◽  
Author(s):  
S.D. Kushch ◽  
P.V. Fursikov ◽  
N.S. Kuyunko ◽  
A.V. Kulikov ◽  
V.I. Savchenko
Keyword(s):  
Catalytic Activity ◽  
Esr Spectroscopy ◽  
Hydrogenation Catalyst ◽  
Spectroscopy Data ◽  
Dangling Bonds ◽  
Catalytic Center ◽  
Fullerene Black ◽  
Amorphous Part

<p>The reactivity of fullerene black in oxidation (by air oxygen or ions MnO<sub>4</sub><sup>–</sup> or Cr<sub>2</sub>O<sub>7</sub><sup>2–</sup> in solution), bromination (by Br<sub>2</sub> or (C<sub>4</sub>H<sub>9</sub>)<sub>4</sub>NBr<sub>3</sub>) and hydrogenolysis (without hydrogenation catalyst) are studied. The dehydrocyclization of <em>n</em>-alkanes over fullerene black is realized via the monofunctional mechanism, <em>i.e. </em>the dehydrogenation and cyclization stages proceed on the same catalytic center. The addition of alumina to the catalyst transforms dehydrocyclization mechanism to bifunctional one, when fullerene black acts as dehydrogenation agent. Reactivity studies and ESR spectroscopy data for initial and annealed fullerene black show the presence in fullerene black structure of both non-conjugated multiple and dangling bonds. Nonconjugated bonds determine catalytic activity and reactivity of fullerene black. They are localized in amorphous part of fullerene black. Technological aspects of fullerene black as alkanes dehydrocyclization catalyst are discussed.</p>

The effect of preparation conditions of a platinum hydrogentaion catalyst on its activity and on the dispersity of platinum crystallites

1979 ◽  
Vol 44 (9) ◽  
pp. 2619-2623 ◽  
Author(s):  
Jiří Hanika ◽  
Karel Sporka ◽  
Vlastimil Růžička ◽  
Jaroslav Bauer
Keyword(s):  
Catalytic Activity ◽  
Liquid Phase ◽  
Hydrogen Chloride ◽  
Active Carbon ◽  
Hydrogenation Catalyst ◽  
Chloroplatinic Acid ◽  
Metallic Platinum ◽  
Preparation Conditions

The paper deals with the preparation of a hydrogenation catalyst, 5% of platinum on active carbon. The support was saturated with aqueous chloroplatinic acid or platinum tetrachloride. After calcination in streaming nitrogen the catalyst was reduced with hydrogen. We studied the effects of temperatures of the calcination and the reduction on 1) the formation of hydrogen chloride in the course of calcination and the following reduction, 2) the dispersity of metallic platinum and 3) the catalytic activity for hydrogenation of 2-methyl-3-butene-2-ol and nitrobenzene in liquid phase. The catalytic activity was found to be proportional to the dispersity of platinum.

Principal component analysis to enhance enantioselective Raman spectroscopy

The Analyst ◽  
2019 ◽  
Vol 144 (6) ◽  
pp. 2080-2086 ◽  
Author(s):  
Claudia C. Rullich ◽  
Johannes Kiefer
Keyword(s):  
Principal Component Analysis ◽  
Raman Spectroscopy ◽  
Esr Spectroscopy ◽  
Principal Component ◽  
Component Analysis ◽  
Data Evaluation ◽  
Spectroscopy Data ◽  
Automatic Data ◽  
Fully Automatic

Principal component analysis (PCA) applied to enantioselective Raman (esR) spectroscopy data enhances the performance of the method and opens up opportunities for a fully automatic data evaluation.

DISPLACEMENT OF C4-HYDROCARBON MOLECULES ADSORBED ON PLATINUM

1964 ◽  
Vol 42 (5) ◽  
pp. 1206-1211 ◽  
Author(s):  
S. Affrossman ◽  
R. J. Cvetanović
Keyword(s):  
Catalytic Activity ◽  
Active Sites ◽  
Hydrogenation Catalyst ◽  
Active Area ◽  
Special Technique ◽  
Hydrocarbon Molecules

A special technique has been used in an attempt to determine the nature and the amount of the C4-hydrocarbons desorbed by displacement with "poisons" (CO, CS2) from the "active" sites of a platinum on asbestos hydrogenation catalyst. The "active" area of the catalyst determined in this way is found to decrease with increasing adsorption of the poison molecules, and is approximately related in the expected manner to the observed catalytic activity for butene hydrogenation. The likely nature of the adsorbed hydrocarbon species is discussed.

Catalytic dehalogenation enhanced by appending dendritic ligands on cobalt porphyrins

2006 ◽  
Vol 10 (08) ◽  
pp. 1066-1070 ◽  
Author(s):  
Takane Imaoka ◽  
Toshio Takatsuka ◽  
Kimhisa Yamamoto
Keyword(s):  
Catalytic Activity ◽  
Reducing Agent ◽  
Turnover Frequency ◽  
Catalytic Center ◽  
Cobalt Porphyrin ◽  
Samarium Iodide ◽  
Solvent Phase ◽  
Cobalt Porphyrins ◽  
Catalytic Dehalogenation ◽  
Electron Mediators

The dehalogenation activities of cobalt porphyrin catalysts with dendritic phenylazomethine units on the meso-positions were studied. Tetrachloroethylene was used as a substrate. By applying samarium iodide as a reducing agent, the tetrachloroethylene conversion into trichloroethylene and dichloroethylene was observed in the presence of the cobalt porphyrin catalyst. The turnover frequency was 1.70 min−1 when a cobalt porphyrin connected with dendritic phenylazomethines (3 generations) was employed as the catalyst. While the turnover frequency was almost the same as that for a non-dendritic porphyrin catalyst (1.57 min−1 by cobalt tetraphenylporphyrin), a significant increase in the turnover frequency was observed when samarium (3.43 min−1) or terbium trifluoromethane sulfonate (8.57 min−1) binds to the phenylazomethine units of the dendrimer. Because these metal ions ( Sm 3+ or Tb 3+) are positioned in a space between the encapsulated catalytic center and the solvent phase, they can act as electron mediators that relay electrons from the reducing agent (samarium iodide) to the catalytic center (cobalt porphyrin). This facile electron transfer would provide an enhancement in the catalytic activity for the tetrachloroethylene reduction leading to dehalogenation.

Synthesis of mesoporous iridium nanosponge: a highly active, thermally stable and efficient olefin hydrogenation catalyst

2017 ◽  
Vol 46 (34) ◽  
pp. 11431-11439 ◽  
Author(s):  
Sourav Ghosh ◽  
Balaji R. Jagirdar
Keyword(s):  
Catalytic Activity ◽  
Hydrogenation Catalyst ◽  
High Catalytic Activity ◽  
Capping Agent ◽  
Thermally Stable ◽  
Olefin Hydrogenation ◽  
Highly Active

Capping agent dissolution of Ir@BNHx nanocomposite affords mesoporous iridium nanosponge which exhibits high catalytic activity towards olefin hydrogenation of a variety of substrates.

scholarly journals Tightly-orchestrated rearrangements govern catalytic center assembly of the ribosome

2018 ◽  
Author(s):  
Yi Zhou ◽  
Sharmishtha Musalgaonkar ◽  
Arlen W. Johnson ◽  
David W. Taylor
Keyword(s):  
Catalytic Activity ◽  
Large Subunit ◽  
Ribosomal Subunit ◽  
Critical Element ◽  
Large Ribosomal Subunit ◽  
Peptidyl Transferase ◽  
Catalytic Center ◽  
Peptidyl Transferase Center ◽  
Final Assembly ◽  
Cytoplasmic Maturation

AbstractThe catalytic activity of the ribosome is mediated by RNA, yet proteins are essential for the function of the peptidyl transferase center (PTC). In eukaryotes, final assembly of the PTC occurs in the cytoplasm by insertion of the ribosomal protein Rpl10. We determine structures of six intermediates in late nuclear and cytoplasmic maturation of the large subunit that reveal a tightly-choreographed sequence of protein and RNA rearrangements controlling the insertion of Rpl10. We also determine the structure of the biogenesis factor Yvh1 and show how it promotes assembly of the P stalk, a critical element for recruitment of GTPases that drive translation. Together, our structures provide a blueprint for final assembly of a functional ribosome.One Sentence SummaryCryo-EM structures of six novel intermediates in the assembly of the large ribosomal subunit reveal mechanism of creating the catalytic center.

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