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  • 1
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    Intermetallic nickel silicide nanocatalyst--A non-noble metal-based general hydrogenation catalyst (2018)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2018-06-09
    Description: Hydrogenation reactions are essential processes in the chemical industry, giving access to a variety of valuable compounds including fine chemicals, agrochemicals, and pharmachemicals. On an industrial scale, hydrogenations are typically performed with precious metal catalysts or with base metal catalysts, such as Raney nickel, which requires special handling due to its pyrophoric nature. We report a stable and highly active intermetallic nickel silicide catalyst that can be used for hydrogenations of a wide range of unsaturated compounds. The catalyst is prepared via a straightforward procedure using SiO 2 as the silicon atom source. The process involves thermal reduction of Si–O bonds in the presence of Ni nanoparticles at temperatures below 1000°C. The presence of silicon as a secondary component in the nickel metal lattice plays the key role in its properties and is of crucial importance for improved catalytic activity. This novel catalyst allows for efficient reduction of nitroarenes, carbonyls, nitriles, N-containing heterocycles, and unsaturated carbon–carbon bonds. Moreover, the reported catalyst can be used for oxidation reactions in the presence of molecular oxygen and is capable of promoting acceptorless dehydrogenation of unsaturated N-containing heterocycles, opening avenues for H 2 storage in organic compounds. The generality of the nickel silicide catalyst is demonstrated in the hydrogenation of over a hundred of structurally diverse unsaturated compounds. The wide application scope and high catalytic activity of this novel catalyst make it a nice alternative to known general hydrogenation catalysts, such as Raney nickel and noble metal–based catalysts.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 2
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    Efficient dehydrogenation of formic acid using an iron catalyst (2011)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2011-09-24
    Description: Hydrogen is one of the essential reactants in the chemical industry, though its generation from renewable sources and storage in a safe and reversible manner remain challenging. Formic acid (HCO(2)H or FA) is a promising source and storage material in this respect. Here, we present a highly active iron catalyst system for the liberation of H(2) from FA. Applying 0.005 mole percent of Fe(BF(4))(2).6H(2)O and tris[(2-diphenylphosphino)ethyl]phosphine [P(CH(2)CH(2)PPh(2))(3), PP(3)] to a solution of FA in environmentally benign propylene carbonate, with no further additives or base, affords turnover frequencies up to 9425 per hour and a turnover number of more than 92,000 at 80 degrees C. We used in situ nuclear magnetic resonance spectroscopy, kinetic studies, and density functional theory calculations to explain possible reaction mechanisms.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Boddien, Albert -- Mellmann, Dorthe -- Gartner, Felix -- Jackstell, Ralf -- Junge, Henrik -- Dyson, Paul J -- Laurenczy, Gabor -- Ludwig, Ralf -- Beller, Matthias -- New York, N.Y. -- Science. 2011 Sep 23;333(6050):1733-6. doi: 10.1126/science.1206613.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Leibniz-Institut fur Katalyse e.V. an der Universitat Rostock, Albert-Einstein Strass 29a, Rostock, 18059, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21940890" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
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    Nanoscale Fe2O3-based catalysts for selective hydrogenation of nitroarenes to anilines (2013)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2013-11-30
    Description: Production of anilines--key intermediates for the fine chemical, agrochemical, and pharmaceutical industries--relies on precious metal catalysts that selectively hydrogenate aryl nitro groups in the presence of other easily reducible functionalities. Herein, we report convenient and stable iron oxide (Fe2O3)-based catalysts as a more earth-abundant alternative for this transformation. Pyrolysis of iron-phenanthroline complexes on carbon furnishes a unique structure in which the active Fe2O3 particles are surrounded by a nitrogen-doped carbon layer. Highly selective hydrogenation of numerous structurally diverse nitroarenes (more than 80 examples) proceeded in good to excellent yield under industrially viable conditions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Jagadeesh, Rajenahally V -- Surkus, Annette-Enrica -- Junge, Henrik -- Pohl, Marga-Martina -- Radnik, Jorg -- Rabeah, Jabor -- Huan, Heming -- Schunemann, Volker -- Bruckner, Angelika -- Beller, Matthias -- New York, N.Y. -- Science. 2013 Nov 29;342(6162):1073-6. doi: 10.1126/science.1242005.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Leibniz-Institut fur Katalyse e.V. an der Universitat Rostock, Albert-Einstein Strasse 29a, D-18059 Rostock, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24288327" target="_blank"〉PubMed〈/a〉
    Keywords: Aniline Compounds/*chemical synthesis ; Catalysis ; Ferric Compounds/*chemistry ; Hydrogenation
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    Low-temperature aqueous-phase methanol dehydrogenation to hydrogen and carbon dioxide (2013)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2013-03-01
    Description: Hydrogen produced from renewable resources is a promising potential source of clean energy. With the help of low-temperature proton-exchange membrane fuel cells, molecular hydrogen can be converted efficiently to produce electricity. The implementation of sustainable hydrogen production and subsequent hydrogen conversion to energy is called "hydrogen economy". Unfortunately, its physical properties make the transport and handling of hydrogen gas difficult. To overcome this, methanol can be used as a material for the storage of hydrogen, because it is a liquid at room temperature and contains 12.6 per cent hydrogen. However, the state-of-the-art method for the production of hydrogen from methanol (methanol reforming) is conducted at high temperatures (over 200 degrees Celsius) and high pressures (25-50 bar), which limits its potential applications. Here we describe an efficient low-temperature aqueous-phase methanol dehydrogenation process, which is facilitated by ruthenium complexes. Hydrogen generation by this method proceeds at 65-95 degrees Celsius and ambient pressure with excellent catalyst turnover frequencies (4,700 per hour) and turnover numbers (exceeding 350,000). This would make the delivery of hydrogen on mobile devices--and hence the use of methanol as a practical hydrogen carrier--feasible.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Nielsen, Martin -- Alberico, Elisabetta -- Baumann, Wolfgang -- Drexler, Hans-Joachim -- Junge, Henrik -- Gladiali, Serafino -- Beller, Matthias -- England -- Nature. 2013 Mar 7;495(7439):85-9. doi: 10.1038/nature11891. Epub 2013 Feb 27.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Leibniz-Institut fur Katalyse Eingetragener Verein an der Universitat Rostock, Albert-Einstein Strasse 29a, Rostock, 18059, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23446345" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 5
    Electronic Resource
    Electronic Resource
    The development of a natural plankton population in an outdoor tank with nutrient-poor sea water. I. Phytoplankton succession (1977)
    Springer
    Marine biology 43 (1977), S. 1-17 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Due to complex hydrodynamic and biological inhomogeneities, the phytoplankton species succession cannot be satisfactorily observed, apart from the seasonal blooms which occur in temperate waters. Large flexible plastic tanks have proved to be useful for such observations. In 1972, for 28 days, a phytoplankton succession in nutrient-poor water in the outer harbor of Helgoland was observed in a flexible plastic tank (3 m3). During this period, 3 phytoplankton biomass maxima were formed with many significant correlations. In the first 7 days the ammonia concentration decreased from over 6 to 2 μ mol 1-1 for 14 days. The nitrate concentration remained in the range of 3–6 μ mol 1-1 and then fell abruptly to 0–2 μ mol 1-1. The phosphate concentration was about 0.1 μ mol 1-1. Lauderia borealis dominated the first period, and its increase was significantly correlated with the decrease in ammonia. The diatom was succeeded by two dinoflagellates, Dinophysis acuminata and Prorocentrum micans. The last period of the experiment was characterized by a stronger development of Rhizosolenia species. The rapid recovery of the crop in the nutrient-poor water points to intensive remineralization processes. The irregular occurrence of ammonia near the surface was correlated with the appearance of Noctiluca miliaris at this depth. It is expected that repetitions of this type of experiment will permit further explanations of statistical correlations which are not yet clear. As a first step, in order to test hypotheses, a correlation analysis was employed to eliminate the statistically non-significant correlations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392567
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  • 6
    Electronic Resource
    Electronic Resource
    Einfache folientanks zur Planktonuntersuchung in situ (1974)
    Springer
    Marine biology 24 (1974), S. 163-166 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung 1. Für Planktonuntersuchungen in situ wurden einfache Tanks (ca. 4 m3, 5 m Tiefe) konstruiert, mit denen im Vorhafen von Helgoland während der Sommermonate 1972 und 1973 Versuche bis zu 28 Tagen durchgeführt wurden. 2. Lichtdurchlässige Kombinationsfolien aus Polyamid und Polyäthylen erwiesen sich für die an diesem Standort vorkommenden mechanischen Belastungen als geeignet. 3. Für eine kontinuierliche Durchmischung des Tankinhalts wurde ein Rührwerk entwickelt. Alle mit dem Tankinhalt in Berührung kommenden Teile waren aus physiologisch unbedenklichem Kunststoffmaterial gefertigt. 4. Die Tanks eignen sich für Simultanversuche, wie in Versuchen mit Monokulturen gezeigt werden konnte.
    Notes: Abstract For studies of in situ interactions between plankton and ambient water, simple, cylindrical, 5 m deep translucent-foil tanks were constructed using polyamide and polyethylene (layers 30 and 100 μm, respectively, with polyamide layer outside). The tanks were suspended in the water by metal frames fixed to a buoy. The whole construction was anchored in an outer basin of the harbour of Helgoland, N. Sea, and was exposed to tides and waves generated by winds of up to 6 Bft (Beaufort scale). Even under these conditions the construction and its material allowed experiments lasting 2 weeks and longer, during the summer months of 1972 and 1973. The banks' volume, of about 4 m3 each permits experiments with naturally occurring concentrations of nutrients and organisms and large sampling volumes for the determination of trace components. In this way, natural plankton populations in 1972, and monocultures of different diatom species in 1973 were investigated. Under these conditions, different monocultures developed almost identically.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00389351
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  • 7
    Electronic Resource
    Electronic Resource
    Natürliche Oberflächenfilme im Seegebiet vor Sylt (1976)
    Springer
    Marine biology 36 (1976), S. 135-146 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The physical and chemical properties of the sea surface can be altered considerably by the formation of slicks and the accumulation of particles (including plankton). Investigations of natural slicks near the island of Sylt consisted of analyses of the dissolved and particulate surface-active substances, as well as the identification of plankton and bacteria collected by a surface-film sampler. The analyzed surface material consisted primarily of phytoplankton (Prorocentrum micans in particular), bacteria, detritus and dissolved compounds of fatty acids. These fatty acid compounds alone would not account for the slick. The slick appeared to be caused by the calm weather, the active accumulation of P. micans at the surface, and the increase in bacteria associated with this accumulation. Here a decrease was observed in the dissolved surface-active substances compared with the concentration usually found in normal surface waters, of which the total fatty acid content in a sample was taken as indicator. In some cases a correlation was found between fatty acids and particulate matter in naturally occurring slicks. Particularly large variations were found in the fatty acid patterns in the filtrate and filter residue at a time when no slick was present and no particulate matter had accumulated at the surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00388436
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of loperamide on jejunal electrolyte and water transport, prostaglandin E 2-induced secretion and intestinal transit time in man (1991)
    Springer
    European journal of clinical pharmacology 41 (1991), S. 239-243 
    Details
    ISSN: 1432-1041
    Keywords: Loperamide ; Intestinal perfusion ; absorption ; transit time ; healthy volunteers ; intestinal transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Jejunal perfusion was performed in 12 healthy volunteers to evaluate the dose dependent effects of loperamide on intestinal absorption, stimulated secretion and transit. In 6 volunteers intestinal perfusion of the jejunal segment with isotonic NaCl solution was followed by addition of loperamide in increasing doses (2–8 mg·l−1). The volunteers were pretreated with 1 mg·l−1 prostaglandin E2 (PgE2) in the perfusate before addition of 4 mg·l−1 loperamide. Phenolsulphonphtalein (PSP) boluses (2 ml) were given to measure mean transit time (MTT). Loperamide 2 mg·l−1 converted the minor secretion after perfusion with the standard solution (water −1.45 ml·min−1, Na −0.09 and Cl −0.04 mmol·min−1) to absorption (water 0.93 ml·min−1, Na 0.23, Cl 0.25 mmol·min−1) within 15 min. Higher doses of loperamide did not increase absorption. The addition of PgE2 induced net secretion of water (−4.48 ml·min−1) and electrolytes (Na −0.57, Cl −0.51 mmol·min−1). Loperamide 4 mg·l−1 significantly diminished the PgE2-induced net secretion by approximately 50%. Loperamide dose dependently increased the MTT from 6 (2 mg·l−1) to 13.3 min (8 mg·l−1). MTT was still delayed 60 min after a wash out period (10.5 min). It is concluded that loperamide had a dual effect or intestinal activities stimulating absorption and prolonging intestinal transit time with rising doses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00315436
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  • 9
    Electronic Resource
    Electronic Resource
    Organische Metallkomplexe-V. I.R.-Spektren von 13C-, 18O- und 2H-markierten Acetylacetonaten
    Amsterdam : Elsevier
    Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy Section 24 (1968), S. 1219-1243 
    Details
    ISSN: 0584-8539
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0584-8539(68)80142-4
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  • 10
    Electronic Resource
    Electronic Resource
    I.R.-Spektrum von [18O]Tropon
    Amsterdam : Elsevier
    Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy Section 24 (1968), S. 1951-1956 
    Details
    ISSN: 0584-8539
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0584-8539(68)80254-5
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