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  • 1
    Electronic Resource
    Electronic Resource
    The location of p-dichlorobenzene in a single crystal of zeolite H-ZSM-5 at high sorbate loading (1996)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 52 (1996), S. 140-144 
    Details
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The crystal structure of a high-loaded complex of H-ZSM-5 with eight molecules of p-dichlorobenzene per unit cell has been solved by single-crystal X-ray diffraction. The orthorhombic space group P212121 with a = 20.102 (6), b = 19.797 (9), c = 13.436 (3) Å and V = 5347 (3) Å3 has four Si23.92Al0.08O48.2C6H4Cl2 units per unit cell. Dx = 2.164 Mg m−3, λ(MoKα) = 0.71073 Å and μ(Mo Kα) = 0.876 mm−1. The final R(wR) = 0.046 (0.039), w = 1/σ2(F), for 6090 observed reflections with I 〉 1.0σ(I) measured at 293 K. The straight channel parallel to [010] is slightly corrugated. The elliptical cross sections have limiting apertures of 6.0 × 4.9 Å (roxygen = 1.35 Å). The sinusoidal channel parallel to [100] is elliptical with major and minor axes of 6.1 × 4.8 Å, respectively. One of the two independent p-dichlorobenzene molecule lies at the intersection of the straight and sinusoidal channels with its long molecular axis almost parallel to (100) and deviating 8̃° from [010]. The second p-dichlorobenzene molecule is in the sinusoidal channel. Its long molecular axis deviates almost 7° from [100] and is practically parallel to (010). The structural aspects are in all details comparable to those in the high-loaded H-ZSM-5/p-xylene complex [van Koningsveld, Tuinstra, van Bekkum & Jansen (1989). Acta Cryst. B45, 423–431] , except for the main interaction forces between the p-dichlorobenzene molecules at the channel intersection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108768195008524
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  • 2
    Electronic Resource
    Electronic Resource
    Beta–type zeolites as selective and regenerable catalysts in the Meerwein–Ponndorf–Verley reduction of carbonyl compounds (1997)
    Springer
    Topics in catalysis 4 (1997), S. 261-268 
    Details
    ISSN: 1572-9028
    Keywords: zeolite Beta ; titanium–Beta ; transition state selectivity ; MPV–reduction ; Oppenauer oxidation ; enantioselective reduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Zeolite Beta, in the Al–form as well as in the Al–free, Ti–containing form, appears to be a selective and regenerable catalyst in the Meerwein–Ponndorf–Verley and Oppenauer (MPVO) reactions. In the liquid–phase MPV reduction of 4–tert–butylcyclohexanone with secondary alcohols, both catalysts display a high stereoselectivity to cis–4–tert–butylcyclohexanol, the isomer of industrial relevance. This stereoselectivity can be explained by considering the two transition states inside the pores of zeolite Beta. By using (S)–2–butanol as the reductant enantioselective reduction of phenylacetone was observed. 4–methylcyclohexanone was studied as the substrate in the gas–phase MPV reduction. Catalyst deactivation is much more pronounced with the acidic Al–Beta catalyst than with the non–acidic Ti–Beta.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019160827175
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  • 3
    Electronic Resource
    Electronic Resource
    Novel isomerization of ω-phenylalkanals to phenyl alkyl ketones over cesium (lanthanum) oxide supported on mesoporous aluminosilicate molecular sieves and related materials (1997)
    Springer
    Catalysis letters 47 (1997), S. 235-242 
    Details
    ISSN: 1572-879X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A novel rearrangement of the ω-phenylalkanals phenylacetaldehyde, 3-phenylpropionaldehyde and 4-phenylbutyraldehyde towards phenyl alkyl ketones is reported. The liquid-phase isomerizations are catalyzed by cesium oxide or binary cesium-lanthanum oxide supported on the mesoporous aluminosilicate molecular sieves MCM-41 and HMS and on amorphous supports like silica-alumina and γ-alumina. Beside the title reaction the aldol condensation is observed as a side-reaction. A mechanism is proposed in which the aromatic ring is involved in the rearrangement process. Factors governing the activities and product selectivities are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019037912152
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  • 4
    Electronic Resource
    Electronic Resource
    Molecular Sieves, Multifunctional Microporous Materials in Organic Synthesis (1998)
    Springer
    Journal of porous materials 5 (1998), S. 289-303 
    Details
    ISSN: 1573-4854
    Keywords: zeolites ; design ; catalysis ; shape selectivity ; adsorption ; properties ; application
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Zeolites and molecular sieves are microporous materials with an increasing number of applications. Established applications of molecular sieves are in the field of oil refining processes, selective adsorption and ion exchange. Nowadays, zeolites come to the fore as clean, selective and recyclable catalysts in petrochemistry, e.g., in aromatic alkylation. Zeolites are considered to have a high potential for the synthesis of commodities and fine chemicals due to their molecular sized pores. Nevertheless, only a few commercial applications in fine chemical synthesis are known. Based on the essential criteria, extracted from the organic reaction under consideration, some of the potential pitfalls in selecting and screening zeolites as potential catalysts are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009690423062
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