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  • Articles: DFG German National Licenses  (3)
  • Rh  (1)
  • SSZ-24  (1)
  • Titania-rhodium catalysts  (1)
  • 1
    Electronic Resource
    Electronic Resource
    The role of alkali cations in zeolite synthesis from silicate solutions containing N,N,N-trimethyl-1-adamantammonium cations (1996)
    Springer
    Catalysis letters 38 (1996), S. 1-9 
    Details
    ISSN: 1572-879X
    Keywords: zeolite synthesis ; SSZ-24 ; SSZ-31 ; alkali cations ; N,N,N-1-adamantammonium cation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Zeolite synthesis from aqueous N,N,N-trimethyl-1-adamantammonium (TMAA+)-alkali (Na+, K+, Rb+, and Cs+) silicate mixtures is studied using X-ray diffraction, elemental analysis, scanning electron microscopy, and29Si magic angle spinning (MAS),1H-13C cross-polarization (CP) MAS and1H-29Si CP MAS NMR spectroscopies. SSZ-24 forms in the presence of potassium cations, and SSZ-31 crystallizes in the presence of sodium cations. This is the first report of SSZ-31 synthesis from Na-TMAA silicate mixtures. Unknown silicates form in the presence of rubidium and cesium cations, whereas no crystalline material is observed in synthesis mixtures devoid of alkali cations. The alkali cations do not appear to serve as templates or void fillers during zeolite crystallization, nor do they stabilize soluble silicate anions which serve as building blocks during zeolite crystallization. Rather, the alkali cations appear to regulate the transformation of the amorphous synthesis gel into either crystalline zeolite or other silicate phases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00806891
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Lewis acidity as an explanation for oxide promotion of metals: implications of its importance and limits for catalytic reactions (1994)
    Springer
    Catalysis letters 27 (1994), S. 243-249 
    Details
    ISSN: 1572-879X
    Keywords: oxide promotion ; acidity ; CO and CO2 hydrogenation ; Rh
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Sub-monolayer quantities of metal oxides are found to influence CO hydrogenation, CO2 hydrogenation, acetone hydrogenation, ethylene hydroformylation, ethylene hydrogenation, and ethane hydrogenolysis over Rh foils. The metal oxides investigated include AlOx, TiOx, VOx, FeOx, ZrOx, NbOx, TaOx, and WOx. Only those reactions involving the hydrogenation of C-O bonds are enhanced by the oxide overlayers. The coverage at which maximum rate enhancement occurs is approximately 0.5 ML for each oxide promoter. Titanium, niobium, and tantalum oxides are the most effective promoters. XPS measurements after reaction show that of the oxides studied titanium, niobium, and tantalum oxide overlayers are stable in the highest oxidation states. The trend in promotion effectiveness is attributed to the direct relationship between oxidation state and Lewis acidity. For the oxide promoters, bonding at the metal oxide/metal interface between the O-end of adsorbed CO and the Lewis acidic oxide is postulated to facilitate C-O bond dissociation and subsequent hydrogenation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00813909
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The effects of titania overlayers on C2H4/CO/H2 reactions over a Rh foil (1991)
    Springer
    Catalysis letters 11 (1991), S. 77-87 
    Details
    ISSN: 1572-879X
    Keywords: Titania-rhodium catalysts ; model oxide-metal catalysts ; hydroformylation over Rh-TiO2 ; combined ethylene and CO hydrogenation over Rh-TiO2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effects of submonolayer deposits of titania on the activity and selectivity of a Rh foil catalyst for C2H4/CO/H2 reactions have been investigated. Reactions were carried out at 1 atm total pressure and at temperature of 488 K and 523 K. The addition of titania to the catalyst enhances the total rate of C3-oxygenate formation. This rate enhancement is due entirely to an increase in the rate of 1-propanol formation, which reaches a maximum at a TiO x . coverage of 0.2 ML. The rate of propanal formation, by contrast, is not enhanced. The rates of formation of methane, ethane, and C3-hydrocarbons also exhibit rate maxima at a TiO x . coverage of 0.2 ML. The rates of formation of C4- and C5-hydrocarbons, on the other hand, are suppressed by titania addition. The higher rate of 1-propanol production in the presence of titania is attributed to an interaction between Ti3+ ions at the edge of TiO x . islands and the carbonyl bond of adsorbed C3-oxygenated species. Such interactions are envisioned to facilitate hydrogenation of the carbonyl bond.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00866904
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    Paper (German National Licenses)
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