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  • 1
    Electronic Resource
    Electronic Resource
    Structural studies of Pt-Sn catalysts on high and low surface area alumina supports (1990)
    Springer
    Catalysis letters 4 (1990), S. 303-308 
    Details
    ISSN: 1572-879X
    Keywords: Pt-Sn catalyst ; bimetallic catalyst on alumina
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract For a series of catalysts containing 1 wt. % Pt and Sn∶Pt ratios ranging from ca. 1 to 8, the only crystalline alloy phase detected by XRD was SnPt (1∶1). The XRD intensity of lines for the SnPt (1∶1) alloy phase increase with increasing Sn∶Pt ratios, indicating the presence of unalloyed Pt in the samples containing low tin loadings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00765315
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  • 2
    Electronic Resource
    Electronic Resource
    Fischer-Tropsch synthesis with an iron catalyst: Incorporation of ethene into higher carbon number alkanes (1990)
    Springer
    Catalysis letters 7 (1990), S. 141-149 
    Details
    ISSN: 1572-879X
    Keywords: Fischer-Tropsch synthesis ; iron catalyst ; tracer studies ; 14C labeled ethene ; alkenes ; chain growth ; radioactivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Tracer studies with C labeled ethene show that for synthesis over a doubly promoted iron catalyst at 7 atm and ca. 60% CO conversion, higher carbon number products are formed from ethene initiation. About 10% of the added ethene (ethene/CO ∼ 0.02) is incorporated into C 5 + products and that ca. 85% of the ethene that is incorporated does so by initiating chain growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00764497
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  • 3
    Electronic Resource
    Electronic Resource
    Enantioselective two-phase hydrogenation of α-amino acid precursors with water soluble rhodium complexes of the cationic ligand (S,S)-2,4-bis[bis-(p-N,N,N-trimethylammoniumphenyl)phosphino]pentane, [CH3CH(P(p-C6H4NMe3)2CH2CH(P(p-C6H4NMe3)2CH3]4+ (1990)
    Springer
    Catalysis letters 5 (1990), S. 183-188 
    Details
    ISSN: 1572-879X
    Keywords: Enantioselective hydrogenation ; rhodium complex ; chiral cationic phosphine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Rhodium complexes of the chiral cationic phosphine, (S,S)-2,4-bis[bis-(p-N,N.N-trimethyl-ammoniumphenyl)phosphino]pentane show excellent enantioselectivity for the hydrogenation of the DOPA precursor. (Z)-3-OMe,4-OAcC6H3CHC(COOH)(NHCOCH3), and dehydro-phenylalanineacetamide as slurries in water. The catalytic reactions may be done in either a two-phase system with the catalyst in the aqueous phase or as a slurry in water provided the substrates have some water solubility. Enantioselectivities of as high as 95% can be obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00763951
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  • 4
    Electronic Resource
    Electronic Resource
    Fischer-Tropsch synthesis. Evidence for two chain growth mechanisms (1990)
    Springer
    Catalysis letters 7 (1990), S. 127-140 
    Details
    ISSN: 1572-879X
    Keywords: Fischer-Tropsch synthesis ; radioisotope, tracer study ; mechanism, Fischer-Tropsch synthesis ; kinetics, Fischer-Tropsch synthesis ; chain growth, Fisher-Tropsch synthesis,14C, tracer studies ; 14C-ethanol ; 14C-1-pentanol ; reactor, CSTR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The results show that n-pentanol serves to initiate Fischer-Tropsch synthesis reactions. Product accumulation in the CSTR is not adequate to explain the deviation from a constant14C activity/mole with increasing carbon number for alkane products. A second Fischer-Tropsch synthesis mechanism that produces only alkanes is needed to explain the deviation of the C activity/mole with increasing carbon number for n-alkanes. Furthermore, the two chain growth pathways must be completely independent without the possibility of a carbon number species that is common to both mechanisms. It is suggested that the pathway that incorporates added14C labeled alcohol has an oxygen containing surface intermediate while the other reaction pathway involves an “oxygen-free” reaction intermediate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00764496
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  • 5
    Electronic Resource
    Electronic Resource
    Multi-attribute hashing with multiple file copies for high performance partial-match retrieval (1990)
    Springer
    BIT 30 (1990), S. 404-423 
    Details
    ISSN: 1572-9125
    Keywords: D.4.3 ; E.2 ; H.3.2 ; partial-match retrieval ; multi-attribute hashing ; multi-key hashing ; clustering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The average cost for answering partial-match queries can be dramatically reduced by storing multiple copies of the data, each with a different clustering. We analyse the cost benefits (in terms of page accesses) of this arrangement and present heuristic algorithms for determining a near-minimal-cost file organisation for a given probability distribution of queries. We also show how constraining the range of values for specific attributes affects the usefulness of maintaining multiple copies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01931657
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  • 6
    Electronic Resource
    Electronic Resource
    Some inequalities for commutators and an application to spectral variation (1990)
    Springer
    Aequationes mathematicae 40 (1990), S. 312-312 
    Details
    ISSN: 1420-8903
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02112304
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  • 7
    Electronic Resource
    Electronic Resource
    129Xe NMR spectroscopy on molecular sieves SAPO-37, AIPO4-5, SAPO-5 and SSZ-24 (1990)
    Springer
    Catalysis letters 6 (1990), S. 331-339 
    Details
    ISSN: 1572-879X
    Keywords: NaY ; SAPO-37 ; AlPO4-5 ; SAPO-5 ; SSZ-24 ; 129Xe NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Xe NMR spectroscopy is used to study SAPO-37, NaY, AlPO4-5, SAPO-5, and SSZ-24. Of these samples, those with FAU topology show that the129Xe chemical shift is dependent upon framework composition while the materials with API topology do not. Values of the129Xe NMR chemical shifts at zero xenon pressure cannot be correlated with the size of the framework void space.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00763999
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  • 8
    Electronic Resource
    Electronic Resource
    High resolution, quasi-equilibrium sorption studies of molecular sieves (1990)
    Springer
    Catalysis letters 5 (1990), S. 333-347 
    Details
    ISSN: 1572-879X
    Keywords: Quasi-equilibrium sorption studies of molecular sieves ; high resolution sorption isotherms of molecular sieves
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Argon, nitrogen, and neopentane adsorption isotherms from molecular sieves are recorded at 87 K, 77 K, and 273 K, respectively, by a quasi-equilibrium, high resolution gas sorption technique. The molecular sieves used in this study are alkali exchanged zeolite X, AlPO4-11, AlPO4-5, VPI-5, KL, CaA, ZSM-5, and ZSM-11. Little relation is observed between the transition pressure for microporous nitrogen adsorption and pore size. Small changes in the effective pore size resulting from variations in cation size are detected in the transition pressure for argon adsorption. Large shifts in the transition pressure for argon adsorption are found for the 10-, 12-, and 18-membered ring pores of AlPO4-11, AlPO4-5, and VPI-5, respectively. Argon adsorption combined with neopentane adsorption on microporous materials provides additional information regarding transitions in the isotherm that result from dual pore systems and effects that may be due to adsorbate packing. The step in the nitrogen isotherm atP/P 0〉 0.1 from ZSM-5 is not observed in the nitrogen isotherm from ZSM-11.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00765175
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  • 9
    Electronic Resource
    Electronic Resource
    Fluorescence Yield Near Edge Spectroscopy (FYNES) of benzene adsorbed in Na-Y zeolite (1990)
    Springer
    Catalysis letters 6 (1990), S. 99-102 
    Details
    ISSN: 1572-879X
    Keywords: Benzene ; Na-Y zeolite ; Fluorescence Yield Near Edge Spectroscopy (FYNES)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Benzene adsorbed in sodium-Y zeolite has been investigated using Fluorescence Yield Near Edge Spectroscopy (FYNES). These studies demonstrate that FYNES measurements are feasible as a direct probe of the local electronic structure of hydrocarbons adsorbed in and on insulating, microporous practical catalysts. The distribution of π energy levels for adsorbed benzene was not significantly altered as compared to the condensed phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00764058
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  • 10
    Electronic Resource
    Electronic Resource
    Thermodynamics of reduction and oxidation reactions on oxidized or reduced Pt supported on γ-Al2O3 (1990)
    Springer
    Catalysis letters 6 (1990), S. 1-12 
    Details
    ISSN: 1572-879X
    Keywords: Thermodynamics of Pt oxidation ; thermodynamics of Pt reduction ; H spillover ; H chemisorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The integral enthalpies of H2 or O2 reactions with oxidized or reduced Pt supported on γ Al2O3 have been measured in a dual calorimeter at 60 ° C. These enthalpies were calculated assuming the formation of Pt x s O and PtsH surface groups and using accepted values of heat of H2 and O2 chemisorption on bare polycrystalline Pt. The calculated and measured reaction enthalpies agree under the following conditions: 1) Pt2O and Pt 2 s O surface stoichiometries are acceptable (1 ⩽ x ⩽ 2) whereas Pt2O2 must be rejected (x = 0.5); 2) the water formed in the reduction or oxidation process must be dissociatively chemisorbed on the γ Al2O3 surface; 3) the spiltover hydrogen is atomic and its enthalpy of combination with surface electron deficient site is about -10 kcal/g atom. The significance of dispersion measurements is discussed in relation with hydrogen spillover. Neglecting spillover in reduction at 60 ° C leads to unrealistic values of dispersion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00764047
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