Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Continuous flow toluene methylation over AlPO4 and AlPO4-Al2O3 catalysts (1994)
    Springer
    Catalysis letters 26 (1994), S. 159-167 
    Details
    ISSN: 1572-879X
    Keywords: aluminum orthophosphate (AlPO4) ; AlPO4-Al2O3 ; toluene methylation ; methanol ; activity ; selectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Toluene methylation with methanol over AlPO4 (AP) and AlPO4-Al2O3 (APAl) catalysts, obtained through different methods, was carried out in a continuous down-flow fixed bed reactor. The main products were xylenes (XYL), although trimethylbenzenes (TMB) were also found over APAl catalysts. The benzene and ethylbenzene selectivities increased slightly with time on stream at the expense of XYL and TMB selectivities. Isomer distribution was approximately 50, 24 and 26 mol% foro-, m- andp-XYL, and 72, 27 and 0 mol% for 1,2,3-, 1,2,4- and 1,3,5-TMB. The initial reaction rate constants were higher on APA1 catalysts and, furthermore, APAl catalysts exhibited similar catalytic activities, although those obtained in ethylene or propylene oxide are the most active ones. The same occurs on AP catalysts. Moreover, the changes in catalytic activity are similar to the changes in the acidic characteristics measured, in gas phase, versus pyridine. Furthermore, the activity decreased with time on stream due to coke deposition according to the expressionk = k0 exp(-βt). The rate of deactivation, evaluated from the deactivation coefficients (β), was greater for APAl than for AP catalysts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00824041
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Phenol methylation over CrPO4 and CrPO4−AlPO4 catalysts (1997)
    Springer
    Reaction kinetics and catalysis letters 62 (1997), S. 47-54 
    Details
    ISSN: 1588-2837
    Keywords: chromium orthophosphate (CrPO4) ; chromium aluminium orthophosphates (CrPO4-AIPO4) ; surface acidity, phenol/methanol and phenol/dimethyl carbonate alkylation ; activity ; selectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The vapor-phase catalytic alkylation of phenol with methanol and dimethyl carbonate on a series of differently prepared CrPO4 (Cr/P=1) and CrPO4-AlPO4 (CrAIP) catalysts, has been studied at different temperatures (473–673 K). The reaction is first order in phenol, giving a mixture of O- and C-alkylated products (C-alkylation taking place preferentially at theortho-position). Moreover, dimethyl carbonate is a better methylating agent than methanol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02475712
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Alkylation of phenol with dimethyl carbonate over AlPO4, Al2O3 and AlPO4-Al2O3 catalysts (1998)
    Springer
    Reaction kinetics and catalysis letters 63 (1998), S. 261-269 
    Details
    ISSN: 1588-2837
    Keywords: Aluminium orthophosphate (AlPO4) ; AlPO4-Al2O3 ; phenol/dimethyl carbonate alkylation ; activity ; anisole-cresol formation ; selectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The vapor-phase catalytic alkylation of phenol with dimethyl carbonate over different AlPO4 (Al/P=1), Al2O3 and AlPO4-Al2O3 (5–25 wt.% Al2O3) catalysts produces anisole (O-alkylation) as the major reaction product althougho-cresol (C-alkylation) and methylanisoles were also found. The reaction is first order in phenol while O-and C-alkylation follow parallel processes. As compared with methanol, DMC is far more effective as a methylating agent, and the methylation proceeds at a lower temperature and with higher O-alkylation selectivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02475397
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Three-dimensional model of a selective theophylline-binding RNA molecule (1996)
    Chicester [u.a.] : Wiley-Blackwell
    Journal of Molecular Recognition 9 (1996), S. 275-286 
    Details
    ISSN: 0952-3499
    Keywords: RNA folding ; binding specificity ; molecular modeling ; QSAR ; theophylline ; SELEX ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A three-dimensional (3D) model for an RNA molecule that selectively binds theophylline but not caffeine is proposed. This RNA, which was found using SELEX (Jenison et al., 1994), is 10 000 times more specific for theophylline (KD = 320 nM) than for caffeine (KD = 3.5 mM), although the two ligands are identical except for a methyl group substituted at N7 (present only in caffeine). The binding affinity for ten xanthine-based ligands was used to derive a comparative molecular field analysis model (R2 = 0.93 for three components, with cross-validated R2 of 0.73), using the SYBYL and GOLPE programs. A pharmacophoric map was generated to locate steric and electrostatic interactions between theophylline and the RNA binding site. This information was used to identify putative functional groups of the binding pocket and to generate distance constraints. On the basis of a model for the secondary structure (Jenison et al., 1994), the 3D structure of this RNA was then generated using the following method: each helical region of the RNA molecule was treated as a rigid body; single-stranded loops with specific end-to-end distances were generated. The structures of RNA-xanthine complexes were studied using a modified Monte Carlo algorithm. The detailed structure of an RNA-ligand complex model, as well as possible explanations for the theophylline selectivity are discussed.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 5
    Electronic Resource
    Electronic Resource
    Numerical analysis of extracellular fluid flow and chemical species transport around and within porous bioactive glass (1994)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 28 (1994), S. 947-960 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Modeling of the physical phenomena present at the biomaterial-tissue interface provides a valuable tool for examining the underlying mechanisms which influence the overall behavior of the implant-host system. Based on histological data from a previous implantation study (E. Schepers, M. De Clercq, P. Ducheyne, and R. Kempeneers, “Bioactive glass particulate materials as a filler for bone lesions,” J. Oral Rehab.; 18, 439-452, 1991, Ref. 1) which documented the differentiation of mesenchymal cells to cells expressing the osteoblastic phenotype in porous bioactive glass, a finite element momentum and mass transport model was constructed. In this analysis, the extracellular compositional variations and fluid flow conditions around and within porous bioactive glass granules were determined. Numerical simulations demonstrated that the interstitial fluid flow around these granules (300-360 μm) is viscosity dominated (low Reynolds number flow) and that the fluid inside the granules remains stagnant. This velocity field results in shear stresses proportional to the velocity gradient at the granule-fluid interface outside the particles and no shear stresses inside the particles. A parametric study on the effect of interstitial fluid flow on chemical species (Na+, Ca+2, HPO4-2) transport outside the granules revealed three domains. At low velocities (0-0.1 μm/s), the transport of species is diffusion controlled. At intermediate velocities (1.0-10 μm/s), diffusion and convection contribute to the species transport. The concentration of chemical species is nearly uniform at high velocities (100-800 μm/s). For all three cases, the transport of chemical species within the granules is diffusion controlled. The differences in transport mechanisms and interstitial fluid flow conditions lead to variations in concentrations, reaction rates, and shear stresses between the inside and the outside of the glass granules. These differences may influence cellular migration, attachment, differention, and the overall response to these bioactive materials.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820280814
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    AlPO4 and AlPO4-Al2O3 as heterogeneous catalysts in the preparation of 1,3-dioxolanes by acetalization of different carbonyl compounds (1994)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 336 (1994), S. 620-622 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19943360713
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Structural investigations and luminescence of In2Ge2O7 and In2Si2O7Dedicated to Professor Heinrich Oppermann on his 60th Birthday (1994)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 1965-1970 
    Details
    ISSN: 0044-2313
    Keywords: Indium digermanate ; indium disilicate ; crystal structure ; indium luminescence ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Strukturuntersuchungen und Lumineszenz von In2Ge2O7 und In2Si2O7Eine Rietveld-Pulverdiagramm-Methode erlaubt die Bestimmung der genauen Strukturen von Thortveitit verwandten In2Ge2O7 und In2Si2O7 Oxyden (Raumgrupe C2/m, Z = 2). Die Verbindungen wurden unter normalem Druck hergestellt. Die Lumineszenz unter 160 und 200 K sollte die Messung der Umwelt Neutrinobestrahlung erlauben. Sie scheint die Folge eines inneren Ladungstransfers in den Indium Sauerstoff Polyedern zu sein. Die optischen Resultate wurden an Hand der bestimmten Strukturen und der chemischen Bindungen diskutiert und mit Werten für andere Indiumoxyde verglichen.
    Notes: The crystal structures of the ordinary pressure forms of indium digermanate In2Ge2O7 and disilicate In2Si2O7 have been studied from X-ray powder diffraction data by Rietveld refinement. They are closely related to that of the thortveitite which crystallizes in the monoclinic system with the space group C2/m and Z = 2. They show luminescence properties below 160 K and 200 K respectively. The luminescence is discussed in terms of crystal structure and compared to that of some other luminescent indium oxides.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19946201121
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...