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Oxidative decomposition of formaldehyde on silver-cerium composite oxide catalyst (1994)

Imamura, Seiichiro ; Uchihori, Daisuke ; Utani, Kazunori ; [et al.]

Springer

Catalysis letters 24 (1994), S. 377-384

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ISSN: 1572-879X

Keywords: Formaldehyde ; oxidative decomposition ; Ag/Ce composite catalyst

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Abstract Silver-cerium composite oxide was active for low temperature oxidative decomposition of formaldehyde. Its high activity was due partly to the high dispersion of active silver on the CeO2. The surface oxygen of this composite catalyst was removed more easily than those on single component Ag2O or CeC2, which also seemed to contribute to the high activity of this catalyst. IR analysis revealed that formaldehyde was decomposed both on silver-cerium composite catalyst and CeO2 in the presence of oxygen to produce methoxide, dioxymethylene, and/or polyoxymethylene even at room temperature. In addition bi-carbonate was formed on silver-cerium composite catalyst and formate was produced on CeO2. These intermediates suffered further oxidation at higher temperatures (373 and 423 K) easily on silver-cerium composite catalyst, whereas degradation of them was rather difficult on CeO2.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00811810

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Effects of substituent groups of polyimides on sorption and diffusion of gases (1992)

Toi, Keio ; Ito, Tomoyasu ; Ikemoto, Isao ; [et al.]

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part B: Polymer Physics 30 (1992), S. 497-503

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ISSN: 0887-6266

Keywords: substituent group of polyimide ; sorption and diffusion of gas ; free volume ; cohesive energy density ; activation energy for diffusion ; Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Physics

Notes: Sorption rate curves of CO2, N2, and He gases below 1 atm were measured for polyimide films prepared from benzophenone tetracarboxylic dianhydride (BTDA) with 3,5-diaminotoluene trifluoride (DATF), 2,4-diaminotoluene (DAT), m-phenylenediamine (MPD), and diaminobenzoic acid (DABA). The molecular structures of these four polyimides differ only in the substituent groups of the diamine structure. These polyimides exhibit dualmode type sorption isotherms for carbon dioxide that are concave to the pressure axis, typical of glassy polymer/gas system. The apparent diffusion coefficients below 1 atm pressure of carbon dioxide for this series of compounds decrease in the order: BTDA-DATF 〉 BTDA-DAT 〉 BTDA-MPD 〉 BTDA-DABA. A linear relation between the logarithm of the apparent diffusion coefficient and the reciprocal of free volume, calculated by the method of Bondi using density data, is found for these polyimides. However, this tendency is not observed for the other two gases. The activation energies of the apparent diffusion coefficients at 20 cmHg pressure of carbon dioxide increase with increasing cohesive energy density of the polyimides. The energy per mole of free volume elements in a liquidlike structure in each cohesive energy density may be equated to the activation energy and used to calculate the free volume. The values from the activation energy are almost the same as those from Bondi's method.

Additional Material: 7 Ill.