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  • CHEMISTRY  (1)
  • Inorganic Chemistry  (1)
  • 1
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On the Heterogen-Catalytical Oxidation and Ammoxidation of Isobutene. 5. Gas-Phase Oxidation of Methacrolein to Methacrylic Acid on Definite 1:1 Vanadium PhosphatesFor the Oxidation of Methacrolein (MA) to Methacrylic Acid (MAA) definite 1:1 vanadium phosphates were used as test catalysts. (VIVO)2P2O7 (1) is directing the reaction with high selectivity to MAA. On using the VV monophosphates α-(2) and β-VOPO4 (3), a valence-mixed “H-V/P mica” (with α-based structure; 46.5% VIV portion) (4), and also the new phosphate VIVO(HPO4) (5), however, only a modest selectivity is observed. Whereas the diphosphate 1 was found to be unchanged after the catalytical reaction, in the case of the monophosphates solid state reactions occured during the catalysis: 2 was reduced to a H-V/P mica (6) with 29% VIV portion, 4 to the hemi-hydrate VIV O(HPO4) · 0.5 H2O (7); and from 3, as new compounds, 5 (see above) and a VIII/VIV phosphate (8) were formed. On preparing 5 as a pure phase and using it for the catalysis it mostly remained unchanged; only a minor part was reduced to 8. - The catalytical action of 1 is discussed.
    Notes: Bei der Oxydation von Methacrolein (MA) zu Methacrylsäure (MAA) wurden als Versuchskatalysatoren definierte 1:1-Vanadiumphosphate eingesetzt. (VIVO)2P2O7 (1) lenkt die Reaktion mit hoher Selektivität zu MAA. Beim Einsatz der VV-Monophosphate α-(2) und β-VOPO4 (3) sowie eines valenzgemischten „H-V/P-Glimmers“ (mit α-Grundstruktur; 46,5% VIV-Anteil) (4) und des neuen Phosphates VIVO(HPO4) (5) sind dagegen nur geringe Selektivitäten festzustellen. Während das Diphosphat 1 nach der Katalysereaktion unverändert vorlag, traten bei den Monophosphaten während der Katalyse Festkörperreaktionen ein: 2 wurde zu einem H-V/P-Glimmer (6) mit 29% VIV-Anteil und 4 zu dem Halbhydrat VIVO(HPO4) · 0,5 H2O (7) reduziert, und aus 3 resultierten als neue Verbindungen 5 (s. o.) sowie ein noch näher zu charakterisierendes VIII/VIV-Phosphat (8). Präparativ phasenrein dargestelltes und zur Katalyse eingesetztes 5 blieb im wesentlichen unverändert; nur eine geringe Menge wurde zu 8 reduziert. - Die katalytische Wirkung von 1 wird diskutiert.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2019-06-27
    Description: In many real-world pollution chemical reaction problems, the rate of reaction problems, the rate of reaction may be greatly affected by unmixedness. An approximate closure scheme for a chemical kinetic submodel which conforms to the principles of invariant modeling and which accounts for the effects of inhomogeneous mixing over a wide range of conditions has been developed. This submodel has been coupled successfully with invariant turbulence and diffusion models, permitting calculation of two-dimensional diffusion of two reacting (isothermally) chemical species. The initial calculations indicate the ozone reactions in the wake of stratospheric aircraft will be substantially affected by the rate of diffusion of ozone into the wake, and in the early wake, by unmixedness.
    Keywords: CHEMISTRY
    Type: NASA-CR-2295 , REPT-193
    Format: application/pdf
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