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  • 1
    ISSN: 1588-2837
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract Фракции кислых центров не цеолитах HNaY, активных в крекинге, изомеризации и дегидогенизации метилциклогексана не увеличиваются линейно с увеличением степени обмена. Реакции изомеризации и дегидрогенизации протекают через образование одинакового активированного комплекса, а крекинт через другой активированный комплекс и нуждается в более сильных кислых центрах. Энергия активации не зависит от степени обмена.
    Notes: Abstract On HNaY zeolites the fractions of acid sites which are active for cracking, isomerization and dehydrogenation of methylcyclohexane do not increase linearly with increasing degree of exchange. Isomerization and dehydrogenation seem to involve a similar activated complex, while cracking proceeds through a different one and requires stronger acid sites. Activation energies are independent of exchange degree.
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  • 2
    ISSN: 1588-2837
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract Было исследовано разложение метилциклогексана на цеолитах H−NaY и PtH−NaY. Было найдено, что присутствие или отсутствие H2 не только влияет на активность этих катализаторов, но также и на селективность образования продуктов дегидрогенизации и изомеризации.
    Notes: Abstract The decomposition of methylcyclohexane on H−NaY and PtH−NaY zeolites has been studied. It has been found that the presence or abscence of H2 affects not only the activity of these catalysts but also their selectivity to dehydrogenation and isomerization products.
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  • 3
    ISSN: 1572-879X
    Keywords: phosphorus-containing catalysts ; tungsten disulfide ; high-resolution electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A series of WS2/Al2O3 catalysts containing a varied amount of phosphorus (0.0,2.5 and 6.0 wt% P2O5), sulfided at two different temperatures (873 and 1073 K), were studied by means of high-resolution transmission electron microscopy (HRTEM). The stacking of (002) layers in the WS2-2H crystallites of the “rag” structure increases with the addition of phosphorus, whereas its length is kept almost constant. At high sulfidation temperatures phosphorus shows a stabilizing effect on the catalysts by retarding the stacking growth of WS2 crystallites. Additionally, an aluminum phosphate crystalline phase is identified in the phosphorus promoted catalysts.
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  • 4
    ISSN: 1572-879X
    Keywords: Zeolites ; hydrodesulfurization ; sulfide catalysts ; cobalt/zeolite ; molybdenum/zeolite ; cobalt-molybdenum/zeolite ; gas oil hydrotreating
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Three series of Co/NaY, Mo/NaY and CoMo/NaY zeolite catalysts with variable metal content, prepared by a conventional impregnation method, were characterized by XRD, IR spectroscopy (oxide state) and acidity measurements (sulfide state), and tested in hydrodesulfurization (HDS) of gas oil at high pressure in the temperature range 275–350°C. The combined results of surface area, XRD and IR showed that in the catalysts with high metal loading a small loss in crystallinity and a partial blockage of the zeolite supercages were produced by Mo oxide species. The number of acid sites, which was lower for the Co/NaY than for the Mo/NaY catalysts, increased with increasing Co or Mo loading, but the strength of the acid sites was stronger for the Co/NaY series. HDS specific activities of the Co/NaY and Mo/NaY monometallic catalysts reached a maximum at very low loadings of Co (∼ 0.10 at. nm−2) or Mo (∼ 0.16 at. nm−2) by the double action of the metal sulfide species and the strong acid sites generated on the zeolite by the Co or Mo incorporation. In the binary CoMo/NaY catalysts, the synergy between Co and Mo species was significant for high Mo contents only.
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  • 5
    ISSN: 1572-879X
    Keywords: HDN ; carbon-supported catalysts ; NiMo catalysts ; sulfided catalysts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The hydrodenitrogenation (HDN) of pyridine over activated carbon-supported Mo and NiMo sulfided catalysts was studied. Without H2S in the feed the catalysts showed a high conversion of pyridine and of piperidine to C5 hydrocarbons at the beginning of reaction, followed by a strong deactivation. A large increase in the conversion of pyridine was observed when H2S was added to the feed at H2S/H2⩾0.006. The conversion of piperidine to C5 hydrocarbons was enhanced by H2S and it increased as the H2S pressure increases up to H2S/H2⩾0.006. The promotion effect of Ni was operative only when H2S was present and it increased with the H2S/H2 ratio. Without H2S, the degree of surface oxidation of the support affected the deactivation of the catalysts. When H2S was added to the feed, the conversion of pyridine was stable and independent of the acid treatment of the support. A more oxidized support enhanced the C-N bond breaking reaction.
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