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  • 1
    ISSN: 1588-2837
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Carbonaceous deposits on HZSM-5 zeolite samples deactivated during coupled methanol/n-butane cracking were investigated by temperature-programmed oxidation. With the progressive dealumination on-stream and the unaccessibility of the active sites, an increased amount of deposited coke could be observed. The H/C ratio found depends both on the concentration of acid sites and on time onstream.
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  • 2
    ISSN: 1588-2837
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract Дезактивадию образцов цеолитов H-ZSM-5 в ходе связан-ного крекинга метанола/углеводорода с н-бутаном на питании исследобали в двух различных модификациях реак-ции (с непосредственным регенерированием и без реге-нериоования). ТПДА была исследована для характеристики сильной Брёнстздной кислотности свежих, регенерирован-ных и отпаренных цеолитов H-ZSM-5. Хотя предотвращение деалюми нирования блокированием кислых центров углерод-ными продуктами может быть улучшено, однако, с увели-чением скорости крекинга скорость конверсии н-бутана и селективность к олефину круто уменьшаются.
    Notes: Abstract The deactivation of H-ZSM-5 zeolite samples during coupled methanol/hydrocarbon cracking (CMHC) with n-butane as feed has been investigated in two different reaction modes (with intermediate regeneration and without regeneration). TPDA was used to characterize strong Brönsted acidity of fresh, regenerated and steamed H-ZSM-5 zeolite. The prevention of dealumination by blocking the acid centers with carbonaceous products could be proved, but the conversion rate of n-butane and the olefin selectivity declined drastically with increasing coking rate.
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  • 3
    ISSN: 1588-2837
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract Показано, что совместная прививка ионов ванадия и фосфоа увеличивает активность и селективность ванадийсодержащих азросилов в реакции окисления н-бутана. Высказано предположение о связи каталитических свойств с образованием окисных группировок, содержащих ванадий и фофор с оптимальными кислотно-основными свойствами.
    Notes: Abstract It has been revealed that simultaneous immobilization of vanadium and phosphorus ions increases the activity and selectivity of vanadium-containing aerosils in n-butane oxidation. The catalytic properties are suggested to be dependent on the formation of mixed oxide surface V−P/SiO2 clusters having optimal acid-base characteristics.
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  • 4
    ISSN: 1588-2837
    Keywords: pillared clays ; zeolites ; catalytic activity ; acidity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In comparison with zeolites, a variety of Al pillared clays did not prove as promising cracking catalysts, possibly because their Brönsted sites are hidden. In the less demanding double bond shift isomerization, both catalyst types were comparable probably due to the presence of Lewis sites on both catalysts.
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  • 5
    ISSN: 1572-879X
    Keywords: Aluminophosphate molecular sieves ; Si and/or Mn modification ; isomerization of 1-butene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Molecular sieve AlPO4-31 and substituted analogues (MnAPO-31,SAPO-31, MnAPSO-31) have been tested for their catalytic properties in the isomerization of 1-butene over 6 h time on stream at 743 K. The conversion of 1-butene proceeds selectively by either double bond or skeletal isomerization. MnAPSO-31 with a molar MnO/P2O5 ratio adjusted to 0.01 yields the highest percentage of isobutene whereas the parent AlPO4-31 leads almost completely to a double bond shift with only minor skeletal isomerization. The results are related to the acidity characteristics that were determined by ammonia thermodesorption. Deactivation is accompanied by a loss of selectivity for the skeletal isomerization.
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  • 6
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Studies on Catalytically Active Surface Compounds. VII. Catalytic Properties of Oxidic Vanadium-Chromium CatalystsThe catalytic properties of silica supported vanadium-chromium catalysts for the oxidation of ethanol, butane, propene, and butene are described and completed by ESR measurements.Differences in catalytic activity of chromium-free vanadium catalysts which are caused by different values of the silanol group concentration of the support are shown to become levelled by the addition of chromium. V—O—Cr species of medium catalytic activity are considered to be the catalytic active center. ESR spectra taken after the reaction show the existence of Cr3+ and VO+2 species. A correlation between the intensity of the VO2+ signal and the catalytic activity of the samples is observed.
    Notes: Die katalytischen Eigenschaften von Vanadiumoxid-Chromoxid-Aufschichtkatalysatoren wurden bei der Oxydation von äthanol, Butan, Buten und Propen untersucht und ergänzende ESR-spektroskopische Messungen durchgeführt.Die großen, durch unterschiedliche Silanolgruppenkonzentration des Trägers bedingten Aktivitätsunterschiede der chromfreien Vanadiumoxid-Aufschichtkatalysatoren werden mit wachsendem Chromoxidgehalt nivelliert. Als katalytisch aktives Zentrum werden V—O—Cr-Gruppierungen mit mittlerer Aktivität diskutiert. ESR-Spektren zeigen die Existenz von Cr3+- und V4+-Ionen nach der katalytischen Reaktion, und es wird ein Zusammenhang zwischen der Intensität des VO2+-Signals und der katalytischen Aktivität der Katalysatoren beobachtet.
    Additional Material: 3 Ill.
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  • 7
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The influence of the porous structure of thr carrier on the dispersion of the catalytically active platinum has been investigated on charcoal catalysts with a content of five percent platinum.Three samples were characterised by adsorption measurements, mercury porosimetry and X-ray small angle diffraction. Their preparation was carried out by impregnation with two different platinum complex compounds under varying the conditions. The dispersion is strongly influenced by the adsorption of the impregnated compound on the carrier surface. The good adsorption of the compound H2PtCl6 leads to highly dispersed platinum, the bad adsorption of Pt(NH3)4Cl2 causes the platinum to be only coarsely dispersed on the surface. Varying the conditions of preparation during impregnation with H2PtCl6 gives no effect, the porous structure of the carrier, however, has a strong influence on the dispersion i. e. microporous carriers yielding highly dispersed platinum, with a high part of the platinum in the micropores.
    Notes: Am Beispiel von 5proz. Platin-Kohle-Katalysatoren wurde der Einfluß der Porenstruktur des Trägers auf die Verteilung des katalytisch aktiven Platins untersucht. Dazu wurden verschiedene Kohlen eingesetzt, deren Porenstruktur durch Adsorptions-, Quecksilberporosimetrie- und Röntgenkleinwinkelmessungen charakterisiert wurden.Die Kontaktherstellung erfolgte durch Tränkung mit zwei verschiedenen Platinkomplexverbindungen. Auch die Bedingungen der Kontaktherstellung wurden variiert.Die Dispersität wird in erster Linie von der Adsorption der Tränkverbindungen auf der Trägeroberfläche bestimmt. Im Falle guter Adsorption der Tränkverbindung (H2PtCl6) auf der Trägeroberfläche werden hohe Platindispersitäten erzielt, im Falle schlechter Adsorption der Tränkverbindung (Pt(NH3)4Cl2) ist das Platin nur in grobdisperser Form auf der Trägeroberfläche verteilt. Bei guter Adsorbierbarkeit der Tränkverbindung haben die Herstellungsbedingungen keinen wesentlichen Einfluß, aber die Porenstruktur des Trägers hat einen großen Einfluß auf die erzielbare Platindispersität. Auf mikroporösen Trägern wird eine hochdisperse Platinverteilung erreicht, wobei sich ein großer Teil des Platins in den Mikroporen befindet.
    Additional Material: 7 Ill.
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  • 8
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Catalytic Properties of Platinum on Charcoal Carriers of Different Pore Structure5% Pt/carbon catalysts have been studied in respect to the influence of carrier pore structure and Pt dispersity on the catalytic properties. Test reactions were the dehydrogenation of cyclohexane and the dehydrocyclization of three isomeric octanes.A biporous carrier characteristic results in optimal activity for cyclohexane dehydrogenation. For the octane dehydrocyclization a strong influence of pore structure on selectivity has been observed; microporosity strongly reduces the selectivity.
    Notes: An 5proz. Platin-Kohle-Katalysatoren wurde der Einfluß der Porenstruktur des Trägers und der Dispersität der Aktivkomponente auf die katalytische Eigenschaften untersucht.Als Testreaktionen wurden die Cyclohexandehydrierung und die Dehydrocyclisierung von drei isomeren Octanen gemessen und festgestellt, daß Träger mit biporösen Eigenschaften optimale Aktivität gegenüber der Cyclohexandehydrierung haben. Bei der Dehydrocyclisierung der Octane wurde ein großer Einfluß der Porenstruktur auf die Selektivität der Reaktion beobachtet, wobei mikroporöse Träger die Selektivität stark herabsetzen.
    Additional Material: 5 Tab.
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  • 9
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Studies on Catalytically Active Surface Compounds. II. On the Existence of Different Vanadium(V) Oxide Surface Phases on SiO2 and their Catalytic PropertiesIn dependence on the SiOH concentration of the Aerosil surface two different disperse vanadium(V) oxide phases are obtained, which differ characteristically in their reflexion spectra, their chemisorption behaviour towards butene and their catalytic properties in the oxidation of butene and ethanol. At high values of the original concentration of SiOH groups a δ″ phase is formed which gives after desorption of adsorbed water at 250°C, a reflexion spectrum that points at a tetrahedral coordination of the Vv; this phase shows a relative low activity for both reactions. At a lower original concentration of SiOH a δ″ phase of the vanadium(V) oxide is formed, the reflexion spectrum of which, points at an octahedrally coordinated vanadium(V) oxide. This phase is considerably more active than the former.
    Notes: In Abhängigkeit von der SiOH-Gruppen-Konzentration der Aerosil-Ober- fläche werden durch Umsetzung mit VOCl3 und anschließende Hydrolyse zwei unterschiedliche, disperse Phasen von Vanadium(V)-oxid erhalten, die sich in charakteristischer Weise in ihrem Reflexionsspektrum, ihrem Chemisorptionsverhalten gegenüber Buten und ihren katalytischen Eigenschaften bei der Buten- und Äthanoloxydation unterscheiden.Bei hoher Ausgangskonzentration an SiOH entsteht eine δ″-Phase, deren Reflexionsspektrum nach Desorption von adsorbiertem Wasser bei 250°C auf eine tetraedrische Koordination des Vv deutet; sie besitzt eine relativ niedrige katalytische Aktivität in beiden Reaktionen. Bei niedriger Ausgangskonzentration an SiOH entsteht eine δ″-Phase des Vanadium(V)-oxids, deren entsprechendes Reflexionsspektrum auf oktaedrisch koordiniertes Vanadium(V)-oxid deutet und eine relativ hohe katalytische Aktivität in den genannten Reaktionen besitzt.
    Additional Material: 5 Ill.
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  • 10
    ISSN: 1572-8943
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung H-, Li-, Na-, Cs-, NH4-, Mg- und Al-Zeolithe ZSM 5 sowie H- und NH4-Mordenit wurden durch DTA, Röntgenbeugung, temperaturprogrammierte Desorption (TPD) und Adsorptionsmessungen untersucht. Die Stabilität gegenüber Dealuminierung und Strukturzusammenbruch hängt von der Art des Kations ab. H- und NH4-ZSM 5 werden im Verlauf der DTA-Messungen im Bereich 973–1273 K zu Silicalit-ähnlichen Phasen dealuminiert. NH4-Mordenit wird unterhalb 873 K bei der Ammoniakabspaltung im TPD-Experiment dealuminiert. Der thermische Zusammenbruch von Na-, Mg-, Al- und Cs-ZSM 5 beginnt um 1400 K. Im ursprünglichen NaZSM 5 vorhandene überschüssige Natriumionen verringern seine thermische Stabilität. Für H- und NH4-Mordenit wird bei 1270 K vollständige Amorphisierung gefunden.
    Abstract: Резюме Методами ДТА,. рентген офазового анализа и адсорбции изучены H, Li, Na, Cs, NH4, Mg, Al ZSM 5 цеолиты и Н-, NН4-морден иты. Устойчивость к деалюминированнию и характер деструкции зависят о т типа катиона. Методо м ДТА установлено, что обра зцы Н- и NH4-ZSM 5 в интервале температ ур 973–1273 подвергаются интенсивному деалюм инированию с образов анием силикатоподобных фа з. При проведении ТПД экспериментов устан овлено, что NH4морденит деалюминируется ниж е температуры 873 К. Терм ическая деструкция образцов ZSM 5 цеолитов, содержащих коны натрия, цезия, маг ния и алюминия, начинается при температуре около 1400 К. Наличие избы точных ионов натрия в исходном образце цеолита NaZSM 5 уменьшает его термоу стойчивость. Полная а морфизация Н/NН4-морденита происхо дит при 1270 К.
    Notes: Abstract H, Li, Na, Cs, NH4, Mg and Al-ZSM 5 zeolites and H and NH4-mordenites were studied by DTA, X-ray diffraction, TPD and adsorption measurements. The stability relating to dealumination and structure destruction depends on the nature of the cation. H and NH4-ZSM 5 were strongly dealuminated to silicalitelike phases in the temperature range 973–1273 K during the course of the DTA measurement. NH4-mordenite was dealuminated below 873 K in the TPD experiment on the deammonization. The thermal destruction of ZSM 5 containing Na+, Mg2+, Al3+ and Cs+ ions begins at about 1400 K. Excess sodium ions present in the original Na-ZSM 5 decreased the thermal stability. For H and NH4-mordenites, complete amorphization was found at 1270 K.
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