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  • 1
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1588-2837
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract Было исследовано получение и гидролиз ванадиевых катализаторов, используя VCl4 в качестве парамагнитной пробы. Химическим анализом было показано, что молекула VCl4 реагирует однажды, дважды и трижды с гидроксильными группами поверхности. Температура предварительной обработки Аэросила влияет на тип реакции. ЭПР измерения указывают на искажение тетраэдрической координации поверхностного комплекса (SiO)nVCl4−n, который является самым сильным в случае трехкратного присоединения VCl4 к поверхности (n=3). Гидролиз сопровождается увеличением координационного числа и приводит к сильно подвижным ванадиевым частицам.
    Notes: Abstract The preparation and hydrolysis of silica supported vanadium catalysts have been investigated using VCl4 as a paramagnetic probe. Chemical analysis shows the possibility of the VCl4 molecule to react one, two, or three hydroxy groups of the surface. The type of reaction is influenced by the temperature of pretreatment of aerosil (TPA). ESR measurements show distortions of the tetrahedral coordination of the (SiO)nVCl4−n surface complex, which is strongest for the threefold attachment (n=3) of VCl4 to the surface. Hydrolysis is accompanied by an increase of the coordination number and leads to highly mobile vanadium species.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Ferrisilicates of MFI structure (HZSM-5) with Si/Fe ratios of 27.5, 35 and 67 have been studied by in situ Mössbauer spectroscopy, and the results are correlated with studies on catalytic conversions of toluene. Various species of iron ions are identified from 300 K spectra recorded after combinations of evacuation and reduction at 570 and 670 K, respectively. The roles of identified species are suggested in catalytic processes.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    ISSN: 1588-2837
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract Адсорбция кислорода на катализаторах Mo-V/SiO2 приводит к совместному образованию радикалов O 2 − (51V) и O 2 − (96Mo). восстановление и измерение радикальной стабильности на бинарных и двух “моно”-катализаторах (V/SiO2, Mo/SiO2) свидетельствуют о том, что наряду с Mo−O−V “фазой” было изолировано много ионов переходных металлов.
    Notes: Abstract Oxygen adsorption studies were carried out on Mo-V/SiO2 catalysts showing the simultaneous formation of O 2 − (51v) and O 2 − (96Mo) radicals. Reduction studies and the measurement of the radical stability on the binary and two “mono”-catalysts (V/SiO2, Mo/SiO2) indicate that besides a Mo−O−V “phase” remarkable parts of transition metal ions are isolated.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1588-2837
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract Было описано получение ванадий-фосфорных катализаторов, для которых было обнаружено значительное влияние фосфора на концентрацию ионов V+4. Окислительные свойства катализаторов были исследованы химическим анализом, а также с помощью ЭПР. Спектры ЭПР, помимо этого, указывают на эначительное влияние влаги на структуру катализатора.
    Notes: Abstract The preparation of vanadium-phosphorus catalysts is described, showing the considerable influence of phosphorus on the concentration of V4+ ions. The oxidation properties were studied by chemical analysis and electron spin resonance. Moreover, ESR spectra show a strong influence of moisture on the structure of the catalysts.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1588-2837
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract Были исследованы условия образования O 2 − на катализаторах VCl4/SiO2. Было показано, что термическая вакуумная обработка негидролизованных катализаторов приводит к частичному гидролизу поверхностного ванадиевого комплекса, вызванному силанольными группами носителя. Было найдено, что способность катализаторов генерировать радикалы O 2 − зависит от степени гидролиза, вызванного термической вакуумной обработкой.
    Notes: Abstract The conditions for the formation of O 2 − on VCl4/SiO2 catalysts have been investigated. It is shown that thermal vacuum treatment (TVT) of unhydrolyzed catalysts leads to partial hydrolysis of the surface vanadium complex caused by the silanol groups of the support. The ability of the catalysts to generate O 2 − radicals was found to depend on the degree of hydrolysis caused by thermal vacuum treatment.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1588-2837
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract Эффект примесей щелочных добавок (Li, Na, K, Rb и Cs) на катализаторы V/SiO2 был исследован методом ЭПР. Щелочные металлы сильно изменяют спектр VO2+. Восстановление приводит к спектрам, согласно которым происходит медленное вращательное движение частиц VO2+ на поверхности носителя. Предложенная интерпретация включает в себя предыдущие структурные модели и образование солей поливанадиевой кислоты.
    Notes: Abstract The effect of alkali metal admixtures (Li, Na, K, Rb, and Cs) on V/SiO2 catalysts was studied by ESR spectroscopy. Alkali metals strongly change the VO2+ spectra. Reduction leads to spectra showing a slow rotational motion of VO2+ species on the support surface. The proposed explanation includes former structural models and the formation of salts of polyvanadium acid.
    Type of Medium: Electronic Resource
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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: Transition Metal Zeolites as Catalysts for the Partial Oxidation of MethanolZeolites containing cations of the 4th period of the periodical system from Ti to Cu have been prepared by ion exchange of a NaY zeolite in aqueous solutions. Structural and surface chemical properties of the zeolites were characterized by adsorption, DTA, thermogastitrimetry, x-ray, ESR, IR, and UV-V is spectroscopy. It could be shown that both localization and coordination state of transition metal ions is fairly different and depends on the thermal treatment of the zeolites. By exchanging sodium ions the acidic properties as well as the ability of the zeolites to interact with H2O or CO2 is changed and depends on the kind of transition metal ion.VO and Cr exchanged zeolites proved to be selective catalysts for the oxidative dehydrogenation of methanol to formaldehyde with a maximum selectivity of 70%. It is concluded that in contrast to oxides where a redox mechanism is assumed the reaction on zeolites occurs via an associative mechanism.
    Notes: Zeolithe, die Kationen der IV. Periode des Periodensystems von Ti bis Cu enthielten, wurden durch Ionenaustausch in wäßriger Lösung aus einem NaY-Zeolith hergestellt. Die strukturellen und oberflächenchemischen Eigenschaften dieser Zeolithe wurden durch Adsorption, Röntgenspektren, DTA, mit Thermogastitrimetrie, UV-VIS-, ESR- und IR-Spektroskopie charakterisiert.Die Zeolithstruktur bleibt in allen Fällen nach dem Austausch erhalten. Die Lokalisierung und der Koordinationszustand der Übergangsmetallionen ist sehr unterschiedlich und wird durch thermische Behandlung beeinflußt. Die aciden Eigenschaften des Zeoliths werden durch den Austausch der Natrium- gegen die Schwermetallionen in unterschiedlicher Weise verändert, ebenso die Fähigkeit des Zeoliths zur Wechselwirkung mit H2O und CO2.Die VO- und Cr-ausgetauschten Zeolithe erwiesen sich als selektive Katalysatoren bei der oxidativen Dehydrierung des Methanols zu Formaldehyd, wobei die Selektivität der Reaktion Werte bis zu 70% erreichte. Es wird angenommen, daß die Reaktion an den Zeolithen nicht wie an Oxiden nach einem Redox-Mechanismus, sondern nach einem assoziativen Mechanismus abläuft.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 56 (1931), S. 166-170 
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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