Untersuchungen an oxidischen Katalysatoren. XXVIII. Einfluß der Vorbehandlungsbedingungen auf Die katalytischen Eigenschaften von NiNaY- und NiCoNaY-Zeolithen

Studies on Oxide Catalysts. XXVIII. Influence of Pretreatment on Catalytic Properties of Zeolites NiNaY and NiCoNaY The influence of the pretreatment conditions on the acidic properties, the reduction degree of nickel, and the catalytic activity and selectivity of zeolites NiNaY and NiCoNaY in the alkylation of benzene with ethylene has been investigated. From the experimental results can be concluded that sec. buthylbenzene from benzene and ethylene is only formed on zeolite samples which contain both together BRÖNSTED acidic centres and Ni²⁺ cations or NiO. Catalysts which contain only metallic nickel are inactive for this reaction. Catalysts with nickel in different forms are active in the formation of ethylbenzene, diethylbenzene, butane and sec. buthylbenzene, the yields depending on the relation of Ni°, Ni²⁺, and NiO. Changing this relation makes possible to regulate the selectivity in the alkylation of benzene with ethylene.     

Untersuchungen an Metallkatalysatoren. XXXII. Zur Legierungsbildung und Dispersität von Nickel-Rhenium-Katalysatoren

Investigations on Metal Catalysts. XXXII. On Alloying and Dispersion of Nickel-Rhenium Catalysts Unsupported Ni? Re catalysts were prepared by reduction of mixtures from NiO and NH₄ReO₄ at 400°C with hydrogen (1^st series), followed by a heat treatment at 650°C in flowing hydrogen (2^nd series). The bimetallic powders were characterized by DTA investigations, X-ray measurements, N₂ adsorption, and CO chemisorption. The degree of alloying and the changes in dispersion as a result of adding a second metal to a basic one is discussed.     

Untersuchungen an oxidischen Katalysatoren. XVII. Zum Zusammenhang zwischen elektrischen und katalytischen Eigenschaften dotierter Zinkoxidkatalysatoren

Studies on Oxide Catalysts. XVII. On the Relations between Electric and Catalytic Properties of Doped Zinc Oxide Catalysts The electric conductivity and thermo EMF of zinc oxide catalysts doped with Li₂O, Ga₂O₃ and Fe₂O₃, and, on the other hand, their activity of dehydrogenation in the catalytic decomposition of isopropanol have been studied. The electric measurements were carried out preferably in an atmosphere of isopropanol. In washed single-phase catalysts doped with Li₂O (n-type semiconductors) the relation between the catalytic activity of dehydrogenation and the FERMI level position postulated by VOL'KEN?TEJN was verified quantitatively. The absorption of the isopropanol is considered to be the rate-determining acceptor step. In unwashed zinc oxide catalysts doped with Li₂O, however, the inversion from n- to p-type (between 0.3 and 0.5 mole-% Li₂O) causes a change in the character of the rate-determining step from an acceptor to a donor step. For the two-phase and three-phase solid systems of ZnO? Ga₂O₃ and ZnO? Fe₂O₃, respectively, it was not possible to find quantitative relations according to the electron theory of catalysis.     

Untersuchungen an Metallkatalysatoren. Zur Dispersität von Pt-Ir-Katalysatoren

Ohne Zusammenfassung     

Untersuchungen an Metallkatalysatoren. Zur Dispersit?t von Pt-Ir-Katalysatoren

Ohne Zusammenfassung     

Untersuchungen an Metallkatalysatoren. XIX. Zur katalytischen Wirksamkeit von Ni?Cu?Re-Katalysatoren

Investigations on Metal Catalysts. XIX. Catalytic Efficiency of Ni? Cu? Re Catalysts Alloying of Ni? Cu catalysts with rhenium causes an increased activity in the case of dehydrogenation of cyclohexane as well as the hydrogenolysis of ethane. The catalytic dehydrogenation activity is essentially determined by the f.c.c. phase of the ternary alloy system. In the case of ethane hydrogenolysis, both the f.c.c. and the h.c.p. phases are active, and both are desactivated by copper. The dehydrogenation activity of Ni? Cu? Re samples with medium copper content and low rhenium content is higher by one order of magnitude in comparison with nickel, and their hydrogenolysis activity is considerably lower.     

Mechanismus der katalytischen Dehydrierung und Dehydratisierung der Ameisensäure an Oxid- und Metallkatalysatoren

Ohne Zusammenfassung     

Untersuchungen an Metallkatalysatoren. XXXIII. Zur Charakterisierung von Nickel-Rhenium-Katalysatoren mittels der ferromagnetischen Resonanz

Investigations on Metal Catalysts. XXXIII. Characterization of Nickel-Rhenium Catalysts by Means of Ferromagnetic Resonance Unsupported nickel-rhenium catalysts (prepared by reduction of NiO? NH₄ReO₄ mixtures at 400°C with hydrogen) were characterized by the method of ferromagnetic resonance. With increasing rhenium content the values of signal intensity, g-factor, and half-width of the resonance line decrease. These facts are indications for the beginning in formation of solid solutions (alloys), which increases by further treatment of the samples at higher temperatures (650°C). The advanced alloying is also indicated by the sign reversal of the anisotropy constant.     

Untersuchungen an Metallkatalysatoren. XI. Untersuchungen an eisen-, kobalt- und nickelmodifizierten Pt-η-Al2O3-Katalysatoren

Investigations on Metal Catalysts. XI. Investigations on Pt? η-Al₂O₃ Catalysts Modifieded by Iron, Cobalt, and Nickel Pt? Me? η-Al₂O₃ catalysts (M: Fe, Co, Ni) were characterized by magnetic investigations, reflectance spectra and determination of dispersity (chemisorption of CO, oxygen-hydrogen titration), respectively. The phase structure of platinum-rich catalysts is composed of a high degree by Pt₃Fe super-structure. All the Pt? Fe? η-Al₂O₃ catalysts contained Fe^III ions in octahedral symmetry. The dispersity of the metallic components is determined essentially by their phase structure.     

Untersuchungen an Alkylmetallalkoxiden der Elemente Aluminium,Gallium und Indium. III. Eigenschaften und Schwingungsspektren von Dialkylgallium- und Indiumalkoxiden

Studies on Alkyl Metal Alkoxides of Aluminium, Gallium, and Indium. III. Properties and Vibrational Spectra of Dialkylgallium- and Indium Alkoxides The preparation and the properties of dialkyl metal alkoxides R₂MOR′ (with R = CH₃, CD₃, C₂H₅; R′ = CH₃, CD₃ and M = Ga, In) are described. The vibrational data (IR and Raman) of the trimeric methyl derivatives point to puckered six-membered M₃O₃-ring systems.     

Untersuchungen an oxidischen Katalysatoren. XXIV [1]. Adsorptions- und katalytische Eigenschaften von CeNaY- und CrNaY-Zeolithen

Studies on Oxide Catalysts. XXIV. Adsorption and Catalytic Properties of CeNaY and CrNaY Zeolites The adsorption of benzene, n-butylamine and ammonia(isotherms and heats of adsorption) on CeNaY and CrNaY zeolites of different exchange degrees has been measured. The acidic properties were characterized by titration with n-butylamine. As function of exchange degree the adsorption and catalytic properties (cracking of cumene) both change in the same manner. Whereas the reaction rate constants up to exchange degrees of 40–50% change only insignificantly, they are exponentially increasing at higher exchange degrees. The energies of activation are nearly independent of the degree and run to 23–25 kcal mol^?1.     

Untersuchungen an Metallkatalysatoren. XLIV [1]. Zur Wirkung von Titan in Reformierkatalysatoren

Investigations on Metal Catalysts. XLIV. Effect of Titanium in Refoming Catalysts Advanced ability for hydrogen activation and increased electron density in the metal crystallites are the striking consequences of titanium addition to reforming catalysts, what enables a marked influence of the selectivity of such catalysts. Prerequisite to this is a homogeneous and disperse distribution of the titanium over the cross section of the carrier spheres, what can be realized by a complexing agent addition to the impregnation solution.     

Untersuchungen an Metallkatalysatoren. XXVIII [1]. Zur Aktivität und Selektivität von Nickel/Träger-Katalysatoren

Investigations on Metal Catalysts. XXVIII. Activity and Selectivity of Supported Nickel Catalysts Titania and alumina supported nickel catalysts (with 1 and 10 wt.-% Ni, resp.) have been tested in ethane hydrogenolysis and conversion of cyclohexane. Titania supported nickel and nickel on high surface aluminas are characterized by small hydrogenolysis activities and high dehydrogenation selectivities. The behaviour of the Ni/Al₂O₃ catalysts is discussed in terms of an interaction between small nickel crystallites and unreduced nickel. In the case of the Ni/TiO₂ catalysts the interpretation is based on the partial poisoning of the nickel surface by titanium cations.     

Untersuchungen an Metallkatalysatoren. 37. Zum Einfluß der Beladung auf Aktivität und Selektivität von Nickel/Träger-Katalysatoren

Investigations on Metal Catalysts. 37. On the Influence of the Loading on Activity and Selectivity of Supported Nickel Catalysts Strong metal-support interactions effect a distinct decrease of the hydrogenolysis activity. They can be detected with diminishing metal loading in the following order: Ni/TiO₂ > Ni/Al₂O₃ > Ni/SiO₂. Strong metal-support interactions mean an influence on the electronic properties of the metal crystallites. On the other hand a mechanical mixture of nickel and η-Al₂O₃ is more active in hydrogenolysis than nickel.     

Untersuchungen an Metallkatalysatoren. XVII. Phasenaufbau,Dispersität und Dehydrieraktivität Molybdän- und wolframmodifizierter Palladiumkatalysatoren

Investigations on Metal Catalysts. XVII. Phase Structure, Dispersity, and Dehydrogenation Activity of Palladium Catalysts Modifided by Molybdenum and Tungsten Molybdenum and tungsten containing palladium catalysts were prepared by reduction of mixtures from Pd(NO₃)₂ with MoO₃ and WO₃, respectively, with hydrogen at 600°C and 800°C. The powders were characterized by means of several methods: Determination of the oxidation state for molybdenum and tungsten, X-ray measurements, N₂ adsorption, CO chemisorption, H₂ sorption, dehydrogenation of cyclohexane. The properties of the samples (heated at 600°C) are determined to a high degree by the co-existence of the palladium phase as well as the molybdenum and tungsten oxide, respectively, in the mean oxidation state +4. The after-reduction at 800°C leads to a great portion of metallic molybdenum and tungsten in the concerned catalysts. There are references that the treatment at 800°C in the presence of hydrogen causes for the Pd? Mo catalysts an increase of the palladium content in the surface of the crystallites.     

Über Chalkogenolate. 79. Untersuchungen über N-Hydroxydithiocarbamidsäure 1. Darstellung und Eigenschaften von N-Hydroxydithiocarbamaten und von Hydroxylammoniumdithiocarbamat

On Chalcogenolates. 79. Studies on N-Hydroxy Dithiocarbamic Acid. 1. Preparation and Properties of N-Hydroxy Dithiocarbamates and of Hydroxylammonium Dithiocarbamate In the presence of the corresponding hydroxide the reactions between hydroxylamine and carbon disulfide lead to N-hydroxy dithiocarbamates and [H₃NOH][S₂C? NH₂], respectively. The unstable compounds have been characterized by different methods.     

Elektronenstruktur und physikalisch-chemische Eigenschaften von Azo-Verbindungen. Teil XIV: Die Konformation des Benzalanilins

A re-evaluation of the electronic spectra of benzalaniline (II), 3, 3-dimethyl-2-phenyl-indolenine (X), mono-aryl substituted azomethines (XI, XIV, XV) and trimethylindolenine (XII) as well as of their conjugate acids strongly supports the hypothesis of ISMAILSKI & SMIRNOV [14] and of EBARA [15] that benzalaniline exists in a preferred peri-perpendicular conformation. The same is true for N-phenylazomethines. The n → π* transition of a ‘planar benzalaniline’ has been located at 27 600 cm^?1 (ε ≈ 60).     

Untersuchungen an Metallkatalysatoren. XXVII. Zum Einfluß verschiedener Träger auf die Dispersität von Nickel

Investigations on Metal Catalysts. XXVII. On the Influence of Several Carriers on the Dispersion of Nickel Nickel supported catalysts (carrier: η-, ?-, α-Al₂O₃, TiO₂) were characterized by chemically determined degree of reduction, CO chemisorption, magnetic susceptibility measurements and FMR. The influence of interaction between carrier and active component in the unreduced state on the size and number of Ni crystallites is discussed.     

Untersuchungen an katalytisch aktiven Oberflächenverbindungen. VII. Katalytische Eigenschaften von Vanadiumoxid-Chromoxid-Aufschicht-Katalysatoren

Studies on Catalytically Active Surface Compounds. VII. Catalytic Properties of Oxidic Vanadium-Chromium Catalysts The 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.     

Untersuchungen an katalytisch aktiven Oberflächenverbindungen. II. Zur Existenz unterschiedlicher Vanadium(V)-oxid-Oberflächenphasen auf SiO2 und ihre katalytischen Eigenschaften

Studies on Catalytically Active Surface Compounds. II. On the Existence of Different Vanadium(V) Oxide Surface Phases on SiO₂ and their Catalytic Properties In 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 V^v; 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.