Untersuchungen an oxidischen Katalysatoren. XVI. Über Zusammensetzung und Struktur dotierter Zinkoxidkatalysatoren

Studies on Oxide Catalysts. XVI. Composition and Structure of Doped Zinc Oxide Catalysts Analytical, x-ray, textural, IR-spectroscopic, and MÖSSBAUER investigations of zinc oxide catalysts doped with Li₂O, Ga₂O₃ and Fe₂O₃ were conducted in order to reveal relations between electronic and catalytic properties. The mixtures ZnO/Li₂CO₃, ZnO/Ga₂O₃, ZnO/Fe₂O₃, and ZnO/⁵⁷Fe(NO₃)₃, after the thermal pretreatment, always exist in the state of a polyphase solid system. In the ZnO/Li₂O system, only a very small part of the added lithium oxide is incorporated into the zinc oxide lattice by substitution. A second part of the Li₂O volatizes during the thermal pretreatment, and the greater part of it exists in the state of a separate solid phase in the catalyst and can be washed out by water. During the pretreatment, according to its temperature and duration, two-phase systems (ZnO, ZnMe₂O₄) or three-phase systems (ZnO, ZnMe₂O₄, Me₂O₃) are formed in the solid systems ZnO/Ga₂O₃ and ZnO/Fe₂O₃. For the reaction of both oxides forming a spinel, an electronic model is proposed.     

Untersuchungen an oxidischen Katalysatoren. XXXVI. Struktur und thermisches Verhalten röntgenamorpher Al2O3–SiO2-Festkörper

Studies on Oxide Catalysts. XXXVI. Structure and Thermal Behaviour of Silica–Alumina The effect of thermal treatment up to 500°C on silica-alumina was studied by i.r. investigation in the lattice vibration region and the condensation degree of the silicate fragments in the silica-alumina was characterized using the molybdato method. The results of both methods demonstrate the proton form of the amorphous alumosilicates to be thermal instable and to undergo extraction of the aluminium from the alumosilicate lattice. The consequences resulting from this process on the catalytic efficiency of silica-alumina in the cracking reaction of cumene are discussed.     

Kryometrische Untersuchungen. IV. Lösungen von oxidischen Mo6+- und Cr6+-Verbindungen in geschmolzenem K2Cr2O7 und KNO3

The depression of freezing point of molten K₂Cr₂O₇ and KNO₃ as solvents was measured after addition of small concentrations of the following compounds: to K₂Cr₂O₇: MoO₃, CrO₃, (NH₄)₂CrO₄, K₂MoO₄, Na₂MoO₄, Li₂MoO₄, and Na₂Mo₂O₇, respectively; to KNO₃: CrO₃, (NH₄)₂Cr₂O₇ K₂Cr₂O₇, K₂CrO₄ and MoO₃, (NH₄)₆(Mo₇O₂₄) · 4 H₂O, K₂Mo₂O₇, K₂MoO₄, Na₂MoO₄ and Li₂MoO₄, respectively. It could be concluded from the measured values of the freezing point depression if a reaction between solvent and solute took place.     

Untersuchungen an oxidischen Katalysatoren. XXXVII. Zum Einfluß der Herstellungsbedingungen auf die Eigenschaften röntgenamorpher Al2O3?SiO2-Festkörper

Studies on Oxide Catalysts. XXXVII. On the Influence of Preparation Conditions on the Properties of Silica-Alumina Silica-alumina samples of different composition were prepared by coprecipitation from aqueous solutions at pH = 6 and pH = 9, respectively. Structures and properties of the solids were characterized (i.r., DTA, X-ray, molybdato method, surface acidity, catalytic activity in the cracking reaction of cumene). Solid composition and pH value of the precipitation medium equally exhibit influence on the structure of the silica-alumina (kind of incorporation of the aluminium) and thereby on the acidic and catalytic properties of the solids. Silica-alumina of equal composition but precipitated at different pH values may widely differ in their properties including activity-composition dependency.     

Über Oxocadmate: K2Cd2O3

New obtained is K₂Cd₂O₃ (brownish red), which – according to single crystal work [487 h 01–h 41, Mo? Kα, R = 9.7₃%, R′ = 10.7₆%] – crystallises monoclinic with a = 6.41₇, b = 6.72₃, c = 6.58₆ Å, β = 116.0° in P2₁/c–C [K⁺, Cd²⁺ and O(1)^2? in 4(e), O(2)^2? in 2(a)] and is isotypic with Na₂Zn₂O₃. [Parameters see text]. The Madelung Part of Lattice Energy is calculated and discussed.     

Untersuchungen an oxidischen Katalysatoren. XXIX. Spektroskopische und katalytische Untersuchungen an Ni2+-, Co2+-, Cr3+- und Cu2+-ausgetauschten Mordeniten

Studies on Oxide Catalysts. XXIX. Spectroscopic and Catalytic Investigations on Ni²⁺-, Co²⁺-, Cr³⁺-, and Cu²⁺-exchanged Mordenites NiNaM, CoNaM, CrNaM und CuNaM (M = Mordenite) have been characterized by UV-VIS, EPR and i.r. spectroscopy and the results were compared with the catalytic activity and the activity-time-dependence in the cracking of n-octane and with the shape selectivity in the cracking of a n-octane and isooctane mixture. Water molecules acting as ligands of the exchanged cations are able to dissociate yielding Brönsted acidity. Brönsted sites may be regarded as catalytic active centers in the cracking reaction. Unreduced transition metal cations facilitate the “coking” of the mordenite. The unreduced chromium and cobalt cations for which a position within the main channel is expected, affect the diffusion of the branched paraffin molecule thus increasing shape selectivity.     

Untersuchungen an oxidischen Katalysatoren. XV. Der Einfluß von Oberflächenhydratation und -acidität der Übergangsformen des Aluminiumoxids auf die katalytische Aktivität bei der Dehydratisierung von Isopropanol

Studies on Oxide Catalysts. XV. The Influence of Surface Hydration and Acidity of Transient Forms of Alumina on the Catalytic Activity in the Dehydration of Isopropanol Surface OH groups were determined quantitatively on a aeries fo different samples of transient aluminas by means of D₂O exchange as well as by interaction with thionyl chloride and potassium vapour, and the acid centers were determined by titration with potassium methoxide and high temperature chemisorption of ammonia. Only the deuterium exchange and chemisorption of ammonia proved to be suitable for a quantitative characterization of the surface chemical properties mentioned in the paper. The catalytic activity is dependent directly on the number of acid centers. Between the number of surface OH groups and the results of the catalytic dehydration of isopropanol, however, no correlation was found.     

Untersuchungen an oxidischen Katalysatoren. XXXIX. Der Einfluß acider Träger auf die katalytische Wirksamkeit von Metallen

Studies on Oxide Catalysts. XXXIX. Influence of Acidic Carriers on the Catalytic Effect of Metals The catalytic behaviour of modified zeolite catalysts containing metal in the isomerization of n-hexane as well as in the dehydrogenation of cyclohexane and in the hydrogenolysis of ethane shows that the catalytic action of the metal can be continuously and reversibly varied by modifying the carrier acidity. From the concept of an electronic interaction between metal and (acid) carrier conclusions can be derived for a directed modification of the catalytic properties of metal/carrier catalysts.     

Untersuchungen an oxidischen Katalysatoren. XXXV. Redoxverhalten des Nickels in NiNaY-Zeolithen 2. Untersuchungen zur Dispersität von Ni- und Ni/NiO-Teilchen in reduzierten und reoxydierten NiNaY-Proben

Studies on Oxide Catalysts. XXXV. Redoxbehaviour of Nickel in Zeolite NiNaY. 2. Investigation on the Dispersion of Ni- und Ni/NiO-Species in Reduced and Reoxidized NiNaY Samples Oxygen chemisorption and electronmicroscopic measurements (ultramicrotome technique) correspondingly show a decrease of the metal dispersion with increasing reduction temperature (470–870 K) and exchange degree (10, 29, 54 equ.-% resp.). Contrary to this results electronmicroscopic measurements with replica technique don't reflect such a dependence. Increase of particle size after reoxidation (470 K) and reduction at 470 to 870 K (regeneration) of the NiNaY samples are attributed on the one hand to the aggregation of oxidic particles and on the other hand to metal sintering by the subsequent reduction step. A decrease of dispersion after a reoxidation process at 670 K is caused by formation and relocalisation of isolated nickel ions.     

Über Kupfer(I)-sulfat Cu2SO4. Darstellung und thermische Eigenschaften

Preparation and Thermal Properties of Copper(I) Sulfate Cu₂SO₄ Copper(I) sulfate Cu₂SO₄ can be prepared in high purity by reaction of Cu₂O with dimethyl sulfate (CH₃)₂SO₄ at 160°C in an argon atmosphere. Using an extremely fine grained Cu₂O, as obtained by reduction of cupric acetate with hydrazine, and a reaction time of 10 minutes a Cu₂SO₄ is obtained that contains less than 1% Cu₂O. Longer reaction times lead to partial decomposition of the Cu₂SO₄ to Cu(met.) and CuSO₄. In a closed system Cu₂SO₄ melts at about 400°C, however, the melt rapidly decomposes to Cu and CuSO₄, solidifying simultaneously. When heated in a thermoanalyzer in flowing argon or in a vacuum, Cu and CuSO₄ react under liberation of SO₂. Increasing the temperature leads to CuO in three steps, which converts to Cu₂O when heated to 1000°C. The question of formation of Cu₂SO₄, occasionally mentioned in the literature, being responsible for the liquid phases observed in the system Cu? S? O at temperatures below 500°C, is discussed.     

Über Chalkogenolate. 139. Untersuchungen über Dialkylester von Chalkogenokohlensäuren. 2. O,Se- und S,Se-Dialkylmonothiomonoselenocarbonate

On Chalcogenolates. 139. Studies on Dialkyl Esters of Chalcogenocarbonic Acids. 2. O,Se- and S, Se-Dialkyl Monothiomonoselenocarbonates The hitherto unknown esters RSe? CS? OR′, where R = C₂H₅, ⁿC₃H₇ and R′ = C₂H₅, ⁿC₃H₇, are formed by reaction of NaSeR with Cl? CS? OR′ and of RSe? CS? Cl with HOR′. At the first time, the esters RSe? CO? SR′ with R = R′ = C₂H₅, ⁿC₃H₇ have been prepared by reaction between NaSeR and Cl? CO? SR′. The compounds have been characterized by means of diverse spectroscopic methods.     

Untersuchungen an oxidischen Katalysatoren. XIV. Die katalytische Aktivität verschiedener Übergangsformen des Aluminiumoxids bei der Dehydratisierung von Isopropanol

Studies on Oxide Catalysts. XIV. The catalytic Activity of some transient Forms of Alumina in the Dehydration of Isopropanol In order to give statements about the influence of the method of preparation of aluminum hydroxides and oxide hydroxides on the catalytic properties of alumina obtained from these compounds in the dehydration of ispropanol, bayerite, nordstrandite, and boehmite were prepared by several methods, carefully excluding impurity ions. Also, hydrargillite containing alkali was included in the investigations. By calcination in oxygen at 550 and 950°C, respectively, two groups of alumina were obtained. The catalytic properties of the oxides in the dehydration of isopropanol were examined by an apparatus working according to the dynamic principle. The specific activities of the different transient forms of alumina were found to vary according to the sequence η-;≈γ->?-≈δ->??(>??-)Al₂O₃.     

Über quantitative Beziehungen zwischen Fragmenten und ihren relativen Intensitäten im Massenspektrometer. II—Untersuchungen Über die Beeinflussung Relativer Ionenintensitäten Durch Experimentelle Faktoren und Ihre Bedeutung für den bei Tertiären Alkoholen AUfgefundenen [Ionenmasseneffekt]

The dependence of ion intensity ratios of competing α-fissions on electron beam energy, source temperature, influences of electron multiplier and ion optics, were investigated. A mass discriminating effect of the ion optics was found. It is shown that the ion mass effect found on tertiary aliphatic alcohols is real. So far as it is known today, this effect is pronounced in such aliphatic compounds which exhibit no molecular ion peak under electron impact and form very stable ions by α-fission. Two alternative explanations are proposed.     

Spektroskopische Untersuchungen und Phasenbeziehungen im System Li2O−Al2O3−Cr2O3

Zusammenfassung Aus Li₂CO₃ und (Al_1–x Cr _x )₂O₃ wurde durch Festkörperreaktionen die Mischkristallreihe LiAl_1–x Cr _x O₂ hergestellt. Die thermische Stabilität der mikrokristallinen Substanzen (-NaFeO₂-Typ, Raumgruppe R3m) wurde röntgenographisch verfolgt. Die diffusen Reflexionsspektren (12 bis 30 kK, 25°C) wurden mit dem Modell der erweiterten Kristallfeldtheorie ausgewertet. Die durch Multiphononen-Struktur charakterisierten spin-erlaubten Banden ergeben für kubische MikrosymmetrieDq- undRacah-B-Werte, die im Gegensatz zur Rubinreihe nur wenig von Cr-Gehalt abhängen.Dq beruht zum Teil auf dem Einfluß von zweitnächsten Li⁺-Nachbarn, wodurch die effektive Ladung der Sauerstoff-Liganden in der Bindung größer ist. Die breite spin-verbotene Bande bei 15 kK deutet auf eine Magnon-Satellitenstruktur durch antiferromagnetische Ordnung hin.

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Optical studies and phase relations in the system Li₂O–Al₂O₃–Cr₂O₃

The series LiAl_1–x Cr _x O₂ was prepared by solid state reactions with Li₂CO₃ and (Al_1–x Cr _x )₂O₃. The thermal stability of the microcrystalline samples (-NaFeO₂ type, space group R3m) was controlled by X-ray methods. The diffuse reflectance spectra at 25 °C in the region from 12 to 30 kK were analyzed by the extended crystal field theory. From the spin-allowed peaks characterized by a multiphonon structureDq-andRacah-B-values were obtained for cubic site symmetry (neglecting trigonal distortions and spin-orbit effects) that are only slightly dependent on the Cr-content, in contrast to the ruby series.Dq is partly due to the influence of the secondnearest Li⁺-neighbours leading to a greater effective charge of the oxygen ligands in the bond. The broad spin-forbidden peak at 15 kK points to a magnon satellite structure caused by antiferromagnetic ordering.

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Mit 1 Abbildung     

Untersuchungen an oxidischen Katalysatoren. XL. Beeinflussung des katalytischen Verhaltens Bifunktioneller Ni/HNaY-Zeolith-Katalysatoren durch Übergangsmetallionen der VI. Nebengruppe

Studies on Oxide Catalysts. XL. Modification of the Catalytic Behaviour of Bifunctional Zeolites Ni/HNaY by Group VIB Transition Metal Ions The catalytic properties of zeolites Ni/HNaY modified by addition of transition metalions of group VIB are investigated in the conversion of n-hexane and cyclohexane. Nature and amount of the component additional introduced into the Ni/HNaY zeolites exhibit strong influence on the catalytic activity, the selectivity, and the sulphur resistance of these catalysts. The action of the added component is discussed considering electronic effects on the nickel metal.