Herstellung und Eigenschaften von geformtem Aluminiumoxid. I. Einfluß der Fällbedingungen des Böhmithydrogels auf die Porenstruktur des geformten Aluminiumoxids

Preparation and Properties of Formed Aluminium Oxide. I. Influence of the Precipitation Conditions of the Boehmite Hydrogel on the Pore Structure of Formed Aluminium Oxide A report is given on the influence of the precipitation conditions of boehmite (pH value, temperature, concentration and residence time in the precipitation suspension) on the cavity structure of aluminium oxide spheres, made by coagulation of boehmite hydrosol in ammonia liquor and subsequent thermal treatment at 110 and 600°C. The boehmite hydrogel was obtained at continuous precipitation conditions by neutralisation of sodium aluminate solution with nitric acid. It is shown that the difference in the pore structure of the formed aluminium oxide obtained by varying the precipitation conditions were caused by the special morphological features of the boehmite crystallization in the precipitation process.     

Herstellung und Eigenschaften von Aluminiumaquoxid. II. Böhmit aus Natriumaluminat und Salpetersäure

Preparation and Properties of Aluminium Hydroxide. II. Boehmite from Sodium Aluminate and Nitric Acid A report is given on the physical-chemical characteristics of aluminium hydroxide which contain mainly boehmite, having been obtained by continuous precipitation from sodium aluminate solution with nitric acid using technical raw materials and conditions being very similar to those applied in production. The influence of the reaction conditions (pH value, temperature, concentration and residence time in the precipitation suspension) on the chemical composition, structure and texture of the hydrogels is studied. With rising precipitation temperature the pH range extends, within which already after short residence times pure-phase, relatively well crystalline boehmite hydrogels are obtained in the precipitated solution.     

Herstellung und Eigenschaften von Aluminiumaquoxid. III. Peptisierung von Böhmit mit Salpetersäure

Preparation and Properties of Aluminium Hydroxide. III. Peptization of Boehmite with Nitric Acid A reaction of the aluminium oxide hydroxide boehmite with nitric acid in dependence on the temperature and the molar ratio HNO₃/Al₂O₃ is studied. The effect of the acid results in the formation of basic aluminium nitrates, which can change the rheological properties of the boehmite hydrogel due to redispersion or desaggregation up to its ?liquefaction”? to boehmite hydrosol. For the dependence of the flow velocity of the boehmite hydrosol on the molar ration HNO₃ Al₂O₃ a maximum correlation is characteristic. It can also be interpreted from the colloid-chemical point of view and it is a technically relevant indicator for the optimization of the peptization. By the peptization conditions of the boehmite hydrogel the pore structure of the Al₂O₃ can be varied in a carefully directed way.     

Herstellung und Eigenschaften von Aluminiumaquoxid. I. Böhmit aus Aluminiumnitrat und Ammoniakwasser

Preparation and Properties of Aluminium Hydroxide. I. Boehmite from Aluminium Nitrate and Ammonia The physical-chemical properties of mainly boehmite containing aluminium hydroxide are studied which were made by continuous precipitation from aluminium nitrate solution with ammonia liquor using technical raw materials and test conditions being very similar to those applied in production. The influence of the precipitation conditions (pH value, temperature, concentration and residence time in the precipitation solution) on the composition, structure and texture of the precipitation products is investigated and information about their effect on the filtration behaviour are given. In the case of a continuous precipitation it is possible to obtain phase-pure boehmite being relatively well crystallised. The crystallinity and dispersity of the precipitated hydroxide determine their filterability and the cavity structure.     

Einfluß der Chelatbildner dppe und dppp auf die Bildung und die Eigenschaften der Pt-Komplexe des tBu2P–P

Coordination Chemistry of P-rich Phosphanes and Silylphosphanes. XV. Influence of the Chelate Compounds dppe and dppp on Formation and Properties of the Pt Complexes of ^tBu₂P–P The chelating ligands dppe and dppp replace the PPh₃ groups in [η²-{^tBu₂P–P}Pt(PPh₃)₂] 1 yielding [η²-{^tBu₂P–P}Pt(dppe)] 2 and [η²-{^tBu₂P–P}Pt(dppp)] 8 . However, they don't replace the phosphinophosphinidene ligand ^tBu₂P–P. dppm does not react at all with 1 . [η²-{H₂C=CH₂}Pt(dppe)] 3 yields in the presence of ^tBu₂P–P=P(Me)^tBu₂ 4 exclusively Pt(dppe)₂ 5 and elemental Pt; no 2 could be detected. Similarly, [η²-{H₂C=CH₂}Pt(dppp)] 7 reacts with 4 to give mainly Pt(dppp)₂ 9 and Pt; [η²-{tBu₂PP}Pt(PPh₃)₂] 8 is present only as a minor product. [η²-{^tBu₂P–P}Pt(dppe)] 2 crystallizes in the monoclinic space group P2₁/c (no. 14) with a = 1834.40(10) pm, b = 1679.70(10) pm, c = 1125.79(6) pm, β = 103.963(5)°.     

Über den Einfluß von Temperatur und Fremdionen auf Eigenschaften und Bau der Natriumwasserglaslösungen

The Influence of Temperature and Impurities Addition on the Properties and the Constitution of Sodium Water Glass Solutions Sodium water glass (NaWG-)solutions of constant composition (SiO₂/Na₂O = 3,3; C_SiO2 = 6,2 M) and different concentration of impurities (Fe, Al, Ti, Cu, chloride, sulfate) were investigated in dependence on temperature by means of the dye absorption method, ¹H- and ²³Na-NMR spectroscopy. It is shown, that the differences in the dye absorption spectra of normalized technical NaWG-solutions, mainly depend on the Fe-concentration in the solutions and their thermal history. From the results follow a crosslinking of polymeric silicate species by Fe? O? Si bonds and/or hydrogen bridges and a fully or partially degradation of these bonds at higher temperatures (150°C).     

Einfluß von Gitterstörungen des Graphits auf die Bildung von Graphithydrogensulfat

Influence of Lattice Defects of Graphite on the Formation of Graphite Hydrogensulfate Various natural and synthetic graphites were oxidized with chromic acid in sulfuric acid to the 1st stage of graphite hydrogensulfate with the intent of determining the inhibition of intercalation by lattice defects. More oxidant than required by stoichiometry is consumed because slow total oxidation to CO₂ is superimposed even at room temperature. The activation energy for total oxidation is reduced by lattice defects. With some graphites, separation of the intercalation reaction from total oxidation was accomplished using calorimetry. The reaction enthalpy in the oxidation of well-crystallized graphites to the graphite salt is ?3.05 kJ/mol C.     

Schichtweis Abscheuern. II. Auswirkung auf die Eigenschaften von Garnen und Textilien

Ohne Zusammenfassung     

Zweidimensionales Modell der mechanischen Eigenschaften von Polymer-Blends Anwendung auf Polypropylen- und Poly?thylen-Blends

Ohne Zusammenfassung     

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.