Möglichkeiten der Röntgenfluoreszenz- und Röntgenemissions-Spektrometrie in der Werkstoffanalytik

The principles and applications of X-ray fluorescence spectrometry and X-ray emission in the electron microprobe analysis and low energy electron induced X-ray spectrometry were described. With the help of soft X-ray spectra, arising from the valence bands, the different aluminum and titanium compounds of precipitates in steel can be investigated. The precipitates were isolated by an galvanostatic electrolysis. For speciation of aluminum the K_βlines in the X-ray fluorescence spectrum were investigated. The composition of aluminum oxide and -nitride in precipitates of special steel qualities can be determined. In the case of the speciation of titanium a direct electron bombardment of the sample is used to generate soft-X-rays. By investigating the L-lines of titanium different species like titaniumcarbide,-nitride or sulphide can be distinguished.     

Bestimmung der sorptionsisothermen lösungsmittelfeuchter sorbentien nach der durchströmungsmethode

The sorption isotherm is defined as the equilibrium moisture content of a sorbent as a function of the relative humidity at constant temperature. It is a measure for the hygroscopic behavior of the sorbent. In this work a simple and reliable method for the determination of sorption isotherms of solvent wetted sorbents is described. The sorption isotherm is determined by passing a nitrogen stream with a given relative humidity through a U-tube filled with the sorbent (through flowing method). The sorption isotherms of gas concrete, brick and clay for the sorbates isopropyl alcohol and water at 20 °C were measured. The reliability of the method was tested by comparing it with two other methods.     

Anwendungsmöglichkeiten der Gasextraktion im Bereich der Fette und Öle

Application Feasibilities of Gas Extraction in the Field of Fats and Oils During the extraction of relatively not volatile substances from solid material the effort which is to expect fairly depends on the capacity of the solvent. The available loading can significantly be increased by the appropriate choice of the solvent, by solvent mixtures and by the extraction in the “completely miscible” field. The material transport resistance of ground oil seed is mainly in the extracting medium. Further possibilities of gas extraction are found in the separation of fatty acids, fats and fat accompanying components. The results of recent work are submitted.     

Destillationsprobleme der Tallölaufbereitung

Problems of Distillation in the Processing of Tall Oil Large scale distillation of tall oil for the separation of the major components, fatty acids and rosin acids, involves difficulties owing to the presence of numerous other components, which, under the conditions of distillation, react with the active groups of the acids and the double bonds. The present communication shows the conditions which minimize such undesirable side reactions and additional thermal and oxidative decompositions, that reduce the yield of fatty acids and rosin acids. According to process, developed by the author, a countercurrent degasing and dewatering treatment with stripping steam is carried out before the separation of pitch, in order to remove rapidly at low temperatures the volatile substances, which negatively affect the odour, colour and colour stability. A vacuum of 100 torr enables the condensation of fairly large amounts of the stripping steam used by means of cooling water. Thus, the vacuum system is not affected. The distillative separation of pitch is carried out in two stages. The temperature of tall oil reaches a maximum of 230°C for the recovery of 90% of the distillate. In the second stage of film evaporation, the temperature of the product reaches 255°C for a short period. In the final distillation of the mixture of fatty acids and rosin acids, free of pitch, ACV-trickle columns and specially constructed falling film evaporators are used, which ensure that the temperature of the still does not exceed 260°C and the excess temperature of the heating medium is not more than 20°C. In case the temperature of the product exceeds 250°C in the falling film evaporator, addition of a few percent of stripping steam at their heads prevents the undesirable formation of anhydride.     

Anwendungsmöglichkeiten der homogenen Übergangsmetallkatalyse in der Fettchemie

Homogeneous Transition Metal Catalysis in Oleochemistry Numerous processes in industrial oleochemistry are carried out using transition metal catalysts. However, in most cases the catalysts applied are heterogeneous. The present review considers the huge number of possible applications of homogeneous transition metal catalysis in oleochemistry. The advantages of homogeneous transition metal catalysis are the high selectivity and the mild reaction conditions. These advantages are often used in petrochemistry, but in industrial oleochemistry exist no similar developments. The results of the laboratory research in the last two decades prove that the special properties of homogeneous transition metal catalysts can be applied in oleochemistry too. Well known chemical reactions could be improved and new reactions could be developed. The present review refers some of the most interesting reaction types, e. g. the selective hydrogenation of manifold unsaturated fatty acids or the possibilities to isomerize the double bonds selectively. Oxidation reactions, reactions with carbon monoxide, metathesis, CC-linkage reactions, telomerizations and additions to the double bonds of unsaturated fatty compounds will also be presented.     

Vergleich der Verteilungskurven der Katalysatorkorngrößen bei der Hydrierung von Fetten

Comparison of the Distribution Curves of the Particle Sizes of Catalysts in the Hydrogenation of Fats In the present paper the particle sizes of 14 hydrogenation catalysts and 2 kinds of commercial kieselguhr were studied using a laser analyzer. Assuming a log-normal distribution the distribution curves for the particle sizes were treated by the least-squares method. From the μ and σ parameters obtained the different characteristics of the catalysts were discussed.     

Zur optimierung der Polymerfraktionierung auf der Grundlage von Lösungsgleichgewichten in Lösungsmittel-Fällungsmittel-Systemen

The phase separation behavior of dilute polydisperse polymer solutions primarily depends on the partial concentration of each polymer component. So the equilibrium data obtained by turbidimetric titration with “calibration” fractions and their mixtures can be used for the construction of a solubility diagram (Claesson-diagram) which generally allows to describe fractionation processes. It can be shown that the characteristic features of precipitation fractionations can well be derived from the solubility diagram. This diagram then offers the possibility for a complete discussion of parameter variation (concentration, step of γ-variation, process-scheme, temperature, solvent/nonsolvent-system) on the efficiency of a fractionation step. On one hand these results correspond – as for the concentration variation – to well known experimentell experiences. On the other hand it is possible for the first time to give definite predictions for the influence of temperature and the solvent/nonsolvent system. The temperature selection can be shown to be inconsiderable for the separation effect. The usual characterization of solvents and nonsolvents as “good” or “poor” is absolutely insufficient, if not misleading, for there is no connection between these properties and the shape of the solubility diagram. Based on the analysis of the single parameters the optimum conditions for the preparation of narrow preparation of narrow precipitation fractions can be derived.