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Two series of LaMnO3supported noble metal (Pt, Pd, Rh) catalysts prepared by the citrate method and calcined in air at 600 and 800 °C, respectively, were investigated. The catalysts resulting from method A were prepared by simultaneous incorporation of the noble metals during perovskite preparation and those following method B were generated by impregnation of the calcined perovskites with the noble metal compounds. The noble metals form solid solutions with the perovskite lattice. Reduction of the catalysts with hydrogen prior to the catalytic reaction led to a significant enhancement of the catalytic activity. During the catalytic reaction, the noble metal clusters are partially transformed to highly dispersed noble metal oxides or nonstoichiometric noble metal oxide phases, which are the catalytically active phases for the total oxidation of methane. The best results were obtained with the Pd containing catalysts prepared by method B.

Der oxidative Abbau von Ameisen-, Essig- und Propionsäure wurde an einem VOx-TiO2-Katalysator in An- und Abwesenheit von Wasser im Bereich von 120 – 280 °C untersucht. Essigsäure ist die gegenüber dem oxidativen Abbau stabilste Carbonsäure. Reaktionsprodukte waren die C-Zahl niedrigeren Carbonsäuren, COx und Wasser sowie Ethylen im Fall von Propionsäure. Wasser im Eduktgasstrom führte zur Blockierung katalytisch aktiver Zentren und somit zur Verringerung des Umsatzes sowie zur Selektivitätserhöhung der niedrigeren Carbonsäuren. Die Ergebnisse können für die Produktsteuerung bei katalytischen Selektivoxidationen und der oxidativen Dehydrierung niederer Kohlenwasserstoffe genutzt werden.

The partial oxidation of acetaldehyde and propionaldehyde on a TiO2supported VOxcatalyst in the presence of water vapor was investigated at temperatures from 120 to 280 °C. Depending on the kind of aldehyde and reaction temperature, the selective oxidation to the appropriate carboxylic acid and an oxidative splitting to lower carboxylic acids took place. Acetaldehyde was oxidized to acetic acid with selectivities up to 82 % at ∼ 200 °C whereas propionic acid was formed only with selectivities of about 20 % at ∼ 140 °C in the oxidation of propionaldehyde. The oxidative cleavage of propionaldehyde led to the formation of more acetic acid than formic acid, which was in agreement with the higher formation of COxcompared to that in the acetaldehyde oxidation. The presence of water and the increasing concentration of oxygen in the feed was found to enhance the selectivity towards the formation of C1to C3carboxylic acids by inhibiting the total oxidation of aldehydes and carboxylic acids.

Während die Wirkungsweise von VOx-TiO2-Katalysatoren bei der katalytischen Oxidation und bei oxidativen Dehydrierreaktionen intensiv untersucht wurde, liegen zum Adsorptionsverhalten von C4-Kohlenwasserstoffen an diesen Katalysatoren keine Angaben vor. Ziel der vorliegenden Arbeit war es, die Adsorption von 1-Buten an einem VOx-TiO2-Katalysator unter den technisch relevanten Reaktionsbedingungen der Selektivoxidation von n-Butan/n-Buten zu untersuchen. Für die mathematische Beschreibung des Reaktionsablaufes sind neben Kenntnissen reaktionskinetischer Parameter auch die von Adsorptions- und Desorptionsprozessen erforderlich.

Die bei thermischen und katalytischen Spaltprozessen anfallenden n-Butengemische werden u. a. als Edukt für Verfahren der Oligomerisierung eingesetzt. Dabei entstehen beim Einsatz von Festkörpersäurekatalysatoren Oligomerisate mit hohen Anteilen an verzweigten Olefinen, die nach Stabilisierung als Vergaserkraftstoff- und als Heizölkomponenten eingesetzt werden. In Gegenwart von Nickelverbindungen enthaltenden Katalysatoren entstehen aus den n-Butenen bevorzugt Octene mit geringem Verzweigungsgrad, die als Rohstoff für die Herstellung von PVC-Weichmachern dienen. Beschrieben werden die etablierten Verfahren und die Eigenschaften der Katalysatoren für die Oligomerisierung der n-Butene. Weiterhin wird zusammenfassend über Ergebnisse von Untersuchungen an NiO-Al2O3-SiO2-Katalysatoren für die Oligomerisierung von n-Butenen berichtet.

The catalytic behavior of ZrO2and ZrO2containing 8 mol‐% Y2O3supported A1–xSrxMnO3(A = La, didymium) perovskites was studied in the total oxidation of methane, chloromethane and dichloromethane considering catalyst deactivation and byproduct formation. The perovskites are dispersed on the support surface; clusters with a perovskite‐like structure were formed. The supported catalysts are characterized by higher specific surface areas compared with the unsupported ones. Partial substitution of A‐site cations by Sr leads to an enhancement of the catalytic activity in the total oxidation of methane, but not in the total oxidation of chlorinated hydrocarbons (CHC). The catalytic activity of supported and unsupported catalysts is comparable in the total oxidation of methane in spite of the significantly lower perovskite content of the supported catalysts. In the CHC conversion the catalytic activity of the supported catalysts is higher than that of the unsupported ones.

No abstracts.

The influence of the kind of A‐site cation in A1–xSrxMnO3perovskites (A = La, Pr, Nd, Di [didymium]) on the catalytic activity in the total oxidation of methane, chloromethane, dichloromethane, and trichloroethylene has been studied. In contrast to methane, the total oxidation of chlorinated hydrocarbons (CHC) is connected with a reversible catalyst deactivation and the formation of byproducts at low reaction temperatures. For the catalysts calcined at 600 and 800 °C, resp., the catalytic activity is determined mainly by specific surface area, amount of oxide admixtures and crystallinity of the perovskite. DiMnO3showed the highest and PrMnO3catalysts the lowest catalytic activity in the total oxidation of methane and CHC. Partial substitution of A by Sr leads to an enhancement of the catalytic activity in the total oxidation of methane, but not in the total oxidation of CHC.

Thermoanalytical measurements (DTG‐DTA‐MS), X‐ray diffraction (XRD), temperature‐programmed reduction (TPR), redox titration and X‐ray photoelectron spectroscopy (XPS) were used to characterize A1–xSrxMnO3perovskite catalysts (A = La, Nd, Pr, Di [didymium]). The catalyst samples were investigated before and after interaction with chloromethane in the temperature range between 300 and 650 °C. XRD and TPR measurements revealed the presence of oxide admixtures in samples calcined at 600 and 800 °C, resp., in air. Crystallinity of the samples and the amount of oxide admixtures depend on the kind of A‐site cations. Interaction of the perovskite samples with chlorinated hydrocarbons at reaction temperatures leads to a decrease of the specific surface areas; the perovskite structure is preserved. Redox titration and TPR measurements showed that the Mn(IV) content in the perovskites increases by partial substitution of La by Sr and decreases after interaction with chloromethane.

The influence of the kind of A-site cation in A1–xSrxMnO3 perovskites (A = La, Pr, Nd, Di [didymium]) on the catalytic activity in the total oxidation of methane, chloromethane, dichloromethane, and trichloroethylene has been studied. In contrast to methane, the total oxidation of chlorinated hydrocarbons (CHC) is connected with a reversible catalyst deactivation and the formation of byproducts at low reaction temperatures. For the catalysts calcined at 600 and 800 °C, resp., the catalytic activity is determined mainly by specific surface area, amount of oxide admixtures and crystallinity of the perovskite. DiMnO3 showed the highest and PrMnO3 catalysts the lowest catalytic activity in the total oxidation of methane and CHC. Partial substitution of A by Sr leads to an enhancement of the catalytic activity in the total oxidation of methane, but not in the total oxidation of CHC.

Thermoanalytical measurements (DTG-DTA-MS), X-ray diffraction (XRD), temperature-programmed reduction (TPR), redox titration and X-ray photoelectron spectroscopy (XPS) were used to characterize A1–xSrxMnO3 perovskite catalysts (A = La, Nd, Pr, Di [didymium]). The catalyst samples were investigated before and after interaction with chloromethane in the temperature range between 300 and 650 °C. XRD and TPR measurements revealed the presence of oxide admixtures in samples calcined at 600 and 800 °C, resp., in air. Crystallinity of the samples and the amount of oxide admixtures depend on the kind of A-site cations. Interaction of the perovskite samples with chlorinated hydrocarbons at reaction temperatures leads to a decrease of the specific surface areas; the perovskite structure is preserved. Redox titration and TPR measurements showed that the Mn(IV) content in the perovskites increases by partial substitution of La by Sr and decreases after interaction with chloromethane.

Nickel and ammonium ion exchanged NaY zeolites have been investigated in dimerization of n-butenes in the liquid phase. The dimerization reaction proceeds by a coordinative as well as carbenium ion reaction mechanism.

By static magnetic measurements it was found that the ability to reduction of an amorphous NiO−Al2O3/SiO2 catalyst decreases in the order: but-2-enes∼hydrogen∼ ∼isobutene>but-1-ene>propene∼ethene. The reduction temperatures are significantly higher than the dimerization reaction temperatures.

Zusammenfassung Aufgeschlüsselt nach Bevölkerungskollektiven mit unterschiedlichen sexuellen Verhaltensweisen wird anhand der bisher bekannten bzw. größenordnungsmäßig abgeschätzten epidemiologischen Daten des „Acquired Immunodeficiency Syndrome“ eine Hochrechnung der Morbiditäts- und Mortalitätsziffern für die Bundesrepublik Deutschland mittels Computer-Simulation vorgenommen; danach könnten in den nächsten 15 Jahren bis ca. 41 000 Personen erkranken. Die Bedeutung der weiblichen Prostituierten und der männlichen Bisexuellen als „Vektoren“ der Infektion aus den bisherigen Risikogruppen in Bevölkerungsteile mit ausschließlich heterosexuellen Verhaltensweisen, der Einfluß infektiologischer Schutzmaßnahmen sowie der Effekt sexueller Verhaltensänderungen breiter Bevölkerungsschichten kann mit diesem Programm ebenfalls untersucht werden.

SINCE the discovery of the polycyclic chemical structure of cholesterol on one hand, and, on the other, of the carcinogenicity of 3-methylcholanthrene, it has often been postulated that certain types of cancer might be due to some abnormality in the metabolism of cholesterol and bile acids, resulting in the formation in the body of one or several carcinogenic polycyclic hydrocarbons1. Along these lines, Bergmann2pointed out the theoretical possibility for cholesterol (I) to be cyclized, with dehydration and dehydrogenation, into the hypothetical hexa-cyclic hydrocarbon (II), which he named ‘steranthrene’ (since, the word ‘steranthrene’ has been used to designate the non-methylated basic hydrocarbon). Although experimental evidence for the existence of such a biochemical transformation is still lacking, it was of great interest to examine hydrocarbons of the steranthrene group for carcinogenicity. One of these hydrocarbons, ‘angular’ steranthrene (III), was recently investigated in mice by Dannenberg3, and found to produce spindle-cell sarcomas by injection and epitheliomas by painting the skin; the substance showed approximately the same degree of activity as 3,4-benzopyrene and 3-methylcholanthrene. We report here the results of our experiments on another such hydrocarbon, F-nor-steranthrene (IV), the synthesis of which has recently been described4.