Phase composition of an iron-bismuth-molybdenum catalyst for propylene ammoxidation

The phase composition of a selective Fe–Bi–Mo oxide catalyst changes under the influence of the reaction medium in the ammoxidation of propylene. It represence a heterogeneous mixture of bismuth and iron(II) molybdates.

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Kinetics of the formation and decomposition of hydroperoxide in the oxidation of 8-pentadecanone

Kinetic parameters for the decomposition of 8-pentadecanone ketohydroperoxides in the oxidized ketone medium and the effect of caprylic acid on the rate and mechanism of hydroperoxide decomposition have been studied. The decomposition of hydroperoxide into molecular products follows mainly the ionic mechanism.

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8- . . , .

     

Sulfur poisoning of Pt/Al2O3 catalysts, I. Determination of sulfur coverage by infrared spectroscopy

In the case of Pt/Al₂O₃ catalysts, a spectroscopic method was proposed to determine the amount of sulfur irreversibly bonded to platinum. Sulfate contamination of Pt/Al₂O₃ samples does not affect the metal properties for reduction temperatures lower than 300°C. Hydrogen treatment at 500°C reduces the sulfate groups into hydrogen sulfide which poisons platinum. This poisoning is strongly dependent on the metal loading. Irreversibly held sulfur sulfur corresponds to a S/Pt_s ratio close to 0.44.

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, , Pt/Al₂O₃, . Pt/Al₂O₃ 300°C. 500°C , . ⤠ . S/Pt_s, 0,44.

     

Development of pork fat reference material for OCPs' BCR-CRM 430

Summary Certification of the content of endogenous organochlorine pesticides and their metabolites (OCPs) in pork fat is described and the certified values are presented. The OCPs include hexachlorobenzene (HCB), -, - and -HCH, -heptachlor epoxide (-hepo), dieldrin, endrin, p,p'-DDT, p,p'-TDE and p,p'-DDE. In a previous paper [1] the preparation of pork fat as a candidate reference material has been described as well as the investigation of its homogeneity and stability. This material, when certified, may serve for the verification of the results of determinations of the above organochlorine pesticides. This paper deals with the certification of these OCPs in pork fat.Part I see [1]     

Product selectivity and qualitative reaction scheme for the dehydrogenation and hydrogenolysis of n-butane over supported ruthenium at high temperature

The dehydrogenation and hydrogenolysis of n-butane (n-C₄) over a Ru–Al₂O₃ catalyst (0.849 w/w% Ru) have been studied at 490°C at different time factors. Some runs have also been made on pure -Al₂O₃ at 490°C and on Ru-black at temperatures between 100 and 490°C, feeding n-butane and hydrogen. The analysis of the selectivity vs. time factor allows to prove that the initial reactions taking place are n-C₄ dehydrogenation to 1-butene and 2-butenes and skeletal isomerization to isobutane. The initial molar selectivity to the n-butenes reaches about 70%. A qualitative reaction scheme is proposed.

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- (-C₄) Ru–Al₂O₃ (0,849 .% Ru) 490°C . -Al₂O₃ 490°C Ru- 100–490°C - . , -C₄ 1- 2- . - 80%. .

     

Methane synthesis from CO/H2O mixture on supported nickel catalysts, I. Influence of the support on the catalytic properties

The behavior of some supported Ni catalysts for methane synthesis from CO and steam in correlation with the specific metal-support interactions is discussed.

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CO . .

     

Direkte Bestimmung von Schwermetallen (Pb, Cd, Ni, Cr, Hg) in Vollblut und Harn mit der Zeeman-Atom-Absorption

Zusammenfassung Durch die kritische Vor- und Aufbereitung der Proben sind bisher nur sehr erfahrene und gut ausgestattete Labors in der Lage, die toxischen Schwermetalle im Blut richtig zu bestimmen. Clean-bench-Bedingungen, sorgfältigste Reinigung und Lagerung der Gefäße, Verwendung von hochreinen Chemikalien sind bei den herkömmlichen Verfahren unerläßlich. Mit der Zeeman-Atom-Absorption und der Verwendung der L'vovschen Plattform ist die Direktanalyse von Vollblut ohne Probenvorbereitung möglich. Die Richtigkeit und Reproduzierbarkeit ist gewährleistet. Damit können solche Analysen auch in kleinen Labors durchgeführt werden, die nicht auf die Spurenanalyse spezialisiert sind. Bei einer begrenzten Anzahl von Proben ist die Analysengeschwindigkeit durch die nicht notwendige Probenvorbereitung höher. Die Analysenkosten sind deutlich niedriger.

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Direct determination of heavy metals (Pb, Cd, Ni, Cr, Hg) in blood and urine by means of Zeeman atomic absorption

Summary Hitherto, only well-equipped and experienced laboratories are able to perform accurate determinations of toxic heavy metals in blood because of the necessary pretreatment of the sample. Clean-bench conditions, careful cleaning and storage of the vessels and use of high-purity chemicals are essential with the conventional methods. However, when employing Zeeman atomic absorption and L'vov platforms direct analysis of blood without prior treatment becomes possible. Accuracy and reproducibility are ensured. Thus, such analyses can also be carried out by small laboratories not specialised in trace analysis. With a limited number of samples the rate of analysis is higher because of the not required pretreatment of the samples. Costs are distinctly lower.