Study of hydroisomerization of n-hexane on natural mordenite catalyst

A mordenite-containing rock sample from the Tokaj Mountains (Hungary) and its various forms modified by chemical treatment have been tested for catalytic properties during isomerization of n-hexane. Addition of Pt to the catalyst leads to a sharp decrease in the rate of cracking and in the rate of deactivation and this results in a catalyst of high selectivity for hexane isomers.

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The specific grain-boundary electrical resistivity of Ni

The purpose of the present study was to provide a reliable value for the specific grain-boundary resistivity ρ_SGBR of Ni metal. New results are presented on the room-temperature electrical resistivity of nanocrystalline (nc) Ni metal samples produced by electrodeposition with various grain sizes. These resistivity data were compared with previous reports on nc-Ni and all results were analysed according to the procedure of Andrews [Phys. Lett. 19, 558 (1965)] who found that the resistivity increment due to grain boundaries is proportional to the grain-boundary surface area per unit volume which is, on the other hand, inversely proportional to the grain size. It is pointed out that the grain size directly accessible by transmission electron microscopy imaging is the relevant parameter for the evaluation of ρ_SGBR whereas the crystallite size deduced from X-ray diffraction line broadening leads to an underestimation of ρ_SGBR because coherency-breaking intragrain defects not contributing significantly to the resistivity also cause a line broadening. From the evaluation of the nc-Ni resistivity data at room temperature, we find that 4.45·10^?16?Ω·m²?ρ_SGBR(Ni)??16?Ω·m² and our upper bound agrees exactly with the most recent calculated value in the literature.     

Coupled membrane process applied to fruit juice concentration

A coupled membrane process of membrane distillation and osmotic evaporation, where the solutions were thermostated separately at different temperatures, was developed. Enhanced water flux was obtained since the total driving force of the coupled process was higher than the sum of the driving forces of single processes. Apple, raspberry, sour cherry, red, and black currant juices were concentrated by the novel, mild technique. Presented at the 33rd International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 22–26 May 2006.     

Unique role of water content in enzymatic synthesis of ethyl lactate using ionic liquid as solvent

Enzymatic synthesis of ethyl lactate was studied in organic solvents and in ionic liquids to determine optimal media for the reaction, and to investigate the effect of water content on the ester yield. Experiments proved that Cyphos 202 ionic liquid is the best solvent affording the highest ethyl lactate yields. Furthermore, 20 times less enzyme sufficed to carry out the reaction in this ionic liquid compared to organic solvents; ionic liquid could be applied as solvent. Using water removal, the ester yield decreased since a side reaction, dimerization of lactic acid, occurred as well. In contrast to these results, without water removal, the produced water was partly consumed by the decomposition of lactoyllactic acid to free lactic acid, increasing thus the substrate concentration of the mixture and enhancing the ester yield.     

Superparamagnetic Relaxation in Nanocrystalline Fe80Zr7B12Cu1 Alloys

Nanocrystalline Fe₈₀Zr₇B₁₂Cu₁ alloys with different amounts and sizes of bcc precipitates were prepared by appropriate annealing of amorphous ribbons. The 6–10 nm ferromagnetic bcc granules are embedded in a residual amorphous tissue with a thickness at least 4 nm. Above room temperature superparamagnetic relaxation characteristic for small magnetic particles was observed with increasing temperature, as indicated by a significant increase in the width of the Mössbauer lines belonging to the bcc precipitates. It shows the absence of magnetic coupling which is stronger than the dipole-dipole interaction between the ferromagnetic nanoparticles.

     

Bestimmung der einzelnen Komponenten bei der Kondensationsreaktion von Chloral und Benzol

Ohne Zusammenfassung

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Determination of the single components in the condensation reaction of chloral and benzene

     

Quantum Interference Enhanced Chemical Responsivity in Single-Molecule Dithienoborepin Junctions

Providing a chemical control over charge transport through molecular junctions is vital to developing sensing applications at the single-molecule scale. Quantum-interference effects that affect the charge transport through molecules offer a unique chance to enhance the chemical control. Here, we investigate how interference effects can be harnessed to optimize the response of single molecule dithienoborepin (DTB) junctions to the specific coordination of a fluoride ion in solution. The single-molecule conductance of two DTB isomers is measured using scanning tunneling microscopy break-junction (STM-BJ) before and after fluoride ion exposure. We find a significant change of conductance before and after the capture of a fluoride ion, the magnitude of which depends on the position of the boron atom in the molecular structure. This single-molecule sensor exhibits switching ratios of up to four orders of magnitudes, suggesting that the boron–fluoride coordination can lead to quantum-interference effects. This is confirmed by a quantum chemical characterization, pointing toward a cross-conjugated path through the molecular structure as the origin of the effect.     

Über die Kinetik der durch Schwefelsäure katalysierten Reaktion von Chloral und Benzol

The kinetical parameters of 1-phenyl-1-hydroxy-2,2,2-trichloro-ethane and 1,1-diphenyl-2,2,2-trichloro-ethane production and the simultaneous sulphonation reaction were determined, taking into account the alteration of the reaction rate constants caused by the dilution of the sulphuric acid catalyst.