Determination of the surface area of dispersed ruthenium by reactive nitrous oxide chemisorption

The interaction of nitrous oxide with ruthenium surfaces was studied in order to develop a fast and reliable method for the determination of the metallic surface area and dispersity of ruthenium catalysts as alternative to the established chemisorption methods using hydrogen, carbon monoxide or oxygen as probe molecule. Studies of the temperature dependence of the reactive or dissociative chemisorption of nitrous oxide using pulse technique showed that an oxygen monolayer of almost constant stoichiometry is formed in a narrow temperature range around 403 K. However, so-called ‘rest nitrogen peaks' were observed after saturation of an O-monolayer revealing a small additional nitrous oxide conversion which could be attributed to formation of subsurface oxygen by means of back-titration of the oxygen totally uptaken. This additional nitrous oxide consumption can be minimised by an adjustment of both the N₂O-sampling loop volume and the catalyst sample weight in order to obtain an oxygen monolayer saturation by few pulses, and moreover, it can be considered as a correction for the calculation of the oxygen monolayer. A specific nitrous oxide consumption of 13.5 μmol/m²_Ru has been determined on ruthenium black by means of alternating measurements of the nitrogen physisorption and N₂O-pulse chemisorption. The reliability of the new method for characterisation of the dispersity or surface area of supported ruthenium was proved with ruthenium highly dispersed on γ-alumina.     

Solubility of Natural Gas in Diesel Fuel

The solubility of commercially available natural gas in commercially available diesel fuel at room temperature and defined pressure is investigated experimentally. The gas phase is considered to be pure methane. The use of Henry's law to model the solubility is discussed. Solubility is given in terms of the mole fraction and the volumetric mass concentration of dissolved gas and the corresponding Henry's coefficients. The solubility is compared to that of pure methane in pure hexadecane, which is similar to diesel fuel with respect to the mean carbon number.     

Mechanism and Kinetics of some Reactions on Silica-Alumina Catalysts

The dehydration of alcohol when its vapor is led over alumina, or some other heterogeneously acting catalysts, is already known from the end of the eighteenth century.     

Transition Metal Ion Photoluminescence as a Technique for the Study of Structures of Oxidic Catalysts

The use of spectroscopic techniques in the study of catalysts is rapidly increasing and has given a stimulus to research in catalysis. All techniques, however, are of restricted applicability; for example, ESR, NMR, reflection spectroscopy, and X-ray electron spectroscopy. Often a number of techniques have to be applied to give the full answer to a problem. The same is true for the technique under discussion in this paper. Luminescence spectroscopy can be helpful for a certain number of systems but is far from being generally applicable. It is, however, specific in the sense that it can solve certain problems, especially in oxidic catalysts, which are very difficult to solve with other techniques.     

EXTRACTION OF COPPER,CADMIUM AND RELATED METALS WITH POLY(SODIUM ACRYLATE - ACRYLIC ACID)HYDROGELS.

ABSTRACT

The extraction of copper, cadmium and related metals (M²⁺) with poly(sodium acrylate - acrylic acid) PAA hydrogels has been studied. pH variations are consistent with a cation exchange process. Saturation of the gel is achieved for a metal/carboxylate ratio R ≈ 1/2 and a gel swelling of ≈ 40 which is that of the uncharged gel : (-COO)₂M complexes are expected to be formed, but also complexes of higher stoichiometry (R = 1/3 for Cu and Cd, R = 1/4 for Pb) at low metal concentrations. The selectivity is that observed in liquid-liquid extraction of metal cations with fatty carboxylic acids (Pb > Cu > Cd > Zn > Ni ≈ Co). Metal stripping from the gel is readily achieved by washing with 0.1 M HNO₃. PAA hydrogel extraction allows to remove cadmium from a diluted aqueous solution down to a final concentration of 5 ppb.     

TBITALEBT ACTINTDES AND LAHTHANIDES USING 1-PHENEYL-3METHYL-4BENZOYL-PYRAZOLONE-5(HPMBP)

ABSTRACT

A solvent aztraotion method based on the preferential extraction of Bc(lll) by 1-phsnyl-,V-methyJ.-4-benzoyl-pyrazolona-5 (HPHBP) has oeen devised for the separation and purification of Sic from otner trivalent aotinides and Ianthanidee. A single ayole purification of Bk(lH) from most of the impurities is obtained by this method An alternate method of purification of BK has been given using extraction chromatography with HEMBP impregnated oelite columns herein decontamination factors of ～10 are obtained from other trivalent aotinidesi ianthanidee and inactive impurities ilka Fe,Cr,Al,Ni For Ce(III) a decontamination faotor of ～60 is obtained     

Cation Exchange Equilibria with Chromium (III) Species by Strong Acid Ion Exchangers

The exchange of hydrogen ions for trivalent chromium species with strongly acidic exchange resins has been investigated. The experiments comprised of systems with chromium chloride and basic chromium sulphate which are applied in leather tanning. Exchange equilibria at ambient temperature were investigated as a function of pH and total chromium concentration. Exchange strongly depends on the speciation in each system. As can be expected, with chromium chloride solutions a strong preference of chromium species occurs. However, a complete pattern is found for systems with basic chromium sulphate where chromium species are not fully preferred.