Search results for " metal"

Electronics and Electromagnetism

2007

Mechanism of stereospecific polymerization of styrene with alkali metal alkyls

2007

Surfactant controlled preparation of mesostructured transition-metal oxide compounds

1994

The use of surfactants as templates allows the synthesis of mesostructured transition-metal oxides by a cooperative, interface controlled condensation process.

Steam-activated FeMFI zeolites. Evolution of iron species and activity in direct N2O decomposition

2003

Abstract In this paper the effect of the composition and steaming conditions of FeMFI catalysts on activity in direct N2O decomposition is investigated. MFI zeolites with different framework compositions (FeAlSi, FeGaSi, and FeSi) and without iron ( 100 mbar H2O in N2) favor the extraction of framework iron, enabling the application of lower activation temperatures. The optimum temperature during steam activation is that at which extraction of framework iron is complete without extensive clustering of extra-framework iron species into oxide particles, as was demonstrated by transmission electron microscopy and electrochemical characterization of the samples. Additional experiments show…

Influence of the preparation method on the thiophene HDS activity of silica supported CoMo catalysts

2002

Abstract The effect of the preparation method of CoMo/SiO2 catalysts with and without sodium ions, on the hydrodesulfurization (HDS) of thiophene was investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and N2 physisorption (BET). The samples were prepared by total sol–gel route, by classic wetness impregnation and by co-impregnation, in the presence of nitrilotriacetic acid (NTA), of commercial and sol–gel prepared silica. The influence of sodium ions added to the sol mixture and to the silica before the impregnation with Co and Mo salt solution, was also considered. The presence of sodium favoured the phase transition of amorphous silica to cristobalite with con…

The initial stages of the heterogeneous degradation of alkali cellulose by oxygen in relation to the morphology of native cotton cellulose

2007

Treatment of cotton cellulose with sodium hydroxide solutions of varying concentration over extended periods in the absence of oxygen markedly decreases the intrinsic viscosity of both the cellulose in cuoxam and its cellulose trinitrate derivative (CTN) in acetone. Light-scattering measurements show that the molecular weight does not change while the radius of gyration decreases and the second virial coefficient increases. The narrow molecular weight distribution of the native cotton is still maintained. Mild oxidation first causes the intrinsic viscosity to increase. At more prolonged oxidation times the viscosity decreases. These results are interpreted by an intramolecular cross-linking…

ChemInform Abstract: Synthesis of Tetrasubstituted 4,4′-Biimidazoles.

2012

Highly substituted 4,4′-biimidazoles were synthesized, in good to excellent yields, through a multicomponent imidazole ring synthesis by using imidazol-4-yl-ethane-1,2-diones as starting materials. The obtained compounds were preliminarily tested as chromogenic and fluorescent sensors for heavy metals.

Revision of Na 2 A1Σ+u state molecular constants by polarization labeling spectroscopy

1997

ABSTRACT. This paper contains the analysis of the A1 of Na2 based on the data obtained from thepolarization labeling spectroscopy experiment on the A' —X' transition. A set of Dunham coefficients is derived, which describes the A state in the wide range of v and J 126) quantum numbers and reproduces the positions of unperturbed rotational lines in the A-X band system towithinO.1 cm'.1. INTRODUCTION.We report' new analysis of the A' state based on the data obtained from polarization labelingspectroscopy (PLS) experiment"2, based on V-type optical—optical double resonance scheme, on the 1 : ' ; band system of sodium dimer. The diatomic alkali molecules, with their simple electronic configurat…

Transition metal ion induced hydrogelation by amino-terpyridine ligands

2014

Hydrogelation behavior of a new class of terpyridine based metallogelators are explored. The gelation and the gel morphology was found to be critically dependent on divalent metal ions, anions and on subtle structural changes on the gelator molecule.

PHOSPHORORGANISCHE VERBINDUNGEN 105.1Synthese chiraler und achiraler ditertiärer 1-Phosphino-2-Aminoethan-Derivate ([dbnd]P [sbnd]CH2[sbnd]CHR[sbnd]N…

1983

Abstract Primary amines with an optical active ligand add to vinyl- and propenylphosphonium salts according the reaction schemes (5) and (6), forming compounds of the type E and F. F contains a new asymmetric center in the bridge giving rise to the formation of a mixture of diastereomers, which can be resolved. Phosphonium salts of type E and F with a benzyl group on the phosphonium center are cleaved reductively by alkali amalgams (Li/Hg; Na/Hg; K/Hg) forming tertiary phosphines with an aminogroup in the β-position. The reductive cleavage with alkali amalgams is superior to the cathodic cleavage. Application: The synthesis of Ni(O)- and Pd(O)-complexes of type J fails. Bis-phosphine comple…