Synergistic extraction of lanthanum(III) from chloride medium by mixtures of 1-phenyl-3-methyl-4-benzoyl-pyrazalone-5 and triisobutylphosphine sulphide

The synergistic effect of 1-phenyl-3-methyl-4-benzoyl-pyrazalone-5 (HPMBP) and triisobutylphosphine sulphide (TIBPS, B) is investigated in the extraction of lanthanum(III) from chloride solution. Lanthanum(III) is extracted by the mixture as LaCl2.PMBP.B-0.5 instead of La(PMBP)(3).(HPMBP) which is extracted by HPMBP alone. The equilibrium constants and thermodynamic functions such as DeltaG, DeltaH and DeltaS are determined. The extraction of other rare earth ions by mixtures of HPMBP and TIBPS is also studied and the possibility of separating rare earth ions is discussed.

Promoter effects of rare earth ions on electrocatalytic oxidation of methanol

The promoter effects of rare earth ions on the electrocatalytic oxidation of methanol at the Pt electrode were studied using the cyclic voltammetry and stable polarization techniques. It was found for the first time that Eu, Ho, Dy ions could accelerate the electrocatalytic oxidation of methanol at the Pt electrode, while Lu, Pr, Yb, Sm ions showed inhibitor effects.

Study on adsorption and oxidation of calf thymus DNA at glassy carbon electrode

The oxidation and adsorption of the temperature-denatured DNA at GC electrode are studied by differential pulse voltammetry and in situ FTIR spectroelectrochemistry. The temperature-denatured DNA is adsorbed and formed a DNA multilayer at electrode surface. The temperature-denatured DNA showing partly reversible process was first observed based on the reduction peaks appearing at negative scans and the reversible spectral change. The oxidation product of the temperature-denatured DNA can not diffuse away from the electrode surface easily due to the impediment of the DNA multilayer, so it can be partly reduced.

Electrochemical and quartz crystal microbalance study for the electrochemical oxidation of 2-mercaptobenzimidazol

With the cyclic voltammetry and quartz crystal microbalance (QCM), the oxidation process and the electrodeposition behavior were studyied during the electrochemical oxidation of 2-mercaptobenzimidazol in aqueous solution. The E-pH diagram was also gained. These results showed the oxidation reaction was one electron reaction. The results from X-ray photoelectron spectrometry verified that the 2-mercaptobenzimidazol was oxidized to bisbenzimidazoyl disulfide.

Studies on electrocatalytic performance of titanium oxide electrode modified with Pt toward the oxidation of methanol

Electrocatalytic performance of the Pr-TiOx/Ti electrode prepared with electrochemical reduction-oxidation method toward the oxidation of methanol has been studied, The experimental results showed that the Pt-TiOx/Ti electrode has a high electrocatalytic activity and good stability for the electrocatalytic oxidation of methanol, By means of electrochemical, XPS, STM and in-situ FTIR techniques, it was found that one reason for the electrode to exhibit an excellent performance is attributed to the high dispersion between nanosized Pt and TiOx particles, The low adsorption ability of the intermediate derived from methanol, such as linearly adsorbed CO species on the electrode surface due to the interaction between Pt and TiOx, also results in the excellent performance.

Low-temperature oxidation of methane to form formaldehyde: role of Fe and Mo on Fe-Mo/SiO2 catalysts, and their synergistic effects

The partial oxidation of methane with molecular oxygen was performed on Fe-Mo/SiO2 catalysts. Iron was loaded on the Mo/SiO2 catalyst by chemical vapor deposition of Fe-3(CO)(12). The catalyst showed good low-temperature activities at 723-823 K. Formaldehyde was a major condensable liquid product on the prepared catalyst. There were synergistic effects between iron and molybdenum in Fe-Mo/SiO2 catalysts for the production of formaldehyde from the methane partial oxidation. The activation energy of Mo/SiO2 decreased with the addition of iron and approached that of the Fe/SiO2. The concentration of isolated molybdenum species (the peak at 1148 K in TPR experiments) decreased as the ion concentration increased and had a linear relationship with the selectivity of methane to formaldehyde. The role of Fe and Mo in the Fe-Mo/SiO2 catalyst was proposed: Fe is the center for the C-H activation to generate reaction intermediates, and Mo is the one for the transformation of intermediates into formaldehyde. Those phenomena were predominant below 775 K.

The development in oxidation of olefins to ketones catalyzed by palladium compounds

The development in the oxidation of olefins to ketones catalyzed by palladium compounds was reviewed. Some improved methods for the oxidation of olefins catalyzed by Wacker-type catalyst systems are also summarized. For this reaction, some new catalyst systems and the reaction mechanism are described. Emphasis has been given to the applications of Pd(I)/HPA(heteropoly acid), Pd(I)/FePc (iron phthalocyanine), Pd (I)/HQ (hydroquinone)/FePc, Pd (I)/HQ/HPA, Pd (I)/CuSO4/HPA catalyst systems in the oxidation of olefins to ketones; the application of Pd(I)/LCoNO2, PdCl2 (MeCN)(2)/CuCl, Pd(OAc)(2)/ pyridine, fluorous biphasic catalyst systems in the oxidation of olefins to ketones is also surveyed.

Oxidation of ascorbic acid by dopamine incorporated in mimetic biomembrane

A kind of mimetic biomembrane-cast lipid film was made onto a glassy carbon electrode. Dopamine can be incorporated into the film. The oxidation of 2.0 x 10(-3) mol/L ascorbic acid with dopamine in the film was investigated. The oxidation overpotential of ascorbic acid was reduced by about 260 mV.

Renewable manganous hexacyanoferrate-modified graphite organosilicate composite electrode and its electrocatalytic oxidation of L-cysteine

Manganous hexacyanoferrate (MnHCF) supported on graphite powder was dispersed into methyltrimethoxysilane-derived gels to yield a conductive composite, which was used as electrode material to construct a renewable three-dimensional MnHCF-modifed electrode. MnHCF acts as a catalyst, graphite powder ensures conductivity by percolation, the silicate provides a rigid porous backbone, and the methyl groups endow hydrophobicity and thus limit the wetting section of the modified electrode. Cyclic voltammetry was exploited to investigate the dependence of electrochemical behavior on supporting electrolytes containing various cations. The chemically modified electrode can electrocatalytically oxidize L-cysteine, and exhibits a distinct advantage of polishing in the event of surface fouling, as well as simple preparation, good chemical and mechanical stability, and good repeatability of surface renewal.

Effect of FePc structure on the activity in the oxidation of cyclohexene catalyzed by pd (OAc)(2)/HQ/FePc

In an acidic aqueous solution of acetonitrile, the catalytic activity of the catalysts consisted of Pd(OAc)(2)/hydroquinone(HQ) with iron phthalocyanine (FePc) from various sources was obviously different in the oxidation of cyclohexene to cyclohexanone, The analysis of the FePc using IR spectroscopy, Mossbauer spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), scanning electron microscopy(SEM) and BET surface area measurement indicated that the catalytic activity of the multicomponent catalytic system composed of iron phthalocyanines depends on the amount of mu -oxo FePc, the crystallinity and the surface structure of iron phthalocyanine.

In situ infrared spectroelectrochemical studies on adsorption and oxidation of nucleic acids at glassy carbon electrode

The adsorption and oxidation of yeast RNA and herring sperm DNA (HS DNA) at glass carbon (GC) electrode are studied by differential pulse voltammetry (DPV) and in situ FTIR spectroelectrochemistry. Two oxidation peaks of yeast RNA are obtained by DPV, whose peak potentials shift negatively with increasing pH. The peak currents decrease gradually in successive scans and no corresponding reduction peaks occur, thus indicating that the oxidation process of yeast RNA is completely irreversible. The IR bands in the 1200-1800 cm-l range, attributed to the stretching and ring vibrations of nucleic acid bases, show the main spectral changes when the potential is shifted positively, which gives evidence that the oxidation process takes place in the base residues. The oxidation process of HS DNA is similar to that of yeast RNA. The results both from DPV and in situ FTIR spectroelectrochemistry confirm that the guanine and adenine residues can be oxidized at the electrode surface, which is consistent with the oxidation mechanism of nucleic acids proposed previously. (C) 2001 Elsevier Science B.V. All rights reserved.

Surface-renewable cobalt(II) hexacyanoferrate-modified graphite organosilicate electrode and its electrocatalytic oxidation of thiosulfate

Cobalt(II) hexacyanoferrate (CoHCF) was deposited on graphite powder by an in situ chemical deposition procedure and then dispersed into methyltrimethoxysilane-derived gels to prepare a surface-renewable CoHCF-modified electrode. The electrochemical behavior of the modified electrode in different supporting electrolyte solutions was characterized by cyclic voltammetry. In addition, square-wave voltammetry was employed to investigate the pNa-dependent electrochemical behavior of the electrode. The CoHCF-modified electrode showed a high electrocatalytic activity toward thiosulfate oxidation and could thus be used as an amperometric thiosulfate sensor.

Synthesis and crystal structure of (1,3-(Bu2C5H3)-Bu-t)(2)Sm(mu-Cl)(2)Li(THF)(2)

Anhydrous SmCl3 reacts with two equal of Li(1-3-(Bu2C5H3)-Bu-t) to give a complex (1,3-(Bu2C5H3)-Bu-t)(2) Sm(mu -Cl)(2)Li(THF)(2) (C34H58Cl2LiO2Sm, M-r = 726.99), monoclinic, space group P2(1)/n, a = 10.615(2), b = 21.037(4), c = 17.166(3) Angstrom, beta = 93.60(3)degrees, V = 3825.7 (13) Angstrom (3), Z = 4, D-c = 1.262 Mg/m(3), mu = 1.699 mm(-1) and F(000) = 1508, final R = 0.0387 and wR = 0.0741 for 5320 observed[I greater than or equal to2 sigma (I)] reflections. The average Sm - C distance is 2.73 Angstrom. Sm - Cl1 and Sm - Cl2 distances are 2.719 (2) and 2. 697 (2) Angstrom, respectively. Two 1, 3-(Bu2C5H3)-Bu-t-ring centroids and two mu (2)-bridging chloride atoms around Sm atom form a distorted tetrahedron.