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Water Dissociation (water + dissociation)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

ChemInform Abstract: Hydrogen Production by Water Dissociation in Surface-Modified BaCoxFeyZr1-x-yO3-, Hollow-Fiber Membrane Reactor with Improved Oxygen Permeation.

CHEMINFORM, Issue 41 2010
Heqing Jiang
Abstract A BaCoxFeyZr1-x-yO3-, hollow-fiber membrane is surface modified by a catalytically active BaCoxFeyZr0.9-x-yPd0.1 O3-, porous layer. [source]

Cation-Enhanced Deprotonation of Water by a Strong Photobase

ISRAEL JOURNAL OF CHEMISTRY, Issue 2 2009
Noga Munitz
We have used picosecond fluorescence spectroscopy to study the proton-dissociation dynamics of bulk water and H2O molecules solvating Mg2+ ions in aqueous solutions. We have analyzed the photo-initiated proton-transfer reaction to a photobase 6-aminoquinoline by the Collins-Kimball approach and have modeled the ensuing bimolecular reaction dynamics by the Smoluchowski equation with radiation boundary conditions. We have found the on-contact proton transfer rate to follow the Marcus free-energy relation for proton transfer and estimate by this rate-equilibrium correlation the considerable enhancement in the acidity of the water molecules solvating the Mg2+ ion. Our findings may be used in the study of metallo-enzymes such as carbonic anhydrases (CAs), which catalyze the reversible addition reaction of OH, to CO2 by increasing the reactivity of the zinc-bound water molecules by means of stabilizing the product of water dissociation, the OH, anion. [source]

Support-dependent activity of noble metal substituted oxide catalysts for the water gas shift reaction

AICHE JOURNAL, Issue 10 2010
Parag A. Deshpande
Abstract The water gas shift reaction was carried out over noble metal ion substituted nanocrystalline oxide catalysts with different supports. Spectroscopic studies of the catalysts before and after the reaction showed different surface phenomena occurring over the catalysts. Reaction mechanisms were proposed based upon the surface processes and intermediates formed. The dual site mechanism utilizing the oxide ion vacancies for water dissociation and metal ions for CO adsorption was proposed to describe the kinetics of the reaction over the reducible oxides like CeO2. A mechanism based on the interaction of adsorbed CO and the hydroxyl group was proposed for the reaction over ZrO2. A hybrid mechanism based on oxide ion vacancies and surface hydroxyl groups was proposed for the reaction over TiO2. The deactivation of the catalysts was also found to be support dependent. Kinetic models for both activation and deactivation were proposed. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source]

Modeling continuous electropermutation with effects of water dissociation included

AICHE JOURNAL, Issue 9 2010
Carl-Ola Danielsson
Abstract The repeating unit consisting of a cell pair of one concentrate and one feed compartment of an electropermutation stack is modeled. Both the feed and the concentrate compartments are filled with an ion-exchange textile material. Enhanced water dissociation taking place at the surface of the membrane is included in the model as a hetrogeneous surface reaction. Results from simulations of nitrate removal for drinking water production are presented and comparisons with previous experimental results are made. The influence of both conductive and inert textile spacers on the process is investigated via simulations. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source]

X-ray-induced debromination of nucleic acids at the Br,K absorption edge and implications for MAD phasing

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2002
E. Ennifar
Multi-wavelength anomalous dispersion (MAD) using brominated derivatives is considered a common and convenient technique for solving chemically synthesized nucleic acid structures. Here, it is shown that a relatively moderate X-ray dose (of the order of 5 × 1015,photons,mm,2) can induce sufficient debromination to prevent structure determination. The decrease in bromine occupancy with radiation dose can be accounted for by a simple exponential, with an estimated rate constant at the absorption-peak wavelength, 7.4,(0.8),MGy, that is not significantly different from its value at the absorption-edge wavelength, 9.2,(2.6),MGy (the given e.s.d.s assess the relative closeness of the two values, not their absolute accuracy, which is probably worse). Chemically, these results (and others) are consistent with bromine cleavage resulting from direct photodissociation and/or from the action of free electrons, rather than from the action of hydroxyl radicals originating from water dissociation. The free bromine species (Br,) diffuse too quickly, even in amorphous ice around 100,K, to allow the determination of a diffusion coefficient. From a practical point of view, it is suggested that a single data collection with a crystal consisting of iodinated instead of brominated derivatives could provide both anomalous scattering and SIR phase information by the progressive cleavage of iodine. [source]