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Gas Evolution (gas + evolution)

Distribution by Scientific Domains

Chemistry	80%

Selected Abstracts

A New Optically Reflective Thin Layer Electrode (ORTLE) Window: Gold on a Thin Porous Alumina Film Used to Observe the Onset of Water Reduction

ELECTROANALYSIS, Issue 1-2 2004

Abstract The fabrication and unique characteristics of a new type of thin layer electrode, an optically reflective thin layer electrode (ORTLE), are described. The electrode was fabricated by the anodization of a thin layer of aluminum sputtered onto a plain glass microscope slide to create a 750,nm-thick porous alumina film. A thin film of gold was then sputtered atop the porous and transparent alumina film. The gold layer remained porous to allow solution into the pores but was optically thick and reflective. Reflectance measurements made through the microscope slide did not interrogate the bulk solution, but show spectral features that shift with the optical properties of the material filling the pores of the alumina film. A simple series of experiments, in which the potential of the ORTLE was stepped negatively to various values in an aqueous sodium sulfate solution, shows that interference fringes shift measurably in the ORTLE spectrum at potentials several hundred millivolts positive of the potential at which gas evolution was visible to the naked eye. [source]

Effect of gas evolution on mixing and conversion in a flow-through electrochemical reactor

AICHE JOURNAL, Issue 9 2009
Matthew A. Petersen
Abstract Flow-through electrolytic reactors (FTER) emplaced below the subsurface may be used to control the migration of groundwater contamination away from source zones. During prior studies with FTERs, water electrolysis and associated gas generation have occurred concurrently with contaminant degradation. Gas evolution-induced mixing within the electrode assembly has the potential to impact system performance. A mathematical model of the system was developed to capture the impact of mixing on transport processes in the system. Corresponding transient and steady-state tracer experiments using ferricyanide as a model contaminant were conducted to quantify mixing-dependent parameters and verify modeling results. Over a range of relevant groundwater flowrates, Peclet numbers were between 0.1 and 10, indicating that mixing was a important process under low-flow conditions. Comparison of experiments and model calculations demonstrated that incorporating gas evolution into the model was necessary for accurate performance prediction. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

Electrolytic pickling of duplex stainless steel

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 8 2005
N. Ipek
Abstract Pickling of duplex stainless steels has proved to be much more difficult than that of standard austenitic grades. Electrolytic pre-pickling is shown to be a key process towards facilitating the pickling process for material annealed both in the production-line and in laboratory experiments. The mechanism for the neutral electrolytic process on duplex 2205 and austenitic 316 steels has been examined and the oxide scale found to become thinner as a function of electrolytic pickling time. Spallation or peeling of the oxide induced by gas evolution did not play a decisive role. A maximum of about 20% of the current supplied to the oxidised steel surface goes to dissolution reactions whereas about 80% of the current was consumed in oxygen gas production. This makes the current utilisation very poor, particularly against the background of reports that in indirect electrolytic pickling only about 30% of the total current, supplied to the process, actually goes into the strip. A parametric study was therefore carried out to determine whether adjustment of process variables could improve the current utilisation. [source]

Synthesis of magnesium dicyclopentadienide catalyzed by titanium and vanadium derivatives,

APPLIED ORGANOMETALLIC CHEMISTRY, Issue 3 2001
Stanislav V. Maslennikov
Abstract Synthesis of magnesium dicyclopentadienide from metal and cyclopentadiene in THF is effectively catalyzed by the derivatives of vanadium and titanium. The kinetics of the synthesis, as well as thermodynamic parameters of reagents adsorption on the magnesium surface, have been determined. The process catalyzed by titanium derivatives is accompanied by the quantitative hydrogenation of cyclopentadiene to cyclopentene whereas the catalysis by vanadium derivatives leads to hydrogen gas evolution. A number of reaction intermediates including Cp2TiCl, Cp2TiH2MgCl, Cp2Ti(cyclo-C5H7) and Cp2V, were identified by the electron spin resonance method. The equilibrium constants, enthalpies and entropies of adsorption of metal halides on the magnesium surface were calculated. Copyright © 2001 John Wiley & Sons, Ltd. [source]