KINETICS OF CORROSION OF RUTHENIUM DIOXIDE HYDRATE BY CEIV IONS

The kinetics of oxidative dissolution of RuO2 .xH2O to RuO4 by Ce(iv) ions are studied. Under conditions of a low [Ce(iv)] : [RuO2 .xH2O] ratio (e.g. 0.35 : 1) and a high background concentration of Ce(III) ions (which impede dissolution) the initial reduction of Ce(iv) ions is due to charging of the RuO2 .xH2O microelectrode particles. The initial rate of charging depends directly upon [RuO2 .xH2O] and has an activation energy of 25 +/- 5 kJ mol-1 Under conditions of a high [Ce(iv] : [RuO2 .xH2O] (e.g. 9 : 1) and a low background [Ce(III] the reduction of Ce(iv) ions is almost totally associated with the dissolution of RuO2 .xH2O to RuO4, i.e. not charging. The kinetics of dissolution obey an electrochemical model in which the reduction of Ce(iv) ions and the oxidation of RuO2 .xH2O to RuO4 are assumed to be highly reversible and irreversible processes, respectively, mediated by dissolving the microelectrode particles of RuO2 .xH2O. Assuming this electrochemical model, from an analysis of the kinetics of dissolution the activation energy for this process was estimated to be 39 +/- 5 kJ mol-1 and the Tafel slope for RuO2 .xH2O corrosion was calculated to be 15 mV per decade. The mechanistic implications of these results are discussed.

Solubility of carbon dioxide, ethane, methane, oxygen, nitrogen, hydrogen, argon, and carbon monoxide in 1-butyl-3-methylimidazolium tetrafluoroborate between temperatures 283 K and 343 K and at pressures close to atmospheric

Experimental values for the solubility of carbon dioxide, ethane, methane, oxygen, nitrogen, hydrogen, argon and carbon monoxide in 1-butyl-3- methylimidazolium tetrafluoroborate, [bmim][BF4] - a room temperature ionic liquid - are reported as a function of temperature between 283 K and 343 K and at pressures close to atmospheric. Carbon dioxide is the most soluble gas with mole fraction solubilities of the order of 10-2. Ethane and methane are one order of magnitude more soluble than the other five gases that have mole fraction solubilities of the order of 10-4. Hydrogen is the less soluble of the gaseous solutes studied. From the variation of solubility, expressed as Henry's law constants, with temperature, the partial molar thermodynamic functions of solvation such as the standard Gibbs energy, the enthalpy, and the entropy are calculated. The precision of the experimental data, considered as the average absolute deviation of the Henry's law constants from appropriate smoothing equations is of 1%. © 2005 Elsevier Ltd. All rights reserved.

Selective methane bromination over sulfated zirconia in SBA-15 catalysts

Methane activation via bromination can be a feasible route with selective synthesis of mono-bromomethane. It is known that the condensation of brominated products into higher hydrocarbons can result in coking and deactivation in the presence of di-bromomethane. In this study, selective production of methyl bromide was investigated over sulfated ZrO2 included SBA-15 structures. It was observed that the higher the ZrO2 amounts the higher the conversion, while the catalyst remained >99% selective for the monobrominated methane. Over 25 mol.% ZrO2 included SBA-15 catalyst with a BET surface area of 246 m(2)/g, methane was brominated with 69% conversion at 340 degrees C and only CH3Br was selectively produced. (C) 2009 Elsevier B.V. All rights reserved

Methane to higher hydrocarbons via halogenation

Activation of methane with a halogen followed by the metathesis of methyl halide is a novel route from methane to higher hydrocarbons or oxygenates. Thermodynamic analysis revealed that bromine is the most suitable halogen for this goal. Analysis of the published data on the reaction kinetics in a CSTR enabled us to judge on the effects of temperature, reactor residence time and the feed concentrations of bromine and methane to the conversion of methane and the selectivity towards mono or dibromomethane. The analysis indicated that high dibromomethane selectivity is attainable (over 90%) accompanied by high methane conversions. The metathesis of dibromomethane can provide an alternative route to the conversion of methane (natural gas) economically with smaller installations than the current syn-gas route. (c) 2005 Elsevier B.V. All rights reserved.