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.

A theoretical examination of known and hypothetical clathrate hydrate materials

The recent synthesis of a new hydrogen binary hydrate with the sH structure has highlighted the potential storage capabilities of water clathrates [T. A. Strobel, C. A. Koh, and E. D. Sloan, J. Phys. Chem. B 112, 1885 (2008) and A. R. C. Duarte, A. Shariati, L. J. Rovetto, and C. J. Peters, J. Phys. Chem. B 112, 1888 (2008)]. In this work, the absorption of hydrogen and the promoters used in the experimental work are considered using a simplified model for the host-guest interaction, which allows one to understand the stabilizing effects of multiple help molecules. Two further hypothetical clathrates, which are isostructural with known zeolite structures, are also investigated. It is shown that the energy gained by absorbing adamantane into these two frameworks is far greater than that gained upon absorption of adamantane into the sH structure. Hence, a clathrate with the same topology as the DDR (Sigma 1) zeolite may be synthesizable with adamantane and hydrogen as guest molecules as, in the conditions explored here, this phase appears to be more stable than the sH structure. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3142503]

Gas Hydrate Inhibition: A Review of the Role of Ionic Liquids

Ionic liquids (ILs) are popular designer green chemicals with great potential for use in diverse energy-related applications. Apart from the well-known low vapor pressure, the physical properties of ILs, such as hydrogen-bond-forming capacity, physical state, shape, and size, can be fine-tuned for specific applications. Natural gas hydrates are easily formed in gas pipelines and pose potential problems to the oil and natural gas industry, particularly during deep-sea exploration and production. This review summarizes the recent advances in IL research as dual-function gas hydrate inhibitors. Almost all of the available thermodynamic and kinetic inhibition data in the presence of ILs have been systematically reviewed to evaluate the efficiency of ILs in gas hydrate inhibition, compared to other conventional thermodynamic and kinetic gas hydrate inhibitors. The principles of natural gas hydrate formation, types of gas hydrates and their inhibitors, apparatuses and methods used, reported experimental data, and theoretical methods are thoroughly and critically discussed. The studies in this field will facilitate the design of advanced ILs for energy savings through the development of efficient low-dosage gas hydrate inhibitors.