Thermodynamic Analysis on Reaction Characteristics of the Coupling Steam, CO2 and O2 Reforming of Methane

This study presents an analysis of coupling steam, CO2 and O2 reforming of CH4 using the thermodynamic equilibrium constant method. Effects of molar ratio of O2/CH4, H2O/CH4 and CO2/CH4 on reforming characteristics in both carbon deposition and carbon-free systems are analyzed. The results indicate that CH4 conversion rate, H2, and CO yield increase with increasing O2/CH4 molar ratio in two systems. In addition, the carbon elimination is achieved when O2/CH4 ratio increases to 0.31, and changing the amount of O2 can be an effective way to alter n(H2)/n(CO) ratio in the carbon deposition systems. CH4 conversion rate increases with increasing H2O/CH4 ratio in the carbon-free system, while it declines in the carbon deposition system. H2O plays a role of altering n(H2)/n(CO) ratio, and its effects on two systems are opposite. The deposited carbon is totally eliminated when H2O/CH4 ratio increases to 0.645. The increase of CO2/CH4 molar ratio leads to a rapid increase of CO2 conversion when CO2/CH4 ratio is less than 0.5. A slightly change of CO2/CH4 ratio can result in a huge difference on n(H2)/n(CO) ratio in both systems, and carbon elimination is achieved at CO2/CH4 = 0.99. The analyzed results have theoretical significance to efficiently catalyze methane coupling.

An insight into thermodynamics of adsorptive removal of fluoride by calcined Ca–Al–(NO3) layered double hydroxide

A framework for determination of thermodynamic equilibrium constant and Gibbs free surface energy change was presented. The interactive effect of temperature on adsorption process was addressed by RSM. Endothermic, spontaneous reaction was observed.

Trace gas adsorption thermodynamics at the air−water interface: Implications in atmospheric chemistry

The thermodynamics of adsorption of gaseous organic compounds such as polycyclic aromatic hydrocarbons (PAHs) on water films is reviewed and discussed. The various experimental methods available to determine the thermodynamic equilibrium constant and the structure–activity relationships to correlate and estimate the same are reviewed. The atmospheric implications of the adsorption and oxidation of PAHs at the air–water interface of thin films of water such as existing in fog droplets, ice films, and aerosols are also enumerated.

Effect of Various Factors on the Sorption of Endosulphan on Two Indian Soils

The effects of exchangeable cations (H+ and Na+), organic matter, non-ionic and anionic surfactants, and temperature on the sorption of endosulphan on two different types of soils were studied. Adsorption studies were performed using the batch technique and adsorption isotherms for all effects/treatments were in close agreement with the Freundlich equation. The adsorptive capacity of endosulphan towards organic matter and clay content in the natural forms of both soils was also evaluated by calculating the corresponding values of the specific adsorption capacity for organic matter, Kom, and the clay content, Kc. Various thermodynamic parameters such as the thermodynamic equilibrium constant (K0), standard free energy changes (ΔG0), standard enthalpy changes (ΔH0) and standard entropy changes (ΔS0) have been calculated in order to predict the nature of the isotherms.

On N-acetylcysteine. Part I. Experimental and theoretical approaches of the N-acetylcysteine/H2O2complexation

The complexation of N-acetylcysteine (RSH) with hydrogen peroxide has been studied experimentally and theoretically. Experimentally we have measured the evolution of RSH, H2O2, and RSSR (N-acetylcystine) as a function of time. Surprisingly, H2O2 decays by a biphasic process, which is not the case for RSH and RSSR. In the first stage of the kinetics, H2O2 disappears without oxidizing the thiol function of RSH. By analogy with glutathione (GSH), the formation of a complex between RSH and H2O2 has been proposed. The thermodynamic equilibrium constant of complex formation has been determined. Theoretical calculations were performed within the SIBFA method to pinpoint the sites of complexation in isolated and hydrated states. A mixed "discrete–continuum" model was used to evaluate the solvent effect. The two stable complexes found in isolated state have different behaviour under the influence of the solvent. Comparison with complexed GSH is discussed.