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The purpose of this study is to test Runge-Kutta algorithm to obtain reliable kinetic parameters for the hydrothermal oxidation of organic compounds. A tubular reactor system was used to carry out the oxidation of several model compounds: acetic acid, methanol and phenol. All experiments were performed in isothermal conditions in a temperature range varying from 250ºC to 500ºC and at a constant pressure of 25 Mpa. Three different methods, namely pseudo first order kinetics, multiple linear regression and Runge-Kutta algorithm, were used to determine the kinetic parameters. Results obtained by these different methods were similar, so that Runge-Kutta algorithm was validate for the determination of kinetic parameters. In contrast with the pseudo first order kinetics and the multi linear regression, Runge-Kutta algorithm was more convenient for the kinetic parameter determination starting from experiments performed at the laboratory scale or in industrial scale pilot plant facilities.

The occurrence of sulfur deposits in natural gas transmission facilities has recently been observed. Only modeling approaches of this subject are available and suggest desublimation of sulfur as the mechanism responsible for the deposit. Quantification of the sulfur deposit is the first step to an experimental study of the phenomenon. The solid present on polluted pieces is recovered by solving it in a toluene bath. Thus, experimental data concerning sulfur solubility in toluene are necessary for the deposit quantification. The analytical method developed in this work is based on the chemical reaction between elemental sulfur and triphenylphosphine to produce triphenylphosphine sulfide. Gas chromatography (GC) coupled with a flame photometric detector (FPD) in phosphorus mode allows sulfur quantification indirectly. This analysis method is used for determining the solubility of sulfur in toluene under atmospheric pressure and temperature ranging from (267.15 to 313.15) K.