Hydrodesulfurization thermodynamics

The thermodynamics of the hydrodesulfurization reaction has been evaluated from the equilibrium constants of typical desulfurization or partial desulfurization reactions such as ... 

The equilibrium constant does, however, decrease with increasing temperature for each particular reaction but still does retain a substantially positive value at 425°C (795°F) which is approaching the maximum temperature at which many of the hydrodesulfurization (especially nondestructive) reactions would be attempted. The data also indicate that the decomposition of sulfur compounds to yield unsaturated hydrocarbons and hydrogen sulfide is not thermodynamically favored at temperatures below 325°C (615°F) and such a reaction has no guarantee of completion until temperatures of about 625°C (1155°F) are reached. However, substantial decomposition of thiols can occur at temperatures below 300°C (570°F) in fact (with only few exceptions), the decomposition of all saturated... 

An interesting monolithic configuration has recently been disclosed that can be suitable for three-phase processes carried out in countercurrent mode [10]. This can be particularly important for processes in which both thermodynamic and kinetic factors favor countercurrent operation, such as catalytic hydrodesulfurization. The flooding of a reactor is a considerable limitation for the countercurrent process run in conventional fixed-bed reactors. Flooding will not occur to that extent in the new monolith. A configuration of channels of the new monolith is such that subchannels open to the eentcrline are formed at the walls. The liquid flows downward, being confined in these subchannels and kept there by surface tension forces. The gas flows upward in the center of the channel. The results of studies on the new monolith concept are presented in Chapter 11 of this book. 

Granados-Aguilar AS, Viveros-Garcla T, Perez-Cisneros ES (2008) Thermodynamic analysis of a reactive distillation process for deep hydrodesulfurization of diesel effect of the solvent and operating conditions. Chem Eng J 143 210-219... 

Chapter 9 focuses on the modeling of a bench-scale reactor in which hydrodemetallization and hydrodesulfurization of Maya crude oil is carried out. All of the aspects that need to be taken into consideration for modeling this type of reactor are described, such as stoichiometric coefficients, reaction rate coefficients, and transport and thermodynamic properties. 

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