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• 1. [Article] Deep desulfurization of diesel fuel using a single phase photochemical microreactor

  There is an urgent need to lower the concentration of sulfur in diesel fuels. Growing concern over environmental effects caused by burning sulfur-containing diesel has led the world to higher standards ...

  Citation × Citation Citation Abstract Copy Title: Deep desulfurization of diesel fuel using a single phase photochemical microreactor Author: Jones, Jacob Aaron There is an urgent need to lower the concentration of sulfur in diesel fuels. Growing concern over environmental effects caused by burning sulfur-containing diesel has led the world to higher standards in fuel refinement. Because of these lower standards, many techniques have been researched to remove sulfur containing compounds or otherwise reduce the sulfur content. Hydrodesulfurization remains the primary method to reduce most light sulfur-containing compounds. This process removes sulfides, sulfates, and thiols using high temperature and pressure reactions but is unable to remove aromatics and long chains containing sulfur molecules. Biodesulfurization has also been considered, utilizing microorganisms to target specific sulfur-containing compounds to remove the sulfur while leaving the high energy fuel intact. Oxidative reactions have also been considered including photocatalytic oxidation in an attempt to oxidize these aromatic compounds so that they may be removed using a polar solvent. An ultraviolet light assisted oxidative reaction occurring in a microreactor was studied. Dibenzothiophene was used as a model refractory organic compound mixed in Decane as a solvent. Dibenzothiophene undergoes a series of oxidative reactions which produce an intermediate, Dibenzothiophene Sulfoxide, and a final product, Dibenzothiophene Sulfone. This reaction only proceeds in the presence of Tert-Butyl Hydroperoxide and ultraviolet light. These reactions are reversible and an equilibrium is established between Dibenzothiophene, Dibenzothiophene Sulfoxide, and Dibenzothiophene Sulfone. The equilibrium is strongly affected by the molar ratios of the reactants. Increasing the molar ratio of Tert-Butyl Hydroperoxide to Dibenzothiophene reduces the concentration of Dibenzothiophene in the product stream or causes the reaction to shift its equilibrium towards the products. Equilibrium may not be affected by Temperature. Previous studies have shown that equilibrium concentrations have a temperature dependence. However, under the conditions of this research there was no indication of a temperature dependence. It is possible that because of the molar ratios used the reaction did not proceed appreciably regardless of temperature so the temperature dependence was not apparent. A Taylor dispersion apparatus was assembled to measure infinite dilution diffusion coefficients for Dibenzothiophene, Dibenzothiophene Sulfoxide, Dibenzothiophene Sulfone, and Tert-Butyl Hydroperoxide were measured. Values were close to those calculated using the Wilke-Chang equation. These coefficients along with measured absorption coefficients were important in developing an accurate mathematical model. A mathematical model was developed to include convective and diffusive flux, fluid transport, and reaction kinetics. COMSOL™ Multiphysics was used to numerically solve the mathematical model. Experimental data is fitted to the model to determine the reaction rate constants for each of the reversible reactions. The model was compared to previously reported data taken at 22°C and 40°C using a reactor thickness of 50 um and 100um. The model fit the data very well and can be implemented in predicting concentrations within the reactor. Title: Deep desulfurization of diesel fuel using a single phase photochemical microreactor Author: Jones, Jacob Aaron There is an urgent need to lower the concentration of sulfur in diesel fuels. Growing concern over environmental effects caused by burning sulfur-containing diesel has led the world to higher standards in fuel refinement. Because of these lower standards, many techniques have been researched to remove sulfur containing compounds or otherwise reduce the sulfur content. Hydrodesulfurization remains the primary method to reduce most light sulfur-containing compounds. This process removes sulfides, sulfates, and thiols using high temperature and pressure reactions but is unable to remove aromatics and long chains containing sulfur molecules. Biodesulfurization has also been considered, utilizing microorganisms to target specific sulfur-containing compounds to remove the sulfur while leaving the high energy fuel intact. Oxidative reactions have also been considered including photocatalytic oxidation in an attempt to oxidize these aromatic compounds so that they may be removed using a polar solvent. An ultraviolet light assisted oxidative reaction occurring in a microreactor was studied. Dibenzothiophene was used as a model refractory organic compound mixed in Decane as a solvent. Dibenzothiophene undergoes a series of oxidative reactions which produce an intermediate, Dibenzothiophene Sulfoxide, and a final product, Dibenzothiophene Sulfone. This reaction only proceeds in the presence of Tert-Butyl Hydroperoxide and ultraviolet light. These reactions are reversible and an equilibrium is established between Dibenzothiophene, Dibenzothiophene Sulfoxide, and Dibenzothiophene Sulfone. The equilibrium is strongly affected by the molar ratios of the reactants. Increasing the molar ratio of Tert-Butyl Hydroperoxide to Dibenzothiophene reduces the concentration of Dibenzothiophene in the product stream or causes the reaction to shift its equilibrium towards the products. Equilibrium may not be affected by Temperature. Previous studies have shown that equilibrium concentrations have a temperature dependence. However, under the conditions of this research there was no indication of a temperature dependence. It is possible that because of the molar ratios used the reaction did not proceed appreciably regardless of temperature so the temperature dependence was not apparent. A Taylor dispersion apparatus was assembled to measure infinite dilution diffusion coefficients for Dibenzothiophene, Dibenzothiophene Sulfoxide, Dibenzothiophene Sulfone, and Tert-Butyl Hydroperoxide were measured. Values were close to those calculated using the Wilke-Chang equation. These coefficients along with measured absorption coefficients were important in developing an accurate mathematical model. A mathematical model was developed to include convective and diffusive flux, fluid transport, and reaction kinetics. COMSOL™ Multiphysics was used to numerically solve the mathematical model. Experimental data is fitted to the model to determine the reaction rate constants for each of the reversible reactions. The model was compared to previously reported data taken at 22°C and 40°C using a reactor thickness of 50 um and 100um. The model fit the data very well and can be implemented in predicting concentrations within the reactor. Close