Catalytic oxidative desulfurization (ODS) of diesel fuel on a continuous fixed-bed reactor

The oxidative desulfurization (ODS) of model sulfur-containing compounds (thiophene, 2-methylthiophene, benzothiophene, 2-methylbezothiophene, dibenzothiophene, 4-methyldibenzothiophene, and 4,6-dimethyldibenzothiophene) with tert-butyl hydroperoxide on different metal-containing molecular sieves has allowed the study the role of the electronics and geometry of the reactant as well as the pore dimensions, topology, and adsorption properties of the catalyst on the rate of desulfurization. The best catalysts were then studied for the ODS of simulated and industrial diesel in a continuous fixed-bed reactor. MoOx/Al2O3 catalysts were active, but rapid deactivation occurs due to metal leaching and sulfone adsorption. Calcined Ti-MCM-41 was more active, did not leach Ti, and deactivated more slowly than MoOx/Al2O3. The amount of adsorbed sulfone was strongly reduced by decreasing the polarity of the Ti-MCM-41 by silylation, with the corresponding increase in catalyst activity and lifetime.