Desulfurization of fuel oils is an essential process employed in petroleum refineries to reduce the sulfur concentration in fossil fuels in order to meet the mandated environmental protection limit of 10 ppm sulfur. The hydrodesulfurization (HDS) process, which is currently being employed for desulfurization, is limited in treating refractory organosulfur compounds as it only reduces sulfur content in fuels to a range of 200-500 ppm sulfur. Oxidative desulfurization (ODS) is considered a new technology for desulfurization of fuel oils as the process is capable of desulfurizing fuels to reach the ultra-low sulfur levels and can serve as a complementary step to HDS. The chapter discusses, briefly, the oxidation of refractory sulfur compounds found in fuels using vanadium as a catalyst to form organosulfones, a first step in ODS process. The chapter also discusses, in detail, the chemistry involved in molecular imprinting of organosulfones on functional polymers, and the electrospinning of the polymeric matrix to produce molecularly imprinted nanofibers employed for selective adsorption of organosulfones from the oxidized mildly hydrotreated fuels, a second step in the ODS process. Chemical interactions, apart from the imprinting effect, that can be exploited in molecularly imprinted polymers for selective extraction of organosulfones, such as hydrogen bonding, p-p interactions, van der Waals forces and electrostatic interactions, were discussed by employing density functional theory calculations. The possibilities of electrospinning on a large scale as well as prospects for future industrial applications of functional molecularly imprinted nanofibers in desulfurization are also discussed.
Advances in Oxidative Desulfurization of Fuel Oils over MOFs-Based Heterogeneous Catalysts
