| Treatment of commercial liquid fuels for removal of heterocycles such as sulfur- and nitrogen-based compounds could be accomplished by selective adsorption processes. This dissertation presents the synthesis, characterization, performance and regeneration of pi-complexation sorbents for desulfurization and denitrogenation of transportation fuels (gasoline, diesel, and jet fuel). During pi-complexation, the thiophenic compounds can bind selectively to the sorbents, especially those with methyl substituents. The latter remain highly unreacted in hydrodesulfurization (HDS) (i.e. "refractory" sulfur). Molecular orbital (MO) calculations and experiments have shown that these refractory compounds (e.g., 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene) bind strongly with the pi-complexation sorbents because of a better electron donation/back-donation ability. The sorbents studied include Ag+, Cu+, Ni2+, and Zn2+ zeolites prepared using various ion exchange techniques. The copper(I)-based zeolites removed up to 12.6 milligrams of sulfur per gram of sorbent before breakthrough conditions occurred. The cuprous sorbents also produced fuels with a total sulfur content of less than 0.20 ppmw. Using the pi-complexation sorbents in layered beds matrices further increases the desulfurization capacity.; Denitrogenation is considerably more difficult than desulfurization because the organo-nitrogen compounds are much less reactive than the organo-sulfur compounds. This work shows that denitrogenation can be achieved effectively by also using pi-complexation sorbents. |
