Oxidative Desulfurization Of Liquid Fuel Using Molecular Oxygen

Deep desulfurization of fuels has become very urgent task for petroleum refiningindustry due to strict environmental regulations to limit sulfur contents. Traditionaldesulfurization technology in refinery is hydrotreating, which operates at high temperatureand pressure, and consumes large amount of hydrogen. The petroleum refinery industy isfacing a major operational and economical challenge to develop highly efficientdesulfurization technologies.This work is mainly concerned with oxidative desulfurization (ODS) of liquid fuelsusing molecular oxygen, and it aims to develop selective oxidative desulfurization approachesto efficiently remove organosulfur compounds from fuels using molecular oxygen as theoxidant under mild conditions. Heterogeneous catalysts were synthesized, characterized, andevaluated for ODS. The influencing factors on ODS were investigated, and the catalyticactivities of catalysts for ODS were studied. This work belongs to the fields of chemicalreaction and separation science and is of important scientific interest and practicalapplications.A new acetonitrile extraction-ozone oxidation approach for ODS was proposed. Resultsshowed that the ODS reaction by ozone was zero-order reaction, and the O3diffusion stepfrom gas-phase to liquid-phase was the rate-determining step. Acetonitrile acted as theextractant and the reaction solvent which could not only selectivily extract organosulfur fromdiesel but also enhanced the reactivity of dibenzothiohenes. The proposed approach was ableto desulfurize commercial diesel from1450μg/g to50μg/g, and the sulfur removal reached97%with fuel loss less than1%.The ODS with carbon nanotube as the catalyst under atmospheric pressure and lowtemperature was studied. Results showed that carbon nanotube was an effective catalyst forODS with molecular oxygen as the oxidant, and its catalytic performance was200-fold higherthan Co3O4/γ-Al2O3and MnO2/γ-Al2O3reported in the literature. Raman spectroscopyanalysis revealed that the CNT with the higher degree of graphitization had higher catalyticactivity for DBT oxidation The deactivated CNT can be effectively regenerated by heattreatment under an argon atmosphere at900°C. After five recycling, the activity of carbonnanotube decreased only4%.ODS of jet fuel using in-situ generated peroxides over CuO-ZrO2-TiO2catalyst with airas the oxidant was studied. The generation rate of peroxides was higher over supported CuOcatalyst than bulk CuO. However, over supported CuO catalyst, the induction time for peroxide formation was longer, and the the induction time increased by decreasing the poresize of catalyst. The higher the peroxides concentration was, the higher the sulfur conversionwas. The proposed approach was able to desulfurize jet fuel from485μg/g to25μg/g with theODS conversion of95%.ODS using in-situ generated peroxides in diesel by light-irradiation was proposed. Theinfluencing factors on the peroxides generation and the catalyst activity for ODS in dieselwere studied. Results showed that the kinetics of peroxide generation in diesel could beimproved by the employment of UV irradiation. Accompanying the main ODS reaction withhydroperoxides over MoO3/SiO2catalyst in diesel, the side reaction of peroxideself-decomposition occurred, and the kinetics increased dramatically with the reactiontemperature. To achieve a high ODS conversion, the reaction temperature can be optimizedbalancing the thermodynamics and kinetics of the two coexisting competing pathways ofperoxides. The larger pore size of MoO3/SiO2facilitated the diffusion of bulky refractorysulfur compounds in diesel over the catalyst, and ultimately it led to the increase of sulfurremoval and utilization of peroxides.A new desulfurization approach by photocatalytic oxidation coupled with adsorptionusing bi-functional Ti(1-x)SixO2was proposed. Results showed that over Ti(1-x)SixO2under lightirradiation, organosulfur compounds could be oxidized to sulfoxides, which was furtheradsorbed on Ti(1-x)SixO2. The Ti/Si ratio of Ti(1-x)SixO2was optimized to be3:7to achieve thebest desulfurization performance. The proposed approach was able to desulfurize commercialdiesel from220μg/g to31μg/g under atmospheric pressure and room temperature.