Catalytic Oxidatve Desulfurization Of Diesel Enhanced By Light Irradiation

The organosulfur compounds in diesel converts to SOx, during combustion of diesel. Theemission of SOxseriously affects the natural environment and human health. Therefore, mostcountries have established strict sulfur regulations to limit the sulfur content in diesel.Ultra-deep desulfurization of diesel has become an important subject for the petroleumrefinery industry. The conventional hydrodesulfurization process not only operates at hightemperature and high pressure, but also consumes large amount of hydrogen. So far, oxidationdesulfurization technology(ODS), which operates under mild reaction conditions and does notneed hydrogen, is considered to be one of the most promising technology.This work is mainly concerned with oxidative desulfurization (ODS) of diesel usingmolecular oxygen enhanced by light irradiation, and it aims to develop selective oxidativedesulfurization approaches to efficiently remove organosulfur compounds from fuels usingmolecular oxygen as the oxidant enhanced by light irradiation under mild conditions.Heterogeneous catalysts were synthesized, characterized, and evaluated for ODS. Theinfluencing factors on ODS were investigated,and the catalytic activities of catalysts for ODSwere studied.This work belongs to the fields of chemical reaction and separation science andis of important scientific interest to practical applications.A new approach to remove sulfur from diesel by two-step oxidation is proposed in thisthesis. The influences of reaction conditions on the in-situ generation of organic peroxides andperformances of ODS catalysts were investigated. Results showed that the increase ofreaction temperature and the employment of UV light greatly enhanced the generation rate ofperoxides.MoO3/SiO2showed higher performance than V2O5/SiO2and WO3/SiO2catalysts. Theoxidation of organosulfur compounds by peroxides and the self-decomposition ofperoxideswere main reaction and side reaction, respectively. On one hand, the catalyticactivity of the catalystfor the oxidation of organosulfur compounds increasedas increasingreaction temperature, and thus, the conversion of organosulfur compounds increased. On theother hand, the self-decomposition rate of peroxides became servereas the temperature increased further, and ultimately the utilization and the conversion of organosulfur decreased.The activity of the deactivated catalyst could be recovered by heat treatment at500℃in air,and after fourcyclic regeneration, the activity of the MoO3/SiO2catalyst kept almost the same.Photocatalytic oxidation desulfurizationusing Ti(1-x)SixO2wasstudied. Results showed thatover Ti(1-x)SixO2under light irradiation, organosulfur compounds could be oxidized tosulfoxides. Ti0.9Si0.1O2showed higher performance than Ti0.9Zr0.1O2andTi0.9Ce0.1O2. The Ti/Siratio of Ti(1-x)SixO2was optimized to be3:7to achieve the best desulfurization performance.The proposed approach was able to desulfurize86%sulfur in commercial diesel in one cycleand96.7%sulfur in two cycles under atmospheric pressure and room temperature.