Research Of Catalytic System Towards Deep Desulfurization Of Diesel Fuel

Extensive use of sulfur-containing fuels causes serious environmental problems such as acid rain and haze/fog events.Ultra deep desulfurization for production of clean fuel is the keynote in refining industry.Oxidative desulfurization?ODS?is widely considered as one of the most promising methods to obtain ultra-low S-content fuels due to its low energy consumption and high selectivity.In this work,towards the development of efficient catalystic systems for ODS,a series of functionalized ionic liquids?ILs?and various organic-inorganic hybrid polyoxometalate-based catalysts were proposed with H₂O₂ as an oxidant.The catalytic activity,stability as well as the reaction mechanism were systemiticly investigated.Extraction conbined with oxidative desulfurization?ECODS?with acidic functional ILs as both the extractants and catalysts is a promising ODS technology.In this research,a class of amide-based ILs and protonated N-octylcaprolactam-based Br?nsted-Lewis acidic ILs[Hnoc]Cl/nZnCl₂ were designed and synthesized.The detailed structure and conformation of ions were investigated by different techniques as well as theoretical calculation.Systemitic experiments for the ODS of model oil were carried out to investigate the influence of some important factors,including reaction temperature,molar ratio of H₂O₂/S,ILs dosage,initial S-content and sulfide species.The ILs exhibited excellent ODS performance and good reusability.Real diesel was also used to evaluate its desulfurization performance.The results of GC-PFPD before and after each ECODS process indicated that almost all the original S-compounds in diesel had been converted to their corresponding oxidation products.The desulfurization performance was actually restricted by extraction capability.The efficient catalytic mechanisms of both kinds of ILs were proposed based on the characterizations and theoretical analyses.The ionic self-assembly between polyoxometalates?POMs?and multivalent cations possesses potential applications in many fields.The multivalent electrostatic interaction is the key in the formation of unique and stable nano-structure.Based on the multivalent electrostatic interaction,a kind of interlinked thin-layer nanowires mesoporous catalysts was constructed through the co-assembly of POMs and cationic polymer under the steric guidance of functional groups.As a further exploration,rigid nanowire catalysts were constructed through the three-dimensional ionic self-assembly of double-valent cation and POMs.Various of charicterization methods were employed to investigate the construction form,analyze the structural feathers and reveal the formation mechanism of those organic-inorganic hybrid polyoxometalate-based catalysts.As is clearly evidenced by the experimental results,whether or not a catalyst possess catalytic activity is closely related to the formation pathway of activated species.The firmly embedding of polyanion in the polymer matrix is responsible for the stability of POMs.As for the desulfurization of real diesel,it was observed that almost all of the original sulfur compounds in diesel could be completely converted and a further solvent extraction with methanol as extractant led to the deep sulfur removal.The catalyst could at least be reused for many times without noticeable changes in catalytic performance and chemical structures.In the end,the catalytic mechanisms of Mo₈O₂₆^4-and H₂W₁₂O₄₂^10-were put forward with the assistant of Raman analysis.