The Oxidative Desulfurization Of Liquid Fuel By Metal Phthalocyanine

The value attached to environmental protection by many countries has brought to stringent regulations on sulfur content in fuels.Ultra-deep desulfurization of fuel is very challenging all over the world.Hydrodesulfurization?HDS?is the prevailing technology for the removal of sulfur-containing compounds in petroleum refining.However,the operation of HDS requires high temperature and pressure.Besides,HDS is highly efficient for the removal of aliphatic and acyclic sulfur compounds,but not of aromatic thiophenes and thiophene derivatives.In order to achieve ultra-deep desulfurization,the development of new approaches is necessary.Porphyrin complexes are widely used by nature in the active sites of enzymes.It is well known that enzymes can efficiently and selectively oxidize the target substances under ambient conditions.However,their use presents main drawbacks: their poor chemical stability and high cost.Phthalocyanine metal complexes?MPc's?,structurally resembling porphyrin complexes,are attractive not only because of their chemical and thermal stability but also due to their convenient synthesis.Therefore,we designed a biomimetic catalytic system composed of iron hexadecachlorophthalocyanine(FePcCl₁₆),H2O2,H2 O and pyridine.First of all,we synthesized the catalyst FePcCl₁₆.And the structure of synthesized FePcCl₁₆ was investigated using ATR-FIIR and UV-vis.Secondly,various experiments was done for studying the factors of this catalytic reaction.The reaction conditions were as follows: V?model oil?= 5 m L,V?H2O?= 10 mL,n?O/S?= 40,m?catalyst?= 15 mg,n?catalyst/pyridine?= 1:100,T = 30°C.Under the above conditions,the conversion of dibenzothiophene?DBT?could reach 100% for 1 h.Moreover,the activation energy evaluated through Arrhenius' equation was found to be equal to 25.5 KJ/mol,indicating that this catalytic system allowed the reaction to happen with a low energetical input.In addition,the desulfurization system can be recycled up to 23 times without a noticeable decrease in activity.Finally,we investigated mechanism of catalytic oxidation of DBT.Mechanistic studies revealed that the high-valent iron?IV?-oxo species were the main active intermediate via the heterolytic O-O bond cleavage of the putative iron?II?-hydroperoxo species.Pyridine binding to iron?II?-hydroperoxo complexes was demonstrated to facilitate the generation of high-valent iron?IV?-oxo species and enhance the reactivity of high-valent iron?IV?-oxo species in ODS.Finally,we investigated the oxidative denitrogenation of liquid fuel by FePcCl₁₆.And acridine,one of nitrogen-containing compounds,could also be removed from liquid fuel by FePcCl₁₆.