| Sulfur-containing compounds in transportation fuels can be converted to SOx through combustion,which not only result in corrosion and acid rain,but also make noble metal catalysts poisoned for reducing SOx emissions,which led to emitting more amount of carbon monoxide,hydrocarbons,nitrogen oxides and particulate matter.Thus,the development of the efficient desulfurization process to produce clean transportation fuels has attracted much attention in both academic and industry.The oxidative desulfurization(ODS)is one of the more promising catalytic desulfurization method.ODS technology is based on the catalytic oxidation of organic sulfur compounds as the core of a deep desulfurization technology,usually in combination with extraction or adsorption.Polyoxometalates(POMs)have high catalytic activity,good selectivity in the mild conditions,the characteristics of anti-corrosion equipment,showing excellent oxidation desulfurization catalytic performance,thus have attracted much attention.POMs have many important properties.They can act as acid,redox or bifunctional catalysts.The catalytic activity of POMs can be adjusted by changing the composition and structure,and thus they have been widely explored in the field of catalytic oxidation.Especially,transition metal substituted polyoxometalates(TM-POMs),similar to metal porphyrin compound,have good catalytic activity and excellent ability to store large amounts of electrons.POMs are well soluble in polar solvent.Although they exhibit high catalytic activity and high efficiency in homogeneous catalysis system,the catalysts is difficult to separate and recycle,which seriously limits their application in laboratory and industry application.Therefore,design and synthesis of new efficient recyclable POMs catalysts for practical application are very urgent.In this paper,a series of transition metal substituted Keggin type heteropolymolybdates with different counter cations have been prepared and characterized by the elemental analysis,IR,XRD,DRS,TG and SEM.With 30%H2O2 as oxidant,catalytic oxidation desulfurization of model oil containing refractory sulfur compounds,dibenzothiophene(DBT),benzothiophene(BT),and 4,6-dimethyldibenzothiophene(4,6-DMDBT),have been investigated.The insoluble salts of transition metal mono-substituted phosphomolybdatesCs5[PMo11M(H2O)O39](CsPMo11M,M = Co,Zn,Ni,Mn)were prepared,and used as heterogeneous catalysts applicating in deep desulfurization with H2O2 as the oxidant and acetonitrile as the extractant.In optimum conditions,simulated gasoline 5 mL(500 ppm DBT),n(catalyst)= 4 ?mol,n(H2O2)/n(DBT)= 5,t = 60 min,T= 50?,the desulfurization rate of CsPMo11M can achieve above 97%,and CsPMo11M catalysts exhibit more excellent catalytic performance than CsPM012 and CsPMo11.The organic ionic liquid-encapsulated transition metal mono-substituted phosphomolybdate anion[Bmim]5[PMo11M(H2O)O39]([Bmim]PMo11M)have been prepared,and used in catalytic desulfurization using the imidazoles ionic liquids as the extractant and hydrogen peroxide as oxidant.The results show that[Bmim]PMo11M can obtain a desulfurization rate of 100%under milder conditions and shorter time than CsPMo11M.The optimum reaction condition is:ionic liquid[Omim]BF4 as extraction agent(1 mL),simulated gasoline 5 mL(500 ppm DBT),n(catalyst)= 4 ?mol,n(H2O2)/n(DBT)= 5,t= 60 min,T = 50?.The order of the catalytic activity of transition metal substituted compounds is Co>Zn>Ni = Mn and CsPMo11Co exhibit the highest activity with almost 100%of the desulfurization efficiency.In addition,the vanadium substituted sulphurmolybdate(tungstate)catalysts have been prepared,and preliminarily explored their catalytic oxidation desulfurization performance.The results show that the vanadium substituted sulphurmolybdate showed higher catalytic activity than the catalysts of CsPMo11M and[Bmim]PMo11M.The optimum reaction condition is:[Omim]PF6 as extraction agent(1 mL),simulated gasoline 5 mL(500 ppm DBT),n(catalyst)= 2 ?mol,n(H2O2)/n(DBT)= 5,t = 30 min,T=35?. |
PDF Full Text Request