Preparation Of New Complex Desulfurizers And Their Selective Removal For Thiophenes In Fuel Oil

The difficulty of desulfurization is the removal of fused ring thiophene sulfides,such as dibenzothiophene(DBT)and its alkyl derivatives(DBTs).The key to develop new desulfurizing agents is to improve their partition and separation selectivity for sulfides.For this,unique strong interaction between new desulfurizer and sulfides is necessary.In this paper,two kinds of complex desulfurizers were prepared,and their removal performance for benzothiophene(BT),DBT and 4,6-dimethyldibenzothiophene(DMDBT)in model oils were studied.First,four activated carbon supported sorbents(NBT/C,NDBT/C,NDBTO2/C and NDMDBT/C)were prepared by nitrifying the corresponding carbon loaded BT,DBT,DBTO2 and DMDBT with mixed acids of H2SO4 and HNO3,their composition and structure were characterized,and their adsorptive desulfurization performance were studied for the first time.The results show that there exists a strong interaction between NDBTO2 and DBT,forming a charge transfer complex.The adsorption isotherms of NDBTO2/C follow the Langmuir equation,with its saturated adsorbance being 87.4,10.6 and 8.3 mg-S·g-1,respectively for BT,DBT and DMDBT in model oils.The used sorbents can be regenerated easily by toluene/methanol washing,and 95%adsorptivity can be remained after four recycles.Second,considering the explosive risk of polynitrogen aromatic compounds,and their crystal structure for the extremely low adsorption rate,we expected to explore some new ?-acceptor materials without nitro groups,which can be dissolved in a solution and used as extractant for extractive desulfurization.Four extractants(NCS-ACN,NBS-ACN,NCP-ACN and NHS-ACN)were prepared by dissolving N-chlorosuccinimide(NCS),N-bromosuccinimide(NBS),N-chlorophthalimide(NCP)and Succinimide(NHS)in acetonitrile(ACN)to thir saturated solubility at 0?.Their complex desulfurization ability was characterized by UV-vis,and the desulfurization performance was studied.The results show that there exists a charge transfer complexation between(NCS?NBS)and(DBT?DMDBT),and the complex ability of NCS is higher than NBS.NCS shows excellent and rapid desulfurization ability.When the agent-oil ratio is 1,DBT or DMDBT in 1000 ?g-S·g-1 model oils can be almost completely removed,and the partition coefficients are 49.0 and 18.2,respectively.Further,the S-content of real diesel can be reduced from 7000?g·g-1 to 1994 ?g·g-1 after three consecutive extractions at a agent-oil ratio of 1.5.The partition coefficients of DBT and DMDBT between the dissolved NCS and model oil are 402.4 and 146.5,respectively,at equilibrium S-content of 50?g·g-1,which is 1?2 orders of magnitude higher than that of traditional adsorbents.The complex of NCS and DBT can be obtained by acetonitrile vaporization,and NCS can be reclaimed via dissolution of DBT by toluene.After 4 recycled uses,the desulfurization performance is still above 95%.In addition,some other complex desulfurizers were explored primarily.They include the complex of polyhalogenated aromatic hydrocarbons and Lewis acid,the ball milled products of polyhalohydrocarbon and CaC2,the ball milled products of transition metal oxides and CaC2,the non-coordinated transition metal salt solution of ionic liquids,and NDBTO2 dispersed in ionic liquid or active carbon.The complex desulfuration mechanism of the desulfurizers was analyzed and their desulfuration effect was studied.Such exploring study reveals the possible interaction mechanism between desulfurizer and thiophene sulfurs,which is of reference significance for the development of efficient complex desulfurizing agents in the future.