Synthesis Of Imidazolium Based Ionic Polymers And Their Adsorption Desulfurization Performance For Thiophenic Sulfur In Fule Oil

The combustion of sulfide in the fuel oil can produce sulfur oxides(SOx),resulting in the smog,acid rain and other air pollutions,so deep desulfurization has increasingly become an important research content.Conventional hydrodesulphurization(HDS),which is widely used in the industry,is effective for the removal of mercaptan,sulfur ether,disulfide ect.,but less efficient for thiophenic sulfurs even in the harsh operating conditions.Therefore,extraction desulfurization(EDS)and adsorption desulfurization(ADS)technologies with simple operation and mild conditions have attracted much attention in recent years.At present,the extraction desulfurization based on ionic liquids(ILs)extractant is prosperous,but its extraction ability is far from satisfactory due to their lower extractability,for example,the partition coefficient of DBT is limited in the range of 0.5?2 for the majority of ILs reported.In order to improve desulfurization performance of ILs,and remove the bottleneck of "liquid" attribute of ILs for their molecular design,synthesis of the polymerized ILs(PILs or ionic polymer)may be an optional solution,because PILs retain the EDS ability of the ILs monomer and have rich micro/mesoporosity that can further improve their desulfurization ability.By using N-vinyl imidazole(VIM)as raw material,several ionic polymers with different composition and structure were synthesised,their ADS performance was studied for model oils,and the tunning methods of their structure and composition were explored.The main work of this thesis is as follows:(1)By using DMF as solvent,VIM and 4-chlorine methyl styrene(VBC)as monomers,and AIBN as free radical initiator,three kinds of ionic polymers were successfully prepared,namely P(VIM-VBC)-1,P(VIM-VBC)-2,P(VIM-VBC)-3,through simultaneous polymerization and quatermization,dripping VBC into prepolymerized VIM,and polymerization of the quaternized ionic monomer,respectively.Their composition,structure,morphology,specific surface area and thermal stability were characterized in terms of Infrared spectrum(IR),solid 13CNMR,elemental analysis,scanning electron microscopy(SEM),N2-adsorption,and thermogravimetry,and their ADS performance was investigated also.The results show that the P(VIM-VBC)s are of mesoporous materialres with their specific surface area being 171.3 m2·g-1,869.5 m2·g-1 and 26.6 m2·g-1 respectively;their TGA curves are similar with starting thermal decomposition temperature of 250 ?,and P(VIM-VBC)-3 shows the best thermal stability.Their adsorption capacity for DBT in model oil follows the order P(VIM-VBC)-1?P(VIM-VBC)-2>P(VIM-VBC)-3.The adsorption selectivity of P(VIM-VBC)-1 for different thiophene sulfides follows the order DBT>BT>4,6-MDBT>T.The used sorbent can be regenerated easily through ethanol washing,and reused with good adsorption performance.(2)By using DMF as solvent,AIBN as initiator,VIM,VBC and DVB as monomers,highly crosslinked ternary copolymers P(VIM-VBC-DVB)were prepared.Their composition,structure,morphology,specific surface area and thermal stability was characterized by IR,solid 13CNMR,elemental analysis,SEM,N2-adsorption,and thermogravimetry,and their ADS performance was investigated.The results show P(VIM-VBC-DVB)with mole ratio 2:2:1 for VIM,VBC and DVB shows the best ADS performance,and its specific surface area is about 256 m2·g-1,average pore size is 2.32 nm,starting thermal decomposition at about 340 ?.Its adsorption selectivity for different thiophene sulfides follows the order DBT>BT>T,adsorption isotherm follows the Freundlich mode,and adsorption capacity being 8 mgS·g-1 for the initial S-concentration of 1000 ppm DBT model oil.The standard Gibbs free energy of the adsorption process was negative,and the adsorption capacity decreases with rising tempertaure.Moreover,a highly crosslinked copolymer HCP(VIM-VBC-DVB)was gotten through Friedel-Crafts alkylation reaction of P(VIM-VBC-DVB)by methylal in 1,2-dichloroethane solvent,it is fluffy with smaller particle size,but its adsorption capacity for DBT was slightly reduced rather than enhanced in comparison with its precurser.(3)Methods of tunning composition and structure of ionic polymers was explored and the ADS performance of the resultant sorbents was analyzed.Frist,some ternary copolymers P(VIM-VBC-DVB)were synthesised by simultaneous polymerization and quaternization,and highly crosslinked ionic polymers HCP(VIM-VBC-DVB)were derived from P(VIM-VBC-DVB)via intermolecular Friedel-Crafts alkylation.Compared to P(VIM-VBC-DVB),the ADS ability of HCP(VIM-VBC-DVB)is enhanced greatly,and HCP(VIM-VBC-DVB)-1 with monomer mole ratio of 2:3:1 shows the best ADS performance with its adsorption capacity being about 11 mgS·g-1 for the 1000 ppmS DBT model oil.Second,mesoporous and highly crosslinked methyl chloride resins,HCP(DCX)or HCP(BCMBP),were synthesized through intermolecular alkylation condensation of DCX or BCMBP,which were further quaternized by PVIM,forming polymeric ionic sorbents HCP(DCX)-PVIM and HCP(BCMBP)-PVIM.The results show that modification of HCP(DCX)and HCP(BCMBP)by PVIM can not enhance their adsorption capacity for DBT.The adsorption capacity of HCP(DCX)-PVIM and HCP(BCMBP)-PVIM is between 7-9 mgS·g-1 for DBT model oil.Third,we synthesized several kinds of complex compounds by using the complexation between imidazoles and Lewis acids,but their adsorption ability for DBT is weak.This may be attributed to the lost Lewis acidity of the metal ions,since their Lewis acid sites or unoccupied d-orbitals have been coordinated with the N atoms of imidazoles,thus their complexing ability with S of DBT disappear.Finally,the ADS performance of ionic polymers with imidazole anion was investigated.The results show that after ion exchange of chloride by imidazole anion,the ADS ability of the resultant ionic polymers does not increase but decrease slightly,this may be due to the decreased porosity of the sorbents and the limited contribution of imidazole anion for the enhancement of the desulfurization.To sum up,in order to further improve the ADS performance of the ionic polymer or PILs,the key lies in controlling pore structure,specific surface area,and introduce special function groups which show specific interaction with S-atom,whereby the adsorption capacity and selectivity of the sorbents for thiophenic sulfurs can be enhanced greatly.