| Sulfur-containing compounds(SCCs)and nitrogen-containing compounds(NCCs)are major impurities in conventional energy fuels and the presence of these impurities seriously affects the quality of the fuel.A large amount of sulfur oxides(SOx)and nitrogen oxides(NOx)are released,when the fuel containing SCCs and NCCs is burned,causing serious problems such as air pollution,water pollution,and global warming.Therefore,countries over the world have attached great importance to the removal of sulfurs and nitrogen in fuels.Adsorption desulfurization(ADS)and adsorption denitrogenation(ADN)is considered as one of the most promising process and has attracted much attention of scientific researchers due to the numerous remarkable advantages such as mild operation conditions,low energy consumption,no need of hydrogen or oxygen,pollution-free and environment friendly nature compare to trasitional desulfurization and denitrogenation technology.MOFs are widely applied in ADS and ADN rencent years,because of their intrinsically high porosity,large specific surface area,easy control of structure the pore and open active site and large porosity.(1)MIL-101 and MIL-101-NH2 were obtained by hydrothermal method,the sulfonate-containing MIL-101-NH2-(CH2)3-SO3H were obtained by post synthetic modification(?51%-NH2 were transformed into-NH-(CH2)3-SO3H)and the MIL-101-NH2-(CH2)3-SO3Ag were obtained by modifying-SO3H with sliver ions(-47%-SO3H were transformed into-SO3Ag).The newly prepared two kinds of MOF materials were characterized through FT-IR,PXRD,SEM and EDS,proving that the sulfonic acid group and silver ions were successfully modified,and the overall structure of the obtained MOFs were not changed.(2)Benzothiophene(BT)and dibenzothiophene(DBT)were selected as representative SCCs,and ND and quinoline(QUI)were selected as the representative NCCs.The ADS and ADN performances of these MOFs were compared and studied in detail.In this dissertation,the time,temperature,initial SCCs/NCCs content,oil/agent ratio and other factors were investigated for the four types of MOFs.Under optimal reaction conditions(reaction time 2h,reaction temperature 30 ?,oil ratio m(oil)/m(adsorbent)400/1),the ADS/ADN capabilities of these MOF materials are approximately as follows:MIL-101<MIL-101-NH2<MIL-101-NH-(CH2)3-SO3H<MIL-101-NH-(CH2)3-S03Ag,indicating modifications of-NH2,-SO3H and-SO3Ag all contributed to the improvement of adsorption performance.Among them,the adsorption capacities of MIL-101-NH2-(CH2)3-SO3Ag for BT,DBT,IND and QUI under optimal conditions were:113.51,152.67,356.52,and 344.72 mg/g,respectively.In addition,the depth desulfurization and denitrigenation performances of these MOFs were also investigated.MIL-101-NH2-(CH2)3-SO3Ag could reduce the BT and DBT of 35 ppms to 6.20 and 5.35 ppmws,and the IND and QUII of 35 ppmN to 1.91 and 3.20 ppmwN.MIL-101-NH2-(CH2)3-SO3H and MIL-101-NH)-(CH2)3-SO3Ag could still maintain a large amount of adsorption denitrigenation capacity when the same amount of BT were added into model oil for adsorption.The remained adsorption amounts of IND was about 7.82 and 8.68 times than the adsorption amounts of BT,indicating that the MOFs modified with-SO3H and-SO3Ag had excellent selectivity for the adsorption of NCCs.(3)The adsorption mechanism was further investigated by adsorption thermodynamics and adsorption kinetics.The results further confirmed that the modification of-SO3H and-SO3Ag greatly improved the ADS/ADN performances.In addition,adsorption thermodynamic results showed that the AG values were all negative,indicating that the adsorption was a spontaneous process.(4)Finally,we tested the recycling performances of these MOFs.They could be recycled after 5 cycles by simple solvent eluent regeneration,keeping close to 90%of initial ADS/ADN capacities. |
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