Adsorptive Denitrogenation Over Modified Zeolite Y And Bimetallic MOFs

Nitrogen-containing compounds(NCCs)in transportation fuels is one of the mainsources of air pollutants,it is particular important and necessary to remove NCCs from fuels at a deep level.Besides hydrodenitrogenation process(HDN)technique,adsorptive denitrogenation(ADN)is regarded as one of the promising alternatives and has been widely investigated to produce cleaner fuels,owing to the simple operation,no hydrogen consumption,and mild conditions.Nowadays,some metal ion-exchanged Y zeolites have been reported in removing basic NCCs by adsorption,and the adosorptive mechanisms have also been investigated.However,there are only limited studies on rare earth ion-exchanged Y zeolites in the field of ADN and the performance of adsorptive removal of neutral NCCs.This dissertation mainly studies the ADN performances of rare earth ions exchanged Y zeolites in terms of both static and fixed-bed adsorption experiments,and tries to modulate the pore structure of Y zeolite by sequential dealumination-desilication,combined with rare earth ions exchange,the effect of pore structure on ADN performance is investigated.In addition,this work also synthesizes bimetallic MOFs by introducing the second metal(Co2+or Ni2+)into the framework of HKUST-1 and studies the effect of the second metals on the ADN performance.Y(?)Y,Ce(IV)Y,La(?)Y are prepared by liquid-phase ion exchange method.Compared with Na Y,the crystal structure of the resultant rare earth ions exchanged Y zeolite adsorbents are mostly maintained,but the surface areas and pore volumes are greatly reduced.Both Lewis and Br?nsted acid sites are observed on YY,Ce Y and La Y.The static adsorption experiments show that YY,Ce Y and La Y,especially YY,display evidently higher ADN selectivity than Na Y in the model fuels containing 20 vol.% of toluene.No decrease in the adsorption capacity of YY is observed in the case of YY removing quinoline.The adsorption isotherms indicate that indole and quinoline adsorbed on Na Y and YY all fit Langmuir model.The Langmuir parameter b,which is the adsorption equilibrium constant,declines as follows:b(YY-Qui,9702 L·mol-1)>> b(Na Y-Qui)> b(YY-Ind)> b(Na Y-Ind,501 L·mol-1),indicating that the superior adsorption selectivity to quinoline of YY is related to the strong interaction between them.As for toluene adsorption,it is absorbed on Na Y and YY via ? electron interaction.The adsorption of toluene on Na Y doesn't fit Langmuir model,but that on YY does.The adsorption capacity of YY for toluene is much smaller than that of Na Y at the same equilibrium concentration.In the fixed-bed adsorption experiment,YY still shows muchhigher breakthrough capacity and better resistance to toluene than Na Y,especially in the case of removing quinoline.The pore structure of Na Y is modulated by sequential dealumination and desilication via EDTA and Na OH treatment.After Y3+ exchange,hierarchically structured YY zeolites are obtained.But unexpectedly,the static adsorption results don't show an improvement in ADN with the creation of large amount of mesopores.The possible reason is that,though the mosopore volumes are largely developed,the micropore volumes either increase or only slightly decrease in the three resultant hierarchically structured YY,therefore," the micropore filling effect" is almost unchanged.Bimetallic MOFs(Cu/Co-BTC and Cu/Ni-BTC)are synthesized by introducing the second metal in the framework of HKUST-1,the resultant Cu/Co-BTC and Cu/Ni-BTC have the same crystal structure as HKUST-1.The static adsorption experiments show that the ADN capacity of MOFs is related to not only the size of NCCs but also the interaction between MOFs and NCCs.Toluene has a significant effect on the denitrogenation capacity of MOFs.