Effect Of Second Metal Component On Desulfurization Performance Of CeY Zeolite Sorbent

Thiophene contained in coking benzene could cause catalyst poisoning and equipment corrosion,and thus severely limits the subsequent utilizaton of coking benzene.Therefore,the deep removal of thiophene from coking benzene is crucial.Adsorption desulfurization has the advantages of low operating cost,mild operating conditions,low environmental pollution,high desulfurization efficiency,and has received wide attention from researchers.Y-type zeolite is widely used for thiophene adsorption,because of its suitable three-dimensional pore structure,large specific surface area,large amount of surface acidity,and excellent ion exchange performance.Previous study have shown that CeY sorbent obtained from the cerium-modified Y zeolite has high adsorption selectivity for thiophene in benzene,but its thiophene adsorption capacity needs to be further improved.The thiophene adsorption capacity of sorbents modified by transition metals is higher,but its thiophene selectivity is poorer.While the thiophene adsorption capacity and selectivity of bimetallic modified sorbents are both higher.Therefore,CeY sorbent requires to be modified by a second metal.Based on this,CeY zeolite was prepared in this thesis and transition metals of Cu,Ni and Ag were selected as the second metal component to modify it,and three kinds of bimetallic modified sorbents were prepared.The adsorption desulfurization activity of sorbents was evaluated by static adsorption experiments.The influences of metal ion exchange sequence and metal precursor solution on desulfurization performance of sorbents were investigated.The sorbents were characterized by XRD,N₂ adsorption,NH₃-TPD,H₂-TPR,XPS and ICP to reveal the reason why the desulfurization efficiency of bimetallic sorbents is higher than that of single metal sorbents,the reason for the synergetic effect between bimetals.The intrinsic mechanism of metal ion exchange sequence and metal precursors'influence on desulfurization performance of bimetallic sorbents are also discussed.The results obtained are shown as follows:?1?When the ratio of simulated solution to sorbent is 10 mL/g,the selectivity order of bimetallic modified sorbents for thiophene in thiophene-benzene solution is:Cu CeY>Ni CeY>AgCeY,which is consistent with the orders of total acid amount and ion exchange degree of sorbents.The desulfurization efficiency of CuCeY sorbent is the highest,reaching 97.3%.?2?The synergistic effect between Cu and Ce in CuCeY sorbent makes its desulfurization efficiency higher than the sum of CuY and CeY desulfurization efficiency.The reason for the synergistic effect between Cu and Ce is probably attributed to the following factors:the Ce ions in the CeY sorbent could affect the location of Cu ions in the copper modification process,resulting that most of the Cu ions locate in the supercages;the transfer of electrons from Ce ions to Cu ions changed the electronic environment of Cu ions,so that the redox reaction of Ce³⁺and Cu²⁺occurred during the calcination process,resulting in the formation of more Ce⁴⁺and Cu⁺,thereby favoring the adsorption of thiophene.?3?The ion exchange degree of sorbent obtained with different ion exchange sequence is different,and the order is Cu CeY>CeCuY>Cu-CeY and NiCeY>CeNiY>Ni-CeY,which is consistent with the desulfurization efficiency of sorbent in the thiophene-benzene solution.?4?When the ratio of simulated solution to sorbent is 14 mL/g,among the CuCeY_S,CuCeY_A and CuCeY_N sorbents prepared with precursors of CuSO₄,Cu?Ac?₂ and Cu?NO₃?₂,the total acid amount and ion exchange degree of CuCeY_A sorbent are the highest,so its desulfurization efficiency is the highest,up to 88.4%.Then,copper ammonia solutions were prepared by the above three cupric salts.Among the NCuCeY_S,NCuCeY_A and NCu CeY_N sorbents prepared by copper ammonia solutions,the total acid amount and the ion exchange degree of NCuCeY_N sorbent are the largest,so its desulfurization efficiency is the highest,reaching 88.9%.The Cu CeY sorbents prepared by copper ammonia solutions have higher ion exchange degree than CuCeY sorbents prepared by copper salt solutions,so their desulfurization efficiency is higher.When the copper source is copper ammonia solutions,Cu?NH₃?₄²⁺mainly react with-OH of CeY sorbent and fall,while a small amount of Cu?NH₃?₄²⁺was ion exchanged with Na⁺.