| In recent years,the processing ratio of high sulfur content crude oil in China has been increasing year by year.In addition,Chinese environmental protection requirements have been increased and the control of sulfur content in fuel oil is also more stringent.The adsorption desulfurization technology not only has mild operation conditions,but also can effectively remove thiophene sulfide compounds in oil products,and it has no effect on the quality of oil products.Therefore,the adsorption desulfurization technology has a broad application research prospect.In this paper,the microporous,multistage aperture?with microporous and mesoporous structure? and integral multistage aperture ZSM-5 zeolites were synthesized by hydrothermal synthesis method.The ZSM-5 zeolites doping Ce and Ni were prepared by the method of the direct hydrothermal.The structural characterization of ZSM-5 materials was conducted through FT-IR,XRD,N2-adsorption,SEM and NH3-TPD.And doping different metal ion to modity ZSM-5 zeolites to adsorption desulfurization performance was studied.Moreover,the effects of the calcination temperature,the adsorbent oil ratio,the metal ion doping amount and the initial concentration of the model oil were discussed on the desulfurization performance.At the same time,the influence of doped different metal ions and silica alumina ratio of zeolites on the structure and desulfurization effect of ZSM-5 zeolite was studied.The adsorption mechanism of metal ion modified ZSM-5 zeolites was deduced by the kinetics and thermodynamics study of adsorption desulfurization.The results are obtained through experiments:?1?different metal ion modified zeolites as adsorbent,the adsorption result is mesoporous zeolite?integral multistage aperture zeolite>microporous zeolite;?2?Multistage pore ZSM-5 zeolite doping different metal ions,the desulfurization effect of Ce and Ni ion modification are better than Cu and Fe ion modification.And the desulfurization were the best when the doping amount of Ce and Ni is 1.3 wt%and 0.6 wt%respectively;?3?Within the scope of the experiment,the best roasting temperature Ce-ZSM-5 and Ni-ZSM-5 zeolite adsorbent is 400?and 500?respectively,the initial concentration of the model oil was 500 mg/L,The ratio of adsorbent and oil is 0.15 g/10 mL;?4?The results of N2-adsorption,FT-IR and NH3-TPD showed that part of the metal ions into the zeolite skeleton make its dielectric distributed volume increases in the form of Mesoporous hole,and part of the Ce,Ni metal ions loading on the zeolite surface lead to strong sour center.The mesoporous channels of zeolite are beneficial to the diffusion of thiophene molecules.On the surface of the zeolite,the strong acid and acid center ions are beneficial to the adsorption of alkaline thiophene molecules.The above two aspects make Ce and Ni modified ZSM-5 zeolites have better adsorption and removal of thiophene.The results of kinetic studies showed that the pseudo-n-order kinetic equation can describe the adsorption desulfurization process of Ce/Ni-ZSM-5 zeolite to thiophene.The adsorption rate constant expression of Ce-ZSM-5 zeolite adsorption desulfurization was obtained by determining the K value fitting of the adsorption isotherm.The adsorption rate constant expression of Ce-ZSM-5 is kCe=3.6×10-1exp?-6.0×102/T?;The adsorption rate constant expression of Ni-ZSM-5 is kNi=3.1×10-1exp?-4.0×102/T?.Under30?,the adsorption kinetics equations of both are:qt1=2.8×10-1-(1.2×10-2t+1.4)-4,qt2=2.7×10-1-(4.3×10-2t+1.9)-2respectively.The apparent adsorption activation energy of both is 5.074 kJ/mol and 3.304kJ/mol respectively.The thermodynamic study showed that the adsorption desulfurization process of the Ce-ZSM-5 zeolite was the endothermic process,and its adsorption enthalpy is 13.599 kJ/mol;The adsorption desulfurization process of the Ni-ZSM-5 zeolite is the exothermic process,and its adsorption enthalpy is 6.38kJ/mol. |
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