The Preparation Of Fe/Mn-based Doping Nanomaterials And Catalytic Performance

This paper includes three main contents:monodispersed Mn-doped Fe2O3 nanostructures with shuttle-like nanostructure synthesized by solvothermal method,Mn3O4 doped with highly dispersed Zr species non-noble metal oxide nanostructure synthesized by solvothermal method and Fe-Mn-Zr magnetite nano-materials synthesized by method of precipitation.During the research process,we researched the influence of different methods,reaction time and temperature to the morphology transformation,growth mechanism,oxidation-reduction ability and oxygen storage capacity by a series of characteristic test methods.Besides,the finally samples were detected in CO catalytic oxidation test,CO+NO catalytic test and three-way catalytic test and the reaction condition of the composite metal oxide material which showed the best catalytic performance were confirmed.The full text aims at the control for synthesis of micro-and nano-structured(size,shape,etc)materials and characterization,and exploring effective methods for constructing micro-and nano-structured metal oxide materials with satisfactory catalytic performance.Facile synthesis of Mn-doped Fe2O3 nanostructures:enhanced CO catalytic performance induced by manganese dopingA facile solvothermal method has been employed to synthesize monodispersed Mn-doped Fe2O3 with shuttle-like nanostructure.The synthesis of the Mn-doped Fe203 nanostructures was carried out via a solvothermal method.In brief,Fe(NO3)3·6H2O(98.5 wt%)and polyvinylpyrrolidone(PVP,K30)were dissolved into 15 mL of N,N-dimethylformamide(DMF),and after stirring for a period of time,a certain amount of Mn(NO3)2 solution(50 wt%)was added to the homogeneous solution.After stirring for another 10 min,the mixture was transferred to a 25 mL Teflon-lined stainless steel autoclave,which was maintained at 180 ? for 24 h.Then the autoclave was spontaneously cooled to room temperature,the solid obtained was centrifuged and thoroughly washed with absolute alcohol six times sequentially.Finally,the products were dried at 60 ? overnight.We also synthesized samples withdifferent dosages of PVP for comparison.The structure of the samples was characterized by powder X-ray diffraction(XRD),transmission electron microscopy(TEM)and scanning electron microscope(SEM).Manganese species doped into the Fe2O3 lattice were then confirmed by Raman spectroscopy,X-ray photoelectron spectroscopy(XPS)and energy dispersive spectrometry(EDS).The test results showed Mn3+ was introduced into the lattice of Fe2O3 and promote the stable Fe-Mn-O structure.The doping of Mn ions led to the formation of the shuttle-like structure and increase of the surface area compared to pure Fe2O3.PVP also played an important role in the formation of the shuttle-like structure.The mechanism for the growth of Mn-doped Fe2O3 was proposed as the recrystallization of metastable precursors(RMP)route.H2-TPR measurement revealed better reduction behavior of the Mn-doped Fe2O3.Finally,the as-prepared Mn-doped Fe2O3(0.1 g PVP,180 ?and 24h)exhibited excellent catalytic performance and cycling stability towards CO oxidation.2.One-step synthesis of Zr-Mn3O4 non-noble metal nanostructure catalyst with enhanced activity for three-way catalysisZirconium-doped manganese oxides have been synthesized through a one-step solvothermal method.The Mn(CH3COO)2·4H2O were dissolved into 15 mL of DMF.Then Zr(NO3)4·5H2O and PVP(K30)were added into the solution.After stirring the above homogeneous solution for 30 min,the mixture was transferred to a 25 mL Teflon-lined stainless steel autoclave,which was maintained for 24 h at 180 ?.When the autoclave was cooled to room temperature,the final precipitates were collected and washed with absolute alcohol six times sequentially.As non-noble metal three-way catalysts(TWCs)for a CO+NO+C2H6 model reaction,the catalytic activities of the as-synthesized samples were evaluated.The samples showed satisfactory three-way catalytic performance.We explored the reason for improved catalytic performance by XPS,Raman spectroscopy and EDS-Mapping.Appropriate Zr4+ doping resulted in lattice distortion,leading to the exposure of more oxygen vacancies and a better oxygen storage capacity(OSC)and more oxygen vacancy than pure Mn3O4.Notably,the catalytic tests showed that the activities of thezirconium-doped samples are higher than that of pure Mn3O4.Furthermore,the ZM-2 sample(with a 20%Zr/Mn molar ratio)shows the best complete conversion of CO,NO and C2H6(nearly 100 ? lower than those of pure Mn3O4)and excellent anti-high temperature performance.3.Synthesis of Fe/Mn/Zr composite metal oxides by method of precipitation and their catalytic activity performance.Based on above researches,we synthesized Fe/Mn/Zr composite materials and applied to tail gas treatment.In the experiment,we prepared a certain concentration of FeCl3·6H2O water solution and kept under 50 ?.In the meantime,certain concentration of MnCl2·4H2O and Zr(NO3)4·5H2O mixed solution(HCl and H2O mixed in ratio of 4:1)were prepared.Then three solution were mixed under 50 ? and after stirring the above solution for 20 min,the mixture was transferred to 3M isopropanolamine solution at 90 ? in erlenmeyer and keep stirring for 2 h.When the erlenmeyer was cooled to room temperature,the final precipitates were collected and washed with absolute alcohol and water three times sequentially.Finally,the products were dried at 70 ? overnight.At last,the products were calcined at 500 ? for 3h under Ar atmosphere.The samples shows a satisfactory performance in CO+NO reaction,which is bedding for three-way catalysis.We compared physicochemical property between different samples through Raman,H2-TPR tests and determined a optimal doping metal ratio(Fe/Mn/Zr 2:2:1),which is conducive to the further research about influence of experimental condition and metal bond on three-way catalysis.