Preparation And Performance Of Ceria-based Catalysts For Steam Reforming Of N-dodecane

As an important way to hydrogen production,steam reforming of liquid hydrocarbon fuels such as n-dodecane has received significant attention.Apart from hydrogen production,steam reforming of n-dodecane for hypersonic vehicle thermal protection has also drawn significant attention.In this work,we chose n-dodecane as model molecular representative compounds of aviation kerosene and study the relationship with catalysts preparation,structure and property in n-dodecane steam reforming.Physical states and chemical properties of the as-synthesized catalysts or spent catalysts have been characterized by XRD,nitrogen adsorption-desorption,H₂-TPR,thermal gravimetric analysis?TG-DTA?,scanning electron microscopy?SEM?,TEM techniques,X-ray photoelectron spectroscopy,Raman spectra,UV-vis spectra,TPH/TPO and other characterization methods.The effects of the performance were investigated in aspcets of different active specie,alloying effects,amount of ceria,calcining temperatures,reaction condition?reaction temperatures,ratio of H₂O/C,liquid hourly space velocity?LHSV??on ceria promoted Ni-Co/Al₂O₃ bi-metal catalysts for n-dodecane steam reforming.The results show that bi-metal Ni-Co catalyst has higher activity than mono-metal catalysts.What's more,ceria-promoted catalysts show higher conversion of n-dodecane and less coke deposition than that un-promoted.The improvement in the performance of n-dodecane steam reforming was ascribed to the enhancement of Ni dispersion on alumina and the acceleration of coke gasification via redox,which has been achieved by Ni-Co alloying and CeO₂ promotion.What's more,higher reaction temperature and ratio of H₂O/C and lower LHSV results to higher conversion of n-dodecane.Further,effects of Ni-Co alloying and ceria promoted Ni-Co/SBA-15 catalyst were investigated.The results show that metal particles are highly dispersed in the mesopores channel of SBA-15.The improvement in the performance of n-dodecane steam reforming was ascribed to alloying of Ni-Co and smaller metal particle size?7.4nm?.Moreover,ceria promoted Ni-Co/SBA-15 show much higher activity and stability,and for 6 wt%of ceria promoted show the highest performance?n-dodecane conversion increase by 10%,and coke deposition reduce by 20%?.This could be ascribed to the smallest size of Ni-Co?6.4 nm?.Based on the above,ceria-promoted Ni-Pt/SBA-15 catalysts were prepared and amounts of Pt and ceria were investigated.The results show that Pt could effectively reduce the reduction temperature of catalysts and enhance lower temperature performance.Moreover,ceria-promoted Ni-Pt/SBA-15 catalysts show much higher activity and stability in lower temperature.But the stability of the catalysts is not so good.In order to exploration the mechanism of cerium oxide on performance of steam reforming.Ceria and Tb ion doped ceria material were prepared via urea-assisted deposition method.And these supported Pt catalyst were prepared by sodium carbonate deposition.The results show that Tb doped ceria supported Pt catalyst exhibite much higher activity and stability than ceria supported Pt catalyst.The improvement in the performance of n-dodecane steam reforming was ascribed to Tb doped into lattices of ceria could highly enhance oxygen vacancies.The activity and stability of catalysts could positively be correlated with the number of oxygen vacancies.This results show that coke deposition could effectively elimination by oxygen vacancies.