Study On Pr And Sm Modified Nickel-based And Copper-based Catalysts For Hydrogen Production From Methanol Steam Reforming

Methanol is the most simple achohol and can be widely available,it has high hydrogen to carbon ratio while its sulphur content(<5ppm)is low.Because of the abcence of C-C bond in molecule,the temperature for steam reforming of methanol(SMR)is low(200-350℃)and by-products could significant be reduced.Steam reforming of methanol provides fuel cells the high purity hydrogen with low content of CO and it is regarded as a promising hydrogen production technology.In the study of SMR,Ni is used for the ability of breaking C-C,O-H and C-H bonds,but the reaction temperature for Ni-based catalysts is high.Cu is also widely used in SMR for its high activity and high hydrogen selectivity.However,Cu has low metal stability,thus Cu-based catalysts are easily been sintered.In this thesis,the effects of Pr and Sm loading content on Ni-based and Cu-based catalysts were investigated,the influence of rare metal on structural propertiese of catalysts and corresponding relationship of structural propertiese and catalytic activity were analyzed by XRD,H2-TPR,XPS,Raman,TGA,O2-TPO,TEM and HAADF/STEM characterization.The primary results were samarized as follow:(1)The Ni/Al2O3 catalysts with different Pr loading content were prepared by incipient wetness method and the effects of Pr loading on Ni/Al2O3 catalyst were investigated.The catalytic acitivity of catalysts were improved when Pr loading content is lower than 12.5wt.%.the optimum loading content of Pr is 10wt%;The presence of Pr in Ni/Al2O3 catalysts resulted in the separation of NiO from NiAl2O4,increasing the amount of active Ni on the surface of catalysts and leading the formation of Pr6011@Ni/NiO sturcture,thus improving the catallytic stability;The amout of active carbon on Pr-containing catalyst is less than that on catalyst without Pr,indicating the effect of Pr to reduce the active carbon.(2)The effects of Sm on Cu/Al2O3 catalyst were also investigated.The catalytic activity decreased with the increase of Sm loading content in the steam reforming of methanol;The presence of Sm inhibited the reducibility of CuO which is not favorable for the formotion of Cu0;Sm led to the clustering of Cu on the surface of catalysts,thus increasing the particle size of Cu species and decreasing the amount of Cu surface area,leading to the decrease of catalytic activity.(3)The interaction between Sm loading content and catalytic activity of Ni/Al2O3 was investigated.Catalytic activity increased with the increase of Sm loading content;The presence of Sm in Ni/Al2O3 catalysts resulted in the separation of NiO from NiAl2O4,which is the same with Pr-containing catalysts,but the catalytic activity of Sm-containing Ni/Al2O3 catalysts are lower than that of Pr-containing Ni/Al2O3 catalysts when the loading content of rare-earth metal are higher than 12.5%;Catalysts impregnated for 12h has better catalytic activity compared with impregnated for Oh and 24h,and catalysts dried for 24h has better catalytic activity compared with dried for 4h.