Structure-property Relationship Of Ni-based Catalysts In Dry Reforming And Bi-refoming Of Methane

Ni-based monometallic and bimetallic catalysts were prepared and applied to dry reforming of methane(DRM)and bi-reforming of methane(combined steam and dry reforming of methane,CSDRM)in this thesis.First,the effects of preparation method,support material and promoter(La)content on DRM over Ni-based monometallic catalysts were investigated.The results showed Ni/SBA-15 prepared by urea precipition method had high DRM activity and anti-sintering property,but with poor anti-coking property.The doping of Ni/SBA-15 with a certain amount of La promoter can,to some extent,prevent the carbon deposition on catalyst.In particular,Ni-La/SBA-15 with 5 wt%of La loading showed the best DRM performance.Next,a series of Ni-Co/SBA-15 bimetallic catalysts with constant metal loading(10 wt%)and different Co/Ni mass ratios were prepared by urea co-precipitation method,and the structure properties were characterized in detail.The results revealed that Ni and Co particles were embedded into the channel of SBA-15 and Ni was alloyed with Co.In addition,the bimetallic catalysts with a Co/Ni ratio(RCo/Ni)lower than 1 had relatively high metal dispersion(ca.17-20%)and small metal particle size(ca.4-5 nm).It was found that the activity and stability of Ni-Co/SBA-15 depended strongly on the metal particle size,indicating the structure-sensitive character of the DRM reaction.Compared to Ni/SBA-15 monometallic catalyst,bimetallic NixCo(10-x)/SBA-15 with RCo/Ni<1 possessed improved activity and stability,which was mainly attributed to the small metal particle size,the synergetic effect of Co and Ni as well as the confinement effect of SBA-15 mesoporous channels.Among all NixCo(10-x)/SBA-15 developed,NigCo1/SBA-15 exhibited the highest DRM performance,with no coke deposition on the catalyst and only a slight growth in mean metal particle size from 4.1 nm to 5.0 nm,indicating excellent coke-and sintering-resistanct properties.Finally,the Ni-based catalysts were applied to the CSDRM process.Preliminary results showed that the Ni metal was subject to oxidation in CSDRM,which resulted in the deactivation of catalyst.