A Highly Efficient Sc_2O_3-promoted Ni-ZrO_2 Catalyst for Methanation of Coal-based Syngas to Produce Synthetic Natural Gas

A type of highly efficient Ni-ZrO2catalysts doped with Sc2O3for co-methanation of CO and CO2 was developed,and displayed high activity and excellent thermal stability.Over a Ni6Zr3Sc1catalyst under the reaction conditions of 0.1 MPa,573 K,V(H2)∶V(CO)∶V(CO2)∶V(N2)=75∶15∶5∶5,GHSV=40 000mL/(h·g)(outlet),the observed conversion of CO and CO2maintained continuously at high levels of 100%and 85%,respectively,during 20-332hafter the reaction started,with the corresponding selectivity of CH4product being 100%.The results of heat-resisting test showed that,over the Ni6Zr3Sc1catalyst after undergoing 24h of the methanation operation at 973Kfollowed by going down to 573K,the total conversion of(CO+CO2)still maintained stable at the level of 80.2%,whereas that of the Sc2O3-free Ni6Zr4catalyst after undergoing the same heat-resisting test fell to 2.7%,implying that it was deactivated due to sintering.The results of the catalyst characterization demonstrated that solution of a considerable amount of Sc3+in the ZrO2lattice resulted in the formation of(Zr-Sc)Oy composite oxide with simple c-ZrO2phase-structure,which was closely associated with the high activity,especially the extremely high thermal stability,of the Ni6Zr3Sc1catalyst.