Influence of Zr,Ce, and La on Co3O4 catalyst for CO2 methanation at low temperature

The Co3O4 and Zr-,Ce-,and La-CosO4catalysts were prepared,characterized,and applied to produce CH4 from CO2 catalytic hydrogenation in low temperature as 140-220 ℃.The results indicated that the addition of Zr,Ce,or La to the Co3O4 decreased the crystallite sizes of Co and the outer-shell electron density of Co3+,and increased the specific surface area,which would provide more active sites for the CO2 methanation.Especially,the addition of Zr also changed the reducing state of Co3O4 via an obvious change in the interaction between CosO4 and ZrO2.Furthermore,Zr doped into the Co3O4 increased the basic intensity of the weak and medium basic sites,as well as the amount of Lewis acid sites,and Brφnsted acid sites were also found on the Zr-Co3O4 surface.The introduction of Zr,Ce,or La favored the production of CH4,and the Zr-Co3O4 catalyst exhibited the highest CO2 conversion (58.2％) and CH4 selectivity (100％) at 200 ℃,and 0.5 MPa with a gaseous hourly space velocity of 18,000 ml·gcat-1· h-1,and the catalytic activity of CO2 methanation for the Zr-,Ce-,and La-Co3O4 exhibited more stable than Co3O4 in a 20-h reaction.