Development of Highly Active Co/SiO2 Catalysts with Chelating Agents for Fischer-Tropsch Synthesis

Novel preparation methods for Co/SiO2 Fischer-Tropsch synthesis (FTS) catalysts were developed based on the impregnation method using aqueous solutions containing various concentrations of Co nitrate and a chelating agent, either nitrilotriacetic acid (NTA) or trans-1,2-diaminocyclohexane-N,N,N’,N’-tetraacetic acid (CyDTA). FTS activity of the Co/SiO2 catalysts with Co loadings of 5-20 wt% as metallic Co was improved by stepwise impregnation with the chelating agents. Catalysts prepared with CyDTA (Co loading = 20 wt%, Co2+/CyDTA = 4 mol mol−1) yielded 1500 g kg-cat−1 h−1 and 815 g kg-cat−1 h−1 of C5+ and C10-20 hydrocarbons, respectively, at 503 K and 1.1 MPa (H2/CO/Ar = 62/33/5). This activity significantly exceeded that of the catalysts prepared from aqueous solution containing Co nitrate and other chelating agents. The surface structures of the reduced and calcined catalysts were investigated using various characterization techniques. The results indicated that control of the interaction between Co2+, chelating agents and SiO2 surface was crucial for the preparation of Co/SiO2 catalysts with high FTS activity.